POSCO Holdings Inc.
ULTRAHIGH-STRENGTH HIGH-DUCTILITY STEEL SHEET HAVING EXCELLENT YIELD STRENGTH, AND MANUFACTURING METHOD THEREFOR

Abstract:

Provided is an ultrahigh-strength high-ductility steel sheet having excellent yield strength, comprising, by wt %, 0.04-0.18% of C, 2% or less of Si, 4-10% of Mn, 0.05% or less of P (except 0%), 0.02% or less of S (except 0%), 0.5% or less of Al (except 0%), 0.02% or less of N (except 0%) and the balance of Fe and the other inevitable impurities, wherein Si+Mn satisfies 6-10% and the microstructure comprises, by volume fraction, 12% or more of retained austenite and 60% or more of annealed martensite.