| 摘要 |
PURPOSE:To prevent generation of a crack in a large-diameter cylindrical part by subjecting a blank pipe to annealing in the stage of subjecting said pipe to intermediate bulging and subjecting further the pipe to bulging in this state and providing the cylindrical part of the diameter larger than the diameter of a pleat part to one body. CONSTITUTION:A blank pipe A is formed to an irregular shaped pipe A' having a large-diameter cylindrical part B' on the opening end side of the pipe A by an upper die and a lower die in the 1st stage. The pipe A' is annealed at a prescribed temp. in the 2nd stage and the annealed pipe A' is put into the dies in the 3rd stage and a liquid pressure is exerted to the pipe. The bellows B having a pleat part B1, the cylindrical part B2 of a large diameter and the collar part B3 is manufactured. |
