JP2011211056A - Rare earth sintered magnet, motor, and automobile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rare earth sintered magnet excellent in residual magnetic flux density and coercive force, especially in the coercive force, and having a high squareness ratio, and also to provide a motor and automobile using the rare earth sintered magnet.SOLUTION: A rare earth sintered magnet 10 is equipped with a group of main phase particles 2 of an R-T-B rare earth magnet, each of which has a core 4 and a shell 6 covering the core 4, wherein R contains a heavy rare earth element and a light rare earth element, and a heavy rare earth Cu compound and a light rare earth Cu compound exist on a two-particle boundary in the main phase particle 2 group. In the rare earth sintered magnet 10, a mass ratio of the heavy rare earth compound to the right rare earth Cu compound on the two-particle boundary of a position of 0.3 mm depth from the surface of the rare earth sintered magnet 10, is equal to or less than five times, the mass ratio of the heavy rare earth compound to the light rare earth Cu compound on the two-particle boundary of a position of 1.5 mm depth from the surface of the rare earth sintered magnet 10.

Description

  The present invention relates to a rare earth sintered magnet, a motor, and an automobile.

  A rare earth magnet having a R-T-B (R is a rare earth element, T is a metal element such as Fe) series composition is a magnet having excellent magnetic properties, and particularly its magnetic properties, particularly residual magnetic flux density (Br) and Many studies have been made with the aim of further improving the coercive force (HcJ) (for example, Patent Document 1).

International Publication No. 2006/43348 Pamphlet

  Here, as a magnetic characteristic of the magnet, the squareness ratio (Hk / HcJ) is one of the important elements. However, the conventional rare earth sintered magnet described in the above-mentioned Patent Document 1 has a squareness ratio. There is room for improvement.

  Therefore, an object of the present invention is to provide a rare earth sintered magnet having excellent residual magnetic flux density and coercive force, particularly coercive force, and having a high squareness ratio, and a motor and an automobile using the rare earth sintered magnet.

  In order to achieve the above object, a rare earth sintered magnet of the present invention comprises a main phase particle group of an R-T-B system rare earth magnet having a core and a shell covering the core, wherein R is a heavy rare earth element (RH). ) And a light rare earth element (RL), and a rare earth sintered magnet having a heavy rare earth Cu compound and a light rare earth Cu compound at the two-particle interface in the main phase particle group, and having a depth of 0 from the surface of the rare earth sintered magnet. The mass ratio (RHCu/RLCu@0.3 mm) of the heavy rare earth compound (RHCu) to the light rare earth Cu compound (RLCu) at the 2-particle interface at a position of 3 mm is 1.5 mm deep from the surface of the rare earth sintered magnet. The mass ratio of the heavy rare earth compound to the light rare earth Cu compound at the two-particle interface at the position (RHCu/RLCu@1.5 mm) is greater than 1 and less than 5 times. The main phase particle group means a plurality of main phase particles. Further, a portion where the ratio of heavy rare earth element to light rare earth element (heavy rare earth element / light rare earth element) is more than twice the ratio in the main phase particle center (core) is defined as a shell.

  The rare earth sintered magnet of the present invention is excellent in residual magnetic flux density and coercive force, particularly coercive force, and has a high squareness ratio.

  In the rare earth sintered magnet, the oxygen element content in the rare earth sintered magnet may be 2500 ppm or less. The particle size of the main phase particles may be 3.0 μm or more and 6.5 μm or less. The rare earth sintered magnet may contain a Ga element in a content ratio of 0.05% by mass or more and 0.40% by mass or less. The thickness of the shell may be 500 nm or less.

  The motor of the present invention includes the rare earth sintered magnet of the present invention.

  When the residual magnetic flux density, coercive force and squareness ratio of the rare earth sintered magnet of the present invention are high, the volume and shape of the sintered magnet of the present invention are the same as those of the conventional R-T-B rare earth sintered magnet The number of magnetic fluxes of the sintered magnet of the present invention is increased as compared with the prior art. Therefore, according to the motor provided with the sintered magnet of the present invention, the energy conversion efficiency is improved as compared with the conventional case.

  Even if the volume of the rare earth sintered magnet of the present invention is smaller than that of the conventional RTB-based rare earth sintered magnet, the rare earth sintered magnet of the present invention has a high residual magnetic flux density, coercive force and squareness ratio. Has the same number of magnetic fluxes as a conventional magnet. That is, the rare earth sintered magnet of the present invention can be reduced in size without reducing the number of magnetic fluxes as compared with the conventional magnet. As a result, according to the present invention, the yoke volume and the amount of winding are also reduced in accordance with the size reduction of the sintered magnet, so that the motor can be reduced in size and weight. Furthermore, since the rare earth sintered magnet of the present invention has a high squareness ratio, high temperature demagnetization can be suppressed.

