JPWO2015012412A1 - Rare earth sintered magnet manufacturing method and rare earth sintered magnet sintering mold - Google Patents

Abstract

In the production of rare earth sintered magnets, the object is to simplify the production process and greatly reduce the production cost. In the rare earth sintered magnet manufacturing method of the present invention, the alloy powder is filled in a sintering mold, and after being oriented in a magnetic field, put in a sintering mold sintering furnace and heated to obtain a sintered body. The sintered mold is consumed. That is, the sintered mold is made of resin or a mixture of a resin and a substance (filler) that does not disappear during sintering and is disposable. The sintered mold has a partition plate that is consumed during sintering, and can simultaneously manufacture a plurality of sintered bodies. The substance contained in the resin that does not disappear during sintering remains even after the shape of the sintering mold or partition plate is lost, and prevents welding between the sintered bodies.

Description

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

Rare earth sintered magnets are widely used in air conditioner compressors, hybrid vehicle motors and generators, hard disk voice coil motors (VCM), etc., helping to reduce the size and energy of equipment, and prevent global warming. Contributing to

In many cases, rare earth sintered magnets used in these applications have a straight flat plate shape or a curved arc segment plate shape. These plate-like rare earth sintered magnets are thin-walled products having a thickness smaller than the vertical or horizontal length of the plate.

Conventionally, two methods have been known as a method for producing a thin plate-like rare earth sintered magnet. A die press method (Non-patent Document 1) for filling a die with alloy powder for rare earth sintered magnet and press-molding in a magnetic field to form a green compact, and sintering the compact, and a rare earth sintered magnet This is a press-less process (PLP method) (Patent Document 1) in which a container alloy powder is filled in a container and oriented by a pulsed magnetic field, and the powder is sintered in a container.

Since it is difficult to press-mold thin-walled products by the mold pressing method, first, a large block-shaped green compact is produced using a large mold, and the block-shaped sintered body is obtained by sintering it. This large block-shaped sintered body was thinly sliced with an outer peripheral blade cutting machine to obtain a thin plate-like product. The slicing process is expensive and a large amount of chips are generated during the slicing process, so that the raw material yield (ratio of the product weight to the raw material input weight) decreases. Therefore, the die press method has a drawback that the product price is high.

In the pressless method (PLP method), a container (hereinafter referred to as “mold”) designed according to the shape and dimensions of a product is filled with a rare earth alloy powder, covered, and then a pulse magnetic field is applied to remove the powder. Oriented and sintered as it is (Patent Documents 1 and 2). By this method, a thin plate rare earth sintered magnet with less bending can be efficiently produced. This method has been used in mass production factories because of its high raw material yield and reduced processing costs.

As a technique for mass production of rare earth magnets, the pressless method (PLP method) has the following problems.
(1) In the PLP method, the mold must be made precisely as much as the mold of the die press method. Making a mold precisely requires processing costs. The high cost of mold production is a problem of the pressless method (PLP method).
(2) Since the PLP method is used for mass production, it is assumed that the mold is used repeatedly. In order to use the mold repeatedly, it is necessary to select the material of the container portion and the partition plate portion constituting the mold and sufficiently increase the thickness. When the thickness of each part of the mold is increased, the material cost increases and the occupied volume of the mold in the process increases, and each unit from the powder filling device, the powder magnetic field orientation device to the sintering device is increased. Productivity decreases.
(3) If the mold is made of metal, the thickness of each part of the mold can be reduced. However, since metal is easily deformed during high-temperature sintering, there is a limit to repeated use. For this reason, attempts have been made to reduce the particle size of the alloy powder and lower the sintering temperature (Patent Document 3), but the deformation of the metal mold cannot be completely eliminated. In addition, since metal molds easily react with rare earth sintered magnet alloys during sintering, it is necessary to apply ceramic powder every time before filling the mold with alloy powder (Patent Document 4). Push up.
(4) Molds for products used for mass production must be made in large quantities. In addition to the mold in the process, the mass production apparatus can be smoothly operated by making a large number of molds on standby before entering the process. In order to increase the productivity of mass production equipment, mold maintenance management is important. The problem is that it is expensive to maintain and manage a large number of molds.

JP 2006-019521 A JP 2009-049202 A JP 2012-060139 A JP 2008-294469 A

Yoshio Tsuji, Ken Ohashi “Rare Earth Permanent Magnet”, Morikita Publishing Co., Ltd., 1999, p. 60-83 Akira Hirota, “Study on Granulation Process and Grain Boundary Structure of Nd—Fe—B System Sintered Magnet”, Doctoral Dissertation, Graduate School of Engineering, Kyoto University, 2000, p. 59

The problems described above are due to the need to repeatedly use a mold that has been produced at a high cost. If the mold can be manufactured at a low cost and can be made disposable, the productivity of the PLP method can be significantly increased.
The problem to be solved by the present invention is that the production cost of rare earth sintered magnets can be greatly reduced by dramatically increasing the productivity of a new sintering mold for rare earth magnets that can be disposable and the PLP method. Is to provide a method.

The rare earth sintered magnet manufacturing method according to the present invention, which has been made to solve the above-described problems, comprises filling a rare earth sintered magnet alloy powder into a rare earth sintered magnet sintering mold, and aligning it in a magnetic field. In the method for producing a rare earth sintered magnet, which is put into a sintering furnace and heated to obtain a sintered body, the sintering mold is consumed during sintering.
Here, exhaustion means that part or all of the material constituting the mold disappears by evaporation or decomposition in one sintering step, and the mold cannot be reused.

The sintered mold for rare earth sintered magnet according to the present invention, which has been made to solve the above problems, orients the alloy powder for rare earth sintered magnet filled therein in a magnetic field, and then puts it in a sintering furnace. It is used in a method for producing a rare earth sintered magnet to obtain a sintered body by heating, and is characterized by being consumed during sintering in a sintering furnace.

The sintered mold for rare earth sintered magnet has a partition plate that is consumed during sintering inside the mold, and has a plurality of cavities partitioned by the partition plate. A plurality of sinters can be simultaneously manufactured by filling a plurality of cavities with rare earth magnet alloy powder. There may be a plurality of partition plates.

