WO2013054678A1 - 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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- WO2013054678A1 WO2013054678A1 PCT/JP2012/075366 JP2012075366W WO2013054678A1 WO 2013054678 A1 WO2013054678 A1 WO 2013054678A1 JP 2012075366 W JP2012075366 W JP 2012075366W WO 2013054678 A1 WO2013054678 A1 WO 2013054678A1
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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
- H01F1/06—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 in the form of particles, e.g. powder
- H01F1/08—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 in the form of particles, e.g. powder pressed, sintered, or bound together
- H01F1/086—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 in the form of particles, e.g. powder pressed, sintered, or bound together sintered
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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
- B22F3/12—Both compacting and sintering
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/02—Making ferrous alloys by powder metallurgy
- C22C33/0257—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements
- C22C33/0278—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements with at least one alloying element having a minimum content above 5%
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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
- H01F1/012—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials adapted for magnetic entropy change by magnetocaloric effect, e.g. used as magnetic refrigerating material
- H01F1/015—Metals or alloys
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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
- 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
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/02—Making metallic powder or suspensions thereof using physical processes
- B22F9/04—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling
- B22F2009/044—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling by jet milling
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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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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C2202/00—Physical properties
- C22C2202/02—Magnetic
Definitions
- the present invention relates to a rare earth permanent magnet and a method for producing a rare earth permanent magnet.
- Permanent magnet motors used in hybrid cars, hard disk drives, and the like have been required to be smaller, lighter, higher in output, and more efficient. Further, in order to realize a reduction in size and weight, an increase in output, and an increase in efficiency in the permanent magnet motor, further improvement in magnetic characteristics is required for the permanent magnet embedded in the permanent magnet motor.
- Permanent magnets include ferrite magnets, Sm—Co magnets, Nd—Fe—B magnets, Sm 2 Fe 17 N x magnets, and Nd—Fe—B magnets with particularly high residual magnetic flux density. Used as a permanent magnet for a permanent magnet motor (see, for example, Japanese Patent No. 3298219).
- a powder sintering method is generally used as a manufacturing method of the permanent magnet.
- the powder sintering method first, raw materials are roughly pulverized, and magnet powder is manufactured by finely pulverizing with a jet mill (dry pulverization) or a wet bead mill (wet pulverization). Thereafter, the magnet powder is put into a mold and press-molded into a desired shape while applying a magnetic field from the outside. Then, it is manufactured by sintering the solid magnet powder formed into a desired shape at a predetermined temperature (for example, 800 ° C. to 1150 ° C. for Nd—Fe—B magnets).
- a predetermined temperature for example, 800 ° C. to 1150 ° C. for Nd—Fe—B magnets.
- JP 3298219 A (pages 4 and 5)
- Nd—Fe—B magnet when used for a permanent magnet motor, it is intended to improve the coercive force of the magnet in order to improve the output of the motor.
- the conventional Nd—Fe—B magnets could not sufficiently improve the coercive force.
- the present invention has been made to solve the above-described conventional problems, and improves the coercive force by setting the nitrogen concentration remaining after sintering in an Nd—Fe—B rare earth permanent magnet to 800 ppm or less. It is an object of the present invention to provide a rare earth permanent magnet and a method for producing a rare earth permanent magnet that can be used.
- the rare earth permanent magnet according to the present invention is an Nd—Fe—B rare earth permanent magnet, characterized in that the concentration of nitrogen remaining after sintering is 800 ppm or less.
- the rare earth permanent magnet according to the present invention includes a step of pulverizing a magnet raw material in a rare gas atmosphere to obtain a magnet powder, a step of forming a molded body by molding the magnet powder in a rare gas atmosphere, and And the step of sintering the molded body.
- the rare earth permanent magnet according to the present invention is characterized in that it is calcined in a hydrogen atmosphere pressurized to atmospheric pressure or higher before sintering the compact.
- the rare earth permanent magnet according to the present invention is characterized in that it is calcined in a hydrogen atmosphere pressurized to atmospheric pressure or higher before the magnet powder is formed.
- the rare earth permanent magnet according to the present invention in the step of forming the molded body, a green sheet is produced as the molded body by molding a mixture of a binder resin and the magnet powder into a sheet shape, The step of scattering the binder resin by maintaining the green sheet at a binder resin decomposition temperature for a certain period of time in a non-oxidizing atmosphere and removing the binder resin as a manufacturing step, and in the step of sintering the molded body, The green sheet from which the resin has been removed is sintered by raising the temperature to a firing temperature.
- the rare earth permanent magnet according to the present invention is characterized in that, in the step of scattering and removing the binder resin, the green sheet is held for a certain period of time in a non-oxidizing atmosphere in which the pressure is increased to atmospheric pressure or higher.
- the method for producing a rare earth permanent magnet according to the present invention is a method for producing an Nd—Fe—B rare earth permanent magnet, comprising pulverizing a magnet raw material in a rare gas atmosphere to obtain a magnet powder, It has the process of forming a molded object by shape
- the method for producing a rare earth permanent magnet according to the present invention is characterized by calcining in a hydrogen atmosphere pressurized to atmospheric pressure or higher before sintering the compact.
- the method for producing a rare earth permanent magnet according to the present invention is characterized in that the magnet powder is calcined in a hydrogen atmosphere pressurized to atmospheric pressure or higher before molding the magnet powder.
