HEAT
RESISTANT
ALLOYS
TABLE OF CONTENTS 1. INTRODUCTION ...................................................................................... 1-1 What Are Heat Resistant Alloys? ....................................................... 1-2 Rolled Alloys Products Nominal Compositions ............................... 1-4 Heat Resistant Alloy Specifications................................................... 1-5 EFECT OF ALLOYING ELEMENTS ...................................................... 2-1 RESISTANCE TO THE ENVIRONMENT................................................. 3-1 Oxidation .............................................................................................. 3-3 Laboratory Oxidation Testing ............................................................ 3-10 Carburization........................................................................................ 3-15 Carburization Testing .......................................................................... 3-14 Vacuum carburizing ............................................................................ 3-19 Metal Dusting/Catastrophic Carburization/Carbon Rot ................... 3-20 Nitriding ................................................................................................ 3-23 Sulphidation ......................................................................................... 3-25 Halogen Gas Hot Corrosion .............................................................. 3-30 Molten Salts.......................................................................................... 3-34 Molten Metals ....................................................................................... 3-36 Magnetism ............................................................................................ 3-41 STRENGTH AT TEMPERATURE ............................................................ 4-1 Hot Tensile Properties ........................................................................... 4-1 Creep and Rupture ................................................................................. 4-3 Creep-Rupture Testing ........................................................................... 4-5 10,000 hour Rupture Strength Data ...................................................... 4-7 0.0001% per hour Minimum Creep Rate Data ...................................... 4-8 THERMAL FATIGUE ............................................................................... 5-1 WEAR, EROSION, GALLING .................................................................. 6-1 PHYSICAL METALLURGY...................................................................... 7-1 Sigma ...................................................................................................... 7-1 Grain Growth.......................................................................................... 7-5 HEAT RESISTANT ALLOY GRADES ..................................................... 8-1 Iron-Chromium Alloys ............................................................................ 8-1 Fe-Cr-Ni alloys, Ni under 20%............................................................... 8-3 Fe-Ni-Cr alloys, Ni 30 to 40% ................................................................ 8-5 Ni-Cr-Fe alloys, Ni 45 to 60% ................................................................ 8-7 Ni-Cr-Fe alloys, Ni over 60%, 15 to 25%Cr .......................................... 8-8 Cast heat resistant grades ..................................................................... 8-10 DESIGN .................................................................................................... 9-1 Thermal Strain......................................................................................... 9-2 Weldments............................................................................................... 9-4 Thermal Expansion................................................................................. 9-5 Thermal Expansion Coefficients ........................................................... 9-6 Section Size............................................................................................. 9-8 i 2. 3. 4. 5. 6. 7. 8. 9. 10. SELECTING THE ALLOY ................................................................................... 10-1 Temperature ....................................................................................................... 10-1 Atmosphere ........................................................................................................ 10-2 CUTTING AND FORMING .................................................................................. 11-1 Shearing.............................................................................................................. 11-1 Bending and Forming ........................................................................................ 11-1 Spinning and Deep Drawing ............................................................................. 11-4 Machining ........................................................................................................... 11-5 Forging................................................................................................................ 11-6 WELDING ............................................................................................................ 12-1 Carbon Steel vs Stainless ................................................................................. 12-2 Shielding Gases ................................................................................................. 12-3 Cold Cracking versus Hot Cracking................................................................. 12-4 Distortion ............................................................................................................ 12-5 Penetration ......................................................................................................... 12-6 Fabrication Time ................................................................................................ 12-6 Welding Austenitic Alloys ................................................................................. 12-7 Alloys under 20% Nickel ................................................................................... 12-8 Alloys over 20% Nickel ...................................................................................... 12-9 Gas Metal Arc Welding ...................................................................................... 12-10 Flux Cored Welding ........................................................................................... 12-11 Shielded Metal Arc Welding .............................................................................. 12-12 Gas Tungsten Arc Welding ............................................................................... 12-14 Plasma Arc Welding .......................................................................................... 12-15 Submerged Arc Welding ................................................................................... 12-16 Resistance Welding ........................................................................................... 12-17 Weld Filler Selection .......................................................................................... 12-18 Dissimilar Metal Joints ...................................................................................... 12-19 Heat Resistant Alloy Weld Filler Metals ........................................................... 12-20 Brazing and Soldering ....................................................................................... 12-21 APPLICATIONS Muffles ................................................................................................................ 13-1 Retorts ................................................................................................................ 13-5 Baskets, rod frame............................................................................................. 13-6 Radiant tubes ..................................................................................................... 13-8 Rotary Kilns & Calciners ................................................................................... 13-12 Cast Link Belts ................................................................................................... 13-15 Neutral Salt Pots ................................................................................................ 13-16 Bolts .................................................................................................................... 13-21 Springs................................................................................................................ 13-22 THUMBNAIL BIOGRAPHIES OF RA ALLOYS.................................................. 14-1 CHEMICAL SYMBOLS ....................................................................................... 14-2 BIBLIOGRAPHY ................................................................................................. 14-3 HISTORY ............................................................................................................. 14-5 TRADEMARKS ................................................................................................... 14-6 GERMAN STANDARDS VS AMERICAN ........................................................... 14-7 11. 12. 13. 14. ii together with our suppliers. to create the present market for RA330®. UNS or AMS chemistries. RA333®. RA 253 MA®.rolledalloys. in fire is iron born and by fire it is subdued. Book XXXVI. Michigan U. Wilson. RA 353 MA®. FAX +1-734-847-3915.com Contact Rolled Alloys Technology & Marketing Services. and with those fabricators who also specialize in heat resistant alloy fabrication. specialty welding fillers and weld overlay wires. Although RA330 and RA333 are both sold to published ASTM. and we have significant market share in others. RA330® and RA333®. Beginning in the 1970’s. Our current laboratory data. our internal purchasing specifications are designed for more rigorous quality control levels than required by these industry-wide specifications. www.A. We. has been generated under the direction of Jason D. Natural History. by fire gold is purified. generated the data to obtain ASME Code coverage of RA330 to 1650°F (900°C). tel +1-734-847-0561. Our technical expertise. and RA 602 CA® alloys.S. By fire minerals are disintegrated. and in the Technical Resource Center of our web site. Rolled Alloys worked with the industrial furnace builders. 2006 ©Rolled Alloys 2006 Note: This document is available in PDF format. Temperance. to which this paper is an introduction. We currently stock a dozen different grades of heat resisting alloys. Bulletin 401 June 5. Pliny the Elder. and copper produced. titanium alloys. 200 Rolled Alloys has specialized in supplying wrought heat and corrosion resistant alloys over a half century now. and alloys designed for corrosion applications. During these years. 1-1 . Several of these are proprietary to Rolled Alloys. Rolled Alloys initiated and drafted eleven separate ASTM specifications for our own alloys.INTRODUCTION We cannot but marvel at the fact that fire is necessary for almost every operation. We have modified the chemistry and mill processing of RA330 on three separate occasions to maximize its effectiveness in heat treat applications. laboratory personnel and a more detailed inventory of heat and specialty corrosion resistant alloys than any other supplier. We have an experienced sales force. aerospace grades used in gas turbine engines. both oxidation testing and metallography. includes documented field experience and laboratory studies back to 1952. 5%Cr (chromium). the same as does iron. mostly included for their benefits in hot working the alloy at the steel mill. In spite of poor strength. An addition of carbon permits the chromium-iron grades to be hardened by heat treatment. with a maximum use temperature of 1200°F (649°C). as they are stronger and more ductile. are those solid solution strengthened alloys (intended) for use at temperatures over 1400°F (760°C) and limited in the extreme to 2400°F (1316°C). are often brittle. including the stainless cookware in your kitchen. the chemistry is about 18% chromium. the “ferritic” and the “austenitic”.2% silicon. Austenitic alloys of interest to us cover the range from about 8 to 80% nickel. These ferritic grades also have a little manganese. They have a body-centered cubic crystal structure. including types 410. With a little higher carbon. neither of these is of any use above 1200°F (~650°C). is used for corrosion resistant applications. 8% nickel. is the austenitic stainless steel produced and used in the greatest quantity world-wide. However. and 314 (20%Ni 25%Cr 2%Si) in continental Europe. B and C. in particular molten copper and its alloys. from our perspective. They are non-magnetic as supplied. often called “18-8 stainless”. 304L. The most commonly used true heat resistant alloy in North America is RA330®. 1-2 . and/or nitrides. At room temperature the austenitics are more ductile and generally easier to fabricate. an iron base alloy of 19% chromium. These materials cannot be strengthened by heat treatment. are simply iron with anywhere from 11% to about 26% chromium added. The highest nickel heat resistant alloy. Ferritic grades have low creep rupture strength. carbides. to sulfur bearing atmospheres. In other parts of the world different alloys predominate. As you might suppose. is RA600. being 15. Nearly all heat resistant alloys of interest to us are austenitic. 35% nickel and 1. 304H is used as a high temperature alloy having good strength and usable oxidation resistance to about 1500°F (816°C). Heat resistant alloys are strengthened by solid solution.What are heat resistant alloys? Heat Resistant alloys. 304 stainless. such as 310 (20%Ni 25%Cr) in much of Asia. although after certain high temperature service conditions some may become magnetic. carbon and nitrogen. and above the temperatures where age hardening mechanisms or martensitic transformation are effective. A low carbon version. There are two fundamental types of heat resistant alloys. They are magnetic. at red heat. The “straight chromium” grades also divide into two more classes of stainless steel. structure is also more resistant to intergranular attack by low melting point metals. again in North America. and may be difficult to weld. Martensitic stainlesses can be heat treated to maintain high strength through about 900°F (482°C). or body-centered-cubic. The ferritic alloys. and the 440’s A. as they are used over very broad temperature ranges. silicon. It is these austenitic alloys that are of primary interest to us. 76%Ni (nickel) and about 8%Fe (iron). with the balance mostly iron. such as RA446. ferritic heat resistant alloys may be used for their good resistance. The ferritic. These constitute the martensitic stainlesses. the martensitic and the precipitation hardening. which is near the melting point of these materials. The austenitic alloys all have much greater creep-rupture strength than do the ferritics. An example is RA310.a. Nb) cerium cobalt chromium copper iron manganese Mo N Ni O Si Ti V W Y Zr molybdenum nitrogen nickel oxygen silicon titanium vanadium tungsten yttrium zirconium 1-3 . with roughly ten times the strength of RA446. RA20 will not withstand hot gas corrosion by sulfur compounds at red heat. With the addition of this 20% nickel to a 25%Cr-iron base. it has almost no resistance to liquid sulfuric acid. There is a class of very low carbon martensitic stainlesses which obtain their high strength by an age-hardening. To make this book easier to read. but they are not resistant to aqueous corrosion by sulphuric acid. the so-called “885°F” (475°C) embrittlement. or precipitation hardening. niobium. But. This structure by its nature is more ductile than the ferritic. all straight chromium grades embrittle severely after being held in the 700 to 1000°F (370 to 540°C) temperature range. A more complete list is on page 140: Al B C Cb Ce Co Cr Cu Fe Mn aluminum boron carbon columbium (a. molybdenum or titanium is responsible for the precipitation hardening mechanism. or body-centered-cubic atomic arrangement. because of its high nickel. and much greater ductility. On the other hand. the alloy becomes austenitic. which uses a copper addition. The one or two letter symbol is normally used for various chemical elements. When enough nickel is added to the iron—chromium mix. The most commonly available of these is 17-4PH®. just like RA446.k. That is. Whereas RA446 might be chosen to resist a sulfidizing atmosphere at 1500°F. process. or RA17-4. which contains 25% chromium. rather than writing out the full name. A point of occasional confusion to note—the ferritic grades have some resistance to hot SO2 or H2S gas. known as face-centered-cubic. An addition of copper. the nickel alloy RA20 (20-Cb-3® stainless) is often chosen to resist sulfuric acid. the atoms form a different arrangement. here are some of the most common elements used in various heat and corrosion resistant alloys.Like the ferritic stainlesses. the alloy becomes austenitic. but also has 20% nickel. 001B 0.15Fe .1 .40C 43Fe 0.5 1.06C 2Fe 0.7 0.5 0.16N 0.2 25 -0.7 0.5 Ti 6Al-4V Titanium --- 6.08Zr 9.5 24 33 5.2 0.03C 70Fe 0.16O 0.6 -----14 15 -1-4 -----0.5 Stainless 304H 316L RA321 RA347 RA410 RA410S RA17-4 18.22N 0.25 21 11 1.3 0.0 19 35 1.02C 67Fe 5Mn 0.14C 87Fe 0.5 15.4 4 ---1.5 0.5 0.Rolled Alloys Products.3Cu 0.4 4V 0.3 0.1Y 0.7 --20 10.2 --Other 0.8 9.5 0.2 3 --0.05C 14Fe 0.9 2.6 13 37.5 0.3 0.0.3 52.7 0.25 19 35 1.10C 2Fe 0.3Cu 0.05C 43Fe 0.15N 73Fe Heat Resistant 25 45 1.7 50 -----0.05C 62Fe 0.2 10.2 1.2 3.7 TM WASPALOY 19 57 RA188 22 22.17N 0.02Zr 0.4 0.02C 1.5 76 0.08 0.4 0.16N 0.5 --4.7 0.02C 40Fe 0.5Cb 0.5 61.4 17.05C 0.08 19Fe 3.4 1.3Cb 0.45 0.4 -Ti ------0.5 61 RA718 19 52 C-263 20 51 ® René 41 19.4 0.9 9 3 5.3 89.22N 0.01C 70Fe 0.5 8.3 17 12 12 15.7 25 35 1.10C 2Fe Aerospace RA X 22 47 RA625 21.1 ------ -------- -------- -------- --0.07 ----6.05C 1.08C 8Fe 0.1 0.3 .2.5 20 22.3 9.6 Cb 0.2 9.4 0.5 L-605 20 10.05C 52Fe 0. Nominal Composition Cr RA333® RA330® RA330HC RA 253 MA® RA 353 MA® RA 602 CA® RA800H/AT RA309 RA310 RA600 RA601 RA446 Ni Si Mo Co 3 -----------3 -----------W 3 -----------Al -----2.3Cu 0.6 1.06C 87Fe 3.2 25 63 -21 31 0.2 .1 -0.05C 5Fe 5Cb 19Fe 0.8 25 20 0.02C 48Fe 3.05Ce 36Fe 0.3 16.08C 0.2 ----- 0.04Ce 65Fe 0.05C 75Fe Corrosion Resistant AL-6XN® RA20 RA2205 LDX 2101 20.7Mn 70Fe 0.3 -2.4 --0.5Fe 0.6 --0.08C 3Fe 0.3 .4 -------0.3.5Cb 0.2 22.04C 70Fe 0.4 23 13 0.05C 18Fe 0.6Mn 69Fe 0.1 21.07C 45Fe 0. strip (1. strip (2.4833 SA-312 A 312 SA-240 A 240 5521 1.4633) Rod. bar. wire Bar. sheet. sheet. tube Welded pipe Welded tube RA330 N08330 Plate.4851 5715 1-5 .1.4633 -B 166 SB-409 B 409 .1. sheet.sheet.4851) Rod.1.4816 5665 5870 2.-SB-408 B 408 .Nr. wire RA800H/AT N08811 Plate.4763) RA600 N06600 Plate. strip (1.4854) Bars and shapes Pipe RA 602 CA N06025 Plate.4886) Bars & shapes Billets & bars Smless pipe. sheet.4845) Bars and shapes Pipe RA446 S44600 Plate. strip (1.(1.) RA333 N06333 Plate.4845 SA-479 A 479 5651 1.4893) Bars and shapes Pipe Welded tube RA 353 MA S35315 Plate.4933) Pipe RA310 S31008 Plate.1. strip (2.Heat Resistant Alloy Specifications alloy UNS Product Form (W.4608) Bar Smless pipe. strip (N08810) Rod and bar Smlss pipe &tube RA309 S30908 Plate.4886 SB-511 B 511 5716 -B 512 SB-535 B 535 SB-710 B 710 -B 739 -B 546 SA-240 A 240 . bar.4893 SA-479 A 479 1.rings Smlss pipe & tube ASME ASTM AMS W.4816) Rod.4845 SA-312 A 312 -A 176 .Nr. sheet. forgings. strip (1. tube Welded pipe Welded tube Fusion weld pipe RA 253 MA S30815 Plate. sheet. sheet. Bars and shapes 1. strip (1.4763 SB-168 SB-166 SB-167 SB-168 SB-166 -SB-167 B 168 B 166 B 167 B 168 B 166 -B 167 -2. wire Smlss pipe & tube RA601 N06601 Plate. strip (2. sheet.4833./EN -B 718 5593 2.4835 SA-312 A 312 SA-249 A 249 ASME Code Case 2033-1 -A 240 .4876) SB-407 B 407 SA-240 A 240 . sheet.4854 ---A 312 -B 168 2. sheet.4833 SA-479 A 479 1.4608 -B 719 5717 -B 722 -B 723 -B 726 SB-536 B 536 5592 1. strip (2. bar. strip (1. When added to a mix of iron and chromium. high temperature strength. the tendency for an alloy to form sigma. Metallurgically speaking. the most important alloying elements in heat resisting alloys are: chromium (Cr) for oxidation resistance and nickel (Ni) for strength and ductility. In some proportions iron is a strengthening element. nickel tends to make the atomic structure “austenitic”. that is. Metallurgically speaking. chromium tends to make the atomic structure “ferritic”. with a face centered cubic (FCC) crystal structure. Other elements are added to improve these properties. with a body centered cubic (BCC) crystal structure. The tendency to form ferrite. Again speaking metallurgically. is counteracted by nickel. both RA446 and RA310 may form sigma when exposed to intermediate temperatures. 2-1 . the alloy RA446 with 25%Cr 75%Fe (iron) is ferritic. and a few are mainly nickel and chromium. and resistance to both carburization and nitriding. For example. or body centered cubic (BCC) crystal structure. in all of the “austenitic” heat resistant alloys. High chromium also contributes to sigma formation. that is. and to carburization resistance. If one were to substitute 20% nickel for some of that iron one the result would be a 25% chromium. Here. Nickel counteracts. High nickel is bad for sulphidation resistance. and to form sigma. but heat resistant alloys are primarily alloys of iron. 75% iron. chromium and nickel. 20% nickel. which. Iron base alloys require a certain amount of nickel to be added before they become austenitic. is a ferritic alloy.EFFECT OF ALLOYING ELEMENTS Starting with a base of iron. Oxidation resistance comes mostly from the chromium content (the same is true of aqueous corrosion resistance). CHROMIUM (symbol Cr) Chromium is the one element present in all heat resisting alloys. iron is a ferritizing element. Nickel decreases the solubility of both carbon and nitrogen in austenite. This is RA310. Chromium adds to high temperature strength. RA446. and rather rather weak. but it is easily oxidized and carburized unless protected by other elements. Iron itself has a ferritic. IRON (symbol Fe) Heat resistant alloys may contain anywhere from 8 to 75% iron. which is essentially 25% chromium. because it is austenitic. but doesn’t necessarily stop. Silicon is one of the most effective elements in contributing carburization resistance. nickel increases ductility. anywhere from 8% up to 80%. NICKEL (symbol Ni) Nickel is present. is much stronger and more ductile than RA446. 55% iron austenitic alloy. 4% C.03%. Carbon is controlled within certain limits in heat resisting alloys as a strengthening element. the 35% nickel content is more than enough to prevent any embrittling sigma to form from the Si. as well as resistance to absorbing nitrogen at high temperature.10% carbon. Nitrogen may be controlled like carbon as a strengthening element in both the heat and the corrosion resistant grades.4841) and 1.4828. such as the Outokumpu grades.35% up to 0. They may be either tolerated at some level as undesirable impurities. is what helps the alloy resist carburization. Phosphorus is quite harmful to weldability in nickel alloys.. just under the chromium oxide scale on the alloy. silicon improves resistance to alkali metal hot corrosion. and the German alloys 314 (1. Rolled Alloys has long been the only company to produce wrought heat resistant alloys containing silicon. nitrogen. In RA330. which is an important variable in the steelmaking process. While strong. Silicon. 2-2 .S. When not used deliberately. and sometimes much less. or controlled for their effects on metal properties. In Europe silicon is used to improve a number of heat resistant alloys. but it also becomes less ductile. not all. under 0. Sulphur is generally undesirable. the cast alloys are not very ductile. Corrosion resistant grades. even a few hundredths of a per cent. with RA 602 CA near 0. RA330® has 1. but some sulphur is used to improve machinability. The metallurgical effects of silicon are that it tends to make the alloy ferritic. SILICON (symbol Si) Silicon improves both carburization and oxidation resistance. The cast heat resisting alloys usually have from 0. In corrosion resistant grades carbon is considered an undesirable element. for example. affects the fluidity of the molten metal. alloys. by contrast. All may be considered impurities arising from the steel making process.2%. Most wrought heat resisting alloys contain around 0.2%Si. Silicon decreases the solubility of carbon in the metal (technically it increases the chemical “activity” of carbon in the alloy).05 to 0. carbon. sulphur and phosphorus. A silica (silicon oxide) layer. the alloy becomes stronger. in part because it increases fluidity of the molten metal.05% or so N in austenitic stainless and nickel alloys.03% carbon. and is kept as low as practical. there may be about 0. RA 253 MA® and RA 353 MA®. continued THE NEXT GROUP of alloying elements present in all heat resisting alloys is silicon. At high enough levels. have less than 0. Silicon can decrease weldability in some. or to form sigma. RA333® about 1% silicon. is a strengthening element. CARBON (symbol C) Carbon.75% carbon.04%. and RA330HC at 0. All the cast heat resistant alloys have silicon. In the U. normally above 0.EFFECT OF ALLOYING ELEMENTS. As the carbon level increases. Carbon may actually be dissolved in the alloy. the steel mill normally refines the metal to a very low sulphur content.3%. To improve hot workability. titanium. AL-6XN stainless. This is fairly easy to do with current melting processes such as the AOD (argon-oxygen decarburization) or ESR (electro-slag remelt) furnaces. It has the benefit of improving machinability. such as Type 303. the nickel weld fillers themselves are normally specified to have no more than 0.010% in most nickel alloys. NITROGEN (symbol N) A small amount of nitrogen serves to strengthen austenitic heat resisting alloys. PHOSPHORUS (symbol P) Phosphorus is harmful to weldability. and even lower P would be preferred.015% phosphorus. 253 MA® and 353 MA®. likewise Haynes® HR-120®. 2-3 . and therefore maximize yields.02%. tungsten. and tends to retard or prevent formation of ferrite and sigma. Nitrogen is used to strengthen Outokumpu’s heat resistant grades 153 MA®. about 0.001% being not uncommon. 0. hard particles called carbides.23% is used in the corrosion resistant alloy AL-6XN® to prevent sigma formation. This causes a little austenite to form (in a predominately ferritic structure) while it is being hot worked. It tends to retard or prevent ferrite and sigma formation. Too much nitrogen can embrittle them. is refined to extremely low sulphur. and increases its resistance to chloride pitting corrosion. may have much higher sulphur. or. It also raises the tensile and yield strengths of AL-6XN. the harmful effects of S on hot working and welding may be reduced to a degree by the addition of some manganese. and is commonly below 0. for example. Phosphorus cannot be removed during the refining process. To produce alloys with low phosphorus. A small amount of nitrogen is specified in RA446. continued Carbon is an “austenitizing element”. more commonly. molybdenum. Along with simply removing the sulphur in the refining process. SULPHUR (symbol S) Sulphur is normally regarded as an impurity. Because phosphorus is so harmful to nickel alloy weldability. These are chemical compounds of carbon with chromium. zirconium or columbium (niobium). so for 304 and 316 bar it is kept up around 0. Sulphur is also detrimental to weldability. it is present as small. This in turn helps keep the ferrite grain size from getting too large. Free machining stainless steels. Nitrogen is also an “austenitizing” element. one must start with low phosphorus raw materials. Nitrogen at 0.CARBON (symbol C). and of ferrite. aluminum. Manganese improves weldability. TUNGSTEN (symbol W) Tungsten is a large.80% max. High cost and variations in availability of cobalt tend to limit the use of cobalt alloys to gas turbine engine applications. Some of these elements are added for strength. such as the 15%Co in cast Supertherm® or 12. so is limited to 2% maximum in most heat resistant alloys. but oxidation resistant only to 1800 or 2000°F (1000 or 1100°C). High levels of tungsten in heat resistant alloys may promote catastrophic oxidation. is used for the electrode in gas tungsten arc welding. and boron. Cobalt base alloys L605 and 188 are very strong. i. Tungsten oxidizes in air readily above 950°F.e. manganese. with thoria or rare earth oxide additions. tungsten. like nickel. titanium. lanthanum and yttrium. Mn decreases solubility for carbon. Manganese is usually considered an austenitizing element. RA330-04 achieves its hot cracking resistance from about 5% manganese added to the 35%Ni 19%Cr base. in RA 253 MA. 6170°F (3410°C). zirconium. Larger amounts are required for a significant strengthening. and restricted further. COBALT (symbol Co) Cobalt at the 3% level in RA333 improves strength slightly and enhances oxidation resistance at extreme temperatures. continued OTHER METALLIC ALLOYING ELEMENTS include cobalt. both as a partial substitute for nickel and to permit a substantial nitrogen addition. decreases the chemical activity of carbon in austenitic alloys.EFFECT OF ALLOYING ELEMENTS. Cobalt is an austenitizing element. 2-4 . others like aluminum and the rare earth elements are largely for oxidation resistance. MANGANESE (symbol Mn) Manganese is used in steelmaking to improve hot workability. to 0. It increases solubility for nitrogen and has for decades been used in the Nitronic® series of stainless steels from AK Steel (formerly Armco). and is added to many austenitic weld fillers. which may incorporate other carbide forming elements such as chromium. molybdenum. it reacts with the carbon in the alloy to form a hard particle.. It is tungsten’s very high melting point. Tungsten also promotes formation of sigma. 3% in RA333. that is. heavy atom used as a strengthening addition. columbium (also called niobium). which is required for this application. Copper and vanadium are used in some corrosion resistant alloys but not in the heat resistant grades. 5% in the cast alloy Supertherm and 14% in Haynes alloy 230. the rare earth elements such as cerium. Tungsten metal. It is mildly detrimental to oxidation resistance.5% in the LBGT combustor alloy 617. Tungsten is a carbide forming element. but is prevented from doing so by the argon or helium weld shielding gas. Al is used in the age hardening (precipitation hardening) alloys. but it is normally used in such small amounts as to be inconsequential in this respect.4% Al. X750. about 0. ALUMINUM (symbol Al) Aluminum is added at the 1 to 5% level for oxidation resistance. heavy atom used to increase high temperature creep-rupture strength. WASPALOYTM and 718.1 to 0. aluminum is added to most nickel alloys as a deoxidizing agent. which is very good for strength but not so good for oxidation at extreme temperatures (2100°F/1150°C) or under stagnant conditions. because of its very high melting point. and high temperature strength. Molybdenum helps weldability in austenitic alloys. Titanium alloys are used up to about 600°F (316°C) in aerospace applications. Molybdenum is also a carbide forming element. 4730°F (2610°C).2% Al. Around 0. 2-5 . type 405. unless counterbalanced by austenitizing elements such as nickel. molybdenum metal has no oxidation resistance above 800°F (427°C) and would literally disappear in a cloud of white smoke if exposed to air at red heat. Commercially pure molybdenum metal is used for vacuum furnace fixturing. RA 602 CA® has 2. In aqueous corrosion alloys titanium is referred to as a “stabilizing” element. Ni3Al. in deoxidation of nickel alloys. the various Nimonic® alloys. e. Titanium metal itself. etc. Aluminum promotes sigma formation. However. both stainless and nickel base. alloy 601 contains 1. It is also a ferritizing element. Aluminum may be added to a Cr-Fe stainless grade. Age hardening alloys used in aerospace. This is about as much Mo as can be tolerated in a heat resistant alloy without serious oxidation problems in heat treat furnace applications. C-263. in which it forms the ductile intermetallic phase gamma prime. as part of steel mill melting practice. Ti is a strong carbide former.. such as A-286.5% aluminum in Haynes alloy 214. cobalt. similar to silicon.g. TITANIUM (symbol Ti) Titanium is added in small amounts. and it is the titanium carbides that strengthen RA800AT. to 3% or so. Renè 41®.7%. in the last stages of AOD refining.2%Ti is used. For the most part.3—0.4%. Molybdenum promotes sigma formation. for their age hardening properties. for strength in austenitic alloys. and there is 4. Aluminum increases the activity of carbon. and is a ferritizer. so that it forms no austenite when welded. the age hardening grades must be nickel plated before brazing. Alloys X. At around 0.1—0. hence does not harden. which increases resistance to carburization. depend upon some larger amount of titanium.MOLYBDENUM (symbol Mo) Molybdenum is another large. Titanium also promotes sigma and ferrite. 625 and 617 all contain 9% molybdenum. is not really a heat resistant metal. 3% Mo is used in RA333. although it has a very high melting point (3040°F/1671°C). The titanium in these grades may form a thin oxide layer on the surface which inhibits flow of braze metal. 182). As yttria. since about 1940 in Germany. tighter and more protective oxide scale. a ferritizing element and promotes sigma formation. Mischmetal is encountered in everyday life as the “flint” in a cigarette lighter. The cerium is added as an alloy of several rare earths. the mill analyzes only for Ce. it also increases oxidation resistance.1%. LANTHANUM (symbol La) Used at the 0. It is added in very small amounts. ZIRCONIUM (symbol Zr) Zirconium is a strong carbide former. while higher amounts are beneficial. called mischmetal. This low amount of Cb is harmful to weldability. also called NIOBIUM (symbol Nb) Columbium is added at the 0. . lanthanum and yttrium are used singly or in combination to increase oxidation resistance in austenitic alloys both wrought and cast. practically speaking around 1800°F/980°C and higher. it is the age hardening element in alloy 718. and in the newer ferritic heat resistant alloys. About 2 to 2.COLUMBIUM (symbol Cb) . but little used. Columbium is a strong carbide former. 2-6 . The technology has been known.05% range to for oxidation resistance in Haynes alloys 230. and in alloy 214. while the 3. CERIUM (symbol Ce) Cerium is the major rare earth element responsible for the excellent oxidation resistance of RA 253 MA. S. YTTRIUM (symbol Y) Used at the 0. to increase strength in RA 602 CA®.1% level for oxidation resistance in 214 and RA 602 CA. Residual cerium oxides in the metal may contribute to creep-rupture strength. It oxidizes (burns) very readily. THE RARE EARTH ELEMENTS cerium.02 to 0. .5%. and to prevent corrosion after welding in 347 stainless and nickel corrosion resistant alloys 20Cb3® (RA20). Columbium is very harmful to oxidation resistance.4 to 0.7%Cb is used in various high nickel weld fillers (82. At the 5% level. and in RA333. 0.8% level for strength in several heat resisting alloys. For this reason we limit the amount of residual Cb that may be present in RA330. less than 0. G-3 and G-30. of yttria (Y2O3 ) is used as an oxide dispersion strengthening element in the oxide dispersion strengthened (ODS) ferritic alloys such as PM 2000l® and Kanthal APM®. For chemistry control purposes. A larger amount.6% Cb in 625 is good for both strength and weldability.005 to 0. In RA 253 MA and RA 353 MA the Ce helps chromium form a thinner. 556 and 188. Robert Peaslee of Wall Colmonoy®.BORON (symbol B) Boron increases creep-rupture strength. Boron is an essential ingredient in many high temperature braze alloys. High boron may reduce the formation of continuous carbide network in austenitic alloys. Boron is somewhat harmful to weldability of nickel alloy plate. Boron is an interstitial element and tends to concentrate at the grain boundaries. 2-7 .002% is typical. For this reason boron may be restricted in nickel alloy weld fillers. 0. and is used at rather low concentrations. specifically the Nickel-SiliconBoron braze alloys developed by Dr. It forms the oxide Cr2O3. Oxidation For our purposes. Only after validation by service experience may this test be considered a useful engineering tool. We would make a distinction between fundamental studies of the nature of oxidation. As oxidation rates vary with thermal cycling. The element most often used to form such a protective oxide layer. and the one of interest to us. among other variables. the data are not directly useful for predicting metal wastage/corrosion rates of high temperature equipment in service. although the alloy rankings should be similar. In the following pages we will present the results of laboratory testing. the precious metals gold (Au) and platinum (Pt). with a critical eye. it may be inert and simply not react chemically with oxygen in the air. carburization. It is even more difficult to obtain data useful as an engineering tool to predict life of equipment in sulphidation. Read all such high temperature laboratory data. The second way a metal may resist oxidation. Of course. But if one takes very fine iron wire—specifically. Simply put.RESISTANCE TO THE ENVIRONMENT It is difficult to run high temperature corrosion tests in the laboratory and obtain results that can be used to predict metal behavior in service. coupled with oxidation resistance. We do regard poor results from the lab test as a very strong indication that the product will be unsatisfactory in service at that temperature. Even iron burns. most metals can burn when they get hot enough. and service experience reported by others. or scale. such as catastrophic oxidation. Results may be very sensitive to exactly how the test was run. There is no actual flame. We must emphasize that laboratory data are a necessary first step. that may not be revealed by our testing. at that test temperature. we have confidence that our oxidation data may be used to compare relative performance of one alloy with another. including these. 0000 steel wool—it may indeed be ignited by a match. like magnesium (once used in flash bulbs) and titanium do burn in the conventional sense and may cause a serious industrial fire. Some. Good performance of a new alloy in this test only indicates that the alloy MAY perform well in service. First. platinum is actually used for some laboratory ware and other items that must withstand extreme temperature. That laboratory test itself must then be validated by documented service experience. as well as to the investigator’s unstated assumptions. There are certain limitations. 3217°F (1769°C). Because of its high melting point. and engineering data. lighting a match to a nail does absolutely nothing. Two examples come to mind. this means the high temperature chemical reaction of a metal with the oxygen in the air. is that the metal or alloy may form an adherent oxide film. Even two laboratories running the same type of test may not come up with numerical results that agree with one another. is chromium. 3-1 . liquid metal environments and other types of high temperature corrosion. but a red hot “coal” develops and enough sparks fly to endanger clothing. which protects it from further oxidation. Based on extensive experience and lab work. also known as chromia. controlled service exposure. There are two basic ways in which a metal may be resistant to oxidation. such as cerium. which is no longer produced. The effectiveness of the chromium oxide scale may be improved by very small additions of rare earth elements. 601 oxidizes internally. Aluminum is also used to improve oxidation resistance. For a high temperature alloy to have useful oxidation resistance. or silica. The chromia scale also protects the alloy against carburization and sulfidation. it is oxidized and a layer of chromium oxide (and oxides of other elements as well) is formed. RA 602 CA does not oxidize internally. the scale must be able to “heal” these defects. One of the most effective is silicon. At the 1. 