JP4835758B2 - Rare earth magnet manufacturing method - Google Patents

Abstract

A method of producing a rare-earth magnet containing a rare-earth compound having a first rare-earth element and a second rare-earth element different from the first rare-earth element includes: a mixing step of mixing rare-earth compound powder including the first rare-earth element and subjected to a process based on hydrogenation disproportionation desorption recombination with a diffusion material including the second rare-earth element; a molding step of molding the mixed powder into a compact in a magnetic field; and a heating step of heating the compact to diffuse the second rare-earth element into the rare-earth compound powder.

Description

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

  A rare earth bonded magnet is known as an embodiment of a rare earth magnet containing a rare earth element. Such rare earth bonded magnets are used in various devices such as motors because they have excellent magnetic properties and can easily cope with complex shapes. Recently, various devices have been reduced in size and increased in efficiency, and accordingly, further improvement in magnetic properties of rare earth bonded magnets is required.

  As a method for producing a rare earth bonded magnet, the following method has been proposed. First, a magnetic powder produced by the HDDR method (hydrocracking / dehydrogenation recombination method) is mixed with a diffusing powder containing a rare earth element such as Tb or Dy and subjected to a diffusion heat treatment so that the rare earth element becomes a surface of the magnetic powder And an anisotropic magnet powder diffused inside is prepared. And this rare earth magnet magnet is knead | mixed with resin, a coupling agent, a lubricant, etc., and a rare earth bond magnet is produced (refer to patent documents 1). In this rare earth bonded magnet manufacturing method, since the anisotropic magnet powder in which rare earth elements such as Tb and Dy are diffused is used, the coercive force and the like can be improved.

Japanese Patent No. 3452254

  However, in the method for producing a rare earth bonded magnet of Patent Document 1 described above, the diffusion state of the rare earth element in the magnet powder is likely to be uneven, and the coercive force and squareness ratio of the obtained rare earth bonded magnet are not so high. Moreover, since it is necessary to heat a magnetic powder at about 700-1000 degreeC at the time of the above-mentioned diffusion heat processing, it exists in the tendency for magnet powder to fuse | melt and form a lump. For this reason, in the method for producing a rare earth bonded magnet as described above, even if magnetic powder having magnetic anisotropy is used, the orientation of each magnetic powder contained in the finally obtained rare earth bonded magnet is disturbed, Magnetic properties such as the squareness ratio will deteriorate.

  This invention is made | formed in view of the said situation, and it aims at providing the manufacturing method of the rare earth magnet which can manufacture the rare earth magnet which has the magnetic characteristics which were fully excellent.

In the present invention, in order to achieve the above object, the rare earth compound powder subjected to the hydrocracking / dehydrogenation recombination method containing the first rare earth element, and the second rare earth element different from the first rare earth element are used. A mixing step of preparing a mixed powder by mixing a diffusing material containing an element; a forming step of forming a mixed powder by forming the mixed powder in a magnetic field; and heating the molded body to convert the second rare earth element into a rare earth compound powder and it possesses a heating step of diffusing, to, the diffusing material, a halide of a second rare-earth element, a hydride of the second rare-earth element, a compound of the second rare earth element and Fe, or the second rare earth Provided is a method for producing a rare earth magnet containing a rare earth compound having a first rare earth element and a second rare earth element, which contains a compound of an element, Fe, and Co.

  According to this manufacturing method, since the rare earth compound powder and the diffusing material are heated in close contact with each other, compared to the case where the diffusion treatment is performed on the mixture of the rare earth compound and the diffusing material mixed in the powder state, The contained second rare earth element can be uniformly diffused in the outer peripheral portion of the rare earth compound particles. For this reason, the rare earth magnet excellent in coercive force (HcJ) and squareness ratio can be manufactured.

  In addition, since the molded body is formed by performing molding in a magnetic field before the heating step, it is possible to perform magnetic field orientation in a state where the magnetic powders are not fused. For this reason, the diffusion treatment is performed in a state in which the orientation of the particles of the rare earth compound powder subjected to the treatment by the hydrocracking / dehydrogenation recombination method is sufficiently enhanced. Therefore, a rare earth magnet having a high degree of orientation and excellent residual magnetic flux density (Br) can be manufactured.

  The production method of the present invention preferably includes an impregnation step of obtaining a rare earth bonded magnet by impregnating a molded body with a resin and curing the resin after the heating step. The rare earth bonded magnet obtained by such a manufacturing method is manufactured using a molded body having a high degree of orientation as described above and in which a diffusing material is uniformly diffused, and thus has excellent magnetic properties. In addition, since the resin is impregnated after forming the molded body, the orientation of the rare earth compound powder (HDDR powder) having magnetic anisotropy is higher than when the resin is mixed before manufacturing the molded body. A rare earth bonded magnet having a high degree of orientation and sufficiently excellent magnetic properties can be obtained without being damaged. Further, according to this method, the change in size before and after the resin curing, that is, the shrinkage can be sufficiently reduced. For this reason, a rare earth bonded magnet with high dimensional accuracy can be manufactured.

