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.

Abstract: An extrusion die is provided with a male die through which a billet is extruded from an upstream side to a downstream side and, the male die adapted for forming an inside shape of a hollow material; and a female die for holding the male die and forming an outside shape of the hollow material. The male die is formed of a spider and a holder for holding the spider. The spider is formed of a mandrel and a plurality of bridge parts for supporting the mandrel, and enabling a distal-end outer peripheral surface to engage with a bridge-holding surface. The distal-end outer peripheral surface of each of the bridge parts and the bridge-holding surface of the holder are joined by shrink-fitting.

Abstract: An extrusion die is provided with a male die through which a billet is extruded from an upstream side to a downstream side and, the male die adapted for forming an inside shape of a hollow material; and a female die for holding the male die and forming an outside shape of the hollow material. The male die is formed of a spider and a holder for holding the spider. The spider is formed of a mandrel and a plurality of bridge parts for supporting the mandrel, and enabling a distal-end outer peripheral surface to engage with a bridge-holding surface. The distal-end outer peripheral surface of each of the bridge parts and the bridge-holding surface of the holder are joined by shrink-fitting.