Importance of the coupling between the induced vapor plume and the melt pool, for Nd-YAG CW laser welding

We discuss the effect of the interaction between the vapor generated by the ablation process occurring on the front keyhole wall (KW) during deep penetration laser welding and the surrounding metallic melt pool. It is shown that the inclination of the front KW determines the importance of that effect. At low welding velocities, the front KW inclination is small and therefore the drag forces induced by the expanding vapor accelerates a liquid thin film around the keyhole and parallel to its axis. At high welding velocities, the front KW inclination becomes large and so the evaporation process. Therefore the expanding metallic vapor impinges the rear KW and opens the keyhole aperture. These effects localize the droplets generation process. By using an adequate side gas jet nozzle, we show that we can stabilize the melt pool fluctuations, and therefore suppress droplets generation and improve the weld seam quality.We discuss the effect of the interaction between the vapor generated by the ablation process occurring on the front keyhole wall (KW) during deep penetration laser welding and the surrounding metallic melt pool. It is shown that the inclination of the front KW determines the importance of that effect. At low welding velocities, the front KW inclination is small and therefore the drag forces induced by the expanding vapor accelerates a liquid thin film around the keyhole and parallel to its axis. At high welding velocities, the front KW inclination becomes large and so the evaporation process. Therefore the expanding metallic vapor impinges the rear KW and opens the keyhole aperture. These effects localize the droplets generation process. By using an adequate side gas jet nozzle, we show that we can stabilize the melt pool fluctuations, and therefore suppress droplets generation and improve the weld seam quality.