JP4706412B2 - Anisotropic composite magnet - Google Patents

Description

  The present invention relates to an anisotropic composite magnet that can continue to generate a strong static magnetic field in a gap facing an iron core, such as a motor, even in an environment exposed to high temperatures for a long period of time.

The Nd ₂ Fe ₁₄ B, αFe / Nd ₂ Fe ₁₄ B, and Fe ₃ B / Nd ₂ Fe ₁₄ B magnet materials obtained by rapid solidification such as melt span are in the form of ribbons and other flakes. Limited to powder. For this reason, in order to obtain a generally used bulk permanent magnet, it is necessary to change the material form, that is, a technique for fixing a ribbon or powder to a specific bulk by some method. Although the basic powder fixing means in powder metallurgy is atmospheric pressure sintering, it is difficult to apply atmospheric pressure sintering because the ribbon needs to maintain magnetic properties based on a metastable state. For this reason, fixing to a bulk of a specific shape was performed exclusively with a binder such as an epoxy resin. For example, R.A. W. Lee et al. Stated that (BH) _max 72 kJ / m ³ isotropic composite magnet could be obtained by fixing a (BH) _max 111 kJ / m ³ ribbon with resin [R. W. Lee, E .; G. Brewer, N.M. A. Schaffel, “Hot-pressed Neodymium-Iron-Boron magnets” IEEE Trans. Magn. , Vol. 21, 1958 (1985)] (see Non-Patent Document 1).

In 1986, the present inventors fixed an Nd ₂ Fe ₁₄ B magnet powder obtained by pulverizing the above melt spun ribbon with an epoxy resin according to Japanese Patent Application Laid-Open No. 62-196057 (BH), a small-diameter annular with a _{maximum of} 72 kJ / m ^3. It has been clarified that isotropic composite magnets are useful for small motors (see Patent Document 1). Thereafter, T.W. Shimoda also compared the small motor characteristics of the small-diameter annular isotropic composite magnet with the small motor characteristics of the Sm-Co radial anisotropic composite magnet, and the former was useful [T. Shimoda, “Compression molding target made rapid-quenched powder”, PERMANENT MAGNETS 1988 UPDATE, Wheeler Associate INC (1988)] (see Non-Patent Document 2). Furthermore, a report that it is useful for a small motor is disclosed in W.W. Baran ["Case history of NdFeB in the European community", The European Business and Technical Outlook for NdFeB Magnets, Nov. (1989)], G.M. X. Huang, W.H. M.M. Gao, S .; F. Yu ["Application of melt-spun Nd-Fe-B bonded magnet to the micro-motor", Proc. ^{of the 11 th International Rare-Earth} Magnets and Their Applications, Pittsburgh, USA, pp. 583-595 (1990)], Kasai ["MQ1, 2 & 3 magnets applied to motors and actuators", Polymer Bonded Magnets T92, Embassie Suite OTare90, 1992. Are widely used as annular magnets for permanent magnet type motors of OA, AV, PC and peripheral devices thereof, and information communication devices (see Non-Patent Documents 3 to 5).

On the other hand, research on magnet materials by melt spinning has been actively conducted since the 1980s, and exchange based on the microstructure of Nd ₂ Fe ₁₄ B system, Sm ₂ Fe ₁₇ N ₃ system or αFe, Fe ₃ B system and the like. In addition to nanocomposite materials using bonding, materials with various alloy compositions and microstructure controlled, in recent years, isotropic rare earth magnet powders with different powder shapes can also be used industrially by rapid solidification methods other than melt spinning. [For example, Yasuhiko Iriyama, “Development Trends of High Performance Rare Earth Bond Magnets”, Ministry of Education, Culture, Sports, Science and Technology Innovation Creation Project / Effective Utilization of Rare Earth Resources and Advanced Materials Symposium, Tokyo, pp. 19-26 (2002), B.I. H. Rabin, B.M. M.M. Ma, “Recent developments in Nd—Fe—B
powder ", 120 ^th Topical Symposium of the Magnetic Society of Japan, pp. 23-28 (2001), B. M. Ma," Recent powder development at magnepne m agneP , H.Kanekiyo, T.Miyoshi, K.Murakami, Y.Shigemoto , T.Nishiuchi, "Structure and magnetic properties of Nd 2 Fe 14 B / FexB-type nanocomposite permanent magnets prepared by strip castin ^{", 9 th Joint MMM / INTERMAG} , CA (2004) FG-05] ( see Non-Patent Document 6-9).

There is also a report by Davies et al. That (BH) _max reaches 220 kJ / m ³ while being isotropic [H. A. Davies, J .; I. Betancourt, C.I. L. Harland, “Nanophase Pr and Nd / Pr based rare-earth-iron-boron alloys”, Proc. of 16 ^th Int. Works on Rare-Earth Magnets and Their Applications, Sendai, pp. 485-495 (2000)] (see Non-Patent Document 10).

However, industrially usable rapidly solidified powder (BH) _max is ^{~134kJ / m 3, (BH)} max of the isotropic composite magnet is estimated to be approximately 80 kJ / m ^3.

