JP2013194260A - Method of producing rare earth sintered magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing a rare earth sintered magnet capable of reducing warping deformation of a molded body caused by sintering compared to the conventional technology without complicating a device configuration of a sintering furnace.SOLUTION: A rare earth magnet material molded body 5 is arranged in an inner part simply enclosed by sandwiching a spacer 4 by a bottom part sintering plate 2a and an upper part sintering plate 2b, and is sintered, and is liquefied at a temperature of 800°C or more, and especially neodymium (Nd) seeps to a front layer, and gasified neodymium stays in a space contacting with a surface of the rare earth magnet material molded body 5. Accordingly, a total amount of the gasified neodymium is reduced. A predetermined space is provided between the upper part sintering plate 2b and the rare earth magnet material molded body 5, and a mesh 3 is disposed under the rare earth magnet material molded body 5, and therefore, almost a same amount of neodymium is gasified from both of an upper surface and a lower surface of the rare earth magnet material molded body 5, and density difference between an upper part and a lower part (the front and back) of the rare earth magnet material molded body 5 is reduced, and warping deformation in a sintering process is suppressed.

Description

  The present invention relates to a method for producing a rare earth sintered magnet containing a rare earth element such as neodymium.

  For example, when a rare earth sintered magnet of R-Fe-B system (R is a rare earth element including Y) is sintered, a rare earth magnet material compact is usually placed in a sintered case, and an inert atmosphere is provided. Alternatively, the sintering case is placed in a vacuum sintering furnace and sintered. Sintering refers to a phenomenon in which solid powder is molded and heated at a temperature lower than the melting point to solidify into an object called a sintered body. The density shrinks and the density of the whole object increases. There are various types of sintering such as solid phase sintering, liquid phase sintering, and vapor phase sintering, but here, liquid phase sintering will be dealt with.

  As the material of the sintered case, titanium (Ti) or zirconium (Zr) is used in the hope of an effect as a carbon getter agent (Patent Document 1), or heat is expected in an effect as an oxygen getter agent. It is known to use molybdenum (Mo) because it has excellent conductivity and does not cause recrystallization at the sintering temperature of the rare earth magnet (Patent Document 2). Also, it is possible to improve the loading efficiency by arranging a plurality of compacts in the sintered case, or by stacking flat shaped compacts in the sintered case as shown in FIG. It has been broken.

  Patent Document 1 discloses a method for producing a rare earth alloy sintered body characterized in that a compact obtained by compression molding rare earth alloy powder is sintered in a sintering furnace in a state where it is placed in a metal container serving as a carbon getter agent. Therefore, it is disclosed that the metal used as a carbon getter agent for preventing deformation and cracking is Ti, Zr, Ta, Nb.

  Patent Document 2 has a configuration in which a flow path is formed by a molybdenum (Mo) getter spacer between a container main body and a lid body in order to suppress generation of a nest after sintering a molded body. As a result of the temperature rise of the molded body housed in the sintering container, the hydrogenated hydrogenated gas and the atmosphere in the sintering container flow out of the sintering container through the flow path. I am doing so. Further, it is disclosed that the getter spacer is an oxidation getter, and even when oxygen enters the sintering container, the getter spacer is oxidized to prevent the molded body from being oxidized. .

  Patent Document 3 is a sintering case used for sintering rare earth magnets, and includes a main body frame having an opening and a door for opening and closing the opening, and a sintered plate on which the rare earth magnet is placed Is inserted into the main body by sliding horizontally on a rod attached to the main body.

  Patent Document 4 can effectively suppress warpage that occurs during sintering of a sintered compact target, particularly a ceramic target, even in a region where the sintering temperature exceeds 1400 ° C., and can correct the generated warpage. Further, as a sintering method capable of improving the production yield and a method and apparatus for correcting the sintered body, it suppresses the occurrence of warping characterized by rotating the sintered body to generate centrifugal force and sintering. A sintering method is disclosed.