3-2 . The protection is by no means perfect. to continue to react with the alloy.5%.5% aluminum in Haynes alloy 214 is enough to form an actual alumina scale. Other elements are added to the alloy to improve the protective nature of this oxide film or scale. This is not a problem in plate gauges. The scale contains defects through which oxygen and other elements may pass.4% Al typical in alloy 601 is not enough to form an alumina scale. and 214 is extremely oxidation resistant above 1800°F/982°C. It is the 0. In RA85H. the silica forms a sub-scale underneath the chromium oxide scale. which is more protective against oxidation because it cracks and spalls off less than would a thicker scale. This silica subscale is how silicon provides resistance to carburization. has a microscopically thin and transparent film of chromium oxide present. in alloys such as RA330. 11Ni alloy. The 1. scale a rather high amount of aluminum is required.Oxidation. but it is enough to enhance oxidation resistance of 601. silicon also contributes to oxidation resistance. 3. continued Although chromium itself oxidizes even more readily than iron. by more chromium diffusing to the surface to form a new protective film. Cerium promotes a thinner scale. In order to actually develop an Al2O3. This may sound like double talk. to a degree. Scale also cracks from both thermal and mechanical strains. When pure chromium or a chromium-bearing alloy is exposed to oxygen. Even the chromium plate on automobiles. At this high level silicon appeared to offer resistance to molten alkali salt corrosion. it is actually the most easily oxidized. This oxide layer forms very quickly at high temperature. At 2. Because of aluminum at this somewhat lower level. even at room temperature. The Protective Film While chromium is given credit for promoting oxidation resistance and is without question the most effective element in this respect. Silicon oxidizes to SiO2.04% cerium in RA 253 MA that is largely responsible for the excellent oxidation resistance of this rather lean 21Cr. and small pieces spall off each time the metal is cooled down. but once formed it protects the metal against further oxidation.2% Si level in RA330.2% aluminum. If enough silicon is present. though perhaps it may be a consideration in thin sheet. The 4. or the cutlery on our dinner tables. the oxide it forms is very thin. but it really isn’t. RA 602 CA alloy will form an alumina subscale. This contributes to the oxidation resistance of RA 602 CA. the silicon was much higher. and adheres tightly to the metal. or alumina. Some examples are 321. Note the crater-like appearance of local oxidation or “warts” the RA309. This in turn depends upon the temperature and availability of oxygen to combine with chromium. It is to be expected that the tube metal temperature would be perhaps 100— 150°F (55—85°C) higher. or the more quickly the metal is heated and cooled. will “pop” the oxide layer. Used at a nominal furnace operating temperature 1750°F (955°C) for annealing malleable iron castings. 3-3 . the metal is protected and further oxidation proceeds very slowly. because the base metal and the oxide expand and contract at different rates. blue or yellow. The more rapid the rate of expanding and contracting. and 309. middle portion RA330 and exhaust end fabricated of RA309. Certain combinations of chromium. the oxide coating becomes green.2metre) on the firing end. the more hazard there is of the protective coating flaking off. depending upon its thickness and which of the numerous chromium oxide compounds is formed. A jam-up in the furnace broke the tube. Several things may tend to destroy our protective layer: Expansion and contraction. nickel. silicon and other oxides are more tightly adhering than others at different temperatures. RA333 for 4 feet (1. as the result of heating and cooling. iron. The oxide layer is dense. and effectively seals out the air or oxygen from the metal underneath. With some alloys it is possible to reach a temperature where the scale or oxide is no longer tightly adhering and will be loose.The Protective Film. an excessive temperature for the specific alloy can destroy the protection normally offered by the oxide layer. continued When formed at high temperatures. which is acceptable at 1600°F (870°C) but scales unacceptably at 1800°F (980°C). thereby offering little or no protection. is inclined to be tightly adhering. Composite radiant tube. Thus. black. So long as the oxide layer is intact. which isn’t very useful above 1900°F (1040°C). To the best of our knowledge. Alloys normally selected for the strength. RA330 and 600 alloy. Laboratory data which do not duplicate cyclic conditions or stresses imposed in actual service can be misleading as a measurement of an alloy’s oxidation resistance. a given item may appear to have insufficient oxidation resistance. When the alloy is exposed to the oxidizing environment.The Protective Film. damaging not only oxidation resistance. so that a normally carburization resistant alloy carburized very quickly and uniformly. Mechanical deformation and creep. we know of one case where minute amounts of potassium nitrate/nitrite austempering salts were present on fixturing used in a carburizing atmosphere. but also carburization resistance. such as the stretch of a bar under load. resulting in apparent porosity of the 11gage (3mm) muffle wall. but the chromium oxide. Green rot might be considered one form of destruction of the protective oxide coating. While the metal is ductile and yields in creep. The presence of this chloride salt resulted in a chemical attack upon the protective oxide coating of the furnace fixtures. which disappears as a powder. In years past. being more stable. 3-4 . the oxygen is free to penetrate to the metal and form another layer of oxide. Another form of chemical destruction that may be encountered is corrosion from welding fluxes. the nickel and other less stable oxides may be reduced to pure metal. The grains were sliding apart so as to leave voids at the triple points. perhaps somewhere above 2370°F. Green rot is the result of the alloy being alternately exposed to oxidizing and reducing conditions. we knew of a few cases where parts being heat-treated were first coated with sal ammoniac (ammonium chloride). oxidation resistance and thermal shock resistance requirements were not suitable. as we previously discussed. may also destroy the protection. green rot tends to be more prevalent in alloys containing about 65% or more nickel. Upon investigation we found that the RA333 had been heated in service to the incipient melting temperature. Fluoride-bearing fluxes from coated welding electrodes must be carefully and thoroughly removed. In service. since there are now voids in the coating where some of the oxides previously existed. the oxide coating is fragile and brittle and will spall off. or “nodules”. is not reduced. occasionally on RA 253 MA. continued When an alloy is used at a temperature exceeding its capabilities the scale may break down locally. We have observed this on 309 (above) and 310. For example. whereas that particular property would have been more than adequate had the strength been sufficient to avoid excessive creep. Upon exposure of the alloy to an oxidizing environment once more. The salts attacked the protective oxide coating. When the alloy is exposed to highly reducing conditions. a protective oxide coating is formed. On one occasion we saw warts on an RA333 brazing muffle. Of great concern are environments that promote the destruction of the protective layer by some chemical reaction. a condition sometimes called “warts”. Otherwise they continue to function as a flux. they act as fluxes and destroy the protective film1. has the appearance of rotten wood. Catastrophic Oxidation Catastrophic oxidation is. and tungsten. the chief problem may be surface stability. with or without other oxides that may have been sufficiently stable to resist reducing. This oxide is likely to form in stagnant atmospheres. vanadium. such as molybdenum. and reduced in section to less than 1/4” (6mm) diameter. It operated at 1800°F (982°C) as an electrical heating element. 3. as its name implies. oxidation that proceeds so rapidly that complete failure of the material occurs in an extremely short time.” 3-5 . Cast Heat-Resistant Alloys for High-Temperature Weldments: “Where in fact the addition of molybdenum has conferred better hot strength. columbium (niobium). continued With continuous exposure to the two conditions. Hence the name. This 316 stainless (S31600) bar was originally 3/4” (19mm) dia. Sections that were covered with ceramic insulation suffered catastrophic oxidation from the 2%Mo in 316. a mass is eventually formed consisting only of porous chromium oxide. Generally 1500°F (816°C) is considered the maximum long-time use temperature of 316 even in a freeflowing atmosphere The effect of molybdenum is important enough that we would like to quote directly from the late Howard S. The typical chemistry of 316 is 16. form oxides that are volatile at relatively low temperatures. This actually has little strength and no ductility. Certain elements. especially in the 1800— 2300°F (980—1260°C) range.The Protective Film.2Ni 2.4Cr 10. with a threshold for trouble around 1400—1500°F (760—816°C). Avery’s classic work on heat resistant alloys.1Mo. 2. green rot. upon fracture. It has the characteristic greenish-black color of chromium oxide and. If these oxides are formed and retained in the scale. This is most serious under those conditions that cause catastrophic oxidation which stems from the volatile nature of molybdenum oxide (MoO3). Most of our data and experience is with plate gauges. or solid deposits under which the atmosphere is of course stagnant. alloy X may not well tolerate stagnant conditions or temperature extremes. Because the atmosphere under the insulation was stagnant. where metal dusting is most likely to occur.7mm) thick.Nr. Alloy X (N06002. rather than metal dusting.020” (1/2mm) per side may not seriously impede the operation of a plate item 1/2” (12. It has. Thin sections have a lesser total amount of chromium available to reform the protective scale. At lower temperatures in free-flowing atmospheres alloy X is highly oxidation resistant. in our opinion the attack shown here is more likely representative of catastrophic oxidation. a stagnant atmosphere. Metal Thickness Thin things burn faster than thick. Alloy X (N06002) bar exposed to a metal dusting environment.4665). That is.Catastrophic oxidation. continued Catastrophic oxidation may be a serious problem under certain operating conditions. and extreme temperatures.6mm) sheet would quite destroy its usefulness. However. To keep the temperature near 1100°F (~600°C). may completely disappear from catastrophic oxidation when heated for some months at 2200°F (1200°F). 22% chromium and 9% molybdenum. after all. But that same loss on 16 gage (1. One should be cautious about applying this experience to thin sheet. For example. The normal concern is that the plate not lose enough thickness that it is no longer structurally sound. 3-6 . served for decades as the primary alloy used in gas turbine flight engine combustors. W. a metal loss of about 0. containing 47% nickel. roughly 3/16—1/2” (~5—13mm). the rod was packed in fibrous insulation. 2. 0. Grain Size As the protective oxide layer flakes away or is otherwise damaged. The diffusion rate of chromium is orders of magnitude greater along grain boundaries than it is through the grain itself. diffusion of chromium to the surface continually reforms. We observed the effect of grain size on oxidation of S30400 stainless flat bar after long time service. This band was used to reinforce corrugated RA309 inner covers used for batch annealing carbon steel coils.005. continued Isothermal oxidation at 2100F (1149C) for 97 hours. Type 304 stainless “belly band”. Test coupon thickness: sheet 0. and 3/8”. cross section 11. 0.Metal Thickness. 3-7 .5 x 38 mm. plate 1/4. the scale. versus thickness of RA330. Fine grain size improves the ability of the scale to re-form and to heal damage4.060. or “heals”.120. The shearing operation heavily cold worked the edges. The ACI exposed samples for 50 hours at 1600°F (871C) in a neutral salt bath containing 55% BaCl2. continued In service this band was exposed to products of combustion of natural gas with excess air at about 1600°F (870°C) for perhaps five years. The bulk of the metal had grain size ASTM 7. The effect of grain size on hot salt corrosion is similar. An Alloy Casting Institute study5 of the grain size effect on intergranular corrosion rates of low carbon cast Ni-Cr-Fe alloys in molten chloride salts is in agreement. This is the zone which was cold worked in the critical range for grain growth. The flat bar for this band was produced by shearing strips from 1/2” (12. A short distance back from the edge.Grain Size.5-3mm from each sheared edge. There was a narrow zone of deep attack parallel to and about 2. The relation between metal wastage and grain size of this 18-8 stainless is shown at left.6mm per side over most of the band. 25%KCl & 20% NaCl. 3-8 . Metal loss due to oxidation was 0. the grain size was as coarse as ASTM 4.7mm) plate. The reduction in attack of HW (12%Cr 60%Ni) and HT (15%Cr 35%Ni) with decreasing grain size is shown at left. The heavily cold worked sheared surfaces recrystallized in service to grains as fine as ASTM 8. coincident with the heavily oxidized zone. with those of existing grades. So. increasing oxidation rates. Results are reported as weight gain. Creep Strain. However they are of value when one compares the data from new alloys. The entire crucible. The numerical results are valid only for the specific conditions of the test.Laboratory Oxidation Testing In order to evaluate new and competitive alloys we perform considerable laboratory oxidation testing at Rolled Alloys. and the assembly allowed to air cool to room temperature. Stagnant Atmospheres. containing specimen and scale. in milligram/centimeter2 . 3. For example. 309 is about the only one of our heat resistant alloys that occasionally gives disappointing performance. For example. We measure weight gain. in static 1000 hour oxidation testing 310 is somewhat superior to RA330. A simple coupon test does not simulate all the things that can happen in service. The tray is then removed from the furnace. 7 . 2. Alloys with high molybdenum contents are subject to catastrophic oxidation under these conditions. Thermal Cycling. we have a great deal of experience with the good performance of RA333 and RA330. though they may perform rather well in our open air test. it is possible for an alloy to look very good in the laboratory and not at all so good in production equipment. more so for some alloys than others. we feel that means it MAY perform well in service. there are a number of conditions. common in high temperature equipment use. Atmospheres other than dry air. Likewise. Creep strain. There is little or no flow of atmosphere in certain areas of electrically heated equipment. as well as thermal cycling. 4. Samples are heated in porcelain crucibles. is then weighed every cycle. This is more or less addressed by cycling the specimen to room temperature weekly. at temperatures up to 2250°F (1232°C)6. and the tests are cyclic. High water content increases the metal wastage of low nickel alloys faster than it does the higher nickel grades 3-9 . More rapid cycling means more scale spalls off. generally around 1900°F (1040°C) or above. increases the amount of scale which spalls off the coupon. The H2O content of the atmosphere affects oxidation rates. lids are quickly placed on the crucibles to contain spalling oxide. While we like to think our tests provide useful guidance. This is not at all addressed in the lab. that is. which are not well simulated by laboratory oxidation testing: 1. If an alloy performs well on test. Which means they are not useful for predicting metal wastage of components in actual service. for about 160 hours (one week) at temperature. When thermal cycling is added. and underneath insulation or solid deposits. 4 to 6 in a tray. RA330 better retains its protective oxide. the total amount of oxygen (and nitrogen) that has reacted with the test specimens. Specimens are usually of plate gages. 3-10 . As this is weight gain data. along with service experience. Thin samples. In our considered view. that one being extrapolated from a 1600 hour run. finally. oxidation data ought in our opinion be viewed qualitatively. continued Oxidation test after 2880 hours at 2200°F (1200°C) And. in order to compare all alloys for about the same exposure time. Data shown on the following bar graphs is all for 3000 hour (~18 weeks) exposure. valid or not. as a guide to an alloy’s usefulness. are not valid. high numbers mean heavy oxidation.A. unlike what is assumed about aqueous corrosion data. One would expect to use these numbers. or other high temperature corrosion data. The declining availability of experienced engineers in the U. small numbers a relatively light degree of oxidation. 3000 hours seems a reasonable length of time to run a test in our laboratory. has generated pressure to extrapolate such data.Laboratory Oxidation Testing. but that is still only about 4 months. If one expects the equipment to last 1. All but the RA309 tests were run for 3000 hours. 2 or 10 years. the laboratory test does not properly simulate time. silicon and aluminum by scaling). We emphasize that. The specimen continually changes chemistry throughout the test (it loses chromium. significant extrapolations of oxidation. may show greater oxidation rates than thick specimens. simply from having less total chromium. it would be hard to make a case that a 4 month test adequately represents service conditions.S. August 1969.Conference Proceedings of the 2 International Conference on Heat-Resistant Materials 11-14 September. By experience.A.H. alloy 600 plate is a useful material for retorts and muffles operating in the 2100-2200°F (1150—1200°C) temperature range. 1995. Vol 41. We would look at the higher alloys. CVD retorts. 980 1095 and 1150C. In static 1000 hour oxidation testing. Likewise RA 353 MA is used quite successfully at such temperatures. 1991 7. which gains 64 mg/cm2 at 1600°F (871°C). Another point to remember is that alloys high in molybdenum and columbium may be sensitive to catastrophic oxidation. Gas Corrosion of Metals. 1949. H. One should also bear in mind that these data still represent simple laboratory oxidation testing. Poland 2. Tennessee 3-11 . Tennessee. 36.C. J. should not lose structural integrity due to metal loss. WRC Bulletin 143. Alloy Casting Bulletin No. Teodor Werber. 16. Wilson. continued Numbers under 20 may give assurance that the alloy. The good resistance to scaling of RA 602 CA in test has also been borne out by service experience in rotary calciners. Oxidation of Metals.. and at least one AOD charge chute. Oxidation Rates of Some Heat Resistant Alloys. for more elevated temperatures. Oxidation Resistance of Eight Heat-Resistant Alloys at 870. 310 is somewhat superior to RA330. Vol. New York. Jackson. 1975. One example is 304 stainless. Welding Research Council. Alloy Casting Institute 6. RA330 better retains its protective oxide.S. New York 4.D. pages 1213-1247. Cast Alloys for Salt-Bath Heat Treating. for example. ASM International 5. Heat Resistant Materials nd II. Kelly and J.D. References. J. Pennsylvania 3. Stanislaw Mrowec. J. Cast Heat-Resistant Alloys for High-Temperature Weldments. Kelly and J. particularly under stagnant atmospheres. U. Conference Proceedings of the 2 International Conference on Heat-Resistant Materials 11-14 September. Note 600 alloy which shows a 153 mg/cm2 weight gain at 2100°F (1149°C). More rapid thermal cycling would not only increase oxidation rates but might also change the relative performance of some alloys. which does not take into account many of the ways by which the protective oxide scale may be damaged. Warsaw. 1995 Gatlinburg. Heatnd Resistant Materials II. Gatlinburg. Nevertheless. Wilson. somewhat differently. Oxidation 1. and in the neighborhood of 300 mg/cm2 at 1800°F (982°C). in plate form..C. Avery. Leslie and Fontana. The alloys were cycled to room temperature once a week.S. Oxidation Rates of Some Heat Resistant Alloys. RA 602 CA is clearly the best by far in our test series. When thermal cycling is added.Laboratory Oxidation Testing. Transactions ASTM. 3/4. Nos. Gene Rundell and James McConnell. One might want a little actual service background when considering alloys with weight gains in the 100-300 mg/cm2 range. we know that 304 1/4” plate will simply disappear in 2-3 months when used in air around 1700-1800°F (930—980°C). ASTM Philadelphia. November 1952. Exposed for 3000 Hours Cycled Every 160 Hours 250 1600F 200 Weight Gain (mg/cm2) 200 1800F 2000F 154* 150 113 2100F 100 64 53 54 32 19 20 5 1 11* 4 50 0 RA304 1 RA309 RA310 Alloys 3-12 RA 253 MA RA330 . Exposed For 3000 Hours Cycled Every 160 Hours 350 333 324 1800F 2000F 2100F 2200F 2250F 300 295 2) 250 232 Weight Gain (mg/cm 200 150 143 145 153 156 138 100 83 58 61 50 36 21 4 11 4 18 34 21 12 11 18 49 50 32 0 RA800H RA625 RA600 RA X RA 353 MA RA333 RA601 RA 602 CA Alloys 3-13 . that they may be powdered fine: mingle well one part of this with as much common Salt. But I shall teach you to temper them excellently G. or low pressure. Pack hardening is uncommon today. was then dumped into water to quench it. These fixtures are made of carburization resistant alloys. This carrier gas is subsequently enriched by a small. forms on or just beneath the surface. C2H2 or cyclohexane. 20. This atmosphere has traditionally been “endothermic”. silicon.CARBURIZATION The temper of Iron for Files It must be made of the best Steel. Sources for the History of the Science of Steel 1532—1786. low carbon steel parts are heated in a prepared furnace atmosphere that provides the carbon that diffuses into the surface layers of the steel. with propylene or other hydrocarbon injected to provide the necessary carbon. B. The surface became very hard. for the Salt will melt with any moisture of the place or Air. 3-14 .7% hydrogen and 0. that the smoak of the powder may not breath out. it is still oxidizing to chromium. some mixture of Cr2O3. charcoal and all.8% nitrogen. Ed. controlled addition of a hydrocarbon gas. make your iron like to a file: then cut it checquerwise. that they may be covered all over: then put on the cover. Temperatures are usually around 1750°F (950°C). and excellently tempered. then raising the temperature of the pack to red heat for several hours. take the chest out from the coals with Iron pinchers. and beat them together. In vacuum. except in a few custom made sporting arms. which is the source of carbon.8% methane. 38. Typical composition1 of an endothermic gas (Class 302) is 39. Even though the atmosphere is reducing to iron. beaten Glas. with a dew point –5°F (–20°C). The end result is that low carbon steel parts acquire a high carbon steel surface. The entire pack. with a sharp edged tool: having made the Iron tender and soft. For perhaps three thousand years it was performed by packing the low carbon wrought iron parts in charcoal. many heat treat cycles. SiO2 and Al2O3. This oxide layer is what provides most of the alloy’s resistance to carburization. 1589. The powder being prepared. When the steel is quenched it combines the hardness and wear resistance of this high carbon steel “case” with the toughness of the low carbon steel interior (core).7% carbon monoxide. radiant tubes and other fixturing in the furnace also pick up carbon through many. Now. using a catalyst to partially burn natural gas. 100% nitrogen. Della Porta. carburizing acetylene. or an easily vaporized liquid. that it may be red-hot about an hour: when you think the powder to be burnt and consumed. This is the usual temper for files. Cyril Stanley Smith Carburizing is one of the most commonly performed steel heat treatments. and put them into it. An oxide scale. and plunge the files into very cold water. and lute well the chinks with clay and straw. and so they will become extremely hard. is used as the source of carbon. for we fear not if the files should be wrested by cold waters. and then lay a heap of burning coals all over it. and put them into an Oven to dry. and crossways. may also be used as a carrier gas. such as propane. and aluminum. from bulk tanks. and fit other iron as it should be: Take Ox hoofs. as I said. and lay them up for your use in a wooden Vessel hanging in the Smoak. The alloy bar frame baskets2. C6H12. strewing on the powders by course. and Chimney-soot. that it may polish. then make an Iron chest to lay up your files in. while the interior or “core” of the part retained the toughness of low carbon steel. This. RA330 usually does the best job for the money. 2. enough ductility may remain while at red heat for the metal to perform its task. Alloy 601 used in a powdered iron sintering muffle. Grain growth is from the operating temperature. RA 353 MA. 3-15 . RA600. Brittle fracture at room temperature comes from the large amount of carbon. so that they can neither be straightened nor weld repaired. In vacuum carburizing there is too little oxygen present to form chromium or silicon oxides for protection. and more importantly. Generally speaking. carbon enters the atmosphere from the organic compounds used as binders in the “green” powder compact. RA333. along with the nickel content. We once examined a sample of 310 sheet which contained 4% carbon.34%. because it is invariably coarse grained. or impacted at room temperature.Carburization. Nickel lowers the solubility of carbon in the alloy. once an alloy has absorbed about 1% carbon it will no longer have measurable room temperature ductility. continued Carburization embrittles high temperature alloys. Among the alloys. With carburized alloy. The degree of embrittlement depends upon the amount of carbon absorbed3. absorbed during service. 800H does not well tolerate the effects of carburization. Carburization resistance in an alloy is conferred almost entirely by the protective oxide scale4. so that a very high nickel grade simply will not carburize to the same level as will a lower nickel material. which will form alumina in this process. The nitrogen-hydrogen atmosphere is not supposed to be carburizing. in part because it lacks silicon but also. Such carburization resistance as an alloy has may come largely from its aluminum content. and upon the microstructure. The oxide scale is primarily chromia. Nevertheless. and could readily be broken by hand. with silicon being a very potent assist5. so long as it is not excessively strained at high temperature. RA601 and RA 602 CA are all more carburization resistant but also more expensive. then. as nitrogen the atmosphere reacts with alloying elements such as chromium. becomes a handy tool to judge whether or not alloy fixturing has enough ductility remaining to be weld repaired or straightened. Finally. The common stainlesses 304 and 316L do not possess adequate resistance to carburization for use as fixturing in commercial carburizing heat treat furnaces. In addition it would be a good idea to include thermal cycles about like the expected service conditions6. There have been laboratory carburization tests run in an atmosphere of hydrogen—2% methane. such as cracks in weld joints or surface defects on castings. which are free of surface defects. On high fire this soot burns out. Such an atmosphere is one way to achieve the objective of actually carburizing most alloys. It literally pries open lack of fusion in the weld or opens small pin-holes in castings into large cavities. One may also wish to consider nitrogen. but a purely mechanical problem that may occur in a carburizing atmosphere is of some concern. for example. in order to form a similar protective scale7. but RA 253 MA is not resistant to carburization. The growth of this soot deposit acts like tree roots growing in rock. duration of the test is important. Very small amounts of oxygen can form enough alumina or titania scale. with no control of oxygen partial pressure. and the alumina scale in some alloys. the silica subscale. Carburization resistance depends upon the chromia scale. to inhibit braze flow in many vacuum furnaces. A pocket magnet. 3-16 . it happens that many also become magnetic. Carburization testing Laboratory carburization testing must be carried out in some approximation of the industrial atmosphere of interest.Carburization. Soot may deposit from the atmosphere and “coke” in any crevices. In the case of wrought alloys. Alloy 800H contains enough titanium to turn light gray in aome vacuum heat treat furnaces. contain an oxygen partial pressure comparable to the expected service atmosphere. continued RA 253 MA has worked as furnace fixturing because it is strong. Not due to carburization. The ferritic grade 446 is quite poor in carburization resistance. The test temperature should be similar to that anticipated in service. In this environment the alloy will not develop much of a protective scale. This is one reason why full penetration welds of the return bend to straight leg are essential for maximum life in radiant tubes. For this reason the test atmosphere should. and may affect carburization. When nickel heat resisting alloys become carburized. On low fire soot may deposited in the root crevice (as well as in surface defects of cast return bends). in our opinion. we emphasize the need to have designs and weldments that do not provide crevices in which carbon deposition may occur. locally overheating and weakening the metal. Even RA309 has somewhat better carburization resistance than does RA 253 MA. 5 2. weight %.14mm) depth on the element and 0. Dr.14a 2. Carbon Content.08 a Final 0. if nothing else.73 Increase 0. 1900°F (1038°C) are from a composite electric heating element made of the five alloys shown. whether based on weight change or on measured depth of carburization.23—0.008 0.0-1.17 0.508mm) depth on the plate sample. Oxygen partial pressure was not indicated. Various depth of cuts were machined in the samples and the carbon contents analyzed. Such films may affect carburization. 3-17 . Alumina and titania will not be dissociated by this atmosphere. ranks several alloys in the same order as does service experience. continued In order to braze even stainless steel (with no Al or Ti) in hydrogen it is normally considered that the dew point should be –60°F (–51°C) or lower8.2%C relative to iron.042 0.2 0. The tests were conducted in an electrically heated industrial carburizing furnace.20” (0. Before and After Testing Alloy 214 RA 602 CA 803 800H 310 Original 0. There is some period of time during which significant carbon absorption does not take place. in H2-CH4. from best to worst is: Haynes® 214.36 0. before their results correlated with service experience.05 range of five specimens When the atmosphere does simulate that of industrial interest. In vacuum carburizing very small amounts of oxygen are present from the furnace leak rate. shared with us.082 0. and 310 stainless. Incoloy® 803. is below. Al and Ti are is the elements most likely to form a scale in this test.3 0. Alloy ranking is approximately in accordance with their aluminum + titanium contents. and 10% of the time reflected air burnout cycles at 100°F (56°C) reduced temperature.19 0. Lai’s ranking of wrought alloys. In both cases the total exposure hours were distributed as follows: 20% of the time in endothermic gas enriched with natural gas to carbon potential 1. 70% of the hours in nitrogen.86—1. The ranking is the same.65 %Al 4.99 1. Recent work by George Lai11.045” (1.Carburization testing. carburization testing may require long exposure. Their test data. and the 1750°F (954°C) results are from plate samples exposed to the actual furnace operating temperature.084 0. This is necessary to dissociate the oxides of most alloying elements. Results here are reported at 0.4 0. N06025 and N0811 would form aluminum and titanium oxide films in a nominal hydrogen—methane atmosphere. One might expect that grades such as N06601. The higher temperature results. Experience related to us from one furnace company indicated that the test had to be run for at least 1000 hours.95 2.91 0. 800H. We might infer that these methane-hydrogen test results could have some relevance to performance of alloy fixturing in a vacuum carburizing furnace.50 0. RA 602 CA©. Some may be introduced through traces of acetone in the acetylene used as a carburizing gas. and will see two cycles per day on average. Baskets are stacked three high.6 1.92 Vacuum Carburizing Vacuum carburizing presents a different environment.56 -1750°F (954°C) 4300 hour exposure %carbon 0. there is always a small amount of oxygen in a vacuum carburizing furnace. 3-18 .096 -3. It is this oxide that is responsible for the alloy’s resistance to carburization in this environment. While not enough to form a stable chromia or silica scale.03 2. Behavior of alloys in conventional atmosphere carburizing do not necessarily predict how they will perform in low pressure carburizing. The leak rate in the furnace will always permit some oxygen to be present.344 0.443 1.98 1. the 2.86 2. Still.53 3. This captive shop processes transmission sprockets and gears at 1650°F (900°C) in Abar Ipsen furnaces with integral oil quench. The carburizing gas is acetylene. RA 602 CA alloy baskets designed for low pressure carburizing.Carburization testing.2% aluminum alloy RA 602 CA will form an alumina film on the surface. continued 1900°F (1038°C) 2260 hour exposure alloy RA333 RA330 617 601 600 310 %carbon 1. k. A bar may look just like a beaver had chewed away on it. RA 602 CA is being tested in several metal dusting environments. Alloys vary greatly in susceptibility to metal dusting. RA333. One direct alloy comparison. typically 800—1200°F (430—650°C) in heat treating furnaces. or “carbon rot”.METAL DUSTING A somewhat aggravating problem in carburizing atmospheres is “metal dusting”. 82 (ERNiCr-3) are the least resistant. In the petrochemical industry. To date it appears superior to RA330. and in some areas of Ipsen® furnace chains. while the 3/16” (4. though not quite so resistant as is RA333. This occurs at lower temperatures. but we do not yet know how it compares with RA333. the metal literally appears worm-eaten on the surface. but the effect is that the metal disappears. while 800H is markedly inferior. Sample from a rotary retort used to carburize small parts at an operating temperature of 1750°F (940°C). Metal dusting was a serious problem with flights at the entry end of the retort. the 3/8” (7.a. RA330 is average. atmosphere sampling tubes or electrical leads pass through furnace walls. Here the cold work pieces chilled the RA310 flights down into the metal dusting temperature range. shows two RA333 GMAW beads with minor smoothing. a. Neither 310 nor 601 will solve metal dusting problems. As the retort was externally fired. Such temperatures exist in a carburizing furnace (nominal 1750°F/950°C) where alloy tube hangers.9mm) 600 alloy shell was above the temperature range for metal dusting. below. a small amount of sulphur (40—50 ppm H2S) is sometimes added to the process gas stream to “poison” the high temperature chemical reaction that is metal dusting. “catastrophic carburization”. Spiral flights of RA310 welded to the inside transport work pieces through the retort. is the best known choice. In other cases. The high silicon grade RA85H (no longer produced) was also good. 3-19 . by four decades’ experience and several years testing in the heat treat industry. The exact mechanism may be disputed.8mm) RA310 plate between them suffered nearly complete loss of section9. Both 600 alloy and its matching weld filler. S. At furnace temperatures the mechanical strength of 5/8” RA333 is comparable to that of 3/4” dia. Failure by metal dusting. 3-20 . with somewhat higher strength and good metal dusting resistance. RA330 carburizing furnace anchor bolt. The longest lasting tube hangers to date are those made of 5/8” (16mm) dia RA333 rod. RA 602 CA. This is an application where RA333 has given the ® best service life in original equipment here in the U. while the metal dusting resistance of RA333 is greatly superior. RA330 gave better life than 600 alloy in this application. Nicrofer 6025HT (RA 602 CA) is being used in Europe. but is still not satisfactory. continued Furnace chain severely attacked by metal dusting.Metal Dusting. 3/4” (19 mm) diameter.A. may replace RA333 in this application. RA330. 3-21 . even the 4. in the metal dusting zone of a Surface Combustion carburizing furnace.472 hours Many pits.422 hours Preoxidizing treatments provided no benefits or were counter productive. operating temperature 1700°F (927°C). no pits at 8122 hours Black. The flights in this rotary carburizing retort were RA330.594 hours (3 years) at temperature. This a most direct performance comparison of RA333 with RA330 in carburizing service.594 hours Some pits at 16. as the pipe passes through the refractory. The atmosphere is endothermic enriched with 0. no pits at 7549 hours Pitted. continued The following test results are from a direct comparison of alloys for 25.7—0. Although surface treatment by aluminum diffusion coat is usually considered to provide resistance to metal dusting.5% nominal aluminum content of alloy 214. and remains even though the RA330 plate on each side has been destroyed.472 hours Pitted—removed from test at 11. did not appear effective. the first RA330 flight is completely corroded through. test stopped at 19. or at least the first set of them. test stopped at 19.264 hours Pitting started at 24.472 hours Many pits. The shell and balance of flights might continue as RA330.Metal Dusting. where the flights are cooled by incoming work pieces.8% methane to a 1. One might consider using RA333 plate for the flights. test stopped at 19.4mm) Sch 40 oxygen probes of various alloys with different surface treatments were inserted through the furnace roof. but they were GMAW welded using RA333 wire. Alloy RA333® RA85H® RA330® 214® HR-120M HR-160® Condition As received Preoxidized As received Preoxidized As received As received Preoxidized As received As received Results Dark. The RA333 weld bead is essentially unaffected. aluminum as an alloy addition. no pits at 27.183 hours Black.20% carbon potential. Metal dusting occurs in the region where temperatures are roughly 1100°F (600°C). in this particular application. Because of the high carbon potential in this furnace. Metal dusting is normally most severe at the entry end. 1” (25. continued Here RA330 plate is compared with alloy 82 (ERNiCr-3) weld filler. 3-22 . GMAW welding with RA333 wire would be appropriate.Metal Dusting. operating 1700°F (927°C) in a high carbon potential atmosphere. The weld bead in this corrugated retort has been selectively attacked. To prevent this. higher than for nitriding but lower than carburizing. and contents as high as 0. A lamellar phase near the grain boundaries was apparently a nitride phase. Patent 2. An absence of nitrides near the surface is probably due to chromium depletion from oxidation. An increase in nitrogen content may normally be expected to occur during high temperature service in air.g.47Si 0.26Ni 24. roughly 1300— 1650°F (705—900°C). Second. or a mixture of both. at top. e. shows some internal oxidation. RA310 or RA 253 MA are not suggested.03Mo 0. Temperatures are high enough to austenitize the steel workpieces. The first stage of the Floe process is done at 925-975°F (495525°C).15%. The life of alloy fixturing in a carbo-nitriding application cannot be expected to equal that in a straight carburizing environment. but the nitrogen content is rarely analyzed. done around 1100°F (600°C). Because of the reduced solubility. carbo-nitriding is carried out in an atmosphere containing both carbon and nitrogen.089N Nitrogen has been associated with blistering and severe reduction of creep-rupture strength in carburized HL (30Cr 20Ni) steam-methane reformer tubes10. due to embrittlement from sigma formation. This locally concentrated the nitrogen.462% were measured. Jessop Steel Co.18C 0. probably for two reasons. may be carried out in an RA600 retort. Commercial nitriding. The needles at 60° angles in this photomicrograph are chromium nitrides.249). Ferritic nitrocarburizing. . because the embrittling effect of carbon and nitrogen combined is more drastic. A higher temperature process. It was postulated that this could result in high nitrogen gas pressure. which the authors associated with microvoids and cracks. First. After exposure nitrogen reached 1. Mill certification.089%. At this temperature grades such as RA309. RA446 plate coupon exposed 3000 hours in air at 2100°F (1150°C). the second at 1025-1050°F (550-565°C). Carburization decreased nitrogen solubility in Ni-Cr-Fe alloys by removing chromium from the matrix. The surface.03Cu 0. That is. the Floe process (U. Heat 26445: 0. because the cycles are much shorter. The initial nitrogen level was 0.70Mn 0. nitrogen then diffused ahead of the advancing carburized front.437. with shorter cycle times than for carburizing.NITRIDING Nitrogen reduces alloy ductility in a manner similar to carbon. usually is done with RA600 alloy fixturing.S. A great deal of attention is given to carbon-pickup in alloys at high temperature. 