Resin is preferred as the material for the sintering mold and the cutting plate according to the present invention.
Resin is low in material cost and easy to process, but it has a sufficiently high mechanical strength near room temperature for filling and orienting rare earth alloy powder, so it can be used as a mold for the PLP method. Since the resin is naturally consumed at high temperatures, the resin mold is naturally disposable. When the mold disappears before sintering, it was thought that the alloy powder filled in the mold would lose its shape and a rare-earth sintered magnet with the desired shape could not be obtained. There was no.
Here, the resin means all organic compounds that can be molded into a mold shape and disappear during sintering. Therefore, it is not necessarily a polymer compound, and a compound such as camphor is also included.

After filling the resin mold with alloy powder and orienting the powder in a magnetic field, the resin mold is placed on a sintering base plate (hereinafter simply referred to as a base plate) that does not melt or deform even at the sintering temperature. Then transported to the sintering furnace. When the temperature of the sintering furnace is increased, the inventor increases the filling density of the filled alloy powder to a certain value or higher even if the resin mold is consumed before the sintering of the alloy powder proceeds. Moreover, it was confirmed that the alloy powder keeps the shape as filled if care is taken not to tilt the base plate or give strong vibration. The filling density required for the shape of the alloy powder to remain unchanged even when the mold is consumed varies greatly depending on the average particle diameter of the powder, the shape of the particles, the presence / absence of addition of a lubricant to the powder, and the amount added. For standard rare earth sintered magnet alloy powders, the packing density required for shape retention must be at least 35% of the theoretical density of the alloy. This value is 40% or more in the powder to which the lubricant is added. As described above, when the alloy powder is filled in the sintered mold with a filling density of a certain value or more, the particles of the alloy powder are entangled with each other, and the shape of the alloy powder is maintained even if the resin mold is consumed before sintering. In addition to increasing the packing density of the alloy powder, the shape retention of the alloy powder is enhanced by applying a magnetic field to the alloy powder and orienting it. This is because the interaction between particles increases by magnetizing the powder. If the shape of the alloy powder is maintained, sintering proceeds with increasing temperature regardless of the presence or absence of a sintering mold.

Any kind of resin can be used as the mold for sintering a rare earth magnet of the present invention. This is because the sintering temperature of the rare earth sintered magnet exceeds 1000 ° C., so that the resin disappears by evaporation or decomposition until reaching such a high temperature.
However, as the resin used for the sintering mold, a resin that is easy to mold and that decomposes and evaporates during sintering at a temperature as low as possible is preferable in order to suppress contamination and deformation of the sintered body. Acrylic resin, polyethylene, polyethylene terephthalate, polypropylene, polystyrene, ABS resin, ethyl cellulose, paraffin wax, styrene / ptadiene copolymer, ethylene / vinyl acetate copolymer, ethylene / ethyl acrylate copolymer, atactic polypropylene, methacrylic acid A thermoplastic resin such as a copolymer, polyamide, polybutene, and polyvinyl alcohol can be preferably used. Moreover, thermosetting resins such as phenol resins and polyester resins can also be used. These resins disappear during the heating process up to about 500 ° C. during rare earth magnet sintering.

In the present invention, sintering is performed in a vacuum or in an inert gas. However, when the present inventors flow hydrogen into the furnace atmosphere during the temperature rising process, the resin forming the mold is decomposed and generated. It was confirmed that the reaction between the organic gas and the rare earth magnet alloy powder could suppress the carbonization of the rare earth component. In order to suppress the reaction between the powder and the organic component as much as possible when the powder contains a large amount of organic component as a binder or lubricant, conventional technology for flowing hydrogen during heating at a temperature below the sintering temperature (non- It has been found that Patent Document 2) is effective for suppressing the reaction between the powder and the mold in the present invention.

These resins are mixed with thermally decomposable organic polymers such as methylstyrene, methyl methacrylate, methyl acrylate and isobutyl, and sublimable substances such as naphthalene and camphor to facilitate thermal decomposition of the resin and sinter. The consumption of the resin in the inside can be accelerated and the productivity of the sintering process can be improved. In addition, by easily decomposing the resin constituting the mold, the reaction between the resin component and the rare earth magnet alloy powder can be suppressed, and contamination of the sintered magnet alloy powder can be reduced.

When a filler made of solid material powder or fiber that does not melt even at the sintering temperature is kneaded in the resin that is the material of the sintering mold, when the alloy powder is sintered at the sintering temperature, the filler is adjacent to each other. Prevents welding of the sintered body. As the filler for preventing welding, ceramic powders such as carbon powder, alumina, B ₄ C, BN, rare earth oxides, fluorides, and oxyfluorides are suitable.

The thin plate-like sintered body may lean against the adjacent sintered body due to vibration of a sintering furnace or the like during sintering and may lean against each other. If they are slanted and lean against each other, the thin plate sintered body may be bent by gravity while it is in a high temperature state even during or after sintering. When this happens, the finished sintered body becomes a distorted defective product.
When a spherical ceramic powder or the like is kneaded in the resin of the resin mold, the occurrence of such defective products can be prevented. Even if the resin disappears due to evaporation or decomposition during the temperature rise to sintering, the spherical ceramic powder remains between the adjacent sintered bodies and falls into the gap between the sintered bodies to form the lower gap. fill in. For this reason, if this method is used, it is possible to prevent the thin plate sintered bodies from leaning against each other. As a result, it is possible to prevent bending during the sintering process of the thin plate sintered body.

The ceramic powder to be kneaded is not limited to a spherical shape. A wide variety of fillers can be used to add to the resin to improve the properties of the resin. Among these fillers, amorphous, spherical, acicular, or plate-like fillers made of ceramic or carbon that do not melt even at the sintering temperature can be used for the purpose of the present invention. As the filler, powders of BN, B ₄ C, or rare earth oxides, fluorides, and oxyfluorides that hardly react with rare earth alloys at high temperatures can be suitably used.

When filler is mixed with the resin of the mold, the amount of resin decomposition gas generated during sintering is reduced, thereby improving the density of the sintered body and increasing the magnetic properties of the sintered magnet. Produces the effect.
When the mold is filled with rare earth alloy powder and sintered after orientation in a magnetic field, the resin is decomposed and discharged until the sintering temperature is reached. At this time, the organic gas generated by decomposition of the resin reacts with the rare earth alloy powder, and the alloy powder is carbonized or oxidized to be contaminated. Further, in the vicinity of the mold surface, the molten resin directly contacts the rare earth alloy powder and strongly contaminates the rare earth alloy powder. Contamination of these alloy powders hinders densification of the sintered body in the sintering process, and deteriorates the magnetic properties of the sintered magnet.
In order to reduce contamination of the alloy powder by the resin decomposition gas as much as possible, it is only necessary to mix as much filler as ceramic powder with the resin as the mold material to reduce the absolute amount of the resin.

