Steel material having low surface hardness and excellent low temperature impact toughness, and method for manufacturing same

A steel material comprising, by weight:

• 0.08 to 0.14% of carbon (C), 0.1 to 0.5% of silicon (Si), 1.2 to 1.7% of manganese (Mn), 0.01% or less of phosphorus (P), 0.01% or less of sulfur(S), 0.01 to 0.05% of aluminum (Al), 0.05% or less of niobium (Nb), 0.01 to 0.5% of chromium (Cr), 0.01 to 0.25% of nickel (Ni), 0.01 to 0.1% of molybdenum (Mo), 0.01 to 0.05% of vanadium (V), 0.003% or less of titanium (Ti), 0.002 to 0.01% of nitrogen (N), with a balance of Fe and inevitable impurities,
• wherein, based on a thickness cross-section, the steel material includes a microstructure, wherein in the microstructure, a surface layer region, from a surface to 0.5 mm consists of 90 area % or more of polygonal ferrite, 10 area % or less of acicular ferrite and 5 area % or less of bainite;
• and a center region other than the surface layer region includes a mixed structure of 30 to 70 area % of acicular ferrite, and a remainder of tempered martensite and tempered bainite.