The Design and Propertiesof Steel Castings PART III Properties W.J. JACKSON - In Part 111of this series the properties of steel castings and their implications for design are discussed. Engineering Properties The effect of carbon content and heat treatment on the tensile properties of plain carbon steels is illustrated in Fig. 1. Typical properties available from low-alloy steels are indicated in Fig. 2 (a) and (b); it is apparent from these diagrams that for this class of steel, quenching and tempering can produce higher strengths 1000 - - - - - - and a superior combination of mechartical properties than normalising and tempering. A summary of minimum specified mechanical properties and typical physical properties is given in Table 1 for some steels to BS 3100. Steels for pressure-containing castings are similar to those in BS 3100, but are covered by BS 1504. A typical application for a high strength steel is shown in Fig. 3 -- how else could such a combination of strength, aesthetic and functional design be achieved, other than by a steel casting? go( 50( ,o~- / ANNEALED NORMALIZED < 40 ~ ~o BO '~<EDUCTION OF AREA - 750 30 10 50 Z ~k~ 0 TENSILE STRENGTH i i 800 TENSILE STRENGTH N mm 2 Z "1" i 600 .~," '~% % I k- i i 1000 Fig. 2 (a) Tensile properties of low alloy cast steels (normalised and tempered). Z 500 -30 Z w p- -20 ~: z < z 0 o 250 Z q YIELD STRENGTH I 0.1 I 0.2 ELONGATION I 0.3 I 0.4 I 0.5 10 I 0.6 CARBON. % Fig. 1 Variation in tensile properties with carbon content and heat treatment, for plain carbon cast steels. M A T E R I A L S IN ENGINEERING, Vol. 2, DECEMBER 1981 For cast steels the endurance ratio (i.e. the ratio of endurance limit to tensile strength) varies from approxirnately 0.40 to 0.50 depending on the tensile strength which in turn depends upon chemical composition and heat treatment. The more rapid the cooling rate from heating the higher will be the fatigue properties and this is illustrated for the annealing and normalising of plain carbon steels in Fig. 4. In general, the endurance ratio is slightly higher for low- and medium-alloy steels than for plain carbon steels. Some typical fatigue 310 45%C AW2 0.2 13.8 A 460 A.2 12.457 A 208.54 43.78 20°C-200°C A N 10.538 A 547 A 75.7 43. DECEMBER 1981 .815 214.212 A 494 A 73.538 A 544 A 79.4 WQT 11. N or QT 7.7 QT 13.677 A 208 ANT 179 193 ANT 229 259 A 208 12.8 12.3 14.1 WQT 13.9 WQT 14.6 20°C-300°C 13.85 A A.65x/A % Angle of Bend Radius of Bend Charpy V-notch Impact.734 MATERIALS IN ENGINEERING.1 14.4 13. N or 460 460 A A 50°C 100°C 50°C 100°C 44.6%C 430 490 540 620 690 230 260 295 325 370 22 120 ° a 1.14 A 2.5 A N 12.2) N/mm 2 Elongation on 5.9 14.6 WQT 12.38 42.2 QT 12.36 13.8 QT 11.74 14.25%C A2 0. J Brinell Hardness Final Heat Treatment Representative Physical Properties Specific Gravity Specific Heat (c) J/Kg C at 29°C Thermal Conductivity (k) W/m°C 20°C-500°C 29°C-600°C Electrical Resistivity (/9) microhm m at 20°C Youngs Modulus (E) N/mm 2 Modulus of Rupture N/mm 2 Modulus of Rigidity N/mm2 Endurance Limit N/mm 2 Notched Un-notched 311 AorN A A 2.7 12.8 14.4 13.2 13.8 13.864-207.4 12.96 47.1 13.2 12.9 12.1 13.5t ab 25 a - 18 90 ° a 1.6 13.9 7.1 Minimum Specified Properties Tensile Strength (Rm)N/mm 2 Yield Stress (ReL) or 0.579-211.9 13.7 A.8 11.84 A or WQT 460 A.4 20°C-400°C 13.5 13.2 QT 14.5 13.8 12. N or WQT 7.7 12.5 14.3 13.3 A 11. 741 QT 216. N or NT A.8 QT 12.Table 1 (a) Specified Minimum Mechanical Properties and Physical Properties of some commonly-used Carbon and Low-Alloy Cast Steels BS 3100 Steel Type A1 0.2% Proof Stress (RpO. N or WQT 7.205 QT 2 1 3 .4 A N 12.1 12.5tab 20 a - 14 12 8 18 c - _ not specified not specified not specified A. N or NT A.4 13.4 14.12 50°C & 100°C Mean Coefficient of Thermal Expansion (c~) x 106/°C 20°C-100°C A N 12. 7 4 9 A 544 A 79.8 14.36 13.8 13.587 210. N or QT 7.360 N 75 N 230 2.354 A 209. 