Profile mother pipe for hydraulic bulging, hydraulic bulging apparatus using the same, hydraulic bulging method, and hydraulic bulged product

摘要

A profile mother pipe for hydraulic bulging of the present invention has a peripheral length whose outer diameter is gradually increased or decreased from one end to the other end in an axial direction. In the profile mother pipe, a holding portion whose peripheral length is increased toward a pipe end face on one end side can be formed on at least one end side and a parallel portion can be formed on the other end side where the holding portion is not formed. In a working apparatus and method in which the profile mother pipe is used, pressing working can be performed from the pipe end toward the axial direction, even in use of the profile mother pipe whose sectional shape is largely varied in the axial direction. Therefore, an expansion ratio larger than ever before can be obtained in a hydraulic bulged product to which hydraulic bulging is performed.