Diffusion source attachment device and method for manufacturing rare earth sintered magnet

Abstract

To uniformly and efficiently apply a diffusion source powder to the surface of a rare earth sintered magnet.SOLUTION: A diffusion source attachment device includes a fluidized tank that stores and fluidizes diffusion source powder to be attached to each of a plurality of rare earth sintered magnet materials, and a conveying device that has two or more wires on which the plurality of rare earth sintered magnet materials are placed and conveyed, and transports the plurality of rare earth sintered magnet materials by moving the wire in a horizontal direction such that the plurality of rare earth sintered magnet materials pass through a predetermined space located above the fluidized tank.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a diffusion source attachment device and a method for producing a rare earth sintered magnet using the diffusion source attachment device. [Background technology]

[0002] R2T 14 RTB sintered magnets, whose main phase is a B-type compound (R is a rare earth element, and T is Fe or Fe and Co), are known as the most high-performance permanent magnets, and are used in a variety of motors, including voice coil motors (VCM) for hard disk drives and motors for hybrid vehicles, as well as in home appliances.

[0003] RTB sintered magnets have an intrinsic coercive force H cJ (Hereafter, simply "H cJ In order to avoid irreversible thermal demagnetization, when used for motors, etc., high H cJ is required to be maintained.

[0004] RTB sintered magnets are R2T 14 When a part of R in the B-type compound phase is replaced by heavy rare earth elements RH (Dy, Tb), H cJ It is known that high H cJ In order to obtain this, it is effective to add a large amount of heavy rare earth element RH to the RTB sintered magnet. However, when R in an RTB sintered magnet is replaced with a heavy rare earth element RH (Nd, Pr), H cJ While the residual magnetic flux density B r (Hereafter, simply "B r Furthermore, because the heavy rare earth element RH is a scarce resource, there is a need to reduce its usage.

[0005] Therefore, in recent years, B r In order to avoid a decrease in the H of RTB-based sintered magnets, less heavy rare earth element RH is added. cJFor example, it has been proposed to apply fluorides or oxides of heavy rare earth elements RH, or various metals M or M alloys, either alone or in combination, to the surface of a sintered magnet, and then heat-treat it in this state to diffuse the heavy rare earth elements RH, which contribute to improving coercivity, into the magnet.

[0006] Patent Document 1 discloses the use of powders of R oxide, R fluoride, and R oxyfluoride (R is a rare earth element).

[0007] Patent Document 2 discloses the use of a powder of an RM (M is one or more selected from Al, Cu, Zn, Ga, etc.) alloy.

[0008] Patent Documents 3 and 4 disclose that by using a mixed powder of an RM alloy (M is one or more selected from Al, Cu, Zn, Ga, etc.), an M1M2 alloy (M1M2 is one or more selected from Al, Cu, Zn, Ga, etc.), and an RH oxide, the RH oxide can be partially reduced by the RM alloy or the like during heat treatment, and the heavy rare earth element RH can be introduced into the magnet. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] International Publication No. 2006 / 043348 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-263179 [Patent Document 3] Japanese Patent Application Laid-Open No. 2012-248827 [Patent Document 4] Japanese Patent Application Laid-Open No. 2012-248828 [Patent Document 5] International Publication No. 2015 / 163397 Summary of the Invention [Problem to be solved by the invention]

[0010] The above Patent Documents 1 to 4 disclose methods of heat-treating a magnet by disposing a mixed powder containing an RH compound powder on the entire surface (entire magnet surface). Specific examples of these methods involve immersing a magnet in a slurry in which the mixed powder is dispersed in water or an organic solvent, and then pulling it up (the immersion-pulling method). In the immersion-pulling method, the magnet pulled up from the slurry is subjected to hot air drying or natural drying. Instead of immersing the magnet in the slurry, it is also disclosed that the slurry is spray-coated onto the magnet (the spray-coating method).

[0011] These methods allow the slurry to be applied to the entire surface of the magnet. This allows the heavy rare earth element RH to be introduced into the magnet from the entire surface of the magnet, and the H cJ However, with the dipping and pulling method, gravity inevitably causes the slurry to concentrate at the bottom of the magnet. Furthermore, with the spray coating method, surface tension causes the coating thickness at the edge of the magnet to become thicker. With either method, it is difficult to distribute the RH compound uniformly on the magnet surface.

[0012] By using a low viscosity slurry to thin the coating layer, the non-uniformity of the coating layer thickness can be improved to some extent. However, since the amount of slurry applied is reduced, the H cJ If the slurry is applied multiple times to increase the amount applied, production efficiency will be significantly reduced. In particular, if a spray application method is used, the slurry will also be applied to the inner wall surface of the spray application device, reducing the yield of the slurry. As a result, there is a problem of wasting the heavy rare earth element RH, which is a scarce resource.

[0013] The applicant discloses a method of performing a diffusion heat treatment in a state in which an RLM alloy powder and an RH fluoride powder are present on the surface of an RTB based sintered magnet in Patent Document 5. However, it is difficult to say that a method for uniformly distributing these powders on the surface of an RTB based sintered magnet has been fully established.

