Regarding the heat treatment expansion technology of bearing rings, the most troublesome thing is the amount of expansion, especially when the bearing ring product has a large amount of expansion after heat treatment, it may be necessary to increase the grinding allowance and grinding times of the bearing ring, or it may directly lead to the scrapping of the bearing ring. What are the factors that cause the amount of expansion of the bearing ring after heat treatment? How to solve this kind of problem? According to the understanding, the relevant knowledge is shared as follows. Factors of expansion of bearing ring after heat treatment As we all know, the quenching expansion of the bearing ring is caused by the specific tolerance difference between the pearlite before quenching and the martensite structure after quenching. In addition to the transformation of the structure, heat treatment of steel also produces thermal stress and structural stress. If the instantaneous stress exceeds the yield strength of the structure, it will cause plastic deformation to change the actual expansion. In addition, the presence of retained austenite and the appearance of non-martensite also affect the amount of swelling. The content of various components and the magnitude of residual stress in the structure formed after quenching are the main factors that determine the size change of bearing steel after quenching and tempering. Solution to the swelling of bearing ring after heat treatment (1) Adding Kerun additives to hot oil can reduce the expansion of quenched products of bearing rings and improve the qualified rate of expansion. (2) Improving the cooling cycle of the quenching oil can reduce the expansion of the bearing ring after quenching. (3) The amount of expansion of the bearing ring after quenching has a large relationship with the structural size of the bearing ring. Some bearing rings swell and some bearing rings shrink. (4) The expansion of bearing ring products selected for cold oil quenching is relatively small.  

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