JP2012248828A - Rare earth permanent magnet and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an R-Fe-B-based sintered magnet that has high productivity, high performance, uses a little amount of Tb or Dy, and has an increased coercive force while suppressing decrease in remanent flux density by use of a powder mixture of alloy powder mainly containing intermetallic compound and an oxide of a rare earth element in a material for application and diffusion on a sintered magnetic body, and a method for producing the same.SOLUTION: In a method for producing a rare earth permanent magnet, heat treatment is performed on a sintered magnetic body at a temperature of the sintering temperature or below of the sintered magnetic body in a state where a powder mixture is disposed on a surface of the sintered magnetic body, the sintered magnetic body having the composition RTMB(R represents a rare earth element, Trepresents Fe or Co, M represents Al or the like, B represents boron, and a, b, c and d represent atomic percentages while 12≤a≤20, 0≤c≤10 and 4.0≤d≤7.0 are satisfied and b represents the balance), and the powder mixture containing an Roxide (Rrepresents a rare earth element) and alloy powder having the composition MM(Mand Meach represents Al or the like, and d and e represent atomic percentages while 0.1≤e≤99.9 is satisfied and d represents the balance) and containing 70 vol. % or more of an intermetallic compound phase. Accordingly, one or two or more elements selected from among R, Mand Mare caused to be diffused to grain boundaries in the interior of the sintered magnetic body or near grain boundaries within the sintered magnetic body primary phase grains.

Description

  The present invention increases the coercive force while suppressing the reduction of the residual magnetic flux density of the sintered magnet body by applying a heat treatment for diffusion to the magnet body coated with a mixture of intermetallic compound and rare earth oxide. The present invention relates to an R—Fe—B permanent magnet and a method for producing the same.

  Nd-Fe-B permanent magnets are increasingly used because of their excellent magnetic properties. In recent years, in response to environmental problems, Nd—Fe—B magnets have been required to have higher performance as the application of magnets has expanded to household appliances, industrial equipment, electric vehicles, and wind power generation.

As the performance index of the magnet, the residual magnetic flux density and the coercive force can be cited. The increase in the residual magnetic flux density of the Nd—Fe—B based sintered magnet has been achieved by increasing the volume fraction of the Nd ₂ Fe ₁₄ B compound and improving the degree of crystal orientation, and various improvements have been made so far. Regarding the increase in coercive force, there are methods such as reducing the grain size, using a composition alloy with an increased amount of Nd, or adding an element having an effect of increasing the coercive force, such as Al and Ga. One method is to use a composition alloy in which a part of Nd is substituted with Dy or Tb.

The coercive force mechanism of the Nd—Fe—B magnet is a new creation type, and it is said that nucleation of reverse magnetic domains at the crystal grain interface dominates the coercive force. In general, the crystal structure is disturbed at the crystal grain interface, but the crystal structure is disturbed by several nm in the depth direction near the interface of the Nd ₂ Fe ₁₄ B compound crystal grain, which is the main phase of the magnet. This causes a decrease in magnetocrystalline anisotropy, promotes the generation of reverse magnetic domains, and reduces the coercive force (Non-patent Document 1). By substituting Nd of the Nd ₂ Fe ₁₄ B compound with Dy or Tb element, the anisotropic magnetic field of the compound phase increases, so that the coercive force can be increased. However, when Dy or Tb is added by a normal method, not only the vicinity of the interface of the main phase but also the inside of the main phase is replaced with Dy and Tb, so a decrease in residual magnetic flux density is inevitable. Furthermore, there is a problem that a lot of expensive Tb and Dy must be used.

On the other hand, various attempts have been made so far in order to increase the coercivity of the Nd—Fe—B magnet. For example, an Nd—Fe—B magnet is produced by mixing and sintering two kinds of alloy powders having different compositions (two alloy method). That is, a powder of an alloy A composed of an R ₂ Fe ₁₄ B main phase (where R is mainly composed of Nd and Pr) and various additive elements (Dy, Tb, Ho, Er, etc.) including Dy and Tb. , Al, Ti, V, Mo, etc.) are mixed, and then an Nd—Fe—B magnet is produced through fine grinding, forming in a magnetic field, sintering, and aging treatment. The obtained sintered magnet does not contain Dy or Tb in the central part of the R ₂ Fe ₁₄ B compound main phase crystal grains, and additional elements such as Dy and Tb are unevenly distributed in the vicinity of the grain boundary part of the crystal grains. A high coercive force can be obtained while suppressing a decrease in the residual magnetic flux density (Patent Documents 1 and 2). However, in this method, since Dy and Tb diffuse into the main phase grains during sintering, the thickness of the uneven distribution of Dy and Tb in the vicinity of the grain boundary portion is about 1 μm or more, which is a depth that causes nucleation of reverse magnetic domains. Compared to this, the thickness is significantly increased, and the effect is not yet sufficient.

  Recently, several means for improving the characteristics by diffusing specific elements from the surface to the inside of the R—Fe—B sintered body have been developed. For example, a method of performing a heat treatment after depositing a rare earth metal such as Yb, Dy, Pr, or Tb, Al, Ta, or the like on the surface of an Nd—Fe—B magnet by vapor deposition or sputtering (Patent Documents 3 to 3). 5, Non-Patent Documents 2 and 3), a method of applying a heat treatment after applying a rare earth inorganic compound powder such as fluoride or oxide on the surface of the sintered body (Patent Document 6). When these methods are used, for example, elements such as Dy and Tb installed on the surface of the sintered body are diffused to the inside of the sintered body through the grain boundary portion of the sintered body structure as a path by heat treatment.

  Thereby, Dy and Tb can be concentrated at a very high concentration in the vicinity of the grain boundary part and the grain boundary part in the sintered body main phase grains, which is more ideal than in the case of the above-described two alloy method. Organization form. Reflecting the structure of the magnet, the magnetic characteristics are further remarkably manifested in suppressing the decrease in residual magnetic flux density and increasing the coercive force. However, in particular, the method using vapor deposition or sputtering has many drawbacks for mass production from the viewpoint of equipment, process, etc., and has the disadvantage of poor productivity.