  The automobile of the present invention includes the motor of the present invention. That is, the automobile of the present invention is driven by the motor of the present invention. In the present invention, the automobile is, for example, an electric vehicle, a hybrid vehicle, or a fuel cell vehicle driven by the motor of the present invention.

  Since the automobile of the present invention is driven by the motor of the present invention, which has higher energy conversion efficiency than before, its fuel efficiency is improved. In the automobile of the present invention, as described above, the motor can be reduced in size and weight, so that the automobile itself can be reduced in size and weight. As a result, the fuel efficiency of the automobile is improved.

  According to the present invention, it is possible to provide a rare earth sintered magnet having excellent residual magnetic flux density and coercive force, particularly coercive force and having a high squareness ratio, and a motor and an automobile using the rare earth sintered magnet.

FIG. 1 is a schematic cross-sectional view of a rare earth sintered magnet according to an embodiment of the present invention. FIG. 2 is a flowchart showing manufacturing steps of a magnet (rare earth magnet) according to a preferred embodiment. FIG. 3 is a diagram showing an internal structure of a motor according to an embodiment of the present invention. FIG. 4 is a conceptual diagram of an automobile according to an embodiment of the present invention. Fig.5 (a) is a graph which shows the element distribution in the vicinity of the two-particle interface measured using TEM-EDS, and FIG.5 (b) is the result of having analyzed the NdCu part. FIGS. 6A and 6B are diagrams showing the results of line analysis using STEM-EDS for the base material and the rare earth sintered magnet, respectively.

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the drawings.

(Rare earth sintered magnet)
FIG. 1 shows an analysis of a rare earth sintered magnet (hereinafter, also simply referred to as “magnet”) manufactured in an example using an energy dispersive X-ray spectrometer (STEM-EDS) included in a scanning transmission electron microscope. 3 is a schematic cross-sectional view of a rare earth sintered magnet according to an embodiment of the present invention created based on the results.

  Rare earth sintered magnet 10 includes a plurality of main phase particles 2 and a grain boundary phase 8 of a group of main phase particles 2. The main phase particle 2 includes a core 4 and a shell 6 that covers the core 4. Of the grain boundary phase 8, a portion particularly between two main phase particles 2 is called a two-particle interface.

The main phase particle 2 is composed of an R-T-B rare earth magnet (for example, R ₂ T ₁₄ B). The rare earth element R includes a light rare earth element and a heavy rare earth element. The light rare earth element may be at least one selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, and Eu. The heavy rare earth element may be at least one selected from the group consisting of Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. The metal element T contains Fe and Co.

  In the present embodiment, the portion where the ratio of heavy rare earth element to light rare earth element (heavy rare earth element / light rare earth element) is at least twice the ratio in the central part (core) of the main phase particle is defined as the shell. .

  The thickness of the shell 6 is 500 nm or less, more preferably 300 nm or less. Moreover, the particle size of the main phase particles 2 is preferably 3.0 to 6.5 μm.

  The grain boundary phase 8 contains a heavy rare earth Cu compound and a light rare earth Cu compound. The mass ratio (RHCu/RLCu@0.3 mm) of the heavy rare earth compound (RHCu) to the light rare earth Cu compound (RLCu) at the two-particle interface at a depth of 0.3 mm from the surface of the rare earth sintered magnet The mass ratio of the heavy rare earth compound to the light rare earth Cu compound (RHCu/RLCu@1.5 mm) at the two-particle interface at a depth of 1.5 mm from the surface of the magnet is greater than 1 and less than 5 times.

  This index means that RHCu diffuses not only to the two-particle interface on the surface of the magnet but also to the inner two-particle interface. Thereby, it is considered that the magnet of the present embodiment has a small difference in coercive force depending on the depth, and a good squareness ratio can be obtained.

  RHCu / RLCu can be obtained as follows. First, using STEM-EDS (Scanning Transmission Electron Microscopy-Energy Dispersive X-ray Spectroscopy), the amount of rare earth element (R) (% by mass) and the amount of Cu (% by mass) are measured while linearly scanning the vicinity of the two-particle interface. taking measurement.

  The spot diameter of the electron beam on the measurement sample surface is preferably 5.0 nm or less, particularly 1.0 nm or less. By doing so, it is possible to measure the element distribution at the interface between two thin particles. The measurement step (the interval between adjacent measurement points) is preferably 5.0 nm or less, particularly 2.0 nm or less. If this measurement step is large, highly accurate element distribution measurement becomes difficult.

  When RH and RL coexist, line analysis is performed at 20 locations at 0.3 mm and 1.5 mm positions from the surface, and the RLCu number and RHCu number are counted in consideration of the mixing ratio, and RHCu / RLCu Is calculated.

  (RHCu/RLCu@0.3 mm) in the sintered body is larger than 1 time and smaller than 5 times (RHCu/RLCu@1.5 mm). When (RHCu/RLCu@0.3 mm) is 1 time (RHCu/RLCu@1.5 mm), it is suggested that heavy rare earth is not diffused from the magnet surface. If it is 5 times or more, the diffusion of heavy rare earth elements in the depth direction is insufficient, and the concentration of heavy rare earth near the surface is high, so the squareness ratio is greatly reduced.

