In addition to rolling friction, sliding friction is also associated with rolling bearings working normally. The main parts of sliding friction are: the contact surface between rolling body and raceway, the contact surface between rolling body and cage pocket, between cage and ring, and between the roller end surface and the guide ring. The existence of sliding friction in the rolling bearing inevitably causes the wear of the bearing parts. If the bearing steel has poor wear resistance, the rolling bearing will lose its accuracy too early due to wear, or the vibration and life of bearing will be reduced due to the decrease of rotational accuracy. Therefore, the bearing steel should be required to have high wear resistance.