JP2011216666A - Method for manufacturing rare-earth sintered magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rare-earth sintered magnet which prevents oxidation of a molded body and absorption of humidity and has high magnetic characteristics by improving its storability, and to provide a method for manufacturing the magnet.SOLUTION: A fine powder of a pulverized neodymium magnet is recovered into an organic solvent containing an organic metal compound represented by a structural formula M-(OR)(wherein M contains at least one kind of rare earth elements Nd, Pr, Dy and Tb, R is an arbitrary one among 2-6 C alkyl groups and may be a straight chain or a branched chain, and x is an arnitrary integer) to generate a slurry 42, and after that, a pressure is applied to the slurry 42 injected into a cavity 54 in a state where a magnetic field is applied to mold the slurry in a molding machine 50, and then, the organic solvent is evaporated to obtain a molded body. Next, the molded body is subjected to temporary baking in hydrogen of a hydrogen atmosphere, and is baked at 800-1,180°C, thereby a permanent magnet is manufactured.

Description

  The present invention relates to a method for producing an R—Fe—B rare earth sintered magnet.

  Rare earth sintered magnets are manufactured using powder metallurgy technology of pulverizing, forming, sintering, heat treatment and processing of ingots obtained by melting raw metal and pouring into a mold. Fe-B rare earth sintered magnets (R is one or more of rare earth elements including Y) are attracting attention as high performance magnets. However, the rare earth sintered magnet alloy powder obtained by pulverizing the ingot is chemically very active, and therefore oxidizes very rapidly in the atmosphere, resulting in deterioration of magnetic properties.

  In addition, the rare earth sintered magnet alloy powder not only generates heat due to rapid oxidation, but also ignites in severe cases, so there is a problem in terms of safety. Conventionally, as a method for preventing such rapid oxidation, a process of stabilizing the surface by leaving it in an inert gas such as nitrogen or argon for a long time has been performed. There was a problem with sex. Further, the alloy powder for rare earth sintered magnets has a hygroscopic property, and when left in the atmosphere, there is a problem that moisture in the atmosphere is adsorbed and the characteristics of the manufactured rare earth sintered magnet are deteriorated.

  With respect to this problem, Japanese Patent Application Laid-Open No. 61-114505 discloses a mixture of an R—Fe—B based (R is one or more of rare earth elements including Y) alloy powder and an organic solvent. A method for producing a permanent magnet has been proposed in which a molded body obtained by compressing an organic solvent in a magnetic field and filtering an organic solvent is dried, sintered and heat-treated. According to this manufacturing method, the problem of oxidation and moisture adsorption is solved because the molding is performed by a wet process.

JP 61-114505 A

  However, in the technique described in Patent Document 1, although the oxygen content is surely reduced, when an organic solvent such as toluene or alcohol is used, fine powder or molded material immersed in the solvent within a relatively short time of about one week. It has been found that there is a problem that the amount of oxygen in the body increases and the characteristics of the obtained sintered body tend to deteriorate.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a rare earth sintered magnet having high magnetic properties by preventing oxidation and moisture adsorption of fine powders and molded products, and having high magnetic properties, and a method for producing the same.

In order to achieve the above object, a method for producing a rare earth sintered magnet according to claim 1 of the present application is an R-Fe-B type (R is one or more of rare earth elements including Y). The body is pulverized dry, and the pulverized powder is represented by the following structural formula M- (OR) _x (wherein M includes at least one of the rare earth elements Nd, Pr, Dy, Tb. R is carbon. Any of alkyl groups of 2 to 6, which may be linear or branched, x is an arbitrary integer), and recovered in an organic solvent containing an organometallic compound represented by And a wet molding with the powder oriented while applying an orientation magnetic field thereto, and sintering the obtained compact.

  Moreover, the manufacturing method of the rare earth sintered magnet according to claim 2 is the manufacturing method of the rare earth sintered magnet according to claim 1, wherein the green body is calcined in a hydrogen atmosphere to obtain a calcined body, The obtained calcined body is sintered.

