JP2013030742A - Rare earth permanent magnet and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rare earth permanent magnet and a manufacturing method of the same, capable of reducing an amount of oxygen contained in a magnet particle before sintering and capable of preventing degradation of magnet characteristics.SOLUTION: A mixture is produced by mixing a magnet powder, formed by pulverizing a magnet raw material, and a binder. The mixture is formed into a sheet-shape, so that a green sheet is manufactured. Then, the produced green sheet is calcined with hydrogen and calcined by plasma heating, and the calcined body is sintered, thereby a permanent magnet 1 is manufactured.

Description

  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. Therefore, in order to realize a reduction in size, weight, output, and efficiency of the permanent magnet motor, it is required to make the permanent magnet embedded in the motor thinner and further improve the magnetic characteristics.

  Here, as a manufacturing method of the permanent magnet used for the permanent magnet motor, a powder sintering method is generally used conventionally. Here, in the powder sintering method, first, magnet powder obtained by pulverizing raw materials by a jet mill (dry pulverization) or the like is manufactured. Thereafter, the magnet powder is put into a mold and press-molded into a desired shape while applying a magnetic field from the outside. And it manufactures by sintering the solid-shaped magnet powder shape | molded by the desired shape at predetermined temperature (for example, 1100 degreeC in a Nd-Fe-B type magnet).

  However, when a permanent magnet is manufactured by the above-described powder sintering method, there are the following problems. That is, in the powder sintering method, it is necessary to ensure a certain porosity in the press-molded magnet powder for magnetic field orientation. When magnet powder having a certain porosity is sintered, it is difficult to uniformly contract during the sintering, and deformation such as warpage and dent occurs after sintering. In addition, since pressure unevenness occurs when the magnet powder is pressed, the sintered magnet can be dense and dense, and distortion occurs on the magnet surface. Therefore, conventionally, it was necessary to compress the magnet powder in a size larger than the desired shape, assuming that the magnet surface can be distorted in advance. Then, after sintering, a diamond cutting and polishing operation is performed to correct the shape into a desired shape. As a result, the number of manufacturing steps increases, and the quality of the manufactured permanent magnet may decrease.

  In particular, when the thin-film magnet is manufactured by cutting out from a large-sized bulk body as described above, the material yield is significantly reduced. In addition, there has been a problem that the number of processing steps greatly increases.

  Therefore, as a means for solving the above problem, a technique has been proposed in which a green sheet is produced by kneading magnet powder and a binder, and a permanent magnet is produced by sintering the produced green sheet (for example, JP-A-1-150303).

Japanese Unexamined Patent Publication No. 1-150303 (pages 3 and 4)

Here, in the case where the magnetic powder is made into a green sheet as in Patent Document 1, particularly when the green sheet is formed into a sheet shape, the surface area of the green sheet increases, so that the rare earth element (for example, Nd) contained in the green sheet is oxidized. There was a problem that was easy to be done. When oxides are formed by the oxidized rare earth element, the magnetic characteristics of the magnet are deteriorated. Further, the rare earth element is combined with oxygen so that the rare earth element is insufficient in comparison with the content based on the stoichiometric composition (for example, Nd ₂ Fe ₁₄ B for neodymium magnets), and αFe is contained in the main phase of the sintered magnet. There is also a problem that the magnetic properties are greatly reduced due to precipitation. In particular, when a rare earth element is not included as a magnet raw material in a large amount relative to the stoichiometric composition, the problem becomes large.

  The present invention has been made in order to solve the above-described problems in the prior art, and the magnet powder contained in the magnet particles is calcined by plasma heating before sintering the magnetic powder formed into a sheet-like green sheet. An object of the present invention is to provide a rare earth permanent magnet and a method for producing a rare earth permanent magnet that can reduce the amount of oxygen in advance and, as a result, prevent deterioration of magnet characteristics.

  In order to achieve the above object, a rare earth permanent magnet according to claim 1 of the present application includes a step of pulverizing a magnet raw material into magnet powder, a step of generating a mixture by mixing the pulverized magnet powder and a binder, Forming the mixture into a sheet to produce a green sheet; dispersing the binder by holding the green sheet at a binder decomposition temperature in a non-oxidizing atmosphere for a certain period of time; and the binder The green sheet from which the carbon is removed is calcined by plasma heating to obtain a calcined body and the calcined body is sintered.

A rare earth permanent magnet according to claim 2 is the rare earth permanent magnet according to claim 1, wherein the pulverized magnet powder has the following general formula M- (OR) _x (wherein M is Dy, It contains at least one of Tb, V, Mo, Zr, Ta, Ti, W, Cu, Al, Nd, Ag, Ga, Co, Bi, Zn, Mg, and Nb, where R is a hydrocarbon substituent. Yes, it may be linear or branched. X is an arbitrary integer.) By adding an organometallic compound represented by the formula, the organometallic compound is attached to the particle surface of the magnet powder to form the mixture. In the step of performing, the mixture is formed by mixing the magnet powder with the organometallic compound attached to the particle surface and the binder.

  A rare earth permanent magnet according to claim 3 is the rare earth permanent magnet according to claim 2, wherein R in the general formula is an alkyl group.

  A rare earth permanent magnet according to claim 4 is the rare earth permanent magnet according to claim 3, wherein R in the general formula is any one of an alkyl group having 2 to 6 carbon atoms. To do.

  Moreover, the rare earth permanent magnet according to claim 5 is the rare earth permanent magnet according to any one of claims 1 to 4, wherein in the step of obtaining the calcined body, the rare earth permanent magnet is calcined by high-temperature hydrogen plasma heating. It is characterized by.

  A rare earth permanent magnet according to claim 6 is the rare earth permanent magnet according to any one of claims 1 to 5, wherein the calcined body is pressurized in the step of sintering the calcined body. It is characterized by sintering.

  A rare earth permanent magnet according to claim 7 is the rare earth permanent magnet according to any one of claims 1 to 6, wherein the green sheet is placed in a hydrogen atmosphere in the step of scattering and removing the binder. Alternatively, it is characterized in that it is maintained for a certain time at 200 ° C. to 900 ° C. in a mixed gas atmosphere of hydrogen and an inert gas.

  The method for producing a rare earth permanent magnet according to claim 8 includes a step of pulverizing a magnet raw material into magnet powder, a step of generating a mixture by mixing the pulverized magnet powder and a binder, and the mixture. A step of forming a green sheet by forming into a sheet, a step of scattering and removing the binder by holding the green sheet at a binder decomposition temperature in a non-oxidizing atmosphere for a certain period of time, and removing the binder The method includes a step of calcining the green sheet by plasma heating to obtain a calcined body, and a step of sintering the calcined body.

A method for producing a rare earth permanent magnet according to claim 9 is the method for producing a rare earth permanent magnet according to claim 8, wherein the pulverized magnet powder has the following general formula M- (OR) _x (formula Among them, at least one of Dy, Tb, V, Mo, Zr, Ta, Ti, W, Cu, Al, Nd, Ag, Ga, Co, Bi, Zn, Mg, and Nb is contained. The organic metal compound is attached to the particle surface of the magnet powder by adding an organometallic compound represented by the following formula: x is an arbitrary integer) In the step of generating the mixture, the mixture in which the magnet powder having the organometallic compound attached to the particle surface and the binder are mixed is generated.

  A rare earth permanent magnet manufacturing method according to claim 10 is the rare earth permanent magnet manufacturing method according to claim 9, wherein R in the general formula is an alkyl group.

  The method for producing a rare earth permanent magnet according to claim 11 is the method for producing a rare earth permanent magnet according to claim 10, wherein R in the structural formula is any one of an alkyl group having 2 to 6 carbon atoms. It is characterized by being.

  A method for producing a rare earth permanent magnet according to claim 12 is the method for producing a rare earth permanent magnet according to any one of claims 8 to 11, wherein in the step of obtaining the calcined body, a high temperature hydrogen plasma is provided. It is characterized by calcining by heating.

