JP2011014631A - R-t-b-based rare-earth permanent magnet, and motor, automobile, generator and wind turbine generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an R-T-B-based rare-earth permanent magnet having a high coercive force (Hcj), and to provide a motor, automobile, generator and wind turbine generator including the R-T-B-based rare-earth permanent magnet.SOLUTION: An R-T-B-based rare-earth permanent magnet comprises a sintered body including a main phase 1 containing an RTB phase (wherein, R represents at least one rare-earth element, T represents a metal essentially comprising Fe, and B represents boron) and a grain boundary phase 2 containing more R than that contained in the main phase 1, wherein the content of Fe in the grain boundary phase 2 is 10-40% by mass.

Description

  The present invention relates to R-T-B rare earth permanent magnets and motors, automobiles, generators, and wind power generators, and particularly R-T-B rare earths that have excellent magnetic properties and are suitably used for motors. The present invention relates to a permanent magnet and a motor, automobile, generator, and wind power generator using the permanent magnet.

Conventionally, R-T-B magnets have been used in various motors. In recent years, in addition to the improvement in heat resistance of R-T-B magnets, the demand for energy saving has increased, so the ratio of motor applications including automobiles has increased.
The RTB-based magnet is mainly composed of Nd, Fe, and B. In the R-T-B magnet alloy, R is obtained by substituting a part of Nd with other rare earth elements such as Pr, Dy, and Tb. T is obtained by substituting a part of Fe with another transition metal such as Co or Ni. B is boron, and a part thereof can be substituted with C or N.

As a material used for the R—Fe—B rare earth permanent magnet, the existing capacity ratio of the R ₂ Fe ₁₄ B phase (where R represents at least one rare earth element) as the main phase component is 87.5 to In an RFeB-based magnet alloy in which the abundance ratio of rare earth or rare earth and transition metal oxide is 0.1 to 3%, the main component is Zr and B in the metal structure of the alloy. ZrB compound, NbB compound consisting of Nb and B, and HfB compound consisting of Hf and B have an average particle size of 5 μm or less and are present adjacent to each other in the alloy. And those in which the maximum distance between compounds selected from HfB compounds is 50 μm or less and uniformly dispersed (see, for example, Patent Document 1).

  The material used for the R—Fe—B rare earth permanent magnet is R—Fe—Co—B—Al—Cu (where R is one or two of Nd, Pr, Dy, Tb and Ho). Thus, in the rare earth permanent magnet material containing 15 to 33% by mass of Nd), an MB compound, an MB-Cu compound, an MC compound (M is one of Ti, Zr, and Hf). Among these, at least two of the seeds or two or more) and an R oxide are further precipitated in the alloy structure (for example, see Patent Document 2).

Japanese Patent No. 3951099 Japanese Patent No. 3911307

However, in recent years, even higher performance RTB-based rare earth permanent magnets have been demanded, and it has been required to further improve the magnetic properties such as coercive force of RTB-based rare earth permanent magnets.
This invention is made | formed in view of the said situation, and it aims at providing the RTB type rare earth permanent magnet from which a high coercive force (Hcj) is obtained.
Moreover, it aims at providing the motor using said R-T-B type rare earth permanent magnet.

  The present inventors investigated the relationship between the concentration of rare earth such as Nd contained in the grain boundary phase of the RTB-based rare earth permanent magnet and the magnetic properties of the RTB-based rare earth permanent magnet. The inventors have found that a high coercive force (Hcj) can be obtained by lowering the concentration of the rare earth generally contained in the grain boundary phase of the RTB-based rare earth permanent magnet by 80% or more. The headline, the present invention has been reached.

That is, the present invention provides the following inventions.
(1) a main phase including an R ₂ T ₁₄ B phase (where R is one or more rare earth elements, T is a metal essentially containing Fe, and B is boron); R-T-B system rare earth permanent, comprising a sintered body having a grain boundary phase containing a large amount of R, wherein the content of Fe in the grain boundary phase is 10% by mass to 40% by mass. magnet.
(2) The R—T—B system rare earth permanent magnet according to (1), wherein the content of R in the grain boundary phase is 70% by mass or less.
(3) The RTB-based rare earth permanent magnet according to (1) or (2), wherein the content of Dy in the grain boundary phase is 6% by mass to 12% by mass.
(4) The RTB rare earth permanent magnet according to any one of (1) to (3), including any one or more of W, Mo, and TiAl alloys.
(5) The RTB-based rare earth permanent magnet according to (4), which contains 0.01% by mass to 2% by mass of any one or more of W, Mo, and TiAl alloys.