- a green sheet is formed as the molded body by molding a mixture of a binder resin and the magnet powder into a sheet shape. And further comprising a step of scattering and removing the binder resin by maintaining the green sheet at a binder resin decomposition temperature for a certain time in a non-oxidizing atmosphere, and in the step of sintering the molded body, The green sheet from which the resin has been removed is sintered by raising the temperature to a firing temperature.
- the method for producing a rare earth permanent magnet according to the present invention is characterized in that, in the step of scattering and removing the binder resin, the green sheet is held for a certain period of time in a non-oxidizing atmosphere pressurized to atmospheric pressure or higher.
- the coercive force can be improved by setting the nitrogen concentration remaining after sintering in the Nd—Fe—B rare earth permanent magnet to 800 ppm or less. Become.
- the step of pulverizing the magnet raw material and the step of forming the compact from the magnet powder are performed in a rare gas atmosphere such as helium or argon, so the concentration of nitrogen remaining after sintering Can be reduced to 800 ppm or less.
- a rare gas atmosphere such as helium or argon
- the impurity amount of neodymium nitride NdN can be reduced, and the coercivity of the rare earth permanent magnet can be improved without wasting the Nd-rich phase.
- the carbon powder contained in the magnet particles is reduced in advance by calcining the compact of the magnet powder in a hydrogen atmosphere pressurized to atmospheric pressure or higher before sintering. Can be made. 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 amount of carbon contained in the magnet particles can be reduced in advance by calcining the magnet powder in a hydrogen atmosphere pressurized to atmospheric pressure or higher before molding. .
- a hydrogen atmosphere pressurized to atmospheric pressure or higher before molding.
- 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 organic compound is more easily pyrolyzed with respect to the whole magnet particles as compared with the case of calcining the molded magnet particles. be able to. That is, the amount of carbon in the calcined body can be reduced more reliably.
- the rare earth permanent magnet is composed of a green sheet obtained by sintering a green sheet formed by mixing a mixture of magnet powder and a resin binder.
- a rare earth permanent magnet can be formed with high dimensional accuracy. Further, even when the rare earth permanent magnet is thinned, it is possible to prevent the processing man-hours from increasing without reducing the material yield.
- the amount of carbon contained in the magnet can be reduced in advance by holding the magnet powder to which the binder resin has been added in a non-oxidizing atmosphere for a predetermined time before sintering. As a result, it is possible to suppress the precipitation of ⁇ Fe in the main phase of the magnet after sintering, to densely sinter the entire magnet, and to prevent the coercive force from being lowered.
- the rare earth permanent magnet according to the present invention in the step of scattering and removing the binder resin, since it is held in a pressurized atmosphere pressurized to atmospheric pressure or higher, the amount of carbon contained in the magnet particles is more reliably ensured. Can be reduced.
- the step of pulverizing the magnet raw material and the step of forming the molded body from the magnet powder are performed in a rare gas atmosphere such as helium or argon, so that it remains after sintering. It is possible to reduce the nitrogen concentration to 800 ppm or less. As a result, the impurity amount of neodymium nitride NdN can be reduced, and the coercivity of the rare earth permanent magnet can be improved without wasting the Nd-rich phase.
- the amount of carbon contained in the magnet particles is obtained by calcining a compact of the magnet powder in a hydrogen atmosphere pressurized to atmospheric pressure or higher before sintering. 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 amount of carbon contained in the magnet particles is reduced in advance by calcining the magnet powder in a hydrogen atmosphere pressurized to atmospheric pressure or higher before molding. be able to.
- a hydrogen atmosphere pressurized to atmospheric pressure or higher before molding.
- 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 organic compound is more easily pyrolyzed with respect to the whole magnet particles as compared with the case of calcining the molded magnet particles. be able to. That is, the amount of carbon in the calcined body can be reduced more reliably.
- the rare earth permanent magnet is constituted by a magnet obtained by sintering a green sheet obtained by molding a mixture in which magnet powder and a resin binder are mixed. Uniform shrinkage does not cause deformation such as warping or dents after sintering, and there is no pressure unevenness during pressing, eliminating the need for conventional post-sintering correction and manufacturing.
- the process can be simplified. Thereby, a rare earth permanent magnet can be formed with high dimensional accuracy. Further, even when the rare earth permanent magnet is thinned, it is possible to prevent the processing man-hours from increasing without reducing the material yield.
- the amount of carbon contained in the magnet can be reduced in advance by holding the magnet powder to which the binder resin has been added in a non-oxidizing atmosphere for a predetermined time before sintering. As a result, it is possible to suppress the precipitation of ⁇ Fe in the main phase of the magnet after sintering, to densely sinter the entire magnet, and to prevent the coercive force from being lowered.
- the method for producing a rare earth permanent magnet according to the present invention in the step of scattering and removing the binder resin, since it is held in a pressurized atmosphere pressurized to atmospheric pressure or higher, the amount of carbon contained in the magnet particles is reduced. It can reduce more reliably.
- FIG. 1 is an overall view showing a permanent magnet according to the present invention.
- FIG. 2 is an enlarged schematic view showing the vicinity of the grain boundary of the permanent magnet according to the present invention.
- FIG. 3 is an explanatory view showing a manufacturing process in the first method for manufacturing a permanent magnet according to the present invention.
