(19)
(11)EP 2 944 403 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
06.05.2020 Bulletin 2020/19

(21)Application number: 15000390.3

(22)Date of filing:  10.02.2015
(51)Int. Cl.: 
B22F 9/04  (2006.01)
B02C 23/12  (2006.01)
C22C 1/04  (2006.01)
B02C 19/06  (2006.01)
H01F 1/057  (2006.01)
H01F 41/02  (2006.01)

(54)

METHODS FOR POWDERING NDFEB RARE EARTH PERMANENT MAGNETIC ALLOY

VERFAHREN ZUM PULVERISIEREN EINER NDFEB-SELTENERDDAUERMAGNETLEGIERUNG

PROCÉDÉS DE PULVÉRISATION D'UN ALLIAGE MAGNÉTIQUE PERMANENT DE TERRES RARES NDFEB


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 11.05.2014 CN 201410194940

(43)Date of publication of application:
18.11.2015 Bulletin 2015/47

(73)Proprietor: Shenyang General Magnetic Co., Ltd
Shenyang, Liaoning 110179 (CN)

(72)Inventor:
  • Sun, Baoyu
    110179 Liaonging (CN)

(74)Representative: Hanna Moore + Curley 
Garryard House 25/26 Earlsfort Terrace
Dublin 2, D02 PX51
Dublin 2, D02 PX51 (IE)


(56)References cited: : 
CN-A- 103 219 117
CN-B- 101 521 069
JP-A- 2002 033 207
JP-A- 2005 118 625
US-A1- 2011 259 982
CN-A- 103 567 051
CN-U- 203 509 043
JP-A- 2002 175 931
JP-A- 2006 283 099
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description

    BACKGROUND OF THE PRESENT INVENTION


    Field of Invention



    [0001] The present invention relates to permanent magnetic devices, and more particularly methods and devices for powdering the NdFeB rare earth permanent magnetic alloy.

    Description of Related Arts



    [0002] The NdFeB rare earth permanent magnetic alloy is increasingly applied because of its excellent magnetism, and widely applied in medical nuclear magnetic resonance imaging, computer hard disk drives, audio equipment and the mobile phones. Along with the benefits of energy-saving and low-carbon economy, the NdFeB rare earth permanent magnetic alloy is further applied in auto parts, household appliances, energy-saving control motors, hybrid power vehicles and wind generators.

    [0003] In 1983, the Japanese patent applications, JP 1,622,492 and JP 2,137,496, initially disclosed the NdFeB rare earth permanent magnetic alloy of the Japan Sumitomo Special Metals Co., Ltd., wherein the features, the constituents and the preparation method of the NdFeB rare earth permanent magnetic alloy are disclosed; an Nd2Fe14B phase is shown as the main phase; and the grain boundary phase mainly comprises a rich Nd phase, a rich B phase and rare earth oxide impurities. Thereafter, the NdFeB rare earth permanent magnetic alloy has been widely applied because of its excellent magnetism, and has also been called the "permanent magnetism king." In 1997, the Japan Sumitomo Special Metals Co., Ltd. was patented with U.S. Patent No. 5,645,651, which further illustrated adding a Co element and a tetragonal structure to the main phase.

    [0004] Along with the wide application of the NdFeB rare earth permanent magnets, the shortage of the rare earth is increasingly severe, especially the heavy rare earth elements which suffer from a resource shortage, so as to result in the continual rising of rare earth market price. Accordingly, many explorations were done by researchers, including double alloy technology, diffusion metalizing technology, grain boundary phase improvement or recombination technology.

    [0005] Chinese patent application publication, CN101521069B, disclosed the NdFeB preparation technology via adding nano-particles of the heavy rare earth hydrides, the preparation method including the steps of: obtaining alloy flakes via strip casting, powdering through the hydrogen pulverization and the jet mill, then mixing the heavy rare earth hydride nano-particles which are prepared through the physical vapor deposition with the powder, and obtaining the NdFeB magnets through techniques such as compacting in the magnetic field and sintering. Although the NdFeB preparation method thereof improved the coercive force of the magnets, the mass production thereof still remains deficient.

    [0006] Chinese patent publication, CN1272809C, disclosed a preparation method of the alloy powder of R-Fe-B series for a rare earth magnet, wherein the jet mill powdering technology includes the steps of: fine pulverizing the alloy via the high-speed gas flow of the inert gas having the oxygen content of 0.02%∼5%, eliminating the readily oxidized super-fine powder having the particle size smaller than 1 µm, and controlling the amount ratio of the super-fine powder to the whole powder below 10%. However, the preparation method and the devices thereof have low yield and waste expensive rare earth raw materials. By improving the structure of the device and the powder collecting system, and improving the powdering method and the preparation method of the NdFeB rare earth permanent magnet, the present invention reduces the amount of the super-fine powder, recycles the super-fine powder which was wasted in the Chinese patent publication CN1272809C, and avoids the waste of the rare earth in the Chinese patent publication CN1272809C.

    [0007] Patent specification number JP2006283099 discloses a method for production of rare earth alloy fine powders by which the rare earth alloy fine powders of a low oxygen content for high magnetic properties are obtained. Patent specification number CN103567051 discloses small-scale lean hematite separation technology comprising multiple steps. Patent specification JP2002033207 discloses a manufacturing method of a rare-earth magnet. Patent specification number CN101521069 discloses a method for preparing a sintered NdFeB permanent magnet. Patent specification number JP2002175931 discloses an RFeB rare earth magnet alloy powder. Patent specification number JP2005118625 discloses a hydrogen grinding apparatus for rare-earth magnet material. Patent specification number CN103219117 discloses a double-alloy neodymium iron boron rare earth permanent magnetic material and a manufacturing method thereof.

    SUMMARY OF THE PRESENT INVENTION



    [0008] An object of the present invention is to provide a powdering which improves magnetism and reduces costs.

    [0009] With the expansion in the application market of NdFeB rare earth permanent magnetic materials, the shortage of the rare earth resources is increasingly severe, especially in the fields of electronic components, energy-saving control electric motors, auto parts, new energy vehicles and wind power generation which needs relatively more heavy rare earth to improve the coercive force. Thus, reducing the usage of the rare earth, especially the usage of the heavy rare earth, is an important issue to be solved. Through applied effort, ingenuity, and innovation, the present invention provides a preparation method of a high-performance NdFeB rare earth permanent magnetic device.

    [0010] Accordingly, in order to accomplish the above objects, the present invention adopts the technical solutions as disclosed in the appended claims.

    [0011] A method for powdering NdFeB rare earth permanet magnetic alloy comprises the step of the appended claim 1.

    [0012] For example, the fine powder which is received and collected by the post cyclone collector is collected through 4 post cyclone collectors which are connected in parallel.