  A method for producing a rare earth permanent magnet according to claim 13 is the method for producing a rare earth permanent magnet according to claim 8 to claim 12, wherein the calcined body is sintered in the step of sintering the calcined body. Is pressure-sintered.

  Furthermore, a method for producing a rare earth permanent magnet according to claim 14 is the method for producing a rare earth permanent magnet according to any one of claims 8 to 13, wherein the binder is scattered to remove the binder. The green sheet is held for a predetermined time at 200 ° C. to 900 ° C. in a hydrogen atmosphere or a mixed gas atmosphere of hydrogen and an inert gas.

According to the rare earth permanent magnet according to claim 1 having the above configuration, the permanent magnet is constituted by a magnet obtained by sintering a green sheet formed by mixing magnet powder and a binder into a sheet shape. Since the deformation becomes uniform, there is no deformation such as warping or dent after sintering, and there is no pressure unevenness during pressing, so there is no need for correction processing after sintering, which has been done in the past. Can be simplified. Thereby, a permanent magnet can be formed with high dimensional accuracy. Further, even when the permanent magnet is thinned, it is possible to prevent the processing man-hours from increasing without reducing the material yield. Furthermore, since the magnet powder formed into a sheet-like green sheet is calcined by plasma heating before sintering, the amount of oxygen contained in the magnet particles can be reduced in advance before sintering. As a result, the precipitation of αFe in the main phase of the magnet after sintering and the generation of oxides are suppressed, and the magnet characteristics are not greatly deteriorated.
In addition, before calcining the green sheet, the green sheet is kept at the binder decomposition temperature for a certain period of time in a non-oxidizing atmosphere so that the binder is scattered and removed, so that the amount of carbon contained in the magnet is reduced in advance. be able to. As a result, it is possible to suppress the precipitation of αFe in the main phase of the magnet after sintering, to densely sinter the entire magnet, and to prevent the coercive force from being lowered.

  Moreover, according to the rare earth permanent magnet of claim 2, in order to improve the magnet characteristics, Dy, Tb, V, Mo, Zr, Ta, Ti, W, Cu, Al, Nd, Ag, Ga, Co, In the case of adding elements such as Bi, Zn, Mg, Nb, etc., each element can be efficiently distributed with respect to the grain boundary of the magnet. As a result, the magnetic characteristics can be improved and the amount of each element added can be made smaller than in the prior art, so that a decrease in residual magnetic flux density can be suppressed. Further, by calcining the magnet powder to which the organometallic compound is added by plasma heating before sintering, Dy and the like existing in a state of being combined with oxygen before calcining can be reduced. Therefore, even when an organometallic compound is added, it is possible to prevent an increase in the amount of oxygen contained in the magnet particles.

  According to the rare earth permanent magnet of claim 3, since the organometallic compound composed of an alkyl group is used as the organometallic compound added to the magnet powder, the organometallic compound can be easily thermally decomposed. It becomes possible. As a result, it is possible to more reliably reduce the amount of carbon in the molded body when calcining.

  According to the rare earth permanent magnet of claim 4, since the organometallic compound composed of an alkyl group having 2 to 6 carbon atoms is used as the organometallic compound to be added to the magnet powder, Thermal decomposition can be performed. As a result, it is possible to easily perform a process for reducing the amount of carbon contained in the magnet particles.

  In addition, according to the rare earth permanent magnet of claim 5, since calcining is performed using high-temperature hydrogen plasma heating, high concentration hydrogen radicals can be generated, and the metal forming the organometallic compound can be stably oxidized. Even if it is present in the magnetic powder as a product, reduction to a metal and reduction of the oxidation number can be easily performed at low temperatures using hydrogen radicals.

  Moreover, according to the rare earth permanent magnet of the sixth aspect, since sintering is performed using pressure sintering, it becomes possible to lower the sintering temperature and suppress grain growth during sintering. Therefore, the magnetic performance can be improved. In addition, since the shrinkage due to sintering is uniform, deformation such as warping and dent after sintering does not occur, and pressure unevenness during pressing is eliminated, so correction processing after sintering that has been performed conventionally is performed There is no need, and the manufacturing process can be simplified. Thereby, a permanent magnet can be formed with high dimensional accuracy. Further, even when the permanent magnet is thinned, it is possible to prevent the processing man-hours from increasing without reducing the material yield.

  According to the rare earth permanent magnet of claim 7, carbon contained in the magnet is obtained by calcining a green sheet kneaded with a binder in a hydrogen atmosphere or a mixed gas atmosphere of hydrogen and an inert gas. The amount can be reduced more reliably.

According to the method for manufacturing a rare earth permanent magnet according to claim 8, the permanent magnet is manufactured by sintering a green sheet formed by mixing magnet powder and a binder into a sheet shape. Permanent magnets do not undergo deformation such as warping or dents after sintering due to uniform shrinkage due to sintering, and there is no pressure unevenness during pressing. The manufacturing process can be simplified. Thereby, a permanent magnet can be formed with high dimensional accuracy. Further, even when the permanent magnet is thinned, it is possible to prevent the processing man-hours from increasing without reducing the material yield. Furthermore, since the magnet powder formed into a sheet-like green sheet is calcined by plasma heating before sintering, the amount of oxygen contained in the magnet particles can be reduced in advance before sintering. As a result, the precipitation of αFe in the main phase of the magnet after sintering and the generation of oxides are suppressed, and the magnet characteristics are not greatly deteriorated.
Before calcining the green sheet, the binder is scattered and removed by holding the green sheet at a binder decomposition temperature in a non-oxidizing atmosphere for a certain period of time, so the amount of carbon contained in the magnet can be reduced in advance. it can. As a result, it is possible to suppress the precipitation of αFe in the main phase of the magnet after sintering, to densely sinter the entire magnet, and to prevent the coercive force from being lowered.

  According to the method for manufacturing a rare earth permanent magnet according to claim 9, Dy, Tb, V, Mo, Zr, Ta, Ti, W, Cu, Al, Nd, Ag, Ga are used to improve the magnet characteristics. When elements such as Co, Bi, Zn, Mg, and Nb are added, each element can be effectively unevenly distributed with respect to the grain boundary of the magnet. As a result, the magnetic characteristics of the permanent magnet to be manufactured can be improved, and the amount of each element added can be made smaller than in the prior art, so that a decrease in residual magnetic flux density can be suppressed. Further, by calcining the magnet powder to which the organometallic compound is added by plasma heating before sintering, Dy and the like existing in a state of being combined with oxygen before calcining can be reduced. Therefore, even when an organometallic compound is added, it is possible to prevent an increase in the amount of oxygen contained in the magnet particles.

  According to the method for producing a rare earth permanent magnet according to claim 10, since the organometallic compound composed of an alkyl group is used as the organometallic compound to be added to the magnet powder, the pyrolysis of the organometallic compound is facilitated. Can be done. As a result, it is possible to more reliably reduce the amount of carbon in the molded body when calcining.

  According to the method for producing a rare earth permanent magnet according to claim 11, since the organometallic compound composed of an alkyl group having 2 to 6 carbon atoms is used as the organometallic compound to be added to the magnet powder, It becomes possible to thermally decompose the metal compound. As a result, it is possible to easily perform a process for reducing the amount of carbon contained in the magnet particles.

  In addition, according to the method for producing a rare earth permanent magnet according to claim 12, since calcining is performed using high-temperature hydrogen plasma heating, a high concentration of hydrogen radicals can be generated, and the metal forming the organometallic compound is Even when it is present in the magnet powder as a stable oxide, it is possible to easily reduce to metal or reduce the oxidation number at low temperatures using hydrogen radicals.

  According to the method for producing a rare earth permanent magnet according to claim 13, since the permanent magnet is sintered using pressure sintering, the sintering temperature is lowered to suppress grain growth during sintering. Is possible. Therefore, the magnetic performance of the manufactured permanent magnet can be improved. In addition, since the permanent magnet to be produced is uniform in shrinkage due to sintering, deformation such as warpage and dent after sintering does not occur, and pressure unevenness during pressing is eliminated. It is not necessary to carry out a correction process after ligation, and the manufacturing process can be simplified. Thereby, a permanent magnet can be formed with high dimensional accuracy. Further, even when the permanent magnet is thinned, it is possible to prevent the processing man-hours from increasing without reducing the material yield.

