| 摘要 |
A method for manufacturing a tube shaped part with different diameters involves carrying out press formation on a metal sheet blank to form a tube shaped part with different diameters constituted of a small diameter part, a large diameter part, and a diameter-changing part between the small diameter part and the large diameter part. The method comprises a step for carrying out press formation on the blank in a U-shaped forming mold, forming a U-shaped molded product, press forming this in an O-shaped forming mold and forming a molded product with a circular cross-sectional surface. A mold that is given a vertical wall length longer than the vertical wall part length of the U-shaped molded product is used for the U-shaped forming mold, and a mold in which a mold alignment line takes a downward slanted direction and the ratio (t/D) of the plate thickness (t) of the blank and the diameter (D) of the mold portion corresponding to the small diameter part and the large diameter part is 0.010 <= t/D <= 0.080 is used for the O-shaped forming mold. The compressive strain in the circumferential direction given by (1) formula: compressive strain in circumferential direction = (blank width in direction of blank width forming the tube circumferential direction minus circumferential length of mold)/circumferential length of mold × 100 (%) is set at 0.5% or greater. |