- FIG. 4 is an explanatory view showing a manufacturing process in the second method for manufacturing a permanent magnet according to the present invention.
- FIG. 5 is a diagram showing a change in the amount of oxygen when the calcination treatment in hydrogen is performed and when it is not performed.
- FIG. 6 is a diagram showing the residual nitrogen concentration and coercive force in the sintered permanent magnet for the permanent magnets of the example and the comparative example.
- FIG. 1 is an overall view showing a permanent magnet 1 according to the present invention.
- 1 has a cylindrical shape, the shape of the permanent magnet 1 varies depending on the shape of the cavity used for molding.
- an Nd—Fe—B rare earth permanent magnet is used as the permanent magnet 1 according to the present invention.
- the permanent magnet 1 is an alloy in which a main phase 11 that is a magnetic phase contributing to a magnetization action and a low melting point Nd-rich phase 12 enriched with rare earth elements coexist.
- FIG. 2 is an enlarged view showing Nd magnet particles constituting the permanent magnet 1.
- the main phase 11 is in a state in which the Nd 2 Fe 14 B intermetallic compound phase (Fe may be partially substituted with Co) having a stoichiometric composition occupies a high volume ratio.
- the Nd-rich phase 12 is an intermetallic compound phase having a higher Nd composition ratio (for example, Nd 2.0 ⁇ ) than Nd 2 Fe 14 B (Fe may be partially substituted with Co) having the same stoichiometric composition. 3.0 Fe 14 B intermetallic compound phase).
- the Nd-rich phase 12 may contain a small amount of other elements such as Dy, Tb, Co, Cu, Ag, Al, Si, and Ga in order to improve magnetic characteristics.
- the Nd rich phase 12 plays the following role.
- the melting point is low (about 600 ° C.), it becomes a liquid phase during sintering, and contributes to increasing the density of the magnet, that is, improving the magnetization.
- the main phase is magnetically insulated to increase the coercive force. Therefore, if the dispersion state of the Nd-rich phase 12 in the sintered permanent magnet 1 is poor, local sintering failure and decrease in magnetism may occur, so that the Nd-rich phase 12 is contained in the sintered permanent magnet 1. It is important that is uniformly dispersed.
- ⁇ Fe is generated in the sintered alloy.
- the cause is that when a permanent magnet is manufactured using a magnet raw material alloy having a content based on the stoichiometric composition, the rare earth element is combined with oxygen and carbon during the manufacturing process, and the rare earth element is compared with the stoichiometric composition. It is mentioned that it becomes insufficiency.
- ⁇ Fe since ⁇ Fe has deformability and remains in the pulverizer without being pulverized, it not only lowers the pulverization efficiency when pulverizing the alloy, but also changes the composition and particle size distribution before and after pulverization. affect.
- the magnetic properties of the magnet are reduced.
- the amount of carbon contained in the magnet particles can be reduced in advance by performing a calcining treatment in hydrogen described below before sintering, thereby avoiding the above problem.
- Nd—Fe—B magnets Another problem that arises in the production of Nd—Fe—B magnets is that the reactivity between Nd and carbon is so high that if a C-containing material remains at a high temperature in the sintering process, carbide is formed. It is done. When the carbide is formed, voids are generated between the main phase of the magnet after sintering and the grain boundary phase (Nd-rich phase) by the formed carbide, and the entire magnet cannot be sintered densely, so that the magnetic performance is improved. There is a problem of significant degradation. However, in the present invention, the amount of carbon contained in the magnet particles can be reduced in advance by performing a calcining treatment in hydrogen described below before sintering, thereby avoiding the above problem.
- the content of all rare earth elements including Nd in the permanent magnet 1 is 0.1 wt% to 10.0 wt%, more preferably 0 than the content (26.7 wt%) based on the stoichiometric composition. Desirably, the amount is within a range of 1 wt% to 5.0 wt%. Specifically, the content of each component is Nd: 25 to 37 wt%, B: 0.8 to 2 wt%, and Fe (electrolytic iron): 60 to 75 wt%.
- the Nd-rich phase 12 can be uniformly dispersed in the sintered permanent magnet 1. Further, even if the rare earth element is combined with oxygen or carbon in the manufacturing process, the rare earth element is not deficient with respect to the stoichiometric composition, and ⁇ Fe is prevented from being generated in the sintered permanent magnet 1. It becomes possible.
- the content of the rare earth element in the permanent magnet 1 is less than the above range, the Nd rich phase 12 is hardly formed. Moreover, the production
- the composition of the rare earth element in the permanent magnet 1 is larger than the above range, the increase in coercive force is slowed and the residual magnetic flux density is lowered, which is not practical.
- the crystal grain size of the main phase 11 is preferably 0.1 ⁇ m to 5.0 ⁇ m.
- the configurations of the main phase 11 and the Nd rich phase 12 can be confirmed by, for example, SEM, TEM, or a three-dimensional atom probe method.
- Dy or Tb having high magnetic anisotropy is included in the Nd-rich phase 12, Dy or Tb can suppress the generation of reverse magnetic domains at the grain boundary, thereby improving the coercive force.
- Nd-rich phase 12 if Vd, Mo, Zr, Ta, Ti, W, or Nb, which are high melting point metals, are included in the Nd-rich phase 12, so-called grain growth in which the average grain size of Nd crystal grains increases during sintering of the permanent magnet 1. Can be suppressed.