[0014] The present disclosure provides a diffusion source attachment device that can efficiently apply diffusion sources for diffusing various elements into a rare earth sintered magnet to the surface of a rare earth sintered magnet material, and a method for manufacturing a rare earth sintered magnet that can diffuse desired elements from the magnet surface into the interior by using the diffusion source attachment device. [Means for solving the problem]

[0015] In an exemplary embodiment, the diffusion source attachment device according to the present disclosure includes a fluidization tank that stores and fluidizes diffusion source powder to be attached to each of a plurality of rare earth sintered magnet materials, and a conveying device that has two or more wires that carry and convey the plurality of rare earth sintered magnet materials, and that moves the wires horizontally to convey the plurality of rare earth sintered magnet materials so that the plurality of rare earth sintered magnet materials pass through a predetermined space located above the fluidization tank.

[0016] In one embodiment, when each of the plurality of rare earth sintered magnet materials transported by the transport device passes through the specified space located above the fluidization tank, an adhesive is applied to the surface of each of the plurality of rare earth sintered magnet materials, and particles of the diffusion source powder floating in the specified space from the fluidization tank are adhered to the adhesive.

[0017] In one embodiment, the apparatus further includes a device for removing unnecessary particles of the diffusion source powder that have passed through the predetermined space and adhered to the adhesive by blowing air thereon.

[0018] In one embodiment, the device further comprises a fluidized bed containing chamber surrounding the fluidized bed and including a recovery section for recovering the diffusion source powder that has overflowed from the fluidized bed, and a circulation mechanism for sending the diffusion source powder recovered by the recovery section to the fluidized bed.

[0019] In one embodiment, a diffusion source powder supplying device is provided that supplies the diffusion source powder from outside the fluidized bed containing chamber to the fluidized bed containing chamber.

[0020] In one embodiment, the device includes a control device that controls the diffusion source powder supplying device and a sensor that detects the amount or height of the diffusion source powder recovered in the recovery section, and when the control device determines that the amount or height of the diffusion source powder in the recovery section has decreased and reached a first value, it starts to newly supply the diffusion source powder from the diffusion source powder supplying device to the fluidized bed accommodating chamber, and when the amount or height of the diffusion source powder in the recovery section has increased and reached a second value greater than the first value, it stops supplying the diffusion source powder from the diffusion source powder supplying device to the fluidized bed accommodating chamber.

[0021] In one embodiment, the circulation mechanism includes a conduit that conveys the diffusion source powder from the recovery section into the fluidized bed by an air flow.

[0022] In one embodiment, the fluidized bed has a porous region on its bottom surface and includes an airflow device that blows gas through the porous region to spray up the diffusion source powder in the fluidized bed.

[0023] In an exemplary embodiment, a method for manufacturing a rare earth sintered magnet according to the present disclosure includes the steps of: attaching a diffusion source powder to each of a plurality of rare earth sintered magnet materials using any of the diffusion source attachment devices described above; and diffusing elements contained in the diffusion source powder attached to each of the plurality of rare earth sintered magnet materials into the interior of each of the rare earth sintered magnet materials. [Effects of the Invention]

[0024] According to an embodiment of the present disclosure, it is possible to provide a diffusion source attachment device that can efficiently apply a diffusion source for diffusing various elements into a rare earth sintered magnet to the surface of a rare earth sintered magnet material, and a method for manufacturing a rare earth sintered magnet that can diffuse desired elements from the magnet surface into the interior by using the diffusion source attachment device.

[0025] Furthermore, according to the embodiments of the present disclosure, it is possible to uniformly and efficiently apply a layer of diffusion source powder particles containing, for example, the heavy rare earth element RH or other elements to the surface of a rare earth sintered magnet material, thereby improving the magnetic performance of the rare earth sintered magnet while reducing the amount of elements, such as rare elements, used. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 is a diagram schematically illustrating an example of the general configuration of a diffusion source attachment apparatus 1000 according to this embodiment. [Figure 2] FIG. 2 is a perspective view schematically illustrating a fluidization tank and a wire positioned above the fluidization tank. [Figure 3] FIG. 1 is a perspective view showing a state in which a plurality of sintered rare earth magnet materials are placed on a wire and transported in the Y-axis direction. [Figure 4] 1 is a cross-sectional view schematically showing a fluidization tank 100 and a wire 20 positioned above it. [Figure 5] 1 is a cross-sectional view showing a state in which a plurality of sintered rare earth magnet materials 10 are being carried in the Y-axis direction by a wire 20 after the diffusion source powder has started to flow in the fluidizing tank 100. FIG. [Figure 6] 1 is a flowchart showing a method for producing a rare earth sintered magnet according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0027] An embodiment of a method for manufacturing a rare earth sintered magnet according to the present disclosure includes a step of attaching a diffusion source powder to each of a plurality of rare earth sintered magnet materials using a diffusion source attachment device, and a step of diffusing elements contained in the diffusion source powder attached to each of the plurality of rare earth sintered magnet materials into the interior of each rare earth sintered magnet material.

