JP2011216695A - Method for manufacturing rare-earth permanent magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a rare-earth permanent magnet having superior stability, high corrosion resistance and high hydrogen barrier performance.SOLUTION: An organic metal compound solution doped with an organic metal compound represented by M-(OR)(wherein M contains at least one kind from among Nd, Pr, Dy, Tb, V, Mo, Zr, Ta, Ti, W and Nb, R is any one of 2-6C alkyl groups and may be a straight chain or a branched chain, and x is an arbitrary integer) is doped to a pulverized magnetic powder, and the organic metal compound is uniformly deposited to the surface of the magnetic particles. After that, the dried magnetic powder is maintained in a vacuum or inert gas atmosphere at 600°C or higher than and lower than 900°C for 0.01 min to less than one hour to execute heat treatment. Further, the heat-treated magnetic powder is molded, baked at 800-1,180°C, cut into a product shape (e.g. like a cube), and polished to finish the surface, and a sintered compact 72 is heat-treated, thereby a permanent magnet 1 is manufactured.

Description

  The present invention relates to a method for producing a rare-earth permanent magnet that is exposed to, for example, an HFC or HCFC refrigerant and a lubricating oil (ester oil or ether oil refrigerating machine oil) for a long time, particularly a permanent magnet effective for a high-efficiency motor.

  Rare earth permanent magnets are used in many fields of electrical and electronic equipment because of their excellent magnetic properties and economy, and their production volume is increasing rapidly in recent years. Among these, rare earth-based permanent magnets have a lower raw material cost because Nd, which is the main element, is more abundant than Sm in comparison with rare earth cobalt magnets, and do not use a large amount of Co. Therefore, it is widely applied not only to small magnetic circuits in which rare earth cobalt magnets have been used, but also to fields where hard ferrites or electromagnets have been used. DC brushless motors that use rare earth magnets instead of conventional induction motors or synchronous rotating machines that use ferrite magnets to increase energy efficiency and reduce power consumption in compressor motors such as air conditioners and refrigerators The transition to is progressing.

  Since R-Fe-B permanent magnets contain rare earth elements and iron as main components, they have the drawback of being easily oxidized in a short period of time in humid air. When incorporated in a magnetic circuit, there have been problems such as a reduction in the output of the magnetic circuit due to these oxidative corrosions, and contamination of peripheral equipment due to the generated rust. For this reason, in general, rare earth magnets are used after surface treatment. As surface treatment methods for rare earth magnets, electroplating, electroless plating, Al ion plating, and various types of coating are used.

  Rare earth permanent magnets used in air conditioner compressor motors and industrial motors used in refrigerants, lubricating oils, or mixed systems thereof are corrosion resistant under high temperature and high pressure in mixed systems of these refrigerants and refrigeration oils. Is required.

  For example, in Japanese Patent Laid-Open No. 11-150930, it is proposed to use a magnet material that is not subjected to surface treatment with a rare earth magnet in the iron core of a rotor in a refrigerant compressor.

Japanese Patent Laid-Open No. 11-150930

  However, the combination of the HFC refrigerant and the ether-based or ester-based refrigerating machine oil may reduce the magnetic characteristics of the incorporated magnet due to high-temperature and long-time operation.

  Further, in an automobile motor that is operated by being immersed in lubricating oil, the corrosion reaction between the lubricating oil and the magnet proceeds, and the magnetic characteristics are deteriorated.

  Therefore, in these applications, application of the above-mentioned various surface treatments is considered. For example, the Al ion plating method is expensive and industrially problematic, and the coating reacts with a solvent or oil. In addition, the plating method cannot be used due to problems with stability at high temperatures, such as the plating film peeling off at the shrink fitting temperature of the rotor and shaft, and these surface treatments are large magnets Is difficult to industrialize, and many plating defects occur.

