HAZ靭性に優れた建築構造用低YR型780MPa級円形鋼管の特性と組織制御技術

摘要

Recently, since thicker steel pipes with higher tensile strength are being used for large building construction and large spans, TS 780MPa steel pipes with high earthquake-resistant performance are in demand. To meet this demand, we have developed TS 780MPa steel pipes (KSAT ? 630) with low YR and excellent HAZ toughness. The application of the DQ-N’-T process and a chemical composition low in carbon, plus the inclusion of Mn, Ni, and Cr in steel plates for steel pipes enables multi-phase microstructural control including M-A and refining of the effective grain size in HAZ. As a result, advanced steel pipes formed from developed steel plates satisfied target properties.