EP0601943B1 - R-Fe-B type magnet powder, sintered magnets therefrom and preparation process - Google Patents

R-Fe-B type magnet powder, sintered magnets therefrom and preparation process Download PDF

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Publication number
EP0601943B1
EP0601943B1 EP93420483A EP93420483A EP0601943B1 EP 0601943 B1 EP0601943 B1 EP 0601943B1 EP 93420483 A EP93420483 A EP 93420483A EP 93420483 A EP93420483 A EP 93420483A EP 0601943 B1 EP0601943 B1 EP 0601943B1
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Prior art keywords
powder
mpa
weight
content
hydrogen
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EP93420483A
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German (de)
French (fr)
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EP0601943A1 (en
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Alain Barzasi
Hiroshi Nagata
Masato Sagawa
Fernand Vial
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Ugimag SA
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Ugimag SA
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Priority claimed from FR9214995A external-priority patent/FR2698999B1/en
Priority claimed from FR9308586A external-priority patent/FR2707421B1/en
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/04—Making non-ferrous alloys by powder metallurgy
    • C22C1/0433—Nickel- or cobalt-based alloys
    • C22C1/0441—Alloys based on intermetallic compounds of the type rare earth - Co, Ni
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
    • H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
    • H01F1/047—Alloys characterised by their composition
    • H01F1/053—Alloys characterised by their composition containing rare earth metals
    • H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
    • H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
    • H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
    • H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
    • H01F1/047—Alloys characterised by their composition
    • H01F1/053—Alloys characterised by their composition containing rare earth metals
    • H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
    • H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
    • H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
    • H01F1/0573—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes obtained by reduction or by hydrogen decrepitation or embrittlement
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
    • H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
    • H01F1/047—Alloys characterised by their composition
    • H01F1/053—Alloys characterised by their composition containing rare earth metals
    • H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
    • H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
    • H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
    • H01F1/0575—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together
    • H01F1/0577—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together sintered

Definitions

  • the invention relates to a magnetic powder and permanent magnets. sintered containing essentially at least one rare earth TR, at least one transition element T and boron, the magnetic powder being obtained by the mixture of at least 2 initial powders of chemical composition and different particle sizes and their method of preparation.
  • the problem is therefore to find a manufacturing method simpler and less expensive according to the conventional route of powder metallurgy to obtain sintered magnets having better magnetic characteristics, especially good afterglow and good resistance to atmospheric corrosion.
  • the magnets can then undergo all the usual operations machining and surface coatings if necessary.
  • phase T1 More precisely, they have a structure made up of grains of phase T1, representing more than 94% of the structure, and of size substantially uniform between 2 and 20 ⁇ m. These are surrounded a thin and continuous secondary phase border rich in TR, thick substantially uniform, not locally having a width ⁇ 5 ⁇ m. This secondary phase contains more than 10% cobalt.
  • the Applicant has noticed that the coercivity, the afterglow and specific energy, although satisfactory, could be further improved by obtaining the powder (B) by a mixture of two powders (C) and (D), without affecting the other properties of use of the sintered magnets, in particular resistance to oxidation and atmospheric corrosion and machining to tolerances by grinding.
  • a suitable choice of powder (D) allowed to significantly reduce the temperature and the duration of the sintering.
  • the magnets can then undergo all the usual operations machining and surface coatings if necessary.
  • the powders (A) and (B) thus obtained were mixed in the weight proportions indicated in Table IV, then they have been then compressed under field (// or ⁇ ), sintered and processed in conditions given in Table V, which also shows the density and the magnetic characteristics obtained on the magnets.
  • Figs. 1 and 2 schematically represent 2 micrographic sections performed in scanning microscopy equipped with an analytical probe and were carried out on two magnets of the same composition corresponding to the examples Ml and Sl: Ml being used according to the invention and Sl being produced according to the prior art by a mono-alloy technique.
  • the powders (A) and (B) thus obtained were mixed in the weight proportions indicated in Table XI, then they have been then compressed under field ( ⁇ ), sintered and processed in conditions shown in Table XII, where also the magnetic characteristics obtained on the magnets.
  • examples M5 -M6 M9 - M10 - M13 - M14 - M21 - M22 - M25 - M26 - M29 - M30 are from powder (A) with a high boron content (1.06%) and their persistence is less than 1.32 T.
  • Examples M31 and M32 correspond to cases where although originating from powder (B) containing powder (D) and powder (A) with low content boron (0.98% by weight), the magnets have a slight remanence less than 1.32 T, because the powder (B) has a B content> 1.5%.
  • the magnets according to the invention have the same structural characteristics as those of application FR 92-14995: absence of phase Nd 1 + ⁇ Fe 4 B 4 , homogeneous structure of grains in size and in slightly angular shape, secondary phase uniformly distributed in fine edges and where cobalt is preferentially localized.

Abstract

The magnetic powder employed for the manufacture of sintered magnets of the RE-T-B class, where RE denotes at least one rare earth, T at least one transition element and B boron, consists of the mixture of 2 powders (A) and (B): a) the powder (A) consisting of grains of RE2T14B tetrahedral structure, T being essentially iron with Co/Fe < 8 % being also capable of containing up to 0.5 % Al, up to 0.05 % Cu and up to 4 % in all of at least one element from the group consisting of V, Nb, Hf, Mo, Cr, Ti, Zr, Ta, W and of the unavoidable impurities, with a Fisher particle size of between 3.5 and 5 mu m; b) the powder (B) being rich in RE and containing Co, having the following composition by weight: RE 52-70 %, including at least 40 % (in absolute value) of one (or more) light rare earth(s) chosen from the group consisting of La, Ce, Pr, Nd, Sm and Eu; Co 20-35 %; Fe 0-20 %; B 0-0.2 %; Al 0.1-4 %; and unavoidable impurities, with a Fisher particle size of between 2.5 and 3.5 mu m. The powder (B) may be obtained by mixing a RE-rich powder (C) containing Co with a B-rich powder (D). <IMAGE>

Description

L'invention concerne une poudre magnétique et des aimants permanents frittés contenant essentiellement au moins une terre rare TR, au moins un élément de transition T et du bore, la poudre magnétique étant obtenue par le mélange d'au moins 2 poudres initiales de composition chimique et de granulométrie différentes et leur méthode de préparation.The invention relates to a magnetic powder and permanent magnets. sintered containing essentially at least one rare earth TR, at least one transition element T and boron, the magnetic powder being obtained by the mixture of at least 2 initial powders of chemical composition and different particle sizes and their method of preparation.

On connaít les demandes de brevets suivantes qui enseignent l'utilisation d'un mélange de 2 alliages initiaux pour la fabrication d'aimants frittés.

  • La demande JP 63-114939 décrit des aimants du type ci-dessus obtenus à partir d'un mélange de 2 poudres, l'une apportant des grains magnétiques de type TR2 T14B, et l'autre, qui constituera la "matrice" contenant soit des éléments à bas point de fusion, soit des éléments à haut point de fusion. Il est également indiqué que cette deuxième poudre doit être rendue extrêmement fine (de 0,02 à 1 µm) ce qui est économiquement pénalisant.
  • La demande JP-2-31402 rapporte l'utilisation d'une deuxième poudre constituée de TR-Fe-B ou TR-Fe à l'état amorphe ou microcristallin, c'est-à-dire obtenue par solidification rapide, ce qui exige des équipements spécifiques peu courants.
  • La demande EP 0447567 décrit un aimant résistant à la corrosion ayant une texture comprenant une phase principale TR2 T14B (T étant Fe Co et/ou Ni) et une phase secondaire à base de composés intermétalliques des séries TR-T, d'eutectiques TR-T ou d'intermétalliques TR-T-B (T étant Ni ou un mélange de Ni avec Fe ou Co), obtenu par frittage d'un mélange de poudre de TR2 T14B et de poudre à bas point de fusion constitué de composés intermétalliques des séries TR-T, d'eutectiques TR-T ou d'intermétalliques TR-T-B.
We know the following patent applications which teach the use of a mixture of 2 initial alloys for the manufacture of sintered magnets.
  • Application JP 63-114939 describes magnets of the above type obtained from a mixture of 2 powders, one providing magnetic grains of type TR 2 T 14 B, and the other, which will constitute the "matrix "containing either elements with a low melting point or elements with a high melting point. It is also indicated that this second powder must be made extremely fine (from 0.02 to 1 μm) which is economically disadvantageous.
  • Application JP-2-31402 reports the use of a second powder consisting of TR-Fe-B or TR-Fe in the amorphous or microcrystalline state, that is to say obtained by rapid solidification, which requires unusual equipment.
  • EP 0447567 describes a corrosion resistant magnet having a texture comprising a main phase TR 2 T 14 B (T being Fe Co and / or Ni) and a secondary phase based on intermetallic compounds of the TR-T series, TR-T eutectics or TR-TB intermetallics (T being Ni or a mixture of Ni with Fe or Co), obtained by sintering a mixture of powder TR 2 T 14 B and powder with low melting point consisting TR-T series intermetallic compounds, TR-T eutectics or TR-TB intermetallics.

Le problème qui se pose est donc de trouver une méthode de fabrication plus simple et moins onéreuse selon la voie conventionnelle de la métallurgie des poudres en vue d'obtenir des aimants frittés ayant de meilleures caractéristiques magnétiques, en particulier une bonne rémanence et une bonne résistance à la corrosion atmosphérique. The problem is therefore to find a manufacturing method simpler and less expensive according to the conventional route of powder metallurgy to obtain sintered magnets having better magnetic characteristics, especially good afterglow and good resistance to atmospheric corrosion.

Sauf indications contraires, les teneurs données ci-après sont les teneurs pondérales.Unless otherwise indicated, the contents given below are the contents by weight.

