660MW汽轮发电机组中压缸汽封螺栓的断裂原因分析

Analysis on Seal Bolt Fracture of 660 MW Turbine Generation Unit

某电厂660MW汽轮发电机组中压缸轴封漏汽严重,检修中发现中压缸前端下部端汽封体垂直结合面螺栓以及下部轴封漏汽盒处端部螺栓均发生断裂现象。通过化学成分分析、力学性能测试、断口宏观形貌观察、金相组织检查、非金属夹杂物分析等手段,分析了螺栓断裂的原因。排除螺栓产生腐蚀疲劳、应力腐蚀、高温脆化断裂、高温蠕变断裂的可能性。最终确定了螺栓断裂原因为疲劳断裂。

A 660 MW steam turbine generator set in a power plant has a serious steam leakage in the middle pressure cylinder shaft seal. During the overhaul, it was found that the bolts on the vertical joint surface of the steam seal body at the lower end of the front end of the middle pressure cylinder and the bolts at the end of the steam leakage box at the lower end of the shaft seal all broke. By chemical composition analysis, mechanical property testing, macroscopic fracture morphology observation, metallographic examination and non-metallic inclusion analysis, the causes of the bolt fracture were analyzed.The possibilities of corrosion fatigue, stress corrosion, high temperature embrittlement fracture, high temperature creep fracture were excluded. At last, the reasons for the fracture of bolt were determined to be fatigue fracture.