基于工作温度8Cr4Mo4V钢制轴承外套圈尺寸及应力变化特征分析

Analysis of outer ring dimension and stress variation characteristics of 8Cr4Mo4V steel bearing based on working temperature

测定了8Cr4Mo4V钢制直壁圆筒形轴承外套圈在不同工作温度下内外径尺寸及表面残余应力的变化特征,分析了引起轴承外套圈尺寸变化和表面残余应力变化的因素,并对轴承外套圈进行了微观组织观察。结果表明,在不同工作温度下,保温300 h后轴承外套圈的尺寸均增加1~2μm,轴承外套圈外径的尺寸变化量大于内径尺寸变化量;工作温度下残留奥氏体转变为马氏体,马氏体深度回火,均会使轴承外套圈内径表面残余压应力增加。工作温度为150℃时,内、外径表面残余压应力绝对值增加幅度最大,随着工作温度的提高,表面残余压应力绝对值增加幅度降低。轴承外套圈内外径表面残余压应力的增大是由于轴承钢中残留奥氏体转变为马氏体,发生体积膨胀引起的。马氏体发生深度回火导致体积收缩,外套圈内外径收缩尺寸量不同将引起内外径表面的残余压应力值变化不同,尺寸收缩将导致内径残余压应力增大,而外径残余压应力减小。

Variation characteristics of inner and outer diameter and surface residual stress of straight wall cylindrical bearing outer ring made of 8 Cr4 Mo4 V steel at different working temperatures were measured,the factors causing the dimension variation and surface residual stress variation of bearing outer ring were analyzed,and the microstructure of the bearing outer ring was observed.The results show that at different working temperatures,the outer diameter increment of bearing outer ring all reaches 1-2μm after holding for 300 h,which is greater than that of inner diameter;And the retained austenite transforms into martensite at the working temperatures,and deep tempering of martensite leads the surface compressive residual stress value at inner diameter of bearing outer ring to increase.When the working temperature is 150℃,the surface compressive residual stress absolute value increment on both the inner and outer diameter reach the most,and with the increase of temperature,the increment in surface compressive residual stress absolute value decreases.The increase of the surface compressive residual stresses on the inner and outer diameters of bearing outer ring is caused by the transformation of retained austenite into martensite,that resulted volume expansion.Deep tempering of martensite leads to volume shrinkage,and different shrinkage of inner and outer diameter will lead to different changes of compressive residual stress value on inner and outer diameter surface.The size shrinkage will lead to the increase of compressive residual stress on inner diameter and decrease of that on outer diameter.