304 stainless. with containers of RA330.84Cr 0. continued The hours or years of exposure are not the important things affecting an alloy’s (quenching fixture) life. R.3-23 Nitriding. Effects of Silicon Content and Oxidation Potential on the Carburization of Centrifugally Cast HK-40. Texas 1976 6. National Association of Corrosion Engineers. D. Metals Handbook® Ninth Edition. Ohio 1981 2. Schley and F. Brazing and Soldering. G. Low-Alloy Steels. Corrosion. Texas 1980 8. Rather it is the total number of cycles that determines life. D. Kane. Houston. January 1985. Thermal fatigue cracking gradually develops and grows with each cycle. J. Houston. ASM Handbook® Volume 6. Houston. Netherlands 1999 10. Houston. Welding. Carburization. Destructive Accumulation of Nitrogen in 30 Cr 20Ni Cast Furnace Tubes in Hydrocarbon Cracking Service at 1100C. H. A part in a carbonitriding environment will receive many more cycles in a given length of time than if it were in a carburizing application. Corrosion 86 Paper Number 377. Carburization of Cast Heat-Resistant Alloys. H. and Tool Steels. References. Proposed Standard Carburization Test Method. B. E. Houston Texas 7. K. Factors affecting carburization behavior of cast austenitic steels. Texas 1986 3. ASM International. National Association of Corrosion Engineers. Corrosion/77 Paper No. Houston. Corrosion/80 Paper Number 168. 1967 National Association of Corrosion Engineers. J. J. James Kelly. Texas 1977 4. Wenschof and J. D. Jones. Ohio 1993 9. R. Hall. Metals Park. Harris. W. September. Houston. National Association of Corrosion Engineers. National Association of Corrosion Engineers. Materials Performance. Texas 1983 5. National Association of Corrosion Engineers. Metal Dusting in the Heat Treating Industry. The Hague. Roach. M. Metals Park. and J. 7. Corrosion 2003 Paper No. Texas 11. National Association of Corrosion Engineers. R. Metal Dusting and Nitriding 1. and its life will be shortened accordingly. Evaluation of Heat Resistant Alloys in Composite Fixtures. A. Volume 4 Heat Treating. Brazing of Heat-Resistant Alloys. George Lai. Corrosion/83 Paper Number 266. R. Rundell. Texas 2003 . ASM. Bennett. Hossain. Furnace Atmospheres. 3473. 9. Stainless Steel World 99 Comference. Carburization of Cast Heat-Resisting Alloys in Synthetic Petrochemical Environments. The Influence of Carburization on the Mechanical Properties of Wrought Nickel Alloys. Kane. Corrosion/76 Paper No. Houston. rather than a chromium sulfide. If sulfur is a problem. This 1/4” (6. operating temperature 1840°F (1004°C). If the deposit contains sulfur. in contact with the metal the actual amount of oxygen available to form a scale is miniscule. in spite of other disadvantages it has. An oxidizing environment is one in which sulfur is present as sulfur dioxide (SO2). carbon monoxide (CO). For example. some rather long. there may be solid deposits on metal in an oxidizing environment. and there is some excess oxygen (O2). Under reducing environments the alloy forms chromium sulfide. which is non-protective. After about a year the RA 253 MA kiln shell had developed holes roughly 3/4” (20mm) across. Under the most severe conditions an alloy completely free of nickel. The atmosphere was air. The higher the nickel the more sensitive the alloy is to sulfidation attack. Sometimes the distinction isn’t obvious. and lasted 2 to 2 1/2 years. environments. or even carbon dioxide (CO2) and/or water vapor (H2O). such as RA446 may be required. RA310. From Rolled Alloys Report Number 94-72 3-25 . at 13% nickel. plus the SO2 and SO3 driven off in the process. we do not suggest using any alloy with more than 20% nickel. and rather little CO2 or H2O. When the environment is oxidizing the alloy is more likely to form a protective chromium oxide scale.3-24 SULFIDATION Environments containing sulfur may rapidly attack high nickel alloys. Underneath those deposits. may be preferred for some applications. An example of under deposit attack is shown below. then the metal may be heavily attacked under the deposit. or low oxygen. regardless of oxygen is in the atmosphere above it. The problem is more severe under reducing. is useful in many sulfur bearing environments. In reducing environments sulfur is in the form of hydrogen sulfide (H2S). Previously used RA310 had failed by more uniform thinning. with 25% chromium and 20% nickel. methane (CH4) or other sources of carbon. RA309. It has been stated that oxygen partial pressures may be about 10-8 under calcium sulfate deposits on fluidized bed components. there may be hydrogen (H2).35mm) RA 253 MA plate sample came from a kiln processing ferrous sulfate monohydrate to red iron oxide pigment. or the sulfur is too high. . K. there exists a threshold value for oxygen partial pressure beyond which a continuous protective oxide scale is developed on the specimens. represented by the kinetic boundaries in the figure.” In our opinion. is ~10 times the oxygen partial pressure for he Cr oxide/Cr sulfide equilibrium. The meaning of these diagrams is simply that if not enough oxygen is present. Natesan of Argonne has done. continued Types of Scale Developed on Type 310 Stainless Steel as a Function of Oxygen and Sulfur Partial Pressures in the Gas Environment at Temperatures of 750. Conversion factor: 1 atm = 0. This threshold 3 oxygen partial pressure. No. Dr.101356 MPa. 875. the sulfide offers little resistance to further attack. 306-79-625 These diagrams illustrate whether oxides or sulfides are formed at equilibrium. and 1000C. the alloy will form a chromium sulfide rather than an oxide. and continues to do. “For a given sulfur partial pressure. the best high temperature corrosion work of our time. ANL 1 Neg.Sulfidation. While the oxide may be protective. In general. The most comprehensive study of heat resistant alloy sulfidation was carried out in the late 1970’s through early 1980’s under the direction of the Metals Properties Council. from the 1987 Final Report. If sufficient molten metal sulfide forms underneath the chromium oxide scale.9 20.2 25. where corrosion rates accelerate dramatically.6 20. continued Nickel reacts chemically with sulfur very readily.0 vol% H2S Met.0 30.9 30.0 22. 1000 hour Alloy 671 657 HL-40A Co-Cr-W No. We present Table 8 from that report. are often molten at operating temperature.5 vol% H2S Cr Met. 1 T63WCB 6B HK-40A 30/50WB RA333 Crutemp 25 310 310 (Al) 446 309 188 556 617B Alloy X 21. Unlike metal oxides. corrosion enters a “break-away” mode2.6 <5 >10 >10 >10 4 >10 10 >10 5 >10 8 >10 6 >10 7 >10 1 >10 6 >5 .9 26.0 24. Grav.3-26 Sulfidation. >10 >10 >10 >10 >10 >10 7 >10 2 >8 ->10 2 -<1 -3 ->10 -10 >10 >10 >10 >10 8 >10 5 >10 2 6 ->10 c -1 -4 -9 ->10 >10 >10 >10 >10 >10 >10 >10 ->10 >10 <10 >10 >10 3 5 >10 10 >10 >10 >10 >10 >10 >10 >10 >10 ->10 >10 3 >10 >10 2 >10 >10 >10 >10 >10 >10 2 >9 4 >10 1 -7 3 10 >10 -<1 3 1 <1 >10 1 1 32X N-155 800H 800H (Al) 21.0 27. the corrosion rate in sulfidation may be more or less parabolic for some period of time. Grav. Grav.1 28. >10 >10 3 >9 2 >10 2 ->8 >10 10 10 -<1 3 1 1 10 1800°F— 0. which at least are solid. the significant measure of sulfidation resistance.0 22. This is. 50.0 vol% H2S Met. or metal-metal sulfide eutectics.0 22.4 25.0 >10 1650°F— 1. time to breakaway corrosion. it may literally wash that scale away. >10 >10 >10 >10 >10 >10 1 -5 >10 1 >10 >4 3 10 ->8 >10 >10 >10 >10 >10 >10 1 -4 >10 <1 >10 1 4 >10 ->8 1 >10 ->5 1800°F— 1. Eventually.2 48. Some of their results.5 vol% H2S Met.6 20.9 >10 1650°F— Wt % 0. are included here. in our view.0 25. Useful corrosion testing for sulfidation resistance requires very long time exposure.0 23. ESTIMATED TIME TO BREAKAWAY CORROSION FOR VARIOUS ALLOYS Based on Metallographic Measurements and Gravimetric Analysis in 1000 psig Tests Estimated Time.0 28.2 28. metal sulfides. Grav. 40 Co-Cr-W No.3-27 Sulfidation.90 20.45Mn 0.60 32.00 9. RA333.8 -3.35 30.10 Fe 1.10 --2.00 21.68 0.50 -----37.00 20.71Mn 1. sulfidized beneath carbon deposits.72Cu Nominal chemistry only (Al) means the sample was aluminum diffusion coated.80 A HK-40 J94204 28.80 310 S31008 25.44 1.30Al 0.72Cu 0. continued Alloys Tested Alloy Name UNS Cr Ni 671 R20500 50.06 -0.00 57.80 A IN-657 R20501 48.09 3. is necessary for any degree of sulfidation resistance.06Mn 0.00 20.06 -0.40 0.00 50.33Ti 1.00 46.5Cb 0.10 -0.51 3.50 -- -0.00 22.08 46.00 20.00 0.69Mn 0.00 -- -0.20 45.70 ® RA333 N06333 26.39 0.00 0.50 1.00 0.05 0. This test data gives an indication of how much sulfur heat resistant alloys might tolerate at what temperature in a mildly reducing atmosphere.50 -1.20 0.94Mn 0.00 W ---12.02La 1.10 -13.68 0.00 ® Crutemp 25 -25.52 1.60 0.37Al 0.20 52.00 20.80 1.0 5.13 A Other 0.00 ® Wiscalloy 30/50W -27.23 0.40 -1.5 2.40Al 0.38Ti 0.00 12.38Ti 0. .10 17.13 800H (Al) N08810 20.50 15.10 0.00 19.40 0.10 0.00 -- -- -- 0. Multimet® 800H ® ® A N06617 N06002 -R30155 N08810 22.07 0.38 0.50Mn 1.10 -3.50Mn 1.1Cb+Ta 0.40 24.50 1.40Mn 2. In the pilot plant exposure part of this test series.60 0. chosen for an oil sands pilot project on the basis of early good results.60 20.90 48.40 0.09 0.00 ® Stellite 6B R30106 28.11 0.80 30.96 20.22Al 0.90 556 A Co ---55.1Cb+Ta 0.1 2.50 47.00 HL-40 J94614 30.71Mn 0. It does not indicate how materials might perform under deposits. The reaction vessels were aluminum diffusion coated 310.10 0.11 0.0 0.37Al 0.60Mn -0. What it says about alloys is that high chromium.7 -----14.00Mn 0.47 --2.40 309 S309008 23.50 2.08 -19. 1 R30001 30.01 1.20 446 S44600 24.90 19.35 54.40 0.10 2.90 47.6 2. burned out after every 1000 hour run.50 2.20 29.50 40.20 36.42 15.90 21.50 -19.00 14.60 62.60 0.40 0.10Mn 1.65Mn 0.72 29.18 R30556 22.00 44.07La 1.50Mn 1.23 0.20 310 (Al) S31008 25.87Mn 1. alloy 671 sulfidized badly beneath calcium sulfate deposits.21Al 0.20 52.94Mn 0.8 -- 8.06 ---0.00 0.24Ti 1.00 617 Alloy X Sanicro 32X N-155 .5 3.10 -47.30Mn 1.54Mn 0.07 -0.20 74.70 ® Haynes 188 R30188 22.0 4.00Al 0.0 -® Thermalloy 63WC -28. at least 25%.40 0.20 47.5 Alloy Compositions Mo Si C -0.78 1. Binary Alloy Phase Diagrams. 1986. Inc. continued The test atmosphere supplied to the reactor for CGA (coal gasification atmosphere) was borderline oxidizing-reducing. Gas Corrosion of Metals. 600. Specifically. where a source of carbon. Thaddeus B.A. CRC Press Inc. High-Temperature Corrosion in Coal Gasification Systems. 65th Edition. That is.5. CrS-Cr2S3 doesn’t melt until 2462°F (1350°C)5. Massalski. 800H. such as methane (CH4) is present along with the hydrogen sulfide Even 1/2% of H2S can be quite destructive. RA333. Stanislaw Mrowec. Low-grade oil is heated with very little oxygen to break it down into soot—which is carbon— or lamp black. FL 1984— 1985 . CORROSION AND MECHANICAL BEHAVIOR OF MATERIALS FOR COAL GASIFICATION APPLICATIONS. 1980 2. 3. The Fe0-FeS eutectic melts at 940C4 . H. 0. alloys X..S. Maurice A. Melting points of some metal-metal sulfide eutectics are3 : 1175°F (635°C) for Ni-Ni3S2. K.1 Balance Gas CO2 CO H2 CH4 HN3 H2 S H2 O Many sulfidation failures occur under highly reducing conditions. Final Report (1 October 1972-31 December 1985) as subcontractor to The Materials Properties Council. Boca Raton. Handbook of Chemistry and Physics. 617 and some of the high cobalt alloys may fail by sulfidation. Ohio 4. ANL-80-5. 1611°F (877°C) for Co-Co4S3 and 1810°F (988°C) for Fe-FeS. One example is in carbon black manufacture. Poland 1978 5. Metals Park. or 0.0. Argonne National Laboratory. Technical and Economic Information. 601..3-28 Sulfidation. RA330. American Society for Metals. Illinois U. translation published by the Foreign Scientific Publications Department of the National Center for Scientific. Howes. Editor. Argonne. from Table A-1 shown below: Inlet Gas Atmosphere for Initial Tests vol% 12 18 24 5 1 1. Teodor Werber. References 1. New York. New York. Warsaw. The oil used as feed-stock normally contains up to 3 percent sulfur. Natesan. High nickel alloys are quite unsuited for high temperature service in the sulfidizing environments of carbon black plants. metal halides are volatile. Corrosion in dry Chlorine Gas Metal Approximate temp. 50°C.3-29 HALOGEN GAS HOT CORROSION Unlike oxides. is exceeded in short time tests in dry Cl2 Corrosion in Dry Chlorine. about 75°C. just slightly lower for CoCl2. the high nickel alloys 600 (UNS N06600) and 400 (N04400) are most commonly chosen for hot halogen gas resistance. For FeCl3 the limit is much lower. As a practical matter. For CrCl3 and NiCl2 that would be about 600°C. and AlCl3. When halogens are present in high temperature environments any oxide scale present becomes porous and non-protective. In order to form a protective scale it is generally considered that the metal chloride vapor pressure must be below 10-4 atmosphere. and CEB-5 for HF and F2. 100% 30 Nickel alloy 600 alloy 400 316 304 Platinum CopperA SteelB Gold Silver A B Suggested upper temp limit for continuous service. °F. °F 60 1000 1000 850 650 600 950 450 350 300 150 120 1100 1050 900 750 650 1000 500 400 350 250 600 1200 1200 1000 850 750 1050 500 450 400 450 1200 1250 1250 1000 900 850 1050 550 450 400 500 1000 1000 800 650 600 500 400 400 --- 950 950 750 600 550 900 350 250 250 100 copper metal ignites in hot Cl2 at about 600°F carbon steel ignites in hot Cl2 at about 450-500°F . mils/year. and lower yet for MoCl5. at which given corrosion rate. about 160°C. and for HCl follow. Data for 100% Cl2. Good discussions of this subject are given in the old INCO® Corrosion Engineering Bulletins CEB-3 for HCl and Cl2. 3-30 Corrosion in Dry Hydrogen Chloride. Auld. mils/year is exceeded in short time tests in dry HCl Corrosion rate. The data were obtained from short-time laboratory tests and offer only a rough guide to maximum practical temperature limit of materials. Chemistry. 600 with finer grains. W. Grain size has an effect. No. & Eng. At 2%Cl2. °F Both of these tables were abstracted from INCO Bulletin CEB-3. °F. 7 pp 839-844 At lower halogen concentrations alloys forming a chromia layer can tolerate higher temperatures. Brown. M. 125µm (ASTM 3). “Corrosion by Chlorine and by Hydrogen Chloride at High Temperatures”. mil/year.5). Paper 00239 Corrosion 2000. same temperature. . 75µm (ASTM 4. 100 hour test. The original data from which INCO developed their table was published in 1947. Ind. Fine grain size increases diffusion rate of chromium to the surface. Vol 39. in dry HCl 30 Nickel alloy 600 alloy 400 316 304 Platinum Copper Steel Gold Silver 850 800 450 700 650 2300 200 500 1800 450 60 950 900 500 700 750 -300 600 -550 120 1050 1000 650 900 850 -400 750 -650 600 1250 1250 900 1100 1100 -600 1050 -850 1200 1300 1350 1050 1200 1200 -700 1150 --950 900 450 800 750 2200 200 500 1600 450 Suggested upper temp limit for continuous service.R.1%Cl2. show that alloy 600 can form a protective oxide at 800°C in 0. DeLong and J. the alloy does not develop a protective scale.B. being superior to 600 with coarser grain size. 100% Metal Approximate temperature.H. at which given corrosion rate. Data in Bender and Schütze. 9 1.3 0.84 797 425 115 2.7 0.1 6.0 0.7 1.3 0.8 11.7 0.3 7. hours 5 24 24* 120 5 24 24* 120 5 24 120 5 5 27 204 370 Corrosion Rate.38 1112 600 24 0.3-31 Longer time tests show lower corrosion rates.0 0.2 1. Most of that data is reproduced below.6 0 2.2 1022 550 12 0.5 25. CEB-5.18 662 350 9 0.23 707 375 15.8 ----3451 80 400 700 1000 200 nickel 304 304L 347 600 All tests were made in flowing fluorine gas.4 4.1 3. type 304/321 stainless. mils per year 2.2 1.39 752 400 33 0.9 100% Chlorine Gas.1 0. Corrosion by dry fluorine gas °F Temperature °C Material 400 Exposure time.0 538 29.1 44.3 21.7 1.2 Corrosion of nickel alloys by hot 100% F2 gas is given in Table 14. 30 day test Temp mils/yr mm/yr F C 572 300 6 0.4 1. 100% Chlorine Gas.5 0.61 1157 625 47 1. except * which were conducted in bombs at initial pressure of 250 psi.15 617 325 7 0.9 -0 1.5 16.1 7.5 0.4 1565 6018 -4248 78. 3-32 .2 0.5 0.6 1.5 0. alloy 600.2 24.5 13.7 2.5 -0.5 0.4 0. 30 day test Temp mils/yr mm/yr F C 977 525 8 0.3 1067 575 15 0. The following industrial data were obtained from 30 day test exposures. General Chemical Division. showed some corrosion from sulphur and phosphorous as well. Allied Chemical Company.05 0. where alloy 617 weld filler was inferior to alloy 600. In atmospheres containing a significant partial pressure of oxygen these laboratory data in pure halogens or halide gases have limited utility as the basis for alloy selection. RA333 has shown good resistance to hot corrosion by the fluoride flux used in aluminum salt bath brazing environments. August 2002.41 0. or possibly RA 602 CA®.2 0. INCO CEB-5 Material Hastelloy® alloy C Inconel® alloy 600 Hastelloy alloy B Nickel 200 Nickel 201 Monel® alloy 400 Monel alloy K-500 70-30 Copper-Nickel Corrosion Rate mils/year mm/yr 0. Examination of the 600 alloy part. it is not clear to us whether it is the better oxidation resistance of the higher chromium alloys. At this writing. that is responsible.02 0.3 0.The original source of this fluorine data was: R.41 Comments iridescent tarnish film “ black film “ “ adherent dark film “ “ Hastelloy is a registered trademark of Haynes International Inconel and Monel are registered trademarks of Special Metals. Alloy 59 (N06059) has performed satisfactorily in an oxidizing atmosphere with HF. Test duration 36 hours. removed from service after many years life. Inc. The heat resistant alloy X (UNS N06002) has outperformed alloy 600 in oxidizing gases containing HCl.36 0. If the customer intends to perform tests in his environment. or some molybdenum effect.” Contract AF 04 (611)-3389 Corrosion Tests in Hydrogen Fluoride Gas Temperature: 930 to 1110F (500 to 600C).33 0.B. we would suggest including a heat resistant alloy such as the 3%Mo alloy RA333® (N06333). “Corrosion of Metals and Alloys by Fluorine. From Table 17.008 0.7 2 9 14 13 16 16 0. Jackson. 3-33 . 2. but instead corrosion products are largely removed by solution of alloying metals as ions in the pre-salt network . The concentration gradient of chromium ions in the salt phase forces chromium diffusion out to the bulk salt where the higher effective oxygen pressure forms Cr2O3 and some chromate ion. granular and thus nonprotective oxides.18 0.chromium diffuses down grain boundaries of the grain network to be deposited at grain boundarypore intersections as chromium ions. Eventually most of the chromium may be removed from the alloy. readily oxidizable alloy components.35 inch 0. Vol. They saw 210 to 252 cycles in preheat salts 700°C (1290°F) and 815°C (1500°F). This loss of alloy constituents causes a counter current flow of vacancies which condense into an interconnecting pore network filled with salt. high heat salt 1200°C (2200°F). .0075 0. RA 253 MA.0069 0.8 1. Oxidation of Ni-20Cr Alloy and Stainless Steels in the Presence of Chlorides. which is non-protective and water soluble. migrate to the surface to form non-adherent. Seybolt. Preheat and high heat salts were mixtures of potassium.MOLTEN SALT CORROSION When Ni-20Cr alloys and stainless steels are oxidized while submerged in molten salt (NaCl or NaCl-KCl). such as 600. Since the salt penetrates into the structure. Corrosion in Molten Chloride Heat Treat Salts. 13-16. are preferred.11 0. weight % RA85H 15 RA 253 MA 11 RA600 76 RA309 13 RA330 35 Silicon.0125 0. more chromium diffusing to the surface reforms the scale. 1970 Hot chloride salts. 2. air cool. 1100-2200°F (600-1200°C) Depth of Intergranular Attack Grade Nickel.2 mm 0. weight % 3. and particularly salt fumes mixed with air. the loss of alloying metals does not require intermetallic diffusion over long distances. The alkali metals in the salt turn the protective chromium oxide scale into an alkali chromate. quench in 600°C (1100°F) nitrate/nitrite salt. In general the higher nickel alloys. U. As fast as the scale is removed.7% silicon grade.19 0. leaving primarily iron and nickel. such as chromium. although we have seen tolerable results from the 1. A more detailed account of hot salt corrosion mechanisms is given under Neutral Salt Pots. are very corrosive to heat resistant alloys.5 1. and in some cases iron.0044 0. No.0138 Plate samples were exposed in a commercial heat treat salt line. 3-34 . Oxidation of Metals. sodium and barium chlorides.2 0. .7 0. A.32 0. A.5Ni) is said to be reasonable. RA330. while HE (28Cr 9. to be unsuitable for aluminum salt bath brazing operations. RA 253 MA and RA310 have all been used or are on trial. Molten fluorides are used to flux metals and alloys for brazing operations. 500 parts per million) of vanadium is “high” enough to be destructive. Along with fluxing the oxide film on the workpiece. Frankly. we might suggest RA333 or RA 253 MA as worth trying.05% (or. RA446. days 197 (end of test—no failure) 112 51 40 14 Other work has shown the 25% chromium ferritic grade. fluorides also attack the chromium oxide film on heat resistant alloy fixturing. When this oil is burned. Venezuelan oil is particularly high in vanadium and is often used in the Northeastern U. while only 0.S. A service trial of various alloy fixtures used in aluminum salt bath brazing at 1125°F (607°C) gave the following results: Alloy RA333 600 Nickel 200 C-276 601 Total Life. we have no good comparative field data for these wrought alloys. along with sodium sulfate. V2O5. A high level of sulphur in the oil might be 2 or 3%. 3-35 . This vanadium pentoxide. continued Fluoride salts are more aggressive than are chloride salts. The alloys with good resistance to fuel ash corrosion are usually cast compositions that are both weak and brittle. and HE is particularly weak and brittle. It will eat away most heat resistant alloys in less than a year. RA625. RA333. but they definitely will not be as good as 50%Cr-50%Ni cast. makes a molten compound which is aggressively corrosive. the vanadium forms vanadium pentoxide. Mostly based on rumor. Vanadium Pentoxide Equipment fired with residual fuel oil suffers corrosion wherever the fuel ash deposits on hot metal. Heavy oils such as No.Molten Salt Corrosion. IN-657 is expensive and readily embrittled. 50Cr-50Ni cast IN-657 (UNS R20501) is the best. 6 or “Bunker C” may contain both sulphur and vanadium. Available wrought alloys are not at all as resistant to fuel ash corrosion but are used for their much better ductility. It had been welded with the 72% nickel 19% chromium 2. likewise for the cobalt alloys. or even the ferritic stainlesses. General Nickel—with respect to nickel-chromium-iron or nickel-chromium alloys. That it has been successful at all is due entirely to the tenacious oxide film on the titanium. ERNiCr-3. which at 2% Mo seems to work better than does 304. Dissimilar Metals—must not be used in contact with molten metals. 3-36 . Depending upon which metals are involved. It failed when the weld bead separated from the base metal. balance Fe) has been used for stoppers in bottom pour aluminum ladles. 6. One example known to us was a lead pot fabricated of heavy RA330 alloy plate. Aluminum—molten aluminum dissolves any Fe. has performed better than 316L at 1000°F (538°C) in 26% aluminum. AL-6XN® alloy. Alloy C-276. As a ROUGH rule of thumb. Analysis of the weld bead showed that it was now a lead alloy. in contact with molten zinc for galvanizing or die casting operations. 7% lead. or may crack. the temperature and the state of stress. Titanium tubing has been used to siphon molten aluminum. the higher the nickel content. and how much molten metal is present. are preferred. Nevertheless. depending upon the stress level.3% Mo. depending upon how long it takes the aluminum to reduce and/or wash away the hot rolling scale from the bar. Wherever molten aluminum splashes on the RA330 it goes right through it like hot water through snow. bar of alloys such as RA446 (25% Cr. the more rapidly the solid metal dissolves in the molten. such as RA600 (76%Ni) tend to be attacked more severely. Life is erratic. 15% Mo. One example is 316L. has been used in continuous zinc galvanizing at about 850°F (454°C). Fe-Cr. Ni-Cr-Fe or Ni-Cr alloy.2%Si balance Fe) 11 gage/3mm wall cooling tubes have been used in an aluminum melting furnace. a molybdenum addition appears to benefit austenitic stainless or nickel alloys. The same molten metal may either dissolve or crack2 the heat resisting alloy. A phenomenum known as mass transfer1 may dissolve the higher nickel alloy preferentially. with about 5% columbium (niobium) and traces of chromium and nickel. Embrittlement—liquid metal embrittlement may occur just below the melting point of the low melting metal. where contact with low melting metals is concerned the lower nickel alloys. right above the metal. 67% zinc. the heat resistant alloy. Molybdenum—in resisting corrosion by molten zinc alloys. High nickel alloys. RA330 (35%Ni 19%Cr 1. that molten metal may dissolve.MOLTEN METALS From time to time one or another heat resistant alloy is used in contact with a low melting point metal in its molten state.7% columbium (niobium) weld filler 82. one American file manufacturer switched from molten lead to bismuth in its 1450°F (788°C) austenitizing baths. When maintained at 1450°F (788°C) no problems have been reported to us. and molten calcium condenses on the retort wall. Volume 10. An induction coil fits through the loops and heats the bismuth. continued Antimony—we have no definite experience. Metals Handbook (ASM). The metallic calcium vapors haven’t been a problem. This is done at high temperature under a hydrogen atmosphere. When too much heat is applied. RA330 fracture surface. RA446. All of the austenitic alloys will fail rapidly in contact with molten copper or copper alloys. 430 stainless (16. Skimmers for removing slag from ladles of molten brass or copper are mild steel. There are indications that lead baths which have been contaminated by antimony. more likely. These pots have two loops of 2” Sch 40 RA330 pipe welded to the bottom. can have the austenite grain boundaries neatly outlined by copper metal. Siphons for handling molten copper have been 446 seamless tubing. are corrosive to Ni-Cr-Fe alloys.25%C) weld filler. However cadmium is said to embrittle steel at temperatures as low as 450°F (232°C). Launders for handling molten copper are successfully made of the high chromium ferritic alloy RA446 (25%Cr. and presumably higher nickel alloys as well. Bismuth—To satisfy OSHA. 8th Edition. 3-37 . Cadmium—We have no experience with the effects of Cd on austenitic alloys. Calcium carbonate has been used as part of the mix. page 60. the loops are attacked. pots are fabricated of RA330 plate welded with RA330-04 (35%Ni 19%Cr %Si 5%Mn 0. austenitized by immersion in molten copper. now bismuth. from using scrap lead. That figure illustrates 2024-T4 aluminum cracked by mercury. nickel-chromium-iron or nickel-chromium alloy.5%Cr. About 6X This fracture surface is very similar in appearance to Figure 12.Molten Metals. balance Fe) and. The lead. Down toward the retort base it is cooler. The retort cracks at this location. for the electronics industry. which is about 160°F (90°C) below its melting point3. balance Fe). Calcium—molten calcium can crack RA330. calcium LME. The hydrogen reduces it to calcium metal. Copper—molten copper and copper base alloys penetrate the grain boundaries of any austenitic iron. The example here is from an RA330 retorts used to process ferrites. Even carbon steel. Life is measured in days. Hydrogen then escapes through the hole and burns like a torch. Eventually some copper braze spills onto the bottom of the muffle. was used to process mining tool bits at 2000°F in air.5% Si grade is no longer available. With an exothermic brazing atmosphere the Ni-Cr-Fe alloy (usually RA330) muffle develops a scale which may be protective enough to prevent small amounts of copper from actually wetting the muffle floor. Haynes® International have made this alloy under their own trade name HS 150. the surrounding area. balance copper. One would expect some amount of zinc to be removed by oxidation in air at this temperature. and sometimes melting. locally overheating. With enough copper the scale may be penetrated and the muffle attacked. bear in mind that all austenitic alloys will eventually fail from molten copper attack. with the appearance of cast bars. continued The old Belgian alloy UMCo-50. was said to function well in contact with molten copper. We have seen some 15 pounds of copper. This 15% Ni 3. Analysis of the yellow metal ranged from 20 to 40% Zn. There is no austenitic alloy that will withstand this service. with RA330® expanded metal. Molten copper attack is a problem in muffles used for copper brazing steel. Even small amounts of spilled copper will completely penetrate the nickel alloy floor along the grain boundaries. removed from the corrugated bottom of an 11 gage/3mm wall RA333 muffle. However. This RA 253 MA® tray. One might consider the 11% nickel—1. A dry hydrogen or hydrogen-nitrogen brazing atmosphere does not permit the muffle to develop any protective oxide film. to keep molten copper from contacting the austenitic alloy muffle.Molten Metals. We have no experience to confirm this. rather than RA330 or RA601. . An applied oxide coating. Excess brass binder melted out and cracked the tray. One practical solution is a sheet of ferritic stainless such as 409 or 430 on the muffle floor. or lining the tray with ferritic stainless are suggested approaches.7% silicon alloy RA 253 MA as a replacement. One manufacturer reported longer life when RA85H was used for muffle bottoms. 50%Co 28%Cr 22%Fe. Copper. RA309. This muffle was intended only for powdered iron sintering. it melted when it was used for iron parts. RA 253 MA and sometimes RA330.3-38 Molten Metals. Iron is sintered above 2000°F (1150°C). we were asked to look at one of them. Cracks as much as a foot long had developed in the sides. are fabricated of mild steel. When a few bearings or bearing powder accumulated in the muffle. Note copper alloy penetration into the RA 253 MA base metal. The lead itself isn’t terribly corrosive to these alloys. RA310. Lead—molten lead heat treating baths. bearing bronze melts perhaps 1850°F (1010°C). RA330 sintering muffle cracked by molten bronze After five RA330 muffles used for sintering powdered iron had failed. although the lower nickel grades may be preferable. Grey phase at left is oxide. . continued Microstructure of cracked area above. Alloy 600 is another matter-this high nickel alloy is dissolved by molten lead. The presence of about an ounce of bronze coming out of this crack indicated that some bronze bearings had inadvertently been sintered in the same muffle. or lead pans. Copper. The lead still oxidizes. Apparently rare earth compounds used in the manufacture of ferrites were reduced to metallic form by the hydrogen atmosphere. respectively. The molten lead is usually covered with so-called charcoal. Ferritic stainlesses are said to be subject to chromium leaching. Had we been asked. Pure lead should be used. RA330 was used as 1” (25mm) diameter fabricated tubular heating elements in five 9’s purity selenium and arsenic selenide at 500 and 600°F (260 and 316°C). Corrosion of RA333 occurs primarily by selective leaching of the nickel. However E-Brite was found more resistant to molten lithium than either nickel or cobalt base alloys. . No degradation of product purity was reported. The nickel-chromium-iron alloy outside provides high temperature strength and oxidation resistance while the carbon steel inside is more compatible with the molten magnesium. magnesium tends to leach the nickel out of Ni-Cr-Fe alloys. we would have suggested first annealing the head to remove forming stresses. nevertheless we urge anyone planning to use RA330 for such an application to run their own test program. Antimony. 10% praseodymium and 1% neodymium. Melting at 1202°F (650°C). not necessarily confirmed in service. Because carbon steel scales on the outside (fireside) of the melting pot. Magnesium—used in reduction of TiCl4 is normally contained in mild steel pots. Lead. continued With other alloys it is the lead oxide on the surface that attacks the metal sides severely at the lead-air interface. Selenium—In the 1970’s. The most direct approach to this local corrosion is to make the metal wall twice as thick at the lead-air interface. caused by this protective covering. Lithium—a vessel fabricated in the 1970’s of RA333 for the US Navy liquid metal embrittled & cracked from residual stress in the formed head. or steel pots lined with 430 stainless. Alloy X behaves in a similar manner. to reduce lead fumes and oxidation. These have been either RA 253 MA or RA330 explosively clad to mild steel. Based on laboratory tests. Rare Earths—the same manufacturer of ferrites who had problems with molten calcium cracking RA330 has also had both cast and fabricated Ni-Cr-Fe alloy grids crack. They dripped on the cooler grid at the bottom end of the retort. TZM molybdenum and pure iron (to 1000°C) are said to have good resistance to molten lithium corrosion. Deposits on the cast grid analyzed 34% samarium. when operated 1650°F (900°C) with molten lithium. These are laboratory test results. more likely sulfur bearing coke of some sort. Sulfidation and carburization also occur at the lead-air interface. brought in when scrap lead is used. A lower nickel alloy would probably have been more satisfactory for these grids. a few experimental clad pots have been tried.3-39 Molten Metals. increases attack from the molten metal itself. i. melts well below the annealing or even stress relieving temperature of the austenitic alloy to be brazed. One reason is that silver braze. depending upon specific conditions. Temperatures are low. and the chloride fluxes used are more of a corrosive problem than is the solder itself.8mm) plate and RA 253 MA sheet have been used for side shields in the tin float process of plate glass manufacture. . The fracture surface was typical of liquid metal embrittlement. molten silver braze alloy dripping on the bottom of an RA330 retort will penetrate this austenitic alloy at the grain boundaries and cause hydrogen leaks. Molten zinc and zinc-aluminum alloys are used for galvanizing and die casting. 316L stainless.. 304 stainless steel. which had leaked full of zinc die casting alloy. AL-6XN and alloy C-276 have all been used in molten zinc/zinc alloy with some degree of success. Zinc die casting pots have been heated by gas fired immersion tubes fabricated of RA309. it looked like RA330 cracked by molten calcium or 2024-T4 aluminum cracked by mercury. Zinc. The high thermal stress coupled with zinc wetting the 309 metal inside cracked the tube. may liquid metal embrittle steel at temperatures as low as about 750°F (400°C)3. For this reason. Our observations have been that commercially pure iron. Zinc is the most commonly used low melting metal which may affect steel or nickel alloys. was heated rapidly with an oxy-acetylene torch to melt out the zinc. Tin at 600°C (1112°F) under hydrogen atmosphere is reported to have dissolved. One failed 309 tube. data and applications experience are more broadly available for Zn than for other low melting metals.e. in contrast to copper braze metal. and it seems reasonable to assume that the other nickel-chromium-iron alloys such as 800H or 600 are as bad or worse. RA85H. Molten zinc can either dissolve or liquid metal embrittle austenitic alloys. RA330 is no good at all in molten zinc.3-40 Silver—silver braze alloys have long been known to crack or dissolve austenitic alloys. Zinc—Zinc and zinc alloys are used for both electroplating and hot-dip galvanizing of steel. Cold worked 300 series stainless steels can not be silver brazed without danger of cracking. but this coating is subject to damage by mechanical abuse. Tin—both RA446 3/16” (4. which melts at 787°F (419C°). again more to withstand the ammonium chloride flux than the Pb-Sn alloy. The 309 weld bead is attacked to a greater degree than the base metal. and to have pock-marked carbon steel in the same bath. In hydrogen atmosphere braze retorts. then re-deposited. Solder (lead-tin)—no molten metal attack reported. The tubes are usually plasma sprayed with zirconia to enhance life. This may occur with both Zn plated bolts and with galvanized structural steel. in the process of decontaminating soil. RA333 alloy has been used in tin can soldering applications. 309. and the 316 did not last long. A Symposium on Behavior of Materials in Reactor Environment. J. 2. Hydrocarbon Processing.0 4. N10276) sheet. as well as for the sink roll itself.E. which was an improvement. 2. Now AL-6XN is used for both the trunnion and the sleeve bearing.0056 (0.2 7. Gurinsky.2008 (5. Piping by liquid metal attack.02) 0. Materials Performance p65 January 1993. The iron sink roll was weld overlaid with 316 stainless. continued When 1” (25mm) round bars of both RA330 and 316 stainless were both used in the same zinc die cast alloy scrap recovery project the 35% nickel alloy was severely eaten away and chromium was selectively leached out.9 3. then Rolled Alloys convinced them to try RA85H. New York. ratio to AL-6XN® 1. This was confirmed in service.0104 (0. as were the journals. AL-6XN looked even better.1164 (2. Initially the company used 316.118 (3. They tried 316 for the trunnion sleeve. Semih Genculu. Houston. We have found definite success with AL-6XN alloy for small sink rolls and bearings for galvanizing wire. and for the past 3 or 4 years they have been using AL-6XN.E. 1973 3. The chute through which the steel sheet passes into the zinc had a tip of C-276 where it entered the molten zinc bath. National Association of Corrosion Engineers. May. Liquid metal embrttlement—Part I.432) 0.6 1.10) 0. Cantwell and R.264) 0.12) metal loss. U.142) 0. Sleeve bearings. At the zinc-atmosphere interface the pot was sheathed with 316 stainless steel.086) 0.017 (0.110 (2.044 (1.594) 0.0 4.A.37) 0.0226 (0. Flare tips by severe cracking. New York.0034 (0.1188 (3. On test. pages 114-117. to ride on these 316 overlaid journals. Texas original thickness average metal loss inch (mm) inch (mm) 0. David H. low silicon nearly pure iron. zinc. were fabricated of C-276 (UNS No. The Behavior of Materials in Aggressive Liquid Metals. Rolled Alloys laboratory immersion testing in molten zinc ranked these alloys similar to how they behaved in service: 250 hour test in molten zinc.00 0. low manganese.96) 0.9 . Institute of Metals Division. pages 5-20.S. 850°F (454°C) alloy AL-6XN 556TM 1008 RA309 RA85H® RA446 316 References 1. over AL-6XN trunnions.0234 (0.574) 0. 