WO2013027592A1 - 磁石用圧粉成形体の製造方法、磁石用圧粉成形体、及び焼結体 - Google Patents
磁石用圧粉成形体の製造方法、磁石用圧粉成形体、及び焼結体 Download PDFInfo
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- WO2013027592A1 WO2013027592A1 PCT/JP2012/070316 JP2012070316W WO2013027592A1 WO 2013027592 A1 WO2013027592 A1 WO 2013027592A1 JP 2012070316 W JP2012070316 W JP 2012070316W WO 2013027592 A1 WO2013027592 A1 WO 2013027592A1
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- 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
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- 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
- H01F1/0555—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 pressed, sintered or bonded together
- H01F1/0557—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 pressed, sintered or bonded together sintered
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- 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
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- 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
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- 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
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- 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
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- 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
- H01F41/0273—Imparting anisotropy
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C2202/00—Physical properties
- C22C2202/02—Magnetic
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- 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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- 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
- H01F1/058—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IVa elements, e.g. Gd2Fe14C
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- 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
- H01F1/059—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and Va elements, e.g. Sm2Fe17N2
Definitions
- the present invention relates to a method for producing a compact for a magnet, which is a raw material for a sintered magnet used for a permanent magnet or the like, a compact for a magnet, and a sintered compact.
- the present invention relates to a method for producing a compact for a magnet, which can produce a compact for obtaining a rare earth magnet having excellent magnet characteristics with high productivity.
- Rare earth magnets are widely used as permanent magnets used in motors and generators.
- Rare earth magnets include sintered magnets manufactured using powder metallurgy and bonded magnets made of a mixture of raw material powder and binder resin. The sintered magnet has a high magnetic phase ratio and excellent magnet characteristics as compared with a bonded magnet in which a binder resin is present.
- a sintered magnet is typically obtained by forming a raw material powder while applying a magnetic field, and sintering the formed body (Patent Document 1, etc.). By applying a magnetic field at the time of molding, the crystal orientation can be improved and the magnet characteristics can be improved.
- fine powder when a powder containing fine particles of 2 ⁇ m or less (hereinafter referred to as fine powder) is used as a raw material, that is, a powder having a particle size distribution, coarse particles are relatively susceptible to a magnetic field when an external magnetic field is applied. Thus, each is rotatable and can be fully oriented. However, since the fine particles have a large specific surface area and a large demagnetizing field, they are relatively difficult to receive a magnetic field. Therefore, even if an external magnetic field is applied, each cannot rotate sufficiently, resulting in insufficient orientation. As a result, when a fine powder is used as the raw material powder, a compacted body having a low orientation with a degree of crystal orientation of about 80% can be obtained.
- the magnetic field that allows the fine particles to sufficiently rotate is of a size that is difficult to generate by external excitation using a general-purpose electromagnet (e.g., solenoid, pulse, etc.) or permanent magnet, i.e., for mass production.
- the size is unsuitable, and the improvement in orientation due to an increase in the magnetic field causes a decrease in industrial productivity.
- conventionally, such fine particles that are difficult to be oriented are removed, and a powder composed of relatively coarse particles has been used as a raw material powder.
- a powder composed of coarse particles 100 is used, even if the crystal orientation of each particle 100 before application of the magnetic field is random as shown in FIG. Thus, it can be oriented in a desired direction.
- the yield is poor, and this leads to a decrease in productivity.
- one of the objects of the present invention is to provide a method for producing a compact for a magnet, from which a rare earth sintered magnet having excellent magnet characteristics can be obtained.
- Another object of the present invention is to provide a compacted green body for a magnet and a sintered body from which a rare earth sintered magnet having excellent magnet characteristics can be obtained.
- the present invention proposes to apply a magnetic field at least twice, to change the direction of application of the magnetic field each time, and to use a superconducting coil for at least one magnetic field.
- the method for producing a green compact for a magnet according to the present invention is a method for producing a green compact to be used for a sintered magnet material, using a powder made of a rare earth alloy containing a rare earth element and iron.
- the following preparation process and molding process are provided.
- molding process comprises the following low pressurization processes, a weak magnetic field application process, and a strong magnetic field application process.
- Preparation step A step of preparing a raw material powder comprising the rare earth alloy and containing fine particles having a particle size of 2 ⁇ m or less of 15% by mass or more and 100% by mass or less.
- Molding step A step of filling the raw material powder into a molding die, pressurizing and compressing it, and applying a magnetic field to form a green compact.
- Low pressurization step a step of pressurizing and compressing the raw material powder filled in the molding die to produce a powder compact having a bulk density of 1.05 to 1.2.
- Weak magnetic field application step a step of applying a weak magnetic field of 1T or more and 2T or less to the powder compact.
- Strong magnetic field application step a step of exciting at 3T or more at an excitation speed of 0.01 T / sec or more and 0.15 T / sec or less, and applying a strong magnetic field of 3T or more to the compact subjected to the weak magnetic field application step.
- the weak magnetic field is applied in a solid angle direction of 90 ° or more and 180 ° or less with respect to a desired direction in which the crystals of the particles constituting the green compact are desired to be oriented.
