| 摘要 |
PURPOSE:To form a large-sized bellows having uniform guality and high strength without requiring a heat treatment facility, by preparing a blank pipe having a diameter smaller than the minor diameter of a bellows, and forming a bellows- shape after expanding it. CONSTITUTION:A work-hardening type aluminum alloy is used for a weld blank pipe 12 for forming a bellows, and the pipe 12 is formed by bending flat plates 10 into curved plates 11 respectively and successively welding the plates 11 after combining them. The outer diameter of the pipe 12 is made smaller than the minor diameter of the bellows. After the pipe 12 is set in a die 13, and the outer peripheries of the upper and lower ends of the pipe 12 are sealed by O-rings 14, etc.; the pipe 12 is deformed by expanding to bring it into contact with the inner wall of the die 13 by loading a hydraulic pressure (p) from the inside and adding simultaneously pressing forces P. Further, the pipe 12 is expanded to the crests of the bellows to form a prescribed bellows by increasing the hydraulic pressure (p) and the pressing forces P. Thereafter, trimming 16 and stabilizing treatment 17 are performed to finish the formation of the bellows. |