    [0013] A device for powdering NdFeB rare earth permanent magnetic alloy (not part of the invention), comprises a jet mill in a protection of nitrogen which comprises a chopper, a feeder, a grinder having a nozzle and a centrifugal sorting wheel with blades, a cyclone collector, at least one post cyclone collector, a nitrogen compressor and a cooler, wherein the chopper is provided at an upper part of the feeder; the feeder is connected to the grinder via a valve; the nozzle and the centrifugal sorting wheel with blades are provided on the grinder; a gas outlet of the centrifugal sorting wheel is intercommunicated with a gas inlet of the cyclone collector through pipelines; a gas outlet of the cyclone collector is parallel connected with at least one post cyclone collector; each post cyclone collector has a filtering pipe; a gas outlet of each post cyclone collector is connected with a first end of a pneumatic valve; a second end of each pneumatic valve is connected with a discharging pipe which is further connected to a gas inlet of the nitrogen compressor; a gas outlet of the nitrogen compressor is connected to a gas inlet of the cooler; and a gas outlet of the cooler is connected to a gas inlet of the nozzle.

    [0014] A method for preparing a NdFeB rare earth permanent magnet, comprises steps of: smelting an alloy of NdFeB rare earth permanent magnet into alloy flakes; processing the alloy flakes with a hydrogen pulverization and then adding the alloy flakes into a first mixing device for a pre-mixing to create a mixed alloy powder; providing the mixed alloy powder obtained from the hydrogen pulverization into a hopper of a feeder and performing the process step of the appended claim 1; after the depositing tank is filled with the fine powder, sending the fine powder into a second mixing device for post-mixing; then obtaining a NdFeB rare earth permanent magnet via compacting in a magnetic field, sintering in vacuum and processing with an aging treatment; and processing the permanent magnet into a rare earth permanent magnetic device with machining and a surface treatment.

    [0015] In some embodiments, the pre-mixing comprises adding the alloy flakes after the hydrogen pulverization into the first mixing device, and adding at least one of an antioxidant and a lubricant during the pre-mixing.

    [0016] In some embodiments, the pre-mixing comprises adding the alloy flakes after the hydrogen pulverization into the first mixing device, and adding micro powder of at least one oxide during the pre-mixing.

    [0017] In some embodiments, the pre-mixing comprises adding the alloy flakes after the hydrogen pulverization into the first mixing device, and adding micro powder of at least one oxide selected from a group consisting of Y2O3, Al2O3 and Dy2O3 during the pre-mixing.

    [0018] In some embodiments, the pre-mixing comprises adding the alloy flakes after the hydrogen pulverization into the first mixing device, and adding micro powder of Al2O3 the during pre-mixing.

    [0019] In some embodiments, the pre-mixing comprises adding the alloy flakes after the hydrogen pulverization into the first mixing device, and adding micro powder of Dy2O3 during the pre-mixing.

    [0020] In some embodiments, the pre-mixing comprises adding the alloy flakes after the hydrogen pulverization into the first mixing device, and adding micro powder of Y2O3 during the pre-mixing.

    [0021] In some embodiments, the post-mixing comprises sending the fine powder into the second mixing device for post-mixing, which generates the fine powder having an average particle size of between 1.6 µm and 2.9 µm.

    [0022] In some embodiments, the post-mixing comprises sending the fine powder into the second mixing device for post-mixing, which generates the fine powder having an average particle size of between 2.1 µm and 2.8 µm.

    [0023] In some embodiments, the method further comprises steps of: smelting raw materials into the alloy and obtaining strip casting alloy flakes from the alloy, which comprises steps of: heating R-Fe-B-M raw materials up over 500°C in vacuum; filling in argon, and continuing heating to melt and refine the R-Fe-B-M raw materials into a smelt alloy, wherein T2O3 micro powder is added to the R-Fe-B-M raw materials; thereafter, casting the smelt alloy liquid into a rotating roller with water quenching through an intermediate tundish, and obtaining the alloy flakes; wherein
    R comprises at least one rare earth element, Nd;
    M is one or more than one member selected from a group consisting of Al, Co, Nb, Ga, Zr, Cu, V, Ti, Cr, Ni and Hf;
    T2O3 is one or more than one member selected from a group consisting of Dy2O3, Tb2O3, Ho2O3, Y2O3, Al2O3 and Ti2O3; and
    an amount of the T2O3 micro powder is: 0≤T2O3≤2%.

    [0024] Preferably, the amount of the T2O3 micro powder is: 0≤T2O3≤0.8%;
    preferably, the T2O3 micro powder is at least one of Al2O3 and Dy2O3;
    further preferably, the T2O3 micro powder is Al2O3; and
    further preferably, the T2O3 micro powder is Dy2O3.

    [0025] In some embodiments, smelting raw materials into the alloy and obtaining strip casting alloy flakes from the alloy, comprises steps of: heating R-Fe-B-M raw materials and T2O3 micro powder over 500°C in vacuum; filling in argon, and continuing the heating to create a smelt alloy liquid; refining and then casting the smelt alloy liquid into a rotating roller with water quenching through an intermediate tundish; and obtaining the alloy flakes from the smelt alloy after quenching by the rotating roller.

    [0026] In some embodiments, processing the alloy flakes with the hydrogen pulverization comprises steps of: providing the alloy flakes into a rotatable cylinder; vacuumizing, and then filling in hydrogen for the alloy flakes to absorb the hydrogen while controlling a hydrogen absorption temperature at 20 °C∼300 °C; rotating the rotatable cylinder while heating up and vacuumizing the alloy flakes to dehydrogenize, wherein a dehydrogenation heat preservation temperature is controlled at between 500°C and 900 °C for between 3 hours and 15 hours; after heat preservation, cooling the rotatable cylinder by stopping the heating and removing a heating furnace, while continuing rotating the rotatable cylinder and vacuumizing; and when the temperature of the rotatable cylinder drops under 500°C, cooling by spraying water onto the cylinder.

    [0027] In some embodiments, processing the alloy flakes with the hydrogen pulverization comprises steps of: providing a continuous hydrogen pulverization device; loading -rare earth permanent magnetic alloy flakes into a load box; passing the load box which is driven by a transmission device through a hydrogen absorption cavity, a heating and dehydrogenizing cavity and a cooling cavity of the continuous hydrogen pulverization device; receiving the load box by a discharging cavity through a discharging valve; pouring out the alloy flakes after the hydrogen pulverization into a storage tank at a lower part of the discharging cavity; sealing up the storage tank under a protection of nitrogen; moving the load box out through a discharging door of the discharging cavity and re-loading the load box for repeating the previous steps, wherein the hydrogen absorption cavity has a temperature controlled at between 50°C and 350°C for absorbing the hydrogen; the continuous hydrogen pulverization device comprises at least one heating and dehydrogenating cavity whose temperature is controlled at between 600°C and 900 °C for dehydrogenating, and at least one cooling room.

    [0028] In some embodiments, the continuous hydrogen pulverization device comprises two heating and dehydrogenating cavities, wherein the load box stays in the two heating and dehydrogenating cavities successively while staying in the respective heating and dehydrogenating cavity for between 2 hours and 6 hours; the continuous hydrogen pulverization device comprises two cooling cavities, wherein the load box stays in the two cooling cavities successively while staying in the respective cooling cavity for between 2 hours and 6 hours.

