| Summary: | By means of the measurement of the residual stress and size, and the observation of the microstructure, the relationship among the size change, the residual stress and carbide precipitation of M50 bearing steel at working temperatures was studied. Results show that the residual stress at the outside and inside of the M50 bearing rings are compressive, which generally exhibits the character of periodic release, and this results in the size increase of the bearing rings. Within the temperature range of 120–250 °C, the amount of secondary carbides increases with the increase of temperature, which however almost remains constant at 300 °C. At the same temperature, the amount of secondary carbides increases with the increase of time. The precipitation of secondary carbides results in the size decrease of bearing rings, but at the same time, the secondary carbides increase the residual compressive stress. During 0–100 h at working temperatures, the main influencing factor on the size change is the release of the compressive residual stress, which causes the size increase of the bearing rings. During 100–250 h, the main influencing factor is the precipitation of secondary carbides, which causes the size decrease of the bearing rings. While during 250–300 h, the main influencing factor turns back to be the release of the compressive residual stress, and this causes the size increase of the bearing rings.
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