JP2019169697A - Method for manufacturing r-t-b based sintered magnet - Google Patents

Abstract

To enhance a magnet property of an R-T-B based sintered magnet.SOLUTION: A method for manufacturing an R-T-B based sintered magnet comprises the steps of: preparing main alloy powder; preparing Pr-Ga alloy powder manufactured by an atomization method; mixing the main alloy powder with the Pr-Ga alloy powder to produce a powder mixture in which the mass ratio of the Pr-Ga alloy powder is 1 mass% or more and 10 mass% or less to a total mass of the powder mixture; and shaping the powder mixture into a compact in a magnetic field. The method further comprises a sintering step of sintering the compact of the powder mixture at a sintering temperature equal to or above 950°C and below 1120°C. When the sintering temperature is T°C and a sintering time is t sec. in the sintering step, the relation given by the following expression holds: 5×(1120-T)<t<10×(1120-T).SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method for producing an RTB-based sintered magnet.

  R-T-B-based sintered magnets (R is at least one of rare earth elements and must contain Nd. T is Fe or Fe and Co, and B is boron) is the highest among permanent magnets. It is known as a high-performance magnet, and is used in various motors such as voice coil motors (VCM) for hard disk drives, motors for electric vehicles (EV, HV, PHV, etc.), motors for industrial equipment, and home appliances.

The RTB-based sintered magnet is composed of a main phase mainly composed of an R ₂ T ₁₄ B compound and a grain boundary phase located at the grain boundary portion of the main phase. The main phase R ₂ T ₁₄ B compound is a ferromagnetic material having a high saturation magnetization and an anisotropic magnetic field, and forms the basis of the characteristics of the RTB-based sintered magnet.

At a high temperature, the coercive force H _cJ (hereinafter sometimes simply referred to as “H _cJ ”) of the _RTB -based sintered magnet decreases, and irreversible thermal demagnetization occurs. Therefore, in particular, an _RTB -based sintered magnet used for an electric vehicle motor is required to have a high _HcJ .

In the RTB-based sintered magnet, a part of the light rare earth element RL (for example, Nd or Pr) contained in R in the R ₂ T ₁₄ B compound is a heavy rare earth element RH (for example, Dy or Tb). Substitution is known to improve _HcJ . As the substitution amount of RH increases, _HcJ improves.

However, when RL in the R ₂ T ₁₄ B compound is replaced with RH, the H _{cJ of the RTB} -based sintered magnet is improved, while the residual magnetic flux density B _r (hereinafter simply referred to as “B _r ”). There is). In particular, RH such as Dy has a problem in that the supply is not stable and the price largely fluctuates due to a small amount of resources and a limited production area. Therefore, in recent years, it has been demanded to improve _HcJ without using RH as much as possible.

Patent Document 1 discloses an RTB-based rare earth sintered magnet having a high coercive force while suppressing the Dy content. The composition of the sintered magnet is limited to a specific range in which the amount of B is relatively smaller than that of a generally used RTB-based alloy, and is selected from Al, Ga, and Cu. It contains more than seed metal element M. As a result, _R 2 _{T 17} phase is produced in the grain boundary, by the volume ratio of the _R 2 _{T 17} transition metal-rich phase formed in the grain boundary from phase _{(R 6 T 13} M) _{increases, H cJ} Will improve.

International Publication No. 2013/008756

The R-T-B rare earth sintered magnets disclosed in Patent Document 1, although a high H _cJ is obtained while reducing the content of Dy, there is a problem that B _r is greatly reduced. In recent years, there has been a demand for _RTB -based sintered magnets having higher _{HcJ in} applications such as electric vehicle motors.

Various embodiments of the present invention, while reducing the content of RH, to provide a method of manufacturing a R-T-B based sintered magnet having a high B _r and high H _cJ.

In the exemplary embodiment, the manufacturing method of the RTB-based sintered magnet of the present disclosure is R: 27.5 mass% or more and 33.0 mass% or less (R is at least one of rare earth elements, Nd is necessarily included), B: 0.85 mass% or more and 0.97 mass% or less, T: 61.5 mass% or more (T is Fe and Co, and 90% or more of T by mass ratio is Fe) A main alloy powder containing, and Pr: 65 mass% or more and 97 mass% or less (30 mass% of Pr can be replaced by another rare earth element), and Ga: 3 mass% or more and 35 mass% % And the step of preparing a Pr—Ga alloy powder prepared by an atomization method, and the main alloy powder and the Pr—Ga alloy powder are mixed. And the Pr to the entire mixed powder A mixed powder in which the mass ratio of the Ga alloy powder is 1% by mass or more and 10% by mass or less is manufactured, and the molded product of the mixed powder is sintered at a sintering temperature of 950 ° C. or more and less than 1120 ° C. in a magnetic field. A sintering step, and when the sintering temperature in the sintering step is T ° C. and the sintering time is t seconds, 5 × (1120−T) ² <t <10 × (1120− T) The relationship ² is established.

