WO2013137133A1 - 希土類永久磁石及び希土類永久磁石の製造方法 - Google Patents
希土類永久磁石及び希土類永久磁石の製造方法 Download PDFInfo
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- WO2013137133A1 WO2013137133A1 PCT/JP2013/056432 JP2013056432W WO2013137133A1 WO 2013137133 A1 WO2013137133 A1 WO 2013137133A1 JP 2013056432 W JP2013056432 W JP 2013056432W WO 2013137133 A1 WO2013137133 A1 WO 2013137133A1
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- 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
- H01F41/0266—Moulding; Pressing
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/10—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/18—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces by using pressure rollers
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F7/00—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression
- B22F7/02—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression of composite layers
- B22F7/04—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression of composite layers with one or more layers not made from powder, e.g. made from solid metal
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
- H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
- H01F1/047—Alloys characterised by their composition
- H01F1/053—Alloys characterised by their composition containing rare earth metals
- H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
- H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
- H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
- H01F1/0575—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together
- H01F1/0577—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together sintered
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F7/00—Magnets
- H01F7/02—Permanent magnets [PM]
- H01F7/0205—Magnetic circuits with PM in general
- H01F7/021—Construction of PM
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/18—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces by using pressure rollers
- B22F2003/185—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces by using pressure rollers by hot rolling, below sintering temperature
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F2301/00—Metallic composition of the powder or its coating
- B22F2301/35—Iron
- B22F2301/355—Rare Earth - Fe intermetallic alloys
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
- B22F2998/10—Processes characterised by the sequence of their steps
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy
Definitions
- the present invention relates to a rare earth permanent magnet and a method for producing a rare earth permanent magnet.
- a powder sintering method is generally used conventionally.
- the powder sintering method first, magnet powder obtained by pulverizing raw materials by a jet mill (dry pulverization) or the like is manufactured. Thereafter, the magnet powder is put into a mold and press-molded into a desired shape. Then, it is manufactured by sintering the solid magnet powder formed into a desired shape at a predetermined temperature (for example, 1100 ° C. for Nd—Fe—B magnets) (for example, Japanese Patent Laid-Open No. 2-266503).
- a predetermined temperature for example, 1100 ° C. for Nd—Fe—B magnets
- permanent magnets are magnetically oriented by applying a magnetic field from the outside in order to improve magnetic characteristics.
- a magnet powder is filled into a mold at the time of press molding, and a magnetic field is applied to orient the magnetic field, and then pressure is applied to form a compacted compact.
- a magnet was molded by applying pressure in an atmosphere to which a magnetic field was applied. Thereby, it becomes possible to form a molded body in which the easy magnetization axis direction of the magnet powder is aligned with the application direction of the magnetic field.
- the permanent magnet is manufactured by the above-described powder sintering method, there are the following problems. That is, in the powder sintering method, it is necessary to ensure a certain porosity in the press-molded magnet powder for magnetic field orientation. When magnet powder having a certain porosity is sintered, it is difficult to uniformly contract during the sintering, and deformation such as warpage and dent occurs after sintering. In addition, since pressure unevenness occurs when the magnet powder is pressed, the sintered magnet can be dense and dense, and distortion occurs on the magnet surface. Therefore, conventionally, it was necessary to compress the magnet powder in a size larger than the desired shape, assuming that the magnet surface can be distorted in advance. Then, after sintering, a diamond cutting and polishing operation is performed to correct the shape into a desired shape. As a result, the number of manufacturing steps increases, and the quality of the manufactured permanent magnet may decrease.
- a magnetic sheet is formed by mixing a magnetic powder with a binder and applying a magnetic field to a plurality of stacked green sheets.
- a method for producing a rare earth permanent magnet includes a step of pulverizing a magnet raw material into magnet powder, a step of producing a mixture in which the pulverized magnet powder and a binder are mixed, and A step of producing a green sheet obtained by forming a mixture into a sheet by hot melt molding, and a step of heating the green sheet and orienting the magnetic field by applying a magnetic field in a state where a plurality of the heated green sheets are laminated. And sintering the green sheet oriented in a magnetic field.
- the method for producing a rare earth permanent magnet according to the present invention is characterized in that, in the magnetic field orientation step, heating is performed in a state where a plurality of the green sheets are laminated.
- the green sheet in the step of producing the green sheet, is produced on the substrate by forming the mixture with respect to the substrate that is continuously conveyed.
- the green sheet continuously conveyed with the base material is heated and a magnetic field is applied to the green sheet.
- the method for manufacturing a rare earth permanent magnet according to the present invention includes a step of winding the green sheet formed by the hot melt molding around a first roll, and the step of magnetic field orientation includes a plurality of the first
- the green sheets are each pulled out from the rolls and laminated, and a magnetic field is applied to the laminated green sheets by applying a magnetic field, and the laminated green sheets after the magnetic field orientation are separated into one sheet.
- the method further includes a step of winding each of the plurality of second rolls.
- the mixture in the step of producing the green sheet, is formed into a sheet shape on the plurality of base materials respectively drawn from a plurality of third rolls.
- the step of producing a plurality of the green sheets and orienting the magnetic field the plurality of green sheets are laminated, and a magnetic field is applied by applying a magnetic field to the laminated green sheets.
- the method further comprises the step of dividing the stacked green sheets into a plurality of fourth rolls.
- the green sheet continuously conveyed together with the base material is passed through a solenoid to which an electric current is applied, whereby On the other hand, a magnetic field is applied.
- the binder is a thermoplastic resin, a long-chain hydrocarbon, a fatty acid methyl ester, or a mixture thereof, and in the step of magnetic field orientation, the green sheet is used as the binder. It heats more than the glass transition point or melting
- the method for producing a rare earth permanent magnet according to the present invention is to scatter the binder by holding the green sheet at a binder decomposition temperature for a certain time in a non-oxidizing atmosphere before sintering the green sheet. It is characterized by removing.
- the rare earth permanent magnet according to the present invention includes a step of pulverizing a magnet raw material into a magnet powder, a step of generating a mixture in which the pulverized magnet powder and a binder are mixed, and the mixture by hot melt molding.
- a step of sintering the green sheet is a step of pulverizing a magnet raw material into a magnet powder, a step of generating a mixture in which the pulverized magnet powder and a binder are mixed, and the mixture by hot melt molding.
- a permanent magnet is manufactured by mixing a magnetic powder and a binder and sintering a green sheet formed by hot melt molding. Due to the uniform shrinkage caused by deformation, deformation such as warping and dent after sintering does not occur, and pressure unevenness at the time of pressing is eliminated, so there is no need for conventional post-sintering correction processing, The manufacturing process can be simplified. Thereby, a permanent magnet can be formed with high dimensional accuracy. Further, even when the permanent magnet is thinned, it is possible to prevent the processing man-hours from increasing without reducing the material yield.
- the magnetic field orientation is performed by heating the molded green sheet and applying a magnetic field to the heated green sheet, the magnetic field orientation can be appropriately performed on the green sheet even after molding.
- the magnetic characteristics of the permanent magnet can be improved.
- the viscosity of the binder is lowered by being transported and heated in a uniform magnetic field, and uniform C-axis orientation is possible only by the rotational torque in the uniform magnetic field.
- the binder is in a sufficiently entangled state, there is no possibility of delamination in the debinding process.
- the green sheets are magnetically oriented in a state where a plurality of green sheets are stacked, C-axis orientation can be performed simultaneously on a large number of green sheets in a single process, greatly increasing manufacturing efficiency. It becomes possible to make it.
- green sheets molded by hot melt molding are less likely to be deformed even when they are laminated compared to molding from slurry, and multiple green sheets can be appropriately laminated. It becomes.
- the method for producing a rare earth permanent magnet according to the present invention since the green sheet is heated in a state where a plurality of green sheets are laminated, the heat treatment is simultaneously performed on a large number of green sheets in one step. This makes it possible to greatly increase the production efficiency.
