JP5501836B2 - R-Fe-B permanent magnet - Google Patents

Description

  The present invention relates to an R—Fe—B permanent magnet.

  Today, typical R-Fe-B permanent magnets (Japanese Patent Laid-Open No. 59-46008) as high-performance permanent magnets have high magnet characteristics in a structure having a main phase of a ternary tetragonal compound and an R-rich phase. The iHc is 25 kOe or more, and the (BH) max is 45 MGOe or more. Further, R-Fe-B permanent magnets having various compositions have been proposed so as to exhibit various magnet characteristics selected according to the application.

  In order to produce R-Fe-B sintered permanent magnets having various compositions described above, it is necessary to produce alloy powders for magnets having the required compositions, and using rare earth raw materials reduced by electrolysis, Casting into a mold to create an alloy lump of the required magnet composition, pulverizing it into an alloy powder of the required particle size, absorbing the alloy lump by hydrogen absorption and disintegrating, or spraying the molten metal to powder Direct reduction diffusion for directly producing a magnet composition alloy powder using a powdering method (Japanese Patent Laid-Open Nos. 60-63304, 60-119701, 60-189901) and rare earth oxides, Fe powder, etc. Method (JP 59-219404, JP 60-77943).

  The dissolution and pulverization method tends to generate Fe primary crystals during casting, and the R-rich phase is greatly segregated. An oxygen content of alloy powder is obtained.

Direct reduction diffusion method, although an advantage that it is possible to omit the step of melting and coarse grinding, etc. when creating the raw material powder for a magnet as compared with the dissolution and powdering methods described above, R 2 _Fe 14 _B main Since the R-rich phase is surrounded by the R-rich phase, and the R-rich phase is smaller and better dispersed than the former, it is easily oxidized during production and has a high oxygen content. In some cases, the rare earth elements are consumed, causing variations in magnet characteristics and the like.

JP-A-60-63304 Japanese Patent Laid-Open No. 60-1190701 JP 60-189901 A JP 59-219404 A JP 60-77943 A

  As described above, in the production of permanent magnets using the raw powder for R-Fe-B permanent magnets by the direct reduction diffusion method, steps such as melting and coarse pulverization can be omitted, and the productivity is improved. Characteristically, the R-rich phase is small and well dispersed so that it is easily oxidized, and the oxygen content is higher than that of the raw material for dissolution / powdering, resulting in variations in magnet characteristics due to slight oxidation during the magnet manufacturing process.

  Therefore, by adding elements such as Co and Ni, the amount of oxygen can be reduced by making the R-rich phase an intermetallic compound that is relatively stable against oxidation. It is impossible to add and control the optimum amount to make the composition.

  That is, in order to obtain predetermined magnet characteristics, it is necessary to change the amount of one or more rare earth elements to be added to required values. For example, when adding Co element to reduce the amount of oxygen, It is impossible to diffuse the Co element only in the R-rich phase to obtain the required phase, and the added Co element is also replaced with Fe in the main phase. In addition, elements such as Co and Ni have a problem of reducing the coercive force of the magnet depending on the amount of addition, and the amount of oxygen cannot be easily reduced.

  Conventionally, regarding the production of raw material powder for R-Fe-B permanent magnets by the dissolution / powdering method or the direct reduction diffusion method, in advance, the target composition according to the magnet characteristics required at the time of dissolution or reduction diffusion is obtained. Adjust the composition.

However, in the case of the dissolution / powdering method, α-Fe crystallizes as the primary crystal other than the R ₂ Fe ₁₄ B phase, and the uniformity of the composition is impaired. On the other hand, in the case of the raw material powder for R—Fe—B permanent magnets by the direct reduction diffusion method, the R rich phase is made of the raw material powder because it has a structure in which an R rich phase exists around the main phase of the R ₂ Fe ₁₄ B phase. In order to adjust to a specific composition according to the magnet characteristics, whether a specific element easily enters the main phase or the R-rich phase It is necessary to always consider the alloy composition and the composition ratio, and when aiming at the required magnet characteristics, the alloy powder must be manufactured aiming at a specific extremely narrow range of composition.

That is, it is difficult to adjust the abundance ratio of the R ₂ Fe ₁₄ B phase and the R rich phase so as to achieve the target composition in either the dissolution / pulverization method or the direct reduction diffusion method. Moreover, crystallization of the α-Fe phase is difficult to avoid in the dissolution / pulverization method, and the direct reduction diffusion method has problems such as an increase in the amount of oxygen contained.

  In view of the present situation of raw material powders used in the production of R-Fe-B permanent magnets, the present invention eliminates problems during raw material powder production in the dissolution / pulverization method and direct reduction diffusion method, The purpose is to improve the quality of the used permanent magnet, and to provide an R—Fe—B permanent magnet manufactured at a blending ratio of raw materials according to various required magnet properties.