(6) A motor comprising the RTB-based rare earth permanent magnet according to any one of (1) to (5).
(7) An automobile comprising the motor according to (6).
(8) A generator comprising the RTB-based rare earth permanent magnet according to any one of (1) to (5).
(9) A wind turbine generator comprising the generator according to (8).

The R-T-B rare earth permanent magnet of the present invention has an R ₂ T ₁₄ B phase (where R is one or more rare earth elements, T is a metal essentially containing Fe, and B is boron). ) And a grain boundary phase containing more R than the main phase, and the Fe content in the grain boundary phase is 10% by mass to 40% by mass. Therefore, compared with the case where the Fe content in the grain boundary phase is less than 10% by mass, the R content in the grain boundary phase is relatively small, and a high coercive force (Hcj) can be obtained. It can be suitably used for motors, automobiles, generators, and wind power generators.

FIG. 1A is a backscattered electron image of an example of the RTB-based rare earth permanent magnet of the present invention, and FIG. 1B is an RTB-based rare earth permanent shown in FIG. It is a schematic diagram for demonstrating a magnet.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1A is a backscattered electron image of an example of the RTB-based rare earth permanent magnet of the present invention, and FIG. 1B is an RTB-based rare earth permanent shown in FIG. It is a schematic diagram for demonstrating a magnet. The reflected electron image shown in FIG. 1A is a result of observing an RTB-based rare earth permanent magnet using an SEM (scanning electron microscope).

The RTB-based rare earth permanent magnet (hereinafter abbreviated as “rare earth permanent magnet”) of this embodiment shown in FIG. 1 is composed of a sintered body having a main phase 1 and a grain boundary phase 2. is there. The main phase 1 includes an R ₂ T ₁₄ B phase (where R is one or more rare earth elements, T is a metal indispensable for Fe, and B is boron). It is the particle-like black part in (a) and FIG.1 (b). The grain boundary phase 2 contains more R than the main phase 1, and is a white portion present in the grain boundary portion of the black particulate main phase 1 in FIGS. 1 (a) and 1 (b).

  The composition of the rare earth permanent magnet of the present embodiment includes 27 to 33% by mass of R, preferably 30 to 32%, and 0.85 to 1.3% by mass of B, preferably 0.87 to 0.98%. , T is preferably composed of the balance and inevitable impurities.

If R is less than 27% by mass, the coercive force may be insufficient, and if R exceeds 33% by mass, magnetization may be insufficient.
R is one or more rare earth elements, and as rare earth elements, Nd, Pr, Dy, Tb, Sc, Y, La, Ce, Pm, Sm, Eu, Gd, Ho, Er, Tm, Yb, Lu Is mentioned. R is preferably composed mainly of Nd, more preferably composed mainly of Nd and containing one or more selected from Pr, Dy, and Tb.

Further, R preferably contains 4% to 10% by mass of Dy, more preferably 6% to 9.5% by mass, and more preferably 7% to 9.5% by mass. More preferably it is included.
Increasing the Dy content of R lowers the magnetization (Br) of the rare earth permanent magnet. For this reason, it is preferable that the Dy content of R is the minimum necessary to ensure a coercive force. For example, when the rare earth permanent magnet only needs to have a coercive force of 30 kOe or more, a Dy content of R of 9.5% by mass or less is sufficient. Further, when the Dy content contained in R is less than 4% by mass, there is a high risk of insufficient heat resistance when used as a motor.

  If B is less than 0.85% by mass, the coercive force may be insufficient, and if B exceeds 1.3% by mass, the magnetization may be significantly reduced. In addition, although B is boron, a part can be substituted with C or N.

  T is a metal indispensable for Fe and may contain other transition metals such as Co and Ni in addition to Fe. When Co is contained in addition to Fe, Tc (Curie temperature) can be improved, which is preferable.

Furthermore, the rare earth permanent magnet preferably contains Al, Cu, or Ga in order to improve the coercive force.
Ga is preferably contained in an amount of 0.03% to 0.3% by mass. When Ga is contained in an amount of 0.03% by mass or more, the coercive force can be effectively improved. However, if the Ga content exceeds 0.3% by mass, the magnetization decreases, which is not preferable.
Al is preferably contained in an amount of 0.01% by mass to 0.5% by mass. When Al is contained in an amount of 0.01% by mass or more, the coercive force can be effectively improved. However, if the Al content exceeds 0.5% by mass, the magnetization is not preferable.

