Patent ID: 9162267
Filing Date: 2015-10-20
Classification: B21C

Abstract:
1. An extrusion die for forming a hollow material, comprising: a male die which forms an inside shape of the hollow material by extruding a billet constituted with an aluminum alloy fed from an upstream side towards a downstream side; and a female die which holds the male die and forms an outside shape of the hollow material, wherein: the male die comprises a spider which forms the inside shape and a holder which holds the spider; the spider comprises a mandrel which corresponds to the inside shape of the hollow material, and a plurality of bridge parts provided in a unified manner with the mandrel and projecting outward from a periphery of the mandrel; a distal-end outer peripheral surface part of each of the bridge parts is formed with a slope surface part which is expanded from the upstream side towards the downstream side and a straight live surface part formed at a downstream side end part of the slop surface part along an extrusion direction of the billet; an inner peripheral surface part of the holder is formed with (i) a holder-side slope surface part corresponding to a slope surface part of the distal-end outer peripheral surface part of the bridge part and (ii) a holder-side slope surface part and a straight line surface part corresponding to the straight line surface part of the bridge part, and the distal-end outer peripheral surface part of each of the bridge parts and the inner peripheral surface part of the holder are bonded by shrink-fitting.