Regardless of the above, the permanent magnet type motors targeted by the present invention are further reduced in thickness, size, output, vibration and noise, or high accuracy in position control under the performance of electric and electronic equipment. There is a constant demand for conversion. Therefore, the improvement of the magnetic characteristics represented by (BH) _max of the magnet powder of the isotropic rare earth bonded magnet is no longer useful for improving the performance of the motor. Therefore, in the field of isotropic rare earth bonded magnet motors, there is an increasing need for application of anisotropic rare earth bonded magnets to permanent magnet motors [Fumitoshi Yamashita, “Application of rare earth magnets to electronic devices. And prospects ”, Ministry of Education, Culture, Sports, Science and Technology Innovation Creation Project / Effective Utilization of Rare Earth Resources and Advanced Materials Symposium, Tokyo, (2002)] (see Non-Patent Document 11)

By the way, the Sm—Co based magnet powder used for the anisotropic composite magnet can obtain a large coercive force H _CJ even if the ingot is pulverized. However, Sm and Co have a great resource balance problem, and are not suitable for general use as industrial materials. On the other hand, Nd and Fe are advantageous from the viewpoint of resource balance. However, even if the Nd ₂ Fe ₁₄ B alloy ingot or sintered magnet is pulverized, _HCJ is small. For this reason, with respect to the production of anisotropic Nd ₂ Fe ₁₄ B magnet powder, research using a rapidly solidified material as a starting material preceded.

In 1989, Tokunaga pulverized a hot upset (Die-upset) bulk of Nd ₁₄ Fe _80-X B ₆ Ga _X (X = 0.4 to 0.5) and HC _J = 1.52 MA / m Anisotropy Nd ₂ Fe ₁₄ B powder and solidified with resin to obtain an anisotropic composite magnet with (BH) _max 127 kJ / m ³ [Masaaki Tokunaga, “Magnetic properties of rare earth bonded magnet”, powder and powder Metallurgy, Vol. 35, pp. 3-7, (1988)] (see Non-Patent Document 12). In 1991, H.C. Sakamoto et al. Hot rolled Nd ₁₄ Fe _79.8 B _5.2 Cu ₁ to produce anisotropic Nd ₂ Fe ₁₄ B powder of H _CJ 1.30 MA / m [H. Sakamoto, M .; Fujikura and T. M
ukai, “Fully-dense Nd-Fe-B magnets prepared from hot-rolled anisotropic powders”, Proc. 11 ^th Int. Workshop on Rare-earth Magnets and Ther Applications, Pittsburg, pp. 72-84 (1990)] (see Non-Patent Document 13). As described above, a powder in which hot workability is improved by addition of Ga or Cu, and Nc ₂ Fe ₁₄ B crystal grain size is controlled to increase the _HCJ is known. 1991, V.C. Panchanathan et al. Used a hot-working bulk pulverization method to make HD (Hydrogen Depreciation) -Nd ₂ Fe ₁₄ B particles, which were dehydrogenated by vacuum heating by intruding hydrogen from the grain boundaries to collapse into Nd ₂ Fe ₁₄ BH _X , ( BH) An anisotropic composite magnet having a _{max of} 150 kJ / m ³ [M. Doser, V.M. Panchanthan, and R.A. K. Misra, “Pulverizing anisotropic”
rapidly solidified Nd-Fe-B materials for bonded magnets ", J.Appl.Phys., Vol.70, pp.6603-6805 (1991)] ( see Non-Patent Document 14). 2001, Iriyama the Nd _0.137 Fe _0.735 Co _0.067 B _0.055 Ga _0.006 was made into particles of 310 kJ / m ³ by the same method and improved to an anisotropic composite magnet of (BH) _max 177 kJ / m ³ [T. Iriyama, “Anisotropic bonded NdFeB magnets made hot-ps. "Powders", Polymer Bonded Magnet 2002, Chicago (2002)] (see Non-Patent Document 15).

Meanwhile, Takeshita et al. Nd—Fe (Co) —B ingot is heat-treated in hydrogen to hydrogenate Nd ₂ (Fe, Co) ₁₄ B phase (Hydrogenation, Nd ₂ [Fe, Co] ₁₄ BHx), 650-1000. The HDDR method is proposed in which phase decomposition (De composition, NdH ₂ + Fe + Fe ₂ B), dehydrogenation, and recombination are performed at ℃ [T. Takeshita, and R.A. Nakayama, "Magnetic properties and micro-structure of the Nd-Fe-B magnet powders produced by hydrogen treatment", Proc. 10 ^th Int. Works on Rare-earth Magnets and Their
Applications, Kyoto, pp. 551-562 (1989)], in 1999, an anisotropic composite magnet having a (BH) _{max of} 193 kJ / m ³ was produced from HDDR-Nd ₂ Fe ₁₄ B particles [K. Morimoto, R.A. Nakayama, K .; Mori, K .; Igarashi, Y. et al. Ishii, M .; Itakura, N .; Kuwano, K .; Oki, “Nd ₂ Fe ₁₄ B-based magnetic powder with high remanufactured produced by HDDR process”, IEEE. Trans. Magn. , Vol. 35, pp. 3253-3255 (1999)] (see Non-Patent Documents 16 and 17).

In 2001, Misima et al. Reported Co-free d-HDDR Nd ₂ Fe ₁₄ B particles [C. Misima, N .; Hamada, H .; Mitarai, and Y.M. Honkura, “Development of a Co-free NdFeB anisotropy magnet produced d-HDDR
processes powder ", IEEE Trans. Magn., Vol. 37, pp. 2467-2470 (2001)], N. Hamada et al. (BH) _max 358 kJ / m ³ of the same d-HDDR anisotropic Nd ₂ Fe _14. B particles were compressed at 0.9 GPa in an orientation magnetic field of 150 ° C. and 2.5 T, and a cubic (7 mm × 7 mm × 7 mm) anisotropic bond with a density of 6.51 Mg / m ³ and (BH) _max 213 kJ / m ³ Magnets [N. Hamada, C. Misima, H. Mitarai and Y. Honkura, “Development of anisotrophic bonded with 27 MGOe”, IEEE. Trans.
3-2956 (2003)] (see Non-Patent Documents 18 and 19). However, the cubic magnet is not compatible with a general permanent magnet type motor. For example, it is necessary to increase the shape-corresponding force to a permanent magnet type motor as an annular or arc-shaped magnetic anisotropic magnet having a thickness of about 1 mm.