  Furthermore, according to the method for producing a rare earth permanent magnet according to claim 14, the green sheet kneaded with the binder is calcined in a hydrogen atmosphere or in a mixed gas atmosphere of hydrogen and an inert gas, so that The amount of carbon contained can be reduced more reliably.

1 is an overall view showing a permanent magnet according to the present invention. It is the figure which expanded and showed the Nd crystal particle which comprises the permanent magnet which concerns on this invention. It is a figure explaining the effect at the time of sintering based on the improvement of the thickness precision of the green sheet concerning the present invention. It is explanatory drawing which showed the manufacturing process of the permanent magnet which concerns on this invention. It is explanatory drawing which showed the formation process of the green sheet especially among the manufacturing processes of the permanent magnet which concerns on this invention. It is a figure explaining the predominance of calcination processing using high temperature hydrogen plasma heating. It is explanatory drawing which showed the pressurization sintering process of the green sheet especially among the manufacturing processes of the permanent magnet which concerns on this invention. It is the figure which showed the spectrum detected in the range of the binding energy of 200 eV-215 eV about the permanent magnet of Example 1 and Comparative Example 1. FIG. It is the figure shown about the result of the waveform analysis of the spectrum shown in FIG. It is the figure which showed the spectrum detected in the range of the binding energy of 147 eV-165 eV about the permanent magnet of Example 2 and Comparative Example 2. FIG. It is the figure shown about the result of the waveform analysis of the spectrum shown in FIG.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS 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 based magnet. In addition, content of each component shall be Nd: 27-40 wt%, B: 1-2 wt%, Fe (electrolytic iron): 60-70 wt%. In order to improve magnetic properties, other elements such as Dy, Tb, V, Mo, Zr, Ta, Ti, W, Nb, Co, Cu, Al, Si, Ga, Pr, Ag, Bi, Zn, and Mg are added. May contain a small amount. FIG. 1 is an overall view showing a permanent magnet 1 according to the present embodiment.

  Here, the permanent magnet 1 is a thin film-like permanent magnet having a thickness of, for example, 0.05 mm to 10 mm (for example, 4 mm). And it is produced by pressure-sintering the molded object (green sheet) shape | molded in the sheet form from the mixture (slurry and compound) with which magnetic powder and the binder were mixed as mentioned later.

Further, in the permanent magnet 1 according to the present invention, as shown in FIG. 2, in the surface portion (outer shell) of the crystal grains of the Nd crystal particles (main phase) 2 constituting the permanent magnet 1, a part of Nd is Dy, Producing layer 3 (hereinafter referred to as outer shell layer 3) substituted with Tb, V, Mo, Zr, Ta, Ti, W, Cu, Al, Ag, Ga, Co, Bi, Zn, Mg, Nb, or the like Thus, Dy and the like are unevenly distributed with respect to the grain boundaries of the Nd crystal particles 2. The Nd crystal particle 2 is composed of, for example, an Nd ₂ Fe ₁₄ B intermetallic compound. In addition to the outer shell layer 3, for example, an Nd-rich phase or the like is also formed at the grain boundary. FIG. 2 is an enlarged view showing Nd crystal particles 2 constituting the permanent magnet 1.

In the present invention, substitution of Dy or the like is performed by adding an organometallic compound containing Dy or the like before forming a pulverized magnet powder as described below. Specifically, before forming the pulverized magnet powder, M- (OR) _x (where M is Dy, Tb, V, Mo, Zr, Ta, Ti, W, Cu, Al, Nd, Ag). , Ga, Co, Bi, Zn, Mg, and Nb, where R is a hydrocarbon-containing substituent, which may be linear or branched, and x is an arbitrary integer. A solvent containing an organometallic compound containing M (for example, niobium ethoxide, dysprosium propoxide, terbium propoxide, etc.) is added and mixed with the magnet powder in a wet state.

At that time, particularly when Dy and Tb are included as M, the organometallic compound containing Dy or Tb is dispersed in an organic solvent, and the organometallic compound containing Dy or Tb is efficiently dispersed on the particle surface of the Nd magnet particle. It becomes possible to adhere. And when sintering the magnetic powder to which the organometallic compound containing Dy or Tb is added, the Dy or Tb in the organometallic compound uniformly adhered to the particle surface of the Nd magnet particles by wet dispersion becomes Nd magnet particles. Substitution is performed by diffusion and penetration into the crystal growth region, and a Dy layer or a Tb layer is formed as the outer shell layer 3 on the surface of the Nd crystal particle 2. As a result, Dy or Tb can be unevenly distributed at the grain boundaries of the magnet particles. The Dy layer is made of, for example, (Dy _x Nd _1-x ) ₂ Fe ₁₄ B intermetallic compound. Then, Dy and Tb unevenly distributed at the grain boundaries suppress the generation of reverse magnetic domains at the grain boundaries, so that the coercive force can be improved. In addition, the amount of Dy or Tb added can be reduced as compared with the conventional case, and a decrease in residual magnetic flux density can be suppressed.

  On the other hand, when M contains a refractory metal element such as V, Mo, Zr, Ta, Ti, W, or Nb (hereinafter referred to as Nb), an organometallic compound containing Nb or the like is dispersed in an organic solvent. It becomes possible to uniformly adhere an organometallic compound containing Nb or the like to the particle surface of the Nd magnet particle. As a result, when the magnet powder is sintered, Nb or the like in the organometallic compound uniformly adhered to the surface of the Nd magnet particles by wet dispersion diffuses and penetrates into the crystal growth region of the Nd crystal particles. And a refractory metal layer is formed as the outer shell layer 3 on the surface of the Nd crystal particle 2. The refractory metal layer is made of, for example, an NbFeB intermetallic compound. The refractory metal layer coated on the surface of the Nd crystal particles functions as a means for suppressing so-called grain growth in which the average particle diameter of the Nd crystal particles increases when the permanent magnet 1 is sintered. As a result, it is possible to suppress grain growth of crystal grains during sintering. In addition, when including a refractory metal element such as Nb as M, the content of all rare earth elements in the magnet raw material at the start of pulverization is a content (26.7 wt%) based on the above stoichiometric composition, It is desirable that the Nd-rich phase is not formed in the grain boundary phase.

  In particular, even when Ag, Ga, Co, Bi, Zn, or Mg is included as M, an effect of improving the magnetic performance of the permanent magnet such as improvement in coercive force by grain boundary control or grain growth suppression can be expected.

  In particular, when Cu or Al is included as M, an effect of increasing the coercive force by uniformly dispersing the rich phase in the sintered permanent magnet 1 can be expected.

  In particular, when Nd is included as M, 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.

Here, M- (OR) _x (wherein M is Dy, Tb, V, Mo, Zr, Ta, Ti, W, Cu, Al, Nd, Ag, Ga, Co, Bi, Zn, Mg, Nb includes at least one type, R is a hydrocarbon substituent, which may be linear or branched, and x is an arbitrary integer.) A metal alkoxide is an organometallic compound that satisfies the general formula: . The metal alkoxide is represented by a general formula M- (OR) _n (M: metal element, R: organic group, n: valence of metal or metalloid). Further, as the metal or semimetal forming the metal alkoxide, Nd, Pr, Dy, Tb, W, Mo, V, Nb, Ta, Ti, Zr, Ir, Fe, Co, Bi, Mg, Ag, Ni, Cu, Zn, Cd, Al, Ga, In, Ge, Sb, Y, lanthanide, etc. are mentioned. However, in the present invention, Dy, Tb, V, Mo, Zr, Ta, Ti, W, Cu, Al, Nd, Ag, Ga, Co, Bi, Zn, Mg, and Nb are used.

