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 welda bility of low carbon automotive galvanized steel. The types of shielding ga s evaluated are helium, carbon dioxide, argon, nitrogen and 50% argon + 50% nitrogen. The weld penetration, strength and formability (Erichsen test) o f laser welds are found to be strongly dependent upon the types of shieldin g gas used. Further, the maximum travel speed and flow rate to form a keyho le weld are also dependent upon types of shielding gas. The ability of shie lding gas in removing plasma plume, and thus increasing weld penetration, i s believed to be closely related to ionization/dissociation potentials, whi ch determine the period of plasma formation and disappearance. Further, the rmal 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. (C) 1999 Elsevier Science S.A. All rights reserve d.