- the strong magnetic field is applied in a desired direction to be oriented using a superconducting coil.
- the compacted green body for magnets of the present invention is a compacted compact that is used as a raw material for sintered magnets and is composed of powder made of a rare earth alloy containing a rare earth element and iron.
- the powder contains 15% by mass or more and 100% by mass or less of fine particles having a particle size of 2 ⁇ m or less.
- the crystal orientation degree of the said compacting body is 95% or more.
- the method for producing a compact for a magnet according to the present invention uses the fine powder containing the fine particles described above as a raw material powder, and applies a magnetic field of a specific magnitude multiple times in a specific direction as described above.
- a compacting body having a high degree of crystal orientation typically, a compacting body for magnets of the present invention
- fine powder for example, as-pulverized powder, that is, powder having a particle size distribution in which fine coarse particles are mixed can be used as raw material powder as it is, and fine particles can be removed as in the past. It does not have to be.
- the method for producing a compact for a magnet according to the present invention can produce a compact with a good productivity with excellent orientation.
- the rare earth sintered magnet excellent in a magnet characteristic is obtained by utilizing the obtained compacting body for a raw material. Therefore, the manufacturing method of the compacting body for magnets of this invention can contribute to the improvement of the productivity of the rare earth sintered magnet which is excellent in a magnet characteristic.
- the method for producing a green compact for a magnet according to the present invention when the obtained green compact is sintered by using a fine powder having a particle size of 2 ⁇ m as a raw material powder, the crystal grains during sintering are used. Since the size of the field can be reduced, it is expected that the coercive force can be increased regardless of the addition of Dy. Therefore, the method for producing a compact for a magnet according to the present invention is expected to contribute to improving the productivity of a sintered magnet having excellent magnet characteristics from the viewpoint of dealing with the Dy resource problem.
- the green compact for magnets of the present invention is excellent in orientation, a rare earth sintered magnet having excellent magnet characteristics can be obtained by using it as a raw material for sintered magnets.
- the sintered body of the present invention obtained by sintering the compacted body for magnets of the present invention is excellent in magnet characteristics by using the compacted body of the present invention having high orientation as a material. It can be suitably used as a rare earth sintered magnet.
- the magnetic field is excited to 3 T or more at an excitation speed of 0.01 T / sec or more and 0.15 T / sec or less, and after reaching 3 T or more, a strong magnetic field of 3 T or more is applied.
- the state which pressurizes and compresses the molded object which passed through the said weak magnetic field application process so that it may become a packing density exceeding 1.2 of bulk density in a state is mentioned.
- the compact can be made dense by further pressurizing and compressing in a state where a strong magnetic field is applied, so that a compact compact having high strength and excellent handling properties can be obtained.
- the magnetic field is excited to 3 T or more at an excitation speed of 0.01 T / sec or more and 0.15 T / sec or less, and after reaching 3 T or more, a strong magnetic field of 3 T or more is applied.
- the compact subjected to the weak magnetic field application process is further pressurized and compressed so that the packing density is more than 1.2 and 1.45 or less in bulk density, and 5 T or more at an excitation speed of 0.01 T / sec or more and 0.15 T / sec or less.
- the above compact is pressed and compressed so that the bulk density is 1.45 or more and 66% or less of the true density with a strong magnetic field of 5T or more applied. It is done.
- pressing and compressing in a state where a larger magnetic field is applied can further enhance the orientation and further densify. It is possible to obtain a compact having a higher strength and higher strength. Moreover, by making the final degree of compression within the specific range, it is possible to prevent the particles from cracking and to suppress the deterioration of the magnet characteristics due to the cracking.
- the superconducting coil is a high-temperature superconducting coil
- the high-temperature superconducting coil has (1) large excitation speed (0.01T / sec or more, further 0.1T / sec or more), (2) large magnetic field can be applied (3T or more, further 5T or more), (3) magnetic field Large application range. Therefore, unlike the normal conducting pulse coil in which the magnetic field application area is small, the above form can be used for a compacted body of any size that can be used as a permanent magnet material, or the content of fine particles is Even if it is high, the orientation can be stably increased, which is industrially significant.
- the method for producing a compact for a magnet according to the present invention can produce a compact for a magnet having excellent orientation with high productivity.
- the compacted green body for a magnet of the present invention and the sintered body of the present invention can provide a rare earth sintered magnet having a high degree of crystal orientation and excellent magnet characteristics.
- a powder made of a rare earth alloy is prepared.
- Raw material powder is obtained by pulverizing a melt-cast ingot made of an alloy having a desired composition or a foil-like body obtained by a rapid solidification method using a crushing device such as a jaw crusher, a jet mill or a ball mill, or by using an atomizing method such as a gas atomizing method. Can be manufactured. You may further grind
- the shape of the particles is not particularly limited, but the closer to a true sphere, the easier it becomes to be densified and the more easily the particles rotate by applying a magnetic field.
- the atomizing method is used, powder with high sphericity can be obtained.
- the particle size of the raw material powder is a value measured by a laser diffraction particle size distribution device. Substantially all of the raw material powder can be made into fine particles of 2 ⁇ m or less (content of fine particles in the raw material powder: 100% by mass).
