42CrMo 
 42CrMo the corresponding International Standards Organization Grade: 42CrMo4 corresponding to the Japanese brands: SCM440 for German Grade: 42CrMo4 similar to the corresponding U.S. trademark: 4140 ● Features and Scope: strength, high hardenability, toughness, and quenching of small deformation, high temperature high creep strength and rupture strength. Requirements for the manufacture of high strength steel than 35CrMo and quenched forging greater cross-section, such as a big locomotive traction gears, supercharger gear, pressure vessels, gear, rear axle, by the great rod and spring load can also be used to 2000m deep oil drill pipe joints and the following fishing tools, and can be used bending machine tooling. 
 Chemical composition 
 Carbon C: 0.38 ~ 0.45% Si Si: 0.17 ~ 0.37% Manganese Mn: 0.50 ~ 0.80% sulfur S: to allow the residual phosphorus content ≤ 0.035% P: ≤ 0.035% to allow the residual content of chromium Cr: 0.90 ~ 1.20% Ni: to allow Residual copper content ≤ 0.030% Cu: ≤ 0.030% to allow the residual content of Mo Mo: 0.15 ~ 0.25% 42CrMo 42CrMo allowable stress allowable stress 186 ~ 310/MPa, yield point 930σs/MPa, 42CrMo strength, high hardenability, toughness Well, when the deformation hardening, high temperature strength and high creep rupture strength. 42CrMo requirements for the manufacture of high strength steel than 35CrMo and quenched forging greater cross-section 
 Mechanical Properties 
 Tensile strength σb (MPa): ≥ 1080 (110) yield strength σs (MPa): ≥ 930 (95) Elongation δ5 (%): ≥ 12 Reduction of ψ (%): ≥ 45 Impact energy Akv (J ): ≥ 63 impact toughness αkv (J/cm2): ≥ 78 (8) Hardness: ≤ 217HB sample size: Sample size of 25mm rough 
 42CrMo heat treatment 
 Annealing annealing No.1 "760 ± 10 ℃ annealing, furnace cooling to 400 ℃ air-cooled. HB220-230 normalization normalize No.4 860 ± 10 ℃ normalizing, baked cooled. Quenched quenching + tempering No.5 840 ± 10 ℃ quenching water or oil (depending on the product shape complexity) ,680-700 degree tempered. HB <217 quenched and quenching + tempering No.6 840 ± 10 ℃ quenching oil, and then 470 degree tempered. HRC41-45 quenched quenching + tempering No.7 840 ± 10 ℃ quenching oil, and then 480 degree tempered. HRC35-45 quenched and quenching + tempering No.8 850 ℃ oil quenching, tempering and then 510 degrees. HRC38-42 quenching and quenching + tempering No.9 850 ℃ oil quenching, tempering and then 500 degrees. HRC40-43 quenched quenching + tempering No.10 850 ℃ quenching oil, and then 510 ℃ tempered. HRC36-42 quenched quenching + tempering No.11 quenching oil 850 ℃, 560 ℃ and then tempered. HRC32-36 quenched quenching + tempering No.12 860 ℃ oil quenching, tempering and then 390 degrees. HRC48-52 
 Mechanical properties after heat treatment 
 42CrMo different sections of steel mechanical properties after heat treatment blank diameter / mm heat treatment system sampling location σb σs δ5 ψ aK / J · cm-2 Notes 
 / MPa /% 
 54 
 55 
 60 850 ℃ 22min oil quenching, 
 540 ℃ 90min tempering water 
 860 ℃ 60min oil quenching 
 540 ℃ 90min tempering water 
 Quenching oil 900 ℃, 600 ℃ back to the Oil Cold 1/2R 
 Center 
 1/2R 
 Center 
 Center 762 
 788 
 806 
 765 
 905 574 
 556 
 638 
 599 23.3 
 21.1 
 20.7 
 19.4 
 24 68.8 
 67.0 
 62.8 
 62.8 
 62.0 191 
 189 
 134 
 140 
 108 (65) 31 
 1 
 1 
 1 
 2 

 Note: 1. Steel composition (%): 0.43 C, 0.88Mn, 1.09Cr, 0.22Mo, 1.017P, 0.027S; 2. Steel composition (%): 0.39C, 1.11Cr, 0.20Mo; 3. Parenthesis value within the lateral impact