  The two-particle interface preferably further contains a Ga compound. Thereby, the wettability of the grain boundary phase 8 is improved, and the penetration of the grain boundary phase into the two-particle interface is promoted.

  The content of oxygen element in the sintered body is preferably 2500 mass ppm or less, and more preferably 1000 ppm or less. The smaller the amount of oxygen, the fewer impurities in the resulting sintered magnet, and the magnetic properties of the sintered magnet are improved. When the amount of oxygen is large, the oxide in the sintered body tends to prevent diffusion of heavy rare earth elements, and the shell 6 tends not to be formed. As a method for reducing the oxygen content in the sintered body, it is possible to maintain the raw material alloy in an atmosphere having a low oxygen concentration from hydrogen storage and pulverization to sintering. However, even if the oxygen content in the sintered body is outside the above range, the sintered magnet of this embodiment can be produced.

The rare earth sintered magnet of the present embodiment may further include other elements such as Ni, Mn, Al, Zr, Nb, Ti, W, Mo, V, Zn, Si, O, and C as necessary. For example, R: 29.0-33.0 mass%,
B: 0.85-0.98 mass%,
Al: 0.03-0.25 mass%,
Cu: 0.01 to 0.15 mass%,
Zr: 0.03 to 0.25% by mass,
Co: 3% by mass or less (excluding 0% by mass),
Ga: 0.05-0.40 mass%,
O: 2500 ppm or less (excluding 0 ppm),
C: 500 ppm to 1500 ppm,
Fe: balance,
It can have the composition which consists of.

  The particle size of the main phase particles in the sintered body is preferably 3.0 μm or more and 6.5 μm or less. If the particle size is less than 3.0 μm, surface oxidation, carbonization, etc. are promoted by increasing the particle surface area, resulting in an increase in impurities in the sintered body and a tendency to suppress the diffusion of heavy rare earth elements. is there. On the other hand, when the particle size is larger than 6.5 μm or more, the coercive force of the rare earth sintered magnet before diffusing the heavy rare earth decreases, and even if the heavy rare earth element is diffused, the effect of improving the coercive force decreases.

(Production method of rare earth sintered magnet)
FIG. 2 is a flowchart showing manufacturing steps of a magnet (rare earth magnet) according to a preferred embodiment.

  In the production of the rare earth magnet of this embodiment, first, an alloy is prepared so that a rare earth magnet having a desired composition can be obtained (step S11). In this process, for example, a simple substance, an alloy, a compound, or the like containing an element such as a metal corresponding to the composition of the rare earth magnet is dissolved in an inert gas atmosphere such as vacuum or argon, and then used for casting or stripping. An alloy having a desired composition is manufactured by performing an alloy manufacturing process such as a casting method.

  Two types of alloys can be used: an alloy having a composition constituting the main phase in the rare earth magnet (main phase alloy) and an alloy having a composition constituting the grain boundary phase (grain boundary phase alloy). When two types of alloys are used in this way, the ratio (RL: RH) of light rare earth metal (RL) to heavy rare earth metal (RH) in the grain boundary phase alloy is 50:50 to 100: 0. It is preferable to do.

  Next, the obtained alloy is coarsely pulverized to obtain particles having a particle size of about several hundred μm (step S12). The coarse pulverization of the alloy is performed by using a coarse pulverizer such as a jaw crusher, a brown mill, a stamp mill, or the like. It can be performed by causing pulverization (hydrogen occlusion pulverization).

  Subsequently, by further finely pulverizing the powder obtained by coarse pulverization (step S13), the raw material powder of a rare earth magnet having a particle diameter of preferably about 1 to 10 μm, more preferably about 3 to 6 μm (hereinafter simply referred to as “ The raw material powder ") is obtained. Fine pulverization is performed by further pulverizing the coarsely pulverized powder using a fine pulverizer such as a jet mill, a ball mill, a vibration mill, and a wet attritor while appropriately adjusting conditions such as pulverization time. To do.

  When two types of main phase alloy and grain boundary phase alloy are prepared in the production of the alloy, coarse pulverization and fine pulverization are performed for each alloy, and the two types of fine powder obtained thereby are mixed. The raw material powder may be prepared by this.

  Next, the raw material powder obtained as described above is formed into a target shape (step S14). The molding is performed while applying a magnetic field, thereby causing the raw material powder to have a predetermined orientation. The molding can be performed, for example, by press molding. Specifically, the raw material powder can be formed into a predetermined shape by filling the raw material powder into the mold cavity and then pressing the filled powder between the upper punch and the lower punch. The shape of the molded body obtained by molding is not particularly limited, and can be changed according to the desired shape of the rare earth magnet, such as a columnar shape, a flat plate shape, or a ring shape. The pressing at the time of molding is preferably performed at 50 to 200 MPa. The applied magnetic field is preferably 950 to 1600 kA. In addition, as a forming method, in addition to dry forming in which the raw material powder is formed as it is, wet forming in which a slurry in which the raw material powder is dispersed in a solvent such as oil is formed can be applied.