Japanese Patent Laid-Open No. 5-171217 JP-A-2005-050915 JP 2000-315611 A JP 2003-238258 A

  For example, when a rectangular shaped compact is sintered, the center is deformed into a concave shape. Furthermore, in a thin flat plate molded body, it is deformed into a bow shape. For this reason, it is processed into the designed dimension by grind | polishing the molded object after sintering, accept | permitting curvature deformation. In addition, let the thin plate molded object said here be a molded object which has thickness within about 5 mm. If warping deformation during sintering is large, the amount of polishing after sintering becomes large, and it is necessary to design a molded body thickness dimension that estimates this, resulting in problems such as increased material loss and high costs. In the case of a thin flat plate molded body, the effect of preventing warpage by the getter agent as in Patent Documents 1 and 2 is small, and in particular, the uppermost molded body is particularly greatly deformed when stacked in multiple stages to improve the loading efficiency. Even if the warp deformation can be eliminated by the technique as in Patent Document 4, the apparatus configuration including the furnace is greatly complicated.

  The present invention has been made in view of such a situation, and the object of the present invention is to reduce warping deformation of a molded body due to sintering as compared with the conventional case without complicating the apparatus configuration such as a sintering furnace. An object of the present invention is to provide a method for producing a rare earth sintered magnet.

One embodiment of the present invention is a method for producing a rare earth sintered magnet. This method
A bottom sintered plate, a mesh placed on the bottom sintered plate, a rare earth magnet material molded body placed on the mesh, a spacer disposed on the bottom sintered plate, and the spacer And a step of sintering the rare earth magnet material compact using a stacking form that is supported by the upper sintered plate and covers the rare earth magnet material compact over the space.

  The distance between the upper surface of the rare earth magnet material molded body and the lower surface of the upper sintered plate may be 3 mm or less.

  A space may be provided between the lower surface of the rare earth magnet material compact and the upper surface of the bottom sintered plate by the mesh.

  The rare earth magnet material compact may be sintered at a sintering temperature of 800 ° C. to 1200 ° C.

  The rare earth magnet material molded body may be sintered under a reduced pressure or vacuum atmosphere of 50 kPa or less.

  A plurality of stacked layers may be stacked, and an upper sintered plate of a certain layer may be used as a bottom sintered plate of an upper layer.

  The rare earth magnet material molded body may be made of an R—Fe—B (R is a rare earth element including Y) rare earth magnet material.

  The rare earth magnet material molded body may be a thin flat plate shape or a tile shape.

  The laminated form may include a mesh placed on the rare earth magnet material molded body.

  It should be noted that any combination of the above-described constituent elements, and those obtained by converting the expression of the present invention between methods and systems are also effective as aspects of the present invention.

  According to the present invention, it is possible to reduce warping deformation of a molded body due to sintering as compared with the conventional case without complicating the configuration of an apparatus such as a sintering furnace. For this reason, the grinding amount after sintering decreases, and material loss and cost can be reduced.

The disassembled perspective view of the stacking form 1 of the rare earth magnet material molded object which concerns on embodiment of this invention. Sectional drawing of the loading form 1. FIG. The schematic explanatory drawing of the generation | occurrence | production principle of the curvature deformation of the rare earth magnet material molded object 5 in a sintering process regarding a comparative example. The typical explanatory view of the principle of prevention of warp deformation of rare earth magnet material fabrication object 5 in a sintering process in an embodiment. Arrangement explanatory drawing in the case of arranging a plurality of rare earth magnet material moldings 5 in the same plane on one bottom sintered plate 2a. The exploded perspective view of the loading form 1 in case the rare earth magnet material molded object 5 is tile shape. The exploded perspective view of the loading form 1 in the case of providing the mesh 6 on the upper surface of the rare earth magnet material molded body 5. Sectional drawing of the loading form 1 in the same case. FIG. 7 is a perspective view in a case where flat plate-shaped molded bodies are stacked in a multistage manner and arranged in a sintered case (however, the lid is shown separately).

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same or equivalent component, member, etc. which are shown by each drawing, and the overlapping description is abbreviate | omitted suitably. In addition, the embodiments do not limit the invention but are exemplifications, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

  FIG. 1 is an exploded perspective view of a stacking form 1 of rare earth magnet material molded bodies according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the loading form 1. The loading form 1 is housed in a sintering case (not shown), and the rare earth magnet material molded body 5 is sintered in a sintering furnace. The sintered case may be the same as the conventional case shown in FIG. 9, and is composed of, for example, a sintered case main body with an upper part opened and a lid.

