| 摘要 |
High-strength steel and method for producing same. A cold-rolled and annealed steel sheet, the chemical composition of which comprises, the contents being expressed by weight: 0.10 ≤ C ≤ 0.13% 2.4 ≤ Mn ≤ 2.8% 0.30 ≤ Si ≤ 0.55% 0.30 ≤ Cr ≤ 0.56% 0.020 ≤ Ti ≤ 0.050% 0.0020 ≤ B ≤ 0.0040% 0.005 ≤ Al ≤ 0.050% Mo ≤ 0.010% Nb ≤ 0.040% 0.002 ≤ N ≤ 0.008% S ≤ 0.005% P ≤ 0.020%, the remainder consisting of iron and inevitable impurities from the preparation, the sheet having a microstructure consisting, in an area ratio, of martensite and/or lower bainite, said martensite comprising fresh martensite and/or self-tempered martensite, the sum of the area ratios of martensite and lower bainite being between 60 and 95%, of between 4 and 35% bainite with a small amount of carbides, of between 0 and 5% ferrite, and of less than 5% residual austenite in the form of islands. |