    [0029] Preferably, a certain amount of hydrogen is filled in before heating and dehydrogenating is over.

    [0030] In some embodiments, compacting in the magnetic field comprises steps of: loading the NdFeB rare earth permanent magnetic alloy powder into an alignment magnetic field compressor under a protection of nitrogen; under the protection of the nitrogen, in the alignment magnetic field compressor, sending the weighed load into a mold cavity of an assembled mold; then providing a seaming chuck into the mold cavity, and sending the mold into an alignment space of an electromagnet, wherein the alloy powder within the mold is processed with pressure adding and pressure holding, within the alignment magnetic field region; demagnetizing magnetic patches, and thereafter, resetting a hydraulic cylinder; sending the mold back to the powder loading position, opening the mold to retrieve the magnetic patch which is packaged with a plastic or rubber cover; then reassembling the mold and repeating the previous steps; putting the packaged magnetic patch into a load plate, and then extracting the packaged magnetic patch out of the alignment magnetic field compressor; and then, sending the extracted magnetic patch into an isostatic pressing device for isostatic pressing.

    [0031] In some embodiments, compacting in the magnetic field comprises semi-automatically compacting in the magnetic field and automatically compacting in the magnetic field.

    [0032] In some embodiments, semi-automatically compacting in the magnetic field comprises steps of: inter-communicating a storage tank filled with the NdFeB rare earth permanent magnetic alloy powder with a feeding inlet of an alignment magnetic field automatic compressor under the protection of nitrogen; thereafter, discharging air between the storage tank and a valve of the feeding inlet of a semi-automatic compressor; then opening the valve of the feeding inlet to introduce the powder within the storage tank into a hopper of a weighing batcher; after weighing, automatically sending the powder into a mold cavity by a powder sender; after removing the powder sender, moving an upper pressing tank of the compressor downward into the mold cavity for magnetizing and aligning the powder, wherein the powder is compressed and compacted in a magnetic field to form a compacted magnet patch; demagnetizing the compacted magnet patch, and then ejecting the compacted magnet patch out of the mold cavity; sending the compacted magnet patch into a load platform within the alignment magnetic field automatic compressor under the protection of nitrogen; packaging the compacted magnet patch with plastic or rubber cover via gloves to create a packaged magnet patch; sending the packaged magnet patch into the load plate for a batch output, and then isostatic pressing the packaged magnet patch by an isostatic pressing device.

    [0033] In some embodiments, isostatic pressing the packaged magnet patch comprises sending the packaged magnet patch into a high-pressure cavity of the isostatic pressing device, wherein an internal space of the high-pressure cavity except the packaged magnet patch is full of hydraulic oil; sealing and then compressing the hydraulic oil within the high-pressure cavity, wherein the hydraulic oil is compressed with a pressure of between 150 MPa and 300 MPa; decompressing, and then extracting the magnet patch from the high-pressure cavity.

    [0034] In some embodiments, the isostatic pressing device has two high-pressure cavities, wherein a first one is sleeved out of a second one, in such a manner that the second one is an inner cavity and the first one is an outer cavity. Isostatic pressing the packaged magnet patch comprises sending the packaged magnet patch into the inner cavity of the isostatic pressing device, wherein an internal space of the inner cavity except the package magnet patch is full of a liquid medium; and filling the outer cavity of the isostatic pressing device with the hydraulic oil, wherein the outer cavity is intercommunicated with a device for generating high pressure; a pressure of the hydraulic oil of the outer cavity is transmitted into the inner cavity via a separator between the inner cavity and the outer cavity, in such a manner that the pressure within the inner cavity increases accordingly; and the pressure within the inner cavity is between 150 MPa and 300 MPa.

    [0035] In some embodiments, automatically compacting in the magnetic field comprises steps of: inter-communicating a storage tank filled with the NdFeB rare earth permanent magnetic alloy powder with a feeding inlet of an alignment magnetic field automatic compressor under the protection of nitrogen; thereafter, discharging air between the storage tank and a valve of the feeding inlet of the automatic compressor; then opening the valve of the feeding inlet to introduce the powder within the storage tank into a hopper of a weighing batcher; after weighing, automatically sending the powder into a mold cavity by a powder sender; after removing the powder sender, moving an upper pressing tank of the compressor downward into the mold cavity for magnetizing and aligning the powder, wherein the powder is compressed and compacted to form a compacted magnet patch; demagnetizing the compacted magnet patch, and then ejecting the compacted magnet patch out of the mold cavity; sending the compacted magnet patch into a load box of the alignment magnetic field automatic compressor under the protection of nitrogen; when the load box is full, closing the load box, and sending the load box into a load plate; when the load plate is full, opening a discharging valve of the alignment sealed magnetic field automatic compressor under the protection of nitrogen to transmit the load plate full of the load boxes into a transmission sealed box under the protection of nitrogen; and then, under the protection of nitrogen, intercommunicating the transmission sealed box with a protective feeding box of a vacuum sintering furnace to send the load plate full of the load boxes into the protective feeding box of the vacuum sintering furnace.

    [0036] In some embodiments, the alignment magnetic field compressor under the protection of nitrogen has electromagnetic pole columns and magnetic field coils which are respectively provided with a cooling medium. The cooling medium can be water, oil or refrigerant; and during compacting, the electromagnetic pole columns and the magnetic field coils form a space for containing the mold at a temperature lower than 25°C.

    [0037] Preferably, the cooling medium can be water, oil or refrigerant; and during compacting, the electromagnetic pole columns and the magnetic field coils form a space for containing the mold at a temperature lower than 5 °C and higher than -10 °C; and the powder is compressed and compacted at a pressure of between 100 MPa and 300 MPa.

    [0038] In some embodiments, sintering the magnetic patch comprises steps of: under the protection of nitrogen, sending the magnet patch into a continuous vacuum sintering furnace for sintering; while driven by a transmission device, sending a load frame loaded with the magnet patch through a preparation cavity, a pre-heating and degreasing cavity, a first degassing cavity, a second degassing cavity, a pre-sintering cavity, a sintering cavity, an aging treatment cavity and a cooling cavity, respectively for removing organic impurities via pre-heating, heating to dehydrogenate and degas, pre-sintering, sintering, aging and cooling; after cooling, extracting the magnet patch out of the continuous vacuum sintering furnace and then sending the magnet patch into a vacuum aging treatment furnace for a second aging treatment, wherein the second aging treatment is executed at a temperature of betweem 450 °C and 650 °C; quenching the magnet patch after the second aging treatment, and obtaining the sintered NdFeB rare earth permanent magnet; and then, processing the sintered NdFeB rare earth permanent magnet into a NdFeB rare earth permanent magnetic device through machining and surface treatment.

    [0039] In some embodiments, the load frame enters a loading cavity before entering the preparation cavity of the continuous vacuum sintering furnace; in the loading cavity, the magnet patch after isostatic pressing is de-packaged and loaded into the load box; further, the load box is loaded onto the load frame which is sent into the preparation cavity through the valve while driven by the transmission device.