In order to reduce contamination of the alloy powder by the resin decomposition gas as much as possible, it is desirable to make the volume fraction of the filler in the mold as large as possible and to make the volume fraction of the resin as small as possible. However, if the volume fraction of the resin is reduced too much, the mechanical strength of the mold decreases, and the mold is damaged when the mold is filled with rare earth alloy powder or oriented in a magnetic field. Further, when the resin content is reduced, it becomes difficult to inject and mold the material constituting the mold into the mold when the mold is manufactured by an injection molding method or the like. The volume fraction of the filler in the mold is desirably 40% or more, and more desirably 60% or more. If the mold is a solid substance of the filler and the resin, the upper limit of the volume fraction of the filler is about 80%. However, the filler volume fraction can be as high as 90% with respect to the total volume occupied by the filler and the resin when the filler particles are merely bonded to each other by the resin and the voids between the particles are not filled with the resin. . From the limit of the mechanical strength of the mold, the upper limit of the volume fraction of the filler in the mold is 95% by volume.

Contamination of the rare earth alloy powder during the sintering process can be further reduced by increasing the volume fraction of the filler near the mold surface. In order to increase the volume fraction of the filler in the vicinity of the mold surface, the filler may be applied to the mold surface after the mold is manufactured. Alternatively, at the time of injection molding of a mold, if a resin mold is produced by applying a filler together with a mold release agent to the mold mold surface, a resin mold having a high concentration of filler near the surface can be obtained.

When producing a rare earth magnet by the method of the present invention, the bottom of the mold may be removed in order to reduce the above-mentioned contamination of the rare earth alloy powder by the organic gas generated from the resin during sintering. The mold from which the bottom is removed is hereinafter referred to as a bottomless mold.
If there is no bottom, organic gas generation from the resin constituting the bottom does not occur.
In addition, the organic gas generated from the side wall and the partition plate of the mold moves along the surfaces of the partition plate and the side wall, and diffuses out of the mold through the gaps at various places. If the bottom of the mold is sealed, the gap is so small that diffusion of organic gas from the mold is hindered. If the bottom of the mold is removed, the gap through which the organic gas diffuses increases accordingly.

The use of a bottomless mold makes it possible to produce rare earth sintered magnets with very little distortion and very high magnetic properties. Note that this effect can be expected to a certain degree even if the hole is not provided in the mold with no bottom and only a hole is provided in a part of the bottom.

When filling the bottomless mold with the alloy powder, it is necessary to attach a base plate to the bottomless mold. The sintered body is lightly bonded to the bottom plate after sintering, and stands stably on the bottom plate even if there is some vibration. For this reason, even if the sintered body is thin and tall, the sintered body does not lean against the adjacent sintered body and bend during sintering. It was confirmed that a carbon plate, a B ₄ C plate, or a BN plate is effective as a base plate that exhibits such an effect.

In a mold made of a mixture of resin and filler, the resin is consumed by sintering and the filler remains. At this time, since the filler is in a powder state, it can be recovered by suction or the like, washed, and reused. Reuse reduces the waste associated with the production of rare earth magnets.

Rare earth sintered magnets include Nd—Fe—B sintered magnets and Sm—Co based sintered magnets. What has been said so far is applicable to both. In the case of the Sm—Co based sintered magnet, it is preferable that the Sm—Co alloy powder filled in the sintered mold is 40% or more of the true density. If this packing density is filled and sintered after magnetic field orientation, an Sm—Co based sintered magnet can be obtained using a sintered mold that is consumed during sintering in the same manner as an Nd—Fe—B sintered magnet. it can.
The sintering temperature of the alloy powder for Sm—Co based sintered magnet is a high temperature reaching 1200 ° C. Therefore, in the conventional press-less method (PLP method) using a conventional non-consumable mold, even if a mold is made with any material, the damage to the mold is so severe that it is difficult to apply as a mass production technique. In the disposable and consumable mold type PLP method of the present invention, a high sintering temperature is not a problem at all. The PLP method using a disposable or consumable mold according to the present invention can be applied to Nd-Fe-B sintered magnets and Sm-Co sintered magnets as mass production techniques.

Since rare earth sintered magnets are used in automobiles and electrical products, the typical production of one type of rare earth sintered magnet is several hundred thousand to several million. Therefore, it is desirable that the sintered mold according to the present invention be manufactured by an injection molding method, a vacuum molding method, or a pressure molding method that can efficiently produce a large number of molded products. In these resin molding methods, the first mold is expensive, but if a large number of resin molds are produced with one mold in response to the mass production of rare earth magnets, the mold accounting for the total production cost of rare earth sintered magnets. The sum of mold cost, resin material cost and resin molding process cost is extremely small.

In the conventional method in which the sintered mold is repeatedly used, the plate thickness of each part of the sintered mold cannot be remarkably reduced in order to ensure the mechanical strength. However, since the resin has very good moldability and mechanical strength is sufficiently high near room temperature, the container portion and partition plate portion of the mold can be made thin. These thicknesses can be 1 mm or less, and further 0.5 mm or less. Even if it is made thin in this manner, it can sufficiently withstand the stress applied to the container portion and the partition plate portion during powder filling and powder orientation.
Since the sintered mold is manufactured by a highly productive resin molding method such as an injection molding method, the mold and its partition plate are integrally manufactured from the same resin.

It has been found that if the mold is made of a resin and the partition plate of the mold is made thin, it is easy to uniformly fill the cavities delimited by the partition plate. When the partition plate is thick, it is necessary to uniformly fill the powder in each cavity in order to avoid powder getting on top of the partition plate. Is inevitable. However, if the partition plate is thin, an enclosure is provided in the upper space of the entire number of cavities formed in one mold, and the powder is uniformly filled in the enclosure, and then the density is increased by vibration or tapping. Thus, all the cavities can be uniformly filled up to a predetermined packing density. In this way, the powder can be uniformly filled in all the cavities by uniformly filling the powder in one space surrounded by the enclosure. Naturally, it is more difficult to uniformly fill a large space with a small number of small cavities separately to reduce the variation in filling amount for each cavity. If the variation in filling amount for each cavity can be reduced, the dimensional variation in the sintered body after sintering can be reduced, and the machining after sintering can be minimized. The reason why a large number of cavities can be filled with powder at the same time and the filling variation between cavities can be reduced is that a mold having a very thin partition plate made of resin can be used. The thickness of the partition plate is preferably 1 mm or less, and more preferably 0.5 mm or less. From the limit of the mechanical strength of the partition plate, the limit of the thickness of the partition plate is 0.1 mm.