  In one embodiment, when [T] is a content of T expressed in terms of mass% and [B] is a content of B expressed in mass%, the RTB-based sintered magnet has [T] / The relationship of 55.85> 14 [B] /10.8 is satisfied.

  In one embodiment, the Nd content in the Pr—Ga alloy powder is less than or equal to the inevitable impurity content.

According to the embodiment of the present disclosure, after forming a compact of a mixed powder obtained by adding a Pr—Ga alloy powder prepared by an atomizing method to a main alloy powder at an appropriate mass ratio, the compact is subjected to a specific condition. in order to sinter it can also reduce the content of heavy rare earth elements such as Dy, the production of R-T-B based sintered magnet having a high B _r and H _cJ.

It is sectional drawing which expands and partially shows a part of RTB system sintered magnet. FIG. 1B is a cross-sectional view schematically showing a further enlarged view of a broken-line rectangular region in FIG. 1A. It is a flowchart which shows the example of the process in the manufacturing method of the RTB type sintered magnet by embodiment of this indication. It is a graph which shows the relationship between sintering temperature T and sintering time t.

FIG. 1A is a cross-sectional view schematically showing a part of an R-T-B system sintered magnet in an enlarged manner, and FIG. 1B is a cross-sectional view schematically showing in a further enlarged view a broken-line rectangular region in FIG. 1A. It is. In FIG. 1A, for example, an arrow having a length of 5 μm is described as a reference length indicating the size for reference. As shown in FIGS. 1A and 1B, the RTB-based sintered magnet includes a main phase 12 mainly composed of an R ₂ T ₁₄ B compound, and a grain boundary phase 14 located in a grain boundary portion of the main phase 12. It consists of and. As shown in FIG. 1B, the grain boundary phase 14 includes two grain boundary phases 14a in which two R ₂ T ₁₄ B compound particles (grains) are adjacent, and grains in which three R ₂ T ₁₄ B compound particles are adjacent. Boundary triple point 14b.

The R ₂ T ₁₄ B compound that is the main phase 12 is a ferromagnetic material having a high saturation magnetization and an anisotropic magnetic field. Therefore, in the R-T-B based sintered magnet, it is possible to improve the _{B r} by increasing the existence ratio of _R 2 _{T 14} B compound is the main phase 12. In order to increase the abundance ratio of the R ₂ T ₁₄ B compound, the R amount, T amount, and B amount in the raw material alloy are set to the stoichiometric ratio of the R ₂ T ₁₄ B compound (R amount: T amount: B amount = It may be close to 2: 14: 1).

As described in Patent Document 1, the amount of B is smaller than that of a general RTB-based sintered magnet, that is, less than the amount of B in the stoichiometric ratio of the R ₂ T ₁₄ B type compound. Then, when Ga is added, a transition metal rich phase (RT-Ga phase) containing Ga is generated in the grain boundary phase 14 and _HcJ is improved.

As a result of intensive studies by the present inventors, since the RTB-Ga phase has magnetization, among the two-grain boundary 14a and the grain boundary triple point 14b of the RTB-based sintered magnet, When two particles grain boundaries 14a to R-T-Ga phase that would mainly affect H _cJ there are _many, it was found that hinder _{H cJ} increased. It was also found that, along with the generation of the R—T—Ga phase, an R—Ga phase considered to have lower magnetization than the R—T—Ga phase was generated at the two-grain grain boundary 14a. Therefore, in order to obtain an _RTB -based sintered magnet having high _HcJ , it is necessary to generate an RT-Ga phase, but a large amount of R-Ga phase is generated at the two-grain boundary 14a. I thought it was important.

  As a result of the experiments by the present inventors, a Pr—Ga alloy powder (atomized powder) produced by the atomizing method is mixed with the powder of the main alloy of the R—T—B system sintered magnet, and a compact of this mixed powder is obtained. It was found that by carrying out a sintering step under predetermined conditions, R and Ga can be introduced into the two-grain boundary 14a with almost no introduction into the main phase crystal grains 12. Thus, according to the embodiment of the present invention, a large number of R-Ga phases can be generated at the two-grain grain boundaries.

