冷处理对8Cr4Mo4V轴承钢尺寸稳定性的影响

Cryogenic treatment for various time was carried out on bearing rings made of 8Cr4Mo4V steel, the microstructure was observed by means of scanning electron microscopy at different stages of heat treatment, the residual austenitewas determined by X-Ray, and dimensional change of the bearing rings was measured by dilatometer in different heat treatment stages. Effect of heat treatment on dimension change of the bearing rings was investigated. The results show that the size of the bearing rings increases after quenching and tempering, but decreases after cryogenic treatment. The transformation from retained austenite to martensite increases the specific volume and brings the increases of the bearing ringsize. Cryogenic treatmentcan reduce the quenching stress and causes martensite to decompose so that the specific volume decreases and the size decreases. Cryogenic treatment can not only promote the transformation of retained austenite into martensite, but also reduce the lattice constant of iron atoms and promote the precipitation of ultrafine carbides and lead to the reduction of dimension.