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核电站用阀门倒密封件裂纹失效分析
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摘要
某核电站在大修期间对阀门进行解体检查工作,发现两个阀门的倒密封阀座表面出现了径向裂纹,且最大深度约为2 mm。本工作利用扫描电镜观察、金相组织观察和成分分析等手段对产生裂纹的倒密封件进行分析,并结合其实际工况和出厂数据,得出倒密封件的裂纹产生于表面,其产生原因主要为焊接残余应力与常规开闭试验中施加的外加应力叠加作用导致。焊接后引入的C和H增大了倒密封件硬质合金层的脆化倾向,裂纹均为沿晶开裂。
The valves are disintegrated for inspection during the overhaul in the nuclear power plant.It finds that radial cracks are appeared on surfaces of two back seals with the maximum depth about 2 mm.In this work,scanning electron microscopy,optical microscopy and composition analysis are used for analysis of back seal cracks.Combining with its actual condition,the results show that cracking starts from the surface.The main reason of cracking is the combined effects of welding residual stress and the applied stress from routine tests.The amount of C and H increase after welding.It can increase embrittlement tendency of stellite alloy in back seal.The cracks are intergranular cracking.
引文
[1]GB 984-2001-T堆焊焊条.
    [2]D.拉达伊编著.焊接热效应温度场、残余应力、变形.熊第京,郑朝云,史耀武译.北京:机械工业出版社,1997.
    [3]陈天佐,李泽高.金属堆焊技术[M].北京:机械工业出版社,1991.
    [4]刘双明,裴玉冰,肖杰.汽轮机阀座堆焊开裂原因分析与对策.大型铸锻件,2012,4.

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