The rare earth permanent magnet preferably contains an oxygen concentration of 0.03% to 0.7% by mass, preferably 0.05% to 0.5% by mass. If the oxygen content is less than 0.03% by mass, there is a risk that the magnet will burn during the manufacturing process of the rare earth permanent magnet. On the other hand, if the oxygen content exceeds 0.7% by mass, the magnetic phase may be damaged by oxidation and the magnetic properties may be significantly deteriorated.
Further, the carbon concentration of the rare earth permanent magnet is preferably as low as possible. However, even if it is contained in an amount of 0.003 to 0.2 mass%, preferably 0.005 to 0.1 mass%, it is sufficient for a motor. Magnetic properties can be achieved. In addition, when carbon content exceeds 0.5 mass%, there exists a possibility that a magnetic characteristic may fall remarkably.

In the rare earth permanent magnet of the present embodiment, the Fe content in the grain boundary phase 2 is 10% by mass to 40% by mass. If the Fe content in the grain boundary phase 2 is less than the above range, the R content in the grain boundary phase 2 is relatively increased, and a sufficiently high coercive force (Hcj) cannot be obtained. Further, when the Fe content in the grain boundary phase 2 exceeds the above range, a precipitate of Fe is generated. The Fe content in the grain boundary phase 2 is more preferably 25% by mass to 40% by mass.
Further, the content of R in the grain boundary phase 2 is preferably 70% by mass or less, and more preferably 65% by mass or less. When the content of R in the grain boundary phase 2 exceeds 70% by mass, a sufficiently high coercive force (Hcj) may not be obtained.

  Moreover, it is preferable that the rare earth permanent magnet of this invention contains any one or more of W, Mo, and a TiAl alloy. The W, Mo, and TiAl alloys are all added as a metal powder to a powder composed of an R-T-B alloy, which is an alloy material for permanent magnets before sintering, thereby mixing the rare earth permanent after sintering. The content of Fe in the grain boundary phase of the magnet is increased and the content of R is decreased to improve the coercive force (Hcj). Such an effect becomes prominent when any one or more of W, Mo, and TiAl alloys are contained in the rare earth permanent magnet in an amount of 0.01% by mass to 2% by mass. Furthermore, when any one or more of W, Mo, and TiAl alloys are contained in the rare earth permanent magnet in an amount of 0.2% by mass to 1% by mass, the above effect becomes more remarkable, and the grain boundary after sintering. A rare earth permanent magnet is obtained in which the Fe content in the phase is 10% by mass to 40% by mass and the R content in the grain boundary phase is 70% by mass or less. If the content of any of W, Mo, and TiAl alloy is less than 0.01% by mass, the effect of improving the coercive force (Hcj) may not be sufficiently obtained. In addition, when the content of any of W, Mo, and TiAl alloy exceeds 2% by mass, the magnetic characteristics such as magnetization (Br) and maximum energy product (BHmax) may be significantly deteriorated.

The rare earth permanent magnet of the present invention can be manufactured using, for example, the following manufacturing method.
First, a permanent magnet alloy material is prepared. As the alloy material for the permanent magnet, it is preferable to use a mixture in which an RTB-based alloy and a metal powder are mixed, and an RTB-based alloy powder and a metal powder are mixed. It is more preferable to use a mixture.

As the metal powder, it is preferable to use any one or more of W, Mo, and TiAl alloys, or an alloy containing one or more of these. The average particle size (d50) of the metal powder is preferably in the range of 0.01 to 300 μm.
In addition, as the powder made of the RTB-based alloy, it is preferable to use a powder having a composition obtained by removing the composition of the metal powder from the material for obtaining the composition of the rare earth permanent magnet. The average particle size (d50) of the powder made of the RTB-based alloy is preferably 3 to 4.5 μm.

