WO2012043692A1 - R-t-b系焼結磁石の製造方法 - Google Patents
R-t-b系焼結磁石の製造方法 Download PDFInfo
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- WO2012043692A1 WO2012043692A1 PCT/JP2011/072318 JP2011072318W WO2012043692A1 WO 2012043692 A1 WO2012043692 A1 WO 2012043692A1 JP 2011072318 W JP2011072318 W JP 2011072318W WO 2012043692 A1 WO2012043692 A1 WO 2012043692A1
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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
- H01F41/005—Impregnating or encapsulating
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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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- 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
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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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
- C22C38/10—Ferrous alloys, e.g. steel alloys containing cobalt
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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
- C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
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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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
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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
- H01F41/0293—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 diffusion of rare earth elements, e.g. Tb, Dy or Ho, into permanent magnets
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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
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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
Definitions
- the present invention relates to a method for producing an RTB-based sintered magnet (R is a rare earth element and T is a transition metal element containing Fe) having an R 2 T 14 B type compound as a main phase.
- An RTB-based sintered magnet mainly composed of an R 2 T 14 B-type compound is known as the most powerful magnet among permanent magnets, such as a hard disk drive voice coil motor (VCM), It is used for various motors such as motors for hybrid vehicles and home appliances.
- VCM hard disk drive voice coil motor
- the RTB-based sintered magnet Since the RTB-based sintered magnet has a reduced coercive force at high temperatures, irreversible thermal demagnetization occurs. In order to avoid irreversible thermal demagnetization, when used for a motor or the like, it is required to maintain a high coercive force even at a high temperature.
- An RTB-based sintered magnet is known to improve coercive force when a part of R in the R 2 T 14 B-type compound phase is substituted with a heavy rare earth element RH (Dy, Tb). .
- RH heavy rare earth element
- the light rare earth element RL (Nd, Pr) is replaced with R with the heavy rare earth element RH, the coercive force is improved, but the residual magnetic flux density is lowered. There is. Further, since the heavy rare earth element RH is a rare resource, it is required to reduce the amount of use thereof.
- Patent Document 1 discloses a technique that diffuses heavy rare earth elements RH from the surface of a sintered magnet and improves the coercive force of the magnet.
- Patent Document 1 as a method for making powder exist on the surface of a sintered magnet (powder processing method), a fine powder of a heavy rare earth element compound containing one or more selected from oxides, fluorides, and oxyfluorides After immersing the sintered magnet in a slurry dispersed in water or an organic solvent, it is dried by hot air or vacuum. Thereafter, heat treatment is performed to introduce the heavy rare earth element RH from the magnet surface.
- Patent Document 1 describes that, in particular, a compound containing fluorine is absorbed by a magnet with high efficiency, and the effect of improving the coercive force is high.
- an RTB-based sintered magnet is embedded in an oxide powder or fluoride powder of heavy rare earth element RH, and is heated at 500 ° C. to 1000 ° C. for 10 minutes to 8 hours in Ar or He. It is described that heat treatment is performed to form an insulating layer in the surface layer portion of the sintered magnet.
- Patent Document 1 oxides, fluorides, and oxyfluorides of heavy rare earth elements are made into a slurry and applied to a sintered magnet body, but the heavy rare earth elements RH are applied from the surface of the sintered magnet with a single application amount. Even if diffused, there was a limit to the effect of improving the coercive force. In order to aim at a high coercive force improving effect, it was necessary to repeatedly apply the slurry.
- Patent Document 2 since the RTB-based sintered magnet is embedded in the oxide powder or fluoride powder of the heavy rare earth element, the amount of diffusion of the heavy rare earth element RH from the surface of the sintered magnet is controlled. It was difficult.
- An object of the present invention is to provide a technique capable of stably diffusing a predetermined amount of heavy rare earth element RH from the surface of an RTB-based sintered magnet body.
- the manufacturing method of the RTB-based sintered magnet of the present invention includes a step of preparing an RTB-based sintered magnet body, Preparing an RH diffusion source comprising at least one of a fluoride containing at least one of Dy and Tb, an oxide, and an oxyfluoride; Charging the RTB-based sintered magnet body and the RH diffusion source into a processing chamber so as to be relatively movable and close to or in contact with each other; While the RTB-based sintered magnet body and the RH diffusion source are moved continuously or intermittently in the processing chamber, the sintered magnet body and the RH diffusion source are moved to 800 ° C. or more and 950 ° C. or less. And an RH diffusion treatment step of heating to the treatment temperature.
