| abstract |
A die for extrusion molding includes a first face, a second face, a raw material supply section, a molding section, and a structure. The molding section has a second through hole that extends from the second face toward the first face so as to communicate with a first through hole. The structure is such that a material for the die is machined to form the material into a predetermined shape and to provide a machining-affected layer on an inner wall surface of the second through hole in the molding section, an oxidized layer is provided by heating the machining-affected layer to oxidize the machining-affected layer so as to convert the machining-affected layer into the oxidized layer, the oxidized layer is removed so that a treated surface is provided, and the treated surface is nitrided by ion implantation to provide a nitride layer. |