  As described above, rare earth permanent magnets used in high-efficiency motors are exposed to high-temperature and high-pressure refrigerants and / or lubricating oils for a long period of time, so that they react with or corrode them, resulting in a deterioration in magnetic properties. There is.

  The present invention solves the above-mentioned problems, and has excellent stability, high corrosion resistance and hydrogen barrier properties even under severe use conditions such as being exposed to a high-temperature and high-pressure refrigerant and / or lubricating oil for a long time. A method for producing a rare earth permanent magnet is provided.

In order to achieve the above object, a method for producing 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, and the pulverized magnet powder having the following structural formula M- (OR) _x ( In the formula, M includes at least one of Nd, Pr, Dy, Tb, V, Mo, Zr, Ta, Ti, W, and Nb, R is any one of alkyl groups having 2 to 6 carbon atoms, The organic metal compound may be attached to the particle surface of the magnet powder by adding an organometallic compound represented by the formula: x is an arbitrary integer), and the organometallic compound. Forming a molded body by molding the magnet powder adhered to the particle surface, sintering the molded body, and cutting and / or polishing the sintered molded body to form a surface. after finishing, the oxygen partial pressure 10 ^- Feature ⁶ 10 Argon is ⁰ Torr, in nitrogen or low-pressure vacuum atmosphere, a step of forming a lower oxides on the surface of the magnet performed 10 minutes to 10 hours heat treatment at 200 ° C. C. to 1100 ° C., to have a And

  In the method for producing a rare earth permanent magnet according to claim 2, the sintered compact has an oxygen concentration of 0.05 wt% to 0.8 wt% and a carbon concentration of 0.03 wt% to 0 wt%. 10% by weight.

According to the method for producing a rare earth permanent magnet according to claim 1 having the above-described configuration, a protective film is formed by heat treatment on the surface of the R-Fe-B permanent magnet that has been subjected to the processing, so that the refrigerant and the lubricating oil are used. A highly oil-resistant sintered permanent magnet having corrosion resistance and hydrogen barrier properties can be provided easily and inexpensively even in an atmosphere of high temperature and high pressure, and its utility value is extremely high in industry.
M- (OR) _x (wherein M includes at least one of Nd, Pr, Dy, Tb, V, Mo, Zr, Ta, Ti, W, and Nb. R has 2 to 6 carbon atoms) And a solvent containing an organometallic compound represented by the following formula is added and mixed with the magnet powder in a wet state. It is possible to disperse organometallic compounds containing Mn in a solvent so that the organometallic compounds containing M are uniformly deposited on the surface of the magnet particles, and the M is unevenly distributed with respect to the grain boundaries of the sintered rare earth magnet. Can be made.

  According to the method for producing a rare earth permanent magnet according to claim 2, the oxygen concentration of the sintered compact is 0.05 wt% to 0.8 wt%, and the carbon concentration is 0.03% wt%. It is possible to produce a rare earth permanent magnet with high magnetic performance because it is ˜0.10 wt%.

1 is an overall view showing a permanent magnet according to the present invention. It is the schematic diagram which expanded and showed the vicinity of the grain boundary of the permanent magnet which concerns on this invention. It is explanatory drawing which showed the manufacturing process in the 1st manufacturing method of the permanent magnet which concerns on this invention. It is explanatory drawing which showed the manufacturing process in the 2nd manufacturing method of the permanent magnet which concerns on this invention.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of a permanent magnet and a method for producing a 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 rectangular parallelepiped shape, but the shape of the permanent magnet 1 varies depending on the method of cutting and polishing the sintered body.

  An R-T-B magnet is used as the permanent magnet 1 according to the present invention. R is Nd or a combination of Nd and one or more other rare earth elements, and T is Fe, or Fe and Co. In addition, content of each component shall be R: 25-37 wt%, T: 60-75 wt%, B: 1-2 wt%. Further, in order to improve the magnetic characteristics, a small amount of other elements such as Co, Cu, Al and Si may be included. Further, a lower oxide (protective film) is formed on the surface of the permanent magnet 1 by performing a heat treatment described later in the manufacturing process. And the corrosion resistance is improved by the lower oxide formed on the surface of the permanent magnet 1.

