Study on Mechanism and Process of Repeated Cryogenic Treatment for High Speed Steel

The repeated cryogenic treatment process of W6Mo5Cr4V2 high speed steel was studied by orthogonal experiment method, the effects of various cryogenic treatment process parameters on mechanical properties were analysed, and the microstructure before and after cryogenic treatment was observed by TEM. The results show that the effect of tempering frequency on mechanical properties is strongest, the cryogenic treatment frequency and time is secondary and tertiary respectively. The ultra-fine carbide particles are precipitated on martensite twins after cryogenic treatment, the amount of carbide particles increases after repeated cryogenic treatment. Under cryogenic treatment time enough, the effect of repeated cryogenic treatment is much better than that of single and long time cryogenic treatment.