Section steel and method for manufacturing same

Abstract

A section steel according to an exemplary embodiment of the present invention is characterized in that it includes an amount of 0.08 to 0.17% by weight of carbon (C), an amount of 0.50 to 1.60% by weight of manganese (Mn), an amount of 0.10 to 0.50% by weight of silicon (Si), an amount of 0.10 to 0.70% by weight of chromium (Cr), an amount greater than 0 and 0.5% by weight or less of copper (Cu), an amount of 0.30 to 0.70% by weight of molybdenum (Mo), an amount greater than 0 and 0.02% by weight or less of phosphorus (P), an amount greater than 0 and 0.01% by weight or less of sulfur(S), an amount greater than 0 and 0.012% by weight or less of nitrogen (N), an amount greater than 0 and 0.003% by weight or less of boron (B), an amount of 0.01 to 0.5% by weight of the sum of at least one or more of nickel (Ni), vanadium (V), niobium (Nb), and titanium (Ti), and the remainder of iron (Fe) and other unavoidable impurities, and has a tensile strength of 490 to 620 MPa, a yield strength of 355 MPa or greater, and a yield ratio of 0.8 or less at room temperature, and a high-temperature yield strength of 273 MPa or greater at a temperature of 600° C.

1 .- 3 . (canceled) 
     
     
         4 . A method for manufacturing section steel, the method comprising the steps of:
 (a) reheating a steel material comprising an amount of 0.08 to 0.17% by weight of carbon (C), an amount of 0.50 to 1.60% by weight of manganese (Mn), an amount of 0.10 to 0.50% by weight of silicon (Si), an amount of 0.10 to 0.70% by weight of chromium (Cr), an amount greater than 0 and 0.5% by weight or less of copper (Cu), an amount of 0.30 to 0.70% by weight of molybdenum (Mo), an amount greater than 0 and 0.02% by weight or less of phosphorus (P), an amount greater than 0 and 0.01% by weight or less of sulfur(S), an amount greater than 0 and 0.012% by weight or less of nitrogen (N), an amount greater than 0 and 0.003% by weight or less of boron (B), an amount of 0.01 to 0.5% by weight of the sum of at least one or more of nickel (Ni), vanadium (V), niobium (Nb), and titanium (Ti), and the remainder of iron (Fe) and other unavoidable impurities to 1200 to 1250° C.;   (b) hot-rolling the steel material so that a rolling end temperature becomes 910 to 950° C.; and   (c) subjecting the hot-rolled steel material to QST (Quenching & Self-Tempering) treatment.   
     
     
         5 . The method of  claim 4 , wherein the QST (Quenching & Self-Tempering) treatment step has a water cooling end temperature and a self-tempering temperature of 765 to 800° C. 
     
     
         6 . The method of  claim 4 , wherein the section steel which has been subjected to the step (c) has a tensile strength of 490 to 620 MPa, a yield strength of 355 MPa or greater, and a yield ratio of 0.8 or less at room temperature, and a high-temperature yield strength of 273 MPa or greater at a temperature of 600° C. 
     
     
         7 . The method of  claim 4 , wherein the step (b) comprises a step of hot-rolling the steel material so that a rolling start temperature becomes 1050 to 1100° C.