- a green sheet is produced by forming a mixture on a continuously conveyed substrate, and the green sheet continuously conveyed with the substrate is heated. Since magnetic field orientation is performed by applying a magnetic field to the green sheet, the production process from green sheet to heating and magnetic field orientation can be performed in a continuous process, simplifying the manufacturing process and improving productivity. It becomes possible to do.
- the green sheet formed by hot melt molding is wound around the first roll, and the green sheets are respectively drawn from the plurality of first rolls and laminated.
- a magnetic field is applied to the stacked green sheets by applying a magnetic field, and the stacked green sheets after the magnetic field alignment are divided into individual sheets and wound on a plurality of second rolls. Therefore, it is possible to carry out from the lamination of the green sheets to the heating and the magnetic field orientation in a continuous process, and it becomes possible to simplify the manufacturing process and improve the productivity.
- a plurality of green sheets are produced by forming the mixture into a sheet shape on a plurality of substrates respectively drawn from a plurality of third rolls.
- a plurality of the green sheets are laminated, and a magnetic field is applied by applying a magnetic field to the laminated green sheets, and the laminated green sheets after the magnetic field orientation are divided into a plurality of sheets. Since each of the four rolls is wound, the green sheet can be formed, heated and magnetically oriented in a continuous process, and the manufacturing process can be simplified and the productivity can be improved.
- the green sheet continuously conveyed with the base material is applied to the green sheet by passing the green sheet through a solenoid to which an electric current is applied.
- a uniform magnetic field can be applied to the green sheet, and the magnetic field orientation can be uniformly and appropriately performed.
- magnetic field orientation is performed on a green sheet softened by heating the green sheet to a glass transition point or a melting point or higher of the binder in the magnetic field orientation step. It becomes possible to perform magnetic field orientation appropriately.
- the green sheet before the green sheet is sintered, the green sheet is held at a binder decomposition temperature in a non-oxidizing atmosphere for a certain period of time to scatter and remove the binder. Therefore, the amount of carbon contained in the magnet particles can be reduced in advance. As a result, it is possible to sinter the entire magnet densely without generating voids between the main phase and the grain boundary phase of the sintered magnet, and to prevent the coercive force from being lowered. . Further, a large number of ⁇ Fe is not precipitated in the main phase of the magnet after sintering, and the magnet characteristics are not greatly deteriorated.
- the permanent magnet is composed of a magnet obtained by mixing magnet powder and a binder and sintering a green sheet formed by hot melt molding. Therefore, deformation such as warping and dent after sintering does not occur, and pressure unevenness at the time of pressing is eliminated, so there is no need for correction processing after sintering, which simplifies the manufacturing process. can do. Thereby, a permanent magnet can be formed with high dimensional accuracy. Further, even when the permanent magnet is thinned, it is possible to prevent the processing man-hours from increasing without reducing the material yield.
- the magnetic field orientation is performed by heating the molded green sheet and applying a magnetic field to the heated green sheet, the magnetic field orientation can be appropriately performed on the green sheet even after molding.
- the magnetic characteristics of the permanent magnet can be improved.
- the viscosity of the binder is lowered by being transported and heated in a uniform magnetic field, and uniform C-axis orientation is possible only by the rotational torque in the uniform magnetic field.
- the binder is in a sufficiently entangled state, there is no possibility of delamination in the debinding process.
- the green sheets are magnetically oriented in a state where a plurality of green sheets are stacked, C-axis orientation can be performed simultaneously on a large number of green sheets in a single process, greatly increasing manufacturing efficiency. It becomes possible to make it.
- green sheets molded by hot melt molding are less likely to be deformed even when they are laminated compared to molding from slurry, and multiple green sheets can be appropriately laminated. It becomes.
- FIG. 1 is an overall view showing a permanent magnet according to the present invention.
- FIG. 2 is an explanatory view showing a manufacturing process of the permanent magnet according to the present invention.
- FIG. 3 is an explanatory view showing a green sheet forming process, in particular, of the manufacturing process of the permanent magnet according to the present invention.
- FIG. 4 is an explanatory diagram showing a green sheet laminating step, a heating step, and a magnetic field orientation step among the manufacturing steps of the permanent magnet according to the present invention.
- FIG. 5 is a diagram showing an example in which the magnetic field is oriented in the in-plane vertical direction of the green sheet.
- FIG. 6 is a diagram illustrating a heating device using a heat medium (silicone oil).
- FIG. 7 is an explanatory diagram showing the pressure-sintering step of the green sheet, among the manufacturing steps of the permanent magnet according to the present invention.
- FIG. 8 is a photograph showing the external shape of the green sheet of the example.
- FIG. 9 is an SEM photograph showing an enlarged green sheet of the example.
- FIG. 10 is a reverse pole figure showing the crystal orientation distribution of the green sheet of the example.
- FIG. 11 is a diagram showing various measurement results for the magnets of the example and the comparative example.
- FIG. 1 is an overall view showing a permanent magnet 1 according to the present invention.
- the permanent magnet 1 shown in FIG. 1 has a fan shape, but the shape of the permanent magnet 1 varies depending on the punched shape.
- the permanent magnet 1 according to the present invention is an Nd—Fe—B anisotropic magnet. The content of each component is Nd: 27 to 40 wt%, B: 0.8 to 2 wt%, and Fe (electrolytic iron): 60 to 70 wt%.
- FIG. 1 is an overall view showing a permanent magnet 1 according to the present embodiment.
- the permanent magnet 1 is a thin-film permanent magnet having a thickness of, for example, 0.05 mm to 10 mm (for example, 1 mm). And it produces by sintering the molded object (green sheet) shape
- resin long chain hydrocarbon, fatty acid methyl ester, a mixture thereof, or the like is used as the binder mixed with the magnet powder.
- a resin is used for the binder, it is preferable to use a polymer that does not contain an oxygen atom in the structure and has a depolymerization property.
- a thermoplastic resin is used to perform magnetic field orientation in a state where the formed green sheet is heated and softened.
- the polymer which consists of 1 type, or 2 or more types of polymers or copolymers chosen from the monomer shown by the following general formula (1) corresponds. (However, R1 and R2 represent a hydrogen atom, a lower alkyl group, a phenyl group or a vinyl group.)
- polystyrene resin examples include polyisobutylene (PIB), which is a polymer of isobutylene, polyisoprene (isoprene rubber, IR), which is a polymer of isoprene, and polybutadiene (butadiene) that is a polymer of 1,3-butadiene.
- PIB polyisobutylene
- IR polyisoprene rubber
- IR isoprene rubber
- IR isoprene rubber
- butadiene butadiene
- Rubber, BR polystyrene as a polymer of styrene, styrene-isoprene block copolymer (SIS) as a copolymer of styrene and isoprene, butyl rubber (IIR) as a copolymer of isobutylene and isoprene, styrene and butadiene
- SIS styrene-isoprene block copolymer
- IIR butyl rubber
- SBS styrene-butadiene block copolymer which is a copolymer of 2-methyl-1-pentene, a polymer of 2-methyl-1-pentene, and a polymer of 2-methyl-1-butene.
- a 2-methyl-1-butene polymer resin a polymer of ⁇ -methylstyrene That there is ⁇ - methyl styrene polymer resin.
- the resin used for the binder may include a small amount of a polymer or copolymer of a monomer containing an oxygen atom (for example, polybutyl methacrylate, polymethyl methacrylate, etc.).
- a monomer that does not correspond to the general formula (1) may be partially copolymerized. Even in that case, it is possible to achieve the object of the present invention.
- thermoplastic resin that softens at 250 ° C. or lower, more specifically a thermoplastic resin having a glass transition point or a melting point of 250 ° C. or lower in order to appropriately perform magnetic field orientation. .
- a long chain hydrocarbon when used for the binder, it is preferable to use a long chain saturated hydrocarbon (long chain alkane) that is solid at room temperature and liquid at room temperature or higher. Specifically, it is preferable to use a long-chain saturated hydrocarbon having 18 or more carbon atoms.
