JPWO2017159576A1 - Method for producing RTB-based sintered magnet - Google Patents

Abstract

R: 28.5 to 33.0% by mass (R is at least one rare earth element and includes at least one of Nd and Pr), B: 0.850 to 0.910% by mass, Ga: 0 2 to 0.7% by mass, Cu: 0.05 to 0.50% by mass, and Al: 0.05 to 0.50% by mass, the balance being T (T is Fe and Co, 90% by mass or more of T is Fe) and inevitable impurities, and the formula (1) (14 [B] /10.8 <[T] /55.85 ([B] is the mass% of B a content, the [T] is a is)) a method for producing R-T-B based sintered magnet that satisfies the content of the T represented by mass%, particle size D ₅₀ and particle size D ₉₉ a step of preparing an alloy powder which satisfies the equation _{(2) (3.8μm ≦ D 50} ≦ 5.5μm) and formula _{(3) (D 99 ≦ 10μm} ) R-, comprising: a molding step of molding the alloy powder to obtain a molded body; a sintering step of sintering the molded body to obtain a sintered body; and a heat treatment step of applying a heat treatment to the sintered body. It is a manufacturing method of a TB type sintered magnet.

Description

  The present disclosure relates to a method for manufacturing an RTB-based sintered magnet.

An R-T-B sintered magnet (R is at least one of rare earth elements and includes at least one of Nd and Pr, T is at least one of transition metal elements and must always contain Fe), R ₂ It is composed of a main phase composed of a compound having a T ₁₄ B-type crystal structure and a grain boundary phase located at the grain boundary portion of this main phase, and is known as the most powerful magnet among permanent magnets. .

  For this reason, it is used for various applications such as various motors such as voice coil motors (VCM) for hard disk drives, motors for electric vehicles (EV, HV, PHV), motors for industrial equipment, and home appliances.

  As the application expands in this way, for example, electric motors for motor vehicles may be exposed to high temperatures such as 100 ° C. to 160 ° C., and stable operation is required even at high temperatures.

However, the conventional _RTB -based sintered magnet has a _problem that the coercive force H _cJ (hereinafter sometimes simply referred to as “H _cJ ”) decreases at a high temperature and irreversible thermal demagnetization occurs. is there. When an R-T-B sintered magnet is used for a motor for an electric vehicle, _HcJ decreases due to use at a high temperature, and there is a possibility that stable operation of the motor cannot be obtained. Therefore, an _RTB -based sintered magnet having high H _cJ at room temperature and high H _cJ even at high temperature is required.

Conventionally, in order to improve _HcJ at room temperature, a heavy rare earth element RH (mainly Dy) has been added to an RTB-based sintered magnet, but residual magnetic flux density B _r (hereinafter simply referred to as “B _r ”) There is a problem that it may decrease). Furthermore, Dy has problems such as supply being unstable and price fluctuating due to the limited production area. Therefore, there is a demand for a technique for improving _HcJ of an R-T-B based sintered magnet without using a heavy rare earth element RH such as Dy as _much as possible.

As such a technique, for example, Patent Document 1 contains a metal element M that is one or more selected from Al, Ga, and Cu while lowering the B amount than a normal RTB-based alloy. The R ₂ T ₁₇ phase is generated by the process, and the volume fraction of the transition metal rich phase (R-T-Ga phase) generated using the R ₂ T ₁₇ phase as a raw material is sufficiently ensured to contain Dy. It discloses that an RTB-based sintered magnet having a high coercive force can be obtained while suppressing the amount.

International Publication No. 2013/008756

However, although the _RTB -based sintered magnet described in Patent Document 1 has improved _HcJ , it is insufficient to satisfy recent requirements.

Then, embodiment of this invention aims at providing the manufacturing method of the _{RTB type |} system _| group sintered magnet which has high coercive force _HcJ .

