WO2015121915A1 - Rare earth permanent magnet and production method for rare earth permanent magnet - Google Patents

Abstract

Provided is a rare earth permanent magnet that can achieve increased holding force through use of Cu, and that additionally suppresses the decomposition of a main component and the precipitation of αFe and does not experience reductions in magnetic properties, even if calcination is performed in an oxygen atmosphere. Also provided is a production method for a rare earth permanent magnet. In the present invention, a magnet source material that does not include Cu is, crushed and a calcination process is conducted whereby a molded body that is formed by molding is kept in an oxygen atmosphere at 200℃-900℃ for several hours to several tens of hours. Afterward, the molded body is sintered by means of vacuum sintering or pressure sintering, and a permanent magnet is produced by sputtering the surface of the sintered body with Cu.

Description

Rare earth permanent magnet and method for producing rare earth permanent magnet

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

In recent years, permanent magnet motors used in hybrid cars, hard disk drives, and the like have been required to be smaller, lighter, higher in output, and more efficient. Further, in order to realize a reduction in size and weight, an increase in output, and an increase in efficiency in the permanent magnet motor, further improvement in magnetic characteristics is required for the permanent magnet embedded in the permanent magnet motor. Permanent magnets include ferrite magnets, Sm—Co magnets, Nd—Fe—B magnets, Sm ₂ Fe ₁₇ N _x magnets, and Nd—Fe—B magnets with particularly high residual magnetic flux density. Used as a permanent magnet for a permanent magnet motor.

However, Nd-based magnets such as Nd—Fe—B have a problem that the heat-resistant temperature is low. Therefore, when an Nd magnet is used for a permanent magnet motor, the residual magnetic flux density of the magnet gradually decreases when the motor is continuously driven. In addition, irreversible demagnetization has also occurred. Therefore, as a means for improving the coercive force of the Nd-based magnet, a trace amount of Cu has been conventionally added.

JP 2007-294917 A (page 7)

Also, as a cause of lowering the magnetic performance of the Nd-based magnet, there is a carbon-containing material remaining in the magnet. In particular, Nd-based magnets have a very high reactivity between Nd and carbon, and therefore, if a carbon-containing material remains at a high temperature in the sintering process, carbide is formed. As a result, there is a problem in that voids are formed between the main phase and the grain boundary phase of the magnet after sintering due to the formed carbide, and the entire magnet cannot be sintered densely, resulting in a significant decrease in magnetic performance. Even when no voids are formed, αFe is precipitated in the main phase of the magnet after sintering by the formed carbide, and there is a problem that the magnetic properties are greatly deteriorated. Therefore, a technique for removing carbon contained by pyrolyzing the carbon-containing material by pre-calcining in a hydrogen atmosphere before sintering the magnet is conceivable.

However, when the calcination treatment is performed in a hydrogen atmosphere, the following reaction (1) may occur in the rare earth magnet.
Nd ₂ Fe ₁₄ B + 2H ₂ → 2NdH ₂ + 12Fe + Fe ₂ B (1)
When the reaction (1) proceeds to the right side, the main phase (Nd ₂ Fe ₁₄ B) of the rare earth magnet is decomposed, and αFe is precipitated, which causes a decrease in magnet characteristics. Although it is considered that a part of the main phase decomposed by the subsequent sintering treatment is recovered, αFe remains.

And if it is set as the structure which includes Cu beforehand in a magnet raw material like the said patent document 1, Cu will be contained in a magnet at the time of performing a calcination process. In that case, there was a problem that the reaction of the above (1) easily proceeds to the right side. Here, FIG. 12 pulverizes, molds and sinters a permanent magnet manufactured by previously crushing, forming and sintering a magnet raw material containing Cu as in Patent Document 1 and a magnet raw material not containing Cu. It is the figure which changed the conditions of calcination processing and compared the coercive force about the permanent magnet manufactured by this.

As shown in FIG. 12, when the calcination treatment is not performed in a hydrogen atmosphere, there is no large difference in coercive force between the permanent magnet containing Cu and the permanent magnet not containing Cu. However, when the calcination treatment is performed in a hydrogen atmosphere, the permanent magnet containing Cu has a lower coercive force than the permanent magnet not containing Cu, and when the temperature at which the calcination treatment is performed is further increased, the difference in coercive force. Becomes larger. That is, when the calcination process is performed in a hydrogen atmosphere, the reaction of (1) above tends to proceed to the right side in the permanent magnet containing Cu, and the decomposition of the main phase and the precipitation of αFe rather than the improvement of the coercive force by decarbonization. It can be predicted that the influence of the decrease in coercive force is increased and the coercive force is decreased.

The present invention has been made to solve the problems in the prior art, and it is possible to improve the coercive force by Cu, and even when calcination is performed in a hydrogen atmosphere, It is an object of the present invention to provide a rare earth permanent magnet and a method for producing a rare earth permanent magnet, in which phase decomposition and αFe precipitation are suppressed and magnetic properties are not deteriorated.

In order to achieve the above object, a rare earth permanent magnet according to the present invention includes a step of pulverizing a magnet raw material into magnet powder, a step of forming a molded body by molding the pulverized magnet powder, and molding the magnet powder. A step of calcining in a hydrogen atmosphere or a mixed gas atmosphere of hydrogen and an inert gas before or after molding and before sintering, and sintering by holding the molded body at a firing temperature. It is manufactured by the process of obtaining, and the process of sputtering Cu on the surface of the said sintered compact, It is characterized by the above-mentioned.

The rare earth permanent magnet according to the present invention is manufactured by a process of diffusing Cu sputtered on the surface of the sintered body into the sintered body by heating the sintered body on which Cu is sputtered. It is characterized by being.

Further, the rare earth permanent magnet according to the present invention is characterized in that when the sintered body sputtered with Cu is heated, it is heated at a temperature lower than the firing temperature.

In the rare earth permanent magnet according to the present invention, in the step of sputtering Cu on the surface of the sintered body, after sputtering Nd on the surface of the sintered body, Cu is sputtered on the surface of the sintered body. It is characterized by.

Further, the rare earth permanent magnet according to the present invention is obtained by adding Al, Dy, Tb, Nd, V, Mo, Zr, Ta, Ti, W, Ag, Ga, Co, Bi, Zn, Mg or the like to the pulverized magnet powder. By adding an organometallic compound that contains Nb and does not contain oxygen and nitrogen atoms, the organometallic compound is adhered to the particle surface of the magnet powder, and the organometallic compound is adhered to the particle surface. A molded body is formed by molding the material.

The rare earth permanent magnet according to the present invention is a metal whose central metal is Al, Dy, Tb, Nd, V, Mo, Zr, Ta, Ti, W, Ag, Ga, Co, Bi, Zn, Mg, or Nb. It is characterized by being a complex or diisobutylaluminum hydride.

In the rare earth permanent magnet according to the present invention, in the step of forming the magnet powder into a molded body, a mixture in which the magnet powder and a binder are mixed is generated, and the mixture is formed into a sheet shape. A green sheet is produced as a body.

The method for producing a rare earth permanent magnet according to the present invention includes a step of pulverizing a magnet raw material into magnet powder, a step of forming a molded body by molding the pulverized magnet powder, and a step of forming the magnet powder before molding. Alternatively, after the molding and before sintering, a step of calcining in a hydrogen atmosphere or a mixed gas atmosphere of hydrogen and an inert gas and sintering by holding the molded body at a firing temperature to obtain a sintered body And a step of sputtering Cu on the surface of the sintered body.

In addition, the method for producing a rare earth permanent magnet according to the present invention diffuses Cu sputtered on the surface of the sintered body by heating the sintered body on which Cu is sputtered. It has the process.

The method for producing a rare earth permanent magnet according to the present invention is characterized in that when the sintered body sputtered with Cu is heated, the sintered body is heated at a temperature lower than the firing temperature.

In the method of manufacturing a rare earth permanent magnet according to the present invention, in the step of sputtering Cu on the surface of the sintered body, after sputtering Nd on the surface of the sintered body, Cu is applied to the surface of the sintered body. It is characterized by sputtering.

In addition, the method for producing a rare earth permanent magnet according to the present invention includes adding Al, Dy, Tb, Nd, V, Mo, Zr, Ta, Ti, W, Ag, Ga, Co, Bi, Zn to the pulverized magnet powder. By adding an organometallic compound that contains Mg or Nb and does not contain oxygen and nitrogen atoms, the organometallic compound is adhered to the particle surface of the magnet powder, and the organometallic compound is adhered to the particle surface. A compact is formed by molding the magnet powder.

Further, in the method for producing a rare earth permanent magnet according to the present invention, the organometallic compound has a central metal of Al, Dy, Tb, Nd, V, Mo, Zr, Ta, Ti, W, Ag, Ga, Co, Bi. , Zn, Mg or Nb, or diisobutylaluminum hydride.

Furthermore, in the method of manufacturing a rare earth permanent magnet according to the present invention, in the step of forming the magnet powder into a molded body, a mixture in which the magnet powder and a binder are mixed is generated, and the mixture is formed into a sheet shape. To produce a green sheet as the molded body.

According to the rare earth permanent magnet of the present invention having the above-described configuration, it is possible to improve the coercive force due to Cu, and even when calcining is performed in a hydrogen atmosphere, It is possible to suppress the precipitation of αFe and prevent the magnetic properties from deteriorating. In addition, when calcining the powdered magnet particles, the surface area of the magnet to be calcined can be increased compared to the case of calcining the molded magnet particles. . That is, the amount of carbon in the calcined body can be reduced more reliably.

Moreover, according to the rare earth permanent magnet of the present invention, the Cu sputtered on the surface of the sintered body is diffused into the sintered body by heating the sintered body on which Cu is sputtered. Without including Cu in the raw material, Cu sputtered after sintering can be appropriately distributed with respect to the grain boundary. That is, the effect of improving the coercive force by Cu can be obtained without previously including Cu in the magnet raw material.

In addition, according to the rare earth permanent magnet of the present invention, when the sintered body on which Cu is sputtered is heated, it is heated at a temperature lower than the firing temperature, so that the sputtered Cu is diffused inside the sintered body. It can prevent that the particle growth of a magnet particle arises in the process to make.

