| 摘要 |
PURPOSE:To prevent occurrence of recesses and creases and obtain stable strength and rigidity by bending a flat plate-shaped material to form a bent part in axial direction and then forming to tubular shape. CONSTITUTION:A flat plate-shaped material 10 is press-worked and bent giving curvature in axial direction of a bent pipe. Next, the material 10 is formed by another press making each 3/8 of circumference at the time of completion of the pipe outer round 13a, 13b and remaining 1/4 inner round 13c. The radius of curvature of outer round 13a, 13b is formed to be equal to the radius of completed pipe. After press forming until the material 10 becomes roughly u-shape, the material is press-formed by holding it from three sides by a slide cam and punches to make the material 10 a true circle. Finally, joggled joint part is welded to obtain a bent pipe. |