  In addition to the above method, after applying rare earth inorganic compound powder such as fluoride or oxide on the surface of the sintered body, heat treatment (Patent Document 6) or mixing Al, Cu, Zn powder and fluoride A method (Patent Document 8) is disclosed in which heat treatment is performed after coating on a magnet. This method is a very simple coating process compared to sputtering or vapor deposition in which a non-metallic inorganic compound powder is dispersed in water and a magnet is immersed in the powder to dry it. The feature is that the productivity is high such that the magnets are not welded to each other. However, since Dy and Tb diffuse by the substitution reaction between the powder and the magnet component, it is difficult to introduce a large amount of them into the magnet.

  Furthermore, a method of applying calcium or calcium hydroxide powder to an oxide or fluoride of Dy or Tb and applying it to a magnet (Patent Document 7) is also disclosed. In this method, a calcium reduction reaction is used to reduce and diffuse Dy and Tb during heat treatment. Although it can be said to be an excellent method from the viewpoint of introducing a large amount of Dy and Tb, it is not easy to handle calcium or calcium hydride powder, and it cannot be said that productivity is good.

  There is a method in which a metal alloy is applied instead of applying a rare earth inorganic compound powder such as fluoride or oxide to the surface of the sintered body, and heat treatment is performed (Patent Documents 9 to 13). In the method of applying only these metal alloys, there is a drawback that it is difficult to apply a large amount and a uniform amount of metal alloy to the magnet surface. In Patent Documents 14 and 15, metal powder containing Dy and / or Tb is diffused into the master alloy, but the oxygen concentration of the master alloy is regulated to 0.5% by mass or less, and the impact media is vibrated and stirred in the container. Diffusion is performed by bringing a rare earth-containing metal powder into close contact with the mother alloy by the barrel painting method. This method is not useful for industrialization because it requires more steps and takes more time than the method in which the mixed powder of intermetallic compound and rare earth oxide in this patent is dispersed in a solvent and applied to the master alloy magnet.

Japanese Patent No. 1820677 Japanese Patent No. 3143156 JP 2004-296773 A Japanese Patent No. 3897724 Japanese Patent Laid-Open No. 2005-11973 Japanese Patent No. 4450239 Japanese Patent No. 4548673 JP 2007-287874 A Japanese Patent No. 4656323 Japanese Patent No. 4482769 JP 2008-263179 A JP 2009-289994 A JP 2010-238712 A WO2008 / 032426 WO2008 / 139690

K. -D. Durst and H.M. Kronmuller, “THE CORCIVE FIELD OF SINTERED AND MELT-SPUN Nd-Fe-B MAGNETS”, Journal of Magnetics and Magnetic Materials 68 (1987) 63-75. K. T.A. Park, K.M. Hiraga and M.M. Sagawa, "Effect of Metal-Coating and Consecutive Heat Treatment on Coercivity of Thin Nd-Fe-B Sintered Magnets", Proceedings of the Sixteenth International Workshop on Rare-Earth Magnets and Their Applications, Sendai, p. 257 (2000) Kenichi Machida, Naoshi Kawamata, Toshiharu Suzuki, Masahiro Ito, Takashi Horikawa, “Granular boundary modification and magnetic properties of Nd-Fe—B based sintered magnets”, Powder and Powder Metallurgy Association Presentation Summary, 2004 Spring Meeting, p . 202

  The present invention has been made in view of the above-described conventional problems, and uses a mixed powder of an alloy powder mainly composed of an intermetallic compound and a rare earth oxide as a material to be applied and diffused on a sintered magnet body. R-Fe-B sintered magnet having excellent productivity, high performance, low amount of Tb or Dy, increased coercive force while suppressing reduction of residual magnetic flux density, and method for producing the same Is intended to provide.

  In order to solve such a problem, the inventors of the present invention should increase the diffusion amount on the surface of the R—Fe—B based sintered body with respect to the rare earth oxide coating most excellent from the viewpoint of productivity. As a result of ingenuity, the oxide is partially reduced during heat treatment by mixing an intermetallic compound or metal powder with an oxide containing rare earth such as Dy or Tb, and a rare earth inorganic compound such as fluoride or oxide. Compared with the method of applying a heat treatment after applying the powder, it has been found that a larger amount of Dy and Tb can be introduced near the interface of the main phase grains in the magnet through the grain boundary part as a residual magnetic flux. The present inventors have found that the coercive force can be increased while suppressing the decrease in density, and are excellent in productivity as compared with the conventional method, and have completed the present invention.

  That is, as a result of creative ingenuity to increase the amount of diffusion for the most excellent oxide coating from the viewpoint of productivity, intermetallic compounds or metal powders are mixed with oxides containing rare earth such as Dy and Tb. As a result, the oxide is partially reduced during the heat treatment, and a larger amount of Dy or Tb is introduced into the magnet as compared with the method of applying the heat treatment after applying a rare earth inorganic compound powder such as fluoride or oxide. The present invention has been found to be possible.

