Effects of torch configuration on arc interaction behaviors and weld defect formation mechanism in tandem pulsed GMAW

Abstract

The effects of interwire distance and angle on arc interaction behaviors and droplet transfer, as well as the weld undercut-defect formation mechanism in tandem pulsed gas metal arc welding (GMAW) with a novel welding torch were studied in this work. The arc interaction behaviors vary with the change of the interwire distance and angle. Generally, the background leading arc is much easier to deflect than the background trailing arc. When the interwire distance is 10 mm and the interwire angle is 10°, the arc climbing phenomenon occurs in the leading arc because of the strong electromagnetic attraction. The pulsed streaming spray and pulsed projected spray are two primary droplet transfer modes occurring in most welding cases. They are greatly influenced by the welding torch configuration. The interwire distance of 15 mm and the interwire angle of 10° are considered to be the best in the present work based on the comprehensive evaluation of arc behaviors, droplet transfer and weld bead formation. When the interwire angle is equal to or greater than 14°, and the interwire distance is kept to be 15 mm, the blocking effect of the trailing arc on the backward fluid driven by the leading arc gets weakened due to the increased inter-wire-tip transverse distance. For this reason, only a handful of molten metal exists under the leading arc. Moreover, the molten metal from the melting of trailing wire cannot reach the right edge of the welding pool that is formed by the leading arc. Thus, an undercut defect occurs in the weld bead.