  In the production method of the present invention, after the heating step, a pulverizing step of pulverizing a compact to prepare a pulverized powder, a mixture of the pulverized powder and a resin is molded in a magnetic field, the resin is cured, and a rare earth bonded magnet is obtained. And obtaining a magnet. In this manufacturing method, since the mixture of the pulverized powder and the resin is molded in a magnetic field, a rare earth bonded magnet having a complicated shape can be easily produced.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the rare earth magnet which can manufacture the rare earth magnet which has the magnetic characteristics which were fully excellent can be provided.

It is a perspective view of the rare earth bonded magnet obtained by the manufacturing method of the rare earth magnet concerning one embodiment of the present invention. It is a figure which shows the magnetic hysteresis loop of the rare earth bond magnet obtained by the manufacturing method of the rare earth magnet which concerns on one Embodiment of this invention.

  In the following, preferred embodiments of the present invention will be described with reference to the drawings as the case may be.

  The manufacturing method of the rare earth magnet of the present embodiment includes an HDDR processing step of preparing a rare earth compound powder by subjecting a raw material compound containing the first rare earth element to a hydrocracking / dehydrogenation recombination method, Mixing a preparation step for preparing a diffusing material containing a rare earth element, a rare earth compound powder subjected to hydrocracking / dehydrogenation recombination containing a first rare earth element, and a diffusing material containing a second rare earth element Then, a mixing step for preparing the mixed powder, a molding step for molding the mixed powder in a magnetic field to produce a compact, and heating the compact to diffuse the second rare earth element to the outer periphery of the rare earth compound powder A heating step and an impregnation step of obtaining a rare-earth bonded magnet by impregnating the molded body with resin and curing the resin. Details of each step will be described below.

  In the HDDR processing step, first, a raw material compound containing a first rare earth element is prepared. As the raw material compound, a compound or alloy obtained by a normal casting method such as a strip casting method, a book mold method, or a centrifugal casting method can be used. Further, a homogenization heat treatment may be performed. The raw material compound may contain an inevitable impurity derived from the raw material metal or the raw material compound or the production process.

  Any rare earth element may be used as the first rare earth element, preferably a light rare earth element, more preferably Nd and / or Pr.

  Note that in this specification, rare earth elements refer to scandium (Sc), yttrium (Y), and lanthanoid elements belonging to Group 3 of the long-period periodic table. Examples of lanthanoid elements include lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy). ), Holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu) and the like. The rare earth elements can be classified into light rare earth elements and heavy rare earth elements. In the present specification, “heavy rare earth element” refers to Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and “light rare earth element” refers to Sc, Y, La, Ce, Pr, Nd, Sm, Eu.

  As a suitable composition of the raw material compound, an R—Fe—B-based material containing at least one of Nd and Pr as a rare earth element, 0.5 to 4.5% by mass of B, and the balance being Fe and inevitable impurities. What has a composition is mentioned. The raw material compound may further contain other elements such as Co, Ni, Mn, Al, Cu, Nb, Zr, Ti, W, Mo, V, Ga, Zn, and Si as necessary.

  After preparing the raw material compound which has the above-mentioned composition, the processing by HDDR method is performed. The HDDR method is a process of sequentially executing hydrogenation, disproportionation, dehydrogenation, and recombination. Details of the HDDR processing will be described below.

  First, the homogenization heat processing which hold | maintains a raw material compound for 5 to 48 hours at the temperature of 1000-1200 degreeC in reduced pressure atmosphere (1 kPa or less) or inert gas atmosphere, such as argon and nitrogen.

  The homogenized raw material compound is preferably pulverized using a pulverizing means such as a stamp mill or a jaw crusher and then sieved. Thereby, a powdery raw material compound having a particle size of 10 mm or less can be prepared.

  In the hydrogen storage step, the powdery raw material compound is held in a hydrogen atmosphere having a hydrogen partial pressure of 100 to 300 kPa at a temperature of 100 to 200 ° C. for 0.5 to 2 hours. Thereby, hydrogen is occluded in the crystal lattice of the raw material compound.

  Next, the raw material compound in which hydrogen is occluded is hydrocracked by holding it at a predetermined temperature in a hydrogen atmosphere to obtain a decomposition product. The hydrogen partial pressure during hydrocracking is preferably 10 to 100 kPa, and the temperature is preferably 700 to 850 ° C. By performing hydrogenolysis under such conditions, it is possible to obtain a rare earth compound powder comprising particles having magnetic anisotropy.

The decomposition product obtained by hydrocracking includes a hydride such as RH _x and an iron compound such as α-Fe and Fe ₂ B. The decomposition products at this stage form a fine matrix of the order of 100 nm.

  Subsequently, by reducing the hydrogen partial pressure, hydrogen is released from the decomposition product to obtain an anisotropic rare earth compound powder containing the first rare earth element. This rare earth compound powder has a composition equivalent to that of the above-mentioned raw material compound. The particle size of the rare earth compound powder is preferably 350 μm or less, more preferably 250 μm or less, and even more preferably 212 μm or less. Although there is no restriction | limiting in particular in the minimum of the particle size of rare earth compound powder, For example, it is preferable to set it as 1 micrometer or more practically.