  Here, as shown in FIG. 2, the permanent magnet 1 is an alloy in which a main phase 11 that is a magnetic phase contributing to a magnetization action and a grain boundary phase 12 coexist. FIG. 2 is an enlarged view showing magnet crystal particles constituting the permanent magnet 1.

Here, the main phase 11 is in a state where the R ₂ T ₁₄ B intermetallic compound phase having a stoichiometric composition occupies a high volume ratio. On the other hand, the grain boundary phase 12 is formed of an R rich phase (for example, R _{2.0 to 3.0} T ₁₄ B intermetallic compound phase) having a higher R composition ratio than the stoichiometric composition R ₂ T ₁₄ B. Has been.

And in the permanent magnet 1, the R rich phase plays the following roles.
(1) The melting point is low (about 600 ° C.), it becomes a liquid phase during sintering, and contributes to increasing the density of the magnet, that is, improving the magnetization. (2) Eliminate grain boundary irregularities, reduce reverse domain nucleation sites and increase coercivity. (3) The main phase is magnetically insulated to increase the coercive force.
Therefore, if the dispersion state of the R-rich phase in the sintered permanent magnet 1 is poor, local sintering failure and a decrease in magnetism may occur. Therefore, the R-rich phase is uniform in the sintered permanent magnet 1. It is important that they are dispersed.

  Moreover, as a problem which arises in manufacture of a R-T-B type magnet, it is mentioned that (alpha) -Fe produces | generates in the sintered alloy. The cause is that when a permanent magnet is manufactured using a magnet raw material alloy having a content based on the stoichiometric composition, the rare earth element is combined with oxygen and carbon during the manufacturing process, and the rare earth element is compared with the stoichiometric composition. It is mentioned that it becomes insufficiency. Here, α-Fe has deformability and remains in the pulverizer without being pulverized, so that not only the pulverization efficiency when pulverizing the alloy is decreased, but also the composition fluctuation and particle size distribution before and after pulverization. It also affects. Furthermore, if α-Fe remains in the magnet after sintering, the magnetic properties of the magnet are lowered.

  The rare earth element content in the permanent magnet 1 is 0.1 wt% to 10.0 wt%, more preferably 0.1 wt% to the content based on the stoichiometric composition (26.7 wt%). It is desirable that the amount be within a range of 5.0 wt%. By setting the content of the rare earth element in the permanent magnet 1 within the above range, the R-rich phase can be uniformly dispersed in the sintered permanent magnet 1. Moreover, even if the rare earth element is combined with oxygen in the manufacturing process, the rare earth element is not insufficient with respect to the stoichiometric composition, and generation of α-Fe in the sintered permanent magnet 1 is suppressed. It becomes possible.

  Note that when the content of the rare earth element in the permanent magnet 1 is less than the above range, the R-rich phase is hardly formed. Moreover, the production | generation of (alpha) -Fe cannot fully be suppressed. On the other hand, when the composition of the rare earth element in the permanent magnet 1 is larger than the above range, the increase in coercive force is slowed and the residual magnetic flux density is lowered, which is not practical.

Further, in the present invention, M- (OR) _x (wherein M is Nd, Pr, Dy, Tb, V, Mo, Zr, Ta, Ti, Including at least one of W and Nb, wherein R is any alkyl group having 2 to 6 carbon atoms, which may be linear or branched, and x is an arbitrary integer. A solvent containing an organometallic compound (for example, neodymium ethoxide, dysprosium propoxide, terbium propoxide, etc.) is added and mixed with the magnet powder in a wet state.

