Method for producing diffusion source powder and rare earth sintered magnet

Abstract

To provide a diffusion source powder that can be uniformly attached to the surface of a rare earth sintered magnet.SOLUTION: A method for producing diffusion source powder includes a step of preparing a molten rare earth alloy, and a step of forming a plurality of atomized powder particles from the molten rare earth alloy heated to a temperature of 1100°C or more and 1400°C or less by an atomization method. The rare earth alloy is an R-M-A alloy. R contains at least one rare earth element and at least one of Nd and Pr. M is at least one selected from the group consisting of Cu, Ga, Co, and Fe. A is at least one selected from the group consisting of Al, Si, Ti, V, Cr, Mn, Co, Ni, Zn, Ge, Zr, Nb, Mo, Ag, and B.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] R2T 14 RTB sintered magnets, whose main phase is a B-type compound (R contains at least one rare earth element and at least one of Nd and Pr, and T is Fe or Fe and Co), are known as the highest performance permanent magnets and are used in voice coil motors (VCM) for hard disk drives, various motors such as motors for hybrid vehicles, and 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 in motors, etc., a high H cJ is required to be maintained.

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

[0005] Therefore, in recent years, B rIn order to prevent the decrease in H of RTB sintered magnets, less heavy rare earth element RH is used. cJ For example, it has been proposed to apply fluorides or oxides of the heavy rare earth element RH, or various metals M or M alloys, either alone or in combination, to the surface of a sintered magnet and then perform a heat treatment in that state, thereby diffusing the heavy rare earth element RH, which contributes to improving the 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, it is possible to partially reduce the RH oxide by the RM alloy or the like during heat treatment and introduce the heavy rare earth element RH into the magnet. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] International Publication No. 2006 / 043348 [Patent Document 2] JP 2008-263179 A [Patent Document 3] JP 2012-248827 A [Patent Document 4] JP 2012-248828 A [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 a method of subjecting the entire magnet surface (entire magnet surface) to a mixed powder containing RH compound powder and then carrying out a heat treatment. In a specific example of these methods, a magnet is immersed in a slurry in which the mixed powder is dispersed in water or an organic solvent, and then pulled up (immersion-pulling method). In the immersion-pulling method, the magnet pulled up from the slurry is dried with hot air or naturally dried. Instead of immersing the magnet in the slurry, it is also disclosed that the slurry is sprayed onto the magnet (spray coating method).

[0011] In these methods, the slurry can be applied to the entire surface of the magnet. Therefore, it is possible to introduce the heavy rare earth element RH into the magnet from the entire surface of the magnet. cJ However, with the dipping and pulling method, the slurry inevitably tends to be concentrated towards the bottom of the magnet due to gravity. Also, with the spray coating method, the coating thickness at the ends of the magnet becomes thicker due to surface tension. With either method, it is difficult to distribute the RH compound uniformly over 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, the amount of slurry applied is reduced, so the H after heat treatment is reduced. cJ If the slurry is applied multiple times in order to increase the amount of slurry applied, production efficiency will drop significantly. 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, lowering the yield of the slurry. As a result, there is a problem that the heavy rare earth element RH, which is a scarce resource, is wasted.

[0013] The applicant has disclosed in Patent Document 5 a method of performing a diffusion heat treatment in a state where an RLM alloy powder and an RH fluoride powder are present on the surface of an RTB sintered magnet. It is difficult to say that a method for distributing these powders uniformly on the surface of an RTB sintered magnet has been fully established. In particular, when the particle size of the diffusion source powder is non-uniform, the surface density of the diffusion source powder attached to the sintered magnet surface is also non-uniform, making it difficult to achieve uniform diffusion.

[0014] The present disclosure provides a diffusion source powder with high particle size uniformity suitable for diffusing various elements into a rare earth sintered magnet, and a method for producing a rare earth sintered magnet that uses the diffusion source powder to diffuse desired elements from the magnet surface to the interior. [Means for solving the problem]

[0015] In one embodiment, the method for producing a diffusion source powder according to the present disclosure includes a plurality of atomized powder particles formed from a rare earth alloy, and includes the steps of preparing a molten rare earth alloy and forming a plurality of atomized powder particles from the molten rare earth alloy heated to a temperature of 1100°C or more and 1400°C or less by an atomization method. The rare earth alloy is an RMA alloy. R includes at least one rare earth element and at least one of Nd and Pr. M is at least one selected from the group consisting of Cu, Ga, Co, and Fe. A is at least one selected from the group consisting of Al, Si, Ti, V, Cr, Mn, Co, Ni, Zn, Ge, Zr, Nb, Mo, Ag, and B.

[0016] In one embodiment, the diffusion source powder of the present disclosure is a diffusion source powder including a plurality of atomized powder particles formed from a rare earth alloy, the rare earth alloy being an RMA alloy. R includes at least one rare earth element and at least one of Nd and Pr. M is at least one selected from the group consisting of Cu, Ga, Co, and Fe. A is at least one selected from the group consisting of Al, Si, Ti, V, Cr, Mn, Co, Ni, Zn, Ge, Zr, Nb, Mo, and Ag. Each of more than half of the particles in the plurality of atomized powder particles has a recess.

[0017] In one embodiment, a method for manufacturing a rare earth sintered magnet according to the present disclosure includes the steps of: preparing the above-mentioned diffusion source powder; preparing a rare earth sintered magnet material having an adhesive layer on at least a portion of its surface; adhering the diffusion source powder to the adhesive layer of the rare earth sintered magnet material; and heating the rare earth magnet material to diffuse elements contained in the diffusion source powder from the diffusion source powder adhered to the adhesive layer into the interior of the rare earth sintered magnet material. Effect of the Invention