Selon l'invention, la poudre initiale est constituée par un mélange de 2 poudres de nature et de granulométrie différentes, et est caractérisée en ce que :

  • a) la poudre (A) est constituée de grains de structure quadratique TR2T14B (en at.), T étant essentiellement du fer avec Co/Fe < 8 %, pouvant également contenir jusqu'à 0,5% Al, jusqu'à 0,05% Cu et jusqu'à 4% au total d'au moins un élément du groupe constitué par V, Nb, Hf, Mo, Cr, Ti, Zr, Ta, W et des impuretés inévitables, de granulométrie Fisher comprise entre 3,5 et 5 µm.
    Sa teneur totale en TR est comprise entre 26,7 et 30% et de préférence entre 28 et 29%; la teneur en Co est de préférence limitée à 5% maximum, et même 2%. La teneur en Al est de préférence comprise entre 0,2 et 0,5%, ou mieux entre 0,25 et 0,35%; la teneur en Cu est tenue de préférence entre 0,02 et 0,05%, et plus particulièrement entre 0,025 et 0,035%. La teneur en B est comprise entre 0,96 et 1,1%, et de préférence 1,0-1,06%. Le reste est constitué par du Fe. La poudre (A) peut être obtenue à partir d'un alliage élaboré par fusion (lingots) ou par co-réduction (poudre grossière), les lingots ou les poudres grossières étant de préférence soumis à un traitement sous H2 dans les conditions suivantes : mise sous vide ou balayage de l'enceinte, application d'une pression de gaz inerte comprise entre 0,1 et 0,12 MPa, élévation de la température à une vitesse située entre 10°C/h et 500°C/h jusqu'à atteindre une température comprise entre 350 et 450°C, application d'une pression partielle absolue d'hydrogène comprise entre 0,01 et 0,12 MPa et maintien de ces conditions de 1 à 4 heures, mise sous vide et application d'une pression d'un gaz inerte de 0,1 à 0,12 MPa, refroidissement jusqu'à la température ambiante à une vitesse comprise entre 5°C/h et 100°C/h. Le gaz inerte utilisé est de préférence l'argon ou l'hélium ou un mélange de ces 2 gaz.
    La poudre (A) est ensuite broyée finement à l'aide d'un broyeur à jet de gaz, de préférence de l'azote, amené à une pression (absolue) comprise entre 0,4 et 0,8 MPa en ajustant les paramètres de sélection granulométrique de façon à obtenir une poudre dont la granulométrie Fisher est comprise entre 3,5 et 5 µm.
  • b) la poudre (B) est riche en TR et contient du Co, et a la composition pondérale suivante :
    TR 52-70%; comprenant au moins 40% (en valeur absolue) d'une (ou plusieurs) terre(s) rare(s) légère(s) choisie(s) dans le groupe constitué par les éléments : La, Ce, Pr, Nd, Sm, Eu; une teneur en H2 (en ppm en poids) supérieure à 130x%TR; Co 20-35%; Fe 0-20%; B 0-0,2%; Al 0,1-4%; et des impuretés inévitables, de granulométrie Fisher comprise entre 2,5 et 3,5 µm.
  • De préférence, elle est pratiquement exempte de B (teneur en B inférieure à 0,05%).
  • Cette poudre (B) est obtenue à partir d'alliages, qui sont traités sous hydrogène dans les conditions suivantes : mise sous vide, application d'une pression de gaz inerte comprise entre 0,1 et 0,12 MPa, élévation de la température à une vitesse située entre 10°C/h et 500°C/h jusqu'à atteindre une température comprise entre 350 et 450°C, application d'une pression partielle absolue d'hydrogène comprise entre 0,01 et 0,12 MPa et maintien de ces conditions de 1 à 4 heures, mise sous vide et application d'une pression d'un gaz inerte de 0,1 à 0,12 MPa, refroidissement jusqu'à la température ambiante à une vitesse comprise entre 5°C/h et 100°C/h.
  • De plus, il est préférable que l'opération ci-dessus soit précédée d'un traitement à l'hydrogène préalable dans les conditions suivantes : maintien de l'alliage initial sous une pression partielle absolue d'hydrogène comprise entre 0,01 et 0,12 MPa pendant 1 à 3 heures, à la température ambiante.
  • Si nécessaire, les opérations de traitement à l'hydrogène préalable ou final indiquées ci-dessus, sont répétées 1 ou 2 fois. Le gaz inerte utilisé est de préférence l'argon ou l'hélium ou un mélange de ces 2 gaz.
  • Elle contient essentiellement un hydrure de TR : TRH2+ε, du Co métal, et un peu de NdCo2.
    • La poudre (B) ainsi obtenue est finement broyée à l'aide d'un broyeur à jet de gaz, avec de préférence de l'azote amené à une pression absolue comprise entre 0,4 et 0,7 MPa en ajustant les paramètres de sélection granulométrique de façon à obtenir une poudre dont la granulométrie Fisher est comprise entre 2,5 et 3,5 µm.
    Il est préférable que la poudre (B) ait une granulométrie Fisher inférieure d'au moins 20% à celle de la poudre (A). Cette poudre (B) donnant essentiellement naissance à une phase secondaire, il est souhaitable que la température de fusion complète (liquidus) de l'alliage (B) soit inférieure à 1080°C.
  • c) Les poudres (A) et (B) ainsi obtenues sont ensuite mélangées de façon à obtenir la composition finale de l'aimant. Pour celle-ci, la teneur des terres rares (TR) est généralement comprise entre 29,0% et 32,0% et de préférence entre 29 et 31%, la teneur en bore est comprise entre 0,94% et 1,04%, la teneur en cobalt est comprise entre 1,0% et 4,3% en poids, la teneur en aluminium est comprise entre 0,2 et 0,5% en poids, la teneur en cuivre est comprise entre 0,02% et 0,05% en poids, le reste étant le fer ainsi que les inévitables impuretés. La teneur en O2 de la poudre magnétique issue du mélange (A)+(B) est en général inférieure à 3500 ppm. La proportion pondérale de poudre (A) dans le mélange (A)+(B) est comprise entre 88 et 95%, et de préférence entre 90 et 94%.
  • Le mélange des poudres (A) et (B) est ensuite orienté sous un champ magnétique parallèle (//) ou perpendiculaire (⊥) à la direction de compression puis compacté par tout moyen adapté, par exemple compression à la presse ou compression isostatique et les comprimés ainsi obtenus, dont la masse spécifique est comprise, par exemple, entre 3,5 et 4,5 g/cm3, sont frittés entre 1050°C et 1110°C et traités thermiquement de manière habituelle.
  • La densité obtenue est comprise entre 7,45 et 7,65 g/cm3.
    • According to the invention, the initial powder consists of a mixture of 2 powders of different types and sizes, and is characterized in that:
  • a) the powder (A) consists of grains of quadratic structure TR 2 T 14 B (in at.), T being essentially iron with Co / Fe <8%, which can also 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 consisting of V, Nb, Hf, Mo, Cr, Ti, Zr, Ta, W and unavoidable impurities, of grain size Fisher between 3.5 and 5 µm.
    Its total TR content is between 26.7 and 30% and preferably between 28 and 29%; the Co content is preferably limited to 5% maximum, and even 2%. The Al content is preferably between 0.2 and 0.5%, or better still between 0.25 and 0.35%; the Cu content is preferably kept between 0.02 and 0.05%, and more particularly between 0.025 and 0.035%. The B content is between 0.96 and 1.1%, and preferably 1.0-1.06%. The rest consists of Fe. The powder (A) can be obtained from an alloy produced by fusion (ingots) or by co-reduction (coarse powder), the ingots or coarse powders being preferably subjected to a treatment under H 2 under the following conditions: evacuation or sweeping of the enclosure, application of an inert gas pressure of between 0.1 and 0.12 MPa, temperature rise at a speed between 10 ° C / h and 500 ° C / h until a temperature between 350 and 450 ° C is reached, application of an absolute partial pressure of hydrogen between 0.01 and 0.12 MPa and maintenance of these conditions from 1 to 4 hours, evacuating and applying an inert gas pressure of 0.1 to 0.12 MPa, cooling to room temperature at a speed between 5 ° C / h and 100 ° C / h . The inert gas used is preferably argon or helium or a mixture of these 2 gases.
    The powder (A) is then finely ground using a gas jet mill, preferably nitrogen, brought to a pressure (absolute) of between 0.4 and 0.8 MPa by adjusting the parameters of particle size selection so as to obtain a powder whose Fisher particle size is between 3.5 and 5 μm.
  • b) the powder (B) is rich in TR and contains Co, and has the following composition by weight:
    TR 52-70%; comprising at least 40% (in absolute value) of one (or more) light rare earth (s) chosen from the group made up of the elements: La, Ce, Pr, Nd, Sm , Eu; an H 2 content (in ppm by weight) greater than 130x% TR; Co 20-35%; Fe 0-20%; B 0-0.2%; Al 0.1-4%; and unavoidable impurities, with a Fisher particle size between 2.5 and 3.5 μm.
  • Preferably, it is practically free of B (B content less than 0.05%).
  • This powder (B) is obtained from alloys, which are treated under hydrogen under the following conditions: evacuation, application of an inert gas pressure of between 0.1 and 0.12 MPa, rise in temperature at a speed between 10 ° C / h and 500 ° C / h until reaching a temperature between 350 and 450 ° C, application of an absolute partial pressure of hydrogen between 0.01 and 0.12 MPa and maintaining these conditions for 1 to 4 hours, evacuating and applying an inert gas pressure of 0.1 to 0.12 MPa, cooling to ambient temperature at a speed of between 5 ° C. / h and 100 ° C / h.
  • In addition, it is preferable that the above operation be preceded by a prior hydrogen treatment under the following conditions: maintenance of the initial alloy under an absolute partial pressure of hydrogen of between 0.01 and 0 , 12 MPa for 1 to 3 hours, at room temperature.
  • If necessary, the preliminary or final hydrogen treatment operations indicated above are repeated 1 or 2 times. The inert gas used is preferably argon or helium or a mixture of these 2 gases.
  • It essentially contains a hydride of TR: TRH 2 + ε , Co metal, and a little NdCo 2 .
    • The powder (B) thus obtained is finely ground using a gas jet mill, preferably with nitrogen brought to an absolute pressure of between 0.4 and 0.7 MPa by adjusting the parameters of particle size selection so as to obtain a powder whose Fisher particle size is between 2.5 and 3.5 μm.
    It is preferable that the powder (B) has a Fisher particle size at least 20% less than that of the powder (A). This powder (B) essentially giving rise to a secondary phase, it is desirable that the complete melting temperature (liquidus) of the alloy (B) be less than 1080 ° C.
  • c) The powders (A) and (B) thus obtained are then mixed so as to obtain the final composition of the magnet. For this, the content of rare earths (TR) is generally between 29.0% and 32.0% and preferably between 29 and 31%, the boron content is between 0.94% and 1.04 %, the cobalt content is between 1.0% and 4.3% by weight, the aluminum content is between 0.2 and 0.5% by weight, the copper content is between 0.02% and 0.05% by weight, the rest being iron as well as the inevitable impurities. The O 2 content of the magnetic powder from the mixture (A) + (B) is generally less than 3500 ppm. The proportion by weight of powder (A) in the mixture (A) + (B) is between 88 and 95%, and preferably between 90 and 94%.
  • The mixture of powders (A) and (B) is then oriented under a magnetic field parallel (//) or perpendicular (⊥) to the direction of compression and then compacted by any suitable means, for example press compression or isostatic compression and the tablets thus obtained, whose specific mass is between, for example, between 3.5 and 4.5 g / cm 3 , are sintered between 1050 ° C and 1110 ° C and heat treated in the usual way.
  • The density obtained is between 7.45 and 7.65 g / cm 3 .