- molding so that it may mention later is magnetic field orientation
- magnetic field orientation is performed in the state which heated the green sheet above melting
- fatty acid methyl ester when used as the binder, it is preferable to use methyl stearate or methyl docosanoate which is solid at room temperature and liquid at room temperature or higher.
- methyl stearate or methyl docosanoate which is solid at room temperature and liquid at room temperature or higher.
- magnetic field orientation magnetic field orientation is performed in the state which heated the green sheet above melting
- the amount of carbon and oxygen contained in the magnet can be reduced.
- the amount of carbon remaining in the magnet after sintering is 2000 ppm or less, more preferably 1000 ppm or less.
- the amount of oxygen remaining in the magnet after sintering is set to 5000 ppm or less, more preferably 2000 ppm or less.
- the amount of binder added is an amount that appropriately fills the gaps between the magnet particles in order to improve the thickness accuracy of the sheet when the heated and melted compound is formed into a sheet.
- the ratio of the binder to the total amount of magnet powder and binder is 1 wt% to 40 wt%, more preferably 2 wt% to 30 wt%, and even more preferably 3 wt% to 20 wt%.
- FIG. 2 is an explanatory view showing a manufacturing process of the permanent magnet 1 according to the present embodiment.
- an ingot made of a predetermined fraction of Nd—Fe—B (eg, Nd: 32.7 wt%, Fe (electrolytic iron): 65.96 wt%, B: 1.34 wt%) is manufactured. Thereafter, the ingot is roughly pulverized to a size of about 200 ⁇ m by a stamp mill or a crusher. Alternatively, the ingot is melted, flakes are produced by strip casting, and coarsely pulverized by hydrogen crushing.
- the coarsely pulverized magnet powder is either (a) in an atmosphere made of an inert gas such as nitrogen gas, Ar gas, or He gas having substantially 0% oxygen content, or (b) having an oxygen content of 0.0001.
- the oxygen concentration of substantially 0% is not limited to the case where the oxygen concentration is completely 0%, but may contain oxygen in such an amount that a very small amount of oxide film is formed on the surface of the fine powder. Means good.
- wet pulverization may be used as a method for pulverizing the magnet raw material.
- the coarsely pulverized magnet powder is finely pulverized to an average particle size of not more than a predetermined size (for example, 0.1 ⁇ m to 5.0 ⁇ m) using toluene as a solvent.
- a predetermined size for example, 0.1 ⁇ m to 5.0 ⁇ m
- the magnet powder contained in the organic solvent after the wet pulverization is dried by vacuum drying or the like, and the dried magnet powder is taken out.
- a binder may be further added and kneaded in the organic solvent without taking out the magnet powder from the organic solvent, and then the organic solvent is volatilized to obtain a compound 12 described later.
- a powdery mixture (compound) 12 composed of the magnet powder and the binder is prepared by mixing the binder with the magnet powder finely pulverized by the jet mill 11 or the like.
- a resin, a long-chain hydrocarbon, a fatty acid methyl ester, or the like is used as the binder.
- a resin a thermoplastic resin made of a depolymerizable polymer that does not contain an oxygen atom in the structure is used.
- a long-chain hydrocarbon when a long-chain hydrocarbon is used, the resin is solid at room temperature or above room temperature. It is preferable to use a long-chain saturated hydrocarbon (long-chain alkane) that is liquid.
- the amount of the binder added is such that the ratio of the binder to the total amount of the magnet powder and the binder in the compound 12 after the addition is 1 wt% to 40 wt%, more preferably 2 wt% to 30 wt%, still more preferably 3 wt%. % To 20 wt%.
- the binder is added in an atmosphere made of an inert gas such as nitrogen gas, Ar gas, or He gas.
- the mixing of the magnet powder and the binder is performed, for example, by putting the magnet powder and the binder in an organic solvent and stirring with a stirrer.
- the compound 12 is extracted by heating the organic solvent containing magnet powder and a binder after stirring, and vaporizing an organic solvent.
- the mixing of the magnet powder and the binder is preferably performed in an atmosphere made of an inert gas such as nitrogen gas, Ar gas, or He gas.
- an inert gas such as nitrogen gas, Ar gas, or He gas.
- the binder is added to the organic solvent and kneaded without taking out the magnet powder from the organic solvent used for pulverization, and then the organic solvent is volatilized to be described later. It is good also as a structure which obtains the compound 12.
- the compound 12 is heated to melt the compound 12 to make it into a fluid state, and then hot melt coating is applied to the support substrate 13 such as a separator. Then, the long sheet-like green sheet 14 is formed on the support base material 13 by heat dissipation and solidifying.
- the temperature at which the compound 12 is heated and melted is 50 to 300 ° C., although it varies depending on the type and amount of the binder used. However, the temperature needs to be higher than the melting point of the binder to be used.
- a method having excellent layer thickness controllability such as a slot die method and a calender roll method as the coating method of the melted compound 12.
- a method having excellent layer thickness controllability such as a slot die method and a calender roll method
- coating is performed by extruding a heated compound 12 in a fluid state by a gear pump and inserting the compound 12 into a die.
- the calendar roll method a certain amount of the compound 12 is charged into the gap between the two heated rolls, and the compound 12 melted by the heat of the roll is applied onto the support base 13 while rotating the roll.
- the support base material 13 for example, a silicone-treated polyester film is used as the support base material 13.
- the film is formed on the support substrate 13 by forming the compound 12 melted by extrusion molding into a sheet shape and extruding it onto the support substrate 13 instead of coating on the support substrate 13. It is good also as composition to do.
- FIG. 3 is a schematic view showing a process of forming the green sheet 14 by the slot die method.
- the die 15 used in the slot die system is formed by superimposing blocks 16 and 17 on each other, and a slit 18 and a cavity (liquid reservoir) 19 are formed by a gap between the blocks 16 and 17.
- the cavity 19 communicates with a supply port 20 provided in the block 17.
- the supply port 20 is connected to a coating liquid supply system constituted by a gear pump (not shown) or the like, and the metered fluid-like compound 12 is quantified in the cavity 19 via the supply port 20. Supplied by a pump or the like.
- the fluid-like compound 12 supplied to the cavity 19 is fed to the slit 18 and discharged from the discharge port 21 of the slit 18 with a predetermined application width with a uniform amount in the width direction at a constant amount per unit time.
- the support base material 13 is continuously conveyed at a preset speed as the coating roll 22 rotates.
- the ejected fluid compound 12 is applied to the support base material 13 with a predetermined thickness, and then heat-radiating and solidifying to form a long sheet-like green sheet 14 on the support base material 13. Is done.
- the sheet thickness of the green sheet 14 after coating is measured, and the gap D between the die 15 and the support base 13 is feedback-controlled based on the measured value. desirable. Further, the fluctuation of the amount of the fluid compound 12 supplied to the die 15 is reduced as much as possible (for example, suppressed to fluctuation of ⁇ 0.1% or less), and the fluctuation of the coating speed is reduced as much as possible (for example, ⁇ 0. It is desirable to suppress the fluctuation to 1% or less. Thereby, it is possible to further improve the thickness accuracy of the green sheet 14.
- the thickness accuracy of the formed green sheet 14 is within ⁇ 10%, more preferably within ⁇ 3%, and even more preferably within ⁇ 1% with respect to the design value (for example, 1 mm).
- the design value for example, 1 mm.
- the set thickness of the green sheet 14 is desirably set in the range of 0.05 mm to 20 mm. When the thickness is less than 0.05 mm, the productivity must be reduced because multiple layers must be stacked.
- a plurality of (for example, six) green sheets 14 formed on the support base material 13 by the hot melt coating described above are laminated. And magnetic field orientation is performed with respect to the green sheet 14 in the state where several sheets were laminated
- the lamination of the green sheets 14 may be performed in a process that is continuous with the coating on the support base material 13, or the green sheets 14 formed by the coating are temporarily wound around a roll (first roll) or the like. Then, a step of laminating a plurality of green sheets 14 drawn out from a plurality of rolls around which the green sheets 14 are wound may be used.