The type of alkoxide is not particularly limited, and examples thereof include methoxide, ethoxide, propoxide, isopropoxide, butoxide, alkoxide having 4 or more carbon atoms, and the like. However, in the present invention, those having a low molecular weight are used for the purpose of suppressing residual coal by low-temperature decomposition as described later. Further, since methoxide having 1 carbon atom is easily decomposed and difficult to handle, ethoxide, methoxide, isopropoxide, propoxide, butoxide and the like having 2 to 6 carbon atoms contained in R are particularly used. It is preferable. That is, in the present invention, M- (OR) _x (wherein, M is Dy, Tb, V, Mo, Zr, Ta, Ti, W, Cu, Al, Nd, etc.) as an organometallic compound added to the magnet powder. And at least one of Ag, Ga, Co, Bi, Zn, Mg, and Nb, R is an alkyl group, which may be linear or branched, and x is an arbitrary integer. Compound, more preferably M- (OR) _x (wherein M is Dy, Tb, V, Mo, Zr, Ta, Ti, W, Cu, Al, Nd, Ag, Ga, Co, Bi, Zn, And at least one of Mg and Nb, wherein R is any one of alkyl groups having 2 to 6 carbon atoms, which may be linear or branched, and x is an arbitrary integer. It is desirable to use

Further, if the molded body is sintered under appropriate firing conditions, it is possible to prevent M from diffusing and penetrating (solid solution) into the main phase. Thereby, in the present invention, even if M is added, the substitution region by M can be made only the outer shell portion. 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.

  In addition, the permanent magnet 1 of the present invention is produced by pressure sintering a green sheet formed from a magnet powder in a slurry state. As the pressure sintering for sintering the green sheet, for example, There are hot press sintering, hot isostatic pressing (HIP) sintering, ultra-high pressure synthetic sintering, gas pressure sintering, discharge plasma (SPS) sintering, and the like. However, in order to suppress the grain growth of the magnet particles during sintering, it is desirable to use a sintering method in which sintering is performed in a shorter time and at a lower temperature. Moreover, it is desirable to use a sintering method that can reduce the warpage generated in the magnet after sintering. Therefore, in the present invention, among the above sintering methods, it is desirable to use uniaxial pressure sintering in which pressure is applied in the uniaxial direction and SPS sintering in which sintering is performed by current sintering.

  Here, SPS sintering is a sintering method in which a graphite-made sintering mold having a sintering object disposed therein is heated while being pressed in a uniaxial direction. In addition, in SPS sintering, in addition to the thermal and mechanical energy used for general sintering, electromagnetic energy and self-heating of the work piece due to pulse energization are achieved by pulse current heating and mechanical pressure. The discharge plasma energy generated between the particles is used as a driving force for the sintering. Therefore, rapid heating / cooling is possible compared to atmosphere heating in an electric furnace or the like, and sintering can be performed in a lower temperature range. As a result, it is possible to shorten the temperature rise and holding time in the sintering process, and it is possible to produce a dense sintered body that suppresses the grain growth of the magnet particles. In addition, since the sintered object is sintered in a state of being pressed in a uniaxial direction, it is possible to reduce the warpage that occurs after sintering.

  Further, when performing SPS sintering, a green body obtained by punching a green sheet into a desired product shape (for example, a fan shape shown in FIG. 1) is placed in a sintering mold of an SPS sintering apparatus. And in this invention, in order to improve productivity, as shown in FIG. 3, the multiple (for example, 10 pieces) molded object 5 is arrange | positioned in the sintering type | mold 6 simultaneously. In the present invention, as will be described later, the thickness accuracy of the green sheet is within ± 5%, more preferably within ± 3%, and even more preferably within ± 1% of the design value. As a result, in the present invention, as shown in FIG. 3A, even if a plurality of (for example, 10) molded bodies 5 are simultaneously placed in the sintering mold 6 and sintered, Since the thickness d of the body 5 is uniform, the pressure value and the sintering temperature do not vary for each molded body 5, and it becomes possible to perform appropriate sintering. On the other hand, when the thickness accuracy of the green sheet is low (for example, ± 5% or more with respect to the design value), as shown in FIG. In the case where the sintering is performed with the arrangement, the thickness d of each molded body 5 varies, so that an imbalance of the pulse current flow for each molded body 5 occurs, and each molded body 5 is pressurized. The value and sintering temperature vary, and it cannot be sintered properly. In addition, when sintering the some molded object 5 simultaneously, you may use the SPS sintering apparatus provided with the some sintering type | mold. And you may comprise so that a molded object may be each arrange | positioned with respect to several sintering type | mold with which an SPS sintering apparatus is equipped, and it sinters simultaneously.

In the present invention, a resin, a long-chain hydrocarbon, a fatty acid methyl ester, a mixture thereof, or the like is used as the binder mixed with the magnet powder when the green sheet is produced.
Further, when a resin is used as the binder, for example, polyisobutylene (PIB), butyl rubber (IIR), polyisoprene (IR), polybutadiene, polystyrene, styrene-isoprene block copolymer (SIS), styrene-butadiene block copolymer Combined (SBS), 2-methyl-1-pentene polymerization resin, 2-methyl-1-butene polymerization resin, α-methylstyrene polymerization resin, polybutyl methacrylate, polymethyl methacrylate, and the like are used. In addition, it is desirable to add a low molecular weight polyisobutylene to the α-methylstyrene polymer resin in order to give flexibility. Further, as the resin used for the binder, in order to reduce the amount of oxygen contained in the magnet, it is desirable to use a polymer (for example, polyisobutylene) that does not contain an oxygen atom in the structure and has a depolymerization property. .
When forming a green sheet by slurry molding, it is desirable to use a resin other than polyethylene and polypropylene as the resin used for the binder in order to appropriately dissolve the binder in a general-purpose solvent such as toluene. On the other hand, when a green sheet is formed by hot melt molding, it is desirable to use a thermoplastic resin in order to perform magnetic field orientation in a state where the formed green sheet is heated and softened.

  On the other hand, when a long-chain hydrocarbon is used as 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. When a green sheet is formed by hot melt molding, when the green sheet is magnetically aligned, the green sheet is heated and softened at a temperature equal to or higher than the melting point of the long-chain hydrocarbon, and magnetic field alignment is performed.

  Similarly, when fatty acid methyl ester is used as the binder, it is preferable to use methyl stearate, methyl docosanoate or the like that is solid at room temperature and liquid at room temperature or higher. And when shape | molding a green sheet by hot-melt shaping | molding, when carrying out magnetic field orientation of a green sheet, a green sheet is heated above the melting | fusing point of fatty acid methyl ester, and magnetic field orientation is performed.

  The amount of the binder added is an amount that appropriately fills the gaps between the magnet particles in order to improve the sheet thickness accuracy when the mixture of the magnet powder and the binder is formed into a sheet shape. For example, the ratio of the binder to the total amount of the magnet powder and the binder in the mixture after addition of the 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 FIG. FIG. 4 is an explanatory view showing a manufacturing process of the permanent magnet 1 according to the present embodiment.

  First, an ingot made of a predetermined fraction of Nd—Fe—B (for example, 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.

  Subsequently, the coarsely pulverized magnet powder is either (a) in an atmosphere made of an inert gas such as nitrogen gas, Ar gas, or He gas having substantially 0% oxygen content, or (b) having an oxygen content of 0.0001. Finely pulverized by a jet mill 11 in an atmosphere made of an inert gas such as nitrogen gas, Ar gas, and He gas of ˜0.5%, and an average particle size of a predetermined size or less (for example, 1.0 μm to 5.0 μm) It is set as the fine powder which has. 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. Note that wet pulverization may be used as a method for pulverizing the magnet raw material. For example, in wet pulverization using a bead mill, the coarsely pulverized magnet powder is finely pulverized to an average particle size of a predetermined size or less (eg, 0.1 μm to 5.0 μm) using toluene as a solvent. Thereafter, the magnet powder contained in the organic solvent after the wet pulverization is dried by vacuum drying or the like, and the dried magnet powder is taken out. Moreover, it is good also as a structure which adds the binder further to the organic solvent and knead | mixes, without taking out magnet powder from an organic solvent, and obtains the below-mentioned slurry 12.

