JP4556236B2 - Rare plate for sintering rare earth magnet and method for producing rare earth magnet using the same - Google Patents

Description

  The present invention relates to a base plate for sintering a rare earth magnet used in a step of sintering a green raw material powder containing a rare earth element and a method for producing a rare earth magnet using the same.

  For example, in a wide range of fields such as a hard disk drive voice coil motor and an automobile drive motor, miniaturization and high performance of the motor are required. In order to reduce the size and performance of motors, it is important to improve the performance of magnets built into motors. In recent years, rare earth magnets such as neodymium iron boron-based sintered magnets that exhibit extremely high magnetic properties are often used. Has been.

  The rare earth magnet is basically manufactured as follows. That is, first, a raw material alloy containing a rare earth element or the like as a main component is coarsely pulverized by hydrogen pulverization and / or mechanical pulverization, and then finely pulverized by an airflow pulverizer or the like to produce a raw material alloy fine powder. Next, the raw material alloy fine powder is compression-molded in a magnetic field to obtain a compact. Next, the compact is sintered in a sintering furnace at, for example, 1000 ° C. to 1300 ° C., and aging is performed at, for example, 500 ° C. to 900 ° C., thereby producing a rare earth magnet.

When mass-producing rare earth magnets, a sintered plate with a plurality of compacts is usually placed in a sintering case, and the sintering case is placed in a sintering furnace to sinter many compacts simultaneously. Process (for example, refer patent document 1 etc.). The material constituting the laying plate (sintered plate) for placing the molded body is required to have sufficient strength when exposed to a high temperature of about 1000 ° C. to 1300 ° C. during handling or during handling. For example, a molybdenum plate is used for the sintered plate of Patent Document 1. In addition, for example, a base plate (see Patent Document 2) in which an oxide such as zirconia, yttrium, or tungsten is thermally sprayed on a base plate body formed of a refractory metal material such as molybdenum has been proposed. Furthermore, Patent Document 3 proposes a heat-resistant covering member in which a carbon substrate is covered with a Y-containing oxide film.
JP 2000-315611 A JP 2001-267163 A JP 2002-371383 A

  However, for example, when a compact is placed on a molybdenum plate as described in Patent Document 1 and sintered, the rare earth component oozes out from the compact during the sintering process. Welding occurs between them. In addition, the sintered body may be damaged due to an impact applied when the sintered body is separated from the molybdenum plate, leading to a decrease in yield. In addition, when the welded sintered body is removed from the laying board by sandblasting or the like, the laying board may be deformed, damaged, or worn, and there is a problem that the replacement cost of the laying board is increased.

  Furthermore, the base plate mainly made of molybdenum has a demerit that it is very heavy. If the base plate for rare earth magnet sintering placed in the sintering case is heavy, the number of sintering cases that can be placed in the sintering furnace, that is, the weight of the compact that can be sintered at a time, decreases, resulting in lower production efficiency. Invite. In Patent Document 2, although an oxide sprayed film is provided on the surface of the base plate body to improve welding between the base plate and the sintered body, the base plate is very similar to Patent Document 1. There is a demerit that it becomes heavy.

  Therefore, the present invention has been proposed in view of such conventional situations, and is for light-weight, high-strength, rare-earth magnet sintering capable of suppressing welding between a floor plate and a sintered body. An object of the present invention is to provide a base plate and a method for producing a rare earth magnet using the same.

In order to achieve the above-mentioned object, the present inventors have made extensive studies. As a result, the knowledge that carbon fiber reinforced carbon composite material, which is a kind of carbon, is lightweight and high in strength, is less likely to be welded to a sintered body, and is extremely effective as a constituent material for a base plate for sintering rare earth magnets. The headline and the present invention have been completed. That is, the floor plates for the rare earth sintered magnet according to the present invention is used for mounting the molded body in the sintering process of the molded body of the magnet raw material powder containing a rare earth element, configure a carbon fiber-reinforced carbon composite material In addition, a zirconium oxide film is formed on the surface on which the molded body is placed, and the zirconium oxide film is obtained by spraying zirconium oxide.