Further, according to the rare earth permanent magnet of the present invention, after sputtering Nd on the surface of the sintered body, Cu is sputtered on the surface of the sintered body, so that the sputtered Cu is diffused inside the sintered body. The process can be performed at a lower temperature.

Moreover, according to the rare earth permanent magnet according to the present invention, Al, Dy, Tb, Nd, V, Mo, Zr, Ta, Ti, W, Ag, Ga, Co, Bi, Zn, Mg contained in the organometallic compound are included. Alternatively, Nb can be efficiently distributed with respect to the grain boundaries of the magnet. As a result, the magnetic performance of the permanent magnet can be improved. In addition, since the amount of addition of Al, Dy, Tb, Nd, V, Mo, Zr, Ta, Ti, W, Ag, Ga, Co, Bi, Zn, Mg, or Nb can be reduced compared to the conventional case, the residual magnetic flux A decrease in density can be suppressed.

Further, according to the rare earth permanent magnet of the present invention, the central metal is Cu, Al, Dy, Tb, Nd, V, Mo, Zr, Ta, Ti, W, Ag, Ga, Co, Bi, Zn, Mg or Since the metal complex that is Nb or diisobutylaluminum hydride is used as the organometallic compound, the organometallic compound can be easily thermally decomposed in the subsequent heating step, and the metal contained in the organometallic compound can be separated from the grain boundary. It is possible to make it unevenly distributed. In addition, the amount of carbon remaining in the magnet can be reduced by performing thermal decomposition. As a result, it is possible to sinter the entire magnet densely without generating voids between the main phase and the grain boundary phase of the sintered magnet, and to prevent the coercive force from being lowered. . Further, a large number of αFe is not precipitated in the main phase of the magnet after sintering, and the magnet characteristics are not greatly deteriorated.

Moreover, according to the rare earth permanent magnet of the present invention, the permanent magnet is composed of a magnet obtained by mixing magnet powder and a binder and sintering a molded green sheet. Deformation such as warping and dent after binding does not occur, and pressure unevenness at the time of pressing is eliminated, so that it is not necessary to perform correction processing after sintering, which can be performed conventionally, and the manufacturing process can be simplified. . Thereby, a permanent magnet can be formed with high dimensional accuracy.

Further, according to the method for producing a rare earth permanent magnet according to the present invention, it becomes possible to improve the coercive force due to Cu, and even when calcination is performed in a hydrogen atmosphere, the main phase is decomposed. And αFe precipitation can be suppressed, and the magnetic characteristics can be prevented from deteriorating. In addition, when calcining the powdered magnet particles, the surface area of the magnet to be calcined can be increased compared to the case of calcining the molded magnet particles. . That is, the amount of carbon in the calcined body can be reduced more reliably.

In addition, according to the method for producing a rare earth permanent magnet according to the present invention, Cu sputtered on the surface of the sintered body is diffused inside the sintered body by heating the sintered body on which Cu is sputtered. In addition, Cu that has been sputtered after sintering can be appropriately unevenly distributed with respect to the grain boundaries without previously including Cu in the magnet raw material. That is, the effect of improving the coercive force by Cu can be obtained without previously including Cu in the magnet raw material.

Further, according to the method for producing a rare earth permanent magnet according to the present invention, when the sintered body with Cu sputtered is heated, it is heated at a temperature lower than the firing temperature. It is possible to prevent the grain growth of the magnet particles from occurring in the step of diffusing inside.

Further, according to the method for producing a rare earth permanent magnet according to the present invention, after sputtering Nd on the surface of the sintered body, Cu is sputtered on the surface of the sintered body. It is possible to carry out the step of diffusing into the substrate at a lower temperature.

Further, according to the method for producing a rare earth permanent magnet according to the present invention, Al, Dy, Tb, Nd, V, Mo, Zr, Ta, Ti, W, Ag, Ga, Co, Bi, contained in the organometallic compound, Zn, Mg, or Nb can be efficiently distributed with respect to the grain boundaries of the magnet. As a result, the magnetic performance of the permanent magnet can be improved. In addition, since the amount of addition of Al, Dy, Tb, Nd, V, Mo, Zr, Ta, Ti, W, Ag, Ga, Co, Bi, Zn, Mg, or Nb can be reduced compared to the conventional case, the residual magnetic flux A decrease in density can be suppressed.

Further, according to the method for producing a rare earth permanent magnet according to the present invention, the central metal is Cu, Al, Dy, Tb, Nd, V, Mo, Zr, Ta, Ti, W, Ag, Ga, Co, Bi, Zn. , Mg or Nb metal complex, or diisobutylaluminum hydride is used as the organometallic compound, so that the pyrolysis of the organometallic compound can be easily performed in the subsequent heating step, and the metal contained in the organometallic compound is granulated. It becomes possible to make it unevenly distributed with respect to the field. In addition, the amount of carbon remaining in the magnet can be reduced by performing thermal decomposition. As a result, it is possible to sinter the entire magnet densely without generating voids between the main phase and the grain boundary phase of the sintered magnet, and to prevent the coercive force from being lowered. . Further, a large number of αFe is not precipitated in the main phase of the magnet after sintering, and the magnet characteristics are not greatly deteriorated.

Furthermore, according to the method for producing a rare earth permanent magnet according to the present invention, a permanent magnet is constituted by a magnet obtained by mixing magnet powder and a binder and sintering a molded green sheet, so that the shrinkage due to sintering becomes uniform. As a result, deformation such as warping and dent after sintering does not occur, and pressure unevenness at the time of pressing is eliminated, so that it is not necessary to carry out correction processing after sintering, which is conventionally performed, and simplifies the manufacturing process. be able to. Thereby, a permanent magnet can be formed with high dimensional accuracy.

FIG. 1 is an overall view showing a permanent magnet according to the present invention. FIG. 2 is an enlarged schematic view showing the vicinity of the grain boundary of the permanent magnet according to the present invention. FIG. 3 is an enlarged schematic view showing the vicinity of the grain boundary of the permanent magnet according to the present invention. FIG. 4 is an explanatory view showing a manufacturing process of the permanent magnet according to the present invention. FIG. 5 is an explanatory view showing a manufacturing process of the permanent magnet according to the present invention. FIG. 6 is an explanatory view showing a green sheet forming step, in particular, among the manufacturing steps of the permanent magnet according to the present invention. FIG. 7 is an explanatory view showing a green sheet heating process and a magnetic field orientation process in the manufacturing process of the permanent magnet according to the present invention. FIG. 8 is a diagram showing an example in which the magnetic field is oriented in the in-plane vertical direction of the green sheet. FIG. 9 is a diagram illustrating a heating device using a heat medium (silicone oil). FIG. 10 is a schematic view showing the pressure-sintering step of the green sheet, among the manufacturing steps of the permanent magnet according to the present invention. FIG. 11 is a diagram showing various measurement results for the magnets of the example and the comparative example. FIG. 12 is a diagram for explaining the problems of the prior art.

Hereinafter, an embodiment embodying a rare earth permanent magnet and a method for producing a rare earth permanent magnet according to the present invention will be described in detail with reference to the drawings.

[Configuration of permanent magnet]
First, the configuration of the permanent magnet 1 according to the present invention will be described. FIG. 1 is an overall view showing a permanent magnet 1 according to the present invention. The permanent magnet 1 shown in FIG. 1 has a fan shape, but the shape of the permanent magnet 1 varies depending on the punched shape.
The permanent magnet 1 according to the present invention is an Nd—Fe—B anisotropic magnet. In addition, Cu, Al, Dy (dysprosium), Tb (terbium), Nb (niobium), V for enhancing the magnetic performance of the permanent magnet 1 are provided at the interfaces (grain boundaries) of the crystal grains forming the permanent magnet 1. (Vanadium), Mo (molybdenum), Zr (zirconium), Ta (tantalum), Ti (titanium) or W (tungsten) are unevenly distributed. The content of each component is Nd: 25 to 37 wt%, Cu, Al, Dy, Tb, Nb, V, Mo, Zr, Ta, Ti, W, Ag, Ga, Co, Bi, Zn, Mg (However, at least Cu is included. Hereinafter, it is referred to as Cu or the like): 0.01 to 5 wt%, B: 0.8 to 2 wt%, Fe (electrolytic iron): 60 to 75 wt%. Moreover, a small amount of other elements such as Si may be included to improve the magnetic characteristics.

Specifically, the permanent magnet 1 according to the present invention includes a layer containing Cu or the like in the surface portion (outer shell) of the crystal grains of the Nd crystal particles (main phase) 2 constituting the permanent magnet 1 as shown in FIG. 3 (hereinafter referred to as the unevenly distributed metal layer 3) causes Cu or the like to be unevenly distributed with respect to the grain boundaries of the Nd crystal particles 2. FIG. 2 is an enlarged view showing Nd crystal particles 2 constituting the permanent magnet 1. The metal uneven distribution layer 3 is preferably non-magnetic.

Here, in the present invention, Cu is sputtered on the surface of the sintered body as will be described later in order to generate the metal uneven distribution layer 3 containing Cu in particular. Specifically, the sintered body is set in a sputtering apparatus, Cu is sputtered onto the surface of the sintered body, and then the sputtered sintered body is heated. As a result, the sputtered Cu diffuses and penetrates into the sintered body to form the unevenly distributed metal layer 3 shown in FIG. In particular, if Nd is sputtered before Cu is sputtered, Cu can be diffused and penetrated in a state of an Nd—Cu alloy (melting point 459 ° C.) having a melting point lower than that of Cu alone. It is possible to diffuse and penetrate into the sintered body.