Since the resin mold is disposable, the cost for maintenance of the mold after using the mold can be reduced. In addition, when production is suspended, in the conventional PLP method, it is necessary to store a large amount of molds until production is next started. A large storage space is required to store a large amount of molds. However, in the PLP method using the disposable mold of the present invention, it is only necessary to store only a mold for making a resin mold. A large storage space is not required for storing the mold, and the storage cost of the mold can be reduced as compared with the conventional PLP method.

When a rare earth sintered magnet is manufactured using a resin mold as described above, the manufacturing cost can be significantly reduced as compared with the conventional method. By this method, it is possible to efficiently produce plate-shaped products such as rectangular flat plate products, irregular-shaped flat plate products, and curved segmented flat plate products by simultaneous sintering.

If a disposable resin sintered mold is used in the production of a rare earth sintered magnet, the mechanical strength required for repeated use is not required. As a result, the thickness of the sintered mold wall and partition plate can be reduced, and it becomes easy to uniformly fill the plurality of cavities of the sintered mold with the alloy powder for rare earth sintered magnet. Further, if the thickness of the wall or partition plate can be reduced, the number of manufactured sintered bodies per unit area of the manufacturing apparatus can be increased, and the production efficiency is increased.

The resin-made sintered mold has sufficient strength necessary for filling of the alloy powder and its orientation in the magnetic field at room temperature, and is consumed and disposable before reaching the sintering temperature. If the packing density of the powder filled in the sintering mold is made higher than a certain value, the shape of the sintered body will not collapse during or after sintering, contrary to conventional technical common sense.

By kneading the resin, which is the material of the sintering mold, with a filler made of a solid material that does not melt even at the sintering temperature, even if the sintered body is thin, Falling and fusing can be prevented. Furthermore, the presence of the filler can reduce the adverse effects caused by using the resin. By increasing the volume fraction of the filler in the vicinity of the inner surface of the mold, it is possible to avoid the adverse effects of the resin while maintaining the strength of the mold.

By making the sintered mold bottomless, adverse effects from the resin due to decomposition product gas and the like can be further reduced.

A resin-made sintered mold can be easily mass-produced at low cost by an injection molding method, a vacuum molding method, or a pressure molding method. By employing a resin-made disposable sintered mold, the manufacturing cost of the rare earth sintered magnet can be greatly reduced.

The present invention can be applied to both Nd—Fe—B sintered magnets and Sm—Co based sintered magnets.

FIG. 1 is a perspective view of an example of a flat plate mold.
FIG. 2 is a diagram of an example of a flat plate mold and a guide set.
FIG. 3 is a perspective view of an example of a segment mold.
FIG. 4 is a perspective view of an example of a VCM mold (fan shape).
FIG. 5 is a diagram of the means for preventing overturning after sintering.
FIG. 6 is a perspective view of an example of a bottomless mold.
FIG. 7 is a cross-sectional view of an example of a bottomless mold.
FIG. 8 is a diagram of an example of a bottomless mold and a powder filling set.
FIG. 9 is a diagram of an example of a magnetic field orientation set for a bottomless mold.
FIG. 10 is an example of a set during sintering of a bottomless mold.
FIG. 11 is a diagram of an example of a state after sintering when a bottomless mold is used.

10 rare earth magnet alloy powder 11 guide 12 mold 13 mold support box 14 sintered body 15 talc 16 bottomless mold 17 bottom base plate 18 mold lid

Examples of the present invention are shown below, but the present invention is not limited to the examples. In each embodiment, the sintering mold may be individually made as a prototype, but in the case of mass production, it is natural that a large number should be manufactured by an injection molding method, a vacuum molding method, or a pressure forming method. .

As rare earth sintered magnets, there are Sm—Co sintered magnets in addition to Nd—Fe—B sintered magnets. In the following examples, the result of the Nd—Fe—B sintered magnet is technically applicable to the Sm—Co based sintered magnet.

(Preparation of fine alloy powder)
NdFeB is obtained by occluding hydrogen in a strip cast alloy having a composition (weight fraction) of 31.5% Nd, 0.99% B, 0.1% Cu, 0.25% Al, and the balance Fe, and performing hydrogen cracking. A coarse alloy powder for a sintered magnet was obtained. This coarse powder was pulverized by a jet mill using nitrogen gas to prepare an alloy fine powder for NdFeB sintered magnet. The particle size of the fine powder was measured by a laser diffraction / scattering method. The average particle size was D ₅₀ = 5.2 μm. To this fine powder, 0.1% by weight of zinc stearate was added and stirred and mixed with a mixer. Hereinafter, in Examples 1 to 8, a sintered magnet was produced using this fine powder.

An acrylic resin sheet having a thickness of 0.5 mm was bonded to produce a flat mold for a rare earth sintered magnet shown in FIG. This mold has five cuboid-shaped cavities filled with powder and is partitioned by a partition plate having a thickness of 0.2 mm. The depth of each cavity was 35.7 mm, the length of the side in the longitudinal direction of the opening was 47.6 mm, and the length of the side in the short direction of the opening (the direction perpendicular to the partition plate) was 9.4 mm. As shown in FIG. 2, a mold support box 13 that holds the mold 12 from the outside, and a guide 11 necessary for powder filling are installed on the upper surface of the support box.

From the upper part of the guide 11, the mold 12 was filled with 271.6g of the alloy fine powder for rare earth sintered magnet described above. The alloy fine powder for rare earth sintered magnet reached the vicinity of the upper end of the guide 11 immediately after filling, as shown in the gray part of FIG. The packing density at this time was about 2 g / cm ³ . When the mold was vibrated together with the mold support box and the powder was lightly pressed from the upper part of the guide while vibrating, the powder level was lowered to the upper end of the mold. At this time, the packing density of the powder filled in each cavity was 3.4 g / cm ³ .
Thereafter, the guide was removed, and a lid was attached to the upper part of the mold. The mold filled with powder and covered was placed in a magnetic field orientation coil with the mold support box attached, and a 5 T pulse magnetic field was applied in a direction perpendicular to the partition plate. After magnetic field orientation, the mold support box was removed.

