A comparison of TIG-MIG hybrid welding with conventional MIG welding in the behaviors of arc, droplet and weld pool

Abstract

The influence of electrode relative position and TIG current variation on arc stability and weld formation of TIG-MIG hybrid welding were studied comparing with that of conventional MIG welding. The welding current-voltage waveform was analyzed to characterize the arc stability. When TIG arc was leading, the hybrid arc was more stable than conventional MIG welding even when the TIG current was as low as 50 A, while the TIG current should be higher than 100 A to avoid spatters when TIG arc was trailing. The arc shape and droplet transfer were investigated to describe the heat and force distribution in weld pool. When TIG arc was leading, the backward arc force and droplet impingement could not decrease the backward flow of molten metal. The increment of MIG arc length dispersed MIG arc heat and resulted in narrower weld width, compared with conventional MIG welding, which was the main factor to suppress undercut defect. When TIG arc was trailing, the forward arc force and droplet impingement significantly decreased the backward flow velocity and gave molten metal more time to spread transversely to suppress undercut defect. Regardless the relative position of TIG and MIG arcs, the hybrid welding speed could reach up to at least 1.5 m/min.