    [0040] In some embodiments, pre-sintering in vacuum comprises steps of: providing a continuous vacuum pre-sintering furnace; loading the load box which is filled with compacted magnet patches onto a sintering load frame; while driving by the transmission device, sending the sintering load frame orderly through a preparation cavity, a degreasing cavity, a first degassing cavity, a second degassing cavity, a third degassing cavity, a first pre-sintering cavity, a second pre-sintering cavity and a cooling cavity of the continuous vacuum pre-sintering furnace, respectively for pre-heating to degrease, heating to dehydrogenate and degas, pre-sintering and cooling, wherein argon is provided for cooling; after cooling, extracting the sintering load frame out of the continuous vacuum pre-sintering furnace, and then loading the load box onto an aging load frame; hanging up the aging load frame, and sending the hanging aging load frame through a pre-heating cavity, a heating cavity, a sintering cavity, a high-temperature aging cavity, pre-cooling cavity, a low-temperature aging cavity and a cooling cavity, respectively for sintering, aging at a high temperature, pre-cooling, aging at a low temperature and rapidly air-cooling.

    [0041] In some embodiments, the sintering load frame is processed with pre-heating to degrease at between 200°C and 400 °C, heating to dehydrogenate and degas at between 400 °C and 900 °C, pre-sintering at between 900 °C and 1050 °C, sintering at between 1010°C and 1085 °C, aging at the high temperature of between 800°C and 950 °C, and then aging at the low temperature of between 450°C and 650 °C; and after a thermal preservation, the sintering load frame is sent into the cooling cavity and then rapidly cooled with argon or nitrogen.

    [0042] In some embodiments, the sintering load frame is processed with pre-heating to degrease at between 200 °C and 400 °C, heating to dehydrogenate and degas at between 550 °C and 850 °C, pre-sintering at between 960 °C and 1025 °C, sintering at between 1030°C and 1070 °C, aging at the high temperature of between 860°C and 940 °C, and then aging at the low temperature of between 460 °C and 640 °C; and after a thermal preservation, the sintering load frame is sent into the cooling cavity and then rapidly cooled with argon or nitrogen.

    [0043] In some embodiments, pre-sintering comprises pre-sintering in a vacuum degree higher than 5×10-1 Pa; the step of sintering comprises sintering in a vacuum degree between 5×10-1 Pa and 5×10-3 Pa.

    [0044] Alternatively, the step of pre-sintering comprises pre-sintering in a vacuum degree higher than 5 Pa; the step of sintering comprises steps of: sintering in a vacuum degree between 500 Pa and 5000 Pa, and filling in argon.

    [0045] In some embodiments, the sintering load frame has an effective width of between 400 mm and 800 mm; and the aging load frame has an effective width of between 300 mm and 400 mm.

    [0046] In some embodiments, pre-sintering generates the magnet patch having a density of between 7.2 g/cm3 and 7.5 g/cm3; and the step of sintering generates the magnet patch having a density of between 7.5 g/cm3 and 7.7 g/cm3.

    [0047] In some embodiments, the NdFeB permanent magnetic alloy comprises a main phase and a grain boundary phase. The main phase has a structure of R2(Fe,Co)14B, wherein a heavy rare earth HR content extending from an outer edge to one third of the phase is higher than the heavy rare earth HR content at a center of the main phase; the grain boundary phase has micro particles of Neodymium oxide; R comprises at least one rare earth element, Nd; HR comprises at least one member selected from a group consisting of Dy, Tb, Ho and Y.

    [0048] In some embodiments, a metal phase of the NdFeB permanent magnetic alloy has a heavy rare earth content surrounding around R2(Fe1-xCox)14B grains higher than a ZR2(Fe1-xCox)14B phase of the R2(Fe1-xCox)14B phase; no grain boundary phase exists between the ZR2(Fe1-xCox)14B phase and the R2(Fe1-xCox)14B phase; the ZR2(Fe1-xCox)14B phases are connected through the grain boundary phase. ZR represents the rare earth of the phase whose heavy rare earth content in the grain phase is higher than a content of the heavy rare earth in an averaged rare earth content; 0≤x≤0.5.

    [0049] In some embodiments, micro particles of Neodymium oxide are provided in the grain boundary phase at boundaries between the grains of at least two ZR2(Fe1-xCOx)14B phases of the metal phase of the NdFeB permanent magnetic alloy. An oxygen content of the grain boundary is higher than an oxygen content of the main phase.

    [0050] In some embodiments, the grains of the NdFeB permanent magnetic alloy have a size of between 3 µm and 25 µm, such as between 5 µm and 15 µm.

    BRIEF DESCRIPTION OF THE DRAWINGS



    [0051] The Figure is a sketch view of a powdering device of a jet mill under a protection of nitrogen according to a preferred embodiment of the present invention.

    DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT



    [0052] In the Figure: 1-hopper; 2-feeder; 3-third valve; 4-grinder; 5-centrifugal sorting wheel; 6-nozzle; 7-pipeline; 8-cyclone collector; 9-first valve; 10-post cyclone collector; 11-filtering pipe; 12-pneumatic valve; 13-discharging pipe; 14-gas compressor; 15-gas cooler; 16-inlet pipe; 17-second valve; 18-depositing device; 19-depositing tank; 20-sampler; 21-gas outlet; 81-cyclone collector gas inlet; 82-cyclone collector gas outlet; 101-post cyclone collector gas outlet; 151-cooler outlet; 83-first depositing mouth; 102-second depositing mouth; 22-powder mixer; 221-stirring device; 84-lower portion of cyclone collector; 103-lower portion of post cyclone collector; 181-lower portion of depositing device; 222-lower portion of powder mixer; 23-upper portion of feeder.

    [0053] As showed in the Figure, a device configured to powder NdFeB rare earth permanent magnetic alloy, comprising:

    a grinder 4 comprising: a nozzle 6 configured to eject a gas to provide a gas flow for grinding powder of NdFeB rare earth permanent magnetic alloy; a centrifugal sorting wheel 5 and a gas outlet 21;

    a cyclone collector 8 comprising: a cyclone collector gas inlet 81 connected to the gas outlet 21 of the centrifugal sorting wheel 5 to receive powder discharged with the gas from the grinder 4; a cyclone collector gas outlet 82 connected in parallel with two post cyclone collectors 10; each of the two post cyclone collectors 10 comprising: a filtering pipe 11 to separate the powder from the gas a after receiving the powder discharged with the gas from the cyclone collector; and a post cyclone collector gas outlet 101 to output the separated gas;

    a gas compressor 14 connected with the post cyclone collector gas outlet 101 via a discharging pipe 13 to compress the separated gas; and

    a gas cooler 15 connected with the gas compressor 14 to cool the separated gas, the gas cooler comprising a cooler outlet 151 connected to an inlet pipe 16 of the nozzle 6 for ejection of the separated gas by the nozzle 6 for grinding.



    [0054] The cyclone collector 8 further comprises a first depositing mouth 83 at a lower portion 84 of the cyclone collector 8. Each of the two post cyclone collectors 10 comprises a second depositing mouth 102 at a lower portion 103 of each the post cyclone collectors 10.

