| 摘要 |
A die 10 has a die case 20 arranged with a pressure receiving surface 22 of a pressure receiving portion 21 facing rearward so as to oppose to an extrusion direction, a male die 30 and a female die 40 mounted in the die case 20. The pressure receiving portion 22 is formed into a rearwardly protruded convex shape. A plurality of metal material introducing portholes 24 are formed in an external periphery of the pressure receiving portion 21. It is configured such that the metal material pressed against the pressure receiving surface 22 is introduced into the die case 20 via the portholes 24 and passes through the extrusion hole 11. B/A is adjusted to 1.8 to 6.0 and D/B is adjusted to 0.15 to 0.4, where “A” is a product circumscribed circle diameter, “B” is a pressure receiving surface external diameter, “C” is a between-hole-wall inlet side minimum thickness size, “n” is the number of the between-hole-walls, and “D” is a between-hole-wall inlet side total thickness size obtained by “C”דn.” |
