EP0608188A1 - Protecting process for magnetic powders and densified permanent magnets of Nd-Fe-B type against oxidation and atmospheric corrosion - Google Patents

Protecting process for magnetic powders and densified permanent magnets of Nd-Fe-B type against oxidation and atmospheric corrosion Download PDF

Info

Publication number
EP0608188A1
EP0608188A1 EP94420016A EP94420016A EP0608188A1 EP 0608188 A1 EP0608188 A1 EP 0608188A1 EP 94420016 A EP94420016 A EP 94420016A EP 94420016 A EP94420016 A EP 94420016A EP 0608188 A1 EP0608188 A1 EP 0608188A1
Authority
EP
European Patent Office
Prior art keywords
powders
fluorine
ppm
atmospheric corrosion
magnets
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP94420016A
Other languages
German (de)
French (fr)
Other versions
EP0608188B1 (en
Inventor
Masato Sagawa
Fernand Vial
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Ugimag SA
Original Assignee
Ugimag SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ugimag SA filed Critical Ugimag SA
Publication of EP0608188A1 publication Critical patent/EP0608188A1/en
Application granted granted Critical
Publication of EP0608188B1 publication Critical patent/EP0608188B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
    • H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
    • H01F41/0253—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets
    • H01F41/026—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets protecting methods against environmental influences, e.g. oxygen, by surface treatment
    • 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
    • H01F1/0572—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 with a protective layer

Definitions

  • the present invention relates to a method of protecting magnetic powders and permanent magnets of the transition metal - rare earth metal type against oxidation and atmospheric corrosion by the introduction of gaseous fluorine during the grinding of the powders. It applies more particularly to powders and magnets of the transition metal - rare earth - boron family, where the metal is essentially iron, and the rare earth essentially of neodymium and / or praseodymium.
  • the process illustrated here by way of example, consists in introducing during the fine grinding step, for example, into a gas jet mill (jet mill) a mixture N 2 + F 2 , which can contain between 1 and 100 ppm in flight. of fluorine, and preferably between 1 and 10 ppm, with the usual carrier gas flow rates and grinding time for this operation (for example 100 Nm 3 / h of nitrogen under a relative pressure of 0.5 Pa, for 3 h ).
  • a gas jet mill jet mill
  • the optimum fluorine content of powders and sintered magnets is between 600 and 2000 ppm. Below 600 ppm, the resistance to powder oxidation and to corrosion in a humid atmosphere of the magnets is insufficient; beyond 2000 ppm, densification defects are noted during densification and weaker intrinsic coercive fields.
  • Powders treated with fluorine are more stable with respect to atmospheric oxidation.
  • the flow rate of the F 2 + N 2 gas mixture was controlled by a calibrated nozzle and by the pressure difference upstream and downstream of the nozzle.
  • the powders thus obtained were axially compressed under an axial field of 1.1 T, at a pressure of 1.6 t / cm 2 in cylindrical samples 15 mm in diameter and 12 mm high.
  • densification was obtained by sintering carried out under vacuum at temperatures between 1060 and 1090 ° C for 4 hours.
  • the blanks thus obtained underwent the usual heat treatments of magnetic hardening, adjusted according to the rare earth content.
  • Alloy powders of the initial composition given in Table V were prepared and ground in a gas mill with or without the introduction of fluorine, under conditions analogous to those of Example 1, the fluorine content in the grinding chamber being 1 ppm (in vol.) in nitrogen.
  • the present process has been illustrated in the production range of powders and magnets by sintering these powders of the TR 2 Fe 14 B type enriched with rare earth.
  • these fine powders are obtained from alloy ingots, but they can also be obtained from coarse powders obtained by the so-called reduction-diffusion process.

Abstract

This invention relates to a method of protecting magnetic powders and permanent magnets containing at least one rare earth, at least one transition metal and boron, against oxidation and atmospheric corrosion by introducing gaseous fluorine during the grinding of the powders. It is characterised in that the fluorine is introduced using a F2 + N2 mixture during the fine grinding of the powders, this mixture containing between 1 and 100 ppm (by volume) of fluorine, and preferably between 1 and 10 ppm. The powders thus obtained are markedly less reactive and the densified magnets are markedly more resistant to atmospheric corrosion than non-fluorinated powders and magnets obtained from the latter.