- the manufacturing method of the compacting body for magnets of the present invention does not exist in the past by applying a magnetic field of a specific magnitude a plurality of times in a specific direction and applying a magnetic field by high-speed excitation of a specific magnitude.
- a powder containing very fine particles for example, 1 ⁇ m or less
- a powder compact is obtained.
- a rare earth sintered magnet having a magnet characteristic equal to or higher than that of a sintered magnet using the green compact obtained by a conventional manufacturing method as a raw material can be obtained.
- the maximum particle size is preferably 20 ⁇ m or less, more preferably 15 ⁇ m or less.
- the content of particles of 2 ⁇ m or less in the raw material powder is preferably 25% by mass or more, more preferably 35% by mass or more, and particularly preferably 50% by mass or more.
- Lubricant can be added to the raw material powder.
- a mixture containing a lubricant is used, each particle constituting the raw material powder is easily rotated when a magnetic field is applied, and the orientation is easily improved.
- various materials and forms (liquid or solid) that do not substantially react with the raw material powder can be used.
- liquid lubricants include ethanol, machine oil, silicone oil, castor oil, and solid lubricants include metal salts such as zinc stearate, hexagonal boron nitride, and wax.
- the amount of lubricant added is about 0.01% to 10% by weight with respect to 100g of raw material powder for liquid lubricants, and about 0.01% to 5% by weight with respect to the weight of raw material powders for solid lubricants. Is mentioned.
- Molding process (Low pressure process) A molding die having a desired shape and size is prepared so that a compact with a desired shape and size can be obtained.
- the mold for molding those conventionally used for the production of a green compact used for a sintered magnet material, typically those having a die and upper and lower punches can be used. .
- hydrostatic pressure Cold Isostatic Press
- Cold Isostatic Press can be used.
- a powder compact is formed. Specifically, the powder compact obtained after pressing and compression is compressed so that the filling density satisfies the bulk density of 1.05 to 1.2.
- the bulk density is the apparent density immediately before pressing / compressing the raw material powder (the mass of the raw material powder filled in the molding die / the volume of the molding region before pressing / compressing in the molding die).
- Magnitude of applied pressure during molding can be appropriately selected depending on the packing density, for example, 0.05ton / cm 2 ⁇ 0.5ton / cm 2. As will be described later, when pressing and compression are performed in multiple stages, the pressing pressure at each molding may be selected according to the filling density.
- the magnetic field application direction is not the direction in which the crystal of the particles constituting the finally obtained green compact is to be oriented, but in the range of 90 ° to 180 ° in solid angle with respect to the direction to be oriented. The direction is shifted. That is, one feature of the method for producing a compact for a magnet of the present invention is that it includes a step of applying a magnetic field in a direction different from the direction to be oriented.
- a magnetic field is not applied in the same direction many times, but at least two magnetic fields are applied in different directions. Also, a direction different from the direction in which the first one of the two times is desired to be oriented. By doing so, the particles rotated by the first application of the magnetic field are rotated in a direction different from the direction in which they are intended to be oriented, so that the particles are also rotated by the second application of the magnetic field.
- the number of rotating particles increases, that is, the size of coarse particles existing around fine particles, coarse particles, and fine particles that did not rotate the first time. Therefore, fine particles having the same particle size can be gathered and rotated as a particle group, so that the fine particles can be easily rotated in the direction in which they are to be oriented.
- the application of the magnetic field in the weak magnetic field application step is mainly an operation for increasing the number of particles that are rotated when the second magnetic field is applied, and is not an operation for rotating the particles in the direction to be oriented. Therefore, in the weak magnetic field application step, it is only necessary to rotate particles larger than 2 ⁇ m, more than 3 ⁇ m, particularly 5 ⁇ m, and therefore a relatively small magnetic field of 1 T or more and 2 T or less may be used.
- a magnet capable of applying a magnetic field of 1T to 2T specifically, a normal conducting magnet having a normal conducting coil such as a copper wire coil, or a superconducting magnet having a superconducting coil is used. Either can be used.
- the strong magnetic field application step is mainly a step for enhancing the orientation of the molded body that has undergone the weak magnetic field application step (hereinafter, this molded body is referred to as a pre-molded body), and is finally obtained a green compact A magnetic field is applied in the direction in which the crystal of the particles constituting the crystal is to be oriented.
- this step one of the features is that high-speed excitation with an excitation speed of 0.01 T / sec or more is performed and a strong magnetic field of 3 T or more is applied.
- rotation of each particle constituting the pre-molded body can be performed simultaneously.
- the excitation speed is as slow as less than 0.01T / sec
- only coarse particles rotate when they reach a magnetic field of about 1T to 2T, and when they reach 3T, there is a risk that the rotation of the coarse particles has ended. is there.
- the excitation speed is set to 0.15 T / sec or less. By setting the excitation speed to 0.15 T / sec or less, it is possible to rotate the particles stably and to produce a compact with high orientation.
- the magnitude of the applied magnetic field is more preferably 5 T or more.
- a normal conducting magnet may be used, but a superconducting magnet, particularly a high-temperature superconducting magnet can be suitably used.
