Abstract: The present invention relates to a cold rolled steel sheet and a manufacturing method therefor, and, more specifically, to a cold rolled steel sheet and a manufacturing method therefor, the cold rolled steel sheet having excellent strength and formability, which can be preferably applied to a structure member such as the members, seat rails, and pillars of a vehicle, and the like.

Abstract: Provided is an ultra-high-strength cold-rolled steel sheet having excellent yield strength and bending properties, which can be used as a structural component for automobiles such as a member, a seat rail, and a pillar, and a method for manufacturing same. The steel sheet includes: by weight: C: 0.03 to 0.12%, Si: 0.03 to 0.3 Mn: 2.1 to 2.9%, Al: 0.005 to 0.07%, Nb: 0.01 to 0.08%, Ti: 0.005 to 0.08%, B: 0.0005 to 0.005%, Cr: 0.7 to 1.4%, Mo: 0.005 to 0.10%, N: 0.008% or less (excluding 0%), with balance of Fe and inevitable impurities. A microstructure thereof includes by area, fresh martensite: 4 to 19%, a sum of tempered martensite and bainite: 78 to 95%, and retained austenite: 0.2 to 2.0%. An average grain size of the microstructure is 0.5 to 6 ?m.

Abstract: Provided are an ultra-high strength cold rolled steel sheet having excellent bendability, and a method of manufacturing the same. The steel sheet includes 0.06 to 0.17% of C, 0.1 to 0.8% of Si, 1.9 to 2.9% of Mn, 0.005 to 0.07% of Nb, 0.004 to 0.05% of Ti, 0.0004 to 0.005% of B, 0.20% or less (excluding 0%) of Cr, and 0.04 to 0.45% of Mo, with a balance of Fe and other unavoidable impurities. a microstructure of the steel sheet includes, by area: 80 to 98% of tempered martensite and a balance of fresh martensite, bainite, ferrite, and residual austenite. An average length of lath short axis of the tempered martensite is 500 nm or less.

Abstract: Provided is an ultra high-strength hot-rolled steel sheet, having tensile strength of 800 MPa, and a method for manufacture same, the method enabling excellent surface quality, workability, weldability as well as significantly reduced deviation of the mechanical property in the width and length directions of the steel sheet by means of an endless rolling mode in a continuous casting-direct rolling process.

Abstract: A continuous casting and rolling apparatus includes: a continuous casting device; a cutting device that is disposed at the output side of the continuous casting device and cuts an inner slab produced from the continuous casting device; a rolling device pressing down on the slab and disposed downstream of the continuous casting device in the moving direction of the inner slab; a tunnel furnace which is disposed between the cutting device and the rolling device and heats the slab disposed on the main path of the inner slab that is transferred from the continuous casting device to the rolling device; and a loading adjustment unit which is disposed adjacent to the tunnel furnace and unloads the slab from the main path from the outlet side of the tunnel furnace and loads the slab onto the main path from the inlet side of the tunnel furnace.

Abstract: Provided is an ultra high-strength hot-rolled steel sheet, having tensile strength of 800 MPa, and a method for manufacture same, the method enabling excellent surface quality, workability, weldability as well as significantly reduced deviation of the mechanical property in the width and length directions of the steel sheet by means of an endless rolling mode in a continuous casting-direct rolling process.

Abstract: Disclosed are a tailor welded blank and a manufacturing method thereof. The tailor welded blank is manufactured by connecting blank elements of different materials or thicknesses, thereby eliminating quality problems in a welded zone. A hot stamped component is manufactured by hot stamping the tailor welded blank formed by laser-welding blank elements made of coated steel plates having different strengths or thicknesses using a filler wire, wherein a laser-welded zone has a martensite structure.

Abstract: Disclosed are a tailor welded blank and a manufacturing method thereof. The tailor welded blank is manufactured by connecting blank elements of different materials or thicknesses, thereby eliminating quality problems in a welded zone. A hot stamped component is manufactured by hot stamping the tailor welded blank formed by laser-welding blank elements made of coated steel plates having different strengths or thicknesses using a filler wire, wherein a laser-welded zone has a martensite structure.

Abstract: Disclosed are a tailor welded blank and a manufacturing method thereof. The tailor welded blank is manufactured by connecting blank elements of different materials or thicknesses, thereby eliminating quality problems in a welded zone. A hot stamped component is manufactured by hot stamping the tailor welded blank formed by laser-welding blank elements made of coated steel plates having different strengths or thicknesses using a filler wire, wherein a laser-welded zone has a martensite structure.

Abstract: Disclosed are a tailor welded blank and a manufacturing method thereof. The tailor welded blank is manufactured by connecting blank elements of different materials or thicknesses, thereby eliminating quality problems in a welded zone. A hot stamped component is manufactured by hot stamping the tailor welded blank formed by laser-welding blank elements made of coated steel plates having different strengths or thicknesses using a filler wire, wherein a laser-welded zone has a martensite structure.