Carbide Dissolution and Grain Growth Behavior of Cr5 Steel Used as Cold Work Roller during Austenitizing

M7C3 type carbide dissolution and grain growth law of Cr5 steel used as cold work roller during heating at temperature range from 900 ℃ to 1 050 ℃ were investigated by means of scanning electron microscopy,optical microscopy and X-ray diffraction.The results show that dissolution amount of M7C3 carbide increased with the increase of temperature and holding time as well as the grains grew gradually.The grains grew slowly in terms of the temperatures below 1 000 ℃,and only a lirttle arbide dissolved.While the grains grew quickly as the temperature closed to 1 050 ℃ and almost all the carbide dissolved.At the beginning of holding stage,M7C3 type carbide dissolved rapidly and dissolution velocity increased with the increase of temperature.The dissolution velocity decreased with the prolongation of holding time.