    • Les aimants peuvent ensuite subir toutes les opérations habituelles d'usinage et de revêtements de surface si nécessaire.The magnets can then undergo all the usual operations machining and surface coatings if necessary.

    Les aimants selon l'invention qui appartiennent à la famille TR-T-B où TR désigne au moins une terre-rare, T au moins un élément de transition tel que Fe et/ou Co, B, le bore, pouvant contenir éventuellement d'autres éléments mineurs, sont essentiellement constitués de grains de phase quadratique TR2 Fe14 B dite "Tl", d'une phase secondaire contenant essentiellement des terres-rares, et d'autres phases mineures éventuelles. Ces aimants possèdent les caractéristiques suivantes :

  • rémanence : Br ≥ 1,25 T (en compression //)
  • rémanence : Br ≥ 1,30 T (en compression ⊥)
  • champ coercitif intrinsèque HcI ≥ 1050 kA/m (
    Figure 00060001
    13 kOe).
    • The magnets according to the invention which belong to the TR-TB family where TR designates at least one rare earth, T at least one transition element such as Fe and / or Co, B, boron, possibly containing other minor elements, essentially consist of grains of quadratic phase TR 2 Fe 14 B called "Tl", of a secondary phase containing essentially rare earths, and of other possible minor phases. These magnets have the following characteristics:
  • afterglow: Br ≥ 1.25 T (in compression //)
  • afterglow: Br ≥ 1.30 T (in compression ⊥)
  • intrinsic coercive field HcI ≥ 1050 kA / m (
    Figure 00060001
    13 kOe).

    • De façon plus précise, ils possèdent une structure constituée de grains de phase T1, représentant plus de 94% de la structure, et de taille sensiblement uniforme comprise entre 2 et 20 µm. Ceux-ci sont entourés d'un liseré fin et continu de phase secondaire riche en TR, d'épaisseur sensiblement uniforme, ne présentant pas, localement, une largeur ≥ 5 µm. Cette phase secondaire contient plus de 10% de cobalt.More precisely, they have a structure made up of grains of phase T1, representing more than 94% of the structure, and of size substantially uniform between 2 and 20 µm. These are surrounded a thin and continuous secondary phase border rich in TR, thick substantially uniform, not locally having a width ≥ 5 µm. This secondary phase contains more than 10% cobalt.

    Cependant, la demanderesse s'est aperçue que la coercitivité, la rémanence et l'énergie spécifique, bien que satisfaisantes, pouvaient encore être améliorées en obtenant la poudre (B) par un mélange de deux poudres (C) et (D), sans affecter les autres propriétés d'emploi des aimants frittés, en particulier la résistance à l'oxydation et à la corrosion atmosphérique et l'usinage aux tolérances par rectification. De plus, la demanderesse s'est aperçue qu'un choix adapté de la poudre (D) permettait de réduire sensiblement la température et la durée du frittage.However, the Applicant has noticed that the coercivity, the afterglow and specific energy, although satisfactory, could be further improved by obtaining the powder (B) by a mixture of two powders (C) and (D), without affecting the other properties of use of the sintered magnets, in particular resistance to oxidation and atmospheric corrosion and machining to tolerances by grinding. Of more, the applicant has noticed that a suitable choice of powder (D) allowed to significantly reduce the temperature and the duration of the sintering.

    Selon l'invention, la poudre additive (B) est obtenue par le mélange de deux poudres grossières (C) et (D) d'alliages de nature différente et broyées simultanément. Par poudre grossière on entend une poudre dont les particules passent au tamis de 1 mm.

