直流叠加脉冲型TIG焊电弧─熔池特性分析

Analysis of arc and weld pool characteristics in direct current added-pulsed TIG welding process

针对乏燃料后处理溶解器腐蚀裂纹等缺陷的快速、一次性、可靠焊接修复工程技术需求,提出一种直流叠加脉冲型TIG深熔焊接方法,在10和16 mm厚304不锈钢板上进行了系列平板堆焊工艺试验.以电弧-熔池特性变化为研究对象,对比分析脉冲电流作用和直流叠加脉冲型电流作用的电弧行为、熔池流动行为及温度场的变化规律,探讨了直流叠加至脉冲电流波形的焊缝熔深增加机理.结果表明,高频脉冲电流使电弧产生电磁收缩效应,且电弧被压缩程度及焊缝熔深与脉冲频率(1~5 kHz)成正相关;叠加直流的高频脉冲电弧具有更高的电流、能量密度,进一步提高了熔池表面液态金属温度及增加了熔池电磁搅拌力使熔池流动加剧、对流换热充分、熔池热惯性作用增强,进而使焊缝熔深增加.试验验证了该方法能够实现5 mm厚304不锈钢板对接可靠的单面焊双面成形.

In view of the technical requirements for rapid and reliable automatic welding repairment of defects such as corrosion cracks in the dissolver for spent fuel reprocessing, a direct current added-high-frequency pulsed tungsten inert gas arc welding method was developed in this paper, and a series of bead on plate welding experiments with 10 and 16 mm thick plate were performed. Taking the variations of arc-weld pool characteristic as the research object, the arc characteristic, and the flow behavior and the temperature field evolution of weld pool of pulsed TIG with adding direct current and without were compared, respectively. The mechanism of increasing weld penetration was discussed. The results show that the high-frequency pulsed current makes the arc to produce electromagnetic contraction, and the compressed degree and the weld penetration positively correlates to the pulsed frequency(1~5 kHz);the reason of the penetration increase in the direct current added-high-frequency pulsed welding process is that the direct current added pulsed arc increases the arc current and energy density and rises the surface liquid metal temperature of weld pool, and increases the electromagnetic stirring force of the molten pool to improve the flow intensify of molten pool, sufficient convection heat exchange, and enhances the thermal inertia of the molten pool, finally. This method is able to reliably realize the one-sided welding and back formation of the butt joint of 5 mm thick stainless-steel plates.