As described above, the RTB-based sintered magnet has a structure in which powder particles of a main alloy for forming a main phase are bonded by sintering, and is mainly composed of an R ₂ T ₁₄ B compound. It consists of a main phase and a grain boundary phase located at the grain boundary portion of this main phase. Since the melting point of the Pr—Ga alloy is lower than the sintering temperature, the powder particles of the Pr—Ga alloy melt in the course of the sintering process and mainly constitute the grain boundary phase of the RTB-based sintered magnet. To do.

Note that the Pr—Ga alloy has poor grindability. For this reason, when normal hydrogen pulverization and fine pulverization are performed on the Pr—Ga alloy, the pulverization takes a long time and there is a problem in mass productivity. When the Pr—Ga alloy is finely pulverized in a state where hydrogen is occluded, the pulverization property is improved, but hydrogen may remain in the obtained sintered magnet and the magnetic characteristics may be deteriorated. For this reason, when hydrogen storage is used, it is necessary to release the hydrogen sufficiently by extending the sintering time or increasing the sintering temperature in order to prevent hydrogen from remaining as much as possible. However, under such sintering conditions, R and Ga diffuse into the main phase crystal grains, and high _HcJ cannot be obtained.

  In the embodiment of the present disclosure, it is possible to obtain powder particles (for example, particles having a particle size of 106 μm or less) without performing pulverization by using an atomized powder of a Pr—Ga alloy. Since it is not necessary to release hydrogen occluded by the alloy during the sintering process, there is no need to lengthen the sintering time or raise the sintering temperature. As a result, it was possible to select suitable sintering conditions for improving the magnetic properties by modifying the grain boundary phase with R and Ga.

  As illustrated in FIG. 2, the manufacturing method of the RTB-based sintered magnet according to the present disclosure includes a step S <b> 10 of preparing a main alloy powder for the RTB-based sintered magnet, and an atomizing method. And a step S20 of preparing the produced Pr—Ga alloy powder. The order of the step S10 for preparing the main alloy powder and the step S20 for preparing the Pr—Ga alloy powder is arbitrary, and the main alloy powder and the Pr—Ga alloy powder manufactured in different places may be used. Good. Further, the manufacturing method of the RTB-based sintered magnet according to the present disclosure is obtained by mixing the main alloy powder and the Pr—Ga alloy powder and forming them in a magnetic field (powder forming step) S30, and forming. And a step (sintering step) S40 of sintering the mixed powder compact.

The main alloy powder in the embodiment of the present disclosure is:
R: 27.5% by mass or more and 33.0% by mass or less (R is at least one kind of rare earth elements and necessarily contains Nd),
B: 0.85 mass% or more and 0.97 mass% or less,
T: 61.5% by mass or more (T is Fe and Co, and 90% or more of T is Fe by mass ratio),
Containing.

On the other hand, the Pr—Ga alloy powder in the embodiment of the present disclosure is:
Pr: 65 mass% or more and 97 mass% or less, and Ga: 3 mass% or more and 35 mass% or less (50 mass% or less of Ga can be substituted with Cu),
Containing.

  In the powder forming step S30 in the embodiment of the present disclosure, when the main alloy powder and the Pr—Ga alloy powder are mixed, the mass ratio of the Pr—Ga alloy powder to the entire mixed powder is 1% by mass or more and 10% by mass or less. To do.

In the sintering step S40 in the embodiment of the present disclosure, the compact of the mixed powder is sintered at a sintering temperature of 950 ° C. or higher and lower than 1120 ° C. Further, when the sintering temperature is T ° C. and the sintering time is t seconds, the sintering conditions are adjusted so that the relationship of the following formula 1 is satisfied.
5 × (1120−T) ² <t <10 × (1120−T) ² (Formula 1)

FIG. 3 is a graph showing the relationship between the sintering temperature T and the sintering time t. The broken line in the graph is a curve indicating 5 × (1120−T) ² that defines the lower limit value of the sintering time t. On the other hand, the dotted line in the graph is a curve indicating 10 × (1120−T) ² that defines the upper limit value of the sintering time t.