  • a) la poudre (C) est riche en TR et contient du Co et a la composition pondérale suivante :
  • TR 52-70 % ; comprenant au moins 40 % (en valeur absolue) d'une (ou plusieurs) terre(s) rare(s) légère(s) choisie(s) dans le groupe constitué par les éléments : La, Ce, Pr, Nd, Sm, Eu ; une teneur en hydrogène (en ppm en poids) supérieure à 130x%TR; Co 20-35 % ;
  • Fe 0-20 % ; B 0-0,2 % ; Al 0,1-4 % ; et des impuretés inévitables.
  • De préférence, elle est pratiquement exempte de B (teneur en B inférieure à 0,05 %).
  • La poudre grossière (C) est obtenue à partir d'alliages, qui sont traités sous hydrogène dans les conditions suivantes : mise sous vide, application d'une pression de gaz inerte comprise entre 0,1 et 0,12 MPa, élévation de la température à une vitesse située ente 10°C/h et 500°C/h jusqu'à atteindre une température comprise entre 350 et 450°C, application d'une pression partielle absolue d'hydrogène comprise entre 0,01 et 0,12 MPa et maintien de ces conditions de 1 à 4 heures, mise sous vide et application d'une pression d'un gaz inerte de 0,1 à 0,12 MPa, refroidissement jusqu'à la température ambiante à une vitesse comprise entre 5°C/h et 100°C/h.
  • De plus, il est préférable que l'opération ci-dessus soit précédée d'un traitement à l'hydrogène préalable dans les conditions suivantes : maintien de l'alliage initial sous une pression partielle absolue d'hydrogène comprise entre 0,01 et 0,12 MPa pendant 1 à 3 heures, à la température ambiante.
  • Si nécessaire, les opérations de traitement à l'hydrogène préalable ou final indiquées ci-dessus, sont répétées 1 ou 2 fois. Le gaz inerte utilisé est de préférence l'argon ou l'hélium ou un mélange de ces 2 gaz.
  • Cette poudre (C) contient essentiellement un hydrure de terre rare : TRH2+ε, du Co métal et un peu de NdCo2.
  • b) La poudre (D) peut être obtenue à partir d'un alliage contenant du bore allié à un ou plusieurs des éléments de la série (Al, Si, V, Cr, Mn, Fe, Co, Ni, Cu, Nb, Mo) et contenant entre 5 % et 70 % en poids de bore, avec les impuretés inévitables. Elle est constituée de préférence par des alliages à base de Fe contenant du bore compris entre 5 % et 30 % (en poids), du cuivre jusqu'à 10 %, de l'aluminium jusqu'à 10 % en poids, du silicium jusqu'à 8 %. Cette poudre (D) est pratiquement exempte de terres-rares (teneur totale ≤ 0,05%). Ces alliages élaborés selon les procédés classiques sont ensuite broyés grossièrement par voie humide ou à sec avec des broyeurs mécaniques ou à jet de gaz, cette poudre (D) grossière est ensuite mélangée avec la poudre grossière (C) ayant subi un des traitements d'hydruration afin que la teneur finale en bore du mélange (B) = (C)+(D) soit comprise entre 0,05 et 1,5 % et de préférence entre 0,4 et 1,2 %. Le mélange (C)+(D) homogénéisé est ensuite broyé jusqu'à une granulométrie Fisher de 2,5 à 3,5 µm. Cette poudre (B) donnant essentiellement naissance à une phase secondaire, il est souhaitable que la température de fusion complète (liquidus) de celle-ci soit inférieure à 1050°C. Il est préférable que la poudre (B) ait une granulométrie Fisher inférieure d'au moins 20% par rapport à la poudre (A).
  • c) la poudre (A) est constituée de grains de structure quadratique TR2T14B (en at.), T étant essentiellement du fer avec Co/Fe < 8 %, pouvant également contenir jusqu'à 0,5 % Al, jusqu'à 0,05 % Cu et jusqu'à 4 % au total d'au moins un élément du groupe constitué par V, Nb, Hf, Mo, Cr, Ti, Zr, Ta, W et des impuretés inévitables, de granulométrie Fisher comprise entre 3,5 et 5 µm.
  • Sa teneur totale en TR est comprise entre 26,7 et 30 % et de préférence entre 28 et 29 % ; la teneur en Co est de préférence limitée à 5 % maximum, et même 2 %. La teneur en Al est de préférence comprise entre 0,2 et 0,5 %, ou mieux entre 0,25 et 0,35 % ; la teneur en Cu est tenue de préférence entre 0,02 et 0,05 %, et plus particulièrement entre 0,025 et 0,035 %. La teneur en B est comprise entre 0,95 et 1,05 % et de préférence 0,96-1,0 %. Le reste est constitué par du Fe.
  • Sa composition globale peut être très proche de TR2T14B, le Cu et l'Al étant assimilés à des métaux de transition.
  • La poudre (A) peut être obtenue à partir d'un alliage élaboré par fusion (lingots) ou par co-réduction (poudre grossière), les lingots ou les poudres grossières étant de préférence soumis à un traitement sous H2 dans les conditions suivantes : mise sous vide ou balayage de l'enceinte, application d'une pression de gaz inerte comprise entre 0,1 et 0,12 MPa, élévation de la température à une vitesse située entre 10°C/h et 500°C/h jusqu'à atteindre une température comprise entre 350 et 450°C, application d'une pression partielle absolue d'hydrogène comprise entre 0,01 et 0,12 MPa et maintien de ces conditions de 1 à 4 heures, mise sous vide et application d'une pression d'un gaz inerte de 0,1 à 0,12 MPa, refroidissement jusqu'à la température ambiante à une vitesse comprise entre 5°C/h et 100°C/h. Le gaz inerte utilisé est de préférence l'argon ou l'hélium ou un mélange de ces 2 gaz.
    La poudre (A) est ensuite broyée finement à l'aide d'un broyeur à jet de gaz, de préférence de l'azote, amené à une pression (absolue) comprise entre 0,4 et 0,8 MPa en ajustant les paramètres de sélection granulométrique de façon à obtenir une poudre dont la granulométrie Fisher est comprise entre 3,5 et 5 µm.
  • d) les poudres (A) et (B) ainsi obtenues sont ensuite mélangées de façon à obtenir la composition finale de l'aimant. Pour celle-ci, la teneur des terres rares (TR) est généralement comprise entre 29,0 % et 32,0 % et de préférence entre 29 et 31 %, la teneur en bore est comprise entre 0,93 % et 1,04 %, la teneur en cobalt est comprise entre 1,0 % et 4,3 % en poids, la teneur en aluminium est comprise entre 0,2 et 0,5 % en poids, la teneur en cuivre est comprise entre 0,02 % et 0,05 % en poids, le reste étant le fer ainsi que les inévitables impuretés. La teneur en O2 de la poudre magnétique issue du mélange (A)+(B) est en général inférieure à 3500 ppm. La proportion pondérale de poudre (A) dans le mélange (A)+(B) est comprise entre 88 et 95 %, et de préférence entre 90 et 94 %.
  • Le mélange des poudres (A) et (B) est ensuite orienté sous un champ magnétique parallèle (//) ou perpendiculaire (⊥) à la direction de compression puis compacté par tout moyen adapté, par exemple compression à la presse ou compression isostatique et les comprimés ainsi obtenus, dont la masse spécifique est comprise, par exemple, entre 3,5 et 4,5 g/cm3, sont frittés entre 1050°C et 1110°C et traités thermiquement de manière habituelle.
  • La masse spécifique obtenue est comprise entre 7,45 et 7,65 g/cm3 et la teneur en oxygène inférieure à 3500 ppm.
    • According to the invention, the additive powder (B) is obtained by the mixture of two coarse powders (C) and (D) of alloys of different nature and ground simultaneously. By coarse powder is meant a powder the particles of which pass through a 1 mm sieve.
  • a) the powder (C) is rich in TR and contains Co and has the following composition by weight:
  • TR 52-70%; comprising at least 40% (in absolute value) of one (or more) light rare earth (s) chosen from the group made up of the elements: La, Ce, Pr, Nd, Sm , Eu; a hydrogen content (in ppm by weight) greater than 130x% TR; Co 20-35%;
  • Fe 0-20%; B 0-0.2%; Al 0.1-4%; and unavoidable impurities.
  • Preferably, it is practically free of B (B content less than 0.05%).
  • The coarse powder (C) is obtained from alloys, which are treated under hydrogen under the following conditions: vacuum, application of an inert gas pressure between 0.1 and 0.12 MPa, increase in the temperature at a speed between 10 ° C / h and 500 ° C / h until reaching a temperature between 350 and 450 ° C, application of an absolute partial pressure of hydrogen between 0.01 and 0.12 MPa and maintenance of these conditions from 1 to 4 hours, evacuation and application of an inert gas pressure from 0.1 to 0.12 MPa, cooling to room temperature at a speed of between 5 ° C / h and 100 ° C / h.
  • In addition, it is preferable that the above operation be preceded by a prior hydrogen treatment under the following conditions: maintenance of the initial alloy under an absolute partial pressure of hydrogen of between 0.01 and 0 , 12 MPa for 1 to 3 hours, at room temperature.
  • If necessary, the preliminary or final hydrogen treatment operations indicated above are repeated 1 or 2 times. The inert gas used is preferably argon or helium or a mixture of these 2 gases.
  • This powder (C) essentially contains a rare earth hydride: TRH 2 + ε , Co metal and a little NdCo 2 .
  • b) The powder (D) can be obtained from an alloy containing boron alloyed with one or more of the elements of the series (Al, Si, V, Cr, Mn, Fe, Co, Ni, Cu, Nb, Mo) and containing between 5% and 70% by weight of boron, with the inevitable impurities. It preferably consists of Fe-based alloys containing boron between 5% and 30% (by weight), copper up to 10%, aluminum up to 10% by weight, silicon up to 'at 8 %. This powder (D) is practically free of rare earths (total content ≤ 0.05%). These alloys produced according to conventional methods are then coarsely ground wet or dry with mechanical or gas jet mills, this coarse powder (D) is then mixed with the coarse powder (C) having undergone one of the treatments. hydriding so that the final boron content of the mixture (B) = (C) + (D) is between 0.05 and 1.5% and preferably between 0.4 and 1.2%. The homogenized mixture (C) + (D) is then ground to a Fisher particle size of 2.5 to 3.5 μm. This powder (B) essentially giving rise to a secondary phase, it is desirable that the complete melting temperature (liquidus) thereof is less than 1050 ° C. It is preferable that the powder (B) has a Fisher particle size at least 20% lower than the powder (A).
  • c) the powder (A) consists of grains of quadratic structure TR 2 T 14 B (in at.), T being essentially iron with Co / Fe <8%, which can also 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 consisting of V, Nb, Hf, Mo, Cr, Ti, Zr, Ta, W and unavoidable impurities, of grain size Fisher between 3.5 and 5 µm.
  • Its total TR content is between 26.7 and 30% and preferably between 28 and 29%; the Co content is preferably limited to 5% maximum, and even 2%. The Al content is preferably between 0.2 and 0.5%, or better still between 0.25 and 0.35%; the Cu content is preferably kept between 0.02 and 0.05%, and more particularly between 0.025 and 0.035%. The content of B is between 0.95 and 1.05% and preferably 0.96-1.0%. The rest is made up of Fe.
  • Its overall composition can be very close to TR 2 T 14 B, Cu and Al being assimilated to transition metals.
  • The powder (A) can be obtained from an alloy produced by fusion (ingots) or by co-reduction (coarse powder), the ingots or coarse powders being preferably subjected to a treatment under H 2 under the following conditions : evacuating or sweeping the enclosure, applying an inert gas pressure of between 0.1 and 0.12 MPa, raising the temperature at a speed between 10 ° C / h and 500 ° C / h until a temperature between 350 and 450 ° C is reached, application of an absolute partial pressure of hydrogen between 0.01 and 0.12 MPa and maintenance of these conditions from 1 to 4 hours, evacuation and application of an inert gas pressure of 0.1 to 0.12 MPa, cooling to room temperature at a speed between 5 ° C / h and 100 ° C / h. The inert gas used is preferably argon or helium or a mixture of these 2 gases.
    The powder (A) is then finely ground using a gas jet mill, preferably nitrogen, brought to a pressure (absolute) of between 0.4 and 0.8 MPa by adjusting the parameters of particle size selection so as to obtain a powder whose Fisher particle size is between 3.5 and 5 μm.
  • d) the powders (A) and (B) thus obtained are then mixed so as to obtain the final composition of the magnet. For this, the content of rare earths (TR) is generally between 29.0% and 32.0% and preferably between 29 and 31%, the boron content is between 0.93% and 1.04 %, the cobalt content is between 1.0% and 4.3% by weight, the aluminum content is between 0.2 and 0.5% by weight, the copper content is between 0.02% and 0.05% by weight, the rest being iron as well as the inevitable impurities. The O 2 content of the magnetic powder from the mixture (A) + (B) is generally less than 3500 ppm. The proportion by weight of powder (A) in the mixture (A) + (B) is between 88 and 95%, and preferably between 90 and 94%.
  • The mixture of powders (A) and (B) is then oriented under a magnetic field parallel (//) or perpendicular (⊥) to the direction of compression and then compacted by any suitable means, for example press compression or isostatic compression and the tablets thus obtained, whose specific mass is between, for example, between 3.5 and 4.5 g / cm 3 , are sintered between 1050 ° C and 1110 ° C and heat treated in the usual way.
  • The specific mass obtained is between 7.45 and 7.65 g / cm 3 and the oxygen content less than 3500 ppm.

    • Les aimants peuvent ensuite subir toutes les opérations habituelles d'usinage et de revêtements de surface si nécessaire.The magnets can then undergo all the usual operations machining and surface coatings if necessary.

    Les aimants selon l'invention qui appartiennent à la famille TR-T-B résultant de l'emploi des poudres (A) et (B), où TR désigne au moins une terre rare, T au moins un élément de transition tel que Fe et/ou Co, B, le bore, pouvant contenir éventuellement d'autres éléments mineurs, sont essentiellement constitués de grains de phase quadratique TR2Fe14B dite "Tl", d'une phase secondaire contenant essentiellement des terres rares, et d'autres phases mineures éventuelles. Ces aimants possèdent les caractéristiques très élevées suivantes :

  • rémanence : Br > 1, 25 T (en compression //)
  • rémanence : Br ≥ 1,32 T (en compression ⊥) et même ≥ 1,35 T
  • champ coercitif intrinsèque HcJ ≥ 1150 kA/m (= 14,3 kOe).
    • The magnets according to the invention which belong to the TR-TB family resulting from the use of powders (A) and (B), where TR designates at least one rare earth, T at least one transition element such as Fe and / or Co, B, boron, which may possibly contain other minor elements, essentially consist of grains of quadratic phase TR 2 Fe 14 B called "Tl", of a secondary phase containing essentially rare earths, and others possible minor phases. These magnets have the following very high characteristics:
  • afterglow: Br> 1, 25 T (in compression //)
  • afterglow: Br ≥ 1.32 T (in compression ⊥) and even ≥ 1.35 T
  • intrinsic coercive field HcJ ≥ 1150 kA / m (= 14.3 kOe).

    • De façon plus précise, ils possèdent une structure constituée de grains de phase Tl, représentant plus de 94 % de la structure, et de taille sensiblement uniforme comprise entre 2 et 20 µm. Ceux-ci sont entourés d'un liseré fin et continu de phase secondaire riche en TR, d'épaisseur sensiblement uniforme, ne présentant pas, localement, une largeur ≥ 5 µm. Cette phase secondaire contient plus de 10 % de cobalt.More precisely, they have a structure made up of grains of phase Tl, representing more than 94% of the structure, and of size substantially uniform between 2 and 20 µm. These are surrounded a thin and continuous secondary phase border rich in TR, thick substantially uniform, not locally having a width ≥ 5 µm. This secondary phase contains more than 10% cobalt.

    L'invention sera mieux comprise à l'aide des exemples suivants illustrés par les fig. 1 et 2.