374 N 212. Vol.5 WQT 13.019 N 213.2 12.7 13.725 209.5%C AW3 0.288 AorN AN or WQT 203.8 14.5 11.04 13.1 13.8 A 460 50°C 100°C 43.0 14.9 12.9 13.5 12.2 WQT 12.7 13.290 2.3 14.81 7.35%C A3 0. 2.2 QT 13. 44 13.4 13.85 7.910 207.5 12.9 13.92 14.580 NT 212.8 12.5tab 30 a 140-212 d 17 120 ° a 3tab 25 a 156-235 d 13 90 ° a 3tab 25 a 179-255 d 11 30 152-270 d 13 _ 25 179-229 d 35 f 201-255 d 201-255NT d N.480 81. 200 NT 3.49 16.0 14.870 - 205.85 7.0 14.1 30.7 13.80 460 e 460 e 460 e _ 50°C 100°C 42.7 50°C & 100°C 460 e _ NT WQT 50°C 1 0 0 ° C 5 0 ° C 100°C 30.571 2.9 13.4 11.514 - 565 602 - 86.400 WQT 639 WQT 83.4 12.1 12. Vol.930 NT QT 218 258 334 403 m 255 M A T E R I A L S IN ENGINEERING.8 13.26 14.5tab 20 a _ 17 120 ° a 1.83 7.421 2.39 14.88 7.100 213.6 12.0 13.0 12.3 13. NT or QT WQT WQT NT WQT ANT 7.6 12.5 NT 12.0 13.4 13.9 WQT 13.4 13.720 NT 213.8 13.7 13.32 12.7 39.A4 1%%Mn A5 1½%Mn B1 C-%Mo B2 1¼%Cr-Mo B3 2¼%Crl%Mo B5 5%Cr-Mo BT1 540 620 460 480 540 620 69O 320 370 260 280 325 420 495 16 - 18 120 ° a 1.080 WQT 661 WQT 83.8 11.767 WQT 209.2 14.5 13.86 7.8 12.6 39.6 13.83 13. NT or QT N.3 12.04 WQT 12.28 15.015 WQT 207.98 13.3 13.50 12.8 WQT 12.3 12.850 NT 653 NT 81. N t o r QT NT NT NT NT or QT QT A.8 _ BW2 C-l~r m 7.1 42.4 12.53 WQT 203. 2.8 NT 11.9 12.7 12.82 7.980 WQT 2. DECEMBER 1981 WQT 309 312 . .d t o~ 6 =.-n Z ~ O I I I N N "~ " eN o O' O o o r-- O o or ~ 0 "~ O o o o O . o o ~"¢1 o I t""- . . ['4 .-. ~ .L. o o o o o o r~.. O~ O 0 ~ N e o 00 o 0 0 0 ~ o o o E O 0 N O O~ o 0o E O e'q 6 a~ o I g ~ ~ o ~ . ~ I I ~ °~ ~ 0 = O mN ~ ~ ~m 313 MATERIALS 0 0 0 0 0 0 0 0 ~ ~ ~ IN ENGINEERING.0 0 0". [-O' O 0 o~...d. ~ Z ° ~ O ~ DECEMBER 1981 . ~0ol e~ ~ ' ~ 0 .-~ e'~ .. V01. o I t~ 0 I Z E O' o E 8 o e'q m '~ E o~ 0 o o I r-:~-- .2.O O 0 I e~ ~ o [ 1 I I I 6 ~. O ~De~ o o o o o ~ . . . earlier in the text.i Fig. :~ .. Fig. Apart from notches... = Oil Quenched.ou0h.. Where due to design of casting.. For design purposes.. yield stength.. 4(a) .. mainly generated b y SCRATA. The as-cast surface. which can be used in a truly quantitative manner for MATERIALS IN ENGINEERING.).. BrineU hardness is only required if requested by the purchaser and stated on the order. 3. annealed Unnotched Wrought Cast test results are given in Table 21 ... 5. 3 I 800 I 1ooo I 12oo / I aoo I T~NS~LE STRENGTH N mm 2 Fig. -60°C. however. Not applicable to free machining steel. o... Vol. it is important to k n o w crack initiation and crack propagation data. and this range becomes wider as carbon content increases. are summarised in Table 4.. = Air Hardened. increasing the carbon content will raise the hardness. In general. the endurance limit is lowered b y 30%.. compared with a polished surface. t= Thickness of test piece Impact test is mandoatory only if specified by purchaser. Provision is made for supply of this steel with specified impact at low temperatures (-196°C) if stated on order.. Recently generated data on these parameters are summarised in Table 3 2. = = g h k m ..... Alloying elements exert their influence on properties b y altering the form and dispersion o f carbon in the steel. Either Charpy or bend test may be specified. 4 Fracture toughness data.... = Tempered. Factors Affecting Mechanical Properties O C3 The element in cast steel that influences properties more than any 2OO I lOa Fig.. For a steel o f a given carbon content. oo . normalised and tempered and comparison \ with wrought steel.. 16oo Tensile properties of low alloy cast steels (quenched and tempered). gives fatigue properties superior to asroiled or as-forged surfaces.. L Plain c a r b o n .. 4(b) S-N curves for plain carbon cast steel.. In such cases the values to be obtained should be agreed between the manufacturer and purchaser at the time of enquiry or order.. 2(b) Bruce Anchor.Legend to Table 1 A and B A N T Q SR WQ OQ H a b c d e f Annealed.. when t h e casting surface remains.IJ~ll¢ lOs lO6 CYCLES TO F A I L U R E lo ~ S-N curves for plain cast steel (annealed) and comparison with wrought steel. without the loss in ductility 314 .