In the present invention, a carbon fiber reinforced carbon composite material, which is a kind of carbon, is used as a constituent material of the base plate for rare earth magnet sintering. The density of carbon 2.3 g / cm ^3, a carbon fiber-reinforced carbon composite material is about 1.5 g / cm ^3, a very low density when compared to the density 10.2 g / cm ³ molybdenum. For this reason, by constructing the sintered magnet sintering base plate with a carbon fiber reinforced carbon composite material, which is a kind of carbon, a significant weight reduction of about 85% is achieved compared to the molybdenum base plate with the same structure. Is done.

  In addition, the carbon fiber reinforced carbon composite material is a material having high strength and excellent breakage resistance. A floorboard made of a carbon fiber reinforced carbon composite material has higher strength than a graphite floorboard having the same shape (thickness). When attempting to achieve the same strength between a graphite floorboard and a carbon fiber reinforced carbon composite floorboard, the graphite floorboard requires about three times the thickness of the carbon fiber reinforced carbon composite floorboard. That is, by using a carbon fiber reinforced carbon composite as a constituent material, sufficient strength can be secured as a base plate for sintering a rare earth magnet, and further, the base plate for sintering a rare earth magnet can be made thin.

  Moreover, the carbon fiber reinforced carbon composite material is a material having high durability against heat. Therefore, the base plate for sintering a rare earth magnet of the present invention hardly causes thermal deformation even when it is repeatedly used in the sintering process.

  Furthermore, the carbon fiber reinforced carbon composite material is a material that is less likely to be welded to a molded body (sintered body) after the sintering process, compared to molybdenum or the like that is a constituent material of a conventional sintering base plate. Therefore, in the base plate for rare earth magnet sintering of the present invention, deformation and cracks of the sintered body due to welding are suppressed. Moreover, damage to the sintered body due to the step of separating the floor plate and the sintered body is suppressed. In addition, since there is no need to remove the sintered body welded to the floorboard, there is no deformation, breakage, wear, etc. of the floorboard accompanying the removal work, and the floorboard can be reused many times, reducing costs. This is effective. In addition, since the base plate for rare earth magnet sintering according to the present invention has a high effect of preventing welding, it is not necessary to spray a base powder for preventing welding.

  In general, when sintering is performed by bringing a base plate composed of graphite and a molded body close to or in contact with each other, the graphite carbonizes the molded body (sintered body), for example, to generate carbides on the surface, and magnetic properties of the molded body. May cause a drop. There is a concern that the same problem as graphite may occur when the material of the base plate is a carbon fiber reinforced carbon composite material, but the carbide generated on the surface can be easily obtained by grinding after the sintering process. It can be removed. Therefore, there is almost no adverse effect on the magnetic properties due to the sole plate made of the carbon fiber reinforced carbon composite material alone. That is, in the base plate for sintering a rare earth magnet of the present invention, a coating film on the molded body mounting surface is basically unnecessary.

  Patent Document 3 discloses a heat-resistant coating member in which a carbon base material is coated with a Y-containing oxide. However, it is assumed that the carbon base material is coated with a Y-containing oxide, and the carbon is not coated. There is no description suggesting that it is used in. It is also completely unexpected to select a carbon fiber reinforced carbon composite.

Further, the method for producing a rare earth magnet according to the present invention is a method for producing a rare earth magnet having a sintering step of a compact of magnet raw material powder containing rare earth elements, and in the sintering step, a carbon fiber reinforced carbon composite material The molded body is placed on a base plate for sintering a rare earth magnet , and a zirconium oxide film is formed on the surface of the base plate for sintering the rare earth magnet. The zirconium oxide film is a thermal spray of zirconium oxide.

  In the sintering process in mass production of rare earth sintered magnets, there are many cases where a plurality of sintering cases with a rare earth magnet sintering base plate are placed in a sintering furnace. By using a rare earth magnet sintering base plate, it is possible to increase the weight of a molded body that can be placed in a sintering furnace as compared with, for example, a molybdenum base plate. Therefore, the production efficiency can be improved. Furthermore, since the base plate for rare earth magnet sintering used has high strength, breakage during use is suppressed, and maintenance costs required for the base plate can be reduced.

