ULTRAHIGH-STRENGTH STEEL SHEET

摘要

An ultrahigh-strength steel sheet which comprises, in terms of wt.%, 0.10-0.60% C, 1.0-3.0% Si, 1.0-3.5% Mn, up to 0.15% P, up to 0.02% S, up to 1.5% Al, and 0.003-2.0% Cr, with the remainder being iron and unavoidable impurities, and in which the crystal grains of residual austenite have an average aspect ratio (major axis/minor axis) of 5 or higher, an average minor-axis length of 1 µm or shorter, and a minimum grain-to-grain distance of 1 µm or shorter. It has excellent unsusceptibility to hydrogen embrittlement.