核电站蝶阀阀瓣断裂原因分析

摘要

利用直读光谱仪、光学显微镜、布氏硬度计、扫描电子显微镜等对某核电站蝶阀阀瓣断裂原因进行了分析.结果表明:该蝶阀阀瓣的失效模式为沿晶腐蚀断裂,造成阀瓣断裂的主要原因是其化学成分不符合JIS G 4303-2005的指标要求,且铸造后未经合适的固溶处理;阀瓣中晶界上有连续碳化物析出,存在敏化问题,在含有腐蚀性元素硫和氯的海水介质中长时间服役后自外向内沿奥氏体晶界发生了沿晶腐蚀断裂.%The fracture reason of the butterfly valve clack used in the nuclear power plant was analyzed by means of optical emission spectrometer, optical microscope, Brinell hardness tester and scanning electron microscope (SEM).The results show that the failure mode of the butterfly valve clack was intergranular corrosion fracture.The chemical composition of the valve clack didn′t meet the specified requirement of JIS G 4303-2005 and the solution treatment was inappropriate after casting,which were the main reasons of the valve clack fracture. Continuous carbide was precipitated at the grain boundaries of the valve clack and the grain boundaries were sensitized,resulting in the intergranular corrosion fracture along the austenite grain boundaries after long service in the sea containing corrosive elements of S and Cl.