- the green sheet 14 is first softened by heating the green sheet 14 that is continuously conveyed together with the support base 13.
- the temperature and time for heating the green sheet 14 vary depending on the number of stacked layers and the type and amount of binder used, but are set to 100 to 250 ° C. for 0.1 to 60 minutes, for example. However, in order to soften the green sheet 14, it is necessary to set the temperature to be equal to or higher than the glass transition point or melting point of the binder used.
- a heating method for heating the green sheet 14 for example, there are a heating method using a hot plate and a heating method using a heat medium (silicone oil) as a heat source.
- a magnetic field is applied simultaneously to the plurality of stacked green sheets 14 by applying a magnetic field in the in-plane direction and the length direction of the green sheets 14 in the stacked state and softened by heating. Alignment is performed.
- the intensity of the applied magnetic field is 5000 [Oe] to 150,000 [Oe], preferably 10,000 [Oe] to 120,000 [Oe].
- the C-axis (easy magnetization axis) of the magnet crystal included in the stacked green sheets 14 is oriented in one direction. Note that the magnetic field may be applied in the in-plane direction and the width direction of the green sheet 14.
- a magnetic field when applying a magnetic field to the green sheet 14, it is good also as a structure which performs the process of applying a magnetic field simultaneously with a heating process, and after applying a heating process and before a green sheet solidifies, a magnetic field is applied. It is good also as performing the process to perform. Moreover, it is good also as a structure which magnetic field orientates before the green sheet 14 apply
- FIG. 4 is a schematic diagram showing a green sheet 14 stacking step, heating step, and magnetic field orientation step.
- the lamination process, the heating process, and the magnetic field orientation process are performed in a process that is continuous with the application to the support base 13 and the magnetic field orientation process is performed simultaneously with the heating process.
- the number of green sheets 14 to be stacked is six.
- lamination, heating, and magnetic field orientation on the green sheet 14 coated by the slot die method described above are performed on the long sheet-like green sheet 14 that is continuously conveyed by a roll. That is, an apparatus for performing lamination, heating, and magnetic field orientation is disposed on the downstream side of the coating apparatus (such as a die), and is performed by a process continuous with the above-described coating process.
- the support base material 13 is pulled out from base material rolls (third rolls) 25 provided at six locations, and a total of six green sheets 14 are formed using the die 15 and the coating roll 22 described above. To do.
- the upper substrate roll 25 and die 15 are omitted, but the substrate roll 25 and die 15 are basically arranged at three locations (6 locations in total) symmetrically in the vertical direction. .
- the solenoid 30 is disposed so that the support base material 13 and the green sheet 14 conveyed in a stacked state pass through the solenoid 30.
- the hot plate 31 is disposed in a pair above and below the green sheet 14 in the solenoid 30. And while heating the some green sheet 14 in a lamination
- a magnetic field is generated in the length direction) in a direction parallel to the sheet surface of the green sheet 14.
- the plurality of green sheets 14 in the laminated state that are continuously conveyed are softened by heating, and a magnetic field is applied in the in-plane direction and the length direction (the direction of arrow 32 in FIG. 4) of the softened green sheets 14.
- a uniform magnetic field can be appropriately oriented with respect to the green sheet 14.
- the surface of the green sheet 14 can be prevented from standing upright by setting the direction in which the magnetic field is applied to the in-plane direction.
- the green sheet 14 formed by coating is once wound up by a roll (1st roll) etc. Thereafter, the green sheet 14 is pulled out from a plurality of rolls around which the green sheet 14 is wound up and continuously conveyed, and the above-described lamination, heating, and magnetic field orientation processes are performed on the plurality of continuously conveyed green sheets 14. .
- a pair of magnetic field coils are arranged on the left and right sides of the green sheet 14 conveyed instead of the solenoid 30. And it becomes possible to generate a magnetic field in the in-plane direction and the width direction of the long sheet-like green sheet 14 by passing a current through each magnetic field coil.
- the magnetic field orientation can be set to the in-plane vertical direction of the green sheet 14.
- the magnetic field application device using a pole piece or the like is used.
- the magnetic field application device 35 using a pole piece or the like includes two ring-shaped coil portions 36 and 37 arranged in parallel so that the central axes are the same, and the coil portion 36. , 37 and two substantially cylindrical pole pieces 38 and 39 respectively disposed in the ring holes, and are spaced apart from the conveyed green sheet 14 by a predetermined distance.
- the film 40 is laminated on the opposite side of the green sheet 14 on which the support base material 13 is laminated as shown in FIG. It is preferable to do. Accordingly, it is possible to prevent the surface of the green sheet 14 from standing upside down.
- FIG. 6 is a diagram illustrating an example of the heating device 41 using a heat medium.
- the heating device 41 forms a substantially U-shaped cavity 43 inside a flat plate member 42 serving as a heating element, and heat heated to a predetermined temperature (for example, 100 to 300 ° C.) in the cavity 43. It is set as the structure which circulates the silicone oil which is a medium.
- the heating device 41 is disposed in a pair above and below the green sheet 14 in the solenoid 30.
- the continuously conveyed green sheet 14 is heated and softened via the flat plate member 42 that is heated by the heat medium.
- the flat plate member 42 may be in contact with the green sheet 14 or may be arranged at a predetermined interval. Then, a magnetic field is applied to the in-plane direction and the length direction (in the direction of arrow 32 in FIG. 4) of the green sheet 14 by the solenoid 30 disposed around the softened green sheet 14.
- An appropriate uniform magnetic field can be oriented.
- the green sheet 14 when the green sheet 14 is formed from a liquid material having high fluidity such as slurry by a general slot die method or doctor blade method without using hot melt molding, a magnetic field gradient is generated.
- the magnetic powder contained in the green sheet 14 is attracted toward the stronger magnetic field, so that the slurry forming the green sheet 14 is closer to the liquid, that is, the thickness of the green sheet 14 is uneven. May occur. Further, when the green sheets 14 are laminated, the green sheets 14 may be deformed.
- the viscosity near room temperature reaches several tens of thousands Pa ⁇ s, and the magnetic powder tends to shift when passing through the magnetic field gradient. It does not occur. Furthermore, the viscosity of the binder is lowered by being transported and heated in a uniform magnetic field, and uniform C-axis orientation is possible only by the rotational torque in the uniform magnetic field. Further, even when the green sheets 14 are laminated, there is no possibility that the green sheets 14 are deformed, and a large number of green sheets 14 can be appropriately laminated.
- the thickness exceeds 1 mm.
- a liquid material having high fluidity such as a slurry containing an organic solvent by a general slot die method or doctor blade method without using hot melt molding
- the thickness exceeds 1 mm.
- foaming due to vaporization of the organic solvent contained in the slurry or the like at the time of drying becomes a problem.
- the drying time is prolonged to suppress foaming, the magnet powder is settled, and accordingly, the density distribution of the magnet powder is biased with respect to the direction of gravity, which causes warping after firing. Therefore, in the molding from the slurry, the upper limit value of the thickness is substantially regulated, so it is necessary to mold the green sheet with a thickness of 1 mm or less and then laminate it.
- the number of stacked green sheets 14 is not limited to six, and may be seven or more or five or less as long as it can pass through the solenoid 30. However, when the number is increased, it is necessary to lengthen the time for heating by the hot plate 31 or the heating device 41.
- a plurality of green sheets 14 in a stacked state subjected to magnetic field orientation are divided into sheets by division rolls 44 to 46 and wound around sheet rolls (second roll, fourth roll) 47, respectively.
- the sheet roll 47 is basically arranged at three positions (total of six positions) symmetrically in the vertical direction. As a result, it is possible to simultaneously manufacture a plurality of green sheets 14 in which the C-axis (easy magnetization axis) of the magnet crystal is aligned in the same direction.
