Effect of ambient atmosphere on penetration geometry in single laser and laser-arc hybrid welding. Welding phenomena in hybrid welding using YAG laser and TIG arc (second report)

Abstract

YAG laser only or YAG laser-TIG arc hybrid welding was carried out on Type 304 stainless steel plate with a low S content in air or in the chamber with Ar gas including 0% to 15% oxygen gas. It was confirmed in both laser and hybrid welding that the penetration and geometry of welds depended upon the volume of the oxygen in the ambient atmosphere, and that a pronounced nail head part disappeared in a weld metal containing a higher content of oxygen in both the laser and the hybrid welding at 100 A. In addition, laser and hybrid welding were performed on polished Type304 plate with high S content and surface-oxidized Type304 plate with low S content in pure Ar atmosphere to discuss the influence of the minor element on the surface-tension driven melt flow. Then the geometry of their weld beads was similar to that made in the chamber with Ar and oxygen gas mixed. These experimental results suggest that convective flow induced by surface-tension driven force produces the upper part of the weld bead and consequently the weld displays a wine glass shape in both laser welding and hybrid welding at 100A in Ar atmosphere.