The design of any machine component is based on its capacity to withstand the load. The capacity of machine components is its ability to sustain the loading conditions without changing its configuration which may not allow the components to perform the intended function. The capacity of the components is measured on the basis of the mechanical properties obtained experimentally. The condition maintained during the testing does not exist in actual service conditions. Moreover, the mechanical properties obtained for two standard test specimens of the same material may not result in same values even when they are tested on the same machine. That is why the minimum value or range of strength is given. The selection of appropriate material property data is the responsibility of the designer to ensure the safety of his design. The design case where safety risk is very high, as in the design of aircraft, space vehicles, automobiles etc, the safest approach is to develop the mechanical property data by conducting tests involving actual loading conditions on the prototype manufactured through the specified processes, so as to emulate the actual conditions as accurately as possible during testing. Stress Quenched, tempered alloy steel High strength, low alloy steel Carbon steel Pure iron Strain Stress U F Proof stress B A 0.002 O H Strain s = e n n n e s s een tg t g + n - n - ¥ = ¥ e Ú = Stress U Stress U F F Su Sy Y Y Strain Strain e e e Cup (a) Cone (b) ( p - - ) s Strain Primary creep Secondary creep Tertiary creep Time Temperature g austenite a ferrite d delta iron d L 1540 1490 d Cementite begins to solidify Primary austenite begins to solidify d g 1400 g L g L Austenite in liquid L Fe 3 C austenite solid solution of carbon in gamma iron 1130 Fe 3 C A2 910 Acm A3 0.025% g + Fe 3 C austenite to pearlite a+g 760 723 Austenite+ledeburite + cementite Cementite + ledeburite A1, 2 ,3 A1 a pearlite + Cementite pearlite + ferrite a + Fe 3 C Cementite, pearlite and transformed ledeburite 210 0.008% 2.0% 0.83% Hypo-eutectoid steel Hyper-eutectoid steel 4.3% 6.67% Carbon % Cast iron ISI Grade Applications GCI 15 Where bending stress < 10 N/mm2: pressure < 5 N/mm2: columns, pedestals, beds, covers, housings, arms, Sliding tables GCI 20 Where bending stress < 30 N/mm2,: pressure < 100 N/mm2: beds, columns, gears, guide ways, pulleys GCI 25 Bending stress < 50 N/mm2; pressure < 200 N/mm2 columns, chucks, gears, ways, hydraulic cylinders, pump body, HP valves, work table, flywheels. Malleable CI Face plate, chuck body, vices, clamps, levers, hand wheels turret body, tool post. Cast Iron Sut MPa Suc MPa Syt MPa E GPa G GPa BHN Applications Gray CI 4.5% C Malleable CI 2% C 170 655 – 69 28 110-150 General industrial castings, pumps, cylinders 345 620 230 165 65 100-140 Automobile parts etc. Note: The properties of same material varies greatly because of different manufacturing processes, chemical composition, internal defects, temperature, measuring errors and many other factors. Consequently, catalogues of manufacturer of the material should be consulted for precise value of the properties. Designation ISI Sut MPa Syt MPa % elong BHN C07 314-392 196 27 — C10 C14 333-412 363-441 206 216 26 26 — 137 C15 363-481 233 25 137 C20 C25 C25Mn75 C30 432-510 432-520 461-560 490-588 245 275 275 294 24 27 22 21 156 170 207 179 C35 C35Mn75 510-608 540-637 304 314 20 20 187 223 C40 570-667 324 18 217 C45 C50 618-696 647-765 353 373 15 13 229 241 C50Mn1 706(min) 392 11 255 C55M75 706(min) 392 13 265 C65 736(min) 422 10 255 Applications Cold forming and deep drawing, Rimming quality used for Automobile bodies and rivets, killed quality used for forgings Cam shafts, cams, light duty gears, worms, gudgeon pins, spindles, ratchets, chain wheels, tappets etc. Cold worked-rivets, General purpose-low stresses components Cold formed levers, Hardened and tempered tie rods, cables, sprockets, hubs and bushes, steel tubes etc. Low stressed components, automobile tubes and fasteners Low stressed parts, cycle and motor frame tubes, fish plates for rails and fasteners Crank shafts, shafts, spindles, axle beams, push rods, connecting rods, studs, bolts, gears etc Shafts, bolts, gears and spindles of machine tools Shafts, keys, cylinders, hardened stock for worms and worm gears Rail steel, bolts, gear shafts, rocking levers and cylinder liners Keys, crank shafts, cylinders, cams, gears, sprockets, parts requiring moderate wear resistance Locomotive carriage and wagon tyres, engine valve springs, washers and thin stamped parts Note: The properties of same material vary greatly because of different manufacturing processes, chemical composition, internal defects, temperature, measuring errors and many other factors. Consequently, catalogues of manufacturer of the material should be consulted for precise value of the properties. Structural carbon steel High-strength steel High-strength low-alloy steels Quenched and tempered carbon steel Quenched and tempered alloy steel ACYZ A ¥ C Y ¥ Z Sulphur Phosphorus cold shortness Silicon Nickel Chromium ISI Grade Sut N/mm2 27 Mn 2 588 – 736 687 – 834 588 – 736 687 – 834 785 – 932 882 – 1030 687 – 834 785 – 932 882 – 1030 981 – 1128 785 – 932 882 – 1030 981 – 1128 687 – 834 785 – 932 882 – 1030 687 – 834 785 – 932 882 – 1030 981 – 1128 687 – 834 785 – 932 1324 min 1520 min 687 – 834 785 – 932 882 – 1030 785 – 932 882 – 1030 687 – 834 785 – 932 882 – 1030 1520 min 785 – 932 882 – 1030 981 – 1128 1080 – 1226 1200 min 37 Mn 2 35 Mn 2 Mo 28 35 Mn 2 Mo 45 40 Cr 1 40 Cr 1 Mo 28 15 Cr 3 Mo 55 40 Cr 3 Mo 1 V 20 40 Cr 2 A1 1 Mo 18 40 Ni 3 35 Ni 1 Cr 60 30 Ni 4 Cr 1 40 Ni 1 Cr 1 Mo 15 31 Ni 3 Cr 65 Mo 55 Syt N/mm2 432 490 432 530 588 687 530 588 687 785 588 687 785 530 588 687 530 588 687 785 530 588 1098 1275 530 588 687 588 687 530 588 687 1275 588 687 785 863 1000 Min % Elongation BHN 18 16 18 18 16 15 18 16 15 13 16 15 13 18 16 15 18 16 15 13 18 16 8 8 18 16 15 16 15 18 16 15 8 16 15 13 11 10 170 – 217 201 – 248 170 – 217 201 – 248 229 – 277 255 – 311 201 – 248 229 – 277 255 – 311 285 – 341 229 – 277 255 – 311 285 – 341 201 – 248 229 – 277 255 – 311 201 – 248 229 – 277 255 – 311 285 – 341 201 – 248 229 – 277 363 min 444 min 201 – 248 229 – 277 255 – 311 229 – 277 255 – 311 201 – 248 229 – 277 255 – 311 444 min 229 – 277 255 – 311 285 – 341 311 – 363 444 min Note: The properties of same material varies greatly because of different manufacturing processes, chemical composition, internal defects, temperature, measuring errors and many other factors. Consequently, catalogues of manufacturer of the material should be consulted for precise value of the properties. ¥ ¥ ¥ ¥ ¥ ¥ ¥ Stress Quenched Tempered Annealed Strain
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