JP5501835B2 - Rare earth permanent magnet - Google Patents

Description

The present invention relates to a rare earth permanent magnet having an R ₂ Fe ₁₄ B system composition.

As a rare earth magnet having high performance, for example, an Nd ₂ Fe ₁₄ B-based magnet described in Japanese Patent No. 1431617 is known.

Further, in Japanese Patent No. 27200040, in order to improve the maximum energy product of the Nd ₂ Fe ₁₄ B-based magnet and to obtain a high coercive force and excellent squareness, Nd and Pr are combined in a total amount of 12 to 17 atomic% (however, Nd and Pr can be partially substituted by 0.2 to 3.0 atomic% with heavy rare earth elements such as Dy and Tb), B is 5 to 14 atomic%, Co is 20 atomic% or less, and Cu is 0.02 to 0.02%. A sintered permanent magnet material containing 0.5 atomic% each and the balance consisting of Fe and inevitable impurities is proposed. In Example 1 of the publication, a sintered magnet having a composition represented by Fe-4Co-14.5Nd-7B-xCu (x = 0.01 to 0.4 atomic%) in atomic ratio is used. 3, sintered magnets each having a composition containing 0.1 atomic% Cu in Fe-2Co-13.5Nd-1.5Dy-7B by atomic ratio are produced. The maximum energy product of the sintered magnet produced in Example 1 is about 40 MGOe (about 318 kJ / m ³ ) as described in FIG. This value is obtained when the Cu content is about 0.15 atomic%, and the coercive force also shows the maximum value at this content.

Japanese Patent No. 1431617 Japanese Patent No. 27200040

The present invention aims at providing a high maximum energy product R ₂ Fe 14 _B sintered magnet as compared with the prior art.

In order to achieve the above object, the rare earth permanent magnet according to claim 1 of the present application includes R (R is at least one kind of rare earth element, and Nd and / or Pr are included as essential elements), Cu, Fe, B Co, which substitutes part of Fe, and oxygen are contained, the R content is 11.7 to 13.5 mol%, the Cu content is 0.01 to 0.1 mol%, and the B content is 5 to 7 Mol%, Co content of 0.8 mol% or less, oxygen content of 3000 ppm or less, balance is substantially Fe, maximum energy product is 400 kJ / m ³ or more, and magnet raw material is pulverized into magnet powder And the following structural formula M- (OR) _x (wherein M includes at least one of Cu and Co. R represents any one of alkyl groups having 2 to 6 carbon atoms). X may be any integer. And a step of attaching the organometallic compound to the particle surface of the magnet powder, and molding the magnet powder having the organometallic compound attached to the particle surface. A step of forming a molded body by the method, a step of calcining the magnet powder with the organometallic compound attached to the particle surface in a hydrogen atmosphere before or after molding and before sintering , and firing the molded body. And the step of bonding.

  The rare earth permanent magnet according to claim 2 is the rare earth permanent magnet according to claim 1, wherein the R content is 12.2 to 13.5 mol%.

  The rare earth permanent magnet according to claim 3 is the rare earth permanent magnet according to claim 1 or 2, wherein the relative density is 99.0% or more.

Furthermore, the rare earth permanent magnet according to claim 4 is the rare earth permanent magnet according to any one of claims 1 to 3, wherein two adjacent crystal grain boundaries exist at the boundary between two adjacent crystal grains, and three adjacent ones. Composition analysis is performed on the polycrystalline grain boundaries present at the boundaries between the crystal grains, and the ratio Cu / R of the Cu amount to the element R amount is determined at each crystal grain boundary. expressed in C _2, when the Cu / R in the polycrystalline grain boundaries, expressed in _{C M,} and satisfies the _C M / C ₂ ≦ 0.7.

When Cu was added to the R ₂ Fe ₁₄ B-based sintered magnet, the maximum energy product and the coercive force were improved as described in the above-mentioned Japanese Patent No. 2720040. However, when the R content is reduced as compared with the example of the publication, the residual magnetic flux density is remarkably improved, and the improvement rate of the coercive force due to the addition of Cu is remarkably increased. It was found that a maximum energy product of 400 kJ / m ³ or higher, which is significantly higher than that, was obtained, and that a maximum energy product of 410 kJ / m ³ or higher and a maximum of 480 kJ / m ³ could be obtained.