~l i lO4 i i iiiiiI i lO 5 i i i IiiiJ i i i i ilJlJ to 6 CYCLES T(] FAILUHF . The presence o f a notch reduces the endurance limit o f b o t h cast and wrought steels. it is not practicable to liquid quench the casting it may not be possible to achieve the specified impact properties. For example... c.. as mentioned Notchea prediction o f service life.. Free machining specification in brackets. = Stress Relieved. = Water Quenched. DECEMBER 1981 other is carbon. Normalised.. surface condition has an important bearing on fatigue properties. while simultaneously ductility is decreased... if agreed between manufacturere and purchaser. and tensile strength o f a steel... Machined castings for use in marine and slow speed diesel engines are shown in Fig.. 2~ . heat treatment can produce a wide range o f properties... = Quenched. 25°C.. They allow for greater hardness and strength." 1 1oc~o zX. that can be used in conjunction with the fatigue propagation data. cast in high strength steel (Courtesy of Bruce Anchor Ltd. 2... 42 0.32 0.1 35.0 14. as the outer layers invariably are the most highly stressed. 7. T605°C Q830 °. Low Temperature Properties Heat treatment.5 Steel Specification and Type Brinell Hardness Number Endurance Limit~ N/mm UnNotched Notched UnNotched Notched Notch Sensitivity factor.2 17. T620°C 669 684 843 437 428 731 58. Alloying additions in excess of those required for minimum hardenability can result in some deterioration in properties.28 0. for a given steel and section size.48 0.and mediumalloy steels are markedly influenced by the tempering temperature used.5 BS 3100 BT1 Cr-Mo N900 °. 9 s . T650°C Q845 °.6 26. it has been found that.31 0.49 0.0 BS 3100 BT2 Ni-Cr-Mo N900 °.30 0. the effect of mass on mechanical properties is due to such factors as segregation. the effect of decreasing the tempering temperature (i. with the result that more complete hardening can take place in thicker sections. However.8 14.5 58. T650°C Q845 v. In steel castings. This slight reduction in endurance ratio is probably of negligible importance with regard to the performance of the section as a whole in bending fatigue. and a slight decrease in notchedbar impact strength 7 .51 * A = Annealed. % Elongation L=4D.53 0. by its effect on microstructure.57 BS 3100 BT3 Ni-Cr-Mo 262 375 434 534 241 332 0. T650°C 761 948 590 865 53. and density.4%C A900°C N900 o. The top curve for the steel containing boron shows that high hardness is maintained at much greater depths in the testpiece. N = Normalised.5 9.5 55. The bigger difference in strength from edge to centre in the quenched steel is merely due to the outer layers having been fully hardened by quenching. T650°C Q845 °.29 0.0 24.% BS 3100 A3 0.43 0. Among factors contributing to the slight decrease in endurance ratio are an increase in grain size. but heat treatment also plays a part.8 18. which would occur if a similar hardness were obtained by increasing the carbon content. and microstructural irthomogeneity associated with inter-dendritic segregation.28 0. This mainly involves running and feeding considerations. with increasing mass. In the main.23 0.43 BS 3100 BT2 Ni-Cr-Mo 223 286 372 448 229 266 0. ~l tempered low.29 BS 3100 A5 1½% Mn 201 201 269 287 333 403 215 218 258 0. has a major influence on impact strength and the effect is of particular importance with ferritic steels for low temperature service. 