POSCO Holdings Inc.
HIGH STRENGTH HOT-ROLLED STEEL SHEET HAVING EXCELLENT HOLE EXPANSION RATIO AND MANUFACTURING METHOD FOR SAME

Abstract:

A high strength hot-rolled steel sheet having an excellent hole expansion ration comprises, by weight %, 0.12% or more and less than 0.30% of carbon (C), 0.1-2.5% of manganese (Mn), 0.5% or less of silicon (Si) (not including 0%), 0.0005-0.005% of boron (B), 0.02% or less of phosphorous (P), 0.01% or less of sulfur (S), and the balance being iron (Fe) and unavoidable impurities, and comprises 95 volume % or more of martensite as a microstructure. And the product of the tensile strength (TS) and hole expansion ratio (HER) can be 30,000 MPa % or greater.