  Moreover, the manufacturing method of the rare earth sintered magnet which concerns on Claim 3 is a manufacturing method of the rare earth sintered magnet of Claim 2, Comprising: It keeps in the wet state with the said organic solvent until the molded object is calcined. It is characterized by that.

  A method for producing a rare earth sintered magnet according to claim 4 is the method for producing a rare earth sintered magnet according to claim 2, wherein the green compact is calcined in a non-oxidizing or reducing atmosphere until calcined. It is characterized by holding.

  Furthermore, the manufacturing method of the rare earth sintered magnet which concerns on Claim 5 is a manufacturing method of the rare earth sintered magnet in any one of Claim 1 thru | or 4, Comprising: The raw material powder for rare earth sintered magnets, and the said organic The filling of the mixture with the solvent into the molding cavity is performed while applying pressure.

According to the method of manufacturing a rare earth sintered magnet according to claim 1, having the above-described configuration, the magnet powder is pulverized, and the pulverized magnet powder is represented by a structural formula M- (OR) _x (wherein M is a rare earth element). At least one of Nd, Pr, Dy, and Tb is included, R is an alkyl group having 2 to 6 carbon atoms, which may be linear or branched, and x is an arbitrary integer. It is recovered in an organic solvent containing the indicated organometallic compound, and an orientation magnetic field is applied to the mixture to wet-form the powder while it is oriented, and the resulting shaped body is sintered. The rare earth sintered magnet having high magnetic properties can be obtained by preventing the adsorption of the magnet and improving the storage stability.

  Further, according to the method for producing a rare earth sintered magnet according to claim 2, the magnet powder containing the organic solvent is calcined in a hydrogen atmosphere before sintering, thereby containing the magnet particles. The amount of carbon can be reduced in advance. 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, according to the method for producing a rare earth sintered magnet according to claim 3, since the molded body is kept in a wet state with an organic solvent until calcined, it is possible to more reliably prevent the molded body from being oxidized. Become.

  In addition, according to the method for producing a rare earth sintered magnet according to claim 4, since the molded body is held in a non-oxidizing or reducing atmosphere until calcination, the molded body is more reliably prevented from being oxidized. Is possible.

  Furthermore, according to the method for manufacturing a rare earth sintered magnet according to claim 5, it is possible to improve the residual magnetic flux density and obtain a rare earth sintered magnet having high magnetic characteristics.

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. 1 has a cylindrical shape, the shape of the permanent magnet 1 varies depending on the shape of the cavity used for molding.
As the permanent magnet 1 according to the present invention, for example, an Nd—Fe—B magnet is used. Further, as shown in FIG. 2, the permanent magnet 1 includes a main phase 11 that is a magnetic phase that contributes to the magnetization action, and a low melting point M-rich phase 12 that is enriched with rare earth elements (M is Nd, which is a rare earth element). , Pr, Dy, and Tb). FIG. 2 is an enlarged view showing Nd magnet particles constituting the permanent magnet 1.

Here, the main phase 11 is in a state in which the Nd ₂ Fe ₁₄ B intermetallic compound phase having a stoichiometric composition (Fe may be partially substituted with Co) occupies a high volume ratio. On the other hand, M-rich phase 12 is also a stoichiometric composition _M 2 _Fe 14 B (Fe partially substituted may be at Co) composition ratio than M is large intermetallic phase (e.g., _{M 2. 0-3.0} Fe ₁₄ B intermetallic compound phase). Further, the M-rich phase 12 may contain a small amount of other elements such as Co, Cu, Al, and Si in order to improve magnetic characteristics.

In the permanent magnet 1, the M rich phase 12 plays the following role.
(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.
Accordingly, if the dispersion state of the M-rich phase 12 in the sintered permanent magnet 1 is poor, local sintering failure and a decrease in magnetism may occur. It is important that is uniformly dispersed.

  Further, a problem that occurs in the production of Nd—Fe—B magnets is that α-Fe is produced 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 during the manufacturing process, and the rare earth element is insufficient with respect to the stoichiometric composition. It becomes a state. Furthermore, if α-Fe remains in the magnet after sintering, the magnetic properties of the magnet are lowered.

