| 摘要 |
<p>PURPOSE: A hot-rolled steel sheet and a manufacturing method thereof are provided to obtain a tensile strength of 862 MPa or more and a yield strength of 758-965 MPa without a QT(Quenching and Tempering) heat treatment by controlling alloy components and hot-rolling process conditions. CONSTITUTION: A manufacturing method of a hot-rolled steel sheet is as follows: a step for reheating a slab, composed of 0.2-0.3 wt.% of C, 0.05-0.40 wt.% of Si, 1.0-1.5 wt.% of Mn, 0.02-0.04 wt.% of Al, 0.01-0.20 wt.% of Ni, 0.01-0.20 wt.% of Cu, 0.05-0.50 wt.% of Cr, 0.006-0.010 wt.% of Ca, 0.01-0.03 wt.% of Ti, 0.001-0.003 wt.% of B, and remaining content of Fe and inevitable impurities, at 1150-1250 degrees C(S110); a step for hot-rolling the reheated slab at 800-900 degrees C(S120); and a step for winding the slab after cooling the slab at 450-500 degrees C(S130). [Reference numerals] (AA) Start; (BB) End; (S110) Slab reheating(SRT: 1150-1250°C); (S120) Hot-rolling(FDT: 800-900°C); (S130) Cooling/coiling(CT: 450-500°C)</p> |
