| 摘要 |
<p>PURPOSE: A hot rolled steel sheet and a manufacturing method thereof are provided to obtain a tensile strength of 550MPa or greater, an elongation ratio of 30% or greater, and excellent surface roughness by controlling the alloy components and hot rolling conditions. CONSTITUTION: A method for manufacturing a hot rolled steel sheet comprises the steps of: reheating steel slab, which comprises 0.18-0.22 wt% of C, 0.13-0.27 wt% of Si, 1.4-1.6 wt% of Mn, 0.015 wt% or less of P, 0.005 wt% or less of S, 0.001-0.004 wt% of Ca, and the remaining amount of Fe and inevitable impurities(S105), hot rolling the steel slab at an FDT(Finishing Delivery Temperature) of 840-870°C(S110), and cooling the hot rolled steel sheet and coiling the steel sheet in the pearlite temperature range(S120). [Reference numerals] (AA) Start; (BB) End; (S105) Reheating slab(SRT: 1150-1300°C); (S110) Hot rolling(FDT: 840-870°C); (S120) Cooling/coiling(CT: 580-630°C)</p> |