  The rare earth compound powder obtained by the HDDR treatment described above may be further pulverized using a fine pulverizer such as a jet mill, a ball mill, a vibration mill, or a wet attritor. Since the rare earth compound powder subjected to HDDR treatment has a small crystal grain size and is anisotropic, a rare earth magnet having a sufficiently high density and excellent magnetic properties can be easily obtained.

  In the preparation step, a powdery diffusion material containing the second rare earth element is prepared. The second rare earth element is not particularly limited as long as it is an element different from the first rare earth element. However, from the viewpoint of obtaining a rare earth magnet having a higher coercive force, the second rare earth element is preferably a heavy rare earth element, and more preferably Dy or Tb. Examples of the diffusing material include general rare earth compounds such as hydrides, oxides, halides and hydroxides of rare earth elements, and rare earth metals. Among these, from the viewpoint of further improving the magnetic properties of the rare earth magnet, it is preferable to use a heavy rare earth compound having a heavy rare earth element as a constituent element.

The heavy rare earth compound may contain an element other than the heavy rare earth metal element, and may be an alloy of the heavy rare earth metal and a metal other than the rare earth metal. The heavy rare earth compound is preferably a hydride or fluoride, more preferably a hydride, from the viewpoint of a rare earth magnet having even more excellent magnetic properties. When such a heavy rare earth compound is used, the amount of impurities remaining in the rare earth magnet can be sufficiently reduced. Further, since the hydride and fluoride are easily decomposed, the second rare earth element can be diffused sufficiently uniformly even to the rare earth compound powder obtained by the HDDR process having a fine structure. Due to these factors, a rare earth magnet having more excellent magnetic properties can be obtained. Preferred heavy rare earth compounds include DyH ₂ , DyF ₃ and TbH ₂ .

  Rare earth compounds and rare earth metals can be produced by conventional methods. A rare earth compound powder or a rare earth metal powder is prepared by a dry pulverization method using a jet mill with a rare earth compound or rare earth metal produced by an ordinary method, or a wet pulverization method using a ball mill or the like after mixing with an organic solvent. be able to.

  The average particle diameter of the diffusing material is preferably 100 nm to 30 μm, more preferably 0.5 to 10 μm, and further preferably 1 to 5 μm. If the average particle diameter of the diffusing material exceeds 30 μm, the diffusion of the second rare earth element into the rare earth compound powder becomes difficult to occur and the effect of improving the sufficiently large HcJ and squareness ratio may be impaired. On the other hand, when the average particle diameter of the diffusing material is less than 100 nm, the rare earth element tends to be oxidized. Thus, when the rare earth oxide is generated, the amount of the second rare earth element diffused into the rare earth compound containing the first rare earth element decreases, and the improvement in coercive force due to the diffusion tends to be small. In addition, the average particle diameter of the diffusing material in the present specification is a volume average particle diameter (d (50)) measured using a commercially available particle size distribution meter.

  In the mixing step, a mixed powder is prepared by mixing the rare earth compound powder containing the first rare earth element that has been subjected to HDDR treatment as described above and the diffusion material containing the second rare earth element. The mixed powder can be obtained, for example, by mixing the rare earth compound powder and the diffusing material in a predetermined mixing ratio into a container and then mixing for 1 to 30 minutes using a specs mixer. The mixing is preferably performed in an inert gas atmosphere such as argon gas from the viewpoint of suppressing the oxidation of the diffusing material and the rare earth compound powder. In addition, the mixing method is not particularly limited, and for example, a method using a V mixer, a ball mill, or a reiki machine may be used. In addition, a lubricant such as zinc stearate that becomes a molding aid during mixing may be added. In this case, the addition amount may be about 0.01 to 0.5% by mass.

  The mixing ratio of the rare earth compound powder and the diffusion material is such that the content of the diffusion material in the mixed powder is preferably 0.5 to 5% by mass, more preferably 1 to 4% by mass, and still more preferably 1.5 to 3%. The ratio should be 5% by mass. If the content is less than 0.5% by mass, the amount of diffusion of the second rare earth element tends to be small, and a sufficiently large HcJ and squareness ratio improving effect tends to be difficult to obtain. On the other hand, when the content exceeds 5% by mass, the second rare earth element diffuses into the rare earth compound powder, so that Br tends to decrease and the material cost tends to increase.

  In the molding step, the above-mentioned mixed powder is molded in a magnetic field to produce a molded body having a desired shape. Molding in a magnetic field is performed while applying a magnetic field, thereby fixing the rare earth compound powder having anisotropy oriented in a predetermined direction. The molding can be performed by, for example, compression molding using a compression molding machine such as a mechanical press or a hydraulic press. Specifically, the mixed powder can be formed into a predetermined shape by filling the mixed powder in the mold cavity and then pressing the filled powder so as to be sandwiched between the upper punch and the lower punch.