  The loading form 1 includes a bottom sintered plate 2a, an upper sintered plate 2b, a Mo mesh 3 (net plate), a spacer 4 for forming an upper space Cb described later, and a rare earth magnet material molded body 5. Prepare. The bottom sintered plate 2a and the upper sintered plate 2b are, for example, Mo plates. The rare earth magnet material molded body 5 is made of, for example, an R—Fe—B based (R is a rare earth element including Y) rare earth magnet material, and has a thin plate shape with a thickness of approximately 5 mm or less, for example. As the spacer 4, a material that hardly reacts with a rare earth and has a small thermal expansion, such as a SUS material (stainless steel), Mo, or carbon can be used.

  The Mo mesh 3 is placed on the bottom sintered plate 2 a inside the spacer 4. The rare earth magnet material molded body 5 is placed on the Mo mesh 3. The Mo mesh 3 provides a lower space Ca (a space between the lower surface of the rare earth magnet material molded body 5 and the bottom sintered plate 2a) of the rare earth magnet material molded body 5. The upper sintered plate 2b is disposed on the spacer 4 so as to close the upper opening of the spacer 4, and covers the upper portion of the rare earth magnet material molded body 5 with a space in between. In other words, the spacer 4 has a height dimension that ensures an upper space Cb of the rare earth magnet material molded body 5 (a space between the upper surface of the rare earth magnet material molded body 5 and the lower surface of the upper sintered plate 2b). . The height of the upper space Cb of the rare earth magnet material molded body 5 (distance between the upper surface of the rare earth magnet material molded body 5 and the lower surface of the upper sintered plate 2b) is, for example, 0 <Cb ≦ 3 mm.

When sintering using the laminated form 1, a plurality of stacked forms 1 are stacked, housed in a sintering case (not shown), and sintered in a reduced pressure or vacuum atmosphere of 50 kPa to 1 × 10 ⁻³ Pa. . Sintering is performed at a sintering temperature of 800 ° C. to 1200 ° C., for example. The reason for 0 <Cb is that when the stacked form 1 is stacked in a state where the rare earth magnet material molded body 5 and the upper sintered plate 2b are in contact with each other, the weight of the upper rare earth magnet material molded body 5 is reduced. This is to prevent the rare earth magnet material molded body 5 from being subjected to a larger load and sintering under a different load state for each layer. When stacking multiple layers of the loading form 1, the upper sintered plate 2b of a certain layer may also serve as the bottom sintered plate 2a of the upper layer.

  FIG. 3 is a schematic explanatory view of the principle of occurrence of warp deformation of the rare earth magnet material molded body 5 during the sintering process, regarding the comparative example. Here, a case where R is neodymium (Nd) will be described as an example. This comparative example corresponds to a case where the rare earth magnet material molded body 5 is sintered without providing the upper sintered plate 2b and the Mo mesh 3 described above. In the process of sintering the rare earth sintered magnet, the rare earth vaporizes and evaporates in the process where the rare earth is liquid phased and sintered at a temperature of 800 ° C. or higher. When a part of the rare earth in the composition of the compact is vaporized and evaporated, a density difference occurs inside the compact during sintering, which causes warpage and deformation of the rare earth magnet material compact 5. That is, sintering is promoted in the dense part and the volume thereof is reduced, but the sparse part is not promoted in sintering and the volume change is small. Within a single substance, a volume-reduced part and a part with little change coexist, leading to the occurrence of warping and deformation.

