| 摘要 |
PURPOSE:To make mass production of the same dies which are given the effect substantially equal to the effect of shrinkage fit and have excellent toughness by packing metallic powder into the product part space of a plunger die and subjecting the metallic powder to compression molding then to sintering in such a manner that the density in the central part is made higher than the density in the outside circumferential part. CONSTITUTION:The prescribed metallic powder P is packed into the space R of the plunger die 1 constituted of a die 2, an outer lower punch 3 and an inner lower punch 4 and is compressively molded to a prescribed die shape by an upper punch 5. The inner lower punch 4 is fixed to a base block 6 and the outer lower punch 3 of a floating type is pushed down to a pressure receiving block 8 together with a platen 7 of an air floating type. The central part Q1 of the molding P1 is thereby made higher in green density than in the outside circumferential part Q2. The molding P1 is then put into a sintering furnace 9 and is sintered by which the outside circumferential part Q2 is shrunk to the larger extent and the effect equal to the effect obtd. by shrinkage-fitting the outside circumferential part Q2 is shrunk to the larger extent and the effect equal to the effect obtd. by shrinkage-fitting the outside circumferential part Q2 to the central part Q1 of higher use frequency is obtd. The product having the excellent toughness is thus obtd. The sintered body P2 is then tempered and is subjected to finishing by grinding, etc., by which the product die D is obtd.
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