A study on shielding gas contamination in laser welding of non-ferrous alloys

Laser welding of non-ferrous alloys is a high-productivity and cost-effective joining technology, which gained an undoubted interest especially in aerospace, chemical and medical industry, where high strength and corrosion resistant mechanical parts are required. Unfortunately some of the most used non-ferrous alloys are highly reactive with respect to the components of the environmental atmosphere: oxygen, nitrogen, hydrogen and humidity. This reactivity leads to the formation of porosities and to oxides and nitrides inclusion, which are responsible for a decrease of ductility and strength in welded joints. According to this a good shielding technique of the weld pool is of primary importance in order to obtain sound beads and reliable manufacturings. This paper deals with the opportunity of simulating the shielding gas behavior by means of Computational Fluid Dynamics software in order to understand the relationship among the outlet position, the shielding gas type and its flow rate. A simulation activity was carried out in order to evaluate the behavior of shielding gas concentration surrounding the weld pool. The simulated welding environment was simplified without considering the presence and the effect of the plasma plume. The main results concern the shielding gas contamination prediction with respect to the distance from the beam-material interaction zone.