  FIG. 4 is a schematic explanatory diagram of the principle of preventing warp deformation of the rare earth magnet material molded body 5 during the sintering process in the present embodiment. In the present embodiment, since the rare earth magnet material molded body 5 is disposed inside the bottom sintered plate 2a and the upper sintered plate 2b, the rare earth magnet material molded body liquidized at 800 ° C. or higher. 5, especially neodymium (Nd) oozes out to the surface layer, and the vaporized and evaporated neodymium (Nd) stays in the space in contact with the surface of the rare earth magnet material molded body 5. For this reason, if the space is saturated in a vaporizing atmosphere such as neodymium (Nd), further vaporization of neodymium (Nd) is eliminated. That is, the total amount of neodymium (Nd) to be vaporized is smaller than that in the comparative example shown in FIG. Further, a predetermined space (0 <Cb ≦ 3 mm) is provided between the upper sintered plate 2b and the rare earth magnet material molded body 5, and the mesh 3 is installed below the rare earth magnet material molded body 5, thereby forming the rare earth material molded body. Since the lower space Ca is provided between the lower sintered plate 5 and the lower sintered plate, the evaporation of evaporation on the upper surface of the rare earth magnet material molded body 5 is reduced while the evaporation of evaporation on the lower surface is increased. Since the amount of neodymium (Nd) is vaporized, the density difference between the upper part and the lower part (front and back) of the rare earth magnet material molded body 5 is reduced. Therefore, the warp deformation of the rare earth magnet material molded body 5 during the sintering process can be reduced as compared with the case where the upper sintered plate 2b and the Mo mesh 3 are not provided (FIG. 3). Further, it is not necessary to complicate the apparatus configuration such as a sintering furnace in order to reduce warping deformation. As described above, in the present embodiment, a vaporizing atmosphere such as neodymium (Nd) is created around the rare earth magnet material molded body 5 during the sintering process so as not to cause density in the structure of the rare earth magnet material molded body 5. By doing so, warp deformation of the rare earth magnet material molded body 5 can be suppressed and sintered.

  In the above description, an example is shown in which one rare-earth magnet material molded body 5 to be sintered is provided on one bottom sintered plate 2a, but the present invention is not limited to this. A plurality of rare earth magnet material molded bodies 5 may be arranged on the same plane on one bottom sintered plate 2a (see FIG. 5).

  A 3 mm-thick thin plate-shaped rare earth magnet material molded body 5 (length 60 × width 30 mm) made of Nd—Fe—B rare earth magnet material is prepared, and Mo mesh 3 is formed on the bottom sintered plate 2a (Mo plate). The lower space Ca was created by placing the rare earth magnet material molded body 5 thereon as a base plate. The Mo mesh 3 used was # 24, linear 0.35 mm. Further, a cover was formed with the upper sintered plate 2b (Mo plate) using the spacer 4 so that the upper space Cb of the molded body was 0.2 mm. Mo plates were used for the bottom sintered plate 2a and the upper sintered plate 2b. This stacking form 1 is stacked in multiple layers (here, 18 sheets per stage, 6 stages, a total of 108 molded bodies), housed in a sintering case and sintered, and the amount of warping deformation of the obtained sintered magnet is determined. Measured and evaluated. The amount of warp deformation was 0.08 mm to 0.15 mm.

  A sintered magnet was produced in the same manner as in Example 1 except that the upper space Cb was changed to 3 mm. The amount of warp deformation was 0.08 mm to 0.15 mm.

  A 1 mm-thick thin plate-shaped rare earth magnet material molded body 5 (length 50 × width 10 mm) made of Nd—Fe—B rare earth magnet material is prepared, and the number of molded bodies is 8 in 2 stages, Sintered magnets were produced in the same manner as in Example 1 except that the total number was 16 (the height of the spacer 4 is lower than that in Example 1 in order to make the upper space Cb 0.2 mm). The amount of warpage deformation was less than 0.05 mm.

(Comparative Example 1)
It was produced in the same manner as in Example 1 except that the upper space was opened (without the upper sintered plate 2b) and the number of formed bodies was three in the same plane. At this time, the distance between the upper surface of the molded body and the lid of the sintered case was about 5 cm. The amount of warp deformation was 0.20 to 0.40 mm.

(Comparative Example 2)
A 3 mm-thick thin plate-shaped rare earth magnet material molded body (length 60 × 30 mm) made of an Nd—Fe—B rare earth magnet material was prepared, and a stacking method (upper sintered plate 2b and Sintered with no Mo mesh 3). Specifically, spread powder for preventing adhesion was sprayed on the sintered plate, and the molded bodies were stacked in four stages at 24 sheets per stage. At that time, a covering powder for preventing adhesion was also sprayed on the surfaces where the compacts were in contact with each other. A Mo plate was used as the sintered plate. This loaded form is stored in a sintered case (the distance between the upper surface of the uppermost molded body and the lid of the sintered case is about 2 cm) and sintered, and the amount of warp deformation of the obtained sintered magnet is determined. Measured and evaluated. The amount of warp deformation was 0.15 to 0.5 mm.