    • La figure 1 représente schématiquement une coupe micrographique d'un aimant fritté selon l'invention (Ml)
    • La figure 2 représente schématiquement une coupe micrographique d'un aimant fritté de même composition obtenu selon la technique du mono-alliage (Sl).
    The invention will be better understood with the aid of the following examples illustrated by FIGS. 1 and 2.
    • FIG. 1 schematically represents a micrographic section of a sintered magnet according to the invention (Ml)
    • FIG. 2 schematically represents a micrographic section of a sintered magnet of the same composition obtained according to the mono-alloy technique (S1).

    . EXEMPLE 1 . EXAMPLE 1

    • Les 8 alliages (A) dont la composition est reportée au Tableau I ont été préparés de la façon suivante :
      • coulée des lingots sous vide
      • traitement à l'hydrogène dans les conditions suivantes :
        • mise sous vide
        • introduction d'Argon sous une pression absolue de 0,1 MPa
        • chauffage à 50°C/h jusqu'à 400°C
        • mise sous vide
        • remplissage par un mélange Argon + hydrogène sous les pressions partielles absolues de 0,06 MPa (H2) et 0,07 MPa (Ar) et maintien durant 2 h
        • mise sous vide
        • remplissage d'Argon sous 0,1 MPa et refroidissement à la température ambiante à 10°C/h
      • broyage avec broyeur à jet de gaz sous azote jusqu'aux granulométries Fisher indiquées au tableau III.
      The 8 alloys (A) whose composition is given in Table I were prepared as follows:
      • casting ingots under vacuum
      • hydrogen treatment under the following conditions:
        • vacuum
        • introduction of Argon under an absolute pressure of 0.1 MPa
        • heating at 50 ° C / h up to 400 ° C
        • vacuum
        • filling with an Argon + hydrogen mixture under absolute partial pressures of 0.06 MPa (H 2 ) and 0.07 MPa (Ar) and holding for 2 h
        • vacuum
        • Argon filling at 0.1 MPa and cooling to room temperature at 10 ° C / h
      • grinding with a gas jet mill under nitrogen up to the Fisher particle sizes indicated in Table III.
    • Les 10 alliages (B), dont la composition est reportée au tableau II, ont été préparés de la façon suivante :
      • fusion sous vide de lingots
      • traitement à l'hydrogène
        • mise sous vide
        • application d'un mélange Ar+H2, sous les pressions partielles absolues de 0,06 MPa (H2) et 0,07 MPa (A) à la température ambiante pendant 2h
        • chauffage à 400°C à raison de 50°C/h dans la même atmosphère et maintien pendant 2 h
        • mise sous vide
        • remplissage d'argon sous 0,1 MPa absolu et refroidissement à la température ambiante à 10°C/h
      • broyage au broyeur à jet de gaz sous azote jusqu'aux granulométries Fisher indiquées au Tableau III.
      The 10 alloys (B), the composition of which is given in Table II, were prepared as follows:
      • vacuum melting of ingots
      • hydrogen treatment
        • vacuum
        • application of an Ar + H 2 mixture, under absolute partial pressures of 0.06 MPa (H 2 ) and 0.07 MPa (A) at room temperature for 2 h
        • heating to 400 ° C at a rate of 50 ° C / h in the same atmosphere and holding for 2 h
        • vacuum
        • Argon filling at 0.1 MPa absolute and cooling to room temperature at 10 ° C / h
      • grinding with a gas jet mill under nitrogen up to the Fisher particle sizes indicated in Table III.

    Les poudres (A) et (B) ainsi obtenues ont été mélangées dans les proportions pondérales indiquées au Tableau IV, puis elles ont été ensuite comprimées sous champ (// ou ⊥), frittées et traitées dans les conditions reportées au Tableau V, où figurent également la densité et les caractéristiques magnétiques obtenues sur les aimants.The powders (A) and (B) thus obtained were mixed in the weight proportions indicated in Table IV, then they have been then compressed under field (// or ⊥), sintered and processed in conditions given in Table V, which also shows the density and the magnetic characteristics obtained on the magnets.

    Les aimants M1, M2, M3, M4, M5, M9 et M13 correspondent à l'invention; les autres exemples sortent du domaine de l'invention pour les raisons suivantes :

    M6 -
    la poudre (B) contient 1% de B, valeur supérieure à la limite autorisée et la densification est très insuffisante.
    M7 -
    la proportion de la poudre (B) dans le mélange (A)+(B) est trop faible et conduit à une mauvaise dispersion de cette poudre (B) et à une mauvaise densification.
    M8 -
    la coercitivité inférieure à 1050 kA/m due à l'utilisation d'un alliage (B) à trop faible teneur en TR.
    M10-
    la présence de V dans l'alliage (B) - 9% en poids - ne permet pas de conduire à de bonnes propriétés.
    M11-
    la présence simultanée de B et de V dans la poudre (B) fait perdre sur toutes les propriétés de l'aimant.
    S1,S2,S3-
    ces compositions sont obtenues à l'aide de la méthode mono-alliage ne permettant pas d'obtenir une densification suffisante ce qui se traduit par de faibles propriétés magnétiques.
    M12-
    la composition est identique à celle de la composition M1, mais obtenue avec une poudre (Al) mélangée à une poudre (B9) qui n'a pas reçu de traitement à l'hydrogène mais un concassage mécanique sous atmosphère inerte avant introduction dans le broyeur à jet de gaz.
    The magnets M1, M2, M3, M4, M5, M9 and M13 correspond to the invention; the other examples are outside the scope of the invention for the following reasons:
    M6 -
    the powder (B) contains 1% B, value greater than the authorized limit and the densification is very insufficient.
    M7 -
    the proportion of the powder (B) in the mixture (A) + (B) is too low and leads to poor dispersion of this powder (B) and to poor densification.
    M8 -
    the coercivity below 1050 kA / m due to the use of an alloy (B) with too low a TR content.
    M10-
    the presence of V in the alloy (B) - 9% by weight - does not lead to good properties.
    M11-
    the simultaneous presence of B and V in the powder (B) causes all the properties of the magnet to be lost.
    S1, S2, S3-
    these compositions are obtained using the mono-alloy method which does not allow sufficient densification to be obtained, which results in weak magnetic properties.
    M12-
    the composition is identical to that of composition M1, but obtained with a powder (Al) mixed with a powder (B9) which has not received a hydrogen treatment but a mechanical crushing under an inert atmosphere before introduction into the mill gas jet.

    Les fig. 1 et 2 représentent schématiquement 2 coupes micrographiques effectuées en microscopie à balayage équipée d'une sonde analytique et ont été réalisées sur deux aimants de même composition correspondant aux exemples Ml et Sl : Ml étant mis en oeuvre selon l'invention et Sl étant réalisé selon l'art antérieur par une technique mono-alliage.Figs. 1 and 2 schematically represent 2 micrographic sections performed in scanning microscopy equipped with an analytical probe and were carried out on two magnets of the same composition corresponding to the examples Ml and Sl: Ml being used according to the invention and Sl being produced according to the prior art by a mono-alloy technique.

    Les différences sont les suivantes :

    • L'aimant Ml possède une structure homogène de grains fins de phase magnétique TR2 Fe14 B -l- dont la taille moyenne est de 9 µm et 95% des grains ayant une taille inférieure à 14 µm et dont la géométrie est peu anguleuse.
    • La phase secondaire, qui est riche en TR -2-, est uniformément répartie en fins liserés autour des grains de phase magnétique TR2 Fe14 B, sans présence de poches dont la taille excède 4 µm.
    • On ne note pas la présence de phase TR1+ε Fe4 B4, la porosité intergranulaire -3- est très faible et le diamètre d'une telle porosité n'excède pas 2 µm. La présence de phase oxyde intergranulaire -4- est faible, la taille de ces oxydes n'excède pas 3 µm.
    • Une analyse quantitative en cobalt de grains de phase Tl (TR2 Fe14 B) et de la phase secondaire montre que le cobalt est principalement localisé dans la phase secondaire intergranulaire avec une teneur moyenne supérieure à 10% en poids et que la phase magnétique TR2 Fe14 B -1- n'en contient qu'une très faible teneur.
    • L'aimant Sl se caractérise par une microstructure constituée de grains de phase magnétique TR2 Fe14 B -1- dont la taille moyenne est de 12 µm avec une population importante de grains dont la taille est de 20 µm, certains pouvant atteindre 30 µm. De plus, les grains ont une forme générale anguleuse. Il est à noter la présence de phase TR Fe4 B4 -5- et de nombreuses et larges porosités -3- pouvant atteindre un diamètre > 5 µm.
    • Des amas d'oxydes -4- sont d'autre part détectés principalement dans les joints triples pouvant atteindre une taille > 5 µm.
    • La teneur en Co de la phase secondaire riche en TR est très faible et correspond à la teneur moyenne dans l'alliage, tout comme dans la phase magnétique TR2 Fe14 B.
    The differences are as follows:
    • The magnet M1 has a homogeneous structure of fine grains of magnetic phase TR 2 Fe 14 B -l- whose average size is 9 μm and 95% of the grains having a size less than 14 μm and whose geometry is not very angular.
    • The secondary phase, which is rich in TR -2-, is uniformly distributed in fine edgings around the grains of magnetic phase TR 2 Fe 14 B, without the presence of pockets whose size exceeds 4 µm.
    • The presence of phase TR 1 + ε Fe 4 B 4 is not noted, the intergranular porosity -3- is very small and the diameter of such porosity does not exceed 2 μm. The presence of intergranular oxide phase -4- is low, the size of these oxides does not exceed 3 μm.
    • A quantitative analysis of cobalt from grains of phase Tl (TR 2 Fe 14 B) and of the secondary phase shows that the cobalt is mainly located in the intergranular secondary phase with an average content greater than 10% by weight and that the magnetic phase TR 2 Fe 14 B -1- contains only a very low content.
    • The magnet Sl is characterized by a microstructure consisting of grains of magnetic phase TR 2 Fe 14 B -1- whose average size is 12 µm with a large population of grains whose size is 20 µm, some of which can reach 30 µm . In addition, the grains have a generally angular shape. Note the presence of TR Fe 4 B 4 -5- phase and many large porosities -3- which can reach a diameter> 5 µm.
    • On the other hand, clusters of oxides -4- are mainly detected in triple joints which can reach a size> 5 µm.
    • The Co content of the secondary phase rich in TR is very low and corresponds to the average content in the alloy, as in the magnetic phase TR 2 Fe 14 B.