On the other hand, in 2001, an injection molded anisotropic composite magnet of (BH) _max ˜119 kJ / m ³ using RD (Reduction & Diffusion) -Sm ₂ Fe ₁₇ N ₃ fine powder was reported [Satoshi Kawamoto, Kayo Shiraishi, Ishizaka Kazutoshi, Junichi Yasuda, “15MGOe-class SmFeN injection molding compound”, Institute of Electrical Engineers of Magnetics, (2001) MAG-01-173] (see Non-Patent Document 20). In 2002, Ohmori also reported an anisotropic composite magnet with (BH) _max 136 kJ / m ³ using (BH) _max 323 kJ / m ³ weatherable RD-Sm ₂ Fe ₁₇ N ₃ fine powder [KH] . Ohmori, “New era of anisotropic bonded SmFeN magnets”, Polymer Bonded.
Magnet 2002, Chicago (2002)] (see Non-Patent Document 21). By using a surface magnet (SPM) rotor to which an anisotropic composite magnet of Sm ₂ Fe ₁₇ N ₃ system of (BH) _max 80 kJ / m ³ by such injection molding is applied, a ferrite sintered magnet motor can be used. There are also reports that have achieved high efficiency [Atsushi Matsuoka, Togo Yamazaki, Hitoshi Kawaguchi, “Examination of high-performance brushless DC motors for blowers”, The Institute of Electrical Engineers of Japan, (2001) RM-01-161] (non- (See Patent Document 22).

However, in the radial orientation magnetic field, when the mold ring cavity is reduced in diameter (or lengthened), most of the magnetomotive force is consumed as the leakage magnetic flux, so that the orientation magnetic field is reduced. Therefore, as the degree of orientation decreases, (BH) _max decreases as the diameter decreases regardless of the composite magnet or sintered magnet [for example, Motoharu Shimizu, Nobuyuki Hirai, “Nd—Fe—B based sintering” Type anisotropic ring magnet ", Hitachi Metals Technical Report, Vol. 6, pp. 33-36 (1990)] (see Non-Patent Document 23). In addition, it is difficult to generate a homogeneous radial magnetic field, and there is a problem that productivity is lower than that of an isotropic composite magnet.

In addition, Nd ₂ Fe ₁₄ B and Sm ₂ Fe ₁₇ N ₃ anisotropic composite magnets are less isotropic and less isotropic than Nd ₂ Fe ₁₄ B isotropic composite magnets, and are isotropic There is no spread like a composite magnet.
JP-A-62-196057 R. W. Lee, E .; G. Brewer, N.M. A. Schaffel, “Hot-pressed Neodymium-Iron-Boron magnets” IEEE Trans. Magn. , Vol. 21, 1958 (1985) T.A. Shimoda, “Compression molding magnet made rapid-quenched powder”, PERMANENT MAGNETS 1988 UPDATE, Wheeler Associate INC (1988) W. Baran “Case history of NdFeB in the European community”, The European Business and Technical Outlook for NdFeB Magnets, Nov. (1989) G. X. Huang, W.H. M.M. Gao, S .; F. Yu ["Application of melt-spun Nd-Fe-B bonded magnet to the micro-motor", Proc. of the 11th International Rare-Earth Magnets and Their Applications, Pittsburgh, USA, pp. 583-595 (1990) Kasai “MQ1, 2 & 3 magnets applied to motors and actors”, Polymer Bonded Magnets T92, Embassiy Suite OTare-Rosemont, Illinois, USA (Illinois 92, USA). Yasuhiko Iriyama, “Development Trend of High Performance Rare Earth Bond Magnets”, Ministry of Education, Culture, Sports, Science and Technology Innovation Creation Project / Effective Use of Rare Earth Resources and Advanced Materials Symposium, Tokyo, pp. 19-26 (2002) B. H. Rabin, B.M. M.M. Ma, “Recent developments in Nd—Fe—B powder”, 120th Topical Symposium of the Magnetic Society of Japan, pp. 23-28 (2001) B. M.M. Ma, “Recent powder development at magneque”, Polymer Bonded Magnets 2002, Chicago (2002) S. Hirazawa, H .; Kanekiyo, T .; Miyoshi, K .; Murakami, Y .; Shigemoto, T .; Nishiuchi, “Structure and magnetic properties of Nd2Fe14B / FexB-type nanocomposite permanent magnets pre-prepared by MMM” 5G H. A. Davies, J .; I. Betancourt, C.I. L. Harland, “Nanophase Pr and Nd / Pr based rare-earth-iron-boron alloys”, Proc. of 16th Int. Works on Rare-Earth Magnets and Their Applications, Sendai, pp. 485-495 (2000) Fumitoshi Yamashita, “Application and Prospect of Rare Earth Magnets for Electronic Equipment”, Ministry of Education, Culture, Sports, Science and Technology Innovation Creation Project / Effective Utilization of Rare Earth Resources and Advanced Materials Symposium, Tokyo, (2002) Masaaki Tokunaga, “Magnetic Properties of Rare Earth Bond Magnets”, Powder and Powder Metallurgy, Vol. 35, pp. 3-7, (1988) T.A. Mukai, “Fully-dense Nd-Fe-B magnets prepared from hot-rolled anisotropic powders”, Proc. 11th Int. Workshop on Rare-earth Magnets and Ther Applications, Pittsburg, pp. 72-84 (1990) M.M. Doser, V.M. Panchanthan, and R.A. K. Misra, “Pulverizing anisotropy rapidly solidified Nd—Fe—B materials for bonded magnets”, J. Am. Appl. Phys. , Vol. 70, pp. 6603-6805 (1991) T.A. Iriyama, “Anisotropic bonded NdFeB magnets made from hot-upset powders”, Polymer Bonded Magnet 2002, Chicago (2002) T.A. Takeshita, and R.A. Nakayama, "Magnetic properties and micro-structure of the Nd-Fe-B magnet powders produced by hydrogen treatment", Proc. 10th Int. Works on Rare-earth Magnets and Ther Applications, Kyoto, pp. 551-562 (1989) K. Morimoto, R.A. Nakayama, K .; Mori, K .; Igarashi, Y. et al. Ishii, M .; Itakura, N .; Kuwano, K .; Oki, “Nd 2 Fe 14 B-based magnetic powder with high remanufactured produced by modified HDDR process”, IEEE. Trans. Magn. , Vol. 35, pp. 3253-3255 (1999) C. Misima, N .; Hamada, H .; Mitarai, and Y.M. Honkura, “Development of a Co-free NdFeB anisotropy magnet produced produced d-HDDR processes powder”, IEEE. Trans. Magn. , Vol. 37, pp. 2467-2470 (2001) N. Hamada, C.I. Misima, H .; Mitarai and Y.M. Honkura, “Development of anisotrophic bonded magnet with 27 MGOe” IEEE. Trans. Magn. , Vol. 39, pp. 2953-2956 (2003) Satoshi Kawamoto, Kayo Shiraishi, Kazutoshi Ishizaka, Junichi Yasuda, “15MGOe-class SmFeN injection molding compound”, The Institute of Electrical Engineers of Japan, (2001) MAG-01-173 K. Ohmori, “New era of anisotropic bonded SmFeN magnets”, Polymer Bonded Magnet 2002, Chicago (2002) Atsushi Matsuoka, Togo Yamazaki, Hitoshi Kawaguchi, “Examination of high performance brushless DC motor for blower”, The Institute of Electrical Engineers of Japan, (2001) RM-01-161 Motoharu Shimizu, Nobuyuki Hirai, “Nd—Fe—B sintered anisotropic ring magnet”, Hitachi Metals, Vol. 6, pp. 33-36 (1990)

