| 摘要 |
This high-strength steel plate contains, in percentages by mass, 0.05 to 0.3% C, 1 to 3% Si, 0.5 to 3% Mn, not more than 0.1% P (including 0%), not more than 0.01% S (including 0%), 0.001 to 0.1% Al, and 0.002 to 0.03% N. The remainder has a component composition comprising iron and impurities, and has a structure containing, in terms of area ratio relative to the entire structure, 50 to 90% bainitic ferrite, 5 to 20% retained austenite (?R), 10 to 50% martensite plus the abovementioned ?R, and not more than 40% polygonal ferrite (including 0%). The abovementioned ?R satisfies a concentration C (C?R) of 0.5 to 1.2 mass %, an average circle equivalent diameter of 0.2 to 2 µm, and an average aspect ratio (maximum diameter/minimum diameter) of less than 3.0. Further, this high-strength steel plate combines both ductility and deep drawability, while maintaining a strength of not less than 980 MPa. |