In order to achieve the above object, an R—Fe—B permanent magnet according to claim 1 of the present application is a magnet whose main phase is an R ₂ Fe ₁₄ B phase (where R is at least one of rare earth elements including Y). The powder is represented by the following structural formula Co- (OR) _x (wherein R is any alkyl group having 2 to 6 carbon atoms and may be linear or branched. _X is an arbitrary integer). A step of causing the organometallic compound to adhere to the particle surface of the magnet powder by adding the organometallic compound represented; and molding the magnet powder having the organometallic compound attached to the particle surface. A step of forming, a step of calcining the magnet powder with the organometallic compound attached to the particle surface before or after molding and in a hydrogen atmosphere before sintering, and a step of sintering the molded body It is manufactured by .

  An R—Fe—B based permanent magnet according to claim 2 is the R—Fe—B based permanent magnet according to claim 1, wherein the metal forming the organometallic compound is formed of the permanent magnet after sintering. It is characterized by uneven distribution at grain boundaries.

  According to the R—Fe—B permanent magnet of claim 1 having the above-described configuration, the added Co can be unevenly distributed at the grain boundaries of the magnet. As a result, it is possible to reduce the amount of Co used, suppress a decrease in residual magnetic flux density, and reduce the amount of oxygen in the R-rich phase due to Co. It is also possible to add and control Co in an optimum amount for obtaining the most effective predetermined composition. Further, decarbonization can be easily performed as compared with the case where other organometallic compounds are added, and there is no possibility that the magnet characteristics are deteriorated by the carbon contained in the sintered magnet. The whole can be sintered precisely.

  In addition, according to the R—Fe—B permanent magnet according to claim 2, since Co is unevenly distributed at the grain boundary of the magnet after sintering, Co unevenly distributed at the grain boundary causes the R-rich phase to be oxidized. A relatively stable intermetallic compound can be obtained, and the amount of oxygen can be reduced. Thereby, a decrease in residual magnetic flux density can be suppressed.

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.

  An R—Fe—B based magnet is used as the permanent magnet 1 according to the present invention. The rare earth element R used in the present invention is a rare earth element including Y and including a light rare earth and a heavy rare earth, and at least one of these, preferably a light rare earth such as Nd and Pr, or Nd, Pr. Etc. are used. That is, as R, Nd, Pr, La, Ce, Tb, Dy, Ho, Er, Eu, Sm, Gd, Pm, Tm, Yb, Lu, and Y can be used. This R may not be a pure rare earth element, and may contain impurities that are unavoidable in production within a commercially available range.

  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 low melting point R-rich phase 12 that is concentrated with a rare earth element coexists. FIG. 2 is an enlarged view showing magnet particles constituting the permanent magnet 1.

Here, the main phase 11 is in a state where the R ₂ Fe ₁₄ B intermetallic compound phase having a stoichiometric composition occupies a high volume ratio. On the other hand, the R-rich phase 12 is derived from an intermetallic compound phase (for example, R _2.0-3.0 Fe ₁₄ B intermetallic compound phase) having a higher R composition ratio than R ₂ Fe ₁₄ B which is also a stoichiometric composition. Become. Further, the R-rich phase 12 contains Co for improving magnetic characteristics.

In the permanent magnet 1, the R-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 R-rich phase 12 in the sintered permanent magnet 1 is poor, local sintering failure and magnetism decrease may be caused. It is important that is uniformly dispersed. It is also important to reduce the amount of oxidation of the R-rich phase 12.

  Further, a problem that occurs in the production of R—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.

  And the content of R in the permanent magnet 1 described above is 0.1 wt% to 10.0 wt%, more preferably 0.1 wt% to 5 wt% than the content based on the stoichiometric composition (26.7 wt%). It is desirable that the amount be in the range of more than 0.0 wt%. Specifically, the content of each component is R: 25 to 37 wt%, B: 1 to 2 wt%, Fe (electrolytic iron): 60 to 75 wt%, and Co: 0.1 to 10 wt%. By setting the rare earth element content in the permanent magnet 1 within the above range, the R-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 R-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, since Co is contained in the R-rich phase 12, the amount of oxygen can be reduced by making the R-rich phase 12 an intermetallic compound that is relatively stable against oxidation.

  Here, in the present invention, the addition of Co to the R-rich phase 12 does not include Co in advance in the magnet raw material to be pulverized, but the organic material containing Co before forming the pulverized magnet powder as described later. This is done by adding a metal compound. Specifically, by adding an organometallic compound containing Co, Co in the organometallic compound is uniformly attached to the particle surfaces of the magnet particles by wet dispersion. By sintering the magnet powder in this state, Co in the organometallic compound uniformly adhered to the particle surfaces of the magnet particles is unevenly distributed at the grain boundaries of the main phase 11, that is, the R-rich phase 12. Thereby, in the present invention, Co can be added and controlled in an optimum amount for obtaining the most effective predetermined composition.