In aspect 1 of the present invention, R: 28.5 to 33.0 mass% (R is at least one rare earth element and includes at least one of Nd and Pr), B: 0.850 to 0.00. 910% by mass, Ga: 0.2 to 0.7% by mass, Cu: 0.05 to 0.50% by mass, Al: 0.05 to 0.50% by mass, the balance being T (T is Fe and Co, 90% by mass or more of T is Fe) and inevitable impurities, and a method for producing an RTB-based sintered magnet satisfying the following formula (1),

14 [B] /10.8 <[T] /55.85 (1)
([B] is the B content in mass%, and [T] is the T content in mass%)

A step of preparing an alloy powder having a particle size D ₅₀ and a particle size D ₉₉ satisfying the following formulas (2) and (3); a forming step of forming the alloy powder to obtain a formed product; It is a manufacturing method of the R-T-B system sintered magnet including the sintering process which couple | bonds together and obtains a sintered compact, and the heat processing process which heat-processes the said sintered compact.

3.8 μm ≦ D ₅₀ ≦ 5.5 μm (2)
D ₉₉ ≦ 10 μm (3)

  Aspect 2 of the present invention is the method for producing an RTB-based sintered magnet according to aspect 1, wherein B in the RTB-based sintered magnet is 0.870 to 0.910 mass%. is there

Aspect 3 of the present invention is the production of the RTB-based sintered magnet according to aspect 1 or 2, wherein the particle diameter D ₅₀ and the particle diameter D ₉₉ further satisfy the following formulas (4) and (5): Is the method.
3.8 μm ≦ D ₅₀ ≦ 4.5 μm (4)
D ₉₉ ≦ 9 μm (5)

According to the embodiment of the present invention, it is possible to provide a method capable of producing an _RTB -based sintered magnet having a high coercive force _HcJ .

FIG. 1 is a diagram illustrating the relationship between the coercivity improvement width ΔH _cJ and the B amount in the embodiment.

  Embodiment shown below illustrates the manufacturing method of the RTB type sintered magnet for materializing the technical idea of this invention, Comprising: This invention is not limited below.

As a result of intensive studies, the present inventors have conducted classification in the production of an RTB-based sintered magnet having a specific composition range as described in the embodiment of the present invention, particularly an extremely narrow specific range of B content. By adjusting the particle size distribution of the alloy powder by removing fine powder having a relatively large particle size using a machine or the like, the _HcJ of the finally obtained R-T-B system sintered magnet is greatly increased. I found that I could rise.

In the production of conventional RTB-based sintered magnets, fine powder having a relatively large particle size has been removed. However, as shown in the examples to be described later, outside the specific composition range of the present invention, the improvement width of _HcJ of the finally obtained _RTB -based sintered magnet is small. Furthermore, in order to remove fine powder having a relatively large particle size, the pulverization time must be lengthened, and the pulverization efficiency is lowered, resulting in deterioration of mass production efficiency. That is, conventionally, _since the improvement in _HcJ is too small to cause deterioration in mass production efficiency, it has not been actively performed in actual mass production.

However, as will be described later, the inventors of the present invention have a specific composition range (particularly, the B content is 0.850 to 0.910% by mass) according to the embodiment of the present invention. The average particle diameter D ₅₀ is 3.8 μm or more and 5.5 μm or less, and D ₉₉ is 10 μm or less (preferably, the average particle diameter D ₅₀ is 3.8 μm or more and 4.5 μm or less, and D ₉₉ is 9 μm or less. The R-T-B system sintered magnet obtained by adjusting the raw material alloy powder so as to be, and molding, sintering, and heat-treating such alloy powder has a mass production efficiency due to the longer pulverization time. As a result, the inventors have found that _HcJ is greatly improved to the extent that it can be actively carried out even if the deterioration of the _temperature is _caused .
The manufacturing method according to the embodiment of the present invention will be described in detail below.

[RTB-based sintered magnet]
First, the RTB system sintered magnet obtained by the manufacturing method according to the embodiment of the present invention will be described.

[Composition of RTB-based sintered magnet]
The composition of the RTB-based sintered magnet according to this embodiment is
R: 28.5 to 33.0% by mass (R is at least one rare earth element and includes at least one of Nd and Pr),
B: 0.850-0.910 mass%,
Ga: 0.2-0.7 mass%,
Cu: 0.05 to 0.50 mass%,
Al: 0.05 to 0.50 mass%,
The balance is T (T is Fe and Co, 90% by mass or more of T is Fe) and inevitable impurities, and satisfies the following formula (1).

14 [B] /10.8 <[T] /55.85 (1)
([B] is the B content in mass%, and [T] is the T content in mass%.)

