核电机组主蒸汽安全阀阀瓣密封面堆焊层开裂原因分析及预防措施  

Cause and prevention measures for Cracking of Surfacing Layer on Sealing Surface of Main Steam Safety Valve Disc in Nuclear Power Units

作　　者：汤恒 银帮耀 王琪 邓江勇 TANG Heng;YIN Bangyao;WANG Qi;DENG Jiangyong(Guangxi Fangchenggang Nuclear Power Co.,Ltd.,Fangchenggang 538001,China)

机构地区：[1]广西防城港核电有限公司,广西防城港538001

出　　处：《电焊机》2024年第4期63-70,共8页Electric Welding Machine

摘　　要：某核电厂大修期间对VVP116VV安全阀进行解体检查,发现阀瓣密封表面堆焊层存在20多条裂纹缺陷。通过宏观检查、化学成分分析、金相检验、硬度测试、残余应力分析、扫描电镜断口分析及能谱分析等方法分析阀瓣密封面堆焊层开裂的原因。结果表明:阀瓣密封面堆焊层的Fe含量明显偏高,表明稀释率过大,这与堆焊工艺控制不当(焊接热输入过大、热处理控制不当)有关。焊接热输入过大引起堆焊层残余应力偏高是开裂的主要原因;层间温度控制不当及焊后热处理不充分可能是促成堆焊层开裂的因素。并根据开裂的原因分析结果给出了处理建议,可以为其他机组的同类问题提供参考。During the overhaul of a certain nuclear power plant,the VVP116VV safety valve was disassembled and inspected,and it was found that there were more than 20 crack defects in the welding layer on the sealing surface of the valve disc.Analyze the reasons for the cracking of the valve disc sealing surface surfacing layer through methods such as macroscopic examination,chemical composition analysis,metallographic examination,hardness testing,residual stress analysis,scanning electron microscopy fracture analysis,and energy spectrum analysis.The results indicate that there is a problem of high dilution rate in the surfacing layer of the valve disc sealing surface.Analysis suggests that it is related to improper control of the surfacing process(excessive welding heat input,improper heat treatment control).The main reason for the cracking of the surfacing layer is the high residual stress in the surfacing layer caused by excessive welding heat input.Improper control of interlayer temperature during the welding process and insufficient post weld heat treatment may be contributing factors to the cracking of the surfacing layer.According to the result of cause analysis,the disposal suggestions are given to provide reference for similar problems of other units.

关 键 词：核电机组 主蒸汽安全阀 密封面 钴基堆焊 Stellite21合金 开裂 

分 类 号：TG441.7[金属学及工艺—焊接]