某高强度螺栓在装配过程中断裂失效，通过宏观观察、化学成分分析、力学性能试验、金相检验、扫描电镜分析等方法对螺栓断裂失效的原因进行了分析。结果表明：螺栓基体硬度偏高，头杆结合处过渡圆角半径偏小，在大扭矩的装配下，扭转和弯曲的综合应力导致螺栓发生断裂失效。

Fracture failure occurred during the assembly process of a high strength bolt. The reasons for the fracture failure of the bolt were analyzed by macroscopic observation, chemical composition analysis, mechanical property test, metallographic examination and scanning electron microscope analysis. The results show that the hardness of the bolt was high, and the radius of the transition round angle of the joint of head and rod was small. In the process of the assembly of large torque, the combined stress of torsional and bending causes fracture failure of the bolt.