  At that time, in particular, when including rare earth elements such as Nd, Pr, Dy, and Tb as M, the content of all rare earth elements in the magnet raw material at the start of pulverization is the content based on the above stoichiometric composition ( 26.7 wt%). And before shape | molding the pulverized magnet powder as mentioned later, the solvent containing the organometallic compound containing M which is a rare earth element is added, and it mixes with a magnet powder in a wet state. As a result, the rare earth element content in the magnet powder after addition of the organometallic compound is more preferably 0.1 wt% to 10.0 wt%, more preferably the content based on the stoichiometric composition (26.7 wt%). Is within the range of 0.1 wt% to 5.0 wt%. Further, by adding it to the solvent, it becomes possible to disperse the organometallic compound containing M in the solvent and uniformly adhere the organometallic compound containing M to the particle surfaces of the magnet particles. 1, the R-rich phase can be uniformly dispersed.

  This method has an advantage that the magnet composition does not vary greatly before and after pulverization, as compared with a method in which the content of rare earth elements contained in the magnet raw material before pulverization is made higher than the content based on the stoichiometric composition in advance. Therefore, there is an advantage that it is not necessary to change the magnet composition after pulverization.

  Furthermore, if Dy or Tb is included as M, Dy or Tb can be unevenly distributed in the grain boundaries of the magnet particles. 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 surface of the Nd crystal particles 35. As a result, when the magnet powder is sintered, Nb or the like in the organometallic compound uniformly attached to the surface of the Nd crystal particles by wet dispersion diffuses and penetrates into the crystal growth region of the Nd crystal particles. And a refractory metal layer is formed on the surface of the Nd crystal particles. 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 R-rich phase is not formed in the grain boundary phase 12.

Here, M- (OR) _x (wherein M includes at least one of Nd, Pr, Dy, Tb, V, Mo, Zr, Ta, Ti, W, and Nb. R has 2 carbon atoms. A metal alkoxide as an organometallic compound satisfying the structural formula: any one of ˜6 alkyl groups, which may be linear or branched, and x is an arbitrary integer. 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, Ni, Cu, Zn, Cd, Al, Ga, In, Ge, Sb, Y, lanthanide, etc. are mentioned. However, in the present invention, Nd, Pr, Dy, Tb, V, Mo, Zr, Ta, Ti, W, and Nb are particularly 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 is easily decomposed and difficult to handle, it is particularly preferable to use ethoxide, methoxide, isopropoxide, propoxide, butoxide, etc., which are alkoxides having 2 to 6 carbon atoms.

Moreover, if the molded object shape | molded by compaction shaping | molding is baked on suitable baking conditions, it can prevent that M carries out a diffusion | penetration penetration (solid solution) in the main phase 11. FIG. 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 R ₂ T 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.

  The crystal grain size of the main phase 11 is preferably 0.1 μm to 5.0 μm. The configurations of the main phase 11 and the grain boundary phase 12 can be confirmed by, for example, SEM, TEM, or a three-dimensional atom probe method.

  The permanent magnet 1 preferably has an oxygen concentration of 0.8% by weight or less, a magnetic property of Br of 12.0 kG to 15.2 kG and iHc of 9 kOe to 35 kOe. Furthermore, an oxygen concentration of 0.05 to 0.8% by weight and a carbon concentration of 0.03 to 0.10% by weight are preferable from the viewpoint of improving coercive force and improving magnetic properties.

[Permanent magnet manufacturing method 1]
Next, the 1st manufacturing method of the permanent magnet 1 which concerns on this invention is demonstrated using FIG. FIG. 3 is an explanatory view showing a manufacturing process in the first manufacturing method of the permanent magnet 1 according to the present invention.

  First, an ingot made of R-T-B (for example, Nd: 26.7 wt%, Fe (electrolytic iron): 72.3 wt%, B: 1.0 wt%) in a predetermined fraction 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. An average particle having a predetermined range of particle sizes (for example, 0.1 μm to 5.0 μm) by pulverizing with a jet mill 41 in an atmosphere composed of inert gas such as nitrogen gas, Ar gas, and He gas of about 0.5% A fine powder having a diameter is used. 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.

