超超临界机组汽轮机X39CrMo17-1不锈钢阀杆断裂失效分析

Fracture failure analysis of X39CrMo17-1 steel valve stem for ultra-supercritical steam turbine

利用化学分析、力学性能测试、光学显微镜和SEM等手段,从成分分析、拉伸性能、冲击性能、组织结构、裂纹形态和断口形貌等方面对失效的某超超临界机组汽泵出口电动阀阀杆进行解剖分析,结合电动阀的安装、使用、运行等方面研究了其断裂的影响因素。结果表明,X39CrMo17-1不锈钢阀杆心部存在大量铁素体,组织状态不佳;冲击性能低于标准下限值;应力较为集中,在拉伸和扭转应力共同作用下,阀杆在最薄弱的退刀槽部位应力过载发生脆性断裂。

By means of chemical analysis,mechanical property test,optical microscope and SEM,a failed ultra-supercritical steam electric pump outlet valve stem was dissected from the aspects of composition analysis,tensile performance,impact performance,microstructure,crack morphology and fracture morphology. Then the factors influencing fracture was studied combined with electric valve installation,use,operation and other aspects. The results show that a large number of ferrite exists in the core of X39CrMo17-1 stainless steel valve stem and with poor microstructure. The impact performance is lower than the standard lower limit. The stress is relatively concentrated,and under the combined action of tensile stress and torsion stress,the brittle fracture is caused by the valve stem overload in the weakest slot position.