ULTRA HIGH STRENGTH HOT-ROLLED STEEL WITH EXCELLENT BALANCE OF STRENGTH?DUCTILITY AND METHOD OF MANU

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PURPOSE : An ultra high strength hot-rolled steel sheet with excellent strength-ductility balance and method of manufacturing the same are provided to improve the surface characteristics of a hot-rolled steel sheet with formability applicable to vehicle parts. CONSTITUTION : A method for manufacturing an ultra high strength hot-rolled steel sheet with excellent strength-ductility balance comprises the steps of : re-heating a slab to 1150-1250°C(S100), hot finish rolling the re-heated plate at 750-950°C(S110), and cooling the hot finish rolled plate to a coiling temperature of 450°C or less and coiling the cooled plate(S120). The slab comprises C of 0.08-0.20 weight%, Al of 0.5-1.0 weight%, Si of 0.01-0.60 weight%, Mn of 1.4-2.5 weight%, Nb of 0.01-0.10 weight%, P of 0.05 weight% or less, S of 0.01 weight% or less, N of 0.01 weight% or less, and Fe and inevitable impurities of the remaining amount.