- the Nd-rich phase 12 in the sintered permanent magnet 1 can be uniformly dispersed, and the coercive force can be increased.
- the concentration of nitrogen remaining after sintering of the permanent magnet 1 is set to 800 ppm or less, more preferably 300 ppm or less.
- FIG. 3 is an explanatory view showing a manufacturing process in the first manufacturing method of the permanent magnet 1 according to the present invention.
- 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. Thereby, coarsely pulverized magnet powder 31 is obtained.
- Nd—Fe—B eg, Nd: 32.7 wt%, Fe (electrolytic iron): 65.96 wt%, B: 1.34 wt
- the coarsely pulverized magnet powder 31 is either (a) in a rare gas atmosphere such as Ar gas or He gas having an oxygen content of substantially 0%, or (b) an oxygen content of 0.0001 to 0.5%.
- a rare gas atmosphere such as Ar gas or He gas
- the powder is finely pulverized by a jet mill 41 to obtain a fine powder having an average particle size of a predetermined size or less (for example, 0.1 ⁇ m to 5.0 ⁇ m).
- a rare gas atmosphere such as Ar gas or He gas
- the powder is finely pulverized by a jet mill 41 to obtain a fine powder having an average particle size of a predetermined size or less (for example, 0.1 ⁇ m to 5.0 ⁇ m).
- an inert gas atmosphere such as Ar or He that does not contain nitrogen among the inert gases
- the nitrogen concentration remaining later can be made 800 ppm or less, more preferably 300 ppm or less.
- 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.
- the coarsely pulverized magnet powder 31 may be pulverized by wet pulverization using a bead mill or the like. Even when wet pulverization is used, it is performed in an atmosphere of a rare gas such as Ar gas or He gas.
- the solvent used for wet grinding is an organic solvent, but the type of solvent is not particularly limited, and alcohols such as isopropyl alcohol, ethanol and methanol, esters such as ethyl acetate, and lower hydrocarbons such as pentane and hexane. Aromatics such as benzene, toluene and xylene, ketones, mixtures thereof, and the like can be used.
- a hydrocarbon solvent that does not contain an oxygen atom in the solvent is used.
- the magnet powder 42 finely pulverized by the jet mill 41 is compacted into a predetermined shape by the molding device 50.
- the coarsely pulverized magnet powder 31 is pulverized by wet pulverization, a dry method in which the cavity is filled with the magnet powder 42 in which the organic solvent is volatilized, and a wet process in which the slurry containing the organic solvent is filled without being dried.
- the organic solvent can be volatilized in the baking stage after molding.
- Compacting is performed in a rare gas atmosphere such as 0.5% Ar gas, He gas or the like. Since the magnet powder 42 is molded in an inert gas atmosphere such as Ar or He that does not contain nitrogen, among the inert gases, the nitrogen concentration remaining after sintering is 800 ppm or less, more preferably as described later. It becomes possible to make it 300 ppm or less.
- a rare gas atmosphere such as 0.5% Ar gas, He gas or the like. Since the magnet powder 42 is molded in an inert gas atmosphere such as Ar or He that does not contain nitrogen, among the inert gases, the nitrogen concentration remaining after sintering is 800 ppm or less, more preferably as described later. It becomes possible to make it 300 ppm or less.
- the molding apparatus 50 includes a cylindrical mold 51, a lower punch 52 that slides up and down with respect to the mold 51, and an upper punch 53 that also slides up and down with respect to the mold 51. And a space surrounded by them constitutes the cavity 54.
- the molding apparatus 50 has a pair of magnetic field generating coils 55 and 56 disposed above and below the cavity 54, and applies magnetic field lines to the magnet powder 42 filled in the cavity 54.
- the applied magnetic field is, for example, 1 MA / m.
- the dried magnet powder 42 is filled in the cavity 54.
- the lower punch 52 and the upper punch 53 are driven, and pressure is applied to the magnet powder 42 filled in the cavity 54 in the direction of the arrow 61 to perform molding.
- a pulsed magnetic field is applied to the magnetic powder 42 filled in the cavity 54 by the magnetic field generating coils 55 and 56 in the direction of the arrow 62 parallel to the pressurization direction. Thereby orienting the magnetic field in the desired direction.
- the direction in which the magnetic field is oriented needs to be determined in consideration of the magnetic field direction required for the permanent magnet 1 formed from the magnet powder 42.
- the slurry when using the wet method, the slurry may be injected while applying a magnetic field to the cavity 54, and wet molding may be performed by applying a magnetic field stronger than the initial magnetic field during or after the injection. Further, the magnetic field generating coils 55 and 56 may be arranged so that the application direction is perpendicular to the pressing direction.
- the molded body may be molded by green sheet molding instead of the above compacting.
- molding there exist the following methods, for example.
- a first method a pulverized magnet powder, an organic solvent, and a binder resin are mixed to generate a slurry, and the generated slurry is subjected to various coating methods such as a doctor blade method, a die method, and a comma coating method.
- a 2nd method it is the method of shape
- magnetic field orientation is performed by applying a magnetic field before the coated slurry is dried.
- magnetic field orientation is performed by applying a magnetic field in a state where the once formed green sheet is heated.
- the molding is performed in an inert gas atmosphere such as Ar or He.
