EARTHQUAKE-PROOF TYPE ULTRAHIGH STRENGTH STEEL FOR STEEL-FRAME STRUCTURE AND ITS PRODUCTION

摘要

PURPOSE: To obtain an ultrahigh strength steel showing high yield strength and high uniform elongation by heating a carbon steel with a specific composition up to a specific temp., hot-working the carbon steel to the prescribed plate thickness, and then performing cooling under specific conditions. ;CONSTITUTION: A steel stock having a composition which consists of, by weight, 0.01-0.25% C, 0.05-1.00% Si, 15.0-25.0% Mn, 0.01-18.0% Cr, 0.10-5.0% Ni, ≤0.15% S, 0.05-0.50% N, 0.001-1.50% sol.Al, and the balance Fe with inevitable impurities and contains, if necessary, one or more elements among Cu, Mo, Nb, V, Ti, and B and/or one or more elements among Se, Te, Pb, and Ca and in which Nieq. represented by equation I satisfies inequality II is prepared. This steel stock is heated up to ≤1250°C, formed to the prescribed plate thickness by means of hot working at 100-600°C finishing temp., and cooled at a velocity not lower than air cooling velocity. By this method, the steel having ≥95kgf/ mm² yield strength and ≥8% elongation can be obtained.;COPYRIGHT: (C)1993,JPO&Japio