Date: 2013-08-22

Bearing rings of cold treatment process analysis

Quenching the workpiece to ambient temperature, immediately placed in an environment below room temperature a certain time, out at room temperature, this is lower than the processing temperature is called cold treatment. Bearing steel cold treatment is often used freezers and dry ice alcohol solution.
1 The role of cold treatment
Precision bearings for higher dimensional stability; ferrule hardened (especially quenching), the internal organization retains more residual austenite, this residual austenite is unstable organization, storage and use of bearings process will continue to change, thus changing the accuracy of the bearing. Therefore the use of cold treatment process, it can reduce tissue retained austenite, slightly increase the hardness of parts.
2 Cold Process
Stay at room temperature after quenching: quenching, must make uniform cooling to room temperature inside and outside the ring 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 changes.
Cold treatment temperature: the temperature of cold treatment based primarily on termination of martensitic transformation temperature of the steel Mf, while also considering the cold treatment on the mechanical properties and process and other factors.
For GCr15 steel, cold treatment selection -70 ℃; accuracy is not very high ferrule or equipment limitations, the cold treatment temperature optionally -40 ~ -70 ℃; super precision bearings in the -70 ℃ ~ -80 ℃ between the cold treatment. Cold temperatures affect the bearing life impact fatigue and exposure.
Cold insulation: Although a large number of martensite is cooled to a certain temperature Tilting moment to complete, but the number of rings to make both surface and core part cold treatment to achieve uniform temperature, requires a certain holding time, usually 1 to 1.5 h.
Cold treatment after tempering: ferrule on the air after the cold treatment, the temperature was slowly warmed to room temperature tempering timely manner. Temperature can not be too fast, or easy to crack; tempering timely, otherwise the internal ferrule large residual stresses can cause cracking rings, generally no more than 2h.

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