[0028] An example of the configuration and operation of the diffusion source attachment device according to this embodiment will be described below.

[0029] First, reference is made to Fig. 1. Fig. 1 is a diagram schematically illustrating an example of the general configuration of a diffusion source attachment apparatus 1000 according to this embodiment. For reference, the figure shows an X-axis, a Y-axis, and a Z-axis that are orthogonal to each other.

[0030] In the example shown in FIG. 1 , the diffusion source attachment device 1000 includes a fluidizing tank 100 and a conveying device 200. The fluidizing tank 100 is a device that stores and fluidizes the diffusion source powder 14 to be attached to each of a plurality of sintered rare earth magnet materials (workpieces) 10. The conveying device 200 has two or more wires 20 that carry and convey the plurality of sintered rare earth magnet materials 10, and can move each wire 20 horizontally (in the Y-axis direction). The wires 20 are driven, for example, by a motor. The conveying device 200 conveys the plurality of sintered rare earth magnet materials 10 so that they pass through a predetermined space S located above the fluidizing tank 100. The height of the predetermined space S is within a range of, for example, 5 mm to 100 mm from the upper end of the fluidizing tank 100. When viewed from the positive direction of the Z-axis, the predetermined space S is included in the region of the diffusion source powder 14 that forms a fluidized bed in the fluidizing tank 100. In a fluidized bed, an air flow above a certain velocity is applied from below the powder, so that the flow resistance acting on the powder particles is equal to gravity, allowing the powder to flow like a boiling liquid. This type of fluidization is called "fluidization."

[0031] Next, reference is made to Figures 2 and 3. Figure 2 is a perspective view schematically showing a fluidization tank 100 and a wire 20 positioned above it. Figure 3 is a perspective view showing a state in which a plurality of sintered rare earth magnet materials 10 are placed on the wire 20 and are being carried by the wire 20 in the Y-axis direction.

[0032] In the example shown in FIG. 2, the fluidization tank 100 has a box-like shape with an open top and four side panels 100S and one bottom panel 100B. When viewed from the positive direction of the Z axis, the fluidization tank 100 in the illustrated example has a rectangular shape with one pair of sides parallel to the Y axis and the other pair of sides parallel to the X axis. The length of one side is, for example, in the range of 100 mm to 300 mm. The height of the side panels 100S of the fluidization tank 100 or the depth of the fluidization tank 100 is, for example, in the range of 20 mm to 200 mm. However, the shape and size of the fluidization tank 100 are not limited to the above example and may be any shape. When viewed from above, the fluidization tank 100 may have a shape other than a rectangle, such as a circle, an ellipse, or a polygon.

[0033] The side surface 100S of the fluidization tank 100 may be formed, for example, from a metal plate. The side surface 100S may have an inclined outer surface or a trapezoidal cross section. Part or all of the bottom surface 100B of the fluidization tank 100 has a large number of holes for allowing air to circulate. Such a bottom surface 100B may be suitably formed, for example, from a porous plate.

[0034] The wire 20 may bend when multiple sintered rare earth magnet materials 10 are placed on it, but it is positioned so that the wire does not come into contact with the fluidizing tank 100 even in a bent state. If the weight of the sintered rare earth magnet materials 10 causes the wire 20 to bend, increasing the inclination angle of the wire 20, the sintered rare earth magnet materials 10 may slip on the wire 20. To prevent such slippage, it is desirable that the inclination angle of the wire 20 be 5 degrees or less. The diameter of the wire 20 may be, for example, in the range of 0.5 mm to 2 mm.

[0035] 2 and 3, the number of wires 20 running in parallel is two. The number of wires 20 is not limited to two, and may be three or more.

[0036] Next, reference is made to Figures 4 and 5. Figure 4 is a cross-sectional view schematically showing a fluidizing tank 100 and a wire 20 positioned above it. In the state shown in Figure 4, diffusion source powder 14 is stored in the fluidizing tank 100, but fluidization has not yet begun. Figure 5 is a cross-sectional view showing a state in which the diffusion source powder has begun to flow in the fluidizing tank 100, and multiple sintered rare earth magnet materials 10 are being carried in the Y-axis direction by the wire 20.

[0037] In the illustrated example, the fluidizing tank 100 has a porous region 120 on its bottom surface. The diffusion source deposition device 1000 in this embodiment includes an airflow device 140 that blows gas through the porous region 120 to spray the diffusion source powder 14 in the fluidizing tank 100. The airflow sent from the airflow device 140 through the porous region 120 into the fluidizing tank 100 fluidizes the diffusion source powder 14 in the fluidizing tank 100 to form a fluidized bed. In the embodiment of the present disclosure, the diffusion source powder 14 is deposited on the surface of the sintered rare earth magnet material 10 outside (above) the fluidizing tank 100, rather than inside the diffusion source powder 14 that forms a fluidized bed inside the fluidizing tank 100. This is because, in the embodiment of the present disclosure, it is sufficient to achieve uniform deposition of about one layer of powder particles, and deposition of a thick particle layer is not necessary. Therefore, when a fluidized bed is formed, the diffusion source powder 14 is preferably sprayed up to a height of about 10 mm to 30 mm from the top surface of the fluidizing tank 100.