2.28 0.49 0. In studies on the effect of mass.8 BS 3100 BT3 Ni-Cr-Mo N900 °.2 27. provided that they are properly designed from the foundry point of view.47 0. and the yield/tensile strength ratios are considerably higher.5 24.5 BS 3100 A5 11/2%Mn N900 ° T425°C N900 °. The fatigue test results in Fig. 75 and 150mm sections do not differ greatly from the normalised and tempered to the quenched and temp- ered conditions. q Endurance Ratio BS 3100 A3 0. the change in endurance ratio is not large. a decrease in density and carbon content. T635°C 777 1010 596 903 43. typical results being given in Fig. The depth-of-hardening capabilities of a steel are measured by the Jominy end-quench test.30 0. This is clearly illustrated by the results of annealing.31 0. the maximum impact values at the higher testing temperatures are lowered by decreasing the tempering MATERIALS IN ENGINEERING. the fatigue properties also tend to be lower in the centre of the section.45 0.48 BS 3100 BT1 Cr-Mo 223 311 354 423 230 279 0. microstructure. the smaller sections exhibit greater strengths and uniformity than the larger pieces. T550°C 871 1160 692 1075 50.7 52.7 34. DECEMBER 1981 . raising the hardness and tensile strength) is to raise the impact and fracture appearance transition temperatures. T = Tempered. Vol. and a similar steel with a boron addition s .46 0. The effect of hardenability on the mechanical properties of three section sizes of a Ni-Cr-Mo steel is shown in Fig. reasonable uniformity of properties can be obtained in castings of fairly complex configuration.5 19.0 20. Since tensile strength tends to follow a similar pattern.45 0. The transition temperatures of hardened a.4%C 156 187 229 259 179 193 0. for a lowcarbon steel shown in Fig.0 14.40 0. Q = Liquid Quenched. Nevertheless. normalising. 315 The section size or mass of any metal part will affect mechanical properties by virtue of its influence on freezing rate and cooling rate after heat treatment.44 0. their purpose is to increase hardenability in thicker sections. 8 show that. there was a decrease in strength and ductility measured at the centre of a section. In addition.Table 2 Fatigue Properties of Typical Cast Steels in Different Conditions of Heat Treatment with Notched and Un-Notched Test Pieces Steel Specification and Type Heat Treatment* Tensile Strength N/mm Yield Strength N/mm Reduction of Area. an increase in inclusion size.40 0.30 0.32 0. The ductilities of the 30. A similar decrease in endurance ratio at the centre of a heavy section is also exhibited by wrought steels. 6 for a 1½% Mn-Mo steel. This is possibly due to increased segregation effects and the presence of retained austenite 6 . and annealing plus normalising. non-metallic inclusions.50 0.e. T650°C 576 649 340 386 46. In general. The important point is that the properties at the centre of each section have been improved by quenching and tempering.68 0.28 0. This is done by altering the thermal transformation characteristics of the steel. N 980°C.01 9.26 x t0.3%C BS 3100 A2 0.3%C BS 3100 A2 0.06 2.59 x 10 `*2 N 200 x 100 x 451) 588 to 604 0. N 975°C.07 10-7 -3.1 3. e.79 1. A fully austenitic structure or a low magnetic permeability is not necessarily a guarantee of good lowtemperature properties.90 5 x 10.25 101765 A 900"C.7 -5. can also have an effect. OQ 9 0 0 ° C . T 5 0 0 ° C and WQ Re-tempered 610°(" and BS 3100 BTI 1½% Mn-M~ wo BS 3100 BT2 Ni-Cr-Mo BS 3100 AW3 Cr-C * A = Annealed: N = Normaliscd.26 x 10. at lower temperatures.80 10-6.3%C BS 3100 A2 0.26 6.04 6. In cases where the temperature is not very greatly higher.58 x 1037 N 200 x 100 x 450 588 to 604 0 2. 2.13 5.38 x 1033 N A 960°C. carbon and stabilising additions should be kept to a very low level.67 1. lowand medium-alloy steels at temperatures down to -60°C.02 x 1029 A 2110 x 200 x 2011 542 1o 574 0.02 10166 31111 x 100 x 132 7411 10-5.25 4. N 960°C.3%C BS 3100 A2 0.17 1013"6 587 1). 5 9 x 10-8 -9.26X 10-8 -24.3%C BS 3100 A2 0. Vol. SR = Stress Relict" Annealed. T 700°C A 900°C. WQ 9 3 0 ° C .2 2.5 2.1)1 9.29 x 10-9 -17.11 8.42 X 1038 21111 x 100 x 4511 545 11 I 1.32 1.7 -4.34 x 1059 31111 x 1011 x 132 430 2. it may generally be said that low-carbon MATERIALS IN ENGINEERING.29 3 . OQ 8 8 0 ° C . Non-stabilised 18/8 type steels are markedly superior to the titanium and niobium-stabilised steels. stress max. although impact strength can rapidly decrease as the temperature is lowered. T 640°C 30(I x 100 x 132 8511 1. WQ = Water Quenched" OQ = Oil Quenched: T = Tempered temperature.9 2.1 x 10.09 10-6.94 10.85 x 1067 542 to 574 0 10 3. 