| 摘要 |
<p>When a steel pipe (6) is to be hydroformed, a tubular deformable assistant member (10) made of an uncompressible material softer than the steel pipe (6) is fitted on the outer peripheral surface of the steel pipe (6). This deformable assistant member (10) is positioned at least in a region opposed to a convex portion (1b) in the inner surface of a die (5) to which the outer peripheral surface of the steel pipe (6) is the first to approach during hydroforming. When the steel pipe (6) is hydroformed, the deformable assistant member (10) produces a plastic flow in the vicinity of corner portions (X1, Y1) where the deformable assistant member (10) contacts the convex portion (1b). This plastic flow promotes peripheral uniform spreading of the steel pipe (6).</p> |
