JP2023003951A - Manufacturing method for rare earth sintered magnet - Google Patents

Abstract

To provide a rare earth sintered magnet having a shape, size, and electrical characteristics that are difficult to obtain by grinding.SOLUTION: A manufacturing method of the rare earth sintered magnet includes the steps of: producing a plurality of sintered body materials from a compact of alloy powders including a rare earth element; producing a laminated sintered body by joining at least two of the sintered body materials using an adhesive layer; and dividing crosswise over the adhesive layer the laminated sintered body into a plurality of sintered body pieces.SELECTED DRAWING: Figure 1

Description

The present application relates to a method for producing a rare earth sintered magnet.

RTB sintered magnets, which are representative examples of rare earth sintered magnets (R is a rare earth element, always contains at least one selected from the group consisting of Nd, Pr and Ce, and T is a transition metal at least one of which necessarily contains Fe and B is boron) is a main phase of a compound having an R ₂ Fe ₁₄ B-type crystal structure, a grain boundary phase located in the grain boundary portion of the main phase, and a trace amount of It is composed of a compound phase generated by the influence of additive elements and impurities. The RTB sintered magnet has a high residual magnetic flux density B _r (hereinafter sometimes simply referred to as “B _r ”) and a high coercive force H _cJ (hereinafter simply referred to as “H _cJ ”). It is known as a magnet with the highest performance among permanent magnets due to its excellent magnetic properties.

For this reason, RTB sintered magnets are used in various motors in the automobile field such as electric vehicles (EV, HV, PHV), renewable energy fields such as wind power generation, home appliances, and industrial fields. ing. RTB based sintered magnets are essential materials for making these motors smaller, lighter, and more efficient and energy saving (improving energy efficiency). RTB sintered magnets are also used in drive motors for electric vehicles.・It also contributes to the prevention of global warming by reducing exhaust gas. In this way, RTB based sintered magnets are greatly contributing to the realization of a green energy society.

Rare earth sintered magnets such as RTB sintered magnets are produced through, for example, a step of preparing alloy powder, a step of press-molding the alloy powder to produce a compact, and a step of sintering the compact. manufactured. The alloy powder is produced, for example, by the following method.

First, an alloy is produced from molten metals of various raw materials by a method such as an ingot method or a strip casting method. The obtained alloy is subjected to a pulverization process to obtain an alloy powder having a predetermined particle size distribution. This pulverization process usually includes a coarse pulverization process and a fine pulverization process. The former uses, for example, the hydrogen embrittlement phenomenon, and the latter uses, for example, a jet mill. will be

The sintered body obtained by the step of sintering the molded body is then subjected to mechanical processing such as grinding and cutting, and singulated into pieces having a desired shape and size. In some cases, the sintered body is required to have electrical insulation (electrical resistance). More specifically, the sintered body is produced by compression-molding the RTB rare earth magnet powder with a press machine to produce a molded body having a size larger than the final magnet product. Then, the molded body is sintered by a sintering process to produce a sintered body. If necessary, the sintered body may be subjected to a diffusion treatment for diffusing a diffusion source containing the rare earth element R from the surface of the magnet to the inside. After sintering or after diffusion, the sintered body is ground by, for example, a cemented carbide blade saw or a rotating grindstone to give it a desired shape. For example, after a block-shaped sintered body is produced, the sintered body is sliced with a blade saw or the like to cut out a plurality of plate-like sintered body portions.

Japanese Patent Application Laid-Open No. 2003-303728

As mentioned above, sintered rare earth magnets are used in a wide variety of applications, and the shapes and properties required are also diverse. It has sometimes been difficult to efficiently obtain a sintered body having the desired properties, size, and electrical properties.

Embodiments of the present disclosure provide a method for producing a rare earth based sintered magnet that can solve such problems.

In an exemplary embodiment, the method for producing a rare earth-based sintered magnet of the present disclosure includes the steps of: producing a plurality of sintered body materials from a molded body of alloy powder containing a rare earth element; The method includes a step of bonding materials with an adhesive layer to produce a laminated sintered body, and a step of cutting the laminated sintered body across the adhesive layer to divide the laminated sintered body into a plurality of laminated sintered body pieces.

In one embodiment, in the laminated sintered body, a coating layer is provided between one of the two sintered body materials sandwiching the adhesive layer and the adhesive layer.

In one embodiment, in the laminated sintered body, a coating layer is provided between each of the two sintered body materials sandwiching the adhesive layer and the adhesive layer.

In one embodiment, the total thickness of the adhesive layer and the coating layer is 4 μm or more and 250 μm or less.

In one embodiment, each of the plurality of laminated sintered body pieces includes at least two portions electrically separated by the adhesive layer and the coating layer.

In one embodiment, the coating layer is formed on the surfaces of the plurality of sintered materials after diffusing the rare earth element from the surfaces.

In one embodiment, the surfaces of the plurality of sintered body materials are roughened before the coating layer is formed.

In one embodiment, the step of producing a plurality of sintered body materials includes a step of compression molding the alloy powder in an oriented magnetic field to produce the compact, and a step of cutting the compact to form a plurality of compacts. The step of dividing into body pieces and the step of sintering the plurality of green body pieces to obtain the plurality of sintered body materials are included.