In addition, in the case where the R content is less than that of the example of the above-mentioned Japanese Patent No. 27200040, if the density of the magnet is set to the above predetermined value or more by adding Cu, the coercive force due to the reduction of the R content. It was found that the drastic decrease in the temperature can be remarkably suppressed, and as a result, the maximum energy product can be remarkably increased. As the magnet density increases, the residual magnetic flux density usually improves, but the coercive force decreases. For example, according to the experiments by the present inventors, the coercive force after aging treatment in an R ₂ Fe ₁₄ B-based magnet containing 14.54 mol% R (Nd: Dy = 78: 22) is the relative density of the magnet. Was 2170 kA / m 2 when the ratio was 99.3% and 2110 kA / m when the relative density of the magnet was 99.6%. That is, as the relative density increases, the coercive force decreases. However, a constant coercive force is required to reflect the improvement in residual magnetic flux density in the maximum energy product. Therefore, even if the residual magnetic flux density is improved by reducing the R content and improving the magnet density, the maximum energy product does not increase if the coercive force decreases. However, when Cu is added to an R ₂ Fe ₁₄ B-based sintered magnet having a relatively small R content, the coercive force is improved as the magnet density is increased, and as a result, the maximum energy product is remarkably improved. all right.

  Further, the MH loop of a magnet having an R content of 12.79 mol% and a Cu content of 0.01 mol%, and a magnet having the same R content and a Cu content of 0.04 mol% When compared with the MH loop, it can be seen that the squareness in the MH loop is remarkably improved by increasing the Cu content in a magnet having a small R content. That is, the residual magnetic flux density improved by reducing the R content can be reflected in the improvement of the maximum energy product.

Moreover, when R content was decreased rather than the Example of the said patent 2722040, it discovered that the dispersion | variation in coercive force became critically large. Then, it has been found that the variation in coercive force is remarkably reduced by the addition of Cu, and as a result, mass production of sintered magnets with uniform coercive force becomes possible. In the R ₂ T ₁₄ B-based sintered magnet, it is considered that a high coercive force can be obtained by coating the R ₂ T ₁₄ B crystal grains as the main phase with the R-rich phase. Therefore, the coercive force tends to vary when the R content is small because the R-rich phase is difficult to be uniformly distributed in the sintered magnet, resulting in non-uniform coating of R ₂ T ₁₄ B crystal grains. Conceivable.

  Further, the element R is easily oxidized, and when the element R is oxidized, the magnet characteristics are greatly deteriorated. Since the sintered magnet of the present invention has a relatively small R content, the margin for oxidation of the element R is small. That is, even if the oxygen content is the same as when the R content is relatively high, the oxidation rate of the element R is high, and as a result, the magnet density is lowered and the magnet characteristics are remarkably lowered. Therefore, in the present invention, the oxygen content in the sintered magnet is suppressed to the predetermined value or less. Thereby, the maximum energy product improvement effect obtained by reducing R content and adding Cu will not be spoiled.

In the magnet of the present invention, Cu / R (C ₂ ) at the _two grain boundaries and Cu / R (C _M ) at the polycrystalline grain boundaries are represented by C _M / C ₂ ≦ 0.7. , The coercive force is higher and the variation in coercive force is smaller. That is, when Cu is present in a large amount at two crystal grain boundaries and hardly exists at a polycrystal grain boundary, the magnet of the present invention can obtain more excellent characteristics. On the other hand, in the conventional magnet having a large R content, the added Cu exists almost uniformly at the two crystal grain boundaries and the polycrystalline grain boundary.

The reason can be considered as follows. When manufacturing a sintered magnet having a small R content, a R-rich phase is sufficiently formed in a polycrystalline grain boundary such as a triple point as in a magnet having a large R content. It is difficult to form an R-rich phase uniformly. Therefore, it is difficult to obtain a high coercive force. However, when Cu is added, a (R—Cu) rich phase rich in Cu is formed, and this (R—Cu) rich phase easily wets the R ₂ Fe ₁₄ B crystal grains. It is thought that it precipitates preferentially to the polycrystalline grain boundary and hardly precipitates at the polycrystalline grain boundary. As a result, in the magnet of the present invention, the (R—Cu) rich phase is uniformly formed at the two crystal grain boundaries, and thereby the R ₂ Fe ₁₄ B crystal grains are coated, so that the coercive force is remarkably improved, And it is thought that the variation in coercive force is reduced.

