Ugimag Sa

Aimants Ugimag Sa

Aimants Ugimag

Fernand Vial

Masato Sagawa

Philippe Tenaud

Hiroshi Nagata

Armand Gabriel

Pierre Turillon

Alain Barzasi

A magnetic powder for the manufacture of sintered magnets of the RE-T-B family, where RE represents at least one rare earth, T represents at least one transition element and B represents boron, the powder possibly containing other minor elements, is constituted by a mixture of two powders (A) and (B): a) Powder (A) consists of grains with a quadratic structure RE.sub.2 T.sub.14 B, T being mainly iron with Co/Fe&lt;8%, and which may possibly contain up to 0.5% Al, up to 0.05% Cu and up to 4% in total of at least one element of the group V, Nb, Hf, Mo, Cr, Ti, Zr, Ta, W and unavoidable impurities, the Fisher granulometry being between 3.5 and 5 .mu.m; b) Powder (B) is rich in RE, contains Co, and has the following composition by weight: RE 52-70%, comprising at least 40% (absolute value) of one or more light rare earth(s) selected from the group La, Ce, Pr, Nd, Sm, Eu; a hydrogen content (in ppm by weight) greater than 130.times.%RE; Co 20-35%; Fe 0-20%; B.ltoreq.0-0.2%; Al 0.1-4%; and unavoidable impurities, the powder having a Fisher granulometry of between 2.5 and 3.5 .mu.m. Powder (B) may be produced by mixing a RE rich powder (C) which contains Co with a B rich powder (D).

Fe-Re-B type magnetic powder, sintered magnets and preparation method

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.

Method of protecting magnetic powders and densified permanent magnets of

The invention relates to a method of obtaining friable and relatively inert TR Fe B type magnetic materials in divided form which lead to magnets having improved corrosion resistance. This method involves treating the material in an atmosphere containing (or capable of containing) hydrogen under the following conditions of absolute pressure (P) and of temperature (T.degree. C.): if P.ltoreq.Pa, 250&lt;T&lt;550; and if P&gt;Pa, 250+100 log (P/Pa)&lt;T&lt;250+100 log (P/Pa) log base 10, Pa being atmospheric pressure. The invention is used for obtaining sintered TR Fe B magnets having improved corrosion resistance.

Method of obtaining a magnetic material of the rare earth/transition

The invention relates to Fe Nd B type alloys for permanent magnets, the permanent magnets thus obtained and a method of producing them. They have high magnetic characteristics with good temperature resistance and good resistance to atmospheric corrosion. They comprise, in at%, 12 to 18% of rare earths, 3 to 30% of Co, 5.9 to 12% of B, 2 to 10% of V, some Al and Cu, the remainder being iron and unavoidable impurities. The V can be substituted by other refractory elements (Nb, W, Cr, Mo, Ti, Zr, Hf, Ta). The method mainly involves sintering at between 1050 and 1110.degree. C. followed by annealing at between 850 and 1050.degree. C. and/or artificial ageing at between 560.degree. C. and 850.degree. C.

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Meylan, France

Fernand Vial