According to the embodiments of the present disclosure, it is possible to efficiently obtain a sintered body having a shape, size, and electrical properties that are difficult to obtain by grinding.

FIG. 1 is a flow chart showing main steps of a method for producing a rare earth sintered magnet according to an embodiment of the present disclosure. FIG. 2 is a diagram schematically showing a cross section of two stacked sintered body materials 16. As shown in FIG. FIG. 3 is a diagram schematically showing a cross section of a plurality of laminated sintered body pieces 30 divided by cutting the laminated sintered body 22 so as to cross the adhesive layer 18. As shown in FIG. FIG. 4 is a diagram schematically showing a cross section of an example in which a coating layer 19 is provided between one of two sintered bodies 16 sandwiching an adhesive layer 18 and the adhesive layer 18 . FIG. 5 is a diagram schematically showing a cross section of a plurality of laminated sintered body pieces 30 divided by cutting the laminated sintered body 22 so as to cross the adhesive layer 18. As shown in FIG. FIGS. 6(a) to 6(d) are diagrams for explaining an example of a process of cutting a molded body to divide it into a plurality of molded body pieces. FIG. 7 is a perspective view showing a configuration example of a wire saw device that can be used in the embodiment of the present disclosure. FIG. 8 is a cross-sectional view schematically showing a wire cross-section. FIGS. 9(a) to 9(d) are diagrams for explaining examples of various processes for the sintered material.

As described above, it may be difficult to obtain a sintered body having a desired shape and size only by grinding the sintered body after sintering or diffusion. For this reason, bonding a plurality of sintered bodies with an adhesive can be considered as an effective countermeasure. If the adhesive has insulating properties, an effect of reducing eddy currents is also expected. However, according to the study of the present inventor, it has been found that applying an adhesive to each of the sintered bodies machined into small sizes to join the sintered bodies together is not suitable for mass production. This is because it takes a long time to apply the adhesive to many small sintered bodies. As a result of further studies by the present inventors, it was found that a laminated structure is produced by bonding a plurality of relatively large sintered body materials, which are in a stage before being processed into small pieces, with an adhesive layer, and the laminated structure is cut. If you create a laminated sintered body that is processed into small pieces with , it becomes unnecessary to apply adhesive to many small sintered bodies, and sintered bodies can be produced efficiently, so mass productivity can be improved. As a result, the present invention has been completed.

An embodiment of a method for producing a rare earth sintered magnet according to the present disclosure will be described below. As shown in the flow chart of FIG. 1, the method for producing a rare earth based sintered magnet according to the present embodiment includes:
- A step of producing a plurality of sintered body materials from a molded body of alloy powder containing a rare earth element (S10);
- A step of bonding at least two sintered body materials with an adhesive layer to produce a laminated sintered body (S20);
A step of cutting the laminated sintered body across the adhesive layer to divide it into a plurality of laminated sintered body pieces (S30);
including.

According to the manufacturing method of the present disclosure, since the adhesive is formed on the relatively large sintered body material before division and laminated, the adhesive is formed on a large number of relatively small pieces after division. More efficient than stacking.

FIG. 2 is a diagram schematically showing a cross section of two stacked sintered body materials 16. As shown in FIG. An adhesive layer 18 is provided between the sintered bodies 16 . FIG. 3 is a diagram schematically showing a cross section of a plurality of laminated sintered body pieces 30 divided by cutting the laminated sintered body 22 so as to cross the adhesive layer 18. As shown in FIG. A cut surface 21 is formed in the laminated sintered body piece 30 by cutting. The adhesive layer 18 is made of an insulating material and can electrically isolate the stacked sintered body materials 16 from each other. Each of the plurality of laminated sintered body pieces 30 includes at least two portions electrically separated by the adhesive layer 18, and has a structure that functions as a so-called "split magnet" to suppress the generation of eddy currents. come true. Thus, according to the rare earth sintered magnet finally obtained from each laminated sintered body piece 30, the occurrence of eddy current due to an alternating magnetic field is suppressed in applications such as being incorporated in the rotor of an electric motor, for example. Therefore, the effect of reducing eddy current loss is obtained.

The adhesive layer 18 can be formed from materials such as an epoxy-based adhesive layer, an acrylic-based adhesive layer, and a urethane-based adhesive layer, for example. The thickness of the adhesive layer 18 is preferably 1 μm or more and 50 μm or less, more preferably 2 μm or more and 30 μm or less.

If the adhesive is applied unevenly, minute gaps may occur in the adhesive layer 18 . When the laminated sintered body 22 is cut in this state, part of the grinding powder (cutting powder) enters the sintered body material 16 through the minute gaps in the adhesive layer 18 and penetrates the adhesive layer 18 to form the laminated sintered body. There is a possibility that the electrical insulation (electrical resistance) between the body materials 16 will be lowered. The size of the grinding powder (shaving powder) is about the size of the crystal grains forming the sintered material 16, and is, for example, 10 μm or less. Therefore, when the thickness of the adhesive layer 18 is less than 10 μm, the possibility of such a phenomenon occurring increases.