Further, in order to generate a metal uneven distribution layer 3 containing a metal element other than Cu (hereinafter referred to as Dy) among Cu and the like, an organometallic compound containing Dy and the like is formed before forming the pulverized magnet powder. Adding to the powder is performed. Specifically, when the magnet powder to which the organometallic compound containing Dy or the like is added is sintered, the Dy or the like in the organometallic compound uniformly adhered to the particle surface of the Nd crystal particles 2 by wet dispersion is Nd. Replacement is performed by diffusing and penetrating into the crystal growth region of the crystal grain 2 to form the unevenly distributed metal layer 3 shown in FIG. The Nd crystal particles 2 are made of, for example, an Nd ₂ Fe ₁₄ B intermetallic compound, and the metal uneven distribution layer 3 is made of, for example, an Nd—Cu intermetallic compound, an Nd—Fe—Cu intermetallic compound, an NbFeB intermetallic compound, (Dy _{x Nd 1-x) 2 Fe} 14 composed of B intermetallic compound. In addition to the metal uneven distribution layer 3, for example, an Nd-rich phase or the like is also formed at the grain boundary.

Further, in the present invention, as described later, an organometallic compound containing Dy or the like and Nd and not containing an oxygen atom and a nitrogen atom, more specifically, a metal complex or diisobutyl hydride whose central metal is Dy or the like and Nd. Aluminum (DIBAL) is added to the organic solvent and mixed with the magnet powder in a wet state. Thereby, an organometallic compound containing Dy or the like and Nd can be dispersed in an organic solvent, and the organometallic compound containing the Dy or the like or Nd can be uniformly attached to the particle surface of the Nd crystal particle 2.

Here, as the metal complex, it is particularly desirable to use a metal alkyl complex whose ligand is an alkyl group. Especially cyclopentadienyl, methyl, benzyl, isobutyl, phenyl, octyl, ethylcyclopentadienyl, isopropylcyclopentadienyl, tetramethylcyclopentadienyl or pentamethylcyclopentadienyl A metal complex containing a group or a metal acetylide complex is desirable. Examples of such metal complexes include tris (ethylcyclopentadienyl) Dy (III), tris (isopropylcyclopentadienyl) Tb (III), bis (cyclopentadienyl) Mg (II), bis ( Cyclopentadienyl) dibenzyl Nb (IV), trihydridobis (pentamethyldicyclopentadienyl) Nb (V), bis (cyclopentadienyl) dimethyl Ti (IV), bis (cyclopentadienyl) dimethyl Zr (IV), dihydridobis (cyclopentadienyl) Zr (IV), tris (tetramethylcyclopentadienyl) Nd (III), trioctyl Al (III), diphenyl Zn (II), triphenyl Bi (III), Ag (I) t-butyl acetylide, mesityl Ag (I), triscyclopentadienyl Ga (III). In the present invention, in order to improve the magnetic performance of the permanent magnet 1 in particular, Al, Dy, Tb, Nd, V, Mo, Zr, Ta, Ti, W, Ag, Ga, Co, Bi, Zn, Mg or Nb is used.

Moreover, if the compact of the magnet powder to which the organometallic compound is added is fired under appropriate firing conditions, Dy and the like can be prevented from diffusing and penetrating (solid solution) into the Nd crystal particles 2. Thereby, in this invention, even if Dy etc. are added, Dy etc. can be unevenly distributed only to a grain boundary after sintering. As a result, as a whole crystal grain (that is, as a whole sintered magnet), the core Nd ₂ Fe ₁₄ B intermetallic compound phase occupies a high volume ratio. Thereby, the fall of the residual magnetic flux density (magnetic flux density when the intensity of an external magnetic field is set to 0) of the magnet can be suppressed.

Moreover, generally, when the sintered Nd crystal particles 2 are in a dense state, it is considered that exchange interaction propagates between the Nd crystal particles 2. As a result, when a magnetic field is applied from the outside, the magnetization reversal of each crystal particle easily occurs, and even if each sintered crystal particle can have a single domain structure, the coercive force decreases. However, in the present invention, the exchange interaction between the Nd crystal particles 2 is separated by the nonmagnetic metal uneven distribution layer 3 coated on the surface of the Nd crystal particles 2, and each crystal particle is applied even when a magnetic field is applied from the outside. Prevents the reversal of magnetization.

In the present invention, since the metal uneven distribution layer 3 is composed of a layer containing at least Cu, it functions as a means for uniformly dispersing the Nd-rich phase in the sintered permanent magnet 1 and increasing the coercive force.

Further, if the metal uneven distribution layer 3 is constituted by a layer containing V, Mo, Zr, Ta, Ti, W or Nb, which is a particularly high melting point metal, the metal uneven distribution layer 3 coated on the surface of the Nd crystal particles 2 When the permanent magnet 1 is sintered, it also functions as a means for suppressing so-called grain growth in which the average grain size of the Nd crystal grains 2 increases.

On the other hand, if the metal uneven distribution layer 3 is composed of a layer containing Dy or Tb having a particularly high magnetic anisotropy, it also functions as means for suppressing the generation of reverse magnetic domains and increasing the coercive force (preventing magnetization reversal).

Further, if the metal uneven distribution layer 3 is composed of a layer containing Al in particular, it also functions as a means for uniformly dispersing the Nd-rich phase in the sintered permanent magnet 1 together with Cu and increasing the coercive force.

Further, even when the metal uneven distribution layer 3 is composed of a layer containing other Ag, Ga, Co, Bi, Zn, or Mg, the magnetic performance of the permanent magnet is improved, such as coercivity improvement by grain boundary control or grain growth suppression. Can be expected.

In addition, if an organometallic compound containing Nd is added, the Nd-rich phase can be uniformly dispersed in the sintered permanent magnet 1. Further, even if the rare earth element is combined with oxygen or carbon in the manufacturing process, the rare earth element is not deficient with respect to the stoichiometric composition, and αFe is prevented from being generated in the sintered permanent magnet 1. It becomes possible.

Further, it is desirable that the particle diameter D of the Nd crystal particles 2 is 0.2 μm to 1.2 μm, preferably about 0.3 μm. Moreover, if the thickness d of the metal uneven distribution layer 3 is about 2 nm, it becomes possible to obtain the effects (grain growth suppression, exchange interaction division, coercive force improvement, etc.) due to the metal uneven distribution layer 3. However, if the thickness d of the metal uneven distribution layer 3 becomes too large, the content of non-magnetic components that do not exhibit magnetism increases, so that the residual magnetic flux density decreases.

As a configuration in which Cu or the like is unevenly distributed with respect to the grain boundaries of the Nd crystal particles 2, a configuration in which grains 4 made of Cu or the like are scattered with respect to the grain boundaries of the Nd crystal particles 2 as shown in FIG. good. Even with the configuration shown in FIG. 3, it is possible to obtain the same effects (grain growth suppression, exchange interaction division, coercive force improvement, etc.). In addition, how Cu or the like is unevenly distributed with respect to the grain boundaries of the Nd crystal particles 2 can be confirmed by, for example, SEM, FIB / SEM system, TEM, or three-dimensional atom probe method.

Further, the unevenly distributed metal layer 3 is composed of Cu compound, Al compound, Dy compound, Tb compound, Nb compound, V compound, Mo compound, Zr compound, Ta compound, Ti compound, Ag compound, Ga compound, Co compound, Bi compound, Zn. It is not necessary to be a layer composed only of a compound, Mg compound or W compound (hereinafter referred to as a compound such as Cu), and may be a layer composed of a mixture of a compound such as Cu and an Nd compound. In that case, a layer made of a mixture of a compound such as Cu and an Nd compound is formed. As a result, liquid phase sintering during the sintering of the Nd magnet powder can be promoted.

Here, the permanent magnet 1 is a thin-film permanent magnet having a thickness of, for example, 0.05 mm to 10 mm (for example, 1 mm). The permanent magnet 1 is manufactured by sintering a molded body (green body) formed by compacting as described below, or a molded body (green body) formed by mixing a mixture of magnet powder and a binder. Further, the green body is produced by forming a mixture (slurry or compound) in which magnet powder and a binder are mixed into a predetermined shape (for example, a sheet shape, a block shape, a final product shape, etc.) as described later. . In addition, it is good also as a structure which makes a final product shape by once shape | molding a mixture into shapes other than a final product shape, and performing punching, cutting, a deformation process, etc. after that. In particular, if the mixture is once formed into a sheet shape and then processed into a final product shape, productivity can be improved by producing in a continuous process, and molding accuracy can also be improved. When the mixture is formed into a sheet shape, for example, a thin film sheet member having a thickness of 0.05 mm to 10 mm (for example, 1 mm) is used. Even in the case of a sheet shape, a large permanent magnet 1 can be manufactured if a plurality of sheets are laminated.

In the present invention, in particular, when the permanent magnet 1 is produced by sintering a green body, a resin, a long-chain hydrocarbon, a fatty acid ester, a mixture thereof, or the like is used as the binder mixed with the magnet powder.
Furthermore, when a resin is used for the binder, it is preferable to use a polymer that does not contain an oxygen atom in the structure and has a depolymerization property. In addition, as described later, in order to reuse the remainder of the mixture generated when the mixture of the magnet powder and the binder is formed into a final product shape, and the magnetic mixture is heated in a softened state. To do so, a thermoplastic resin is used. Specifically, the polymer which consists of 1 type, or 2 or more types of polymers or copolymers chosen from the monomer shown by the following general formula (1) corresponds.

(However, R1 and R2 represent a hydrogen atom, a lower alkyl group, a phenyl group or a vinyl group.)

Examples of the polymer satisfying the above conditions include polyisobutylene (PIB), which is a polymer of isobutylene, polyisoprene (isoprene rubber, IR), which is a polymer of isoprene, and polybutadiene (butadiene) that is a polymer of 1,3-butadiene. Rubber, BR), polystyrene as a polymer of styrene, styrene-isoprene block copolymer (SIS) as a copolymer of styrene and isoprene, butyl rubber (IIR) as a copolymer of isobutylene and isoprene, styrene and butadiene A styrene-butadiene block copolymer (SBS) which is a copolymer of 2-methyl-1-pentene, a polymer of 2-methyl-1-pentene, and a polymer of 2-methyl-1-butene. A 2-methyl-1-butene polymer resin, a polymer of α-methylstyrene That there is α- methyl styrene polymer resin. Incidentally, it is desirable to add low molecular weight polyisobutylene to the α-methylstyrene polymer resin in order to give flexibility. The resin used for the binder may include a small amount of a polymer or copolymer of a monomer containing an oxygen atom (for example, polybutyl methacrylate, polymethyl methacrylate, etc.). Furthermore, a monomer that does not correspond to the general formula (1) may be partially copolymerized. Even in that case, it is possible to achieve the object of the present invention.
As the resin used for the binder, it is desirable to use a thermoplastic resin that softens at 250 ° C. or lower, more specifically a thermoplastic resin having a glass transition point or a melting point of 250 ° C. or lower in order to appropriately perform magnetic field orientation. .