  The shape of the molded body obtained by molding is not particularly limited, and is determined according to the desired shape of the rare earth bonded magnet, such as a columnar shape, a flat plate shape, or a ring shape. The pressurization during molding in a magnetic field is preferably 580 to 1400 MPa. Moreover, it is preferable that an orientation magnetic field shall be 800-2000 kA / m. In addition, as a shaping | molding method, the wet shaping | molding which shape | molds the slurry which disperse | distributed mixed powder in solvents, such as oil other than dry shaping | molding which shape | molds mixed powder as it is as above-mentioned, can also be applied.

  In the present embodiment, the rare earth compound powder subjected to HDDR treatment is used, and the mixed powder is molded in a magnetic field without being mixed with the resin before the heat treatment for diffusion. For this reason, it is possible to sufficiently align the orientation of the rare earth compound powder having magnetic anisotropy. Therefore, it is possible to obtain a rare earth bonded magnet that is particularly excellent in residual magnetic flux density. That is, the magnetic characteristics of the highly anisotropic rare earth compound powder obtained by the HDDR process can be sufficiently exhibited.

  In the heating step, the molded body obtained by molding in a magnetic field is heated to such an extent that the second rare earth element contained in the diffusing material can be diffused to the outer periphery of the rare earth compound powder. Specifically, the compact is held under reduced pressure or in an inert gas atmosphere such as argon gas, preferably at 700 to 1100 ° C., more preferably at 700 to 950 ° C., and even more preferably at 800 to 900 ° C. for 10 minutes to 12 hours. To do. By heating under such conditions, the second rare earth element diffuses into the outer peripheral portion of the rare earth compound powder, and the inner layer rich in the first rare earth element and the outer layer rich in the second rare earth element covering the inner layer. Are formed. This makes it possible to form a rare earth bonded magnet having a sufficiently high coercive force. In addition, although there are fine cracks in the HDDR-treated rare earth compound powder, the diffusion material can enter the cracks and fill the cracks. For this reason, the oxidation resistance and strength of the finally obtained rare earth bonded magnet can be improved.

  In the heating process, if the heating temperature of the molded body is too high or the heating time is excessively long, the sintering of the rare earth compound powder proceeds, making it difficult to impregnate the molded body with the resin in the subsequent impregnation process. Tend. Moreover, phase decomposition of the anisotropic magnetic powder obtained by performing the HDDR treatment may occur, and high magnetic properties may be impaired. On the other hand, if the heating temperature of the molded body is too low or the heating time is too short, the diffusion of the second rare earth element tends not to proceed sufficiently. Therefore, it is preferable to set the heating temperature and the heating time according to the types of the first and second rare earth elements and the particle size of the rare earth compound powder.

  In the manufacturing method of the present embodiment, since the heat treatment is performed in the state of the molded body, the adhesion between the rare earth compound powder and the diffusing material is good, and the second rare earth element contained in the diffusing material is replaced with the rare earth compound powder. It becomes possible to diffuse more uniformly in the outer periphery. Therefore, a rare earth bonded magnet having a sufficiently high squareness ratio and coercive force can be obtained.

  In the impregnation step, the molded body is impregnated with a resin and heated to cure the resin, thereby obtaining a rare earth bonded magnet containing rare earth compound particles and a resin filled between the rare earth compound particles. Specifically, first, the molded body subjected to the heat treatment is immersed in a resin-containing solution prepared in advance and degassed by reducing the pressure in a sealed container so that the resin-containing solution penetrates into the voids of the molded body. Thereafter, the molded body is taken out from the resin-containing solution, and excess resin-containing solution attached to the surface of the molded body is removed. A centrifuge or the like may be used to remove excess resin-containing solution. In addition, defoaming is promoted and the amount of resin impregnation can be increased by immersing the molded body in a sealed solution before immersing in the resin-containing solution and immersing in a solvent such as toluene while maintaining a reduced pressure atmosphere. , Voids in the molded body can be reduced.

  Examples of resins contained in the resin-containing solution include thermosetting resins such as epoxy resins and phenol resins, polyamide-based elastomers such as styrene, olefin, urethane, polyester, and nylon, ionomers, and ethylene propylene copolymers. (EPM) and thermoplastic resins such as ethylene-ethyl acrylate copolymer. Among these, a thermosetting resin is preferable, and an epoxy resin or a phenol resin is more preferable.

  The resin-containing solution can be prepared by dissolving the above resin in a solvent. As the solvent, a general organic solvent such as toluene, acetone, ethyl alcohol or the like can be used. The solvent is preferably selected according to the type of resin used in order to sufficiently dissolve the resin. Although there is no restriction | limiting in particular in resin content in a resin containing solution, in order to obtain the rare earth bonded magnet with a high density and few voids, the one where the resin content is higher is preferable.