  The content of all rare earth elements including Nd and M in the permanent magnet 1 is preferably 0.1 wt% to 10.0 wt%, more preferably the content based on the stoichiometric composition (26.7 wt%). Is preferably in the range of more than 0.1 wt% to 5.0 wt%. Specifically, the content of each component is Nd: 25 to 37 wt%, M: 0.1 to 10.0 wt%, B: 1 to 2 wt%, and Fe (electrolytic iron): 60 to 75 wt%. By setting the content of the rare earth element in the permanent magnet 1 within the above range, the M-rich phase 12 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 M-rich phase 12 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.

In the present invention, the content of all rare earth elements including Nd and M in the magnet powder at the time of pulverization is a content (26.7 wt%) based on the above stoichiometric composition. And, as will be described later, M- (OR) _x (wherein M includes at least one of Nd, Pr, Dy, and Tb, which are rare earth elements. R is any one of alkyl groups having 2 to 6 carbon atoms. An organic metal compound containing M represented by (for example, neodymium ethoxide, dysprosium propoxide, terbium propoxide) is added to an organic solvent. And added to the magnet powder after pulverization 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 using an organic solvent, it becomes possible to disperse the organometallic compound containing M in the organic solvent, and to uniformly adhere the organometallic compound containing M to the particle surface of the Nd magnet particle, and sintering. The M-rich phase 12 can be uniformly dispersed in the later permanent magnet 1.

Here, M- (OR) _x (wherein M includes at least one of Nd, Pr, Dy, and Tb, which are rare earth elements. R is any one of alkyl groups having 2 to 6 carbon atoms. A metal alkoxide is an organometallic compound that satisfies the structural formula: x 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, particularly rare earth elements Nd, Pr, Dy, and Tb 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 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.

  As described above, in the present invention, the content of the rare earth element is increased by adding the organometallic compound to the pulverized magnet powder. 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, it is not necessary to change the magnet composition after pulverization.

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 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, when an organic metal compound is mixed in an organic solvent and wet-added to the magnet powder, an organic compound such as an organic metal compound or an organic solvent remains in the magnet even if the organic solvent is volatilized later by vacuum drying or the like. Will be. And since the reactivity of Nd and carbon is very high, if a C content remains up to a high temperature in the sintering process, carbide is formed. As a result, voids are formed between the main phase of the magnet after sintering and the grain boundary phase (Nd-rich phase) due to the formed carbide, and the entire magnet cannot be sintered densely, resulting in a significant decrease in magnetic performance. There is. However, in the present invention, the amount of carbon contained in the magnet particles can be reduced in advance by performing a hydrogen calcining process described later before sintering.

  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 M-rich phase 12 can be confirmed by, for example, SEM, TEM, or a three-dimensional atom probe method.

  If Dy or Tb is used as M, Dy or Tb can be unevenly distributed at 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.

[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 a predetermined fraction of Nd—Fe—B (for example, Nd: 26.7 wt%, Fe (electrolytic iron): 72.3 wt%, B: 1.0 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 41 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, 0.1 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.

Meanwhile, an organometallic compound solution to be added to the fine powder finely pulverized by the jet mill 41 is prepared. Here, an organometallic compound containing a rare earth element is added in advance to the organometallic compound solution and dissolved. The organometallic compound to be dissolved is M- (OR) _x (wherein M includes at least one of the rare earth elements Nd, Pr, Dy, and Tb. R is an alkyl having 2 to 6 carbon atoms. An organometallic compound (for example, neodymium ethoxide, dysprosium propoxide, terbium propoxide, etc.) corresponding to any of the groups, which may be linear or branched, and x is an arbitrary integer. Further, the amount of the organometallic compound containing the rare earth element to be dissolved is not particularly limited, but as described above, the content of the rare earth element contained in the permanent magnet is more than the content based on the stoichiometric composition (26.7 wt%). It is preferable that the range be 0.1 wt% to 10.0 wt%, more preferably 0.1 wt% to 5.0 wt%.

