| 摘要 |
A mother pipe (TP2) for hydraulic bulging having such a peripheral length that an outer diameter is gradually increased or decreased from one to the other end thereof in the axial direction, wherein holding parts (TP2a, TP2b) having the peripheral length increasing toward the end face of the pipe on the one end are formed at least on the one end. A parallel part may be formed on the other end where the holding part is not formed. In a method and a device for bulging using the mother pipe, even when the mother pipe having a cross sectional shape largely varying in the axial direction is used, the push- bulging from the end of the pipe in the axial direction is allowed. Thus, a hydraulically bulged product to which hydraulic bulging is applied can obtain an expanding ratio larger than before.
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