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: The present invention discloses a metal separator for a fuel cell including a reaction gas channel formed to protrude from a first face of the metal separator to a second face thereof, a coolant channel formed between the reaction gas channels protruding from the second face of the metal separator, a reaction gas manifold opened to introduce a reaction gas into the metal separator, a coolant manifold opened to introduce a coolant into the metal separator, and a stepped portion positioned at any one of the space between the reaction gas channel and the reaction gas manifold, and the reaction gas channel. This configuration serves to widen the reaction gas flowing portion and the coolant flowing portion on the metal separator, and prevent deformation of the reaction gas flowing portion and the coolant flowing portion, thereby improving efficiency of the fuel cell.

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 herein is an air-cooled metal separator that does not need cooling water. The air-cooled metal separator includes a channel section formed in the middle of a metal plate, the channel section including a reaction gas channel depressed into a front surface of the metal plate to protrude from a rear surface thereof and an air channel defined between the reaction gas channels protruding from the rear surface of the metal plate; a first gasket continuously formed along a rim of a front surface of the channel section; and a second gasket discontinuously formed along a rim of a rear surface of the channel section to allow a discontinuous portion of the second gasket to provide a flow passage of air.

Abstract: The present disclosure relates to a high strength steel sheet having good wettability, a tensile strength of 590 MPa or more and a strength-ductility balance (TS×El) of 16,520 MPa·% or more, and a manufacturing method thereof. The high strength steel comprises, in % by weight, C: 0.03˜0.1%, Si: 0.005˜0.105%, Mn: 1.0˜3.0%, P: 0.005˜0.04%, S: 0.003% or less, N: 0.003˜0.008%, Al: 0.05˜0.4%, Mo or Cr satisfying the inequality 10?50·[Mo %]+100·[Cr %]?30, at least one of Ti: 0.005˜0.020%, V: 0.005˜0.050% and B: 0.0005˜0.0015%, and the balance of Fe and unavoidable impurities, wherein a microstructure of the steel sheet is a multi-phase structure comprising, in an area ratio of cross-sectional structure, 70% or more ferrite phase having a Vickers hardness Hv of 120˜250 and 10% or more martensite phase having a Vickers hardness Hv of 321˜555.

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 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 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: 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: The present invention discloses a metal separator for a fuel cell including a reaction gas channel formed to protrude from a first face of the metal separator to a second face thereof, a coolant channel formed between the reaction gas channels protruding from the second face of the metal separator, a reaction gas manifold opened to introduce a reaction gas into the metal separator, a coolant manifold opened to introduce a coolant into the metal separator, and a stepped portion positioned at any one of the space between the reaction gas channel and the reaction gas manifold, and the reaction gas channel. This configuration serves to widen the reaction gas flowing portion and the coolant flowing portion on the metal separator, and prevent deformation of the reaction gas flowing portion and the coolant flowing portion, thereby improving efficiency of the fuel cell.

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).