5 -4.76 10197 31111 x 1011 x 132 6611 1..64 1. These effects are illustrated in Fig. stress Test Block Type Heat Treatment* and/or Size mm 0.7 -15.t -4. T 680°C SR 6 8 0 ° C .3%C BS 3100 A2 0.02 6.27 x 10.11 5. although large amounts of delta ferrrite in 18/8 types of steel will lower impact properties.78 X 1060 21)(I x 100 x 4511 774 0 11. Y 640°C A 960°C.09 x 1085 125 x 32 x 3110 619 0 10 2.9 -3.8 -10. Other factors.49 6. N 960°C A 950°C.03 x 10.g.06 2.11 10-6. for optimum lowtemperature properties. austenitic steels are required.93 2. 10 for a 2½% Ni-Cr-Mo steel tempered to three hardness levels s .29 3.3%C BS 3100 A2 0. T 6 0 0 ° C and 200 x 200 x 20(1 565 to 608 0.9 x 10.8 -9.3 x 1030 N 125x32x300 619 I).29 x 10-9 -4.7.90 5 X 10-9 -18.35 7.9 -8. In general.21 2.98 x 1035 A 200 x 1011 x 4511 554 to 576 0.64 1.1 X 10-8 -18.3%C BS 3100 A2 0.3%C BS 3100 A2 0.5 3.93 8.5 3.53 101515 31111 x 100 x 132 5011 2. Elevated Temperature Properties Steel castings are widely used in environments where the temperature is above that of normal room temperature.8 -12.3%C BS 3100 A2 0. grain size or distribution of carbides.8 -9.8 -16.9 X 10-8 -9.38 x 1063 A 125 x 32 x 3011 2.43 x 1038 0 10 2.32 1. no distinction is made between the properties at that 316 .2% Proof Stress N]mm 2 A 125 x 32 x 300 587 0 A 2 0 0 x 100 x 450 5541o576 A 200 x 200 x 201/ N A Ko MN/m J/ 2 n c 9 2.Table 3 Fatigue Crack Initiation and Propagation Data for Cast Steels Steel Specification and Type BS 3100 A2 0.8 A 900°C 3011 x 100 x 132 360 2.5 2.45 x 1066 N 200 x 200 x 200 565 to 608 0 3.8 -8. WQ 9 0 0 ° C . DECEMBER 1981 cast steel is satisfactory at temperatures down to 4 0 ° C or -50°C.98 1.3%C BS 3101/A2 0.3%C BS 3100 A4 1½%M n BS 3100 B7 Cr-Mo-V BS 3100 BT2 Ni-Cr-Mo BS 3100 A4 1½% Mn BS 31/)0 B7 Cr-Mo-V BS 3100 BT 1 Mn-Ni-Cr-Mo R value min. Austenitic stainless steels usually retain a high toughness at very low temperatures.11 8.63 X 1021 2011 x 1110 x 4511 411 0 9. A 960°C.0 1020.03 X 10.5 4 6 m B wo A 900°C.5 2.1 1.65 3. To summarise the applicability of the various types of steels. 1 0.026 to 0. COD** tSi or ~c mm (N/mm 3/2) K~C/Oy m½ BS 3100 B2 Plain Carbon A 950°C 25 323 0. nozzle segments.057 to 0. T 6 8 0 ° C and T 700°C 25 504 46 (1454) 0.066 to 0.173 0. T 600°C 40 750 to 820 66 to 96 (2086 to 3034) BS 3100 BT2 Ni-Cr-Mo A 900°C .021 to 0.03 0. as shown for various steels in Fig. T = T c m p c r c d .29 BS 3100 A4 1½%M n A 960°C . T 680°C 60 367 It) 54 to 69 (1706 to 2180) 0. N = Normaliscd. temperature and room temperature properties. T 6 0 0 ° C and WQ 25 742 BS 3100 BT2 Ni-Cr-Mo A 900°C .Table 4 Room Temperature Fracture Toughness Data for a Variety of Cast Steels Material Specification and Type Heat Treatment* Section Size mm 0. N 1050°C. For any given instance it may be important to know the short-time. At temperatures ranging up to 750°C. the strength properties deteriorate.02 0. T 635°C 25 46(1 48 (1517) 0. For many applications the design life of the component is much longer than a practical laboratory test and it becomes necessary to extrapolate the experimental data. SR = Stress Relief Anncalcd. 12(a)) used in the Rolls Royce Olympus engine (Fig. 12 (b)). and scaling properties of a cast steel.07 0. long-time.01 0.07 550 520 to 585 0. N 960°C 25 427 0 . at temperatures of the order of 300°C.084 to 0. N 870°C . This is particularly true in the case of engineering components operating at temperatures up to about 317 750°C.14 BS 3100 BW2 1% Cr-C A 920°C .050 0.11 20 0.058 to 0.032 to 0. 50 52 to 71 (1643 Io 2244) 0. 