Patent ID: 8104318

Claim:
An extrusion die for metallic material, comprising: a die holding case having a dome portion and a base portion, the dome portion having an external surface configured to be a metallic material pressure receiving surface, the metallic material pressure receiving surface of the dome portion being disposed so as to face rearward with respect to an extrusion direction of the metallic material; a male die having a mandrel held in the die holding case and positioned on a central axis of the die holding case; and a female die held in a front portion of the die holding case, the female die having a die hole for defining an extrusion hole by and between the female die and the mandrel, wherein the metallic material pressure receiving surface of the dome portion is formed into a convex configuration protruded rearward, a porthole for introducing the metallic material is formed in a periphery of the dome portion, a central axis of the porthole is inclined to a central axis of the die holding case so that the central axis of the porthole gradually approaches the central axis of the die holding case toward a downstream side, the dome portion has a front end wall portion which is formed continuously in a peripheral direction of the dome portion, the metallic material pressed against the metallic material pressure receiving surface is introduced into the die holding case through the porthole and passes through the extrusion hole, and an inner side surface and an outer side surface on an inner periphery of the porthole are positioned approximately in parallel with each other and approximately in parallel to the central axis of the porthole.