- the RH diffusion treatment step is performed by inserting a stirring auxiliary member into the treatment chamber.
- a predetermined amount of heavy rare earth element RH can be stably diffused into the RTB-based sintered magnet body by adjusting the processing temperature and processing time in the RH diffusion processing step. This makes it possible to stably produce a target RTB-based sintered magnet having a high coercive force.
- the method for producing an RTB-based sintered magnet of the present invention includes an RH diffusion source comprising at least one of fluoride, oxide, and oxyfluoride containing at least one of Dy and Tb, and the RT-
- the B-based sintered magnet body is inserted into the processing chamber so as to be relatively movable and close to or contactable, and the RTB-based sintered magnet body and the RH diffusion source are continuously connected in the processing chamber.
- the sintered magnet body and the RH diffusion source are heated to a processing temperature of 800 ° C. or higher and 950 ° C. or lower while moving the target or intermittently.
- an RH diffusion source is composed of at least one of fluoride, oxide, and oxyfluoride containing at least one of Dy and Tb
- the supply of the rare earth element RH by vaporization (sublimation) and R— Diffusion into the TB sintered magnet body can be performed simultaneously (RH diffusion treatment).
- the RH diffusion treatment to the RTB-based sintered magnet body can be stably performed by adjusting the treatment temperature and the treatment time.
- the RH diffusion source and the RTB-based sintered magnet body are loaded into the processing chamber so as to be relatively movable and close to or in contact with each other, and can be moved continuously or intermittently. Therefore, it is not necessary to place the RH diffusion source and the RTB-based sintered magnet body in a predetermined position.
- an RH diffusion source comprising at least one of a fluoride, an oxide, and an acid fluoride containing at least one of Dy and Tb is continuously or intermittently used at 800 ° C. to 950 ° C. or less.
- the contact point between the RH diffusion source and the RTB system sintered magnet body increases in the processing chamber, and the heavy rare earth element RH is converted into the RTB system sintered magnet body.
- the temperature range of 800 ° C. or more and 950 ° C. or less is a temperature range in which RH diffusion is promoted in the RTB-based sintered magnet, and the heavy rare earth element RH is contained in the RTB-based sintered magnet body.
- RH diffusion can be performed in a situation where it is easy to diffuse.
- the method of moving the RTB-based sintered magnet body and the RH diffusion source continuously or intermittently in the processing chamber is as follows. Any method can be adopted as long as the mutual arrangement relationship between the RH diffusion source and the RTB-based sintered magnet body can be changed without causing chipping or cracking. For example, a method of rotating or swinging the processing chamber or applying vibration to the processing chamber from the outside can be employed. Further, stirring means may be provided in the processing chamber.
- RTB-based sintered magnet body that is an object of diffusion of the heavy rare earth element RH is prepared.
- This RTB-based sintered magnet body has the following composition.
- Rare earth element R 12 to 17 atomic% B (part of B may be substituted with C): 5 to 8 atomic%
- Additive element M selected from the group consisting of Al, Ti, V, Cr, Mn, Ni, Cu, Zn, Ga, Zr, Nb, Mo, Ag, In, Sn, Hf, Ta, W, Pb, and Bi At least one): 0 to 2 atomic% T (which is a transition metal mainly containing Fe and may contain Co) and inevitable impurities: the balance
- the rare earth element R is at least one selected from light rare earth elements RL (Nd, Pr) Although it is an element, it may contain a heavy rare earth element. In addition, when a heavy rare earth element is contained, it is preferable that at least one of Dy and Tb is included
- the RH diffusion source is a compound of heavy rare earth element RH (at least one of Dy and Tb) and at least one of F and O.
- the compound of F and heavy rare earth element RH is mainly RHF 3, but is not limited to RHF 3 .
- a compound of O and heavy rare earth element RH is mainly RH 2 O 3, but is not limited to RH 2 O 3 .
