냉간압연률에 따르는 STS316L의 감쇠능, 고유주파수 및 Laser 용접된 STS304L의 기계적 특성

Abstract

This study was investigated mechanical properties, damping capacity and natural frequency using STS316L steel with different thickness and cold rolled STS316L steel. Austenitic stainless steel was transformed into martensite by cold rolling. And the Vickers hardness was evaluated by stochastic properties by Weibull distribution analysis. As the cold rolling ratio increased, γ phase austenite decreased, ε and phase martensite increased. The amount of martensite increased as the amount of cold rolling increased. As the cold rolling ratio increased, tensile and yield strength increased, and elongation decreased. Vickers hardness increased up to 184% as the cold rolling ratio increased. The Vickers hardness of the cold-rolled specimen is well matched by the Weibull distribution because it is expressed as a straight line in Weibull distribution probability. The fracture probability of 63.2% was 94.5-181.5% higher than that of the as-received specimen. As the cold rolling ratio increased, the shape parameters showed larger values and less variance. The austenite phase was transformed into a martensite phase by cold rolling. Tensile strength increased with increasing of the degree of cold rolling, but elongation decreased. The damping capacity was decreased as the degree of cold rolling increased. The natural frequency showed a tendency to decrease slightly as the degree of cold rolling increased, and increased as the thickness increased. The natural frequency of the FFT analysis was found to be the secondary frequency. The natural frequency ratios showed a constant value, and there was no structure effect. The thickness of 6 mm STS304L of austenitic phase was butt welded using laser and TIG and mechanical properties were compared and analyzed. Joints of laser welding show better tensile and impact properties than that of TIG. However the bending properties were worse than that of TIG.