ASTM A928

ASTM A928 / A928MAbstract This specification covers standard requirements for ferritic/austenitic (duplex) stainless steel pipe that is electric fusion welded with addition of filler metal suitable for corrosive service. Heat treatment shall be performed after welding and in accordance with specified temperature and quench conditions. Several grades of ferritic/austenitic steel shall conform to the requirements of the applicable specification and grade designation. Heat and product analyses shall be conducted and shall conform to the requirements for the particular grade. The plate used in making the pipe shall conform to the required tensile properties. The steel pipe shall undergo several mechanical tests including transverse tension test, transverse guided-bend test, nondestructive test, hydrostatic test, and nondestructive electric test. This abstract is a brief summary of the referenced standard. It is informational only and not an official part of the standar d; the full text of the standard itself must be referred to for its use and application. ASTM does not give any warranty express or implied or make any representation that the contents of this abstract are accurate, complete or up to date. 1. Scope 1.1 This specification covers electric-fusion-welded steel pipe suitable for corrosive service. Note 1²The dimensionless designator NPS (nominal pipe size) has been substituted in this specification for traditional terms such as nominal diameter, size, and nominal size. 1.2 This specification covers grades of ferritic/austenitic steel as indicated in Table 1. The selection of the proper alloy and requirements for heat treatment shall be at the discretion of the purchaser, dependent on the service conditions to be encountered. 1.3 Five classes of pipe are covered as follows: 1.3.1 Class 1²Pipe shall be double welded by processes using filler metal in all passes and shall be radiographed completely. 1.3.2 Class 2²Pipe shall be double welded by processes using filler metal in all passes. No radiograph is required. 1.3.3 Class 3²Pipe shall be single welded by processes using filler metal in all passes and shall be radiographed completely. 1.3.4 Class 4²Same as Class 3, except that the weld pass exposed to the inside pipe surface is permitted to be made without the addition of filler metal (see 6.2.2.1 and 6.2.2.2). 1.3.5 Class 5²Pipe shall be double welded by processes using filler metal in all passes and shall be spot radiographed. 1.4 Supplementary requirements covering provisions ranging from additional testing to formalized procedures for manufacturing practice are provided. Supplementary Requirements S1 through S4 are included as options to be specified in the purchase order when desired. Within the text. and Strip A941 Terminology Relating to Steel. each system shall be used independently of the other. Duplex stainless steel--specifications. and Strip for Pressure Vessels and for General Applications A480/A480M Specification for General Requirements for Flat-Rolled Stainless and HeatResisting Steel Plate. Combining values from the two systems may result in non-conformance with the standard. Sheet.30 Consumable Weld Inserts for Gas Tungsten Arc Welding Index Terms arc welded steel pipe. Ferritic steel pipe--specifications. Stainless steel pipe-specifications. Austenitic stainless steel pipe--specifications. therefore. welded steel pipe. Electricfusion-welded steel pipe. Sheet. Austenitic Stainless Steel and Similar Alloys ASME Boiler and Pressure Vessel Code SectionIX. The documents listed below are referenced within the ASTM Standards A240/A240M Specification for Chromium and Chromium-Nickel Stainless Steel Plate. The inch-pound units shall apply unless the M designation of the specification is specified in the order. The values stated in each system may not be exact equivalents. Corrosive service applications--pipe (steel). the SI units are shown in brackets. corrosive service. Stainless Steel. Referenced Documents(purchase separately) subject standard but are not provided as part of the standard. duplex (austenitic-ferritic) stainless steel. When duplex stainless steel is melted it solidifies from the liquid phase to a completely ferritic structure. The picture shows the yellow austenitic phase as ³islands´ surrounded by the blue ferritic phase.40 (Welding joints and welds) Duplex Stainless Steel Duplex stainless steels are called ³duplex´ because they have a two-phase microstructure consisting of grains of ferritic and austenitic stainless steel. Related Alloys. As the .1.160. ICS Number Code 25. steel pipe.WeldingQualifications AWS Specifications A5. 