某3Cr2W8V合金钢轴承套圈用热挤压芯棒发生断裂失效，通过断口宏观分析、化学成分分析、硬度测试、金相检验等方法，分析了其断裂失效的原因。结果表明：该芯棒的结构设计不合理且机加工表面质量不良，在拉-压交变应力和扭转应力复合作用下产生应力集中，于应力集中的过渡圆角部位的夹杂物相处开裂形成疲劳裂纹源，发生早期疲劳断裂。

Fracture failure of a hot extruded mandrel for bearing ring of 3Cr2W8V alloy steel has occurred, the causes of fracture failure were analyzed by means of fracture macroscopic analysis, chemical composition analysis, hardness test, metallographic examination and so on. The results show that the structure design of the mandrel was unreasonable and the surface quality of the mandrel was bad, and the stress concentration was caused by the combined action of tension-compression alternating stress and torsional stress. The fatigue crack source was formed when the inclusions in the transition fillet parts were concentrated along the stress concentration, and early fatigue fracture occurred.