11. N 920°C .08 BS 3100 A4 1V2%Mn A 960°C . WQ = Water Quenched. DECEMBER 1981 . Vol.155 BS 3100 BTI Mn-Ni-Cr-Mo SR 6 8 0 ° ~ WQ 930°C.097 0.016 to 0. N 870°C . OQ 8 8 0 ° C T 640°C 25 853 BS 3100 BT2 Ni-Cr-Mo A 950°C . OQ = Oil Quenched. impellers. T 640°C 30 715 to 740 85 (2686) BS 3100 BT2 1¼%Mn-Mo A 930t)C . OQ 880°C. ** The nomenclature for COD measurements varies according to the behaviour of the test piece. N 975°C . which enable a master curve to be constructed from M A T E R I A L S IN E N G I N E E R I N G .018 to 0. WQ 8 9 0 ° C . An explanation is containcd in BS 5762. However. N 960°C 50 20 412 0.024 to 0.5%C A 900°C 25 360 0. and here furnace and kiln parts may be quoted as examples. T 635°C 60 419 59 (1860) 0.1 BS 3100 B7 ½%Cr-½%Mo-¼%V A 950°C .026 0. turbine housings.15 BS 3100 B7 ½%Cr-½%Mo-¼%V A 960°C . 1 8 to 0.12 72 (2275) 0. An example is given of a stator ring (Fig.05 * A = Annealed.133 T 700°C 20 BS 3100 AW3 0. creep properties are frequently more important for design purposes. and accumulators. While it is obviously important to know the instantaneous or short-time strength properties of a steel at its operating temperature.02 0. the most common being based upon timetemperature parameters. such as valve parts. oxidation resistance is of secondary importance to creep resistance but.2~ Proof Stress N/mm 2 KIC 3/~ MN/m ~.05 to 0. 2.09 BS 3100 B7 ½%Cr-½%Mo-¼%V A 1000°C.129 to 0. T 680°C 60 366 to 446 0. N 1000°C.122 0.117 0. N 980°C . as operating temperatures exceed this order of temperature. There are several methods for data extrapolation.04 to 0. T 6 5 0 ° C and WQ 30 640 t() 758 BS 3100 BW2 1% Cr-C A 920°C .09 BS 3100 410C21 13%Cr A 1050°C. SR 6 0 0 ° C .04 t o 0.095 to 0.09 to 0.08 0.11 to 0. the order of importance is reversed. I 24 ..n 800 700 > I g 600 500 ~"~. . 39 . I 6 . and it is for this reason that the maximum amount permitted in Fig. However. To obtain high permeability. I . . one of the most common being plots of stress vs temperature for lines of constant rupture life. . the carbon content of the steel should be very low. 5 Selection of steel castings for the marine industry. 13. rather than average values and in recent years an internationally agreed method has been evolved for deriving the former values from test data. The designer is interested in the minimum 20 10 30 40 b() 60 . DECEMBER 1981 318 . Typical minimum 0. I 9 . 2. . Examples of the use of high-permeability steel castings include electromagnetic clutches and brakes. as to the design safety factors to be applied. strength is an additional requirement of some importance. Consequently. 1/16in. and this sometimes leads to confusion.2% proof stress properties for 2¼% Cr-Mo and ½% Cr-½% Mo-¼% V low alloy steels are given in Figs. . I 15 .2% for carbon and low alloy (ferritic) steels. Magnetic Properties Because of their excellent combination of strength and suitable magnetic properties. 3 . AM1 having a lower carbon content and better magnetic properties than AM2 which in turn has the better strength. 169 . which stress rupture properties can be determined at temperatures other than the original test temperatures. = I 27 . Fig. Mn Mo 300 200 . The proof stress values in current use are the 0. for many applications in electrical engineering. yokes for electromagnets.. and the 1. thus giving a complete description of the mechanical properties over wide temperature ranges. . There are several ways of presenting the stress rupture data. I 21 . I . and stator housings and armatures for electric motors and dynamos. (Courtesy of British Steel Corporation). . Although the tensile strength provides useful information. . I 33 . steel castings are very widely used in electrical plant and machinery.. i 18 .0% for austenitic steels. 172'/. in BS 3100 there are two steels. I .. These curves are frequently plotted on the same diagram with curves showing the proof stress results from short-time tensile tests.expected value. 