Description

Cette invention concerne une méthode de protection des poudres magnétiques et des aimants permanents de type métal de transition - métal de terre rare contre l'oxydation et la corrosion atmosphérique par introduction de fluor gazeux lors du broyage des poudres. Elle s'applique plus particulièrement aux poudres et aimants de la famille métal de transition - terre rare - bore, où le métal est essentiellement du fer, et la terre rare essentiellement du néodyme et/ou praséodyme.The present invention relates to a method of protecting magnetic powders and permanent magnets of the transition metal - rare earth metal type against oxidation and atmospheric corrosion by the introduction of gaseous fluorine during the grinding of the powders. It applies more particularly to powders and magnets of the transition metal - rare earth - boron family, where the metal is essentially iron, and the rare earth essentially of neodymium and / or praseodymium.

L'introduction de fluor dans les aimants frittés type Fe Nd B est connue, notamment par les demandes de brevetJP 3-188241 de SUMITOMO, dans lequel le fluor est introduit via un fluorure de Li au cours du broyage de pulvérisation ou encore JP 62-188757 dans lequel l'aimant contient un fluorure de Ba, Sr, Ca ou Pb.The introduction of fluorine into sintered magnets of the Fe Nd B type is known, in particular from patent applications JP 3-188241 by SUMITOMO, in which the fluorine is introduced via a Li fluoride during pulverization grinding or else JP 62- 188757 in which the magnet contains a fluoride of Ba, Sr, Ca or Pb.

Cependant, ces aimants et la méthode de production possèdent les inconvénients suivants :

  • La dispersion de façon homogène d'une poudre représentant une faible proportion d'un mélange donné est une opération difficile à réaliser. Ces ajouts introduisent des tiers éléments réactifs (Li, Ba, Sr, Ca) dont le comportement à l'oxydation et à la corrosion est incertain, et probablement néfaste.
However, these magnets and the method of production have the following disadvantages:
  • The homogeneous dispersion of a powder representing a small proportion of a given mixture is a difficult operation to carry out. These additions introduce third reactive elements (Li, Ba, Sr, Ca), the oxidation and corrosion behavior of which is uncertain and probably harmful.

Pour éviter ces inconvénients, selon l'invention, le procédé, ici illustré à titre d'exemple, consiste à introduire lors de l'étape de broyage fin, par exemple, dans un broyeur à jet de gaz (jet mill) un mélange N2 + F2, pouvant contenir entre 1 et 100 ppm en vol. de fluor, et de préférence entre 1 et 10 ppm, avec les débits de gaz vecteur et temps de broyage habituels pour cette opération (par exemple 100 Nm3/h d'azote sous une pression relative de 0,5 Pa, pendant 3 h).To avoid these drawbacks, according to the invention, the process, illustrated here by way of example, consists in introducing during the fine grinding step, for example, into a gas jet mill (jet mill) a mixture N 2 + F 2 , which can contain between 1 and 100 ppm in flight. of fluorine, and preferably between 1 and 10 ppm, with the usual carrier gas flow rates and grinding time for this operation (for example 100 Nm 3 / h of nitrogen under a relative pressure of 0.5 Pa, for 3 h ).

La teneur optimale en fluor des poudres et aimants frittés est comprise entre 600 et 2000 ppm. Au-dessous de 600 ppm, la résistance à l'oxydation des poudres et à la corrosion en atmosphère humide des aimants est insuffisante ; au-delà de 2000 ppm, on constate des défauts de densification lors de la densification et des champs coercitifs intrinsèques plus faibles.The optimum fluorine content of powders and sintered magnets is between 600 and 2000 ppm. Below 600 ppm, the resistance to powder oxidation and to corrosion in a humid atmosphere of the magnets is insufficient; beyond 2000 ppm, densification defects are noted during densification and weaker intrinsic coercive fields.

Les ai mants densifiés obtenus avec ce procédé présentent sur les ai mants de l'art antérieur les avantages suivants :

  • - l'introduction de fluor sous forme gazeuse permet de passiver de façon uniforme et efficace toute la surface développée de la poudre
  • - l'introduction de fluor diminue d'un facteur 2 env. la prise d'oxygène durant la phase de broyage.
The densified magnets obtained with this process have the following advantages over the magnets of the prior art:
  • - the introduction of fluorine in gaseous form makes it possible to passivate the entire developed surface of the powder in a uniform and efficient manner
  • - the introduction of fluorine decreases by a factor of 2 approx. oxygen uptake during the grinding phase.

