Current-independent metal transfer by utilizing droplet resonance in gas metal arc welding

Separate control of heat input and metal transfer is an essential way to resolve the contradiction between low heat input and stable metal transfer in GMAW, to meet the possible requirement from different welding tasks, e.g., the thin plate welding. To this end, the resonance of the pendant droplet excited by mechanical means is utilized to achieve current-independent metal transfer at any reasonably low current that can sustain the arc. The natural frequency of the pendant droplet decreases with the rise of the droplet size. When the natural frequency declines to close to the excitation frequency with the droplet growth, resonance occurs, and the oscillation amplitude of the droplet increases significantly. In the resonant region, the downward inertial force resulting from the downward moving droplet induces the drop detachment in advance, resulting in much faster metal transfer and smaller detached drop diameter compared with conventional GMAW with the same welding parameters. The improved metal transfer process leads to an enhancement of the continuity and uniformity of the bead formation.