To provide an iron powder for a powder magnetic core, which has an insulation layer with high heat resistance thereon.
The iron powder for the powder magnetic core has the insulation layer on its surface, which is substantially formed from a condensed phosphate, or a condensed phosphate and a hydrogen phosphate. The insulation layer can contain a small amount of talc. The condensed phosphate is preferably condensed ammonium phosphate, and the hydrogen phosphate is preferably ammonium hydrogenphosphate. The insulation film is formed on the surface of the iron powder by mixing the iron powder and an aqueous solution of the hydrogen phosphate, and heating and drying the mixture at 190°C or higher to cause a melt and condensation reaction in the hydrogen phosphate. The deposition amount of the insulation film is preferably 1 to 10 g with respect to the iron powder of 1 kg. Even after the iron powder for the powder magnetic core has been compacted and has been heated and annealed at the temperature of 600°C or higher, the compact can maintain a high specific resistance value.
COPYRIGHT: (C)2009,JPO&INPIT
Maki Hamaguchi
Hiroyuki Mitani
Akagi Nobuaki
Keifumi Hojo
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