A Study on the Materials Characteristics of SM570TMC Plates

SM570TMC 강재의 재료특성에 관한 연구

There is increasing need for high-strength steel especially for the high-rise steel building structure. High- strength steels, however, may have mechanical properties that are significantly different from those of the conventional steels.The application of high-strength steels to building structures should be reviewed as to whether inelastic behavior equivalent to that of conventional steels can be attained or not. In this study, SM570TMC steel, which was developed recently in Korea, was tested to evaluate mechanical properties and welding characteristics for use as a structural steel. Yield phenomenon of SM570TMC steel, which is continuous yielding, is quite different from that of conventional steel. The distributions of yield strength of SM570TMC steel were uniform regardless of thickness, while the minimum yield strength was 440MPa. Also, the flat distributions of hardness in z-direction were found to comprise one of the important properties. Results of the charpy impact tests at -5oC revealed toughness values of SM570TMC steel, which were higher than those of equivalent as rolled steel. Carbon equivalent(Ceq) values of SM570TMC steel, which were related to welding performance, were lower than those of equivalent as rolled steel.

건축물이 고층이 될 수록 고강도 강재의 사용요구가 증대된다. 그러나 고강도 강재는 일반 강재와는 전혀 다른 기계적 특성을 갖고 있다. 고강도 강재를 건축구조물에 적용하기 위해서는 비탄성 영역에서의 거동이 일반 강재와 동등한가를 확인해야 한다. 본 연구에서는 최근 국내에서 개발된 SM570TMC 강재를 건축구조용으로 사용하기 위해서 기계적 성질 및 용접부 특성을 평가하였다. 연속항복현상을 보이는 SM570TMC 강재는 판두께가 증대되어도 강도저감이 발생되지 않았으며, 최소 항복강도가 440MPa로 나타났다. 또한 판두께 방향으로 균일한 경도분포를 보였다. -5oC에서의 Charpy 충격값도 충분한 인성을 보였다. 용접성과 관련있는 탄소당량은 기존 건축구조용 강재보다 훨씬 낮았으며, 용접부 특성도 우수하였다.