The standard steel number of China's GB is 40Cr;

chemical composition
C: 0.37 ~ 0.44
Si: 0.17 ~ 0.37
Mn: 0.50 ~ 0.80
Cr: 0.80 ~ 1.10
Ni: ≤0.30
P: ≤0.035
S: ≤0.035
Cu: ≤0.030
Mo: ≤0.10
German DIN standard material number 1.7035 / 1.7045, German DIN standard steel number 41Cr4 / 42Gr4;
British EN standard steel number 18, British BS standard steel number 41Cr4;
French AFNOR standard steel number 42C4, French NF standard steel number 38Cr4 / 41Cr4;
Italy UNI standard steel number 41Cr4;
Belgium NBN standard steel number 42Cr4;
Swedish SS standard steel number 2245;
American AISI / SAE / ASTM standard steel number 5140;
Japanese JIS standard steel number SCr440 (H) / SCr440;
ISO Standard Steel Number 41Cr4.
【Critical point temperature】
(Approximate value) Ac3 = 780 ℃
【Normalizing Specification】
Temperature 850 ~ 870 ℃, hardness 179 ~ 229HBW.
【Specifications for softening cold pressed blanks】
The temperature is 740 ~ 760 ℃, the holding time is 4 ~ 6h, and then the cooling rate is 5 ~ 10 ℃ / h, and the temperature is reduced to ≤600 ℃.
Hardness before treatment ≤217HBW, hardness after softening ≤163HBW.
[Pig iron scrap protection swing tempering specification]
(670 ± 10) ℃ × 2h, increase with the furnace, (710 ± 10) ℃ × 2h, decrease with the furnace;
(670 ± 10) ℃ × 2h, heat up with the furnace, (710 ± 10) ℃ × 2h, then cool down with the furnace;
(670 ± 10) ℃ × 2h, heat up with the furnace, (710 ± 10) ℃ × 2h, cool down with the furnace;
A total of 3 cycles, and then reduce the temperature to 550 ℃, air cooling. The hardness after treatment is 153 HBW.
[Specifications for quenching and tempering]
Quenching temperature 850 ℃ ± 10 ℃, oil cooling; tempering temperature 520 ℃ ± 10 ℃, water, oil, air cooling.

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