- the compact 71 formed by compacting or the like is pressurized to atmospheric pressure or higher (for example, 0.5 MPa or 1.0 MPa).
- the calcination treatment in hydrogen is performed by maintaining at 200 ° C. to 900 ° C., more preferably 400 ° C. to 900 ° C. (for example, 600 ° C.) for several hours (for example, 5 hours) in a mixed gas atmosphere of active gas.
- the amount of hydrogen supplied during calcination is 5 L / min.
- the calcination treatment in hydrogen so-called decarbonization is performed in which the remaining organic compound is thermally decomposed to reduce the amount of carbon in the calcination body.
- the calcination treatment in hydrogen is performed under the condition that the amount of carbon in the calcined body is 1500 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.
- a green body When a green body is molded by green sheet molding, it is used in a non-oxidizing atmosphere pressurized to atmospheric pressure or higher (for example, 0.5 MPa or 1.0 MPa) (particularly in the present invention, under a hydrogen atmosphere or with hydrogen.
- a calcining treatment in hydrogen is performed by holding the binder resin decomposition temperature for several hours (for example, 5 hours).
- the binder resin can be decomposed into monomers by a depolymerization reaction or the like and scattered to be removed.
- the binder resin decomposition temperature is determined based on the analysis result of the binder resin decomposition product and decomposition residue.
- 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.
- it is set to 200 ° C. to 900 ° C., more preferably 400 ° C. to 600 ° C. (eg 600 ° C.).
- the molded body 71 calcined by the above-described calcining treatment in hydrogen has a problem that NdH 3 exists and is easily combined with oxygen.
- the molded body 71 is preliminarily hydrogenated. Since it moves to the below-mentioned baking without making it contact with external air after baking, a dehydrogenation process becomes unnecessary. During the firing, hydrogen in the molded body is released.
- the pressurization condition at the time of performing the calcination treatment in hydrogen described above may be a pressure higher than the atmospheric pressure, but is preferably 15 MPa or less. Moreover, you may carry out by atmospheric pressure (about 0.1 MPa).
- the sintering process which sinters the molded object 71 calcined by the calcination process in hydrogen is performed.
- a sintering method of the molded body 71 it is also possible to use pressure sintering which sinters in a state where the molded body 71 is pressed in addition to general vacuum sintering.
- the temperature is raised to about 800 ° C. to 1080 ° C. at a predetermined rate of temperature rise and held for about 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.
- FIG. 4 is an explanatory view showing a manufacturing process in the second manufacturing method of the permanent magnet 1 according to the present invention.
- the magnet powder 42 in a hydrogen atmosphere in which the magnet powder 42 is pressurized to atmospheric pressure or higher (eg, 0.5 MPa or 1.0 MPa), it is 200 ° C. to 900 ° C., more preferably 400 ° C. to 900 ° C. (eg 600 ° C.) for several hours.
- a calcination process in hydrogen is performed.
- the amount of hydrogen supplied during calcination is 5 L / min.
- decarbonization is performed in which the remaining organic compound is thermally decomposed to reduce the amount of carbon in the calcination body.
- the calcination treatment in hydrogen is performed under the condition that the amount of carbon in the calcined body is 1500 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.
- dehydrogenation treatment is performed by holding the powder-like calcined body 82 calcined by calcination in hydrogen at 200 to 600 ° C., more preferably at 400 to 600 ° C. for 1 to 3 hours in a vacuum atmosphere. I do.
- the degree of vacuum is preferably 0.1 Torr or less.
- FIG. 5 shows the magnet powder with respect to the exposure time when the Nd magnet powder subjected to the calcination treatment in hydrogen and the Nd magnet powder not subjected to the calcination treatment in hydrogen are respectively exposed to an atmosphere having an oxygen concentration of 7 ppm and an oxygen concentration of 66 ppm. It is the figure which showed the amount of oxygen in the inside.
- the oxygen content in the magnet powder increases from 0.4% to 0.8% in about 1000 seconds.
- the powder-like calcined body 82 subjected to the dehydrogenation treatment is compacted into a predetermined shape by the molding apparatus 50.
- the details of the molding apparatus 50 are the same as the manufacturing steps in the first manufacturing method already described with reference to FIG.
- a sintering process for sintering the formed calcined body 82 is performed.
- the sintering process is performed by vacuum sintering, pressure sintering, or the like, as in the first manufacturing method described above. Since the details of the sintering conditions are the same as those in the manufacturing process in the first manufacturing method already described, description thereof will be omitted. And the permanent magnet 1 is manufactured as a result of sintering.
- the first manufacturing method in which the magnet particles after molding are calcined in hydrogen are used.
- the thermal decomposition of the remaining organic compound can be more easily performed on the entire magnet particle. That is, it becomes possible to more reliably reduce the amount of carbon in the calcined body as compared with the first manufacturing method.
- the molded body 71 moves to firing without being exposed to the outside air after hydrogen calcination, so that a dehydrogenation step is unnecessary. Therefore, the manufacturing process can be simplified as compared with the second manufacturing method.
- the dehydrogenation step is not necessary when the firing is performed without contact with the outside air after the hydrogen calcination.
- the alloy composition of the neodymium magnet powder of the example is a ratio of Nd rather than a fraction based on the stoichiometric composition (Nd: 26.7 wt%, Fe (electrolytic iron): 72.3 wt%, B: 1.0 wt%).
