低电流TIG电弧辅助MIG高速焊咬边缺陷抑制机理及措施的研究

Suppression Mechanism of Low Current Auxiliary TIG Arc on High Speed TIG-MIG Hybrid Welding and Process Optimization

基于温度场、流场、熔滴过渡以及电弧形态检测,开展低电流钨极氩弧焊(Tungsten inert gas welding,TIG)辅助熔化极惰性气体保护(Metal inert gas welding,MIG)高速焊工艺试验。从传热、传质以及受力等角度分析低电流TIG辅助电弧对高速MIG咬边缺陷的抑制机理,并分析各工艺参数对最终焊缝成形的影响。相比常规MIG高速焊,低电流TIG辅助电弧能有效降低MIG高速焊前部熔池边缘的温度梯度,延长熔池存在时间,促进液态金属向焊缝边缘填充。电弧力和熔滴冲击力是影响高速焊咬边缺陷的主要作用力,低电流TIG辅助电弧对MIG熔滴冲击力改变较小,但两电弧耦合后,电弧静、动压力明显降低,可有效地抑制MIG高速焊中咬边缺陷的产生。此外,正交工艺试验显示,丝-极间距和焊枪倾角是影响复合焊工艺的重要参数,而钨极距工件距离和TIG焊接电流则对咬边缺陷的影响较小,通过对丝-极间距和焊枪倾角的调节能快速实现该复合焊工艺参数的优化,抑制咬边缺陷。

The low current auxiliary TIG arc assisted high speed MIG process is carried out to analyze the suppression mechanism of undercut defect from the aspects of heat transfer,mass transfer and force field.The influence of the welding parameters on undercut defect is also analyzed.The low current auxiliary TIG arc can effectively reduce the temperature gradient around the edge of the weld pool during high speed MIG,which prolongs the existence time of the molten pool and promotes the filler metal to the edge of the weld to prevent undercut defect.The arc force and the droplet impact play major roles in the formation of the undercut defect.The auxiliary of low current TIG presents slight influence on MIG droplet,however,it can reduce the arc static and dynamic pressure obviously to mitigate or even inhibit undercut defect during the high-speed welding process.The orthogonal test shows that the inclination angle of welding torch,and the spacing of wire-pole are the important parameters affecting the formation of undercut defect compared with TIG current and tungsten distance workpiece distance.Optimizing torch angle and wire-pole spacing is a fast and economical way to improve low current auxiliary TIG-MIG hybrid welding to suppress undercut defect.