Hitachi Chemical Company, Ltd.

Hitachi Powdered Metals Co., Ltd.

Jiro Shima

Chio Ishihara

Takashi Inagaki

Kazunori Maekawa

Noriyuki Nakayama

The compact for a magnetic core is manufactured by filling a soft magnetic powder in the die hole, pressing it to form a compact at a density ratio of the soft magnetic powder being 91% or more, and extruding it from the die hole. Before filling the soft magnetic powder to the die hole, a lubricating coating containing lubricating oil and molybdenum disulfide particles is formed on the inner surface of the die hole. It is more effective when further containing insulating ceramic particles. On the extrusion-sliding surface, the compact has a surface layer of the structure that molybdenum disulfide particles and the insulating ceramic particles are interposed between the soft magnetic powder particles, and insulation of soft magnetic powder particles in the surface layer is not destroyed by extrusion. This provides a powder magnetic core suitable for high frequency application.

Powder magnetic core, method of manufacturing powder compact for magnetic core, die and die assembly for manufacturing powder magnetic core, and die lubricating composition for manufacturing powder magnetic core

The cross-sectional shape of a main part except for both end portions is generally divided into a lower arc surface extending along a base circle and an upper arc surface of which a top portion corresponds to the base circle. Side edge portions extending inward from the base circle are formed on both side surfaces of the upper arc surface. Curved edge portions which concavely curves upward from the side edge portions to end surfaces and continues to the end surfaces and chamfer portions extending from the end surfaces to the side surfaces which planes the edges and curves so that width thereof gradually narrows, are formed on both ends in a longitudinal direction.

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Matsudo, Japan

Jiro Shima