  Further, in the sintering process, by using a base plate for sintering a rare earth magnet having a carbon fiber reinforced carbon composite material as a constituent material, for example, welding of the sintered body to the base plate is suppressed compared to the case of using a molybdenum base plate, Deformation of the sintered body, generation of cracks, and breakage of the sintered body due to the process of separating the sintered body are suppressed. In addition, since there is no need to remove the sintered body welded to the floor plate, there is no deformation, breakage, wear, etc. of the floor plate due to the removal operation, and the floor plate can be reused many times. It is effective in. In addition, by using the base plate for rare earth magnet sintering of the present invention, it is not necessary to spray a base powder for preventing welding on the base plate for each sintering process.

  Furthermore, when using a base plate for sintering a rare earth magnet comprising a carbon fiber reinforced carbon composite material as a constituent material in the sintering process, there is a concern that the magnetic properties may be deteriorated due to an adverse effect on the surface of the molded body. Etc. can be easily removed. Therefore, a rare earth magnet with almost no deterioration in characteristics can be obtained.

  Here, the sintering step in the present invention is both a step of sintering a compact of magnet raw material powder containing rare earth elements and a step of aging the compact after sintering (sintered compact). It is a concept that includes

  According to the present invention, a base plate for sintering a rare earth magnet that realizes a significant reduction in weight, has excellent strength, and can suppress welding of a rare earth magnet (sintered body) when used in a rare earth magnet sintering process. Can be provided. In addition, according to the method for manufacturing a rare earth magnet of the present invention, the use of a base plate for sintering a rare earth magnet that is lightweight, has high strength, and suppresses welding of the rare earth magnet (sintered body) can dramatically increase production efficiency. It is possible to improve and reduce the manufacturing cost required for the floorboard, and to manufacture rare earth magnets with a high yield.

  Hereinafter, a base plate for sintering a rare earth magnet to which the present invention is applied and a method for producing a rare earth magnet using the same will be described in detail with reference to the drawings.

  For example, as shown in FIG. 1, the base plate 1 for sintering a rare earth magnet comes into contact with the molded body 2 when the molded body 2 of the magnet raw material powder containing rare earth elements is sintered in the sintering process. It is a plate-like sintering jig used for mounting, and a carbon fiber reinforced carbon composite material is a main constituent material.

Here, the carbon fiber reinforced carbon composite material is manufactured using a carbon fiber non-woven fabric as a starting material, and the base plate composed of the carbon fiber reinforced carbon composite material, for example, impregnates the carbon fiber non-woven fabric with a resin. The prepreg is molded into a predetermined shape to obtain a molded body, and then the molded body is obtained by carbonization and graphitization. From the viewpoint of strength and thermal conductivity, the density of the carbon fiber reinforced carbon composite is preferably 1.2 to 1.8 g / cm ³ .

  The carbon fiber reinforced carbon composite material is lighter than a metal material such as molybdenum, and is extremely advantageous in terms of reducing the weight of the base plate 1 for sintering a rare earth magnet.

  In addition, since the carbon fiber reinforced carbon composite material has high strength, the use of the carbon fiber reinforced carbon composite material as a constituent material increases the breakage resistance of the base plate 1 for sintering the rare earth magnet, and also sinters the rare earth magnet. The floor board 1 can be thinned. There is graphite as a lightweight material, but the carbon fiber reinforced carbon composite material is very advantageous as a material for the floor board because it has higher strength than graphite. In addition, graphite uses carbon as a raw material, and a base plate made of graphite is, for example, a pulverization process, a kneading process, a molding process, a carbonization process, a densification process (a carbonization process, a densification process as necessary). And the graphitization step.

