Abstract: A welded member includes: a first steel sheet including a base steel sheet and a zinc-based plating layer formed on a surface of the base steel sheet; and a second steel sheet spot-welded on the first steel sheet and facing the zinc-based plating layer of the first steel sheet, a spot-welded zone being formed between the first steel sheet and the second steel sheet. A surface layer of the base steel sheet has a decarburization ratio of 30% or more. The decarburization ratio is represented by equation: Decarburization ratio (%) of surface layer=(1?average carbon concentration in surface layer/bulk carbon concentration)*100 where the surface layer refers to a region of the base steel sheet from the surface thereof to a depth of 35 ?m. A shoulder portion of the spot-welded zone includes a B-type crack having a length of 100 ?m or less, and no C-type crack.

Abstract: The present invention relates to a zinc plated steel sheet having excellent surface quality and spot weldability, and a manufacturing method therefore. A zinc plated steel sheet according to one aspect of the present invention comprises a base steel sheet and a zinc-based plating layer formed on the surface of the base steel sheet, wherein the GDOES profile of oxygen, which is measured in the depth direction from the surface of the base steel sheet, has a form in which a local minimum point and a local maximum point alternately appear in the depth direction from the surface, and the difference (a local maximum value?a local minimum value) between the oxygen concentration (a local minimum value) at the local minimum point and the oxygen concentration (a local maximum value) at the local maximum point can be 0.1 wt % or more.

Abstract: Provided is a cold-rolled steel sheet including: by weight %, C: 0.10 to 0.16%, Si: 0.3 to 0.8%, Al: 0.01 to 0.5%, Mn: 2.0 to 3.0%, Cr: 0.001 to 0.5%, Mo: 0.001 to 0.5%, B: 0.0001 to 0.001%, Nb: 0.001 to 0.05%, Ti: 0.001 to 0.05%, P: 0.04% or less (excluding 0%), S: 0.01% or less (excluding 0%), N: 0.01% or less (excluding 0%), a remainder of Fe, and other unavoidable impurities, as a microstructure, by area %, ferrite: 10% or less (excluding 0%), retained austenite: more than 1% to 5% or less, martensite: 25% or more but less than 50%, and bainite: 35% or more but less than 70%. An average size of martensite-austenite (MA) in the bainite is 0.35 to 0.55 ?m.

Abstract: The present invention relates to a zinc plated steel sheet having excellent surface quality and spot weldability, and a manufacturing method therefore. A zinc plated steel sheet according to one aspect of the present invention comprises a base steel sheet and a zinc-based plating layer formed on the surface of the base steel sheet, wherein the GDOES profile of oxygen, which is measured in the depth direction from the surface of the base steel sheet, has a form in which a local minimum point and a local maximum point alternately appear in the depth direction from the surface, and the difference (a local maximum value?a local minimum value) between the oxygen concentration (a local minimum value) at the local minimum point and the oxygen concentration (a local maximum value) at the local maximum point can be 0.1 wt % or more.

Abstract: A welded member includes: a first steel sheet including a base steel sheet and a zinc-based plating layer formed on a surface of the base steel sheet; and a second steel sheet spot-welded on the first steel sheet and facing the zinc-based plating layer of the first steel sheet, a spot-welded zone being formed between the first steel sheet and the second steel sheet. A surface layer of the base steel sheet has a decarburization ratio of 30% or more. The decarburization ratio is represented by equation: Decarburization ratio (%) of surface layer=(1?average carbon concentration in surface layer/bulk carbon concentration)*100 where the surface layer refers to a region of the base steel sheet from the surface thereof to a depth of 35 ?m. A shoulder portion of the spot-welded zone includes a B-type crack having a length of 100 ?m or less, and no C-type crack.

Abstract: According to one aspect of the present invention, it is possible to provide a tailor welded blank, a hot press formed part, and a method for manufacturing same, the tailor welded blank having a weld part that can effectively prevent deterioration of properties after hot press forming.

Abstract: One embodiment of the present invention provides a carbon filament wire for laser welding of a steel sheet having an aluminum-based coating layer, a laser welding method of a steel sheet having an aluminum-based coating layer by using same, and a welded product produced by same, the carbon filament wire comprising: a resin matrix; and two or more carbon filaments provided inside the resin matrix.

Abstract: An embodiment of the present invention provides a method for manufacturing a tailor welded blank using a steel sheet for hot pressing having an Al-Fe-based intermetallic alloy layer, the method comprising the steps of: preparing a plated steel sheet having a base steel sheet and an aluminum-based plated layer formed on one surface or both surfaces of the base steel sheet; heat-treating the plated steel sheet so that the aluminum-based plated layer becomes an Al-Fe-based intermetallic alloy layer; and subjecting the heat-treated plated steel sheet to butt welding, wherein, before the welding, a part or the entirety of the Al-Fe-based intermetallic alloy layer located in an area to be welded is removed.

Abstract: The present invention relates to a zinc plated steel sheet having excellent surface quality and spot weldability, and a manufacturing method therefore. A zinc plated steel sheet according to one aspect of the present invention comprises a base steel sheet and a zinc-based plating layer formed on the surface of the base steel sheet, wherein the GDOES profile of oxygen, which is measured in the depth direction from the surface of the base steel sheet, has a form in which a local minimum point and a local maximum point alternately appear in the depth direction from the surface, and the difference (a local maximum value—a local minimum value) between the oxygen concentration (a local minimum value) at the local minimum point and the oxygen concentration (a local maximum value) at the local maximum point can be 0.1 wt % or more.

Abstract: Provided is a galvanized steel sheet having excellent spot weldability; and a method for producing same. The galvanized steel sheet includes a base steel sheet and a zinc-based plating layer formed on the base steel sheet, wherein the surface layer of the base steel sheet may have a decarburization rate of at least 30% as represented by equation 1. [Equation 1]: Decarburization rate (%) of surface layer=(1?average carbon concentration in surface layer/bulk carbon concentration)*100, where the surface layer refers to a region extending to a depth of 35 ?m from the surface of the base steel sheet.

Abstract: There are provided a method for manufacturing an electrical steel sheet laminated core having reduced core loss and improved strength, and a laminated core produced by the manufacturing method. The method includes: stacking electrical steel sheets to obtain a lamination; and welding an outer surface of the lamination, wherein during the welding, a welding wire having a resistivity of 6.5×10?7 ?m or greater, a relative permeability of less than 1.02, and a melting point lower than that of the electrical steel sheets is used as a welding material.

Abstract: There are provided a method for manufacturing an electrical steel sheet laminated core having reduced core loss and improved strength, and a laminated core produced by the manufacturing method. The method includes: stacking electrical steel sheets to obtain a lamination; and welding an outer surface of the lamination, wherein during the welding, a welding wire having a resistivity of 6.5×10?7 ?m or greater, a relative permeability of less than 1.02, and a melting point lower than that of the electrical steel sheets is used as a welding material.