[0018] According to the embodiments of the present disclosure, a diffusion source powder with high particle size uniformity suitable for diffusing various elements into a rare earth sintered magnet can be provided, and a manufacturing method for a rare earth sintered magnet in which a desired element is diffused from the magnet surface to the inside by using the diffusion source powder can be provided. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a cross-sectional view showing a schematic diagram of particles of a diffusion source powder adhered to a rare earth sintered magnet material in a conventional example. [Figure 2A] FIG. 11 is another cross-sectional view showing, in schematic form, particles of a diffusion source powder in a conventional example attached to a rare earth sintered magnet material. [Figure 2B] FIG. 11 is a cross-sectional view showing a schematic diagram of particles of a diffusion source powder in a conventional example adhered to another rare earth sintered magnet material. [Diagram 3] 1 is a flow chart illustrating a method for producing a diffusion source powder in an embodiment of the present disclosure. [Figure 4] 1 is a graph showing the particle size distribution of powder produced by spraying molten metal at 1300°C in the process (S2) of forming atomized powder particles in this embodiment, and the particle size distribution of powder produced by spraying molten metal at 750°C in the process of forming atomized powder particles in a conventional example (dashed line). [Diagram 5] FIG. 2 is a diagram showing an example of an electron microscope photograph of a plurality of particles constituting the diffusion source powder in the present embodiment. [Figure 6A] 1 is a cross-sectional view showing a schematic diagram of particles of a diffusion source powder according to an embodiment of the present invention adhered to a rare earth sintered magnet material. [Figure 6B] FIG. 2 is a cross-sectional view showing a schematic diagram of particles of the diffusion source powder in this embodiment adhered to another rare earth sintered magnet material. [Figure 7] FIG. 1 is a diagram illustrating an example of a schematic configuration of a diffusion source attachment apparatus 1000 according to an embodiment of the present invention. [Figure 8] FIG. 2 is a perspective view showing a schematic diagram of a flow tank and a wire positioned above the flow tank; [Figure 9] 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 10] FIG. 1 is a cross-sectional view showing a schematic diagram of a flow tank 100 and a wire 20 positioned above the flow tank 100. [Figure 11] 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 when the diffusion source powder has started to flow in a fluidizing tank 100. FIG. [Figure 12] 2 is a flowchart showing a method for producing a rare earth sintered magnet according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The present disclosure provides a diffusion source powder including a plurality of atomized powder particles formed from a rare earth alloy and a method for producing the same.

[0021] Atomized powder particles are produced by the atomization method. When molten metal or alloy is made to flow out of a small opening at the bottom of a crucible and sprayed against a high-speed fluid or a rotating disk, etc., powder particles of the rapidly solidified metal or alloy can be formed. This powder production method is called the atomization method, and powder produced by the atomization method is called atomized powder. Here, the particles that make up atomized powder may be called atomized powder particles.

[0022] Unlike powder particles produced by mechanically pulverizing a metal or alloy ingot, atomized powder particles have an almost spherical shape. Also, the distribution of particle sizes (particle diameters) contained in atomized powder is sharper than that of mechanically pulverized powder. Therefore, a diffusion source powder containing a plurality of atomized powder particles formed from a rare earth alloy is more suitable for achieving uniform diffusion than a diffusion source powder made of powder particles formed by mechanically pulverizing a rare earth alloy.

[0023] However, according to the study of the present inventor, when using diffusion source powder produced by the conventional atomization method, the surface density of the diffusion source powder attached to the surface of the sintered magnet material may become non-uniform, making it difficult to achieve uniform diffusion. After extensive study of the cause, the inventor found that the diffusion source powder produced by the conventional atomization method does not necessarily have sufficient uniformity in particle size.

[0024] FIG. 1 is a cross-sectional view showing atomized powder particles 14P of a diffusion source powder 14 in a conventional example attached to a rare earth sintered magnet material (work) 10. Hereinafter, for simplicity, the atomized powder particles 14P may be simply referred to as "particles 14P". In this example, an adhesive layer (adhesive) 12 is provided on the surface of the rare earth sintered magnet material 10. The particles 14P are attached to the adhesive layer 12 by a diffusion source attachment device described below. With such a diffusion source attachment device, as shown in FIG. 1, the particles 14P can be attached to the adhesive layer 12 of the rare earth sintered magnet material 10 with a thickness of about one layer. If the size (particle diameter) of the attached particles 14P varies greatly depending on the position, the amount and concentration of elements diffused from the particles 14P at each position into the rare earth sintered magnet material 10 during the diffusion process will be different.

[0025] In addition, in the diffusion source adhering device described later, the particles 14P of the diffusion source powder 14 suspended in the fluidized bed are adhered to the adhesive layer 12 of the rare earth sintered magnet material 10. Therefore, when the particle size distribution of the diffusion source powder supplied to the fluidized bed has a wide range, depending on the timing of the adhering, the rare earth sintered magnet material 10 may have mainly particles 14P with a relatively large particle size adhered thereto, and the rare earth sintered magnet material 10 may have mainly particles 14P with a relatively small particle size adhered thereto. For example, at a certain timing in the adhering process, the relatively small particles 14P of the diffusion source powder 14 are adhered to the adhesive layer 12 of the rare earth sintered magnet material 10 as shown in Fig. 2A, but at another timing, the relatively large particles 14P of the diffusion source powder 14 may be adhered thereto as shown in Fig. 2B. In such a case, the particle size of the particles 14P adhering to the rare earth sintered magnet material 10 varies greatly for each manufacturing process, and the amount of elements diffused from the diffusion source powder 14 into the rare earth sintered magnet material 10 changes, resulting in large variations in the magnetic properties of the individual rare earth sintered magnets.

[0026] According to the embodiment of the present invention, it is possible to produce the diffusion source powder 14 having a narrow particle size distribution, and therefore it is possible to solve such a problem.

[0027] As shown in FIG. 3, the manufacturing method of the diffusion source powder in this embodiment includes a step (S1) of preparing a molten rare earth alloy, and a step (S2) of forming a plurality of atomized powder particles by an atomization method from the molten alloy heated to a temperature of 1100° C. or more and 1400° C. or less.

[0028] The rare earth alloy is an RMA alloy. Here, R includes at least one rare earth element and includes at least one of Nd and Pr. M is at least one selected from the group consisting of Cu, Ga, Co, and Fe. A is at least one selected from the group consisting of Al, Si, Ti, V, Cr, Mn, Co, Ni, Zn, Ge, Zr, Nb, Mo, Ag, and B. A is not an essential element for the RMA alloy. If the RMA alloy does not include A, the RMA alloy can be described as an "RM alloy", but in this disclosure, it will be described as an "RMA alloy" to adopt a consistent expression format. In a preferred embodiment, A is at least one selected from the group consisting of Al, Si, Ti, V, Cr, Mn, Co, Ni, Zn, Ge, Zr, Nb, Mo, and Ag. Here, each group of M and A includes an overlapping element (Co), but when this overlapping element is selected for one of M and A, it is not selected overlappingly for the other.

[0029] In one embodiment, the composition ratio of R is 65% by mass or more and 95% by mass or less of the entire RMA alloy, the composition ratio of M is 5% by mass or more and 35% by mass or less of the entire RMA alloy, and the composition ratio of A is 0% by mass or more and 3% by mass or less of the entire RMA alloy.

[0030] The total composition ratio of Nd and Pr is 60 mass % or more of the whole of R. M contains at least one of Cu and Ga. The total composition ratio of Cu and Ga is 50 mass % or more of the whole of M. The step (S2) of forming atomized powder particles includes spraying the molten metal whose temperature has been adjusted to a range of 1100°C or more and 1400°C or less (preferably, 1250°C or more and 1350°C or less).

