核电厂定位销局部干法水下TIG焊接工艺

Local dry underwater TIG welding process of positioning pin in nuclear power plant

以核电厂定位销水下焊接为研究对象,研制双层气体保护的局部干法水下TIG旋转焊枪,运动轨迹通过直流电机带动钨极绕固定直径转动实现.对核级材料Z2CN19-10控氮奥氏体不锈钢进行焊接,研究局部干法水下TIG焊接焊缝成形,优化工艺参数,结合热循环曲线及电弧形态,分析焊接接头显微组织及力学性能.结果表明,当焊枪的内层和外层保护气均通氩气时,焊缝成形良好,电弧形态稳定;增大焊接电流或减小焊接速度均使焊缝熔深增大,熔宽增大;对比水下焊接接头和陆上焊接接头发现,水的快速冷却作用会促使熔合线附近的铁素体的形态由树枝状转变为板条状,奥氏体含量减少,焊缝中心晶粒细化;水下焊接接头的显微硬度和力学性能略高于陆上焊接接头.

Taking the underwater welding of positioning pin in nuclear power plant as the research object,an underwater TIG welding gun with double-layer gas protection is developed.The motion trajectory is realized by DC motor driving the tungsten pole to rotate around a fixed diameter.The nuclear grade material Z2CN19-10 nitrogen-controlled stainless steel was welded.The weld formation of local dry underwater TIG welding was studied.The process parameters were optimized.The microstructure and mechanical properties of the joint were analyzed by combining the thermal cycle curve and arc shape.The results show that when the inner and outer layers are filled with argon,the weld is well formed and the arc shape is stable.Increasing the welding current or reducing the welding speed increases the weld penetration and the weld width.By comparing the underwater and onshore welded joints,it is found that the rapid cooling of water will promote the ferrite near the fusion line to change from dendritic to lath,reduce the austenite content and refine the grain.The microhardness and mechanical properties of underwater joints are slightly higher than those of onshore joints.