  When using a permanent magnet, there are two factors that influence its performance: (1) magnitude of magnetic flux density and (2) magnetic stability.

Regarding the magnitude of the magnetic flux density of (1) above, the present inventors compression-molded a compound of a binder and a magnet powder, and mechanically stretched the inter-crosslinking macromolecule formed by self-organization of the binder. , Manufacturing technology of radial anisotropic composite magnet that controls the flexibility of plane perpendicular magnetic anisotropic thin plate magnet and changes the direction of magnetic anisotropy from vertical to radial direction by utilizing the flexibility , And (BH) _max ˜160 kJ / m ³ , the improvement of initial demagnetization by short-time high-temperature exposure by improving the squareness (Hk / HcJ) of the demagnetization curve under high-temperature exposure was disclosed [F. Yamashita, S .; Tsusumumi, H .; Fukunaga, “Radially Anisotropic Ring- or Arc-Shaped Rare-Earth Bonded Magnets Using Self-Organization Technique”, IEEE Trans. Magn. , Vol. 40, no. 4 pp. 2059-2064 (2004)]. As a result, it is possible to manufacture a radial anisotropic composite magnet in which the magnetic properties in the radial direction are hardly deteriorated even when the diameter is reduced (or lengthened).

  However, in order to apply the above-mentioned magnet to a motor, it is necessary to maintain a constant level even if the static magnetic field due to the magnetization of the magnet is exposed to a high temperature for a long period of time. It is necessary to clarify the magnetic stability over the range. External factors that disturb the magnetic stability of permanent magnets include thermal effects, mechanical stress, and external magnetic fields. However, since motors are exposed to high temperatures, it is necessary to clarify the thermal effects over a long period of time.

The change in magnetization with time is divided into two types, so-called permanent demagnetization in which the magnetic phase decreases due to structural changes such as precipitation or oxidation of a nonmagnetic phase, and irreversible demagnetization that does not depend on structural changes.

  First, as an example of the thermal effect, consider demagnetization when the temperature of the magnet rises from room temperature to high temperature and then returns to room temperature. At this time, the demagnetization caused by the structural change such as oxidation does not return to the original state while the magnetization is reduced even if re-magnetization is performed. Therefore, it is called permanent demagnetization. In order to suppress permanent demagnetization with a composite magnet using rare earth magnet powder, the magnet is generally shielded from the atmosphere with a magnet surface coating.

  On the other hand, the coercive force of a magnet in a high temperature state decreases due to the temperature change of saturation magnetization. In a finite length magnet, the direction of the magnetic moment of the magnet is reversed by the demagnetizing field, or the magnetization is reduced by the domain wall movement. This decrease in magnetization is called irreversible demagnetization because it does not recover when energy is not applied from the outside when the magnet is cooled.

  Next, consider the case where the magnet is exposed to a high temperature and the magnetization is measured at the high temperature. As in the case of measurement at room temperature, permanent demagnetization (aging) occurs due to a structural change. When the change in magnetization other than that is returned to room temperature, the decrease in magnetization due to the change in temperature of the saturation magnetization itself is a reversible change that completely returns to the initial magnetization state when returned to room temperature, and the other irreversible Divided into change. The reversible change is caused by a decrease in saturation magnetization at a high temperature, and the rate of decrease is small. Further, when the temperature is returned to room temperature, the magnetization is reversibly returned, which does not pose a major problem in the use of the magnet. The irreversible change in magnetization is usually called irreversible demagnetization.

