Process and Property Optimization of Isothermal Quenching for 60Si2Mn Spring Steel

Due to the brittle fracture or wear of drilling tools made of 60Si2Mn spring steel after isothermal quenching,the Rockwell hardness and impact toughness of 60Si2Mn specimens under different factor levels were tested through orthogonal experiments. The influences of process parameters such as austenitizing temperature, austenitizing time, isothermal temperature and isothermal time on Rockwell hardness and impact toughness were evaluated through range analysis. The microstructure and impact fracture morphologies of samples with different heat treatment process parameters were analyzed.The results show that isothermal temperature is the main factor affecting the microstructure and properties of 60Si2Mn after heat treatment. The optimal scheme obtained by the comprehensive equilibrium method is as follows:austenitizing temperature of 840 ℃, austenitizing time of 20 min, isothermal temperature of 230 ℃, isothermal time of 70 min, and the hardness and impact energy of the sample are 56.6 HRC and 4.7 J, respectively. The microstructure of the specimens contains a large amount of martensite, which is fine. There are a small amount of fiber and shear lip areas on the fracture surface, which has good comprehensive mechanical properties.