  Examples 1 and 2 of the present invention can increase the warpage suppressing effect by about 60% compared to Comparative Example 1 and about 45-70% compared to Comparative Example 2, and reduce the amount of polishing after sintering. Therefore, material loss is reduced, leading to cost reduction. As is clear from Example 3, the amount of warpage deformation is small in the case of a 1 mm thin molded body, and the same effect can be obtained.

  The present invention has been described above by taking the embodiment as an example, but it will be understood by those skilled in the art that various modifications can be made to each component and each processing process of the embodiment within the scope of the claims. It is a place. Hereinafter, modifications will be described.

  The rare earth magnet material molded body 5 may have a tile shape or other shapes as well as a thin flat plate shape. FIG. 6 is an exploded perspective view of the stacking form 1 when the rare earth magnet material molded body 5 has a tile shape. In the laminated form 1 shown in this figure, the upper surface of the bottom sintered plate 2a and the Mo mesh 3 are curved in accordance with the curved shape of the rare earth magnet material molded body 5, and the spacer 4 is compared with that shown in FIG. It differs in that it is placed on a flat surface portion of the upper surface of the bottom sintered plate 2a that is not curved, and is identical in other points.

  The rare earth magnet material molded body 5 may be an R—Fe—B system other than the Nd—Fe—B system, or a rare earth magnet material other than the R—Fe—B system.

  Instead of the Mo mesh 3, another material that hardly reacts with the rare earth, for example, a mesh made of SUS material or carbon may be used.

  The spacer 4 may have an integral shape, or may have a columnar shape such as a cylinder. The spacer 4 may be disposed directly on the bottom sintered plate 2a, or may be disposed on the bottom sintered plate 2a with the Mo mesh 3 interposed therebetween. Further, the bottom sintered plate 2a and the spacer 4 may be integrated.

  As shown in FIGS. 7 and 8, in the stacking mode 1, a mesh 6 made of Mo, SUS, or carbon may be provided on the upper surface of the rare earth magnet material molded body 5. In this case, the conditions for vaporization and evaporation of the rare earth and the like on the upper surface and the lower surface of the rare earth magnet material molded body 5 are closer, and the difference in the amount of vaporization evaporation from the upper and lower surfaces during sintering is further reduced. This is advantageous for preventing warpage deformation of the molded body 5.

1 Loading Form 2a Bottom Sintered Plate 2b Upper Sintered Plate 3 Mo Mesh 4 Spacer 5 Rare Earth Magnet Material Molded Body Ca Lower Space Cb Upper Space

Claims (9)

  A bottom sintered plate, a mesh placed on the bottom sintered plate, a rare earth magnet material molded body placed on the mesh, a spacer disposed on the bottom sintered plate, and the spacer A rare earth sintered magnet having a step of sintering the rare earth magnet material molded body using a loading form including an upper sintered plate that is supported by and covers an upper portion of the rare earth magnet material molded body with a space interposed therebetween. Production method.   The method for producing a rare earth sintered magnet according to claim 1, wherein the distance between the upper surface of the rare earth magnet material compact and the lower surface of the upper sintered plate is 3 mm or less.   The method for producing a rare earth sintered magnet according to claim 1 or 2, wherein a space is provided between the lower surface of the rare earth magnet material molded body and the upper surface of the bottom sintered plate by the mesh.   The method for producing a rare earth sintered magnet according to any one of claims 1 to 3, wherein the rare earth magnet material compact is sintered at a sintering temperature of 800 ° C to 1200 ° C.   The method for producing a rare earth sintered magnet according to any one of claims 1 to 4, wherein the rare earth magnet material molded body is sintered in a reduced pressure or vacuum atmosphere of 50 kPa or less.   The method for producing a rare earth sintered magnet according to any one of claims 1 to 5, wherein the stacking form is a stack of a plurality of layers, and an upper sintered plate of a certain layer is also used as a bottom sintered plate of an upper layer. .   The method for producing a rare earth sintered magnet according to any one of claims 1 to 6, wherein the rare earth magnet material molded body is made of an R-Fe-B-based (R is a rare earth element including Y) rare earth magnet material.   The method for producing a rare earth sintered magnet according to any one of claims 1 to 7, wherein the rare earth magnet material molded body is a thin flat plate shape or a tile shape.   The method for producing a rare earth sintered magnet according to any one of claims 1 to 8, wherein the laminated form includes a mesh placed on the rare earth magnet material molded body.