  Next, the molded body is fired, for example, by performing a treatment in vacuum or in the presence of an inert gas at 1010 to 1110 ° C. for 2 to 6 hours (step S15). Thereby, the raw material powder undergoes liquid phase sintering, and a sintered body (sintered body of rare earth magnet) in which the volume ratio of the main phase is improved is obtained.

  The sintered body is preferably subjected to surface treatment for treating the surface of the sintered body with an acid solution, for example, after being appropriately processed into a desired size and shape (step S16). As the acid solution used for the surface treatment, a mixed solution of an aqueous solution such as nitric acid or hydrochloric acid and an alcohol is suitable. This surface treatment can be performed, for example, by immersing the sintered body in an acid solution or spraying the acid solution on the sintered body.

  By such surface treatment, dirt, oxide layer, etc. adhering to the sintered body can be removed to obtain a clean surface, and adhesion and diffusion of the heavy rare earth compound described later are advantageous. From the viewpoint of performing better removal of dirt and oxide layers, surface treatment may be performed while applying ultrasonic waves to the acid solution.

Thereafter, a heavy rare earth compound containing a heavy rare earth element is adhered to the surface of the sintered body that has been subjected to the surface treatment (step S17). The heavy rare earth element contained in the heavy rare earth compound is preferably Dy or Tb from the viewpoint of obtaining a rare earth sintered magnet having a high coercive force. Examples of heavy rare earth compounds include hydrides, oxides, halides, and hydroxides of heavy rare earth elements. Of these heavy rare earth compounds, DyH ₂ , DyF ₃ or TbH ₂ is preferred.

  The heavy rare earth compound to be adhered to the sintered body is preferably in the form of particles, the average particle diameter is preferably 100 nm to 50 μm, more preferably 1 μm to 10 μm, and even more preferably 1 to 5 μm, It is still more preferable that it is 1-3.5 micrometers. If the particle size of the heavy rare earth compound is less than 100 nm, the amount of the heavy rare earth compound diffused into the sintered body by the heat treatment becomes excessively large, and the resulting rare earth magnet may have insufficient Br. On the other hand, if it exceeds 50 μm, diffusion of the heavy rare earth compound into the sintered body becomes difficult to occur, and the effect of improving HcJ may not be sufficiently obtained. In particular, when the average particle size of the heavy rare earth compound is 5 μm or less, adhesion of the heavy rare earth compound to the sintered body is advantageous, and a higher HcJ improvement effect tends to be obtained.

  Examples of the method for attaching the heavy rare earth compound to the sintered body include, for example, a method in which particles of the heavy rare earth compound are directly sprayed on the sintered body, a method in which a solution in which the heavy rare earth compound is dissolved in a solvent is applied to the sintered body, Examples include a method of applying a slurry in which compound particles are dispersed in a solvent to a sintered body. Especially, the method of apply | coating a slurry to a sintered compact is preferable from the fact that a heavy rare earth compound can adhere uniformly to a sintered compact, and also the diffusion by the heat processing mentioned later arises favorably.

  Moreover, when apply | coating a slurry to a sintered compact, the method of immersing a sintered compact in a slurry and the method of putting a sintered compact in a slurry and stirring with a predetermined medium are mentioned, for example. As the latter method, for example, a ball mill method can be applied. By stirring together with the media in this way, the adhesion of the heavy rare earth compound to the sintered body can be more reliably generated, and the amount of heavy rare earth compound deposited can be stabilized by reducing the dropout after the adhesion. It becomes possible to do. Moreover, it becomes possible to process a large amount of sintered bodies at a time by such a method. Depending on the shape of the sintered body, the former method of immersion may be more advantageous for adhesion, so in practice, both methods may be appropriately selected and used.

  As the solvent used in the slurry, those that can be uniformly dispersed without dissolving the heavy rare earth compound are preferable, and examples thereof include alcohols, aldehydes, and ketones, and alcohols are particularly preferable. Moreover, application | coating of the slurry to a sintered compact can be performed by immersing a sintered compact in a slurry, or dropping a slurry on a sintered compact.

  When using a slurry, the content of the heavy rare earth compound in the slurry is preferably 10 to 60% by mass, and more preferably 40 to 50% by mass. If the content of the heavy rare earth compound in the slurry is too small or too large, the heavy rare earth compound tends to be difficult to uniformly adhere to the sintered body, and it may be difficult to obtain a sufficient squareness ratio. Moreover, when there are too many, the surface of a sintered compact may become rough and formation of plating etc. for improving the corrosion resistance of the magnet obtained may become difficult.

