Process and defect analysis of retaining rings heat treatment by ultrasonic induction heating equipment

The retaining ring is an important part of the automobile generator. It is used to tighten the end coils at both ends of the automobile generator rotor. In order to make the retaining ring work better and improve the wear resistance and service life of the retaining ring, it is necessary to use an ultrasonic induction heating power supply to heat treat the retaining ring. So, what is the heat treatment process of the retaining ring? What defects will occur during heat treatment?

The heat treatment of retaining ring forgings includes solution treatment and stress relief annealing. The stress relief annealing process is to hold at (250±10)℃ for 4 hours or at (300±10)℃ for 10h, slowly cool for 10-12h, and be released when the workpiece temperature is lower than 100℃.

The defects that are prone to occur when the retaining ring is heat treated are as follows:

1. The retaining ring has low plasticity and poor forming ability. This is caused by insufficient solid solution of carbides. Therefore, during the heat treatment process, the solid solution temperature and holding time should be sufficient, the quenching into the water should be fast, the water temperature should be low, and the water cooling time should be sufficient. Water cooling should be used after hot forging to prevent excessive carbides from precipitating during the cooling process.

2. Coarse crystals and mixed crystals appear. The grain size of the retaining ring is mainly determined by forging. In order to avoid coarse grains and mixed grains, the forging temperature and deformation amount should be strictly controlled. The final forging temperature should be reasonable and the deformation amount should be uniform. The solid solution temperature and holding time should be reasonable, and the temperature should be raised reasonably and quickly.

3. The strength of the retaining ring is offset. The main reason is that the heating temperature is too high, the time is too long or the temperature is uneven, resulting in high local stress. If the temperature is too high, it will cause carbide precipitation, reduce stress corrosion resistance, and be detrimental to magnetic properties. Therefore, the heating temperature should be lowered or the heating time should be shortened.

This is an introduction to the defects that occur when the retaining ring is heat treated with ultrasonic induction heating equipment. I hope it will be helpful to your work. If you want to know more information, please call us.