[0031] 4 is a graph showing the particle size distribution of powder produced by spraying molten metal at 1300°C in the step (S2) of forming atomized powder particles of this embodiment (solid line) and the particle size distribution of powder produced by spraying molten metal at 750°C in the step of forming atomized powder particles of a conventional example (dashed line). Note that the particle size distribution is a frequency distribution, which is a value obtained by differentiating the cumulative distribution by the particle size. The vertical axis of FIG. 4 shows the frequency, and the horizontal axis shows the particle size.

[0032] As is clear from Fig. 4, according to this embodiment, the particle size distribution is sharper and the width of the particle size distribution is narrower than in the conventional example. This means that the variation in particle size is reduced. More specifically, the tail of the distribution on the relatively small particle size side, which was noticeable when the molten metal was tapped at 750°C, is reduced by tapping at 1300°C. One of the reasons for this is thought to be that by increasing the molten metal temperature, the viscosity of the molten metal at the time of tapping is reduced, and the stability of the molten metal at the time of tapping is increased.

[0033] According to this embodiment, it is possible to produce an atomized powder having a sharp particle size distribution with a volumetric median diameter d50 of 50 μm or more and 150 μm or less. The median diameter d50 means the particle diameter (median diameter) at which the cumulative particle size distribution (volume basis) from the small particle diameter side is 50%. For example, d50 can be determined by measuring with a particle size distribution measuring device "HELOS&RODOS" manufactured by Sympatec under the conditions of dispersion pressure: 4 bar, measurement range: R2, and calculation mode: HRLD.

[0034] In this embodiment, in the step (S2) of forming the atomized powder particles, the molten metal adjusted to a temperature in the range of 1100°C to 1400°C (preferably 1250°C to 1350°C) is sprayed, so that the dents are generated in the atomized powder particles 14P. One of the causes is considered to be the volumetric contraction of the molten metal droplets that occurs when they are rapidly cooled from a high temperature of 1100°C or higher (preferably 1250°C or higher). More specifically, when the high-temperature droplets fly through the gas and are cooled, solidification starts from the droplet surface located in front of the flight direction, and a shell portion (solid phase) is generated. Thereafter, as the solidified region (solid phase) grows from the shell portion, the temperature of the droplets drops and the volume shrinks, and a dent is generated, completing the solidification.

[0035] FIG. 5 is a diagram showing an example of an electron microscope photograph of particles (atomized powder particles) 14P produced at high temperature in this embodiment. More specifically, FIG. 5 is a backscattered electron image of atomized powder particles produced by spraying molten metal at a temperature of 1300° C., taken with an electron microscope of JCM-6000Plus manufactured by JEOL Ltd. For example, as shown in FIG. 5, it is preferable that more than half of the particles have a recess when counting the number of particles in the field of view in a photograph of atomized powder particles placed on a flat surface. In the example of FIG. 5, about 70% of the particles in the field of view had a recess. In this way, most of the particles 14P in this embodiment have a recess 14X. Even by the conventional atomization method in which molten metal is ejected at a temperature lower than 1250° C. and rapidly cooled, there is a possibility that a recess is formed in some particles. However, in the past, atomized powder particles with such recesses formed are removed as defective products and are not used. In this embodiment, the atomized powder particles 14P with such recesses 14X formed are actively used. The presence of the recesses 14X reduces the fluidity of the diffusion source powder 14, but increases the ratio of the surface area to the volume of each particle 14P, thereby providing the effect of increasing the adhesive force to the adhesive layer described below. In this embodiment, the "recesses" of the atomized powder particles refer to regions on the surface of the particles that are recessed toward the side where the center of gravity of the particles is located, and the maximum diameter of the outer edge of the recessed region is 20% or more of the diameter of the atomized powder particle. The number of recesses that the atomized powder particles have is not limited to one, and may be multiple.

[0036] According to the diffusion source powder 14 of this embodiment, the particle size distribution is sharp, so that at any timing of the adhering step, the diffusion source powder 14 adheres to the adhesive layer 12 of the rare earth sintered magnet material 10 as particles 14P with similar particle size, as shown in Figures 6A and 6B. Therefore, the particle size of the particles 14P adhering to the rare earth sintered magnet material 10 is prevented from fluctuating significantly for each manufacturing step, and the amount of elements diffused from the diffusion source powder 14 to the rare earth sintered magnet material 10 is uniform. As a result, the magnetic properties of the individual rare earth sintered magnets are prevented from fluctuating significantly.

[0037] Hereinafter, a configuration example and an operation example of a diffusion source attachment device suitably used for attaching the diffusion source powder 14 to the rare earth sintered magnet material in this embodiment will be described.

[0038] First, reference is made to Fig. 7. Fig. 7 is a diagram that illustrates a schematic configuration example of a diffusion source attachment apparatus 1000 in this embodiment. For reference, an X-axis, a Y-axis, and a Z-axis that are orthogonal to each other are illustrated in the diagram.

[0039] In the example of FIG. 7, the diffusion source attachment device 1000 includes a fluidization tank 100 and a conveying device 200. The fluidization tank 100 is a device that stores and fluidizes the diffusion source powder 14 to be attached to each of the multiple rare earth sintered magnet materials (workpieces) 10. The diffusion source powder 14 in this embodiment is an atomized powder manufactured by the above-mentioned manufacturing method. Most of the particles 14P contained in the diffusion source powder 14 have recesses 14X formed therein. The conveying device 200 has two or more wires 20 that carry and convey the multiple rare earth sintered magnet materials 10, and can move each wire 20 in the horizontal direction (Y-axis direction). The wires 20 are driven by, for example, a motor. The conveying device 200 conveys the multiple rare earth sintered magnet materials 10 so that the multiple rare earth sintered magnet materials 10 pass through a predetermined space S located above the fluidization tank 100. The height range of the predetermined space S is, for example, 5 mm to 100 mm from the upper end of the fluidization tank 100. The predetermined space S is included in the region of the diffusion source powder 14 that forms a fluidized bed in the fluidization tank 100 in a top view seen from the positive direction of the Z axis. The fluidized bed is a state in which an airflow of a certain flow rate or more is applied from below the powder, so that the flow resistance applied to the powder particles is equal to gravity, and the powder can flow like a boiled liquid. This type of fluidization is called "fluidization." The presence of recesses in the particles 14P does not directly affect the fluidization.

[0040] Next, reference is made to Fig. 8 and Fig. 9. Fig. 8 is a perspective view showing a schematic diagram of a flow tank 100 and a wire 20 positioned above it. Fig. 9 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 in the Y-axis direction by the wire 20.

