Abstract
The high performance of bearing steel balls (BSBs) depends on the microstructure. Carbide spheroidization is the main mechanism in warm deformation, which leads to the metal flow dynamic softening of bearing steel. Process parameters of warm skew rolling (SR) such as roller angle, rolling temperature and roller rotating speed have a significant influence on the carbide spheroidization of bearing steel. A simulation system of microstructure was developed based on unified visco-plastic constitutive equations to predict the microstructure evolution of BSB during warm SR. Next, a series of FE simulations were conducted to investigate the effect of process parameters of warm SR on the microstructure of BSB. The predicted results show that the degree of carbide spheroidization decreases with the increase of roller angle, rolling temperature and roller rotating speed. The optimal process parameters of warm SR were selected as a roller angle of 2.0 degrees, rolling temperature of 650 degrees C and roller rotating speed of 70 min(-1). More carbides participation and sufficient carbide spheroidization were achieved under the optimal process parameters of warm SR. The application of optimal process parameters into the formation of BSB with 30 mm diameter can reduce the special carbide spheroidization annealing time and energy consumption, and improve productivity.