| 摘要 |
PURPOSE:To mold a collar part having a prescribed inside diameter, by making a beforehand hole on a pipe wall, forming a collar part having a small diameter, and subsequently making a prescribed jig pass through the hole. CONSTITUTION:As the first process, a jig 2 having an almost conical side or a semispherical side is passed through a hole, and a primary working collar part 4 having a ratio d/D<1 of a collar inside diameter (d) and a base pipe inside diameter D is formed. Subsequently, as the second process, a secondary working collar part 4 is worked by a rotary jig 3, and a collar part 5 of d/D=1 is formed. According to said constitution, the height of the collar is increased, a welding work is elevated, the thickness reduction ratio is decreased, and mechanical strength of a branch pipe joint part is elevated remarkably. |