  The molded body in which the resin-containing solution is infiltrated into the voids is held at 120 to 230 ° C. for 1 to 5 hours, for example, in a constant temperature bath under a reduced pressure atmosphere (1 kPa or less) or an inert gas atmosphere such as argon gas or nitrogen gas. By doing so, the solvent contained in the resin-containing solution is evaporated and the resin is cured. Thereafter, an anisotropic rare earth bonded magnet can be obtained by performing a surface treatment as necessary.

  The resin content of the rare earth bonded magnet is preferably 0.5 to 10% by mass, more preferably 1 to 5% by mass from the viewpoint of achieving both excellent magnetic properties and excellent shape retention. This resin impregnation amount can be adjusted by changing the resin concentration in the resin-containing solution and the molding pressure at the time of molding.

  FIG. 1 is a perspective view of a rare earth bonded magnet obtained by the manufacturing method of the present embodiment. The rare earth bonded magnet 10 obtained by the manufacturing method of this embodiment contains particles having a rare earth compound as a main component and a resin filled between the particles. The rare earth compound has a first rare earth element and a second rare earth element as constituent elements. The rare earth bonded magnet 10 has a sufficiently high HcJ and squareness ratio because the second rare earth element contained in the diffusing material diffuses more uniformly than the conventional one in the outer peripheral portion of the rare earth compound particles. In addition, since anisotropic rare earth compound powder is molded in a magnetic field without being mixed with heat treatment and resin, it is possible to align the orientation of each particle of the rare earth compound as compared with the conventional one, and the degree of orientation is increased. It becomes high and can be set as the rare earth bond magnet excellent in the magnetic characteristic.

  Next, a modification of the above embodiment will be described. In the rare earth magnet manufacturing method of the present modification, a pulverizing step of preparing a pulverized powder by pulverizing a molded body formed of a rare earth compound powder in which the second rare earth element is diffused in the outer periphery, obtained in the heating step; And a magnet manufacturing step of forming a mixture of the pulverized powder and the resin in a magnetic field and curing the resin to obtain a rare earth bonded magnet.

  The manufacturing method in the present modification is the same as that in the above-described embodiment until a heating step for producing a molded body and diffusing the second rare earth element contained in the diffusing material into the rare earth compound powder.

  In the pulverization step, the compact is pulverized with a stamp mill and sieved as necessary to prepare a pulverized powder having an average particle size of 100 to 300 μm. The crushing method is not particularly limited, and a jaw crusher and various known crushing means can be used.

  In the magnet manufacturing step, first, a bonded magnet compound that is a mixture of pulverized powder and resin is prepared. Specifically, a compound for a bonded magnet can be obtained by mixing the pulverized powder and the same resin-containing solution as in the above embodiment and heating to volatilize at least part of the solvent in the resin-containing solution. . The resin content in the compound for bonded magnet is preferably 0.5 to 10% by mass, more preferably 1 to 5% by mass, and still more preferably 1 to 3% by mass.

  Next, the bonded magnet compound is molded in a magnetic field to produce a molded body. Molding in a magnetic field can be performed in the same manner as in the above embodiment. Then, the produced compact is held in a constant-temperature bath, for example, at 120 to 230 ° C. for 1 to 5 hours under a reduced pressure atmosphere (1 kPa or less) or an inert gas atmosphere such as argon gas or nitrogen gas, thereby removing the solvent. Evaporate and cure the resin. Then, the rare earth bond magnet 10 shown in FIG. 1 can be obtained by performing a surface treatment as necessary.

  In the manufacturing method of this modification, as in the above embodiment, the heat treatment is performed in the state of the compact after being molded in a magnetic field, so that the second rare earth element contained in the diffusing material is present on the outer peripheral portion of the rare earth compound powder. , Spread more uniformly than the conventional one. Therefore, a rare earth bonded magnet having a sufficiently high HcJ and squareness ratio can be obtained. In addition, since a pulverized powder containing a rare earth compound powder and a diffusion material and a resin-containing solution can be mixed and then molded, a complex-shaped rare earth bonded magnet can be easily manufactured.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment. In the said embodiment, although the rare earth bonded magnet was mentioned as a rare earth magnet, the aspect in which the resin is not impregnated may be sufficient as the rare earth magnet obtained by the manufacturing method of this invention. Examples of such rare earth magnets include those obtained by the heating process of the above embodiment.

  The content of the present invention will be described in detail below using examples and comparative examples, but the present invention is not limited to the following examples.

Example 1
[Preparation of rare earth bonded magnet]
A raw material compound having the following composition containing Nd ₂ Fe ₁₄ B as a main component was prepared by a strip casting method.

Nd: 28.0% by mass
B: 1.1% by mass
Ga: 0.35 mass%
Nb: 0.30 mass%
Cu: 0.03 mass%
Co: 3.8% by mass
Fe and inevitable impurities: balance

This raw material compound contained a small amount of inevitable impurities (0.5% by mass or less in the whole raw material compound). This raw material compound was held in a reduced pressure atmosphere (1 kPa or less) in a temperature range of 1000 to 1200 ° C. for 24 hours (homogenization heat treatment step). The product (Nd ₂ Fe ₁₄ B) obtained by the homogenization heat treatment was pulverized using a stamp mill and sieved to obtain a raw material powder (particle diameter of 1 to 2 mm).