[0041] In the example shown in FIG. 8, the fluidization tank 100 has a box shape with an open top, and has four side portions 100S and one bottom portion 100B. When viewed from the positive direction of the Z axis, the fluidization tank 100 in the illustrated example has a rectangular shape with a pair of sides parallel to the Y axis direction and another pair of sides parallel to the X axis direction. The length of one side is, for example, in the range of 100 mm to 300 mm. In addition, the height of the side portion 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 are arbitrary. The fluidization tank 100 may have a shape other than a rectangle, for example, a circle, an ellipse, or a polygon, when viewed from above.

[0042] 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. A part or all of the bottom surface 100B of the fluidization tank 100 has a large number of holes that allow air to circulate. Such a bottom surface 100B may be suitably formed, for example, from a porous plate.

[0043] The wire 20 may bend when multiple sintered rare earth magnet materials 10 are placed on it, but is positioned so that the wire does not come into contact with the fluidized bed tank 100 even in the bent state. If the weight of the sintered rare earth magnet materials 10 causes the wire 20 to bend and the inclination angle of the wire 20 to increase, the rare earth sintered magnet materials 10 may slip on the wire 20. To prevent such slippage, it is desirable for the inclination angle of the wire 20 to be 5 degrees or less. The diameter of the wire 20 may be in the range of, for example, 0.5 mm or more and 2 mm or less.

[0044] 8 and 9, 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.

[0045] Next, reference is made to Figures 10 and 11. Figure 10 is a cross-sectional view that typically shows a fluidization tank 100 and a wire 20 positioned above it. In the state shown in Figure 10, the diffusion source powder 14 is stored in the fluidization tank 100, but fluidization has not yet started. Figure 11 is a cross-sectional view that shows a state in which the diffusion source powder has started to flow in the fluidization tank 100, and multiple rare earth sintered magnet materials 10 are being carried in the Y-axis direction by the wire 20.

[0046] In the illustrated example, the fluidized bed 100 has a porous region 120 on the bottom surface. The diffusion source attachment device 1000 in this embodiment includes an airflow device 140 that causes gas to flow in from the porous region 120 to blow up the diffusion source powder 14 in the fluidized bed 100. The airflow sent from the airflow device 140 through the porous region 120 into the fluidized bed 100 fluidizes the diffusion source powder 14 in the fluidized bed 100 to form a fluidized bed. In the embodiment of the present disclosure, the diffusion source powder 14 is attached to the surface of the rare earth sintered magnet material 10 outside (above) the fluidized bed 100, not inside the diffusion source powder 14 that forms a fluidized bed inside the fluidized bed 100. This is because in the embodiment of the present disclosure, it is sufficient to uniformly realize the attachment of about one layer of powder particles, and attachment of a thick particle layer is not necessary. For this reason, when the fluidized bed is formed, it is preferable that the diffusion source powder 14 is blown up to a height of about 10 mm to 30 mm from the upper surface of the fluidized bed 100.

[0047] In this embodiment, when each of the plurality of rare earth sintered magnet materials 10 conveyed by the wire 20 of the conveying device 200 passes through the predetermined space S located above the fluidized bed 100, the surface of each of the plurality of rare earth sintered magnet materials 10 has an adhesive layer 12 formed thereon. Such an adhesive layer 12 can be formed by applying an adhesive liquid to the rare earth sintered magnet material 10 on the wire 20 using a spraying device or the like. The particles 14P of the diffusion source powder 14 suspended in the predetermined space S from the fluidized bed 100 adhere to the adhesive layer 12 of the rare earth sintered magnet material 10 moving in the horizontal direction. At this time, the particles 14P directly contact and adhere to the adhesive layer 12 to form one particle layer. However, the particles 14P may form another particle layer on such a particle layer. However, the particles 14P constituting such another particle layer do not directly contact and adhere to the adhesive layer 12. Therefore, the other particle layers can be easily removed by the subsequent air blowing process, and a state in which one particle layer essentially covers the entire surface of the adhesive layer 12 can be formed. This allows for control of the adhesive force of the diffusion source powder. As a result, it becomes possible to perform uniform diffusion with good reproducibility, and the variation in magnetic properties is suppressed.

[0048] In order to carry out the above-mentioned spraying process, the diffusion source attachment apparatus 1000 or a manufacturing facility including the diffusion source attachment apparatus 1000 may further include a device (not shown) for removing unnecessary particles from among the particles of the diffusion source powder 14 that have passed through the specified space S and adhered to the adhesive layer 12 by air blowing.

[0049] Referring again to FIG.

[0050] In this embodiment, the diffusion source attachment device 1000 further includes a fluidized bed accommodation chamber 300 surrounding the fluidized bed 100, and a circulation mechanism 400. The fluidized bed accommodation chamber 300 includes a recovery section 30 that recovers the diffusion source powder 14 overflowing from the fluidized bed 100. The fluidized bed accommodation chamber 300 preferably has a funnel-shaped inclination at its lower end, and the recovery section 30 is provided at its lower end. The recovery section 30 is configured so that the particles of the diffusion source powder 14 floating in the fluidized bed accommodation chamber 300 fall by their own weight and then collect. The circulation mechanism 400 is configured to send the diffusion source powder 14 recovered by the recovery section 30 to the fluidized bed 100.

[0051] In this embodiment, the circulation mechanism 400 has a pipe 40 that conveys the diffusion source powder 14 from the collection section 30 into the fluidized tank 100 by an air flow. Specifically, the air flowing through the pipe 40 conveys the diffusion source powder 14 in the collection section 30 by the operation of the ejector E1. A gas such as air pressurized by a pump (not shown) is supplied to the ejector E1 through a valve V1.

[0052] The pipe 40 communicates with the fluidized bed chamber 300. In the fluidized bed chamber 300, the end of the pipe 40 is arranged so as to supply the diffusion source powder 14 to the fluidized bed 100. A funnel-shaped intermediate container may be provided between the end of the pipe 40 and the fluidized bed 100. Such an intermediate container has a small opening at the bottom and can function as a buffer device for adjusting the supply rate so that a large amount of the diffusion source powder 14 carried by the pipe 40 is not given to the fluidized bed 100 at once. The intermediate device separates the diffusion source powder 14 from the conveying air and functions to prevent the collected diffusion source powder 14 from falling directly on the work 10. By providing such an intermediate device, it is possible to steadily advance the adhesion of the diffusion source powder 14 from the fluidized bed 100 to the work 10 and prevent fluctuations due to the collected diffusion source powder 14.

