Abstract: Disclosed are a double water pipe manufactured via hydroforming and a method of manufacturing the same via hydroforming. The method includes (a) inserting an inner pipe into an outer pipe made of steel, the inner pipe being made of a corrosion resistant material selected from among stainless steel, titanium and aluminum, and having a smaller outer diameter than an inner diameter of the outer pipe; (b) placing the outer pipe on a die unit and sealing opposite ends of the die unit with sealing members each having a through-hole connected to a fluid supply unit for supplying a fluid to the inner pipe; (c) supplying the fluid to the inner pipe to perform plastic expansion of the inner pipe and elastic expansion of the outer pipe; and (d) discharging the fluid from the inner pipe to allow frictional coupling between the inner pipe and the outer pipe through elastic restoration of the outer pipe.

Abstract: A stainless steel separator for fuel cells and a method of manufacturing the same are disclosed. The method includes preparing a stainless steel sheet as a matrix, performing surface modification on a surface of the stainless steel sheet to form a Cr-rich passive film having a comparatively increased amount of Cr in a superficial layer of the stainless steel sheet by decreasing an amount of Fe in the superficial layer of the stainless steel sheet, and forming a coating layer on the surface of the surface-modified stainless steel sheet. The coating layer is one selected from a metal nitride layer (MNx), a metal/metal nitride layer (M/MNx), a metal carbide layer (MCy), and a metal boride layer (MBz) (where 0.5?x?1, 0.42?y?1, 0.5?z?2).

Abstract: Disclosed herein is a method of manufacturing a metallic bipolar plate for fuel cells, which can maintain good corrosion resistance and contact resistance without any side effect not only initially but also after a predetermined period of time even in an environment of severe vibration as in vehicles while allowing a continuous process to provide high productivity.

Abstract: A method for surface treatment of a stainless steel separator for a fuel cell comprises preparing a stainless steel sheet containing nickel, chrome and iron, and having a passive film on a surface of the stainless steel sheet, and dipping the stainless steel sheet into a mixed etching solution of nitric acid (HNO3) and sulfuric acid (H2SO4) at a temperature of 50-70° C. for 30 seconds to 30 minutes to selectively lower an amount of Fe in the passive film formed on the surface of the stainless steel sheet.

Abstract: Disclosed are a preparation method of a steel product capable of local reinforcement using laser heat treatment, and a heat hardened steel used in the method. According to the present invention, the preparation method of a steel part comprises the following steps: (a) preparing a material comprising 0.1-0.5 wt % of C, 0.1-0.5 wt % of Si, 0.5-3.0 wt % of Mn, 0.1 wt % or less of P, 0.05 wt % or less of S, 0.01-1.0 wt % of Cr, 0.1 wt % or less of Al, 0.2 wt % or less of Ti, 0.0005-0.08 wt % of B, and the balance of Fe and inevitable impurities; (b) preparing a formed product by forming the material into a predetermined shape; and (c) locally reinforcing the high strength portion by carrying out laser heat treatment on a portion requiring high strength at the formed product.

Abstract: Disclosed herein is a method for manufacturing a metal steel separator for fuel cells that has corrosion resistance and contact resistance not only at an initial stage but also after being exposed to high temperature/high humidity conditions in the fuel cell for a long period of time. The method includes preparing a stainless steel sheet as a matrix of the metal separator, forming a discontinuous coating film on the surface of the stainless steel sheet, the coating film being composed of at least one selected from gold (Au), platinum (Pt), ruthenium (Ru), iridium (Ir), ruthenium oxide (RuO2), and iridium oxide (IrO2), and heat treating the stainless steel sheet having the discontinuous coating film to form an oxide film on a portion of the stainless steel sheet on which the coating film is not formed. A metal separator for fuel cells manufactured by the method is also disclosed.

