High power chemical oxygen-iodine laser welding

The present paper describes the welding characteristics with a 10kW class Chemical Oxygen-Iodine Laser (COIL), whose wavelength is 1.32 mu m. Bead-on-plate welding tests of 304 stainless steel plates were carried out at laser power 8.5kW and 11kW. Three different shielding gases (N-2, Ar and He) were used through a coaxial conical shape nozzle under the lens. In COIL welding, the interaction between the laser beam and the laser induced plasma is very small because the wavelength of COIL is shorter than that of CO2 laser, so that the laser beam reaches on the workpiece without absorption by the plasma. As the result of the welding tests, the welded bead shapes did not depend on a type of the shielding gas. Radiograph and longitudinal section tests of the welded beads were carried out. When He and Ar gases were used as the shielding gas, there were several porosities. On the other hand, the use of N-2 gas made no porosity. The full penetration on 10mm thick plate was achieved in the high aspect ratio without the welding defects under the condition of laser power 8.5kW and welding speed 1.5m/min.