In some cases, the surface of the sintered material 16 is also formed with fine irregularities having a size equal to or smaller than the diameter of the crystal grains. Even if the surface of the sintered material 16 is roughened, such fine unevenness may remain. For this reason, there is a possibility that fine projections present on the surface of the sintered body material 16 penetrate through the adhesive layer 18 and reduce the electrical resistance of the adhesive layer 18 .

FIG. 4 is a diagram schematically showing a cross section of an example in which a coating layer 19 is provided between one of two sintered bodies 16 sandwiching an adhesive layer 18 and the adhesive layer 18 . FIG. 5 is a diagram schematically showing a cross section of a plurality of laminated sintered body pieces 30 divided by cutting the laminated sintered body 22 across the adhesive layer 18. As shown in FIG. Also in this example, a cut surface 21 is formed in the laminated sintered body piece 30 by cutting. Although the coating layer 19 is formed on one of the two sintered bodies 16 in the illustrated example, the coating layer 19 may be formed on both of the sintered bodies 16 .

The coating layer 19 is made of an insulating material and exhibits the function of increasing the electric resistance (insulating property) between the opposing sintered body materials 16 via the adhesive layer 18 . Further, according to the studies of the present inventors, even if part of the grinding powder of the sintered material 16 penetrates the adhesive layer 18 when cutting the laminated sintered body 22, the presence of the coating layer 19 causes an electric current. It was found that the thermal insulation can be secured. Thus, by providing both the adhesive layer 18 and the coating layer 19 on one of the two sintered bodies 16 with the adhesive layer 18 interposed therebetween, the electrical insulation can be more reliably ensured. The coating layer 19 is formed by coating the surface of the magnet, and can be made of materials such as epoxy resin, acrylic resin, urethane resin, and silicone resin, for example. The thickness of the coating layer 19 is preferably 3 μm or more and 100 μm or less, more preferably 5 μm or more and 70 μm or less. Further, the total thickness of the adhesive layer and the coating layer is preferably 4 μm or more and 150 μm or less.

In addition, when the coating layer is included in both of the two sintered body materials sandwiched between the adhesive layers 18, the total thickness of the coating layers in both the adhesive layer and the sintered body material is set to 5 μm or more and 250 μm or less. is preferred.

Incidentally, in order to improve the magnetic properties, the rare earth element R may be diffused from the surfaces of the plurality of sintered body materials 16 before forming the coating layer 19 . Moreover, the surfaces of the plurality of sintered body materials 16 are preferably flattened by processing before the adhesive layer 18 and the coating layer 19 are formed.

Hereinafter, a method for producing a rare earth based sintered magnet according to the present embodiment will be described in detail.

First, the step (S10) of producing a plurality of sintered body materials from a molded body of alloy powder containing a rare earth element will be described. This step includes, for example, a step (1) of compressing the alloy powder in an oriented magnetic field to produce a compact, a step (2) of cutting the compact to divide it into a plurality of compact pieces, and a step (2) of dividing the compact into a plurality of compact pieces. and step (3) of sintering the compact pieces to obtain a plurality of sintered compact materials. Further, the step (4) of diffusing the rare earth element from the surface of each sintered body may be performed before stacking the plurality of sintered body materials. Examples of these steps will be described below in sequence.

(1) Step of compacting the alloy powder in an oriented magnetic field to produce a compact <Alloy composition>
In this embodiment, an RTB based sintered magnet alloy is used. Here, R is a rare earth element and always contains at least one selected from the group consisting of Nd, Pr and Ce. Preferably, combinations of rare earth elements represented by Nd--Dy, Nd--Tb, Nd--Dy--Tb, Nd--Pr--Dy, Nd--Pr--Tb and Nd--Pr--Dy--Tb are used.

Of R, Dy and Tb are particularly effective in improving _HcJ . In addition to the above elements, other rare earth elements such as La may be contained, and misch metal and didymium can also be used. Moreover, content is 27 mass % or more and 35 mass % or less, for example. Preferably, the R content of the rare earth sintered magnet is 31 mass % or less (27 mass % or more and 31 mass % or less, preferably 29 mass % or more and 31 mass % or less).

T is at least one of transition metals and necessarily contains Fe, and 50% or less of Fe may be replaced by cobalt (Co) in mass ratio (including the case where T is substantially composed of iron and cobalt ). Co is effective in improving temperature characteristics and corrosion resistance, and the alloy powder may contain Co in an amount of 10% by mass or less. The content of T may account for the remainder of R and B or R and B and M described later.

The content of B may also be a known content, and the preferred range is, for example, 0.9% by mass to 1.2% by mass. If it is less than 0.9% by mass, high _HcJ may not be obtained, and if it exceeds 1.2% by mass, _Br may decrease. Note that part of B can be substituted with C (carbon).

