Shielding Gas Coaxial Jet Pipes Numerical Study of a Vertical Laser Welding Process of AZ91 Magnesium Alloy

The laser welding of magnesium alloys, largely used in many fabrication applications, has gained considerable interest especially in aerospace, electronics, automotive industry etc. Unfortunately, this process is associated to an undesired phenomenon which is “oxidation”. For this reason, a good shielding system of the welding zone is of major importance. This paper presents a numerical study using computational fluid dynamics (CFD) of a laser welding process employing a moving volumetric heat source. Starting with the turbulence model validity, a parametric study of this welding process in a vertical position aiming to optimize the design of protection gas device, the gas jet inclination, the appropriate welding direction and the gas type is, then, proposed. The optimum parametric combination ensuring the largest gas coverage area is the one where the shielding gas is Argon, supplied by the coaxial nozzles at a downward inclination angle with respect to the laser beam axis, and a downward welding direction.