Influence of interwire angle on undercutting formation and arc behavior in pulsed tandem narrow-gap GMAW

Abstract

The tandem narrow-gap gas metal arc welding was adopted in this study. The effects of interwire angle on the welding process stability and arc behavior were investigated. With the interwire angle increasing, the welding process stability gets improved. The arc interruptions which frequently occur in the leading arc are eliminated when the interwire angle is >0°. The mutual electromagnetic attraction between the two arcs decreases with the interwire angle increasing due to the increased arc distance. The two arcs move from the groove bottom to the sidewalls, which transfer more heat to the sidewalls resulting in increased weld width. This leads to serious undercutting defects especially when the interwire angle is 20°. The molten metal under the arcs flows to the rear of welding pool under the action of plasma drag force, arc pressure and droplet impingement. As a result, there is no adequate molten metal to fill the sidewalls, giving rise to undercutting defects. The undercutting at the groove sidewall close to the trailing arc is smaller. This is because the liquid metal under the trailing arc is more massive, which means more molten metal flows to the sidewall, alleviating the undercutting defect.