On the other hand, when a long chain hydrocarbon is used for the binder, it is preferable to use a long chain saturated hydrocarbon (long chain alkane) that is solid at room temperature and liquid at room temperature or higher. Specifically, it is preferable to use a long-chain saturated hydrocarbon having 18 or more carbon atoms. Then, when the mixture of the magnetic powder and the binder is magnetically oriented as described later, the magnetic field orientation is performed in a state where the mixture is heated and softened at a temperature equal to or higher than the melting point of the long-chain hydrocarbon.

Similarly, when a fatty acid ester is used as the binder, it is also preferable to use methyl stearate or methyl docosanoate which is solid at room temperature and liquid at room temperature or higher. And, as will be described later, when the magnetic powder and binder mixture is magnetically oriented, the magnetic field orientation is performed in a state where the mixture is heated and softened above the melting point of the fatty acid ester.

By using a binder that satisfies the above conditions as a binder to be mixed with the magnet powder, the amount of carbon and oxygen contained in the magnet can be reduced. Specifically, the amount of carbon remaining in the magnet after sintering is 2000 ppm or less, more preferably 1000 ppm or less. Further, the amount of oxygen remaining in the magnet after sintering is set to 5000 ppm or less, more preferably 2000 ppm or less.

In addition, the amount of the binder added is an amount that appropriately fills the gaps between the magnet particles in order to improve the thickness accuracy of the molded body when molding a slurry or a heated and melted compound. For example, the ratio of the binder to the total amount of magnet powder and binder is 1 wt% to 40 wt%, more preferably 2 wt% to 30 wt%, and even more preferably 3 wt% to 20 wt%.

[Permanent magnet manufacturing method]
Next, a method for manufacturing the permanent magnet 1 according to the present invention will be described with reference to FIGS. 4 and 5 are explanatory views showing the manufacturing process of the permanent magnet 1 according to this embodiment.

First, an ingot made of a predetermined fraction of Nd—Fe—B (eg, Nd: 32.7 wt%, Fe (electrolytic iron): 65.96 wt%, B: 1.34 wt%) is manufactured. Thereafter, the ingot is roughly pulverized to a size of about 200 μm by a stamp mill or a crusher. Alternatively, the ingot is melted, flakes are produced by strip casting, and coarsely pulverized by hydrogen crushing. Thereby, coarsely pulverized magnet powder 10 is obtained.

Next, the coarsely pulverized magnet powder 10 is finely pulverized by a wet method using a bead mill 11 or a dry method using a jet mill. For example, in the fine pulverization using the wet method with the bead mill 11, the coarsely pulverized magnet powder 10 is finely pulverized in a solvent to a predetermined particle size (for example, 0.1 μm to 5.0 μm) and the magnet powder is dispersed in the solvent. . Moreover, there is no restriction | limiting in particular in the kind of solvent used for grinding | pulverization, Alcohols, such as isopropyl alcohol, ethanol, methanol, Esters, such as ethyl acetate, Lower hydrocarbons, such as pentane and hexane, Aromatics, such as benzene, toluene, xylene , Ketones, mixtures thereof and the like. In addition, Preferably, the solvent which does not contain an oxygen atom in a solvent is used.

On the other hand, in fine pulverization using a dry method using a jet mill, coarsely pulverized magnet powder is (a) in an atmosphere composed of an inert gas such as nitrogen gas, Ar gas, and He gas having substantially 0% oxygen content. Or (b) finely pulverized by a jet mill in an atmosphere made of an inert gas such as nitrogen gas, Ar gas, and He gas having an oxygen content of 0.0001 to 0.5%, A fine powder having an average particle diameter of 0.7 μm to 5.0 μm. The oxygen concentration of substantially 0% is not limited to the case where the oxygen concentration is completely 0%, but may contain oxygen in such an amount that a very small amount of oxide film is formed on the surface of the fine powder. Means good.

Next, an organometallic compound is added to the solvent containing the magnet powder after wet pulverization and mixed to adhere the organometallic compound to the particle surface of the magnet powder. As described above, the organometallic compound to be dissolved includes an organometallic compound containing Dy or the like and Nd and not containing an oxygen atom and a nitrogen atom, more specifically, a metal complex having a central metal of Dy or the like or Nd ( For example, tris (ethylcyclopentadienyl) Dy (III), tris (isopropylcyclopentadienyl) Tb (III), bis (cyclopentadienyl) Mg (II), bis (cyclopentadienyl) dibenzyl Nb ( IV), trihydridobis (pentamethyldicyclopentadienyl) Nb (V), bis (cyclopentadienyl) dimethyl Ti (IV), bis (cyclopentadienyl) dimethyl Zr (IV), dihydridobis (cyclopenta) Dienyl) Zr (IV), tris (tetramethylcyclopentadienyl) Nd (III), trioctylAl (III), diph It is desirable to use phenyl Zn (II), triphenyl Bi (III), Ag (I) t-butyl acetylide, mesityl Ag (I), triscyclopentadienyl Ga (III), etc.) or DIBAL. Further, the amount of the organometallic compound to be dissolved is not particularly limited, but the amount is such that the content of Dy or the like in the sintered magnet is 0.001 wt% to 10 wt%, preferably 0.01 wt% to 5 wt%. Is preferred. The organometallic compound may be added to the solvent before the pulverization step, and pulverization and mixing may be performed simultaneously. Moreover, when using the dry method by a jet mill, the organometallic compound is made to adhere to the particle | grain surface of a magnet powder by adding the pulverized magnet powder and the organometallic compound to a solvent, respectively, and mixing. Thereafter, the magnet powder contained in the solvent after the wet pulverization is dried by vacuum drying or the like, and the dried magnet powder is taken out.

Next, the magnet powder with the organometallic compound attached to the particle surface is molded into a desired shape. In addition, in the shaping | molding of magnet powder, there exist compacting which shape | molds to a desired shape, for example using a metal mold | die, and green body shaping | molding which shape | molds the mixture which mixed magnetic powder and the binder to the desired shape. Further, there are two types of compacting: a dry method in which a dried fine powder is filled into a cavity, and a wet method in which a slurry containing magnet powder is filled into a cavity without drying. On the other hand, in green body molding, the mixture may be directly molded into the final product shape, or the mixture is once molded into a shape other than the final product shape and magnetic field orientation is performed, and then punching, cutting, deformation, etc. are performed. It is good also as a final product shape by doing. In the following examples, the mixture is once formed into a sheet shape (hereinafter referred to as a green sheet) and then processed into a final product shape. In addition, when the mixture is formed into a sheet shape, for example, hot melt coating that forms a sheet shape after heating a compound in which a magnet powder and a binder are mixed, or a slurry containing a magnet powder, a binder, and an organic solvent. There is molding by slurry coating or the like that forms a sheet by coating the substrate on a substrate.

Hereinafter, green sheet forming using hot melt coating will be described.
First, a powdery mixture (compound) 12 composed of magnet powder and binder is prepared by mixing a binder with magnet powder. Here, as the binder, a resin, a long-chain hydrocarbon, a fatty acid ester, a mixture thereof, or the like is used as described above. For example, when a resin is used, a thermoplastic resin made of a depolymerizable polymer that does not contain an oxygen atom in the structure is used. On the other hand, when a long-chain hydrocarbon is used, the resin is solid at room temperature or above It is preferable to use a long-chain saturated hydrocarbon (long-chain alkane) that is liquid. Moreover, when using fatty acid ester, it is preferable to use methyl stearate, methyl docosanoate, or the like. Further, as described above, the amount of the binder added is such that the ratio of the binder to the total amount of the magnet powder and the binder in the compound 12 after the addition is 1 wt% to 40 wt%, more preferably 2 wt% to 30 wt%, still more preferably 3 wt%. % To 20 wt%.

In addition, an additive for promoting orientation may be added to the compound 12 in order to improve the degree of orientation in a magnetic field orientation step performed later. As the additive for promoting the orientation, for example, a hydrocarbon-based additive is used, and it is particularly preferable to use an additive having polarity (specifically, an acid dissociation constant pKa of less than 41). Moreover, the addition amount of the additive depends on the particle diameter of the magnet powder, and it is necessary to increase the addition amount as the particle diameter of the magnet powder is smaller. The specific addition amount is 0.1 to 10 parts, more preferably 1 to 8 parts, with respect to the magnet powder. The additive added to the magnet powder adheres to the surface of the magnet particles and has a role of assisting the rotation of the magnet particles in the magnetic field orientation process described later. As a result, orientation is easily performed when a magnetic field is applied, and the easy magnetization axis directions of the magnet particles can be aligned in the same direction (that is, the degree of orientation can be increased). In particular, when a binder is added to the magnet powder, since the binder is present on the particle surface, the frictional force at the time of orientation is increased and the orientation of the particles is lowered, so that the effect of adding the additive is further increased.

The binder is added in an atmosphere made of an inert gas such as nitrogen gas, Ar gas, or He gas. The mixing of the magnet powder and the binder is performed, for example, by putting the magnet powder and the binder in an organic solvent and stirring with a stirrer. In addition, heating and stirring may be performed to promote kneading properties. And the compound 12 is extracted by heating the organic solvent containing magnet powder and a binder after stirring, and vaporizing an organic solvent. The mixing of the magnet powder and the binder is preferably performed in an atmosphere made of an inert gas such as nitrogen gas, Ar gas, or He gas. In particular, when the magnet powder is pulverized by a wet method, the binder is added to the solvent without kneading the magnet powder from the solvent used for pulverization, and then the solvent is volatilized. It is good also as a structure to obtain.