Among irreversible demagnetization, when demagnetization due to short-time exposure to high temperature is initial demagnetization and subsequent demagnetization is long-term demagnetization, Sm ₂ Fe ₁₇ N ₃ fine particles having an average particle diameter of 1 to 5 μm according to the present invention The long-term demagnetization of an anisotropic composite magnet composed of Nd ₂ Fe ₁₄ B particles having an average particle diameter of 50 to 150 μm, a binder, and an additive that is added as necessary, and the cause thereof are clarified. It is necessary to clarify the durability of the mold motor as a magnet.

Neel is a magnetic aftereffect magnitude ΔI generated between times t ₁ and t ₂ when the change in magnetization due to thermal activation changes linearly with respect to logarithmic time in an infinite length magnet.

[L. Neel: J.M. phys. Rad. , Vol. 11, 49 (1950)]. Here, χ _irr is an irreversible magnetic susceptibility, and Sv is a magnetic aftereffect constant.

  On the other hand, in the case of a finite length magnet, the magnitude of the demagnetizing field changes due to a change in magnetization during measurement, so the effective applied magnetic field, which is the sum of the applied magnetic field and the demagnetizing field, changes. Since it is common to measure in a negative applied magnetic field with a magnet material, the effective magnetic field gradually decreases during the measurement. Therefore, it is considered that the magnetic aftereffect is smaller than that of the sample having no infinite length demagnetizing field.

In the present invention, the apparent magnetic aftereffect ΔIT before demagnetizing field correction is expressed by (Expression 2) to (Expression 4). Where N is the demagnetizing factor, μ _o is the vacuum permeability, χ _tot is the total differential susceptibility, and χ _rev is the reversible susceptibility.

The above are the equations for the change in magnetization due to magnetic aftereffect in a finite-length magnet. From these equations, demagnetization due to magnetic aftereffect can be greatly affected by the irreversible magnetic susceptibility and magnetic aftereffect constant before and after demagnetizing field correction. Recognize.

When the magnet is exposed to high temperature, magnetization reversal occurs in some crystal grains due to magnetic aftereffect. When the demagnetization at this high temperature exposure is ΔI, the magnetization at that temperature is I _w (T _EX ) −ΔIT. When the temperature is returned to room temperature from this state, the magnetization I can be set to −α (° C. ⁻¹ ) as the magnetization I _w (T _EX ) at high temperature exposure and the temperature coefficient of the residual magnetization Jr between the temperatures T _EX and T _RT.

It becomes. Therefore, the long-term irreversible demagnetization factor FLlon is

It becomes. Therefore, from the relationship between (2) and (6), the relationship between the long-term irreversible demagnetization factor FL _lon , the irreversible magnetic susceptibility χT _irr , and the magnetic aftereffect constant Sv is expressed by equation (7).

The present invention relates to a composite magnet composed of Sm ₂ Fe ₁₇ N ₃ fine particles having an average particle diameter of 1 to 5 μm, Nd ₂ Fe ₁₄ B particles having an average particle diameter of 50 to 150 μm, a binder, and additives that are appropriately added as necessary. The long-term demagnetization is quantitatively clarified by the equation (7), and with a high (BH) _max of 140 kJ / m ³ or more compared to the anisotropic composite magnets of Sm ₂ Fe ₁₇ N ₃ and Nd ₂ Fe ₁₄ B system An object of the present invention is to provide a magnet that stably generates a strong static magnetic field over a long period of time by reducing long-term demagnetization FL _lon .

The present invention relates to a composite magnet composed of Sm ₂ Fe ₁₇ N ₃ fine particles having an average particle diameter of 1 to 5 μm, Nd ₂ Fe ₁₄ B particles having an average particle diameter of 50 to 150 μm, a binder, and additives that are appropriately added as necessary. The magnetic aftereffect constant S _v at 120 ° C. is set to 3.1 kA / m or less. More preferably, the maximum energy product (BH) _max is 140 kJ / m ³ or more, and the direction of anisotropy is changed from the direction perpendicular to the plane by stretching of the inter-crosslinking macromolecule formed by self-assembly of the binder. An anisotropic composite magnet that can be changed in the radial direction.

As a result, an effect of reducing long-term demagnetization FL _lon with a high (BH) _max of 140 kJ / m ³ or more as compared with Sm ₂ Fe ₁₇ N ₃ and Nd ₂ Fe ₁₄ B-based anisotropic composite magnets, for example, A magnet useful for a permanent magnet type motor is provided.

The present invention is an anisotropy composed of Sm ₂ Fe ₁₇ N ₃ fine particles having an average particle diameter of 1 to 5 μm, Nd ₂ Fe ₁₄ B particles having an average particle diameter of 50 to 150 μm, a binder, and additives that are appropriately added as necessary. by the magnetic aftereffect constant S _v at 120 ° C. of the composite magnet than _{3.1kA / m, Sm 2 Fe 17} N 3 or Nd ₂ Fe ₁₄ 140kJ / m ³ or more in comparison with the B system anisotropic hybrid magnet This has the effect of reducing the long-term demagnetization FL _lon with a high (BH) _{max of} , and is useful for, for example, a permanent magnet type motor.

  First, the rare earth magnet powder suitable for the anisotropic composite magnet according to the present invention will be described.

