| 摘要 |
Disclosed are hot-rolled steel sheets with an excellent strength capable of improving impact characteristics by addition of boron, titanium and niobium and a manufacturing method thereof. The manufacturing method of hot-rolled steel sheets according to the present invention is characterized by comprising; a step of hot-rolling at a finish rolling temperature (FDT) of 820~860°C of slab sheet materials comprising; carbon (C) : 0.10~0.20 wt%, silicon (Si) : less than 0.25 wt% , manganese (Mn) : 0.5~1.0 wt%, phosphor (P) : less than 0.02 wt% , sulfur (S) : less than 0.005 wt% , nitrogen (N) : less than 0.006 wt% ,niobium (Nb) :less than 0.1 wt% , titanium (Ti) : less than 0.1 wt% ,boron (B) : less than 0.1 wt% in addition to a balance of iron (Fe) and unavoidable impurities; and a step of cooling the hot-rolled sheet materials to wind at a winding temperature of 600~650°C. [Reference numerals] (AA) START; (BB) Slab reheating (SRT : 1150 ~1300°C); (CC) Hot rolling (FDT : 820 ~880°C); (DD) END; (S120) Cooling/ winding (CT : 600 ~ 650°C) |