- Nd / Fe / B 32.7 / 65.96 / 1.34 at wt%.
- dry pulverization was used as a pulverization method, and pulverization was performed in a He atmosphere. Further, the calcination process and the dehydrogenation process were omitted.
- compacting of the molded body was performed under Ar atmosphere using compacting. In addition, the compact was sintered by vacuum sintering. The other steps are the same as those in [Permanent magnet manufacturing method 1] described above.
- FIG. 6 shows the measurement results.
- the example and the comparative example are compared, when the pulverization of the magnet raw material and the molding of the compact are performed in a rare gas atmosphere not containing nitrogen, the pulverization of the magnet raw material and the compact of the compact are performed. It can be seen that the nitrogen concentration in the sintered magnet can be greatly reduced as compared with the case where the molding is performed in a nitrogen atmosphere.
- the concentration of nitrogen remaining in the sintered magnet can be 800 ppm or less, more specifically 300 ppm or less. And it turns out that it is possible to improve a coercive force in the Example with low nitrogen concentration after sintering compared with the comparative example with high nitrogen concentration.
- the Nd—Fe—B rare earth permanent magnet is pulverized by dry pulverization in a rare gas atmosphere, and thereafter Similarly, the green compact molded in a rare gas atmosphere is fired at 800 ° C. to 1180 ° C. to produce a permanent magnet 1 having a nitrogen concentration remaining after sintering of 800 ppm or less, more preferably 300 ppm or less.
- the impurity amount of neodymium nitride NdN can be reduced, and the coercive force of the permanent magnet can be improved without wasting the Nd-rich phase.
- the compact of the magnet powder is calcined in a hydrogen atmosphere pressurized to atmospheric pressure or higher before sintering, the amount of carbon contained in the magnet particles can be reduced in advance.
- the amount of carbon contained in the magnet particles can be reduced in advance.
- the permanent magnet 1 is formed by sintering a green sheet obtained by molding a mixture in which magnet powder and a resin binder are mixed, warping and dents after sintering are caused by uniform shrinkage due to sintering.
- the permanent magnet 1 can be molded with high dimensional accuracy. Further, even when the permanent magnet 1 is thinned, it is possible to prevent an increase in the number of processing steps without reducing the material yield.
- the amount of carbon contained in the magnet can be reduced in advance by holding the magnet powder to which the binder resin has been added in a non-oxidizing atmosphere for a predetermined time before sintering.
- the step of removing the binder resin by scattering is performed by holding the green sheet in a non-oxidizing atmosphere pressurized to atmospheric pressure or higher for a certain period of time, so that the organic compounds remaining before sintering are thermally decomposed.
- the carbon contained in the magnet particles can be burned out in advance (the amount of carbon is reduced), and carbide is hardly formed in the sintering process.
- 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.
- this invention is not limited to the said Example, Of course, various improvement and deformation
