Effect of Assistant Gas Pressure on Cutting Performance when 80mmt Stainless Steel Laser Cutting in Pressurized Underwater Environment

Abstract

Various studies are being conducted on underwater cutting using lasers for nuclear power plant dismantling environment. The depth of pressure vessels for most reactors is more than 10 m. When cutting a structure contained in a reactor with 10 m or more depth, pressure is applied, and the shape of the cut due to the cutting gas in this environment needs to be identified. Though several studies exist on laser cutting of stainless steel underwater, laser cutting research in pressurized underwater environment is insufficient. This study investigated the relationship between the cutting kerf width and the assistant gas flow at a depth of 10 m or more in underwater environments. Laser cutting was performed on 80 mm^t stainless steel in a pressurized underwater environment. The conditions for obtaining sound cut surface quality were derived by analyzing the kerf shape and roughness of the test piece according to the assistant gas pressure. Additionally, the relationship between the kerf width and the assistant gas flow was established by visualizing the flow of gas through Schlieren analysis and by analyzing the shape of the drag line according to the kerf width and assistant gas flow.