The mold 12 filled with the alloy fine powder for rare earth sintered magnet was put on a stainless steel plate (sintered base plate) having a thickness of 3 mm and put in a sintering furnace with the lid covered. After the whole was evacuated, the temperature of the sintering furnace was increased. Hydrogen is introduced into the sintering furnace simultaneously with the start of temperature increase, and the pump exhaust rate and the hydrogen introduction amount are adjusted so that the hydrogen pressure is maintained at about 1 Pa, and the temperature is increased to 500 ° C. at a temperature increase rate of 3 ° C./min. The temperature rose. After holding at 500 ° C. for 1 hour in an atmosphere with a hydrogen pressure of 1 Pa, the supply of hydrogen was stopped. While evacuating with a turbo molecular pump, the temperature was raised to 800 ° C. at a heating rate of 5 ° C./min, held at 800 ° C. for 1 hour, and then raised to 1050 ° C. at a heating rate of 5 ° C./min. After holding at 1050 ° C. for 2 hours, heating was stopped and the mixture was cooled to room temperature in a furnace.

The sintered body was gently taken out of the sintering furnace together with the sintered base plate. The mold was completely lost. The five sintered bodies were aligned at regular intervals without falling on the sintering base plate. It was confirmed that the weights of all the five sintered bodies were extremely well aligned.

The following was confirmed by the above-described experiment conducted using the mold shown in FIG.
(1) As shown in FIG. 2, even if powder is simultaneously supplied to a plurality of cavities, a high-density powder filling state can be simultaneously and efficiently achieved in each cavity by mechanical vibration and pressing of a light load. The partition plate that divides each cavity is thin, and it has been confirmed that the powder remains in the upper part of the partition plate and does not interfere with the powder distribution to each cavity. After the sintering, it was confirmed that the weight and dimensions of the sintered bodies were very well aligned between the cavities.
(2) Even when the mold was consumed before the completion of sintering, the filled powder did not scatter or lost shape. The shape defect of the sintered body, which was a concern due to the consumption of the mold container before sintering, did not occur.

The arc segment mold as shown in FIG. 3 and the VCM mold as shown in FIG. 4 were produced by laminating a 0.2 mm thick styrene film. The rare earth sintered magnet made by the segment mold has a curved surface and is used by being attached to the outer periphery of the rotor of a motor or generator. The rare earth sintered magnet made by the VCM mold is flat but curved up and down, and is used for a voice coil motor (VCM) that drives a magnetic head in a hard disk drive. These two types of shapes are the shapes most often used as rare earth magnets in combination with the rectangular plate-like plate shape produced in Example 1.

The mold support box and guide having the same configuration as in FIG. 2 are attached to the arc segment mold in FIG. 3 and the VCM mold in FIG. 4, and the same rare earth sintered magnet alloy powder as in Example 1 is filled in each cavity of the mold. It was filled so as to have a density of 3.4 g / cm ³ . The guide was then removed and the mold was capped. The mold filled with the powder was placed in a magnetic field orientation coil with the mold support box attached, and a 5 T pulse magnetic field was applied in a direction perpendicular to the partition plate of the mold. In the segment mold, the magnetic field application direction is a direction perpendicular to the partition plate at the center of the partition plate. After the magnetic field orientation, the mold support box and the lid were put on the sintering base plate, placed in a sintering furnace, sintered under the same sintering conditions as in Example 1, and the sintered body was taken out. Both types of sintered bodies were sintered in an aligned state on the sintering base plate. It was confirmed that an arc segment shape and a VCM-shaped Nd—Fe—B sintered magnet could be produced by the arc segment mold and the VCM mold.

The flat plate mold of FIG. 1 and the flat plate mold in which the length in the vertical direction is halved without changing the number of partition plates and all other dimensions are the same, and the thickness is 0.2 mm including 40% by weight of talc. It was produced using an acrylic resin film. The average particle size of talc is 10 μm. Using this mold, powder filling and orientation in a magnetic field were performed under the same conditions as in Example 1. After that, the mold support box and the lid were attached and placed on the sintering table, put into a sintering furnace, and sintered under the same sintering conditions as in Example 1 to produce an Nd—Fe—B sintered magnet. The size of the sintered body thus obtained was exactly half the thickness of the flat plate sintered body in Example 1, and the other dimensions were exactly the same as those of the sintered body produced in Example 1. As described above, since the mold was made of resin and talc, the resin was not consumed due to decomposition or evaporation during the sintering process, but the talc remained without disappearing and dropped to the lower part of the space between the sintered bodies. It was confirmed that it functions to prevent the thin sintered body from falling.

As a comparative example, the same experiment as described above was performed using a flat plate mold prepared using an acrylic resin containing no talc. Each sintered body leaned against the adjacent sintered body. There were only sintered bodies that were leaning and sticking together and sintered bodies that were bent due to gravity, and there were no sintered bodies that stood on the sintering base plate and had no deformation.
As described above, when a thin flat plate-like sintered body is produced using a mold made of only resin, the sintered body may fall down due to vibration of the sintering furnace during the sintering, or the adjacent sintered body. It was confirmed that the sintered body might bend due to leaning against it. From this experiment, when producing a thin flat plate-like sintered body, it was confirmed that it is useful to include a substance that does not disappear by sintering in the mold material resin.

Using the same mold as in Example 3, the same powder filling and magnetic field orientation as in Example 3 were performed. FIG. 5A shows a cross-sectional view of the mold filled with powder. Thereafter, in order to examine whether the side wall and bottom surface of the mold support box during sintering are all necessary, the side wall on the side perpendicular to the partition plate of the mold was removed, leaving the side wall and bottom surface on the side parallel to the partition plate. The mold was put on a sintering base plate with a lid and placed in a sintering furnace. In this state, sintering was performed under the same conditions as in Example 3. After the sintering, the product was taken out together with the sintered base plate. As in Example 3, the five sintered bodies were aligned and there was no distortion. FIG.5 (b) has shown the side view or sectional drawing of this state. The sintered body 14 was supported by a talc 15 that functions to prevent overturning. It was confirmed that the fall prevention effect is effective.
When producing an extremely thin plate-like sintered body, a side wall parallel to the mold partition plate of the mold support box is necessary to prevent the sintered body from falling, but the side wall on the side perpendicular to the mold partition plate of the mold support box is necessary. This example confirmed that the sidewalls may be removed.

