Suppression of humping bead in high-speed triple-wire gas indirect arc welding

Triple-wire gas indirect arc welding (TW-GIA) is a new technology with the advantages of low heat input and high deposition rate. However, the humping bead restricts the improvement of welding efficiency. In this article, the high-speed cameras and infrared thermal imaging system were used to characterize the formation mechanism of the TW-GIA humping bead. The physical model was established to discuss the force mechanism of the weld poor. And the influence of process parameters on humping bead was studied. The results show that the increase of the welding angle reduced the arc pressure and droplet impact force in the opposite direction of welding, which was beneficial to eliminate the hump. When the welding height was lower than 3 mm, the excessive arc pressure led to the humping bead with arc crater. When the welding height was greater than 20 mm, the distance between the droplets of side wires was far, forming the humping bead with "double bead" defect. In addition, the flow distance of the liquid metal shortened as the welding current decreased, which could suppress the humping bead. When the ratio of the total wire feeding speed to the welding speed was 10, the critical current was 360 A, and the critical current increased as the ratio increased. The maximum TW-GIA welding speed of bead-on-plate was 4.2 m/min, which was 137% higher than that of high-speed GMAW.