42 DISTANCE FROM QUENCHED END OF JOMINY BAR. Many standards however still contain elevated temperature proof stress minima based upon the wide experience of the steel industry. Vol. MATERIALS IN ENGINEERING. The effect of carbon content is typified in Fig. 14 and 15 together with average tensile properties. Manganese acts in the same way as carbon in impairing magnetic properties. 36 .~ 400 "r" ~'~. I 12 • . 6 Jominy end-quench hardenability curves for lY2%Mn-Mo steels with and without boron. the parameter used in designing components is the proof stress. A typical graph of this type for a 1¼% Cr-Mo steel is shown in Fig. I 30 . . . have no significant effect on magnetic properties 14. 1 3 Aluminium.25%) 1 o .34%. 10 40 I 30Z '-30 mm( 1v. hysteresis loss varies from of normal commercial carbon content 9. P. after normalising and tempering. non-magnetism is not necessarily a criterion when considering the possibility of embrittlement at elevated temperatures by sigma phase. carbon is preferred since it gives the most favourable relationship between gain in yield strength and loss in magnetic induction 11.9 tesla.600 to 11. grinding or high-stress abrasion.dn) .003. DECEMBER 1981 . Three general types of wear have been recognised. magnetic properties have no relation to the applicability of the casting. cast austenitic manganese steel is excellent. lowering the manganese content to 10. and adding approximately 7. when small and evenly distributed. it is important to know the hysteresis curve of Silicon and residual elements (S.2% added weight) 12 . Pb.) section of Ni-Cr-Mo cast steel. N & T 30mm(11/. the steel.2%. and scratching or low-stress abrasion. Where improved machinability on non-magnetic steel is required. 1 2 . when used in normal amounts (e. If. the carbon content may be raised or alloying additions may be made. For carbon contents between 0. V) have only represent considerable energy loss.0%. but also of the environmental conditions. (e. the residual magnetism should be low 1 s Designers of electrical apparatus sometimes require non-magnetic cast steels. down-time on the machine can represent a considerable loss.g.600 ergs/cc/cycle for a 319 flux density of 1.0% of nickel. Of the usual alloying elements.e. gouging abrasion. Vol. Section thickness can also influence magnetic properties. which is very necessary for deoxidation of low carbon steels also has no significantly adverse effect upon magnetic properties.5 per cent I o When selecting the grade required for a particular application.10 and are insignificant when the steel is and 0. For this purpose.002 to 1. whether in worked or cast form. Nonmetallic inclusions. 2. i._ 75 mm(3in) 150 mm (6in) -I Fig.Ni-Cr-Mo STEEL. With regard to the general corrosion resistance of 18/8 type steel at normal temperatures. but also it is able to withstand severe wear16. as not only is it virtually non-magnetic with a permeability of 1. the composition may be modified by lowering the carbon content to 0. In any particular service. Wear-Resisting Properties The replacement of steel parts that wear in service can be an expensive item and may form a major part of the cost of the process being carried out. Furthermore. 7(a) Distribution of tensile properties across a 150mm (6 in. very low magnetic properties of steel castings need only be a requirement in electrical applications where nonmagnetic material is essential. Apart from the actual cost of replacements. This is because of the presence of a small amount of ferrite. Cu. MATERIALS IN ENGINEERING. Resistance to abrasion by nonmetallic materials is a function not only of the steel. small effects upon magnetic properties. such as in magnetic brakes and clutches. these steels is U. as wide hysteresis loops Cr.g. Mo. In applications where there is an alternative magnetic field. a material of very much higher strength is required. however. less than 0. a compromise must be made between these opposing factors. Consequently. Ni. non-magnetic corrosion-resisting steels may be required. more than one of these types of wear may operate. Austenitic chromium-nickel steel is occasionally found to be slightly magnetic. as illustrated by the data I 8 in Table 5. For applications involving intermittently applied magnetic fields. Sn.in 1 O SECTION~ 100(] TENSILE STRENG'~H rl 7~mm(3in) SECTION !150mm (6in) A SECTION 800 % I E 600 Z J ~ 600 40C ~ 50 40- 30- I ~ 20- 0. For other purposes. not more than 0. resulting from a particular balance of alloying elements 17. 