Abstract: One aspect of the present invention relates to an ultrahigh-strength steel sheet having an excellent yield ratio, comprising, by wt %, 0.3-0.5% of C, 2.0% (excluding 0%) of Si, 3.0-6.5% of Mn, 0.02% or less of P, 0.01% or less of S, 0.01-3.0% of Al, 0.02% or less (excluding 0%) of N, and the balance of Fe and other inevitable impurities, and a microstructure comprises 5-30% of remaining austenite by area fraction and comprises 5% or less of secondary martensite.

Abstract: Provided is an ultra-high-strength steel sheet having an excellent hole expandability and yield ratio, including, in terms of wt %: 0.05-0.2% of carbon (C); 2.0% or less of silicon (Si); 4.1-9.0% of manganese (Mn); 0.05% or less (excluding 0%) of phosphorus (P); 0.02% or less (excluding 0%) of sulfur (S); 0.5% or less (excluding 0%) of aluminum (Al); 0.02% or less (excluding 0%) of nitrogen (N); and a balance of iron (Fe) and other inevitable impurities, wherein the following Equation 1 is satisfied, and wherein microstructures includes, in volume percentage, 10-30% or retained austenite, 50% or more of annealed martensite, and 20% or less of other phases including alpha martensite and epsilon martensite, Equation 1: C/12+Ti/48+Nb/93+V/51+Mo/96?0.015.

Abstract: The present invention relates to an apparatus for continuous annealing of a strip, capable of manufacturing a high-strength and highly ductile cold-rolled steel sheet having both excellent strength and ductility, and to a method for continuous annealing of a strip. The continuous annealing apparatus, according to the present invention, is capable of continuous annealing by cooling after heating, and then reheating, unlike an existing continuous annealing apparatus which heats only once and then cools or provides an overaging treatment. As a result, the continuous annealing apparatus, according to the present invention, can preliminarily render a homogeneous texture or control the texture as desired, and then perform another reheating heat treatment to stabilize the texture or control the shape thereof to a desired state.

Abstract: Provided is an ultrahigh-strength steel sheet for a vehicle and, more specifically, to an ultrahigh-strength and high-ductility steel sheet having excellent yield ratio and a manufacturing method therefor. Provided is an ultrahigh-strength and high-ductility steel sheet for cold press forming and a manufacturing method therefor, the steel sheet ensuring ultrahigh strength and high ductility since an alloy component of steel and manufacturing conditions are controlled and, simultaneously, having excellent impact characteristics due to a high yield strength ratio (yield ratio). Provided is the steel sheet capable of satisfying formability and impact stability, which are required for a vehicle steel sheet for cold forming, and replacing a conventional steel sheet for hot press forming, thereby reducing manufacturing costs.

Abstract: Provided is a high-strength steel sheet for use in lightening materials for electronic products and materials for vehicles including automobiles, trains and ships and, more particularly, to a high-strength cold rolled steel sheet, a coated steel plate, and a method for manufacturing the same, wherein yield strength and ductility are improved by controlling the internal oxidation depth and the amount of residual austenite after first annealing operation, and the high-strength cold rolled steel sheet and the coated steel plate is stably manufactured and provided without any dent defects during the manufacturing thereof.

Abstract: Provided is an ultra high-strength steel sheet having excellent hole expandability. The ultra high-strength steel sheet includes: 0.15 to 0.30% of C, 1.0 to 3.0% of Si, 3.0 to 5.0% of Mn, 0.020% or less of P, 0.010% or less of S, 0.01 to 3.0% of Al, and 0.020% or less of N (excluding 0%) by weight, with the remainder consisting of Fe and other inevitable impurities, wherein a microstructure contains 5% to 20% by area fraction of retained austenite with the remainder including ferrite, bainite and fresh martensite.

Abstract: Provided is a warm-pressed member comprising, by weight %, C: 0.01% to 0.5%, Si: 3.0% or less (excluding 0%), Mn: 3% to 15%, P: 0.0001% to 0.1%, S: 0.0001% to 0.03%, Al: 3.0% or less (excluding 0%), N: 0.03% or less (excluding 0%), and the balance of Fe and inevitable impurities. After a warm press forming process and a cooling process, the warm-pressed member has a microstructure comprising: 5 volume % to 50 volume % of retained austenite; and at least one of ferrite, martensite, tempered martensite, and bainite as a remainder.