[0038] In this embodiment, when the plurality of sintered rare earth magnet materials 10 conveyed by the wire 20 of the conveying device 200 pass through the predetermined space S above the fluidizing bath 100, the surface of each of the plurality of sintered rare earth magnet materials 10 is coated with an adhesive 12. The adhesive 12 can be formed by applying an adhesive liquid to the sintered rare earth magnet materials 10 on the wire 20 using a sprayer or the like. The particles 14P of the diffusion source powder 14 suspended in the predetermined space S from the fluidizing bath 100 adhere to the adhesive 12 of the sintered rare earth magnet materials 10 moving horizontally. At this time, the particles 14P directly contact and adhere to the adhesive 12, forming a particle layer. However, the particles 14P may form another particle layer on top of the particle layer. However, the particles 14P constituting the other particle layer do not directly contact and adhere to the adhesive 12. Therefore, the other particle layers are easily removed in the subsequent air blowing step, and a state can be formed in which one particle layer essentially covers the entire surface of the adhesive 12. This allows for control of the adhesive force of the diffusion source powder, contributes to uniform diffusion with good reproducibility, and suppresses variations in the magnetic properties.

[0039] In order to perform the above-mentioned spraying process, the diffusion source attachment device 1000 or the manufacturing equipment including the diffusion source attachment device 1000 may further be equipped with a device (not shown) that removes unnecessary particles from the particles of the diffusion source powder 14 that have passed through the specified space S and adhered to the adhesive 12 by air blowing.

[0040] Referring again to FIG.

[0041] In this embodiment, the diffusion source deposition device 1000 further includes a fluidizing tank accommodation chamber 300 surrounding the fluidizing tank 100, and a circulation mechanism 400. The fluidizing tank accommodation chamber 300 includes a recovery unit 30 that recovers the diffusion source powder 14 that overflows from the fluidizing tank 100. The fluidizing tank accommodation chamber 300 preferably has a funnel-shaped slope at its bottom, with the recovery unit 30 provided at its bottom end. The recovery unit 30 is configured to allow particles of the diffusion source powder 14 floating in the fluidizing tank accommodation chamber 300 to fall under their own weight and then collect. The circulation mechanism 400 is configured to send the diffusion source powder 14 recovered by the recovery unit 30 to the fluidizing tank 100.

[0042] In this embodiment, the circulation mechanism 400 has a conduit 40 that carries the diffusion source powder 14 from the recovery section 30 into the fluidized bed 100 by an air flow. Specifically, by the operation of the ejector E1, air flowing through the conduit 40 carries the diffusion source powder 14 in the recovery section 30 by the air flow. A gas such as air pressurized by a pump (not shown) is supplied to the ejector E1 via a valve V1.

[0043] The conduit 40 communicates with the fluidizing tank accommodating chamber 300. Within the fluidizing tank accommodating chamber 300, the tip of the conduit 40 is positioned so as to supply the diffusion source powder 14 to the fluidizing tank 100. A funnel-shaped relay container may be provided between the tip of the conduit 40 and the fluidizing tank 100. Such a relay container has a small opening at the bottom and can function as a buffer device to adjust the supply rate so that a large amount of the diffusion source powder 14 transported by the conduit 40 is not supplied to the fluidizing tank 100 at once. The relay device separates the diffusion source powder 14 from the transporting air and prevents the recovered diffusion source powder 14 from falling directly onto the workpiece 10. By providing such a relay device, the diffusion source powder 14 from the fluidizing tank 100 can be steadily adhered to the workpiece 10, preventing fluctuations due to the recovered diffusion source powder 14.

[0044] The diffusion source attachment device 1000 in this embodiment includes a diffusion source powder supply device 500 that supplies new diffusion source powder 14 from the outside of the fluidizing tank accommodating chamber 300 into the fluidizing tank accommodating chamber 300. As described above, particles 14P of the diffusion source powder 14 sprayed out of the fluidizing tank 100 adhere to the adhesive 12 of the rare earth sintered magnet material 10 passing above the fluidizing tank 100, gradually reducing the amount of diffusion source powder 14 present inside the fluidizing tank accommodating chamber 300. Particles 14P of the diffusion source powder 14 that overflow from the fluidizing tank 100 are collected and returned to the fluidizing tank 100 by the circulation mechanism 400. However, as the amount of diffusion source powder 14 present inside the fluidizing tank accommodating chamber 300 decreases, naturally, the particles 14P of the diffusion source powder 14 that are collected also decrease, resulting in a shortage of diffusion source powder 14 stored in the fluidizing tank 100. The diffusion source powder supplying device 500 supplies new diffusion source powder 14 into the fluidizing tank accommodating chamber 300 so that there is no shortage of the diffusion source powder 14 stored in the fluidizing tank 100. This supply is performed by ejecting the diffusion source powder stored in the diffusion source powder supplying device 500 into the fluidizing tank accommodating chamber 300 through a pipeline using an ejector E2. A gas such as pressurized air is supplied to the ejector E2 via a valve V2.