For example, when the sintering temperature T is set to 1020 ° C., 5 × (1120−T) ² that defines the lower limit value of the sintering time t is 5 × 100 ² = 50000 seconds, which is about 13 hours and 50 minutes. is there. Further, 10 × (1120−T) ² that defines the upper limit of the sintering time t is 10 × 100 ² = 100000 seconds, which is about 27 hours and 46 minutes. Therefore, if the sintering temperature T is 1020 ° C., the sintering time t is selected from the range of about 13 hours 50 minutes to about 27 hours 46 minutes.

According to the present disclosure, sintering is performed on the powder compact formed by mixing the main alloy powder and the Pr—Ga alloy powder under the specific conditions, so that sintering and R-Ga phase formation in the grain boundary phase proceeds appropriately. As a result, the grain boundary phase of the R-T-B based sintered magnet to realize a reformed with high B _r and H _cJ throughout the internal magnet. When the RTB-based sintered magnet material is prepared by sintering and then Pr and Ga are diffused and introduced from the surface of the RTB-based sintered magnet material, Since a concentration gradient is generated in Ga, even within the grain boundary phase of the R-T-B system sintered magnet, the region close to the surface of the R-T-B system sintered magnet and the R-T-B system sintering There is a difference in the amount of R-Ga phase produced from the inside of the magnet. However, according to the embodiment of the present disclosure, Pr and Ga are added from the stage before sintering and are present inside the powder compact, so that the problems due to the conventional method are solved.

  In the embodiment of the present disclosure, the Pr—Ga alloy powder is produced by an atomizing method. The powder produced by the atomization method is sometimes called “atomized powder”.

  The atomizing method is a kind of powder preparation method called a molten metal spraying method, and includes known atomizing methods such as a gas atomizing method and a plasma atomizing method. For example, according to the gas atomization method, a metal or alloy is melted in a melting furnace to form a molten metal, and the molten metal is sprayed and solidified in an inert gas atmosphere such as nitrogen or argon. Since the sprayed molten metal scatters as fine droplets, it is cooled and solidified at a high speed. Since the produced powder particles each have a spherical shape, it is not necessary to perform pulverization. The size of the powder particles produced by the atomizing method is distributed in the range of 10 μm to 200 μm, for example.

  According to the atomizing method, since the droplets of the molten alloy to be sprayed are small and the surface area relative to the weight of each droplet is relatively large, the cooling rate is increased. Therefore, the formed powder particles are amorphous or microcrystalline. These powder particles may be additionally heat-treated before mixing to crystallize amorphous.

  The particle size of the Pr—Ga alloy powder can be adjusted by sieving. In addition, if the amount of powder excluded by sieving is within 10% by mass, the influence is small, and it may be used without sieving.

  After the sintering process, an additional heat treatment may be performed in a vacuum or an inert gas atmosphere at a temperature lower than the sintering temperature. Another process, such as a cooling process, may be performed between the sintering process S40 and the process of performing the additional heat treatment.

The RTB-based sintered magnet manufactured by the manufacturing method of the present disclosure has the following composition, for example.
R: 27.5% by mass or more and 34.0% by mass or less (R is at least one of rare earth elements and always includes at least one of Nd and Pr),
B: 0.85 mass% or more, 0.93 mass% or less,
Ga: 0.20 mass% or more, 0.70 mass% or less,
Cu: 0.05% by mass or more, 0.70% by mass or less, and T: 61.5% by mass or more (T is Fe and Co, and 90% or more of T by mass ratio is Fe), And [T] is the content of T expressed in mass%, and [B] is the content of B expressed in mass%, [T] /55.85> 14 [B] /10.8 To establish.

  Hereinafter, the composition of each alloy will be described in more detail.

1. Composition of main alloy (R) Content of R is 27.5-33.0 mass%. R is at least one kind of rare earth elements and necessarily contains Nd. When R is less than 27.5% by mass, a liquid phase is not sufficiently generated in the sintering process, and it becomes difficult to sufficiently densify the sintered body. On the other hand, even if R exceeds 33.0% by mass, the effect of the present invention can be obtained, but the alloy powder in the manufacturing process of the sintered body becomes very active, and the alloy powder is significantly oxidized or ignited. Since it may occur, 33.0 mass% or less is preferable. R is more preferably 28% by mass to 33.0% by mass, and further preferably 29% by mass to 33% by mass. The content of the heavy rare earth element RH is preferably 5% by mass or less. In an embodiment of the present invention, it is possible to obtain a high B _r and high H _cJ without using the heavy rare-earth element RH, even if required a higher H _cJ, reduce the amount of heavy rare-earth element RH it can.