    [0055] The device further comprises a depositing device 18 connected to the first depositing mouth 83 of the cyclone collector 8 and the second depositing mouth 102 of the two post cyclone collectors 10 to receive the powder from the cyclone collector 8 and the two post cyclone collectors 10.

    [0056] The device further comprises a depositing tank 19 connected to a lower portion 181 of the depositing device 18, wherein the depositing device 18 comprises a sampler 20.

    [0057] The device further comprises: a powder mixer 22 which is connected to the first depositing mouth 83 through a first valve 9, and to the second depositing mouth 102 of each of the two post cyclone collectors 10 through two second valves 17, wherein the powder mixer 22 comprises a stirring device 221; and the depositing tank 19 is connected to a lower portion 222 of the powder mixer 22.

    [0058] The device further comprises: a feeder 2 connected to the grinder 4 via a third valve 3, and a hopper 1 disposed at an upper portion 23 of the feeder 2.

    [0059] The device further comprises two pneumatic valves 12 that open and close, each of the two pneumatic valves 12 connected between the post cyclone collector gas outlet 101 of each of the two post cyclone collectors 10 and the discharging pipe 13.

    [0060] The present invention is further illustrated through following embodiments.

    Example 1



    [0061] 600 Kg of an alloy having a component of Nd30Dy1Co1.2Cu0.1B0.9Al0.1Ferest was heated to melt, and then added with Dy2O3 micro powder. The alloy at a melt state was cast onto a rotating copper roller with water quenching, and cooled to form alloy flakes. A continuous vacuum hydrogen pulverization furnace was provided for a hydrogen pulverization, wherein the R-Fe-B-M alloy flakes were firstly loaded into a hanging load bucket, and then sent orderly into a hydrogen absorption cavity, a heating and dehydrogenating cavity and a cooling cavity, respectively for absorbing hydrogen, heating to dehydrogenate and cooling. Then, in a protective atmosphere, the alloy after the hydrogen pulverization was loaded into a storage tank and mixed. After mixing, according to Example 1 of the present invention, the mixture was powdered by a jet mill having two post cyclone collectors under a protection of nitrogen, wherein an atmosphere oxygen content of the jet mill was 0∼50 ppm. Powder collected by a cyclone collector and fine powder collected by the two post cyclone collectors were collected inside a depositing tank, next mixed by a mixing device under a protection of nitrogen, and then sent to be aligned and compacted by an alignment magnetic field compressor under the protection of nitrogen. A protective box having an oxygen content of 150 ppm, an alignment magnetic field intensity of 1.8 T, and a mold cavity inner temperature of 3 °C was provided. The compacted magnet patch had a size of 62 mm×52 mm×42 mm, and was aligned at a direction of 42 mm; the compacted magnet was sealed into the protective box. Then, the compacted magnet was extracted out of the protective box for an isostatic pressing at an isostatic pressure of 200 MPa; thereafter, a sintered NdFeB permanent magnet was obtained through sintering and an aging treament; the sintered NdFeB permanent magnet was machined into blocks of 50 mmx30 mm×20 mm; and the blocks are electroplated to form a rare earth permanent magnetic device. Table 1 shows test results of Example 1.

    Example 2



    [0062] 600 Kg of an alloy having a component of Nd30Dy1Co1.2Cu0.1B0.9Al0.1Ferest was heated to melt. The alloy at a melt state was cast onto a rotating copper roller with water quenching, and cooled to form alloy flakes. A vacuum hydrogen pulverization furnace was provided for a hydrogen pulverization; thereafter, the pulverized alloy flakes were mixed while being added with micro powder of Y2O3 and a lubricant. After mixing, according to Example 2 of the present invention, the mixture was powdered by a jet mill having three post cyclone collectors under a protection of nitrogen, wherein an atmosphere oxygen content of the jet mill was 0∼40 ppm. Powder collected by a cyclone collector and fine powder collected by the three post cyclone collectors were collected inside a depositing tank, next mixed by a mixing device under a protection of nitrogen, and then sent to be aligned and compacted by an alignment magnetic field compressor under the protection of nitrogen. The compacted magnet patch had a size of 62 mm×52 mm×42 mm, and was aligned at a direction of 42 mm; the compacted magnet was sealed into a protective box. Then, the compacted magnet was extracted out of the protective box for an isostatic pressing; thereafter, a sintered NdFeB permanent magnet was obtained through sintering and an aging treatment; then the sintered NdFeB permanent magnet was machined into blocks of 50 mm×30 mm×20 mm; and then, the blocks are electroplated to form a rare earth permanent magnetic device. Table 1 shows test results of Example 2.

    Example 3



    [0063] 600 Kg of an alloy having a component of Nd30Dy1Co1.2Cu0.1B0.9Al0.1Ferest was heated to melt. The alloy at a melt state was cast onto a rotating copper roller with water quenching, and cooled to form alloy flakes. A vacuum hydrogen pulverization furnace was provided for a hydrogen pulverization; thereafter, the pulverized alloy flakes were mixed while being added with micro powder of Al2O3. After mixing, according to Example 3 of the present invention, the mixture was powdered by a jet mill having four post cyclone collectors under a protection of nitrogen, wherein an atmosphere oxygen content of the jet mill was 0∼20 ppm. Powder collected by a cyclone collector and fine powder collected by the four post cyclone collectors were collected inside a depositing tank, next mixed by a mixing device under a protection of nitrogen, and then sent to be aligned and compacted by an alignment magnetic field compressor under the protection of nitrogen. The compacted magnet patch had a size of 62 mm×52 mm×42 mm, and was aligned at a direction of 42 mm; the compacted magnet was sealed into a protective box. Then, the compacted magnet was extracted out of the protective box for an isostatic pressing; thereafter, a sintered NdFeB permanent magnet was obtained through sintering and an aging treatment; then the sintered NdFeB permanent magnet was machined into blocks of 50 mm×30 mm×20 mm; and then, the blocks are electroplated to form a rare earth permanent magnetic device. Table 1 shows test results of Example 3.

    Example 4



    [0064] 600 Kg of an alloy having a component of Nd30Dy1Co1.2Cu0.1B0.9Al0.1Ferest was heated to melt. The alloy at a melt state was cast onto a rotating copper roller with water quenching, and cooled to form alloy flakes. A vacuum hydrogen pulverization furnace was provided for a hydrogen pulverization; thereafter, the pulverized alloy flakes were mixed while being added with micro powder of Dy2O3. After mixing, according to Example 4 of the present invention, the mixture was powdered by a jet mill having five post cyclone collectors under a protection of nitrogen, wherein an atmosphere oxygen content of the jet mill was 0∼18 ppm. Powder collected by a cyclone collector and fine powder collected by the four post cyclone collectors were collected inside a depositing tank, next mixed by a mixing device under a protection of nitrogen, and then sent to be aligned and compacted by an alignment magnetic field compressor under the protection of nitrogen. The compacted magnet patch had a size of 62 mm×52 mmx42 mm, and was aligned at a direction of 42 mm; the compacted magnet was sealed into a protective box. Then, the compacted magnet was extracted out of the protective box for an isostatic pressing; thereafter, a sintered NdFeB permanent magnet was obtained through sintering and an aging treatment; then the sintered NdFeB permanent magnet was machined into blocks of 50 mm×30 mm×20 mm; and then, the blocks are electroplated to form a rare earth permanent magnetic device. Table 1 shows test results of Example 4.