- RH 4 O 4 or RH 4 O 7 can be used.
- the oxyfluoride containing F and O is mainly RHOF, but is not limited to RHOF.
- RH 2 O 3 which is a product formed in the process of heating a rare earth oxide and an anhydrous hydrogen fluoride stream at a high temperature, contains oxyfluoride containing a small amount of F, and conversely contains a large amount of F. It may be an acid fluoride.
- the form of the RH diffusion source is arbitrary, for example, spherical, linear, plate-like, block-like, or powder. Further, the shape and size of the RH diffusion source are not particularly limited.
- the fluoride, oxide, and oxyfluoride RH diffusion source containing at least one of Dy and Tb may be a powder of several micrometers, a powder of several hundred micrometers, or a larger lump.
- the manufacturing method of RH diffusion source is shown below, a manufacturing method is not limited to the described method. You may manufacture by another method.
- the oxide of the heavy rare earth element is obtained by adding ammonium and ammonium hydrogen carbonate or ammonium carbonate to an aqueous solution of a rare earth element inorganic salt to crystallize the rare earth element carbonate, filtering, washing with water, and then adding an organic solvent to the carbonate. In addition, it is produced by heating, distilling off water, separating the organic solvent from the carbonate-containing layer, drying the carbonate under reduced pressure, and firing.
- the heavy rare earth element fluoride for example, hydrofluoric acid or a compound that can be dissociated in water to generate hydrogen fluoride is added to a sol or slurry solution containing a precipitation of a rare earth element hydroxide.
- the precipitate is fluorinated, filtered, dried, and calcined at a temperature of 700 ° C. or lower as necessary.
- the heavy rare earth element oxyfluoride is produced, for example, by heating a rare earth oxide and an anhydrous hydrogen fluoride stream to a high temperature (for example, 750 ° C.) or heating the fluoride to a high temperature.
- the RH diffusion source may be a mixture of at least two of fluorides, oxides, and oxyfluorides of heavy rare earth elements RH.
- a stirring auxiliary member In the embodiment of the present invention, it is preferable to introduce a stirring auxiliary member into the processing chamber in addition to the RTB-based sintered magnet body and the RH diffusion source.
- the agitation auxiliary member promotes contact between the RH diffusion source and the RTB-based sintered magnet body, and the heavy rare earth element RH once attached to the agitation auxiliary member is indirectly applied to the RTB-based sintered magnet body.
- the stirring assisting member also has a role of preventing chipping due to contact between the RTB-based sintered magnet bodies or between the RTB-based sintered magnet body and the RH diffusion source in the processing chamber.
- the stirrer auxiliary member has a shape that can easily move in the processing chamber, and the stirrer assisting member is mixed with the RTB-based sintered magnet body and the RH diffusion source to rotate, swing, and vibrate the processing chamber.
- the shape that easily moves include a spherical shape, an elliptical shape, and a cylindrical shape having a diameter of several hundred ⁇ m to several tens of mm.
- the stirring auxiliary member is preferably made of a material having a specific gravity of 6 g / cm 3 or more and a material that does not easily react even if it comes into contact with the RTB-based sintered magnet body and the RH diffusion source during the RH diffusion treatment.
- the ceramic agitation auxiliary member can be suitably formed from ceramics of zirconia, silicon nitride, silicon carbide and boron nitride, or a mixture thereof.
- the RTB-based sintered magnet body and the stirrer assisting member made of a metal material that hardly reacts with RH diffusion may be made of a metal containing Mo, W, Nb, Ta, Hf, Zr, or a mixture thereof. Can also be formed.
- FIG. 1 A preferred example of the diffusion treatment process according to the present invention will be described with reference to FIG.
- an RTB-based sintered magnet body 1 and an RH diffusion source 2 are inserted into a stainless steel cylinder 3.
- zirconia spheres or the like are inserted into the tube 3 as a stirring auxiliary member.
- the cylinder 3 functions as a “processing chamber”.
- the material of the cylinder 3 is not limited to stainless steel, and has heat resistance that can withstand temperatures of 800 ° C. or more and 950 ° C. or less, and is a material that does not easily react with the RTB-based sintered magnet body 1 and the RH diffusion source 2. It is optional if it exists.