The powder made of an R-T-B alloy is produced by casting a molten alloy by, for example, SC (strip casting) method to produce a cast alloy flake, and the obtained cast alloy flake is disintegrated by, for example, a hydrogen crushing method. It is obtained by a method of pulverizing and pulverizing with a pulverizer.
As the hydrogen crushing method, the cast alloy flakes are occluded at room temperature, heat-treated at a temperature of about 300 ° C., degassed by depressurization, and then heat-treated at a temperature of about 500 ° C. For example, a method of removing hydrogen from the inside. In the hydrogen crushing method, since the volume of the cast alloy flakes in which hydrogen is occluded expands, a large number of cracks (cracks) are easily generated inside the alloy and crushed.
Moreover, as a method of pulverizing the hydrogen-crushed cast alloy flakes, the average particle size of 3-4. Examples thereof include a method of pulverizing to 5 μm to obtain a powder.

  As a method for producing a rare earth permanent magnet using the thus obtained permanent magnet alloy material, for example, 0.02% by mass to 0.03% by mass of stearin as a lubricant is added to the permanent magnet alloy material. A method of forming a rare earth permanent magnet by adding zinc acid, press molding using a molding machine in a transverse magnetic field, sintering in vacuum at 1030 ° C. to 1080 ° C., and then heat treating at 400 ° C. to 800 ° C. Etc.

  In the above-described example, the case where the RTB-based alloy is manufactured using the SC method has been described. However, the RTB-based alloy used in the present invention is manufactured using the SC method. It is not limited to things. For example, an RTB-based alloy may be cast using a centrifugal casting method, a book mold method, or the like.

In addition, as described above, the RTB-based alloy and the metal powder may be mixed after the cast alloy flakes are pulverized to form a powder consisting of the RTB-based alloy. Before pulverizing the flakes, the cast alloy flakes and the metal powder may be mixed to obtain an alloy material for permanent magnets, and then the permanent magnet alloy material containing the cast alloy flakes may be pulverized. In this case, the permanent magnet alloy material composed of cast alloy flakes and metal powder is pulverized in the same manner as the cast alloy flake pulverization method, and then molded and sintered as described above. It is preferable to produce an R-T-B rare earth permanent magnet.
Further, the mixing of the RTB-based alloy and the metal powder may be performed after adding a lubricant such as zinc stearate to the powder composed of the RTB-based alloy.
The metal powder in the permanent magnet alloy material of the present invention may be finely and uniformly distributed, but may not be finely and uniformly distributed. For example, the particle size may be 1 μm or more, The effect is exhibited even if the particles are aggregated to 5 μm or more.

The rare earth permanent magnet obtained by molding and sintering the permanent magnet alloy material of the present embodiment has a high coercive force (Hcj) and is used in motors, automobiles, generators, wind power generators, and the like. This is suitable as a magnet.
The higher the coercive force (Hcj) of the RTB rare earth permanent magnet, the better. When used as a magnet for a motor, it is preferably 30 kOe or more. If the coercive force (Hcj) is less than 30 kOe in a motor magnet, the heat resistance of the motor may be insufficient.
Also, the higher the magnetization (Br) of the R-T-B rare earth permanent magnet, the better. However, the higher the Dy content, the lower the Br, so the Dy content should be the minimum necessary to ensure a coercive force. Is preferred.

The rare earth permanent magnet of the present embodiment is a main phase composed of an R ₂ T ₁₄ B phase (where R is one or more rare earth elements, T is a metal indispensable for Fe, and B is boron). 1 and a grain boundary phase 2 containing more R than the main phase 1, and the Fe content in the grain boundary phase is 10% by mass to 40% by mass. Compared with the content of Fe in the boundary phase 2 being less than 10% by mass, the content of R in the grain boundary phase 2 is relatively small, and a high coercive force (Hcj) is obtained. It will be suitably used for motors, automobiles, generators, and wind power generators.

  Further, when the R content in the grain boundary phase 2 of the rare earth permanent magnet of the present embodiment is 70% by mass or less, the R content in the grain boundary phase 2 is more than 70% by mass. A higher coercive force (Hcj) can be obtained.

"Experiment 1"
Nd metal (purity 99 wt% or more), Pr metal (purity 99 wt% or more), Dy metal (purity 99 wt% or more), ferroboron (Fe 80%, B20 w%), Al metal (purity 99 wt% or more), Co metal (purity 99 wt%) %), Cu metal (purity 99 wt% or more), Ga metal (purity 99 wt% or more), iron ingot (purity 99% wt or more) are weighed so as to have the component composition of alloy A shown in Table 1, and alumina crucible Loaded.
Thereafter, the inside of the high-frequency vacuum induction furnace containing the alumina crucible was replaced with Ar, heated to 1450 ° C. and melted, poured into a water-cooled copper roll, the roll peripheral speed was 1.0 m / sec, and the average thickness was 0 Cast alloy flakes were obtained by SC (strip cast) method so as to be about 3 mm.

