| 摘要 |
PURPOSE:To provide a wrinkle-free stepped and drawn steel pipe having exact plural diameters by fixing a die and a tap movably in a drawing direction, providing plural bearing parts thereto, combining suitably the bearing faces and drawing the steel pipe. CONSTITUTION:A die 2 having bearing parts of a large diameter d1 and a small diameter d2 is fixed to a support base and is made movable on a frame. A plug 4 having bearing parts of a small diameter d3 and a large diameter d4 is provided movably by means of a hydraulic cylinder. The d2 face of the die 2 and the d3 face of the plug 4 are positioned to face to each other and a steel pipe is drawn, whereby a pipe having the outside diameter d2 and the inside diameter d3 is formed. The d2 face of the die 2 and the d4 face of the plug 4 are then placed to face to each other and the steel pipe is drawn, whereby the pipe having the outside diameter d2 and the inside diameter d4 is formed. The d1 face of the die 2 and the d4 face of the plug 4 are further positioned to face to each other and the pipe is drawn, whereby the pipe having the outside diameter d1 and the inside diameter d4 is formed. A steel pipe 7b having the outside diameters d1, d2 and the inside diameters d3, d4 is thus obtd. |