  Further, the carbon fiber reinforced carbon composite is an excellent material in that the welding with the sintered body is suppressed in the sintering process as compared with molybdenum. By performing the sintering process using the base plate 1 for sintering rare earth magnets of the present invention, welding with the sintered body can be suppressed, and rare earth magnets can be manufactured with high yield. Moreover, since the operation | work which removes the sintered compact welded to the flooring board is unnecessary, a flooring board can be utilized repeatedly and it is effective at the point which aims at cost reduction. In addition, it is not necessary to spray a floor powder for preventing welding on the floor board.

  The carbon fiber reinforced carbon composite material is less expensive than molybdenum and has an advantage that the amount of deformation is small even when the sintering treatment is performed at a high temperature of about 1000 ° C. to 1300 ° C. Therefore, by using the carbon fiber reinforced carbon composite material for the floor plate, the sintered body deformation due to the floor plate deformation can be suppressed. This is particularly effective for thin shapes.

  Further, the rare earth magnet sintering base plate 1 made of a carbon fiber reinforced carbon composite material is applied to the molded body (sintered body) 2 even when it is brought into contact with the molded body 2 and sintered. It has the advantage of less adverse effects.

  The carbon fiber reinforced carbon composite material can be used alone as a constituent material of the base plate 1 for sintering a rare earth magnet as shown in FIG. 1. For example, as shown in FIG. A zirconium oxide film 4 may be formed on the surface on which the molded body 2 of the base plate body 3 made of a fiber reinforced carbon composite material is placed. By forming the zirconium oxide film 4 on the mounting surface of the molded body 2 of the base plate 1 for sintering the rare earth magnet, contact between the carbon component of the carbon fiber reinforced carbon composite and the molded body 2 is prevented, and the molded body (baked Adverse effects on the compact (sintered body) 2 such as carbonization of the compact 2) are reliably suppressed. In addition, when an oxide film is formed on the surface of a carbon fiber reinforced carbon composite or the like, there is a concern that the oxide film may be peeled off by repeated sintering treatment, but the adhesion of zirconium oxide to the carbon fiber reinforced carbon composite Since the strength is high, peeling of the zirconium oxide film 4 is relatively difficult to occur.

  Here, the zirconium oxide film 4 is formed by thermal spraying, for example. The zirconium oxide film 4 is basically made of zirconium oxide, but may contain inevitable impurities.

  The film thickness of the zirconium oxide film 4 is preferably, for example, 5 μm to 30 μm, and more preferably 10 μm to 20 μm, from the viewpoint of reliably preventing contact between the carbon fiber reinforced carbon composite and the molded body 2.

  Next, the rare earth magnet to be manufactured will be described. The rare earth magnet is a rare earth sintered magnet mainly composed of a rare earth element, such as a neodymium iron boron magnet or a samarium cobalt magnet. The neodymium iron boron-based magnet is, for example, R-T-B (where R is one or more of rare earth elements, where the rare earth element includes Y. T is a transition metal in which Fe or Fe and Co are essential. 1 or 2 or more elements. B is boron.), Rare earth element R is 20% by mass to 40% by mass, boron B is 0.5% by mass to 4.5% by mass, and the balance Has a composition that becomes a transition metal element T. Here, R is one or more selected from rare earth elements, that is, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, and Lu. Especially, since Nd is abundant in resources and relatively inexpensive, the main component is preferably Nd. Further, the inclusion of Dy is effective in improving the coercive force Hcj because it increases the anisotropic magnetic field.

  Alternatively, the additive element M can be added to form an R-T-B-M rare earth sintered magnet. In this case, examples of the additive element M include Al, Cr, Mn, Mg, Si, Cu, C, Nb, Sn, W, V, Zr, Ti, Mo, Bi, and Ga. A seed | species or 2 or more types can be selected and used. The addition amount of these additive elements M is preferably 3% by mass or less in consideration of magnetic characteristics such as residual magnetic flux density. If the amount of additive element M added is too large, the magnetic properties may be deteriorated.

  The present invention can be applied not only to neodymium iron boron-based magnets but also to the samarium-cobalt-based magnets (SmCo-based rare earth sintered magnets), and is not limited to these, and can be applied to all known rare earth magnets. Needless to say.