1956. The 316 bars merely developed a galvanized coating with no appreciable metal loss. How to Avoid Alloy Failures in: 1.79) 0. Bryant. Nuclear Metallurgy.05) 0.0) 0.1328 (3. February 20. American Institute of Mining and Metallurgical Engineers.3-41 Molten Metals.120 (3. Temperature was about 1000°F (540°C) We observed that one steel company involved in continuous hot-dip galvanizing of sheet made the 850°F (454°C) zinc pot and sink arms of low carbon. even though it has an austenitic (face centered cubic) structure. Carburization makes nickel heat resisting alloys become magnetic because the chromium reacts chemically with carbon to form chromium carbides. at least on a cold day. and austenitic stainless and nickel alloys are usually non-magnetic. with 76% nickel and 8% iron. This is approximately illustrated by the following Fe-Ni-Cr ternary diagram of magnetism vs alloy content2. Usually this indicates that for one reason or other the metal is no longer fit for service. of course. Even RA600. Iron. are magnetic.) is also magnetic. and a face centered cubic structure at higher temperatures. is non-magnetic. commercially pure nickel is an austenitic metal. the magnetic properties sharply increasing at about 30% nickel and being highest in the range 50 to 80% nickel1. It is easy to confuse ferritic and austenitic with magnetic and non-magnetic. in their pure state.5% chromium. but depending upon the exact chemistry. Lower nickel grades such as RA310 or RA 253 MA do not so readily become magnetic when carburized. Cobalt is the third magnetic element. Consider going the other way. and we have observed metal which used to be RA330 but which had become a 1%Cr-Fe-Ni alloy. because of its 15. the small amount of ferrite in an austenitic stainless weld bead (E308. There are three metallic elements which. Older Canadian coins are a high nickel-copper alloy. And. Although the chromium is still present in the alloy. even though they may be austenitic. iron and chromium. is magnetic and has a ferritic (body centered cubic) structure. E309. It is the addition of chromium that makes alloys based on iron and nickel (or cobalt) become non-magnetic. of course. the new 85. in all combinations. to save on nickel). with a hexagonal close packed structure at temperatures below 783°F (417°C). But. and many European coins are magnetic. it is effectively removed from the solid solution matrix of nickel. are magnetic. and removing chromium. a particular heat may be magnetic. internal attack by molten salts or selective attack by some molten metal. Alloys of iron and nickel are magnetic. Likewise ironnickel alloys. Pure nickel is also magnetic. Service conditions that cause this magnetism are often carburization. austenitic alloy. Chromium is physically removed from the alloy by the normal corrosion mode in neutral salt pots. The 66% nickel 31% copper alloy 400 is usually non-magnetic.3-42 MAGNETISM Austenitic heat resistant alloys are non-magnetic as produced. . RA330 depleted to 12-15% Cr is common. and are magnetic (the newer are not. If 10. nor is it capable of being weld repaired.5% of that chromium were removed and replaced by nickel (and the %ages recalculated). Ferritic stainlesses are magnetic. and it is also a magnetic metal. some austenitic alloys can also be magnetic. After high temperature service they sometimes become rather strongly magnetic.3%Ni 8%Fe 5%Cr alloy would become a magnetic. etc. Burns. when a leaner stainless such as 304 is cold worked it becomes magnetic because a small amount of the austenite actually transforms to martensite (a hard. just enough to feel with a magnet. J. Semih Genculu. The specified chemistry range of 309S stainless (UNS S30908) is broad enough that a small amount of ferrite may be present in the hot rolled annealed metal. 10. B. Paper No. Constitution of Iron-Nickel-Chromium Alloys at 650° to 800°C. There are a couple other times when austenitic stainless steels may be magnetic. and A. so it is possible that a slight degree of magnetism felt on a used fixture is simply the scale. References 1. National Association of Corrosion Engineers. Texas . Liquid metal embrttlement—Part I. scale. magnetic phase). Krikke. R. W. and has been used for structural elements around the superconducting magnets in MRI equipment for hospitals. largely chromium oxide. Cook.P. July 1949 JISI 3. right down to liquid nitrogen temperatures. RA310 is normally non-magnetic. Monitoring the Carburization of Furnace Tubes in Ethylene Plants.3-43 Magnetism. continued The iron oxide component of scale is also magnetic. because austenitic heat resistant alloys are supposed to be non-magnetic. Hoving and K. Their will also be a slight chromium-depleted zone underneath the.J. rather than carburization. Materials Performance p65 January 1993. and especially so in deep drawn sheet components. This can be very upsetting to customers who think they have the wrong material.D. Houston. This is evident on sheared edges. Texas 1976 2. Rees. National Association of Corrosion Engineers. Houston. Smit. H. Also. Corrosion 76. Cold working has little or no effect on the magnetism of higher alloys such as RA330 or RA333. 3-44 . 3-45 STRENGTH AT TEMPERATURE The strength of a metal at high temperature is measured differently than at room temperature. For room temperature applications—steel guitar strings, automobile frames, claw hammers, etc.—the designer needs to know the tensile strength, yield strength or hardness. At cherry red heat, though, the only important mechanical property is creep or rupture strength. Above about 1000-1200°F (540-650°C), tensile or yield strength can NOT be used as a basis for design. This is important. Tensile Strength Tensile strength, or ultimate strength, is the stress required to pull a specimen until it breaks apart in two pieces. It is calculated by dividing the breaking load, in pounds (Newtons), by the specimen cross sectional area, in square inches (mm2), to give pounds/inch2 (Newtons/millimeter2) . The strength of wire, both steel and nickel alloy, is usually reported only by its tensile strength in psi (N/mm2, or MPa). The tensile test is carried out by mounting a specimen in a machine which pulls on it with a slowly increasing load until it breaks. The load in pounds (Newtons) is measured and recorded throughout the test. Elastic Modulus In the early stages of the tensile test the specimen is stretching elastically, like a rubber band. Were the test to be stopped, when the load was removed the specimen would go back to its original length. This is the “elastic” portion of the tensile test, where a plot of stress versus strain would be a straight line. The slope of that line, stress divided by strain, is the Elastic Modulus, also called Young’s Modulus, with the symbol E. This is the measure of the stiffness of the metal, or how “springy” it is. At ordinary temperatures, for example, the modulus of steel is about 30,000,000 psi (207 GPa), while that of 6061-T6 aluminum is only about 10,000,000 psi (69 GPa). One may say that steel is three times stiffer than aluminum. This means that, in the elastic range (room temperature, stress less than the yield strength) for a given stress aluminum will stretch or bend three times as much as will steel. At room temperature the modulus of RA333 is 29,200,000 psi (201 GPa). The modulus decreases at higher temperatures. By about 1000°F (538°C) the material is no longer elastic. 4-1 Yield Strength At some point during the tensile test, usually well before the specimen breaks, it takes a permanent stretch. This is called the “Yield Strength” (or Proof Strength). For austenitic alloys it is usually recorded on the mill test report as either the 0.1% Offset Yield Strength, or, more commonly in the U.S., the 0.2% Offset Yield Strength. Ductility Before the specimen breaks it has stretched out a great deal, and has necked down in the area where it breaks. The amount it had stretched when it broke is the “% Elongation”, and the amount it necked down is the “% Reduction of Area”. Both are measures of ductility. For example, at room temperature an RA333 tensile specimen might have 48% Elongation and 62% Reduction of Area. The Tensile Strength could be 107,000 psi (738 MPa, or N/mm2) and the 0.2% Offset Yield Strength 47,000 psi (324 MPa) When designing a machine part, obviously the design stress has to be below the tensile strength of the metal, or the thing would break in two. But the machine would also be useless if its parts bent, or yielded, so the designer must keep the stress somewhere below the yield strength of the metal. For heat resistant alloys, yield and tensile strength may be used for design up to about 1000°F (5380°C). Above this temperature, the life of the part will be limited by the metal’s creep-rupture properties, and not by its tensile properties. 4-2 People tend to have rather strong feelings about one or the other creep measurement. maybe years. say. is reported as both a stress. until it finally breaks in two. The ASME uses for one of its criteria 100% of the extrapolated stress for 1% in 100.Creep-Rupture Why creep and rupture strength? Metals behave much differently at high temperatures than they do near room temperature. so whenever possible we provide both minimum creep and total creep data. creep rate. when it wasn’t even loaded up to the yield strength (as measured by a short-time tensile test). or deform. or “secondary creep rate”. The other measure of creep. Theoretically. weeks. in % per hour. at which the metal is stretching. very slowly. or 100% of the extrapolated 1% in 100. the designer might settle on an acceptable amount of creep deformation over the projected life of the equipment. or 0. and a number of hours. It will keep on stretching for hours. unless it corrodes away or stress-corrosion cracks.000 hour rupture stress. at high temperature one must assume that the metal is going to creep.0001% per hour. This is true even for light loads. Design stress may be set at some fraction of this number. or “Creep-Rupture Strength”. Nothing will happen. That is. the stress required for the specimen to actually stretch a total of. or 0. This is the “minimum creep rate”. ASME uses whichever is lower. Creep rate is expressed as per cent deformation per hour.00001%/hr. 67% of the extrapolated 100. If a metal bar is loaded to just below its yield strength at room temperature. For some period of time the creep rate is more or less constant. that load can be left there practically forever. Now let us say that this metal bar is loaded. 4-3 . Minimum creep rate data and total creep rate data are not interchangeable. and the one used in Europe. again keeping the stress below the yield strength—while it is glowing cherry red. but very. that is. to some degree. The minimum creep rate (mcr) is used as one basis for design at high temperature. 1%.000 hour minimum creep rate. It is the stress required to completely break a specimen within a given amount of time. acceptable in his application. is called its “creep rate”. Creep The rate. In practice. in the furnace industry one design criterion is the stress required for a minimum creep rate of 1% in 10.000 hours. 1500°F (816°C). In the furnace industry another common criterion for setting design stresses is to use some fraction of the stress that would result in rupture at 10. or speed. Then that metal bar will begin to stretch. That is.000 hour mcr. A very small amount of deformation will occur at first (first stage creep). Rupture “Rupture Stress”. is “total creep”. All this.000 hours. He would then pick his design strength based on the speed of deformation. The least expensive way to obtain high creep-rupture strength is by giving the alloy a high temperature solution anneal. whereas one of RA309 or RA310 would collapse.9--4. The supposedly “weaker” RA330. they all have good to excellent thermal fatigue resistance in quench applications. with a medium-fine grain size.000 hour rupture strength. at 1800°F (982°C) the alloys RA330. However. RA85H. This does depend on how that strength is achieved. these stainless heat resisting grades have only 40—55% of the creep strength of RA330 at 1800°F (982°C). Normally we expect the strongest alloy to do the best job. can give very good life in quenching service. about 560--660 psi (3. coarse grained materials lose thermal fatigue resistance as they gain creep strength. An aim of ASTM 5 or coarser grain size gives much better creep and rupture strength than does a finer grain size. The reason is. with its finer grain. In our experience. About full scale Creep strength is more important than rupture strength. made of 800H would resist creep deformation but quickly break up in pieces from thermal fatigue. for example. RA 253 MA and RA 353 MA are strengthened by various alloy additions. A quenching fixture. For example. RA333. 4-4 . RA309 and RA310 all have comparable 10.The picture below shows a broken creep-rupture specimen of RA330. However in service an RA330 muffle or retort can retain its shape for years. tested at 2000°F (1093°C).6 N/mm2). For example. material with grain size coarser than ASTM 4 will be unsatisfactory in liquid quench applications. As a result. U.4mm) diameter test specimens with those from 0.83mm dia. This can be seen by comparing the 2000°F (1093°C) results obtained using 0. at Joliet Metallurgical Laboratories.252” (6. RA333 is considerably less affected at this temperature. as the test specimen diameters are rarely recorded.A.Creep-Rupture Testing Above 1800°F (982°C) oxidation affects the results of a creep-rupture test. As the creep voids oxidize the material undergoes an apparent strengthening.505” (12.) test specimens in RA333 are probably affected. Joliet.. This makes it difficult to compare very high temperature creep rupture data from different sources. 4-5 . For both RA330 and RA333 all currently published creep-rupture data was obtained using the larger diameter specimens.S.83mm) diameter specimens. Illinois.505”/12. By 2200°F (1204°C) even the largest available (0. For an alloy such as RA330 the results from the thinner specimen are so influenced by oxidation as to be unrealistically high. These five alloys were held at 1600°F (871°C) for 500 hours. caused by its own weight. RA309 sagged 6 inches (152 mm) in the first six hours. 4-6 . RA85H and RA601 sagged very little in 500 hours.Cantilever Beam Creep Test RA85H RA601 RA330 RA310 RA309 For design purposes. creep and rupture data are usually plotted on log-log charts. with RA330 showing slightly more deformation. The maximum stress in each beam. RA310 sagged 6 inches (152mm) in about 48 hours. A visual illustration of relative creep strengths is obtained by simply clamping alloy strips at one end and measuring how much they sag or droop from their own weight. and continued to bend in the opposite direction once the free end touched the furnace floor. was calculated to be 1890 psi (13 N/mm2). 000 1300 --6.100 5.200 12.300 7.000 7.050 1.000 5.500 4.200 9.200 3.200 23.800 4.400 11.800 27. psi TEMPERATURE °F ALLOY COR-TEN B RA446 304L 304.200 2350 1850 --- 1700 --------1.500 1.000 17.500 8.500 23.500 7.000 -98.300 3.600 22.000 -- 1500 --2.000 -----42.500 12.250 3.100 3.700 -3700 3600 --- 1600 -450 1.000 --17.500 15.900 15.100 4.Average 10.500 30.600 3.200 1.000 36.200 16.500 -25. 304H 316L 321 321H 347.300 5.300 5.500 -- 1400 -1.050 2.200 15.500 1.000 -19.200 11.000 -9000 13.600 5.000 8.000 -128.400 2.000 1100 -3.300 1.800 14.650 1.000 ---29.150 560 660 630 1.400 7.500 70.000 + 2.280 3.300 6200 7000 12.700 3.200 4.700 5.050 1490 1150 820 --- 1900 --------860 --400 -930 630 990 ----- 2000 --------680 --(280) -680 360 670 -(330) --- 2100 -------------(450) -440 -(200) --- 2200 -------------(320) 140 ------ RA800AT RA 353 MA RA333 ® RA 602 CA RA600 RA601 RA625 RA718 ------ COR-TEN B is a registered trademark of US Steel Corporation RA600 and RA601 data from EN 10095 + One Heat Tested ( ) Extrapolated data 4-7 .700 5.500 2.300 25.347H RA 253 MA RA309 RA310 RA330 ® ® ® 900 22.800 12.000 42.500 31.000 --------------® 1000 12.000 940 1.000 39.500 8.000 7.200 13.100 3.600 5.000 --48.400 9.200 9.750 2.700 2.600 14.000 -21.000 17.800 2180 1650 1200 --- 1800 -230 ------1.500 22.600 1.800 2.500 22.000 14.000 1200 2.500 24.900 1.200 11.000 Hour Rupture Strength.500 22.700 13.860 1.400 -----2.700 9.900 3.000 8. 900 7.Average Stress.500 --53.000 -25.800 5.500 23.700 16.000 100.700 + 1.700 8.600 2.000 7.400 2. psi.000 14.000+ 1400 -260 2.400 1.500 14.800 7.700 2.100 3.050 4.300 27.500 -22.000 ---21.350 2.600 2.050 880 760 -- 1900 --------490 -------- 2000 --------(250) -----430 -- 2100 ----------------- 2200 --------- --------- RA800AT RA333 ® RA601 RA718 * COR-TEN B A Registered trademark of US Steel Corporation + One Heat Tested ( ) Extrapolated 4-8 .900 3.800 12.700 -4.000 9.000 27.200 43.900 1.000 20.80 0 16.400 4. 347H RA 253 MA RA309 RA310 RA330 ® ® ® 900 20.800 11.500 2.800 18.300 8.100 2.200 2.000 20.100 7.500 4.700 -- 1600 --------2.000 --10.850 7.100 2.750 750 2.700 4.000 1.200 7.000 74.000 3.150 3.100 -- 1500 -130 1.950 1.300 1.950 10.900 5.300 9.100 5.000 1200 1.600 17.800 8.000 --41.500 1.700 7.400 3.100 7.650 --- 1800 --------890 220 280 500 1. 304H 316L 321 321H 347.500 600 570 1.000 -- 1700 --------1.300 3.000 1300 -680 3.300 2.000 14.200 4.000 6.00 0 --------------® 1000 11.000 4. for 0.100 6.500 18.600 16.0001% Per Hour Minimum Creep Rate TEMPERATURE °F ALLOY COR-TEN B RA446 304L 304.600 6.000 -- 1100 -3. if possible. In fixtures or bar baskets. not only with respect to different parts of the same fixture. Individual round bars crack because the surface of the metal heats. This is common in vacuum heat treating of tool steels and some stainless grades.) Grain size & alloy choice. 2. Thinner metal heats and cools more uniformly than thick. Metal Progress August 1959 Thermal fatigue is the cracking which happens after a metal is repeatedly heated and cooled rapidly. and give no external sign that anything is wrong until it suddenly breaks. In neutral hardening operations the bar may begin to crack internally. Even a nitrogen gas quench is effectively a rapid cool if carried out from 2000°F (1100°C). Heat resistant alloys also have low thermal conductivity. Rapid cooling is usually thought of as oil or water quenching. serpentine rather than straight flat bars and loose. selection of alloys that combine high hot strength with low thermal expansion coefficients. and by favorable operating conditions. one area individually quenches faster than another. and then contracts the same amount when cooled again. The bottom members of deep bar frame baskets cool and contract before the middle and top do. Experimental work and theoretical analysis indicate the cause to be plastic flow induced by expansion and contraction during heating and cooling. In carburizing service. No alloy will compensate for inadequate design where cracking from thermal cycling is concerned. is the rule for heat resistant alloy service. The Mechanism of Thermal Fatigue. Material for thermal cycling service should have a grain size ASTM 4 or finer. The most important items to consider regarding equipment which will be thermally cycled are: 1.THERMAL FATIGUE Metal parts exposed to fluctuating temperatures for long periods eventually deteriorate. perhaps one fourth that of carbon steels. This may include corrugations. and in salt bath heat treating. The effect can be minimized by proper design. 3. After some number of these strain cycles the metal cracks. Most will expand at a rate of about 2/10 inch per foot (17mm per meter) when heated from room temperature to 1800°F (982°C). pinned joints rather than rigidly welded. cracks start at the surface and grow deeply. Avery.) Light sections. H. Uneven heating and cooling. before the center does. 5-1 . Heat resistant alloys all have high coefficients of thermal expansion.) Design—basically flexible or loose. In a rigidly welded angle frame design the long bottom side pieces may crack while the shorter ends and the top frame remain sound. S. or cools. this alternately strains the center and the outside surface. but from surface to center of the metal itself. Since metal expands when heated. of course. bars.7mm) dia. 5-2 . That is.Thermal Fatigue. so the thermal strains are lower. if the designer makes use of RA333’s strength to use thinner plate and smaller diameter bars. But the thermal strains from quenching the larger bar are significantly greater. Ductility alone is not enough. but RA333 survives repeated quenching better because of its strength. RA333 has been our best alloy in resisting thermal fatigue. Both strength and ductility are important. It is thermal stresses that cause more distortion and cracking in heat resistant alloy equipment than do the mechanical loads imposed on the part. And for that matter. continued Some alloys are better than others. because it is both strong and ductile. We had one customer who cut his life in half simply by going from 1/2” (12. RA600 is ductile. can permit additional life improvement. which he was where load carrying ability was concerned. The use of the lightest possible metal sections cannot be overemphasized. in turn. the tensile ductility of RA333 at 1600°F (871°C) has been measured at 75% elongation. Thinner sections heat and cool more uniformly. The strength. RA330 in his bar frame basket.9mm) dia. up to 5/8” (15. He thought he was making the basket stronger. 188.071 0.5W 0. in particularly erosive areas. The situation does not improve at elevated temperatures. Erosion Erosion resistance appears somewhat related to oxidation resistance. The alloy Nitronic 60® (S21800. 4200 hours fired with wood waste and 1800 hrs with Polish coal. The cobalt alloys in question form a relatively soft. lubricious oxide that prevents galling. 556.6 0.5Ni 7. practical approach to minimizing galling problems. with peak bed temperatures of 1920F (1050C) Grade RA 153 MA® RA 253 MA RA 353 MA Maximum Thickness Reduction inch mm 0.5Cr 54Co 10. A combination of a cobalt base against nickel or iron base alloy is a good. But even at room temperature. These austenitic heat resistant alloys do not possess wear resistance in the conventional sense.8 0. are considered to have the best galling resistance at high temperature. Galling Austenitic stainless and nickel alloys are known to be susceptible to galling at room temperature.024 0. AvestaPolarit provided the following information for their “MA” grades: Coupons of three different MA grades were exposed in the cyclone of the Nässjö plant in Sweden. solid solution or carbide strengthened grades--NOT the hardfacing Stellite® alloys. X-40 (25. e.2 Until the development of the 25Cr 35Ni grade RA 353 MA.13N) ) is one of the few austenitic alloys that resist galling at room temperature. 6-1 . and for galling resistance. the 21Cr 11Ni alloy RA 253 MA had been considered one of the most erosion resistant materials for fluidized bed cyclone construction.5Ni 8Mn 4Si . There is some limited information available for erosion. L605. These are relatively soft. We are aware of no published data regarding its galling resistance at elevated temperature. tube shields of RA 353 MA were installed in-bed in a number of coal fired fluidized bed boilers.50C). Final results are still pending.008 1.g. nominal 17Cr 8. Normally the cobalt alloys. However we do know that axles of Nitronic 60 greatly outperform those of RA330 when used with cast heat resistant alloy wheels roughly 1600°F (870°C).WEAR Wear resistance is often related to hardness at room temperature. Normal temperatures 1580-1635F (860-890C).. During 1999. heat resistant alloys are rarely harder than Rockwell B100 (Brinell 240). but rather a material that forms a soft. used cast cobalt alloy X-40 linkage in the afterburner system.4964. The X40 parts were regarded as “self lubricating”. where cost permits.2. covered electrodes covered by AMS 5797. lubricious oxide at high temperatures. 6-2 . for example. Boron nitride spray is used for high temperature lubrication.Galling. Note that this is not a hard-facing wire. used to power military aircraft. L605 (Haynes 25) on one of the nickel or stainless parts would function to prevent galling against the other side of the couple. In other industries it may be that a weld overlay of. continued Due to the cost of cobalt alloys. The weld wire specification is AMS 5796. L-605 is also known as Haynes 25. or even known.Nr. their anti-galling properties are rarely used. In the 1960’s General Electric’s J79 engine. European specification W. For severe high temperature galling problems. outside of the gas turbine industry. consider weld overlaying one side with a high cobalt alloy such as L-605. UNS R30605. such as Stellite® 6. The most common problem is that the alloy forms a hard. heavy wall 310S muffle. an alloy steel may lose ductility to such an extent that its usefulness may be seriously impaired. It operated about 1200°F (650°C) with a vacuum inside. brittle sigma phase can be formed.A. the possibility of the occurrence of phases other than the well-known alpha and gamma may sometimes be overlooked in the consideration of alloys suitable for high temperature applications. low nickel grades such as 309 and 310. the 310 roof cracked badly. Some high alloy ferrous metals are subject to embrittlement at certain elevated temperatures as a result of the formation of a constituent called the “sigma phase. And these cracks grew further when they tried to weld repair them. Ideally. and embrittles more severely. and are ductile and non-magnetic when they are placed in service. 7-1 . After a few years the user inserted jacks and tried to jack up the roof which had fallen in. instead of straightening.PHYSICAL METALLURGY An important property of alloys utilized for heat resistant service is the ability of the metal to retain its desirable characteristics throughout the range of probable operating temperatures. The Sigma Phase. aluminum and titanium promote sigma. and AMS 5521 1. Sigma Phase All of our nickel-bearing stainless and nickel base alloys have an austenitic structure. Alloy Casting Institute. Sigma forms in the 1100-1600°F (600-870°C) temperature range. One example of a failure due to sigma involved a long. The ASTM specifications for 310S (N31008) permit 1. brittle nonmagnetic phase. New York. columbium. The overall chemical composition of the alloy remains the same.” If appreciable amounts of the extremely hard. Sigma may not seriously harm the alloy while it is operating at high temperature. silicon. It happens more quickly. All RA310 plate. a heat resistant alloy should retain these qualities throughout its service life. New York. when the alloy has been cold worked. called sigma. Alloy Casting Bulletin Number 5.00% silicon. But enough sigma can completely embrittle the alloy when it reaches room temperature. molybdenum. But. Chromium. Although the existence of this phase has been observed for a number of years. Foley. to reduce sigma in RA310.5% silicon maximum.S.75% maximum. sheet and bar is made to restricted silicon. which tended to collapse it. Nickel. U. 0. Some materials change after a few hundred or thousand hours in service. and become brittle instead of tough and ductile1. This usually happens with high chromium. July 1945. carbon and nitrogen retard its formation. Francis B. Sigma phase. will not embrittle as badly as 310S. below about 1400°F (760°C) these two grades have limited usefulness. after it goes back into service. that even silicon as high as 2% would be unlikely to result in sigma. where RA330 has embrittled from sigma. along with moderate chromium. Of course. The following is taken from work done for the ASME on superheater tube materials2. which will form a certain amount of sigma. sigma will again begin to form. can take a long time to occur and is less harmful at elevated temperature than at room temperature. Even 304H. There are no recorded instances. Indeed. either in service or laboratory test. Although RA330 might normally be regarded as overkill for a 1200°F (650°C) application. We mentioned that silicon promotes sigma. This will re-dissolve the sigma and restore ductility so that the metal can be straightened and weld repaired. but that RA330 does not embrittle from sigma. continued The solution would be not to use 310S or 309S at this low temperature. Faced with an existing. Charpy V-notch energy. foot-pounds (J) Test Temp Condition 304 321 100 (136) 100 (136) 75 (102) 100 (136) 95 (129) -100 (136) 100 (136) 100 (136) --100 (136) 100 (136) 100 (136) 100 (136) 100 (136) 100 (136) 347 100(136) 50 (68) 35 (47) 90 (122) 45 (61) 65 (88) -----100 (136) 85 (115) 85 (115) 100 (136) 100 (136) 100 (136) Alloy 316 -65 (88) 40 (54) 70 (95) 30 (41) -65 (88) 35 (47) -25 (34) -100 (136) 100 (136) 100 (136) 100 (136) 95 (129) 85 (115) 310 100 (136) 25 (34) 10 (14) 10 5 (14) (7) 800 100 (136) 50 (68) 55 (75) 60 30 (81) (41) 68°F unexposed 100 (136) (20°C) 18 mo 1200°F 100 (136) 36 mo 1200°F 50 (68) 68°F 18 mo 1350°F 85 (115) (20°C) 36 mo 1350°F 75 (102) 68°F 4 mo 1500°F (20°C) 6 mo 1500°F 18 mo 1500°F 30 mo 1500°F 34 mo 1500°F 36 mo 1500°F -100 (136) 70 (95) ---- 20 (27) -----100 (136) 85 (115) 60 (81) -35 (47) 40 (54) -100 (136) ----100 (136) 75 (102) 80 (108) -85 (115) 70 (95) 1200°F unexposed 100 (136) (649°C) 18 mo 1200°F 100 (136) 36 mo 1200°F 100 (136) 1350°F unexposed -(732°C) 18 mo 1350°F 100 (136) 36 mo 1350°F 100 (136) 7-2 . The embrittlement due to sigma varies from alloy to alloy. This is because RA330 has sufficient nickel. brittle 310S muffle the only thing to do is to anneal it by heating 1900°F (1038°C) or higher. RA330 does not form sigma or embrittle at any temperature range. 3% nickel C average nickel content of current production 316L is about 10.100 87.6 RA % 63.600 84.019 0.9 35. Yield.23 --0.Sigma Phase.500 27.060 --- 310 Heat No.100 23.8 24.600 14.8 48.2% Offset Tensile.9 40. continued 1500°F unexposed (816°C) 4 mo 1500°F 6 mo 1500°F 12 mo 1500°F 18 mo 1500°F 30 mo 1500°F 34 mo 1500°F 100 -100 100 100 --100 (136) -100 (136) 100 (136) 100 (136) 100 (136) -100 (136) 100 (136) -----100 (136) -100 (136) 100 (136) 100 (136) -40 (54) 100 (136) 30 (41) -----100 (136) -100 (136) ----- Chemical Compositon of Tube Materials Tested Above alloy UNS Cr Ni Mo Cb Ti C Fe A 304 S30400 18. 24659.69 34.200 32. 7-3 . The following are some test results: Test Temp ºF 80 80 80 80 1200 1500 1800 Condition AR PE 1200 PE 1500 PE 1800 PE 1200 PE 1500 PE 1800 Ultimate 0.06 bal 310 S31008 24.45 0.90 -0.56 21. was too short for much sigma formation to occur.000 72.4 64.96 --0. Washington.8 54.79 12. mill annealed PE – pre-exposed 1000 hours at temperature.93 10.6 34.93 ---0.06 bal C 316 S31600 16.07 bal D 800 N08800 20.15--0.66 ---0. psi psi 92.3 76.05 bal A current production 304 averages 9% nickel B 321 currently melted to typical 9.1 Elong % 46.07 bal 321B S32100 17.60% each The Metal Properties Council3 performed studies on 310 and other materials after various elevated temperature exposures.070 0.2% D titanium and aluminum not reported.800 7.600 52.300 26.77 13. 1 inch thick plate. 1000 hours. specification is 0.500 86.4 39. from Jessop Steel Co. ºF All data is average of three tests Some reduction of Charpy V-notch energy is shown after exposure at 1500F.20 1.48 10.400 10.200 33.0 57.5 44. However the exposure time.2 ---Lateral Expansion.7 87.7 47.05 bal 347 S34700 17.600 38.065 0.6 -Charpy energy ft-lb 88.56 -0. inches 0. Pennsylvania AR –as received.42 ---0..2 60. 5 65 -RA % 70 60. Exposure time.900 32.500 35.000 88.5 40.2% Offset Elong Yield. annealed PE = pre-exposed at 1400°F This 1989 Rolled Alloys study. by Gene R.9 11. indicates that 309 may retain better impact strength than does 310.2 11.7 73 58.6 3.9 7.Sigma Phase.4 25 72 204 6. hours RA309 ft-lb J RA310 ft-lb J RA 253 MA ft-lb J 500 1200 54 43.4 8.5 11. at least after exposure to 1600°F (871°C).600 18.4 5.7 34 ----4. foot-pounds RA 353 MA RA 253 MA 310S 8. Rundell.4 13. psi % 34. 85.5 59 -Charpy V-notch impact energy. three tests per alloy.1 7-4 .800 -47. material exposed 1600F (871°C).4 3. foot-pounds 240 (test machine limit) 96 167 130 AR=as received.000 -0. continued Both RA 353 MA® and RA 253 MA show a reduction in toughness after intermediate exposure.9 15.7 16 ----- RA330® shows retains high tensile ductility and Charpy V-notch energy after 1000 hour exposure to 1400ºF5: Test Temp ºF 75 75 1400 1400 Condition AR PE 1400 AR PE 1400 Ultimate Tensile.9 7. Exposed 5000 hours at ºF 1292 1472 1652 200 hours at ºF 1742 1832 1922 2012 Charpy V-notch Impact. Room Temperature Charpy V-notch testing.8 8. In this case chromium nitride precipitation is in part responsible4.3 17. usually somewhere in the range ASTM 3-8 (125-10µm) for the smaller bar.5) 4 (90) 4 (90) 3 (127) 3 (127) 2 (180) (63.A.58 0. Because of the long time exposure. 800H/AT is a definite exception. RA310 and RA330 all experienced significant grain growth. the grain size of a metal sample can be an aid to estimating what temperature the metal may been subject to in service.192 4. chemical company for 1862 hours at 1850°F (1010°C). Alloy RA333 RA 253 MA RA330 RA310 RA309 Sample thickness inch mm 0. minutes 10 15 30 60 120 (63. Although the initial grain size was not recorded.Grain Growth Most Rolled Alloys heat resisting alloys are produced to a medium-fine grain size.88 Final Grain Size ASTM µm 5 62 4 88 00 508 4-00 88-508 00 and 508 and coarser coarser 7-5 . arc furnace melted (no AOD remelt).5) 4 (90) 4 (90) 3 (127) 3 (127) 2 (180) (90) 4 (90) 4 (90) 3 (127) 2 (180) 2 (180) (90) 3 (127) 3 (127) 3 (127) 2 (180) 1 (254) (90) 3 (127) 2 (180) 2 (180) 2 (180) 1 (254) (127) 3 (127) 3 (127) 2 (180) 1 (254) 1 (254) (127) 3 (127) 2 (180) 1 (254) 1 (254) 00 (508) 5 5 5 4 4 4 3 3 Light plate coupons were exposed6 in a vortex finder at an Eastern U. RA309. The following is old data.04% carbon alloy.17 0. box annealed. hot rolled hand mill sheet. Response to grain growth may vary from heat to heat. this grade being annealed 2150°F (1177°C) minimum to deliberately coarsen grain size.83 0.243 6.190 4.259 6. and may be influenced by prior mill processing: Temperature F C 1900 1038 1950 1066 2000 1093 2050 1121 2100 1149 2150 1177 2200 1204 ASTM Grain Size Number (µm) Time at temperature. these particular materials most likely were produced with ASTM 4-7 (88-31µm) initial grain size. With the exception of 800H/AT. as compared with the maximum 2 hours of the above table.242 6.15 0. laboratory annealing of 0. while RA 253 MA and RA333 showed no measurable effect. sheet and light plate sizes. Grain size of RA330 versus time and temperature.S. Michigan. U. New York. New York. Behavior of Superheater Alloys in High Temperature.S. ASTM. High Pressure Steam. August. August. Symposium on the Nature. Rundell. Rolled Alloys Investigation 27-84. Rolled Alloys Bulletin 1353.S. Occurrence and Effects of Sigma Phase. Rundell. Private communications of January 10 and June 22. Rolled Alloys Investigation 27-84. 1968 3. Special Technical Publication No. ® 7-6 .Grain Growth.S. 1984 Temperance. Crucible Inc. U. 1000 hours RA 602 CA® 601 GC® RA601 RA333® RA600 RA 353 MA® RA330® 8 7 6 5 4 3 2 1 0 00 References 1. George E.A. RA 353 MA alloy 5. U. Gene R. The American Society of Mechanical Engineers. 110.S. including a version of 601 specifically intended to resist grain growth. Michigan. 1972. 6. Materials Research Center..A. 1950 2. Grain Growth Exposure to 2050°F (1121°C). continued A test was run to compare the resistance to grain growth of RA 602 CA and several other alloys. Gene R. Pennsylvania. 4.A. Philadelphia.A. 1000 hours exposure to 2050°F (1121°C) had no measurable effect on RA 602 CA. Lien. editior. U. 1984 Temperance. June. 410S is a lower carbon. 430 sheet has been used to line the bottom half of RA330 brazing muffles. These alloys have low ductility. as is a columbium (niobium) stabilized solid wire. Very cheap. 410 is a martensitic grade. formerly called MF-1 by Allegheny Ludlum. magnetic. having enough carbon. 430 is the most broadly available ferritic stainless. that being the temperature of most severe embrittlement. A matching composition flux cored wire is available. 409 has usable oxidation resistance up to about 1200°F (650°C). 8-1 . “silverware” is 430. 409. This embrittlement is well known in the petrochemical field.14% C. and some of the environmental and mechanical requirements to be met in service. 409 is processed in the mill to be a minimum cost grade. their use is limited to non-stressed parts. used for both corrosion resistance and as a heat resistant grade. and requires both pre-heat and immediate post weld anneal to keep the weldment from cracking.HEAT RESISTANT ALLOY GRADES Now that we have reviewed the influence of the various alloying elements.000 hours service. through enhanced oxidation resistant grades from AK Steel (formerly Armco) & Allegheny Ludlum to advanced oxide dispersion strengthened (ODS) alloys from Kanthal® and Special Metals®. It is called “885°F” (475°C) embrittlement. such as RA446. comparable to or slightly lower than that of carbon steel. about 0. Iron-Chromium Alloys These range from simple ferritic or martensitic grades such as 409. It has the advantage of being low enough in Cr to avoid 885°F/475°C embrittlement for some time. The iron-chromium alloys have low coefficients of thermal expansion. RA446 and RA410. 409 is formable and weldable. and those with higher chromium contents. All ferritic or martensitic alloys with 12% or more chromium embrittle very severely when held in the 800-1000F (430-540°C) temperature range. as are stainless exhaust systems. might even be called brittle. The metal can lose ductility to the point that it will crack in several pieces just from clamping it in a vise. it is time to take a look at some of the available alloys on the market today. more weldable version of 410. Because of their low strength at temperature (excepting the ODS versions). although it is reported to embrittle after some 50. Commercial kitchens and bake ovens use quantities of 430. is the lowest chromium alloy that qualifies as stainless. 409 plate is sometimes welded with alloy 82 wire for better weld bead toughness. Being very low carbon and titanium stabilized. It also hardens when welded. Automotive catalytic converter shells are made of 409. that it can be hardened by heat treatment. to protect the austenitic alloy muffle bottom from braze attack. RA446. Saqndvik has in recent years begun extruding Kanthal APM into finished radiant tubes for industrial furnace use. No longer available in sheet gages (under 3/16 inch/4. This means that at room temperature RA446 plate may crack when hit in a mechanical press break. RA446 has a very high ductile-to-brittle impact transition temperature. at least 250°F (120°C). 18SR sheet is available in full coil lots only. along with no nickel at all. It is not broadly available from distributors. AK Steel’s (formerly Armco) 18 SRTM uses both silicon and a critical ratio of titanium to aluminum to achieve oxidation resistance well in excess of what would be expected from its chromium level. RA446 is used for applications where nothing else will handle the corrosive environment. Allegheny Ludlum’s ALFA-IVTM uses aluminum and rare earths to achieve extremely good oxidation resistance with 20%Cr. In spite of its mechanical properties. There has been some degree of success with laser seam welding 1/4” (6. As a result. having at best less than 10% the creep strength of an austenitic nickel alloy. This grade is made only in very light gage strip for automotive catalyst support systems.8mm). RA446 is very weak at red heat. At Rolled Alloys we have used Kanthal APM to 2100°F (1150°C) in our oxidation test tray (currently it is RA 602 CA). The disadvantages of the ODS materials at this time include cost in the neighborhood of $50/lb ($110/kg). into the Fe-Cr-Al matrix. Y2O3. This high chromium. 8-2 . at 25% chromium. Melting from arc welding destroys the oxide dispersion. leaving the weldment with only the (very low) strength of a conventional ferritic stainless. by about 5% aluminum with rare earths. that is.35mm) MA956 plate. the ODS alloys have very high creep rupture strength. and titanium stabilized. continued 439 is about a percent higher in chromium. This permits it to be used around molten copper or brass.Heat Resistant Grades. The ODS ferritic grades available in the US are Inconel® MA956 and Kanthal® APM. limited availability and fabrication. quite unlike conventionally produced ferritic grades. These alloys are produced by mechanically incorporating the rare earth oxide. The largest single use may be as electrodes for heating neutral salt baths. gives RA446 the best resistance to sulphidation—usually—of the heat resistant alloys. Oxide dispersion strengthened (ODS) grades achieve extreme temperature oxidation resistance in the same manner as ALFA-IV. Currently. has the oxidation resistance needed for 2000°F (1100°C) service. likewise dual certified.05 0. it retains strength at temperature. But for constant temperature or slow heating and cooling. is rarely used because it is not broadly available.5 17.02 0.5 Y2O3 -- Iron-Chromium-Nickel Alloys. Because 304 is austenitic. only RA85H and 314 (W.Nr.5 Al ----1. Although the “L” grade is principally used for appearance or for aqueous corrosion resistance.5 -Ti 0. Ferritic and Martensitic Alloys alloy 409 410 430 439 18 SR ALFA IV Kanthal APM MA956 RA446 UNS S40900 S41000 S43000 S43035 ---S67956 S44600 EN -1.6 0.4 25 Si 0.3 0.3 0.8 4.3 20 22 19. With 0. continued Nominal Chemistry. 