Study on the Process of Vacuum Low Pressure Carburizing and High Pressure Gas Quenching for Carburizing Steels

The vacuum low pressure carburizing and high pressure gas quenching processes of 20CrMo, 20CrMnTi and 20Cr2Ni4 with acetylene as carburizing medium were investigated. The results show that the carburizing and diffusion time significantly affected the carburizing performance. Carburized with the process of C2H2 flow rate 10L/min, N2 flow rate 10L/min, carburizing pressure 3kPa, carburizing time 42min, diffusion time 140min and gas quenching pressure 1.5MPa, 20CrMo, 20CrMnTi and 20Cr2Ni4 can obtain the surface carbon content of 0.74%-0.78% and carburizing depth of 0.81mm-0.83mm. Meanwhile, the microstructure showed first grade carbide, and there was no internal oxidation laye on the surface. The carburizing constant and the diffusion time to carburizing time ratio were modified to be more suitable for the carburizing process.