  For the production of the rare earth magnet, for example, powder metallurgy is employed. Hereinafter, a method for producing a rare earth magnet, for example, a neodymium iron boron-based magnet by a powder metallurgy method will be described.

  The manufacturing process of rare earth magnets by powder metallurgy is basically based on alloying process, coarse pulverization process, fine pulverization process, magnetic field forming process, sintering process including aging process, machining process, film forming process, etc. Composed. In the present invention, a base plate for sintering a rare earth magnet using the above-described carbon fiber reinforced carbon composite as a constituent material is used in the sintering step. In order to prevent oxidation, most of the steps up to after the sintering step are performed in a vacuum or in an inert gas atmosphere (such as in a nitrogen atmosphere or an argon atmosphere).

  In the alloying process, a metal or alloy as a raw material is blended in accordance with the magnet composition, melted in a vacuum or an inert gas, for example, an argon atmosphere, and alloyed by casting. As a casting method, a strip casting method (continuous casting method) in which molten high-temperature liquid metal is supplied onto a rotating roll and an alloy thin plate is continuously cast is preferable from the viewpoint of production efficiency and the like. It is not limited. As the raw material metal (alloy), pure rare earth elements, rare earth alloys, pure iron, ferroboron, and alloys thereof can be used.

  As the alloy, a single alloy having an almost final magnet composition may be used, or a plurality of types of alloys having different compositions may be mixed so as to obtain the final magnet composition. The mixing may be performed in any of the alloying process, the coarse pulverization process, and the fine pulverization process, but in consideration of the mixing property, the mixing before the pulverization process is preferable.

  In the coarse pulverization step, the previously cast thin plate or ingot of the raw material alloy is pulverized until the particle size becomes about several tens of μm. As the pulverizing means, a stamp mill, a jaw crusher, a brown mill, or the like can be used. In order to improve the coarse pulverization property, it is effective to perform coarse pulverization after hydrogen storage or after hydrogen storage and hydrogen release.

  The coarse pulverization step can be constituted by a plurality of steps in which a plurality of pulverization means are combined. For example, two steps of a hydrogen pulverization step and a mechanical coarse pulverization step can be performed. The hydrogen pulverization step is a step in which hydrogen is occluded in the cast raw material alloy and pulverized in a self-destructive manner utilizing the fact that the hydrogen occlusion amount varies depending on the phase. Thereby, it can grind | pulverize to the magnitude | size about particle size several mm. The mechanical coarse pulverization step is a step of pulverizing using a mechanical method such as a brown mill as described above. The raw alloy powder pulverized to a size of about several millimeters by the hydrogen pulverization step is used. Then, pulverize until the particle size is about several tens of μm. When performing the hydrogen pulverization step, the mechanical coarse pulverization step may be omitted.

  After the coarse pulverization step, a fine pulverization step is performed. This fine pulverization step is performed using, for example, a jet mill. The fine pulverization conditions may be set as appropriate according to the airflow type pulverizer to be used, and the raw material alloy powder is finely pulverized until the average particle size becomes about 1 to 10 μm, for example, 3 to 6 μm. A jet mill releases a high-pressure inert gas (for example, nitrogen gas) from a narrow nozzle to generate a high-speed gas flow. The high-speed gas flow accelerates powder particles, and the powder particles collide with each other. Or it is a method of generating a collision with a target or a container wall and crushing. Jet mills are generally classified into jet mills that use fluidized beds, jet mills that use vortex flow, jet mills that use impingement plates, and the like. In this pulverization step, for example, a fatty acid compound or the like may be added as a pulverization aid or a release agent before, after, or before and after pulverization, or about 0.01% by mass to 0.5% by mass.

