Process gas optimization and quality assurance in CO2-laser welding by means of on line process monitoring and process control

Process gas plays an important role for getting sound weld seams. Whereas in conventional welding techniques process gas mainly is used as shielding gas, for preventing the weld bead from oxidation, in laser beam welding process gas in addition is needed for control of the laser induced plasma. For that purpose inert gas helium is the most efficient but most expensive one. The use of other process gases than helium in laser beam welding can produce plasma shieling and in consequence process interruption caused by fluctuations in process or production parameters. This paper presents a method of control called PSC (plasma shielding control) that avoids the formation of strong plasma shielding. In aluminium welding PSC opens a range of process gas application with improvement of process efficiency and weld seam quality. In welding steel PSC is able to reduce gas costs.