Abstract: Provided is a ferritic lightweight high-strength steel sheet having excellent stiffness and ductility and a method of manufacturing the same. The steel sheet including 0.02 wt % to 0.1 wt % of carbon (C), 4 wt % to 15 wt % of manganese (Mn), 4 wt % to 10 wt % of aluminum (Al), 2.0 wt % or less (excluding 0) of silicon (Si), 0.01 wt % to 0.3 wt % of titanium (Ti), 0.005 wt % to 0.2 wt % of antimony (Sb), and iron (Fe) as well as unavoidable impurities as a remainder, and having a value of 0.25×Ti/C ranging from 0.17 to 1.0 and a value of Mn/Al×Log(C×Ti×10000) ranging from 1.0 to 10.

Abstract: The present invention relates to: a high-strength steel sheet used for construction materials and transportation means such as vehicles and trains and, more specifically, to a high-strength cold rolled steel sheet having excellent ductility, a hot-dip galvanized steel sheet, and a method for manufacturing the same.

Abstract: An apparatus for continuous annealing of a strip comprises: a first heating zone configured to firstly heat a strip; a first cooling or constant temperature maintaining zone configured to cool the strip firstly heated in the first heating zone or to maintain the strip at a constant temperature; a second heating and soaking zone configured to secondarily heat and soak the strip cooled or remaining at the constant temperature in the first cooling or constant temperature maintaining zone; and a second cooling zone configured to cool the strip heated and soaked in the second heating and soaking zone.

Abstract: Provided is a ferritic lightweight high-strength steel sheet having excellent stiffness and ductility and a method of manufacturing the same. The steel sheet including 0.02 wt % to 0.1 wt % of carbon (C), 4 wt % to 15 wt % of manganese (Mn), 4 wt % to 10 wt % of aluminum (Al), 2.0 wt % or less (excluding 0) of silicon (Si), 0.01 wt % to 0.3 wt % of titanium (Ti), 0.005 wt % to 0.2 wt % of antimony (Sb), and iron (Fe) as well as unavoidable impurities as a remainder, and having a value of 0.25×Ti/C ranging from 0.17 to 1.0 and a value of Mn/Al×Log(C×Ti×10000) ranging from 1.0 to 10.

Abstract: Provided are a steel sheet for warm press forming that can have high strength, good elongation, and thus improved crashworthiness after being warm pressed, and a warm-pressed member formed of the steel sheet, and manufacturing methods thereof. The steel sheet for warm press forming includes, by weight %, C: 0.01% to 0.5%, Si: 3.0% or less (excluding 0%), Mn: 3% to 15%, P: 0.0001% to 0.1%, S: 0.0001% to 0.03%, Al: 3.0% or less (excluding 0%), N: 0.03% or less (excluding 0%), and the balance of Fe and inevitable impurities.

Abstract: The present invention relates to a hot press forming steel plate made of a composition comprising: 0.3-1.0 wt % of C; 0.0-4.0 wt % of Mn; 1.0-2.0 wt % of Si; 0.01-2.0 wt % of Al; 0.015 wt % or less of S; 0.01 wt % or less of N; and the remainder being Fe and unavoidable impurities. Further, the present. invention relates to a method for manufacturing the hot press forming steel plate, characterized by comprising the steps of: heating, to between 1100 and 1300° C., a steel slab having the composition; performing hot rolling finishing between. an Ar3 transformation point and 950° C.; and performing winding between MS and 720° C. Further, the present invention. relates to a hot press formed member characterized by having the composition, and having a dual phase microstructure made of bainite and residual austenite.

Abstract: A carbon steel sheet having high formability due to a microscopic and uniform carbide distribution and having a good characteristic of final heat treatment, and a manufacturing method thereof. The carbon steel sheet having excellent formability includes, in wt %, C at 0.2-0.5%, Mn at 0.1-1.2%, Si at less than or equal to 0.4%, Cr at less than or equal to 0.5%, Al at 0.01-0.1%, S at less than or equal to 0.012%, Ti at less than or equal to 0.5×48/14×[N]% to 0.03% when the condition of B and N is not satisfied, B at 0.0005-0.0080%, N at less than or equal to 0.006%, Fe, and extra inevitable elements; an average size of carbide is less than or equal to 1 ?m; and an average grain size of ferrite is less than or equal to 5 ?m.