That is, the present invention provides the following rare earth permanent magnet and method for producing the same.
Claim 1:
Composition R _a T ¹ _{b Mc} B _d (R is one or more selected from rare earth elements including Y and Sc, T ¹ is ^one or two of Fe and Co, M is Al, Si 1 selected from C, P, Ti, V, Cr, Mn, Ni, Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ag, In, Sn, Sb, Hf, Ta, W, Pb, Bi Species or 2 or more types, B is boron, a, b, c, d are atomic percentages, 12 ≦ a ≦ 20, 0 ≦ c ≦ 10, 4.0 ≦ d ≦ 7.0, b is the balance , A + b + c + d = 100), the composition M ¹ _d M ² _e (M ¹ , M ² is Al, Si, C, P, Ti, V, Cr, Mn, Fe, Co, Ni, One or more selected from Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ag, In, Sn, Sb, Hf, Ta, W, Pb, Bi M ¹ and M ² are different from each other, d and e are atomic percentages, 0.1 ≦ e ≦ 99.9, d is the balance, d + e = 100), and the intermetallic compound phase and an average particle diameter 500μm or less of the alloy powder containing 70 vol% or more, average particle diameter of less oxide of R ¹ 100 [mu] m (R ¹ is at least one element selected from rare earth elements inclusive of Sc and Y) In a state where the mixed powder containing 10% by mass or more is present on the surface of the sintered magnet body, the sintered magnet body and the mixed powder are vacuumed at a temperature lower than the sintering temperature of the sintered magnet body. Alternatively, by performing heat treatment in an inert gas, one or more elements of R ¹ , M ¹ , and M ² are converted into grain boundary portions inside the sintered magnet body and / or sintered magnet body. A method for producing a rare earth permanent magnet, characterized by diffusing in the vicinity of a grain boundary in a main phase grain.
Claim 2:
Composition R _a T ¹ _{b Mc} B _d (R is one or more selected from rare earth elements including Y and Sc, T ¹ is ^one or two of Fe and Co, M is Al, Si 1 selected from C, P, Ti, V, Cr, Mn, Ni, Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ag, In, Sn, Sb, Hf, Ta, W, Pb, Bi Species or 2 or more types, B is boron, a, b, c, d are atomic percentages, 12 ≦ a ≦ 20, 0 ≦ c ≦ 10, 4.0 ≦ d ≦ 7.0, b is the balance in a + b + c + d = 100) made of a sintered magnet body to the mean of the powder (M ¹ particle size 500μm following M ¹ is Al, Si, C, P, Ti, V, Cr, Mn, Fe, Co, Ni, One kind selected from Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ag, In, Sn, Sb, Hf, Ta, W, Pb, Bi Is a mixed powder containing 10% by mass or more of R ¹ oxide (R ¹ is one or more selected from rare earth elements including Sc and Y) having an average particle size of 100 μm or less. The sintered magnet body and the mixed powder are subjected to a heat treatment in a vacuum or an inert gas at a temperature lower than the sintering temperature of the sintered magnet body in a state where the sintered magnet body is present on the surface of the sintered magnet body. To diffuse one or more elements of R ¹ and M ^{1 in} the vicinity of the grain boundary in the sintered magnet body and / or in the vicinity of the grain boundary in the main phase grain of the sintered magnet body. A method for producing a rare earth permanent magnet.
Claim 3:
The rare earth according to claim 1 or 2, wherein the heat treatment is performed for 1 minute to 30 hours at a temperature of (T _S -10) ° C. or lower and 200 ° C. or higher with respect to a sintering temperature T _S of the sintered magnet body. A method for manufacturing a permanent magnet.
Claim 4:
The mixed powder is applied to the surface of the sintered magnet body by dipping the sintered magnet body in a slurry in which the mixed powder is dispersed in an organic solvent or water, and then dried, followed by heat treatment. The method for producing a rare earth permanent magnet according to any one of claims 1 to 3.
Claim 5:
The method for producing a rare earth permanent magnet according to any one of claims 1 to 4, wherein a size of a minimum part of the sintered magnet body to be heat-treated has a shape of 20 mm or less.
Claim 6:
Composition R _a T ¹ _{b Mc} B _d (R is one or more selected from rare earth elements including Y and Sc, T ¹ is ^one or two of Fe and Co, M is Al, Si 1 selected from C, P, Ti, V, Cr, Mn, Ni, Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ag, In, Sn, Sb, Hf, Ta, W, Pb, Bi Species or 2 or more types, B is boron, a, b, c, d are atomic percentages, 12 ≦ a ≦ 20, 0 ≦ c ≦ 10, 4.0 ≦ d ≦ 7.0, b is the balance , A + b + c + d = 100), the composition M ¹ _d M ² _e (M ¹ , M ² is Al, Si, C, P, Ti, V, Cr, Mn, Fe, Co, Ni, One or more selected from Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ag, In, Sn, Sb, Hf, Ta, W, Pb, Bi M ¹ and M ² are different from each other, d and e are atomic percentages, 0.1 ≦ e ≦ 99.9, d is the balance, d + e = 100), and the intermetallic compound phase and an average particle diameter 500μm or less of the alloy powder containing 70 vol% or more, average particle diameter of less oxide of R ¹ 100 [mu] m (R ¹ is at least one element selected from rare earth elements including Sc and Y) In a state where the mixed powder containing 10% by mass or more is present on the surface of the sintered magnet body, the sintered magnet body and the mixed powder are vacuumed at a temperature lower than the sintering temperature of the sintered magnet body. Alternatively, by performing heat treatment in an inert gas, one or more elements of R ¹ , M ¹ , and M ² are converted into grain boundary portions inside the sintered magnet body and / or sintered magnet body. A rare earth permanent magnet characterized by being diffused in the vicinity of a grain boundary in a main phase grain.
Claim 7:
Composition R _a T ¹ _{b Mc} B _d (R is one or more selected from rare earth elements including Y and Sc, T ¹ is ^one or two of Fe and Co, M is Al, Si 1 selected from C, P, Ti, V, Cr, Mn, Ni, Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ag, In, Sn, Sb, Hf, Ta, W, Pb, Bi Species or 2 or more types, B is boron, a, b, c, d are atomic percentages, 12 ≦ a ≦ 20, 0 ≦ c ≦ 10, 4.0 ≦ d ≦ 7.0, b is the balance M ¹ powder having an average particle diameter of 500 μm or less (M ¹ is Al, Si, C, P, Ti, V, Cr, Mn, Fe, Co, Ni, Cu) for a sintered magnet body made of a + b + c + d = 100) , Zn, Ga, Ge, Zr, Nb, Mo, Ag, In, Sn, Sb, Hf, Ta, W, Pb, Bi And two or more), an average particle diameter of the oxide of the following R ¹ 100 [mu] m (R ¹ is a powder mixture containing one or more) more than 10 wt% selected from rare earth elements inclusive of Sc and Y By subjecting the sintered magnet body and the mixed powder to heat treatment in a vacuum or an inert gas at a temperature equal to or lower than the sintering temperature of the sintered magnet body in the state of being present on the surface of the sintered magnet body. , R ¹ , M ¹ , or two or more elements are diffused near the grain boundary in the sintered magnet body and / or in the vicinity of the grain boundary in the sintered magnet body main phase grain. Rare earth permanent magnet characterized by

  According to the present invention, as a result of creative ingenuity to increase the amount of diffusion on the surface of the R—Fe—B based sintered magnet body, which is the most excellent rare earth oxide coating from the viewpoint of productivity, A method in which an intermetallic compound is mixed with an oxide containing a rare earth element such as Tb, whereby the oxide is partially reduced during the heat treatment, and the heat treatment is performed after applying a rare earth inorganic compound powder such as fluoride or oxide. Compared to the above, a larger amount of rare earth elements such as Dy and Tb can be introduced in the vicinity of the interface of the main phase grains in the magnet through the grain boundary part as a path, and the coercive force is suppressed while suppressing the decrease in residual magnetic flux density R-Fe-B, which has higher productivity than conventional methods, has high performance and uses less Tb or Dy, and has increased coercive force while suppressing reduction of residual magnetic flux density To provide sintered magnets That.

