The results showed that the main reasons of reductor shaft fracture are weld cracks, slag inclusions and massive inclusions which exist in the structure of the reductor shaft.

• 结果发现断轴组织内部存在焊接裂纹、夹渣及块状夹杂物等缺陷，这些缺陷形成微小裂纹源，使减速机轴在弯曲旋转作用力下发生疲劳断裂。