METHOD OF MANUFACTURING HIGH STRENGTH STRUCTURAL STEEL OF 750MPA GRADE AND HIGH TENSILE STRENGTH AND STRUCTURAL STEEL USING THEREOF

摘要

PURPOSE: A 750MPa grade high strength and toughness structural steel material and a method for manufacturing the same are provided to secure high strength and elongation ratio without controlled rolling by minimizing the load of a rolling mill. CONSTITUTION: A manufacturing method for a 750MPa grade high strength and toughness structural steel material comprises the steps of: reheating steel slab(S100), rolling the steel slab(S200), and cooling the rolled steel material(S300). The steel slab comprises carbon of 0.17-0.20 weight%, silicon of 0.25-0.35 weight%, manganese of 1.25-1.35 weight%, phosphorus of 0.03 weight% or less, sulfur of 0.015 weight% or less, vanadium of 0.25-0.35 weight%, titanium of 0.05-0.08 weight%, nitrogen of 0.008-0.013 weight%, one or more among nickel of 0.1-0.15 weight%, chrome of 0.07-0.15 weight%, copper of 0.15-0.2 weight%, niobium of 0.015-0.025 weight%, and aluminum of 0.01-0.02 weight%, and iron and inevitable impurities of the remaining amount.