某110 kV变电站用铸造ZA33锌铝合金蜗轮在设备运行时发生断裂。采用宏观观察、化学成分分析、力学性能测试、金相检验、断口及能谱分析等方法对该蜗轮的断裂原因进行了分析。结果表明:该蜗轮中存在粗大的树枝晶组织和疏松等铸造缺陷,以及机构缓冲橡胶垫严重硬化,导致蜗轮销轴孔处产生裂纹,设备运行中裂纹扩展,导致蜗轮断裂。改善蜗轮的铸造工艺以消除铸造缺陷,以及将缓冲结构更换为碟簧型缓冲结构,可以延长蜗轮的运行寿命。

The cast ZA33 zinc-aluminum alloy worm gear in a 110 kV substation fractured during equipment operation. The fracture causes of the worm gear were analyzed by means of macro observation, chemical composition analysis, mechanical property testing, metallographic examination, fracture and energy spectrum analysis. The results show that there were casting defects such as coarse dendritic structure and porosity in the worm wheel, and the buffer rubber blanket of the mechanism was severely hardened. It caused cracks to occur at the pin shaft hole of the worm gear, and the cracks expanded during equipment operation, causing the worm gear to break. Improving the casting process of worm wheel to eliminate casting defects and replacing the buffer structure with disc spring buffer structure could prolong the service life of worm gear.