(B) Content of B is 0.85-0.97 mass%. By sintering mixed with the main alloy powder and Pr-Ga alloy powder content was contained 0.85 to 0.97 wt% of B, it is possible to obtain a high _{B r} and high _{H cJ.} There is a possibility that the content of B is lowered and _{B r} is less than 0.85 wt%, there is a possibility _{that H cJ} is reduced when it exceeds 0.97 wt%. A part of B can be replaced with C.

(Ga) The Ga content in the main alloy powder is 0 to 0.8 mass%. In the present invention, by adding the Pr—Ga alloy powder to the main alloy powder, Ga is introduced into the grain boundary phase, so the Ga content of the main alloy powder is made relatively small (or does not contain Ga). . If the Ga content exceeds 0.8% by mass, the main phase magnetization may decrease due to the Ga content in the main phase, and high _Br may not be obtained. Preferably, the Ga content is 0.5% by mass or less. Higher _Br can be obtained.

(M) Content of M is 0-2 mass%. M is at least one of Cu, Al, Nb, and Zr, and even if it is 0% by mass, the effect of the present invention can be obtained, but the total of Cu, Al, Nb, and Zr is 2% by mass or less. Can do. By containing Cu and Al, _HcJ can be improved. Cu and Al may be positively added, or those unavoidably introduced in the production process of the raw materials and alloy powders may be utilized. Moreover, the abnormal grain growth of the crystal grain at the time of sintering can be suppressed by containing Nb and Zr. M preferably contains Cu, and contains 0.05 to 0.30% by mass of Cu. It is because _HcJ can be improved more by containing _0.05-0.30 mass% of Cu.

(T) T is Fe or Fe and Co. It is preferable that 90% or more of T by mass ratio is Fe. A part of Fe can be substituted with Co. However, the substitution amount of Co is greater than 10% of the total T by mass ratio is not preferable because the B _r drops. The content of T is 61.5% by mass or more. If the T content is less than 61.5% by mass, Br may be significantly reduced. Preferably, T is the balance.

  The main alloy powder in the present disclosure includes didymium alloy (Nd—Pr), electrolytic iron, ferroboron, etc., inevitable impurities usually contained in the manufacturing process, and a small amount of other elements (the above R, B). , Elements other than Ga, M, and T). For example, Ti, V, Cr, Mn, Ni, Si, La, Ce, Sm, Ca, Mg, O (oxygen), N (nitrogen), C (carbon), Mo, Hf, Ta, W, etc., respectively May be.

The main alloy powder can be prepared by using a general method for producing an RTB-based sintered magnet represented by an Nd-Fe-B-based sintered magnet. For example, a raw material alloy produced by a strip casting method or the like is pulverized to a particle size D ₅₀ of 1 μm to 10 μm (preferably, a particle size D ₅₀ of 3 μm to 8 μm) using a jet mill or the like. It can be prepared by molding in a magnetic field and sintering at a temperature of 900 ° C. or higher and 1100 ° C. or lower.

If the pulverized particle size of the raw material alloy (volume center value obtained by measurement by the airflow dispersion type laser diffraction method = D ₅₀ ) is less than 1 μm, it is very difficult to produce pulverized powder, and the production efficiency is greatly reduced. It is not preferable. On the other hand, if the pulverized particle size exceeds 10 μm, the crystal particle size of the finally obtained main alloy powder for _RTB -based sintered magnet becomes too large, and it is difficult to obtain high _HcJ, which is not preferable. .

Preferably, the main alloy powder satisfies Equation 2.
[T] /55.85> 14 [B] /10.8 (Formula 2)

By satisfying Formula 2, the B content is less than that of a general RTB-based sintered magnet. In general R-T-B based sintered magnets, [T] /55.85 (atomic weight of Fe) so that an Fe phase and an R ₂ T ₁₇ phase are not generated in addition to the main phase R ₂ T ₁₄ B phase. Is less than 14 [B] /10.8 (the atomic weight of B) ([T] is the content of T expressed in mass%, and [B] is the content of B expressed in mass%) Is).

  In a preferred embodiment of the present disclosure, unlike a general RTB-based sintered magnet, [T] /55.85 (Fe atomic weight) is more than 14 [B] /10.8 (B atomic weight). Is defined by Formula 2. Note that T in the main alloy powder uses the atomic weight of Fe because Fe is the main component.