[0045] The diffusion source deposition device 1000 in this embodiment includes a control device 600 that controls the diffusion source powder supply device 500 and a sensor 52 that detects the amount or height of the diffusion source powder 14 collected in the collection section 30. The control device 600 is configured by a computer and includes a processor and a storage device. The processor is one or more semiconductor integrated circuits, and is also called a central processing unit (CPU) or microprocessor. The processor sequentially executes a computer program stored in the storage device to achieve desired processing. Such processing can also be performed by a programmable logic controller (PLC).

[0046] When the control device 600 determines that the amount or height of the diffusion source powder 14 in the recovery section 30 has decreased and reached a first value, it starts to newly supply the diffusion source powder 14 from the diffusion source powder supply device 500 to the fluidized bed 100. Then, when the amount or height of the diffusion source powder 14 in the recovery section 30 has increased and reached a second value greater than the first value, the control device 600 stops supplying the diffusion source powder 14 from the diffusion source powder supply device 500 to the fluidized bed accommodating chamber 300. In this way, the new diffusion source powder 14 supplied from the diffusion source powder supply device 500 to the fluidized bed accommodating chamber 300 is recovered by the recovery section 30 and supplied to the fluidized bed 100 by the action of the circulation mechanism 400.

[0047] The sensor 52 may include two height detectors located at different heights. Such a height detector may have, for example, a configuration in which a light-emitting element and a light-receiving element are arranged across the space within the collection unit 30. By using such a height detector, the light-receiving element detects that the diffusion-source powder 14 in the collection unit 30 blocks the light emitted from the light-emitting element, thereby determining that the height of the diffusion-source powder 14 in the collection unit 30 has reached a predetermined height. Examples of the sensor 52 include a photoelectric sensor, an ultrasonic sensor, a laser sensor, and a pulse vibration level sensor. Among these, a pulse vibration level sensor is preferred from the viewpoint of accurately detecting the height of the powder particles of the diffusion-source powder 14. According to this embodiment, the particles 14P of the diffusion-source powder 14 can be stably adhered to the adhesive 12 of the rare earth sintered magnet material 10. The timing and amount of new diffusion-source powder 14 supplied to the fluidized bed chamber 300 are monitored based on the amount of diffusion-source powder 14 in the collection unit 30, thereby maintaining and controlling the required amount of diffusion-source powder without the need for additional expensive sensors.

[0048] Hereinafter, embodiments of a method for manufacturing a rare earth sintered magnet according to the present disclosure will be described. The above diffusion source adhesion device 1000 can adhere various diffusion source powders to a rare earth sintered magnet material, and there is no restriction on the composition of the diffusion source powder. Here, embodiments of a method for manufacturing an R-T-B system sintered magnet including a step of adhering a diffusion source powder containing a heavy rare earth element by the above diffusion source adhesion device will be described.

[0049] <Method for Manufacturing R-T-B System Sintered Magnet> As shown in FIG. 6, the method for manufacturing a rare earth sintered magnet in the present embodiment includes a step S10 of preparing an R1-T-B system sintered magnet material, a step S20 of preparing a diffusion source powder such as an R2-M alloy, a step S30 of applying an adhesive to the surface of the R1-T-B system sintered magnet material, a step S40 of adhering the diffusion source powder to the surface of the R1-T-B system sintered magnet material, and a diffusion step S50. The diffusion step S50 is a heat treatment step of heating the R1-T-B system sintered magnet material to which the diffusion source powder of the R2-M alloy is adhered on the surface at a temperature of 700°C or higher and 1100°C or lower in a vacuum or an inert gas atmosphere to diffuse R2 and M into the R1-T-B system sintered magnet material. In the present disclosure, the rare earth sintered magnet before and during the diffusion step may be referred to as an "R1-T-B system sintered magnet material", and the rare earth sintered magnet after the diffusion step may be simply referred to as an "R-T-B system sintered magnet". Hereinafter, each of these steps will be described in more detail.

[0050] (Step of Preparing R1-T-B System Sintered Magnet Material) First, the composition of the R1-T-B system sintered magnet material will be described.

[0051] The R1-T-B system sintered magnet material has, for example, the following composition. R1: 26.6 mass% or more and 31.5 mass% or less (R1 is a rare earth element). B: 0.8 mass% or more and 1.0 mass% or less, preferably 0.88 mass% or more and 0.97 mass% or less. M: 0 mass% or more and 1.0 mass% or less (M is selected from Ga, Cu, Zn, and Si) M1: 0 mass% or more and 2.0 mass% or less (M1 is at least one selected from the group consisting of Al, Ti, V, Cr, Mn, Ni, Zr, Nb, Mo, Ag, In, Sn, Hf, Ta, W, Pb, and Bi) The balance consists of T (T is Fe or Fe and Co) and unavoidable impurities.

[0052] Next, a method for preparing a sintered R1-TB based magnet material will be described.

[0053] First, an alloy for an RTB sintered magnet is prepared, and then this alloy is roughly crushed by, for example, a hydrogen crushing method.