In addition to the above elements, M element can be added to improve _HcJ . M element is one or more selected from the group consisting of Al, Si, Ti, V, Cr, Mn, Ni, Cu, Zn, Ga, Zr, Nb, Mo, In, Sn, Hf, Ta and W . The amount of M element to be added is preferably 5.0% by mass or less. This is because if the content exceeds 5.0% by mass, Br may decrease. In addition, unavoidable impurities can also be allowed.

<Preparation of alloy>
The manufacturing process of the alloy for rare earth system sintered magnets is illustrated. An alloy ingot can be obtained by an ingot casting method in which metals or alloys preliminarily prepared to have the composition described above are melted and put into a mold. In addition, it is represented by the strip casting method or centrifugal casting method in which the molten metal is brought into contact with a single roll, twin rolls, a rotating disk, or a rotating cylindrical mold, etc. and rapidly cooled to produce a solidified alloy that is thinner than the alloy made by the ingot method. Alloy flakes can be produced by a quenching method.

Materials manufactured by either the ingot method or the quenching method can be used in the embodiments of the present disclosure, but are preferably manufactured by a quenching method such as strip casting. The thickness of the quenched alloy produced by the quenching method is usually in the range of 0.03 mm to 1 mm and is in the form of flakes. The molten alloy begins to solidify from the surface in contact with the chill roll (roll contact surface), and crystals grow in a columnar shape from the roll contact surface in the thickness direction. The quenched alloy is cooled in a shorter time than the alloy (ingot alloy) produced by the conventional ingot casting method (die casting method), so the structure is refined and the crystal grain size is small. In addition, the area of the grain boundary is wide. Since the R-rich phase spreads widely within the grain boundary, the rapid cooling method is excellent in the dispersibility of the R-rich phase. Therefore, it is easy to break at the grain boundary by the hydrogen pulverization method. By hydrogen-pulverizing the quenched alloy, 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 thus obtained is pulverized by a jet mill.

<Alloy pulverization process>
Powders of alloys for rare earth sintered magnets are active and easily oxidized. For this reason, the gas used in the jet mill is nitrogen, argon, helium, etc., in order to avoid the risk of heat generation and ignition and to reduce the oxygen content as an impurity to improve the performance of the magnet. An inert gas is used.

The object to be pulverized (coarsely pulverized powder) fed into the jet mill is, for example, pulverized into a fine powder having a particle size distribution with an average particle size (median diameter: d50) of 2.0 μm or more and 4.5 μm or less and collected by a cyclone. It will be collected by device 0. Cyclone collectors are used to separate powder from the air stream that carries it. Specifically, the coarsely pulverized powder of the rare earth sintered magnet alloy is pulverized by the preceding jet mill, and the fine powder produced by the pulverization is supplied to the cyclone collector together with the gas used for the pulverization. A mixture of inert gas (pulverization gas) and pulverized fine powder forms a high-speed air stream and is sent to the cyclone collector. Cyclone collectors are utilized to separate these grinding gases and fines. Fine powder separated from the grinding gas is collected in a powder collector.

<Step of producing molded body>
Next, a molded body is produced from the above-mentioned fine powder by pressing in a magnetic field. In magnetic field pressing, it is preferable to form a compact by pressing in an inert gas atmosphere or by wet pressing from the viewpoint of suppressing oxidation. Particularly in wet pressing, the surfaces of the particles constituting the compact are coated with a dispersant such as an oil agent, and contact with oxygen and water vapor in the atmosphere is suppressed. Therefore, it is possible to prevent or suppress the particles from being oxidized by the atmosphere before, during or after the pressing process.

When wet pressing is performed in a magnetic field, a slurry is prepared by mixing a fine powder with a dispersion medium, supplied to a cavity in a mold of a wet pressing device, and press-molded in a magnetic field.

- Dispersion medium The dispersion medium is a liquid in which the alloy powder can be dispersed to obtain a slurry.

Mineral or synthetic oils can be mentioned as preferred dispersion media for use in the present disclosure. The type of mineral oil or synthetic oil is not specified, but if the kinematic viscosity at normal temperature exceeds 10 cSt, the increase in viscosity will strengthen the bonding force between the alloy powders, and the orientation of the alloy powders during wet compaction in a magnetic field. may adversely affect Therefore, the kinematic viscosity of the mineral oil or synthetic oil at room temperature is preferably 10 cSt or less. If the fraction point of the mineral oil or synthetic oil exceeds 400° C., it becomes difficult to remove the oil after obtaining the molded body, and the amount of residual carbon in the sintered body increases, which may reduce the magnetic properties. Therefore, the fraction point of mineral oil or synthetic oil is preferably 400° C. or less. Moreover, you may use vegetable oil as a dispersion medium. Vegetable oil refers to oil extracted from a plant, and the type of plant is not limited to a specific plant.

-Preparation of Slurry A slurry can be obtained by mixing the obtained alloy powder and a dispersion medium.

