Method of and apparatus for forging hollow blank member

摘要

A method of and an apparatus for shaping a hollow blank member by a forging operation is provided. The interior of a hollow blank member is filled with a liquid pressure medium which is enclosed therein in sealed condition. An external pressure is applied to the hollow blank member, and the pressure of the pressure medium is maintained as an internal pressure which opposes the external pressure, and part of the pressure medium is discharged externally while applying a desired plastic deformation to the hollow blank member.