The Sm ₂ Fe ₁₇ N ₃ fine powder referred to in the present invention is, for example, a melting casting method described in Japanese Patent Laid-Open No. 2-57663, a reduction disclosed in Japanese Patent No. 17025441, Japanese Patent Laid-Open No. 9-157803, and the like. An R—Fe based alloy or an R— (Fe, Co) based alloy is produced by a diffusion method, and after nitriding this, it is obtained by pulverization. The fine pulverization refers to a finely pulverized product such as a jet mill, a vibrating ball mill, a rotating ball mill, etc., which is finely pulverized so as to have a Fisher average particle size of 1.5 μm or less, preferably 1.2 μm or less. The reason why x≈3 in the intermetallic compound Sm ₂ Fe ₁₇ N _x is that the coercive force H _CJ of the fine powder shows a maximum value when x≈3. In order to improve handling properties such as prevention of ignition, fine powders are disclosed in, for example, JP-A-52-54998, JP-A-59-170201, JP-A-60-128202, JP-A-3-211203. As disclosed in Japanese Patent Laid-Open No. 46-7153, Japanese Patent Laid-Open No. 56-55503, Japanese Patent Laid-Open No. 61-154112, Japanese Patent Laid-Open No. 3-126801, etc. What formed the deoxidation film on the surface is desirable. JP-A-5-230501, JP-A-5-234729, JP-A-8-143.
No. 913, Japanese Patent Application Laid-Open No. 7-268632, outlines of lectures of the Japan Institute of Metals (Spring convention in 1996, No. 446, p184) and the like, and Japanese Patent Publication No. 6-17015 JP, 1-234502, JP 4-217024, JP 5-213601, JP 7-326508, JP 8-153613, JP 8-183601, etc. One or more kinds of surface-treated Sm ₂ Fe ₁₇ N ₃ fine powder may be used, such as a method of forming an inorganic film by the method.

On the other hand, the Nd ₂ Fe ₁₄ B particles referred to in the present invention are HDDR treatment (hydrogen decomposition / recombination), that is, hydrogenation (Hydrogenation, R) of a rare earth-iron alloy (R ₂ [Fe, Co] ₁₄ B) phase. ₂ [Fe, Co] ₁₄ BHx), phase-decomposition (decomposition, RH ₂ + Fe + Fe ₂ B) at 650 to 1000 ° C., dehydrogenation (desorption), recombination (recombination), so-called HDDR process, etc. Is preferred. If the essential element R is less than 10 atomic%, the crystal structure has the same cubic structure as that of α-Fe. Therefore, high magnetic properties, particularly high coercive force H _CJ cannot be obtained. The rich nonmagnetic phase increases and the saturation magnetization Js decreases. Therefore, R is preferably in the range of 10 to 30 atomic%. In addition, when the essential element B is less than 2 atomic%, the rhombohedral structure becomes the main phase, and a high coercive force H _CJ cannot be obtained, and when it exceeds 28 atomic%, the B-rich nonmagnetic phase increases and the saturation magnetization Js is increased. descend. Therefore, B is preferably in the range of 2 to 28 atomic%.

When the essential element Fe of the Nd ₂ Fe ₁₄ B particles is less than 65 atomic%, the saturation magnetization Js decreases, and when it exceeds 80 atomic%, a high coercive force H _CJ cannot be obtained. Therefore, the Fe content is desirably 65 to 80 atomic%. Further, replacing part of Fe with Co can improve the temperature coefficient of the residual magnetization Jr in the actual operating temperature range by increasing the Curie temperature Tc without impairing the magnetic properties of the magnet powder. However, the saturation magnetization Js decreases when the Fe substitution amount of Co exceeds 20 atomic%. That is, when the Co substitution amount is in the range of 5 to 15 atomic%, the residual magnetization Jr generally increases, which is preferable for obtaining a high (BH) _max .

Next, the reason why the Nd ₂ Fe ₁₄ B particles as described above are used in combination with the Sm ₂ Fe ₁₇ N ₃ fine powder in the present invention will be described below.

The Nd ₂ Fe ₁₄ B particles are so-called polycrystalline aggregated particles in which Nd ₂ Fe ₁₄ B crystals of 500 nm or less are aggregated, and the average particle diameter thereof is about 50 to 150 μm. The combined use of such Nd ₂ Fe ₁₄ B particles can increase the volume fraction of the magnetic powder of the anisotropic composite magnet according to the present invention, and as a result, the magnet can have a high (BH) _max .

On the other hand, when Nd ₂ Fe ₁₄ B particles are directly compression molded, they are densified while in contact with each other. Then, crushing of the particles, generation of a new surface due to generation of cracks, and surface damage due to friction are inevitable. Nd ₂ Fe ₁₄ B particles generally have no grain boundary phase. For this reason, the crystal exposed as a new surface is oxidized, the squareness (Hk / H _CJ ) of the demagnetization curve of the composite magnet is deteriorated, and the initial demagnetization rate is increased. During molding to address these challenges, Nd ₂ Fe ₁₄ B particles must be prevented from being densified with direct contact, Sm ₂ Fe ₁₇ for the N ₃ fine powder Nd ₂ Fe ₁₄ Isolate B particles.

In addition, one of the reasons why low-pressure compression molding is suitable, such as compression molding at 50 MPa or less in a magnetic field of 1 MA / m or more under the melting of the binder component, is the magnetic properties of Nd ₂ Fe ₁₄ B particles in the molding process. It is for suppressing deterioration of the.

From the above-described Sm ₂ Fe ₁₇ N ₃ fine particles having an average particle diameter of 1 to 5 μm, Nd ₂ Fe ₁₄ B particles having an average particle diameter of 50 to 150 μm, a binder, and additives appropriately added as necessary. In order to obtain an anisotropic composite magnet having a magnetic aftereffect constant S _v at 120 ° C. of 3.1 kA / m or less of the constructed composite magnet, the proportion of Sm ₂ Fe ₁₇ N ₃ fine particles in the magnet powder component is ₂₀ to 48%. It is preferable that

  Next, a more preferable binder component and manufacturing method of the anisotropic composite magnet according to the present invention will be described.