- the low-temperature superconducting magnet generally requires about 5 to 10 minutes for 1T fluctuation, and the excitation speed is less than 0.01 T / sec.
- a high-temperature superconducting magnet can change 1T within 10 seconds, that is, an excitation speed of 0.1 T / sec or more is possible, and a strong magnetic field of 3 T or more and 5 T or more can be easily formed.
- the high-temperature superconducting magnet can be excited at a speed of 0.1 T / sec or less, for example, 0.01 T / sec or more, and can cope with a low speed to a high speed.
- the high temperature superconducting magnet has a larger application range than the normal conducting magnet and can apply a large magnetic field to a wide space. Therefore, the high-temperature superconducting magnet can be used for manufacturing a small green compact and a large green compact, and has a high degree of freedom in the size of a magnetic field application target. Furthermore, since the magnetic field fluctuation can be performed at high speed, the application of the magnetic field can be controlled quickly.
- the high-temperature superconducting magnet can generate a strong magnetic field for a longer time than a normal conducting pulse coil, and can rotate the raw material powder even in a relatively low magnetic field.
- the vaporized lubricant can be removed by suction under reduced pressure).
- the amount of lubricant used may be reduced or the lubricant may be omitted.
- a high-temperature superconducting magnet is typically used by cooling a superconducting coil composed of an oxide superconductor by conduction cooling using, for example, a refrigerator (operating temperature is about ⁇ 260 ° C. or more).
- the application direction of the magnetic field in the strong magnetic field application step is the direction in which the crystals of the particles constituting the finally obtained green compact are to be oriented. That is, the manufacturing method of the compacting body for magnets of the present invention is characterized in that it includes a step of improving the orientation by applying a magnetic field in a direction different from the weak magnetic field applying step. As described above, in the weak magnetic field application step, after applying a magnetic field in a direction different from the direction to be oriented (typically the reverse direction), the magnetic field is applied again in the direction to be oriented. By applying a strong magnetic field by high-speed excitation, even when fine particles are contained, the particles can be sufficiently and stably rotated, and a compacted article having excellent orientation can be obtained.
- the pre-molded body is excited with 3T or more at an excitation speed of 0.01T / sec or more and 0.15T / sec or less, and after reaching 3T or more, a strong magnetic field of 3T or more is applied. Is further pressed and compressed (hereinafter, this pressurization is referred to as a first densification pressurization) to obtain a dense powder compact.
- this pressurization is referred to as a first densification pressurization
- the pre-molded body is pressed and compressed so as to have a bulk density exceeding 1.2 of the bulk density
- the compacted body whose strength has been increased by densification (having a bulk density exceeding 1.2 of the bulk density)
- a green compact one form of the green compact of the present invention) is obtained.
- the particles can be sufficiently rotated to enhance the above-described orientation during excitation.
- pressure and compression are performed in a state where a magnetic field of 3 T or more is applied, it is difficult to reduce the orientation during pressing, and fine particles can be rotated sufficiently and stably by applying a strong magnetic field.
- the orientation can be further improved.
- this form provides a dense green compact with a higher degree of crystal orientation.
- the larger the magnetic field at the time of starting pressurization / compression on the pre-molded body the higher the orientation tends to be, and the magnetic field is more preferably 5T or more.
- the first densification pressure is applied so that the packing density becomes more than 1.2 and 1.45 or less of the bulk density, and then the excitation speed is 0.01 T / sec or more and 0.15 T / sec or less.
- the first densification pressurization is carried out so that the bulk density is 1.45 or more and 66% or less of the true density when a strong magnetic field of 5T or more is applied after excitation at 5T or more.
- the applied molded body hereinafter, this molded body is referred to as a densified molded body
- this pressurization is referred to as a second densified pressure).
- the second densification pressurization is also a high-speed excitation of a specific size, so that the orientation of fine particles in the densified molded body can be further enhanced while suppressing a decrease in orientation during excitation. Densification can be achieved.
- a green compact one form of the green compact of the present invention having a filling density of 1.45 or more of the bulk density and 66% or less of the true density is obtained.
- the larger the magnetic field at the time of starting pressurization / compression on the densified compact, the higher the orientation, and the more preferable the magnetic field is 5.5T or more.
- the magnetic field is preferably 10T or less, and more preferably 8T or less.
- the excitation speed of both the first densification pressure and the second densification pressure is more preferably 0.1 T / sec or more.
- the above-described weak magnetic field and strong magnetic field can be formed. Therefore, the application of the weak magnetic field and the application of the strong magnetic field can be performed using one superconducting magnet.
- the high magnetic field application process requires high-speed excitation, so it is necessary to demagnetize the magnetic field in the weak magnetic field application process and then re-excited. Time is needed.
- the superconducting magnet is used regardless of whether a magnetic field is generated by the magnet used in the weak magnetic field application process.
- the manufacturing time can be shortened.
- the magnitude of the magnetic field by the superconducting magnet can be adjusted so as to cancel the weak magnetic field.
- the compacted body for magnet of the present invention contains fine particles having a particle size of 2 ⁇ m or less.
- the content of fine particles can be changed by the raw material powder.
