Abstract: Disclosed are a double water pipe manufactured via hydroforming and a method of manufacturing the same. The method includes: 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; 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; supplying the fluid to the inner pipe to perform plastic expansion of the inner pipe and elastic expansion of the outer pipe; and 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: 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 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: Disclosed are a double water pipe manufactured via hydroforming and a method of manufacturing the same. The method includes: 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; 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; supplying the fluid to the inner pipe to perform plastic expansion of the inner pipe and elastic expansion of the outer pipe; and 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 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 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: 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 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: 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: 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 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: 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: 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: 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: 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 a metal surface treatment solution that can provide superior corrosion resistance and paint adhesion and method for treating the surface of a steel sheet using the metal surface treatment solution. 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.

Abstract: The present invention relates a hot-dip galvanized steel sheet having transformation induced plasticity, mainly used in supporting or reinforcing structure of cars. The galvanized steel sheet comprises C: 0.05 to 0.20 wt. %, Si: 0.05 to 0.35 wt. %, Mn: 1.0 to 2.5 wt. %, Al: 0.01 to 1.5 wt. %, P: 0.02 wt % or less, Co: 0.3 to 0.8 wt. %, remained are Fe and inevitable impurities, satisfying relations between the above Si and Al, as 0.6?Si+0.78 Al(%)?1.2. This galvanized steel sheet is produced by steps of hot rolling of the steel slab comprising the above chemical compositions, and coiling the hot-rolled steel sheet at 500 to 700° C., recrystallization annealing treatment at the temperature range of 740° C. to 880° C. for 1-5 minutes and coiling, and cooling to 300° C. to 580° C. with cooling rate of 2 to 100° C./sec. and preserving at temperature range of 300 to 580° C. for not more than 10 min. and, zinc plating.