油气管道环焊缝自动焊未熔合影响因素

Factors influencing incomplete fusion in automatic girth welding of oil and gas pipelines

针对油气管道环焊缝全自动焊过程中出现的未熔合问题,采用焊接工艺试验和数值仿真相结合的方法,对未熔合的影响因素进行了研究。结果表明:在焊接位置由3:00移动至6:00的过程中,焊炬的摆动宽度逐渐增大,如保持焊接热输入量不变,则焊接工艺由大电流、高焊速转变为小电流、慢焊速。适当增加摆动宽度有助于加大坡口侧壁的熔池深度,保证熔滴过渡的稳定性,降低侧壁未熔合的出现概率;焊接位置在4:30至6:00时,焊缝成型通常较差,当前焊道出现的“驼峰”焊道将使下一焊道出现未熔合的概率增大;摆动焊接时的焊接温度场呈现出“锯齿形”,当摆动频率达到5次/s及以上时,可有效消除该“锯齿形”形貌。研究成果可为提升管道自动焊的质量与效率提供参考。

In view of the incomplete fusion occurred in the automatic girth welding of oil and gas pipelines,the factors influencing the incomplete fusion were studied with the welding procedure test and numerical simulation in combination.The results show that the swing width of the welding torch gradually increases for welding within the range from 3:00 to 6:00 o'clock.During this process,the welding process has the welding current decreased and the welding speed slowed down if the heat input remains unchanged.In this case,a larger swing width is helpful to increase the welding pool depth on the groove wall,thus guaranteeing the stability of weld droplet transition and reducing the risk of incomplete fusion on the wall.Besides,the weld morphology at the position of 4:30-6:00 was very poor,and the“hump weld”in the current pass will increase the probability of incomplete fusion in the next pass.In addition,the welding temperature field is in a serrated shape during the swing welding,which can be effectively eliminated at the swing frequency of 5 times/s or above.The research results can provide reference for improving the quality and efficiency of pipeline automatic welding.