Il en résulte qu'il est possible de diminuerla teneuren terres rares (TR), non piégées sous forme d'oxydes, ce qui permet un gain d'environ 0,04 T sur la rémanence par % de réduction de la teneur totale en terres rares.As a result, it is possible to reduce the content of rare earths (TR), not trapped in the form of oxides, which allows a gain of about 0.04 T on the remanence per% reduction in the total earth content. rare.

Les poudres traitées au fluor sont plus stables vis-à-vis de l'oxydation atmosphérique.Powders treated with fluorine are more stable with respect to atmospheric oxidation.

La résistance à la corrosion atmosphérique humide des aimants densifiés est considérablement augmentée.The resistance to wet atmospheric corrosion of densified magnets is considerably increased.

Le broyage des poudres est plus aisé.Grinding powders is easier.

L'invention sera mieux comprise à l'aide des exemples suivants :The invention will be better understood using the following examples:

Exemple 1Example 1

Une poudre magnétique de composition chimique suivante (en poids %)

Figure imgb0001

obtenue par traitement sous H2 à 400° C de lingots broyés mécaniquement à une granulométrie moyenne de 500 f..lm, a été pulvérisée dans un broyeur à jet de gaz comportant une chambre d'environ 2 litres par un mélange N2 + F2 à raison de 100 m3/h sous la pression relative de 0,5 MPa pendant 3 heures, dans les conditions données au Tableau I.A magnetic powder with the following chemical composition (by weight%)
Figure imgb0001
obtained by treatment under H 2 at 400 ° C of ingots milled mechanically to an average particle size of 500 f..lm, was pulverized in a gas jet mill comprising a chamber of approximately 2 liters with an N 2 + F mixture 2 at a rate of 100 m 3 / h under the relative pressure of 0.5 MPa for 3 hours, under the conditions given in Table I.

Le débit du mélange F2+N2 gazeux était contrôlé par un ajutage calibré et par la différence de pression amont et aval de l'ajutage.The flow rate of the F 2 + N 2 gas mixture was controlled by a calibrated nozzle and by the pressure difference upstream and downstream of the nozzle.

Des essais comparatifs ont été effectués sans introduction de fluor.Comparative tests were carried out without the introduction of fluorine.

Les poudres ainsi obtenues ont été comprimées axialement sous champ axial de 1,1 T, à la pression de 1, 6 t/cm2 en échantillons cylindriques de 15 mm de diamètre et de 12 mm de haut.The powders thus obtained were axially compressed under an axial field of 1.1 T, at a pressure of 1.6 t / cm 2 in cylindrical samples 15 mm in diameter and 12 mm high.

Dans ces exemples, la densification a été obtenue par frittage effectué sous vide à des températures comprises entre 1060 et 1090° C pendant 4 heures.In these examples, densification was obtained by sintering carried out under vacuum at temperatures between 1060 and 1090 ° C for 4 hours.

Les ébauches ainsi obtenues ont subi les traitements thermiques habituels de durcissement magnétique, ajustés selon la teneur en terre rare.The blanks thus obtained underwent the usual heat treatments of magnetic hardening, adjusted according to the rare earth content.

On a relevé :

  • - la prise d'oxygène à l'air ambiant (23°C, 55 % humidité relative) des poudres broyées jusqu'à 24 h (Tableau II)
  • - les caractéristiques magnétiques des aimants densifiés (Tableau III)
  • - leur résistance à la corrosion en milieu humide a été caractérisée par la perte de poids des échantillons nettoyés aux ultra-sons, après maintien dans les conditions suivantes :
We noted:
  • - the oxygen intake in the ambient air (23 ° C, 55% relative humidity) of the ground powders up to 24 hours (Table II)
  • - the magnetic characteristics of the densified magnets (Table III)
  • - their resistance to corrosion in a humid environment was characterized by the loss of weight of the samples cleaned with ultrasound, after maintenance under the following conditions:

115° C, 0,15 MPa, 100 % humidité relative, jusqu'à 120 h (Tableau IV)

Figure imgb0002
Figure imgb0003
Figure imgb0004
Figure imgb0005
 115 ° C, 0.15 MPa, 100% relative humidity, up to 120 h (Table IV)
Figure imgb0002
Figure imgb0003
Figure imgb0004
Figure imgb0005

Exemple 2Example 2

Des poudres d'alliages de la composition initiale donnée au Tableau V ont été élaborées et broyées au broyeur à gaz avec ou sans introduction de fluor, dans des conditions analogues à celles de l'exemple 1, la teneur en fluor dans la chambre de broyage étant de 1 ppm (en vol.) dans de l'azote.Alloy powders of the initial composition given in Table V were prepared and ground in a gas mill with or without the introduction of fluorine, under conditions analogous to those of Example 1, the fluorine content in the grinding chamber being 1 ppm (in vol.) in nitrogen.

