Arc shape and dynamic behavior of the Tri-Arc twin-wire GMAW process

The triple-arc (Tri-Arc) twin-wire gas metal arc welding (GMAW) is a novel twin-wire welding method, compared with the conventional twin-wire GMAW process; it decouples heat input and deposition rate by creating an inter-electrode arc between the two wire ends, called the middle-arc (M-arc). To determine the arc shape and dynamic behavior of this special welding process and to clarify the decoupling characteristics of it, in this paper, a high-speed camera and a synchronized data acquisition system captured dynamic arc shapes and welding current signals. The analysis of the experimental results indicates that the Tri-Arc twin-wire welding has three operating modes: single-wire single-arc, twin-wire dynamic double-arc, and twin-wire dynamic three-arc. At least two arcs exist in the twin-wire dynamic three-arc welding process, dynamically forming two different arc shapes and their respective mirror image shapes: a "mu" shape and a "Gamma" shape. In addition, the process for forming the "Gamma"-shaped arc is clarified. The mechanism of deposition rate improvement and heat input reduction of the Tri-Arc twin-wire welding process is that the M-arc increases the current to melt one welding wire while preheating the other wire without passing through the workpiece.