  This raw material powder was filled in a molybdenum-made container, loaded into a tubular heat treatment furnace having an infrared heating method, and subjected to a treatment by hydrocracking / dehydrogenation recombination (HDDR treatment) under the following conditions.

  First, a hydrogen occlusion process was performed in which a raw material powder was held for 2 hours at a hydrogen partial pressure of 100 to 300 kPa and a temperature of 100 ° C. in a hydrogen gas atmosphere. Subsequently, the hydrocracking step of lowering the hydrogen partial pressure in the furnace and raising the temperature in the furnace to hold the raw material powder storing the hydrogen gas for 1.5 hours under the conditions of a hydrogen partial pressure of 40 kPa and a temperature of 850 ° C. Went.

Thereafter, the hydrogen pressure was reduced while maintaining the temperature in the furnace at 850 ° C., and a dehydrogenation recombination step was performed. Thus, HDDR-treated anisotropic magnetic powder was obtained. The obtained magnetic powder was pulverized using a stamp mill in a nitrogen gas atmosphere and sieved to obtain Nd ₂ Fe ₁₄ B powder having a particle size of 300 μm or less.

Next, apart from the Nd ₂ Fe ₁₄ B powder, a diffusion material was prepared as follows. First, Dy powder was occluded at 350 ° C. for 1 hour in a hydrogen atmosphere, followed by treatment at 600 ° C. for 1 hour in an Ar atmosphere to obtain a Dy hydride. The obtained Dy hydride was confirmed to be DyH ₂ by X-ray diffraction measurement. The obtained DyH ₂ powder was placed in an ethanol solution and ball milled to obtain DyH ₂ fine powder having an average particle size [d (50)] of 3 μm.

Nd ₂ Fe ₁₄ B powder obtained by the above-described method and DyH ₂ fine powder as a diffusing material were mixed using a V mixer to prepare a mixed powder. The mixing ratio of the Nd ₂ Fe ₁₄ B powder and the diffusing material was such that the diffusing material was 3% by mass based on the entire mixed powder obtained. Moreover, 0.1 mass% of zinc stearate was added and mixed with respect to the total amount of the mixed powder. The mixed powder was molded in a magnetic field under the conditions of a molding pressure of 980 MPa and an orientation magnetic field of 1.2 T, to obtain a rectangular parallelepiped shaped molded body 10 as shown in FIG. The magnetic field application direction was the a direction in FIG. The dimensions and density of the molded body 10 were as shown in Table 1.

The molded body was subjected to a diffusion treatment in which Dy contained in the diffusing material was diffused into the outer peripheral portion of the Nd ₂ Fe ₁₄ B powder by a heat treatment in which an atmosphere of argon gas was heated at 900 ° C. for 30 minutes. The relative density of the molded body after the diffusion treatment was about 80%.

  Next, the molded body is placed in a vacuum bell jar together with a container containing toluene, and after the molded body is immersed in toluene and subjected to defoaming treatment in which the pressure in the container is kept at 10 kPa or less for 30 minutes, Returned to pressure.

  Apart from the molded article, an epoxy resin was dissolved in toluene to prepare an epoxy resin solution (epoxy resin content: 50% by mass). The above-mentioned epoxy resin solution and the molded product subjected to the diffusion treatment and defoaming treatment were sequentially put into a vacuum bell jar. The inside of the vacuum bell jar was decompressed to 10 kPa or less and held for 60 minutes, and the epoxy resin solution was infiltrated into the molded body.

  The molded body was taken out from the epoxy resin solution, and the epoxy resin solution adhering to the surface of the molded body was removed by a centrifuge. Thereafter, the molded body impregnated with the epoxy resin solution was held in a constant temperature bath (atmosphere: nitrogen gas) at a temperature of 150 ° C. for 5 hours to cure the epoxy resin in the molded body, and thus a rare earth bonded magnet 10 was obtained. The size and mass of the obtained rare earth bonded magnet 10 were measured, and the density of the rare earth bonded magnet was determined. Tables 1 and 2 show the dimensions and density of the rare earth bonded magnet.

[Evaluation of magnetic properties]
The magnetic properties of the rare earth bonded magnet produced as described above were measured with a BH tracer. From the obtained results, residual magnetic flux density (Br), coercive force (HcJ), and squareness ratio (Hk / iHc) were determined. Further, Hk and bHc were obtained from the magnetic hysteresis loop, and the squareness ratio was obtained by the following formula (1) using HcJ and Hk. The evaluation results are shown in Table 2.

  The squareness ratio is an index of magnet performance and represents the degree of squareness in the second quadrant of the magnetic hysteresis loop measured using a BH tracer. Hk in equation (1) is the external magnetic field strength when the ratio of magnetization to the residual magnetic flux density is 90% in the second quadrant of the magnetic hysteresis loop.