2. Filler metals. fusion welded steel pipe. and Ferroalloys A999/A999M Specification for General Requirements for Alloy and Stainless Steel Pipe E426 Practice for Electromagnetic (Eddy-Current) Examination of Seamless and Welded Tubular Products.5 The values stated in either SI units or inch-pound units are to be regarded separately as standard. they do not reach the excellent values of austenitic grades. Duplex stainless steels have a two-phase microstructure of austenite and ferrite grains. due to its increased yield strength compared to austenitic stainless steel. corrosion resistance depends mostly on the composition of the stainless steel.g. molybdenum and nitrogen content are most important.g. i. it may often be possible to reduce the section thickness of duplex stainless steel. elevated temperature) for standard austenitics such as Types 304 and 316.e from Type 304 or 316 (e. Stress corrosion cracking resistance: Duplex stainless steels show very good stress corrosion cracking (SCC) resistance. SAF 2507©) stainless steels. SCC can be a problem under certain circumstances (chlorides. a property they have ³inherited´ from the ferritic side. their chromium. LDX 2101©) to 6% molybdenum (e. The duplex structure gives this family of stainless steels a combination of attractive properties: Strength: Duplex stainless steels are about twice as strong as regular austenitic or ferritic stainless steels. Duplex stainless steel grades have a range of corrosion resistance. however. The combination . Toughness and ductility: Duplex stainless steels have significantly better toughness and ductility than ferritic grades. Additionally. Due to the lower alloying content. The result is a microstructure of roughly 50% austenite and 50% ferrite. Cost: Duplex stainless steels have lower nickel and molybdenum contents than their austenitic counterparts of similar corrosion resistance. especially in times of high alloy surcharges. about half of the ferritic grains transform to austenitic grains (³islands´). For chloride pitting and crevice corrosion resistance. Corrosion resistance: As with all stainless steels. duplex stainless steels can be lower in cost. humidity.material cools to room temperature. similar to the range for austenitic stainless steels. they are not as resistant to this form of attack as ferriticstainless steel. i. tougher than ferriticstainless steel. Duplex stainless steel are in most cases. a property that can be used to easily differentiate them from common austenitic grades of stainless. EN or other standards may cover products sold by Aalco. This combination of properties can mean some compromise when compared with pure austenitic and pure ferritic grades. . the most widely used duplex stainless steel is 2205. The name 2205 comes from a typical composition of 22% Chromium and 5% Nickel. Their microstructures consist of a mixture of austenite and ferrite phases. Whilst duplex stainless steelare considered resistant to stress corrosion cracking. Other designations for 2205 are given in the table below. duplex stainless steels display properties characteristic of both austenitic and ferriticstainless steels. Duplex stainless steelare also magnetic. UR52N+ is a popular ³super duplex´ grade that has high strength and exceptional corrosion resistance. As a result.can lead to significant cost and weight savings compared to a solution in austenitic stainless steels. However. Alloy Designations Due to excellent corrosion resistance and high strength. Topics Covered Background ASTM A240/A240M Alloy Designations Chemical Composition of Duplex stainless steel Properties of Duplex stainless steel Mechanical Properties of Duplex stainless steel Physical Properties of Duplex stainless steel Corrosion Resistance of Duplex stainless steel Heat Resistance of Duplex stainless steel Fabrication of Duplex stainless steel Heat Treatment of Duplex stainless steel Machinability Welding of Duplex stainless steel Applications of Duplex stainless steel Supplied Forms Background Duplex stainless steelare extremely corrosion resistant. ASTM. 304 and 316.e. work hardenable alloys. ASTM A240/A240M Property data given in this document is typical for flat rolled products covered by ASTM A240/A240M. It is reasonable to expect specifications in these standards to be similar but not necessarily identical to those given in this article. the corrosion resistance of the least resistant Duplex stainless steel is greater than that for the most commonly used grades of stainless steel. Strengths of duplex stainless steels can in some cases be double that for austenitic stainless steels. 5-8.0 .02 24-26 3. like sulphuric acid. Some standard designations for duplex stainless steel alloys Euronorm 1.03 max 2.4462 1.02 21-23 2.This grade differs in composition to 2205 stainless steel in that it contains an addition of copper.5-3.0-5.5-6. Typical chemical composition for two duplex stainless steel alloys % C Mn Si P S Cr Mo Ni N Cu 2205 0.0 0.8 0.2-0.08-0.0 1.03 0.5 0.0 0.5-3.2 UR52N+ 0.4507 UNS S31803 S32205 S32520 S32550 BS 318S13 En Grade 2205 UR52N+ Chemical Composition of Duplex stainless steel Table 2. UR52N+ is the widely used registered trade name of the Usinor group. Other designations it is known by are given in the table below.5 4.035 0. Table 1. There are many other duplex stainless steel most of which are proprietary grades developed and produced by individual manufacturers. This gives greatly improved resistance to hot chlorides and strong reducing acids.5 0.03 max 1.0 5.35 0. 