Effect of Heat Treatment Process on Liquid-precipitated Carbides in MC5D roller Blank for Cold-rolling Application

In this paper,the effect of heat treatment process on liquid-precipitated carbides in MC5D cold-rolling roller blank was investigated.The phase transformation and type of carbides in MC5D steel at equilibrium state were calculated by JMatoPro software,and the microstructure of the blank was observed by scanning electron microscopy.And the transition of liquid-precipitated carbides during the heating process was analyzed by ultra-high temperature confocal microscopy.The results show that the liquid-precipitated carbides in MC5D blank are mainly M₇C₃,which start to dissolve into the matrix at about 765℃.The liquid-precipitated carbides can be almost dissolved into the matrix when the heating temperature reaches 1 000℃,but a small amount of carbides still exist until the temperature reaches 1 252℃ where the matrix around the carbides starts to melt.Based on the analysis results of ultra-high temperature confocal microscopy,two sets of heat treatment process were designed,including "heating at 1 050℃ for 1 h,oil cooling" and "heating at 1 070℃ for 1 h,oil cooling".By implementing these twosets of heat treatment,the level of liquid-precipitated carbides can be reduced from 4.0 to 0.5,which proves the feasibility of the designed heat treatment processes.