| 摘要 |
The present invention realizes a high-tension steel sheet with a high yield strength, a high tensile strength, excellent basic material toughness, excellent bending workability, excellent toughness after bending processing, a superior HAZ toughness, and a superior weldability (welding crack resistance) even though the sheet is thick. The steel sheet of the present invention satisfies a certain substance composition, and the welding crack sensitivity composition P_CM is defined with a certain formula 1 as being 0.20% or lower. The fraction of acicular ferrite in the entire tissue of steel is 70 area% or higher, and the average crystal grain diameter (circle equivalent diameter) of the entire tissue is 7 μm or shorter. The fraction of MA is 0.5 area% or lower, and the maximum value of Vickers hardness of the steel sheet surface unit is 220 or lower. |