  The present invention applies a diffusion treatment by applying a mixed powder of an alloy powder mainly composed of an intermetallic compound and a rare earth oxide or a mixed powder of a metal powder and a rare earth oxide on a sintered magnet body. The present invention relates to an obtained R-Fe-B sintered magnet having high performance and a small amount of Tb or Dy and a method for producing the same.

In the present invention, in the R _a T ¹ _b M _c B _d sintered magnet body as the base material, R is one or more selected from rare earth elements including Sc and Y, specifically, Sc, Y La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, and Lu, preferably Nd and / or Pr. These rare earth elements including Sc and Y are preferably 12 to 20 atomic% (12 ≦ a ≦ 20), particularly 13 to 18 atomic% (13 ≦ a ≦ 18) of the entire sintered body. In this case, Nd and Pr are preferably 50 to 100 atomic%, particularly 70 to 100 atomic% of the whole rare earth. T ¹ is one or two of Fe and Co. M is Al, Si, C, P, Ti, V, Cr, Mn, Ni, Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ag, In, Sn, Sb, Hf, Ta, W, Pb, One or two or more selected from Bi is preferably 0 to 10 atomic% (0 ≦ c ≦ 10), particularly 0 to 5 atomic% (0 ≦ c ≦ 5) of the whole sintered body. B is a boron element and is preferably 4 to 7 atomic% (4 ≦ d ≦ 7) of the entire sintered body. In particular, in the case of 5 to 6 atomic% (5 ≦ d ≦ 6), the coercive force is greatly improved by the diffusion treatment. The balance is T ¹ but is preferably 60 to 84 atomic% (60 ≦ b ≦ 84), particularly preferably 70 to 82 atomic% (70 ≦ b ≦ 82) (note that a + b + c + d = 100). .

An alloy for producing a sintered magnet base material is prepared by melting a raw metal or alloy in a vacuum or an inert gas, preferably in an Ar atmosphere, and then casting it in a flat mold or a book mold, or by a strip casting method. It is obtained with. Also, an alloy close to the composition of the R ₂ Fe ₁₄ B compound, which is the main phase of this alloy, and a rare earth-rich alloy that serves as an auxiliary aid at the sintering temperature are separately prepared, and weighed and mixed after coarse pulverization. Alloy methods are also applicable to the present invention. However, for alloys close to the main phase composition, primary α-Fe tends to remain depending on the cooling rate during casting and the alloy composition, and is necessary for the purpose of increasing the amount of R ₂ Fe ₁₄ B compound phase. A homogenization process is performed according to the conditions. The conditions are heat treatment at 700 to 1,200 ° C. for 1 hour or more in a vacuum or Ar atmosphere. Alternatively, an alloy close to the main phase composition can be made by a strip casting method. In addition to the above casting method, a so-called liquid quenching method or a strip casting method can be applied to the rare earth-rich alloy serving as the liquid phase aid.

  The alloy is generally coarsely pulverized to 0.05 to 3 mm, particularly 0.05 to 1.5 mm. Brown mill or hydrogen pulverization is used for the coarse pulverization process, and hydrogen pulverization is preferable in the case of an alloy produced by strip casting. The coarse powder is usually finely pulverized to 0.2 to 30 μm, particularly 0.5 to 20 μm, for example, by a jet mill using high-pressure nitrogen.

The fine powder is formed by a compression molding machine in a magnetic field and put into a sintering furnace. Sintering is usually performed at 900 to 1,250 ° C., particularly 1,000 to 1,100 ° C. in a vacuum or an inert gas atmosphere. The obtained sintered magnet body contains 60 to 99% by volume, particularly preferably 80 to 98% by volume of a tetragonal R ₂ Fe ₁₄ B compound as a main phase, and the balance is 0.5 to 20% by volume of rare earth. It contains at least one of a rich phase, 0.1 to 10% by volume of rare earth oxides and carbides, nitrides and hydroxides produced by inevitable impurities, or a mixture or composite thereof.

The obtained sintered magnet body block can be ground into a predetermined shape. In the present invention, M ¹ , M ^2, and R ¹ diffusing into the sintered magnet body are supplied from the surface of the sintered magnet body. Therefore, when the dimension of the minimum part of the sintered magnet body base material is too large, The effect cannot be achieved. Therefore, it is required that the dimension of the minimum part is 20 mm or less, preferably 10 mm or less, and the lower limit is 0.1 mm or more. Moreover, there is no upper limit to the dimension of the maximum part of the sintered magnet body base material, but it is preferably 200 mm or less.

Next, as a material to be applied onto the sintered magnet body base material and subjected to diffusion treatment, an alloy having an average particle diameter of 500 μm or less having a composition of M ¹ _d M ² _e and containing 70% by volume or more of an intermetallic compound phase ( Hereinafter, this alloy is referred to as a diffusion alloy) or a metal powder having an average particle size of 500 μm or less and an R ¹ oxide having an average particle size of 100 μm or less (R ¹ is one selected from rare earth elements including Sc and Y The sintered magnet body and the mixed powder are put into the sintered magnet body in a state where the mixed powder containing 10% by mass or more of the whole mixed powder is present on the surface of the sintered magnet body. The oxide is partially reduced by mixing the intermetallic compound or the metal powder with the rare earth oxide by performing a heat treatment in a vacuum or an inert gas at a temperature equal to or lower than the sintering temperature. ^1, one of M ² and R ¹ or Inside the grain boundary portion of the seed or more elements the sintered magnet body, and / or can be diffused into the vicinity of the grain boundaries of the sintered magnet body main phase grains.

