Quality improvement of laser beam welds by plasma control

An investigation of the influence of plasma control gas flow rate and welding speed on the penetration capability and weld bead porosity in 304 stainless steel laser welds is presented. Helium gas was used for both shielding and plasma control purposes and plasma control gas flow rates up to 45 lmi exp --1 were used. It was shown that the penetration depth increased with an increase in plasma control gas flow rate and then decreased after the gas flow rate exceeded a critical amount. The same tendencies were observed with different welding speeds.