  In the present invention, by adding an organometallic compound containing Cu or Co to the magnet powder, Cu or Co contained in the organometallic compound may be pre-distributed with respect to the grain boundaries of the magnet before sintering. It becomes possible. In addition, the amount used can be reduced, and the added Co or Cu can be efficiently distributed on the grain boundaries of the magnet. For Cu, it is necessary to increase the sintering temperature and the sintering time in the manufacturing process of the permanent magnet as compared with the case where pulverization and sintering are performed in the state of being previously contained in the magnet raw material. There is no. As a result, it is possible to prevent the main phase from growing and to uniformly disperse the rich phase. For Co, it is possible to sufficiently improve the Curie temperature and the corrosion resistance of the grain boundary phase.

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 permanent magnet 1 of the present invention contains R (R is at least one rare earth element, and Nd and / or Pr are included as essential elements), Cu, Fe and B. R content is 11.7-13.5 mol%.

  If the R content is too small, a high coercive force cannot be obtained, so that the maximum energy product cannot be increased. On the other hand, when there is too much R content, the effect of this invention will not be implement | achieved but a maximum energy product will become small. In order to fully realize the effects of the present invention, the R content is preferably 12.2 to 13.5 mol%. The element R necessarily contains Nd and / or Pr. The ratio between Nd and Pr is not particularly limited. Only Nd and Pr may be used as the element R, but rare earth elements other than these, that is, Y, Sc, La, Ce, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu At least one of these may be used. Of these, Dy and / or Tb are preferred. In order not to deteriorate the magnet characteristics, the total amount of elements other than both Nd and Pr is preferably 10 mol% or less of the entire element R. In addition, when using 2 or more types of elements as the element R, mixtures, such as a misch metal, can also be used as a raw material.

  Moreover, Cu content is 0.01-0.1 mol%, Preferably it is 0.01 mol% or more and less than 0.1 mol%, More preferably, it is 0.01-0.08 mol%, More preferably, it is 0.00. It is 02-0.06 mol%. When there is too little Cu content, the effect of this invention mentioned above will not be realized. On the other hand, if the Cu content is too large, the coercive force is reduced and the residual magnetic flux density is also reduced, so that the maximum energy product is reduced.

  Moreover, B content is 5-7 mol%, Preferably it is 5.5-6.5 mol%. If the B content is too small, the coercive force becomes low because rhombohedral fabric is formed. On the other hand, if the B content is too large, the B-rich non-magnetic phase increases and the residual magnetic flux density decreases.

  The balance is substantially Fe, but a part of Fe is replaced with Co. By adding Co, the temperature dependency of the coercive force and the corrosion resistance can be improved, and the residual magnetic flux density can also be improved. However, since the coercive force is reduced by the addition of Co and the rate of reduction of the coercive force is increased in the magnet of the present invention having a small element R content, the Co content is 0.8 mol% or less.

  In the sintered magnet of the present invention, in addition to the above-mentioned elements, as trace additives or unavoidable impurities, for example, C, P, S, Al, Ti, V, Cr, Mn, Bi, Nb, Ta, Mo, W , Sb, Ge, Sn, Zr, Ni, Si, Hf, Ga, Zn and the like may be contained. However, in order to suppress deterioration in magnet characteristics, the total content of these is preferably 3 mol% or less.

Furthermore, in the present invention, as described later, at least one of the above Cu and Co is not included in advance in the magnet raw material to be pulverized, but M- (OR) _x (wherein M is Cu, Co And at least one of them, 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. An organometallic compound containing at least one kind (for example, copper ethoxide, copper isopoloxide, cobalt isopropoxide, etc.) is added to an organic solvent and mixed with the magnet powder in a wet state to add to the magnet powder.

  Further, in the present invention, unlike a conventional magnet having a relatively large R content, the coercive force improves as the magnet density increases. In the present invention, if the relative density of the sintered magnet is preferably 99.0% or more, more preferably 99.2% or more, and even more preferably 99.4% or more, a high coercive force can be obtained and the maximum energy product can be increased. High enough.

The relative density of the magnet is a value obtained by dividing the measured density of the magnet by its theoretical density. The theoretical density of the magnet in this specification is the density of R ₂ Fe ₁₄ B described in Table 1 of “Solid Physics Vol.21, No.1, 37-45 (1986)” (Agne Technical Center), For example, Nd ₂ Fe ₁₄ B is 7.58 Mg / m ³ and Dy ₂ Fe ₁₄ B is 8.07 Mg / m ³ . When two or more elements R are used, linear approximation is performed according to the ratio of each element. Specifically, when Nd and Dy are used as the element R and the molar ratio thereof is Nd: Dy = x: y, the theoretical density is (7.58x + 8.07y) / (x + y).