[0053] The diffusion source attachment device 1000 in this embodiment includes a diffusion source powder supply device 500 that newly supplies the diffusion source powder 14 from the outside of the fluidized bed housing chamber 300 to the inside of the fluidized bed housing chamber 300. As described above, the particles 14P of the diffusion source powder 14 spouted from the fluidized bed 100 adhere to the adhesive layer 12 of the rare earth sintered magnet material 10 passing above the fluidized bed 100, so that the amount of the diffusion source powder 14 present inside the fluidized bed housing chamber 300 gradually decreases. The particles 14P of the diffusion source powder 14 overflowing from the fluidized bed 100 are collected and returned to the fluidized bed 100 by the action of the circulation mechanism 400. When the amount of the diffusion source powder 14 present inside the fluidized bed housing chamber 300 decreases, the particles 14P of the diffusion source powder 14 that are collected naturally also decrease, and the diffusion source powder 14 stored in the fluidized bed 100 becomes insufficient. The diffusion source powder supplying device 500 supplies new diffusion source powder 14 to the inside of the fluidized tank accommodating chamber 300 so that the diffusion source powder 14 stored in the fluidized tank 100 does not run short. This supply is performed by ejecting the diffusion source powder stored in the diffusion source powder supplying device 500 into the fluidized tank accommodating chamber 300 through a pipeline by the ejector E2. Pressurized gas such as air is supplied to the ejector E2 through a valve V2.

[0054] The diffusion source attachment 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 a microprocessor. The processor sequentially executes a computer program stored in the storage device to realize a desired process. Such a process may also be executed by a programmable logic controller (PLC).

[0055] When the control device 600 determines that the amount or height of the diffusion source powder 14 in the collection 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 tank 100. Then, when the amount or height of the diffusion source powder 14 in the collection 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 tank accommodating chamber 300. In this way, the new diffusion source powder 14 supplied from the diffusion source powder supply device 500 to the fluidized tank accommodating chamber 300 is collected by the collection section 30 and supplied to the fluidized tank 100 by the action of the circulation mechanism 400.

[0056] The sensor 52 may include two height detectors provided at different heights. Such a height detector may have a configuration in which a light emitting section and a light receiving section are arranged across a space in the collection section 30. By using such a height detector, it is possible to determine that the height of the diffusion source powder 14 in the collection section 30 has reached a predetermined height by detecting with the light receiving section that the diffusion source powder 14 in the collection section 30 has blocked the light emitted from the light emitting section. Examples of the sensor 52 include a photoelectric sensor, an ultrasonic sensor, a laser sensor, and a pulse vibration level sensor. Among these, the pulse vibration level sensor is preferable 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 attached to the adhesive layer 12 of the rare earth sintered magnet material 10. The timing and amount of the new diffusion source powder 14 to be supplied to the fluidized bed accommodation chamber 300 are monitored based on the amount of the diffusion source powder 14 in the collection section 30, so that the amount of the required diffusion source powder can be maintained and controlled without providing other expensive sensors.

[0057] Hereinafter, an embodiment of the method for producing a rare earth sintered magnet according to the present disclosure will be described. The above-mentioned diffusion source attachment device 1000 can attach various diffusion source powders to a rare earth sintered magnet material, and there are no restrictions on the composition of the diffusion source powder. Here, an embodiment of the method for producing an RTB sintered magnet including a step of attaching a diffusion source powder containing a heavy rare earth element by the above-mentioned diffusion source attachment device will be described.

[0058] <Method of manufacturing rare earth sintered magnets> 12, the method for producing a rare earth sintered magnet in this embodiment may include a step S10 of preparing an R1-TB sintered magnet material, a step S20 of preparing a diffusion source powder such as an RMA alloy, an adhesive application step S30 of applying an adhesive layer to the surface of the R1-TB sintered magnet material, a diffusion source powder attachment step S40 of attaching the diffusion source powder to the surface of the R1-TB sintered magnet material, and a diffusion step S50. The diffusion step S50 is a heat treatment step in which the magnet material having the rare earth alloy diffusion source powder attached to its surface is heated at a temperature of 700°C to 1100°C in a vacuum or inert gas atmosphere to diffuse the elements contained in the diffusion source powder into the R1-TB sintered magnet material.

[0059] In this disclosure, the R1-TB sintered magnet before and during the diffusion process may be referred to as the "rare earth sintered magnet material," and the rare earth sintered magnet after the diffusion process may be simply referred to as the "rare earth sintered magnet." Each of these processes will be described in more detail below.

[0060] In this embodiment, in the step S20 of preparing the diffusion source powder, the diffusion source powder including a plurality of atomized powder particles formed from a rare earth alloy is prepared by the above-mentioned atomization method. Specifically, the method includes a step of preparing a molten rare earth alloy, and a step of forming a plurality of atomized powder particles by the atomization method from the molten rare earth alloy heated to a temperature of 1100°C or more and 1400°C or less (preferably, 1250°C or more and 1350°C or less). In addition, this rare earth alloy is an RMA alloy. Here, R includes at least one rare earth element and includes at least one of Nd and Pr. M is at least one selected from the group consisting of Cu, Ga, Co, and Fe. A is at least one selected from the group consisting of Al, Si, Ti, V, Cr, Mn, Co, Ni, Zn, Ge, Zr, Nb, Mo, Ag, and B.

[0061] (Preparing rare earth sintered magnet material) The rare earth (R1-TB) sintered magnet material in this embodiment 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 at least one selected from the group consisting of 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.

[0062] Next, a method for producing the rare earth sintered magnet material having the above composition will be described.

[0063] First, an alloy for a rare earth sintered magnet is prepared, and then the alloy is roughly crushed by, for example, a hydrogen crushing method.

[0064] The following is an example of a method for producing an alloy for a rare earth sintered magnet. An alloy ingot can be obtained by an ingot casting method in which a metal or alloy previously adjusted to have the above-mentioned composition is melted and poured into a mold to solidify. The alloy may also be produced by a strip casting method in which a molten metal or alloy previously adjusted to have the above-mentioned composition is brought into contact with a single roll, twin rolls, rotating disk, or rotating cylindrical mold, etc., and quenched to produce a rapidly solidified alloy. Alternatively, a flake-shaped alloy may be produced by other quenching methods, such as centrifugal casting.

[0065] In the embodiment of the present disclosure, alloys manufactured by either the ingot method or the quenching method can be used, but it is preferable to use alloys manufactured by a quenching method such as a strip casting method. The thickness of the alloys manufactured by the quenching method is usually in the range of 0.03 mm to 1 mm, and they are in a flake shape. By subjecting the obtained alloy to hydrogen pulverization, the size of the hydrogen pulverized powder (coarsely pulverized powder) can be, for example, 1.0 mm or less. The coarsely pulverized powder thus obtained is pulverized by a jet mill.

