The ball bearing is mainly composed of four basic elements: ball, inner ring, outer ring and retainer also called cage or retainer. General industrial ball bearings meet the AISI 52100 standard. Balls and rings are usually made of high-chrome steel with a Rockwell C-scale hardness of about 61-65. The hardness of the retainer is lower than that of the ball and the ring. The material of the retainer is metal (such as: medium carbon steel, aluminum alloy) or non-metal (such as: Teflon, PTEF, polymer material). The ball bearing has a smaller rotational frictional resistance than a journal bearing, so at the same rotational speed, the temperature produced by the friction will be lower.
Contact between Roller and Raceway
Point Contact and Line contact as below