085x10 -6 UR52N+ 7.m) Thermal Conductivity (W/m. causes embrittlement at temperatures over about 300°C.085x10-6 17 at 100°C 13. .805 200 0.2% (MPa) Elongation A5 (%) Hardness Rockwell C 2205 620 450 25 31 UR52N+ 770 550 25 - Physical Properties of Duplex stainless steel Table 4. Typical mechanical properties of two duplex stainless steel alloys Grade Tensile Strength (MPa) Proof Stress 0. Duplex grades can readily be used down to at least -50°C. The super duplex grades are even more resistant to corrosion. Fabrication of Duplex stainless steel Fabrication of all stainless steel should be done only with tools dedicated to stainless steel materials.810 205 0.Properties of Duplex stainless steel Mechanical Properties of Duplex stainless steel Table 3. Heat Resistance of Duplex stainless steel The high chromium content of Duplex stainless steel that p rotects against corrosion. Typical mechanical properties of two duplex stainless steel alloys Property Density (g. They have high resistance to intergranular corrosion. Duplex stainless steel exhibit very high resistance to stress corrosion cracking.5x10-6 to 200°C 19 at 100°C 13. These precautions are necessary to avoid cross contamination of stainless steel by easily corroded metals that may discolour the surface of the fabricated product. Tooling and work surfaces must be thoroughly cleaned before use.cm3) Modulus of Elasticity (GPa) Electrical Resistivity ( .7x10-6 to 100°C Corrosion Resistance of Duplex stainless steel Duplex stainless steelare extremely corrosion resistant.K) 2205 7.K) Thermal Expansion (m/m. At low temperatures duplex stainless steels have better ductility than the ferritic and martensitic grades. Even in chloride and sulphide environments. Dull edges cause excess work hardening. All standard welding processes can be used. Applications of Duplex stainless steel Duplex stainless steel are typically used in: Chemical processing. They can however be work hardened. Solution treatment or annealing can be done by rapid cooling after heating to around 1100°C. Machining can be enhanced by using the following rules: Cutting edges must be kept sharp. Machinability Although machinable. transport and storage Oil and gas exploration and offshore rigs Oil and gas refining Marine environments Pollution control equipment Pulp & paper manufacturing Chemical process plant y y y y y y y Supplied Forms . machining of 2205 is around 20% slower than for 304. They are not quite as easily welded as the austenitic grades but low thermal expansion in duplex grades reduces distortion and residual stresses after welding. As an example. Chip breakers should be employed to assist in ensuring swarf remains clear of the work Low thermal conductivity of austenitic alloys results in heat concentrating at the cutting edges.Heat Treatment of Duplex stainless steel Duplex stainless steel cannot be hardened by heat treatment. Welding of Duplex stainless steel Duplex stainless steelhave good weldability. The recommended filler material for 2205 stainless steel is 2209. Cuts should be light but deep enough to prevent work hardening by riding on the surface of the y y material. This y y means coolants and lubricants are necessary and must be used in large quantities. the high strengths of Duplex stainless steelmakes machining difficult. making their use cost-effective for many applications. and S32003. although in commercial alloys the ratio may be 40/60. S32304. . and S32550 (Ferralium). crevice corrosion and stress corrosion cracking. They are characterized by high chromium (19±28%) and molybdenum (up to 5%) and lower nickel contents than austenitic stainless steels. S32750 (2507). The standard duplex is 22% chromium with S31803/S32205 known as 2205 being the most widely used. the aim usually being to produce a 50/50 mix. Super duplex refers to 25% chromium grades such as S32760 (Zeron 100). Lean duplex refers to grades such as UNS S32101 (LDX 2101). The properties of duplex stainless steels are achieved with an overall lower alloy content than similar-performing super-austenitic grades. particularly pitting. Duplex stainless steels have roughly twice the strength compared to austenitic stainless steels and also improved resistance to localized corrosion. Duplex grades are characterized into groups based on their alloy content and corrosion resistance.Aalco typically supplies 2205 duplex stainless steel in the following forms: Round bar CCP plate Quarto plate y y y y Duplex stainless steels have a mixed microstructure of austenite and ferrite. Hyper duplex refers to higher chromium grades such as S32906.