  In addition, you may further contain components other than a heavy rare earth compound in a slurry as needed. Examples of other components that may be contained in the slurry include a dispersant for preventing aggregation of particles of the heavy rare earth compound.

  Although the heavy rare earth compound adheres to the sintered body by the method as described above, the amount of such heavy rare earth compound attached may be within a certain range from the viewpoint of obtaining particularly good magnetic property improvement effect. preferable. Specifically, the adhesion amount (adhesion rate;%) of the heavy rare earth compound to the mass of the rare earth magnet (total mass of the sintered body and the heavy rare earth compound) is preferably 0.1 to 3% by mass, 0 More preferably, it is 1-2 mass%, and it is further more preferable that it is 0.2-1 mass%.

  Subsequently, heat treatment is performed on the sintered body to which the heavy rare earth compound is adhered (step S18). As a result, the heavy rare earth compound adhering to the surface of the sintered body diffuses into the sintered body. The heat treatment can be performed in, for example, a two-stage process. In this case, it is preferable to perform the heat treatment at about 800 to 1000 ° C. for 10 minutes to 10 hours in the first stage and to perform the heat treatment at about 500 to 600 ° C. for 1 to 4 hours in the second stage. In such a two-stage heat treatment, for example, the heavy rare earth compound is mainly diffused in the first stage, and the second-stage heat treatment becomes a so-called aging treatment and contributes to the improvement of magnetic properties (particularly HcJ). Note that the heat treatment is not necessarily performed in two stages, and may be performed so that at least diffusion of the heavy rare earth compound occurs.

  The heat treatment causes diffusion of the heavy rare earth compound from the surface to the inside of the sintered body. At this time, the heavy rare earth compound mainly follows the boundary of the main phase particles constituting the sintered body and the grain boundary phase. It is thought to spread. As a result, in the obtained magnet, heavy rare earth elements derived from heavy rare earth compounds are unevenly distributed in the outer edge region and grain boundary phase of the main phase particles, thereby covering the main phase particles with the layer of heavy rare earth elements. Such a structure is formed.

  Thereafter, the sintered body in which the heavy rare earth compound is diffused is cut to a desired size or subjected to a surface treatment as necessary to obtain a target rare earth magnet. In addition, the obtained rare earth magnet may further be provided with a protective layer for preventing deterioration of a plated layer, an oxide layer, a resin layer, or the like on the surface.

(motor)
FIG. 3 is an explanatory diagram showing an example of the internal structure of the motor of this embodiment. The motor 100 of the present embodiment is a permanent magnet synchronous motor (IPM motor), and includes a cylindrical rotor 20 and a stator 30 disposed outside the rotor 20. The rotor 20 is housed in a cylindrical rotor core 22, a plurality of magnet housing portions 24 that house the rare earth sintered magnet 10 at predetermined intervals along the outer peripheral surface of the cylindrical rotor core 22, and the magnet housing portion 24. A plurality of rare earth sintered magnets 10.

  The rare earth sintered magnets 10 adjacent to each other in the circumferential direction of the rotor 20 are accommodated in the magnet accommodating portion 24 so that the positions of the N pole and the S pole are opposite to each other. Thereby, the rare earth sintered magnets 10 adjacent along the circumferential direction generate lines of magnetic force in opposite directions along the radial direction of the rotor 20.

  The stator 30 has a plurality of coil portions 32 provided at predetermined intervals along the outer peripheral surface of the rotor 20. The coil portion 32 and the rare earth sintered magnet 10 are disposed so as to face each other. The stator 30 applies torque to the rotor 20 by electromagnetic action, and the rotor 20 rotates in the circumferential direction.

  The IPM motor 100 includes the rare earth sintered magnet 10 according to the above embodiment in the rotor 20. The rare earth sintered magnet 10 has an excellent magnetic property and a plating film that does not easily peel off. For this reason, the IPM motor 100 is excellent in reliability. The IPM motor 100 can maintain a high output for a longer period than before. The IPM motor 100 can be manufactured by an ordinary method using ordinary motor parts except for the rare earth sintered magnet 10.

  In the case of a permanent magnet synchronous motor, the motor of the present invention is not limited to an IPM motor, and may be an SPM motor. In addition to the permanent magnet synchronous motor, a permanent magnet DC motor, a linear synchronous motor, a voice coil motor, and a vibration motor may be used.

(Car)
FIG. 4 is a conceptual diagram showing a power generation mechanism, a power storage mechanism, and a drive mechanism of an automobile according to the present embodiment. However, the structure of the automobile according to the present embodiment is not limited to that shown in FIG. As shown in FIG. 4, the automobile 50 according to the present embodiment includes the motor 100, the wheels 48, the storage battery 44, the generator 42, and the engine 40 of the present embodiment.

  Mechanical energy generated in the engine 40 is converted into electric energy by the generator 42. This electrical energy is stored in the storage battery 44. The stored electrical energy is converted into mechanical energy by the motor 100. The mechanical energy from the motor 100 rotates the wheels 48 and drives the automobile 50.

