Immediately after quenching cooling to room temperature, placed in the environment below room temperature to stay a certain time, take out at room temperature, below room temperature treatment called cold processing. Bearing steel, cold treatment is often used freezer and dry ice alcohol solution.

The role of cold treatment

Precision bearings require a higher dimensional stability; ferrule quenching (especially after quenching), the internal organization retains more residual austenite, the retained austenite is unstable organization, storage and use of bearing process, will continue to change, thus changing the bearing accuracy. To do this using the cold process, it can reduce the retained austenite in the organization, and slightly improve the hardness of the parts.

(2) Cold treatment processes

Stay at room temperature after quenching: after quenching, be sure to make the rings inside and outside the uniform cold to room temperature after the cold treatment, or easy to crack, cooled to room temperature immediately after cold treatment (usually no more than 30min), otherwise it will abort the austenite to martensite transformation.

Cold treatment temperature: the temperature of the cold treatment to terminate under the steel of the martensite transformation temperature Mf, while also considering the cold treatment the mechanical properties and process factors such as.

GCr15 steel, cold treatment selection -70 ° C; precision ferrule or device is not very high limit, the optional cold treatment temperature -40 ~ -70 ° C; super-precision bearings, -70 ° C ~ -80 ° C between the cold treatment. The cold temperatures affect bearing the impact of fatigue and exposure to life.

Cold treatment insulation: Although a large number of martensitic transformation is to a certain temperature in the cold Immediately the completed between surface and core part of the number of rings to cold treatment temperature, requires a certain holding time, generally 1 to 1.5 h.

Tempering after the cold treatment: rings cold treatment on the air, the temperature slowly rose to room temperature in a timely manner for tempering. The temperature rise can not be too fast, or easy to crack; tempering in a timely manner, otherwise the larger rings internal residual stress will lead to ring cracking, generally no more than 2h.


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