1.Heat Resistant Grades.015 0. dual certified with 304.4 --0. 304 can be considered and is used quite extensively.4006 -------Cr 11 12 16. Nevertheless the 316L is chosen to better resist aqueous corrosion for fans which must operate part of the time at high temperature. even though it would be stronger at high temperatures. at temperatures not above 1500°F/815°C.015 0. 316H. 8-3 . 304 The basic “18-8” stainless is AISI type 304. Nickel 20% and under These range from the high volume 304 and 321 up to a true heat resistant alloy. 304 is limited to this temperature by oxidation resistance.5 0. All of these grades can embrittle from sigma formation to some degree.08 0. We would prefer some other material for an item that was to be heated and cooled rapidly. 316L Not really a heat resistant alloy but used as such anyway.4 0.05 0. or 304H.4841) have sufficient carburization resistance for heat treat service.015 0.4 -C 0. Oxidation resistance and strength include some of the best available (RA 253 MA). Flat rolled products are usually either 304L.05 Other -----0.14 0.25 --0.03% carbon maximum the design stresses at 1500°F (816°C) might be about 40% lower than for 304H. It has a fairly high coefficient of expansion. particularly for fans. This is also the group from which alloys with useful sulphidation resistance are chosen.5 0. RA310. with 304L and 304H bar also available.02 0.03 Ce+La rare earths 0.2 17. and also near room temperature.7 5 5. the “H” version of this steel may be used to about 1500°F (815°C).4 0. Bar may actually be just plain 304.5 0. nitrogen and silicon. Intermediate temperature embrittlement can be a problem. a heavy calcium deoxidation. and 309 weld fillers are often used for dissimilar metal welds. Low cost. 8-4 . tolerating some 12% SO2 for extended periods at 1800F (982C). RA 253 MA® achieves excellent strength and oxidation resistance through rare earths. The ferritic RA446 and the lower nickel RA309 might be preferred for very strongly reducing environments with sulphur present. RA309 (really 309S. In oxidizing atmospheres RA253 MA has very good resistance to SO2 (sulphur dioxide).. HR3C. Fabrication is simple. In a more complex mix of chemicals RA310 is generally superior to RA309 in hot corrosion and is considered one of the standard materials of construction for coal gasifier and coal fired fluid bed combustor internals. RA310 maintains useable oxidation resistance beyond 2100°F (1150°C).Fe-Cr-Ni alloys. Thousands of feet of steam boiler tubing are on test at TVA. It was the first commercial NiCrFe alloy to use this technology. previously restricted to electrical resistance alloys (and the cobalt alloy 188).08% max carbon) is one of the most widely used heat resistant alloys. RA309 tolerates carburization well enough to be the grade of choice in carbon saggers. RA310 is one of the three alloys which should be considered where sulphidation is concerned. useful cyclic oxidation resistance to around 1850-1900°F (1010-1040°C) and fairly good sulphidation resistance characterize this grade. better than RA330 at constant temperature but not so good as RA330 when the temperature cycles. also known as 310HCbN. it is suggested that welded fabrications of 321 be heat treated for 4 hours at 1600°F (871°C). hence resistance to polythionic acid stress corrosion cracking. and is used up to 1600°F (871°C). RA310 has very good oxidation resistance. The columbium (niobium) addition helps hot corrosion resistance at moderate temperature but is harmful to oxidation resistance around 1800°F (982°C) and upwards. which is too high for the grade to develop titanium carbides. with two to three times the creep strength of RA309. ASTM specifications require 321 to be annealed 1900°F (1038°C) minimum. continued 321 This is a modification of the basic 18-8 grade with the addition of titanium to stabilize it against carbide precipitation in high temperature service or from the heat of welding. be properly stabilized. i. 0. The maximum suggested continuous use temperature for RA 253 MA is 2000°F (1100°C). 321 resists oxidation in high temperature service to about a 100°F (56°C) higher temperature than does 304. For maximum resistance to carbide precipitation in service. is a nitrogen-columbium strengthened version of 310 with improved hot corrosion resistance up to perhaps 1600°F (870°C). the other two being RA446 and RA309.e. Nickel 20% and under. RA 253 MA is not particularly carburization resistant (RA309 is slightly better) nor has it performed well in REDUCING sulphidizing conditions (H2S). RA 253 MA is strong. This has been suggested as the cause of cracking problems.A.S.) High temperature grain coarsening anneal.17 ---0. This.8 3. 2100°F (1149°C) minimum.05 0. commonly resulting in grain size ASTM 1-3. First.5 0.2Ti 70Fe 0. For the money.25 -Other 70Fe 0..10 N --0. RA 353 MA®.4845 --Cr 18. 314 may have lower creep strength than 310. and may be why the 800AT chemistry has been less well accepted in Europe.5 25 25 25 Ni 9 9. 0.k. Silicon increases the already good oxidation resistance of 310 and adds both carburization and nitriding resistance. a. The origin of this grade goes back to an economic situation quite unlike today.3 17. Nickel 20% and under. N08811. There are three versions of “800” alloy.4841) is essentially 310 with 2% silicon.05 0. of sigma formation. much as RA330 is the basic heat treat alloy.5 0. and one of the more recent. Nominal Chemistry.5 2. However.0 C 0. 800HT®. such as RA330 and 800H.10% 3. and amount. for thicknesses up to 1inch (25mm).20 0. largely keeps 800AT out of heat treat service. it is the German mills that make this grade. was announced in July 1951.06-0. 800AT gets its strength by a combination of: 1. Nickel 30-40% This nickel range covers some of the most successful heat resistant grades. The cracking problem may be avoided by heat treating the welded fabrication 1625°F (885°C) for 1 1/2 hours.7 1. and to the Korean War nickel shortage. Nickel 20% and under alloy 304 321 RA 253 MA RA309 RA85H RA310 HR3C 314 UNS S30400 S32100 S30815 S30908 S30615 S31008 -S31400 EN 1. Fe-Cr-Ni Alloys. 1.01 0.05 0.5 0.20%.) Carbon 0. and is often casually referred to as “310” there. Nr. silicon also increases the rate. Add one hour per inch (25mm) of thickness greater than 1” (25mm)1.3 11 13 14. RA800ATTM. 2. coupled with mediocre oxidation resistance. it is hard to beat the strength of 800AT. The original “Incoloy®”.a.7 0. is a very strong alloy broadly used in the petrochemical and refining industries.4541 1. For the most part. 8-5 .4Cb 52Fe 51Fe Iron-Nickel-Chromium alloys.4835 --1.Fe-Cr-Ni alloys.04Ce 65Fe 62Fe 1Al 61Fe 52Fe 0.08 0. 314 is widely used in Europe.851.10% max (no minimum) carbon.5 20 20 20 Si 0.06 0. coupled with the high chromium.4301 1. In these industries 800AT is used as their basic structural material. The second disadvantage is that the high combined aluminum + titanium content causes 800AT to form a very small amount of the age hardening constituent gamma prime at around 1100°F (600°C) or so. continued 314 (W. The alloy does have some drawbacks. Rolled Alloys supplanted 314 with RA330 a generation ago in the U.) Combined aluminum + titanium 0. the very coarse grains which are necessary for high creep-rupture strength are detrimental to thermal fatigue/ thermal shock resistance.3 21 23 18. 25% silicon addition enhances both carburization and oxidation resistance. In response the carbon was increased slightly to 0. MISCO promoted their 35%Ni 15%Cr alloy.Nr. Misco Metal. Incoloy 800 Grade 1 was fine grained. The majority of all wrought alloy fixturing in use today is RA330. 8-6 . Calrod is a GE registered trademark. and alloys 600. RA330® is truly the workhorse alloy of the heat treating industry. Incoloy 840 (W.Iron-Nickel-Chromium alloys. A combination of fairly high melting point. Calrod producers list the limiting temperature for Incoloy in this application as 1600°F (670°C). 1200°F (650C) for 304/316/321 stainless. 35% nickel has been found by experience to be the optimum level for carburization resistance and strength in the Fe-Ni-Cr alloy system. 2450°F (1343°C) and good oxidation resistance permits RA330 to be used at extreme temperatures. directly to the heat treater. Inco faced loss of all of the Calrod business unless they could offer some metal containing less than 75% nickel 15% chromium. Nickel 30-40%. By applying a minimum carbon of 0.06-0. has been developed for this application. 601 and RA 602 CA.4847) 20%Cr 20%Ni. Our highest temperature well documented experience with RA330 was a palladium brazing muffle. the War Production Board issued a decree prohibiting the use of an alloy containing more than about 55% nickel plus chromium for most heat resisting applications. Incoloy was born for the Calrod industry at that time. better oxidation resistance and higher strength. with some AISI 330 and a smaller amount of RA333®. and the Al + Ti controlled. During the 1980’s the ASME design stresses for 800H were challenged. RA 353 MA now has the advantage at very high temperatures. Grade 2 became Incoloy 800H in the early 1970’s. 11 gage (3mm) operating 2300 to 2370°F (1260 to 1300°C). Eventually Incoloy became Incoloy 800. RA330 has much better resistance to deformation (creep strength) than RA309 or RA310.7% typical to about 1% typical. By the time of the Korean War the Rolled Products Division of Michigan Steel Casting Company had begun to establish a reputation in the heat treat industry. version. lower cost.10%. continued Prior to this time the majority of Calrod® units for electric ranges or other electrical heaters were made using alloy 600. and was available in two grades. Inco were said to apply a commodity price for this application which made it cost just a little more than type 304 stainless.05%. annealed around 1800°F (980°C). It is not uncommon for RA330 retorts to operate as high as 2250°F (1230°C) metal temperature. and raised from 0. The 1. Since then a lower nickel. and Grade 2 was solution annealed for greater creep-rupture strength. Due to the nickel shortage. With comparable melting point. Misco Metal was the predecessor to RA330. Prior to Incoloy the only heat resistant alloy Inco promoted was the 76%Ni alloy 600. 1. At intermediate temperatures RA330 never embrittles from sigma like RA309 or RA310. “Inconel®” tubing for the sheath. outlasting muffles of alloys 600 and 601. Direct service comparison with 601 in the same furnace has confirmed the superiority of RA333. It has excellent oxidation resistance in freeflowing atmospheres to rather high temperature.40 0. This was a problem for us when some RA333 Mo reduction muffles were welded with alloy X covered electrodes. Oxidizing hot corrosion resistance is good. or matching RA 353 MA GTAW and GMAW bare wire.RA330HC uses 0.. Nickel 45-60% These alloys include RA333 and other superalloys developed for gas turbine use. Nominal Chemistry. Because of its oxidation resistance.2 C 0. RA333 maintains oxidation resistance to 2200°F (1200°C). RA333® has long been one of the best performing wrought alloys for industrial heating applications. weldability by GMAW. 8-7 . through 2200°F (1200°C). as are its hot erosion capabilities in cyclone applications.4886 -1. In service the weld beads disappeared.05 Other 0.6Ti 45Fe 43Fe 43Fe 0.05 0. It is now slowly being replaced by alloys 188 and 230 in flight engines. Welding is by either RA 353 MA DC lime type covered electrodes. RA333 is particularly good in resisting erosion from flame impingement. For example. developed in the early 1950’s by Haynes® as Hastelloy® alloy X.05Ce 36Fe Nickel-Chromium-Iron alloys. and usage tends to be in niche markets. tungsten and molybdenum. usually with cast HT links. where it has twice the strength. RA X. as in radiant tubes.4% carbon to provide high shear strength for use as pins in cast link belts. while alloy X plate at that temperature may completely disappear.2 1. 2100°F (1150°C).4 1. Costs are higher. and 100°F (56°C) higher melting point.4Al 0. brazing muffles. kilns. RA333 is strengthened with 3% each of cobalt.06 0. at more extreme temperatures or under stagnant atmospheres the 9% molybdenum content may render this alloy susceptible to catastrophic oxidation. has been for years the standard alloy for gas turbine engine combustors. and by 230 and 617 in land based gas turbines. and has a 1% silicon addition to enhance carburization resistance. as well as advanced grades for thermal processing. radiant tubes. Fe-Ni-Cr alloys. utility coal burners and boiler tube shields. without danger of burning a hole through the tube. thus better heat transfer and energy efficiency.2 1. Rather few people use X in heat treat service. RA 353 MA® may be regarded as an improved RA330 for use at 1830°F (1000°C) and higher. Nickel 30-40% alloy RA800H/AT RA330 RA330HC RA 353 MA UNS N08811 N08330 -S35315 EN -1.4854 Cr 21 19 19 25 Ni 31 35 35 35 Si 0. compared to 601. Nevertheless. causing the whole muffle to fail. RA333 permits a thinner tube.16N 0. RA 353 MA is finding extensive use in retorts. Nickel-Chromium-Iron alloys. continued RA333. In its highest temperature application. and oxidation resistant to reasonably high temperature. used to harden steel shot.8 mm) RA333 plate. RA333 is highly resistant to metal dusting. 617 alloy is strong. with good retention of ductility and excellent oxidation resistance. Because of its 9% molybdenum.03 0. and RA600. 602CA has been used in Germany for steel mill annealing furnace rolls 8-8 .08 0. as shown by both years of experience and longterm comparative testing. It has been used for kilns operating as high as 2100°F (1150°C). RA 602 CA resists grain growth in high temperature service. Nickel 45-60% alloy RA333 RA X 617 230 UNS N06333 N06002 N06617 N06230 W/Nr 2.a. developed by James Hosier. It was introduced in the 1960’s.4 C 0. It is carburization resistant at high temperatures. It is used for retorts and muffles.08 0.05 0. RA 602 CA® is the strongest and most oxidation resistant wrought alloy for service above 1900°F (1040°C). an AOD chute. Nominal Chemistry. Nickel 45-60%. as well as powdered iron sintering muffles.4663 -Cr 25 22 22 22 Ni 45 47 54 60 Si 1 0.02La Nickel over 60%. and has been used for land based gas turbine combustors. Using RA 602 CA weld fillers is suggested to address this problem. and for parts of high temperature vacuum retorts. 15 to 25% Chromium This group includes RA601. which is not. Although 601 is very oxidation resistant.4665 2. often simply called by Inco’s tradename “Inconel®” RA601 is a strong.5Mo 0.7Co 0.3 0. continued Rotary retorts of 3/16” (4. CVD retorts and vacuum heat treat trays up to 2260°F (1240°C). RA 602 CA.4608 2.10 Other 3Co 3Mo 3W 18Fe 9Mo 1. it may be susceptible to catastrophic oxidation under stagnant conditions.5Co 9Mo 1Al 0. as the old 82 (columbium/niobium bearing) weld disappears. It has also been used in nitric acid catalyst support grids. carburization resistant and very oxidation resistant alloy.6W 19Fe 12. it is commonly welded with alloy 82 (ERNiCr-3). As a consequence 601 fabrications may require frequent rewelding. have been giving 10 year life since the 1960’s. the ThyssenKrupp VDM alloy Nicrofer 6025HT (a. RA333 kilns 35 foot (1070 mm) long have been used to calcine zeolites for a decade now. 230 is a strong alloy.4Ti 1Fe 14W 1.3Al 0.k. Ni-Cr-Fe alloys. bar product being relatively uncommon. it has outperformed both RA 353 MA and Haynes 230. and in nitric acid catalyst support grids. 4Al 14Fe 2Al 0. to heat treat 50 pounds of work. Therefore. We think one of our alloys will perform to best advantage in almost every application.Nickel over 60%.5Fe 0. Nominal Chemistry. in 1944. A bit of history. This comes from its relatively low chromium. not high temperature.5 Ni 61. RA600 has good resistance to corrosion by neutral heat treat salts and salt fumes. stresses and cyclic conditions. As an aqueous corrosion alloy.5 63 76 Si 0.4851 22.2Ti 8Fe This concludes our general discussion of the various wrought materials that might be selected for a given application and those that we have selected to cover the range of temperatures.2 -0. was renamed RA330. for carburizing boxes. RA600 has good resistance to dry chlorine and dry hydrogen chloride gas at temperatures up to 900-1000°F (480-540°C). we are fulfilling our slogan.08Zr 9. In 1953 Mr. 600 is nearly as oxidation resistant but somewhat lower in creep strength. working from the Chicago office of Steel Sales. It is appropriate for automated salt pot fixturing. READY WHEN YOU NEED THEM”.1Y 0. Previously. and very good carburization resistance.4816 15. Compared to RA330. and the 35-15 alloy.05 0. contents. Economics generally favor RA309 or RA330 for the salt pot itself. 15 to 25% Chromium.2 0. even in oxidizing atmospheres (sulfur present as SO2). 15 to 25% Chromium alloy RA601 602CA RA600 UNS W/Nr Cr N06601 2. “ALL THE BEST HEAT RESISTING ALLOYS. Buick had used cast boxes weighing 200 pounds. continued RA600 has moderate hot strength.08 Other 1. Misco Metal. 8-9 . good ductility and resistance to oxidation. In 1938 a salesman named Paul Goetcheus.2 C 0. Goetcheus became the first president of Rolled Alloys. atmospheres. in their terminology) 35Ni 15Cr alloy. concentrated caustic (sodium or potassium hydroxide) solutions.4633 25 N06600 2. sold the first Inconel sheet to Buick Motor Division. “Inconel” was originally sold for corrosion applications. Nickel over 60%. and high nickel. RA600 has poor resistance to sulfidation. Goetcheus moved on to head up the Rolled Products Division of Michigan Steel Casting Company.5 N06025 2. There he worked to promote the use of a wrought (“rolled”. Mr. RA600 is resistant to hot. 2. and weld repair is extremely difficult. Advantages of Cast Alloy 1. Many cast alloys quickly become very brittle in service. the price per pound of fixture may be lower. Two aspects which influence whether one’s experience with either is good or bad. When equipment is down. They are unable to withstand rough handling when cold. among other things. are: 1. With radiant tubes and muffles thicker cast walls increase fuel costs for the same volume of work heat treated. 3. In fabrications this usually means the welds.) Design. 1. Appropriate design may influence life more than the simple choice of wrought versus cast. upon experience. Creep Strength. Similar compositions are inherently stronger at high temperature in the cast form than in wrought. Compositions. This increases the non-productive weight that goes through each heat treat cycle. 2. Cast parts are almost invariably thicker and heavier than the equivalent fabrication. Disadvantages of Cast Alloy Delivery. to those of the wrought alloys. 3. In addition there are a number of chemistries that are only available as castings. may last only a few months. This effect of design may or may not get factored into the user’s evaluation of his own experience. Some alloys are available only as castings. Cast grids. economics and delivery time. cutting and welding of a fabrication. depending on the foundry source.) Quality. Initial Cost. although never identical. Certain shapes can be cast that are not commonly available hot rolled. With castings it is internal shrinkage. This is because of the microstructure. 8-10 . porosity and residual casting stresses. Since cast parts avoid all the forging. or that cannot be fabricated economically from available wrought product forms. 4. 2. fabrications can often be delivered in a couple of days to get back on stream. A good design in either metal form may outlast a poor one in the other. for example. or for many years. Selection of cast versus wrought will depend. and because cast heat resistant alloys are usually much higher carbon than the wrought “equivalent”. because they lack sufficient ductility to be worked into wrought forms. Weight. Embrittlement. rolling.Cast Heat Resistant Alloys2 Heat resistant alloy castings are available in chemistries similar. This is particularly true of the very high chromium alloys. This is rarely true of castings. Shapes. internal shrinkage cavities. promote better resistance to thermal cycling and shock. Wrought heat resisting alloys are available from stock in numerous product forms. Thermal Fatigue. Soundness. Section Size.Cast Heat Resistant Alloys. are available only as castings. A pattern must be made for each different part design. 8-11 . 3. Wrought materials are normally free of the internal and external defects such as shrink. Availability. The smooth surface of wrought alloy helps avoid focal points for accelerated corrosion by molten salts or carbon deposits. Wrought alloys are available right down to nearly foil thickness. Few wrought alloys match the high strength of heat resistant castings. 5. this must be considered in product design.. Fabrications are quickly procured to maximize production up-time. Castings invariably have some degree of porosity. This is all right for production runs but quite uneconomical for one’s and two’s at a time. Thinner sections often permit weight reduction of 50% or more. Where creep-rupture is truly important. internal oxides and cold shuts. 2. porosity. all with excellent hot corrosion and/or carburization resistance. Creep strength. 5. Surface Finish. Disadvantages of Wrought Alloy 1. found in castings. and the inherently greater ductility of wrought metal. 2. Composition. With lighter sections handling the fixture is easier. When these defects open to the surface they are subject to attack by carbon deposits or molten salts. etc. and much less unproductive metal goes through each furnace cycle. Soundness. Pattern cost. continued 4. Alloys such as 50Cr 50Ni. Advantages of Wrought Alloy 1. Thinner sections that reduce thermal stresses. 28Cr 10Ni or 35Cr 46Ni. 4. 5 0. When the cast HT (35%Ni 17%Cr) grid was practically new and had been exposed to only a few cycles. a particular job required increased working area for the grid. quenched in either molten salt.3 1.5 ------5 3 5 ---Co -----------15 3 ----Other 67Fe 63Fe 61Fe 60Fe 59Fe 0.4 1.5 W ----0.4 0. oil or brine.4339 J93633 1.5 0.45 0.3Cb 1. The work was neutral hardening from temperatures up to 1850°F (1010°C).4. As can be seen in the photo.5 0.4837 --J94003 -J94204 1.4 2 C 0.5 1 1 1 0.4 1.5Cb 0. The wrought alloy RA330 exhibited very little surface attack and no fractures.4857 -----2.Cast Heat Resistant Alloys.4865 J95705 1.4813 N06006 .3 0.8 1. Note the cracks in the center of the cast ribs which occur along the plane of weakness of the dendritic structure.4 0.7 1. 8-12 Cast Heat Resistant Alloys.4 0.7 1.3 0. Cast Heat Resistant Alloys3.06 0.3 0.4879 --R20501 2. the cast alloy portion suffered surface attack from soot and the quenching salt. RA330-108. The application was a grid for suspending loads in a gantry furnace at a commercial heat treat shop.45 0. and failed from thermal fatigue.5 1 1 1 1. continued Nominal Chemistry.5 66 Si 0.4840 J94614 -J94605 -J95405 1.4 0.5 alloy HC HD HE HH-2 Thermax® 40B HI HK HL HT HU HP Supertherm® HOM-3 22H® MO-RE® 40MA IN-657 HX UNS W/Nr J92605 -J93005 -J93403 1. RA330 alloy plate was formed and welded to the outside of the existing cast grid.4 0. continued The effect of cast alloy surface and internal defects versus wrought alloy soundness on service performance is illustrated by our old case history.5 1.5 0.Cr 28 29 28 25 25 28 25 30 17 18 26 26 26 28 35 50 17 Ni 2 5 9 13 13 16 20 20 35 38 35 35 46 48 46 47.3Ti 54Fe 54Fe 47Fe 44Fe 40Fe 36Fe 13Fe 16Fe 3Mo 16Fe 14Fe 1.5 0.5Fe 13Fe . Metals & Alloys in the Unified Numbering System. Michigan 48182 U. Steel Founders’ Society of America. 24 Nothing has changed in eighty years. Germany. Bulletin 113. 2. Proceedings of ASTM. One must design to permit free expansion (and contraction) or the metal will bend. 1998. Selecting the Alloy. and on Supertherm for cast fixturing. 3. . A. 8th Edition. Inc. This simple statement is so obvious. And it is destructive chiefly because the engineer does not include in his design proper allowance for or provision against temperature inequalities or because the operator imposes temperature differentials which cause localized dimensional changes with accompanying stresses greater than the elastic strength of the alloy at the given temperature. D-71672 Marbach. one large captive shop has standardized on RA333 as their wrought alloy. 5. Warrendale. Section VIII. buckle or crack. ISBN 0-7680-04071 1999 Society of Automotive Engineers. paragraph UNF-56 (page 205).A. Midwestern experience has been that they contribute to heavy sooting in carburizing furnaces. 18th Edition. both grades being found extremely resistant to metal dusting (carbon rot). the resulting stresses will equal the yield strength of the metal at temperature. or shear) due to unequal temperature distribution and non-uniform temperature gradients. Division 1. The first and most important is that metals expand in volume with heat. Temperance. Stahlschlüssel. 1924 V. However. nor at least emphasized. We have been told that nickel-aluminide alloy castings for heat treat service are quite strong. Heat Series. . If thermal expansion is somehow restrained. High temperature equipment design has certain unique features not commonly found. 1973 4. ASME. References 1. .Where metal dusting is a problem. High Alloy Data Sheets. tensile. 1998 ASME Boiler & Pressure Vessel Code. New York. Verlag Stahlschlüssel Wegst GmbH. New York. ASTM DS-56G. Pennsylvania. to about 90 per cent of the total number of cases. in mechanical engineering texts.S. 8-13 DESIGN Stresses (compressive. Fahrenwald. U.S.A. Some Principals Underlying the Successful Use of Metals at High Temperatures.. cause more failures in high—temperature equipment than all other influences combined amounting . yet often dismissed or given but slight consideration in design. Rolled Alloys. F. and be clearly aware of the range over which temperature will be controlled in service. Thermal Strain This point is such an important consideration for high temperature equipment design that it must be examined in some detail. to fatigue from the rotation. and possibly more in creep. . Although modulus data are published at elevated temperatures. For example. there is considerable scatter. an increase in service temperature from 1700°F (927°C) to 1800°F (982°C) could drop the life of an RA330 component from 10 years down to only 15 months. An item of some minor confusion is elastic modulus.00001%/hour minimum rupture stress.000 hour 9-1 Design.A corollary to this is that most heat resistant alloys have rather poor thermal conductivity. at the service temperature. are the rule and not the exception in high temperature equipment. and the modulus data has no real meaning. are often designed to much higher stresses than are static components. designs to an allowable stress of one half the stress 0. When using published average creep-rupture data for design one must include a safety factor. such as kilns. In other words. These data are obtained under very closely controlled laboratory conditions of constant temperature and stress. the furnace industry often required for a minimum creep rate of ASME Boiler & Pressure Vessel Code extrapolated 0. in rupture data. or 67% of the extrapolated 100. In practice. Thermal gradients. It can be surprising how rapidly mechanical strength drops off with temperature. Even so. whichever is lower. In practice.0001% per hour. if ever. 15 to 20%. hence thermal strains. less than 1/4 that of carbon steel and only 1/30 that of copper. under the same load. At such temperatures strain is proportional to both time and stress. one should be aware of the significance. A large portion of the many field failures reported to us happen because the designer or user did not appreciate the significance of thermal expansion. but rarely. and not simply to stress alone. The is more conservative. more often to flite design. continued Rotating components. at red heat these alloys are simply not elastic. Kiln failures may be due to hot corrosion. the numbers are obtained by a means involving the speed of sound through the material. designing to either 100% of the creep rate. This expansion must be accommodated not only by design but by installation practice as well. of creep-rupture data. Next. above about 1000°F (540°C) stress is no longer proportional to strain. One cannot calculate a simple beam deflection at 1650°F (900°C) using anyone’s published modulus data. and the limitations. this repeated strain will fatigue the metal and the equipment will break. As well as being the cause of distortion in service.5x106 psi (196 GPa) to 19.6 mm)—more than 11/16”—in overall length.2. Since the bottom of the basket enters the quench while the top frame is still red hot. oil quenched from 1550°F (843°C) will contract 0. for whatever that is worth. In general any piece of metal which is hotter on one side will. a mechanically strong and rigid welded angle frame design may be inclined to crack or distort.200 psi (256 MPa) at room temperature. This expansion is roughly 3/16” to 1/4” for each foot of length (16 mm per meter). The equation for calculating thermal stress in the elastic region is: S = αETK 1—ν α = coefficient of thermal expansion E = elastic modulus . A flexible bar frame design may tolerate this.692 (17. in typical heat treat service. A 48” (1220 mm) long RA330 heat treat basket. become concave on what was the hot side. it will stretch. this principle may be used to straighten metal parts1. for example. But. or 15. If the metal is not free to expand. The short-term modulus. bend or warp permanently with each thermal cycle.Heat resistant alloys expand a great deal when heated. continued As temperature goes up the metal not only expands but diminishes rapidly in strength. Eventually. The combination of differential thermal expansion/contraction and reduction in strength at heat is why quenched grids or large bar frame baskets tend to bow like a rocking chair. when heated from room temperature to 1800°F (982°C). 9-2 Thermal strain. It is important to recognize just how large the total expansion can be. averages about 37. This is because this “strong” design cannot accommodate the relative thermal contraction of the bottom versus the top of the frame. convex to the quench. when cooled. The short-term yield strength of RA330. drops from 28.5x106 psi (134 GPa). but only 40% of that figure.400 psi (106 MPa) at 1600F (871C). the bottom members contract before the top does. for example. Since this crack cannot be seen from the outside. Theory of Elasticity. one may assume that a temperature differential of only 200°F (110°C) in this temperature range would cause permanent plastic deformation. New York. Assume a plate 1000F on one side and 800F (538 to 427°C) on the other. α = 9. butt or fillet.297 The calculated stress = 62.8 x 106 psi T = 200°F K = 1 ν = 0. McGraw-Hill. So.Timoshenko. 9-3 Weldments Weldments can fail from repeated thermal cycles. Average 0.T = temperature difference ν = Poisson’s ratio K = restraint coefficient The formula may be found in S.970 psi. one rough.3 x 10-6 inch/inch°F E = 23. rule of thumb is that a 200°F (110°C) temperature differential will yield most austenitic heat resistant alloys. The restraint coefficient in real structures will be some number less than one. All welds.000 psi. a small step each cycle. the unwelded areas behave as large cracks or notches. NY 1934 Apply this formula to RA330. In thermal or mechanical cycling. Nevertheless.2% offset yield strength of RA330 at 1000°F (538°C) is 25. there is no warning sign that the part is about to break. . Repeated thermal strains cause the “crack” to grow outward through the weld bead. but good. must be completely fused. or when the basket is straightened. continued during operation.This fully welded joint can The unfused void in this fillet resist both thermal and weld acts as a stress riser and mechanical fatigue. Incidentally. But no weld filler will compensate for inadequate weld joint design. It is really a volume expansion. Eventually. 1.33 to get how many millimeters each meter of metal will expand) Remember that thermal expansion occurs in all three dimensions. which is how much (in inches) each foot of metal will expand. Thermal Expansion A simple way to calculate the thermal expansion of a fixture is to use the chart below. Pick the alloy. This is because centrifugal force. All welds of fan blades to the hub must be fully penetrated. This happens even though the remaining weld metal is still ductile. Bar frame heat treating baskets. More root gap may be required to achieve full penetration in a nickel alloy. A joint design that makes a good fan in 316L stainless (W. A couple of examples: 1. The result can be that the nickel alloy fan fails even though a stainless fan of same design performed well. The blades may also flutter or vibrate 9-4 Weldments. 2. read down the column to the operating temperature and read the number. which causes more fatigue crack growth. A higher strength weld filler such as RA333 may be helpful in resisting mechanical loads. gas loading and the temperature differential between blade and hub all stress the blades. just starting and stopping the fan will cause low cycle fatigue failure of incompletely penetrated welds. may cause premature failure. it is more difficult to achieve weld penetration by the arc in nickel alloys than in stainless. Incompletely penetrated weld joints will not tolerate thermal strains and are the most common cause of weldment failure in high temperature service. (Multiply by 83. Furnace fans. it goes through one fatigue cycle.Nr. Incompletely fused welds crack a little more each time the basket is quenched. not just an expansion in one direction. The weld may break in service. Each time the fan starts up.4404) may well not allow adequate weld penetration in RA330. So . 208 in/ft X 3 ft = 36. How far will the free end expand? Looking down the RA330 column we find a total expansion of 0.208 in/ft X 20 ft = 4. it is also increasing in width and height. Example: An RA330 D-muffle 36 inches wide and 20 feet long operates at 1800°F. incidentally.while the fixture is increasing in length. How wide will it be in the hottest zone? 36 inches + 0. 9-5 . Multiply this figure by the length of the muffle.208 inches/foot at 1800°F (982°C). will expand at the same rate as the piece of solid metal that would just fill that hole. A hole. 0.16 inches total expansion.624 inches. which shows essentially no cracking. Flame Straightening Technology for Welders. rather than thick. LaSalle. RA330. We have seen baskets used for neutral hardening (which see many. Quebec Canada H8R 2N9. The basket vertical members were 5/8” (15.9 mm) dia. About 4X 1/2” (12. to permit more uniform heating and cooling. bar. LaSalle. on the right. John P. In quenching service.9 mm) diameter. 1989 9-8 . Stewart. The lightest possible section size should be used. the effects of repeated thermal shock can be as important as mechanical loading.7 mm) dia. References 1.7 mm) diameter RA330 bar. 9773 LaSalle Boulevard. Even though this heavier bar should be mechanically stronger. many quench cycles) last twice as long when made of 1/2” (12. as when they were constructed of 5/8” (15. One of these is shown in cross-section. Quebec Canada H8R 2N9.9 mm) dia. John P. was used for the basket’s top frame. A dramatic example of the effect bar diameter has on quench cracking is shown below. This 5/8” (15.9 mm) dia.Section Size Thin. bar has cracks extending in depth to one half its radius. it is clearly weaker in resisting thermal shock. Stewart. sections reduce the thermal gradients inherent in heat resistant alloys used under conditions of rapid thermal cycling. Bear in mind that these alloys combine high thermal expansion coefficients with low thermal conductivity. Distortion Control. 1981 2.7 mm) diameter bar. 9773 LaSalle Boulevard. RA330 from same heat treat basket A 1/2” (12. basket top frame About 4X 5/8” (15. SELECTING THE ALLOY Technical data illustrating the properties of heat resistant alloys are very helpful guides in selecting an alloy suitable for a given application. However the behavior of alloys during long exposure to the many environments and temperatures that may be encountered cannot be completely documented nor described by laboratory tests. Experience obtained from many actual installations is most helpful. One must develop the judgment needed to determine which of the many factors involved are the most important. A few points to consider. Temperature is often the first—and sometimes the only—data point given when we are asked for suggestions regarding alloy selection. One cannot successfully chose an alloy based on temperature alone. Nevertheless one simple first guide to alloy selection is knowing the maximum temperature at which a given alloy may have useful long term engineering properties. Picking oxidation in air, or strength, as a limiting factor one might rate alloys as follows, in plate form. Thin sheet will have a lower limiting temperature due to proportionally greater losses to oxidation. Carbon steel, such as ASTM A 387 Grade 22 (2¼ Cr, 1 Mo). Typically considered 950°F (510°C), above which 304H is stronger. 409 ferritic stainless (UNS S40900, Werkstoff Nr. and EN 1.4512) 1200°F (650°C), limited by oxidation. Subject to embrittlement after several years’ service above about 600°F (316°C). Formable, weldable. 410S low carbon martensitic stainless (UNS S41008, W.Nr. 1.4000) 1200°F (650°C), limited by oxidation. Subject to “885°F” embritlement after long service above about 600°F (326°C). 410 martensitic stainless (UNS S41000, W. Nr. 1.4024) 1200°F (649°C), limited by oxidation. Subject to embrittlement after several years’ service above about 600°F (316°C). Can be hardened by heat treatment, difficult to weld. 304/304H & 316 stainless (S30400/S30409, W.Nr. 1.4301 & S31600, 1.4401) 1500°F (816°C). If product contamination by scale particles is a consideration, consider a 1200°F (649°C) limitation, and move up to RA309 for 1500°F (816°C) service. 