With the above composition, the amount of B is smaller than that of a general RTB-based sintered magnet, and Ga and the like are contained. Therefore, an RT-Ga phase is generated at the two-grain grain boundary, High H _cJ can be obtained. Here, the R—T—Ga phase is typically an Nd ₆ Fe ₁₃ Ga compound. The R ₆ T ₁₃ Ga compound has a La ₆ Co ₁₁ Ga ₃ type crystal structure. Moreover, the R ₆ T ₁₃ Ga compound may be an R ₆ T _13-δ Ga _{1 + δ} compound (δ is typically 2 or less) depending on the state. For example, Cu in R-T-B based sintered magnet, if the Al is contained relatively _large, may have been the _{R 6 T 13-δ (Ga} 1-x-y Cu x Al y) 1 + δ is there.
Below, each composition is explained in full detail.

(R: 28.5-33.0% by mass)
R is at least one of rare earth elements and includes at least one of Nd and Pr. Content of R is 28.5-33.0 mass%. R is may become difficult to densification during sintering is less than 28.5% by mass may main phase proportion exceeds 33.0% by weight can not be obtained a high B _r drops . The content of R is preferably 29.5 to 32.5% by mass. If R is in such a range, higher _Br can be obtained.

(B: 0.850 to 0.910 mass%)
Content of B is 0.850-0.910 mass%. Especially if narrow range content, such as the B-in the embodiment of the present invention, in the step of obtaining the alloy powder to be described later, the particle size D ₅₀ and D ₉₉ of the alloy powder is in a predetermined specified in the embodiment of the present invention By managing so that it may become a range, _HcJ of the _RTB system sintered magnet finally obtained can be improved significantly. When the B content is less than 0.850 mass% and exceeds 0.910 mass%, a high _HcJ improvement effect cannot be obtained. Preferably, the content of B is 0.870 to 0.910 mass%. A higher _HcJ improvement effect can be obtained.

Furthermore, the content of B satisfies the following formula (1).

14 [B] /10.8 <[T] /55.85 (1)

By satisfying the formula (1), the content of B becomes smaller than that of a general RTB-based sintered magnet. A general R-T-B type sintered magnet has [T] /55.85 (so that an R ₂ T ₁₇ phase, which is a soft magnetic phase, is not generated in addition to an R ₂ T ₁₄ B phase, which is a main phase. The atomic weight of Fe is less than 14 [B] /10.8 (the atomic weight of B) ([T] is the content of T expressed in mass%). The R-T-B system sintered magnet of the embodiment of the present invention differs from a general R-T-B system sintered magnet in that [T] /55.85 is greater than 14 [B] /10.8. It is defined by equation (1) so as to increase. In addition, since the main component of T in the RTB-based sintered magnet of the embodiment of the present invention is Fe, the atomic weight of Fe was used.

(Ga: 0.2-0.7 mass%)
The Ga content is 0.2 to 0.7% by mass. If Ga is less than 0.2% by mass, the amount of R—T—Ga phase produced is so small that R ₂ T ₁₇ phase cannot be lost and high H _cJ may not be obtained. It will be present unnecessary Ga exceeds 0.7 weight%, there is a possibility that B _r decreases to decrease the main phase proportion.

(Cu: 0.05 to 0.50 mass%)
The content of Cu is 0.05 to 0.50 mass%. If Cu is less than 0.05% by mass, high H _cJ may not be obtained, and if it exceeds 0.50% by mass, sinterability may deteriorate and high H _cJ may not be obtained.

(Al: 0.05 to 0.50 mass%)
The Al content is 0.05 to 0.50 mass%. By containing Al, _HcJ can be improved. Al is usually contained in an amount of 0.05% by mass or more as an inevitable impurity in the production process, but it may be contained in an amount of 0.5% by mass or less in total of the amount contained by the inevitable impurity and the amount intentionally added. Good.