- the manufactured green sheet 14 is punched into a desired product shape (for example, a fan shape shown in FIG. 1), and a formed body 48 is formed.
- a desired product shape for example, a fan shape shown in FIG. 1
- a non-oxidizing atmosphere (particularly a hydrogen atmosphere or hydrogen in the present invention) in which the molded body 48 is pressurized to atmospheric pressure or a pressure higher or lower than atmospheric pressure (for example, 1.0 Pa or 1.0 MPa). And an inert gas mixed gas atmosphere) at a binder decomposition temperature for several hours (for example, 5 hours) to perform a calcination treatment.
- the supply amount of hydrogen during calcination is set to 5 L / min.
- decarbonization for reducing the amount of carbon in the molded body 48 is performed.
- the calcining treatment is performed under the condition that the carbon content in the molded body 48 is 2000 ppm or less, more preferably 1000 ppm or less. Accordingly, the entire permanent magnet 1 can be densely sintered by the subsequent sintering process, and the residual magnetic flux density and coercive force are not reduced.
- the binder decomposition temperature is determined based on the analysis results of the binder decomposition product and decomposition residue. Specifically, a temperature range is selected in which decomposition products of the binder are collected, decomposition products other than the monomers are not generated, and products due to side reactions of the remaining binder components are not detected even in the analysis of the residues. Although it varies depending on the type of the binder, it is set to 200 ° C. to 900 ° C., more preferably 400 ° C. to 600 ° C. (eg 600 ° C.).
- the calcining treatment is performed at the thermal decomposition temperature and binder decomposition temperature of the organic compound constituting the organic solvent. Thereby, the remaining organic solvent can be removed.
- the thermal decomposition temperature of the organic compound is determined depending on the type of the organic solvent to be used, but basically the thermal decomposition of the organic compound can be performed at the binder decomposition temperature.
- NdH 3 (high activity) in the molded body 48 produced by the calcination process is changed stepwise from NdH 3 (high activity) ⁇ NdH 2 (low activity).
- the activity of the molded body 48 activated by the calcination treatment is reduced.
- the sintering process which sinters the molded object 48 calcined by the calcining process is performed.
- a sintering method of the molded body 48 it is also possible to use pressure sintering or the like in which the molded body 48 is sintered in a pressurized state in addition to general vacuum sintering.
- the temperature is raised to a firing temperature of about 800 ° C. to 1080 ° C. at a predetermined temperature increase rate and held for about 0.1 to 2 hours.
- vacuum firing is performed, but the degree of vacuum is preferably 5 Pa or less, and preferably 10 ⁇ 2 Pa or less.
- it is cooled and heat-treated again at 300 ° C. to 1000 ° C. for 2 hours.
- the permanent magnet 1 is manufactured as a result of sintering.
- pressure sintering examples include hot press sintering, hot isostatic pressing (HIP) sintering, ultrahigh pressure synthetic sintering, gas pressure sintering, and discharge plasma (SPS) sintering.
- HIP hot isostatic pressing
- SPS discharge plasma
- the SPS is uniaxial pressure sintering that pressurizes in a uniaxial direction and is sintered by current sintering. Sintering is preferably used.
- the pressure value is set to, for example, 0.01 MPa to 100 MPa, the pressure is increased to 940 ° C.
- FIG. 7 is a schematic view showing a pressure sintering process of the compact 48 by SPS sintering.
- a molded body 48 is placed on a graphite sintering mold 51.
- the calcining process described above may also be performed in a state where the molded body 48 is installed in the sintering mold 51.
- the compact 48 installed in the sintering die 51 is held in the vacuum champ 52, and an upper punch 53 and a lower punch 54 made of graphite are set.
- a low-voltage and high-current DC pulse voltage / current is applied using the upper punch electrode 55 connected to the upper punch 53 and the lower punch electrode 56 connected to the lower punch 54.
- a load is applied to the upper punch 53 and the lower punch 54 from above and below using a pressure mechanism (not shown).
- the molded body 48 installed in the sintering mold 51 is sintered while being pressurized.
- the binder polyisobutylene (PIB) was used. Further, the heated and melted compound was applied to the substrate by a slot die method to form a green sheet. In addition, 6 green sheets were laminated, heated for 5 minutes with a hot plate heated to 200 ° C. in a laminated state, and a 12 T magnetic field was applied to the green sheet in the in-plane direction and in the length direction. Magnetic field orientation was performed.
- PIB polyisobutylene
- the green sheet punched into a desired shape after magnetic field orientation is calcined in a hydrogen atmosphere, and then SPS sintering (pressure value: 1 MPa, sintering temperature: increased to 940 ° C. at 10 ° C./min, 5 minutes) Sintered).
- SPS sintering pressure value: 1 MPa, sintering temperature: increased to 940 ° C. at 10 ° C./min, 5 minutes
- the other steps are the same as those described in the above [Permanent magnet manufacturing method].
- Example 2 The binder to be mixed was a styrene-isoprene block copolymer (SIS) which is a copolymer of styrene and isoprene. Other conditions are the same as in the first embodiment.
- SIS styrene-isoprene block copolymer
- Example 3 The binder to be mixed was octacosane, which is a long-chain alkane. Other conditions are the same as in the first embodiment.
- FIG. 8 is a photograph showing the external shape of the green sheet after magnetic field orientation of Example 1.
- the green sheet after magnet orientation of Example 1 showed no handstand on the magnet surface. Therefore, in the permanent magnet of Example 1 in which the green sheet shown in FIG. 8 is punched to have a desired shape, it is not necessary to perform correction processing after sintering, and the manufacturing process can be simplified. Thereby, a permanent magnet can be formed with high dimensional accuracy.
- FIG. 9 is an SEM photograph of the green sheet after magnetic field orientation of Example 1 observed from the direction perpendicular to the C axis (that is, the in-plane direction and the length direction of the green sheet, which is the direction in which the magnetic field is applied).
- FIG. 10 is a reverse pole figure showing the crystal orientation distribution analyzed using EBSP analysis for the range surrounded by the frame in FIG. Referring to FIG. 10, it can be seen that in the green sheet of Example 1, the magnet particles are oriented in the ⁇ 001> direction compared to the other directions. That is, in Example 1, the magnetic field orientation is appropriately performed even when the magnetic field orientation is performed in a state where the green sheets are laminated, and the magnetic characteristics of the permanent magnet can be improved. If the green sheet is then sintered, the orientation direction of the magnet particles can be further improved. On the other hand, in Comparative Example 1 in which the magnetic field orientation was not performed, the bias as in the example was not observed.
- FIG. 11 shows a list of measurement results.
- the amount of carbon in the magnet can be greatly reduced as compared with the case where the calcination treatment is not performed.
- the amount of carbon remaining in the magnet after sintering is 2000 ppm or less, more specifically 1000 ppm or less, without causing voids between the main phase and the grain boundary phase of the magnet, Moreover, it becomes possible to make the whole magnet into the state sintered precisely, and it can prevent that a residual magnetic flux density falls.
- the compound 12 is generated by pulverizing the magnet raw material into magnet powder and mixing the pulverized magnet powder and the binder. .
- the green sheet 14 which shape
- the permanent magnet 1 is manufactured by bonding.
- the manufacturing process can be simplified. Thereby, a permanent magnet can be formed with high dimensional accuracy. Further, even when the permanent magnet is thinned, it is possible to prevent the processing man-hours from increasing without reducing the material yield. Moreover, since the magnetic field orientation is performed by heating the molded green sheet and applying a magnetic field to the heated green sheet, the magnetic field orientation can be appropriately performed on the green sheet even after molding. The magnetic characteristics of the permanent magnet can be improved. Further, there is no risk of liquid deviation, that is, uneven thickness of the green sheet 14 during magnetic field orientation.