[0054] Here is an example of a method for producing an alloy for an RTB sintered magnet. An alloy ingot can be obtained by ingot casting, in which a metal or alloy previously prepared to have the above-mentioned composition is melted and poured into a mold to solidify. Alternatively, the alloy can be produced by strip casting, in which a molten metal or alloy previously prepared to have the above-mentioned composition is brought into contact with a single roll, twin rolls, rotating disk, or rotating cylindrical mold, where it is rapidly cooled to produce a rapidly solidified alloy. Alternatively, flake-shaped alloys can be produced by other rapid-cooling methods, such as centrifugal casting.

[0055] In the embodiments of the present disclosure, alloys produced by either the ingot method or the quenching method can be used, but it is preferable to use alloys produced by a quenching method such as strip casting. The thickness of alloys produced by the quenching method is usually in the range of 0.03 mm to 1 mm, and they are in the form of flakes. By subjecting the obtained alloy to hydrogen pulverization, the size of the hydrogen pulverized powder (coarsely pulverized powder) can be reduced to, for example, 1.0 mm or less. The coarsely pulverized powder obtained in this manner is pulverized in a jet mill.

[0056] Jet mill pulverization is carried out in an inert atmosphere such as nitrogen, etc. Pulverization may also be carried out using a jet mill in a humid atmosphere, for example.

[0057] As long as the fine powder used to produce the R1-TB based sintered magnet material satisfies the above-mentioned conditions, it may be produced from one type of raw material alloy (single raw material alloy), or may be produced by mixing two or more types of raw material alloys (blending method).

[0058] In a preferred embodiment, a powder compact is produced from the above-described fine powder by magnetic field pressing, and then this powder compact is sintered. When performing magnetic field pressing, it is preferable to form the powder compact by pressing in an inert gas atmosphere or wet pressing, from the viewpoint of suppressing oxidation. In particular, wet pressing coats the surfaces of the particles constituting the powder compact with a dispersant such as an oil, suppressing contact with oxygen or water vapor in the atmosphere. This prevents or suppresses oxidation of the particles by the atmosphere before, during, or after the pressing process. This makes it easy to control the oxygen content within a predetermined range. When performing magnetic field wet pressing, a slurry is prepared by mixing the fine powder with a dispersant, and this slurry is supplied to a cavity in a mold of a wet pressing device and press-molded in a magnetic field.

[0059] The compact is then sintered to obtain a sintered R1-TB based magnet material. The sintering of the compact is preferably carried out under a pressure of 0.13 Pa (10-3 Torr) or less, more preferably 0.07 Pa (5.0 × 10-4 Torr) or less, at a temperature in the range of 1000°C to 1150°C. To prevent oxidation during sintering, residual gas in the atmosphere can be replaced with an inert gas such as helium or argon. The resulting sintered compact (sintered R1-TB based magnet material) may be subjected to a heat treatment. Known conditions, such as the heat treatment temperature and heat treatment time, can be used.

[0060] (Step of preparing diffusion source powder) In this embodiment, for example, powder of an R2-M alloy is used as the diffusion source powder. In the R2-M alloy, R2 is a rare earth element and always contains at least one of Tb and Dy and at least one of Nd and Pr, and M is at least one selected from the group consisting of Cu, Ga, Fe, Co, Ni, and Al. Preferably, R2 is 65 mass% or more and 97 mass% or less of the entire R2-M alloy, and M is 3 mass% or more and 35 mass% or less of the entire R2-M alloy. More preferably, R2 is 85 mass% or more and 95 mass% or less of the entire R2-M alloy, and M is 5 mass% or more and 15 mass% or less of the entire R2-M alloy. Higher H cJ The content of Tb and Dy in R2 is preferably 3 mass% or more and 24 mass% or less of the entire R2-M alloy. The content of Pr in R2 is preferably 65 mass% or more and 86 mass% or less of the entire R2-M alloy. M preferably always contains at least one of Ga and Cu. Higher H cJ Preferably, the Pr content of the R2-M alloy is 50 mass% or more of the entire R2, and more preferably, R2 consists of only Pr and Tb. The inclusion of Pr facilitates diffusion in the grain boundary phase, allowing Tb to diffuse more efficiently, resulting in a higher H cJ can be obtained.

[0061] Next, a method for producing an R2-M alloy will be described.

[0062] The R2-M alloy can be prepared using a raw material alloy production method commonly used in the production of RTB sintered magnets, such as die casting, strip casting, single-roll rapid cooling (melt spinning), or atomization. Alternatively, the R2-M alloy may be prepared by pulverizing the alloy obtained by the above method using a known pulverization method such as a pin mill. The R2-M alloy in this embodiment is in the form of a powder, which is an aggregate of particles. The diffusion source is not limited to the R2-M alloy, and may contain other types of alloys or compounds instead of or in addition to the R2-M alloy.

[0063] (Adhesive application process) In this embodiment, the adhesive application step is carried out before the diffusion source powder attachment step.

