Operating temperature of rolling bearings: Since bearings are used in many occasions and environments, the operating temperature of bearings is not a problem in most cases. However, some applications will have extremely high rotational speeds or operating temperatures. At this time, special attention must be paid to the operating temperature not to exceed the limit temperature of the bearing. The minimum limit temperature is mainly based on lubricating capacity, the maximum limit temperature is usually limited by the material and/or lubricant, but may also be limited by the accuracy requirements of the equipment in which the bearing is used. These limitations are described below. Bearing material limitations: Standard heat treated ordinary bearing steel cannot maintain a hardness of at least 58 HRC when the temperature exceeds 120C. The correct heat treatment process ensures the stable external dimensions of Timken bearings. Ordinary Timken tapered roller bearings and ball bearings can maintain stable external dimensions at temperatures from -54C to 120C, common spherical roller bearings maintain stable external dimensions at a maximum temperature of 200C, and common cylindrical roller bearings can maintain stable external dimensions at a maximum temperature of 150C maintain a stable form factor. These bearings are available upon request to provide higher stability as follows. These indicators conform to DIN standard 623. Stability index Maximum working temperature C FS0 150 302S1 200 392S2 250 482S3 300 572S4 350 662 Dimensionally stable products may still undergo dimensional changes due to microstructural deformation during operation, these deformations are mainly martensite tempering and retained austenite Decomposition of the body. The degree of variation depends on the operating temperature and temperature duration, as well as the forming and heat treatment of the steel. For temperatures above the limits in Table 19, special high temperature steels are required. Consult your Timken engineer for bearing options for non-standard thermally stable or high temperature steel grades. Recommended ball, ring, and roller materials at various operating temperatures are listed, along with recommended chemical composition, hardness, and dimensional stability. Operating temperature affects lubricating oil film thickness and operating clearance, both of which will directly affect the service life of the bearing. Extremely high temperatures can thin the lubricating oil film, resulting in poor lubrication of the contact areas. Operating temperature also affects the performance of cages, seals and shields, which in turn affects bearing performance. The materials for these parts and their operating temperature ranges are shown in Table 21.