| 摘要 |
PURPOSE:To manufacture a branch pipe excellent in quality by forming a projecting part at the outer-surface side of a pipe by a plug attached laterally to a mandrel through the mandrel inserted in a flat pipe stock and providing a branching work of plug-drawing method to the projecting part. CONSTITUTION:A primary flat pipe 23 obtained by pressing a round pipe stock by flat dies 21, 22, is turned by 90 deg. to make its major axis vertical, and a plug 24 attached to a mandrel 25 inserted in the pipe 23 is set by directing the plug 24 to the die hole 26 of die 22; the pipe 23 is pressed in this state to force the plug 24 from the pipe inner surface into the wall-thiciness direction through the mandrel 25 in order to obtain a secondary flat pipe 27 having a projecting part 28 formed at the pipe outer-surface of a predetermined part of branching. Next, the pipe 27 is hot formed by dies 35, 35, to correct its out of roundness in order to obtain a pipe 38 of predetermined shape having a round main part 2'. Next, after removing the mandrel 25 and the plug 24, the part 28 is drawn by a drawing plug 10 to form a branch part 3', and required machining is provided to the part 3' to finish the pipe 38 into a branch pipe. |
