采用宏观检验、化学成分分析、力学性能测试、金相检验、扫描电镜分析等方法，分析了某核电减速机轮毂与辐条连接螺栓的断裂失效原因。结果表明：螺栓断裂是由于螺栓松动后，辐条上下滑动，使螺栓承受较大的剪切应力，最终导致其多源双向疲劳断裂；螺栓材料中存在大量超尺寸脆性硅酸盐类夹杂物，在一定程度上加速了疲劳裂纹的形成和扩展。

The fracture reasons of the bolts connecting the wheel hub and spokes of a reduction gear in a nuclear power plant were analyzed by macroscopic examination, chemical composition analysis, mechanical property testing, metallographic examination and scanning electron microscopy (SEM) analysis. The results show that the failure form of the bolts was multi-source bidirectional fatigue fracture which was mainly related to the high shear stress caused by the spoke slide after the bolt looseness. A lot of super-sized brittle silicate inclusions existing in the raw material might accelerate the formation and propagation of the fatigue cracks.