The mixing ratio of the alloy powder and the dispersion medium is not particularly limited, but the concentration of the alloy powder in the slurry is preferably 70% or more (that is, 70% or more by mass) by mass. This is because, at a flow rate of 20 to 600 cm ³ /sec, the alloy powder can be efficiently supplied into the cavity and excellent magnetic properties can be obtained. The concentration of the alloy powder in the slurry is preferably 90% or less in mass ratio. The method of mixing the alloy powder and the dispersion medium is not particularly limited. The alloy powder and the dispersion medium may be separately prepared, weighed in predetermined amounts, and mixed. Also, when coarsely pulverized powder is dry-pulverized with a jet mill or the like to obtain alloy powder, a container containing a dispersion medium is placed at the alloy powder discharge port of the pulverizer such as a jet mill, and the alloy powder obtained by pulverization may be collected directly into the dispersion medium in the container to obtain a slurry. In this case, it is preferable that the inside of the vessel is also filled with an atmosphere of nitrogen gas and/or argon gas, and the obtained alloy powder is recovered directly into the dispersion medium without exposing it to the atmosphere to form a slurry. Furthermore, it is also possible to wet-pulverize the coarsely pulverized powder in a dispersion medium using a vibrating mill, a ball mill, an attritor, or the like to obtain a slurry comprising the alloy powder and the dispersion medium.

By molding the slurry thus obtained with a known wet press apparatus, a molded body having a predetermined size and shape can be obtained. Conventionally, it is common to obtain a sintered body by sintering this powder compact, but in the present embodiment, the compact is divided by a wire saw before sintering, as described below.

(2) Step of cutting the molded body into a plurality of molded body pieces Here, referring to Figs. 6(a) to 6(d), the molded body is cut and divided into a plurality of molded body pieces. An example of the process to do is explained.

First, as shown in FIG. 6A, a compact 10 of alloy powder produced through the above steps is prepared. In the example of FIG. 6(a), the molded body 10 has a block shape. For reference, the direction M of the aligning magnetic field is indicated by an arrow. This direction M is called a "magnetic field orientation direction". The aligning magnetic field is applied to the powder particles when the rare earth sintered magnet alloy powder is pressed to produce a compact, and the direction of each powder particle is oriented in the magnetic field orientation direction M. Ultimately, it is magnetized in a direction parallel to this magnetic field orientation direction M.

Next, as shown in FIG. 6B, the green body 10 is cut (sliced) to divide the green body 10 into a plurality of green body pieces. In a preferred embodiment, the compact 10 can be made with a wire saw. Details of the wire saw will be described later.

In the example of FIG. 6(b), the compact 10 is cut into a plurality of compact pieces 12 along the direction parallel to the magnetic field orientation direction M of the compact. That is, the magnetic field orientation direction M is the longitudinal direction of each compact piece 12 . The molded body 10 may be cut a plurality of times to divide the molded body pieces 12 as necessary. In order to perform the dividing step (S30), the compact piece 12 is divided into shapes and sizes larger than the final magnet component. In the present embodiment, the plate-shaped piece 12 divided as shown in FIG. 6(c) is further cut as shown in FIG. 6(d) to obtain a plurality of bar-shaped pieces 12. FIG. The magnetic field orientation direction M in each compact piece is not limited to the illustrated example.

In the production method of the present disclosure, after the step (S20) of bonding a plurality of sintered body materials with an adhesive layer to produce a laminated sintered body, the laminated sintered body is cut into a plurality of laminated sintered body pieces. The step of dividing (S30) is performed. Therefore, the shape and size of the sintered material at the stage before joining are defined by the shape and size of the compact piece 12 . Therefore, it is preferable that the portion of the surface of the molded body piece 12 that will eventually form the adhesive layer has a flat surface. In addition, in order to efficiently apply the adhesive, it is preferable that the area of the flat surface on which the adhesive layer is to be formed is set to, for example, 25 cm ² or more among the individual molding pieces.

Such cutting of the molded body 10 and the molded body piece 12 can be performed by a wire saw device shown in FIG. 7, for example.

Here, a configuration example of a wire saw device that can be used in this embodiment will be described with reference to FIG. FIG. 7 is a perspective view showing a configuration example of the wire saw device 100 according to the embodiment of the present disclosure. For reference, the figure shows an xyz coordinate system with mutually orthogonal x-, y-, and z-axes. In this example, the xy-plane is horizontal and the z-axis is oriented vertically.

The wire saw device 100 of FIG. 7 has rollers 50 a , 50 b , 50 c arranged so that their central axes of rotation are parallel to each other, and a single continuous wire 60 . The molded body 10 of the molded body prepared in step S10 is supported by the fixing base 40 .

The fixing base 40 moves up and down in the z-axis direction while the molded body 10 is fixed. This vertical movement can be performed by a driving device (not shown). The driving device may be driven by a hydraulic cylinder or may be operated by a motor.

The rollers 50a, 50b, and 50c are arranged at predetermined intervals so that the axis of the center of rotation is positioned at the vertex of the triangle when viewed in a direction parallel to the x-axis. A plurality of grooves are provided on each side surface of the rollers 50a, 50b, 50c. The wire 60 is sequentially wound around the plurality of grooves of the rollers 50a, 50b, 50c. The center-to-center spacing (pitch) of the grooves defines the width of the elements separated by the wire saw cut. Both ends of the wire 60 are wound around, for example, recovery bobbins (not shown).

