Effect of relative position in low-power pulsed-laser–tungsten-inert-gas hybrid welding on laser-arc interaction

In laser-arc hybrid welding, the appropriate position between the laser beam and arc will be helpful in forming an intensive interaction and significantly increasing penetration depth. In this paper, first, an orthogonal experiment with three factors and four levels were carried out on the inclination angle of the welding torch, the arc length, and the distance between laser beam and TIG electrode, Dla, to find the optimal positional parameters with the strongest laser-arc interaction. The composite plasma behaviors and interaction mechanism between laser and arc were then analyzed under different position parameters; on this basis, the influence of laser power on the laser-arc interaction was further analyzed. Results reveal that the interaction is a decided difference under different positions. When the distance Dla is small, the arc will be significantly compressed; when the laser acts on the arc center, the pre-heating of the arc will greatly improve the laser absorption rate, a shorter arc length will help to further increase the penetration. When the distance Dla, the arc length, and the welding torch angle are 1.5, 1 mm, and 45°, respectively, the laser-arc interaction reaches its strongest level and the weld penetration is the deepest. In this case, the arc tail is obviously shortened, and the laser-arc composite plasma volume in the central region is greatly increased. Further, when the laser-power percentage is 10%–50%, the weld profile shows the characteristics of laser heat-conduction welding; when the laser-power percentage is 50%–80%, the weld profile shows the characteristics of laser deep penetration welding; and when the laser-power percentage is 80%–100%, the valid penetration is shallow and accompanied by a large splash due to the very short laser duration. But the weld profile should also be characterized by typical laser deep-penetration welding when the duration of laser action is enough long.