- the tube 3 is provided with a lid 5 that can be opened and closed or removed.
- a protrusion can be installed so that the RH diffusion source and the RTB-based sintered magnet body can efficiently move and contact.
- the cross-sectional shape perpendicular to the major axis direction of the cylinder 3 is not limited to a circle, and may be an ellipse, a polygon, or other shapes.
- the cylinder 3 in the state shown in FIG. 1 is connected to an exhaust device 6. The inside of the cylinder 3 can be depressurized by the action of the exhaust device 6.
- An inert gas such as Ar can be introduced into the cylinder 3 from a gas cylinder (not shown).
- the cylinder 3 is heated by a heater 4 disposed on the outer periphery thereof. By heating the cylinder 3, the RTB-based sintered magnet body 1 and the RH diffusion source 2 housed therein are also heated.
- the cylinder 3 is supported so as to be rotatable around the central axis, and can be rotated by the variable motor 7 during heating by the heater 4.
- the rotational speed of the cylinder 3 can be set, for example, to 0.01 m or more per second on the inner wall surface of the cylinder 3. It is preferable to set it to 0.5 m or less per second so that the RTB-based sintered magnet bodies in the cylinder are vigorously contacted and not chipped by rotation.
- the cylinder 3 rotates, but the present invention is not limited to such a case. It suffices that the RTB-based sintered magnet body 1 and the RH diffusion source 2 are relatively movable and contactable in the cylinder 3 during the RH diffusion treatment process. For example, the cylinder 3 may swing or vibrate without rotating, or at least two of rotation, swinging and vibration may occur simultaneously. Next, the operation of the RH diffusion process performed using the processing apparatus of FIG. 1 will be described.
- the lid 5 is removed from the cylinder 3, and the inside of the cylinder 3 is opened. After the plurality of RTB-based sintered magnet bodies 1 and the RH diffusion source 2 are inserted into the cylinder 3, the lid 5 is attached to the cylinder 3 again.
- the exhaust device 6 is connected and the inside of the cylinder 3 is evacuated. After the internal pressure of the cylinder 3 is sufficiently reduced, the exhaust device 6 is removed. After heating, an inert gas is introduced to a required pressure, and heating by the heater 4 is performed while rotating the cylinder 3 by the motor 7.
- the inside of the cylinder 3 at the time of the RH diffusion treatment is an inert atmosphere.
- the “inert atmosphere” in this specification includes a vacuum or an inert gas.
- the “inert gas” is a rare gas such as argon (Ar), but may be a gas that does not chemically react between the RTB-based sintered magnet body 1 and the RH diffusion source 2.
- it can be included in an “inert gas”.
- the pressure of an inert gas is below atmospheric pressure. In this embodiment, since the RH diffusion source 2 and the RTB-based sintered magnet body 1 are close to or in contact with each other, the RH diffusion treatment can be performed at a high pressure.
- the correlation between the degree of vacuum and the supply amount of heavy rare earth element RH is relatively small, and even if the degree of vacuum is further increased, the supply amount of heavy rare earth element RH (degree of improvement in coercive force) is not greatly affected.
- the supply amount is more sensitive to the temperature of the RTB-based sintered magnet body than the atmospheric pressure.
- an RH diffusion source 2 comprising at least one of fluoride, oxide, and oxyfluoride containing at least one of heavy rare earth elements RH, Dy and Tb, and an RTB-based sintered magnet body 1 are used.
- the RTB-based sintered magnet body 1 and the RH diffusion source 2 are heated to a processing temperature of 800 ° C. or higher and 950 ° C. or lower while moving continuously or intermittently in the cylinder (processing chamber) 3.
- the heavy rare earth element RH can be directly diffused from the RH diffusion source 2 to the surface of the RTB-based sintered magnet body 1 and diffused inside.
- the peripheral speed of the inner wall surface of the processing chamber during the diffusion process can be set to 0.01 m / s or more, for example.
- the rotational speed is low, the movement of the contact portion between the RTB-based sintered magnet body 1 and the RH diffusion source 2 is slowed down, and welding is likely to occur. For this reason, it is preferable to increase the rotation speed of the processing chamber as the diffusion temperature is higher.
