Extrusion die for forming hollow material

Abstract

An extrusion die for forming a hollow material that extrudes a billet comprising a high-strength alloy having high extrusion force and forms a hollow material including a partition wall, comprises a male-type member that extrudes a billet on a downstream side and forms the inner shape of a material and a female-type member that forms the outer shape of the material, wherein a billet guide hole that guides one part of the billet toward the downstream side is provided to the central area of a mandrel section that constitutes the male-type member, four inner formation pieces are mounted in a fixed manner to positions that face the downstream-side opening of the billet guide hole, and the female-type member is provided with an outer formation die hole that faces all of the outer peripheral surfaces of the inner formation pieces and that forms the outer shape of the hollow material.

1 . An extrusion die for forming a hollow material, comprising: a male-type member which forms an inner shape of the hollow material while guiding a billet constituted with an aluminum alloy fed from an upstream side toward a downstream side; and a female-type member which holds the male-type member with an outer circumferential part and forms an outer shape of the hollow material, wherein:
 the male-type member comprises a mandrel section for forming the inner shape, and a holder section connected integrally to an outer circumferential part of the mandrel section via a plurality of bridge sections;   a billet guide hole for guiding a part of the billet toward the downstream side is provided in a center region of the mandrel section;   an upstream-side opening area of the billet guide hole is formed larger than a downstream-side opening area; and   a plurality of inner formation pieces are fixedly mounted on a downstream side of the billet guide hole and at positions for forming continuous partition walls inside the hollow material while keeping a billet flow-in gap space forming a merging space of the billet flowing in from each of the bridge sections toward the downstream side.   
     
     
         2 . The extrusion die for forming the hollow material as claimed in  claim 1 , wherein
 the billet guide hole is formed as a stepped hole constituted with an upstream-side large opening hole and a downstream-side small opening hole formed in the bottom part of the large opening hole.   
     
     
         3 . The extrusion die for forming the hollow material as claimed in  claim 2 , wherein
 an inner wall face of the upstream-side large opening hole is formed in a tapered shape in which an opening side has a larger opening area than a bottom part of the large opening hole.   
     
     
         4 . The extrusion die for forming the hollow material as claimed in  claim 1 , wherein
 the billet guide hole is formed in a tapered shape narrowed from the upstream-side opening toward the downstream-side opening.   
     
     
         5 . The extrusion die for forming the hollow material as claimed in  claim 2 , wherein a plurality of the downstream-side small opening holes are provided. 
     
     
         6 . (canceled) 
     
     
         7 . The extrusion die for forming the hollow material as claimed in  claim 3 , wherein a plurality of the downstream-side small opening holes are provided. 
     
     
         8 . The extrusion die for forming the hollow material as claimed in  claim 5 , wherein the small opening holes of the billet guide hole are disposed by opposing to intersection points of gaps for forming a plurality of partition walls set by the plurality of inner formation pieces. 
     
     
         9 . The extrusion die for forming the hollow material as claimed in  claim 7 , wherein the small opening holes of the billet guide hole are disposed by opposing to intersection points of gaps for forming a plurality of partition walls set by the plurality of inner formation pieces.