  Subsequently, the organometallic compound solution is added to the fine powder finely pulverized 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. Incidentally, by collecting the fine powder finely pulverized by the jet mill 41 in the organometallic compound solution, a slurry 42 in which the fine powder of the magnet raw material and the organometallic compound solution are mixed may be 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 generated slurry 42 is injected into the cavity 54 formed in the molding apparatus 50. 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. In addition, a pair of magnetic field generating coils 55 and 56 are disposed in the molding apparatus 50 at the upper and lower positions of the cavity 54, and the lines of magnetic force are applied to the slurry 42 filled in the cavity 54. The applied magnetic field is, for example, 1 MA / m.

  When compacting, the magnetic field is applied to the cavity 54 by the magnetic field generating coils 55 and 56 before the slurry 42 is injected into the cavity 54. In this state, first, the slurry 42 is injected into the cavity 54 with a magnetic field applied to 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 slurry 42 filled in the cavity 54 to form the slurry. Thereby, a pulse magnetic field is applied to the slurry 42 filled in the cavity 54 simultaneously with the pressurization by the magnetic field generating coils 55 and 56 in the direction of the arrow 62 parallel to the pressurization direction. As a result, the magnetic field is oriented in a desired direction. 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 slurry 42. Further, it is desirable that the molding apparatus 50 pressurizes the slurry 42 while filling the cavity 54. Thereby, the residual magnetic flux density and the maximum energy product can be increased.

  In the molding step, a magnetic field may be applied to the slurry 42 in the cavity 54 by the magnetic field generating coils 55 and 56 after the slurry 42 is injected into the cavity 54. Even in such a configuration, it is possible to apply a pulsed magnetic field to the slurry 42 filled in the cavity 54 simultaneously with pressurization by the magnetic field generating coils 55 and 56 in the direction of the arrow 62 parallel to the pressurization direction. . 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 in a wet state with the molding apparatus 50 is inserted into a sintering furnace, and is 200 ° C. to 900 ° C., more preferably 400 ° C. to 900 ° C. (for example, 600 ° C.) in a hydrogen atmosphere. ℃)) for several hours (e.g., 5 hours) to perform calcination treatment in hydrogen. In addition, it is desirable to preserve | save the molded object 71 in the gas of the non-oxidizing or reducing atmosphere in the wet state by an organic solvent until it inserts in a sintering furnace. In addition, the supply amount of hydrogen 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.

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 permanent magnet 1 is manufactured as a result of sintering.

[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.

  First, an ingot made of a predetermined fraction of Nd—Fe—B (Nd: 26.7 wt%, Fe (electrolytic iron): 72.3 wt%, B: 1.0 wt%) is manufactured. Thereafter, the ingot is roughly pulverized to a size of about 200 μm by a stamp mill or a crusher. Alternatively, the ingot is melted, flakes are produced by strip casting, and coarsely pulverized by hydrogen crushing. Thereby, coarsely pulverized magnet powder 81 is obtained.

Next, the coarsely pulverized magnet powder 81 is finely pulverized into a predetermined range of particle size (for example, 0.1 μm to 5.0 μm) by a wet method using a bead mill, and the magnet powder is dispersed in a solvent to prepare a slurry 82. In the wet pulverization, 4 kg of toluene is used as a solvent for 0.5 kg of magnet powder. In addition, an organometallic compound containing a rare earth element is added to the magnet powder during wet grinding. Thereby, the organometallic compound containing the rare earth element is dispersed in the solvent together with the magnet powder. The organometallic compound to be dissolved is M- (OR) _x (wherein M includes at least one of the rare earth elements Nd, Pr, Dy, and Tb. R is an alkyl having 2 to 6 carbon atoms. An organometallic compound (for example, neodymium ethoxide, dysprosium propoxide, terbium propoxide, etc.) corresponding to any of the groups, which may be linear or branched, and x is an arbitrary integer. Further, the amount of the organometallic compound containing the rare earth element to be added is not particularly limited. However, as described above, the content of the rare earth element contained in the permanent magnet is more than the content based on the stoichiometric composition (26.7 wt%). It is preferable that the range be 0.1 wt% to 10.0 wt%, more preferably 0.1 wt% to 5.0 wt%.
Detailed dispersion conditions are as follows.
・ Dispersion equipment: Bead mill ・ Dispersion media: Zirconia beads

  The solvent used for pulverization is an organic solvent, but the type of solvent is not particularly limited, and alcohols such as isopropyl alcohol, ethanol and methanol, lower hydrocarbons such as pentane and hexane, aromatic substances such as benzene, toluene and xylene. Groups, ketones, mixtures thereof and the like can be used.