Example 1
First, a raw material metal for a rare earth magnet was prepared, and the composition of the base material of Example 1 shown in Table 1 (23.50 wt% Nd-1.50% Dy-7.00 wt% Pr-0.90) was prepared by using a strip casting method. The raw material alloy was prepared so as to obtain wt% Co-0.20wt% Al-0.10wt% Cu-0.10wt% Ga-0.97wt% B-bal.Fe). Next, after hydrogen was occluded in the obtained alloy, hydrogen crushing treatment was performed in which dehydrogenation was performed at 600 ° C. for 1 hour in an Ar atmosphere. Subsequently, the powder after the hydrogen pulverization treatment was further pulverized to obtain a raw material powder having an average particle diameter (D50) of 3.2 μm.

  This raw material powder was filled in a mold placed in an electromagnet and molded in a magnetic field to produce a molded body. In molding, the raw material powder was pressurized at 120 MPa while applying a magnetic field of 1200 kA / m to the raw material powder.

  The molded body was sintered at 980 to 1060 ° C. in vacuum for 4 hours, and then rapidly cooled to obtain a sintered body. In addition, each process from a hydrogen crushing process to sintering was performed in the atmosphere whose oxygen concentration is less than 100 ppm.

  The sintered body was processed into 5 mm (magnetic anisotropic direction) × 15 mm × 6 mm. The sintered body after processing was subjected to two stages of heat treatment to obtain a substrate 1. In the first stage heat treatment, the sintered body was heated at 900 ° C. for 6 hours in an Ar atmosphere. In the second heat treatment, the sintered body was heated at 540 ° C. for 2 hours in an Ar atmosphere.

Further, separately from the base material 1, the DyH ₂ powder was applied to the entire surface by the dipping method on the sintered body after the above processing, and then subjected to the same two-stage heat treatment as described above, and the rare earth sintered magnet of Example 1 Was made. In the application, the weight of the DyH ₂ powder with respect to the application area was set to 4.7 mg / cm ² .

(Examples 2-4, Comparative Examples 1-4)
Except that the average particle diameter of the raw material powder and the oxygen content in the sintered body were changed as shown in Table 1, in the same manner as in Example 1, the substrates 2 to 8 and Examples 2 to 4 and Comparative Examples 1 to 4 rare earth sintered magnets were produced.

(Example 5)
Rare earth sintering of Example 5 in the same manner as in Example 1 except that Dy was vapor deposited using a Dy alloy (including pure Dy) as a vapor deposition source instead of applying DyH ₂ powder to the sintered body after processing. A magnet was produced.

(Example 6)
Rare earth sintering of Example 6 in the same manner as Example 2 except that Dy was vapor deposited using a Dy alloy (including pure Dy) as a vapor deposition source instead of applying DyH ₂ powder to the sintered body after processing. A magnet was produced.

(Comparative Example 5)
A main phase alloy having the composition of 24.7wt% Nd-7.4wt% Pr-0.9wt% Co-0.2wt% Al-0.03wt% Cu-0.1wt% Ga-1.02wt% B-bal.Fe was prepared by strip casting. did. A grain boundary phase alloy having a composition of 30 wt% Dy-0.2 wt% Al-1.4 wt% Cu-bal.Fe was prepared by strip casting. Next, after blending the main phase alloy and the grain boundary phase alloy in a mass ratio of 95: 5, hydrogen crushing treatment is performed and further pulverized to obtain a raw material powder having an average particle diameter (D50) of 3.2 μm. It was. In addition, by blending the main phase alloy and the grain boundary phase alloy at such a mass ratio, 23.50 wt% Nd-1.50% Dy-7.00 wt% Pr-0.90 wt% Co-0.20 wt% Al-0.10 wt% Cu A sintered body having a composition of -0.10 wt% Ga-0.97 wt% B-bal.Fe is obtained.

  This raw material powder was filled in a mold placed in an electromagnet and molded in a magnetic field to produce a molded body. In molding, the raw material powder was pressurized at 120 MPa while applying a magnetic field of 1200 kA / m to the raw material powder.

  The molded body was sintered at 980 to 1060 ° C. in vacuum for 4 hours, and then rapidly cooled to obtain a sintered body. In addition, each process from a hydrogen crushing process to sintering was performed in the atmosphere whose oxygen concentration is less than 100 ppm.

  The sintered body was processed into 5 mm (magnetic anisotropic direction) × 15 mm × 6 mm. The sintered body after processing was subjected to two stages of heat treatment to obtain a base material 9. In the first stage heat treatment, the sintered body was heated at 900 ° C. for 6 hours in an Ar atmosphere. In the second heat treatment, the sintered body was heated at 540 ° C. for 2 hours in an Ar atmosphere.