On a contrôlé la prise d'oxygène durant le broyage, la stabilité des poudres vis à vis de l'oxydation à l'air, dans les mêmes conditions que l'exemple 1, ainsi que les propriétés magnétiques des aimants densifiés préparés dans les mêmes conditions que l'exemple 1.

Figure imgb0006
Figure imgb0007
Figure imgb0008
 The oxygen uptake during the grinding, the stability of the powders with respect to oxidation in air was controlled under the same conditions as in Example 1, as well as the magnetic properties of the densified magnets prepared in the same conditions as in example 1.
Figure imgb0006
Figure imgb0007
Figure imgb0008

On constate que l'introduction de fluor durant le broyage fin confère aux poudres une bonne stabilité à l'air et conduit à des aimants à hautes caractéristiques magnétiques, particulièrement pour des teneurs totales en terres rares inférieures à 30%.It is found that the introduction of fluorine during fine grinding gives the powders good air stability and leads to magnets with high magnetic characteristics, particularly for total rare earth contents of less than 30%.

Le présent procédé a été illustré dans la gamme de production de poudres et d'aimants par frittage de ces poudres de type TR2 Fe14 B enrichis en terre rare. En général, ces poudres fines sont obtenues à partir de lingots d'alliage, mais elles peuvent également être obtenues à partir de poudres grossières obtenues par le procédé dit de réduction-diffusion.The present process has been illustrated in the production range of powders and magnets by sintering these powders of the TR 2 Fe 14 B type enriched with rare earth. In general, these fine powders are obtained from alloy ingots, but they can also be obtained from coarse powders obtained by the so-called reduction-diffusion process.

Claims (4)

1. Méthode de protection de poudres magnétiques et d'aimants permanents densifiés contenant au moins une terre rare, au moins un métal de transition et du bore contre l'oxydation et la corrosion atmosphérique, caractérisée en ce que on introduit du fluor par un mélange gazeux F2 + N2 au cours du broyage fin des poudres, ce mélange gazeux contenant de 1 à 100 ppm (en vol.) de fluor.1. Method for protecting magnetic powders and densified permanent magnets containing at least one rare earth, at least one transition metal and boron against oxidation and atmospheric corrosion, characterized in that fluorine is introduced by a mixture gaseous F 2 + N 2 during the fine grinding of the powders, this gaseous mixture containing from 1 to 100 ppm (in vol.) of fluorine. 2. Méthode selon la revendication 1, caractérisée en ce que la teneur en fluor du mélange gazeux est comprise entre 1 et 10 ppm.2. Method according to claim 1, characterized in that the fluorine content of the gas mixture is between 1 and 10 ppm. 3. Poudre obtenue selon l'une des revendications 1 ou 2, caractérisée en ce qu'elle contient entre 600 et 2000 ppm de fluor.3. Powder obtained according to one of claims 1 or 2, characterized in that it contains between 600 and 2000 ppm of fluorine. 4. Aimant permanent densifié obtenu à partir de la poudre selon l'une des revendications 1 ou 2, caractérisé en ce qu'il contient entre 600 et 2000 ppm de fluor.4. Densified permanent magnet obtained from the powder according to one of claims 1 or 2, characterized in that it contains between 600 and 2000 ppm of fluorine.
EP94420016A 1993-01-22 1994-01-19 Protecting process for magnetic powders and densified permanent magnets of Nd-Fe-B type against oxidation and atmospheric corrosion Expired - Lifetime EP0608188B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9300840A FR2700720B1 (en) 1993-01-22 1993-01-22 Process for the protection of densified magnetic powders and permanent magnets type Fe Nd B against oxidation and atmospheric corrosion.
FR9300840 1993-01-22

Publications (2)

Publication Number Publication Date
EP0608188A1 true EP0608188A1 (en) 1994-07-27
EP0608188B1 EP0608188B1 (en) 1996-10-02