The cast alloy flakes thus obtained were crushed by the hydrogen crushing method shown below. First, the cast alloy flakes were roughly pulverized so as to have a diameter of about 5 mm, and inserted into hydrogen at room temperature to occlude hydrogen. Subsequently, heat treatment was performed to heat the cast alloy flakes coarsely pulverized and occluded with hydrogen up to 300 ° C. Thereafter, the pressure was reduced and the hydrogen was deaerated, and further heat treatment was performed to heat to 500 ° C. to release and remove hydrogen in the cast alloy flakes, which were then crushed by cooling to room temperature.
Next, 0.025 wt% of zinc stearate was added as a lubricant to the hydrogen-crushed cast alloy flakes, and hydrogen-crushed using a high-pressure nitrogen of 0.6 MPa with a jet mill (Hosokawa Micron 100 AFG). The cast alloy flakes were pulverized to an average particle size of 4.5 μm to obtain a powder.

The powder (alloy A) having the average particle size shown in Table 1 obtained as described above (alloy A) was mixed with the metal powder having the particle size shown in Table 2 in the proportion shown in Table 3 (alloy for permanent magnet). An alloy material for a permanent magnet was manufactured by adding and mixing at a concentration (mass%) of metal powder contained in the material.
The particle sizes of the alloy A and the metal powder were measured with a laser diffractometer.

Next, the permanent magnet alloy material thus obtained was press-molded at a measured pressure of 0.8 t / cm ² using a transverse magnetic field molding machine to obtain a green compact. Thereafter, the obtained green compact was sintered in a vacuum at a temperature of 1050 ° C., heat-treated at 500 ° C. and cooled, thereby producing rare earth permanent magnets of Experimental Examples 1 to 4.

The magnetic properties of each of the rare earth permanent magnets of Experimental Example 1 to Experimental Example 4 obtained using the alloy material for permanent magnets containing metal powder or the alloy material for permanent magnets not containing metal powder were measured using the BH curve tracer (Toei It was measured with industrial TPM 2-10). The results are shown in Table 3.
In Table 3, “Hcj” is the coercive force, “Br” is the magnetization, “SR” is the squareness, and “BHmax” is the maximum energy product. Moreover, the value of these magnetic characteristics is the average of the measured value of each five R-T-B system rare earth permanent magnets.

  Further, for each of the rare earth permanent magnets of Experimental Examples 1 to 4, the content of each element contained in the main phase and the grain boundary phase was measured using EPMA (X-ray microanalyzer). The results are shown in Table 4. Note that all elements described in Table 4 but not in Table 1 are impurities contained in the raw material.

  As shown in Table 3 and Table 4, in Experimental Example 1 to Experimental Example 3 in which the R content in the grain boundary phase is 70% by mass or less, the R content in the grain boundary phase exceeds 70% by mass. Compared with the experimental example 4 which is, the high coercive force (Hcj) was obtained.

1 ... main phase, 2 ... grain boundary phase.

Claims (9)

A main phase including an R ₂ T ₁₄ B phase (where R is one or more rare earth elements, T is a metal in which Fe is essential, and B is boron), and more R than the main phase. An RTB-based rare earth permanent magnet comprising a sintered body including a grain boundary phase, wherein the content of Fe in the grain boundary phase is 10% by mass to 40% by mass.   The R-T-B rare earth permanent magnet according to claim 1, wherein the content of R in the grain boundary phase is 70% by mass or less.   The RTB-based rare earth permanent magnet according to claim 1 or 2, wherein the content of Dy in the grain boundary phase is 6% by mass to 12% by mass.   The RTB-based rare earth permanent magnet according to any one of claims 1 to 3, comprising any one or more of W, Mo, and TiAl alloys.   The RTB-based rare earth permanent magnet according to claim 4, comprising 0.01 mass% to 2 mass% of any one or more of W, Mo, and TiAl alloys.   A motor comprising the RTB-based rare earth permanent magnet according to any one of claims 1 to 5.   An automobile comprising the motor according to claim 6.   The generator provided with the RTB system rare earth permanent magnet in any one of Claims 1-5.   A wind turbine generator comprising the generator according to claim 8.