| 摘要 |
The present invention provides a wire rod having a high strength and impact toughness, and a method to manufacture the same. The wire rod comprises: 0.05-0.15 wt% of carbon (C); 0.1 wt% or less of silicon (Si); 3.0-5.0 wt% of manganese (Mg); 0.5-2.0 wt% of chromium (Cr); 0.010-0.030 wt% of niobium (Nb); 0.020 wt% or less of phosphorus (P); 0.020 wt% or less of sulfur (S); and the remaining consisting of residual iron (Fe) and inevitable foreign substances. The method to manufacture the wire rod comprises: a step of preparing steel having the composition described above, and reheating the steel at a temperature in the range of Ae3 + 150°C to Ae3 + 250°C; a step of starting hot rolling to the reheated steel, and finishing the hot rolling at temperatures in a range of Ar3 + 200°C to Ar3 + 300°C; a step of cooling the rolled steel which has undergone hot rolling at a cooling speed of 0.2 °C/s or more up to a temperature in a range of Mf to Mf - 50°C; and a step of performing air cooling to the cooled steel at room temperature. |