- the viscosity of the binder is lowered by being transported and heated in a uniform magnetic field, and uniform C-axis orientation is possible only by the rotational torque in the uniform magnetic field. Furthermore, even when the green sheet 14 having a thickness exceeding 1 mm is produced, the binder is sufficiently entangled without foaming, so there is no possibility of delamination in the debinding process (calcination process). Further, when the green sheets 14 are magnetically oriented, a plurality of the green sheets 14 are stacked, so that the C-axis orientation can be simultaneously performed on a large number of the green sheets 14 in one process, thereby improving the production efficiency. It becomes possible to raise significantly.
- the green sheet formed by hot melt molding is less likely to cause deformation of the green sheet 14 even when it is laminated as compared with the case of molding from a slurry, and a plurality of green sheets 14 are appropriately laminated. Is possible.
- the green sheet 14 is heated in a state in which a plurality of green sheets 14 are stacked, it is possible to perform heat treatment on a large number of green sheets 14 at the same time in one process, which greatly increases the production efficiency. It can be raised.
- the green sheet 14 is produced by applying the compound 12 to the support substrate 13 that is continuously conveyed, and further, the green sheet 14 that is continuously conveyed with the support substrate 13 is heated and the green sheet 14 is heated.
- the magnetic field orientation is performed by applying a magnetic field
- the production from the green sheet 14 to the heating and the magnetic field orientation can be performed in a continuous process, and the manufacturing process can be simplified and the productivity can be improved. Is possible.
- the magnetic field orientation process is not performed in a process that is continuous with the coating process
- the green sheet formed by hot melt molding is temporarily wound around the first roll, and the green sheets are formed from the plurality of first rolls. Are drawn out and laminated, and a magnetic field is applied by applying a magnetic field to the laminated green sheets.
- the laminated green sheets after the magnetic field orientation are divided into a plurality of sheet rolls ( (Second roll) 47 is wound around each.
- the said structure can carry out in a continuous process from shaping
- the green sheet 14 continuously conveyed with the support base material 13 is passed through the solenoid 30 to which an electric current is applied, a magnetic field is applied to the green sheet 14, so that a uniform magnetic field is applied to the green sheet 14. Can be applied, and magnetic field orientation can be performed uniformly and appropriately.
- the magnetic sheet orientation is performed on the green sheet 14 softened by heating the green sheet 14 to the glass transition point or the melting point of the binder or higher, so that the magnetic field orientation can be appropriately performed. Become.
- the binder is scattered and removed by holding the green sheet 14 at a binder decomposition temperature in a non-oxidizing atmosphere for a certain period of time. Can be reduced. As a result, it is possible to sinter the entire magnet densely without generating voids between the main phase and the grain boundary phase of the sintered magnet, and to prevent the coercive force from being lowered. . Further, a large number of ⁇ Fe is not precipitated in the main phase of the magnet after sintering, and the magnet characteristics are not greatly deteriorated. In the calcination treatment, the green sheet kneaded with the binder is held at a temperature of 200 ° C.
- the amount of carbon contained in the magnet can be more reliably reduced. Further, if a thermoplastic resin or a long-chain hydrocarbon made of a polymer or copolymer of a monomer that does not contain an oxygen atom is used as the binder, the amount of oxygen contained in the magnet can be reduced. Furthermore, the green sheet 14 once formed can be softened by heating, and the magnetic field orientation can be appropriately performed.
- the pulverization conditions, kneading conditions, lamination conditions, magnetic field orientation conditions, calcining conditions, sintering conditions, etc. of the magnet powder are not limited to the conditions described in the above examples.
- the magnet raw material is pulverized by dry pulverization using a jet mill, but may be pulverized by wet pulverization using a bead mill.
- the green sheet is formed by the slot die method, but other methods (for example, calendar roll method, comma coating method, extrusion molding, injection molding, mold molding, doctor blade method, etc.) can be used. It may be used to form a green sheet. However, it is desirable to use a method that can form a fluid compound on a substrate with high accuracy.