Family

ID=9443427

Family Applications (1)

Application Number Title Priority Date Filing Date
EP94420016A Expired - Lifetime EP0608188B1 (en) 1993-01-22 1994-01-19 Protecting process for magnetic powders and densified permanent magnets of Nd-Fe-B type against oxidation and atmospheric corrosion

Country Status (10)

Country Link
US (1) US5411603A (en)
EP (1) EP0608188B1 (en)
JP (1) JP3400840B2 (en)
AT (1) ATE143745T1 (en)
CA (1) CA2112868A1 (en)
DE (1) DE69400618T2 (en)
FI (1) FI940318A (en)
FR (1) FR2700720B1 (en)
MX (1) MX9400180A (en)
SI (1) SI9400020A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6580820B1 (en) 1999-06-09 2003-06-17 Xerox Corporation Digital imaging method and apparatus for detection of document security marks

Families Citing this family (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5437544B2 (en) * 2001-06-11 2014-03-12 株式会社三徳 Manufacturing method of negative electrode for secondary battery
JP4747562B2 (en) * 2004-06-25 2011-08-17 株式会社日立製作所 Rare earth magnet, manufacturing method thereof, and magnet motor
US8211327B2 (en) * 2004-10-19 2012-07-03 Shin-Etsu Chemical Co., Ltd. Preparation of rare earth permanent magnet material
TWI364765B (en) * 2005-03-23 2012-05-21 Shinetsu Chemical Co Rare earth permanent magnet
TWI413137B (en) 2005-03-23 2013-10-21 Shinetsu Chemical Co Functionally graded rare earth permanent magnet
TWI413136B (en) * 2005-03-23 2013-10-21 Shinetsu Chemical Co Rare earth permanent magnet
TWI417906B (en) * 2005-03-23 2013-12-01 Shinetsu Chemical Co Functionally graded rare earth permanent magnet
JP4656323B2 (en) * 2006-04-14 2011-03-23 信越化学工業株式会社 Method for producing rare earth permanent magnet material
US7955443B2 (en) * 2006-04-14 2011-06-07 Shin-Etsu Chemical Co., Ltd. Method for preparing rare earth permanent magnet material
JP4840606B2 (en) 2006-11-17 2011-12-21 信越化学工業株式会社 Rare earth permanent magnet manufacturing method
DE102007032406B3 (en) * 2007-07-10 2008-10-23 Gkss-Forschungszentrum Geesthacht Gmbh Process to form an alloy for e.g. gas turbine engine by combination of molten titanium and aluminum in presence of halogen-enriched gas
JP2012039017A (en) * 2010-08-11 2012-02-23 Hitachi Ltd Magnet material, magnet molding and rotary machine
CN113444982A (en) * 2020-03-25 2021-09-28 Neo新材料技术（新加坡）私人有限公司 Alloy powder and preparation method thereof

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH01205502A (en) * 1988-02-12 1989-08-17 Seiko Epson Corp Rare earth and iron-based resin-bonded magnet

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS61124502A (en) * 1984-11-21 1986-06-12 Mitsui Mining & Smelting Co Ltd Stable magnetic metallic powder and its production

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH01205502A (en) * 1988-02-12 1989-08-17 Seiko Epson Corp Rare earth and iron-based resin-bonded magnet

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
J.H.SWISHER ET AL, JOURNAL OF THE ELECTROCHEMICAL SOCIETY, vol. 117, no. 4, April 1970 (1970-04-01), MANCHESTER, NEW HAMPSHIRE US, pages 537 - 540 *
PATENT ABSTRACTS OF JAPAN vol. 13, no. 509 (E - 846) 15 November 1989 (1989-11-15) *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6580820B1 (en) 1999-06-09 2003-06-17 Xerox Corporation Digital imaging method and apparatus for detection of document security marks

Also Published As

Publication number Publication date
FI940318A0 (en) 1994-01-21
DE69400618D1 (en) 1996-11-07
JP3400840B2 (en) 2003-04-28
CA2112868A1 (en) 1994-07-23
MX9400180A (en) 1994-07-29
EP0608188B1 (en) 1996-10-02
FR2700720B1 (en) 1995-05-05
JPH07320917A (en) 1995-12-08
DE69400618T2 (en) 1997-02-27
FI940318A (en) 1994-07-23
FR2700720A1 (en) 1994-07-29
US5411603A (en) 1995-05-02
ATE143745T1 (en) 1996-10-15
SI9400020A (en) 1994-09-30