During cutting, the rollers 50a, 50b, 50c and the collection bobbins rotate. The direction of rotation of the rollers 50a, 50b, and 50c depends on their arrangement and how the wire 60 is wound. In the wire saw device 100 shown in FIG. 7, the rollers 50a, 50b, 50c rotate in the same direction.

After the predetermined length of wire 60 has been wound on one of the collection bobbins, the collection bobbins and rollers 50a, 50b and 50c are rotated in opposite directions. As a result, the wire 60 moves in the opposite direction, and by repeating this, the wire 60 can be reciprocated (moved).

A fixed abrasive wire is used for the wire 60, for example. Specifically, it is possible to use one in which abrasive grains with high hardness suitable for cutting high-hardness materials are adhered to the wires by electrodeposition. Abrasive grains with high hardness are also called superabrasive grains, and a typical example is diamond grains.

FIG. 8 schematically shows a cross section of the wire 60. As shown in FIG. The wire 60 includes a wire (core wire) 62 , abrasive grains 64 located on the outer peripheral surface of the wire 62 , and an adhesive layer 66 . The fixing layer 66 is made of a plated metal such as Ni, for example. The abrasive grains 64 are located on the surface of the wire 62, and the surface of the wire 62 surrounding the abrasive grains 64 and the abrasive grains 64 are entirely covered with the fixing layer 66, thereby fixing the abrasive grains 64 to the wire 62. can be made Adhesion of abrasive grains 64 may be achieved by other methods. The average grain size of the abrasive grains 64 is, for example, 1 μm or more and 24 μm or less.

The step of cutting the molded body 10 with a wire saw is preferably performed with the molded body 10 submerged in a liquid. When the compact 10 is a compact formed by wet pressing, a preferred example of this liquid is a dispersion medium such as an oil (mineral oil or synthetic oil) used in wet pressing.

(3) A step of sintering a plurality of molded body pieces to obtain a plurality of sintered body materials obtain the material). The step of sintering the compact pieces is performed, for example, at a pressure of 0.13 Pa (10 ⁻³ Torr) or less, preferably 0.07 Pa (5.0×10 ⁻⁴ Torr) or less, at a temperature of 1000° C. to 1150° C. can be done in the range of Residual gases in the atmosphere may be replaced by inert gases such as helium, argon, etc. to prevent oxidation due to sintering.

An example of a process for producing a rare earth based sintered magnet from a sintered material will now be described with reference to FIGS. 9(a) to 9(d).

(4) Step of Diffusion of Rare Earth Element First, as shown in FIG. 9(a), a plurality of sintered body materials 16 produced from the green body pieces 12 in the above steps are prepared. Thereafter, as shown in FIG. 9(b), the diffusion source powder 20 containing the rare earth element R is brought into contact with at least one of the upper surface and the lower surface in the thickness direction of each sintered body 16, and heat treatment is performed. Due to this heat treatment, the elements contained in the diffusion source powder 20 are diffused from the surface of the sintered material 16 to the inside. In order to obtain higher magnetic properties, it is preferable to bring the diffusion source powder 20 into contact with both the upper surface and the lower surface of the sintered body 16 and perform the heat treatment.

An alloy containing Pr, Tb and Ga is preferably used as the diffusion source. A diffusion source containing Pr, Tb and Ga is hereinafter referred to as a "Pr--Tb--Ga alloy". By this heat treatment, at least part of Pr, Tb and Ga contained in the Pr--Tb--Ga alloy powder 20 is diffused inward from at least the upper surface and the lower surface of each sintered body 16. As shown in FIG. By diffusing these elements from the surface of the sintered material to the inside, the coercive force can be efficiently increased. The diffusion process method is not particularly limited. A known method can be adopted.

The Pr--Tb--Ga alloy will be described below.

The Pr--Tb--Ga alloy may contain rare earth elements other than Pr and Tb. Preferably, the total amount of Pr and Tb contained in the Pr-Tb-Ga-based alloy is 65 mass% or more and 97 mass% or less of the entire Pr-Tb-Ga-based alloy, and Ga accounts for the entire Pr-Tb-Ga-based alloy. It is 3 mass % or more and 35 mass % or less.

The preferred Tb content in the Pr--Tb--Ga alloy is 3% by mass or more and 24% by mass or less of the entire Pr--Tb--Ga alloy. In addition, 50 mass% or less of Ga can be replaced with at least one of Cu and Sn. The Pr--Tb--Ga alloy may contain unavoidable impurities. In the present disclosure, “50% or less of Ga can be replaced with Cu” means that the content (mass%) of Ga in the Pr—Tb—Ga alloy is 100%, of which 50% is Cu means that you can replace with Preferably, the Pr content of the Pr--Tb--Ga alloy is 50 mass % or more of the total rare earth elements contained in the Pr--Tb--Ga alloy. All the rare earth elements contained in the Pr--Tb--Ga alloy preferably consist of Pr and Tb only. The inclusion of Pr facilitates diffusion in the grain boundary phase, so that Tb can be diffused more efficiently and a higher _HcJ can be obtained.