Three types of molds composed of a mixture of camphor and BN containing only camphor and 40% by volume and 60% by volume of BN were produced from the flat mold for rare earth sintered magnet of FIG. 1 by press molding. . The thickness of the mold side wall, the bottom plate, and the partition plate was 0.5 mm. These three types of molds have five rectangular parallelepiped cavities filled with powder, and are partitioned by a partition plate having a thickness of 0.5 mm. The thickness of the mold side wall and the bottom plate is also 0.5 mm. The depth of each cavity was 35.7 mm, the length of the opening and the side in the longitudinal direction was 47.6 mm, and the length of the side in the direction in which the opening was short (perpendicular to the partition plate) was 9.4 mm. As shown in FIG. 2, a mold support box for holding the mold from the outside, and a guide necessary for powder filling were installed on the upper surface of the support box.

From the upper part of the guide, 271.6 g of the above-mentioned fine alloy powder for sintered NdFeB magnet was filled in a mold. The alloy fine powder for NdFeB sintered magnet reached the vicinity of the upper end of the guide immediately after filling, as shown in the gray part of FIG. The packing density at this time was about 2 g / cm ³ . When the mold was vibrated together with the mold support box and the powder was lightly pressed from the upper part of the guide while vibrating, the powder level was lowered to the upper end of the mold. At this time, the packing density of the powder filled in each cavity was 3.4 g / cm ³ .
Thereafter, the guide was removed, and a lid was attached to the upper part of the mold. The mold filled with powder and covered was placed in a magnetic field orientation coil with the mold support box attached, and a 5 T pulse magnetic field was applied in a direction perpendicular to the partition plate. After magnetic field orientation, the mold support box was removed.
The procedure so far is the same as that of the first embodiment.

The mold filled with the alloy fine powder for rare earth sintered magnet was put on a 3 mm thick carbon plate (sintered base plate) with a lid, and placed in a sintering furnace. After the whole was evacuated, the temperature of the sintering furnace was increased. The temperature was increased to 350 ° C. at a temperature increase rate of 11 ° C./hour. Subsequently, the temperature was raised to 800 ° C. at a temperature rising rate of 5 ° C./minute, held at 800 ° C. for 1 hour, and then heated again to 1035 ° C. at a temperature rising rate of 5 ° C./minute. After holding at 1035 ° C. for 4 hours, heating was stopped and the furnace was cooled to room temperature in a furnace. Unlike the case of Example 1, hydrogen was not put into the sintering furnace at this time.

The sintered body was gently taken out of the sintering furnace together with the sintered base plate. The mold was completely lost. The five sintered bodies were aligned at regular intervals without falling on the sintering base plate. It was confirmed that none of the sintered bodies was distorted and that all the sizes and weights were well aligned.
The following was confirmed by the above-described experiment conducted using the mold shown in FIG.
(1) As shown in FIG. 2, even if powder is simultaneously supplied to a plurality of cavities, a high-density powder filling state can be simultaneously and efficiently achieved in each cavity by mechanical vibration and pressing of a light load. The partition plate that divides each cavity is thin, and it has been confirmed that the powder remains in the upper part of the partition plate and does not interfere with the powder distribution to each cavity. After the sintering, it was confirmed that the weight and dimensions of the sintered bodies were very well aligned between the cavities.
(2) Even when the mold was consumed before the completion of sintering, the filled powder did not scatter or lost shape. The shape defect of the sintered body, which was a concern due to the consumption of the mold container before sintering, did not occur.
(3) If the sintered mold was produced only with camphor, there was no problem even if hydrogen was not put into the sintering furnace during sintering.

The sintered body produced by the above-described experiment is heated to 800 ° C. in a vacuum, held for 1 hour, then rapidly cooled to room temperature, then again heated to 500 ° C. in a vacuum, held for 1 hour, and then rapidly cooled to room temperature. did. A sample having a magnetic pole surface of 7 mm square and a magnetization direction of 5 mm was cut out from the sintered body subjected to such heat treatment, and the magnetic characteristics were measured with a pulse magnetization measuring instrument. Table 1 shows the result of repeating this experiment five times and averaging the sintered body density of the prepared sample and the coercivity of the sample after the heat treatment.

From this example, it can be concluded that the molding material affects the sintered body density and the coercive force of the sintered body of the Nd—Fe—B sintered magnet produced according to the present invention. The more the BN component that is an inorganic filler as the mold material, the higher the sintered body density and coercive force of the Nd—Fe—B sintered magnet produced by the mold. The density and coercive force of the sintered body are the most important management items for the quality control of the Nd—Fe—B sintered magnet. According to Table 1, in order to produce a rare earth magnet having a high sintered body density and a high sintered body coercive force, the inorganic filler content in the mold material used is preferably 40% or more, more preferably 60% or more. I understand.

A BN powder having an average particle diameter of 5 μm was applied to the inner surface of the cavity of the mold of Example 5 with 100% camphor with a brush. The same experiment as in Example 5 was performed using a mold of 100% camphor coated with this BN powder. This experiment was repeated 5 times, and it was confirmed that the average value of the sintered body density and coercive force of the produced sintered body was almost equivalent to the result when the BN volume% in Table 1 was 40%. By applying a filler to the inner surface of the mold, the contamination of the Nd—Fe—B alloy powder by the resin decomposition gas was reduced.

The mold having the flat plate-like cavity shown in FIG. 1 and the mold having the arc segment-like cavity shown in FIG. 3 were produced by an injection molding method using a mixture of PVA, B ₄ C, BN and water. After injection molding, these molds were heated at 75 ° C. for 1 day to evaporate moisture. The composition of the mold material after drying is 10% by volume of PVA, 85% by volume of B ₄ C, and 5% by volume of BN. Thereafter, the shape and dimensions are adjusted by mechanical polishing, so that a side wall and a partition plate having a thickness of 0.3 mm, a bottom plate having a thickness of 0.1 mm, and an arc segment-like cavity are shown in FIGS. A mold was prepared.

As shown in FIG. 2, a polyacetal mold support box and a guide were attached to these molds. From the upper part of the guide, the same fine powder of NdFeB sintered magnet alloy as the powder used in Example 5 was filled in the mold. The alloy fine powder for NdFeB sintered magnet reached the vicinity of the upper end of the guide immediately after filling, as shown in the gray part of FIG. The packing density at this time was about 2 g / cm ³ . When the mold was vibrated together with the mold support box and the powder was lightly pressed from the upper part of the guide while vibrating, the powder level was lowered to the upper end of the mold. At this time, the packing density of the powder filled in each cavity was 3.4 g / cm ³ . Thereafter, the guide was removed, and a lid was attached to the upper part of the mold. The mold filled with powder and covered was placed in a magnetic field orientation coil with the mold support box attached, and a 5 T pulse magnetic field was applied in a direction perpendicular to the partition plate. After magnetic field orientation, the mold support box was removed.

