Bearing steel is the steel used to manufacture ball bearings, rollers, and bearing rings. Bearing steel has high and uniform hardness and wear resistance, as well as high elastic limit. The requirements for the uniformity of chemical composition, content and distribution of non-metallic inclusions, and distribution of carbides in bearing steel are very strict, making it one of the most demanding steel grades in all steel production. In 1976, the International Organization for Standardization (ISO) included some common bearing steel grades in international standards, dividing bearing steel into four categories: fully quenched bearing steel, surface hardened bearing steel, stainless bearing steel, and high-temperature bearing steel, totaling 17 steel grades.