For example, 38.20 parts by weight of Sm ₂ Fe ₁₇ N ₃ fine powder, 57.44 parts by weight of Nd ₂ Fe ₁₄ B particles are coated with 1 part by weight of oligomer A, and then melt-kneaded with polymer B at 120 to 130 ° C. Cool to room temperature and coarsely pulverize to produce a compound in which 0.28 parts by weight of chemical contact C is mixed. Further, in order to enable low-pressure compression molding, for example, a mold cavity heated to 160 ° C. is filled, and compression molding is performed at a pressure of 50 MPa or less in a parallel magnetic field of 1.4 MA / m or more. Powder is produced. At this time, the volume fraction of the magnet powder was 77 vol. % Or more, a void amount of 2% or less, and a thickness of 1.35 mm or less are preferable. An increase in the magnet volume fraction is effective in improving the (BH) _max of the magnet, and 140 to 160 kJ / m ³ can be easily obtained. Also, the void volume is effective in suppressing the decrease in (BH) _max of the obtained magnet and the squareness (Hk / H _CJ ) of the demagnetization curve when the binder component is self-assembled by heating the green compact. This is because the upper limit of the thickness is effective in suppressing anisotropy change due to mechanical stretching.

  Next, the binder component of the perpendicular magnetic anisotropic thin plate compact according to the present invention is heated and self-assembled to generate an intercrosslinking macromolecule.

As described above, a high level (BH) _max and maintaining a certain level even when a static magnetic field due to magnetization of a magnet that can change the direction of anisotropy from a plane perpendicular direction to a radial direction is exposed to a high temperature for a long period of time. An anisotropic composite magnet that can be obtained is obtained.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the examples.

[Preparation of anisotropic composite magnet 1]
RD-Sm ₂ Fe ₁₇ N ₃ fine particles are weighed at a ratio of 0, 10, 20, 30, 40, 50, 60, 80, 100% to HDDR-Nd ₂ Fe ₁₄ B particles (100 g per sample) And mixed well at room temperature.

  To 97 g of the mixed magnetic powder, 2.5 g of solid novolak epoxy resin is weighed, and after making the resin 50% acetone solution, the magnetic powder and the resin solution are mixed, then heated at 70 ° C. for 30 minutes, cooled to room temperature, The granule was 350 μm or less.

  To 99.5 g of the above granules having a particle size of 350 μm or less, 0.5 g of an imidazole derivative having an average particle diameter of 3 μm and 0.2 g of calcium stearate were added and mixed to obtain a compound.

  Next, in an orthogonal magnetic field of 1.4 MA / m, a cube of 8 mm at a temperature of 150 to 160 ° C. and a pressure of 0.6 GPa, and heat-cured at 140 ° C. for 15 minutes and applied to the present invention or anisotropy for comparison A composite magnet was used.

[Long-term demagnetization, irreversible magnetic susceptibility, magnetic aftereffect constant]
FIG. 1 shows that the RD-Sm ₂ Fe ₁₇ N ₃ fine particles are produced at a ratio of 0, 10, 20, 30, 40, 50, 60, 80, 100% with respect to HDDR-Nd ₂ Fe ₁₄ B particles. long demagnetization FL _lon of isotropic composite magnet, Figure 2 shows the irreversible susceptibility KaiT _irr, magnetic aftereffect constant Sv.

However, the long-term demagnetization rate FL _lon is obtained by magnetizing an 8 mm cubic magnet with a pulse magnetic field of 4 MA / m, from the magnetic flux φ ₁ after exposure at 120 ° C. for 1 hour and the magnetic flux φ ₂ after exposure for 300 hours to [(φ ₁ was determined from -φ ₂₎ / φ _1]. The magnetic flux is measured by the search coil drawing method.

On the other hand, total differential magnetic susceptibility χT _tot and reversible magnetic susceptibility χT _rev were measured by VSM. The demagnetization curve at a high temperature was measured as shown in FIG. 3, the irreversible magnetic susceptibility χT _irr was calculated from the equation (4), and the magnetic aftereffect constant Sv was calculated from the equation (3).

FIG. 3 schematically shows a demagnetization curve at a high temperature before demagnetizing field correction. First, on the demagnetization curve, the magnetic field is held for 1000 seconds with the magnetic field H1 near the operating point. Magnetization decreases from point a to point b due to magnetic aftereffect. Next, the magnetic field is increased to H2 (about 800 kA / m) (from b to c), and the magnetic field is held again for 1000 seconds. Also at the point c, a change due to the magnetic aftereffect occurs as in the case of a to b, and the magnetization moves from the point c to the point d. The reversible magnetic susceptibility χT _rev was obtained from the slope of the straight line connecting points b and d. The magnetic field is reduced to H1 and held for 1000 seconds. The total differential magnetic susceptibility χT _tot was obtained as the slope of the straight line bf by changing the magnetic field to H3 and holding it for 1000 sec.

As is clear from FIG. 1, the long-term demagnetization FL _lon of the anisotropic composite magnet according to the present invention varies depending on the proportion of Sm ₂ Fe ₁₇ N ₃ fine particles. First, the long-term demagnetization FL _{lon in} the region where the ratio of Sm ₂ Fe ₁₇ N ₃ fine particles is up to 30% is reduced according to the amount of Sm ₂ Fe ₁₇ N ₃ fine particles. However, when it exceeds 40%, it starts to increase, and at about 60%, it is equivalent to the case where the Sm ₂ Fe ₁₇ N ₃ fine particles are zero, and when the Sm ₂ Fe ₁₇ N ₃ fine particles increase further, the long-term demagnetization FL _lon deteriorates. .