    Example 5



    [0065] 600 Kg of an alloy having a component of Nd30Dy1Co1.2Cu0.1B0.9Al0.1Ferest was heated to melt. The alloy at a melt state was cast onto a rotating copper roller with water quenching, and cooled to form alloy flakes. A vacuum hydrogen pulverization furnace was provided for a hydrogen pulverization; thereafter, according to Example 5 of the present invention, the pulverized alloy flakes was powdered by a jet mill having six post cyclone collectors under a protection of nitrogen, wherein an atmosphere oxygen content of the jet mill was 0∼20 ppm. Powder collected by a cyclone collector and fine powder collected by the four post cyclone collectors were collected inside a depositing tank, next mixed by a mixing device under a protection of nitrogen, and then sent to be aligned and compacted by an alignment magnetic field compressor under the protection of nitrogen. The compacted magnet patch had a size of 62 mm×52 mm×42 mm, and was aligned at a direction of 42 mm; the compacted magnet was sealed into a protective box. Then, the compacted magnet was extracted out of the protective box for an isostatic pressing; thereafter, a sintered NdFeB permanent magnet was obtained through sintering and an aging treatment; then the sintered NdFeB permanent magnet was machined into blocks of 50 mm×30 mm×20 mm; and then, the blocks are electroplated to form a rare earth permanent magnetic device. Table 1 shows test results of Example 5.

    Comparison example



    [0066] 600 Kg of an alloy having a component of Nd30Dy1Co1.2Cu0.1B0.9Al0.1Ferest was heated to melt. The alloy at a melt state was cast onto a rotating quenching roller, and cooled to form alloy flakes. The alloy flakes were roughly pulverized by a vacuum hydrogen pulverization furnace, then processed by a conventional jet mill, and then sent to be aligned and compacted by an alignment magnetic field compressor under a protection of nitrogen. The compacted magnet patch had a size of 62 mm×52 mm×42 mm, and was aligned at a direction of 42 mm; the compacted magnet was sealed into a protective box. Then, the compacted magnet was extracted out of the protective box for an isostatic pressing at an isostatic pressure of 200 MPa; thereafter, a sintered NdFeB permanent magnet was obtained through sintering and an aging treatment; then the sintered NdFeB permanent magnet was machined into blocks of 50 mm×30 mm×20 mm; and then, the blocks are electroplated to form a rare earth permanent magnetic device.
    Table 1 Performance Test Results of Examples and Comparison Example
    OrderNumberOxide micro power content (%)Magnetic energy product (MGOe)Coercive force (KOe)Magnetic energy product (MGOe) + coercive force (KOe)Weightlessness (g/cm3)
    1 Example 1 0.1 48.8 23.4 72.2 4.2
    2 Example 2 0.2 48.2 24.2 72.4 3.2
    3 Example 3 0.3 47.8 22.8 70.6 2.8
    4 Example 4 0.1 48.6 23.1 71.7 3.5
    5 Example 5 0 48.3 22.6 70.9 3.8
    6 Comparison example 0 47.5 17.8 65.3 7.5


    [0067] By a comparison between the examples and the comparison example, the method and the device provided herein improves magnetism and corrosion resistance of the magnets.


    Claims

    1. A method for powdering NdFeB rare earth permanent magnetic alloy, comprising steps of:

    sending mixed powder of NdFeB rare earth permanent magnetic alloy to a grinder (4);

    grinding the mixed powder via a gas flow of gas which is ejected by a nozzle (6) of the grinder (4) to create a ground powder;

    discharging fine powder along with the gas flow from the grinder (4), the fine powder discharged along with the gas flow comprising a first portion of the ground powder below a required particle size;

    separating, by a filtering pipe (11), the fine powder and the gas from the fine powder discharged along with the gas flow;

    providing the gas through a gas discharging pipe (13);

    compressing, by a compressor (14), and cooling, by a cooler (15), the gas which is discharged from the gas discharging pipe (13); and

    sending the compressed and cooled gas into an inlet pipe (16) of the nozzle (6) for recycling the gas;

    characterized by further comprising steps of:

    providing the ground powder along with the gas flow, under protection of nitrogen, to a centrifugal sorting wheel (5);

    providing rough powder beyond the required particle size back to the grinder (4) under a centrifugal force to continue grinding, and fine powder which is selected out by the centrifugal sorting wheel (5) into a cyclone collector (8) for collecting, the cyclone collector (8) comprising the gas discharging pipe (13) and the fine powder collected by the cyclone collector (8) comprising a second portion of the ground powder below the required particle size; and

    receiving and collecting, by between 2 and 6 post cyclone collectors (10) which are connected in parallel (10) and wherein the post cyclone collectors are connected in parallel with a cyclone collector gas outlet (82), under protection of nitrogen, the fine powder comprising the first portion of the ground powder which is discharged from the gas discharging pipe (13) of the cyclone collector (8), the post cyclone collector (10) including the filtering pipe (11); and wherein the NdFeB rare earth permanent magnetic alloy comprises Nd30Dy1Co1.2Cu0.1B0.9Al0.1Ferest and wherein the oxygen content in the post cyclone collector is between 0-50ppm;

    collecting, by a powder mixer (22) which is provided at a lower part of the cyclone collector (8), the fine powder which is collected by the cyclone collector (8);

    collecting, by the powder mixer (22), the fine powder which is collected by the post cyclone collectors (10);

    mixing the fine powder which is collected by the cyclone collector (8) and the fine powder which is collected by the post cyclone collectors (10) by the powder mixer (22) to create a mixed fine powder;

    wherein the collecting, by the powder mixer (22), the fine powder which is collected by the cyclone collector (8) comprises passing the fine powder which is collected by the cyclone collector (8) through a first valve (9) that opens and closes alternatively; and

    collecting, by the powder mixer (22), the fine powder which is collected by the post cyclone collectors (10) comprises passing the fine powder which is collected by the post cyclone collector (10) through a second valve (17) that opens and closes alternatively; and

    introducing, by a depositing device (18), the powder collected by the cyclone collector
    (8) and the powder collected by the post cyclone collectors (10) into a depositing tank (19).


     
    2. The method, as recited in Claim 1, further comprising steps of:

    mixing powder of NdFeB rare earth permanent magnetic alloy which is processed with a hydrogen pulverization to create the mixed powder;

    providing the mixed powder into a hopper (1) of a feeder (2); and sending, by the feeder (2), the mixed powder to the grinder (4).