    Le procédé de mélange de deux poudres (A) et (B) correspondant à la méthode revendiquée possède par rapport aux procédés de l'art antérieur, les avantages suivants :

    • la méthode d'obtention de poudres (B) contenant essentiellement du Co et des TR conduit, grâce au traitement à l'hydrogène, à l'obtention d'une dispersion fine et homogène de ses constituants. Il en résulte une meilleure densification, même pour les teneurs totales en TR inférieures à celles de l'art antérieur, et des propriétés magnétiques élevées (Br,HcJ) ainsi qu'une meilleure résistance à la corrosion;
    • la composition de la poudre (B) permet de donner à la phase secondaire riche en TR des propriétés particulières telles que la résistance à la corrosion atmosphérique, apportée par le Co, ou une meilleure frittabilité apportée par le Cu et l'Al.
    The method of mixing two powders (A) and (B) corresponding to the claimed method has the following advantages over the methods of the prior art:
    • the method for obtaining powders (B) containing essentially Co and TR leads, thanks to the hydrogen treatment, to obtain a fine and homogeneous dispersion of its constituents. This results in better densification, even for total TR contents lower than those of the prior art, and high magnetic properties (Br, HcJ) as well as better corrosion resistance;
    • the composition of the powder (B) makes it possible to give the secondary phase rich in TR particular properties such as resistance to atmospheric corrosion, brought by Co, or better sinterability brought by Cu and Al.

    Ainsi, par exemple, des aimants frittés préparés selon l'invention (TR=30,5% en poids) et selon l'art antérieur obtenus à la même densité par une technique de métallurgie des poudres mono-alliage (TR=32% en poids) maintenus en autoclave sous une pression relative de 1,5 bar (0,15 MPa) pendant 120h à 100°C sous atmosphère humide (100% d'humidité relative) accusent les pertes de poids suivantes :

    • invention   2 à 7,10-3 g/cm2
    • art antérieur   3 à 7,10-2 g/cm2
    Thus, for example, sintered magnets prepared according to the invention (TR = 30.5% by weight) and according to the prior art obtained at the same density by a technique of metallurgy of mono-alloy powders (TR = 32% by weight) maintained in an autoclave under a relative pressure of 1.5 bar (0.15 MPa) for 120 h at 100 ° C in a humid atmosphere (100% relative humidity) show the following weight losses:
    • invention 2 at 7.10 -3 g / cm 2
    • prior art 3 to 7.10 -2 g / cm 2

    Pour des aimants dont la composition de la base et les éléments d'addition sont comparables, on voit que le gain sur la tenue à la corrosion est significativement différent un facteur de 10 à l'avantage des aimants obtenus selon l'invention.

    • la microstructure de l'aimant fritté est plus homogène en ce qui concerne la taille des grains de Tl et la bonne répartition d'une quantité plus faible de phase riche en TR confère une augmentation importante de la coercivité.
    For magnets of which the composition of the base and the addition elements are comparable, it can be seen that the gain on the corrosion resistance is significantly different a factor of 10 to the advantage of the magnets obtained according to the invention.
    • the microstructure of the sintered magnet is more homogeneous as regards the size of the grains of Tl and the good distribution of a smaller quantity of phase rich in TR confers a significant increase in coercivity.

    Dans l'intervalle de proportion de mélange des poudres (A) et (B) défini, les variations de la teneur en bore et des TR correspondent pratiquement à l'optimum du rapport TR/B évitant la formation importante de la phase TR1+εFe4 B4 et confirment ainsi une grande souplesse de la méthode pour ajuster la composition de la poudre et maximaliser les propriétés magnétiques.Within the defined proportion of the mixture of powders (A) and (B), the variations in the boron content and the TR correspond practically to the optimum of the TR / B ratio avoiding the significant formation of the TR 1+ phase. ε Fe 4 B 4 and thus confirm a great flexibility of the method for adjusting the composition of the powder and maximizing the magnetic properties.

    . EXEMPLE 2. EXAMPLE 2

    • Les 2 alliages (A) dont la composition est reportée au Tableau VI ont été préparés de la façon suivante :
      • coulée des lingots sous vide
      • traitement à l'hydrogène dans les conditions suivantes :
        • mise sous vide
        • introduction d'Argon sous une pression absolue de 0,1 MPa
        • chauffage à 50°C/h jusqu'à 400°C
        • remplissage par un mélange Argon + hydrogène sous les pressions partielles absolues de 0,06 MPa (H2) et 0,07 MPa (Ar) et maintien durant 2 h
        • mise sous vide
        • remplissage d'Argon sous 0,1 MPa et refroidissement à la température ambiante à 10°C/h
      • broyage avec broyeur à jet de gaz sous azote jusqu'aux granulométries Fisher indiquées au Tableau X.
      The 2 alloys (A), the composition of which is given in Table VI, were prepared as follows:
      • casting ingots under vacuum
      • hydrogen treatment under the following conditions:
        • vacuum
        • introduction of Argon under an absolute pressure of 0.1 MPa
        • heating at 50 ° C / h up to 400 ° C
        • filling with an Argon + hydrogen mixture under absolute partial pressures of 0.06 MPa (H 2 ) and 0.07 MPa (Ar) and holding for 2 h
        • vacuum
        • Argon filling at 0.1 MPa and cooling to room temperature at 10 ° C / h
      • grinding with a gas jet mill under nitrogen up to the Fisher particle sizes indicated in Table X.
    • Les 2 alliages (C), dont la composition est reportée au Tableau VII, ont été préparés de la façon suivante :
      • fusion sous vide de lingots
      • traitement à l'hydrogène
        • mise sous vide
        • application d'un mélange Ar+H2, sous les pressions partielles absolues de 0,06 MPa (H2) et 0,07 MPa (A) à la température ambiante pendant 2 H
        • chauffage à 400°C à raison de 50°C/h dans la même atmosphère et maintien pendant 2 h
        • mise sous vide
        • remplissage d'argon sous 0,1 MPa absolu et refroidissement à la température ambiante à 10°C/h
      The 2 alloys (C), the composition of which is given in Table VII, were prepared as follows:
      • vacuum melting of ingots
      • hydrogen treatment
        • vacuum
        • application of an Ar + H 2 mixture, under absolute partial pressures of 0.06 MPa (H 2 ) and 0.07 MPa (A) at room temperature for 2 H
        • heating to 400 ° C at a rate of 50 ° C / h in the same atmosphere and holding for 2 h
        • vacuum
        • Argon filling at 0.1 MPa absolute and cooling to room temperature at 10 ° C / h

    La taille maximale de la poudre grossière ainsi obtenue est inférieure à 900 µm.

    • L'alliage (D) dont la composition est reportée au Tableau VIII a été traité de la façon suivante :
      • concassage mécanique d'un lingot sous atmosphère particulière d'azote jusqu'à une granulométrie < 3 mm
      • prébroyage dans un broyeur à jet de gaz sous azote jusqu'à une granulométrie < 500 µm.
    • Les 8 mélanges (B) de (C)+(D) dont les compositions sont reportées dans le Tableau IX ont été préparés de la façon suivante :
      • mélange des poudres grossières (C) et (D) dans les proportions pondérales réparties dans le Tableau IX
      • homogénéisation dans un mélangeur rotatif
      • broyage avec un broyeur à jet de gaz sous azote jusqu'aux granulométries indiquées au Tableau X.
    The maximum size of the coarse powder thus obtained is less than 900 μm.
    • The alloy (D), the composition of which is given in Table VIII, has been treated as follows:
      • mechanical crushing of an ingot under a particular nitrogen atmosphere up to a particle size <3 mm
      • pre-grinding in a gas jet mill under nitrogen to a particle size <500 µm.
    • The 8 mixtures (B) of (C) + (D) whose compositions are given in Table IX were prepared as follows:
      • mixture of coarse powders (C) and (D) in the weight proportions distributed in Table IX
      • homogenization in a rotary mixer
      • grinding with a gas jet mill under nitrogen up to the particle sizes indicated in Table X.

    Les poudres (A) et (B) ainsi obtenues ont été mélangées dans les proportions pondérales indiquées au Tableau XI, puis elles ont été ensuite comprimées sous champ (⊥), frittées et traitées dans les conditions reportées au Tableau XII, où figurent également les caractéristiques magnétiques obtenues sur les aimants.The powders (A) and (B) thus obtained were mixed in the weight proportions indicated in Table XI, then they have been then compressed under field (⊥), sintered and processed in conditions shown in Table XII, where also the magnetic characteristics obtained on the magnets.

    Les aimants M7-M8 ; M11-M12 ; M23-M24 ; M27 ; M28 correspondent à l'invention, les autres exemples sortent du domaine de l'invention pour les raisons suivantes :

  • M13 à M16 et M29 à M32 proviennent d'alliage (B) à trop forte teneur en B
  • M1 - M2 - M3 - M4 , M17 - M18 - M19 - M20 sont issus de mélanges dans lesquels la poudre (B) ne contient pas d'addition de poudre (D). La conséquence est que la valeur de rémanence des aimants ainsi obtenus est toujours plus faible que pour des compositions identiques d'aimants issus de l'invention.
    • The magnets M7-M8; M11-M12; M23-M24; M27; M28 correspond to the invention, the other examples depart from the field of the invention for the following reasons:
  • M13 to M16 and M29 to M32 come from alloy (B) with too high a B content
  • M1 - M2 - M3 - M4, M17 - M18 - M19 - M20 come from mixtures in which the powder (B) does not contain powder addition (D). The consequence is that the remanence value of the magnets thus obtained is always lower than for identical compositions of magnets from the invention.

    • Bien qu'issus de poudres (B) contenant la poudre (D), les exemples M5 -M6 M9 - M10 - M13 - M14 - M21 - M22 - M25 - M26 - M29 - M30 sont issus de poudre (A) dont la teneur en bore est élevée (1,06 %) et leur rémanence est inférieure à 1,32 T.Although produced from powders (B) containing the powder (D), examples M5 -M6 M9 - M10 - M13 - M14 - M21 - M22 - M25 - M26 - M29 - M30 are from powder (A) with a high boron content (1.06%) and their persistence is less than 1.32 T.