  Squareness ratio (%) = Hk / HcJ × 100 (1)

(Example 2)
A rare earth bonded magnet was prepared and evaluated in the same manner as in Example 1 except that the mixing ratio of the diffusing material (DyH ₂ fine powder) was changed from 3% by mass to 1% by mass with reference to the entire mixed powder. It was. The evaluation results are shown in Table 2.

(Example 3)
The molded body was subjected to a diffusion treatment in the same manner as in Example 1. The formed product after the diffusion treatment was pulverized using a stamp mill in a nitrogen gas atmosphere to prepare a pulverized powder having a particle size of 250 μm or less. This pulverized powder and an epoxy resin solution prepared in the same manner as in Example 1 were mixed at a ratio such that the epoxy resin content of the molded product was 3% by mass, and then toluene was evaporated to form a magnetic powder and a resin. A compound for a bonded magnet was prepared. This bonded magnet compound was molded in a magnetic field under the conditions of a molding pressure of 980 MPa and an orientation magnetic field of 1.2 T to obtain a rectangular parallelepiped shaped molded body.

  This molded body was held in a thermostatic bath at a temperature of 150 ° C. for 5 hours, and the epoxy resin in the molded body was cured to obtain a rare earth bonded magnet. Then, in the same manner as in Example 1, the obtained rare earth bonded magnet was evaluated. The evaluation results are shown in Table 2.

Example 4
A rare-earth bonded magnet was prepared and evaluated in the same manner as in Example 1 except that DyH ₂ fine powder having an average particle diameter of 1 μm was used instead of DyH ₂ fine powder having an average particle diameter of 3 μm. The evaluation results are shown in Table 2. The average particle size of the DyH ₂ fine powder was adjusted by changing the ball milling conditions.

(Example 5)
The same procedure as in Example 1 was performed except that a fine powder of Dy-Fe compound [Dy: Fe = 80: 20 (molar ratio)] having an average particle diameter of 3 μm was used as the diffusing material in place of the fine powder of DyH _2. A rare earth bonded magnet was prepared and evaluated. The evaluation results are shown in Table 2. The fine powder of the Dy-Fe compound was prepared as follows. First, a DyFe alloy and Fe (electrolytic iron) were weighed and blended so as to have a desired composition, melted by high frequency dissolution, and then a Dy-Fe compound was obtained by a strip casting method. The obtained Dy-Fe compound was pulverized using a jaw crusher and then pulverized in an ethanol solution at 100 rpm for 120 hours using a ball mill to obtain a fine powder of Dy-Fe compound having an average particle size of 3 μm. .

(Example 6)
Except for using a fine powder of Dy-Fe-Co compound [Dy: Fe: Co = 80: 10: 10 (molar ratio)] having an average particle size of 3 μm instead of DyH ₂ fine powder as the diffusing material, A rare earth bonded magnet was prepared and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 2. The fine powder of the Dy-Fe-Co compound was prepared as follows. First, DyFe alloy, Fe (electrolytic iron) and Co were weighed and blended so as to have a desired composition, and melted and solidified by arc melting to obtain a Dy-Fe-Co compound. This Dy-Fe-Co compound was roughly pulverized in a nitrogen atmosphere using a stamp mill, and then pulverized in an ethanol solution at 100 rpm for 60 hours using a ball mill. A fine powder was obtained.

(Example 7)
A rare-earth bonded magnet was prepared and evaluated in the same manner as in Example 1 except that DyF ₃ fine powder having an average particle size of 3 μm was used as the diffusing material in place of DyH ₂ fine powder. The evaluation results are shown in Table 2. The DyF ₃ fine powder was prepared by pulverizing DyF ₃ powder manufactured by Japan Yttrium Co., Ltd. in an ethanol solution at 100 rpm for 12 hours using a ball mill.

(Example 8)
A rare earth bonded magnet was prepared and evaluated in the same manner as in Example 7, except that the mixing ratio of the diffusing material (DyF ₃ fine powder) was changed from 3% by mass to 1% by mass based on the entire mixed powder. It was. The evaluation results are shown in Table 2.

(Comparative Example 1)
In the same manner as in Example 1, a mixed powder of Nd ₂ Fe ₁₄ B powder and a diffusion material (DyH ₂ fine powder) was obtained. The mixed powder was subjected to a diffusion treatment in which Dy contained in the diffusion material was diffused into the Nd ₂ Fe ₁₄ B powder by a heat treatment in which the mixed powder was heated at 900 ° C. for 30 minutes in an argon gas atmosphere.

  After mixing the mixed powder subjected to the diffusion treatment and the epoxy resin solution prepared in the same manner as in Example 1, the compound for bonded magnet composed of magnetic powder and resin is prepared by evaporating toluene, and the compound is subjected to molding pressure. Molding was performed in a magnetic field under conditions of 980 MPa and an orientation magnetic field of 1.2 T to obtain a molded body.

  This molded body was held in a thermostatic bath at a temperature of 150 ° C. for 5 hours, and the epoxy resin in the molded body was cured to obtain a rare earth bonded magnet. Then, the rare earth bonded magnet was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 2.