  After the pulverization step, the magnet raw material powder is formed in the magnetic field in the magnetic field forming step. Specifically, the magnet raw material powder obtained in the fine pulverization step is filled in a mold in which an electromagnet is arranged, and is molded in a magnetic field in a state where crystal axes are oriented by applying a magnetic field. Forming in the magnetic field may be either longitudinal magnetic field shaping or transverse magnetic field shaping. The molding in the magnetic field may be performed at a pressure of about 50 MPa to 160 MPa in a magnetic field of about 800 kA / m to 1500 kA / m, for example.

Density of the molded body is preferably, for example, ^{3.9g / cm 3 ~4.6g / cm 3} . When the density of the molded body is less than the above range, the shape retention property is lowered. Therefore, when the sintering process is performed by interposing a plurality of molded bodies and interposing the powder between the molded bodies as described later, the effect of the bed powder is obtained. There is a risk that it will not be fully utilized. On the other hand, if the density of the green body exceeds the above range, the degree of orientation of the green body may be reduced, and the residual magnetic flux density Br of the magnet after the sintering process may be reduced.

  Next, the compact is sintered in a sintering step to form a rare earth magnet (neodymium iron boron magnet). In the present invention, the floor plate 1 for sintering a rare earth magnet using a carbon fiber reinforced carbon composite as a constituent material is used as the floor plate with which the molded body 2 is in direct contact. The base plate 1 for sintering a rare earth magnet is placed on the mounting surface, and is placed on, for example, the bottom surface of a sintered case made of Fe, Ni, Mo, Ta, W, or an alloy material thereof. For example, it may be arranged in the sintering furnace in a state of being accommodated in the sintering case.

  Moreover, in order to perform an efficient sintering process, a sintering process may be performed in the state which the molded object 2 piled up. For example, as shown in FIG. 3, the molded body 2 may be subjected to a sintering process in a plurality of stages, for example, four stages. In this case, for the purpose of preventing the molded bodies 2 from being welded to each other, the spread powder 5 is spread on the molded bodies 2 and then the molded bodies 2 are further stacked, so that the spread powder 5 is placed between the molded bodies 2. It is preferable to be in a state of intervening. For example, iron powder or metal oxide powder can be used as the bed powder 5.

  Moreover, the molded body 2 may be stacked through a plate material made of a carbon fiber reinforced carbon composite material instead of the floor powder 5, and the sintering process may be performed. Since the carbon fiber reinforced carbon composite material is a very light material, the weight load applied to the molded body 2 can be minimized by using the carbon fiber reinforced carbon composite material.

  In the sintering step, for example, the molded body 2 in the state shown in FIGS. 1 to 3 is placed in a sintering furnace and the molded body is sintered. Although it is necessary to adjust sintering temperature according to various conditions, such as a composition, a grinding | pulverization method, a difference in a particle size and a particle size distribution, for example, it sinters at 1000 to 1300 degreeC for about 1 to 10 hours. The atmosphere during the sintering process is a vacuum or an inert gas atmosphere (such as an argon gas atmosphere).

  After the sintering treatment, the obtained sintered body is preferably subjected to an aging treatment. This aging treatment is an important step in controlling the coercive force Hcj of the obtained rare earth magnet, and is performed, for example, in a vacuum or in an inert gas atmosphere. As the aging treatment, a two-stage aging treatment is preferable. The second stage aging treatment is held at a temperature of about 800 ° C. for 1 hour to 3 hours in the first stage aging treatment process, and is kept at a temperature of about 600 ° C. for 1 hour to 3 hours in the second stage aging treatment process. You can do it. Since the coercive force Hcj is greatly increased by heat treatment at around 600 ° C., when the aging treatment is performed in one stage, it is preferable to perform the aging treatment at around 600 ° C.

  After the sintering process, a machining process and a film forming process are performed to complete a product. The machining process is a process of mechanically processing into a desired shape. The film forming step is a step performed for the purpose of suppressing oxidation of the obtained rare earth magnet, and is a step of forming, for example, a plating film or a resin film on the surface of the rare earth magnet.