(Remainder: T and inevitable impurities)
The balance is T and inevitable impurities. Here, T is Fe and Co, and 90% by mass or more of T is Fe. Although the corrosion resistance can be improved by containing Co, if the substitution amount of Co exceeds 10% by mass of Fe, high _Br may not be obtained.
Furthermore, the RTB-based sintered magnet of the embodiment of the present invention includes Cr, Mn, Si, La, Ce as inevitable impurities usually contained in didymium alloy (Nd—Pr), electrolytic iron, ferroboron, and the like. , Sm, Ca, Mg and the like can be contained. Furthermore, O (oxygen), N (nitrogen), C (carbon), etc. can be illustrated as an inevitable impurity in a manufacturing process. Moreover, you may contain a small amount (about 0.1 mass%) of V, Ni, Mo, Hf, Ta, W, Nb, Zr, etc.

  Below, the detail of the manufacturing method of the RTB type | system | group sintered magnet which concerns on embodiment of this invention is demonstrated.

[Method for producing RTB-based sintered magnet]
The manufacturing method of the RTB system sintered magnet which has the composition mentioned above is explained. The manufacturing method of a RTB system sintered magnet has a process of obtaining alloy powder, a forming process, a sintering process, and a heat treatment process.
Hereinafter, each step will be described.

(1) Step of obtaining alloy powder In this step, it has the same composition as the RTB-based sintered magnet described above, the particle size D ₅₀ is 3.8 μm or more and 5.5 μm or less, and the particle size D An alloy powder with ₉₉ of 10 μm or less is obtained. Particle size D ₅₀ and D ₉₉ is such a range, In addition, by using the prepared alloy powder having the composition of the R-T-B based sintered magnet according to the present embodiment, the finally obtained The obtained _RTB -based sintered magnet can have a high coercive force _HcJ .

Such an alloy powder can be obtained, for example, as follows.
A metal or alloy (melting raw material) of each element is prepared so as to have the composition of the above-described RTB-based sintered magnet, and a flaky raw material alloy is produced by a strip casting method or the like. Next, an alloy powder is produced from the flaky raw material alloy. The obtained flaky raw material alloy is pulverized with hydrogen to obtain coarsely pulverized powder of, for example, 1.0 mm or less. Next, the coarsely pulverized powder was finely pulverized by a jet mill or the like in an inert gas, by using a classifier to remove a large finely pulverized powder particle size, the particle size D ₅₀ is not more than 5.5μm or 3.8μm There is obtained finely pulverized powder (alloy powder) having a particle size D ₉₉ of 10 μm or less. An _RTB -based sintered magnet having a high coercive force _HcJ is obtained by manufacturing an _RTB -based sintered magnet having the above-described composition using an alloy powder having such a particle size distribution. be able to. Alloy powder had a particle size _{D 50} is at 4.5μm or less than 3.8 .mu.m, and more preferably _{D 99} is 9μm or less. If it is such a range, _HcJ of the _RTB system sintered magnet finally obtained can be improved more.

  As the alloy powder, one kind of alloy powder (single alloy powder) may be used, or a so-called two alloy method may be used in which an alloy powder (mixed alloy powder) is obtained by mixing two or more kinds of alloy powder. The alloy powder may be produced using a known method or the like so as to obtain the composition of the embodiment of the present invention. A known lubricant may be added as an auxiliary agent to the coarsely pulverized powder before jet mill pulverization, and the alloy powder during and after jet mill pulverization.

As described above, the alloy powder according to the present embodiment has a specific range of particle diameters D ₅₀ and D ₉₉ , and the particle diameters D ₅₀ and D ₉₉ are determined based on the air flow dispersion type laser diffraction method (JIS Z 8825: 2013). According to the revised version). That is, in the present specification, D ₅₀ means a particle size (median diameter) at which the integrated particle size distribution (volume basis) from the small particle size side is 50%, and D ₉₉ is an integration from the small particle size side. It means the particle size at which the particle size distribution (volume basis) is 99%.
Note _{D 50} and _{D 99} in the embodiment of the present invention, dispersing pressure in Sympatec Co. particle size distribution measuring apparatus "HELOS &RODOS": 4 bar
Measurement range: R2
Calculation mode: HRLD
It shows D ₅₀ and D ₉₉ measured under the following conditions.

(2) Forming step Using the obtained alloy powder, forming in a magnetic field is performed to obtain a formed body. In the magnetic field molding, a dry alloy method in which a dry alloy powder is inserted into a mold cavity and molded while applying a magnetic field, a slurry in which the alloy powder is dispersed is injected into the mold cavity, Any known forming method in a magnetic field may be used, including a wet forming method of forming while discharging the slurry dispersion medium.