     
    3. A method for preparing a NdFeB rare earth permanent magnet, comprising steps of powdering NdFeB rare earth permanent magnetic alloy according to the method of any of claims 1 to 2 and further comprising the following steps:

    obtaining a NdFeB rare earth permanent magnet from the fine powder by compacting in a magnetic field, sintering in vacuum and processing with an aging treatment; and

    processing the permanent magnet into a rare earth permanent magnetic device with machining and a surface treatment.


     
    4. The method, as recited in Claim 3, wherein compacting in the magnetic field comprises steps of:

    under protection of nitrogen, sending the fine powder into an alignment magnetic field compressor;

    under the protection of nitrogen, aligning in the magnetic field and compacting through pressure;

    packaging and extracting a packaged magnet out of the alignment magnetic field compressor in the protection of nitrogen;

    sending the extracted magnet into an isostatic pressing device for isostatic pressing;

    sending the packaged magnet into a nitrogen protective box and de-packaging the magnet in the protection of nitrogen; and

    loading the de-packaged magnet into a sintering load box and sintering by a continuous vacuum sintering furnace.


     


    Ansprüche

    1. Verfahren zum Pulverisieren von NdFeB-Seltene-Erden-Permanentmagnetlegierung, umfassend die folgenden Schritte:

    Senden von gemischtem Pulver aus NdFeB-Seltene-Erden-Permanentmagnetlegierung in ein Mahlwerk (4);

    Mahlen des gemischten Pulvers über einen Gasfluss von Gas, das von einer Düse (6) des Mahlwerks (4) ausgestoßen wird, um ein gemahlenes Pulver zu erzeugen;

    Ausspeisen von feinem Pulver zusammen mit dem Gasfluss vom Mahlwerk (4), wobei das feine Pulver, das zusammen mit dem Gasfluss ausgespeist wird, einen ersten Anteil des gemahlenen Pulvers unterhalb einer erforderlichen Partikelgröße umfasst;

    Trennen, anhand eines Filterrohrs (11) des feinen Pulvers und des Gases von dem feinen Pulver, das zusammen mit den Gasfluss ausgespeist wird;

    Bereitstellen des Gases durch ein Gasausspeiserohr (13);

    Verdichten, mittels eines Verdichters (14) und Abkühlen, mittels eines Kühlgeräts (15), des Gases, das aus dem Gasausspeiserohr (13) ausgespeist wird; und

    Senden des verdichteten und abgekühlten Gases in ein Einlassrohr (16) der Düse (6) zum Recyclen des Gases;

    dadurch gekennzeichnet, dass es ferner die folgenden Schritte umfasst:

    Bereitstellen des gemahlenen Pulvers zusammen mit dem Gasfluss unter Stickstoffschutz an ein Zentrifugalsortierrad (5);

    Bereitstellen von grobem Pulver oberhalb der erforderlichen Partikelgröße zurück an das Mahlwerk (4) unter einer Zentrifugalkraft, um das Mahlen fortzusetzen, und von feinem Pulver, das vom Zentrifugalsortierrad (5) aussortiert wurde in einen Zyklonsammler (8) zum Sammeln, wobei der Zyklonsammler (8) das Gasausspeiserohr (13) umfasst und das feine Pulver, das vom Zyklonsammler (8) gesammelt wird, einen zweiten Anteil des gemahlenen Pulvers unterhalb der erforderlichen Partikelgröße umfasst; und

    Empfangen und Sammeln, mittels zwischen 2 und 6 nachgelagerten Zyklonsammlern (10), die parallel verbunden sind (10), und wobei die nachgelagerten Zyklonsammler parallel mit einem Zyklonsammler-Gasauslass (82) verbunden sind, des feinen Pulvers unter Stickstoffschutz, das den ersten Anteil des gemahlenen Pulvers umfasst, das vom Gasausspeiserohr (13) des Zyklonsammlers (8) ausgespeist wird, wobei der nachgelagerte Zyklonsammler (10) das Filterrohr (11) umfasst; und wobei die NdFeB-Seltene-Erden-Permanentmagnetlegierung Nd30Dy1Co1,2Cu0,1B0,9Al0,1Ferest umfasst, und wobei der Sauerstoffgehalt im nachgelagerten Zyklonsammler zwischen 0-50 ppm liegt;

    Sammeln, mittels eines Pulvermischgeräts (22), das in einem unteren Teil des Zyklonsammlers (8) vorgesehen ist, des feinen Pulvers, das vom Zyklonsammler (8) gesammelt wird;

    Sammeln, mittels des Pulvermischgeräts (22), des feinen Pulvers, das von den nachgelagerten Zyklonsammlern (10) gesammelt wird;

    Mischen des feinen Pulvers, das vom Zyklonsammler (8) gesammelt wird, und des feinen Pulvers, das von den nachgelagerten Zyklonsammlern (10) gesammelt wird, mittels des Pulvermischgeräts (22), um eine gemischtes feines Pulver zu schaffen;

    wobei das Sammeln, mittels des Pulvermischgeräts (22), des feinen Pulvers, das vom Zyklonsammler (8) gesammelt wird, das Hindurchleiten des feinen Pulvers, das vom Zyklonsammler (8) gesammelt wird, durch ein erstes Ventil (9) umfasst, das sich alternativ öffnet oder schließt; und

    das Sammeln, mittels des Pulvermischgeräts (22), des feinen Pulvers, das von den nachgelagerten Zyklonsammlern (10) gesammelt wird, das Hindurchleiten des feinen Pulvers, das vom nachgelagerten Zyklonsammler (10) gesammelt wird, durchdurch ein zweites Ventil (17) umfasst, das sich alternativ öffnet oder schließt; und

    Einführen, mittels einer Absetzvorrichtung (18), des Pulvers, das vom Zyklonsammler (8) gesammelt wird, und des Pulvers, das von den nachgelagerten Zyklonsammlern (10) gesammelt wird, in einen Absetztank (19).


     
    2. Verfahren nach Anspruch 1, das ferner die folgenden Schritte umfasst:

    Mischen von Pulver aus NdFeB-Seltene-Erden-Permanentmagnetlegierung, das mit einer Wasserstoffpulverisierung verarbeitet wird, um das gemischte Pulver zu schaffen;

    Bereitstellen des gemischten Pulvers in einem Fülltrichter (1) eines Beschickers (2), und Senden des gemischten Pulvers zum Mahlwerk (4) vonseiten des Beschickers (2).


     
    3. Verfahren zum Zubereiten eines NdFeB-Seltene-Erden-Permanentmagneten, das die Schritte des Pulverisierens von NdFeB-Seltene-Erden-Permanentmagnetlegierung gemäß dem Verfahren nach einem der Ansprüche 1 bis 2 umfasst und ferner die folgenden Schritte umfasst:

    Erzielen eines NdFeB-Seltene-Erden-Permanentmagneten aus dem feinen Pulver durch Verdichten in einem Magnetfeld, Sintern im Vakuum und Verarbeiten mit einer Alterungsbehandlung; und

    Verarbeiten des Permanentmagneten in eine Seltene-Erden-Permanentmagnetvorrichtung mit Zerspanen und einer Oberflächenbehandlung.


