Method of protecting magnetic powders and densified permanent ma

Details Method of protecting magnetic powders and densified permanent ma Method of protecting magnetic powders and densified permanent ma

1993-12-07

1995-05-02

Sheehan, John P.

Metal treatment

Process of modifying or maintaining internal physical...

Magnetic materials

148104, 148105, H01F 4102

Patent

active

054116031

ABSTRACT:
The invention concerns a method of protecting magnetic powders and permanent magnets containing at least one rare earth, at least one transition metal and boron from oxidation and atmospheric corrosion, by the introduction of gaseous fluorine during the grinding of the powders. It is characterized in that the fluorine is introduced by a mixture of F.sub.2 +N.sub.2 during the fine grinding of the powders, the mixture containing from 1 to 100 ppm (by volume) of fluorine, and preferably from 1 to 10 ppm. The powders thus obtained are far less reactive and the densified magnets are far more resistant to atmospheric corrosion than non fluorinated powders and magnets obtained therefrom.

REFERENCES:
Patent Abstracts of Japan, vol. 13, No. 509 (E-846), Nov. 15, 1989, JP-12 05 502.
Journal of the Electrochemical Society, vol. 117, No. 4, Apr. 1970, pp. 537-540, Swisher et al.

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