Patent ID: 8181500

Claim:
An extrusion molding die for metal material, comprising: a die case having a pressure receiving portion with an outer surface functioning as a metal material pressure receiving surface, wherein the die case is disposed so that the metal material pressure receiving surface faces rearward so as to oppose to an extrusion direction of the metal material; a male die mounted in the die case; and a female die mounted in the die case so as to form an extrusion hole by and between the female die and the male die, wherein the pressure receiving surface is formed into a rearwardly protruded convex shape, and a plurality of metal material introducing portholes are formed in an external periphery of the pressure receiving portion at intervals in a circumferential direction around an axial center of the die case, wherein it is configured such that the metal material pressed against the metal material pressure receiving surface is introduced into the die case via the portholes and passes through the extrusion hole, and wherein B/A is adjusted to 1.8 to 6.0 and D/B is adjusted to 0.15 to 0.4, where “A” (product circumscribed circle diameter) is a diameter of a minimum circumscribed circle of a cross-section of an extrusion molded product, “B” (pressure receiving surface external diameter) is an external diameter of the metal material pressure receiving surface, “C” (between-hole-wall inlet side minimum thickness size) is a porthole inlet side minimum thickness size of a between-hole-wall formed by a wall portion between a pair of adjacent portholes, “n” is the number of the between-hole-walls, and “D” is a between-hole-wall inlet side total thickness size obtained by multiplying the number “n” of the between-hole-walls by the between-hole-wall inlet side minimum thickness size “C.”