Subsequently, a green sheet is formed by forming the compound 12 into a sheet shape. In particular, in hot melt coating, the compound 12 is heated to melt the compound 12 to form a fluid, and then the coating is applied on the support substrate 13 such as a separator. Then, the long sheet-like green sheet 14 is formed on the support base material 13 by heat dissipation and solidifying. The temperature at which the compound 12 is heated and melted is 50 to 300 ° C., although it varies depending on the type and amount of the binder used. However, the temperature needs to be higher than the melting point of the binder to be used. When slurry coating is used, magnet powder and a binder (additional additives may be added) are dispersed in a large amount of organic solvent, and the slurry is placed on a support substrate 13 such as a separator. Apply. Then, the green sheet 14 of a long sheet shape is formed on the support substrate 13 by drying and volatilizing the organic solvent.

Here, the coating method of the melted compound 12 is preferably a method having excellent layer thickness controllability such as a slot die method or a calendar roll method. In particular, in order to achieve high thickness accuracy, a die method or comma coating method that is particularly excellent in layer thickness controllability (that is, a method capable of applying a high-accuracy thickness layer on the surface of a substrate) It is desirable to use For example, in the slot die method, coating is performed by extruding a heated compound 12 in a fluid state by a gear pump and inserting the compound 12 into a die. In the calendar roll method, a certain amount of the compound 12 is charged into the gap between the two heated rolls, and the compound 12 melted by the heat of the roll is applied onto the support base 13 while rotating the roll. Moreover, as the support base material 13, for example, a silicone-treated polyester film is used. Furthermore, it is preferable to sufficiently defoam the film so that bubbles do not remain in the spreading layer by using an antifoaming agent or performing heating vacuum defoaming. In addition, the green sheet is formed on the support substrate 13 by molding the compound 12 melted by extrusion molding or injection molding into a sheet shape and extruding the support substrate 13 instead of coating on the support substrate 13. 14 may be formed.

Hereinafter, the process of forming the green sheet 14 by the slot die method will be described in more detail with reference to FIG. FIG. 6 is a schematic view showing a process of forming the green sheet 14 by the slot die method.
As shown in FIG. 6, the die 15 used in the slot die system is formed by superimposing the blocks 16 and 17 on each other, and a slit 18 and a cavity (liquid reservoir) 19 are formed by a gap between the blocks 16 and 17. Form. The cavity 19 communicates with a supply port 20 provided in the block 17. The supply port 20 is connected to a coating liquid supply system constituted by a gear pump (not shown) or the like, and the metered fluid-like compound 12 is quantified in the cavity 19 via the supply port 20. Supplied by a pump or the like. Further, the fluid-like compound 12 supplied to the cavity 19 is fed to the slit 18 and discharged from the discharge port 21 of the slit 18 with a predetermined application width with a uniform amount in the width direction at a constant amount per unit time. . On the other hand, the support base material 13 is continuously conveyed at a preset speed as the coating roll 22 rotates. As a result, the ejected fluid compound 12 is applied to the support base material 13 with a predetermined thickness, and then heat-radiating and solidifying to form a long sheet-like green sheet 14 on the support base material 13. Is done.

In the process of forming the green sheet 14 by the slot die method, the sheet thickness of the green sheet 14 after coating is measured, and the gap D between the die 15 and the support base 13 is feedback-controlled based on the measured value. desirable. Further, the fluctuation of the amount of the fluid compound 12 supplied to the die 15 is reduced as much as possible (for example, suppressed to fluctuation of ± 0.1% or less), and the fluctuation of the coating speed is reduced as much as possible (for example, ± 0. It is desirable to suppress the fluctuation to 1% or less. Thereby, it is possible to further improve the thickness accuracy of the green sheet 14. The thickness accuracy of the formed green sheet 14 is within ± 10%, more preferably within ± 3%, and even more preferably within ± 1% with respect to the design value (for example, 1 mm). In the other calendar roll method, it is possible to control the transfer film thickness of the compound 12 onto the support base 13 by similarly controlling the calendar conditions based on the actually measured values.

The set thickness of the green sheet 14 is desirably set in the range of 0.05 mm to 20 mm. When the thickness is less than 0.05 mm, the productivity must be reduced because multiple layers must be stacked.

Next, magnetic field orientation of the green sheet 14 formed on the support base material 13 is performed by the hot melt coating described above. Specifically, the green sheet 14 is first softened by heating the green sheet 14 that is continuously conveyed together with the support base material 13. Specifically, the green sheet 14 is softened until the viscosity becomes 1 to 1500 Pa · s, more preferably 1 to 500 Pa · s. Thereby, the magnetic field orientation can be appropriately performed.

The temperature and time for heating the green sheet 14 vary depending on the type and amount of the binder used, but for example, 100 to 250 ° C. and 0.1 to 60 minutes. However, in order to soften the green sheet 14, it is necessary to set the temperature to be equal to or higher than the glass transition point or melting point of the binder used. As a heating method for heating the green sheet 14, for example, there are a heating method using a hot plate and a heating method using a heat medium (silicone oil) as a heat source. Next, magnetic field orientation is performed by applying a magnetic field to the in-plane direction and the length direction of the green sheet 14 softened by heating. The intensity of the applied magnetic field is 5000 [Oe] to 150,000 [Oe], preferably 10,000 [Oe] to 120,000 [Oe]. As a result, the C axis (easy magnetization axis) of the magnet crystal included in the green sheet 14 is oriented in one direction. Note that the magnetic field may be applied in the in-plane direction and the width direction of the green sheet 14. Moreover, it is good also as a structure which orientates a magnetic field simultaneously with respect to the several green sheet 14. FIG.

Furthermore, when applying a magnetic field to the green sheet 14, a configuration in which a magnetic field is applied at the same time as the heating process may be performed, or a magnetic field may be applied after the heating process and before the green sheet solidifies. It is good also as performing the process to perform. Moreover, it is good also as a structure which magnetic field orientates before the green sheet 14 apply | coated by hot-melt application solidifies. In that case, the heating step is not necessary.

Next, the heating process and the magnetic field orientation process of the green sheet 14 will be described in more detail with reference to FIG. FIG. 7 is a schematic view showing a heating process and a magnetic field orientation process of the green sheet 14. In the example shown in FIG. 7, an example in which the magnetic field orientation process is performed simultaneously with the heating process will be described.

As shown in FIG. 7, heating and magnetic field orientation on the green sheet 14 coated by the slot die method described above are performed on the long green sheet 14 in a state of being continuously conveyed by a roll. That is, an apparatus for performing heating and magnetic field orientation is disposed on the downstream side of the coating apparatus (die or the like), and is performed by a process continuous with the above-described coating process.

Specifically, the solenoid 25 is disposed on the downstream side of the die 15 and the coating roll 22 so that the transported support base material 13 and the green sheet 14 pass through the solenoid 25. Further, the hot plates 26 are arranged in a pair above and below the green sheet 14 in the solenoid 25. The green sheet 14 is heated by a pair of upper and lower hot plates 26 and an electric current is passed through the solenoid 25, so that the in-plane direction of the long green sheet 14 (that is, the sheet surface of the green sheet 14). A magnetic field in the longitudinal direction). Thereby, the continuously conveyed green sheet 14 is softened by heating, and a magnetic field is applied to the in-plane direction and the length direction (in the direction of arrow 27 in FIG. 7) of the softened green sheet 14. On the other hand, it becomes possible to orient a uniform magnetic field appropriately. In particular, the surface of the green sheet 14 can be prevented from standing upright by setting the direction in which the magnetic field is applied to the in-plane direction.
Moreover, it is preferable that the heat dissipation and solidification of the green sheet 14 performed after the magnetic field orientation is performed in a transported state. Thereby, the manufacturing process can be made more efficient.

When the magnetic field orientation is performed in the in-plane direction and the width direction of the green sheet 14, a pair of magnetic field coils are arranged on the left and right of the green sheet 14 that is conveyed instead of the solenoid 25. And it becomes possible to generate a magnetic field in the in-plane direction and the width direction of the long sheet-like green sheet 14 by passing a current through each magnetic field coil.

It is also possible to make the magnetic field orientation perpendicular to the surface of the green sheet 14. When the magnetic field orientation is performed in a direction perpendicular to the surface of the green sheet 14, for example, the magnetic field application device using a pole piece or the like is used. Specifically, as shown in FIG. 8, the magnetic field application device 30 using a pole piece or the like includes two ring-shaped coil portions 31 and 32 arranged in parallel so that the central axes are the same, and the coil portion 31. , 32 and two substantially cylindrical pole pieces 33, 34 respectively disposed in the ring holes, and are spaced apart from the conveyed green sheet 14 by a predetermined distance. And a magnetic field is produced | generated to a perpendicular | vertical direction with respect to the surface of the green sheet 14 by sending an electric current through the coil parts 31 and 32, and the magnetic field orientation of the green sheet 14 is performed. In the case where the magnetic field orientation direction is perpendicular to the surface of the green sheet 14, the film 35 is also formed on the opposite surface of the green sheet 14 on which the support base material 13 is laminated as shown in FIG. Are preferably laminated. Accordingly, it is possible to prevent the surface of the green sheet 14 from standing upside down.

Further, instead of the heating method using the hot plate 26 described above, a heating method using a heat medium (silicone oil) as a heat source may be used. Here, FIG. 9 is a diagram showing an example of a heating device 37 using a heat medium.
As shown in FIG. 9, the heating device 37 forms a substantially U-shaped cavity 39 inside a flat plate member 38 serving as a heating element, and heat heated to a predetermined temperature (for example, 100 to 300 ° C.) in the cavity 39. It is set as the structure which circulates the silicone oil which is a medium. Then, instead of the hot plate 26 shown in FIG. 7, the heating device 37 is disposed in a pair above and below the green sheet 14 in the solenoid 25. Thereby, the continuously conveyed green sheet 14 is heated and softened through the flat plate member 38 that is heated by the heat medium. The flat plate member 38 may be brought into contact with the green sheet 14 or may be arranged at a predetermined interval. A magnetic field is applied to the in-plane direction and the length direction of the green sheet 14 (in the direction of the arrow 27 in FIG. 7) by the solenoid 25 arranged around the softened green sheet 14. An appropriate uniform magnetic field can be oriented. Note that the heating device 37 using the heat medium as shown in FIG. 9 does not have a heating wire inside unlike the general hot plate 26, so even if it is placed in a magnetic field, There is no possibility that the heating wire vibrates or is cut, and the green sheet 14 can be appropriately heated. In addition, when performing control by electric current, there is a problem that causes fatigue failure due to vibration of the heating wire when the power is turned on or off, but by using the heating device 37 using a heat medium as a heat source, Such a problem can be solved.