(Comparative Example 2)
A rare earth bonded magnet was produced and evaluated in the same manner as in Comparative Example 1 except that the content of the DyH ₂ fine powder in the mixed powder was changed from 3 mass% to 1 mass%. The evaluation results are shown in Table 2.

(Comparative Example 3)
A rare earth bonded magnet was prepared in the same manner as in Example 1 except that only the Nd ₂ Fe ₁₄ B powder was used instead of the mixed powder of the Nd ₂ Fe ₁₄ B powder and the diffusion material (DyH ₂ fine powder). Evaluation was performed. The evaluation results are shown in Table 2.

(Comparative Example 4)
In the same manner as in Example 1, Nd ₂ Fe ₁₄ B powder having a particle size of 300 μm or less was obtained. Then, the epoxy resin solution prepared in the same manner as in Example 1 and the Nd ₂ Fe ₁₄ B powder were mixed at a ratio such that the epoxy resin content of the molded body was 3% by mass, and then toluene was evaporated. A compound for a bonded magnet made of magnetic powder (Nd ₂ Fe ₁₄ B powder) and a resin was prepared. This bonded magnet compound was molded in a magnetic field under the conditions of a molding pressure of 980 MPa and an orientation magnetic field of 1.2 T to obtain a rectangular parallelepiped shaped molded body.

  This molded body was held in a thermostatic bath at a temperature of 150 ° C. for 5 hours, and the epoxy resin in the molded body was cured to obtain a rare earth bonded magnet. Then, in the same manner as in Example 1, the obtained rare earth bonded magnet was evaluated. The evaluation results are shown in Table 2.

(Comparative Example 5)
An ingot having a predetermined composition is melted in a high-frequency melting furnace, pulverized using a stamp mill in a nitrogen gas atmosphere, sieved, and Nd ₂ Fe ₁₄ B powder having a particle size of 300 μm or less is obtained. Obtained. A rare earth bonded magnet was produced in the same manner as in Example 1 except that this Nd ₂ Fe ₁₄ B powder not subjected to HDDR treatment was used in place of the Nd ₂ Fe ₁₄ B powder obtained after HDDR treatment. And evaluated. The evaluation results are shown in Table 2.

As shown in Table 2, in Examples 1 to 8 where the diffusion treatment of the diffusing material was performed in the state of the molded body, compared with Comparative Examples 1 and 2 where the diffusion treatment of the diffusing material was performed in the state of powder, the magnetic properties Was expensive. In particular, the coercive force and the squareness ratio were greatly improved. In addition, Comparative Examples 3 and 4 that were not subjected to the diffusion treatment had lower magnetic properties than Examples 1-8. Comparative Example 5 using rare earth compound powder not subjected to HDDR treatment had considerably lower magnetic properties than Examples 1-8. This is because the rare earth compound powder (Nd ₂ Fe ₁₄ B powder) that has not been subjected to HDDR treatment is not an anisotropic powder composed of a fine structure, so that even if the diffusion material diffuses into the rare earth compound powder. This is thought to be because the coercive force does not improve.

  FIG. 2 is a magnetic hysteresis loop measured using a BH tracer. In FIG. 2, the curve “1” is the magnetic hysteresis loop of the rare earth bonded magnet of Example 1, and the curve “2” is the magnetic hysteresis loop of the rare earth bonded magnet of Comparative Example 1. It was confirmed that the rare earth bonded magnet of Example 1 was superior in squareness to Comparative Example 1.

  10: Rare earth bonded magnet (molded body).

Claims (4)

Mixing and mixing a rare earth compound powder that has been subjected to a hydrocracking / dehydrogenation recombination process that includes a first rare earth element, and a diffusion material that includes a second rare earth element different from the first rare earth element A mixing step to prepare the powder;
A molding step of molding the mixed powder in a magnetic field to produce a molded body;
A heating step of diffusing the second rare-earth element by heating the molded body in the rare-earth compound powder, and have a,
The diffusing material comprises a halide of the second rare earth element, a hydride of the second rare earth element, a compound of the second rare earth element and Fe, or a compound of the second rare earth element and Fe and Co. A method for producing a rare earth magnet containing the rare earth compound containing the first rare earth element and the second rare earth element. 2. The rare earth magnet manufacturing method according to claim 1, wherein the second rare earth element and Fe compound is a Dy—Fe compound, and the second rare earth element, Fe and Co compound is a Dy—Fe—Co compound. Method. After said heating step, with an impregnating step of obtaining a rare-earth bonded magnet by curing the resin by impregnating a resin into the molded body, method of producing the rare-earth magnet according to claim 1 or 2. After the heating step,
Crushing step of crushing the molded body to prepare a pulverized powder;
Wherein a mixture of pulverized powder and a resin molded in a magnetic field, having a magnet producing step of obtaining a rare-earth bonded magnet by curing the resin, the method of producing the rare-earth magnet according to claim 1 or 2.

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