从断口形貌、显微组织、非金属夹杂物、硬度和化学成分入手,对齿轮轴的断裂原因进行了分析,并提出相应预防措施。结果表明,齿轮轴断裂的主要原因是热点矫直遗留的淬火斑点未进行充分回火和齿轮轴心部出现淬火欠热组织造成。通过改进淬火工艺、矫直及机加工工序后,齿轮轴再无断裂发生。 Starting from the fracture morphology, microstructure, non-metallic inclusions, hardness and chemical composition, the reasons for the fracture of the gear shaft were analyzed and the corresponding preventive measures were put forward. The results show that the main reason of gear shaft fracture is that the quenching spot left by hot spot straightening has not been fully tempered and the quenching and underheating structure of gear shaft center appears. By improving the quenching process, straightening and machining processes, the gear shaft and no fracture occurred.