Further, separately from the base material 9, the DyH ₂ powder was applied to the entire surface by the dipping method on the processed sintered body, and then subjected to the same two-stage heat treatment as described above. Was made. In the application, the weight of the DyH ₂ powder with respect to the application area was set to 4.7 mg / cm ² .

(Comparative Example 6)
A main phase alloy having a composition of 30.5 wt% Nd-0.5 wt% Co-0.2 wt% Al-0.2 wt% Zr-0.95 wt% B-bal.Fe was prepared by strip casting. A grain boundary phase alloy having a composition of 50 wt% Dy-10 wt% Co-0.2 wt% Al-1.4 wt% Cu-3.0 wt% Ga-bal.Fe was prepared by strip casting. Next, after blending the main phase alloy and the grain boundary phase alloy in a mass ratio of 95: 5, hydrogen crushing treatment is performed and further pulverized to obtain a raw material powder having an average particle size (D50) of 4.3 μm. It was. In addition, by blending the main phase alloy and the grain boundary phase alloy at such a mass ratio, 29.00 wt% Nd-2.50 wt% Dy-0.50 wt% Co-0.20 wt% Al-0.10 wt% Cu-0.20 wt% A sintered body having a composition of Zr-0.15wt% Ga-0.95wt% B-bal.Fe is obtained.

  This raw material powder was filled in a mold placed in an electromagnet and molded in a magnetic field to produce a molded body. In molding, the raw material powder was pressurized at 120 MPa while applying a magnetic field of 15 kOe to the raw material powder.

  The molded body was sintered in vacuum at 1040 ° C. for 4 hours, and then rapidly cooled to obtain a sintered body. In addition, each process from a hydrogen crushing process to sintering was performed in the atmosphere whose oxygen concentration is less than 100 ppm. The oxygen content in the sintered body was 580 ppm. The particle size of the main phase particles of the sintered body was 4.5 μm.

  The sintered body was processed into 5 mm (magnetic anisotropic direction) × 15 mm × 6 mm. The sintered body after processing was subjected to two stages of heat treatment to obtain a base material 10. In the first stage heat treatment, the sintered body was heated at 900 ° C. for 6 hours in an Ar atmosphere. In the second heat treatment, the sintered body was heated at 540 ° C. for 2 hours in an Ar atmosphere.

Further, apart from the base material 10, the DyH ₂ powder was applied to the entire surface of the sintered body after the above processing by the dipping method, and then subjected to the same two-stage heat treatment as described above. Was made. In the application, the weight of the DyH ₂ powder with respect to the application area was set to 4.7 mg / cm ² .

(Comparative Example 7, Examples 7-9)
Except that the composition of the main phase alloy and the composition of the grain boundary phase alloy were changed as shown below, respectively, in the same manner as in Comparative Example 6, the base materials 11 to 14 and Comparative Examples 7 and Examples 7 to 9 A heavy rare earth diffusion magnet was produced. In any case, the amount of oxygen in the sintered body was 570 to 590 ppm. The particle size of the main phase particles of the sintered body was 4.5 to 4.7 μm.
<Comparative Example 7>
Main phase alloy: 30.5wt% Nd-0.75wt% Dy-0.5wt% Co-0.2wt% Al-0.2wt% Zr-0.95wt% B-bal.Fe
Grain boundary phase alloy: 35wt% Dy-15wt% Nd-10wt% Co-0.2wt% Al-1.4wt% Cu-3.0wt% Ga-bal.Fe
<Example 7>
Main phase alloy: 30.3wt% Nd-1.50wt% Dy-0.5wt% Co-0.2wt% Al-0.2wt% Zr-0.95wt% B-bal.Fe
Grain boundary phase alloy: 20wt% Dy-30wt% Nd-10wt% Co-0.2wt% Al-1.4wt% Cu-3.0wt% Ga-bal.Fe
<Example 8>
Main phase alloy: 30.5wt% Nd-2.5wt% Dy-0.5wt% Co-0.2wt% Al-0.2wt% Zr-0.95wt% B-bal.Fe
Grain boundary phase alloy: 50wt% Nd-10wt% Co-0.2wt% Al-1.4wt% Cu-3.0wt% Ga-bal.Fe
<Example 9>
Main phase alloy: 30.3wt% Nd-1.50wt% Dy-0.5wt% Co-0.2wt% Al-0.2wt% Zr-0.95wt% B-bal.Fe
Grain boundary phase alloy: 20wt% Dy-30wt% Nd-10wt% Co-0.2wt% Al-1.4wt% Cu-bal.Fe

[Characteristic evaluation of base materials and rare earth magnets]
The characteristics of the base materials and rare earth magnets obtained in Examples and Comparative Examples were measured by the following methods. The results are shown in Tables 1 and 2.

(Residual magnetic flux density, coercive force, squareness ratio)
The magnetic properties of the measurement samples obtained using the base materials and rare earth magnets obtained in Examples and Comparative Examples were measured with a BH tracer. From the obtained results, the residual magnetic flux density (Br), coercive force (HcJ), and squareness ratio (Hk / HcJ) of each measurement sample were determined.