  As described above, according to the present invention, since the carbon fiber reinforced carbon composite material is used as the constituent material of the rare earth magnet sintering base plate 1, for example, a base plate made of other carbon such as graphite is used alone. Compared to the case, welding of the molded body (sintered body) 2 to the floor plate in the sintering process is suppressed, and the yield of the rare earth magnet can be increased. Further, the decrease in the magnetic properties of the compact (sintered body) 2 during the sintering treatment is small, and a rare earth magnet exhibiting high magnetic properties can be produced. In addition, the carbide | carbonized_material etc. which are formed in the sintered compact (molded object) 2 surface by reaction with the baseplate 1 for rare earth magnet sintering can be easily removed by, for example, a machining process after the sintering process, and influence on the magnetic properties. There is almost no.

  Moreover, since the base plate 1 for sintering a rare earth magnet using a carbon fiber reinforced carbon composite material has high strength, breakage during use is prevented, and the manufacturing cost of the rare earth magnet can be reduced. In addition, since it can be thinned while maintaining high strength, for example, the molded body 2 is placed on the thinned rare earth magnet sintering base plate 1 and the rare earth magnet sintering base plate 1 and the molded body 2 are sintered. When the sintering process is performed in the state of being accommodated in the binding case, the substantial volume of the sintering case is relatively increased as compared with the case where a conventional thick base plate is used. Therefore, since the capacity of the compact in the sintered case can be greatly increased, the production efficiency of the rare earth magnet can be improved.

  Furthermore, in the sintering process when mass-producing rare earth magnets, for example, in order to increase production efficiency, a plurality of sintering cases each having a rare earth magnet sintering base plate 1 are arranged in a sintering furnace and simultaneously sintered. However, since the weight of the molded body 2 that can be placed in the sintering furnace can be relatively increased by reducing the weight of the base plate 1 for sintering a rare earth magnet, the production efficiency can be improved. .

  Furthermore, by forming the zirconium oxide film 4 by, for example, thermal spraying on the molded body mounting surface of the base plate 1 for sintering the rare earth magnet, the adverse effect such as carbonization of the molded body (sintered body) 2 is reliably suppressed, and the rare earth magnet It is possible to further suppress the deterioration of the magnetic properties. By forming the zirconium oxide film 4 by thermal spraying on the molding surface, it is possible to enhance the effect of preventing the welding of the molding (sintered body) 2.

  In the present embodiment, the case where the base plate for rare earth magnet sintering of the present invention is used when the molded body is sintered in the sintering process has been described as an example. The base plate for rare earth magnet sintering of the present invention may be used when aging the green body (sintered body).

  Hereinafter, specific examples to which the present invention is applied will be described based on experimental results. In addition, this invention is not limited to description of a following example.

<Sample 1>
A plate made of a carbon fiber reinforced carbon composite material of 300 mm × 200 mm × 1 mm was placed inside the molybdenum sintering case as a floor plate. The formed body (50 mm × 30 mm × 15 mm) was directly placed on the floor plate made of the carbon fiber reinforced carbon composite material so that the surface of 50 mm × 30 mm was in contact with the floor plate without spraying the floor powder. Twenty-five compacts were placed. This case for sintering was placed in a sintering furnace, subjected to sintering treatment at 1100 ° C. for 2 hours, and subsequently subjected to aging treatment at 600 ° C. for 1 hour. When the sintered body was taken out after the sintering treatment, welding between the sintered body and the floor plate did not occur, and a good sintered body could be obtained.

<Sample 2>
Except that a 300 mm × 200 mm × 1 mm carbon fiber reinforced carbon composite material was sprayed with ZrO ₂ (zirconium oxide) so as to have an average film thickness of 15 μm, and this was used as a floor plate, the same as in Example 1. Sintering was performed. When the sintered body was taken out after the sintering treatment, welding between the sintered body and the floor plate did not occur, and a good sintered body could be obtained. Further, the sintering process was repeated 20 times using this flooring plate, but no deformation or damage (peeling of sprayed zirconium oxide, etc.) was found on the flooring plate.