On the other hand, an organometallic compound solution (organic solvent) to be added to the fine powder finely pulverized by the jet mill 41 is prepared. Here, an organometallic compound containing M is added in advance to the organometallic compound solution and dissolved. As an organometallic compound to be dissolved, M- (OR) _x (wherein M includes at least one of Nd, Pr, Dy, Tb, V, Mo, Zr, Ta, Ti, W, and Nb). R is an alkyl group having 2 to 6 carbon atoms, which may be linear or branched, and x is an arbitrary integer.) (For example, neodymium ethoxide, dysprosium propoxide) Terbium propoxide, etc.). Further, the amount of the organometallic compound containing M to be dissolved is not particularly limited, but the amount of M with respect to the sintered magnet is 0.001 wt% to 10 wt%, preferably 0.01 wt% to 5 wt%. It is preferable to do this.

  Subsequently, the organometallic compound solution is added to the fine powder classified by the jet mill 41. Thereby, the slurry 42 in which the fine powder of the magnet raw material and the organometallic compound solution are mixed is generated. 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, the produced slurry 42 is dried in advance by vacuum drying or the like before molding, and the dried magnet powder 43 is taken out. Thereafter, the dried magnet powder is compacted into a predetermined shape by the molding device 50. There are two types of compacting: a dry method in which the dried fine powder is filled into the cavity, and a wet method in which the powder is filled into the cavity after slurrying with a solvent or the like. In the present invention, the dry method is used. Illustrate. Further, the organometallic compound solution can be volatilized in the firing stage after molding.

As shown in FIG. 3, the molding apparatus 50 includes a cylindrical mold 51, a lower punch 52 that slides up and down with respect to the mold 51, and an upper punch 53 that also slides up and down with respect to the mold 51. And a space surrounded by them constitutes the cavity 54.
The molding apparatus 50 has a pair of magnetic field generating coils 55 and 56 disposed above and below the cavity 54, and applies magnetic field lines to the magnet powder 43 filled in the cavity 54. The applied magnetic field is, for example, 1 MA / m.

And when compacting, first, the dried magnet powder 43 is filled into the cavity 54. Thereafter, the lower punch 52 and the upper punch 53 are driven, and pressure is applied in the direction of the arrow 61 to the magnetic powder 43 filled in the cavity 54 to perform molding. Simultaneously with the pressurization, a pulse magnetic field is applied to the magnetic powder 43 filled in the cavity 54 by the magnetic field generating coils 55 and 56 in the direction of the arrow 62 parallel to the pressurization direction. Thereby orienting the magnetic field in the desired direction. Note that the direction in which the magnetic field is oriented needs to be determined in consideration of the magnetic field direction required for the permanent magnet 1 formed from the magnet powder 43.
Further, when using the wet method, the slurry may be injected while applying a magnetic field to the cavity 54, and wet molding may be performed by applying a magnetic field stronger than the initial magnetic field during or after the injection. Further, the magnetic field generating coils 55 and 56 may be arranged so that the application direction is perpendicular to the pressing direction.

  Next, the compact 71 formed by compacting is held in hydrogen by holding it in a hydrogen atmosphere at 200 ° C. to 900 ° C., more preferably 400 ° C. to 900 ° C. (eg 600 ° C.) for several hours (eg 5 hours). Perform calcination. The amount of hydrogen supplied during calcination is 5 L / min. In the calcination treatment in hydrogen, so-called decarbonization is performed in which the organometallic compound is thermally decomposed to reduce the amount of carbon in the calcined body. Further, the calcination treatment in hydrogen is performed under the condition that the carbon content in the calcined body is 1000 ppm or less, more preferably 500 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.

Here, the molded body 71 calcined by the above-described calcining treatment in hydrogen has a problem that NdH ₃ exists and is easily combined with oxygen. However, in the first manufacturing method, the molded body 71 is preliminarily hydrogenated. Since it moves to the below-mentioned vacuum baking without making it contact with external air after baking, a dehydrogenation process becomes unnecessary. During the firing, hydrogen in the molded body is released.

