某型号风机在运转过程中，其齿轮箱中的齿轮轴发生断齿。采用宏观观察、断口分析、能谱分析、硬度测试、金相检验等方法对其断齿原因进行分析。结果表明：齿轮轴齿部断裂特征为疲劳断裂，裂纹源处存在大尺寸B类氧化铝夹杂物，引起该处明显的应力集中，导致齿轮轴发生断齿。最后提出了整改措施，经过整改后，该风机齿轮轴未出现断齿现象。

During the operation of a certain type of fan, the gear shaft in the gearbox had broken teeth. The causes of tooth breakage were analyzed by macroscopic observation, fracture analysis, energy spectrum analysis, hardness test and metallographic examination. The results show that the fracture characteristics of the gear shaft were fatigue fracture. There were large-scale B-type alumina inclusions at the crack source, which caused obvious stress concentration, and led to the broken tooth of the gear shaft. Finally, the rectification measures were put forward. After rectification, there was no broken tooth in the fan gear shaft.