【摘要】 通过对发生断裂失效的主给水电动闸阀阀杆进行宏观检查及宏观断口分析、化学成分分析、拉伸试验、冲击试验、硬度试验、金相检验以及扫描电子显微镜分析,综合分析了其断裂原因。结果表明:阀杆断裂为低周疲劳断裂,阀杆断裂的主要原因是阀杆T型头倒角处结构突变及倒角半径较小造成该部位应力集中,加之闸阀运行过程中一些不利因素的影响,使得特定工况下该阀杆T型头倒角处处于应力值较高状态,在闸阀开启过程中产生裂纹源,在闸阀动作时的交变应力的作用下,由于裂纹的扩展,最终导致阀杆T型头单侧断裂失效。更多还原

【Abstract】 Macro examination, chemical composition analysis, tensile test, impact test, hardness test, metallographic examination, and scanning electron microscope test were performed on a fractured main feedwater line electric gate valve stem to backtrack and analyze the failure processes and reasons. The result shows that the failure was mainly caused by the low cyclic fatigue fracture. The structural abrupt change in stem T joint chamfer and undersize chamfering radius result in the stress concentration, some negative factors bring on detrimental side effects to the stem, causing high stress tension in T joint chamfer and accompanying crack initiation. Eventually, the alternating stress and the propagation of crack in operation process lead to the unilateral faulting of stem T joint.更多还原