[0064] Examples of adhesives that can be applied to the surface of the R1-TB sintered magnet material include PVA (polyvinyl alcohol), PVB (polyvinyl butyral), and PVP (polyvinylpyrrolidone). If the adhesive is water-based, the R1-TB sintered magnet material may be preheated before application. The purpose of preheating is to remove excess solvent, control adhesive strength, and ensure uniform adhesion of the adhesive. The heating temperature is preferably 60 to 100°C. This step may be omitted if the adhesive is a highly volatile organic solvent-based adhesive.

[0065] Any method can be used to apply the adhesive to the surface of the sintered R1-TB magnet material. Specific examples of application methods include spraying, dipping, and application using a dispenser. In a preferred embodiment, the adhesive is applied to the entire surface (whole surface) of the sintered R1-TB magnet material. The adhesive may be applied to only a portion of the surface of the sintered R1-TB magnet material, rather than the entire surface. Particularly when the thickness of the sintered R1-TB magnet material is thin (e.g., approximately 2 mm), it may be possible to diffuse the necessary elements throughout the magnet by simply applying the diffusion source powder to one of the largest surfaces of the sintered R1-TB magnet material. According to the manufacturing method of the present disclosure, the diffusion source powder can be applied to multiple surfaces of the sintered R1-TB magnet material with different normal directions in a single process. The thickness of the adhesive layer is preferably between 10 μm and 100 μm.

[0066] (Diffusion source powder attachment process) In this embodiment, a diffusion source attachment device 1000 such as that shown in FIG. 1 is used to attach a diffusion source powder of an R2-M alloy to the surface of a sintered R1-TB magnet material.

[0067] 5, the deposition of the diffusion source powder is completed while the sintered R1-TB based magnet material is being transported by the wire 20. In this embodiment, the transport speed of the wire 20 is in the range of 500 mm / min to 2000 mm / min, and it takes only about 1 to 2 seconds to deposit the diffusion source powder on one sintered R1-TB based magnet material. Furthermore, because the diffusion source powder is deposited on the sintered R1-TB based magnet material while it is supported by the thin wire, the diffusion source powder can be deposited uniformly over almost the entire surface of the sintered R1-TB based magnet material.

[0068] In this embodiment, the bottom area of ​​the collection section 30 is 2700 mm 2The control device 600 is set so as to supply the diffusion source powder 14 from the diffusion source powder supply device 500 to the fluidized bed accommodating chamber 300 when the height of the diffusion source powder 14 in the recovery section 30 decreases and reaches a first value (85 mm), and to stop the supply when the height of the diffusion source powder 14 increases and reaches a second value (140 mm). This maintains the amount of the diffusion source powder 14 in the fluidized bed 100 within an appropriate range, suppresses variations in the amount of adhesion in the diffusion source adhesion step, and achieves highly uniform adhesion.

[0069] (Diffusion process) A diffusion process is carried out by heating an R1-TB sintered magnet material with an R2-M alloy diffusion source powder adhered to its surface in a vacuum or inert gas atmosphere at a temperature of 700°C to 1100°C, diffusing R2 and M into the R1-TB sintered magnet material. This generates a liquid phase containing R2 and M from the R2-M alloy, and this liquid phase diffuses from the surface of the sintered body to the interior via the grain boundaries in the R1-TB sintered magnet material. At this time, it is preferable to increase the content of the heavy rare earth element RH (preferably Tb) in the R1-TB sintered magnet material by an extremely small amount, between 0.05 mass% and 0.30 mass%. This allows for extremely high H while suppressing consumption of the heavy rare earth element RH. cJ This can achieve an improvement effect. To increase the RH content in an R1-TB sintered magnet material by 0.05 mass% or more and 0.30 mass% or less, various conditions, such as the amount of R2-M alloy, the heating temperature during treatment, the particle size (if the R2-M alloy is in particulate form), and the treatment time, can be adjusted. Among these, the amount of R2-M alloy and the heating temperature during treatment can be adjusted to relatively easily control the amount of heavy rare earth element RH introduced (the increase).

[0070] In this specification, for example, "increasing the Tb content by 0.05 mass% or more and 0.30 mass% or less" means that the Tb content, expressed in mass%, increases by 0.05 mass% or more and 0.30 mass% or less. For example, if the Tb content of the R1-TB based sintered magnet material before the diffusion process is 0.50 mass%, and the Tb content of the RTB based sintered magnet after the diffusion process is 0.60 mass%, then the diffusion process will increase the Tb content by 0.10 mass%. Whether the content (RH amount) of at least one of Tb and Dy has increased by 0.05 mass% or more and 0.30 mass% or less can be calculated by measuring the RH amounts of the R1-TB based sintered magnet material before the diffusion step and the RTB based sintered magnet (as a whole) after the diffusion step, and determining how much the RH amount has increased before and after diffusion. Furthermore, if there is an R2-M based alloy concentrated area on the surface of the RTB based sintered magnet after diffusion, it is desirable to remove the concentrated area by cutting or the like before measuring the RH amount.

[0071] If the heating temperature is less than 700°C, the amount of liquid phase containing, for example, Tb, Pr, and M is too small, resulting in a high H cJ On the other hand, when the temperature exceeds 1100℃, H cJ The temperature is preferably 850°C or higher and 980°C or lower. cJ can be obtained.

