The effect of shielding gas types on CO2 laser tailored blank weldability of low carbon automotive galvanized steel

This study deals with the effects of shielding gas types on CO2 laser weldability of low carbon automotive galvanized steel. The types of shielding gas evaluated are helium, carbon dioxide, argon, nitrogen and 50% argon+50% nitrogen. The weld penetration, strength and formability (Erichsen test) of laser welds are found to be strongly dependent upon the types of shielding gas used. Further, the maximum travel speed and flow rate to form a keyhole weld are also dependent upon types of shielding gas. The ability of shielding gas in removing plasma plume, and thus increasing weld penetration, is believed to be closely related to ionization/dissociation potentials, which determine the period of plasma formation and disappearance. Further, thermal conductivity and reactivity of the gas with the molten pool also have a strong effect on penetration and porosity formation which in turn affect formability and strength.