321 (S32100, W.Nr. & EN 1.4541) stainless has about a 100°F (55°C) advantage over 304, and is used to 1600°F (1202°C). In Europe 316Ti (W.Nr. & EN 1.4571) is used to 1650°F (899°C), whether because of technical advantage over 321 or difference in philosophy we do not know at this time. RA309 (S30908, W.Nr. & EN 1.4833) is useful to about 1850-1900°F (1010-1038°C) above which our customers seem dissatisfied with its oxidation performance. RA800H/AT (UNS N08811) is a little more oxidation resistant, still we’d suggest keeping it below 2000°F (1093°C) 10-1 Selecting The Alloy, continued RA 253 MA® (UNS S30815, W.Nr. 1.4893, EN 1.4835) has superior oxidation resistance to a fairly definite upper limit of 2000°F (1093°C). Above this temperature the oxidation resistance may be adequate but no longer exceptional. RA310 (S31008, W.Nr. & EN 1.4845) is reasonably oxidation resistant to about 2150°F (1177°C), although the strength is quite low. RA330® (N08330) combines useful oxidation resistance and fairly high melting point so that it will tolerate more extreme temperature abuse than any other fabricable austenitic grade with which we are familiar. RA330 muffles are regularly used at 2100-2150°F (1149-1177°C). In one exceptional case an 11 gage (3mm) wall RA330 muffle provided six months service brazing with 65% palladium 35% cobalt filler at 2370°F (1300°C). RA 353 MA® (S35315, EN 1.4854 ) has a melting point similar to that of RA330, with better oxidation resistance in laboratory tests. Field experience at this time is with muffles and calciners. Based on its chemistry and test results we would expect it to tolerate extreme temperature at least as well as does RA330. RA333® (N06333, W.Nr. 2.4608) in open air use is limited more by its incipient melting point than by oxidation. Temperatures to 2200°F (1204°C) may be considered, though stagnant conditions might not be desirable. We have no experience with this grade at 2300°F (1260°C). RA600 (N06600, W.Nr. 2.4816) excellent carburization resistance. Oxidation resistance does not drop off rapidly with temperature. RA600 is used at the same high temperatures as RA330, although somewhat more creep deformation may occur in service. RA601 (N06601, W.Nr. 2.4851) has deformed more than RA333 in 2150F (1177C) applications and should have a somewhat lower maximum temperature use. RA X (N06002, W.Nr. 2.4665) is designed for gas turbine combustors where the hot gases continually sweep over the metal surface. Due to its 9% molybdenum content this grade may be subject to catastrophic oxidation under stagnant conditions, or in open air above roughly 2150°F (1177°C). Know the atmosphere which the alloy must resist—is it air, inert gas, reducing, etc.? Or vacuum? Vacuum—obviously, metal loss from oxidation doesn’t exist so rather lean alloys may be used to extreme temperature if mechanical properties suit. Occasionally chromium is a concern, as it can evaporate from the alloy fixture, then deposit on cooler areas of the furnace. Sometimes parts will diffusion bond themselves to the fixture at very high temperature. One cure for this is to paint braze stop-off on the parts or fixture. Nicrobraze® Orange Stop-Off, from Wall Colmonoy Corp. is used for this purpose. Alloys commonly used as fixturing for vacuum heat treating tool or stainless steel include RA330, RA600 and RA601. 10-2 Selecting The Alloy—atmosphere, continued Air—those alloys useful in just plain hot air are also suited for oxidizing products of combustion of natural gas and even coal. Generally oxidation and strength are the only issues. “Oxidation” usually refers to metal wastage, but concern about product contamination from scale is an occasional issue. For example, glass forming operations take place around 1100-1400°F (600-760°C) where 304 stainless might suit as a structural element. But because scale from this stainless gets onto the glass, RA330 is used for its much higher oxidation resistance. With respect to oxidizing products of combustion of coal, a major end use of RA 253 MA is for coal nozzles in powdered coal fired utility boilers. Oxidizing products of combustion from heavy fuel oils may be corrosive due mostly to small amounts of vanadium in the oil, particularly in oil from Venezuela. The vanadium pentoxide formed is very corrosive at red heat. The only alloy said to resist V2O5 hot corrosion is the cast 50Cr-48Ni alloy (“50-50”), UNS R20501. Short of that, one might consider RA333, although it is definitely not as resistant as the 50%Cr alloy. While oxidizing products of combustion of coal can readily be handled by alloys such as RA 253 MA, or higher nickel grades if one prefers, reducing products of coal combustion are another matter. In reducing atmospheres, which do occur in certain areas of the current generation of low-NOx burners, sulphidation from both coal and oil fuels can be a serious matter. We would not suggest use of any alloy with higher nickel than RA310. That is, limit nickel content of the alloy to about 20%, to minimize sulphidation attack. In all other atmospheres there may be some potential for carburization or hot corrosion. If the atmosphere really is hydrogen, argon or nitrogen then no reaction with the alloy should occur. But sometimes the atmosphere as it exists in the furnace is unintentionally different than the pure gas pumped into the furnace. A classic case is a coil annealing cover for carbon steel. The atmosphere is nominally nitrogen-hydrogen, which would be quite neutral. But residual palm oil from cold rolling steel sheet vaporizes and makes the atmosphere carburizing enough to deposit soot inside the cover. This “inert” atmosphere will also mildly carburize the cover itself, usually RA309 or RA330. When steel rod coils are annealed the carbon potential of the atmosphere is controlled to 0.4%C, to be neutral to the AISI 4140 or 1045 steel rod being annealed. This atmosphere is actually carburizing to Ni-Cr-Fe heat resistant alloy, and tends to embrittle RA 253 MA. A less common situation is sulphidation of alloy fixturing used to anneal copper cathodes, electrolytically refined copper. The cathodes have residual copper sulphate from the electrolyte used in this process. This is the source of sulphur, which will attack nickel alloy furnace fans, in particular, used for annealing cathodes in a reducing or neutral atmosphere. 10-3 RA333. RA600 and RA601. When some amount of oxygen is also present. has useful carburization resistance in heat treat furnaces. RA X has good carburization resistance and is occasionally used. and too low in silicon. with only moderate halogen levels. RA600 is the usual choice. Resistance to embrittlement from carbon absorbtion is largely conferred by the total chromium . Under oxidizing conditions chromium. continued Intentionally carburizing atmospheres are commonly used in heat treatment of steel parts. Wrought alloys commonly used to resist carburization include RA330. In high chlorine. nickel and silicon content of the heat resistant alloy. atmospheres high nickel alloys are preferred. Of the lower nickel grades only RA85H. RA800H/AT is too coarse grained. at 3 1/2% silicon. for practical use in such applications. molybdenum and tungsten form highly volatile oxychlorides. or fluorine. RA601 may be useful. 10-4 .Selecting The Alloy—atmosphere. 11-1 . A typical plate might have a Rockwell B hardness of 84. Shear capacity. The ferritic grade RA446 does not form well at room temperature. In the 1200 to 1600°F (650-870°C). then cooling quickly with an air blast. It could be returned to RB 84 by heating to 1950°F (1065°C) and holding at this temperature for five minutes. There are some rules to know. On our shear rated 3/8” (9. than mild steel. for example. Bending and Forming Austenitic heat resisting alloys should almost always be bent cold. These alloys always harden on deformation and cannot be worked beyond a limit without rupture.7 mm) alloy plate. A given size will have limits on hardness. After work hardening. Heating without adequate temperature control is dangerous because of the narrow working range and the possibility of over or under heating. rated 3/4” (19 mm) mild steel. and reduction of area. that had been formed into a 4” (100 mm) tube might have had its hardness raised from the original Rockwell B 84 up to RB 96. the mass. Every lot of RA material is checked for these properties.35 mm) and thicker should be preheated 250-400°F (120-205°C) for any bending or forming. Shearing In the first place. Extremely severe forming may require annealing between operations. but before rupturing. both 18-8 stainless and the nickel heat resisting grades will tear or rupture in forming.8 mm) plate. for example. close tolerance surface. we regularly shear 1/4” (6. the alloys will take a lot of deformation without rupture. and the hardness. Failure to preheat may result in some plates cracking apart. and elongation of 35% and a reduction of area of 60%. the material can be restored to its original mechanical properties by annealing. range. There probably would be little reason for annealing this shape. or red heat. will handle 1/2” (12. Good shearing practice cuts about 20% of the metal and fractures the remaining 80%.5 mm) mild steel. It will take more power to form these alloys than it takes to form mild steel. Our stock materials have all been scientifically annealed. unless it was to be formed again. but for the most part designing and fabricating alloys is using common sense based on the properties of the alloys and what you expect them to accomplish. and their tensile strengths a lot higher. while others may be formed successfully. and the mill certifications of the material delivered to you are kept on file for ten years at Rolled Alloys. A piece of 3/16” (4. The hydraulic shear.35 mm) heat resisting alloy. but because of good ductility. and it is well to know the product you are working with to get the most out of it. The process varies with the alloy. and it were required to be soft to permit further cold work. has to be about 50% greater. elongation. the yield strengths of heat resisting alloys in the annealed condition are a little higher. Plates 1/4” (6. which produce a smooth.CUTTING AND FORMING Mild steel and heat resisting alloys do handle differently. Records on your order are kept by RA for six years. Heavier thickness plate is best cut by abrasive wheels. After RA333.Bending and Forming. therefore. RA600 is somewhat softer and weaker. The work hardened surface of a sheared or punched edge limits the amount of forming possible before cracking. RA 602 CA. A thermal expansion of some 3/16” per lineal foot (16 mm per meter) is going to occur between room temperature and the average service temperature. so it should be pointed in the right direction. may be accomplished by heating for one hour per inch (25 mm) of thickness to 1800°F (982°C). which. A generous radius is better for keeping the metal solid in service as well as during forming. minimizing the thermal stresses created by heating and cooling.7 mm) RA333 plate. It is far better to avoid a design that makes use of minimum radii. and the metal is going to move. This in itself is seldom detrimental. With a ground or bandsawn edge. As a minimum precaution. can be hardened only by cold working. Removing the shear burr permitted a 90° bend with some cracks. the shear burr or drag should be ground off. the plate cracked after only a 40° bend. continued These solid solution strengthened materials. the work hardened metal must be removed from the edge to be formed. and furnace cooling until black. The austenitic alloys will take a bend of 180° with a minimum inside radius equal to twice the thickness of the material. For extreme bends or the harder alloys it is better to bend across the grain. then air cooling. They will sometimes accept a bend flat on themselves. RA309 and RA310 are a little weaker. but they are not guaranteed to do so. The photo on page 80 shows the effect of edge condition on formability of 1/2” (12. rather than having the grain parallel to the bending axis. The resulting stresses are great. and softened by annealing. in the case of RA330. Occasionally tooling for aerospace requires to be stress relieved after rough machining. likewise they are slightly tougher to work. with no cracking. The fabricator must perform bends with small radii and his own risk and be prepared to weld cracks that may develop. nearly flat on itself. If severe forming is anticipated. The ferritic RA446 is less ductile and requires preheating before bending. 11-2 . The first sign of overstretching is an orange peel appearance. but the fracture soon to follow with further forming is incurable except by welding. Its high nickel makes it “gummier” than alloys with more iron. by a slight margin RA 353 MA. With an as-sheared edge. material from the same plate was bent 180°. because it gives the structure freedom to expand and contract. and RA 253 MA are the strongest metals of the group in most temperature ranges. 7 Scale RA333 1/2 inch (12. Bent 180° flat on itself. Left . Middle . formed with different edge preparations.Sheared edge ground.Shear burr removed. Bend 90° before cracking.As-sheared. Right. Cracked at 40° bend angle.About 0.7 mm) plate. burr up. 11-3 . no cracks. None of the heat resistant alloys will deep draw as well as 304 stainless. as results will be different. Dies for drawing the heat resistant alloys ought not be proofed with 304. work hardening. RA330 spins rather well.SPINNING AND DEEP DRAWING Spinning and deep drawing can be accomplished by taking into consideration the physical properties. roughly comparable to 305 stainless. 11-4 . Illustrated below is an 11 gage RA 602 CA spun half for a radiant tube return bend. and annealing. Don’t trade dollars in machine time for pennies in tool cost. Inc. Remember— cutting edges. Speed Surface ft/min 30-45 40-60 45-60 50-65 65 65 70 70 75 75 75 75 60 100 Speed as a % of B1112 18-27 25-35 28-35 30-40 40 40 42 42 45 45 45 45 36 60 Material AISI B112 René 41 25 (L-605) 188 N-155 TM WASPALOY 718 625 RA X ® RA333 A-286 601 RA800H/AT Ti 6Al-4V sol’n annealed aged RA330 and RA333 are registered trademarks of Rolled Alloys 253 MA and 353 MA are registered trademarks of Outokumpu René 41 is a registered trademark of Teledyne Industries. with chips that are stringy and tough. Do not use fluids containing chlorine or other halogens (fluorine. in order to avoid risk of corrosion problems. Both workpiece and tool should be held rigidly. Machine tools should be rigid and used to no more than 75% of their rated capacity. Make sure that tools are always sharp. Sulfur-chlorinated petroleum oil lubricants are suggested for all alloys but titanium. Rigidity is particularly important when machining titanium. particularly throw-away inserts. Slow speeds are generally required with heavy cuts. speeding up tool wear and failure. higher speeds are used with carbide tooling. Such lubricants may be thinned with paraffin oil for finish cuts at higher speeds. The metal is “gummy”. Use an air jet directed on the tool when dry cutting. WASPALOY is a trademark of United Technologies Corp. The following speeds are for single point turning operations using high speed steel tools. as titanium has a much lower modulus of elasticity than either steel or nickel alloys. Speed Surface ft/min 165 12 15 15 20 20 20-40 20 20 20-25 30 25-36 25-35 30-40 15-45 Speed as a % of B1112 100 7 9 9 12 12 12-24 12 12 12-15 18 15-21 15-21 18-30 8-27 Material RA330 ® RA 353 MA ® RA 253 MA RA2205 RA20 ® AL-6XN RA309 RA310 304 321 RA446 ® 17-4PH sol’n treated aged H1025 303 ® Feed rate should be high enough to ensure that the tool cutting edge is getting under the previous cut. to significantly increase tool life. 11-5 . The tool should not ride on the work piece as this will work harden the material and result in early tool dulling or breakage. thus avoiding word-hardened zones. Change to sharpened tools at regular intervals rather than out of necessity. tool overhang should be minimized. Lubricants or cutting fluids for titanium should be carefully selected. are expendable. 17-4PH is a registered trademark of AK Steel Corp. This information is provided as a guide to relative machinability. Slender work pieces of titanium may deflect under tool pressures causing chatter. Titanium chips in particular tend to gall and weld to the tool cutting edges.MACHINING The alloys described here work harden rapidly during machining and require more power to cut than do the plain carbon steels. tool rubbing and tolerance problems. bromine or iodine). FORGING Hot forging should be used only if cold pressing cannot do the job. We know the materials are forgeable, because they all came from large cast ingots; but the working ranges are narrow, and close control of temperature, time, heating atmosphere and reduction are all important. Heat resistant alloys must be heated throughout the section thickness. Typically, forging should begin when the metal is around 2100-2200°F (1150-1200°C), and finish before the metal cools below 1700°F (930°C). The exact temperature ranges vary from alloy to alloy. Forging either too hot or, more likely, too cold may cause cracking. Never, never attempt to bend or form any austenitic alloy in the 1100-1600°F (590-870°C) temperature range. Whether 304 stainless or nickel alloy 600, all will tear when formed at these temperatures. Unlike carbon steel, heating locally with a torch to make bending easier just doesn’t work. It is too difficult to heat nickel alloys uniformly hot enough throughout the section. 1/2” (12.7 mm) diameter RA330 scale: 1 7/8 X Torch heated to bend. Although the operator thought it was hot enough, the brown temper color in the crack is typical of about 1200°F (650°C) Torch heated to bend. The operator thought it was hot enough, but the brown temper color in the crack is typical of about 1200°F (650°C). This is right about the temperature where the austenitic alloys tear rather than bend. 11-6 WELDING Welding heat resistant alloys is covered in general in our Bulletin No. 115, and in more detail in No.’s 201 & 207 for RA330, 202 for RA 253 MA, 209 for RA 353 MA, with Bulletin 120 covering RA333 welding products. For our corrosion resistant alloys see Bulletins 203 for AL6XN®, 1071 for RA2205, XXXX for LDX 2101, and Bulletin 205 for 20Cb-3 stainless. Heat resistant alloys are readily welded but they do require more time, and a DIFFERENT approach than stainless, or carbon steel. A few important rules: 1. Make reinforced, stringer beads. Do not weave. Shallow fillet welds or broad, flat weld beads tend to crack down the center as they solidify. Cover or fill in craters, to prevent them from cracking. 2. Keep heat input low. Do not ever preheat, except to dry moisture off of the metal. Keep the temperature of the metal between weld passes low, below 212°F (100°C). 3. For RA330 specifically, use RA330-04 or RA330-80-15 weld fillers. Do not use AWS E330 weld wire, as it will be crack sensitive. Absolutely do not try to weld RA330 with stainless rods such as E308, E309, or E310 as they will crack. E312 electrodes, in particular, are often sold under various tradenames for general shop repair welding and dissimilar metal welds. However, E312 weldments are not suited for high temperature service. They embrittle severely with exposure above 600°F (1100°C). At red heat E312 welds are very weak, as well as brittle. 12-1 4. Make full penetration weld joints. Incompletely welded areas will open up as cracks during normal heat treat thermal cycles. Incompletely penetrated weld joints are the most common cause of weld failures in service. Weld joints in fans, in particular, must be fully penetrated. Let us back up a bit, and first describe some of the differences between welding carbon steels, and welding either stainless or nickel alloys. Then, we will cover the important differences between stainless (under 20% nickel) and the higher nickel alloys. CARBON STEEL VERSUS STAINLESS Some important differences between welding the carbon or low alloy structural steels and the austenitic stainless and nickel alloys include: A. Surface Preparation B. Shielding Gases C. Cold cracking vs Hot Cracking D. Distortion E. Penetration F. Fabrication Time. A. Surface Preparation When fabricating carbon steels it is common practice to weld right over scale (a so-called “mill finish” is a layer of blue-black oxide, or scale, on the metal surface), red rust and even paint. The weld fillers normally contain sufficient deoxidizing agents, such as manganese and silicon, to reduce these surface iron oxides back to metallic iron. The resultant Mn-Si slag floats to the weld surface. Iron oxide, or “scale”, melts at a lower temperature, 2500°F (1371°C)1, than does the steel itself. One can see this in a steel mill when a large ingot is removed from the soaking pit for forging—the molten scale literally drips off of the white hot steel. Stainless steel, by contrast must be clean and free of any black scale from hot rolling, forging or annealing operations. Of course, stainless normally comes from the mill with a white or bright finish. A few users of heat resistant alloys, though, do prefer “black plate”, that is, plate with the mill hot rolling scale intact. This scale is thought to provide additional environmental protection at red heat. 12-2 WELDING, Surface Preparation, continued Stainless steel melts at a lower temperature than does its chromium oxide scale, and the stainless weld filler chemistry is not capable of reducing this scale back to metallic chromium. As a result, with gas shielded processes it is difficult to get the weld bead to even “wet”, or stick to, a scaled piece of stainless. With SMAW a weld of sorts can be made, as the coating fluxes away most of the scale. The need to clean or grind down to bright metal is more likely to cause trouble when stainless is being joined to carbon steel. That is because in this dissimilar metal joint it is necessary to grind that carbon steel to bright metal, on both sides of the joint, free of all rust, such as 400 alloy (Monel®. are alloy 182 covered electrode. will stabilize the arc (prevent arc wander). either stainless or nickel alloy. the appropriate weld fillers for this particular joint. A very small amount of CO2. One exception to this high CO2 prohibition is when using flux cored wire. When 75% argon 25% helium is used for GMAW a true arc transfer cannot be obtained. Helium provides a hotter arc. and weld metal A. Some of these cored wires are specifically formulated to run best with 75%Ar 25%CO2. E309 electrodes are commonly used but may leave a hard layer on the steel side. For this reason it is necessary to clean these alloys thoroughly of all trades of grease and oil before welding. B. ERNiCrFe-5. which may crack. Weldability is greatly improved by adding from 10 to 20% helium. Short-circuiting arc welding generally requires the 75%Ar 25%He mix. to minimize the hard martensitic layer on the steel side. Metallic zinc paint is a common way to protect structural steel from corrosion. . but a 90%He 7 1/2%Ar 2 1/2%CO2 “tri-mix” is commonly used. 75% argon 25% CO2 (carbon dioxide) or 100% CO2. Both stainless and high nickel alloys which are designed for corrosion resistance are produced to very low carbon contents. Even a small amount of that zinc paint overspray on stainless will cause the stainless to crack badly when welded. . far too oxidizing for use with stainless or nickel alloys. clouds of red smoke are coming off when I weld your 310. Any higher carbon will reduce the metal’s corrosion resistance. or commercially pure nickel 200/201. Rather. are sensitive to weld cracking from the sulphur in oil. less than 0. Shielding gases. grease and paint.01% carbon. ENiCrFe-2 covered electrodes are also used. heavy spatter. . about 1%. These are suitable with carbon or low alloy steel welding wire but far. or alloy 82 bare wire. . This helps burn away the stable chromium oxide film which does impair weldability of stainless and chromium-nickel alloys. MIG) carbon steel the shielding gases are usually 95% argon 5% oxygen. Incidentally. Also the very high nickel alloys. . the arc transfer somewhat resembles the globular transfer mode. There are shops where this is preferred.03% and sometimes less than 0. Consider completing all stainless welding before painting the structural steel in the area. 12-3 B. Shielding Gases For gas metal arc welding (a.a.” and then learn that the shielding gas used was 75%Ar 25%CO2. .mill scale. . A fine gas for carbon steel but not for stainless. ENiCrFe-3. UNS N04400). It is not unknown to hear the complaint “. Alloy 62 bare wire. continued Stainless and nickel alloys are often GMAW spray-arc welded with 100% argon. ERNiCr-3.k. Cold Cracking versus Hot Cracking Carbon steel weldments may harden. chromium. as it permits more opportunity for hot tearing to occur. High nickel alloys are susceptible to cracking in restrained joints. which slows down the cooling rate. For this reason preheating.3 12-4 Stainless steel has poor thermal conductivity. D. or heavy sections. are more likely when the steel contains over 0. to retard the cooling rate of the weld and avoid martensite formation. beyond what may be necessary to dry it. Welds should be sequenced about the neutral axis of the fabrication to balance welding stresses. is also applied to some steels. The combination of these two factors means that stainless or nickel alloy fabrications distort significantly more than similar designs in carbon steel.25% carbon. Back step welding is also helpful. Hydrogen pickup from moisture in the air causes underbead cracking in steels that harden as they cool from welding. nor to post weld heat treat it. and may damage the corrosion resistance of some grades. molybdenum. can be positively harmful. as they cool from welding. Austenitic stainless and nickel alloys do NOT harden no matter how fast they cool from welding. This means the welding heat tends to remain concentrated. Distortion 2. and the resulting cracking. hence minimize distortion. That is. such as manganese. Stainless also expands with heat about half again as much as does carbon steel. As a matter of fact preheating stainless. the weld bead tears rather than stretching. only about one fourth that of A 36 structural steel. as the bead contracts upon solidifying. So. The faster a nickel alloy weld freezes solid. rather than spread out. not a cold crack. High hardness. or for certain applications. Alloying elements which increase hardenability. This is a hot tearing. tack welds need to be more closely spaced in stainless/nickel alloy welds. Postweld heat treatment. This hot tearing/hot cracking has nothing to do with hardness.C. more rarely by aluminum. is actually harmful. can make steels of lower carbon content also harden. To prevent such cracking the steel is usually preheated before welding. etc. Stress relief 1100-1200°F (600-650°C) as applied to carbon steel is ineffective with stainless or nickel alloys. possibly by zinc or copper. it is not necessary to preheat stainless. Stainless steel welds generally do not crack unless contaminated. and crack. or stress relief. Among other things. the less time it spends in the temperature range where it can tear. . 12-5 D. If the tacks are simply done in order from one end.Tack welds should be sequenced. Back step welding helps reduce distortion. continued . Distortion. the plate edges close up and the gap disappears. Increasing welding current will not solve the problem! Stainless.E. Penetration is even less in high nickel alloys. Penetration The arc will not penetrate a stainless nearly as deeply as it will carbon steel. so that the weld metal may be placed in the joint. maybe even three times as long. to do the stainless fabrication. Lack of weld penetration is the single most important reason why austenitic alloy weldments fail in high temperature service. maintaining low interpass temperatures and even machining add up to more time spent fabricating stainless than carbon steel. A shop experienced with stainless may require one and a half times as long to complete the same fabrication in stainless. 12-6 WELDING AUSTENITIC ALLOYS . single or double beveled. joints must be more open. Fabrication Time Cleanliness. with a root gap. F. distortion control measures. and especially nickel alloy. A good carbon steel shop encountering stainless or nickel alloys for the first time can easily spend twice as long. as in carbon steel. as it would the same job in carbon steel. continued . is harmful whereas 2 to 4% columbium is quite beneficial in many nickel base weld fillers. Columbium at the 0. In higher nickel grades. molybdenum and carbon serve in one way or another to reduce the austenitic propensity for weld hot cracking. 2% Mo contributes to 316 as being the most weldable of the stainless steels. The one welding electrode specifically using very high carbon to promote sound welds is the heat resistant grade RA330-80-15 (UNS W88338). This ferrite acts to nullify the effects of the elements responsible for hot cracking in the Ni-Cr-Fe austenitics. to about 1/10%.5% level. Molybdenum isn’t necessarily a common addition specifically for weldability but it does enhance the properties of RA333-70-16 covered electrodes. 12-7 Welding austenitic alloys. Most ferrite containing (stainless) weld fillers are useless with nickel alloy base metal. In these stainless grades the weld metal composition is adjusted. which require high purity weld fillers. and is reported as a Ferrite Number.The fundamental problem to be overcome in welding austenitic nickel bearing alloys is the tendency of the weld to hot tear upon solidification. is an important one to remember. Certain alloy additions such as manganese. Simply beginning with low phosphorus alloying elements. Foremost among these is to use high purity raw materials in the manufacture of weld fillers. and reducing the amounts of harmful sulfur and silicon in the weld metal improves its ability to make a sound weld. as in 347 stainless. may be not quite so crack resistant when contaminated by phosphorus from 316L. cast alloy 20 (CN-7M). such as ER320LR. The amount of ferrite in the weld may be measured magnetically. must be kept below 0. usually by slightly higher chromium and reduced nickel. These elements are chiefly phosphorus. in particular. to form a small amount of ferrite upon solidification. Maintaining a weld deposit chemistry of some 0.015% in the weld wire itself. sulphur. This matter is readily handled in alloys of up to about 15% or so nickel. it is metallurgically not possible to form any measurable amount of ferrite. as dilution of the weld bead with nickel from the base metal eliminates this ferrite. Therefor other means of minimizing hot cracking must be used. With respect to welding there are some distinctions between those alloys intended for use above 1000°F (540°C). FN. which depend upon ferrite to ensure weldability. columbium (niobium). and those meant for aqueous corrosion service. silicon and boron. Manganese ranges from about 2% in AWS E310-15 covered electrodes to 5% in RA330-04 wire & electrodes and 8% in alloy 182 (ENiCrFe-3) covered electrodes. Phosphorus. Likewise a high purity nickel alloy weld filler.85% carbon permits this electrode to make sound welds in either wrought or cast 35% Ni high silicon heat resistant alloys. High molybdenum is responsible for the popularity of the various “C type” electrodes (15Cr 15Mo balance Ni) in repair welding. The distinction between the lower nickel stainless grades. or carbon steel base metal. Carbon is slightly elevated in 310 weld fillers. and the high nickel alloys. about 20% nickel and over. 04 .4% carbon. The cast grades are usually welded with high carbon. RA310.One difference is in carbon content. and typically much lower. In the past it was possible for 310S (UNS N031008) base metal to contain as much as 1. It is sometimes overlooked in heat resistant alloy fabrication and even less often considered in repair of high temperature alloy fixturing. Phosphorus in the weld wire may still be an issue with some lots of ER310 welding wire. in practice all 310 varieties now melted in North America have less than 0. Corrosion resistant grades are generally limited to 0. For both classes of alloy. RA 253 MA. grow. In high temperature carburizing service crevices are where carbon (soot) can deposit. RA309.75% maximum. 310 welds have a reputation for fissuring. In both classes of material.03%P max.015%P max. fully austenitic electrodes of similar or higher nickel. at the 0. and pry the joint apart like tree roots in rock. All save RA310 and the cast alloys depend upon some level of ferrite in the weld bead to prevent solidification defects. incompletely penetrated welds and open crevices must be avoided in fabrication design. having neither ferrite nor any particular alloy addition for weldability. With the advent of 310H (UNS S31009) ASTM limited silicon to 0. while RA330HC belt pin stock and the cast heat resistant alloys have a nominal 0. To avoid melting two chemistries of 310. Heats on the high side of silicon and phosphorus were definitely a problem to weld (Rolled Alloys traditionally limited silicon in RA310 to 0. RA85H. Heat resistant alloys by contrast typically require 0. weldability alone is not the entire issue. They may also have small additions of columbium or titanium.75% max). Restriction of carbon. or tying it up with a stabilizing element (Cb or Ti) is necessary to prevent heat affected zone (HAZ) intergranular corrosion and stress corrosion cracking (SCC) due to carbide precipitation.50% silicon in the ASTM/ASME specifications. For 310 welding wire to be of practical use the phosphorus must be kept under 0. Serious aqueous corrosion can begin in crevices. and the cast heat resistant alloys HH and HK. 12-8 ALLOYS OVER 20% NICKEL . Not surprisingly.0. RA310 stands in an odd position between the stainless and the nickel alloys. RA 602 CA is even higher. Usually this point is addressed in fabricating corrosion resistant alloys.75% Si.010% carbon for good hot strength. Heat resistant alloys with 20% or less nickel include 304H.2% level. 321. ALLOYS UNDER 20% NICKEL Most austenitic grades containing less than 20% nickel are joined with weld fillers that utilize perhaps 4-12 FN (Ferrite Number) to ensure weldability. This is far too high. The current AWS limit for ER310 wire is 0. In the absence of a wet corrosive environment a little intergranular carbide precipitation is not particularly harmful to a heat resistant alloy.03% carbon maximum. The weld filler must also have the mechanical and environmental resistance required for its intended service. formerly known as MIG (Metal Inert Gas). but are not limited to. Practically speaking it won’t work for GMAW (MIG) welding. Cleanliness includes NOT using oxygen additions to the GMAW shielding gases for nickel alloys. and Nimonic 75. L605. The cobalt alloys N155. The dial on a Constant Current machine reads in amperes. The least volume of work is done by Gas Tungsten Arc Welding (GTAW). Welding technique and attention to cleanliness. sulphur. 601. Haynes alloys HR-120. The most common. RA333. Other nickel weld fillers contain manganese. RA 353 MA. 309. particularly cross wire resistance welding. Titanium may be added for deoxidation. modified only by restrictions on phosphorus. Constant Potential (voltage) machines are used for GMAW (MIG) welding. 188. or just plain “stick” welding. The dial regulates voltage. and the current is regulated by this dial. with covered electrodes. columbium or molybdenum to improve resistance to fissuring and hot cracking. RA800H/AT. Stainless steel weld metal (308. the additional nickel melted into the weld bead makes it fully austenitic. 556. Techniques include reinforced. and HR-160 may be treated in similar fashion with appropriate weld fillers. 803. Without ferrite. in North America. formerly called TIG (Tungsten Inert Gas) and originally trade named Heliarc. convex stringer beads and low interpass temperature. and is marked with numbers in the 20-40 range. 12-9 Gas Metal Arc Welding . 600. Such chemistry modifications are rarely as effective as is the use of ferrite in the lower nickel stainless weld fillers. with no ferrite at all. There are two basic types of welding machines. Constant Current. is often used in heat resistant alloy fabrication. and Constant Potential. In addition resistance welding. But when a stainless rod is deposited on a high nickel base metal. WELDING PROCESSES Five different arc welding processes are generally used with heat resisting alloys.Heat resistant alloys in this category include. 230 and 214. Many nickel alloys are joined with matching composition weld fillers. A constant current machine is used for GTAW (TIG) and SMAW (stick) welding. is Gas Metal Arc Welding (GMAW).) depends upon a small amount of deposited ferrite to ensure a sound weld. It is worth repeating here that high nickel alloys can not reliably be welded using stainless steel weld fillers. alloy X (UNS N06002). They don’t work well with covered electrodes (SMAW). then. Two other methods are Plasma Arc Welding (PAW) and Submerged Arc Welding (SAW). the stainless weld bead may crack. become increasingly important to ensure the soundness of fully austenitic welds. Next in popularity is Shielded Metal Arc Welding (SMAW). 617. high carbon. RA 602 CA. etc. using spooled bare wire filler. ilicon and boron. RA330. CO2 above 5% adds carbon to the low carbon stainless grades. typically on 25-30 pound (11-14 kg) spools. and argon shielding is used for the spray-arc transfer mode.035” (0. appropriately. While the manufacturer is often blamed for feeding problems. as for welding long tubes. do not use oxygen additions to the gas when welding nickel alloys and NEVER use 75% argon 25% carbon dioxide for GMAW welding either stainless or nickel alloys. Although very small amounts of CO2 may be used in argon. At lower current. One suggested mixture is 90%Ar 5%He 5%N2. Current is always Electrode Positive (DCRP. though 0.89 mm) and 0. characterized by a noisy arc and low heat input. The care with which the filler metal is wound on the spool affects how smoothly the wire feeds. Choice of shielding gas is important. there may be feeding problems. The most common size is 0. It can be automated. First.89 mm) wire. Wire is fed continuously through a hollow cable to the welding gun. For short-circuiting arc transfer 75% Ar 25% He is used. through the weld torch and around the wire. at above 15% CO2 in argon the arc transfer mode is no longer spray. For spray-arc welding the most common gas is 100% argon. This is known as short-arc. roughly 100 amperes for 0. about 190-220 amperes for 0. A mix of 75%Ar 25%He is also used. where it makes electrical contact. continued . as is the commonly available 90%He 7 1/2% Ar 2 1/2% CO2. 12-10 WELDING. gas metal arc. The metal is protected from oxidation by a continuous flow of inert shielding gas. more often than not proper attention to machine set up will ensure freedom from “bird’s nests”.14 mm) wire. Because the welding wire must be pushed through a cable. with 75% argon 25% helium shielding. respectively. This shuts down the operation until the welder clears it. Welding with relatively high current.045” (1. Molten weld filler transfers as either a spray of fine drops. RA 602 CA requires an addition of nitrogen to the shielding gas. to prevent hot cracking. or as larger globs.0625” (1. the molten weld metal transfers as large.59 mm) are also stocked. The result can be a tangle of wire known. welding. ranging from 10 to 15 foot (3 to 4 1/2m) long. as a “bird’s nest”. The GMAW process is fast and well suited to high volume work. or short-circuiting arc.045” (1.035” (0. molten weld metal crosses the arc to the work as a fine spray. the weld filler metal is bare wire. 10 to 20% helium and a very small amount of CO2 may be added to the argon. In this mode. The patented gas developed in Germany specifically for GMAW RA 602 CA is. Oxygen above 2% starts burning out major alloying elements. direct current reverse polarity). but rather a hot globular transfer with a great deal of spatter.In this process. To improve bead contour and reduce arc wander. although the transfer mode will then not quite be a true spray-arc. individual drops.14 mm). usually argon. The arc between weld wire and workpiece melts the metal. . ER308 or ER316L). and the arc is “softer”. continued . As a result there is greater overall productivity with flux cored wire. there is not enough pressure. Many heat resistant alloy weld wires are much higher in strength than stainless wire (e.045 inch (1. A heavy duty contact tip is preferred instead of a standard contact tip. Form a circle not less than 15 in. Adjust the pressure until you just can not hold the wire. and will give more room for the wire to flex.9 for stainless. V groove rolls are used with solid stainless/nickel alloy wire.045”/1. and should be left in its sealed plastic bag until ready to use.g. Both AWS A5. or bird’s nest. occurs the first thing we suggest is to examine machine set-up.3m) in diameter 2. 