Then, the sintering process which sinters the molded object 71 calcined by the calcination process in hydrogen is performed. In the sintering process, the temperature is raised to about 800 ° C. to 1180 ° C. at a predetermined rate of temperature rise and held for about 2 hours. During this time, vacuum firing is performed, but the degree of vacuum is preferably 10 ⁻⁴ Torr or less. Thereafter, it is cooled and heat-treated again at 600 ° C. for 2 hours. And the sintered compact 72 which sintered the molded object 71 is obtained.

  Thereafter, after the sintered body 72 is cooled, the sintered body 72 is cut into a product shape (for example, a rectangular parallelepiped shape). Also, the surface is finished by polishing.

Subsequently, the sintered body 72 is heat-treated, thereby improving the corrosion resistance. In this case, the heat treatment temperature is preferably 200 to 1100 ° C, more preferably 300 to 600 ° C, still more preferably 450 to 550 ° C. If the heat treatment temperature is too high, the magnetic properties deteriorate, and if it is too low, the durability against the refrigerant and / or lubricating oil may be deteriorated. The atmosphere of the heat treatment, the oxygen partial pressure is 10- ⁶ to 10 ⁰ Torr, a argon, nitrogen or low-pressure vacuum atmosphere is more preferably 10 ^-5 to 10 ^-4 Torr, the heat treatment time is 10 minutes to 10 Time, more preferably 10 minutes to 6 hours, still more preferably 30 minutes to 3 hours. In addition, you may cool the sintered compact 72 heat-processed by desired atmosphere and temperature at the cooling rate of 10-2000 degreeC / min. In some cases, it is possible to perform heat treatment in multiple stages. And as a result of heat-processing with respect to the sintered compact 72, the permanent magnet 1 is manufactured.

By performing heat treatment as described above, a lower oxide can be formed on the surface of the magnet, and a high-efficiency rare earth permanent magnet for motors with good corrosion resistance can be obtained. The magnets obtained by the present invention are particularly solvents such as HFC (for example, R410A, R134a, R125, etc.) and HCFC (R22, R32, etc.) and lubricating oil (refrigerator oil: mineral oil, ester oil, ether oil, etc.) ) Is resistant to corrosion.
[Permanent magnet manufacturing method 2]
Next, the 2nd manufacturing method which is another manufacturing method of the permanent magnet 1 which concerns on this invention is demonstrated using FIG. FIG. 4 is an explanatory view showing a manufacturing process in the second manufacturing method of the permanent magnet 1 according to the present invention.

  The process until the slurry 42 is generated is the same as the manufacturing process in the first manufacturing method already described with reference to FIG.

  First, the produced slurry 42 is dried in advance by vacuum drying or the like before molding, and the dried magnet powder 43 is taken out. Thereafter, the dried magnet powder 43 is calcined in hydrogen by holding it in a hydrogen atmosphere at 200 ° C. to 900 ° C., more preferably 400 ° C. to 900 ° C. (eg 600 ° C.) for several hours (eg 5 hours). The amount of hydrogen supplied during calcination is 5 L / min. In the calcination treatment in hydrogen, so-called decarbonization is performed in which the organometallic compound is thermally decomposed to reduce the amount of carbon in the calcined body. Further, the calcination treatment in hydrogen is performed under the condition that the carbon content in the calcined body is 1000 ppm or less, more preferably 500 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.

  Next, dehydrogenation treatment is performed by holding the powder-like calcined body 82 calcined by calcination in hydrogen at 200 to 600 ° C., more preferably at 400 to 600 ° C. for 1 to 3 hours in a vacuum atmosphere. I do. The degree of vacuum is preferably 0.1 Torr or less.