2. Composition of Pr—Ga alloy powder (Pr) Pr of the Pr—Ga alloy powder is 65 to 97 mass% of the entire Pr—Ga alloy. 30% by mass or less of this Pr can be replaced with other rare earth elements. Specifically, 30% by mass or less of Pr can be substituted with Nd, and 20% by mass or less of Pr can be substituted with Dy and / or Tb.

  (Ga) Ga is 3 mass% to 35 mass% of the whole Pr—Ga alloy, and 50 mass% or less of Ga can be substituted with Cu. The Pr—Ga alloy may contain inevitable impurities.

  In the present disclosure, “30% or less of Pr can be replaced with Nd” means that the Pr content (% by mass) in the Pr—Ga alloy is 100%, and 30% of the Pr can be replaced with Nd. Means. For example, if Pr in the Pr—Ga alloy is 70 mass% (Ga is 30 mass%), Nd can be substituted up to 21 mass%. That is, Pr is 49% by mass and Nd is 21% by mass. The same applies to Dy, Tb, and Cu.

By mixing Pr-Ga alloy powder with Pr and Ga in the above range with the main alloy powder, Pr and Ga are concentrated in the grain boundary phase in the sintering process and dispersed throughout the magnet in the grain boundary phase. be able to. A part of Pr in the Pr—Ga alloy may be substituted with Nd, Dy and / or Tb. However, if the amount of each substitution exceeds the above range, the amount of Pr is too small, so that high _Br and high H _cJ cannot be obtained. Preferably, the Nd content of the Pr—Ga alloy is unavoidable impurity content or less (approximately 1% by mass or less). Ga can replace 50% or less with Cu, but if the amount of substitution of Cu exceeds 50%, _HcJ may decrease.

  The Pr—Ga alloy powder in the present disclosure is produced by an atomizing method. For this reason, even if it does not perform mechanical crushing, it has a spherical shape as described above.

The sintered magnet thus obtained may be subjected to additional heat treatment for the purpose of further improving the magnetic properties. For example, the one-step heat treatment may be performed at a temperature lower than the sintering temperature (400 ° C. or higher and 600 ° C. or lower). Alternatively, after the first heat treatment is performed at a relatively high temperature (700 ° C. or more and sintering temperature or less), the second heat treatment may be performed at a relatively low temperature (400 ° C. or more and 600 ° C. or less) (two steps). Heat treatment). Specific examples of the two-stage heat treatment may include a first heat treatment at a temperature of 750 ° C. to 850 ° C. for about 5 minutes to 500 minutes and a second heat treatment at a temperature of 440 ° C. to 550 ° C. for about 5 minutes to 500 minutes. . Between 1st heat processing and 2nd heat processing, you may cool to room temperature, or you may cool to the temperature of 440 degreeC or more and 550 degrees C or less. The R ₆ T ₁₃ Ga phase produced during cooling after sintering can be lost by a relatively high temperature heat treatment. When the amount of the R ₆ T ₁₃ Ga phase is reduced before the second heat treatment, the grain boundary phase is expanded and H _cJ can be increased. In addition, the heat treatment at a relatively low temperature can promote the generation of the R—T—Ga phase and the R—Ga phase.

  Any heat treatment is desirably performed in a vacuum atmosphere or an inert gas (such as helium or argon).

  The present disclosure will be described in more detail by way of examples, but the present disclosure is not limited thereto.

Example 1
No. 1 in Table 1 Each element was weighed so as to have the composition shown in A and cast by a strip casting method to obtain a flaky alloy. The obtained flaky alloy was hydrogen embrittled in a hydrogen-pressurized atmosphere, and then subjected to a dehydrogenation treatment in which it was heated and cooled in vacuum to 550 ° C. to obtain coarsely pulverized powder. Next, after adding and mixing 0.04% by mass of zinc stearate as a lubricant with respect to 100% by mass of the coarsely pulverized powder, the resulting coarsely pulverized powder was mixed with an airflow pulverizer (jet mill device). was dry milled in a nitrogen atmosphere, the particle diameter _{D 50} was obtained main alloy powder 4.3 [mu] m. The results of component analysis of the obtained main alloy powder are shown in Table 1. Shown in A. Each component in Table 1 was measured using high frequency inductively coupled plasma optical emission spectrometry (ICP-OES). Hereinafter, the compositions of the main alloy powder, the Pr—Ga alloy powder, and the RTB-based sintered magnet were also measured in the same manner.