  By using the wet pulverization, the magnet raw material can be pulverized to a finer particle size than dry pulverization. However, if wet pulverization is performed, there is a problem that an organic compound such as an organic solvent remains in the magnet even if the organic solvent is volatilized later by vacuum drying or the like. However, by performing the calcining process described later, the organic compound remaining together with the binder and the organometallic compound can be thermally decomposed to remove carbon from the magnet.

On the other hand, an organometallic compound solution to be added to the fine powder finely pulverized by the jet mill 11 or the like is prepared. Here, the organometallic compound solution contains Dy, Tb, V, Mo, Zr, Ta, Ti, W, Cu, Al, Nd, Ag, Ga, Co, Bi, Zn, Mg, or Nb in advance as a solvent. Add organometallic compound and dissolve. The organometallic compound to be dissolved is M- (OR) _x (wherein M is Dy, Tb, V, Mo, Zr, Ta, Ti, W, Cu, Al, Nd, Ag, Ga, Co, At least one of Bi, Zn, Mg, and Nb, R is a hydrocarbon-containing substituent, which may be linear or branched, and x is an arbitrary integer.) For example, niobium ethoxide, dysprosium propoxide, terbium propoxide, etc.) are preferably used. The solvent is not particularly limited, and alcohols such as isopropyl alcohol, ethanol and methanol, lower hydrocarbons such as pentane and hexane, aromatics such as benzene, toluene and xylene, esters such as ethyl acetate, Ketones and mixtures thereof can be used, but toluene or ethyl acetate is used. The amount of the organometallic compound to be dissolved is not particularly limited, but the amount of Dy or the like with respect to the sintered magnet is 0.001 wt% to 10 wt%, preferably 0.01 wt% to 5 wt%. Is preferred.

  Subsequently, the organometallic compound solution is added to the fine powder classified by the jet mill 11 or the like. Thereby, an organometallic compound containing Dy, Tb, V, Mo, Zr, Ta, Ti, W, Cu, Al, Nd, Ag, Ga, Co, Bi, Zn, Mg or Nb on the particle surface of the magnet particle. Adhere. The addition of the organometallic compound solution is performed in an atmosphere made of an inert gas such as nitrogen gas, Ar gas, or He gas.

  Thereafter, a binder is further added to the fine powder to which the organometallic compound solution is added. Thereby, a slurry 12 is produced in which a fine powder of a magnet raw material in which an organometallic compound is uniformly attached to the particle surface, a binder, and an organic solvent are mixed. Here, as the binder, resin, long chain hydrocarbon, fatty acid methyl ester, a mixture thereof, or the like is used as described above. Moreover, you may add a binder in the state diluted with the solvent. Further, the amount of binder added is such that the ratio of the binder to the total amount of magnet powder and binder in the slurry after addition is 1 wt% to 40 wt%, more preferably 2 wt% to 30 wt%, and even more preferably 3 wt% as described above. It is preferable to set the amount to be 20% by weight to 20% by weight. The binder is added in an atmosphere made of an inert gas such as nitrogen gas, Ar gas, or He gas.

  Subsequently, a green sheet 13 is formed from the generated slurry 12. As a method for forming the green sheet 13, for example, the produced slurry 12 can be applied by an appropriate method on a support substrate 14 such as a separator and dried as necessary. The coating method is preferably a method having excellent layer thickness controllability such as a doctor blade method, a die method, or a comma coating method. Further, in order to achieve high thickness accuracy, it is desirable to use a die method or a comma coating method that is particularly excellent in layer thickness controllability (that is, a method capable of high accuracy on the base material). For example, in the following embodiments, a die method is used. Moreover, as the support base material 14, for example, a silicone-treated polyester film is used. The green sheet 13 is dried by holding at 90 ° C. for 10 minutes and then holding at 130 ° C. for 30 minutes. Furthermore, it is preferable to sufficiently defoam the mixture so that bubbles do not remain in the spreading layer by using an antifoaming agent in combination.

Below, the formation process of the green sheet 13 by a die system is demonstrated in detail using FIG. FIG. 5 is an explanatory view showing a process of forming the green sheet 13 by a die method.
As shown in FIG. 5, the die 15 used in the die system is formed by overlapping the blocks 16 and 17 with 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 slurry supply system constituted by a metering pump (not shown) or the like, and the measured slurry 12 is supplied to the cavity 19 via the supply port 20 by a metering pump or the like. Is done. Further, the slurry 12 supplied to the cavity 19 is fed to the slit 18 and is discharged from the discharge port 21 of the slit 18 with a predetermined application width with a uniform amount in the width direction by a constant amount per unit time. On the other hand, the support base material 14 is conveyed at a preset speed with the rotation of the coating roll 22. As a result, the discharged slurry 12 is applied to the support base material 14 with a predetermined thickness.

  Moreover, in the formation process of the green sheet 13 by a die system, it is desirable to actually measure the sheet thickness of the green sheet 13 after coating, and to feedback-control the gap D between the die 15 and the support substrate 14 based on the actually measured value. . Further, the fluctuation of the amount of slurry 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 further reduced as much as possible (for example, fluctuation of ± 0.1% or less). It is desirable that Thereby, it is possible to further improve the thickness accuracy of the green sheet 13. The thickness accuracy of the green sheet 13 to be formed is within ± 5%, more preferably within ± 3%, and even more preferably within ± 1% with respect to the design value (for example, 4 mm).

  The set thickness of the green sheet 13 is desirably set in the range of 0.05 mm to 10 mm. When the thickness is less than 0.05 mm, the productivity must be reduced because multiple layers must be stacked. On the other hand, if the thickness is greater than 10 mm, it is necessary to reduce the drying speed in order to suppress foaming during drying, and productivity is significantly reduced.

  In addition, when the magnet powder having the organometallic compound adhered to the surface and the binder are mixed, the mixture is not made into the slurry 12, but a powdery mixture of the magnet powder and the binder without adding an organic solvent ( Hereinafter, it may be referred to as a compound). And you may perform the hot melt coating which melts a compound by heating a compound, makes it a fluid state, and coats it on the support base materials 14, such as a separator. A long sheet-like green sheet 13 can be formed on the support substrate 14 by solidifying the compound coated by hot melt coating by releasing heat. The temperature at which the compound is heated and melted varies depending on the type and amount of the binder used, but is 50 to 300 ° C. However, the temperature needs to be higher than the melting point of the binder to be used. 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. Then, after stirring, the compound is extracted by heating the organic solvent containing the magnet powder and the binder to vaporize the organic solvent. In particular, when magnet powder is pulverized by a wet method, an organic metal compound or binder is added and kneaded in the organic solvent without removing the magnet powder from the organic solvent used for pulverization, and then the organic solvent is volatilized. It is good also as a structure which is made to obtain a compound.

  In addition, a pulsed magnetic field is applied to the green sheet 13 coated on the support substrate 14 in a direction that intersects the transport direction before drying. The strength of the applied magnetic field is 5000 [Oe] to 150,000 [Oe], preferably 10,000 [Oe] to 120,000 [Oe]. The direction in which the magnetic field is oriented needs to be determined in consideration of the direction of the magnetic field required for the permanent magnet 1 formed from the green sheet 13, but is preferably in the in-plane direction. When a green sheet is formed by hot melt molding, magnetic field orientation is performed in a state where the green sheet is heated and softened above the glass transition point or melting point of the binder. Further, magnetic field orientation may be performed before the molded green sheet is solidified.

  Next, the green sheet 13 formed from the slurry 12 is punched into a desired product shape (for example, a fan shape shown in FIG. 1), and a formed body 25 is formed.

  Thereafter, the molded body 25 is temporarily maintained in hydrogen by holding it for several hours (for example, 5 hours) at a binder decomposition temperature in a non-oxidizing atmosphere (in particular, a hydrogen atmosphere or a mixed gas atmosphere of hydrogen and an inert gas in the present invention). Perform baking. 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 a calcination treatment in hydrogen, the binder can be decomposed into monomers by a depolymerization reaction or the like and scattered to be removed. That is, so-called decarbonization for reducing the amount of carbon in the molded body 25 is performed. Further, the calcination treatment in hydrogen is performed under the condition that the carbon content in the molded body 25 is 1500 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.

