Study on the influence of process parameters in twin tungsten electrode-wire electrode indirect arc welding

Twin tungsten electrode-wire electrode indirect arc welding (TTW-IAW) is a new welding method, in which the twin tungsten electrodes are connected to the power source together with the welding wire, while the base metal is not connected to the power source, so that the indirect arc is formed between the twin tungsten electrodes and the welding wire. Currently, only the arc characteristics and the droplet transition behavior have been studied, which limits the application of this process in practical welding. In this paper, the thin-plate butt welding process is applied for the first time in TTW-IAW, and the effects of process parameters on weld formation, microstructure, and its hardness are investigated. Additionally, the formation mechanisms of burn-through and hump defects are revealed by the static model and hydraulic jump model of the molten pool, respectively. The results show that TTW-IAW achieves stable weld formation at a maximum welding speed of 600 mm/min, a fourfold increase compared to conventional cold-wire single-TIG welding (conventional cold-wire STW), which reflects its advantages of large deposition rate and high welding efficiency. The degree of influence of the welding current on the penetration of base metal is greater than the welding speed, and the increase in welding current is conducive to the increase in the base metal penetration and the heat-affected zone (HAZ) width, while the increase in welding speed can reduce the convex height of the weld. However, excessive welding currents cause the downward component of arc force and droplet impact to be increased and the upward component of surface tension to be decreased, which results in destabilization of the molten pool, leading to the formation of burn-through defects. Excessive welding speed causes the flow rate of the liquid in the molten pool to be increased and the critical value for the occurrence of a hydraulic jump is exceeded, leading to the formation of a hump.