(3) Sintering process A sintered compact (sintered magnet) is obtained by sintering a molded object. A known method can be used for sintering the molded body. In addition, in order to prevent the oxidation by the atmosphere at the time of sintering, it is preferable to perform sintering in a vacuum atmosphere or atmospheric gas. The atmosphere gas is preferably an inert gas such as helium or argon.

(4) Heat treatment process It is preferable to perform the heat processing for the purpose of improving a magnetic characteristic with respect to the obtained sintered magnet. Known conditions can be used for the heat treatment temperature, the heat treatment time, and the like. For example, heat treatment (one-step heat treatment) only at a relatively low temperature (400 ° C. or more and 600 ° C. or less) may be performed, or heat treatment is performed at a relatively high temperature (700 ° C. or more and sintering temperature or less (eg, 1050 ° C. or less)). After performing, heat treatment (two-stage heat treatment) may be performed at a relatively low temperature (400 ° C. or more and 600 ° C. or less). Preferable conditions are as follows: heat treatment at 730 ° C. to 1020 ° C. for 5 minutes to 500 minutes, cooling (after cooling to room temperature or after cooling to 440 ° C. to 550 ° C.), and further at 440 ° C. to 550 ° C. Heat treatment for about 500 minutes to 500 minutes. The heat treatment atmosphere is preferably a vacuum atmosphere or an inert gas (such as helium or argon).

  For the purpose of obtaining a final product shape, the obtained sintered magnet may be subjected to machining such as grinding. In that case, the heat treatment may be performed before or after machining. Furthermore, you may surface-treat to the obtained sintered magnet. The surface treatment may be a known surface treatment, and for example, a surface treatment such as Al deposition, electric Ni plating, or resin coating can be performed.

  The present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

Example 1
Sample No. in Table 1 Each element was weighed so as to have the composition of the RTB-based sintered magnet shown in 1-27, and an alloy was produced by strip casting. Each obtained alloy was coarsely pulverized by a hydrogen pulverization method to obtain a coarsely pulverized powder. The coarsely pulverized powder was finely pulverized by a jet mill under any of conditions A to C described below (however, only sample No. 13 was finely pulverized under condition C).

(Condition A)
Condition A was that fine pulverization was performed at a feed rate of 200 g / min to the jet mill and a classification rotor rotation speed of 4500 rpm. The grinding time was about 10 minutes. Condition A is normal pulverization conditions, and target values are a particle size D ₅₀ : 4 μm and a particle size D ₉₉ : 12 μm. The D ₅₀ and the D ₉₉ are respectively a particle size and a small particle in which the cumulative particle size distribution (volume basis) from the small particle size side is 50% in the particle size distribution obtained by the laser diffraction method by the air flow dispersion method. The particle size at which the cumulative particle size distribution (volume basis) from the diameter side is 99%. D ₅₀ and D ₉₉ were measured under the conditions of dispersion pressure: 4 bar, measurement range: R2, and calculation mode: HRLD using a particle size distribution measuring apparatus “HELOS & RODOS” manufactured by Sympatec.

(Condition B)
Condition B was fine pulverization with the raw material supply rate to the jet mill set to 50 g / min and the classification rotor rotation speed set to 5500 rpm. The grinding time was about 40 minutes. Condition B is performed to obtain the particle diameters (D ₅₀ and D ₉₉ ) of the embodiment of the present invention, and the target values are the particle diameter D ₅₀ : 4 μm and the particle diameter D ₉₉ : 9.5 μm. Condition C was that fine pulverization was performed with the raw material supply rate to the jet mill set to 50 g / min and the classification rotor rotation speed set to 6000 rpm. The grinding time was about 40 minutes.

(Condition C)
Condition C is performed in order to obtain preferable particle diameters (D ₅₀ and D ₉₉ ) of the embodiment of the present invention, and target values are a particle diameter D ₅₀ : 4 μm and a particle diameter D ₉₉ : 8.5 μm.

