Patent ID: 6862910
Filing Date: 2005-03-08
Classification: B21C,B21D,Y10T

Abstract:
1. A method of manufacturing a hollow metal body having a cross-sectional shape which varies in a longitudinal direction, comprising the steps of: providing a tool mold having a desired final contour; disposing a tubular hollow body having an approximately uniform wall thickness in said tool mold; applying an internal pressure to the tubular hollow body such that the tubular hollow body forms an extended bubble with gentle transitions during expansion and the bubble has a largest size in a region of a greatest degree of deformation; heating the tubular hollow body to a highest temperature in zones of greatest deformation; reducing the temperature in the zones of highest deformation once the hollow body fits against an inner wall of the tool mold such that the temperature is subsequently highest in adjacent zones with lower degrees of deformation until the hollow body again contacts the inner wall of the tool mold; and applying a tensile stress axially to the hollow body during deformation in individual sections of having different degrees of deformation.