- the heating process and magnetic field orientation process of the green sheet 14 will be performed simultaneously, even if it performs a magnetic field orientation process after performing a heating process and before the green sheet 14 solidifies. good. Further, when the magnetic field orientation is performed before the coated green sheet 14 is solidified (that is, the green sheet 14 is already softened without performing the heating process), the heating process may be omitted. . In addition, a heating process may be performed before the green sheets 14 are stacked, and then a stacking process and a magnetic field orientation process may be performed.
- resin long chain hydrocarbon or fatty acid methyl ester is used as the binder, but other materials may be used.
- the coating process by the slot die method, the heating process, and the magnetic field orientation process are performed by a series of continuous processes, but may be configured not to be performed by the continuous processes. Moreover, it is good also as performing by the process which divided
- the Nd—Fe—B type magnet is described as an example, but other magnets (for example, a cobalt magnet, an alnico magnet, a ferrite magnet, etc.) may be used.
- the Nd component is larger than the stoichiometric composition in the present invention, but it may be stoichiometric.
- the present invention can be applied not only to anisotropic magnets but also to isotropic magnets. In that case, the magnetic field orientation process for the green sheet 14 can be omitted.
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Abstract
Description
また、グリーンシートを磁場配向する際には、グリーンシートを複数枚積層した状態で行うので、多数枚のグリーンシートに対して一の工程で同時にC軸配向が可能となり、製造効率を大幅に上昇させることが可能となる。更に、ホットメルト成形により成形したグリーンシートは、スラリーから成形する場合と比較して積層した場合であってもグリーンシートの変形等が生じ難く、適切に複数枚のグリーンシートを積層することが可能となる。
また、グリーンシートを磁場配向する際には、グリーンシートを複数枚積層した状態で行うので、多数枚のグリーンシートに対して一の工程で同時にC軸配向が可能となり、製造効率を大幅に上昇させることが可能となる。更に、ホットメルト成形により成形したグリーンシートは、スラリーから成形する場合と比較して積層した場合であってもグリーンシートの変形等が生じ難く、適切に複数枚のグリーンシートを積層することが可能となる。
先ず、本発明に係る永久磁石1の構成について説明する。図1は本発明に係る永久磁石1を示した全体図である。尚、図1に示す永久磁石1は扇型形状を備えるが、永久磁石1の形状は打ち抜き形状によって変化する。
本発明に係る永久磁石1はNd-Fe-B系の異方性磁石である。尚、各成分の含有量はNd:27~40wt%、B:0.8~2wt%、Fe(電解鉄):60~70wt%とする。また、磁気特性向上の為、Dy、Tb、Co、Cu、Al、Si、Ga、Nb、V、Pr、Mo、Zr、Ta、Ti、W、Ag、Bi、Zn、Mg等の他元素を少量含んでも良い。図1は本実施形態に係る永久磁石1を示した全体図である。
更に、バインダーに樹脂を用いる場合には、構造中に酸素原子を含まず、且つ解重合性のあるポリマーを用いるのが好ましい。また、後述のようにホットメルト成形によりグリーンシートを成形する場合には、成形されたグリーンシートを加熱して軟化した状態で磁場配向を行う為に、熱可塑性樹脂が用いられる。具体的には以下の一般式(1)に示されるモノマーから選ばれる1種又は2種以上の重合体又は共重合体からなるポリマーが該当する。
尚、バインダーに用いる樹脂としては、磁場配向を適切に行う為に250℃以下で軟化する熱可塑性樹脂、より具体的にはガラス転移点又は融点が250℃以下の熱可塑性樹脂を用いることが望ましい。
次に、本発明に係る永久磁石1の製造方法について図2を用いて説明する。図2は本実施形態に係る永久磁石1の製造工程を示した説明図である。
図3に示すようにスロットダイ方式に用いられるダイ15は、ブロック16、17を互いに重ね合わせることにより形成されており、ブロック16、17との間の間隙によってスリット18やキャビティ(液溜まり)19を形成する。キャビティ19はブロック17に設けられた供給口20に連通される。そして、供給口20はギアポンプ(図示せず)等によって構成される塗布液の供給系へと接続されており、キャビティ19には供給口20を介して、計量された流体状のコンパウンド12が定量ポンプ等により供給される。更に、キャビティ19に供給された流体状のコンパウンド12はスリット18へ送液されて単位時間一定量で幅方向に均一な圧力でスリット18の吐出口21から予め設定された塗布幅により吐出される。一方で、支持基材13はコーティングロール22の回転に伴って予め設定された速度で連続搬送される。その結果、吐出した流体状のコンパウンド12が支持基材13に対して所定厚さで塗布され、その後、放熱して凝固することにより支持基材13上に長尺シート状のグリーンシート14が成形される。
また、磁場配向した後に行うグリーンシート14の放熱及び凝固は、搬送状態で行うことが好ましい。それによって、製造工程をより効率化することが可能となる。
図6に示すように、加熱装置41は発熱体となる平板部材42の内部に略U字型の空洞43を形成し、空洞43内に所定温度(例えば100~300℃)に加熱された熱媒体であるシリコーンオイルを循環させる構成とする。そして、図4に示すホットプレート31の代わりに、加熱装置41をソレノイド30内においてグリーンシート14に対して上下一対に配置する。それによって、連続搬送されるグリーンシート14を、熱媒体により発熱された平板部材42を介して加熱し、軟化させる。尚、平板部材42はグリーンシート14に対して当接させても良いし、所定間隔離間させて配置しても良い。そして、軟化したグリーンシート14の周囲に配置されたソレノイド30によって、グリーンシート14の面内方向且つ長さ方向(図4の矢印32方向)に対して磁場が印加され、グリーンシート14に対して適切に均一な磁場を配向させることが可能となる。尚、図6に示すような熱媒体を用いた加熱装置41では、一般的なホットプレート31のように内部に電熱線を有さないので、磁場中に配置した場合であってもローレンツ力によって電熱線が振動したり切断される虞が無く、適切にグリーンシート14の加熱を行うことが可能となる。また、電流による制御を行う場合には、電源のON又はOFFで電熱線が振動することにより疲労破壊の原因となる問題が有るが、熱媒体を熱源とした加熱装置41を用いることによって、そのような問題を解消することが可能となる。
また、特に磁石原料を有機溶媒中で湿式粉砕により粉砕した場合には、有機溶媒を構成する有機化合物の熱分解温度且つバインダー分解温度で仮焼処理を行う。それによって、残留した有機溶媒についても除去することが可能となる。有機化合物の熱分解温度については、用いる有機溶媒の種類によって決定されるが、上記バインダー分解温度であれば基本的に有機化合物の熱分解についても行うことが可能となる。
図7に示すようにSPS焼結を行う場合には、先ず、グラファイト製の焼結型51に成形体48を設置する。尚、上述した仮焼処理についても成形体48を焼結型51に設置した状態で行っても良い。そして、焼結型51に設置された成形体48を真空チャンパー52内に保持し、同じくグラファイト製の上部パンチ53と下部パンチ54をセットする。そして、上部パンチ53に接続された上部パンチ電極55と下部パンチ54に接続された下部パンチ電極56とを用いて、低電圧且つ高電流の直流パルス電圧・電流を印加する。それと同時に、上部パンチ53及び下部パンチ54に対して加圧機構(図示せず)を用いて夫々上下方向から荷重を付加する。その結果、焼結型51内に設置された成形体48は、加圧されつつ焼結が行われる。また、生産性を向上させる為に、複数(例えば10個)の成形体に対して同時にSPS焼結を行うことが好ましい。尚、複数の成形体48に対して同時にSPS焼結を行う場合には、一の空間に複数の成形体48を配置しても良いし、成形体48毎に異なる空間に配置するようにしても良い。尚、成形体48毎に異なる空間に配置する場合には、空間毎に成形体48を加圧する上部パンチ53や下部パンチ54は各空間の間で一体とする(即ち同時に加圧ができる)ように構成する。
尚、具体的な焼結条件を以下に示す。
加圧値:1MPa
焼結温度:940℃まで10℃/分で上昇させ、5分保持
雰囲気:数Pa以下の真空雰囲気
(実施例1)
実施例はNd-Fe-B系磁石であり、合金組成はwt%でNd/Fe/B=32.7/65.96/1.34とする。また、バインダーとしてはポリイソブチレン(PIB)を用いた。また、加熱溶融したコンパウンドをスロットダイ方式により基材に塗工してグリーンシートを成形した。また、成形したグリーンシートを6枚積層するとともに、積層した状態で200℃に加熱したホットプレートにより5分間加熱し、更に、グリーンシートに対して面内方向且つ長さ方向に12Tの磁場を印加することにより磁場配向を行った。そして、磁場配向後に所望の形状に打ち抜いたグリーンシートを水素雰囲気で仮焼し、その後、SPS焼結(加圧値:1MPa、焼結温度:940℃まで10℃/分で上昇させ、5分保持)に焼結した。尚、他の工程は上述した[永久磁石の製造方法]と同様の工程とする。
混合するバインダーをスチレンとイソプレンの共重合体であるスチレン-イソプレンブロック共重合体(SIS)とした。他の条件は実施例1と同様である。
混合するバインダーを長鎖アルカンであるオクタコサンとした。他の条件は実施例1と同様である。
磁場配向を行わずにグリーンシートを焼結することにより永久磁石を製造した。他の条件は実施例と同様である。