  In addition, as shown in FIG. 2, the permanent magnet 1 according to the present invention is composed of a main phase 11 that is a magnetic phase that contributes to the magnetization action, and a low-melting R-rich phase that is nonmagnetic and enriched with rare earth elements. 12 is an alloy in which both coexist. FIG. 2 is an enlarged view showing the main phase 11 and the R-rich phase 12 constituting the permanent magnet 1.

Here, the main phase 11 is in a state where the R ₂ Fe ₁₄ B intermetallic compound phase (Fe may be partially substituted with Co) having a stoichiometric composition occupies a high volume ratio. On the other hand, the R-rich phase 12 has an intermetallic compound phase (for example, R ₂ Fe ₁₄ B) having a higher R composition ratio than R ₂ Fe ₁₄ B (Fe may be partially substituted with Co), which is also a stoichiometric composition _{. 0-3.0} Fe ₁₄ B intermetallic compound phase). The R-rich phase 12 contains Cu for improving magnetic characteristics.

  In the present invention, since Cu is contained in the R-rich phase 12, the R-rich phase 12 can be uniformly dispersed in the sintered permanent magnet 1.

  Here, in the present invention, the addition of Cu to the R-rich phase 12 can be performed by adding an organometallic compound containing Cu before forming the pulverized magnet powder as described above. Specifically, by adding an organometallic compound containing Cu, Cu 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, Cu 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. Similarly, in the present invention, Co can be added to the permanent magnet 1 by adding an organometallic compound containing Co before forming the magnet powder. 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 is unevenly distributed at the grain boundaries. Note that both Cu and Co may be added by an organometallic compound, or only one of them may be added by an organometallic compound. Further, elements not added by the organometallic compound may be included in advance in the magnet raw material to be pulverized.

In the present invention, M- (OR) _x (wherein, M includes at least one of Cu and Co. R is any one of an alkyl group having 2 to 6 carbon atoms, as described later) An organic metal compound containing at least one of Cu and Co (for example, copper ethoxide, copper isopropoxide, cobalt isopropoxide). Add to organic solvent and mix with magnet powder in wet state. Thereby, an organometallic compound containing at least one of Cu and Co can be dispersed in an organic solvent, and the organometallic compound containing at least one of Cu and Co can be efficiently attached to the particle surface of the magnet particle. It becomes possible.

Here, M- (OR) _x (wherein M includes at least one of Cu and Co. R is any one of alkyl groups having 2 to 6 carbon atoms, and may be linear or branched. And x is an arbitrary integer.) A metal alkoxide is an organometallic compound that satisfies the structural formula. The metal alkoxide is represented by a general formula M- (OR) _n (M: metal element, R: organic group, n: valence of metal or metalloid). 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, in the present invention, Cu and Co are used in particular.

  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.

Moreover, in this invention, since the influence on the magnet characteristic by oxidation becomes large, the oxygen content in a magnet becomes like this. Preferably it is 3000 ppm or less, More preferably, it is 2500 ppm or less. In addition, although oxygen content is so preferable that there is little oxygen content, since oxidation in a manufacturing process is unavoidable, oxygen content cannot be made into zero and usually 500 ppm or more is contained. In order to suppress the oxygen content, each process such as pulverization, mixing, and molding is performed in a non-oxidizing atmosphere such as Ar and N ₂ during production, and the oxygen partial pressure in the atmosphere is strictly controlled. It is preferable to do.

  The permanent magnet 1 has a main phase with a substantially tetragonal crystal structure.

Further, the permanent magnet 1 of the present invention is characterized by an element distribution at the grain boundary. The magnet of the present invention was subjected to composition analysis for the two crystal grain boundaries and the polycrystalline grain boundary, and at each crystal grain boundary, the ratio Cu / R of the Cu amount to the element R amount was determined. / R a represents at _{C 2,} when the Cu / R in the polycrystalline grain boundaries, expressed in _{C M,} preferably _C M / _{C 2} ≦ 0.7, more preferably _C M / _{C 2} ≦ 0.5, further Preferably C _M / C ₂ ≦ 0.35
It is. Magnet of the present invention, the value of C ₂ is large and the coercive force is increased when the value of C _M is small, when the C M _/ C ₂ is within the above limit range, a higher coercive force is obtained, In addition, the variation in coercive force is further reduced. Note that C _M / C ₂ may be zero. This is because when the amount of Cu present in the polycrystalline grain boundary is extremely small, the amount of Cu may be calculated to be zero because the amount of Cu becomes lower than the background noise in the measurement by TEM-EDS described later. is there. That is, even if C _M / C ₂ is zero, it does not mean that no single atom of Cu exists in the polycrystalline grain boundary. However, C _M / C ₂ = 0, that is, C _M = 0 is usually when the amount of Cu added is considerably small, and when Cu is added to such an extent that the coercive force is remarkably improved, , 0 <C _M / C ₂ , especially 0.01 ≦ C _M / C ₂ .

