POSCO Holdings Inc.
HIGH-STRENGTH HOT-ROLLED PLATED STEEL SHEET, AND METHOD FOR PRODUCING SAME

Abstract:

Provided is a high-strength hot-rolled plated steel sheet, including: in a unit of wt %, C at 0.05-0.5 wt %, Mn at 0.1-3.s0 wt %, Si at 0.5 wt % or less (excluding 0 wt %), P at 0.05 wt % or less (excluding 0 wt %), S at 0.03 wt % or less (excluding 0 wt %), Nb at 0.01 wt % or less (excluding 0 wt %), B at 0.0005-0.005 wt %, Ti at 0.005-0.2 wt %, and the remainder of Fe and inevitable impurities, wherein a microstructure thereof includes, as a volume fraction, 90 vol % or more of tempered martensite and 5 vol % or less of one crystal phase of bainite, ferrite, pearlite, and residual austenite; a tensile strength thereof is 650 MPa or more, and a yield strength thereof is 550 MPa or more; and as a ratio of the strengths, a yield ratio (yield strength/tensile strength) is 0.85 or more.