- the fine particle content may be 25% by mass or more, particularly 35% by mass or more, and further 50% by mass or more.
- the compacted body for magnet of the present invention has a very high degree of crystal orientation and can be in a form satisfying 95% or more, and more preferably 97% or more. A method for measuring the degree of crystal orientation will be described later.
- the size and material of the particles constituting the magnet compact of the present invention substantially maintain the size and material of the raw material powder.
- the size of the particles constituting the green compact is obtained by, for example, observing the surface or cross section of the green compact with a microscope, extracting the particle contour from the observed image, and calculating the area of the extracted contour.
- the diameter of a circle having an equivalent area can be used as the particle size of the particles. This particle size can be easily calculated using a commercially available image processing apparatus.
- the composition of the particles constituting the green compact can be confirmed, for example, by X-ray diffraction.
- the sintered compact of the present invention can be obtained by sintering the green compact for magnets of the present invention.
- the sintering conditions include temperature: 1000 ° C. to 1200 ° C., holding time: 0.5 hours to 3 hours, atmosphere: vacuum, argon, and the like.
- heat treatment for example, aging treatment
- the heat treatment conditions include temperature: 500 ° C. to 800 ° C., holding time: 1 hour to 10 hours, atmosphere: vacuum, argon, and the like.
- the obtained sintered body can be suitably used for rare earth sintered magnets, typically permanent magnets.
- [Raw material powder] A melt cast ingot made of an Nd 2.2 FeB alloy was prepared, subjected to solution treatment at 1100 ° C. for 10 hours, and then pulverized with a ball mill to produce a raw material powder. A plurality of powders having different particle size distributions were produced by varying the pulverization time. The particle size distribution was measured with a commercially available laser diffraction particle size distribution analyzer. Table 1 shows the particle size distribution of the prepared raw material powder and the content (% by mass) of particles of 2 ⁇ m or less. In any of the raw material powders, particles exceeding 15 ⁇ m are substantially absent. Each raw material powder was kneaded with 0.8% by mass of zinc stearate (lubricant).
- the molding die 50 is arranged with a die 51 having a through hole, a columnar lower punch 53 inserted through the die 51, and opposed to the lower punch 53, and pressurizes and compresses the raw material powder P together with the lower punch 53. It has an upper punch 52.
- the die 51 and the lower punch 53 form a molding space, the molding space is filled with the raw material powder P, and the upper punch 52 and the lower punch 53 are pressurized and compressed.
- a magnetic field can be formed by appropriately energizing each of the coils 60 and 70, and a magnetic field can be applied to the molded body 10 in the molding space.
- the direction in which the particles constituting the finally formed green compact are to be oriented is set in advance, and the solid angle formed by the direction in which the magnetic fields of both coils 60 and 70 are applied to the desired orientation is within the desired range.
- Both coils 60 and 70 are arranged so that For example, as shown in FIG. 1, when both coils 60 and 70 are arranged coaxially, the direction of the magnetic field application can be reversed by reversing the direction of the energizing current of each coil 60 and 70. (A broken line arrow and a two-dot chain line arrow in the figure illustrate the application direction of the magnetic field). That is, in this case, the magnetic field application direction of the superconducting coil 60 can be set to a solid angle of 180 ° with respect to the magnetic field application direction of the normal conductive coil 70.
- the direction in which the magnetic field is applied by the high-temperature superconducting coil is set to the solid angle shown in Table 2 with respect to the direction in which the magnetic field is applied to the normal conducting coil.
- the direction in which the magnetic field is applied by the high-temperature superconducting coil is opposite to the direction in which the magnetic field is applied by the normal conducting coil, that is, the direction in which the final compact is to be oriented.
- a sample having a solid angle of 0 ° means that a magnetic field by a high-temperature superconducting coil is applied in the same direction as the direction of application of the magnetic field by the normal conducting coil.
- the application direction of the magnetic field by the normal conducting coil and the high-temperature superconducting coil was set to the direction in which the orientation is desired.
- the position of the normal conducting coil was changed from the position shown in FIG. 1 so as to satisfy the solid angle.
- the above-mentioned weak magnetic field was demagnetized by turning off the energization of the normal conducting coil.
- the magnetic field of “superconducting coil I” was excited at the excitation speed shown in Table 2 to the magnetic field of “superconducting coil II” shown in Table 2, and the magnetic field was applied by the high-temperature superconducting coil.
- the compact was pressed and compressed by applying a magnetic field of the “superconducting coil I” while adjusting the pressure so that the packing density was 66% or less of the bulk density of 1.45 and the true density.
- the direction of application of the magnetic field was the same as in the superconducting coil I.
- the green compact 1 (FIG. 2C) is obtained.
- grains which comprise a compacting body substantially satisfy
- the degree of crystal orientation was examined for each obtained compacted body. The results are shown in Table 2.
- the degree of crystal orientation was measured as follows. In the green compact, the plane perpendicular to the direction in which the magnetic field is applied by the superconducting coil (here, the plane perpendicular to the pressing direction and the surface in contact with the upper punch or the lower punch) is used as the measurement surface. A pole figure analysis of X-ray diffraction was performed. Then, the (006) plane diffraction spot whose solid angle with the direction of application of the magnetic field of the superconducting coil is within 3 ° is measured, and the ratio of the (006) plane diffraction spot to the diffraction spot of the entire measurement surface is crystal orientation Degree. For sample No. 35 that could not be excited, the degree of crystal orientation was not examined.