Further, in the present invention, as described later, Co— (OR) _x (wherein R is any one of C 2 to C 6 alkyl groups, and may be linear or branched. _X is an arbitrary integer. The organic metal compound containing Co represented by (for example, cobalt ethoxide, cobalt isopropoxide) is added to an organic solvent and mixed with the magnet powder in a wet state. Thereby, the organometallic compound containing Co is dispersed in an organic solvent, and the organometallic compound containing Co can be efficiently attached to the particle surfaces of the magnet particles.

Here, the structural formula of Co— (OR) _x (wherein R is any alkyl group having 2 to 6 carbon atoms and may be linear or branched. _X is an arbitrary integer). There is a metal alkoxide as an organometallic compound satisfying the above requirement. The metal alkoxide is represented by a general formula M- (OR) _n (M: metal element, R: organic group, n: valence of metal or metalloid). In addition, as the metal or semimetal forming the metal alkoxide, 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, Co is particularly used in the present invention.

  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.

The crystal grain size D of the main phase 11 is desirably 0.1 μm to 5.0 μm. The thickness d of the R-rich phase 12 is 1 nm to 500 nm, preferably 2 nm to 200 nm. As a result, as a whole crystal grain (that is, as a whole sintered magnet), the core R 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. The configurations of the main phase 11 and the R-rich phase 12 can be confirmed by, for example, SEM, TEM, or a three-dimensional atom probe method.

[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 R—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 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 Co is previously added to the organometallic compound solution and dissolved. The organometallic compound to be dissolved is Co— (OR) _x (wherein R is any one of C 2 to C 6 alkyl groups, which may be linear or branched. _X is an arbitrary integer) An organic metal compound (for example, cobalt ethoxide, cobalt isopropoxide, etc.) is used. Further, the amount of the organometallic compound containing Co to be dissolved is not particularly limited, but as described above, the content of Co in the sintered magnet is 0.1 wt% to 10 wt%, preferably 0.1 wt% to 5 wt%. It is preferable that the amount is as follows.

  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. 5, 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, there is a problem that NdH ₃ and NdH ₂ exist in the molded body 71 calcined by the above-described calcination process in hydrogen and is easily combined with oxygen. However, in the first manufacturing method, the molded body 71 has a problem. Since it moves to the below-mentioned vacuum baking without touching the outside air after hydrogen calcination, the dehydrogenation step 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 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.

  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. And the permanent magnet 1 is manufactured as a result of sintering.

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 this embodiment, Co— (OR) _x (wherein R is an alkyl having 2 to 6 carbon atoms) is used for the pulverized magnet powder. Any of a group, which may be linear or branched. X is an arbitrary integer.) An organometallic compound solution to which an organometallic compound represented by A metal compound is deposited. Thereafter, the green compact is subjected to calcination treatment in hydrogen by holding it in a hydrogen atmosphere at 200 ° C. to 900 ° C. for several hours. Then, the permanent magnet 1 is manufactured by baking at 800 to 1180 degreeC. Thereby, even if the amount of Co added is small compared to the conventional case, the added Co can be effectively unevenly distributed at the grain boundaries of the magnet. As a result, it is possible to reduce the amount of Co used, suppress a decrease in residual magnetic flux density, and reduce the amount of oxygen in the R-rich phase due to Co. It is also possible to add and control Co in an optimum amount for obtaining the most effective predetermined composition. Further, decarbonization can be easily performed as compared with the case where other organometallic compounds are added, and there is no possibility that the coercive force is lowered by the carbon contained in the sintered magnet. The whole can be sintered precisely.
In addition, since Co is unevenly distributed at the grain boundaries of the magnet after sintering, Co unevenly distributed at the grain boundaries can make the R-rich phase a relatively stable intermetallic compound against oxidation, reducing the amount of oxygen. be able to. Thereby, a decrease in residual magnetic flux density can be suppressed.
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 pyrolysis of the organometallic compound is performed in comparison with the case of calcining the molded magnet particles. This can be done more easily for the whole 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, 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 in hydrogen and a dehydrogenation process.

Moreover, in the manufacturing method mentioned above, although it is set as the structure added by adding the organometallic compound shown by Co- (OR) _x to magnet powder, it is good also as a structure included in an ingot beforehand. .

1 Permanent magnet 11 Main phase 12 R rich phase

Claims (2)

A magnetic powder having an R ₂ Fe ₁₄ B phase (where R is at least one of rare earth elements including Y) as a main phase is represented by the following structural formula Co— (OR) _x
(In the formula, R is any alkyl group having 2 to 6 carbon atoms and may be linear or branched. 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;
A step of calcining the magnet powder having the organometallic compound attached to the particle surface before or after molding and before sintering in a hydrogen atmosphere; and
Sintering the molded body;
An R—Fe—B permanent magnet manufactured by: The R-Fe-B permanent magnet according to claim 1, wherein the metal forming the organometallic compound is unevenly distributed at grain boundaries of the permanent magnet after sintering.

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