Here, when the green sheet 14 is formed from a liquid material having high fluidity such as slurry by a general slot die method or doctor blade method without using hot melt molding, a magnetic field gradient is generated. When the green sheet 14 is carried in, the magnetic powder contained in the green sheet 14 is attracted toward the stronger magnetic field, so that the slurry forming the green sheet 14 is closer to the liquid, that is, the thickness of the green sheet 14 is uneven. May occur. On the other hand, when the compound 12 is molded into the green sheet 14 by hot melt molding as in the present invention, the viscosity near room temperature reaches several tens of thousands to several hundred thousand Pa · s, and the magnetism when passing through the magnetic field gradient is reached. There is no powder slippage. Furthermore, the viscosity of the binder is lowered by being transported and heated in a uniform magnetic field, and uniform C-axis orientation is possible only by the rotational torque in the uniform magnetic field.

Further, when the green sheet 14 is molded by a liquid material having high fluidity such as a slurry containing an organic solvent by a general slot die method or doctor blade method without using hot melt molding, the thickness exceeds 1 mm. When an attempt is made to produce a sheet, foaming due to vaporization of the organic solvent contained in the slurry or the like during drying becomes a problem. Further, if the drying time is prolonged to suppress foaming, the magnet powder is settled, and accordingly, the density distribution of the magnet powder is biased with respect to the direction of gravity, which causes warping after firing. Therefore, in the molding from the slurry, the upper limit value of the thickness is substantially regulated, so it is necessary to mold the green sheet with a thickness of 1 mm or less and then laminate it. However, in such a case, the entanglement between the binders becomes poor, and delamination occurs in the subsequent binder removal step (calcination process), which causes a decrease in C-axis (easy magnetization axis) orientation, that is, residual magnetic flux density ( Br) decreases. On the other hand, when the compound 12 is molded into the green sheet 14 by hot melt molding as in the present invention, since it does not contain an organic solvent, even when a sheet having a thickness exceeding 1 mm is prepared, Concerns are resolved. And since the binder is in a sufficiently entangled state, there is no possibility of delamination in the debinding process.

When applying a magnetic field to a plurality of green sheets 14 at the same time, for example, a plurality of (for example, six) green sheets 14 are continuously conveyed, and the stacked green sheets 14 pass through the solenoid 25. Configure to pass. As a result, productivity can be improved.

Thereafter, the green sheet 14 subjected to the magnetic field orientation is punched into a desired product shape (for example, a fan shape shown in FIG. 1), and a formed body 40 is formed.

Subsequently, a non-oxidizing atmosphere (particularly a hydrogen atmosphere or hydrogen in the present invention) in which the molded body 40 is pressurized to atmospheric pressure, or a pressure higher or lower than atmospheric pressure (for example, 1.0 Pa or 1.0 MPa). Several hours to several tens of hours at a binder decomposition temperature in a mixed gas atmosphere of an inert gas and an inert gas (a temperature satisfying a condition equal to or higher than the thermal decomposition temperature of the additive if an additive that promotes orientation is added) For example, the calcining process is performed by holding for 5 hours. In the case of performing in a hydrogen atmosphere, for example, the supply amount of hydrogen during calcination is set to 5 L / min. By performing the calcination treatment, an organic compound such as a binder can be decomposed into a monomer by a depolymerization reaction or the like and scattered to be removed. Also, carbon can be removed while pyrolyzing the organometallic compound and leaving the metal element at the grain boundary. That is, so-called decarbonization for reducing the amount of carbon in the molded body 40 is performed. The calcining treatment is performed under the condition that the carbon content in the molded body 40 is 2000 ppm or less, more preferably 1000 ppm or less. Accordingly, the entire permanent magnet 1 can be densely sintered by the subsequent sintering process, and the residual magnetic flux density and coercive force are not reduced. Moreover, when performing the pressurization conditions at the time of performing the calcining process mentioned above by the pressure higher than atmospheric pressure, it is desirable to set it as 15 Mpa or less. In addition, if the pressurizing condition is a pressure higher than atmospheric pressure, more specifically 0.2 MPa or more, the effect of reducing the carbon amount can be expected.

The binder decomposition temperature is determined based on the analysis results of the binder decomposition product and decomposition residue. Specifically, a temperature range is selected in which decomposition products of the binder are collected, decomposition products other than the monomers are not generated, and products due to side reactions of the remaining binder components are not detected even in the analysis of the residues. Although it varies depending on the kind of the binder, it is set to 200 ° C. to 900 ° C., more preferably 400 ° C. to 600 ° C. (eg, 450 ° C.). Further, the thermal decomposition temperature of the organometallic compound is determined depending on the kind of the organometallic compound to be added, but basically the thermal decomposition of the organometallic compound can be performed at the binder decomposition temperature. In addition, when shape | molding (for example, compacting) without mixing a binder with magnet powder, a calcination process is performed at the thermal decomposition temperature of an organometallic compound.
In particular, when the magnet raw material is pulverized by wet pulverization in an organic solvent, the calcining treatment is performed at the thermal decomposition temperature and binder decomposition temperature of the organic compound constituting the organic solvent. Thereby, the remaining organic solvent can be removed. The thermal decomposition temperature of the organic compound is determined depending on the type of the organic solvent to be used, but basically the thermal decomposition of the organic compound can be performed at the binder decomposition temperature.

Further, in the calcining process, it is preferable that the heating rate is reduced as compared with a case where a general magnet is sintered. Specifically, the temperature rising rate is set to 2 ° C./min or less (for example, 1.5 ° C./min). Therefore, when performing the calcining treatment, the temperature is increased at a predetermined temperature increase rate of 2 ° C./min or less, and after reaching a preset set temperature (binder decomposition temperature), at the set temperature for several hours to Calcination is performed by holding for several tens of hours. By reducing the heating rate in the calcination treatment as described above, the carbon in the molded body 40 is not removed rapidly but is removed in stages, so that the density of the sintered permanent magnet is increased ( That is, it is possible to reduce the air gap in the permanent magnet. And if a temperature increase rate shall be 2 degrees C / min or less, the density of the permanent magnet after sintering can be made 95% or more, and a high magnet characteristic can be anticipated.

Moreover, you may perform a dehydrogenation process by hold | maintaining the molded object 40 calcined by the calcination process in a vacuum atmosphere succeedingly. In the dehydrogenation treatment, NdH ₃ (high activity) in the molded body 40 produced by the calcination treatment is changed stepwise from NdH ₃ (high activity) → NdH ₂ (low activity). The activity of the molded body 40 activated by the calcination treatment is reduced. Thereby, even when the compact 40 that has been calcined by the calcining process is subsequently moved to the atmosphere, Nd is prevented from being combined with oxygen, and the residual magnetic flux density and coercive force are reduced. There is no. Moreover, the effect of returning the structure of the magnet crystals from NdH ₂ etc. to _Nd 2 _{Fe 14} B structure can be expected.

Subsequently, a sintering process for sintering the compact 40 that has been calcined by the calcining process is performed. In addition, as a sintering method of the molded body 40, it is also possible to use pressure sintering which sinters in a state where the molded body 40 is pressed in addition to general vacuum sintering. For example, when sintering is performed by vacuum sintering, the temperature is raised to a firing temperature of about 800 ° C. to 1080 ° C. at a predetermined temperature increase rate and held for about 0.1 to 2 hours. During this time, vacuum firing is performed, but the degree of vacuum is 5 Pa or less, preferably 10-2 Pa or less. Thereafter, it is cooled and heat-treated again at 300 ° C. to 1000 ° C. for 2 hours. As a result of the sintering, a sintered compact of the magnet (hereinafter referred to as “sintered body 50”) is obtained.

On the other hand, examples of pressure sintering include hot press sintering, hot isostatic pressing (HIP) sintering, ultrahigh pressure synthetic sintering, gas pressure sintering, and discharge plasma (SPS) sintering. . However, in order to suppress the grain growth of the magnet particles during sintering and to suppress the warpage generated in the sintered magnet, the SPS is uniaxial pressure sintering that pressurizes in a uniaxial direction and is sintered by current sintering. Sintering is preferably used. When sintering is performed by SPS sintering, the pressure value is set to, for example, 0.01 MPa to 100 MPa, the pressure is increased to 940 ° C. at 10 ° C./min in a vacuum atmosphere of several Pa or less, and then held for 5 minutes. Is preferred. Thereafter, it is cooled and heat-treated again at 300 ° C. to 1000 ° C. for 2 hours. As a result of sintering, a sintered body 50 is obtained.

Below, the pressure sintering process of the molded object 40 by SPS sintering is demonstrated in detail using FIG. FIG. 10 is a schematic diagram showing a pressure sintering process of the compact 40 by SPS sintering.
As shown in FIG. 10, when performing SPS sintering, first, the compact 40 is installed in the sintering die 41 made of graphite. The calcining process described above may also be performed in a state where the molded body 40 is installed in the sintering mold 41. Then, the compact 40 placed in the sintering die 41 is held in the vacuum chamber 42, and an upper punch 43 and a lower punch 44 made of graphite are set. Then, a low-voltage and high-current DC pulse voltage / current is applied using the upper punch electrode 45 connected to the upper punch 43 and the lower punch electrode 46 connected to the lower punch 44. At the same time, a load is applied to the upper punch 43 and the lower punch 44 from above and below using a pressure mechanism (not shown). As a result, the compact 40 placed in the sintering die 41 is sintered while being pressurized. In order to improve productivity, it is preferable to perform SPS sintering simultaneously on a plurality of (for example, 10) shaped bodies. In addition, when performing SPS sintering with respect to the some molded object 40 simultaneously, you may arrange | position the several molded object 40 in one space, and arrange | position in the space which is different for every molded object 40. Also good. In addition, when arrange | positioning in the space which differs for every molded object 40, the upper punch 43 and the lower punch 44 which pressurize the molded object 40 for every space are united between each space (namely, one united one). And driving the upper punch 43 and the lower punch 44 to simultaneously pressurize a plurality of molded bodies in each space).