- the obtained green compacts were subjected to vacuum sintering at 1050 ° C. for 3 hours and aging treatment at 650 ° C. for 5 hours to obtain sintered bodies.
- the degree of crystal orientation, the residual magnetic flux Br (T), and the coercive force Hc (MA / m) were determined. The results are shown in Table 3.
- the degree of crystal orientation of the sintered body was measured in the same manner as the green compact.
- the residual magnetic flux Br and the coercive force Hc were obtained by magnetizing each sintered body in the same direction as the direction of the magnetic field applied by the high-temperature superconducting coil, and using the demagnetization curve after this magnetization.
- the crystal orientation of the particles is random.
- the arrow in the particle indicates the direction of the easy axis of magnetization.
- the green compact obtained by the above specific manufacturing method including the fine particles and having excellent orientation, has substantially maintained orientation even after sintering.
- the sintered body obtained by sintering this compacted body is the same magnet as the sintered body (sample No. 6, No. 7) using raw material powder containing a lot of relatively coarse powder exceeding 2 ⁇ m. It can be seen that it has excellent magnetic properties.
- the present invention is not limited to the embodiment described above, and can be appropriately changed without departing from the gist of the present invention.
- the composition of the raw material powder, the shape / size of the compact, the excitation speed, the sintering conditions, and the like can be changed as appropriate.
- the sintered body of the present invention can be suitably used as a permanent magnet, for example, a permanent magnet used in various motors, in particular, a high-speed motor provided in a hybrid vehicle (HEV) or a hard disk drive (HDD). .
- the powder compact for magnets of the present invention can be suitably used as the material for the sintered body of the present invention.
- the method for producing a compact for a magnet according to the present invention can be suitably used for producing a compact formed as a material for a rare earth sintered magnet having a high degree of crystal orientation and excellent magnet characteristics.
- the method for producing a compact for a magnet of the present invention includes Sr-Fe-O, Ba-Fe-O, La-Sr-Fe-Co-O, La-Ca-Fe-Co-O ( It can also be used suitably for the production of hard) ferrite magnets.
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Abstract
Description
準備工程:上記希土類合金からなり、粒径が2μm以下の微細粒子を15質量%以上100質量%以下含む原料粉末を準備する工程。
成形工程:上記原料粉末を成形用金型に充填して加圧・圧縮すると共に、磁場を印加して、圧粉成形体を形成する工程。