(Measurement of oxygen content in sintered body)
The oxygen content was measured with a metal gas analyzer. As a detection method, a sample was gasified with a graphite crucible (oxygen was CO), and CO was detected with a non-dispersive infrared detector.

(Measurement of RHCu (DyCu) / RLCu (NdCu + PrCu) at the two-particle interface)
By the method described above, RHCu / RLCu was measured at positions of 0.3 mm and 1.5 mm from the surface.

  Specifically, using STEM-EDS (Scanning Transmission Electron Microscopy-Energy Dispersive X-ray Spectroscopy), the base material and the rare earth magnet obtained in Examples and Comparative Examples are in the vicinity of the two-particle interface (FIG. 5B). The amount (mass%) of rare earth elements (Nd, Pr and Dy) and the amount of Cu (mass%) were measured while linearly scanning (Line).

  FIG. 5A is a graph showing an example of the element distribution in the vicinity of the two-particle interface measured in this way. In the figure, the horizontal axis indicates the position on the measurement line, and the vertical axis indicates the amount of Fe, Nd, or Cu.

  FIG. 5B is an example of the result of analyzing the NdCu portion. When Nd and Dy are mixed, line analysis is performed at 20 points at 0.3 mm and 1.5 mm from the surface, and the NdCu number and DyCu number are counted in consideration of the mixing ratio, and DyCu / NdCu is calculated. To do.

(Line analysis using STEM-EDS)
About the base material and rare earth sintered magnet obtained in the Example, the line analysis was performed using the energy dispersive X-ray spectrometer (STEM-EDS) with which a scanning transmission electron microscope is equipped. FIG. 6A is a diagram showing an analysis result for a base material, and FIG. 6B is a diagram showing an analysis result for a rare earth sintered magnet.
As apparent from FIG. 6 (a), although the Nd concentration in the base material is rapidly increased in the vicinity of the grain boundary phase, the heavy rare earth element for the light rare earth element (Nd) is present in the vicinity of the grain boundary phase of the main phase particles. There is no portion in which the ratio (Dy / Nd) of the element (Dy) is more than twice the ratio in the main phase particle central portion (core), and there is no shell portion. On the other hand, as is clear from FIG. 6 (b), in the rare earth sintered magnet, the concentration of Nd is rapidly increased in the vicinity of the grain boundary phase, and Dy / Nd is mainly increased in the vicinity of the grain boundary phase of the main phase particles. There is a portion that is twice or more of the ratio in the center portion of the phase particle, and a shell portion exists. In addition, the part shown with the double arrow in FIG.6 (b) corresponds to a shell part.

  As is clear from Tables 1 and 2, the rare-earth magnets of Examples 1 to 9 have a small decrease in the squareness ratio (Hk / HcJ) and a residual magnetic flux density (Br) and a coercive force (HcJ), particularly a coercive force. Excellent. On the other hand, the rare earth magnets of Comparative Examples 1 to 7 have a large decrease in squareness ratio and are inferior in coercive force.

  2 ... main phase particles, 4 ... core, 6 ... shell, 8 ... grain boundary phase, 10 ... rare earth sintered magnet, 20 ... rotor, 22 ... rotor core, 24 ... magnet housing part, 30 ... stator, 32 ... coil part, DESCRIPTION OF SYMBOLS 40 ... Engine, 42 ... Generator, 44 ... Storage battery, 48 ... Wheel, 50 ... Car, 100 ... IPM motor.

Claims (7)

An R-T-B rare earth magnet main phase particle group having a core and a shell covering the core;
R includes heavy rare earth elements and light rare earth elements,
A rare earth sintered magnet in which a heavy rare earth Cu compound and a light rare earth Cu compound are present at the two-particle interface in the main phase particle group,
The mass ratio of the heavy rare earth compound to the light rare earth Cu compound at the two-particle interface at a depth of 0.3 mm from the surface of the rare earth sintered magnet is 1.5 mm deep from the surface of the rare earth sintered magnet. A rare earth sintered magnet that is greater than 1 and less than or equal to 5 times the mass ratio of the heavy rare earth compound to the light rare earth Cu compound at the two-particle interface at a position.   The rare earth sintered magnet according to claim 1, wherein a content ratio of oxygen element in the rare earth sintered magnet is 2500 ppm or less.   The rare earth sintered magnet according to claim 1 or 2, wherein a particle diameter of the main phase particles is 3.0 µm or more and 6.5 µm or less.   The rare earth sintered magnet according to any one of claims 1 to 3, wherein the rare earth sintered magnet contains a Ga element in a content ratio of 0.05 mass% or more and 0.40 mass% or less.   The rare earth sintered magnet according to any one of claims 1 to 4, wherein the shell has a thickness of 500 nm or less.   A motor comprising the rare earth sintered magnet according to any one of claims 1 to 5.   An automobile comprising the motor according to claim 6.