  Next, Pr—Ga alloy powder (No. a) of an alloy having the composition shown in Table 2 was produced by an atomizing method. The particle size of the obtained Pr—Ga alloy powder was 106 μm or less.

Next, the main alloy powder (No. A) and the Pr—Ga alloy powder (No. a) were put into a V-type mixer and mixed to prepare a mixed powder (finely pulverized powder). The mass ratio of the Pr—Ga alloy powder to the entire mixed powder was 3% by mass. After adding and mixing 0.05 mass% of zinc stearate as a lubricant with respect to 100 mass% of finely pulverized powder, the mixed powder was molded in a magnetic field to obtain a molded body. In addition, what was called a right-angle magnetic field shaping | molding apparatus (transverse magnetic field shaping | molding apparatus) in which the magnetic field application direction and the pressurization direction orthogonally crossed was used for the shaping | molding apparatus. The obtained molded body was sintered at the sintering temperature and the sintering time shown in Table 3. In addition, when the sintering time satisfies the formula 1 (5 × (1120-T) ² <t <10 × (1120-T) ² ) of the present disclosure, it is described as ◯, and when it is not satisfied, it is described as x. ing. The sintering temperature and the sintered magnet were measured by attaching a thermocouple to the compact. The sintered R-T-B sintered magnet is subjected to a heat treatment in which it is kept at 900 ° C. for 2 hours in a vacuum, then cooled to room temperature, then kept at 500 ° C. in a vacuum for 2 hours, and then cooled to room temperature. An RTB-based sintered magnet (No. 1 to 9) was obtained. When the components of the obtained RTB-based sintered magnet were confirmed, all were (No. 1 to 9) by mass ratio, Nd: 22.5%, Pr: 9.77%, B: 0.00. 88%, Co: 0.87%, Al: 0.1%, Cu: 0.18%, Ga: 0.5%, Zr: 0.1%, Fe: around 64.85%. The following formula 2 ([T] /55.85> 14 [B] /10.8) was satisfied. The sintered magnets (Sample Nos. 1 to 9) after heat treatment are machined to prepare samples having a length of 7 mm, a width of 7 mm, and a thickness of 7 mm, and characteristics of each sample (B _r and H _cJ ) by a BH tracer Was measured. Table 3 shows the measurement results.

As shown in Table 3, the inventive examples, both while the R-T-B based sintered magnet having a high B _r and high H _cJ are obtained, out of range sintering time of the present disclosure Comparative example is has the R-T-B based sintered magnet having both high B _r and high H _cJ not obtained.

Example 2
No. in Table 4 Each element was weighed so as to have the composition shown in B to I and cast by a strip cast method to obtain a flaky alloy. The obtained flaky alloy was pulverized in the same manner as in Example 1 to obtain a main alloy powder. Table 4 shows the composition of the obtained main alloy powder.

  Next, as in Example 1, Pr—Ga alloy powders (No. a to e) having the compositions shown in Table 5 were prepared by the atomizing method and prepared. The particle size of the obtained Pr—Ga alloy powder was 106 μm or less.

Next, the main alloy powder and the Pr—Ga alloy powder were put into a V-type mixer under the conditions shown in Table 6 and mixed to prepare a mixed powder (finely pulverized powder). No. 11 is No. C (main alloy powder) and No. a (Pr—Ga alloy powder) is mixed, and the mass ratio of the Pr—Ga alloy powder to the entire mixed powder is 1% by mass. No. 12 to 21 are also described in the same manner. No. No. 10 was a main alloy powder alone and no Pr—Ga alloy powder was mixed. The mixed powder was molded in the same manner as in Example 1 to obtain a molded body. The obtained molded body was sintered at 1040 ° C. for 36000 seconds (10 hours). The sintering temperature and the sintering time are within the scope of the present disclosure. The obtained sintered body was subjected to the same heat treatment as in Example 1 to obtain RTB-based sintered magnets (Nos. 11 to 21). No. No. 10 is No. except that only the main alloy powder was not mixed with the Pr—Ga alloy powder. The RTB system sintered magnet was produced like 11-21. Table 7 shows the composition of the RTB-based sintered magnet. When the expression 2 of the present disclosure is satisfied, “O” is indicated, and when it is not satisfied, “X” is indicated. By machining the R-T-B based sintered magnet (Sample No.10~21), vertical 7 mm, transverse 7 mm, to prepare a sample having a thickness of 7 mm, the characteristics of each sample by the B-H tracer _{(B r} and H _cJ ) was measured. Table 6 shows the measurement results.