[0066] The jet mill pulverization is performed in an inert atmosphere such as nitrogen, etc. The pulverization may be performed, for example, by using a jet mill in a humid atmosphere.

[0067] As long as the fine powder used to produce the rare earth sintered magnet material satisfies the above-mentioned conditions, it may be produced from one type of raw material alloy (single raw material alloy), or it may be produced by using two or more types of raw material alloys and mixing them (blending method).

[0068] In a preferred embodiment, a powder compact is produced from the fine powder by pressing in a magnetic field, and then the powder compact is sintered. In the case of pressing in a magnetic field, it is preferable to form the powder compact by pressing in an inert gas atmosphere or by wet pressing from the viewpoint of suppressing oxidation. In particular, in wet pressing, the surface of the particles constituting the powder compact is covered with a dispersant such as an oil agent, and contact with oxygen or water vapor in the air is suppressed. Therefore, it is possible to prevent or suppress the particles from being oxidized by the air before, during, or after the pressing process. Therefore, it is easy to control the oxygen content within a predetermined range. When performing wet pressing in a magnetic field, a slurry is prepared by mixing the fine powder with a dispersion medium, and the slurry is supplied to a cavity in a mold of a wet pressing device and press-molded in a magnetic field.

[0069] Next, the compact is sintered to obtain a rare earth sintered magnet material. The compact is preferably sintered at a pressure of 0.13 Pa (10 -3 Torr) or less, preferably 0.07 Pa (5.0 x 10 -4 The sintering is carried out at a pressure of 1000 to 1150°C under a pressure of 1000 Torr or less. To prevent oxidation due to sintering, residual gas in the atmosphere may be replaced with an inert gas such as helium or argon. The obtained sintered body (rare earth sintered magnet material) may be subjected to a heat treatment. Known conditions may be adopted for the heat treatment temperature, heat treatment time, and other heat treatment conditions.

[0070] (Step of Preparing Diffusion Source Powder) In this embodiment, the atomized powder of the RMA alloy produced by the above-mentioned method is used as the diffusion source powder. R contains at least one rare earth element and at least one of Nd and Pr. M is at least one selected from the group consisting of Cu, Ga, Co, and Fe. A is at least one selected from the group consisting of Al, Si, Ti, V, Cr, Mn, Co, Ni, Zn, Ge, Zr, Nb, Mo, Ag, and B. More preferably, A is at least one selected from the group consisting of Al, Si, Ti, V, Cr, Mn, Co, Ni, Zn, Ge, Zr, Nb, Mo, and Ag.

[0071] In one embodiment, the composition ratio of R is 65% by mass or more and 95% by mass or less of the entire RMA alloy, the composition ratio of M is 5% by mass or more and 35% by mass or less of the entire RMA alloy, and the composition ratio of A is 0% by mass or more and 3% by mass or less of the entire RMA alloy. cJ To obtain this, it is preferable that R is 85% by mass or more and 95% by mass or less of the entire RMA alloy, and M is 5% by mass or more and 15% by mass or less of the entire RMA alloy.

[0072] Preferably, the total composition ratio of Nd and Pr is 60 mass % or more of the entire R. M contains at least one of Cu and Ga, and the total composition ratio of Cu and Ga is 50 mass % or more of the entire M.

[0073] The content of Tb and Dy in R is preferably 3% by mass or more and 24% by mass or less of the entire RMA alloy. The content of Pr in R is preferably 65% ​​by mass or more and 86% by mass or less of the entire RMA alloy. M preferably always contains at least one of Ga and Cu. cJ Preferably, the Pr content of the RMA alloy is 50 mass % or more of the total R, and more preferably, R consists of only Pr and Tb. The inclusion of Pr facilitates diffusion in the grain boundary phase, so that Tb can be diffused more efficiently, resulting in a higher H cJ can be obtained.

[0074] Next, a method for preparing the diffusion source powder made of an RMA alloy will be described.

[0075] The diffusion source powder made of the RMA alloy can be prepared by atomizing a molten metal at a higher temperature than in the conventional example described above. Note that the diffusion source powder is not limited to the RMA alloy powder, and may contain powder of other types of alloys or compounds instead of or in addition to the RMA alloy powder.

[0076] (Adhesive application process) In this embodiment, an adhesive application step (adhesive layer formation step) is carried out before the diffusion source powder attachment step.

[0077] Examples of adhesives that can be applied to the surface of the rare earth sintered magnet material include PVA (polyvinyl alcohol), PVB (polyvinyl butyral), and PVP (polyvinylpyrrolidone). If the adhesive layer is a water-based adhesive, the rare earth sintered magnet material may be preheated before application. The purpose of the preheating is to remove excess solvent to control the adhesive strength and to adhere the adhesive layer uniformly. The heating temperature is preferably 60 to 100°C. In the case of an adhesive layer based on a highly volatile organic solvent, this step may be omitted.

[0078] Any method may be used to apply the adhesive to the surface of the rare earth sintered magnet material. Specific examples of application include spraying, dipping, and application with a dispenser. In a preferred embodiment, the adhesive is applied to the entire surface (whole surface) of the rare earth sintered magnet material. The adhesive may be applied to a part of the surface of the rare earth sintered magnet material rather than the entire surface. In particular, when the thickness of the rare earth sintered magnet material is thin (for example, about 2 mm), it may be possible to diffuse the necessary elements into the entire magnet by simply attaching the diffusion source powder to one surface of the rare earth sintered magnet material that has the largest area. According to the manufacturing method of the present disclosure, the diffusion source powder can be attached to multiple surfaces of the surface of the rare earth sintered magnet material that have different normal directions in a single process. The thickness of the adhesive layer is preferably 10 μm or more and 100 μm or less.

[0079] (Diffusion source powder attachment process) In this embodiment, a diffusion source attachment device 1000 as shown in FIG. 7 is used to attach the RMA alloy diffusion source powder to the surface of the rare earth sintered magnet material.

[0080] At this time, as shown in FIG. 11, the attachment of the diffusion source powder is completed while the rare earth sintered 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 the time required to attach the diffusion source powder to one rare earth sintered magnet material is only about 1 to 2 seconds. In addition, since the diffusion source powder is attached to the rare earth sintered magnet material while it is supported by the thin wire, the diffusion source powder can be attached uniformly to almost the entire surface of the rare earth sintered magnet material. According to this embodiment, the atomized powder particles in which the diffusion source powder is made from high-temperature molten metal have a sharp particle size distribution as shown in FIG. 4. Therefore, the particle size of the atomized powder particles attached to the rare earth sintered magnet material is uniformed. In addition, since the atomized powder particles have recesses formed therein, the ratio of the surface area to the particle size increases. As a result, the contact area between the adhesive layer and the atomized powder particles increases, improving the adhesive force. As a result, the atomized powder particles can be prevented from being separated from the adhesive layer.

