Characteristics of high-power CO2 laser welding and porosity suppression mechanism with nitrogen shielding. Study of high-power laser welding phenomena

Abstract In its role as a welding heat source providing high energy density in ambient air, the laser can be used to perform high-precision, deep penetration welding under low-strain conditions. In the wake of the substantial high-power and high-beam quality enhancements of laser oscillators, the laser has most recently seen growing applications in a wide variety of industrial fields.1, 2 Available applications, however, are largely focused on high-precision welding of thin sheet metal in the automotive industry.3, 4 Deep penetration welding applications as another viable application avenue have been reported in shipbuilding and nuclear power generation, but remain relatively little documented.5 This is reportedly due to the fact that, with the increasing penetration depth of laser welding, welding defects such as porosity and solidification cracking more readily occur. Particularly in partial penetration welding of carbon steel, development of porosity prevention methods intended to allow laser welding t...