火电机组汽动给水泵轴断裂原因分析

Analysis on Fracture of Steam Feed Pump Shaft in a Thermal Unit

某火电机组汽动给水泵在运行过程中,推力瓦烧毁,泵轴发生断裂。通过断口形貌分析、力学性能测试以及金相组织检验等方法,对断裂泵轴的失效原因进行研究。结果表明:汽动给水泵轴的金相组织状态异常,存在大量的脆性δ-铁素体相,造成材料韧性不足。泵轴上套装叶轮的定位键与键槽配合不良,使得键槽边缘损伤形成缺口,裂纹源产生后不断延伸,最终引发泵轴的高周低应力疲劳断裂。

During the operation of steam feed pump in a thermal unit,the thrust tile burned and the pump shaft broke. The fracture reason of steam feed pump shaft was studied by means of fracture morphology observation,mechanical properties test and metallographic examination.Results showed that the metallographic structure of steam feed pump shaft was abnormal,and there were a lot of brittle δ-ferrite phases,which caused insufficient material toughness. Moreover,the positioning key of set impeller on the pump shaft was not well matched with the key groove,creating a breach in the edge of the key groove,and the continuous expansion of crack caused the high-cycle low stress fatigue,which led to the fracture of steam feed pump shaft.