- a preferable rotation speed varies depending not only on the diffusion temperature but also on the shape and size of the RH diffusion source.
- the temperature of the RH diffusion source 2 and the RTB-based sintered magnet body 1 is maintained within a range of 800 ° C. or higher and 950 ° C. or lower.
- This temperature range is a preferable temperature range for the heavy rare earth element RH to diffuse through the grain boundary phase of the RTB-based sintered magnet body 1 to the inside.
- the RH diffusion source 2 is made of at least one of fluoride, oxide, and oxyfluoride containing at least one of Dy and Tb, and the heavy rare earth element RH is not excessively supplied at a processing temperature of 800 ° C. or higher and 950 ° C. or lower. In the present invention, even if the particle size of the RH diffusion source 2 exceeds 100 ⁇ m, the effect of the RH diffusion treatment can be obtained.
- the time for the RH diffusion treatment is, for example, not less than 10 minutes and not more than 72 hours. Preferably it is 1 hour or more and 12 hours or less.
- the holding time is the ratio of the amounts of the RTB-based sintered magnet body 1 and the RH diffusion source 2 charged during the RH diffusion treatment process, the shape of the RTB-based sintered magnet body 1, the RH diffusion It is determined in consideration of the shape of the source 2 and the amount of heavy rare earth element RH (diffusion amount) to be diffused into the RTB-based sintered magnet body 1 by the RH diffusion treatment.
- the pressure of the atmospheric gas during the RH diffusion treatment process can be set, for example, within a range of 10 ⁇ 3 Pa to atmospheric pressure.
- the rotation of the cylinder 3 is performed during the RH diffusion treatment process for homogeneous RH diffusion to the charged R—T—B system sintered magnet body, but the rotation may be stopped after the RH diffusion treatment process, The rotation may be continued while performing the first heat treatment and the second heat treatment described later.
- a first heat treatment may be performed on the RTB-based magnet body 1 for the purpose of homogenizing the diffused heavy rare earth element RH.
- the heat treatment is performed at a temperature of 800 ° C. or more and 950 ° C. or less at which the heavy rare earth element RH can substantially diffuse after removing the RH diffusion source.
- the supply of the heavy rare earth element RH to the RTB-based sintered magnet body 1 does not occur, but the heavy rare earth element RH is not contained inside the RTB-based sintered magnet body 1. Since diffusion occurs, the heavy rare earth element RH can be diffused deeply from the surface side of the sintered magnet, and the coercive force of the entire magnet can be increased.
- the time for the first heat treatment is, for example, not less than 10 minutes and not more than 72 hours. Preferably it is 1 hour or more and 12 hours or less.
- the atmospheric pressure of the heat treatment furnace for performing the first heat treatment is equal to or lower than the atmospheric pressure. Preferred is 100 kPa or less.
- a second heat treatment (400 ° C. or more and 700 ° C. or less) is performed.
- the first heat treatment (800 ° C. or more and 950 ° C. or less) is performed. It is preferable to carry out later.
- the first heat treatment (800 to 950 ° C.) and the second heat treatment (400 to 700 ° C.) may be performed in the same treatment chamber.
- the time for the second heat treatment is, for example, not less than 10 minutes and not more than 72 hours. Preferably it is 1 hour or more and 12 hours or less.
- the atmospheric pressure of the heat treatment furnace for performing the second heat treatment is equal to or lower than the atmospheric pressure.
- RH diffusion processing was performed using the apparatus of FIG.
- the cylinder volume was 128000 mm 3
- the input weight of the RTB-based sintered magnet body was 50 g
- the input weight of the RH diffusion source was 50 g.
- An irregular RH diffusion source was used.
- Samples 1 to 11 When the RH diffusion treatment was performed using various RH diffusion sources (samples 1 to 11), the results shown in Table 1 were obtained. Although it was substantially several ⁇ m in size, Samples 1 to 8 and 11 used RH diffusion sources that passed through a sieve having an opening of 25 ⁇ m according to JIS standard Z-8801. Sample 9 used an RH diffusion source having a size of 106 ⁇ m to 150 ⁇ m. Sample 10 used an RH diffusion source having a size of 250 ⁇ m to 325 ⁇ m.
