What are the heat treatment specifications for 42CrMo steel? What are the quenching temperature, tempering temperature (low temperature, medium temperature, high temperature), holding time and tempering brittleness temperature?

Normalizing of 42CrMo steel:
860 ± 10 ℃, air cooling.

Quenching and tempering of 42CrMo steel:
1) 840 ± 10 ℃ quenching in water or oil (depending on the complexity of of 42CrMo steel product shape), 680-700 ℃ tempering. HB<217
2) Quenching in oil at 840 ± 10 ℃ and tempering at 470 ℃. HRC41-45
3) Quenching in oil at 840 ± 10 ℃ and then tempering at 480 ℃. HRC35-45
4) Quenching in oil at 850 ℃ and tempering at 510 ℃. HRC38-42
5) Quenching in oil at 850 ℃ and tempering at 500 ℃. HRC40-43
6) Quenching in oil at 850 ℃ and tempering at 510 ℃. HRC36-42
7) Quenching in oil at 850 ℃ and tempering at 560 ℃. HRC32-36
8) Quenching in oil at 860 ℃ and tempering at 390 ℃.
Among them, 2 is medium temperature tempering, 8 is low temperature tempering and others are high temperature tempering for 42CrMo steel.