  Thereafter, the generated slurry 82 is injected into the cavity 54 formed in the molding apparatus 50 to perform wet molding. The subsequent molding process, hydrogen calcining process, and sintering process are the same as the manufacturing process in the first manufacturing method already described with reference to FIG.

As described above, in the first manufacturing method of the permanent magnet 1 according to this embodiment, the magnet powder and the structural formula M- (OR) _x (wherein M is a rare earth element, Nd, Pr, Dy, Tb). 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. Applying an orientation magnetic field to the mixture with the solvent to wet-form the powder while it is oriented and sinter the resulting molded body, preventing the molded body from oxidizing and adsorbing moisture, and improving its storage stability Thus, a rare earth sintered magnet having high magnetic properties can be obtained.
Further, in the first manufacturing method of the permanent magnet 1, the magnet powder is pulverized, and the pulverized magnet powder is converted into a structural formula M- (OR) _x (wherein M is a rare earth element Nd, Pr, Dy, Tb). 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. Recovered in a solvent, applied an orientation magnetic field to the mixture and wet-molded with the powder oriented, and sintered the resulting molded body, preventing oxidation and moisture adsorption of the molded body, A rare earth sintered magnet having improved magnetic properties and high magnetic properties can be obtained.
Further, in the second manufacturing method of the permanent magnet 1, the magnet raw material is structural formula M- (OR) _x (wherein M includes at least one of the rare earth elements Nd, Pr, Dy, and Tb). Is an alkyl group having 2 to 6 carbon atoms, which may be linear or branched. X is an arbitrary integer.) Wet pulverization using an organic solvent containing an organometallic compound represented by Applying an orientation magnetic field to the mixture and wet-molding while the powder is oriented, and sintering the resulting molded body prevents oxidation of the molded body and moisture adsorption, and improves its storage stability and high A rare earth sintered magnet having magnetic properties can be obtained.
In addition, a magnet to which an organic solvent containing an organometallic compound is added is calcined in a hydrogen atmosphere before sintering, so that the organometallic compound is thermally decomposed and the carbon contained in the magnet particles is previously burned out (carbon amount) Can be reduced), and 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.
Moreover, since the molded body wet-molded by the molding apparatus 50 is kept in a wet state with an organic solvent and in a non-oxidizing or reducing atmosphere until calcination, oxidation of the molded body is more reliably prevented. It becomes possible.

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, etc. of the magnet powder are not limited to the conditions described in the above examples.
Further, the hydrogen calcination step may be omitted.

1 Permanent magnet 11 Main phase 12 M rich phase

Claims (5)

R-Fe-B type (R is one or more of rare earth elements including Y) Rare earth sintered magnet raw material is finely pulverized by dry process, and the finely pulverized powder is represented by the following structural formula M- (OR) _x
(In the formula, M includes at least one of Nd, Pr, Dy, and Tb, which are rare earth elements. R is an alkyl group having 2 to 6 carbon atoms, and may be linear or branched. Is an arbitrary integer.)
To obtain a mixture of the powder and the organic solvent, wet-molded while applying the orientation magnetic field to the powder and orienting the powder, A method for producing a rare earth sintered magnet, comprising sintering.   The method for producing a rare earth sintered magnet according to claim 1, wherein the formed body is calcined in a hydrogen atmosphere to obtain a calcined body, and the obtained calcined body is sintered.   3. The method for producing a rare earth sintered magnet according to claim 2, wherein the compact is kept wet with the organic solvent until calcined.   The method for producing a rare earth sintered magnet according to claim 2, wherein the compact is held in a non-oxidizing or reducing atmosphere until calcined.   The rare earth sintered magnet production according to any one of claims 1 to 4, wherein the filling of the mixture of the raw material powder for rare earth sintered magnet and the organic solvent into the molding cavity is performed under pressure. Method.

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