结合核电AP1000蒸汽发生器产品结构, 研究了管子-管板全位置TIG焊不同焊接保护气体对焊道成形、焊喉尺寸的影响, 研究了100%Ar保护下在较高热输入下焊接时焊缝根部裂纹的形貌和形成机理。结果表明: 相同焊接工艺参数下, 100%Ar保护下的焊道最窄, 100%He保护下的焊道最宽, 95%Ar+5%H2保护下的焊缝最光亮; 100%He, 95%Ar+5%H2, 75%He+25%Ar保护下焊接形成焊缝的焊喉尺寸均满足技术要求, AP1000蒸汽发生器管子-管板TIG焊采用95％Ar+5％H2保护气体时其焊接质量较好; 通过提高热输入并降低焊接速度, 100%Ar保护下的有效焊喉尺寸可满足技术要求, 但焊缝根部出现裂纹的几率增加, 裂纹为高温裂纹。

Based on the structure of AP1000 steam generator, the effects of various shield gases on the welding shape and throat dimension of tube to tubesheet joint welded by all-position TIG welding were studied. The morphology and forming mechanism of the cracks appeared during welding under 100%Ar gas and higher heat input were also studied. The results show that under the same welding parameters, the weld pass was the narrowest at the atmosphere of 100%Ar and the widest under 100%He gas. The weld surface was the brightest under 95%Ar+5%H2 gas. The dimension of welding throat can meet with the technical requirements when welded under the atmosphere of 100%He, 95%Ar+5%H2 and 75%He+25%Ar. The optimum quality of tube to tubesheet joint was obtained when using TIG welding at the atmosphere of 95%Ar+5%H2. When improving heat input and lowering weld speed, the dimension of welding throat with 100%Ar could meet the technical requirements, but the probability of thermal cracks also increased. Those cracks were high temperature cracks.