Next, as shown in FIG. 5, the sintered body 50 sintered by the above sintering treatment is set in a sputtering apparatus, and Nd sputtering is performed on the surface of the sintered body 50. The sputtering conditions are, for example, 300 mA and 60 minutes. Note that Nd sputtering is performed on both sides of the sintered body 50 when the sintered body 50 has a thin plate shape as shown in FIG. As a result, an Nd thin film 51 is formed on the surface of the sintered body 50.

Subsequently, Cu is further sputtered on the surface of the sintered body 50 on which the Nd sputtering has been performed. The sputtering conditions are, for example, 300 mA and 15 minutes. Cu sputtering is performed on both surfaces of the sintered body 50 when the sintered body 50 has a thin plate shape as shown in FIG. As a result, a Cu thin film 52 is also formed on the surface of the sintered body 50 so as to overlap the Nd thin film 51.

Thereafter, by heating the sintered body 50 on which the Nd thin film 51 and the Cu thin film 52 are respectively formed by the sputtering process, Cu sputtered on the surface of the sintered body 50 is diffused into the sintered body 50. The diffusion process is performed. The diffusion treatment is performed at a temperature lower than the sintering temperature in a vacuum atmosphere and higher than the melting point of an intermetallic compound of Cu and Nd (for example, Nd—Cu) (for example, 600 ° C. to 800 ° C.) for a certain time (for example, 5 hours) by heating. As a result, Cu sputtered on the surface of the sintered body 50 becomes a liquid phase at the stage of diffusion treatment and penetrates into the grain boundaries, and Cu can be unevenly distributed in the grain boundaries.

Here, Cu has a lower melting point in an alloy with Nd than in a single metal. Therefore, the diffusion treatment can be performed at a low temperature, and there is no possibility of grain growth at the stage of the diffusion treatment. Further, even when the amount of Cu added is small (for example, 0.1 wt%), Cu can be appropriately unevenly distributed with respect to the grain boundary. And as a result of performing the said diffusion process, the permanent magnet 1 is manufactured.

Further, the sintered body 50 after the sintering by the sintering process and before or after the diffusion process may be further heat-treated. The heat treatment is performed by once releasing the heat of the sintered body and heating it in a vacuum atmosphere at a temperature lower than the sintering temperature (460 ° C. to 600 ° C.) for a certain time (for example, 1 hour).

Here, in the cooling stage after the sintering process, Dy and Nd contained in the organometallic compound form a eutectic in the sintered body. In particular, when Dy or the like contained in the organometallic compound is a specific metal (for example, Al, Ag, Ga (hereinafter referred to as Al or the like)), the eutectic has a lower melting point than Nd alone. Therefore, if heat treatment is performed at a temperature higher than the melting point of eutectic of Al and the like contained in the organometallic compound after sintering, the melting point is lowered by eutectic with Al and the like contained in the organometallic compound. The Nd-rich phase becomes a liquid phase at the stage of heat treatment and penetrates into the grain boundaries, and a uniform Nd-rich phase can be formed at the grain boundaries. As a result, the coercive force of the permanent magnet 1 can be improved. In addition, since the heat treatment is performed at a low temperature, there is no possibility of grain growth at the stage of the heat treatment.

Furthermore, if the heat treatment is performed at a temperature higher than the melting point of the eutectic of Cu or the like contained in the organometallic compound and Nd, an alloy made of Al or the like that has become a liquid phase together with the Nd-rich phase is allowed to penetrate into the grain boundaries. It becomes possible. As a result, even when the amount of the organometallic compound added is small (for example, 0.1 wt%), Al or the like contained in the organometallic compound can be appropriately unevenly distributed with respect to the grain boundary.

Examples of the present invention will be described below in comparison with comparative examples.
(Example)
The alloy composition of the neodymium magnet powder of Example 1 is Nd / Fe / B = 32.7 / 65.96 / 1.34 in wt%. And it shape | molded into the molded object of thickness 3mm by green sheet shaping | molding. The calcining treatment is carried out at 450 ° C. in a hydrogen atmosphere at atmospheric pressure (in this example, it is assumed that the atmospheric pressure at the time of manufacture is the standard atmospheric pressure (about 0.1 MPa) in particular in this embodiment). Performed by holding time. Further, after the calcined body is vacuum-sintered, Nd sputtering is performed on the upper and lower surfaces of the sintered body at a current value of 300 mA for 60 minutes, and subsequently, the current value of 300 mA is also applied to the upper and lower surfaces of the sintered body. Then, sputtering of Cu was performed for 15 minutes. As the sputtering apparatus, an MSP-30T magnetron sputtering apparatus (manufactured by vacuum device) was used. Moreover, the amount of Cu contained in the sintered body after sputtering was 0.13 wt%. Further, after performing sputtering of Cu, diffusion treatment was performed by holding the sintered body at 800 ° C. in a vacuum atmosphere for 5 hours. After that, the sintered body was further heat-treated by holding it at 500 ° C. for 1 hour in a vacuum atmosphere. The other steps are the same as those described in the above [Permanent magnet manufacturing method].

(Comparative example)
The magnet raw material was previously configured to include 0.1 wt% Cu, and the magnet raw material containing Cu was pulverized to produce a neodymium magnet powder. Further, Nd and Cu were not sputtered onto the sintered body, and the diffusion treatment was also omitted. Other conditions are the same as in the example.

(Comparison study of magnet characteristics of Example and Comparative Example)
The coercive force [kOe] of each permanent magnet of the example and the comparative example was measured. FIG. 11 shows a list of measurement results.

Here, when the coercive force of each of the permanent magnets of the example and the comparative example is compared, the amount of added Cu is substantially the same, but Cu is not included in the magnet raw material and is unevenly distributed at the grain boundaries by sputtering. The permanent magnet of the example showed higher coercivity than the permanent magnet of the comparative example. That is, in the permanent magnet of the comparative example, Cu is already contained in the molded body at the time when the molded body is calcined in a hydrogen atmosphere. It is predicted that the reaction of) was easy to proceed to the right.
Nd ₂ Fe ₁₄ B + 2H ₂ → 2NdH ₂ + 12Fe + Fe ₂ B (2)
The reaction (2) proceeds to the right, whereby the main phase (Nd ₂ Fe ₁₄ B) of the rare earth magnet is decomposed and αFe is precipitated, resulting in a decrease in coercive force. It is done.

On the other hand, in the permanent magnet of the example, when the calcining treatment of the molded body is performed in a hydrogen atmosphere, since the molded body does not contain Cu, the reaction (2) above is performed on the right side when performing the calcining treatment. It is predicted that it was difficult to proceed. As a result, in the rare earth permanent magnets of the examples, it is considered that the main phase (Nd ₂ Fe ₁₄ B) of the rare earth magnet is not decomposed, the precipitation of αFe is suppressed, and a high coercive force is exhibited.

As described above, in the permanent magnet 1 and the method for manufacturing the permanent magnet 1 according to the present embodiment, the magnet raw material not containing Cu is pulverized, and the molded body is molded at 200 ° C. to 900 ° C. for several hours in a hydrogen atmosphere. Calcination is performed by holding for tens of hours. Thereafter, the compact is sintered by vacuum sintering or pressure sintering, and the permanent magnet 1 is manufactured by sputtering Cu on the surface of the sintered body. As a result, it is possible to improve the coercive force due to Cu, and even when calcination is performed in a hydrogen atmosphere, the decomposition of the main phase and the precipitation of αFe are suppressed, and the magnetic properties are reduced. Can be prevented.
In addition, by heating the sintered body on which Cu is sputtered, Cu sputtered on the surface of the sintered body is diffused inside the sintered body, so that Cu is not included in the magnet raw material in advance before sintering. It becomes possible to appropriately distribute the sputtered Cu with respect to the grain boundary. That is, the effect of improving the coercive force by Cu can be obtained without previously including Cu in the magnet raw material.
Further, when heating the sintered body on which Cu is sputtered, it is heated at a temperature lower than the firing temperature (for example, 800 ° C.), so in the step of diffusing the sputtered Cu inside the sintered body, It is possible to prevent grain growth.
In addition, since Cu is sputtered onto the surface of the sintered body after Nd is sputtered onto the surface of the sintered body, the step of diffusing the sputtered Cu inside the sintered body can be performed at a lower temperature. .
In addition, the pulverized magnet powder contains Al, Dy, Tb, Nd, V, Mo, Zr, Ta, Ti, W, Ag, Ga, Co, Bi, Zn, Mg, or Nb and oxygen atoms and An organometallic compound that does not contain nitrogen atoms is added, the organometallic compound is uniformly attached to the surface of the magnet particles, and a compact is formed by molding the magnet powder with the organometallic compound attached to the surface of the particles. Therefore, Al, Dy, Tb, Nd, V, Mo, Zr, Ta, Ti, W, Ag, Ga, Co, Bi, Zn, Mg, or Nb contained in the organometallic compound is efficient with respect to the grain boundary of the magnet. Can be unevenly distributed. As a result, the magnetic performance of the permanent magnet can be improved. In addition, since the amount of addition of Al, Dy, Tb, Nd, V, Mo, Zr, Ta, Ti, W, Ag, Ga, Co, Bi, Zn, Mg, or Nb can be reduced compared to the conventional case, the residual magnetic flux A decrease in density can be suppressed.
In addition, a metal complex whose central metal is Al, Dy, Tb, Nd, V, Mo, Zr, Ta, Ti, W, Ag, Ga, Co, Bi, Zn, Mg, or Nb, or diisobutylaluminum hydride is organic. Since it is used as a metal compound, the organometallic compound can be easily thermally decomposed in the subsequent heating step, and the metal contained in the organometallic compound can be appropriately distributed with respect to the grain boundaries. In addition, the amount of carbon remaining in the magnet can be reduced by performing thermal decomposition. As a result, it is possible to sinter the entire magnet densely without generating voids between the main phase and the grain boundary phase of the sintered magnet, and to prevent the coercive force from being lowered. . Further, a large number of αFe is not precipitated in the main phase of the magnet after sintering, and the magnet characteristics are not greatly deteriorated.
In addition, a permanent magnet is composed of a magnet obtained by mixing magnet powder and a binder and sintering a molded green sheet, so deformation due to sintering becomes uniform and deformation such as warpage and dent after sintering occurs. In addition, since pressure unevenness during pressing is eliminated, there is no need to perform post-sintering correction processing, which has been conventionally performed, and the manufacturing process can be simplified. Thereby, a permanent magnet can be formed with high dimensional accuracy.