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. (for example, 600 ° C.).
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.

  Thereafter, the compact 25 that has been calcined in hydrogen is further subjected to a calcining process by plasma heating using high-temperature hydrogen plasma. Specifically, the molded body 25 is put into a “2.45 GHz high frequency microwave” plasma heating apparatus, and plasma excitation is performed by applying a voltage to a mixed gas of hydrogen gas and an inert gas (for example, Ar gas). The calcining process is performed by irradiating the formed body 25 with the generated high-temperature hydrogen plasma. The flow rate of the gas to be supplied is 1 L / min to 10 L / min for the hydrogen flow rate, 1 L / min to 5 L / min for the argon flow rate, the output power when the plasma is excited is 1 kW to 10 kW, and the plasma irradiation time is 1 second to Perform in 60 seconds.

In the calcining treatment by the above plasma heating, a metal such as Dy existing in a state associated with oxygen can be reduced to a metal Dy or the like, or the oxidation number to DyO or the like can be reduced, and contained in the magnet powder. The oxygen to be reduced can be reduced in advance. As a result, it is possible to prevent the precipitation of αFe without bonding Dy or the like and oxygen to form Dy oxide or the like in the subsequent sintering step. Further, since the green sheet 13 formed into a sheet shape has a large surface area and is easily oxidized, a particularly high effect can be expected. Furthermore, particularly in calcination by high-temperature hydrogen plasma heating, hydrogen radicals can be generated, and reduction to the metal Dy or the like and reduction of the oxidation number can be easily performed at low temperatures using the hydrogen radicals. In addition, when high-temperature hydrogen plasma is used, the concentration of hydrogen radicals can be increased as compared with the case where low-temperature hydrogen plasma is used. Therefore, it is possible to appropriately reduce a stable metal oxide (for example, Dy ₂ O ₃ , Nb ₂ O _5, etc.) having low free energy of formation.

Hereinafter, the superiority of the calcination treatment by plasma heating will be described in more detail with reference to FIG.
In general, in order to reduce a stable metal oxide (eg, Dy ₂ O ₃ ) having low free energy of formation to metal, (1) Ca reduction, (2) Molten salt electrolysis, (3) Laser reduction, etc. A powerful reduction method is required. However, if such a powerful reduction method is used, the object to be reduced becomes very hot, and therefore, if it is applied to Nd magnet particles as in the present invention, the Nd magnet particles may be melted. .
Here, as described above, high-temperature hydrogen radicals can be generated by calcination by high-temperature hydrogen plasma heating. And in the reduction | restoration by a hydrogen radical, as shown in FIG. Therefore, metal oxides with low free energy of formation such as Dy ₂ O ₃ can be reduced at a lower temperature than the reduction methods (1) to (3). In addition, it can be judged from the fact that Nd magnet particles after calcination are not melted can be reduced at a low temperature.

  Moreover, in order to reduce the activity of the calcined body activated by the calcining treatment in hydrogen, the calcined body is subjected to a vacuum atmosphere at 200 ° C. to 600 ° C., more preferably 400 ° C. to 600 ° C. after the calcining treatment. You may perform a dehydrogenation process by hold | maintaining for 1-3 hours. However, the dehydrogenation step is not necessary when firing is performed without contact with the outside air after hydrogen calcination.

  Then, the sintering process which sinters the molded object 26 calcined by the plasma calcining process is performed. In the present invention, sintering is performed by pressure sintering. Examples of pressure sintering include hot press sintering, hot isostatic pressing (HIP) sintering, ultra-high pressure synthetic sintering, gas pressure sintering, and discharge plasma (SPS) sintering. However, in the present invention, as described above, in order to suppress the grain growth of the magnet particles during sintering and to suppress the warpage generated in the magnet after sintering, it is uniaxial pressure sintering in which pressure is applied in a uniaxial direction and energization is performed. It is desirable to use SPS sintering which sinters by sintering.

Below, the pressure sintering process of the compact | molding | casting 26 by SPS sintering is demonstrated in detail using FIG. FIG. 7 is an explanatory view showing a pressure sintering process of the compact 26 by SPS sintering.
When performing SPS sintering as shown in FIG. 7, first, the compact 26 is placed on a graphite sintering die 31. Note that the above-described calcination treatment in hydrogen may also be performed in a state where the molded body 26 is installed in the sintering die 31. And the compact | molding | casting 26 installed in the sintering type | mold 31 is hold | maintained in the vacuum champ 32, and the upper punch 33 and the lower punch 34 made from a graphite are set similarly. Then, using the upper punch electrode 35 connected to the upper punch 33 and the lower punch electrode 36 connected to the lower punch 34, a low-voltage and high-current DC pulse voltage / current is applied. At the same time, a load is applied to the upper punch 33 and the lower punch 34 from above and below using a pressure mechanism (not shown). As a result, the molded body 26 installed in the sintering mold 31 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 26 simultaneously, you may arrange | position the several molded object 26 to the one sintering die 31, and the sintering die 31 which is different for every molded object 26 is used. You may make it arrange | position to. In addition, when arrange | positioning to the different sintering type | mold 31 for every molded object 26, it sinters using the SPS sintering apparatus provided with the several sintering type | mold 31. FIG. The upper punch 33 and the lower punch 34 that pressurize the molded body 26 are configured so as to be integrated (that is, can be pressed simultaneously) among the plurality of sintering dies 31.
Specific sintering conditions are shown below.
Pressurized value: 30 MPa
Sintering temperature: raised to 940 ° C. at 10 ° C./min and held for 5 minutes Atmosphere: vacuum atmosphere of several Pa or less

  After performing the SPS sintering, it is cooled and heat-treated again at 600 ° C. to 1000 ° C. for 2 hours. And the permanent magnet 1 is manufactured as a result of sintering.

Examples of the present invention will be described below in comparison with Comparative Examples 1 and 2.
Example 1
Example 1 is an Nd—Fe—B magnet, and the alloy composition is Nd / Fe / B = 32.7 / 65.96 / 1.34 in wt%. Further, niobium ethoxide was added as an organometallic compound, toluene was used as a solvent, and polyisobutylene was used as a binder. In the calcining treatment by plasma heating, the gas flow rate was 3 L / min, the argon flow rate was 3 L / min, the output power during plasma excitation was 3 kW, and the plasma irradiation time was 60 seconds. The green sheet was sintered by SPS sintering. The other steps are the same as those described in the above [Permanent magnet manufacturing method].

(Example 2)
Dysprosium ethoxide was added as an organometallic compound. In the calcining treatment by plasma heating, the gas flow rate was 10 L / min, the argon flow rate was 2 L / min, the output power during plasma excitation was 6 kW, and the plasma irradiation time was 12 seconds. Other conditions are the same as in the first embodiment.

(Comparative Example 1)
It manufactured without performing the calcination process by plasma heating. Other conditions are the same as in the first embodiment.

(Comparative Example 2)
It manufactured without performing the calcination process by plasma heating. Other conditions are the same as in the second embodiment.

(Comparison study between Example 1 and Comparative Example 1 based on the presence or absence of calcination treatment by plasma heating)
The permanent magnets of Example 1 and Comparative Example 1 were each analyzed by an X-ray photoelectron spectrometer (ECSA). FIG. 8 is a diagram showing spectra detected in the range of the binding energy of 200 eV to 215 eV for the permanent magnets of the example and the comparative example. FIG. 9 is a diagram showing the results of the waveform analysis of the spectrum shown in FIG.

As shown in FIG. 8, the permanent magnet of the example and the permanent magnet of the comparative example have different spectral shapes. Here, for each spectrum, the mixing ratio of the spectrum is calculated based on the spectrum of the standard sample, and the ratio of Nb, NbO, Nb ₂ O ₃ , NbO ₂ , Nb ₂ O ₅ is calculated, and the result shown in FIG. 9 is obtained. . As shown in FIG. 9, in the permanent magnet of the example, the ratio of Nb is 81%, and the ratio of NbO that is Nb oxide is 19%. On the other hand, in the permanent magnet of the comparative example, the ratio of Nb is approximately 0%, and the ratio of Nb ₂ O ₅ that is an Nb oxide is approximately 100%.

