On the effects of gravity and sulfur content on the weld shape in horizontal narrow gap GTAW of stainless steels

A simplified 2D axisymmetric model and a comprehensive 3D weld pool model, accounting for the free surface deformation and the filler metal addition, have been developed to investigate the factors that lead to asymmetric bead shapes in horizontal GTA welding of stainless steels. Buoyancy-induced flow and the sagging of the pool free surface, under the action of gravity, are found to be responsible for the weld asymmetry and the decrease in the weld penetration at the bottom sidewall. The numerical results clearly emphasized the beneficial role of the Marangoni shear stress in limiting the asymmetry of horizontal GTA welds. An additional experimental investigation showed that the asymmetry in the weld shape can be reduced when placing the lowest sulfur content component at the bottom side.

► The weld shape is asymmetrical in horizontal narrow gap GTA welding of stainless steels. ► Buoyancy convection and the free surface sagging are responsible for the weld asymmetry. ► The Marangoni shear stress has a beneficial role in reducing the weld asymmetry. ► Reducing the sulfur content of the bottom steel plate reduces significantly the weld asymmetry.