Effect of gas shielding delivery mode on high power CO2 laser welding

Abstract

During a laser welding operation, the assist gas is usually brought by a nozzle directed towards the interaction zone with a given inclination angle. A few tens liters per minute, and a several millimeters nozzle radius are the usual parameters of welders to assist a laser welding operation. Previous studies showed that the assist gas flow influenced laser mater interaction, process stability and weld quality. In this study, the parametric influence related to the shielding gas for two types of protections: Back Protection (noted BP, gas flow in the welding direction) and Front Protection (noted FP, gas flow in the opposed welding direction) were investigated through statistical analysis of weld bead seam cross sections. This analysis shows significant differences between the two protections. The assist gas velocity effects on laser mater interaction and process stability for a FP is much better than for a BP: The FP comparatively to a BP can increase by 15 % the penetration depth and reduce by more than 40 % the penetration depth fluctuations. The morphological weld bead seam characteristic fluctuations (as the spiking phenomena) were mainly attributed to the plasma plume fluctuations. In addition the BP ensures a better welding pool protection against oxidation than the FP.During a laser welding operation, the assist gas is usually brought by a nozzle directed towards the interaction zone with a given inclination angle. A few tens liters per minute, and a several millimeters nozzle radius are the usual parameters of welders to assist a laser welding operation. Previous studies showed that the assist gas flow influenced laser mater interaction, process stability and weld quality. In this study, the parametric influence related to the shielding gas for two types of protections: Back Protection (noted BP, gas flow in the welding direction) and Front Protection (noted FP, gas flow in the opposed welding direction) were investigated through statistical analysis of weld bead seam cross sections. This analysis shows significant differences between the two protections. The assist gas velocity effects on laser mater interaction and process stability for a FP is much better than for a BP: The FP comparatively to a BP can increase by 15 % the penetration depth and reduce by more than ...