4140 alloy steel, this steel has excellent workability, processing small deformation, fatigue performance is quite good, and so is in the hardenability of steel, 4140, after heat treatment has a good strength and good mechanical properties, good technology, finished product rate with a maximum use temperature of 427 degrees Celsius. 4140 strength, high hardenability, toughness, and quenching of small deformation, high temperature strength and high creep rupture strength. Requirements for the manufacture of higher intensity than 35CrMo steel and larger cross-section of quenched and tempered forgings, such as the large locomotive traction gears, supercharger drive gear, rear axle, by the great link and spring load can also be used The following 2000m deep oil drill pipe joints and fishing tools, and can be used for bending machine tooling.

Chemical composition
Carbon (C) 0.38 ~ 0.43, manganese (Mn) 0.75 ~ 1.00, phosphorus (P) ≤ 0.030, sulfur (S) ≤ 0.040, Nickel (Ni) ≤ 0.030, [1] chromium (Cr) 0.80 ~ 1.10 4140 picture
Mechanical properties
Tensile strength σb (MPa): ≥ 1080 (110) yield strength σs (MPa): ≥ 930 (95) Elongation δ5 (%): ≥ 12 Reduction of area ψ (%): ≥ 45 impact energy Akv (J ): ≥ 63 impact toughness αkv (J/cm2): ≥ 78 (8) hardness: ≤ 217HB Sample Size: Sample size is 25mm rough
4140 Heat Treatment
Annealing annealing No.1 "760 ± 10 ℃ annealing, furnace cooling to 400 ℃ air-cooled.
 HB220-230 normalizing normalize No.4 860 ± 10 ℃ normalizing, baked cooled.
 Quenching quenching + tempering No.5 840 ± 10 ℃ quenching water or oil (depending on the product shape complexity) ,680-700 degree tempered. HB <217
Quenching quenching + tempering No.6 840 ± 10 ℃ quenching oil, 470 degrees and then tempered. HRC41-45
Quenching quenching + tempering No.7 840 ± 10 ℃ quenching oil, 480 degrees and then tempered. HRC35-45
Quenching quenching + tempering No.8 850 ℃ quenching oil, 510 degrees and then tempered. HRC38-42
Quenching quenching + tempering No.9 850 ℃ quenching oil, then tempered to 500 degrees. HRC40-43
Quenching quenching + tempering No.10 850 ℃ quenching oil, and then 510 ℃ tempering. HRC36-42
 Quenching quenching + tempering No.11 850 ℃ quenching oil, and then 560 ℃ tempering. HRC32-36
  Quenching quenching + tempering No.12 860 ℃ quenching oil, 390 degrees and then tempered. HRC48-52