The mold filled with the alloy fine powder for NdFeB sintered magnet was put on a 3 mm thick carbon plate (sintered base plate) with the lid covered, and put in separate sintering furnaces. After the whole was evacuated, the temperature of the sintering furnace was increased. The temperature was raised to 500 ° C. at a rate of 3 ° C./min. Subsequently, the temperature was raised to 800 ° C. at a temperature rising rate of 5 ° C./minute, held at 800 ° C. for 1 hour, and then heated again to 1035 ° C. at a temperature rising rate of 5 ° C./minute. After holding at 1035 ° C. for 4 hours, heating was stopped and the furnace was cooled to room temperature in a furnace.

The sintered body was gently taken out from the two sintering furnaces together with the sintered base plate. The mold was completely lost. Each of the five sintered bodies produced from the respective molds were aligned at regular intervals without falling on the sintered base plate. It was confirmed that none of the sintered bodies was distorted, and that all the sizes and weights were well aligned. The sintered body had a high density and reached an average of 7.53 g / cm ³ . High magnetic properties were obtained as follows.
B _r = 14.1 kG
H _cJ = 12.4 kOe
(BH) _max = 48 MGOe

A mold without a bottom as shown in FIG. 6 (bottomless mold) was produced. This cross section is shown in FIG. This mold is made from a kneaded mixture of B ₄ C (boron carbide) with an average particle size of 20 μm, BN (boron nitride) with an average particle size of 10 μm, PVA and water, using both injection molding and mechanical polishing. did. The composition of this mold after injection molding and heat drying is B ₄ C 60% by volume, BN 30% by volume, and PVA 10% by volume. The thickness of the partition plate and the mold side wall is 0.5 mm.

When filling the bottomless mold with powder, it is necessary to attach the bottom base plate 17, and the powder filling set is shown in FIG. It is a feature of the present invention that the powder filling set simultaneously fills all cavities delimited by the partition plate from the upper opening. Since the partition plate is thin, even if the powder is filled in all the cavities at the same time, the powder does not get on the upper end of the partition plate and the powder filling into the cavities is not hindered. It was confirmed that even if the lid was placed with a small amount of powder on the upper end, the partition plate was consumed during the sintering, so that it had no effect on the formation of the sintered body formed in the cavity. In the conventional PLP method (Patent Document 1) in which the mold is not consumed, if there is powder on the upper end of the partition plate, the sintered body is pulled by the partition plate and deformed.

After the powder is filled to the upper end of the mold by the powder filling set in FIG. 8, the lid 18 is applied to the mold as shown in FIG. 9, and a magnetic field is applied in the direction of the arrow in FIG. 9 to orient the powder in the mold. . After that, as shown in FIG. 10, the mold holding the filled and oriented powder was put in a sintering furnace with the lid 18 and the bottom plate 17 attached to the upper and lower sides of the mold. Here, the lid and the bottom plate need not be the same for the sintering of FIG. 10 and the magnetic field application of FIG. After magnetic field orientation, both or one of the plates can be replaced as needed. The same NdFeB alloy powder as in Example 5 was filled to a packing density of 3.4 g / cm ^{3 using} the powder filling set shown in FIG. At the time of sintering in FIG. 10, a carbon plate having a thickness of 3 mm was used as the mold lid and the bottom base plate. Sintering was performed under the same conditions as in Example 6.

After sintering, the sintered body 19 was pulled out of the sintering furnace while standing on the mold bottom plate as shown in FIG. In FIG. 11, the partition plate and the side wall of the mold are indicated by broken lines. This shows that after the sintering process, they lose shape. If the partition plate and the side wall collapse, the mold lid 18 supported by these also falls on the sintered body, but in FIG. 11, it is drawn as it was before sintering. In the actual process, the mold lid can also be removed before sintering. After such a sintering process, it was found in this example that the sintered body 19 was lightly bonded to the mold bottom plate, and the sintered body did not fall down with some vibrations. Standing stable. By utilizing this phenomenon, a thin and tall flat-plate rare earth magnet can be stably produced in the present invention. If this phenomenon does not occur, tall sheet products will lean against each other during sintering and bend. As shown in Example 3, it is also possible to prevent the ceramic powder contained in the mold from falling between the thin plate sintered bodies and falling over. However, as in this embodiment, it is also an effective method as a production technique to prevent the thin plate sintered body from falling over by utilizing the light adhesive effect between the sintered body and the mold bottom plate.

In this example, 20 molds were produced, and a large number of simultaneous sintering tests were also performed. As a result, the 100 sintered bodies produced in this example all reached a density of 7.54 g / cm ³ , had no deformation or distortion, and had extremely small dimensional and weight variations. The average magnetic properties were as follows.
B _r = 14.2 kG
H _cJ = 12.6 kOe
(BH) _max = 49 MGOe

The method of this embodiment has the following advantages.
(1) Since organic gas generated from the mold during sintering easily escapes from the upper end and lower end of the mold through the gap between the mold lid and the mold bottom plate, contamination of the rare earth alloy powder by the organic gas is reduced. For this reason, rare earth magnets produced by such a bottomless mold have less deformation during sintering compared to the same magnet produced by using a mold with a bottom, even if many magnets are sintered at the same time. To achieve high density and high magnetic properties.
(2) Because of the light adhesive effect between the mold bottom plate and the sintered body during sintering, even a tall sintered body stands stably on the bottom plate after sintering, so bending and deformation due to the sintered body falling over Can be prevented.

(Example of Sm-Co sintered magnet)
An alloy of 15% Fe, 8% Cu, 25.5% Sm, 1.5% Zr, and 50% Co by weight ratio is prepared by a high-frequency melting method, coarsely pulverized by a brown mill, and jet milled by nitrogen gas Thus, Sm—Co—Fe—Cu—Zr alloy fine powder having a pulverized particle size of 5 μm measured by a laser diffraction method was produced.
A bottomless mold similar to that shown in FIG. 6 and having 85% by volume of BN (boron nitride) having an average particle diameter of 20 μm and 15% by volume of PVA was produced. The thickness of the partition plate and the mold side wall is 0.5 mm. The above-mentioned Sm—Co—Fe—Cu—Zr alloy fine powder was filled to a packing density of 3.8 g / cm ³ by the same powder filling set as in FIG. A BN plate having a thickness of 3 mm was used for the mold bottom plate and the mold lid during sintering.