- FIG. 2 is a graph showing a change (heat pattern) in the processing chamber temperature after the start of heating.
- evacuation was performed while the temperature was raised by the heater.
- the temperature rising rate is about 10 ° C./min.
- the temperature was maintained at, for example, about 600 ° C. until the pressure in the processing chamber reached a desired level. Thereafter, rotation of the processing chamber is started.
- the temperature was raised until the RH diffusion treatment temperature was reached.
- the temperature rising rate was about 10 ° C./min.
- After reaching the RH diffusion treatment temperature the temperature was maintained for a predetermined time. Thereafter, heating by the heater was stopped and the temperature was lowered to about room temperature.
- the sintered magnet body taken out from the apparatus of FIG. 1 is put into another heat treatment furnace, and the first heat treatment (800 ° C. to 950 ° C. ⁇ 4 hours to 6 hours) is performed at the same atmospheric pressure as that during the RH diffusion treatment. Further, a second heat treatment after diffusion (450 ° C. to 550 ° C. ⁇ 3 hours to 5 hours) was performed.
- the processing temperature and time of the first heat treatment and the second heat treatment are set in consideration of the amount of the RTB-based sintered magnet body and the RH diffusion source input, the composition of the RH diffusion source, the RH diffusion temperature, and the like. It was.
- the magnetic characteristics in Table 1 are as follows. Each surface of the magnet body after the RH diffusion treatment is ground by 0.2 mm and processed into a 7.0 mm ⁇ 7.0 mm ⁇ 7.0 mm cube, and then the magnet is measured with a BH tracer. The characteristics are being evaluated.
- the “RH diffusion source” column shows the composition and size of the RH diffusion source used in the diffusion treatment process.
- the “peripheral speed” column the peripheral speed of the inner wall surface of the cylinder 3 shown in FIG. 1 is shown.
- the “RH diffusion temperature” column the temperature in the cylinder 3 held during the diffusion process is shown.
- the column “RH diffusion time” indicates the time during which the RH diffusion temperature is maintained.
- “Atmospheric pressure” indicates the pressure at the start of the diffusion treatment.
- the amount of increase in coercive force H cJ after RH diffusion treatment is indicated by “ ⁇ H cJ ”
- the amount of increase in residual magnetic flux density B r after RH diffusion treatment is indicated by “ ⁇ B r ”.
- a negative value indicates that the magnetic properties of the RTB-based sintered magnet body before the RH diffusion treatment were deteriorated.
- Example 2 RH diffusion treatment was performed under the same conditions as in Experimental Example 1 except that a zirconia sphere having a diameter of 5 mm was added as a stirring auxiliary member with a weight of 50 g, and RH diffusion treatment and first heat treatment were performed, and magnetic characteristics were evaluated. However, the results shown in Table 2 were obtained. Samples 12 to 18 and 21, which were substantially several ⁇ m in size, used an RH diffusion source that passed through a sieve having an opening of 25 ⁇ m according to JIS standard Z-8801. Sample 19 used an RH diffusion source having a size of 106 ⁇ m to 150 ⁇ m. Sample 20 used an RH diffusion source having a size of 250 ⁇ m to 325 ⁇ m.
- the RH diffusion source made of DyF 3 used in sample 12 and the RH diffusion source made of Dy 2 O 3 used in sample 14 were mixed and used.
- the mixing ratio is 1: 1. Also in the sample 21, the decrease in the residual magnetic flux density was suppressed and the coercive force was improved.
- a processing chamber in which an RH diffusion source made of any one of fluoride, oxide, and oxyfluoride containing at least one of Dy and Tb and an RTB-based sintered magnet body are heated. If the contact point is not fixed and the contact point is not fixed, the heavy rare earth element RH is effectively introduced into the grain boundary of the sintered magnet body by a method suitable for mass production, thereby improving the magnet characteristics. Is possible.
- the heat pattern that can be executed by the diffusion processing of the present invention is not limited to the example shown in FIG. 2, and other various patterns can be adopted. Further, the evacuation may be performed until the diffusion treatment is completed and the sintered magnet body is sufficiently cooled.
- an RTB-based sintered magnet having a high residual magnetic flux density and a high coercive force can be stably produced.
