Arc characteristic of multi-cathode three-electrode GTAW (TE-GTAW)

This work presents pioneering research on gas tungsten arc welding (GTAW) using three electrodes (TE-GTAW). A special torch that accommodates three tungsten electrodes was designed and constructed, and experiments were conducted to evaluate the arc morphology by varying the distances and angles between the electrodes. The results indicate that distances smaller than 5 mm between electrodes provide more stable and centralized arcs, while larger distances result in greater arc deviation towards the torches. The analysis also revealed that the average arc voltage increases with the distance between the electrodes, implying a higher energy demand to maintain arc stability. The sharpening of the electrode angle and the torch angle was also evaluated, with the best results obtained using angles of 40° and 20°, respectively. Analytical models were proposed to explain the arc deviation behavior for three electrodes, and these were compared with the two-electrode process. A trial using a 1.2-mm steel wire feed in the center of the electrodes was conducted, demonstrating that TE-GTAW is capable of producing a stable filler metal melting condition. The major conclusion is that TE-GTAW produces a stable arc with a distinct morphology, where the arc is primarily deviated towards the center (where the filler metal is located), rather than being primarily directed towards the workpiece as in conventional GTAW.