Here, in the M ¹ _d M ² _e alloy, M ¹ and M ² are Al, Si, C, P, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Zr, One or more selected from Nb, Mo, Ag, In, Sn, Sb, Hf, Ta, W, Pb, and Bi, but M ¹ and M ² are different from each other. In the M ¹ _d M ² _e alloy, d and e represent atomic percentages, and 0.1 ≦ e ≦ 99.9, preferably 10 ≦ e ≦ 90, more preferably 20 ≦ e ≦ 80, and d is the balance. is there.
In the metal powder M ^1, M ¹ is Al, Si, C, P, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ag , In, Sn, Sb, Hf, Ta, W, Pb, and Bi.

  These diffusion alloys may contain inevitable impurities such as nitrogen (N) and oxygen (O), but the allowable amount is 4 atomic% or less, preferably 2 atomic% or less, more preferably 1 atomic% in total. It is as follows.

The diffusion alloy containing 70% by volume or more of the intermetallic compound phase represented by M ¹ _d M ² _e is the same as the alloy for producing a sintered magnet base material, and the raw metal or alloy is vacuum or inert gas, preferably Can be obtained by melting in an Ar atmosphere and then casting into a flat mold or book mold, or by high frequency melting or strip casting. This alloy is usually coarsely pulverized to about 0.05 to 3 mm, particularly about 0.05 to 1.5 mm using means such as a brown mill or hydrogen pulverization, and then, for example, a ball mill, a vibration mill or a jet using high-pressure nitrogen. It is pulverized by a mill. The smaller the particle size of this powder, the higher the diffusion efficiency. Therefore, the intermetallic compound phase represented by M ¹ _d M ² _e has an average particle size of 500 μm or less, preferably 300 μm or less, more preferably 100 μm or less. Preferably there is. However, if the particle size is too small, the effect of surface oxidation is great and handling becomes dangerous. Therefore, the lower limit of the average particle size is preferably 1 μm or more. In the present invention, the average particle diameter is, for example, as a mass average value D ₅₀ (that is, a particle diameter or a median diameter when the cumulative mass becomes 50%) using a particle size distribution measuring device by a laser diffraction method or the like. Can be sought.

In addition, the metal powder represented by M ¹ is roughly pulverized into a metal lump usually 0.05 to 3 mm, particularly 0.05 to 1.5 mm using means such as a jaw crusher or a brown mill. For example, it can be finely pulverized by a ball mill, a vibration mill or a jet mill using high-pressure nitrogen. Alternatively, the molten metal can be finely pulverized by an atomizing method in which a molten metal is ejected from a small hole and is made into a mist by high pressure gas. The average particle diameter of the metal powder of M ¹ is 500 μm or less, preferably 300 μm or less, more preferably 100 μm or less. However, if the particle size is too small, the effect of surface oxidation is great and handling becomes dangerous. Therefore, the lower limit of the average particle size is preferably 1 μm or more. In the present invention, the average particle diameter is, for example, as a mass average value D ₅₀ (that is, a particle diameter or a median diameter when the cumulative mass is 50%) using a particle size distribution measuring apparatus by a laser diffraction method or the like. Can be sought.

On the other hand, the oxide of R ¹ may be any rare-earth oxide containing Y and Sc, but is preferably an oxide containing Dy or Tb. The average particle diameter is 100 μm or less, preferably 50 μm or less, and more preferably 20 μm or less. The amount of the R ¹ oxide used is 10% by mass or more, preferably 20% by mass or more, more preferably 30% by mass or more, based on the entire mixed powder of the diffusion alloy powder. When the content is less than 10% by mass, the mixing effect of the rare earth oxide is reduced. The upper limit of the amount of R ¹ oxide used is 99% by mass or less, particularly 90% by mass or less.

The oxide of the diffusion alloy powder or the M ¹ metal powder with an average particle size of less 100 [mu] m R ¹ (R ¹ is at least one element selected from rare earth elements inclusive of Sc and Y) a powder mixture The mixed powder containing 10% by mass or more of the above is present on the surface of the sintered magnet body base material, and the sintered magnet body in which the mixed powder of the diffusion alloy powder and the oxide of R ¹ is present on the surface is vacuum or Heat treatment is performed at a temperature equal to or lower than the sintering temperature in an inert gas atmosphere such as Ar or He. Hereinafter, this processing is referred to as diffusion processing. The oxide is partially reduced by mixing the intermetallic compound with the rare earth oxide by diffusion treatment, and R ¹ , M ¹ , and M ² of the mixed powder are larger than conventional ones at the grain boundary portion inside the sintered magnet body. And / or diffused in the vicinity of the grain boundary in the sintered magnet body main phase grains.

As a method of allowing the powder of the diffusion alloy or the mixed powder of M ¹ metal powder and R ¹ oxide to exist on the surface of the sintered body base material, for example, the mixed powder is dispersed in an organic solvent or water, After immersing the sintered magnet base material in this slurry, it may be dried by hot air or vacuum, or naturally dried. In addition, application by spraying is also possible. In addition, what is necessary is just to make content of the said mixed powder in a slurry into 1-90 mass%, and it is especially preferable to set it as 5-70 mass%.

Diffusion treatment conditions vary depending on the type and constituent elements of the mixed powder, but R ¹ , M ¹ , and M ² are near the grain boundary in the sintered magnet body and in the sintered magnet body main phase grains. The conditions for thickening are preferable. The diffusion treatment temperature is equal to or lower than the sintering temperature of the sintered magnet body base material. The reasons for limiting the treatment temperature are as follows. When treated at a temperature higher than the sintering temperature of the sintered magnet body base material (referred to as T _S ° C), (1) the structure of the sintered magnet body is altered and high magnetic properties cannot be obtained. (2) Heat Since problems such as the inability to maintain the processed dimensions of the sintered magnet body occur due to deformation, the processing temperature is set to the sintering temperature or lower, preferably (T _S -10) ° C. or lower. The lower limit is preferably 200 ° C or higher, particularly 350 ° C or higher, and more preferably 600 ° C or higher. The diffusion treatment time is 1 minute to 30 hours. If less than 1 minute, the diffusion treatment is not completed, and if it exceeds 30 hours, the structure of the sintered magnet body is altered, unavoidable oxidation or evaporation of components adversely affects the magnetic properties, or R ¹ , There arises a problem that M ¹ and M ² do not concentrate only in the vicinity of the grain boundary part or the grain boundary part in the main phase grain of the sintered magnet body but diffuse to the inside of the main phase grain. More preferably, it is 1 minute-10 hours, More preferably, it is 10 minutes-6 hours.