As shown in Table 6, the inventive examples, while the R-T-B based sintered magnet is obtained having both high B _r and high H _cJ, uses Pr-Ga alloy powder No. No. 10 and the mass ratio of the Pr—Ga alloy powder to the whole alloy powder exceeds 10% by mass. No. 16 and Pr. 18 and no. Comparative example 19, R-T-B based sintered magnet having both high _{B r} and high _{H cJ} can not be obtained.

Example 3
No. in Table 8 Each element was weighed so as to have the composition shown in J and cast by a strip casting method to obtain a flaky alloy. The obtained flaky alloy was pulverized in the same manner as in Example 1 to obtain a main alloy powder. Table 8 shows the composition of the obtained main alloy powder.

  Next, in the same manner as in Example 1, Pr—Ga alloy powders (No. f and g) having the compositions shown in Table 9 were prepared by the atomizing method and prepared. The particle size of the obtained Pr—Ga alloy powder was 106 μm or less.

Next, the main alloy powder and the Pr—Ga alloy powder were put into a V-type mixer and mixed under the conditions shown in Table 10 to prepare a mixed powder (finely pulverized powder). No. No. 22 J (main alloy powder) and No. f (Pr—Ga alloy powder) is mixed, and the mass ratio of the Pr—Ga alloy powder to the entire mixed powder is 3 mass%. No. 23 is described similarly. The mixed powder was molded in the same manner as in Example 1 to obtain a molded body. The obtained molded body was sintered at 1070 ° C. for 14400 seconds (4 hours). The sintering temperature and the sintering time are within the scope of the present disclosure. The obtained sintered body was subjected to the same heat treatment as in Example 1 to obtain RTB-based sintered magnets (No. 22 and 23). Table 11 shows the composition of the RTB-based sintered magnet. R-T-B system sintered magnets (Sample Nos. 22 and 23) are machined to prepare samples having a length of 7 mm, a width of 7 mm, and a thickness of 7 mm, and characteristics of each sample ( _Br and H _cJ ) was measured. Table 10 shows the measurement results.

As shown in Table 10, the inventive examples, R-T-B based sintered magnet having both high B _r and high H _cJ are achieved.

According to the present invention, it is possible to produce R-T-B based sintered magnet having a high B _r and high H _cJ. The sintered magnet of the present invention is suitable for various motors such as a motor for mounting on a hybrid vehicle exposed to high temperatures, home appliances, and the like.

Main phase 14 composed of 12 R ₂ T ₁₄ B compound Grain boundary phase 14 a Two-grain grain boundary phase 14 b Grain boundary triple point

Claims (3)

R: 27.5% by mass or more and 33.0% by mass or less (R is at least one kind of rare earth elements and necessarily contains Nd),
B: 0.85 mass% or more and 0.97 mass% or less,
T: 61.5% by mass or more (T is Fe and Co, and 90% or more of T is Fe by mass ratio),
Preparing a main alloy powder containing
Pr: 65 mass% or more and 97 mass% or less (30 mass% of Pr can be replaced with other rare earth elements), and Ga: 3 mass% or more and 35 mass% or less (50 mass% or less of Ga can be replaced with Cu)
A step of preparing a Pr—Ga alloy powder prepared by an atomizing method,
The main alloy powder and the Pr—Ga alloy powder are mixed, and a mixed powder in which the mass ratio of the Pr—Ga alloy powder to the entire mixed powder is 1% by mass or more and 10% by mass or less is produced. Molding process;
A sintering step of sintering the compact of the mixed powder at a sintering temperature of 950 ° C. or higher and lower than 1120 ° C .;
Including
When the sintering temperature in the sintering step is T ° C. and the sintering time is t seconds,
5 × (1120−T) ² <t <10 × (1120−T) ² A manufacturing method of an RTB-based sintered magnet in which the relationship ² is established. When [T] is the content of T expressed in mass% and [B] is the content of B expressed in mass%, the RTB-based sintered magnet is:
[T] /55.85> 14 [B] /10.8
The manufacturing method of the RTB type | system | group sintered magnet of Claim 1 which satisfies these relationships.   The manufacturing method of the RTB system sintered magnet according to claim 1 or 2 whose Nd content in said Pr-Ga alloy powder is below inevitable impurity content.

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