Effect of Austenitizing Time on Spheroidized Microstructure of Bearing Steel GCr15

After hot-rolling and subsequent perforating,austenitizing at 805℃ for different lengths of time and three different spheroidizing annealing processes,the microstructures of bearing steel GCr15 were investigated using optical microscope and SEM.The results show that there are two types of microstructures in the GCr15,including relatively big proeutectoid carbide particles and small carbide particles.As time prolongs at a holding temperature of 805℃,the lamellar pearlite gradually disappears,and small carbide particles are also reduced in number and become smaller in size while the size and distribution pattern of proeutectoid carbide particles remain basically unchanged.The hardness of specimens is similar under three spheroidizing annealing processes.