| 摘要 |
<p>Disclosed are shape steel capable of ensuring high strength and excellent low temperature toughness due to grain refinement of steel by controlling an alloy component and a process condition; and a method to manufacture the same. According to the present invention, the method to manufacture the shape steel comprises: a step of re-heating a slab comprising 0.06-0.12 wt% of carbon (C), 0.15-0.4 wt% of silicon (Si), 1.25-1.6 wt% of manganese (Mn), 0.001-0.025 wt% of phosphorus (P), 0.001-0.025 wt% of sulfur (S), 0.001-0.055 wt% of aluminum (Al), 0.001-0.05 wt% of niobium (Nb), 0.001-0.1 wt% of vanadium (V), 0.001-0.025 wt% of titanium (Ti), 0.0001-0.012 wt% of nitrogen (N), and the remainder consisting of iron (Fe) and inevitable impurities at 1120-1180°C which is a slab reheating temperature (SRT); a step of hot rolling the re-heated slab at 770-830°C which is a finishing delivery temperature (FDT); and a step of quenching and self-tempering (QST) cooling the hot rolled steel.</p> |