The constituent elements R ¹ , M ¹ , and M ² of the mixed powder applied to the surface of the sintered magnet body base material are mainly subjected to an optimum diffusion treatment, so that the grain boundary portion of the sintered magnet body structure is mainly used. It diffuses inside the sintered magnet body as a path. Thereby, a structure in which R ¹ , M ¹ , and M ² are concentrated in the vicinity of the grain boundary portion in the sintered magnet body and / or in the vicinity of the grain boundary portion in the sintered magnet body main phase grain is obtained.

In the permanent magnet obtained as described above, the structure in the vicinity of the main phase grain interface inside the structure is modified by the diffusion of R ¹ , M ¹ and M ² , and the magnetocrystalline anisotropy of the main phase grain interface is lowered. Is suppressed, or a new phase is formed at the grain boundary, thereby improving the coercive force. Further, since these diffusion alloy elements are not diffused to the inside of the main phase grains, it is possible to suppress a decrease in residual magnetic flux density and to be used as a high-performance permanent magnet. Furthermore, in order to increase the effect of increasing the coercive force, the magnet body subjected to the above diffusion treatment may be further subjected to an aging treatment at a temperature of 200 to 900 ° C.

  Hereinafter, although the specific content of this invention is explained in full detail with an Example and a comparative example, the content of this invention is not limited to this.

[Example 1, Comparative Examples 1 and 2]
Nd, Co, Al, Fe metal having a purity of 99% by mass or more and ferroboron are weighed in predetermined amounts and melted at high frequency in an Ar atmosphere, and this molten alloy is poured into a single copper roll in an Ar atmosphere by a so-called strip casting method. A thin plate-like alloy was used. The composition of the obtained alloy was 12.8 atomic% Nd, 1.0 atomic% Co, 0.5 atomic% Al, 6.0 atomic% B, and the balance Fe. Called. The alloy A was occluded with hydrogen and then heated to 500 ° C. while being evacuated to partially release hydrogen, so that a coarse powder of 30 mesh or less was obtained by so-called hydrogen pulverization. Further, Nd, Dy, Fe, Co, Al, Cu metal having a purity of 99% by mass or more and ferroboron were weighed in predetermined amounts, melted by high frequency in an Ar atmosphere, and then cast. The composition of the resulting alloy is Nd 23 atom%, Dy 12 atom%, Fe 25 atom%, B 6 atom%, Al 0.5 atom%, Cu 2 atom%, and Co as the balance. This is referred to as Alloy B. Alloy B was coarsely pulverized to 30 mesh or less using a brown mill in a nitrogen atmosphere.

Subsequently, 94% by mass of alloy A powder and 6% by mass of alloy B powder were weighed and mixed for 30 minutes in a V-blender purged with nitrogen.
This mixed powder was finely pulverized to a mass median particle size of 4 μm by a jet mill using high-pressure nitrogen gas. The obtained mixed fine powder was molded at a pressure of about 1 ton / cm ² while being oriented in a magnetic field of 15 kOe under a nitrogen atmosphere. Next, this compact was put into a sintering furnace in an Ar atmosphere and sintered at 1,060 ° C. for 2 hours to produce a magnet block having dimensions of 10 mm × 20 mm × thickness 15 mm. The magnet block was ground on the whole surface to 4 mm × 4 mm × 2 mm (direction of magnetic anisotropy) with a diamond cutter.
The ground magnet body was washed with an alkaline solution, and then washed with an acid and dried. A cleaning process with pure water is included before and after each cleaning.
This was used as a sintered magnet base material. The composition was Nd _13.3 Dy _0.5 Fe _bal Co _2.4 Cu _0.1 Al _0.5 B _6.0 .

Using Al and Co metals having a purity of 99% by mass or more, high frequency melting was performed in an Ar atmosphere, and a diffusion alloy having a composition of Al ₅₀ Co ₅₀ and mainly composed of an intermetallic compound phase of AlCo was produced. This alloy was finely pulverized to a mass median particle size of 8.9 μm by a ball mill using an organic solvent. This alloy had an AlCo intermetallic phase of 94% by volume as observed by EPMA.
Next, Al ₅₀ Co ₅₀ diffusion alloy and terbium oxide having an average powder particle size of 1 μm are mixed at a mass ratio of 1: 1, and then mixed with pure water at a mass fraction of 50%, and an ultrasonic wave is applied to the magnet body. Was soaked for 30 seconds. The magnet pulled up was immediately dried with hot air. This was subjected to a diffusion treatment at 900 ° C. for 8 hours in an Ar atmosphere, and further subjected to an aging treatment at 500 ° C. for 1 hour, followed by rapid cooling to obtain a magnet body of Example 1.
Further, terbium oxide having an average powder particle size of 1 μm was mixed with pure water at a mass fraction of 50%, and the magnet body was immersed for 30 seconds while applying ultrasonic waves thereto. The magnet pulled up was immediately dried with hot air. This was subjected to a diffusion treatment in an Ar atmosphere at 900 ° C. for 8 hours, and further subjected to an aging treatment at 500 ° C. for 1 hour, followed by rapid cooling to obtain a magnet body of Comparative Example 1. Moreover, only the sintered compact base material was similarly heat-treated at 900 ° C. for 8 hours in vacuum without using the mixed diffusion powder, so that Comparative Example 2 was obtained.