Sintering was performed in vacuum at a rate of 10 ° C./min from room temperature to 1200 ° C., held at 1200 ° C. for 2 hours, and cooled in a furnace. After the sintering, the sintered body was pulled out from the sintering furnace while standing on the mold bottom plate as shown in FIG. In FIG. 11, the partition plate and the side wall of the mold are indicated by broken lines. This shows that after the sintering process, they lose shape. After such a sintering process, the sintered body was lightly bonded to the mold bottom plate, and the sintered body did not fall down with some vibrations and stood on the mold bottom plate stably. All of the five sintered bodies reached a density of 8.4 g / cm ³ , had no deformation or distortion, and had extremely small dimensional and weight variations. The sintered body was heated again to 1200 ° C in Ar gas and then rapidly cooled, and multistage aging of 800 ° C for 30 minutes, 700 ° C for 30 minutes, 600 ° C for 1 hour, 500 ° C for 2 hours, and 400 ° C for 6 hours Treated. The average magnetic properties of the Sm—Co—Fe—Cu—Zr magnet after the multi-stage aging treatment were as follows.
B _r = 11.0 kG
H _cJ = 6.7 kOe
(BH) _max = 29.6 MGOe

Claims (25)

A method for producing a rare earth sintered magnet in which a rare earth sintered magnet alloy powder is filled into a sintering mold for a rare earth sintered magnet, oriented in a magnetic field, and then put into a sintering furnace together with the sintered mold and heated to obtain a sintered body. In
A method for producing a rare earth sintered magnet, wherein the sintering mold is consumed during sintering. The method for producing a rare earth sintered magnet according to claim 1, wherein the sintered mold has a partition plate that is consumed during sintering, and a plurality of sintered bodies can be produced simultaneously. The method for producing a rare earth sintered magnet according to claim 1, wherein a material of the sintered mold and the partition plate is a resin. The method for producing a rare earth sintered magnet according to claim 3, wherein the resin is camphor. 3. The rare earth sintering according to claim 1, wherein a material of the sintering mold and the partition plate is a mixture of a resin and a substance (filler) that does not disappear during sintering. Magnet manufacturing method. 6. The method for producing a rare earth sintered magnet according to claim 5, wherein the substance (filler) that does not disappear during the sintering is 40% by volume or more and 95% by volume or less of all the substances constituting the mold. 6. The method for producing a rare earth sintered magnet according to claim 5, wherein a volume fraction of a substance (filler) that does not disappear during the sintering is large on a mold surface in contact with the rare earth alloy powder filled in the mold. BN or B ₄ C or rare earth oxide, rare earth fluoride, rare earth oxyfluoride, or a mixture thereof is used as a substance (filler) in which the resin does not disappear during sintering. The method for producing a rare earth sintered magnet according to any one of claims 5 to 7. 9. The mold support box for holding a side surface and a bottom surface of the sintered mold from the outside during filling of the alloy powder and during magnetic field orientation of the powder is used. Rare earth sintered magnet manufacturing method. The method for producing a rare earth sintered magnet according to claim 9, wherein the mold support box has a side surface parallel to a magnetic field orientation direction removed during sintering. The method for producing a rare earth sintered magnet according to any one of claims 1 to 10, wherein the sintering is performed in an atmosphere containing hydrogen. The rare earth sintered magnet alloy powder filled therein is oriented in a magnetic field, and then used in a method for producing a rare earth sintered magnet to be heated in a sintering furnace to obtain a sintered body,
A sintering mold for rare earth sintered magnets, which is consumed during sintering in a sintering furnace. The sintered mold for a rare earth sintered magnet according to claim 12, further comprising: a partition plate that is consumed during sintering, and a plurality of cavities that hold the rare earth magnet alloy powder. The sintered mold for rare earth sintered magnet according to claim 12 or 13, wherein the material is a resin. The sintered mold for rare earth sintered magnet according to claim 14, wherein the resin is camphor. 14. The rare earth sintered magnet sintering mold according to claim 12, wherein the material is a mixture of a resin and a substance (filler) that does not disappear during sintering. The material (filler) in which the resin does not disappear during sintering is BN or B ₄ C, rare earth oxide, rare earth fluoride, rare earth oxyfluoride, or a mixture thereof. 16. A sintered mold for rare earth sintered magnets according to 16. The sintered mold for a rare earth sintered magnet according to any one of claims 13 to 17, wherein the partition plate has a thickness of 1 mm or less and 0.1 mm or more. The rare earth sintered magnet according to any one of claims 13 to 18, wherein the plurality of cavities for holding the rare earth magnet alloy powder have no bottom or have holes in the bottom. Sintered mold. The sintered mold for rare earth sintered magnet according to claim 19, wherein the bottomless mold uses a material having adhesiveness to the sintered magnet as a base plate. There are a plurality of the partition plates, the partition plates are rectangular or square flat plates, the cavity formed by the partition plates is a rectangular parallelepiped, and the length of the cavity of the rectangular parallelepiped in the direction perpendicular to the surface of the partition plate The rare earth sintered magnet according to any one of claims 13 to 20, wherein is smaller than one third of the dimension of the longer side of the vertical or horizontal side of the partition plate. Sintered mold. There are a plurality of the partition plates, the partition plates have a flat shape that is not curved, the planar shape is neither square nor rectangular, and the cavity formed by the partition plates is a solid composed of a flat surface that is not curved. The cross section is neither square nor rectangular, and the length of the cavity in the direction perpendicular to the surface of the partition plate is smaller than one third of the longest length of the surface of the partition plate. The sintered mold for rare earth sintered magnet according to any one of claims 13 to 20. The sintered mold for a rare earth sintered magnet according to any one of claims 13 to 20, wherein the partition plate has a curved plate shape. The sintered mold for a rare earth sintered magnet according to any one of claims 21 to 23, wherein the sintered mold has at least five partition plates and is used when a large number of thin sintered bodies are simultaneously manufactured. 25. The sintered mold for a rare earth sintered magnet according to any one of claims 12 to 24, wherein the sintered mold is integrally formed with the partition plate by an injection molding method, a vacuum molding method or a pressure forming method.