[0081] In this embodiment, the bottom area of ​​the collection section 30 is 2700 mm 2 The control device 600 is set to supply the diffusion source powder 14 from the diffusion source powder supply device 500 to the fluidized bed housing 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 allows the amount of the diffusion source powder 14 in the fluidized bed 100 to be maintained within an appropriate range. As a result, the variation in the amount of adhesion in the diffusion source adhesion step is suppressed, and highly uniform adhesion is achieved.

[0082] (Diffusion process) A diffusion process is carried out by heating the rare earth sintered magnet material with the RMA alloy diffusion source powder attached to its surface at a temperature of 700°C to 1100°C in a vacuum or inert gas atmosphere to diffuse R and M into the rare earth sintered magnet material. As a result, a liquid phase containing R and M is generated from the RMA alloy, and this liquid phase is diffused from the surface of the sintered body to the inside via the grain boundaries in the rare earth sintered magnet material. At this time, it is preferable to increase the content of the heavy rare earth element RH (preferably Tb) in the rare earth sintered magnet material by an extremely small amount of 0.05 mass% to 0.30 mass%. This allows for extremely high H while suppressing the consumption of the heavy rare earth element RH. cJ In order to increase the amount of RH contained in the rare earth sintered magnet material by 0.05 mass% or more and 0.30 mass% or less, various conditions such as the amount of RMA alloy, the heating temperature during processing, the particle size (if the RMA alloy is particulate), and the processing time may be adjusted. Among these, the amount of the heavy rare earth element RH introduced (increased amount) can be relatively easily controlled by adjusting the amount of the RMA alloy and the heating temperature during processing. According to this embodiment, the particle size of the atomized powder particles attached to the rare earth sintered magnet material is made uniform, so that the amount of the heavy rare earth element RH introduced (increased amount) can be controlled with high precision, and the variation in the magnetic properties is reduced.

[0083] In this specification, for example, "increasing the Tb content by 0.05 mass% or more and 0.30 mass% or less" means that the 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 rare earth sintered magnet material before the diffusion process is 0.50 mass% and the Tb content of the RTB sintered magnet after the diffusion process is 0.60 mass%, the Tb content is increased by 0.10 mass% by the diffusion process. 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 amount of the rare earth sintered magnet material before the diffusion process and the RTB sintered magnet (as a whole) after the diffusion process, and determining how much the RH amount has increased before and after diffusion. In addition, if there is an RMA alloy enriched portion on the surface of the RTB sintered magnet after the diffusion process, it is desirable to remove the enriched portion by cutting or the like before measuring the RH amount.

[0084] 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 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.

[0085] In addition, a powder of a fluoride, oxide, acid fluoride, etc. of the heavy rare earth element RH may be attached to the surface of the RTB sintered magnet material together with the diffusion source powder of the RMA alloy. This allows the light rare earth elements RL and M to be diffused into the RTB sintered magnet material together with the heavy rare earth element RH. Examples of the fluoride, oxide, and acid fluoride of the heavy rare earth element RH include TbF3, DyF3, Tb2O3, Dy2O3, Tb4OF, and Dy4OF.

[0086] (Heat treatment process) The RTB sintered magnet after the diffusion treatment step 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, and lower than the temperature used in the diffusion treatment. cJ can be obtained.

[0087] The present disclosure includes the inventions described in the following items. [Item 1] 1. A method for producing a diffusion source powder comprising a plurality of atomized powder particles formed from a rare earth alloy, the method comprising: preparing a molten rare earth alloy; forming a plurality of atomized powder particles from the molten metal heated to a temperature of 1100° C. or more and 1400° C. or less by an atomization method; Including, the rare earth alloy is an RMA alloy; R contains at least one rare earth element and at least one of Nd and Pr; M is at least one selected from the group consisting of Cu, Ga, Co, and Fe; A method for producing a diffusion source powder, wherein A is at least one selected from the group consisting of Al, Si, Ti, V, Cr, Mn, Co, Ni, Zn, Ge, Zr, Nb, Mo, Ag, and B. [Item 2] The composition ratio of R is 65% by mass or more and 95% by mass or less of the entire RMA alloy. The composition ratio of M is 5% by mass or more and 35% by mass or less of the entire RMA alloy. 2. The method for producing a diffusion source powder according to item 1, wherein the composition ratio of A is 0 mass % or more and 3 mass % or less of the entire RMA alloy. [Item 3] Item 3. The method for producing a diffusion source powder according to item 2, wherein A is at least one selected from the group consisting of Al, Si, Ti, V, Cr, Mn, Co, Ni, Zn, Ge, Zr, Nb, Mo, and Ag. [Item 4] The total composition ratio of Nd and Pr is 60 mass% or more of the total R, 4. The method for producing a diffusion source powder according to item 2 or 3, wherein M contains at least one of Cu and Ga, and the total composition ratio of Cu and Ga is 50 mass % or more of the entire M. [Item 5] 5. The method for producing a diffusion source powder according to any one of items 1 to 4, wherein the step of forming the atomized powder particles includes spraying the molten metal whose temperature is adjusted to a range of 1250° C. or more and 1350° C. or less. [Item 6] 6. The method for producing a diffusion source powder according to any one of items 1 to 5, wherein the step of forming the atomized powder particles includes forming recesses in each of at least half of the atomized powder particles. [Item 7] A diffusion source powder comprising a plurality of atomized powder particles formed from a rare earth alloy, the rare earth alloy is an RMA alloy; R contains at least one rare earth element and at least one of Nd and Pr; M is at least one selected from the group consisting of Cu, Ga, Co, and Fe; A is at least one selected from the group consisting of Al, Si, Ti, V, Cr, Mn, Co, Ni, Zn, Ge, Zr, Nb, Mo, Ag, and B; The diffusion source powder, wherein at least half of the particles in the plurality of atomized powder particles each have a recess. [Item 8] The composition ratio of R is 65% by mass or more and 95% by mass or less of the entire RMA alloy. The composition ratio of M is 5% by mass or more and 35% by mass or less of the entire RMA alloy. 8. The diffusion source powder according to item 7, wherein the composition ratio of A is 0% by mass or more and 3% by mass or less of the entire RMA alloy. [Item 9] 9. The diffusion source powder according to item 7 or 8, wherein A is at least one selected from the group consisting of Al, Si, Ti, V, Cr, Mn, Co, Ni, Zn, Ge, Zr, Nb, Mo, and Ag. [Item 10] The total composition ratio of Nd and Pr is 60 mass% or more of the total R, 10. The diffusion source powder according to any one of items 7 to 9, wherein M contains at least one of Cu and Ga, and the total composition ratio of Cu and Ga is 50 mass % or more of the entire M. [Item 11] 11. The diffusion source powder according to any one of items 7 to 10, having a volumetric median diameter d50 of 50 μm or more and 150 μm or less. [Item 12] A step of preparing a diffusion source powder according to any one of items 7 to 11; A step of preparing a rare earth sintered magnet material having an adhesive layer on at least a portion of its surface; a step of adhering the diffusion source powder to the adhesive layer of the rare earth sintered magnet material; a step of heating the rare earth magnet material to diffuse elements contained in the diffusion source powder from the diffusion source powder attached to the adhesive layer into the rare earth sintered magnet material; A method for producing a rare earth sintered magnet comprising the steps of: [Item 13] The step of attaching the diffusion source powder to the adhesive layer includes: placing said diffusion source powder in a fluidized bed; fluidizing the diffusion source powder; bringing the flowing diffusion source powder into contact with the adhesive layer of the rare earth sintered magnet material moving on a wire; Item 13. A method for producing a rare earth sintered magnet according to item 12, comprising: [Item 14] A step of preparing a diffusion source powder by the manufacturing method according to any one of items 1 to 6; A step of preparing a rare earth sintered magnet material having an adhesive layer on at least a portion of its surface; a step of adhering the diffusion source powder to the adhesive layer of the rare earth sintered magnet material; a step of heating the rare earth magnet material to diffuse elements contained in the diffusion source powder from the diffusion source powder attached to the adhesive layer into the rare earth sintered magnet material; A method for producing a rare earth sintered magnet comprising the steps of: [Item 15] The step of attaching the diffusion source powder to the adhesive layer includes: placing said diffusion source powder in a fluidized bed; fluidizing the diffusion source powder; bringing the flowing diffusion source powder into contact with the adhesive layer of the rare earth sintered magnet material moving on a wire; Item 15. A method for producing a rare earth sintered magnet according to item 14, comprising: [Industrial Applicability]

