극저온 저장탱크용 SUS316L 맞대기 용접부의 단면 형상 및 기계적 특성에 미치는 파이버 레이저 용접 조건의 영향 = Effect of Fiber Laser Welding Conditions on Cross-Sectional Geometry and Mechanical Properties of SUS316L Butt Joints for Cryogenic Storage Tanks

다국어 초록 (Multilingual Abstract)

Fiber laser welding is a promising joining process for cryogenic stainless steel structures because of its high energy density, narrow heat-affected zone, and low thermal distortion. In particular, SUS316L stainless steel has been considered a suitable candidate material for cryogenic storage systems due to its favorable corrosion resistance, weldability, and mechanical stability at low temperatures. In this study, butt welding of 10 mm-thick SUS316L plates was performed using a fiber laser process, and the effects of welding conditions on weld cross-sectional geometry and mechanical properties were investigated.
Five welding conditions were applied by varying laser power and welding speed, and double-sided 2-pass welding was conducted for all cases. Cross-sectional observation was carried out to evaluate bead geometry, including bead width, concave geometry, and penetration depth. Tensile tests and Charpy impact tests at -196 °C were also performed on the welded joints. The results showed that decreasing welding speed and increasing laser power generally increased bead width and penetration depth. Yield strength ranged from 288.6 to 306.6 MPa, tensile strength from 584.3 to 595.7 MPa, elongation from 47.4 to 50.0%, and cryogenic impact value from 37.0 to 52.7 J. Among the tested conditions, the 4.0 kW-0.7 mpm condition showed the most balanced mechanical performance, especially in terms of elongation and cryogenic impact toughness. These results provide useful basic data for selecting reliable fiber laser welding conditions for SUS316L cryogenic storage structures.