| 摘要 |
Disclosed is a method of manufacturing a steel material which can improve an impact value characteristic of a surface portion by controlling a temperature of reheating an alloy component and a slab. According to the present invention, the method of manufacturing the steel material includes (a) a step of reheating a steel slab formed of 0.05-0.1 wt% of carbon (C), 0.2-0.4 wt% of silicon (Si), 1.0-1.7 wt% of magnesium (Mn), equal to or less than 0.5 wt% of aluminum (Al), equal to or less than 0.012 wt% of phosphorous (P), equal to or less than 0.003 wt% of sulfur (S), 0.2-0.5 wt% of nickel (Ni), 0.05-0.2 wt% of copper (Cu), 0.01-0.03 wt% of niobium (Nb), equal to or less than 0.0005 wt% of boron (B), 0.01-0.02 wt% of titanium (Ti), equal to or less than 0.005 wt% of nitrogen (N), and the remainder consisting of iron (Fe) and inevitable impurities at a 1,000-1,100°C condition with respect to a surface temperature; (b) a step of primarily rolling the reheated steel material at a temperature ranging from a recrystallization stop temperature (RST) to RST+100°C; (c) a step of secondarily rolling the primarily-rolled steel material at a temperature ranging from a rolling completion temperature Ar3+70°C to Ar3+80°C condition; and (d) a step of cooling the secondarily-rolled steel material. |