- the pulverization conditions, kneading conditions, calcination conditions, dehydrogenation conditions, sintering conditions, etc. of the magnet powder are not limited to the conditions described in the above examples.
- the calcination process or the dehydrogenation process may be omitted.
- the calcination treatment is performed in a hydrogen atmosphere pressurized to 0.5 MPa, but other pressure values may be set as long as the pressure is higher than atmospheric pressure. Moreover, you may set to atmospheric pressure.
- the sintering is performed by vacuum sintering, but the sintering may be performed by pressure sintering such as SPS sintering.
- the Nd—Fe—B system magnet has been described as an example, but other magnets may be used. Further, in the present invention, the Nd component is larger than the stoichiometric composition in the present invention, but it may be stoichiometric.
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Abstract
Description
更に、粉末状の磁石粒子に対して仮焼を行うので、成形後の磁石粒子に対して仮焼を行う場合と比較して、有機化合物の熱分解を磁石粒子全体に対してより容易に行うことができる。即ち、仮焼体中の炭素量をより確実に低減させることが可能となる。
更に、粉末状の磁石粒子に対して仮焼を行うので、成形後の磁石粒子に対して仮焼を行う場合と比較して、有機化合物の熱分解を磁石粒子全体に対してより容易に行うことができる。即ち、仮焼体中の炭素量をより確実に低減させ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は円柱形状を備えるが、永久磁石1の形状は成形に用いるキャビティの形状によって変化する。
本発明に係る永久磁石1としては例えばNd-Fe-B系希土類永久磁石を用いる。また、図2に示すように、永久磁石1は磁化作用に寄与する磁性相である主相11と、非磁性で希土類元素の濃縮した低融点のNdリッチ相12とが共存する合金である。図2は永久磁石1を構成するNd磁石粒子を拡大して示した図である。
(1)融点が低く(約600℃)、焼結時に液相となり、磁石の高密度化、即ち磁化の向上に寄与する。(2)粒界の凹凸を無くし、逆磁区のニュークリエーションサイトを減少させ保磁力を高める。(3)主相を磁気的に絶縁し保磁力を増加する。
従って、焼結後の永久磁石1中におけるNdリッチ相12の分散状態が悪いと、局部的な焼結不良、磁性の低下をまねくため、焼結後の永久磁石1中にはNdリッチ相12が均一に分散していることが重要となる。
次に、本発明に係る永久磁石1の第1の製造方法について図3を用いて説明する。図3は本発明に係る永久磁石1の第1の製造方法における製造工程を示した説明図である。
また、成形装置50には一対の磁界発生コイル55、56がキャビティ54の上下位置に配置されており、磁力線をキャビティ54に充填された磁石粉末42に印加する。印加させる磁場は例えば1MA/mとする。
また、湿式法を用いる場合には、キャビティ54に磁場を印加しながらスラリーを注入し、注入途中又は注入終了後に、当初の磁場より強い磁場を印加して湿式成形しても良い。また、加圧方向に対して印加方向が垂直となるように磁界発生コイル55、56を配置しても良い。
次に、本発明に係る永久磁石1の他の製造方法である第2の製造方法について図4を用いて説明する。図4は本発明に係る永久磁石1の第2の製造方法における製造工程を示した説明図である。
図5は水素中仮焼処理をしたNd磁石粉末と水素中仮焼処理をしていないNd磁石粉末とを、酸素濃度7ppm及び酸素濃度66ppmの雰囲気にそれぞれ暴露した際に、暴露時間に対する磁石粉末内の酸素量を示した図である。図5に示すように水素中仮焼処理した磁石粉末は、高酸素濃度66ppm雰囲気におかれると、約1000secで磁石粉末内の酸素量が0.4%から0.8%まで上昇する。また、低酸素濃度7ppm雰囲気におかれても、約5000secで磁石粉末内の酸素量が0.4%から同じく0.8%まで上昇する。そして、Ndが酸素と結び付くと、残留磁束密度や保磁力の低下の原因となる。
そこで、上記脱水素処理では、水素中仮焼処理によって生成された仮焼体82中のNdH3(活性度大)を、NdH3(活性度大)→NdH2(活性度小)へと段階的に変化させることによって、水素仮焼中処理により活性化された仮焼体82の活性度を低下させる。それによって、水素中仮焼処理によって仮焼された仮焼体82をその後に大気中へと移動させた場合であっても、Ndが酸素と結び付くことを防止し、残留磁束密度や保磁力を低下させることが無い。
一方、第1の製造方法では、成形体71は水素仮焼後に外気と触れさせることなく焼成に移るため、脱水素工程は不要となる。従って、前記第2の製造方法と比較して製造工程を簡略化することが可能となる。但し、前記第2の製造方法においても、水素仮焼後に外気と触れさせることがなく焼成を行う場合には、脱水素工程は不要となる。
(実施例)
実施例のネオジム磁石粉末の合金組成は、化学量論組成に基づく分率(Nd:26.7wt%、Fe(電解鉄):72.3wt%、B:1.0wt%)よりもNdの比率を高くし、例えばwt%でNd/Fe/B=32.7/65.96/1.34とする。また、粉砕方式としては乾式粉砕を用い、He雰囲気下で粉砕を行った。また、仮焼処理や脱水素処理については省略した。また、成形体の成形は圧粉成形を用い、Ar雰囲気下で成形を行った。また、成形体の焼結は真空焼結により行った。尚、他の工程は上述した[永久磁石の製造方法1]と同様の工程とする。
磁石原料の粉砕及び成形体の成形を、それぞれ窒素雰囲気下で行った。他の条件は実施例と同様である。
実施例と比較例の永久磁石について、焼結後の永久磁石中の残存窒素濃度[ppm]と保磁力[kOe]を測定した。図6は測定結果を示した図である。
図6に示すように、実施例と比較例とを比較すると、磁石原料の粉砕及び成形体の成形をそれぞれ窒素を含まない希ガス雰囲気下で行った場合は、磁石原料の粉砕及び成形体の成形をそれぞれ窒素雰囲気下で行った場合と比較して、焼結後の磁石中の窒素濃度を大きく低減させることができることが分かる。特に、実施例では、焼結後の磁石中に残存する窒素濃度を800ppm以下、より具体的には300ppm以下とすることができる。そして、焼結後の窒素濃度の低い実施例では、窒素濃度の高い比較例と比較して保磁力を向上させることが可能となることが分かる。
また、磁石粉末の成形体を焼結前に大気圧以上に加圧した水素雰囲気下で仮焼することとすれば、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、磁石粉末を成形前に大気圧以上に加圧した水素雰囲気下で仮焼することとすれば、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。