The shape and size of the Pr--Tb--Ga alloy are not particularly limited and are arbitrary. Pr--Tb--Ga based alloys can be in the form of films, foils, powders, blocks, particles and the like.

Pr--Tb--Ga-based alloys are produced by methods for producing raw material alloys that are employed in general methods for producing sintered rare-earth magnets, such as die casting, strip casting, and single-roll ultra-quenching (melt spinning method), atomization method, or the like. Also, the Pr--Tb--Ga alloy may be obtained by pulverizing the alloy obtained by the above method by a known pulverizing means such as a pin mill.

In the diffusion step, powder of a diffusion source containing R (preferably a Pr-Tb-Ga alloy) is brought into contact with at least one of the upper surface and the lower surface in the thickness direction of the sintered body material, and is placed in a vacuum or an inert gas atmosphere. The first heat treatment is performed at a temperature of 450° C. or more and 950° C. or less. This heat treatment allows R (preferably Pr, Tb, and Ga) to diffuse inside the sintered material.

The diffusion temperature is, for example, 450° C. or higher and 950° C. or lower.

The above heat treatment can be performed by disposing a diffusion source powder having an arbitrary shape on the surface of the sintered material and using a known heat treatment apparatus. For example, the surface of the sintered body material can be covered with a Pr--Tb--Ga alloy powder layer and the above heat treatment can be performed. For example, a slurry in which a Pr--Tb--Ga alloy is dispersed in a dispersion medium is applied to the surface of the sintered material, and then the dispersion medium is evaporated to bring the Pr--Tb--Ga alloy and the sintered material into contact. may Examples of dispersion media include alcohols (ethanol, etc.), aldehydes, and ketones.

The sintered material subjected to the heat treatment for diffusion is heat treated in a vacuum or inert gas atmosphere at a temperature of 450° C. or more and 750° C. or less and a temperature lower than the temperature of the heat treatment for diffusion. (Second heat treatment) may be performed. A higher _HcJ can be obtained by performing the second heat treatment. The second heat treatment may be performed after the step of S50, that is, on the laminated sintered piece.

Next, the step (S20) of producing a laminated sintered body will be described.

A coating layer is preferably formed on at least one of the upper surface and the lower surface of the sintered body material 16 by a method such as electrodeposition or spraying. A spray method is suitable for forming a coating layer on one side of the sintered material 16 . The coating layer may be formed from a material such as, for example, epoxy resin, as described above. The thickness of the coating layer is preferably 3 μm or more and 100 μm or less, more preferably 5 μm or more and 70 μm or less. Thereafter, an adhesive is applied to the coating layer to form an adhesive layer (if there is no coating layer, the adhesive is applied to the surface of the sintered body material). Adhesive application can be performed by a variety of methods. For efficient application over a wide area, the adhesive may be arranged in dots using, for example, a dispenser. The adhesive layer can be formed from a material such as, for example, a one-component epoxy adhesive, as described above. The thickness of the adhesive layer is preferably 1 μm or more and 50 μm or less, more preferably 2 μm or more and 30 μm or less. Thereafter, as shown in FIG. 9(c), at least two sintered body materials 16 are laminated to produce a laminated sintered body 22. Next, as shown in FIG. The number of layers of the sintered material 16 included in the laminated sintered body 22 is not limited to two, and may be three or more. In the illustrated example, the sizes (thicknesses) of the stacked sintered body materials 16 in the stacking direction are equal, but these sizes (thicknesses) may be different from each other. The magnetic field orientation direction M need not be parallel to the stacking direction, and may be inclined or perpendicular to the stacking direction. Moreover, the magnetic field orientation directions M of the stacked sintered body materials 16 do not need to be parallel.

Next, the step (S30) of cutting the laminated sintered body 22 to divide it into a plurality of laminated sintered body pieces will be described.

In this embodiment, each laminated sintered body 22 is cut from the upper surface to the lower surface so as to traverse the adhesive layer and the coating layer, thereby dividing into a plurality of laminated sintered body pieces 30 as shown in FIG. 9(d). do. From the viewpoint of mass productivity, the number of the plurality of laminated sintered body pieces 30 to be divided is preferably 3 or more, more preferably 50 or more. This dividing step may be performed by the wire saw device described above, or may be performed by another cutting device. Further, the laminated sintered body piece may be further ground to obtain the final product shape and size. Each laminated sintered body piece 30 can have, for example, a size (thickness) of about 1 to 5 mm in the magnetic field orientation direction, a width of about 3 to 20 mm, and a length of about 5 to 100 mm.

According to this embodiment, each laminated sintered body piece 30 is a "divided magnet" in which a plurality of electrically insulated divided parts are joined together. Although a cutting step is performed across the adhesive layer, the presence of the coating layer more reliably maintains high electrical insulation (eg, high resistance of 50Ω or higher). Moreover, since the adhesive is applied to a relatively large sintered body material before division, it is more efficient than applying the adhesive to a large number of relatively small pieces after division.

