| 摘要 |
<p>Disclosed are steel materials with an excellent strength and low-temperature toughness and a manufacturing method thereof. The manufacturing method of steel materials according to the present invention is characterized by comprising; a step of reheating of steel slabs containing in weight % ; carbon (C) : 0.16~0.20%, silicon (Si) : 0.3~0.4%, manganese (Mn) : 1.1~1.3%, phosphor (P) : less than 0.02% , sulfur (S) : less than 0.005% , aluminum (Al) : 0.01~0.05%, copper (Cu) : 0.1~0.2%, niobium (Nb) : 0.01~0.02%, nickel (Ni) : 0.15~0.25%, chromium (Cr) : 0.15~0.25%, molybdenum (Mo) : less than 0.08% , calcium (Ca) : 0.0005~0.004% in addition to a balance of iron (Fe) and unavoidable impurities; and a step of hot-rolling of the reheated steel materials; and a step of cooling down the hot-rolled steel materials; and a step of normalizing heat treatment of the cooled steel materials at 840~940°C. [Reference numerals] (AA) START; (BB) END; (S110) Reheat a slab; (S120) Hot-rolling; (S130) Cooling; (S140) Normalizing heat treatment</p> |