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 heat-hardened steel with excellent crashworthiness and a method for manufacturing heat-hardenable parts using the same. The heat-hardened steel according to the invention comprises, based on wt %; C: 0.12-0.8%; Cr: 0.01-2%; Mo: 0.2% or less; B: 0.0005-0.08%; Ca: 0.01 or less; Sb: 1.0% or less; and Ti and/or Nb: 0.2%; and the reminder being Fe and inevitable impurities. In addition, the heat-treatment hardening steel satisfies anyone of following conditions i)-iv), wherein condition i) comprises Si: 0.5-3%; Mn: 1-10% and Al: 0.05-2%; condition ii) comprises Si: 1% or less; Mn: 0.5-5%; Al: 0.1-2.5%; and Ni: 0.01-8%; condition iii) comprises Si: 0.5-3%; Mn: 1-10%; Al: 0.1% or less; and Ni: 0.01-8%; and condition iv) comprises Si: 0.5-3%; Mn: 1-10%; Al: 0.1-2.5%; and Ni: 0.01-8%.

Abstract: Disclosed are a metal separator for fuel cells, which exhibits excellent properties in terms of corrosion resistance, electrical conductivity and durability, and a method of manufacturing the same. The metal separator for fuel cells includes a separator-shaped metal matrix and a coating layer formed on the metal matrix. The coating layer has a concentration gradient of a carbon element C and a metal element Me according to a thickness thereof such that the carbon element C becomes gradually concentrated in the coating layer with increasing distance from the metal matrix, and the metal element Me becomes gradually concentrated in the coating layer with decreasing distance from the metal matrix.

Abstract: Disclosed herein is a method of manufacturing a stainless steel separator for a fuel cell. The stainless steel separator includes a stainless steel sheet, a first coating layer comprising metal/metal nitride films (M/MNx) (0.5?x?1) on a surface of the stainless steel sheet, and a second coating layer comprising a metal oxynitride film (MOyNz) (0.05?y?2, 0.25?z?1.0).

Abstract: Disclosed is a method and apparatus for forming a coating layer using a physical vapor deposition apparatus equipped with a sputtering apparatus and an arc ion plating apparatus, comprising: a first coating step of forming a Mo coating layer on a base material using a the sputtering apparatus and a Mo target and Ar gas; a nitrating step of forming a nitride film forming condition using an arc ion plating apparatus and Ar gas and N2 gas; a second coating step of forming a nano composite coating layer of Cr—Mo—N using the Mo target and Ar gas of the sputtering apparatus and the Ar gas, N2 gas and a Cr source of the arc ion plating apparatus at the same time; and a multi-coating step of forming a multi-layer having alternating Cr—Mo—N nano composite coating layers and Mo coating layers by revolving the base material around a central pivot.

Abstract: The present disclosure relates to a dual phase steel sheet and a method of manufacturing the same. The steel sheet comprises C: 0.05˜0.10% wt %, Si: 0.03˜0.50 wt %, Mn: 1.50˜2.00 wt %, P: greater than 0 wt %˜0.03 wt %, S: greater than 0 wt %˜0.003 wt %, Al: 0.03˜0.50 wt %, Cr: 0.1˜0.2 wt %, Mo: 0.1˜0.20 wt %, Nb: 0.02˜0.04 wt %, B: greater than 0 wt %˜0.005 wt %, N: greater than 0 wt %˜0.01 wt %, and the balance of Fe and other unavoidable impurities. To impart excellent formability, bake hardenability, dent resistance, high Ri value and plating characteristics to the steel sheet for exterior and interior panels of automobiles, the steel sheet is processed to have a dual phase structure through cold rolling, annealing, and hot-dip galvanizing.

Abstract: Disclosed herein is a stainless steel separator for a fuel cell and method of manufacture. The stainless steel separator includes a stainless steel sheet, a first coating layer comprising metal/metal nitride films (M/MNx) (0.5?x?1) on a surface of the stainless steel sheet, and a second coating layer comprising a metal oxynitride film (MOyNz) (0.05?y?2, 0.25?z?1.0).