低加圧工程:上記成形用金型に充填された上記原料粉末を加圧・圧縮して、嵩密度の1.05以上1.2以下の充填密度である粉末成形体を作製する工程。
弱磁場印加工程:上記粉末成形体に、1T以上2T以下の弱磁場を印加する工程。
強磁場印加工程:0.01T/sec以上0.15T/sec以下の励磁速度で3T以上に励磁して、3T以上の強磁場を上記弱磁場印加工程を経た成形体に印加する工程。
上記弱磁場は、上記圧粉成形体を構成する粒子の結晶を配向させたい所望の方向に対して立体角で90°以上180°以下の方向に印加する。また、上記強磁場は、超電導コイルを用いて、上記配向させたい所望の方向に印加する。
〔製造方法〕
[準備工程]
原料粉末として、希土類合金からなる粉末を用意する。希土類合金は、RE=Y,La,Ce,Pr,Nd,Dy,Tb及びSmから選択される少なくとも1種、X=B,C及びNから選択される1種、ME=Co,Cu,Mn及びNiから選択される少なくとも1種とするとき、RE-Fe-X合金、又はRE-Fe-ME-X合金が挙げられる。より具体的には、Nd-Fe-B合金、Nd-Fe-C合金、Sm-Fe-N合金、Nd-Fe-Co-B合金などが挙げられる。希土類焼結磁石に利用されている公知の希土類合金からなる粉末を原料粉末に利用することができる。
(低加圧工程)
所望の形状・大きさの圧粉成形体が得られるように、所望の形状・大きさの成形用金型を用意する。成形用金型は、従来、焼結磁石の素材に用いられている圧粉成形体の製造に利用されているもの、代表的には、ダイ、上下パンチを具えるものを利用することができる。その他、静水圧加圧(Cold Isostatic Press)を利用することができる。
上記粉末成形体に磁場を印加する。この磁場は、比較的小さくする(1T~2T)。かつ、磁場の印加方向は、最終的に得られる圧粉成形体を構成する粒子の結晶を配向させたい方向ではなく、当該配向させたい方向に対して立体角で90°~180°の範囲でずれた方向とする。即ち、本発明の磁石用圧粉成形体の製造方法では、配向させたい方向とは異なる方向に磁場を印加する工程を具えることを特徴の一つとする。粉末成形体を構成する粒子が粒度分布を有する場合や上述の微細粒子である場合、1回の磁場の印加によって全ての粒子を同じ方向に揃えることが難しく、一部の粒子しか十分に回転しない。そこで、磁場の印加を1回とするのではなく、複数回とすることが考えられる。しかし、微細粒子は、上述のように磁場が印加されても粗大な粒子よりも回転し難いことから、複数回の磁場を同じ方向に印加しても、1回目の磁場の印加により回転した粒子は、以降の磁場の印加により実質的に回転せず、当該微細粒子は十分に回転できないままになる。そこで、本発明の磁石用圧粉成形体の製造方法では、何回も同じ方向に磁場を印加するのではなく、少なくとも2回の磁場を異なる方向に印加する。また、この2回のうちの1回目を配向させたい方向とは異なる方向とする。こうすることで、1回目の磁場の印加により回転した粒子は、本来、配向させたい方向と異なる方向に回転しているため、2回目の磁場の印加でも回転することになる。その結果、2回目の磁場の印加時、回転する粒子数が多くなる、即ち、微細粒子の周囲に存在する粗大な粒子や、粗大な粒子と、1回目に回転しなかった微細な粒子の大きさと同程度の粒子サイズの微細な粒子とが集まって粒子群となって回転できるため、微細粒子を配向させたい方向に回転させ易くすることができる。
強磁場印加工程は、主として、上記弱磁場印加工程を経た成形体(以下、この成形体をプレ成形体と呼ぶ)の配向性を高めるための工程であり、最終的に得られる圧粉成形体を構成する粒子の結晶を配向させたい方向に磁場を印加する。特に、この工程では、励磁速度が0.01T/sec以上という高速励磁を行うと共に、3T以上という強磁場を印加することを特徴の一つとする。高速励磁を行うことで、微粗混合の場合でも、磁場を受け易い粗大粒子の回転時に、微細粒子も同時に回転することができる。即ち、上記プレ成形体を構成する各粒子の回転を同時に行える。励磁速度が0.01T/sec未満と遅い場合、1T~2T程度の磁場に到達した段階で粗大な粒子のみが回転し、3Tに到達した時点では、粗大な粒子の回転が終了している恐れがある。3T以上の強磁場を印加していても微細粒子の周囲の粒子がほとんど回転しないことから、これら周囲の粒子のモーメントによる微細粒子の回転援助を行えず、微細粒子の回転が不十分となり、配向性を高められなくなる。励磁速度が大きいほど、上記プレ成形体を構成する粒子において、同時に回転する粒子数を多くし易いことから、0.05T/sec以上、0.1T/sec以上がより好ましい。一方、パルス励磁のように、励磁速度が大き過ぎると、粒子が回転し過ぎるなどして配向性を高められ難い恐れがあることから、励磁速度は、0.15T/sec以下とする。励磁速度を0.15T/sec以下とすることで、安定して粒子を回転でき、配向性が高い圧粉成形体を良好に製造できる。
本発明の磁石用圧粉成形体は、粒径が2μm以下といった微細粒子を含有する。原料粉末によって、微細粒子の含有量を変化させられる。例えば、微細粒子の含有量が25質量%以上、特に35質量%以上である形態、更に50質量%以上である形態とすることができる。
本発明の磁石用圧粉成形体を焼結することで本発明の焼結体が得られる。焼結条件は、例えば、温度:1000℃~1200℃、保持時間:0.5時間~3時間、雰囲気:真空、アルゴンなどが挙げられる。焼結後、磁石特性を調整するための熱処理(例えば、時効処理)を適宜施すことができる。この熱処理条件は、温度:500℃~800℃、保持時間:1時間~10時間、雰囲気:真空、アルゴンなどが挙げられる。得られた焼結体は、希土類焼結磁石、代表的には永久磁石に好適に利用できる。
以下、試験例を挙げて、本発明のより具体的な実施形態を説明する。
この試験では、希土類-鉄-ホウ素系合金からなり、種々の粒度分布を有する原料粉末を用意し、低加圧成形→弱磁場印加→強磁場印加という成形工程を経て圧粉成形体を作製し、得られた圧粉成形体の配向性を調べた。また、得られた圧粉成形体を焼結し、得られた焼結体の配向性及び磁気特性を調べた。