    Les exemples M31 et M32 correspondent à des cas où bien qu'issus de poudre (B) contenant de la poudre (D) et de poudre (A) à faible teneur en bore (0,98 % poids), les aimants présentent une rémanence légèrement inférieure à 1,32 T, car la poudre (B) a une teneur en B > 1,5%.Examples M31 and M32 correspond to cases where although originating from powder (B) containing powder (D) and powder (A) with low content boron (0.98% by weight), the magnets have a slight remanence less than 1.32 T, because the powder (B) has a B content> 1.5%.

    Les aimants selon l'invention possèdent les mêmes caractéristiques structurales que ceux de la demande FR 92-14995 : absence de phase Nd1+ε Fe4B4, structure homogène de grains en taille et en forme peu anguleuse, phase secondaire uniformément répartie en fins liserés et où le cobalt se localise préférentiellement.The magnets according to the invention have the same structural characteristics as those of application FR 92-14995: absence of phase Nd 1 + ε Fe 4 B 4 , homogeneous structure of grains in size and in slightly angular shape, secondary phase uniformly distributed in fine edges and where cobalt is preferentially localized.

    Le procédé, objet de l'invention présente les avantages suivants :

    • Par comparaison avec l'Exemple 1, on obtient donc une meilleure densification avec un frittage réalisé à plus basse température et/ou pour une durée moindre, ce qui améliore l'induction rémanente et la coercitivité.
    • La poudre additive (B) contient tous les éléments d'addition permettant, au cours de l'opération de frittage, pratiquée à basse température (1050°C - 1070°C), de former la phase riche en TR, liquide, contenant du cobalt et d'autres éléments tels que l'aluminium, le cuivre, le silicium et impuretés et au cours du refroidissement après frittage de donner naissance à la formation de phase magnétique TR2Fe14B additionnelle, sans nécessiter la dissolution difficile de la phase TR1+ε Fe4B4 nécessaire dans l'art antérieur, et conduisant ainsi a l'obtention de propriétés magnétiques très élevées.
    • On constate par ailleurs que l'aimant fritté selon l'invention ne contient pas de phase TR1+ε Fe4B4.
    • le traitement d'hydruration de la poudre (C) permet, comme dans l'art antérieur, l'obtention d'une fine et homogène dispersion de ses constituants et de faciliter ainsi la densification lors du frittage à basse température même pour les basses teneurs en TR et l'obtention de propriétés magnétiques élevées (Br, Hcj) ainsi qu'une meilleure résistance à la corrosion.
    • l'adjonction de la poudre (D) contenant le bore dans la poudre (C) permet un ajustement fin de la teneur finale de cet élément afin de maximaliser la rémanence de l'aimant final. Compositions (A) (en poids %) Nd Dy B Al V Cu Fe A1 27,0 1,5 1,06 0,3 0 0,03 ba1 A2 27,5 1,0 1,06 0,3 0 0,03 ba1 A3 26,0 1,5 1,06 0,3 0 0,03 ba1 A4 27,0 1,5 1,0 0,3 0 0,03 ba1 A5 27,0 1,5 1,15 0,3 0 0,03 ba1 A6 28,1 0 1,17 0 1,0 0,03 69,43 A7 28,1 0 1,13 0 0 0,03 70,7 A8 28,1 0 1,0 0 0 0,03 70,9 Compositions (B) (en poids %) Nd Dy Co Fe Al V Cu B B1 59,1 1,5 32,0 7,1 0,3 0 0,03 0 B2 59,8 1,0 32,0 6,9 0,3 0 0,03 0 B3 59,0 1,5 32,0 6,1 0,3 0 0,03 1,05 B4 67,2 1,5 31,0 0 0,3 0 0,03 0 B5 50,0 1,5 33,0 15,2 0.3 0 0,03 0 B6 52,0 10,0 33,0 2,0 3,0 0 0,03 0 B7 52,0 10,0 24,0 2,0 3,0 9,0 0,03 0 B8 52,0 10,0 24,0 1,0 3,0 9,0 0,03 1,10 B9 59,1 1,5 32,0 7,1 0,3 0 0,03 0 B10 59,1 1,5 32,0 6,9 0,3 0 0,03 0,2 Caractéristiques des poudres Repère FSSS 02 ppm A1 4,5 2900 A2 4,7 3100 A3 4,5 2800 A4 4,7 2800 A5 4,8 3000 A6 4,2 3000 A7 4,5 3200 A8 4,6 2900 B1 3,2 5100 B2 3,3 4800 B3 3,9 6000 B4 3,1 5200 B5 3,4 4800 B6 3,5 5000 B7 3,4 4900 B8 3,3 5200 B9 3,4 10200 B10 3,3 5500
      Figure 00200001
      Figure 00210001
      Compositions (A) -en poids %- Nd Dy B Al Cu Si Fe A1 27,0 1,5 1,06 0,3 0,03 0,05 reste A2 27,0 1,5 0,98 0,3 0,03 0,05 reste Compositions (C) -en poids %- Nd Dy B Co Al Cu Si Fe C1 59,1 1,5 0 32,0 0,3 0,03 0,05 reste C2 59,1 1,5 0,2 32,0 0,3 0,03 0,05 reste Composition (D) -en poids %- B Al Cu Si Fe D1 17,0 2,0 0,5 0,5 reste
      Figure 00230001
      Caractéristiques des poudres fines Repères FSSS O2 ppm A1 4,1 2 800 A2 4,2 3 100 B1 3,0 4 300 B2 2,8 5 500 B3 3,3 4 600 B4 3,1 4 800 B5 2,8 4 700 B6 2,5 6 200 B7 3,1 5 000 B8 2,9 5 100
      Figure 00250001
      Figure 00260001
    The process which is the subject of the invention has the following advantages:
    • By comparison with Example 1, a better densification is therefore obtained with a sintering carried out at a lower temperature and / or for a shorter duration, which improves the residual induction and the coercivity.
    • The additive powder (B) contains all of the addition elements allowing, during the sintering operation, carried out at low temperature (1050 ° C - 1070 ° C), to form the phase rich in TR, liquid, containing cobalt and other elements such as aluminum, copper, silicon and impurities and during cooling after sintering give rise to the formation of additional magnetic phase TR 2 Fe 14 B, without requiring the difficult dissolution of the phase TR 1 + ε Fe 4 B 4 necessary in the prior art, and thus leading to obtaining very high magnetic properties.
    • It can also be seen that the sintered magnet according to the invention does not contain a TR 1 + ε Fe 4 B 4 phase.
    • the hydriding treatment of the powder (C) makes it possible, as in the prior art, to obtain a fine and homogeneous dispersion of its constituents and thus to facilitate densification during sintering at low temperature even for low contents in TR and obtaining high magnetic properties (B r , H cj ) as well as better corrosion resistance.
    • the addition of the powder (D) containing the boron in the powder (C) allows a fine adjustment of the final content of this element in order to maximize the persistence of the final magnet. Compositions (A) (by weight%) Nd Dy B Al V Cu Fe A1 27.0 1.5 1.06 0.3 0 0.03 ba1 A2 27.5 1.0 1.06 0.3 0 0.03 ba1 A3 26.0 1.5 1.06 0.3 0 0.03 ba1 A4 27.0 1.5 1.0 0.3 0 0.03 ba1 AT 5 27.0 1.5 1.15 0.3 0 0.03 ba1 A6 28.1 0 1.17 0 1.0 0.03 69.43 A7 28.1 0 1.13 0 0 0.03 70.7 AT 8 28.1 0 1.0 0 0 0.03 70.9 Compositions (B) (by weight%) Nd Dy Co Fe Al V Cu B B1 59.1 1.5 32.0 7.1 0.3 0 0.03 0 B2 59.8 1.0 32.0 6.9 0.3 0 0.03 0 B3 59.0 1.5 32.0 6.1 0.3 0 0.03 1.05 B4 67.2 1.5 31.0 0 0.3 0 0.03 0 B5 50.0 1.5 33.0 15.2 0.3 0 0.03 0 B6 52.0 10.0 33.0 2.0 3.0 0 0.03 0 B7 52.0 10.0 24.0 2.0 3.0 9.0 0.03 0 B8 52.0 10.0 24.0 1.0 3.0 9.0 0.03 1.10 B9 59.1 1.5 32.0 7.1 0.3 0 0.03 0 B10 59.1 1.5 32.0 6.9 0.3 0 0.03 0.2 Characteristics of powders Landmark FSSS 02 ppm A1 4.5 2900 A2 4.7 3100 A3 4.5 2800 A4 4.7 2800 AT 5 4.8 3000 A6 4.2 3000 A7 4.5 3200 AT 8 4.6 2900 B1 3.2 5100 B2 3.3 4800 B3 3.9 6000 B4 3.1 5200 B5 3.4 4800 B6 3.5 5000 B7 3.4 4900 B8 3.3 5200 B9 3.4 10200 B10 3.3 5500
      Figure 00200001
      Figure 00210001
      Compositions (A) - by weight% - Nd Dy B Al Cu Yes Fe A1 27.0 1.5 1.06 0.3 0.03 0.05 rest A2 27.0 1.5 0.98 0.3 0.03 0.05 rest Compositions (C) - by weight% - Nd Dy B Co Al Cu Yes Fe C1 59.1 1.5 0 32.0 0.3 0.03 0.05 rest C2 59.1 1.5 0.2 32.0 0.3 0.03 0.05 rest Composition (D) - by weight% - B Al Cu Yes Fe D1 17.0 2.0 0.5 0.5 rest
      Figure 00230001
      Characteristics of fine powders Landmarks FSSS O 2 ppm A1 4.1 2,800 A2 4.2 3,100 B1 3.0 4,300 B2 2.8 5,500 B3 3.3 4,600 B4 3.1 4,800 B5 2.8 4,700 B6 2.5 6,200 B7 3.1 5,000 B8 2.9 5,100
      Figure 00250001
      Figure 00260001

    Claims (29)