Abstract: The present invention relates to a separator plate for a fuel cell and to a method for producing the same, and relates to an invention wherein a surface-modification layer is formed through the use of low temperature plasma processing such that it is possible to prevent the hydrophobic characteristics which occur during gasket forming and to have outstanding hydrophilic characteristics, and such that it is possible to obtain the advantageous effect of highly outstanding corrosion resistance and electrical conductivity not only initially but also even after long-term use in a fuel-cell operating environment, and also such that it is possible to maintain outstanding durability even when using a normal low-price stainless-steel sheet base material, and it is possible to reduce the unit cost of production of the separator plate for the fuel cell since surface processing can be carried out at low cost.

Abstract: Disclosed herein is a metal surface treatment solution that can provide superior corrosion resistance and paint adhesion. The metal surface treatment solution includes 9˜13 wt % of an epoxy-based silane coupling agent, 5˜9 wt % of an amino-based silane coupling agent, 0.5˜1 wt % of a vanadium compound, 0.5˜1 wt % phosphoric acid; 0.5˜1 wt % of an organic acid, 0.1˜10 wt % of a Ti-Alkoxide, 0.1˜2 wt % of a chelating agent, 0.1˜5 wt % of a calcium phosphate-based compound,. 0.2˜10 wt % of a colloidal silica, and the balance of solvents. A method of manufacturing a surface treated steel sheet using the same is also disclosed.

Abstract: Disclosed herein is a method and apparatus for manufacturing a panel for a vehicle. When a steel sheet is machined to form a panel for a vehicle, a blanking-texturing machine conducts a blanking process for cutting the steel sheet and a texturing process for forming depressions in the steel sheet at the same time. Therefore, the present invention reduces the number of manufacturing processes, thus enhancing the productivity, and reducing the production cost and provides a steel sheet with uniform depressions across the surface of the steel sheet, thereby reducing the coefficient of friction during the pressing process consistently.

Abstract: The present disclosure relates to a dual phase steel sheet and a method of manufacturing the same. The steel sheet comprises C: 0.05˜0.10 % wt %, Si: 0.03˜0.50 wt %, Mn: 1.50˜2.00 wt %, P: greater than 0 wt %˜0.03 wt %, S: greater than 0 wt %˜0.003 wt %, Al: 0.03˜0.50 wt %, Cr:0.1˜0.2 wt %, Mo: 0.1˜0.20 wt %, Nb: 0.02˜0.04 wt %, B: greater than 0 wt %˜0.005 wt %, N: greater than 0 wt %˜0.01 wt %, and the balance of Fe and other unavoidable impurities. To impart excellent formability, bake hardenability, dent resistance, high Ri value and plating characteristics to the steel sheet for exterior and interior panels of automobiles, the steel sheet is processed to have a dual phase structure through cold rolling, annealing, and hot-dip galvanizing.

Abstract: Disclosed is a method of manufacturing a multilayered tube, including: preparing an outer tube, an inner tube having an outer diameter of 95˜98% of an inner diameter of the outer tube, and dies with a shaping void having a diameter of 100.20˜100.

Abstract: The present invention relates to a method of manufacturing ultra-high strength steel products and, more particularly, to a method of manufacturing ultra-high strength steel products suitable for production of articles having a complicated shape or a high processing depth. The method includes preparing a steel sheet by blanking the steel sheet having hardenability to form a rough shape of a final product, cold-pressing the steel sheet to form a 50˜80% shape of the final product, precisely trimming the cold-formed steel sheet along a contour line corresponding to an outer contour of the final product, and hot-pressing the trimmed product to form the remaining 20˜50% shape of the final product and quenching simultaneous with hot-pressing, after heating the trimmed product to an austenite region of 700° C. or more.

Abstract: Disclosed herein is method of manufacturing an automobile part having different local strengths, more particularly, a method of manufacturing an automobile part using a steel sheet subjected to heat-treatment hardening and having different local thicknesses. The method includes preparing blank sheets using steel sheets subjected to heat-treatment hardening and having different thicknesses or different material properties according to desired strength; forming a blank assembly by joining the blank sheets to each other via laser welding; cold-pressing the blank assembly; and heating the cold-pressed part to a temperature of AC3 or more, followed by quenching the cold-formed part received within dies to remove residual stress while increasing strength of the automobile part.