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 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: 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.