Improving arc current window in low-power pulsed laser-MAG hybrid welding with different heat source arrangements

Expanding the welding process window is the key to improve the level of automation and even intelligence of large-scale industrial production with dynamic working conditions. In this study, pulsed laser was employed to widen arc current window in the metal active gas (MAG) welding process in this paper, and its variation and mechanism were studied systematically with seven heat source arrangements. The findings indicate that the arc current window was expanded significantly by the pulsed laser with a minimum increase of 20 A and a maximum of 40 A. Compared to other heat source arrangements, the joint exhibited the widest arc current window and the highest heat penetration capability in laser-lead (LL) mode when the arc was perpendicular. The expansion was attributed to the laser-induced enhancement of arc energy density, which reduced the molten pool volume and optimized the balance between the base metal (BM) support force and surface tension, additionally enabling penetration at lower currents. The weld achieved full penetration with lower heat input when the arc was vertical than when the laser was vertical because the heat source arrangement altered the spatial energy distribution. Moreover, the laser beam modified the temperature distribution and produced limited grain refinement in the weld metal without causing a pronounced increase in crystallographic anisotropy. Finally, full penetration was achieved even when the butt gap was reduced from 2 mm to 1 mm, validating the feasibility of one-sided welding with back formation in low-power pulsed laser–MAG hybrid welding.