2 8.7 1. when gritty materials are crushed between the two surfaces.2O .Ni-Cr-Mo STEEL. which can be the main factor deciding the selection of a suitable wear-resistant material.005 1. lo 40 ELONGATION IN 5 0 m n (2inl 3o -3-.0 I0..) section of Ni-Cr-Mo cast steel.659 2. so that relatively brittle materials can be used.105 1.084 1. Gouging abrasion is actually a cutting process that occurs when rocks or other lump materials cut into a wearing surface. In this type of abrasion.315 3. 2. and can be accompanied by severe impact. 75mm Magnetic Ferrite Magnetic Permability (%) Permeabifity 1. Scratching or low-stress abrasion or erosion occurs when loose particles move freely on the wearing surface.005 1.5 7.0 320 .150 1.8 3. 7(b) Distribution of tensile properties across a 150mm (6 in.3 7. While overall loads may be low.753 MATERIALS IN ENGINEERING. Grinding or high-stress abrasion occurs when two surfaces rub together in the presence of an abrasive material.2 1. DECEMBER 1981 Ferrite (%) 0 0.025 1. t I ~0 I i 150 m m (6in) SECTION SIZE Fig.615 1.0 19. Vol. e.t' Y I F L D STRENGTH 800 I 50 REDUCTION OF AREA 40 - I I 3o ~ 20 3. 150mm Z~ (6m) SECTION ~ :N _E E 80 ~ z tj ? " 10oo- ( :. the stress on individual areas is very high. after quenching and tempering..010 1. WQ & T 30mm (1'/4in) TEN7SlLI~ STRENGTH I O SECTION [] mn~ (3in) SECTIC~N ~ . 20ram Thick Section. ."'t"3~ ~ C ~ . impact forces are low. Table 5 Magnetic Permeability of Thick and Thin Sections of 18/8 Steel Castings in Relation to Ferrite Content Thin Section.g.I but it is usually possible to isolate the dominant type.4 2. It can occur at high or low velocities.0 16.665 2.829 0 0 0.316 1. ml t~ o O 321 MATERIALS IN ENGINEERING.. m ~1~ \~ !J! \ ~ .'== o o = l I I I I ! I 0 c - I < m o r~ =~ o_ B = =. I _ 0 I O 0 i . I I I ~3 I r.% FIBROUS FRACTURE CHARPY V-NOTCH IIVIPACT ENERGY(J) . 0 O o ~Zr~ . 2.-~ .-t i X. DECEMBER 1981 .=k ~. X~. .\. t ¢. . Vol. ~~.0 -- 0 N I I I I | 0 to- o O I \ x... Vol.5 .J .. 2... DECEMBER 1981 322 ..~ !?) ~ = 63~ A U.\'\" \\ \ % U..I e~ \\ _ a z h- e- I-- r- t0 z < \ \ O >- ~ o o I I 0 0 0 L~ I I I I I I oW 0 3EIfIIC)VU=I snoEI813 % (r) AE)EI~IN3 IOVdlAII H~)ION-A AdEI~H3 Q. Z ~J O0 r- oc]~ 0 0 ~uJUJlN 111/~17 30NVEInQN3 MATERIALS IN ENGINEERING. E 0 ¢- . tO r- t0 ~ . \ \ \ o~ - • • \ \ x ..5 E E E E Z E E P3 t'~ i ~ .. O E eC13 o=N .E N O N cO o °( m.I < . - AN. D E C E M B E R 1981 .¢40-- 7oo 7O 320-300-- REDUCTION OF AREA - TENSILE STRENGTH z 780F 760- z 500 00 < 5o 50000 h z ?4t 2~t ~.2% proof stress and average stress rupture values for 1¼%Cr-Mo Cast steel (BS 1504-621).~oo /. C Mean values and typical minimum 0. C 1 t 100 200 t I. NORMALfSED ..ro~ ¢60 . 2.proofstres ~ ~ ~ s J. 13 Typical minimum 0.2% proof stress for ~%Cr-~%Mo-¼%V cast steel (BS 1504-660).o 1oo ELONGATION . Vol.. Fig..10% and 0.. 15 Average values and typical minimum 0.o 200 :c ELONGATION 1or ii! I I too 2o0 t 3O0 I I 400 500 / 60 o o TEMPERATURE. 323 MATERIALS IN E N G I N E E R I N G . TEMPERATURE. .~ .2% proof stress for 2¼%Cr-Mo cast steel (BS 1504-622). 400 ^ Z < 18[ 3o _g Min02.....o < rt r~SILE STHENGTH . Fig.. 300 400 I I 500 600 Fig.ea~eo ~ % I loo I I J MAGNETI~NG FIELD ~ A~ rl .o'o 2~o ' 300 ' 4OO " 5 0 ' 60O ..34% carbon steels in the annealed and normalised conditions.... 14 Fig. 16 Magnetisation curves for 0..
Report "The Design and Properties of Steel Castings"