Table 1 shows the composition of sintered magnet body base material and diffusion alloy, diffusion rare earth oxide, and diffusion mixture powder mixing ratio (mass) in Example 1 and Comparative Examples 1 and 2, and their diffusion treatment temperature (° C.). Table 2 shows the diffusion treatment time (h) and magnetic characteristics. The coercive force of the magnet of Example 1 according to the present invention was found to be increased by 90 kAm ⁻¹ compared to the magnet of Comparative Example 1. Further, the decrease in residual magnetic flux density was only 3 mT as compared with Comparative Example 1. Furthermore, the coercive force of the magnet of Example 1 according to the present invention was found to increase by 1,040 kAm ⁻¹ compared to the magnet of Comparative Example 2. The decrease in residual magnetic flux density was 4 mT.

[Example 2, Comparative Example 3]
Nd, Co, Al, Fe metal having a purity of 99% by mass or more and ferroboron are weighed in predetermined amounts and melted at high frequency in an Ar atmosphere, and this molten alloy is poured into a single copper roll in an Ar atmosphere by a so-called strip casting method. A thin plate-like alloy was used. The composition of the obtained alloy was 12.8 atomic% Nd, 1.0 atomic% Co, 0.5 atomic% Al, 6.0 atomic% B, and the balance Fe. Called. The alloy A was occluded with hydrogen and then heated to 500 ° C. while being evacuated to partially release hydrogen, so that a coarse powder of 30 mesh or less was obtained by so-called hydrogen pulverization. Further, Nd, Dy, Fe, Co, Al, Cu metal having a purity of 99% by mass or more and ferroboron were weighed in predetermined amounts, melted by high frequency in an Ar atmosphere, and then cast. The composition of the resulting alloy is Nd 23 atom%, Dy 12 atom%, Fe 25 atom%, B 6 atom%, Al 0.5 atom%, Cu 2 atom%, and Co as the balance. This is referred to as Alloy B. Alloy B was coarsely pulverized to 30 mesh or less using a brown mill in a nitrogen atmosphere.

Subsequently, 94% by mass of alloy A powder and 6% by mass of alloy B powder were weighed and mixed for 30 minutes in a V-blender purged with nitrogen.
This mixed powder was finely pulverized to a mass median particle size of 4.1 μm by a jet mill using high-pressure nitrogen gas. The obtained mixed fine powder was molded at a pressure of about 1 ton / cm ² while being oriented in a magnetic field of 15 kOe under a nitrogen atmosphere. Next, this compact was put into a sintering furnace in an Ar atmosphere and sintered at 1,060 ° C. for 2 hours to produce a magnet block having dimensions of 10 mm × 20 mm × thickness 15 mm. The magnet block was ground on the whole surface to 4 mm × 4 mm × 2 mm (direction of magnetic anisotropy) with a diamond cutter.
The ground magnet body was washed with an alkaline solution, and then washed with an acid and dried. A cleaning process with pure water is included before and after each cleaning.
This was used as a sintered magnet base material. The composition was Nd _13.3 Dy _0.5 Fe _bal Co _2.4 Cu _0.1 Al _0.5 B _6.0 .

Using a Ni or Al metal having a purity of 99% by mass or more, high frequency melting was performed in an Ar atmosphere, and a diffusion alloy having a composition of Ni ₂₅ Al ₇₅ and mainly including an intermetallic compound phase of NiAl ₃ was produced. This alloy was finely pulverized to a mass median particle size of 9.3 μm by a ball mill using an organic solvent. This alloy had a NiAl ₃ intermetallic compound phase of 94% by volume as observed by EPMA.
Next, Ni ₂₅ Al ₇₅ diffusion alloy was mixed with Tb ₄ O ₇ having an average powder particle diameter of 1 μm at a mass ratio of 1: 1, and then mixed with pure water at a mass fraction of 50%, while applying ultrasonic waves thereto. The magnet body was immersed for 30 seconds. The magnet pulled up was immediately dried with hot air. This was subjected to a diffusion treatment in an Ar atmosphere at 900 ° C. for 8 hours, and further subjected to an aging treatment at 500 ° C. for 1 hour, followed by rapid cooling to obtain a magnet body of Example 2. Further, only the sintered magnet body base material was heat-treated at 900 ° C. for 8 hours in the same vacuum without using the mixed diffusion powder, and Comparative Example 3 was obtained.

The composition of sintered magnet body and diffusion alloy, diffusion rare earth oxide, diffusion mixture powder mixing ratio (mass) in Example 2 and Comparative Example 3 are shown in Table 3, diffusion treatment temperature (° C.), diffusion Table 4 shows the processing time (h) and magnetic characteristics. The coercive force of the magnet of Example 2 according to the present invention was increased by 1,010 kAm ⁻¹ compared to the magnet of Comparative Example 3. The decrease in residual magnetic flux density was 4 mT.

[Examples 3 to 41]
In the same manner as in Example 1, powders in which various diffusion alloys and rare earth oxides were mixed were applied to various sintered base materials, and various diffusion treatment temperatures and times were applied. Table 5 shows the composition of the sintered body base material and the diffusion alloy or metal, the diffusion rare earth oxide, and the mixing ratio (mass) of the diffusion mixed powder. The diffusion processing temperature (° C.) and the diffusion processing time (h) , Min) and magnetic properties are shown in Table 6. In addition, the amount of intermetallic compounds in the following diffusion alloys was 70% by volume or more.

Claims (7)