    1. 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 such as Fe and/or Co, B represents boron, the powder possibly containing other minor elements, the powder having a structure consisting mainly of grains of quadratic phase RE2T14B, a secondary phase consisting mainly of RE, and possibly comprising other minor phases, the initial magnetic powder being constituted by a mixture of two powders (A) and (B) :
      a) Powder (A) consists of grains with a quadratic structure RE2T14B, T being primarily iron with Co/Fe < 8 %, and which may also 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 µm;
      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 x %RE; Co 20-35 %; Fe 0-20 %; B ≤ 0-0.2 %; Al 0.1-4 %; and unavoidable impurities, the powder having a Fisher granulometry of between 2.5 and 3.5 µm.
    2. Magnetic powder according to claim 1 characterised in that the granulometry of powder (B) is lower than that of powder (A) by at least 20 %.
    3. Magnetic powder according to claim 1 or claim 2, characterised in that powder (B) is practically free of boron.
    4. Magnetic powder according to any one of claims 1 to 3, characterised in that the liquidus temperature of powder (B) is less than or equal to 1080°C.
    5. Magnetic powder according to claim 4, characterised in that the liquidus temperature is less than 1050°C.
    6. Magnetic powder according to any one of claims 1 to 5, characterised in that powder (A) represents 88 to 95 % (by weight) of the mixture (A) + (B).
    7. Magnetic powder according to claim 6, characterised in that powder (A) represents 90 to 94 % (by weight) of the mixture (A) + (B).
    8. Method of manufacture of a powder (B) as defined in any one of claims 1 to 4, wherein the initial alloy is treated with hydrogen before milling under the following conditions: put under vacuum, introduction of an inert gas at a pressure of between 0.1 and 0.12 MPa, raise temperature at a rate of between 10°C/h and 500°C/h up to a temperature of between 350 and 450°C, introduction of hydrogen at an absolute partial pressure of between 0.01 and 0.12 MPa and maintain these conditions for 1 to 4 hours, then put under vacuum and introduction of an inert gas at a pressure of 0.1 to 0.12 MPa, cooling to room temperature at a rate of between 5°C/h and 100°C/h.
    9. Method according to claim 8, characterised in that the hydrogen treatment is preceded by a prior hydrogen treatment step consisting of holding the initial alloy at an absolute partial pressure of hydrogen of between 0.01 and 0.12 MPa for 1 to 3 hours at room temperature.
    10. Method according to claim 8 or claim 9,
      characterised in that the prior (cold) and principal (hot) treatment steps under hydrogen are repeated up to two times.
    11. Method according to any one of claims 8 to 10, characterised in that the inert gas is argon or helium or a mixture of the two gases.
    12. Method of manufacture of powder (A) as defined in claim 1, wherein the initial alloy is treated with hydrogen before milling under the following conditions: put under vacuum, introduction of an inert gas at a pressure of between 0.1 and 0.12 MPa, raise temperature at a rate of between 10°C/h and 500°C/h up to a temperature of between 350 and 450°C, introduction of hydrogen at an absolute partial pressure of between 0.01 and 0.12 MPa and maintain these conditions for 1 to 4 hours, then put under vacuum and introduction of an inert gas at a pressure of 0.1 to 0.12 MPa, cooling to room temperature at a rate of between 5°C/h and 100°C/h.
    13. Method according to claim 12, characterised in that the inert gas is argon or helium or a mixture of the two gases.
    14. Magnetic powder produced in accordance with claim 1, characterised in that the RE content is between 29 and 32 % by weight.
    15. Magnetic powder according to claim 14, characterised in that the O2 content is less than 3500 ppm.
    16. Magnetic powder according to claim 14, characterised in that the RE content is between 29 and 31 % by weight.
    17. Sintered magnet of the RE-T-B family, resulting from the use of the powder of claim 1 where RE represents at least one rare earthn, T represents at least one transition element such as Fe and/or Co, B represents boron, the powder possibly containing other minor elements, the powder having a structure consisting mainly of quadratic phase (T1) RE2T14B, a secondary phase consisting mainly of RE, and possibly other minor phases, characterised in that the Co is mainly located in the secondary phase with an average Co content ≥ 10% by weight.
    18. Magnet according to claim 17, characterised in that it contains less than 3500 ppm of oxygen.
    19. Additive powder (B) according to any one of claims 1 or 2, this additive powder consisting of a mixture of powders (C) and (D):
      a) powder (C) is rich in RE, contains Co and has the following composition by weight :
      RE 52-70% ; comprising at least 40 % (absolute) of one or more light rare earth(s) selected from the group La, Ce, Pr, Nd, Sm, Eu; a hydrogen content (ppm by weight) of greater than 130 x %RE; Co-20-35 % ; Fe 0-20% ; B 0-0.2% ; Al 0.1-4%; and unavoidable impurities.
      b) powder (B) is composed of B alloyed with at least one of the following elements :
      Al, Si, V, Cr, Mn, Fe, Co, Ni, Cu, Nb, Mo,
      and containing between 5 and 70 % by weight of boron along with unavoidable impurites.
    20. Additive powder (B) according to claim 19, characterised in that the B content is between 0.4 and 1.2%.
    21. Magnetic powder consisting of a mixture of 88 to 95% of powder (A) and 5 to 12% of powder (B) according to any one of claims 19 or 20, powder (A) consisting of quadratic grains RE2T14B, T consisting mainly of iron with Co/Fe ≤ 8% and containing 0.95 to 1.05% B and possibly also containing 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 powder having a Fisher granulometry of between 3.5 and 5µm.
    22. Additive powder (B) according to any one of claims 19 to 21, characterised in that RE rich powder (C) is practically free of boron.
    23. Additive powder (B) according to claim 22, characterised in that the liquidus temperature is lower than or equal to 1050°C.
    24. Additive powder (B) according to claim 22, characterised in that it is mixed with a powder (A) which has a composition very close to that of the magnetic phase RE2 T14B
    25. Magnetic powder according to claim 24, characterised in that the granulometry of powder (B) is at least 20% lower than that of powder (A).
    26. Sintered permanent magnet resulting in particular from the use of the powder of claim 1 and comprising 29 to 32% RE, 0.93 to 1.04% B, 1 to 4.3% Co, 0.2 to 0.5% Al, 0.02 to 0.05% Cu, the remainder consisting of Fe and unavoidable impurities, characterised in that the remanance is greater than 1.32 T.
    27. Permanent magnet according to claim 26, characterised in that the remanance is greater than 1.35 T.
    28. Permanent magnet according to claim 26 or claim 27, characterised in that the intrinsic coercivity is greater than 1150 kA/m.
    29. Permanent magnet according to any one of claims 26 to 28, characterised in that the oxygen content is less than 3500 ppm.
    EP93420483A 1992-12-08 1993-12-07 R-Fe-B type magnet powder, sintered magnets therefrom and preparation process Expired - Lifetime EP0601943B1 (en)

    Applications Claiming Priority (4)

    Application Number Priority Date Filing Date Title
    FR9214995 1992-12-08
    FR9214995A FR2698999B1 (en) 1992-12-08 1992-12-08 Magnetic powder of Fe-TR-B type and corresponding sintered magnets and their method of preparation.
    FR9308586A FR2707421B1 (en) 1993-07-07 1993-07-07 Additive powder for the manufacture of sintered magnets type Fe-Nd-B, manufacturing method and corresponding magnets.
    FR9308586 1993-07-07

    Publications (2)

    Publication Number Publication Date
    EP0601943A1 EP0601943A1 (en) 1994-06-15
    EP0601943B1 true EP0601943B1 (en) 1998-05-20

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    EP93420483A Expired - Lifetime EP0601943B1 (en) 1992-12-08 1993-12-07 R-Fe-B type magnet powder, sintered magnets therefrom and preparation process

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    US (1) US5482575A (en)
    EP (1) EP0601943B1 (en)
    JP (1) JP3594326B2 (en)
    AT (1) ATE166488T1 (en)
    CA (1) CA2110846A1 (en)
    DE (1) DE69318682T2 (en)
    ES (1) ES2117117T3 (en)
    FI (1) FI113209B (en)
    SI (1) SI9300639A (en)

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    EP0789367A1 (en) * 1996-02-09 1997-08-13 Crucible Materials Corporation Method for producing selected grades of rare earth magnets using a plurality of particle batches
    DE19636285C2 (en) * 1996-09-06 1998-07-16 Vakuumschmelze Gmbh Process for producing an SE-Fe-B permanent magnet
    JP3901259B2 (en) * 1996-09-30 2007-04-04 本田技研工業株式会社 SmFe-based magnetostrictive material
    US6425961B1 (en) * 1998-05-15 2002-07-30 Alps Electric Co., Ltd. Composite hard magnetic material and method for producing the same
    US20050062572A1 (en) * 2003-09-22 2005-03-24 General Electric Company Permanent magnet alloy for medical imaging system and method of making
    JP4534553B2 (en) * 2004-03-30 2010-09-01 Ｔｄｋ株式会社 R-T-B system sintered magnet and manufacturing method thereof
    JP5115511B2 (en) * 2008-03-28 2013-01-09 Ｔｄｋ株式会社 Rare earth magnets
    JP2011258935A (en) * 2010-05-14 2011-12-22 Shin Etsu Chem Co Ltd R-t-b-based rare earth sintered magnet
    JP7099924B2 (en) * 2018-09-21 2022-07-12 トヨタ自動車株式会社 Rare earth magnets and their manufacturing methods
    KR102589893B1 (en) * 2019-09-26 2023-10-16 주식회사 엘지화학 Method for preparing sintered magnet and sintered magnet
    CN110957125B (en) * 2019-12-24 2021-11-05 厦门钨业股份有限公司 Sintering method of neodymium iron boron permanent magnet material and neodymium iron boron permanent magnet material
    CN111180158A (en) * 2019-12-30 2020-05-19 宁波韵升股份有限公司 R-T-B series sintered permanent magnet and preparation method thereof

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    DE69318682T2 (en) 1998-11-26
    CA2110846A1 (en) 1994-06-09
    ATE166488T1 (en) 1998-06-15
    ES2117117T3 (en) 1998-08-01
    FI935472A0 (en) 1993-12-07
    SI9300639A (en) 1994-06-30
    JP3594326B2 (en) 2004-11-24
    EP0601943A1 (en) 1994-06-15
    JPH06231916A (en) 1994-08-19
    FI935472A (en) 1994-06-09
    DE69318682D1 (en) 1998-06-25
    FI113209B (en) 2004-03-15
    US5482575A (en) 1996-01-09

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