12-11 Flux Cored Arc Welding. for example. and can handle more heat. use a 1/16 inch (1. The following discussion is based on information from Ron Stahura. inlet guide and outlet guide all clean? Incidentally. will do the following: 1. Use minimal pressure on the feed rolls—more is not better.7mm) helix. (25mm) at any location” Our RA 253 MA wire. the more tension in the feed rolls. For 0. Inc. with flux and metal alloy powders inside. U groove for copper or aluminum and serrated rolls for flux cored wire.14mm) wire. Are the feed rolls.14mm conduit. A rule of thumb is to hold the wire between the fingers as it enters the feed rolls. and the wire may swell into the tip and jam it. typically has 36 to 42 inch (915 to 1070mm) cast and 1/2 inch (12. When tangling. The heavy duty tip simply has more copper. when cut from the spool and laid unrestrained on a flat surface. Because this wire contains its own flux. even with nickel alloys! The advantage of flux cored wire is that welding is easier than when solid wire is used. then give it another half turn beyond that.14 for nickel alloy wire require cast and helix of wire on 12 inch (300mm) spools to be4 “such that a specimen long enough to produce a single loop.6mm) conduit. instead of a 0. gas shielding may be 75% Argon 25% CO2. When spray-arc welding the tip runs hot. Flux Cored Arc Welding FCAW is similar to GMAW except that the wire used is tubular. and therefore require more care to feed smoothly.Smooth feeding depends on the cast and helix of the spooled wire. AvestaPolarit Welding Products. The oversize conduit won’t hurt. and A5. If you can hold it back. (380mm) in diameter and not more than 50 in. Flux cored wire is sensitive to moisture pick-up. (1. Does this problem occur on more than one machine? How long is the cable—the longer the cable. Rise above the flat surface no more than 1 in. Shielded Metal Arc Welding Covered welding electrodes consist of an alloy core wire and a flux coating. and controls the bead shape Adds more alloying elements. a 35%Ni 15%Cr AWS E330 core wire is used. During welding. but not always. such as manganese. Provides a gas that shields the metal crossing the arc from oxidation Produces a molten slag which further protects the molten weld bead from oxidation. 3. continued . these additions melt in and adjust the chemistry of the weld bead to the specified composition. The core wire is usually. various alloy additions are made in the coating itself. affects out-of-position weldability. manganese and chromium required in the weld deposit are added to the flux coating. carbon or chromium Promotes electrical conductivity across the arc and helps to stabilize the arc. so that the weld bead chemistry will not be the same as the chemistry of the core wire itself. RA333-70-16 electrodes do use RA333 core wire. however. 4. In the case of RA330-80-15 or -16. about the same composition as the base metal. The additional carbon. Often. and RA330-04-15 covered electrodes. 2. The electrode coating does four basic jobs: 1. important when alternating current (AC) is used 12-12 Shielded Metal Arc Welding. but not on AC. “-16”. RA333-70-16 and RA330-80-16 both have AC/DC coatings. Otherwise the slag destroys the protective chromium oxide scale on the metal. not unless that AC current is turned up so high that the whole electrode glows red and the coating spalls off. it will indeed run on DC current. After welding. They have compounds of potassium and titanium in the coating which stabilize the arc. That is. or Electrode Positive). That is. Weld repair with RA333-70-16 covered electrodes is best accomplished using direct current. the electrode simply won’t run. In any reducing atmosphere the fluoride flux will scavenge enough sulphur from the atmosphere5. This means it will not extinguish itself as the current reverses direction (and goes to zero) 60 times a second on normal 60 cycle current (50 cycle in Europe). RA330-04-15 and RA330-80-15 both have DC (Direct Current) lime coatings. reverse polarity (DCRP). electrons are emitted from the work and go toward the electrode. Well. 12-13 Gas Tungsten Arc Welding . If the welder attempts to use a DC electrode with an AC (alternating current) setting on the welding machine.There are three types of coatings used on Rolled Alloys electrodes. but every couple of years someone complains that RA330-0415 “won’t run”. In a carburizing atmosphere small traces of slag will cause local carburization to proceed rapidly. The slag from the electrode coating is extremely corrosive at elevated temperatures. to cause sulphidation attack of the base metal. DC. AC/DC electrodes may also be used with direct current. This is very basic knowledge. designated by “-15”. the electrode is positive and the workpiece is the negative electrical pole of the circuit. He will not be able to keep the arc going. The AC/DC titania coated electrodes are designated -16. which also operates on alternating current. or “-17” after the alloy number. even a very low-sulphur atmosphere. RA 253 MA-17 is currently the only electrode we stock with this coating. Coating type is DC lime-type coatings are designated -15. prior to using the fabrication at elevated temperature. In fact. This means that these electrodes can ONLY be used with direct current. they run better when using DC. as well as on direct current. all traces of this slag must be removed. These electrodes may be used with alternating current (AC). Under oxidizing conditions this simply results in excessive loss of metal to oxidation. The more recent coating designation is -17. Normally the current is reverse polarity (DCRP. 12-14 Gas Tungsten Arc Welding. but it is relatively slow. The arc between the tungsten electrode and the work is what melts the workpiece. that is. and this process makes the best quality weld. Argon is used for manual welding. For faster welding speed helium is added to the argon shielding gas.In GTAW. A helium addition may be used for automated welding. Remember--the core wire of RA330-04-15 covered electrodes is AWS ER330. This is to resist hot cracking. and was originally patented as Heliarc ®. In automatic GTAW the wire is fed into the joint from a spool of wire. just like GMAW wire. where a hotter arc is preferred. For aluminum welding the electrode is pure tungsten. The weld filler metal is fed by hand into the molten puddle. In the case of RA 602 CA. This process used to be called TIG (Tungsten Inert Gas). No oxygen or carbon dioxide can be tolerated or the tungsten electrode would literally burn up. GTAW is often used to make the root pass in pipes or whenever the joint can only be made from one side. It may be automated for volume production. Do not do this with RA330-04-15 or the RA330-80 electrodes. The argon shielding gas. Shielding gas must be pure argon or helium. in 10 pound (4 1/2 kg) tubes. is brought in through a nozzle or gas cup which is around the electrode. tungsten metal with 1 or 2% thorium oxide added to improve the emissivity of electrons. Welders sometimes knock the coating off an electrode and use the core wire as GTAW filler. which protects both the hot tungsten electrode and the molten weld puddle. direct current straight polarity. The welder has the most control when using gas tungsten arc. a name still used occasionally. and not RA330-04 chemistry. without the benefit of the alloying elements which were in the coating. it is necessary to add 2 to 2 ½% nitrogen to the argon shielding. continued . Rare earth oxides are also used. both of which are faster. GTAW weld wire for heat & corrosion resistant alloys is sold as 36” (914 mm) straight lengths of bare wire. The electrode is usually thoriated tungsten. the arc is struck between the workpiece and a tungsten electrode. up to 4% nitrogen is added. The work is electrically positive and the tungsten electrode is the negative electrical pole. This AWS ER330 will make a crack-sensitive weld. which remains unmelted. such as AL-6XN® or RA2205. For both stainless and nickel alloys the current used is DCSP. The rest of the weld may be built up with either GMAW or SMAW. used with AC (alternating current). For some corrosion alloys. This may cause some erosion of the tungsten electrode but improves weld bead properties in these particular alloys. Gas cup size depends upon what diameter tungsten electrode is being used. is a potential cause of porosity. shielding gas flow rates. cup size and consider the use of a gas lens.4mm) electrode should use anywhere from a No. Minimize the arc length. A 3/32” (2. the shielding gas will be just that much more sensitive to atmospheric contamination. a wire screen which serves to reduce turbulence of the shielding gas flow. It is this turbulence which causes air to get mixed in with the argon shielding gas. no more than 1/4 to 3/8 inch (6-9. 8 (12. 8 cup (9. and has been used to weld RA330 without added filler (with GTAW this would be extremely difficult). Gas Metal Arc (MIG) Gas Tungsten Arc (TIG) Plasma Arc Welding The plasma arc torch is roughly analogous to a GTAW torch. When using a 2—4% nitrogen addition for welding the corrosion alloys.5mm). Consider using a gas lens. No. An 1/8 inch (3. Look at work to tip distance. It generates intense heat in a very narrow zone. 12-15 Submerged Arc Welding .2mm) electrode requires a No.7mm) cup. The longer the arc length. 7 (11mm) being about right.5-12. as from strong winds or too long an arc length.7mm cup dia).Atmospheric contamination. the greater the opportunity to entrain air into the shielding gas. PAW is an excellent welding process for heat resisting alloys. 6 to No. and electrode tip contours may all need to be modified accordingly.14 mm) dia. Absolutely do not use acid fluxes or any flux meant for stainless steel.045” (1. and markedly from those used for carbon steel. Wire. a hopper feeds granulated flux into the arc to shield the arc and molten weld puddle. welding current and time. Heat resistance alloys may have twice the yield strength of stainless and considerably higher electrical resistivity. larger sizes such as 1/16 or 3/32” (1. but this heat must be kept to a minimum to avoid centerbead cracking in fully austenitic alloys. Electrode force. such as Avesta Flux 805 or Böhler-Thyssen’s RECORD NiCrW. continued . SAW is a process naturally inclined to high heat input. Instead of shielding gas.6 or 2.4 mm) are generally preferred.Submerged arc uses a spool of weld wire. While it is possible to use 0. For this reason 1/8” (3. Resistance Welding6 Spot and seam welding parameters for heat resistant alloys will differ from those used with stainlesses such as 304L or 316L. For nickel alloys such as RA330 a strongly basic flux must be used. 12-16 Resistance Welding.2 mm) wire is not suggested for submerged arc welding the nickel heat resistant alloys. Heat input must be as low as possible. much like GMAW. 8901. U. Cambridge University Press. American Welding Society. Average dome radius may be 3 inch (76 mm) for material up to 11 gage (3mm).14/A5. Resistance Welder Manufacturers’ Association. as: Métallurgie du soudage des aciers inoxydables et 127esistant à chaud. Avesta Welding AB.A. 12-17 Suggested Weld Fillers . ISBN 0-87170-262American Society for Metals. ISBN 0 521 20431 3. References 1.S.6 to 3mm) a 5 to 8 inch (127 to 203mm) radius dome is sometimes preferred. Paris. SANDVIK Welding Handbook. Likewise cool time should be sufficient that welded areas are not remelted. or a sound weld cannot be made. ISBN 0-87171-543-0. Miami. Corrosion of Nickel-Chromium-Iron Alloys by Welding Slags. by Dunod. Inf. The metal must be clean and free of all grease. Specification for Nickel and Nickel-Alloy Bare Welding Electrodes and Rods. Massalski.S. The best general reference we know for welding this class of materials is: R. Sweden 1989 3. 1989 th 6. Volume 1. J. Pease.34 E. First published. R. Berthold Lundqvist. Sandvik publication 0. Philadelphia. to avoid porosity and cracking. Sweden June. Florida. ANSI/AWS A5. 1900 Arch Street. Welding Journal Research Supplement. 1956 Resistance Welding Manual. U. Avesta handbook for the welding of stainless steel.J.A. ISBN 0-09624382-0-0. For a larger nugget size in material 16 to 11 gage (1. 1986 2. Ohio. In seam welding heat time should be adjusted to ensure that the wheel maintains pressure until the weld nugget has solidified. 4 Edition. de Cadenet. 5. Metals Park. 1975. Sandvik AB. Sandviken. Binary Alloy Phase Diagrams. Editor-in-Chief. Welding Metallurgy of Stainless and Heat-resisting Steels. in French. Thaddeus B. Pennsylvania 19103 U.S.. Castro & J. S-74401 Avesta. G. 1977 4. September.14M-97.A. 1968.A restricted-dome electrode is suggested for spot welding. RA 353 MA. The X weld bead may be subject to catastrophic oxidation at the higher service temperatures where RA333 is commonly used. RA333-70-16 ERNiCrCoMo-1 RA330-04. RA82 RA333-70-16 ERNiCrWMo-1 ERNiCrCoMo-1 (lacks oxidation resistance) -RA330-04 -RA333. RA333. It is better not to use alloy X (ERNiCrMo-2. *Where sulphidation is an issue. as well as for weldability issues. RA800H/AT).. ENiCrMo-2) weld fillers on RA333 base metal. do not use high nickel fillers such as RA330-04 12-18 . Alternates RA333-70-16. and the welds will crack.g. Do not use—any stainless weld filler on nickel alloys (e. RA330-04-15 General: Do choose the weld filler for its performance under the expected service conditions. RA330.Base Metal bare wire RA330® RA333 RA 602 CATM RA601 RA600 RA 353 MA® RA 253 MA® RA800H/AT RA309 RA310 RA446 HK. RA601. HU RA330-04 -RA333 Preferred covered electrodes RA330-04-15 RA330-80-15 RA333-70-16 Alternates RA333® . HT. EL-NiCr25FeAlY) RA333 601 82 RA 353 MA RA 253 MA RA333 556 ER309 ER310 ER309 ER310 RA333-70-16 6225 Al 182 RA 353 MA RA 253 MA-17 RA333-70-16 -E309-16 E310-15 E309-16 E310-15 RA330-80-15 DC lime is the preferred 35% nickel rod for cast heat resistant alloys. Dilution by nickel will eliminate ferrite. ENiCrFe-2 RA330-04* RA330-04* E312-16 S 6025 6225 Al (SG-. RA600. A 617 (ERNiCrCoMo-1) lacks the oxidation resistance of RA 602 CA B The weldability of RA333 weld filler used on RA 602 CA has not yet been determined C These high nickel fillers are not suggested for sulfur bearing environments. blue-black hot rolling scale and paint must be removed before welding with any stainless or nickel alloy weld wires. Weld Filler Guidelines Considerations in selecting a filler metal for a dissimilar metal weld joint include the expected service conditions at the joint. These alloys lack the deoxidation characteristics of carbon steel weld wires. HP RA330-80-15 RA330-04 RA333-70-16 RA 353 MA RA330-80-15 617 RA333-70-16 RA333-70-16 RA330-80-15 RA333-70-16 RA330-80-15 RA330-80-15 RA330-80-15 RA333-70-16 RA333-70-16 -- RA330 182 RA800H/AT RA333 RA333 182 RA333 RA 353 MA 182 RA 353 MA RA 353 MA RA 353 MA RA 602 CA 82 182 82 182 617 RA333* RA 253 MA E309-16 RA 253 MA RA 253 MA RA333 RA600 RA601 RA309 RA310 RA446 82 182 82 182 82 182 82 182 RA333 RA333-70-16 RA333 RA333-70-16 E309-16 RA 253 MA RA 253 MA -E309-16 ER309 E309-16 E309-16 182 ER309 E309-16 E309-16 182 E310-15 E309-16 E309-16 E310-15 E310-15 Note: The carbon steel joint must be ground to bright metal. 12-19 .316) RA330-04 RA330-04 RA333 RA 253 MA RA 602 CA RA333 RA333 RA330-04 617A RA333B 617A RA333B 617A S 6025 6225 Al 617 RA333B 82 182 S 6025 6225 Al 82C 182C 82C 182C 82C 182C Cast Alloys HK. A “mill finish” is not acceptable.Dissimilar Metal Joints. relative thermal expansion coefficients of the three metals involved. and freedom from weld metal hot cracking. All rust. HT. Base Metals Carbon Steel Stainless (304. The final selection should be approved by the end user and weld procedures qualified by the fabricator. 12-20 . a high nickel alloy.BRAZING and SOLDERING Heat resistant alloys are normally assembled by welding. are commonly joined with nickel-silicon-boron braze fillers. In torch brazing the source of stress is the thermal stress caused by the local heating (which is normal practice when brazing steel). The acid chloride flux is corrosive and should be washed off after soldering. SOLDERING Copper cooling coils may be lead-tin soldered to heat resistant alloys. by contrast. Aluminum Brazing From the standpoint of the heat resistant alloy supplier. from liquid metal embrittlement. Silver Brazing Often used to join carbon and low alloy steels. Austenitic alloys are prone to crack when silver brazed. BRAZING One of the issues in brazing Ni-Cr or Ni-Cr-Fe alloys is the furnace atmosphere. Brazing is used on occasion to attach cooling coils or thermocouples. To be effective with stainless. the incoming hydrogen atmosphere should have a dew point1 –80°F ( —60°C) or lower. Technically speaking. The age hardening aerospace grades. These may be alloyed with about 2% of either silver or antimony. This atmosphere must prevent formation of any oxide film which would prevent the braze alloy from flowing. the major issue in aluminum brazing is the flux. consider stress relief annealing the assembly prior to brazing. in the presence of molten silver braze alloy will crack. Stressed austenitic alloy. has somewhat better resistance to the fluoride flux. To furnace silver braze an austenitic alloy. Residual stresses are responsible for cracking during furnace brazing. If too much flux is applied to the aluminum work pieces. such as 600. Temperatures are low enough that aluminum braze muffles are commonly made of 304 or 316L stainless. that flux may spill onto the muffle. 12-21 . Keep the flux off of the alloy fixturing. Somewhat better strength may be obtained by using a tin base solder. But the nickel alloy is unlikely to last long enough to be worth the higher cost. whether stainless or high nickel. Anything that will flux aluminum oxide will quickly eat holes through stainless. as the braze temperature is not high enough to reduce these stresses. If there is no stress on the stainless. will penetrate austenitic alloys intergranularly it is unlikely to either crack or seriously attack the metal during the brazing cycle. it will not crack. which would vaporize. One approach that has been described to us is to play the torch back and forth about 6 inches (150mm) on each side of the area to be brazed. raising the remelt temperature of the braze alloy. Successful torch silver brazing of austenitic stainless depends upon technique. It is not usually chosen to join either heat or corrosion resistant alloys. Vacuum brazing requires fillers containing neither cadmium nor zinc. The process temperature for copper brazing is usually 2050°F (1120°C). continued The lower melting silver braze alloys may require the use of flux when atmosphere brazing stainless. Even though copper.5% boron. preventing braze flow. greatly lowers the melting point. in the alloy as well as the atmosphere. The metal should be heated uniformly in the area to be brazed. One indication of nitrogen as the brazing problem is an Iridescent bluish-gray color to the base metal.025mm) of nickel electroplate. Nickel Brazing Nickel-base braze alloys are used to join age-hardening nickel base alloys for aerospace applications. Pure copper itself melts at 1981°F (1083°C). This may be coupled with rapid heating and short process time to prevent diffusion of nitrogen through the nickel plate. These temperatures will quickly anneal out residual stresses from the stainless or nickel alloy parts.001 inch (0.03% nitrogen2 can be difficult to braze. With AMS 4777 the brazing range is 1850—2150°F (1010— 1180°C). given time enough. Such treatment might include about 0. Silver braze cracking is not an issue with ferritic stainless steel. During the braze operation boron from the filler diffuses into the base metal. 12-22 . Dry hydrogen may not be sufficiently reducing to chromium oxide at brazing temperatures below 1800°F (980°C).Silver Brazing. in some alloys including up to 3. without special treatment. It is the austenitic structure that is sensitive to intergranular cracking by molten braze alloy. Alloys containing more than about 0. Addition of as much as 10% silicon. Boron can react with nitrogen. This minimizes thermal stress where the molten silver braze will contact the austenitic alloy. Copper Brazing Copper brazing is a common means of joining carbon steel assemblies. Brazing Q&A is authored by Dr.A. Hydrogen brazing requires a slightly thicker plate.com . 1993 3. American Welding Society. January 1991 Welding Journal 12-23 .001 to 0. Brazing Q&A. This column began in 1989 and continues as of this writing. in ASM Handbook Volume 6. The plating does need to be an electroplate and not electroless nickel.Nickel Brazing. 0.025mm) is sufficient. Robert L. Welding. Case Studies in High-Temperature Brazing. Dr. 2002. Dr. Nickel base braze alloys simply lower the alloy melting point. in Welding Journal. Peaslee. enough spilled braze can melt a hole through the muffle. ASM International. Maimi. .038mm).0015” (0. The braze temperature should not exceed the solution annealing temperature for the alloy in question.001” (0. This is far and above the best source for thorough. Peaslee. 2. Robert L. enough so to depress the melting point to 1610°F (877°C)3. Further Information Detailed insight into all manner of brazing issues is available from the Monthly Column “Brazing Q&A”.S. by R. There will not be another man so knowledgeable in this field during our lifetimes. 3-37—39). in-depth discussion of brazing matters is: Brazing Footprints. but of course will not be present in vacuum brazing. Michigan wcc@wallcolmonoy. that prevent braze flow. Florida U. Brazing and Soldering. Otherwise.. Peaslee invented the nickel base brazing alloys about 50 years ago. Reference 1. Peaslee invented the nickel base brazing alloys about 50 years ago. in-depth discussion of brazing problems. The absolute best source for thorough. Brazing Q&A. For vacuum brazing 0. Brazing of Stainless Steels. Peaslee. Madison Heights. An oxide coating on the alloy helps minimize this effect. continued Alloys containing aluminum and titanium require first to be electroplated with nickel. Electroless nickel contains phosphorus. Effects on Furnace Equipment Excess silver or copper braze alloys dripping onto the nickel alloy muffle or fixturing will attack that alloy intergranularly (see Copper. ©2003 Wall Colmonoy Corporation.025 to 0. Likewise spilled flux is corrosive to the fixturing. even in the best of atmospheres. L. September 2001 Welding Journal 4. of Wall Colmonoy. oxides of Al and Ti will form. Over a four-year period the Americans shipped them only one new muffle. or N2) or slightly oxidizing to the heat resistant alloy used (endothermic). Because of its high strength and oxidation resistance. 13-1 . same design. RA601—oxidation resistant. RA333—at one time the traditional first choice for copper brazing muffles. not quite as strong as either RA 602 CA or RA333 above 2000°F (1100°C). RA 353 MA—the best choice for copper brazing and for annealing stainless 1950-2100°F (1070-1150°C). probably for use as a spare. RA600 is not suited for sulfur bearing environments. RA330—the most widespread choice for muffles up into the 2100°F (1150°C) and over range. RA600—used for very high temperature iron sintering in strongly reducing or carburizing atmospheres. To minimize leaks in weld seams consider welding with RA 602 CA or RA333 or weld fillers. for maximum heat transfer. One 601 muffle regularly replaced every 6 months now last 2—3 years made of RA 353 MA. A Singapore company with 3 or 4 furnaces. RA 253 MA—used for hydrogen and/or nitrogen atmospheres.35 mm) thick. Technically performs well.APPLICATIONS Muffles Alloy Selection depends upon temperature and atmosphere. RA333 is strong enough to be used in 11 gage (3 mm) wall. Some 3/16” (4. May also suit for the bottoms of brazing muffles. but RA330 has proven more cost-effective here. sintering powdered iron 2100—2150F had been getting 8—10 month life with 601 muffles. In powdered iron sintering products from binding agents tend to carburize the muffle alloy.8 to 6. RA 602 CA—For longer life in brazing muffles operating over 2150°F (1180°C). Greater strength. rather than the commonly used 82. For brazing muffles the atmosphere is either reducing (cracked ammonia. Experience to date has been that muffles of 3/16—1/4” (5—6mm) RA 353 MA plate typically outlast those of 601 by a factor of two. 11 gage (3mm) wall is appropriate with RA 602 CA brazing muffles. being somewhat more tolerant of spilled copper than are the higher nickel heat resistant alloys. Then they tried their first 1/4” wall RA 353 MA muffle. H2. This is for muffles fabricated in the same shop. not suitable for carburizing environments. Used for applications from copper brazing to powdered iron sintering. Large muffles used in the production of iron powder itself are of RA 253 MA. oxidation and carburization resistance than does 601.8 mm) RA333 has been used. used in the same service. RA330 muffles are most commonly 3/16 to 1/4” (4. RA330 “D” muffle for copper brazing. neutral hardening or sintering bronze powder. brass and steel. Today we would suggest RA 253 MA for greater strength. This is an old muffle design.8 mm) RA309 plate. Muffle of 3/16” (4. bright annealing copper. perhaps in 11gage (3mm) for better heat transfer. 13-2 . Not for a carburizing atmosphere. under 1800°F (980°C). endothermic atmosphere. lined with 430 for protection against copper spills. Typical life 4-5 years. RA309—bright annealing. Can be used for carbon fiber production when sulfur may be a problem. Gas fired 12001600°F (650-870°C). dry hydrogen or hydrogen-nitrogen mixtures leave the muffle inside bright. as well as for entire muffle sections. but they absolutely must be free to expand in the other direction. our experience has been that attack is erratic. The key is to leave them on—it is cheaper to pay the electricity 7 days/week than to replace a muffle that has been periodically shut down to “save” money. more properly called a “semi-metal”. continued Muffle Installation and Operation Muffles are normally fixed at one end. Type S. SiO2 on it. has a melting point of 2577°F (1414°C). or powder from bronze sintering operations can attack the muffle bottom. This is primarily because silicon and nickel form an eutectic which melts at 1767°F (964°C). This clean surface is quite susceptible to attack by a small amount of copper alloy. A type K thermocouple can drift 25°F (15°C) in 4-6 weeks. Spilled copper braze alloy. made of a mixture of SiC and carbon. most commonly with the 75% nickel alloy 600. Some shops weld U-bolts on the flange of the free end and run a chain over a pulley to some dead weights. or more accurately silicon-silicon carbide composite. or apply tension by some other means. The formed compact is then sintered 3630°F (2000°C) or higher. Replace the thermocouple at least quarterly. melting a hole right through the muffle. Copper goes right through the grain boundaries. silicon carbide elements top and bottom are the least problem. With RA330. it also happens with RA330. For electrically heated muffles. This overheats the surrounding area and often burns away any obvious traces of the cause. and the reaction product bonds the compact together. the leaking atmosphere burns. Silicon carbide hearth plates can form a eutectic with nickel alloys. are preferred.Muffles. refractory is used for hearth plates. 13-3 . one hearth plate may attack the metal and the next not. A rule of thumb is to pull on the muffle with about half of its own weight. Good. Endothermic atmospheres. It is made by infiltrating compacts. Ribbon or rod elements may sag and create a hot spot. with liquid metallic silicon. Bonding agents such as borates may be added. More common with 600 alloy muffles. platinum. reducing to iron but actually oxidizing to chromium leave a scale on the muffle inside which provides some protection against this. If the compact is sintered in air. Silicon itself. it will have a surface layer of silica. Silicon Carbide Silicon carbide. This refractory has long been known to react with nickel alloys. to aid the lengthening caused by thermal expansion. Silicon metal reacts with the carbon to form SiC. One form of this is “reaction bonded silicon carbide”. Once a hole forms. One may also separate the Si-SiC plate from the muffle with alumina or zirconia inert refractory cloth or board. Holes in the bottom of an RA330 muffle sintering powdered iron. They begin on the outside surface. continued The only known way to prevent this attack is to keep the silicon carbide from contacting the muffle.Silicon Carbide. or it might be thinned and applied like heavy paint. and are not attack from any contaminate inside the muffle (dark streaks in this photo are water marks). One refractory supplier suggests that the alumina should be applied to the silicon carbide. These holes are from the Si-SiC hearth plate. not to the metal muffle. In this case only one hearth plate attacked the muffle. The castable might be plastered on. 13-4 . One approach is to coat either the silicon carbide hearth plate or the muffle itself with alumina castable. so that the atmosphere may be retained using an organic seal ring. RA601. or may be water cooled for an organic seal ring. is the beginning of such a bulge. As the retort is externally fired. RA333. depending upon the blade to be coated.. closed at one end. What in this photo is just a different colored band. Both of these retorts use a water-cooled base. which may incorporate a sand seal. and RA 602 CA. carburizing. which manifests itself as a circumferential bulge. An RA 353 MA® retort is used for diffused aluminide coating of turbine blades. brazing and coating operations. The wide range of materials used includes RA309. 30” (762mm) diameter coating retort for the aluminide coating of gas turbine blades. the retort wall may be expected to operate about 100°F (50-60°C) above process temperature. RA330. At this temperature RA 602 CA has greater rupture strength and superior oxidation resistance. 230. RA 602 CA replaced N06230 in this application. Roughly the bottom 1—1-1/2 foot (300— 450mm) experiences a sharp thermal gradient between the process temperature and the 212F (100C) maximum temperature of the water cooled seal. X. RA310. The other end rests on a base.Retorts A retorts is simply a large cylinder. RA 253 MA. They are used for annealing. 13-5 . Process temperature is 1680 to 1960°F (915 to 1070°C). Operating temperature 1975°F (1080°C). near the bottom of the retort. The invariable result is permanent distortion from this thermal strain. The early beginnings of this may be seen on the bottom retort. Most of the retort operates at very high temperature. g. with very good carburization resistance. In vacuum heat treating of tool and stainless steels. Alloys such as RA 353 MA and RA 602 CA are among the strongest at such temperatures. Although 601 is very oxidation resistant. 230 and RA 602 CA. The most important alloy attribute for this service is a fine grain size. rather than 82. Bar Frame Baskets Baskets having a frame of nickel alloy bars 3/8—5/8” dia. carburize badly in low pressure carburizing service. with woven wire mesh liner. the weld filler used here is not. Alloy selection for vacuum hardening and carburizing is still in a state of flux. Fully penetrated weldments are necessary. 13-6 . Because this service includes repeated liquid quenching from red heat. a fine grain size is preferred to resist thermal fatigue damage is as important as carburization. could eliminate this condition. The grooves in the retort are weld beads of filler metal 82 (ERNiCr-3). A ductile weld filler. often above 1900°F (1040°C). and may include RA330. e. Most wrought alloy used for conventional atmosphere heat treat is RA330. temperatures are high. 601. continued It is a good idea to choose a weld filler with properties comparable to the retort base metal. HR-120. 600. Strength is important to minimize fixture weight. This 601 retort was used around 2200°F (1200°C). Most carburization resistant alloys. ASTM 5 or finer. Use of RA 602 CA weld wire. are used to carry work into the heat treat furnace. RA330. Initial grain size is of somewhat less consequence as temperatures are high enough that most alloys will grain coarsen in service anyway.Retorts. Usually this is achieved by pressure welding (cross-wire resistance welding) the frame members. Aluminum is the only common alloying element capable of forming an oxide scale under these conditions. In vacuum carburizing the oxygen potential is too low to form protective chromium or silicon oxides. but inadequate oxidation resistance above 1800°F (982°C). 600 and 601. 035 0. continued RA 602 CA baskets for hardening high speed steel drill bits. This permitted a 15% increase in payload. including both weight of drill bits and alloy fixturing.5 35 35 76 Cr 25 25 22.112 0.056 0. Results in this particular furnace favor RA 602 CA. Baskets of 3/8” dia RA 602 CA gave a 25 lb.90 1.2 Al 2. 13-7 .7 2.Bar frame baskets. Tests run in other furnaces.1 1. 600 alloy does tend to form a deep case of moderate carbon content.4 --0. The maximum permissable load in this vacuum furnace is 600 pounds.4 1. and retain a greater amount of ductility than do lower nickel grades. Tests were run exposing plate coupons of various alloys in a low pressure carburizing furnace between 1650°F and 1900°F (900—1040°C) for 300 hours of boost time. vacuum treated at 2050-2150°F. may give different results. Bits are made of M2 and M-50 tool steels. followed by a 2 bar nitrogen quench. double tempered 1050°F.2 1.043 0.2 1. In this test series RA 602 CA had less than half the case depth of the other alloys.40 0. Alloy RA 602 CA RA333 RA601 RA 353 MA RA330 RA600* Case Depth inch mm 0.5 25 19 15. (11kg) weight reduction over the previously used 1/2” 600 alloy.2 -1.2 *The deep case on RA600 should not be interpreted to mean that this alloy is more embrittled than the others. This photo shows the loaded baskets hanging from a scale.016 0.068 0. with different partial pressure of oxygen. A typical cycle is 20-45 minutes.8 Nominal Chemistry Ni 63 35 61.2 0.5 Si -1 0. 601 (ERNiCrFe-11) has excellent oxidation resistance. and RA 602 CA. Alloy 82 has oxidation resistance inferior to any commonly used base metal. RA333-70-16. excepting 309. Firing legs may collapse because they are restrained from expanding by the cooler. in double the number. Foremost. The local thermal gradient from the hot spot may also be a problem. RA330-80-15. Some heat treaters are considering moving away from U-tubes in their first zone to singleended tubes. U-tubes are supported by a “horn”. Intermediate supports essentially block heat flow out of the tube. This may be addressed either by a bellows on one or the other leg. both the seam weld and the weld of return bend to straight leg. For GTAW only. Lighter tubes can often be changed in less time. We suggest avoiding filler metal 82 (ERNiCr-3). RA333 and RA 602 CA. Likewise furnace cycle time is shortened. the tube deforms over the support. This is in order to double their heat input to the first zone. Covered electrodes include RA330-04-15. if not most. stronger exhaust leg. all available as both GTAW and GMAW. rather than welding it securely. Many. U-tubes consist of two straight legs. Welds made using filler metal 82 (ERNiCr-3) are low in strength. Being weakened here. Tube Design & Installation Tube life is commonly limited by collapse of the firing leg. or chunk of pipe. not necessarily of the same diameter or wall thickness.Radiant Tubes Fabricated radiant tubes of 11 gauge (3mm) alloy offer several advantages over heavy wall cast tubes. above 1800°F (980°C). Appropriate bare welding wires include RA330-04. the thinner wall can mean 8-12% energy savings because of better heat transfer. and sagging or cracking at intermediate supports. not well suited for radiant tube service. maximizing furnace up-time. or by permitting the exhaust leg to move through packing. U-tubes One of the most common tube designs. and cause a local hot spot. welded to a semi-circular return bend. Breaks at this weld due to lack of weld penetration are a common failure mode for both wrought and cast tubes. This weld of straight leg to return bend must be full penetration. 13-8 . welded to the return bend. Weld fillers should be chosen that match the strength and oxidation resistance of the tube metal. Reliable performance requires full penetration welds. or of 10 gauge (3. and were replaced with RA330. The tubes were fabricated with a 6 inch OD x 11ga. or of a stronger alloy. This may be caused by the hot spot where the bottom tubes are supported. For 309 radiant tubes a convenient strength (and oxidation) upgrade for the return bends is RA 253 MA. Operating conditions. vertical RA333 tubes have given 10 years life in a pit furnace deep case carburizing. The RA333® U-tube on the next page was in a General Motors plant in Northern Ohio. and is readily welded to 309. RA 602 CA weld fillers. For an 11 gauge (3mm) RA330 tube it might be appropriate to make the return bend either of 11 gauge RA333. 13-9 . With good maintenance and appropriate alloy. After several years the tubes carburized. such as a long flame. the tube producer must deal with such conditions. RA 602 CA has considerably greater creep-rupture strength. Common approaches are to make the bend one gauge thicker. Return bends may collapse. In the case of 601 radiant tubes we would suggest upgrading to RA 602 CA® for return bends or firing legs. At another location. Early promotion of RA 253 MA included U-tubes such as these below.Radiant tubes. as-needed. Over the years our experience has been that RA 253 MA is inclined to carburize in heat-treat service. may be responsible. This is a 17-year old photo of the RA 253 MA tubes after 10 months in service. continued When the furnace has top and bottom U-tubes. This alloy has comparable thermal expansion coefficient. fabricated tubes have given 6 to 10 years service in carburizing furnaces. but with RA330 tubes. wall ( 152mm x 3mm) firing leg and a 5 inch OD x 11ga wall (127mm x 3mm) exhaust leg.4mm) RA330. failures occur first in the bottom tubes. Nevertheless. In 2004 this same furnace was still in operation. including covered electrodes. and about twice the oxidation resistance of 601. This furnace is typically used for annealing steel at 1800°F (980°C) in a nitrogen atmosphere enriched with propylene. are compatible with 601 base metal. with top supported by a horn and bottom just resting on a refractory ledge. high carbon potential. 120”). continued Fabricated 11 gage RA333 radiant tubes have given 8 to 10 years life in carburizing furnaces. the metal is weaker. permitting the legs to expand at different rates. This effect can be minimized by use of a bellows. These 309 U-tubes are used in an aluminum mill.Radiant tubes. This particular tube failed from local overheating after some 8-1/2 years’ service. the firing leg also expands more than the cooler (and stronger) return leg. Firing legs are 3/16” wall. Most distortion in radiant tubes occurs in the firing leg. Being hotter. Here 321 stainless bellows are used on the exhaust legs to reduce distortion from differential expansion of the two legs. The carbon steel box section filled with fibrous refractory is referred to as the bung. As this is the hotter leg. 13-10 . When both legs are firmly affixed to the furnace wall. exhaust legs 11 gauge (0. Similar bellows are used on both cast and fabricated tubes. this differential expansion contributes to firing leg collapse. The metal dusting/carbon rot shown above is being addressed by fabricated RA330 U-tubes with 2 feet (610mm) of RA333 on the firing leg. at top. Cast Tridents are said to crack here >>> Trident radiant tube formed out of 11ga RA 602 CA sheet. can increase life. In Trident® tubes thermal expansion of the two firing legs is restrained by the central exhaust leg. The traditional choice has been RA333. A bellows on the exhaust leg can reduce such deformation and increase useful life. which runs cooler. rather than welding it solidly to the bung.35mm wall) cast tubes. The 250 pound (113kg) fabrications replace 500 pound (226kg) 6-5/8” dia 1/4” wall (168mm dia 6. The lighter RA 602 CA tubes are preferred over castings.Radiant tubes. This collapses the firing legs. 13-11 . continued Metal dusting of the firing leg is a problem in some carburizing furnaces. Likewise permitting the exhaust leg to expand through packing. A set of these fabricated tubes replaced HT cast tubes in 1650°F (900°C) carburizing service. This RA330 Utube metal dusted in the firing leg. One solution is to make just this portion of the firing leg of a metal-dusting resistant alloy. and may be changed in less time than a casting. which meant the flame was rich in gas. one half of the stress for 1% in 10. High temperature design of static members is often based on creep or rupture strength. Or.000 hour rupture strength. or breaking. ROTARY KILNS & CALCINERS Alloy selection covers the range of available high temperature grades—RA309. Some failures were by cracking in the base metal of the return bends. 