混合するバインダーをポリブチルメタクリレートとした。他の条件は実施例1と同様である。
仮焼処理に関する工程は行わずに製造した。他の条件は実施例1と同様である。
ここで、図8は実施例1の磁場配向後のグリーンシートの外観形状を示した写真である。図8に示すように実施例1の磁石配向後のグリーンシートでは磁石表面に逆立ちは見られなかった。従って、図8に示すグリーンシートを打ち抜いて所望の形状とする実施例1の永久磁石では、焼結後の修正加工をする必要がなく、製造工程を簡略化することができる。それにより、高い寸法精度で永久磁石を成形可能となる。
また、グリーンシート14を磁場配向する際には、グリーンシート14を複数枚積層した状態で行うので、多数枚のグリーンシート14に対して一の工程で同時にC軸配向が可能となり、製造効率を大幅に上昇させることが可能となる。更に、ホットメルト成形により成形したグリーンシートは、スラリーから成形する場合と比較して積層した場合であってもグリーンシート14の変形等が生じ難く、適切に複数枚のグリーンシート14を積層することが可能となる。
また、グリーンシート14を複数枚積層した状態でグリーンシート14の加熱についても行うので、多数枚のグリーンシート14に対して一の工程で同時に加熱処理を行うことが可能となり、製造効率を大幅に上昇させることが可能となる。
また、連続搬送される支持基材13に対してコンパウンド12を塗工することによりグリーンシート14を作製し、更に、支持基材13とともに連続搬送されるグリーンシート14を加熱するとともにグリーンシート14に対して磁場を印加することにより磁場配向が行われるので、グリーンシート14の作製から加熱及び磁場配向までを連続した工程で行うことができ、製造工程の簡略化及び生産性の向上を実現することが可能となる。
また、塗工工程と連続した工程で磁場配向工程を行わない場合には、ホットメルト成形によって成形されたグリーンシートを一旦第1のロールに巻き取るとともに、複数個の第1のロールからグリーンシートをそれぞれ引き出して積層するとともに、積層された前記グリーンシートに対して磁場を印加することにより磁場配向し、更に、磁場配向後の積層されたグリーンシートを1枚毎に分けて複数のシートロール(第2のロール)47にそれぞれ巻き取る構成とする。上記構成とすれば、グリーンシートの積層から加熱及び磁場配向までを連続した工程で行うことができ、製造工程の簡略化及び生産性の向上を実現することが可能となる。
また、塗工工程と連続した工程で磁場配向工程を行う場合には、複数個の基材ロール(第3のロール)25からそれぞれ引き出した複数の基材上に混合物をそれぞれシート状に成形することにより複数のグリーンシートを作製し、複数の前記グリーンシートを積層するとともに、積層されたグリーンシートに対して磁場を印加することにより磁場配向し、更に、磁場配向後の積層されたグリーンシートを1枚毎に分けて複数のシートロール(第4のロール)47にそれぞれ巻き取る。上記構成とすれば、グリーンシートの成形から加熱及び磁場配向までを連続した工程で行うことができ、製造工程の簡略化及び生産性の向上を実現することが可能となる。
また、支持基材13とともに連続搬送されるグリーンシート14を、電流を加えたソレノイド30内へ通過させることにより、グリーンシート14に対して磁場を印加するので、グリーンシート14に対して均一な磁場を印加することが可能となり、磁場配向を均一且つ適切に行うことが可能となる。
また、磁場配向する工程では、グリーンシート14をバインダーのガラス転移点又は融点以上に加熱することにより軟化したグリーンシート14に対して磁場配向を行うので、磁場配向を適切に行わせることが可能となる。
また、グリーンシート14を焼結する前に、グリーンシート14を非酸化性雰囲気下でバインダー分解温度に一定時間保持することによりバインダーを飛散させて除去するので、磁石粒子の含有する炭素量を予め低減させることができる。その結果、焼結後の磁石の主相と粒界相との間に空隙を生じさせることなく、また、磁石全体を緻密に焼結することが可能となり、保磁力が低下することを防止できる。また、焼結後の磁石の主相内にαFeが多数析出することなく、磁石特性を大きく低下させることがない。
また、上記仮焼処理では、バインダーが混練されたグリーンシートを水素雰囲気下又は水素と不活性ガスの混合ガス雰囲気下で200℃~900℃、より好ましくは400℃~600℃に一定時間保持するので、磁石内に含有する炭素量をより確実に低減させることができる。
また、バインダーとして、酸素原子を含まないモノマーの重合体又は共重合体からなる熱可塑性樹脂や長鎖炭化水素を用いれば、磁石内に含有する酸素量を低減させることができる。更に、加熱することにより一旦成形されたグリーンシート14を軟化させることができ、磁場配向を適切に行わせることが可能となる。
例えば、磁石粉末の粉砕条件、混練条件、積層条件、磁場配向条件、仮焼条件、焼結条件などは上記実施例に記載した条件に限られるものではない。例えば、上記実施例ではジェットミルを用いた乾式粉砕により磁石原料を粉砕しているが、ビーズミルによる湿式粉砕により粉砕することとしても良い。また、上記実施例では、スロットダイ方式によりグリーンシートを形成しているが、他の方式(例えばカレンダーロール方式、コンマ塗工方式、押出成型、射出成型、金型成型、ドクターブレード方式等)を用いてグリーンシートを形成しても良い。但し、流体状のコンパウンドを基材上に高精度に成形することが可能な方式を用いることが望ましい。
11 ジェットミル
12 コンパウンド
13 支持基材
14 グリーンシート
15 ダイ
25 基材ロール
26~28 積層ロール
30 ソレノイド
31 ホットプレート
44~46 分割ロール
47 シートロール
48 成形体
Claims (9)
- 磁石原料を磁石粉末に粉砕する工程と、
前記粉砕された磁石粉末とバインダーとが混合された混合物を生成する工程と、
前記混合物をホットメルト成形によってシート状に成形したグリーンシートを作製する工程と、
前記グリーンシートを加熱するとともに、加熱された前記グリーンシートを複数枚積層した状態で磁場を印加することにより磁場配向する工程と、
磁場配向された前記グリーンシートを焼結する工程と、を有することを特徴とする希土類永久磁石の製造方法。 - 前記磁場配向する工程では、前記グリーンシートを複数枚積層した状態で加熱することを特徴とする請求項1に記載の希土類永久磁石の製造方法。
- 前記グリーンシートを作製する工程では、連続搬送される基材に対して前記混合物を成形することにより前記基材上に前記グリーンシートを作製し、
前記磁場配向する工程では、前記基材とともに連続搬送される前記グリーンシートを加熱するとともに前記グリーンシートに対して磁場を印加することを特徴とする請求項1又は請求項2に記載の希土類永久磁石の製造方法。 - 前記ホットメルト成形によって成形された前記グリーンシートを第1のロールに巻き取る工程を備え、
前記磁場配向する工程では、複数個の前記第1のロールから前記グリーンシートをそれぞれ引き出して積層するとともに、積層された前記グリーンシートに対して磁場を印加することにより磁場配向し、
磁場配向後の積層された前記グリーンシートを1枚毎に分けて複数の第2のロールにそれぞれ巻き取る工程を更に備えることを特徴とする請求項3に記載の希土類永久磁石の製造方法。 - 前記グリーンシートを作製する工程では、複数個の第3のロールからそれぞれ引き出した複数の前記基材上に前記混合物をそれぞれシート状に成形することにより複数の前記グリーンシートを作製し、
前記磁場配向する工程では、複数の前記グリーンシートを積層するとともに、積層された前記グリーンシートに対して磁場を印加することにより磁場配向し、
磁場配向後の積層された前記グリーンシートを1枚毎に分けて複数の第4のロールにそれぞれ巻き取る工程を更に備えることを特徴とする請求項3に記載の希土類永久磁石の製造方法。 - 前記磁場配向する工程は、前記基材とともに連続搬送される前記グリーンシートを、電流を加えたソレノイド内へ通過させることにより、前記グリーンシートに対して磁場を印加することを特徴とする請求項3に記載の希土類永久磁石の製造方法。
- 前記バインダーは熱可塑性樹脂、長鎖炭化水素、脂肪酸メチルエステル又はそれらの混合物であって、
前記磁場配向する工程では、前記グリーンシートを前記バインダーのガラス転移点又は融点以上に加熱することを特徴とする請求項1に記載の希土類永久磁石の製造方法。 - 前記グリーンシートを焼結する前に、前記グリーンシートを非酸化性雰囲気下でバインダー分解温度に一定時間保持することにより前記バインダーを飛散させて除去することを特徴とする請求項1のいずれかに記載の希土類永久磁石の製造方法。
- 磁石原料を磁石粉末に粉砕する工程と、
前記粉砕された磁石粉末とバインダーとが混合された混合物を生成する工程と、
前記混合物をホットメルト成形によってシート状に成形したグリーンシートを作製する工程と、
前記グリーンシートを加熱するとともに、加熱された前記グリーンシートを複数枚積層した状態で磁場を印加することにより磁場配向する工程と、
磁場配向された前記グリーンシートを焼結する工程と、により製造されることを特徴とする希土類永久磁石。
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- 2013-03-08 KR KR20147004672A patent/KR20140131904A/ko not_active Application Discontinuation
- 2013-03-08 US US14/234,538 patent/US20140152408A1/en not_active Abandoned
- 2013-03-08 WO PCT/JP2013/056432 patent/WO2013137133A1/ja active Application Filing
- 2013-03-08 EP EP13761597.7A patent/EP2827350A4/en not_active Withdrawn
- 2013-03-12 TW TW102108732A patent/TW201351459A/zh unknown
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JPH088111A (ja) * | 1994-06-23 | 1996-01-12 | Murata Mfg Co Ltd | 異方性永久磁石及びその製造方法 |
JP2003026928A (ja) * | 2001-07-02 | 2003-01-29 | Three M Innovative Properties Co | 熱伝導性組成物 |
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KR20140131904A (ko) | 2014-11-14 |
TW201351459A (zh) | 2013-12-16 |
EP2827350A1 (en) | 2015-01-21 |
JP5411957B2 (ja) | 2014-02-12 |
JP2013191615A (ja) | 2013-09-26 |
CN103959410A (zh) | 2014-07-30 |
US20140152408A1 (en) | 2014-06-05 |
EP2827350A4 (en) | 2016-01-20 |
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