That is, in the permanent magnet of the example that was subjected to the calcining treatment by plasma heating, most of the Nb oxides (NbO, Nb ₂ O ₃ , NbO ₂ , Nb ₂ O ₅ ) existing in a state of being combined with oxygen, It turns out that it can reduce | restore to metal Nb. Further, even when metal Nb cannot be reduced, reduction to an oxide having a lower oxidation number such as NbO (that is, reduction of the oxidation number) can be performed, and oxygen contained in the magnet powder can be reduced in advance. it can. As a result, in the permanent magnet of the example, oxygen contained in the magnet powder can be reduced in advance by reducing the Nb oxide and the like contained in the magnet powder before sintering. As a result, Nd and oxygen are not combined in the subsequent sintering step to form an Nd oxide. Therefore, in the permanent magnet of the example, the precipitation of αFe can be prevented without deteriorating the magnet characteristics due to the metal oxide. That is, it becomes possible to realize a permanent magnet having high quality.
On the other hand, since a large amount of Nb oxide remains in the permanent magnet of the comparative example, Nd and oxygen are combined in the sintering process to form an Nd oxide. In addition, a lot of αFe is precipitated. As a result, the magnetic characteristics are degraded.

(Comparison study between Example 2 and Comparative Example 2 based on the presence or absence of calcination treatment by plasma heating)
The permanent magnets of Example 2 and Comparative Example 2 were each analyzed by an X-ray photoelectron spectrometer (ECSA). FIG. 10 is a diagram showing spectra detected in the range of the binding energy of 147 eV to 165 eV for the permanent magnets of the example and the comparative example. FIG. 11 is a diagram showing the results of the waveform analysis of the spectrum shown in FIG.

As shown in FIG. 10, the permanent magnet of the example and the permanent magnet of the comparative example have different spectral shapes. Here, for each spectrum, the mixing ratio of the spectrum is calculated based on the spectrum of the standard sample, and the ratio of Dy, Dy ₂ O, DyO, and Dy ₂ O ₃ is calculated, and the result shown in FIG. 11 is obtained. As shown in FIG. 11, in the permanent magnet of the example, the ratio of Dy is 75%, and the ratio of Dy oxides (Dy ₂ O, DyO, Dy ₂ O ₃ ) is 25%. On the other hand, in the permanent magnet of the comparative example, the ratio of Dy is approximately 0%, and the ratio of Dy oxides (Dy ₂ O, DyO, Dy ₂ O ₃ ) is approximately 100%.

In other words, in the permanent magnet of the example subjected to the calcining process by plasma heating, most of the Dy oxide (Dy ₂ O, DyO, Dy ₂ O ₃ ) existing in a state of being combined with oxygen is converted into the metal Dy. It turns out that it can reduce. Further, even when the metal Dy cannot be reduced, reduction to an oxide having a lower oxidation number such as DyO (that is, reduction of the oxidation number) can be performed, and oxygen contained in the magnet powder can be reduced in advance. it can. As a result, in the permanent magnet of the example, oxygen contained in the magnet powder can be reduced in advance by reducing the Dy oxide and Tb oxide contained in the magnet powder before sintering. As a result, Nd and oxygen are not combined in the subsequent sintering step to form an Nd oxide. Therefore, in the permanent magnet of the example, the precipitation of αFe can be prevented without deteriorating the magnet characteristics due to the metal oxide. That is, it becomes possible to realize a permanent magnet having high quality.
On the other hand, since a large amount of Dy oxide remains in the permanent magnet of the comparative example, Nd and oxygen are combined in the sintering process to form an Nd oxide. In addition, a lot of αFe is precipitated. As a result, the magnetic characteristics are degraded.

As described above, in the permanent magnet 1 and the manufacturing method of the permanent magnet 1 according to the present embodiment, the magnet raw material is pulverized into magnet powder, and the mixture (slurry, compound, etc.) is obtained by mixing the pulverized magnet powder and the binder. ) Is generated. And the produced | generated mixture is shape | molded in a sheet form, and a green sheet is produced. Thereafter, the produced green sheet is calcined by plasma heating, and the calcined calcined body is sintered to produce the permanent magnet 1. As a result, the amount of oxygen contained in the magnet particles can be reduced in advance before sintering by calcination by plasma heating. Accordingly, the precipitation of αFe in the main phase of the magnet after sintering and the generation of oxides are suppressed, and the magnet characteristics are not greatly deteriorated.
In addition, a permanent magnet is manufactured by mixing magnet powder and a binder and sintering the formed green sheet. Therefore, the manufactured permanent magnet is warped after sintering due to uniform shrinkage due to sintering. No deformation such as dents and dents occur, and there is no pressure unevenness during pressing, so that it is not necessary 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. Further, even when the permanent magnet is thinned, it is possible to prevent the processing man-hours from increasing without reducing the material yield.
Also, magnets can be added by adding organometallic compounds including Dy, Tb, V, Mo, Zr, Ta, Ti, W, Cu, Al, Nd, Ag, Ga, Co, Bi, Zn, Mg, Nb, etc. Since the organometallic compound is adhered to the powder particle surface and then sintered, Dy, Tb, V, Mo, Zr, Ta, Ti, W, Cu, Al, Nd, Ag are used to improve the magnet characteristics. In the case of adding elements such as Ga, Co, Bi, Zn, Mg, and Nb, each element can be effectively unevenly distributed with respect to the grain boundary of the magnet. As a result, the magnetic characteristics of the permanent magnet to be manufactured can be improved, and the amount of each element added can be made smaller than in the prior art, so that a decrease in residual magnetic flux density can be suppressed. In addition, by calcining the magnet powder to which the organometallic compound is added by plasma heating before sintering, Dy and the like existing in a state of being combined with oxygen before calcining can be reduced to metal Dy and the like. It is possible to reduce the oxidation number to DyO or the like. Therefore, even when an organometallic compound is added, it is possible to prevent an increase in the amount of oxygen contained in the magnet particles. Further, since the green sheet 13 formed into a sheet shape has a large surface area and is easily oxidized, a particularly high effect can be expected.
In addition, the calcination treatment by plasma heating is performed at an output power of 1 kW to 10 kW, a hydrogen flow rate of 1 L / min to 10 L / min, an argon flow rate of 1 L / min to 5 L / min, and an irradiation time of 1 second to 60 seconds. By calcining the magnet powder or the molded body under appropriate conditions using heating, the amount of oxygen contained in the magnet particles can be more reliably reduced. Furthermore, since calcining is performed using high-temperature hydrogen plasma heating, high-concentration hydrogen radicals can be generated, and even when the metal forming the organometallic compound is present as a stable oxide in the magnet powder. Further, reduction to a metal and reduction of the oxidation number using hydrogen radicals can be easily performed at a low temperature.
In addition, by maintaining the binder decomposition temperature for a certain period of time in a non-oxidizing atmosphere, the binder is decomposed into monomers by a depolymerization reaction or the like and removed by scattering, and the green sheet from which the binder has been removed is subjected to pressure firing such as SPS sintering. The permanent magnet 1 is manufactured by sintering by sintering. As a result, since the permanent magnet 1 is sintered using pressure sintering, it becomes possible to lower the sintering temperature and suppress grain growth during sintering. Therefore, the magnetic performance of the manufactured permanent magnet can be improved. In addition, since the permanent magnet to be produced is uniform in shrinkage due to sintering, deformation such as warpage and dent after sintering does not occur, and pressure unevenness during pressing is eliminated. It is not necessary to carry out a correction process after ligation, and the manufacturing process can be simplified. Thereby, a permanent magnet can be formed with high dimensional accuracy. Further, even when the permanent magnet is thinned, it is possible to prevent the processing man-hours from increasing without reducing the material yield.
In addition, before the green sheet is sintered by pressure sintering, the binder is scattered and removed by performing a calcination process in which the green sheet is held at a binder decomposition temperature for a certain period of time in a non-oxidizing atmosphere. The amount of carbon contained therein can be reduced in advance. As a result, it is possible to suppress the precipitation of αFe in the main phase of the magnet after sintering, to densely sinter the entire magnet, and to prevent the coercive force from being lowered.
In addition, if an organometallic compound composed of an alkyl group, more preferably an organometallic compound composed of an alkyl group having 2 to 6 carbon atoms, is used as the organometallic compound to be added, the magnet powder is calcined in a hydrogen atmosphere. In this case, it is possible to perform thermal decomposition of the organometallic compound at a low temperature. Thereby, the thermal decomposition of the organometallic compound can be more easily performed on the entire magnet particle.
Further, in the calcining treatment, the green sheet in which the binder is kneaded is held at 200 ° C. to 900 ° C., more preferably 400 ° C. to 600 ° C. for a certain time in a hydrogen atmosphere or a mixed gas atmosphere of hydrogen and an inert gas. The amount of carbon contained in the magnet can be more reliably reduced.

