高强度钢板用于城市中的高层建筑的框架材料。另一方面,从Hyogoken-Nanbu地震中横梁边缘焊接处断裂破坏的角度来看,对于具有低屈服比、高硬度和建筑钢结构上好的焊接性能的高性能钢产品有着急切的需求。最近,对于在箱型柱中使用的HAZ中具有大的焊接热输入的高韧性钢产品也有很迫切的需求。为了满足这些要 High-strength steel for high-rise buildings in urban frame material. On the other hand, there is an urgent need for high-performance steel products with low yield ratio, high hardness and good weldability on building steel structures, from the viewpoint of fracture damage at the edge weld of the Hyogoken-Nanbu earthquake. Recently, there is also an urgent need for highly ductile steel products with a large welding heat input in the HAZ used in box columns. In order to meet these needs