Tables 2 and 3 show the actual measured values of the particle diameters (D ₅₀ and D ₉₉ ) of the finely pulverized powder obtained by pulverizing under each condition. In “Condition A” of Table 2, sample No. Measured values of the particle size of finely pulverized powder obtained by finely pulverizing 1-27 under condition A are shown. In “Condition B” in Table 2, sample No. The measured value of the particle size of the finely pulverized powder obtained by pulverizing 1-27 under the condition B is shown. In “Condition A” of Table 3, sample No. The actual measured value of the particle size obtained by pulverizing 13 under condition A is shown. In “Condition C” of Table 3, sample No. The measured value of the particle size obtained by pulverizing 13 under the condition C is shown.

After adding and mixing 0.05 parts by mass of zinc stearate as a lubricant with respect to 100 parts by mass of finely pulverized powder, the resulting finely pulverized powder (alloy 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 (lateral magnetic field shaping | molding apparatus) in which the magnetic field application direction and the pressurization direction orthogonally cross was used for the shaping | molding apparatus. The obtained molded body was sintered in vacuum at 1030 to 1070 ° C. for 4 hours according to the composition to obtain an RTB-based sintered magnet. The density of the sintered magnet was 7.5 Mg / m ³ or more. Further, the sintered RTB-based sintered magnet was held at 800 ° C. for 2 hours, then rapidly cooled to room temperature, then held at 500 ° C. for 2 hours and then cooled to room temperature.

  In order to determine the components of the obtained sintered magnet, the contents of Nd, Pr, Tb, B, Co, Al, Cu, Ga, Nb, Zr, and Fe were measured by ICP emission spectroscopy. Further, O (oxygen amount) was measured using a gas melting-infrared absorption method, N (nitrogen amount) was measured using a gas melting-heat conduction method, and C (carbon amount) was measured using a combustion-infrared absorption method. . The results are shown in Table 1.

The sintered magnet after the heat treatment was machined to prepare samples having a length of 7 mm, a width of 7 mm, and a thickness of 7 mm, and the characteristics (B _r and H _cJ ) of each sample were measured with a _BH tracer. The measurement results are shown in Tables 2 and 3.
The “examples of the present invention” described in the remarks column of Tables 2 and 3 mean examples that satisfy the requirements defined in the embodiments of the present invention.

In “Condition A” of Table 2, the sample No. The characteristic values of sintered magnets obtained by pulverizing an alloy having a composition of 1 to 27 under condition A and sintering and heat-treating the obtained finely pulverized powder are shown. In “Condition B” in Table 2, the sample No. Alloy was milled in condition B the having a composition of 1 to 27, sintering the finely pulverized powder obtained, the characteristic values of the sintered magnet obtained by heat treatment (the value of B _r and H _cJ) is shown ing. Further, “Condition B—Condition A” in Table 2 _shows the improvement width (ΔH _cJ ) of the sintered magnet by changing the pulverization condition from Condition A to Condition B. That is, ΔH _cJ in Table 2 is the difference in H _cJ in the R-T-B system sintered magnet obtained by producing finely pulverized powder under Condition A or Condition B (R obtained using Condition B). The value obtained by subtracting the value of _HcJ of the _RTB -based sintered magnet obtained using Condition A from the value of _HcJ of the TB-based sintered magnet).

In “Condition A” of Table 3, the sample No. The characteristic values of a sintered magnet obtained by finely pulverizing an alloy having a composition of 13 under condition A and sintering and heat-treating the finely pulverized powder obtained are shown. In “Condition C” of Table 3, the sample No. The characteristic values of a sintered magnet obtained by finely pulverizing an alloy having a composition of 13 under condition C and sintering and heat-treating the obtained finely pulverized powder are shown. “Condition C—Condition A” in Table 3 _shows the improvement width (ΔH _cJ ) of H _cJ of the sintered magnet by changing the pulverization condition from Condition A to Condition C. That is, ΔH _cJ in Table 3 is the difference in H _cJ in the R-T-B system sintered magnet obtained by producing finely pulverized powder under condition A or condition C (R obtained using condition C). The value obtained by subtracting the value of _HcJ of the _RTB -based sintered magnet obtained using Condition A from the value of _HcJ of the TB-based sintered magnet).