13-12 . during a discussion of radiant tubes. Here the problem was that the combustion air blower filter clogged. with an average of 50 Btu/in2 •°F. & tend to burn out the tube in this location). continued Burner Matters One burner manufacturer.Radiant tubes. RA 253 MA. RA330. heat transfer through tube wall commonly averages 35-50 Btu/inch2•°F. brought to our attention the tube life advantage of recuperative burners.000 of profit/day. so long as it is kept turning while hot. RA601. The design and attachment of flites inside is very important. This means they will not only expand less. Rotating equipment. reducing peak temperature & extending tube life. giving the long flame that burnt out the return bends (conversely. Downtime is costly! A Midwestern captive shop had serious failures in return bends due to inadequate combustion air. alternately sags one way. it may be mistaken for fatigue or rupture failure. Bowing caused by a heavy load is not a common problem. Tube life matters greatly to mills with large strip anneal lines. rotating equipment is usually designed to a operating stress than is a static part of comparable alloy and operating temperature. The burner manufacturer’s view was that with a recuperative burner they even out the heat transfer. producing some $300. For these reasons the flights must be free to move or they will indeed crack the hotter. A common approach is to set design stress at one half of the 10. then the other. weaker shell from effects of differential thermal expansion.000 hours minimum creep rate. which caused a long flame to overheat the return bends. for a 1750°F (954°C) furnace operating temperature. The flight will operate cooler than the shell in an externally fired retort or calciner. As an example. RA 602 CA. with too much air the flame would be concentrated right at the burner. cracks running in the direction of the bend. For this reason. However the heat profile is such that heat transfer peaks at 130 Btu/in2•°F in large W-tubes. The concern is with the part sagging. RA 353 MA and RA333. Best success has been to weld only in the cooler zones. This is one reason that radiant tubes burn out on the firing leg. When such cracking occurs. but they will be stronger than the shell alloy. 25. Flites were originally welded solidly to the shell. circumferential welds when the alloy used embrittles from sigma at the temperature of that weld location.000. Not only will the flites expand less.5m dia). and more commonly at fewer revolutions per minute.000 cycle fatigue strength of alloy 602 CA at 0. experienced rotating kiln designers use some proprietary mix of hot tensile and creeprupture data.4 N/mm2). It processes kaolin clay to zeolite catalyst for refineries Initially RA330. The maintenance engineer solved the shell cracking by a redesign. it may be mistaken for fatigue or rupture failure. Hot tensile strength at this temperature is 11. However useful high temperature fatigue data is rarely available. Best success has been to weld only in the cooler zones.Rotary Kilns & Calciners. the flights must be free to move or they will crack the hotter. The design and attachment of flites inside is important. weaker shell from effects of differential thermal expansion. There have been circumferential cracks associated with thermal strains from burner set-up. Many shell cracks are assoicated with flite attachment. while the 10. the 1. but they will be stronger than the shell alloy. We have yet to see a shell crack that in our opinion was from mechanical loading alone. The flites will operate cooler than the shell in an externally fired unit. 13-13 . As a result. This matter is discussed by ThyssenKrupp VDM in their VDM REPORT No.7 m long.1Hz (6 rpm) is about 4350 psi (30 N/mm2) at 2012°F (1100°C). 5 ft diameter (10.400 psi (79 N/mm2) These particular numbers are not directly useful in design. When such cracking occurs. increased duty cycle and higher temperatures necessitated a stronger alloy. as one would at room temperature for any rotating member. They are no longer welded to the shell in the hot zone. continued One might prefer to design on the basis of fatigue. This caused transverse cracks in RA330 units. For these reasons. Just to illustrate.000 hour rupture strength at this temperature is only 640 psi (4. For one thing. 1. We see cracks in. RA333 rotary calciner about 35 ft long. and adjacent to. kilns rotate many more cycles over their lifetime. The flites now consist of long bars held in cages at either end of the kiln. developed in the shell. This kiln shell was fabricated of 3/8” (9.5mm) RA330 plate. ® 13-14 . approximately 2” (50mm) long. The resulting thermal strain is what cracks the shell. continued Attention to flite attachment is important in all rotary kilns.Rotary Kilns & Calciners. by incinerating hydrocarbons at about 1200°F (600°C). about every 8 inches (200mm) or so to reduce the thermal strains. they do not thermally expand as much as does the adjacent shell. The flites had been welded solidly to the kiln shell. Then air-arc out the cracks and reweld them. Because these flites are cooled by the product inside of the eternally fired kiln. Being cooler. After two years numerous branching cracks. A repair to this condition might be to cut slots in the existing flites. the flites are also stronger than the shell metal. It was used for soil remediation. all along their entire 2-3 foot (600900mm) length. Alloy 120 pins occasionally break after long service at around 16001700°F (870-930°C) or so. deforms until it looks like an automobile engine’s crankshaft3. Pins must be of an alloy with sufficient high temperature shear strength to avoid “crankshafting”. For service 1800°F (980°C) or above. Interlocking links are designed to take up the shear loading on the casting itself. Links are cast of alloys ranging from HT to Supertherm. With a pin-bearing link the belt pin is heavily loaded in shear. Where strength but not carburization resistance is needed. that is.Cast Link Furnace Belts Flexible belts made of cast links pinned together are used to carry heavy loads through continuous furnaces. If the pin is not strong enough it “crankshafts”. usually with cast HT links. as well as resistance to carburization and some degree of toughness. Inadequate anneal during manufacture Belt pins for this service have largely been RA330HC for several decades. RA 602 CA is more appropriate. The two basic types of cast link belts are pin-bearing. These interlocking links are from a belt misalignment failure 13-15 . both RA330 round bar and RA330 hexagonal bar have been used to pin interlocking link belts. crankshafted pin. due to a wider range of grain size as produced. and interlocking. alloys X and HR-120® pins are also used. As pin stresses are low. X grade may not be as consistent. But alloy choice is outweighed in importance perhaps 50 to 1 by how the pot is maintained. the presence of black “cobwebs” hanging off the radiant tubes. Neutral Salt Pots1 The most common industrial use of molten salts is to heat treat steel. Otherwise sodium chromate will form at high temperatures. Michigan. The following points are important for good life in a metallic pot for neutral salt heat treating: 1. continued For more than 30 years the majority of belt pin failures which we have been called on to examine have been caused by belt misalignment. Alloy selection does matter somewhat.) Idle the pot with salt still molten. We understand that another indication is. Presence of sodium contamination is indicated by a bright greenishyellow showing. Contamination by sodium or potassium salts from parts washing operations can cause formation of bulky oxide that shortens the life of a belt by reducing freedom of movement between pin and link. and hearth rolls sized to move at the same surface speed as the belt.) Ensure that there is no salt whatsoever in the combustion chamber of a gas-fired pot or about the elements of an electrically heated pot. and continue to oxidize.) Rectify and desludge neutral chloride salts at least daily. or in sodium hydroxide. Metallic salt pots used to contain neutral heat treating salts may last anywhere from 2 days to 18 months. 2. once the black scale has been scraped away. This causes a reaction which will oxidize.. rather than skid tiles. and not black as might be expected . Inc. Battle Creek. Suggestions include the use of return rolls. 3. Hearth rolls must be level and parallel (perpendicular to the belt travel direction). which fatigues the pin.Cast Link Furnace Belts. coupled with brickwork which is white. The following paragraphs are based largely on discussions with Omega Castings. the alloy components. in a carburizing furnace. For maximum belt life the furnace must be designed to minimize stress on the belt. 13-16 . When parts are washed in ionized detergents containing sodium. or occasionally by carbon and/or salt deposits which freeze the belt solid. those parts must be rinsed in water and then dried before running through the furnace. borate or phosphate. depending upon maintenance and operating procedures. rather than shutting down completely and letting the salt freeze solid. This is crucial. until the volume of oxide simply freezes up the belt. 13-17 . and permeates the entire thickness of the salt pot wall. Regarded as “neutral” salts. sodium.Salt Pots. Those alkali chloride fumes will attack the chromium oxide scale on the outside of the pot. the inevitable oxygen content of the bath is quite destructive. until the pot begins to leak through to the outside. continued 4. Mixtures of potassium. and because air is always brought into the bath with the workpieces. If a new pot is put into a furnace contaminated with leaked salt from the previous pot. Eventually the molten salt physically penetrates the grain boundaries. This occasionally happens in as little as three days. all welded joints must be full penetration welds. the alkali chlorides strip or flux that scale. or pores develop in the grain boundaries2. such as the fusion line of the weld or in the weld bead itself. sodium and barium chlorides are widely used as heating media that neither oxidize nor decarburize carbon. The destructive part is that as fast as the alloy forms a protective chromium oxide scale. engineering alloy and tool steels. they are actually quite oxidizing to the chromium in the Ni-Cr-Fe alloys used for pots and fixtures. While the chloride salts themselves are indeed neutral. And that is why it is most important to clean out all the spilled salt from the previous pot. As fast as chromium from the alloy diffuses to the surface to re-form the oxide scale.) Do not put oily work or any foreign matter (no floor sweepings!) into the pot. when installing a new one. Only after these five points have been addressed should alloy selection be reviewed. Let us examine the reasons behind some of these points.) In both pots and fixtures. Eventual failure in or near a weld does not necessarily mean that weld was defective. and the hot air or products of combustion provide more than enough oxygen to scale right through the pot. It is the combination of alkali chloride salts and oxygen that attacks the pot. Oxygen is present because the surface of the bath is open to the air. forming potassium. and/or barium chromates. This is somewhat more likely to occur in coarse grained regions. The chromium diffuses along grain boundaries orders of magnitude faster than through the grains themselves. the scale is dissolved. 5. that salt will volatilize when heated. and diffusion voids. This may be done by introducing methyl chloride (well away from electrodes and metallic pot sidewalls).This photomicrograph. If the pot is not rectified well and frequently. that salt must be rectified. shows corrosion attack and corrosion assisted cracking in the fusion line between RA330 plate. The inorganic rectifiers form a metallic sludge in the bottom of the pot. To prevent the steel workpieces from decarburizing. oxygen builds up in the salt itself. the oxygen content will shorten the life of the pot by corrosion from the inside. the oxygen content of the bath must be reduced to low levels. In this salt pot the attack along weld fusion lines was so bad that entire lengths of the weld bead could be removed with a few blows of a hammer. Solid rectifiers such as powdered silicon. which converts the alkali oxides back to chlorides. bottom. ferrosilicon or dicyandiamide are also used. and the RA33004-15 weld bead. In this case the solution was to replace this blanket insulation each time a new pot is installed. top. 99-66. from Rolled Alloys Investigation No. Operating temperature was about 1700-1750°F (930-950°C) using a non-cyanide carburizing salt. This happens even at oxygen levels which will not harm the steel workpieces. In normal operation. That is. silica. The failure occurred simply because the firebox refractory still contained the spilled salt from the previous salt failure. 13-18 . Etchant: Oxalic Acid Magnification: 25X Crack near the fusion line. while the sidewalls are still in good condition. 6 days per week. in this case over two inches (50mm) deep in the bottom. Neutral salt pots here were failing by leaks at the bottom weld in 4 to 6 weeks of operation. causing the bottom of the pot to overheat. 3/8” (9.Salt Pots. inner weld bead of the RA309 pot above. lest it act as an insulator. are increased by nearly a factor of two. This sample came from a Western US heat treat shop. usually in or near a weld. 13-19 . Pot idled 1200°F (650°C) on Sundays. even without overheating. Operation was neutral salt at 1400—1600°F (760—870°C) 24 hours per day. continued This sludge must be removed frequently. Alloy Casting Institute3 studies of salt baths show that corrosion rates in the sludge itself.5mm) RA309 salt pot bottom 3/4 scale Rolled Alloys Report #01-55 The photo above is a classic example of pot failure due to metallic sludge build-up. Leaving the sludge in can overheat the bottom to the point that it fails. some after as little as 2 weeks. perhaps twice daily. full penetration welds are necessary. as the salt melts first on the bottom. it is a good idea to ladle out most of the salt before it freezes. Quenching into a nitrate-nitrite mixture from a chloride high heat pot may considerably shorten the life of the former. it expands and cracks open the pot. or of cast HK. continued When salt freezes it contracts in volume. performance often follows the alloy’s resistance to chloride salts. the higher the nickel alloy. in our opinion. One is that. Either RA600 or RA330 is. However. Salt Pot Alloy Selection Since the 1930’s the most popular alloys have been the wrought alloys RA309. Aluminum foil left over from someone’s lunch. If that were all there were to it. Sulphur from whatever will attack the nickel in the pot. and all electrodes in ceramic pots RA600 or commercially pure nickel. If the pot is full of solid salt. If one plans a shut-down. In some shops RA600 has the advantage over RA330. may be made either of carbon steel or of 304 stainless. Almost none are pure nickel. with RA600 distinctly in the minority. superior to RA309. This alloy selection discussion is for pots containing chloride salts. But in practice the majority of metallic pots today are RA330 or RA309. with a very. either in a weld or along the knuckle radius of a dished head.Salt Pots. The higher chromium content of RA310. Floor sweepings can do interesting things to salt pots. all metallic salt pots would be RA600 or HW. will melt and go right through the bottom of the pot. the worse the attack. in others there is no clear difference. In all cases. Alternately. once sufficient salt has melted. the volume expansion may cause it to explode through the remaining frozen layer on top. contamination by chloride salts will increase corrosion rate. there are a couple of unpleasant possibilities. One of our fabricator customers related an incident in which short life of RA309 pots was indeed traced to the practice of disposing of floor sweepings in the heat treat pots at night. is disadvantageous in salt. that salt will go through a volume increase when remelted on start-up. for example. With respect to fixtures for automated salt lines. which are mixtures of sodium nitrate and sodium nitrite. 13-20 . If a salt pot is shut down and allowed to freeze solid. Almost all submerged or over-the-top heating electrodes are RA446. RA330 and RA600. This increase can be about 3/8 to 1/2 inch per foot (31 to 42 mm/metre) of pot depth. Tempering salts. very few being RA330 or RA600. Both laboratory studies and observations of fixtures are reasonably consistent in showing that the higher nickel grades usually have better resistance to alkali chloride salts. It is the case that the various ills that may befall metallic pots obscure any theoretical advantages of higher nickel to the extent that 35% or 13% nickel grades are considered more cost-effective. or the cast grades HT (17Cr 35Ni) and HW (12Cr 60Ni). in which some steel piece will be austenitized. No. Seybolt. At high temperatures relaxation is the primary limitation to the use of threaded fasteners to maintain a clamping load. 46. so that the assembly is loose once it cools back down.Salt Pots. or MP-35N®. From 900 to 1200°F (480 to 650°C). A good discussion of fasteners in the chemical process industry has been presented by Robert Smallwood1. A286. Above this temperature. a less expensive age hardening stainless. 450 to 900°F (230 to 480°C). Bolts Bolts are commonly used at elevated temperature to withstand a shear load. Oxidation of Ni-20Cr Alloy and Stainless Steels in the Presence of Chlorides. to about 1400-1500°F (760-816°C) the choices narrow down to René 41®. RA330 threaded rod. currently of Det Norske Veritas. If the metal to be clamped expands faster than the bolt. though of questionable availability. LaChance. nor is it as available in various bar sizes. Above 1200°F up to 1600°F (650 to 870°C). Jackson and M. continued References 1. A286 and 718 . and the alloy from which the bolt is made. 2. There are newer alloys that may be technically quite suitable. an age hardening nickel base alloy. Neutral Salt Pot Alloy Life: Maintenance is the Key. Much of the published high temperature bolting experience has been with WASPALOY. Vol. 2. In addition to selecting a strong bolt material it is important to look at the relative expansion coefficients of the alloy to be clamped. Transactions of the ASM Vol. one of the grades in ASTM A 193. low alloy steel. A. 13-21 . H. 1970 3. James Kelly. Heat Treating. What appear to us as fairly liberal alloy selection suggestions are offered by the Industrial Fasteners Institute as2: Below 450°F (230°C). April 1990 2. J.U. Oxidation of Metals. pp 157-183. For example. The most commonly available alloy choice for applications up to 1150 or 1200°F (620-640°C) is RA718. that expansion will add to the tensile load in the bolt and may stretch it. WASPALOYTM. is sometimes suggested but has neither the high temperature capability of RA718. Resistance of Cast Fe-Nf-Cr Alloys to Corrosion in Molten Neutral Heat Treating Salts. René 41 or WASPALOY. 1954. H. nuts and washers are used to assemble high temperature equipment where loose joints are desired to accommodate thermal expansion & contraction during thermal cycling. Bolts. guide to alloy selection would be: Max. but approximate. WASPALOYTM. If copper gets carried into an area where the metal is operating above 1981°F (1083°C) it will melt and embrittle or or eat holes through any austenitic alloy it touches. continued Some cautions: Never. 13-22 . NEVER use anti-seize compounds that contain copper. about a 1% drop in modulus for every 100°F (56°C) temperature increase. AISI 6150 chromium-vanadium steel 302 stainless cold drawn. This embrittlement may even occur slightly below the melting point of zinc. “A bar loaded to an initial stress of say. 40. Springs Metals used as springs at elevated temperature are subject to relaxation under load. RA718 or alloy X750 are practical choices for applications up to 1150-1200°F (620-650°C). X-750 WASPALOY. The total strain remains fixed but part of the elastic strain is replaced with inelastic strain4”. One intentional example of stress relaxation is the reduction of stress in a fabrication due to a stress relief anneal.000psi (MPa) is called stress relaxation. zinc or aluminum anywhere near high temperature equipment. or galvanized coatings embrittle austenitics and can also embrittle steel bolts at moderately elevated temperatures. alloy selection is the same as for bolts. 787°F (419°C). This time-dependent stress reduction of 10. Above that. From the standpoint of availability. A more complete. Zinc. or MP-35N® are the remaining practical choices. plus 900°F (482°C) 1 hour age A286 RA718. to 1400-1500°F (760-816°C) René 41®. Use temperature °F 200 500 750 1000 1200 1500 °C 100 260 400 540 650 816 Alloys music wire. Molten aluminum is essentially the Universal Solvent for most alloys. René 41 Elastic modulus decreases with temperature.000psi (MPa) and then held at a constant strain and temperature may after a time period have a remaining stress of only 30. K-500 17-7PH® condition CH900 (50% cold reduction.000psi (MPa). 410. Analyzing Belt Pin Failures. Corrosion 91 Paper No. Bruce McLeod. Texas 2. Philadelphia Pennsylvania 13-23 .References 1.A. Metals Park.E. Compilation of Stress-Relaxation Data for Engineering Alloys. Houston.S. Metal Progress August. ASM. 1505 East Ohio Building. Fastener Problems in the Process Industry. R. 1973. Smallwood. 6th Edition. Fastener Standards. Ohio 4. ASTM DS-60. 1717 East Ninth Street. 3. Ohio 44114 U. NACE. 161. Cleveland. available from: Industrial Fasteners Institute. 1982 ASTM. because it does more jobs better and for less money. glass molds. An upgrade over 601. RA310 Good oxidation resistance beyond 2000°F (1093°C) under mildly cyclic conditions. Field installations have proven it has excellent resistance to carburization. Resists hot chlorine gas to 1000°F (538°C) RA601 Stronger and more oxidation resistant than RA600. RA333 A superior product that also costs more. thermal fatigue and distortion in quenching applications. RA 253 MA High strength. excellent carburization resistance. The combination of 3% cobalt. excellent oxidation resistance to 2000°F (1093°C). RA600 Lower strength but more ductility. 25% chromium and 1% silicon. 14-1 . soot blowers. RA309 Preferred for oxidizing atmospheres under 1900°F (1038°C) where resistance to carburizing or nitriding atmospheres is not necessary. appropriate silicon to resist absorption of carbon and nitrogen. enough nickel for good ductility. Use for muffles. 3% molybdenum and 3% tungsten adds high-temperature strength to a base of 45% nickel. RA 353 MA Twice the strength of RA330 in the 1800-2200°F (980-1200°C) temperature range. thermowells. etc. where the hot corrosion resistance of maximum chromium is required. yet has above-average strength at operating temperatures. let us briefly summarize the chief characteristics of each RA product. such as salt bath electrodes. rotary calciners. Has enough chromium for good oxidation resistance. Oxidation resistance approximates that of 601 and RA333.. with good carburization resistance. coal nozzles. copper launders. Almost always preferred for carburizing atmospheres. RA446 Special applications. Has the best sulfidation resistance but very. Good resistance to sulfidation. but the melting point of RA 353 MA is about 100°F (56°C) higher. Good sulfidation resistance. very low strength and ductility. and potential alternate to alloys 617 or 230. RA330 The work horse of the furnace industry. generally good hot corrosion resistance. bent and welded without troubles. RA 602 CA The strongest and most oxidation resistant high temperature alloy we offer. Most cost-effective above 1900°F. Good oxidation.THUMBNAIL BIOGRAPHIES OF RA ALLOYS To conclude this discussion of heat resisting alloys. Withstands a lot of thermal shock. Can be cut. The Rockwell B scale (Rb. Brinell is usually abbreviated BHN (Brinell Hardness Number) on mill certifications. However. 3) mean coarse grains. µm. Disclaimer Clause: The data and information in this printed matter are believed to be reliable. indirect. 14-2 .CHEMICAL SYMBOLS Al aluminum Ar argon As arsenic B boron C carbon CO carbon monoxide CO2 carbon dioxide CH4 methane Ca calcium Cb columbium (niobium) Ce cerium Cl chlorine (the gas. Cl2) Co cobalt Cr chromium Cu copper F fluorine Fe iron H hydrogen HCl hydrochloric acid He helium H2O water La lanthanum Mn manganese Mo molybdenum N nitrogen (as the gas. Rolled Alloys makes no warranty and assumes no legal liability or responsibility for results to be obtained in any particular situation. ASTM 3 to 8 grain size would be 125 to 22 µm. N2) NH3 ammonia Nb niobium (columbium) Ni nickel O oxygen (as the gas. typical for RA 253 MA. 2. This material is subject to revision without prior notice. HRB) is most common for our alloys. special or consequential damages therefrom. Outokumpu and ThyssenKrupp VDM report grain size in micrometers. ASTM 4-7 is about average for RA330. Larger numbers (7. 9) mean finer grain size. Small numbers (ASTM 0. Grain size is in ASTM numbers. and shall not be liable for any direct. Rockwell C is for heat treated steel. O2) P phosphorus Pb lead S sulfur (sulphur) SO2 sulfur dioxide H2 S hydrogen sulfide H2SO4 sulfuric acid Sb antimony Si silicon Sn tin Ta tantalum Ti titanium V vanadium W tungsten Y yttrium Zr zirconiuim Hardness is measured by Rockwell or Brinell machines. this material is not intended as a substitute for competent professional engineering assistance which is a requisite to any specific application. 8. Number 2 H. L. 1929 W. Cast Heat-Resistant Alloys for High—Temperature Weldments. Proc.J. p 310—347. Chemical and Metallurgical Engineering. Heat Resisting Alloys and Their Use in the Steel Plant. 28. Vol. 1974 James Kelly. Neutral Salt Pot Alloy Life: Maintenance is the Key. October 1965.S. Michigan February 25—March 1. SAE Paper No. 36. S. Vol. Fahrenwald. Corwin. ASTM. Rundell. A. 1986 James Kelly. 811. 1923 F. 6. 1924 J. Burns.859 Feb. August. R. High-Nickel Alloys for High-Temperature Springs. F. B. Vol. A. 1955 Ralph H. Industrial Heating. Roy. p 680—681. Vol. M. Added Life for Brazing Fixtures. Oxidation Resistance of Eight Heat-Resistant Alloys at 870o. March & April. JISI July. NACE Paper Number 377. Evaluation of Heat Resistant Alloys in Composite Fixtures. and J. SPRINGS Magazine. June 27. Fahrenwald. Steel. 3 / 4. Performance of Heat—Resistant Alloys in Emission—Control Systems. April 26.D. April. 740093. Oxidation of Metals. 1969 This is the best discussion of heat resistant alloys ever printed. Metals for High Temperature. Nos. Rees. 1991 14-3 . Cook. Lai. Detroit. 1990 George Y. September and October 1972 A. Constitution of Iron-Nickel-Chromium Alloys at 650 to 800C. and A. Electric Resistance Element. Heat Treating. p 157—194. Marsh. 1949 Charles Emery and Paul Goetcheus. Some Principles Underlying the Successful Use of Metals at High Temperatures. Understanding Conditions that Affect Performance of Heat Resisting Alloys. Iron and Steel Engineer. April. Patent No. Avery. Corrosion 86. March 17—21. 1979 G. High-Temperature Corrosion of Engineering Alloys. Automotive Engineering Congress. WRC Bulletin 143. 4.P. 24. Industrial Heating. Hagen. and 1150oC. 1906 F.BIBLIOGRAPHY A. 980o. A. U. Moeller. Cracking in Type 309 High Temperature Fabrications and How to Combat It. 1990 ASM International Gene Rundell and James McConnell. D. Corfield. Bruce McLeod. 1095o. April. KCI Publishing BV. Steward. Heat Resistant Alloy Performance. July 1993 J. Gatlinburg. Heat – Resistant Materials II. Heat Treating. Metal dusting in the heat treat industry. Oxidation Rates of Some Heat Resistant Alloys. Wilson. Heat Resistant Alloy Corrosion—More Problems than Solutions. NL 1999 14-4 . Corrosion 91. Of the 2nd International Conference on Heat-Resistant Materials 11—14 September. Influence of Composition and Microstructure on Performance of Wrought Heat Resisting Alloys. Proc.Bibliography. Kelly. 1992 James Kelly. Conf. NACE Paper Number 166. Stainless Steel World 1999 Conference. 1991 James Hamer and James McConnell. March 11—15. D. Flame Straightening Technology. C. 1981 LaSalle. Tennessee John P. 1995. Industrial Heating. continued James C. Kelly and J. Zutphen. Quebec James Kelly. along with Rolled Alloys’ attendance at numerous committee meetings RA330 was approved by AMSE Case 1654-1 for use to 800°F (427°C).08% max and. Feb. 1963 14-5 . The RA330 silicon range was tightened at that time. Reference 1. The cost included new springs for the Buick & a couple of replacement mill rolls for Simonds Saw & Steel Co. 1913. patents for Strauss’ alloys were issued on June 25. dated 1934. edited by Cyril Stanley Smith. The Rolled Products Division of Michigan Steel Casting Company initially developed the market for rolled Misco Metal in the heat treating industry. after several years of creeprupture and tensile testing. Patent No. In 1958 Rolled Alloys lowered the carbon to 0. In that same year work began at Simonds. The Sorby Centennial Symposium On The History Of Metallurgy. What we now call 310 was developed by Adolf Fry. The electrical resistance wire Nichrome®.859. who did the rolling. balance nickel electrical resistance alloy. to 1. for a 15-25% Cr. and shepherded through the committee meetings. to maintain the strength. John Johnson. introduced to Germany in 1910 for high temperature applications1. All of the ASTM specifications for RA330 were written by Rolled Alloys technical personnel.00-1. He drove it from Detroit to Lockport.S. and the European alloy Nimonic® 75. U. nominally 80Ni 20Cr. L. When Rolled Alloys was founded as an independent company in 1953. New York. containing 35% nickel and 13-14% chromium. 1906.HISTORY Austenitic heat resistant alloys and stainless steels as we know them today were invented by Benno Strauss1 of Friedrich Krupp before World War I. loaded an ingot of the cast alloy HT. in 1926. 6. raised chromium to the present 19% Cr. this alloy was renamed RA330. A few years later RA330 was approved for use to 1650°F (899°C). also at Krupp. at that time 35Ni 15Cr. Our 35Ni 19Cr alloy RA330 may trace its roots to Nichrotherm® 4. In 1975. Marsh’s U. in the trunk of his Buick. Volume 27. We have a folder from The Simonds Saw & Steel Company. RA333. nominal 76Ni 20Cr. Cleveland. Ohio October 22-23. on the stronger and more carburization resistant grade.50%. would appear to be developments of A. Rolled Alloys’ verbal history says that in the early 1930’s the Misco sales manager.S. in conjunction with Rolled Alloys. which includes data and microstructures for a wrought 15% Cr 35% Ni alloy. 811. to be rolled to the wrought alloy trademarked Misco Metal. Business Unit Fibers and Composites René 41 is a registered trademark of Teledyne Industries Incorporated Stellite is a a registered trademark of Deloro Stellite. 239. 253 MA and 353 MA are registered trademarks of Outokumpu AB 602 CA is a registered trademark of ThyssenKrupp VDM AL-6XN is a registered trademark of ATI Properties. Incorporated MO-RE. RE for Ray English) Thermax and Thermalloy are registered trademarks of ElectroAlloys Corporation WASPALOY is a trademark of United Technologies Corporation 17-4PH and 18SR are registered trademarks of AK Steel Corporation 14-6 . HR-120 and HR-160 are registered trademarks of Haynes International Kanthal is a registered trademark of Kanthal AB Nimonic. MA956 and 800HT are registered trademarks of Special Metals. 22H and Supertherm are registered trademarks of Duraloy Technologies. Hastelloy. Incorporated Refrasil is a registered trademark of SGL Carbon Group. Monel.TRADEMARKS RA330 and RA333 are registered trademarks of Rolled Alloys. Inconel. Inc. Incoloy. Incorporated 153 MA. Inc. 20Cb-3 is a registered trademark of Carpenter Technology Corporation Haynes. 214. (MO stands for Marty Ornitz. COMPARISON – German & European Standards with American Grade UNS No. Werkstoff Nr. DIN Designation EN Number 1.4002 1.4006 -1.4000 1.4005 1.4016 -1.4362 1.4462 -1.4410 1.4372 1.4305 1.4307 1.4301 -1.4401 1.4404 1.4571 1.4438 1.4541 --1.4818 -1.4835 1.4833 --1.4845 -------1.4886 1.4854 ---------ferritic stainless 405 S40500 1.4002 X6CrAl13 410 S41000 1.4006 X12Cr13, X10Cr13 410 S41000 1.4024 X15Cr13 410S S41008 1.4000 X6Cr13 416 S41600 1.4005 X 12 CrS 13 430 S43000 1.4016 X6Cr17 446 S44600 1.4763 X8Cr24 duplex stainless 2304 S32304 --2205 S31803 1.4462 X2CrNiMoN22-5-3 2205 S32205 1.4462 X2CrNiMoN22-5-3 2507 S32750 1.4410 X2CrNiMoN25-7-4 austenitic stainless 201 (stainless) S20100 1.4372 X12CrMnNiN 17-7-5 303 S30300 1.4305 X8CrNiS18-9 304L S30403 1.4307 X2CrNi18-9 304 S30400 1.4301 X 5 CrNi 18 10 (X4CrNi18-10) 304H S30409 1.4301 X 5 CrNi 18 10 (X4CrNi18-10) 316 S31600 1.4401 X 5 CrNiMo 17 12 2 316L S31603 1.4404 X2CrNiMo17-12-2 316Ti S31635 1.4571 X6CrNiMo17-12-2 317L S31703 1.4438 X2CrNiMo18-15-4 321 S32100 1.4541, 1.4878 X6CrNiTi18-10, X12CrNiTi18-9 321H S32109 1.4541, 1.4878 X6CrNiTi18-10, X12CrNiTi18-9 347 S34700 1.4550 X6CrNiNb18-10 heat resistant alloys ® 153 MA S30415 1.4891 X 4 CrNiSiN 18 10 --1.4828 X15CrNiSi20-12 ® RA 253 MA S30815 1.4893 (EN: X9CrNiSiNCe21-11-2) 309S S30908 1.4833 X12CrNi24-12, X 7 CrNi 23 14 309 S30900 1.4833 X12CrNi24-12, X 7 CrNi 23 14 ® RA85H S30615 --310S S31008 1.4845 X8CrNi25-21 310H S31009 1.4845 X8CrNi25-21 310 S31000 1.4845 X12CrNi25-21 314 S31400 1.4841 X15CrNiSi25-20 800 N08800 1.4876 X10NiCrAlTi32-20 800H N08810 1.4876 X10NiCrAlTi32-20 ® TM 800HT /AT N08811 (1.4959 similar) (X8NiCrAlTi32-21, similar) ® Incoloy DS - -similar to - -1.4864 - -similar to - -X12NiCrSi36 16 ® RA330 N08330 -(EN: X10NiCrSi35-19) ® RA 353 MA S35315 -(EN: X6NiCrSiNCe35-25) 45 TM N06045 2.4889 NiCr28FeSiCe ® RA333 N06333 2.4608 NiCr26MoW X N06002 2.4665 NiCr 22 Fe 18 Mo 617 N06617 2.4663 NiCr23Co12Mo 601 N06601 2.4851 NiCr 23 Fe 602CA N06025 2.4633 NiCr25FeAlY 603GT N06603 2.4647 NiCr25FeAlYC 600 N06600 2.4816 NiCr 15 Fe ® Nimonic 75 N06075 2.4951 NiCr 20 Ti weld filler metals—SG designates bare wire, EL is for covered electrodes RA333 X FM 602 CA FM 617 FM 718 -(ERNiCrMo-2) -(ERNiCrCoMo-1) (ERNiFeCr-2) (AWS spec) 2.4608 2.4613 2.4649 2.4627 2.4667 NiCr26MoW SG-NiCr21Fe18Mo SG-NiCr25FeAlY SG-NiCr22Co12Mo SG-NiCr19NbMoTi ------ 14-7 COMPARISON—German & European Standards with American, continued Grade 17-4PH A-286 X-750 718 C-263 René 41 TM WASPALOY cobalt alloys 188 L-605 904L 1925hMo ® AL-6XN ® Sanicro 28 3127hMo 3033 ® 20Cb-3 3620Nb 825 G-30 G G-3 625 C-4 C-276 C-22 690 B B-2 B-3 B-4 B-10 FM B-10 200 (nickel) 201 (nickel) 400 K-500 90-10 Cu-Ni 70-30Cu-Ni K-500 C-276 C-276 C-22 C-22 625 112 82 182 ® UNS No. S17400 S66286 N07750 N07718 N07263 N07041 N07001 R30188 R30605 N08904 N08926 N08367 N08028 N08031 R20033 N08020 N08020 N08825 N06030 N06007 N06985 N06625 N06455 N10276 N06022 N06690 N10001 N10665 N10675 N10629 N10624 -N02200 N02201 N04400 Werkstoff Nr. 1.4548 1.4980 2.4669 2.4668 2.4650 2.4973 2.4654 2.4683 2.4964 DIN Designation X5CrNiCuNb17-4-4 X5CrNiTi26-15 NiCr15Fe7TiAl NiCr19NbMo NiCo 20 Cr 20 MoTi NiCr19CoMo NiCr 19 Co 14 Mo 4 Ti CoCr22NiW CoCr 20 W 15 Ni X1NiCrMoCu 25 20 5 X 1 NiCrMoCu 25 20 6 -X1NiCrMoCu31-27-4 X1NiCrMoCu32-28-7 X1CrNiMoCuN33-32-1 -NiCr20CuMo NiCr21Mo -NiCr 22 Mo 6 Cu NiCr 22 Mo 7 Cu NiCr22Mo9Nb NiMo 16 Cr 16 Ti NiMo 16 Cr 15 W NiCr21Mo14W NiCr29Fe -NiMo 28 -NiMo29Cr ?? ?? Ni 99.2 LC-Ni 99 NiCu30Fe 2.4375 CuNi10Fe1Mn EN Number 1.4542 ------------------------------------- age hardening alloys corrosion resistant alloys 1.4539 1.4529 -1.4563 1.4562 1.4591 -2.4660 2.4858 -2.4618 2.4619 2.4856 2.4610 2.4819 2.4602 2.4642 -2.4617 -2.4600 2.4710 2.4702 2.4066 2.4068 2.4360 N05500 C70600 2.0872 ERCuNi 2.0837 -2.4373 ERNiCrMo-4 EniCrMo-4 ERNiCrMo-10 ENiCrMo-10 ERNiCrMo-3 ENiCrMo-3 ERNiCr-3 2.4806 ENiCrFe-3 2.4620 NiCu 30 Al weld filler metals—SG designates bare wire, EL is for covered electrodes SG-CuNi30Fe -SG-NiCu 30 Al -2.4886 SG-NiMo16Cr16W 2.4887 EL-NiMo15Cr15W 2.4635 SG-NiCr21Mo14W 2.4638 EL-NiCr20Mo14W -2.4831 SG-NiCr21Mo9Nb 2.4621 EL-NiCr20Mo9Nb SG-NiCr20Nb -EL-NiCr16FeMn -- ---- UNS chemistries generally overlap the German standards shown but they are NOT identical. When the customer requires DIN certification of stock material, it can be re-certified by the producing mill. Two exceptions are AL-6XN and 20Cb-3, as they have no direct German equivalents. RA330 does now have an EN spec, designation X10NiCrSi35-19, EN number 1.4886. DIN 50049 3.1.B is a general quality specification which can apply to any alloy. The producing mill can certify to this specification, or Rolled Alloys can provide a certificate of conformance. Many of the EN (European Harmonized Standards) numbers and designations are the same as DIN, others are not. 14-8 CORPORATE OFFICE ROLLED ALLOYS 125 WEST STERNS ROAD TEMPERANCE, MICHIGAN 48182 1-800-521-0332 1-734-847-0561 FAX: 1-734-847-6917 E-MAIL:
[email protected] www.ROLLEDALLOYS.COM NORTH AMERICAN LOCATIONS: CALIFORNIA, CONNECTICUT, ILLINOIS, OHIO, OKLAHOMA, TEXAS ALBERTA, ONTARIO GLOBAL LOCATIONS: CHINA, FRANCE, GERMANY, THE NETHERLANDS, SCOTLAND, SINGAPORE, SPAIN, UNITED KINGDOM 0502 0.175 0.0710 0.133 0.0115 0.0471 -0.0566 0. Note that these coefficients are all multiplied by 10-6.0854 0.144 0.0145 0. For that 20 ft long RA330 muffle operating 1800°F 982°C) this is: 20 ft X 12 inches/foot X (1800-70F) X 10.204 0.129 0. Multiply the length in inches.174 0.122 0.180 0.193 0.0131 0.0496 0.227 The more general way to calculate thermal expansion is to use the mean coefficients of thermal expansion.224 -0.0526 0.201 0.181 0.0317 0.0727 0.104 --0.245 0.152 inches.148 0.142 0.0937 0.0372 0.0141 0.152 -0.0348 0.0604 0.111 0.115 0.0681 0.0915 0.174 0.0591 -0.0876 0. times the expansion coefficient.214 0.0281 0.0137 0.237 -- RA 253 MA RA310 RA 353 MA RA330 RA333 RA601 RA600 RA 602 CA 0.00874 0.204 0.870 -----0.0134 0.236 0.160 0. times the difference between room temperature and operating temperature.0345 0. such as those given on the next page.0341 0.164 0. continued Temperature Range °F 70-200 -400 -600 -800 -1000 -1200 -1400 -1600 -1800 -2000 Total Thermal Expansion.167 0.0796 0. To convert these numbers to the metric system.106 0.0370 0.0566 0.102 0. which is the same as dividing by one million.0305 0.173 0.147 0.154 0.209 -0.0806 0.0610 0.120 0.0104 0.208 -0.0516 0.0225 -0.0119 0.115 0.0960 0.0797 0.193 -0.123 0.0569 0.33 to get millimeters expansion per meter of length 9-6 .108 --0. inches/foot RA309 0.117 0.0859 0.0949 0.201 -0.104 0.137 0.0297 0.0x10-6 = 240 inch X 1730F X 10x10-6 = 4.185 --- SA-387 RA446 RA321 0. multiply by 83.0109 ---0.144 0.0710 0.0129 0.0103 0.0356 0.186 0.Thermal Expansion. 1 9. .5 --- 1700 ---------9.95 8.1 700 ----9.1 10.4 ----- 1400 ---10.9 8.3 9.37 -- 500 --7.98 9.7 8.2 -9.3 8.81 --8.3 -10.2 ----8.1 9.8 5.06 5.4 8.9 5.1 8.04 HR-120 RA 353 MA RA800AT RA446 ® RA600 RA601 RA 602 CA RA333 HH HK HT HP E-BRITE 825 20Cb-3 ® ® ® ------- 10.5 -9.88 9.8 -10.9 9.9 ---6.6 9.8 6.1 8.66 9.9 8. room temp to indicated temp.5 6.85 9.6 1300 ----------------------6.8 for metric units.6 8.6 6.67 8.9 -10.8 9.5 8.14 -5.5 9.8 8.4 8.68 8.2 6.1 ----- 1900 --------------------- 2000 -----10.4 6.1 9.3 8.51 9.0 ----5.42 -- 600 9.5 8.82 9.87 10.7 --6 800 ---10.9 4.1 ---8.17 7.8 ---8.9 ---9.65 8.09 ---- 1200 10.8 ---8.4 --- 1600 ---11.4 6.2 10.4 8.05 -7.3 9.33 9.1 10.5 9.97 -9.5 7.3 -- 400 --7.3 8.0 9.72 9.22 9.86 10.4 ------------6.0 9.3 -10.3 8.0 -7.59 -8.3 8.6 7.8 -10.3 7.4 ------------5.3 ----6.6 -9.80 9.8 9.7 9.56 8.7 10.9 9.52 9.0 8.4 9.0 9.3 -8.3 9.6 6.9 8.96 5.4 10.9 -® 300 --7.6 5.7 9.24 9.9 -----------8.1 --10.8 9.4 ----9.6 8.8 AL-6XN TiGr 2 NOTE: All coefficients are reported as inch/inch °F x 10 .4 8.0 9.34 -8.0 6.2 9.4 9.0 -9.3 9.87 8.5 9.6 9.44 8.3 7.8 8.3 8.15 -10.2 --------------8.7 -------9.7 9.3 --9.37 -5.2 6.15 9.3 5.5 8.3 8.7 -8.5 9.57 9.0 --7.2 9.0 ----9.5 10.0 ---5.8 10.6 ---------10.8 -- 900 ---------9.2 -8.85 -- 1000 10.4 1100 ---10.72 -9.5 -----9.3 -8.4 10.3 --- 1500 -11.2 7.6 7.88 ----- 1800 ---11. Multiply by 1.4 10.6 ------ 5.19 9.48 7.29 8.9 9.7 -10.5 9.2 9.09 9.9 6.95 8.5 ---8.46 9.6 9.MEAN COEFFICIENTS OF THERMAL EXPANSION ALLOY 304 316 2205 RA321 RA309 RA310 SA-387 RA 253 MA 410 RA330 ® ® ® ® 200 9.95 7.2 8.05 -10.56 --8.9 8.7 ---5.4 -10.0 8.7 9.5 9.5 ----6.8 -10.7 10.01 7.56 10.7 -9.6 ---8.11 7.8 7.07 9.7 9.0 -9.61 --8.8 8.18 9.6 8.9 7.7 9.85 9.4 7.27 9.7 7.5 9.14 6.