오스테나이트계 스테인리스강의 레이저 용접 시 용접 파라미터에 따른 기계적 특성에 대한 연구

Abstract

Austenitic stainless steel is used in the nuclear industry as structural materials and coatings because it has excellent workability, weldability and high temperature characteristics. Nuclear power plant structures are mainly large structures manufactured using welding which is mainly arc welding. Arc welding is a welding method with relatively high heat input. However, austenitic stainless steel requires low heat input because it has high thermal expansion coefficient and lower thermal conductivity than that of carbon steels. Over heat input may cause various welding defects such as severe deformation and coarsening of the grain in the joint, which may result in deterioration of the mechanical properties. In recently, laser welding has been proposed to solve the problem of heat input. This study investigated the effect of shielding gas on the mechanical properties of austenitic stainless steels using Ar and N2. Weldments showed similar appearance and microstructure. Fusion zone of shielding gas N2 could not find nitrides. Mechanical properties as tensile, bend and impact were similar regardless of types of shielding gas. As a results, shielding gas N2 welding showed similar characteristics to those of Ar welding. It is considered that shielding gas N2 is suitable for austenitic stainless steels at laser welding.