As shown in Table 2, sample no. Any of the sintered magnet 1-27, the finely pulverized powder used (finely pulverized powder produced in the condition B) The particle size of the embodiment of the present invention the particle size D ₅₀ and particle size D ₉₉ of the (alloy powder) by, as compared to a regular particle size (prepared under the conditions a), H _cJ without loss of B _r is improved ([Delta] H _cJ is greater than 0). However, the sample No. which does not satisfy the composition of the embodiment of the present invention. In the comparative examples of _{15 to 26} , the improvement width (ΔH _cJ ) of H _cJ of the sintered magnet was not sufficient at 36 to 57 kA / m. On the other hand, in the composition range of the embodiment of the present invention (sample Nos. 1 to 14 and 27), ΔH _cJ is 87 to ₁₀₁ kA / m, which is significantly about 1.5 to 2.5 times that of the comparative example. Improved. Thus, by satisfying the composition of an embodiment of the present invention, a high B _r and high H _cJ are achieved. As described above, when the condition A (normal particle size) is changed to the condition B (particle size of the embodiment of the present invention), the pulverization time is increased from 10 minutes to 40 minutes. Therefore, when the composition of the embodiment of the present invention is not satisfied, the improvement width of _HcJ is small, so that the pulverization is not performed with the particle size of the embodiment of the present invention. However, since the _HcJ is greatly improved within the composition range of the embodiment of the present invention, it is sufficiently worth even if the pulverization time is increased.

Here, FIG. 1 shows the relationship between the B amount shown in Table 1 and the coercivity improvement width ΔH _cJ shown in Tables 2 and 3. In FIG. 1, the vertical axis represents ΔH _cJ of the inventive example and the comparative example, and the horizontal axis represents the B amount. A square plot (■) in FIG. 1 is an example of the present invention, and a triangular plot (▲) is a comparative example. As shown in FIG. 1, it can be seen that a high ΔH _cJ is obtained in a very narrow range of B amount of 0.850 to 0.910 mass%. In addition, a higher B content (90 kA / m or more) ΔH _cJ is obtained when the B content is 0.870 to 0.910 mass%.

Moreover, as shown in Table 3, the particle size D ₅₀ and the particle size D ₉₉ in the finely pulverized powder (alloy powder) are preferably in the preferred embodiments of the present invention (3.8 μm ≦ D ₅₀ ≦ 4.5 μm and D ₉₉ ≦ If it is 9 .mu.m), without loss of _{B r} is [Delta] H _cJ and 173kA / m, even higher _{B r} and high _{H cJ} are achieved.

  This application is accompanied by a priority claim based on a Japanese patent application filed on March 17, 2016, Japanese Patent Application No. 2006-054153. Japanese Patent Application No. 2006-054153 is incorporated herein by reference.

Claims (3)

R: 28.5 to 33.0% by mass (R is at least one rare earth element and includes at least one of Nd and Pr),
B: 0.850-0.910 mass%,
Ga: 0.2-0.7 mass%,
Cu: 0.05 to 0.50 mass%,
Al: 0.05 to 0.50 mass%,
The balance is T (T is Fe and Co, 90% by mass or more of T is Fe) and inevitable impurities, and a method for producing an R-T-B system sintered magnet satisfying the following formula (1) Because

14 [B] /10.8 <[T] /55.85 (1)
([B] is the B content in mass%, and [T] is the T content in mass%)

Preparing an alloy powder having a particle size D ₅₀ and a particle size D ₉₉ satisfying the following formulas (2) and (3);
3.8 μm ≦ D ₅₀ ≦ 5.5 μm (2)
D ₉₉ ≦ 10 μm (3)
A molding step of molding the alloy powder to obtain a molded body;
Sintering step for obtaining a sintered body by sintering the molded body;
A heat treatment step for heat-treating the sintered body;
The manufacturing method of the RTB type | system | group sintered magnet containing this.   The manufacturing method of the RTB system sintered magnet according to claim 1 whose B in said RTB system sintered magnet is 0.870-0.910 mass%. Satisfies the particle diameter _{D 50} and particle size _{D 99} is further following formula (4) and (5) The method of manufacturing a R-T-B based sintered magnet according to claim 1 or 2.
3.8 μm ≦ D ₅₀ ≦ 4.5 μm (4)
D ₉₉ ≦ 9 μm (5)

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