A lot of factors and solutions for the expansion of bearing rings after heat treatment

Regarding the technology of heat treatment and expansion of bearing rings, the most troublesome thing is the large amount of expansion, especially when the bearing ring products have a large amount of expansion after heat treatment, ranging from the increase of the grinding allowance of the bearing ring, the number of grinding, and the heavy The bearing ring will be scrapped directly. What are the factors that cause a large amount of expansion after heat treatment of the bearing ring? How to solve this problem?

Factors of large expansion of bearing ring after heat treatment

It is well known that the expansion of bearing rings during quenching is caused by the specific tolerance of pearlite before quenching and the martensite structure after quenching. In addition to structural transformation, thermal stress and structural stress are produced during heat treatment of steel. If the instantaneous stress exceeds the yield strength of the tissue, it will cause plastic deformation to change the actual swelling amount.

In addition, the presence of retained austenite and the appearance of non-martensite also affect the amount of swelling. The content of various components in the structure formed after quenching and the size of the residual stress are the main factors that determine the changes in the bearing steel quenching and tempering dimensions.

The solution of the large amount of expansion of bearing ring after heat treatment

(1) Adding Kerun additives to hot oil can reduce the swelling of bearing ring quenching products and increase the passing rate of swelling.

(2) Improving the cooling cycle of the quenching oil can reduce the amount of expansion of the bearing ring after quenching.

(3) The amount of expansion of the bearing ring after quenching is greatly related to the structural size of the bearing ring. Some bearing rings swell and some bearing rings shrink.

(4) The selection of cold oil-quenched bearing ring products is relatively small.

For more information, read"Material of bearing rings and rolling elements" written by BTON Bearings engineers.

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Category: Ball Bearings