[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, it is composed of R—Fe—B (for example, Nd: 12.79 mol%, B: 5.95 mol%, Fe :, Fe: 81.26 mol%) satisfying the above-described composition ratio. Manufacture ingots. Further, a small amount of Dy or Tb may be included to improve the coercive force. 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 at least one of Cu and Co is previously added to the organometallic compound solution and dissolved. Note that the organometallic compound to be dissolved is M- (OR) _x (wherein M includes at least one of Cu and Co. R is any one of alkyl groups having 2 to 6 carbon atoms; An organic metal compound (for example, copper ethoxide, copper isopropoxide, cobalt isopropoxide, or the like) corresponding to a chain or a branch may be used. Further, the amount of the organometallic compound to be dissolved is not particularly limited, but the content of Cu and Co in the sintered magnet is within the above-described range (Cu is 0.01 to 0.1 mol%, preferably 0.01 Mol% or more and less than 0.1 mol%, more preferably 0.01 to 0.08 mol%, still more preferably 0.02 to 0.06 mol%, and the Co content is 0.8 mol% or less). Amount.

  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 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 the present embodiment, M- (OR) _x (in the formula, with respect to the fine powder of the pulverized R-Fe-B magnet) M represents at least one of Cu and Co. R represents any of an alkyl group having 2 to 6 carbon atoms, which may be linear or branched, and x is an arbitrary integer. An organometallic compound solution to which a metallic compound is added is added, and the organometallic compound is uniformly attached to the surface of the magnet particles. 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. Here, by adding an organometallic compound containing Cu or Co to the magnet powder, Cu or Co contained in the organometallic compound can be pre-distributed with respect to the grain boundary of the magnet before sintering. . In addition, the amount used can be reduced, and the added Co or Cu can be efficiently distributed on the grain boundaries of the magnet. For Cu, it is necessary to increase the sintering temperature and the sintering time in the manufacturing process of the permanent magnet as compared with the case where pulverization and sintering are performed in the state of being previously contained in the magnet raw material. There is no. As a result, it is possible to prevent the main phase from growing and to uniformly disperse the rich phase. For Co, it is possible to sufficiently improve the Curie temperature and the corrosion resistance of the grain boundary phase.
In addition, according to the R—Fe—B rare earth permanent magnet 1 of the present invention, the maximum energy product obtained is improved by reducing the R content and adding Cu.
Further, when Cu / R (C ₂ ) at the _two grain boundaries and Cu / R (C _M ) at the polycrystalline grain boundaries have a relationship represented by C _M / C ₂ ≦ 0.7, the coercive force Becomes higher and variation in coercive force can be further reduced. That is, when Cu is present in a large amount at two crystal grain boundaries and hardly exists at a polycrystal grain boundary, the magnet of the present invention can obtain more excellent characteristics.
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 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.

1 Permanent magnet 11 Main phase 12 R rich phase

Claims (4)

R (R is at least one kind of rare earth element, Nd and / or Pr are included as essential elements), Cu, Fe, B, Co which substitutes a part of Fe and oxygen, and R content Is 11.7 to 13.5 mol%, Cu content is 0.01 to 0.1 mol%, B content is 5 to 7 mol%, Co content is 0.8 mol% or less, and oxygen content is 3000 ppm or less, the balance is substantially Fe, and the maximum energy product is 400 kJ / m ³ or more,
Crushing magnet raw material into magnet powder;
The pulverized magnet powder has the following structural formula M- (OR) _x
(In the formula, M contains at least one of Cu and Co. R is an 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
A rare earth permanent magnet produced by a step of sintering the compact.   2. The rare earth permanent magnet according to claim 1, wherein the R content is 12.2 to 13.5 mol%.   The rare earth permanent magnet according to claim 1 or 2, wherein a relative density is 99.0% or more. Composition analysis is performed on two crystal grain boundaries present at the boundary between two adjacent crystal grains and a polycrystalline grain boundary present at the boundary between three or more adjacent crystal grains. At each crystal grain boundary, the amount of element R When the ratio Cu / R of the amount of Cu with respect to Cu is determined by C ₂ and the Cu / R at the polycrystalline grain boundary is expressed by C _M ,
C _M / C ₂ ≦ 0.7
The rare earth permanent magnet according to any one of claims 1 to 3, wherein:

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