Hitachi, Ltd.

Hiroyuki Kawawa

Hisanobu Kanamaru

Yasushi Ohuchi

When cylindrical parts are produced by extrusion from a metallic material having high mechanical strength, the dies tend to be easily broken and worn, and it is difficult to secure accuracy of finishing of the product. According to the present invention, with regard to the form of a die, the ironing portion is reduced in contact area thereof, is formed into such a configuration that the contact area thereof does not increase even if the dies are worn to some extent, and a die angle and configurations of an ironing portion and a relief portion are selected properly, thus preventing the dies from being easily broken or worn.

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Katsuta, Japan

Hiroyuki Kawawa