In addition, this invention is not limited to the said Example, Of course, various improvement and deformation | transformation are possible within the range which does not deviate from the summary of this invention.
For example, the pulverization conditions, kneading conditions, magnetic field orientation process, calcining conditions, sintering conditions, sputtering conditions, diffusion treatment conditions, heat treatment conditions, etc. of the magnet powder are not limited to the conditions described in the above examples. For example, in the above embodiment, the green sheet is formed by the slot die method, but other methods (for example, calendar roll method, comma coating method, extrusion molding, injection molding, mold molding, doctor blade method, etc.) can be used. It may be used to form a green sheet. Moreover, it is good also as producing a green sheet by producing | generating the slurry which mixed magnet powder and a binder with the solvent, and shape | molding the slurry produced | generated after that in the sheet form. In that case, it is also possible to use other than the thermoplastic resin as the binder. Moreover, as long as the atmosphere at the time of calcination is a non-oxidizing atmosphere, the atmosphere may be other than a hydrogen atmosphere (for example, a nitrogen atmosphere, a He atmosphere, or an Ar atmosphere). Alternatively, only Cu sputtering may be performed without performing Nd sputtering. However, in that case, the heating temperature for diffusing the sputtered Cu into the sintered body needs to be higher. Further, the order of sputtering of Cu and Nd may be changed.

In the above embodiment, the magnetic field orientation is performed after the mixture of the magnet powder and the binder is once molded into a sheet shape. However, the magnetic field orientation may be performed after molding into a shape other than the sheet shape. For example, it may be molded into a block shape. Then, the block-shaped molded body oriented in the magnetic field is further processed to form a final product shape.

In the above embodiment, resin, long chain hydrocarbon or fatty acid ester is used as the binder, but other materials may be used.

Further, the permanent magnet may be manufactured by calcining and sintering a molded body formed by molding other than green sheet molding (for example, compaction molding). Even in such a case, the decarburization effect by calcining can be achieved for C-containing materials (added organometallic compounds, organic compounds remaining by wet pulverization, etc.) remaining in the molded body other than the binder. I can expect. Furthermore, in the above embodiment, calcining is performed in a hydrogen atmosphere or a mixed gas atmosphere of hydrogen and an inert gas after the magnet powder is molded. It is good also as manufacturing a permanent magnet by shape | molding the magnetic powder which is a body into a molded object, and performing sintering after that. With such a configuration, since the powdered magnet particles are calcined, the surface area of the magnet to be calcined is increased compared to the case of calcining the molded magnet particles. can do. That is, the amount of carbon in the calcined body can be reduced more reliably. However, when molding with a green body, it is desirable to perform a calcining treatment after molding in order to thermally decompose the binder by the calcining treatment.

Moreover, in the said Example, although it is supposed that the heating process and magnetic field orientation process of the green sheet 14 will be performed simultaneously, even if it performs a magnetic field orientation process after performing a heating process and before the green sheet 14 solidifies. good. Further, when the magnetic field orientation is performed before the coated green sheet 14 is solidified (that is, the green sheet 14 is already softened without performing the heating process), the heating process may be omitted. .

Further, in the above embodiment, the coating process by the slot die method, the heating process, and the magnetic field orientation process are performed by a series of continuous processes, but may be configured not to be performed by the continuous processes. Moreover, it is good also as performing by the process which divided | segmented into the 1st process to a coating process, and the 2nd process after a heating process, respectively. In that case, the coated green sheet 14 can be cut to a predetermined length, and the green sheet 14 in a stationary state can be configured to perform magnetic field orientation by heating and applying a magnetic field. is there.

In the above embodiment, tris (ethylcyclopentadienyl) Dy (III), tris (isopropylcyclopentadienyl) Tb (III), bis (cyclopentadienyl) Mg ( II), bis (cyclopentadienyl) dibenzyl Nb (IV), trihydridobis (pentamethyldicyclopentadienyl) Nb (V), bis (cyclopentadienyl) dimethyl Ti (IV), bis (cyclopenta Dienyl) dimethyl Zr (IV), dihydridobis (cyclopentadienyl) Zr (IV), tris (tetramethylcyclopentadienyl) Nd (III), trioctyl Al (III), diphenyl Zn (II), triphenyl Bi (III), Ag (I) t-butyl acetylide, mesityl Ag (I), triscyclopentadienyl Ga (II I), DIBAL is used, but contains Al, Dy, Tb, Nd, V, Mo, Zr, Ta, Ti, W, Ag, Ga, Co, Bi, Zn, Mg, or Nb and oxygen atoms and nitrogen Other organometallic compounds may be used as long as they do not contain atoms. For example, a metal complex other than a metal alkyl complex may be used. In addition, the organometallic compound may include an element other than the metal element (for example, Si).

In the present invention, the Nd—Fe—B type magnet has been described as an example, but other magnets (for example, samarium type cobalt magnet, alnico magnet, ferrite magnet, etc.) may be used. Further, in the present invention, the Nd component is larger than the stoichiometric composition in the present invention, but it may be stoichiometric. Further, the present invention can be applied not only to anisotropic magnets but also to isotropic magnets. In that case, the magnetic field orientation process for the green sheet 14 can be omitted.

DESCRIPTION OF SYMBOLS 1 Permanent magnet 2 Nd crystal particle 3 Metal uneven distribution layer 12 Compound 14 Green sheet 40 Forming body

Claims (14)

1. Crushing magnet raw material into magnet powder;
   Forming a molded body by molding the pulverized magnet powder;
   A step of calcining the magnet powder in a hydrogen atmosphere or a mixed gas atmosphere of hydrogen and an inert gas before or after molding and before sintering;
   Sintering by holding the molded body at a firing temperature to obtain a sintered body;
   A rare earth permanent magnet manufactured by sputtering Cu on the surface of the sintered body.
2. 2. The method according to claim 1, wherein Cu is sputtered on a surface of the sintered body to be diffused into the sintered body by heating the sintered body on which Cu is sputtered. The rare earth permanent magnet described.
3. 3. The rare earth permanent magnet according to claim 2, wherein the sintered body on which Cu is sputtered is heated at a temperature lower than the firing temperature.
4. 4. The step of sputtering Cu on the surface of the sintered body includes sputtering Cu on the surface of the sintered body after sputtering Nd on the surface of the sintered body. The rare earth permanent magnet according to any one of the above.
5. The pulverized magnet powder contains Al, Dy, Tb, Nd, V, Mo, Zr, Ta, Ti, W, Ag, Ga, Co, Bi, Zn, Mg, or Nb and oxygen atoms and nitrogen atoms. By adding no organometallic compound, the organometallic compound is attached to the particle surface of the magnet powder,
   The rare earth permanent magnet according to any one of claims 1 to 4, wherein a molded body is formed by molding the magnet powder in which the organometallic compound is adhered to the particle surface.
6. The organometallic compound is a metal complex or hydrogenation whose central metal is Al, Dy, Tb, Nd, V, Mo, Zr, Ta, Ti, W, Ag, Ga, Co, Bi, Zn, Mg or Nb. 6. The rare earth permanent magnet according to claim 5, wherein the rare earth permanent magnet is diisobutylaluminum.
7. In the step of forming the magnet powder into a molded body,
   Producing a mixture in which the magnet powder and the binder are mixed;
   The rare earth permanent magnet according to claim 1, wherein a green sheet is produced as the formed body by forming the mixture into a sheet shape.
8. Crushing magnet raw material into magnet powder;
   Forming a molded body by molding the pulverized magnet powder;
   A step of calcining the magnet powder in a hydrogen atmosphere or a mixed gas atmosphere of hydrogen and an inert gas before or after molding and before sintering;
   Sintering by holding the molded body at a firing temperature to obtain a sintered body;
   And a step of sputtering Cu on the surface of the sintered body.
9. 9. The method according to claim 8, further comprising a step of diffusing Cu sputtered on the surface of the sintered body into the sintered body by heating the sintered body on which Cu is sputtered. A method for producing a rare earth permanent magnet.
10. The method for producing a rare earth permanent magnet according to claim 9, wherein when the sintered body sputtered with Cu is heated, the sintered body is heated at a temperature lower than the firing temperature.
11. 11. The step of sputtering Cu on the surface of the sintered body includes sputtering Cu on the surface of the sintered body after sputtering Nd on the surface of the sintered body. The manufacturing method of the rare earth permanent magnet in any one of.
12. The pulverized magnet powder contains Al, Dy, Tb, Nd, V, Mo, Zr, Ta, Ti, W, Ag, Ga, Co, Bi, Zn, Mg, or Nb and oxygen atoms and nitrogen atoms. By adding no organometallic compound, the organometallic compound is attached to the particle surface of the magnet powder,
    The method for producing a rare earth permanent magnet according to any one of claims 8 to 11, wherein a molded body is formed by molding the magnet powder having the organometallic compound attached to the particle surface.
13. The organometallic compound is a metal complex or hydrogenation whose central metal is Al, Dy, Tb, Nd, V, Mo, Zr, Ta, Ti, W, Ag, Ga, Co, Bi, Zn, Mg or Nb. The method for producing a rare earth permanent magnet according to claim 12, which is diisobutylaluminum.
14. In the step of forming the magnet powder into a molded body,
    Producing a mixture in which the magnet powder and the binder are mixed;
    The method for producing a rare earth permanent magnet according to any one of claims 8 to 13, wherein a green sheet is produced as the formed body by forming the mixture into a sheet shape.

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