Failure analysis and countermeasure of welding process for pressurizer electric heating element

稳压器电加热元件焊接工艺失效分析与对策 Failure analysis and countermeasure of welding process for pressurizer electric heating element 唐国军 TANG Guojun 1 first-author 张涛 ZHANG Tao 1 李浩 LI Hao 1 东方电气集团东方锅炉股份有限公司 东方电气集团东方锅炉股份有限公司 Dongfang Boiler Group Co.,Ltd. Dongfang Boiler Group Co.,Ltd. 稳压器是压水堆核电站一回路调节系统压力的主设备,其关键元件电加热器的焊接采用自动TIG焊。介绍了一起电加热元件接头按原成熟的自动TIG焊工艺无法焊透的事件。分析认为母材中S元素含量过低,改变了熔池的流动及传热方向,致使焊接热量更多地流向焊缝两侧边缘,从而导致熔深变浅,无法焊透接头。根据现有的低S母材特性,通过工艺实验调试出新的焊接参数,通过两步焊接的方式,既能保证焊透,也能保证最终接头表面凹陷度不超标。同时对后续稳压器电加热元件的焊接及已运行的稳压器电加热器的更换工艺提出了改进建议。 Pressurizer is one of the main equipment in the primary loop of PWR nuclear power plant. As the key element of pressurizer,the electric heater is welded by automatic TIG welding. In this paper,a case of incomplete penetration of the joint of electric heating element according to the original mature automatic TIG welding process is introduced. The analysis shows that that too low content of S element in the base metal changes the flow and heat transfer direction of the molten pool,and causes more welding heat to flow to the two sides of the weld,as a result,the depth of penetration becomes shallow and incomplete penetration of joint can not be solved. According to the characteristics of the existing low S base metal,the new welding parameters are adjusted through the process experiment.The two-step welding method can not only guarantee complete penetration,but also ensure that the surface depression of the final joint does not exceed the standard. Furthermore,the improvement suggestions are put forward for the welding of the electric heating element of the follow-up project and the replacement process of the electric heaters of the pressurizer in service. 稳压器 电加热元件 自动TIG 未焊透 低S母材 pressurizer electric heating element automatic TIG incomplete penetration low S base metal TM623.91 2022-03-08 7 51