Composition R _a T ¹ _{b Mc} B _d (R is one or more selected from rare earth elements including Y and Sc, T ¹ is ^one or two of Fe and Co, M is Al, Si 1 selected from C, P, Ti, V, Cr, Mn, Ni, Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ag, In, Sn, Sb, Hf, Ta, W, Pb, Bi Species or 2 or more types, B is boron, a, b, c, d are atomic percentages, 12 ≦ a ≦ 20, 0 ≦ c ≦ 10, 4.0 ≦ d ≦ 7.0, b is the balance , A + b + c + d = 100), the composition M ¹ _d M ² _e (M ¹ , M ² is Al, Si, C, P, Ti, V, Cr, Mn, Fe, Co, Ni, One or more selected from Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ag, In, Sn, Sb, Hf, Ta, W, Pb, Bi M ¹ and M ² are different from each other, d and e are atomic percentages, 0.1 ≦ e ≦ 99.9, d is the balance, d + e = 100), and the intermetallic compound phase and an average particle diameter 500μm or less of the alloy powder containing 70 vol% or more, average particle diameter of less oxide of R ¹ 100 [mu] m (R ¹ is at least one element selected from rare earth elements inclusive of Sc and Y) In a state where the mixed powder containing 10% by mass or more is present on the surface of the sintered magnet body, the sintered magnet body and the mixed powder are vacuumed at a temperature lower than the sintering temperature of the sintered magnet body. Alternatively, by performing heat treatment in an inert gas, one or more elements of R ¹ , M ¹ , and M ² are converted into grain boundary portions inside the sintered magnet body and / or sintered magnet body. A method for producing a rare earth permanent magnet, characterized by diffusing in the vicinity of a grain boundary in a main phase grain. Composition R _a T ¹ _{b Mc} B _d (R is one or more selected from rare earth elements including Y and Sc, T ¹ is ^one or two of Fe and Co, M is Al, Si 1 selected from C, P, Ti, V, Cr, Mn, Ni, Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ag, In, Sn, Sb, Hf, Ta, W, Pb, Bi Species or 2 or more types, B is boron, a, b, c, d are atomic percentages, 12 ≦ a ≦ 20, 0 ≦ c ≦ 10, 4.0 ≦ d ≦ 7.0, b is the balance in a + b + c + d = 100) made of a sintered magnet body to the mean of the powder (M ¹ particle size 500μm following M ¹ is Al, Si, C, P, Ti, V, Cr, Mn, Fe, Co, Ni, One kind selected from Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ag, In, Sn, Sb, Hf, Ta, W, Pb, Bi Is a mixed powder containing 10% by mass or more of R ¹ oxide (R ¹ is one or more selected from rare earth elements including Sc and Y) having an average particle size of 100 μm or less. The sintered magnet body and the mixed powder are subjected to a heat treatment in a vacuum or an inert gas at a temperature lower than the sintering temperature of the sintered magnet body in a state where the sintered magnet body is present on the surface of the sintered magnet body. To diffuse one or more elements of R ¹ and M ^{1 in} the vicinity of the grain boundary in the sintered magnet body and / or in the vicinity of the grain boundary in the main phase grain of the sintered magnet body. A method for producing a rare earth permanent magnet. The rare earth according to claim 1 or 2, wherein the heat treatment is performed for 1 minute to 30 hours at a temperature of (T _S -10) ° C. or lower and 200 ° C. or higher with respect to a sintering temperature T _S of the sintered magnet body. A method for manufacturing a permanent magnet.   The mixed powder is applied to the surface of the sintered magnet body by dipping the sintered magnet body in a slurry in which the mixed powder is dispersed in an organic solvent or water, and then dried, followed by heat treatment. The method for producing a rare earth permanent magnet according to any one of claims 1 to 3.   The method for producing a rare earth permanent magnet according to any one of claims 1 to 4, wherein a size of a minimum part of the sintered magnet body to be heat-treated has a shape of 20 mm or less. Composition R _a T ¹ _{b Mc} B _d (R is one or more selected from rare earth elements including Y and Sc, T ¹ is ^one or two of Fe and Co, M is Al, Si 1 selected from C, P, Ti, V, Cr, Mn, Ni, Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ag, In, Sn, Sb, Hf, Ta, W, Pb, Bi Species or 2 or more types, B is boron, a, b, c, d are atomic percentages, 12 ≦ a ≦ 20, 0 ≦ c ≦ 10, 4.0 ≦ d ≦ 7.0, b is the balance , A + b + c + d = 100), the composition M ¹ _d M ² _e (M ¹ , M ² is Al, Si, C, P, Ti, V, Cr, Mn, Fe, Co, Ni, One or more selected from Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ag, In, Sn, Sb, Hf, Ta, W, Pb, Bi M ¹ and M ² are different from each other, d and e are atomic percentages, 0.1 ≦ e ≦ 99.9, d is the balance, d + e = 100), and the intermetallic compound phase and an average particle diameter 500μm or less of the alloy powder containing 70 vol% or more, average particle diameter of less oxide of R ¹ 100 [mu] m (R ¹ is at least one element selected from rare earth elements inclusive of Sc and Y) In a state where the mixed powder containing 10% by mass or more is present on the surface of the sintered magnet body, the sintered magnet body and the mixed powder are vacuumed at a temperature lower than the sintering temperature of the sintered magnet body. Alternatively, by performing heat treatment in an inert gas, one or more elements of R ¹ , M ¹ , and M ² are converted into grain boundary portions inside the sintered magnet body and / or sintered magnet body. A rare earth permanent magnet characterized by being diffused in the vicinity of a grain boundary in a main phase grain. Composition R _a T ¹ _{b Mc} B _d (R is one or more selected from rare earth elements including Y and Sc, T ¹ is ^one or two of Fe and Co, M is Al, Si 1 selected from C, P, Ti, V, Cr, Mn, Ni, Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ag, In, Sn, Sb, Hf, Ta, W, Pb, Bi Species or 2 or more types, B is boron, a, b, c, d are atomic percentages, 12 ≦ a ≦ 20, 0 ≦ c ≦ 10, 4.0 ≦ d ≦ 7.0, b is the balance M ¹ powder with an average particle diameter of 500 μm or less (M ¹ is Al, Si, C, P, Ti, V, Cr, Mn, Fe, Co, Ni, Cu) , Zn, Ga, Ge, Zr, Nb, Mo, Ag, In, Sn, Sb, Hf, Ta, W, Pb, Bi And two or more), an average particle diameter of the oxide of the following R ¹ 100 [mu] m (R ¹ is a powder mixture containing one or more) more than 10 wt% selected from rare earth elements inclusive of Sc and Y By subjecting the sintered magnet body and the mixed powder to heat treatment in a vacuum or an inert gas at a temperature equal to or lower than the sintering temperature of the sintered magnet body in the state of being present on the surface of the sintered magnet body. , R ¹ , M ¹ , or two or more elements are diffused near the grain boundary in the sintered magnet body and / or in the vicinity of the grain boundary in the sintered magnet body main phase grain. Rare earth permanent magnet characterized by