Plasma Control and Gas Protection System for Laser Welding of Stainless Steel

An integrated plasma nozzle and a shield gas box have been investigated for laser welding of 2 mm stainless steel sheets. Different gases for plasma control and gas protection of the weld seam have been used. The gas types, welding speed and coaxial and plasma flow show the impact on process stability and protection against oxidation.

Also oxidation related to special conditions at the starting edge has been investigated. The interaction between coaxial and plasma gas flow show that the coaxial flow widens the band in which the plasma gas flow suppresses the metal plasma. In this band the welds are oxide free. With 2.7 kW power welds have been performed at 3000 mm/min with Ar / He (70%/30%) as coaxial, plasma and shield gas.