Here, the calcined body 82 calcined by the above-described calcining process in hydrogen has a problem that NdH ₃ exists and is easily combined with oxygen.
Stage Therefore, the dehydrogenation process, NdH ₃ calcined body of 82 produced by calcination process in hydrogen (activity Univ), NdH ₃ (activity Univ) → NdH ₂ to (activity small) Thus, the activity of the calcined body 82 activated by the treatment during the hydrogen calcination is lowered. Thereby, even when the calcined body 82 calcined by the calcining process in hydrogen is moved to the atmosphere after that, Nd is prevented from being combined with oxygen, and the residual magnetic flux density and coercive force are reduced. There is no reduction.

  Thereafter, the powder-like calcined body 82 subjected to the dehydrogenation treatment is compacted into a predetermined shape by the molding apparatus 50. The details of the molding apparatus 50 are the same as the manufacturing steps in the first manufacturing method already described with reference to FIG.

Thereafter, a sintering process for sintering the formed calcined body 82 is performed. In the sintering process, the temperature is raised to about 800 ° C. to 1180 ° C. at a predetermined rate of temperature rise and held for about 2 hours. During this time, vacuum firing is performed, but the degree of vacuum is preferably 10 ⁻⁴ Torr or less. Thereafter, it is cooled and heat-treated again at 600 ° C. for 2 hours. Then, a sintered body 72 obtained by sintering the formed calcined body 82 is obtained.

  Thereafter, similarly to the manufacturing process in the first manufacturing method already described with reference to FIG. 3, the sintered body 72 is cut into a product shape (for example, a rectangular parallelepiped shape) and polished to finish the surface. After that, the sintered body 72 is heat-treated, and the permanent magnet 1 is manufactured.

In the second manufacturing method described above, since the powdered magnet particles are calcined in hydrogen, the first manufacturing method in which the magnet particles after molding are calcined in hydrogen are used. In comparison, there is an advantage that the pyrolysis of the organometallic compound can be more easily performed on the entire magnet particle. That is, it becomes possible to more reliably reduce the amount of carbon in the calcined body as compared with the first manufacturing method.
On the other hand, in the first manufacturing method, the compact 71 does not come into contact with the outside air after hydrogen calcination, and moves to vacuum firing described later, so that a dehydrogenation step is unnecessary. Therefore, the manufacturing process can be simplified as compared with the second manufacturing method. However, also in the second manufacturing method, the dehydrogenation step is not necessary when the firing is performed without contact with the outside air after the hydrogen calcination.