[0072] In addition to the R2-M alloy diffusion source powder, a powder of a fluoride, oxide, or oxyfluoride of the heavy rare-earth element RH may be attached to the surface of the RTB sintered magnet material. This allows the light rare-earth elements RL and M to diffuse simultaneously into the interior of the RTB sintered magnet material along with the heavy rare-earth element RH. Examples of fluorides, oxides, and oxyfluorides of the heavy rare-earth element RH include TbF3, DyF3, Tb2O3, Dy2O3, Tb4OF, and Dy4OF.

[0073] (Heat treatment process) After the diffusion treatment step, the RTB based sintered magnet may be subjected to a heat treatment in a vacuum or inert gas atmosphere at a temperature of 450°C to 750°C, both inclusive, which is lower than the temperature used in the diffusion treatment. cJ can be obtained. [Industrial Applicability]

[0074] The embodiment of the present invention is characterized in that the H content of the RTB-based sintered magnet is reduced by using less heavy rare earth element RH. cJ Therefore, the present invention can be used to manufacture sintered rare earth magnets that require high coercivity. The present invention can also be widely applied to technologies that require diffusing metal elements other than the heavy rare earth element RH into a sintered rare earth magnet from the surface. [Explanation of symbols]

[0075] 10. Sintered rare earth magnet material 12. Adhesive 14. Diffusion source powder 20 wire 30. Recovery section 100...Fluidization tank 200...Transportation device 300 Fluidization tank containing chamber 400...Circulation mechanism 500···Diffusion source powder feeder 600 Control device 1000... Diffusion source attachment device

Claims

1. a fluidization tank for storing and fluidizing the diffusion source powder to be attached to each of the plurality of rare earth sintered magnet materials; a conveying device having two or more wires on which the plurality of sintered rare earth magnet materials are placed and conveyed, and which conveys the plurality of sintered rare earth magnet materials by moving the wires in a horizontal direction so that the plurality of sintered rare earth magnet materials pass through a predetermined space located above the fluidized bed; Equipped with The diffusion source attachment device, wherein the two or more wires are arranged at intervals in a direction perpendicular to the conveying direction, and the plurality of rare earth sintered magnet materials are supported by the wires.

2. A fluidization tank for storing and fluidizing a diffusion source powder to be attached to each of a plurality of rare earth sintered magnet materials; a conveying device having two or more wires on which the plurality of sintered rare earth magnet materials are placed and conveyed, and which conveys the plurality of sintered rare earth magnet materials by moving the wires in a horizontal direction so that the plurality of sintered rare earth magnet materials pass through a predetermined space located above the fluidized bed; Equipped with When each of the plurality of rare earth sintered magnet materials transported by the transport device passes through the specified space located above the fluidized bed, an adhesive is applied to the surface of each of the plurality of rare earth sintered magnet materials, and the particles of the diffusion source powder floating in the specified space from the fluidized bed are adhered to the adhesive.

3. The diffusion source adhering device according to claim 2 , further comprising a device for removing unnecessary particles of the diffusion source powder that have passed through the predetermined space and adhered to the adhesive by blowing air therethrough.

4. A fluidizing tank containing chamber surrounding the fluidizing tank and including a recovery section for recovering the diffusion source powder overflowing from the fluidizing tank; a circulation mechanism that sends the diffusion source powder recovered by the recovery unit to the fluidized bed; The diffusion source deposition apparatus according to claim 1 , further comprising:

5. The diffusion source attachment device according to claim 4 , further comprising a diffusion source powder supplying device for newly supplying the diffusion source powder from outside the fluidized bed containing chamber to the fluidized bed containing chamber.

6. a control device for controlling the diffusion source powder supply device; a sensor for detecting the amount or height of the diffusion source powder collected in the collection section; Equipped with The control device When it is determined that the amount or height of the diffusion source powder in the recovery section has decreased and reached a first value, the diffusion source powder is newly supplied from the diffusion source powder supply device to the fluidized bed accommodating chamber, 6. The diffusion source deposition device of claim 5, wherein when the amount or height of the diffusion source powder in the recovery section increases and reaches a second value greater than the first value, the supply of the diffusion source powder from the diffusion source powder supply device to the fluidized tank containing chamber is stopped.

7. The circulation mechanism includes:

7. The diffusion source deposition device according to claim 4, further comprising a pipe for conveying the diffusion source powder from the recovery section into the fluidized bed by an air flow.

8. The fluidized bed has a porous region on its bottom surface, The diffusion source deposition device according to claim 1 , further comprising an airflow device that blows gas through the porous region to blow up the diffusion source powder in the fluidized bed.

9. a step of adhering a diffusion source powder to each of a plurality of rare earth sintered magnet materials using the diffusion source adhering device according to any one of claims 1 to 8; diffusing elements contained in the diffusion source powder from the diffusion source powder attached to each of the plurality of sintered rare earth magnet materials into the interior of each of the sintered rare earth magnet materials; A method for producing a rare earth sintered magnet, comprising:

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