Nd2.2FeB合金からなる溶解鋳造インゴットを用意し、1100℃×10時間の溶体化処理を施した後、ボールミルで粉砕して原料粉末を作製した。粉砕時間を異ならせることで、粒度分布が異なる複数の粉末を作製した。粒度分布は、市販のレーザ回折式粒度分布測定装置で測定した。表1に、用意した原料粉末の粒度分布、2μm以下の粒子の含有量(質量%)を示す。なお、いずれの原料粉末も15μm超の粒子は実質的に存在していない。各原料粉末には、0.8質量%のステアリン酸亜鉛(潤滑剤)を混練した。
次に、上記原料粉末を加圧・圧縮する成形用金型、及び成形体に磁場を印加する磁石を説明する。この試験では、弱磁場の印加に常電導コイル(ここでは銅線コイル)を具える常電導磁石を用い、強磁場の印加に高温超電導コイルを具える高温超電導磁石を用いた。ここでは、図1に示すように、高温超電導コイル60と常電導コイル70とを同軸に配置し、これらコイル60,70の内周に成形用金型50を配置した。成形用金型50は、貫通孔を有するダイ51と、ダイ51に挿通配置される柱状の下パンチ53と、下パンチ53に対向配置され、下パンチ53と共に原料粉末Pを加圧・圧縮する上パンチ52を具える。ダイ51と下パンチ53とで成形空間を形成し、成形空間に原料粉末Pを充填し、上パンチ52と下パンチ53とで加圧・圧縮する。このとき、各コイル60,70に適宜通電することで、磁場を形成することができ、成形空間内の成形体10に磁場を印加することができる。
50 成形用金型 51 ダイ 52 上パンチ 53 下パンチ
60 高温超電導コイル 70 常電導コイル
P 原料粉末 100 粗大な粒子 150 微細粒子
Claims (7)
- 焼結磁石の素材に利用され、希土類元素と鉄とを含む希土類合金からなる粉末により構成された磁石用圧粉成形体であって、
前記粉末は、粒径が2μm以下の微細粒子を15質量%以上100質量%以下含み、
前記圧粉成形体の結晶配向度が95%以上である磁石用圧粉成形体。 - 希土類元素と鉄とを含む希土類合金からなる粉末を用いて、焼結磁石の素材に利用される圧粉成形体を製造する磁石用圧粉成形体の製造方法であって、
前記希土類合金からなり、粒径が2μm以下の微細粒子を15質量%以上100質量%以下含む原料粉末を準備する準備工程と、
前記原料粉末を成形用金型に充填して加圧・圧縮すると共に、磁場を印加して、圧粉成形体を形成する成形工程とを具え、
前記成形工程は、
前記成形用金型に充填された前記原料粉末を加圧・圧縮して、嵩密度の1.05以上1.2以下の充填密度である粉末成形体を作製する低加圧工程と、
前記粉末成形体に、1T以上2T以下の弱磁場を印加する弱磁場印加工程と、
0.01T/sec以上0.15T/sec以下の励磁速度で3T以上に励磁して、3T以上の強磁場を前記弱磁場印加工程を経た成形体に印加する強磁場印加工程とを具え、
前記弱磁場は、前記圧粉成形体を構成する粒子の結晶を配向させたい所望の方向に対して立体角で90°以上180°以下の方向に印加し、
前記強磁場は、超電導コイルを用いて、前記配向させたい所望の方向に印加する磁石用圧粉成形体の製造方法。 - 前記強磁場印加工程では、
0.01T/sec以上0.15T/sec以下の励磁速度で3T以上に励磁して、3T以上に達した後、3T以上の強磁場を印加した状態で、嵩密度の1.2超の充填密度となるように前記弱磁場印加工程を経た成形体を更に加圧・圧縮する請求項2に記載の磁石用圧粉成形体の製造方法。 - 前記強磁場印加工程では、
0.01T/sec以上0.15T/sec以下の励磁速度で3T以上に励磁して、3T以上に達した後、3T以上の強磁場を印加した状態で、嵩密度の1.2超1.45以下の充填密度となるように前記弱磁場印加工程を経た成形体を更に加圧・圧縮し、
0.01T/sec以上0.15T/sec以下の励磁速度で5T以上に励磁して、5T以上に達した後、5T以上の強磁場を印加した状態で、嵩密度の1.45以上真密度の66%以下となるように前記成形体を加圧・圧縮する請求項3に記載の磁石用圧粉成形体の製造方法。 - 前記超電導コイルは、高温超電導コイルである請求項2~4のいずれか1項に記載の磁石用圧粉成形体の製造方法。
- 請求項2~5のいずれか1項に記載の製造方法により得られた磁石用圧粉成形体。
- 請求項1又は6に記載の磁石用圧粉成形体を焼結して得られた焼結体。
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CN104361989A (zh) * | 2014-12-03 | 2015-02-18 | 湖南航天磁电有限责任公司 | 一种大尺寸高密度粘结永磁体的制备方法 |
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JP2016207710A (ja) * | 2015-04-16 | 2016-12-08 | 株式会社ジェイテクト | 磁石の製造方法及び磁石 |
JP6502765B2 (ja) * | 2015-06-29 | 2019-04-17 | 住友電工焼結合金株式会社 | 焼結体の製造装置、及び焼結体の製造方法 |
KR102045394B1 (ko) | 2017-04-26 | 2019-11-15 | 성림첨단산업(주) | 희토류 영구자석의 제조방법 |
EP3675143B1 (en) * | 2018-12-28 | 2024-02-14 | Nichia Corporation | Method of preparing bonded magnet |
CN110165847B (zh) * | 2019-06-11 | 2021-01-26 | 深圳市瑞达美磁业有限公司 | 不同宽度波形的径向各向异性多极实心磁体的生产方法 |
CN111112605B (zh) * | 2020-02-29 | 2022-03-29 | 江西开源自动化设备有限公司 | 一种稀土永磁体的粉末磁场成型方法 |
CN113555206B (zh) * | 2020-11-11 | 2024-02-02 | 华为杰通(北京)科技有限公司 | 目标空间极弱磁场的建立方法、磁化设备及磁化产品 |
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