High-strength steel material having excellent low-temperature strain aging impact properties and welding heat-affected zone impact properties and method for manufacturing same

A method for manufacturing a high-strength steel material having excellent low-temperature strain aging impact properties and welding heat-affected zone impact properties, the method comprising:

• reheating a steel slab including 0.04-0.14 wt % of carbon (C), 0.05-0.60 wt % of silicon (Si), 0.6-1.8 wt % of manganese (Mn), 0.005-0.06 wt % of soluble aluminum (sol. Al), 0.005-0.05 wt % of niobium (Nb), 0.01 wt % or less (exclusive of 0 wt %) of vanadium (V), 0.012-0.030 wt % of titanium (Ti), 0.01-0.4 wt % of copper (Cu), 0.01-0.6 wt % of nickel (Ni), 0.01-0.2 wt % of chromium (Cr), 0.001-0.3 wt % of molybdenum (Mo), 0.0002-0.0040 wt % of calcium (Ca), 0.006-0.012 wt % of nitrogen (N), 0.02 wt % or less (exclusive of 0 wt %) of phosphorus (P), and 0.003 wt % or less (exclusive of 0 wt %) of sulfur (S), with a balance of Fe and other inevitable impurities in a temperature range of 1080-1250° C.;
• controlled rolling the reheated slab so that a rolling end temperature is 780° C. or more, thereby being manufactured into a hot-rolled steel plate;
• cooling the hot-rolled steel plate by air cooling or water cooling;
• and
• after the cooling, subjecting the hot-rolled steel plate to normalizing heat treatment in a temperature range of 850-960° C.