Similar Documents

Publication Publication Date Title
EP0608188A1 (en) Protecting process for magnetic powders and densified permanent magnets of Nd-Fe-B type against oxidation and atmospheric corrosion
JP5561170B2 (en) Method for producing RTB-based sintered magnet
JP4831253B2 (en) R-T-Cu-Mn-B sintered magnet
JP5477282B2 (en) R-T-B system sintered magnet and manufacturing method thereof
JP2006210450A (en) R-t-b series sintered magnet
JP2019012796A (en) Method of producing rare earth magnet
JP2009224413A (en) MANUFACTURING METHOD OF NdFeB SINTERED MAGNET
JP6717230B2 (en) Method for manufacturing sintered RTB magnet
EP0428718A1 (en) Improved magnetic materials and process for producing the same
JPH06188113A (en) Manufacture of permanent magnet composed mainly of ndfeb
WO2015182705A1 (en) Method for manufacturing r-t-b sintered magnet
JP7315889B2 (en) Alloy for RTB Permanent Magnet and Method for Producing RTB Permanent Magnet
CN111489874A (en) Method for producing R-T-B sintered magnet
EP0707739B1 (en) Cobalt/rare earth type magnetic powders containing fluorine and corresponding densified permanent magnets and process for the preparation thereof
EP0468903B1 (en) Method for obtaining powdered magnetic material of the rare earth-transition metal-boron type for corrosion resistant magnets
CN112086256B (en) R-Fe-B rare earth sintered magnet and preparation method thereof
JP7380369B2 (en) Manufacturing method of RTB sintered magnet and alloy for diffusion
US20220384072A1 (en) Rare earth sintered magnet and making method
Lee et al. Coercivity Enhancement of Nd-Fe-B Powders via Grain Boundary Diffusion with a Tb/Cu Mixture
JP2021153146A (en) Method for manufacturing r-t-b based sintered magnet
US20230005646A1 (en) Rare-earth sintered magnet
JPH06200307A (en) Production of raw material alloy for rare earth magnet
WO2023080169A1 (en) R-t-b based permanent magnet
SU710791A1 (en) Method of making permanent magnets
JP2021057565A (en) R-t-b based sintered magnet

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AT CH DE ES GB IT LI NL SE

17P Request for examination filed

Effective date: 19940822

17Q First examination report despatched

Effective date: 19951002

GRAH Despatch of communication of intention to grant a patent

Free format text: ORIGINAL CODE: EPIDOS IGRA

GRAH Despatch of communication of intention to grant a patent

Free format text: ORIGINAL CODE: EPIDOS IGRA

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): AT CH DE ES GB IT LI NL SE

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: NL

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 19961002

Ref country code: IT

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRE;WARNING: LAPSES OF ITALIAN PATENTS WITH EFFECTIVE DATE BEFORE 2007 MAY HAVE OCCURRED AT ANY TIME BEFORE 2007. THE CORRECT EFFECTIVE DATE MAY BE DIFFERENT FROM THE ONE RECORDED.SCRIBED TIME-LIMIT

Effective date: 19961002

Ref country code: ES

Free format text: THE PATENT HAS BEEN ANNULLED BY A DECISION OF A NATIONAL AUTHORITY

Effective date: 19961002

Ref country code: AT

Effective date: 19961002

REF Corresponds to:

Ref document number: 143745

Country of ref document: AT

Date of ref document: 19961015

Kind code of ref document: T

REF Corresponds to:

Ref document number: 69400618

Country of ref document: DE

Date of ref document: 19961107

GBT Gb: translation of ep patent filed (gb section 77(6)(a)/1977)

Effective date: 19961104

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: SE

Effective date: 19970102

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: LI

Effective date: 19970131

Ref country code: CH

Effective date: 19970131

NLV1 Nl: lapsed or annulled due to failure to fulfill the requirements of art. 29p and 29m of the patents act
PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

REG Reference to a national code

Ref country code: CH

Ref legal event code: PL

26N No opposition filed
REG Reference to a national code

Ref country code: GB

Ref legal event code: IF02

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 20060112

Year of fee payment: 13

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: GB

Payment date: 20060118

Year of fee payment: 13

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DE

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20070801

GBPC Gb: european patent ceased through non-payment of renewal fee

Effective date: 20070119

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20070119