On the other hand, there is a trade-off between the irreversible susceptibility KaiT _irr magnetic aftereffect constant Sv anisotropic hybrid magnet with respect to the proportion of Sm ₂ Fe ₁₇ N ₃ fine particles Looking at FIG. The irreversible magnetic susceptibility χT _irr is linearly approximated with respect to the ratio of Sm ₂ Fe ₁₇ N ₃ fine particles, but the magnetic aftereffect constant Sv (kA / m) is 4 × 10 ⁶ C ³ −2 × 10 ⁴ C ^2. A polynomial approximation of + 0.0436C + 1.0389 is established (correlation coefficient is 0.9947).

From the above, the Sm ₂ Fe ₁₇ N ₃ fine particles reduce the long-term demagnetization FL _lon from the decrease in the irreversible magnetic susceptibility χT _irr of the anisotropic composite magnet. On the other hand, it is understood that the effect of reducing the long-term demagnetization FL _lon disappears when the magnetic aftereffect constant Sv is increased and exceeds a certain value.

By the way, isotropic composite magnets (alloy composition Nd _4.19 Fe _76.88 B _18.93 , Nd _4.75 Fe _72.76 Co _3.01 B _18.50 Ga _0.98 , Nd _3.81 Dy _1.05 Fe _72.07 Co _3.05 B ₁₈₉ Ga _1.02 , Nd _5.28 Fe _69.48 Co _3.02 B _19.19 Cr _3.03 , Nd _5.83 Fe _65.3 Co _4.94 B _18.91 Cr _5.02 , Nd ₁₂ Fe ₇₇ Co ₅ B ₆ ) represents the long-term irreversible demagnetization FL _lon after 1 hr exposure to high temperature (7) The irreversible demagnetization rate per logarithmic time dFL on the left side of equation (7) / D {ln (t _a )} mainly depends on the irreversible magnetic susceptibility χT _irr . In addition, the magnetic aftereffect constant Sv of all the samples measured at 80 and 120 ° C. is approximately constant at about 2.3 kA / m [Y. Kanai, S .; Hayashida, H .; Fukunaga, F.A. Yamashita, “Flux loss in Nano-composite Magnets”, IEEE Trans. Magn. , Vol. 35. No. 5. pp. 3292-3294 (1999)].

On the other hand, the magnetic aftereffect constant Sv of an isotropic composite magnet (alloy composition Nd _12.2 Fe ₇₇ Co _5.4 B _5.4 ) at 20 to 120 ° C. is 2.6 to 3.1 kA / m [[H. Nishio and
H. Yamamoto: J. Mag. Soc. Jpn. , Vol. 16, 131 (1992)].

That is, it is composed of Sm ₂ Fe ₁₇ N ₃ fine particles having an average particle diameter of 1 to 5 μm, Nd ₂ Fe ₁₄ B particles having an average particle diameter of 50 to 150 μm, a binder, and an additive that is appropriately added as necessary. The magnetic aftereffect constant S _v at 120 ° C. of the anisotropic composite magnet needs to be 3.1 kA / m or less.

That is, the ratio C of Sm ₂ Fe ₁₇ N ₃ fine particles in FIG. 2 and the Sv polynomial approximation Sv = 4 × 10 ⁶ C ³ −2 × 10 ⁴ C ² +0.0436 C + 1.0389 to Sv = 3.1 kA / m C Is about 48, and the ratio of Sm ₂ Fe ₁₇ N ₃ fine particles in which the magnetic aftereffect constant Sv of the anisotropic composite magnet according to the present invention is 3.1 kA / m or less is 48% or less.

FIG. 4 is a characteristic diagram showing (BH) _max and long-term demagnetization FL _lon with respect to the ratio of Sm ₂ Fe ₁₇ N ₃ fine particles. As apparent from FIG, Sm ₂ Fe ₁₇ N ₃ fine particles having a mean particle size of 1~5μm of Sm ₂ Fe ₁₇ N ₃ fine particles according to the present invention the ratio was less than 48%, an average particle diameter of 50 to 150 [mu] m Nd ₂ An anisotropic composite magnet composed of Fe ₁₄ B particles, a binder, and an additive that is added as needed is used as an Sm ₂ Fe ₁₇ N ₃ or Nd ₂ Fe ₁₄ B single anisotropic composite magnet. In comparison, a high (BH) _max value of 140 kJ / m ³ or more can be obtained, and the long-term demagnetization FL _lon can be reduced.

  The anisotropic composite magnet of the present invention is useful for a permanent magnet type motor that is operated in an environment exposed to a high temperature for a long period of time.

Characteristic diagram showing long-term demagnetization FL _lon of anisotropic composite magnet Characteristic diagram showing irreversible magnetic susceptibility χ ^T _irr and magnetic _aftereffect constant Sv Schematic diagram of demagnetization curve at high temperature before demagnetization correction (BH) Characteristic chart showing _max and long-term demagnetization FL _lon

Explanation of symbols

(BH) _max maximum energy product FL _lon long-term demagnetization

Claims (1)

A magnet composed of Sm2Fe17N3 fine particles having an average particle diameter of 1 to 5 μm, Nd2F14B particles having an average particle diameter of 50 to 150 μm, a binder, and additives that are appropriately added as necessary, and the content ratio of Sm2Fe17N3 fine particles is 20 to 48 An anisotropic composite magnet that is compression molded at 50 MPa or less in a parallel magnetic field of 1.4 MA / m or more and has a magnetic aftereffect constant Sv at 120 ° C. of 3.1 kA / m or less.