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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％H 2保护下的焊缝最光亮；100％ He,95％Ar＋5％ H 2,75％ 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％H 2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%H 2 gas.The dimension of welding throat can meet with the technical requirements when welded under the atmosphere of 100%He,95%Ar+5%H 2 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% H 2 .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.