<Sample 3>
Example 2 except that Y ₂ O ₃ (yttrium oxide) was sprayed on a plate made of a carbon fiber reinforced carbon composite of 300 mm × 200 mm × 1 mm so that the average film thickness was 15 μm, and this was used as a floor plate. Sintering was performed in the same manner. When the sintered body was taken out after sintering, welding between the sintered body and the base plate did not occur, and a good sintered body could be obtained. However, when repeated sintering was performed 20 times using this flooring, a portion where the yttrium oxide film was partially peeled and the carbon fiber reinforced carbon composite material was exposed was observed.

<Sample 4>
A sintering process was performed in the same manner as in Example 1 except that ZrO ₂ (zirconium oxide) was sprayed on a 300 mm × 200 mm × 1 mm molybdenum plate so that the average film thickness was 15 μm, and this was used as a floor plate. It was. When the sintered body was taken out after sintering, no welding occurred between the sintered body and the bottom plate, but because the thermal expansion coefficient of the thermal spray coating and molybdenum differed, Warpage of 1.5 mm occurred.

<Sample 5>
Sintering was performed in the same manner as in Example 1 except that a 300 mm × 200 mm × 1 mm molybdenum plate (no thermal spraying) was used as a floor plate. Since the sintered body and the base plate were welded after the sintering treatment, a step of separating them (core peeling step by impact) was required. In addition, the sintered body was chipped by the impact applied in the separation step, resulting in a decrease in yield.

<Sample 6>
A plate made of 300 mm × 200 mm × 1 mm molybdenum (not sprayed) is used as a floor plate, and 150 particles / cm of ZrO ₂ particles (average particle size 120 μm) having a particle size distribution of 80 μm to 200 μm as a floor powder for preventing welding. ^A sintering process was performed in the same manner as in Example 1 except that the powder was spread on the floor plate so as to be ² . When the sintered body was taken out after the sintering treatment, welding between the sintered body and the floor plate did not occur, but ZrO ₂ sprayed as the bed powder adhered to the surface of the sintered body to remove it. Shot blasting is required.

  When Sample 1 and Sample 6 were examined for the amount of carbon on the surface of the sintered body, the results shown in Table 1 below were obtained. By grinding the surface layer of the sintered body in sample 1, a carbon content equivalent to the case where no carbon fiber reinforced carbon composite material was used was realized, and no decrease in magnetic properties was observed.

It is an example of the base plate for rare earth magnet sintering to which the present invention is applied, and is a schematic view showing a state where a molded body is placed. It is another example of the base plate for rare earth magnet sintering to which the present invention is applied, and is a schematic view showing a state where a molded body is placed. It is a schematic diagram which shows the state which laminated | stacked the molded object in multiple steps.

Explanation of symbols

1 Rare earth magnet sintering base plate, 2 molded body, 3 base plate body, 4 zirconium oxide film, 5 base powder

Claims (5)

Used for mounting the molded body in the sintering process of the molded body of the magnet raw material powder containing a rare earth element, oxide together made up of carbon fiber reinforced carbon composite material, the surface for placing the green body Zirconium film is formed,
A base plate for sintering a rare earth magnet , wherein the zirconium oxide film is obtained by spraying zirconium oxide . 2. The rare earth magnet sintering base plate according to claim 1, wherein the zirconium oxide film has a thickness of 5 μm to 30 μm. A method for producing a rare earth magnet having a sintering step of a compact of magnet raw material powder containing rare earth elements, wherein, in the sintering step, the rare earth magnet sintering base plate made of a carbon fiber reinforced carbon composite material is used. It is characterized by placing a molded body ,
Furthermore, a zirconium oxide film is formed on the surface on which the molded body of the base plate for sintering the rare earth magnet is placed,
A method for producing a rare earth magnet, wherein the zirconium oxide film is obtained by spraying zirconium oxide . 4. The method for producing a rare earth magnet according to claim 3, wherein the zirconium oxide film has a thickness of 5 to 30 [mu] m. The method for producing a rare earth magnet according to claim 3 or 4, wherein the sintering process in the sintering step is performed at 1000 ° C to 1300 ° C.

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