As described above, in the permanent magnet 1 and the method for manufacturing the permanent magnet 1 according to the present embodiment, M- (OR) x (where M is Nd, Pr, Dy, Tb) with respect to the pulverized magnet powder. , V, Mo, Zr, Ta, Ti, W, Nb, at least one of them, R is any one of alkyl groups having 2 to 6 carbon atoms, and may be linear or branched. An organometallic compound solution to which an organometallic compound represented by (2) is added is added to uniformly adhere the organometallic compound to the surfaces of the magnet particles. Then, heat treatment is performed by holding the dried magnet powder in a vacuum or in an inert gas atmosphere at 600 ° C. or more and less than 900 ° C. for 0.01 minute or more and less than 1 hour. Further, the heat-treated magnet powder is molded, fired at 800 ° C. to 1180 ° C., cut into a product shape (for example, a rectangular parallelepiped shape), and polished to finish the surface, and then sintered. The permanent magnet 1 is manufactured by performing heat treatment on 72. In the heat treatment, the lower oxide is formed on the surface of the magnet by performing heat treatment at 200 ° C. to 1100 ° C. for 10 minutes to 10 hours in an argon, nitrogen or low pressure vacuum atmosphere having an oxygen partial pressure of 10 ⁻⁶ to 10 ⁰ Torr. By forming a protective film by heat treatment on the surface of the R-Fe-B permanent magnet that has been processed, high oil resistance that has corrosion resistance and hydrogen barrier properties even in an atmosphere of high temperature and high pressure due to refrigerant and lubricating oil The sintered sintered permanent magnet can be provided simply and inexpensively, and its utility value is extremely high in industry.
Since the sintered compact has an oxygen concentration of 0.05 wt% to 0.8 wt% and a carbon concentration of 0.03 wt% to 0.10 wt%, a rare earth permanent magnet with high magnetic performance can be obtained. It can be manufactured.
M- (OR) _x (wherein M includes at least one of Nd, Pr, Dy, Tb, V, Mo, Zr, Ta, Ti, W, and Nb. R has 2 to 6 carbon atoms) And a solvent containing an organometallic compound represented by the following formula is added and mixed with the magnet powder in a wet state. It is possible to disperse organometallic compounds containing Mn in a solvent so that the organometallic compounds containing M are uniformly deposited on the surface of the magnet particles, and the M is unevenly distributed with respect to the grain boundaries of the sintered rare earth magnet. Can be made.
In addition, a magnet to which an organometallic compound is added is calcined in a hydrogen atmosphere before sintering, so that the organometallic compound is thermally decomposed and carbon contained in the magnet particles is preliminarily burned out (the amount of carbon is reduced). The carbide is hardly formed in the sintering process. 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, αFe is not precipitated in the main phase of the magnet after sintering, and the magnet characteristics are not greatly deteriorated.
In particular, in the second manufacturing method, since the powdered magnet particles are calcined, the remaining organic compound is thermally decomposed as compared with the case of calcining the molded magnet particles. This can be performed more easily on the entire magnet particle. That is, the amount of carbon in the calcined body can be reduced more reliably. Further, by performing the dehydrogenation treatment after the calcination treatment, the activity of the calcined body activated by the calcination treatment can be reduced. As a result, the magnet particles are prevented from being combined with oxygen thereafter, and the residual magnetic flux density and coercive force are not 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.
Moreover, the pulverization conditions, kneading conditions, calcination conditions, sintering conditions, heat treatment conditions, etc. of the magnet powder are not limited to the conditions described in the above examples.
Moreover, you may abbreviate | omit about a calcination process and a dehydrogenation process.

In the manufacturing method described above, for Nd, Pr, Dy, Tb, V, Mo, Zr, Ta, Ti, W, and Nb, M- (OR) _x (where M is Nd, Pr) , Dy, Tb, V, Mo, Zr, Ta, Ti, W, Nb, and at least one of them, R is an alkyl group having 2 to 6 carbon atoms, and may be linear or branched. x is an arbitrary integer.) By adding the organometallic compound represented by (2), the composition is added. However, a part of the composition may be included in the ingot in advance.

1 Permanent magnet 11 Main phase 12 R rich phase

Claims (2)

Crushing magnet raw material into magnet powder;
The pulverized magnet powder has the following structural formula M- (OR) _x
(In the formula, M includes at least one of Nd, Pr, Dy, Tb, V, Mo, Zr, Ta, Ti, W, and Nb. R is any one of alkyl groups having 2 to 6 carbon atoms. It may be linear or branched, and x is an arbitrary integer.)
A step of attaching the organometallic compound to the particle surface of the magnet powder by adding an organometallic compound represented by:
Forming the molded body by molding the magnet powder having the organometallic compound attached to the particle surface;
Sintering the molded body;
After the sintered compact is cut and / or polished to finish the surface, it is 200 ° C. to 1100 ° C. in an argon, nitrogen or low pressure vacuum atmosphere having an oxygen partial pressure of 10 ⁻⁶ to 10 ⁰ Torr. Performing a heat treatment for 10 minutes to 10 hours to form a lower oxide on the surface of the magnet;
A method for producing a rare earth permanent magnet, comprising:   The oxygen concentration of the sintered compact is 0.05 wt% to 0.8 wt%, and the carbon concentration is 0.03 wt% to 0.10 wt%. The manufacturing method of the rare earth permanent magnet of description.

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