Abstract: A high carbon steel sheet having superior strength and ductility and a method for manufacturing the same comprising: 0.2 to 1.0 wt % carbon (C), 0 to 3.0 wt % silicon (Si), 0 to 3.0 wt % manganese (Mn), 0 to 3.0 wt % chromium (Cr), 0 to 3.0 wt % nickel (Ni), 0 to 0.5 wt % molybdenum (Mo), 0 to 3.0 wt % aluminum (Al), 0 to 0.01 wt % boron (B), 0 to 0.5 wt % titanium (Ti), and the remainder substantially being iron (Fe) and inevitable impurities. The contents of carbon, manganese, chromium, and nickel satisfy the following Equation 1, and the contents of silicon and aluminum satisfy the following Equation 2: (3.0?2.5×C)wt %?(Mn+Cr+Ni/2)?8.5 wt %—(Equation 1) Si+Al>1.0 wt % (Equation 2).

Abstract: A carbon steel sheet having high formability due to a microscopic and uniform carbide distribution and having a good characteristic of final heat treatment, and a manufacturing method thereof. The carbon steel sheet having excellent formability includes, in wt %, C at 0.2-0.5%, Mn at 0.1-1.2%, Si at less than or equal to 0.4%, Cr at less than or equal to 0.5%, Al at 0.01-0.1%, S at less than or equal to 0.012%, Ti at less than or equal to 0.5×48/14×[N] % to 0.03% when the condition of B and N is not satisfied, B at 0.0005-0.0080%, N at less than or equal to 0.006%, Fe, and extra inevitable elements; an average size of carbide is less than or equal to 1 ?m; and an average grain size of ferrite is less than or equal to 5 ?m.

Abstract: A carbon steel sheet having high formability due to a microscopic and uniform carbide distribution and having a good characteristic of final heat treatment, and a manufacturing method thereof. The carbon steel sheet having excellent formability, includes, in wt %, C at 0.2-0.5%, Mn at 0.1-1.2%, Si at less than or equal to 0.4%, Cr at less than or equal to 0.5%, Al at 0.01-0.1%, S at less than or equal to 0.012%, Ti at less than or equal to 0.5×48/14×[N]% when the condition of B(atomic %)/N(atomic %)>1 is satisfied or by 0.5×48/14×[N]% to 0.03% when the condition of B and N is not satisfied, B at 0.0005-0.0080%, N at less than or equal to 0.006%, Fe, and extra inevitable elements; an average size of carbide is less than or equal to 1 ?m; and an average grain size of ferrite is less than or equal to 5 ?m.

Abstract: A high carbon steel sheet having superior strength and ductility and a method for manufacturing the same comprising: 0.2 to 1.0 wt % carbon (C), 0 to 3.0 wt % silicon (Si), 0 to 3.0 wt % manganese (Mn), 0 to 3.0 wt % chromium (Cr), 0 to 3.0 wt % nickel (Ni), 0 to 0.5 wt % molybdenum (Mo), 0 to 3.0 wt % aluminum (Al), 0 to 0.01 wt % boron (B), 0 to 0.5 wt % titanium (Ti), and the remainder substantially being iron (Fe) and inevitable impurities. The contents of carbon, manganese, chromium, and nickel satisfy the following Equation 1, and the contents of silicon and aluminum satisfy the following Equation 2: (3.0?2.5×C)wt %?(Mn+Cr+Ni/2)?8.5 wt %—(Equation 1) Si+Al>1.0 wt % (Equation 2).

Abstract: A carbon steel sheet having high formability due to a microscopic and uniform carbide distribution and having a good characteristic of final heat treatment, and a manufacturing method thereof. The carbon steel sheet having excellent formability, includes, in wt %, C at 0.2-0.5%, Mn at 0.1-1.2%, Si at less than or equal to 0.4%, Cr at less than or equal to 0.5%, Al at 0.01-0.1%, S at less than or equal to 0.012%, Ti at less than or equal to 0.5×48/14×[N]% when the condition of B(atomic %)/N(atomic %)>1 is satisfied or by 0.5×48/14×[N]% to 0.03% when the condition of B and N is not satisfied, B at 0.0005-0.0080%, N at less than or equal to 0.006%, Fe, and extra inevitable elements; an average size of carbide is less than or equal to 1 ?m; and an average grain size of ferrite is less than or equal to 5 ?m.