Sumitomo Special Metals Co., Ltd.

Toda Kogyo Corporation

Sumitomo Metal Mining Company, Ltd.

Atsushi Hamamura

Nanao Horiishi

Tomoyuki Imai

Takaki Hamada

Toshiki Matsui

Hiroko Nakamura

Yuji Kaneko

Katsumi Okayama

Shuji Okada

Yasuhiro Okajima

Kaname Takeya

Kouki Tokuhara

Yukimitsu Miyao

It is an object of the present invention to provide a process of producing calcined materials for ferrite magnet, whereby foreign phase produced in calcined powders is eliminated and the ferrite magnet having a superior magnetic properties is obtained easily. Since mill scales roughly milled into a mean particle size of 20 .mu.m or less is subjected to primary oxidation treatment to change its oxidation percentage 95% or higher, and oxidized completely by secondary oxidation treatment in an inclined rotary kiln up to 700.degree. C. in an atmosphere containing O.sub.2 content of 8% to 10% at a charging side of raw material, foreign phase is not produced in the calcined powders during ferrite formation at high temperatures, and the ferrite magnet having a superior magnetic properties can be obtained.

Process of producing calcined materials for ferrite magnet

A powder for producing permanent magnets, comprising a blend of powders [A] and [B] or [C] wherein:

Powder material for rare earth-iron-boron based permanent magnets

To obtain an anticorrosive Fe-B-R type permanent magnet; in particular, to reduce deterioration rate of the initial magnetic properties below 10% after the magnet has been kept at 80.degree. C. in 90% relative humidity for 500 hours, the surface of the sintered permanent magnet is coated with metallic coating film layers of at least one noble metal layer and at least one base metal layer disposed on the noble metal layer. Diffusion heat treatment further improves the adhesiveness of the coating film layers.

Process for producing a corrosion resistant permanent magnet

A corrosion-resistant R-Fe-B type sintered permanent magnet exhibiting deterioration of not more than 5 % from the initial magnetic properties after being tested for 500 hours under the conditions of a temperature of 80.degree. C. and a relative humidity of 90 % is produced by:

Corrosion-resistant permanent magnet and method for preparing the same

Corrosion resistant permanent magnet

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Kyoto, Japan

Atsushi Hamamura