Current-independent metal transfer by using pulsed laser irradiation Part 2: Affecting factors

The ideal current-independent metal transfer characterized by ensured robust droplet detachment at a relatively small size at any reasonable low current, which can sustain the arc, has been successfully realized in the first part of this study by applying a high-power-density pulsed fiber laser to irradiate the droplet neck. The desired one-droplet-per-laserpulse (ODPP) mode was ensured. The droplet flying trajectory deflected from the wire axial due to the use of a single laser. This second part of the study focuses on how relevant parameters influence the metal transfer behavior, especially the droplet deflection that affects the controllability of bead formation. To facilitate the study, the relevant parameters were categorized into three major types: laser positioning, laser pulse waveform, and arc parameters. A series of experiments was conducted to examine their effects on successful ODPP transfer and deflection minimization. In particular, the optimal laser incident point and angle for most submissive droplet detachment and smallest droplet deflection were first determined. Secondly, the minimums of the laser peak power and duration for stable ODPP were determined. Finally, the droplet deflections under different welding currents in the desirable low range, as well as different torch orientations and arc lengths, were measured and analyzed.