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, calcination conditions, sintering conditions, etc. of the magnet powder are not limited to the conditions described in the above examples. For example, in the above embodiment, the magnet raw material is pulverized by dry pulverization using a jet mill, but may be pulverized by wet pulverization using a bead mill. Here, when pulverizing by wet pulverization, the magnet raw material is wet pulverized in an organic solvent, and then a slurry is generated by adding a binder to the organic solvent containing the pulverized magnet powder. The timing of adding the organometallic compound may be before wet pulverization, during wet pulverization, or after wet pulverization. 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. However, it is desirable to use a method capable of forming a slurry or fluid compound on a substrate with high accuracy. Moreover, in the said Example, although the magnet was sintered by SPS sintering, you may sinter a magnet using other pressure sintering methods (for example, hot press sintering etc.).

  Further, the calcination treatment in hydrogen may be omitted. Even in that case, the binder is thermally decomposed during the sintering, and a certain decarburizing effect can be expected. Further, the calcination treatment may be performed in an atmosphere other than hydrogen.

  In the present embodiment, the organometallic compound and the organic solvent are first added to the magnet powder, and the binder is added after the organometallic compound is attached to the surface of the magnet particles. However, the organometallic compound and the binder are added to the magnet powder. It is good also as producing | generating a slurry, adhering an organometallic compound to the particle | grain surface by mixing with an organic solvent. In that case, it is desirable that the amount of the organometallic compound to be added is larger than that in the above-described embodiment.

In Examples 1 and 2, Dy, Tb, V, Mo, Zr, Ta, Ti, W, Cu, Al, Nd, Ag, Ga, Co, Bi, Zn, Mg, Nb, etc. added to the magnet powder Niobium ethoxide and dysprosium ethoxide are used as organometallic compounds containing M, but M- (OR) _x (wherein M is Dy, Tb, V, Mo, Zr, Ta, Ti, W, Cu, Al , Nd, Ag, Ga, Co, Bi, Zn, Mg, Nb, at least one of them, R is a hydrocarbon substituent, which may be linear or branched, and x is an arbitrary integer As long as it is an organometallic compound represented by.), Other organometallic compounds may be used. Furthermore, it may be configured not to add organometallic compounds including Dy, Tb, V, Mo, Zr, Ta, Ti, W, Cu, Al, Nd, Ag, Ga, Co, Bi, Zn, Mg, Nb and the like. good. Even in that case, the amount of oxygen contained in the magnet particles can be reduced in advance before sintering by performing a calcining treatment by plasma heating. Accordingly, it is possible to achieve the object of the present invention by suppressing the precipitation of αFe in the main phase of the magnet after sintering and the generation of oxides.

  Moreover, in the said Example, although resin, long chain hydrocarbon, and fatty acid methyl ester are used as a binder, you may use another material.

  In the present invention, the Nd—Fe—B system magnet has been described as an example, but other magnets (for example, a cobalt magnet, an alnico magnet, a 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.

1 Permanent magnet 11 Jet mill 12 Slurry 13 Green sheet 15 Die 25, 26 Molded body

Claims (14)

Crushing magnet raw material into magnet powder;
Producing a mixture by mixing the pulverized magnet powder and a binder;
Forming the mixture into a sheet and producing a green sheet;
A step of scattering and removing the binder by holding the green sheet at a binder decomposition temperature for a certain period of time in a non-oxidizing atmosphere;
A step of calcining the green sheet from which the binder has been removed by plasma heating to obtain a calcined body;
A rare earth permanent magnet produced by sintering the calcined body. The pulverized magnet powder has the following general formula M- (OR) _x
(In the formula, M includes at least one of Dy, Tb, V, Mo, Zr, Ta, Ti, W, Cu, Al, Nd, Ag, Ga, Co, Bi, Zn, Mg, and Nb. R Is a hydrocarbon substituent, which may be linear or branched, and x is an arbitrary integer.)
By adding the organometallic compound represented by the above, the organometallic compound is attached to the particle surface of the magnet powder,
2. The rare earth permanent magnet according to claim 1, wherein in the step of generating the mixture, the mixture obtained by mixing the magnet powder with the organometallic compound attached to the particle surface and the binder is generated. 3.   The rare earth permanent magnet according to claim 2, wherein R in the general formula is an alkyl group.   The rare earth permanent magnet according to claim 3, wherein R in the general formula is any one of an alkyl group having 2 to 6 carbon atoms.   The rare earth permanent magnet according to any one of claims 1 to 4, wherein in the step of obtaining the calcined body, calcining is performed by high-temperature hydrogen plasma heating.   The rare earth permanent magnet according to any one of claims 1 to 5, wherein in the step of sintering the calcined body, the calcined body is subjected to pressure sintering.   In the step of removing the binder by scattering, the green sheet is maintained at 200 ° C to 900 ° C for a predetermined time in a hydrogen atmosphere or a mixed gas atmosphere of hydrogen and an inert gas. Item 7. The rare earth permanent magnet according to Item 6. Crushing magnet raw material into magnet powder;
Producing a mixture by mixing the pulverized magnet powder and a binder;
Forming the mixture into a sheet and producing a green sheet;
A step of scattering and removing the binder by holding the green sheet at a binder decomposition temperature for a certain period of time in a non-oxidizing atmosphere;
A step of calcining the green sheet from which the binder has been removed by plasma heating to obtain a calcined body;
And a step of sintering the calcined body. The pulverized magnet powder has the following general formula M- (OR) _x
(In the formula, M includes at least one of Dy, Tb, V, Mo, Zr, Ta, Ti, W, Cu, Al, Nd, Ag, Ga, Co, Bi, Zn, Mg, and Nb. R Is a hydrocarbon substituent, which may be linear or branched, and x is an arbitrary integer.)
By adding the organometallic compound represented by the above, the organometallic compound is attached to the particle surface of the magnet powder,
The rare earth permanent magnet according to claim 8, wherein in the step of generating the mixture, the mixture of the magnet powder in which the organometallic compound is attached to a particle surface and the binder is generated. Production method.   The method for producing a rare earth permanent magnet according to claim 9, wherein R in the general formula is an alkyl group.   The method for producing a rare earth permanent magnet according to claim 10, wherein R in the general formula is any one of an alkyl group having 2 to 6 carbon atoms.   The method for producing a rare earth permanent magnet according to any one of claims 8 to 11, wherein in the step of obtaining the calcined body, calcining is performed by high-temperature hydrogen plasma heating.   The method for producing a rare earth permanent magnet according to any one of claims 8 to 12, wherein in the step of sintering the calcined body, the calcined body is subjected to pressure sintering. 9. The step of removing the binder by scattering, wherein the green sheet is held at 200 ° C. to 900 ° C. for a predetermined time in a hydrogen atmosphere or a mixed gas atmosphere of hydrogen and an inert gas. Item 14. A method for producing a rare earth permanent magnet according to Item 13.

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