Control of Hardness and Microstructure of 42CrMo Alloy Steel Bar

Aiming at the problem of excessive hardness of 42CrMo alloy steel bar after rolling, the microstructure transformation of 42CrMo alloy steel during cooling was studied by Gleeble thermal simulation test machine, and the hardness and microstructure of 42CrMo alloy steel after conventional rolling and low temperature rolling were compared. The results show that bainite transformation begin to appear in 42CrMo alloy steel when the cooling rate was above 0.3 ℃·s^-1. When the cooling rate was 1.0~10.0 ℃·s^-1, only bainite and martensite transformation occurred. By conventional rolling process, the hardness of the 42CrMo alloy steel was between 300~320 HBW, and the microstructure was mainly ferrite+pearlite+bainite. By low temperature rolling process, the hardness of the 42CrMo alloy steel can be reduced to 240 HBW and the microstructure was mainly ferrite + pearlite when the finishing rolling temperature was controlled at 800 ℃.