| 摘要 |
<p>Disclosed are a steel which is provided to have excellent shock resistance by ensuring the property of low yield ratio and controlling fraction to have a composite tissue including acicular ferrite and bainitic ferrite by controlling an alloy component and a process condition, and a method for manufacturing the steel. According to the present invention, the method for manufacturing the steel includes: (a) a step of reheating a slab at a slab reheating temperature of 1150-1200°C, wherein the slab includes: 0.04-0.11 wt% of carbon (C), 0.1-0.4 wt% of silicon (Si), 1.5-2.5 wt% of manganese (Mn), 0.01 wt% or less of phosphorous (P), 0.01 wt% or less of sulfur (S), 0.1-0.5 wt% of chrome (Cr), 0.3-1.0 wt% of nickel (Ni), 0.15-0.50 wt% of Molybdenum (Mo), 0.01-0.06 wt% of aluminum (Al), 0.2-1.0 wt% of copper (Cu), 0.01-0.03 wt% of titanium (Ti), 0.005-0.070 wt% of niobium (Nb), 0.03-0.10 wt% of vanadium (V), 0.0005-0.002 wt% of boron (B), 0.002-0.007 wt% of nitrogen (N), and the remainder consisting of iron (Fe) and inevitable impurities; (b) a step of finish hot rolling the reheated slab at a finish rolling temperature (FRT) of 800-850°C; (c) a step of waiting for the hot-rolled slab at a temperature of 730-830°C for 2-5 minutes in an air-cooling manner; and (d) a step of cooling the slab processed in the (c) step down to a temperature of 350-450°C.</p> |