- the sintered magnet of the present invention is suitable for various motors such as a motor for mounting on a hybrid vehicle exposed to high temperatures, home appliances, and the like.
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Abstract
Description
DyおよびTbの少なくとも一方を含むフッ化物、酸化物、酸フッ化物の少なくともいずれかからなるRH拡散源を準備する工程と、
前記R-T-B系焼結磁石体と前記RH拡散源とを相対的に移動可能かつ近接または接触可能に処理室内に装入する工程と、
前記R-T-B系焼結磁石体と前記RH拡散源とを前記処理室内にて連続的または断続的に移動させながら、前記焼結磁石体および前記RH拡散源を800℃以上950℃以下の処理温度に加熱するRH拡散処理工程と、を包含する。
まず、本発明では、重希土類元素RHの拡散の対象であるR-T-B系焼結磁石体を準備する。このR-T-B系焼結磁石体は、以下の組成からなる。
希土類元素R:12~17原子%
B(Bの一部はCで置換されていてもよい):5~8原子%
添加元素M(Al、Ti、V、Cr、Mn、Ni、Cu、Zn、Ga、Zr、Nb、Mo、Ag、In、Sn、Hf、Ta、W、Pb、およびBiからなる群から選択された少なくとも1種):0~2原子%
T(Feを主とする遷移金属であって、Coを含んでもよい)および不可避不純物:残部
ここで、希土類元素Rは、主として軽希土類元素RL(Nd、Pr)から選択される少なくとも1種の元素であるが、重希土類元素を含有していてもよい。なお、重希土類元素を含有する場合は、DyおよびTbの少なくとも一方を含むことが好ましい。
上記組成のR-T-B系焼結磁石体は、公知の製造方法によって製造される。
RH拡散源は、重希土類元素RH(Dy、Tbの少なくともいずれか)とFおよびOの少なくともいずれかとの化合物である。Fと重希土類元素RHとの化合物はRHF3が主であるが、RHF3に限定されない。Oと重希土類元素RHとの化合物はRH2O3が主であるが、RH2O3に限定されない。例えばRH4O4、RH4O7等を用いることができる。FとOを含む酸フッ化物では、RHOFが主であるがRHOFに限定されない。例えば、希土類酸化物と無水フッ化水素気流とを高温で加熱している過程でできる生成物であるRH2O3にFが微量に含まれた酸フッ化物や、逆にFを多く含んだ酸フッ化物であってもよい。
本発明の実施形態では、R-T-B系焼結磁石体とRH拡散源に加えて、攪拌補助部材を処理室内に導入することが好ましい。攪拌補助部材はRH拡散源とR-T-B系焼結磁石体との接触を促進し、また攪拌補助部材に一旦付着した重希土類元素RHをR-T-B系焼結磁石体へ間接的に供給する役割をする。さらに、攪拌補助部材は、処理室内において、R-T-B系焼結磁石体同士やR-T-B系焼結磁石体とRH拡散源との接触による欠けを防ぐ役割もある。
図1を参照しながら、本発明による拡散処理工程の好ましい例を説明する。
図1に示す例では、R-T-B系焼結磁石体1およびRH拡散源2がステンレス製の筒3の内部に装入されている。また、図示していないが、ジルコニア球などを攪拌補助部材として筒3の内部に装入されていることが好ましい。この例では、筒3が「処理室」として機能する。筒3の材料は、ステンレスに限定されず、800℃以上950℃以下の温度に耐える耐熱性を有し、R-T-B系焼結磁石体1およびRH拡散源2と反応しにくい材料であれば任意である。例えば、Nb、Mo、Wまたはそれらの少なくとも1種を含む合金を用いてもよい。筒3には開閉または取り外し可能な蓋5が設けられている。また筒3の内壁には、RH拡散源とR-T-B系焼結磁石体とが効率的に移動と接触を行い得るように、突起物を設置することができる。筒3の長軸方向に垂直な断面形状も、円に限定されず、楕円または多角形、あるいはその他の形状であってもよい。図1に示す状態の筒3は排気装置6と連結されている。排気装置6の働きにより、筒3の内部は減圧され得る。筒3の内部には、不図示のガスボンベからArなどの不活性ガスが導入され得る。