     
    4. Verfahren nach Anspruch 3, wobei das Verdichten im Magnetfeld die folgenden Schritte umfasst:

    unter Stickstoffschutz, Senden des feinen Pulvers in einen Ausrichtungs-Magnetfeldverdichter;

    unter Stickstoffschutz, Ausrichten im Magnetfeld und Verdichten durch Druck;

    Verpacken und Extrahieren eines verpackten Magneten aus dem Ausrichtungs-Magnetfeldverdichter im Stickstoffschutz;

    Senden des extrahierten Magneten in eine isostatische Pressvorrichtung zum isostatischen Pressen;

    Senden des verpackten Magneten in einen stickstoffgeschützten Kasten und Entpacken des Magneten im Stickstoffschutz; und

    Laden des entpackten Magneten in einen Sinterkasten und Sintern anhand eines Durchlauf-Vakuumsinterofens.


     


    Revendications

    1. Procédé de réduction en poudre d'un alliage magnétique permanent de terres rares NdFeB, comprenant les étapes suivantes :

    l'envoi d'une poudre mélangée d'alliage magnétique permanent de terres rares NdFeB à un broyeur (4) ;

    le broyage de la poudre mélangée par l'intermédiaire d'un flux gazeux de gaz qui est éjecté par une buse (6) du broyeur (4) pour obtenir une poudre broyée ;

    l'évacuation de poudre fine avec le flux gazeux provenant du broyeur (4), la poudre fine évacuée avec le flux gazeux comprenant une première partie de la poudre broyée d'une taille de particules inférieure à une taille de particules requise ;

    la séparation, au moyen d'un tuyau de filtrage (11), de la poudre fine et du gaz de la poudre fine évacuée avec le flux gazeux ;

    l'alimentation du gaz à travers un tuyau d'évacuation de gaz (13) ;

    la compression, au moyen d'un compresseur (14), et le refroidissement, au moyen d'un refroidisseur (15), du gaz qui est évacué du tuyau d'évacuation de gaz (13) ; et

    l'envoi du gaz comprimé et refroidi dans un tuyau d'entrée (16) de la buse (6) pour recycler le gaz ;

    caractérisé en ce qu'il comprend en outre les étapes suivantes :

    l'alimentation de la poudre broyée avec le flux gazeux, sous protection d'azote, à une roue de triage centrifuge (5) ;

    le renvoi d'une poudre brute d'une taille de particules supérieure à la taille de particules requise au broyeur (4) sous l'effet d'une force centrifuge pour continuer le broyage, et d'une poudre fine qui est sélectionnée par la roue de triage centrifuge (5) dans un collecteur à cyclone (8) pour être collectée, le collecteur à cyclone (8) comprenant le tuyau d'évacuation de gaz (13) et la poudre fine collectée par le collecteur à cyclone (8) comprenant une seconde partie de la poudre broyée d'une taille de particules inférieure à la taille de particules requise ; et

    la réception et la collecte, au moyen de 2 à 6 collecteurs post-cyclone (10) qui sont reliés en parallèle (10) et dans lequel les collecteurs post-cyclone sont reliés en parallèle à une sortie de gaz de collecteur à cyclone (82), sous protection d'azote, la poudre fine comprenant la première partie de la poudre broyée qui est évacuée du tuyau d'évacuation de gaz (13) du collecteur à cyclone (8), le collecteur post-cyclone (10) comprenant le tuyau de filtrage (11) ; et dans lequel l'alliage magnétique permanent de terres rares NdFeB comprend du Nd30Dy1Co1.2Cu0.1B0.9Al0.1Ferest et dans lequel la teneur en oxygène dans le collecteur post-cyclone est comprise entre 0 et 50 ppm ;

    la collecte, au moyen d'un mélangeur de poudre (22) qui est prévu au niveau d'une partie inférieure du collecteur à cyclone (8), de la poudre fine qui est collectée par le collecteur à cyclone (8) ;

    la collecte, par le mélangeur de poudre (22), de la poudre fine qui est collectée par les collecteurs post-cyclone (10) ;

    le mélange de la poudre fine, qui est collectée au moyen du collecteur à cyclone (8), et de la poudre fine, qui est collectée au moyen des collecteurs post-cyclone (10), au moyen du mélangeur de poudre (22) pour obtenir une poudre fine mélangée ;

    dans lequel la collecte, au moyen du mélangeur de poudre (22), de la poudre fine qui est collectée au moyen du collecteur à cyclone (8) comprend le passage de la poudre fine qui est collectée au moyen du collecteur à cyclone (8) à travers une première soupape (9) qui s'ouvre et se ferme alternativement ; et

    la collecte, au moyen du mélangeur de poudre (22), de la poudre fine qui est collectée par les collecteurs post-cyclone (10) comprend le passage de la poudre fine qui est collectée au moyen du collecteur post-cyclone (10) à travers une seconde soupape (17) qui s'ouvre et se ferme alternativement ; et

    l'introduction, au moyen d'un dispositif de dépôt (18), de la poudre collectée au moyen du collecteur à cyclone (8) et de la poudre collectée au moyen des collecteurs post-cyclone (10) dans un réservoir de dépôt (19).


     
    2. Procédé, selon la revendication 1, comprenant en outre les étapes suivantes :

    le mélange de poudre d'alliage magnétique permanent de terres rares NdFeB qui est traitée avec une pulvérisation d'hydrogène pour obtenir la poudre mélangée ;

    l'alimentation de la poudre mélangée dans une trémie (1) d'un alimentateur (2) ; et l'envoi, au moyen de l'alimentateur (2), de la poudre mélangée au broyeur (4).


     
    3. Procédé de préparation d'un aimant permanent de terres rares NdFeB, comprenant des étapes de réduction en poudre d'un alliage magnétique permanent de terres rares NdFeB conformément au procédé selon l'une quelconque des revendications 1 et 2 et comprenant en outre les étapes suivantes :

    l'obtention d'un aimant permanent de terres rares NdFeB à partir de la poudre fine par un compactage dans un champ magnétique, un frittage sous vide et un traitement avec un traitement de vieillissement ; et

    le traitement de l'aimant permanent dans un dispositif magnétique permanent de terres rares par un usinage et un traitement de surface.


     
    4. Procédé, selon la revendication 3, dans lequel le compactage dans le champ magnétique comprend les étapes suivantes :

    sous protection d'azote, l'envoi de la poudre fine dans un compresseur de champ magnétique d'alignement ;

    sous protection d'azote, l'alignement dans le champ magnétique et le compactage par pression ; l'emballage et l'extraction d'un aimant emballé hors du compresseur de champ magnétique d'alignement sous protection d'azote ;

    l'envoi de l'aimant extrait dans un dispositif de compression isostatique pour une compression isostatique ;

    l'envoi de l'aimant emballé dans une boîte sous protection d'azote et le déballage de l'aimant sous protection d'azote ; et

    le chargement de l'aimant déballé dans une boîte de charge de frittage et le frittage au moyen d'un four de frittage sous vide continu.


     




    Drawing






    REFERENCES CITED IN THE DESCRIPTION



    This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

    Patent documents cited in the description