更に、粉末状の磁石粒子に対して仮焼を行うので、成形後の磁石粒子に対して仮焼を行う場合と比較して、有機化合物の熱分解を磁石粒子全体に対してより容易に行うことができる。即ち、仮焼体中の炭素量をより確実に低減させることが可能となる。
また、磁石粉末と樹脂バインダーとが混合された混合体を成形したグリーンシートを焼結することにより永久磁石1を構成すれば、焼結による収縮が均一となることにより焼結後の反りや凹みなどの変形が生じず、また、プレス時の圧力むらが無くなることから、従来行っていた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1を成形可能となる。また、永久磁石1を薄膜化した場合であっても、材料歩留まりを低下させることなく、加工工数が増加することも防止できる。また、バインダー樹脂が添加された磁石粉末を、焼結前に非酸化性雰囲気下で一定時間保持することにより、磁石内に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内にαFeが析出することを抑え、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、バインダー樹脂を飛散させて除去する工程では、グリーンシートを大気圧以上に加圧した非酸化性雰囲気下で一定時間保持することにより行うので、焼結前に残存する有機化合物を熱分解させて磁石粒子中に含有する炭素を予め焼失(炭素量を低減)させることができ、焼結工程でカーバイドがほとんど形成されることがない。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、磁石粉末の粉砕条件、混練条件、仮焼条件、脱水素条件、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、仮焼処理や脱水素処理については省略しても良い。例えば、上記実施例では仮焼処理を0.5MPaに加圧した水素雰囲気下で行っているが、大気圧より高い加圧雰囲気下であれば他の圧力値に設定しても良い。また、大気圧に設定しても良い。但し、大気圧より高い加圧雰囲気下で行えば仮焼処理による脱炭の効果が大きくなることが期待できる。また、実施例では真空焼結により焼結を行っているが、SPS焼結等の加圧焼結により焼結しても良い。
11 主相
12 Ndリッチ相
42 磁石粉末
71 成形体
82 仮焼体
Claims (11)
- Nd-Fe-B系の希土類永久磁石であって、
焼結後に残存する窒素濃度が800ppm以下であることを特徴とする希土類永久磁石。 - 磁石原料を希ガス雰囲気下で粉砕して磁石粉末を得る工程と、
前記磁石粉末を希ガス雰囲気下で成形することにより成形体を形成する工程と、
前記成形体を焼結する工程と、
により製造されることを特徴とする請求項1に記載の希土類永久磁石。 - 前記成形体を焼結する前に大気圧以上に加圧した水素雰囲気下で仮焼することを特徴とする請求項2に記載の希土類永久磁石。
- 前記磁石粉末を成形する前に大気圧以上に加圧した水素雰囲気下で仮焼することを特徴とする請求項2に記載の希土類永久磁石。
- 前記成形体を形成する工程では、バインダー樹脂と前記磁石粉末とが混合された混合物をシート状に成形することにより前記成形体としてグリーンシートを作製し、
前記グリーンシートを非酸化性雰囲気下でバインダー樹脂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樹脂を飛散させて除去する工程を製造工程として更に備え、
前記成形体を焼結する工程では、前記バインダー樹脂を除去した前記グリーンシートを焼成温度に温度を上昇して焼結することを特徴とする請求項2に記載の希土類永久磁石。 - 前記バインダー樹脂を飛散させて除去する工程では、前記グリーンシートを大気圧以上に加圧した非酸化性雰囲気下で一定時間保持することを特徴とする請求項5に記載の希土類永久磁石。
- Nd-Fe-B系の希土類永久磁石の製造方法であって、
磁石原料を希ガス雰囲気下で粉砕して磁石粉末を得る工程と、
前記磁石粉末を希ガス雰囲気下で成形することにより成形体を形成する工程と、
前記成形体を焼結する工程と、を有することを特徴とする希土類永久磁石の製造方法。 - 前記成形体を焼結する前に大気圧以上に加圧した水素雰囲気下で仮焼することを特徴とする請求項7に記載の希土類永久磁石の製造方法。
- 前記磁石粉末を成形する前に大気圧以上に加圧した水素雰囲気下で仮焼することを特徴とする請求項7に記載の希土類永久磁石の製造方法。
- 前記成形体を形成する工程では、バインダー樹脂と前記磁石粉末とが混合された混合物をシート状に成形することにより前記成形体としてグリーンシートを作製し、
前記グリーンシートを非酸化性雰囲気下でバインダー樹脂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樹脂を飛散させて除去する工程を更に備え、
前記成形体を焼結する工程では、前記バインダー樹脂を除去した前記グリーンシートを焼成温度に温度を上昇して焼結することを特徴とする請求項7に記載の希土類永久磁石の製造方法。 - 前記バインダー樹脂を飛散させて除去する工程では、前記グリーンシートを大気圧以上に加圧した非酸化性雰囲気下で一定時間保持することを特徴とする請求項10に記載の希土類永久磁石の製造方法。
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US14/342,095 US20140210582A1 (en) | 2011-10-14 | 2012-10-01 | Rare-earth permanent magnet and method for manufacturing rare-earth permanent magnet |
CN201280050452.XA CN103875047A (zh) | 2011-10-14 | 2012-10-01 | 稀土类永久磁铁和稀土类永久磁铁的制造方法 |
KR1020147011142A KR20140090164A (ko) | 2011-10-14 | 2012-10-01 | 희토류 영구 자석 및 희토류 영구 자석의 제조 방법 |
EP12840800.2A EP2767988A4 (en) | 2011-10-14 | 2012-10-01 | Rare-term permanent magnet and method for producing the rare-earth permanent magnet |
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CN104252940B (zh) * | 2014-09-12 | 2016-10-05 | 沈阳中北通磁科技股份有限公司 | 一种氮含量低的钕铁硼永磁铁及制造方法 |
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CN108597709B (zh) * | 2018-04-26 | 2020-12-11 | 安徽省瀚海新材料股份有限公司 | 一种耐腐蚀烧结钕铁硼的制备方法 |
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JP2013089687A (ja) | 2013-05-13 |
CN103875047A (zh) | 2014-06-18 |
TW201330024A (zh) | 2013-07-16 |
KR20140090164A (ko) | 2014-07-16 |
EP2767988A1 (en) | 2014-08-20 |
JP5969750B2 (ja) | 2016-08-17 |
US20140210582A1 (en) | 2014-07-31 |
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