The laminated sintered body piece 30 obtained in this way is subjected to a surface treatment process and a magnetization process as necessary to complete a final rare earth based sintered magnet. Thus, in the method for producing a rare earth sintered magnet of the present disclosure, diffusion is not performed after the final cutting. Post-adhesion treatment may be performed at a temperature at which the adhesive does not melt (for example, 180° C. or lower).

It should be noted that the method for producing a rare earth based sintered magnet according to the present disclosure is not limited to the above embodiments. The molded body may be produced by a dry press method, and the shape and size of the molded body before and after cutting are arbitrary.

Examples will be described in more detail, but the present disclosure is not limited thereto.

Experimental example 1
Nd: 24.5% by mass, Pr: 5.5% by mass, B: 0.93% by mass, Cu: 0.3% by mass, Ga: 0.5% by mass, Co: 0.45% by mass, Al: An alloy powder having a composition of 0.12% by mass, 0.05% by mass of Zr, and the balance of Fe was prepared. The particle size d50 was 3.5 μm. Using these powders, compacts were produced with a wet press. A plurality of sintered body materials were produced from the molded body by sintering the obtained molded body (selecting a temperature at which densification by sintering occurs sufficiently). The dimensions of the sintered body were 4 mm thick×8 mm wide×10 mm long. A laminated sintered body A was produced by joining the obtained two sintered body materials with an adhesive layer (joining surfaces of 8 mm×10 mm). A one-liquid epoxy adhesive was used as the adhesive, and the thickness of the adhesive layer was in the range of 5 to 20 μm. Further, one sintered body material thus obtained was coated with an electrodeposition resin to form a coating layer on the surface of the sintered body material. The thickness of the coating layer was in the range of 30-40 μm. A sintered material with a coating layer and a sintered material without a coating layer (not coated with electrodeposition resin) are joined by an adhesive layer (8 mm × 10 mm surfaces are joined) and laminated. A body B was produced. The bonding conditions are the same as those for the laminated sintered body A. Then, the laminated sintered body A was cut across the adhesive layer to divide into two laminated sintered body pieces (sample A). Similarly, the laminated sintered body B was cut across the adhesive layer to divide into two laminated sintered body pieces (sample B). The electrical resistance of the obtained sample A and sample B was measured. In the present disclosure, it is determined that electrical resistance is 1Ω or more and electrical insulation is ensured. Furthermore, when the resistance is 50Ω or more, it is determined that the electrical insulation is further ensured. When the electrical resistance was measured, the sample A was 7.3Ω and the sample B was 1000Ω. Therefore, in both samples A and B, an adhesive is formed on the sintered body material before division and laminated, which is more efficient than lamination by forming an adhesive on a large number of individual pieces after division. , and electrical insulation is ensured. In addition, comparing the electrical resistance of sample A and sample B, sample B (a sample in which a coating layer is provided between one of two sintered body materials sandwiching an adhesive layer and the adhesive layer) The electric resistance is more greatly suppressed in the case of . Therefore, it is more excellent in electrical insulation.

DESCRIPTION OF SYMBOLS 10... Molded body (green), 16... Sintered material, 18... Adhesive layer, 19... Coating layer, 20... Laminated sintered body, 22... Cut surface, 30 ... Laminated sintered body piece 40 ... Fixed base 50a, 50b, 50c ... Roller 60 ... Wire saw 100 ... Wire saw device

Claims (8)

a step of producing a plurality of sintered body materials from a molded body of alloy powder containing a rare earth element;
a step of bonding at least two of the sintered body materials with an adhesive layer to produce a laminated sintered body;
a step of cutting the laminated sintered body across the adhesive layer to divide it into a plurality of laminated sintered body pieces;
A method for producing a rare earth sintered magnet, comprising: 2. The rare earth-based firing according to claim 1, wherein in said laminated sintered body, a coating layer is provided between said adhesive layer and one of said two sintered body materials sandwiching said adhesive layer. A method for producing a condensed magnet. 2. The laminated sintered body according to claim 1, wherein a coating layer is provided between each of the two sintered body materials sandwiching the adhesive layer and the adhesive layer. A method for producing a rare earth sintered magnet. 4. The method for producing a rare earth sintered magnet according to claim 2, wherein the adhesive layer and the coating layer have a total thickness of 4 [mu]m or more and 150 [mu]m or less. 5. The rare earth sintered body according to any one of claims 2 to 4, wherein each of the plurality of laminated sintered body pieces includes at least two portions electrically separated by the adhesive layer and the coating layer. Method of manufacturing magnets. 6. The production of a rare earth based sintered magnet according to any one of claims 2 to 5, wherein the coating layer is formed on the surfaces of the plurality of sintered body materials after the rare earth elements are diffused from the surfaces. Method. 7. The method of manufacturing a rare earth sintered magnet according to claim 6, wherein said surfaces of said plurality of sintered body materials are processed before said coating layer is formed. The step of producing the plurality of sintered body materials includes:
a step of compression-molding the alloy powder in an oriented magnetic field to produce the compact;
cutting the compact into a plurality of compact pieces;
a step of sintering the plurality of molded body pieces to obtain the plurality of sintered body materials;
The method for producing a rare earth sintered magnet according to any one of claims 1 to 6, comprising

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