次に、図1の処理装置を用いて行うRH拡散処理の動作を説明する。
RH拡散処理工程後に、拡散された重希土類元素RHをより均質化する目的でR-T-B系磁石体1に対する第1熱処理を行っても良い。熱処理は、RH拡散源を取り除いた後、重希土類元素RHが実質的に拡散し得る800℃以上950℃以下の温度で実行される。この第1熱処理では、R-T-B系焼結磁石体1に対して重希土類元素RHの供給は生じないが、R-T-B系焼結磁石体1の内部において重希土類元素RHの拡散が生じるため、焼結磁石の表面側から奥深くに重希土類元素RHを拡散し、磁石全体として保磁力を高めることが可能になる。第1熱処理の時間は、例えば10分以上72時間以下である。好ましくは1時間以上12時間以下である。ここで、第1熱処理を行なう熱処理炉の雰囲気圧力は、大気圧以下である。好ましいのは100kPa以下である。
また、必要に応じてさらに第2熱処理(400℃以上700℃以下)を行うが、第2熱処理(400℃以上700℃以下)を行う場合は、第1熱処理(800℃以上950℃以下)の後に行うことが好ましい。第1熱処理(800℃以上950℃以下)と第2熱処理(400℃以上700℃以下)は、同じ処理室内で行っても良い。第2熱処理の時間は、例えば10分以上72時間以下である。好ましくは1時間以上12時間以下である。ここで、第2熱処理を行う熱処理炉の雰囲気圧力は、大気圧以下である。
まず、組成比Nd=26.0、Pr=4.0、Dy=0.5、B=1.0、Co=0.9、Al=0.1、Cu=0.1、Ga=0.1、残部=Fe(質量%)のR-T-B系焼結磁石体を作製した。これを機械加工することにより、7.4mm×7.4mm×7.4mmの立方体のR-T-B系焼結磁石体を得た。作製したR-T-B系焼結磁石体の磁気特性をB-Hトレーサによって測定したところ、熱処理(500℃)後の特性で保磁力HcJは1050kA/m、残留磁束密度Brは1.42Tであった。
ここで、直径5mmのジルコニア球を重量50g、攪拌補助部材として追加してRH拡散処理、第1熱処理を行った以外は、実験例1と同じ条件でRH拡散処理を行い、磁気特性を評価したところ、表2の結果となった。実質的には数μmサイズであったがサンプル12から18、21はJIS規格 Z-8801による目開き25μmのふるいを通ったRH拡散源を用いた。サンプル19は106μmから150μmのサイズのRH拡散源を用いた。サンプル20は250μmから325μmのサイズのRH拡散源を用いた。
2 RH拡散源
3 ステンレス製の筒(処理室)
4 ヒータ
5 蓋
6 排気装置
Claims (2)
- R-T-B系焼結磁石体を準備する工程と、
DyおよびTbの少なくとも一方を含むフッ化物、酸化物、酸フッ化物の少なくともいずれかからなるRH拡散源を準備する工程と、
前記R-T-B系焼結磁石体と前記RH拡散源とを相対的に移動可能かつ近接または接触可能に処理室内に装入する工程と、
前記R-T-B系焼結磁石体と前記RH拡散源とを前記処理室内にて連続的または断続的に移動させながら、前記R-T-B系焼結磁石体および前記RH拡散源を800℃以上950℃以下の処理温度に加熱するRH拡散処理工程と、
を包含するR-T-B系焼結磁石の製造方法。 - 前記RH拡散処理工程は、攪拌補助部材を前記処理室内に装入して行う請求項1に記載の焼結磁石の製造方法。
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JP2014160760A (ja) * | 2013-02-20 | 2014-09-04 | Hitachi Metals Ltd | R−t−b系焼結磁石の製造方法 |
KR101460912B1 (ko) | 2013-10-15 | 2014-11-12 | 고려대학교 산학협력단 | 영구 자석의 제조 방법 |
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WO2013002170A1 (ja) * | 2011-06-27 | 2013-01-03 | 日立金属株式会社 | Rh拡散源およびそれを用いたr-t-b系焼結磁石の製造方法 |
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