[0088] The embodiment of the present invention is characterized in that the H 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 rare earth sintered magnets that require high coercivity. The present invention can also be widely applied to techniques that require diffusing metal elements other than the heavy rare earth element RH into a rare earth sintered magnet from the surface. [Explanation of symbols]

[0089] 10...Rare earth sintered magnet material 12...adhesive layer 14. Diffusion source powder 14P··Atomized powder particles 14X··Depressions in atomized powder particles 20 wire 30. Recovery section 100...Fluidization tank 200...Transportation device 300....Flow chamber 400...Circulation mechanism 500···Diffusion source powder feeder 600...Control device 1000... Diffusion source attachment device

Claims

1. 1. A method for producing a diffusion source powder comprising a plurality of atomized powder particles formed from a rare earth alloy, the method comprising: preparing a molten rare earth alloy; forming a plurality of atomized powder particles from the molten metal heated to a temperature of 1100° C. or more and 1400° C. or less by an atomization method; Including, the rare earth alloy is an R-M-A alloy; R contains at least one rare earth element and at least one of Nd and Pr; M is at least one selected from the group consisting of Cu, Ga, Co, and Fe; A method for producing a diffusion source powder, wherein A is at least one selected from the group consisting of Al, Si, Ti, V, Cr, Mn, Co, Ni, Zn, Ge, Zr, Nb, Mo, Ag, and B.

2. The composition ratio of R is 65% by mass or more and 95% by mass or less of the entire R-M-A alloy, The composition ratio of M is 5% by mass or more and 35% by mass or less of the entire R-M-A alloy, 2. The method for producing a diffusion source powder according to claim 1, wherein the composition ratio of A is 0% by mass or more and 3% by mass or less of the entire RMA alloy.

3. The total composition ratio of Nd and Pr is 60 mass% or more of the entire R, 3. The method for producing a diffusion source powder according to claim 2, wherein M contains at least one of Cu and Ga, and a total composition ratio of Cu and Ga is 50 mass % or more of the entire M.

4. 4. The method for producing a diffusion source powder according to claim 3, wherein the step of forming the atomized powder particles includes spraying the molten metal whose temperature is adjusted to a range of 1250° C. or more and 1350° C. or less.

5. The method for producing a diffusion source powder according to claim 1 , wherein the step of forming the atomized powder particles includes forming a recess in each of at least half of the atomized powder particles.

6. A diffusion source powder comprising a plurality of atomized powder particles formed from a rare earth alloy, the rare earth alloy is an R-M-A alloy; R contains at least one rare earth element and at least one of Nd and Pr; M is at least one selected from the group consisting of Cu, Ga, Co, and Fe; A is at least one selected from the group consisting of Al, Si, Ti, V, Cr, Mn, Co, Ni, Zn, Ge, Zr, Nb, Mo, Ag, and B; The diffusion source powder, wherein at least half of the particles in the plurality of atomized powder particles each have a recess.

7. The composition ratio of R is 65% by mass or more and 95% by mass or less of the entire R-M-A alloy, The composition ratio of M is 5% by mass or more and 35% by mass or less of the entire R-M-A alloy, 7. The diffusion source powder according to claim 6, wherein the composition ratio of A is 0% by mass or more and 3% by mass or less of the entire RMA alloy.

8. The total composition ratio of Nd and Pr is 60 mass% or more of the entire R, 8. The diffusion source powder according to claim 7, wherein M contains at least one of Cu and Ga, and the total composition ratio of Cu and Ga is 50 mass % or more of the entire M.

9. The diffusion source powder according to claim 8, having a volumetric median diameter d50 of 50 μm or more and 150 μm or less.

10. Providing a diffusion source powder according to any one of claims 6 to 9; A step of preparing a rare earth sintered magnet material having an adhesive layer on at least a portion of its surface; a step of adhering the diffusion source powder to the adhesive layer of the rare earth sintered magnet material; a step of heating the rare earth magnet material to diffuse elements contained in the diffusion source powder from the diffusion source powder attached to the adhesive layer into the rare earth sintered magnet material; A method for producing a rare earth sintered magnet comprising the steps of:

11. The step of attaching the diffusion source powder to the adhesive layer includes: placing said diffusion source powder in a fluidized bed; fluidizing the diffusion source powder; bringing the flowing diffusion source powder into contact with the adhesive layer of the rare earth sintered magnet material moving on a wire; The method for producing a rare earth sintered magnet according to claim 10, comprising:

Images