JP2021057564A - Method for manufacturing r-t-b based sintered magnet - Google Patents

Abstract

To provide a method for manufacturing an R-T-B based sintered magnet having high Br and high HcJ while a content of a heavy rare earth element is decreased.SOLUTION: A method for manufacturing an R-T-B based sintered magnet comprises the step of performing a thermal treatment at a temperature of 450 to 500°C in vacuum or inert gas atmosphere with at least part of an R2-M based alloy put in contact with at least part of a surface of an R1-T1-B based sintered compact. In the R1-T1-B based sintered compact, a molar ratio ([T1]/[B]) of T1 to B is over 14.0 and equal to or smaller than 15.0. In the R2-M based alloy, R2 is at least one kind of rare earth elements, and always includes La, a content of R2 is 55 mol% or more and 90 mol% or less; a rate of La to a total quantity of the rare earth elements is higher than a rate of La to a total quantity of the rare earth elements in the R1-T1-B based sintered compact; M includes Cu or both of Cu and Al; and a content of M is 5 mol% or more and 40 mol% or less.SELECTED DRAWING: Figure 1

Description

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

R-TB-based sintered magnets (R is at least one of the rare earth elements. T is at least one of the transition metal elements and always contains Fe. B is boron) are the most permanent magnets. Known as a high-performance magnet, it 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. .. As used herein, the rare earth element means at least one element selected from the group consisting of scandium (Sc), yttrium (Y), and lanthanoids. Here, lanthanoid is a general term for 15 elements from lanthanum to lutetium.

R-T-B based sintered magnet is mainly grain boundary phase located in the grain boundary of the main phase and the main phase consisting of R _{2 T} 14 _B compound (hereinafter, simply referred to as "grain boundary") from the It is configured. R 2 _T 14 _B compound has the foundation characteristics of high magnetization are ferromagnetic phase with an R-T-B based sintered magnet.

_{The RTB} -based sintered magnet has a problem that irreversible thermal demagnetization occurs because the coercive force H cJ (hereinafter, may be simply referred to as “coercive force” or “H _{cJ”) decreases at a high temperature.} Therefore, in a particularly R-T-B based sintered magnet used in an electric vehicle motor, having a high H _cJ even at high temperatures, that is, required to have a higher H _cJ at room temperature.

In the RTB-based sintered magnet, a part of the light rare earth elements (mainly Nd and / or Pr) contained in R _{in the R 2} T _{14 B compound is a heavy rare earth element (mainly Dy and / or Tb).} Substitution is known to improve _{H cJ. H cJ} improves as the amount of replacement of heavy rare earth elements increases.

_However, while improving the _{H cJ} of R _{2 T 14} B when the light rare earth element in the compound is replaced with the heavy rare-earth element R-T-B based sintered magnet, the remanence _{B r} (hereinafter, simply _{"B r"} In some cases) decreases. In addition, heavy rare earth elements, especially Dy, have problems such as unstable supply due to a small amount of resources present and limited production areas, and prices fluctuate significantly. Therefore, in recent years, users _{have requested to improve HcJ} without using heavy rare earth elements as much as possible.

Patent Document 1 discloses an RTB-based rare earth sintered magnet in which the coercive force is increased while reducing the Dy content. The composition of this sintered magnet is limited to a specific range in which the amount of B is relatively small as compared with the generally used RTB-based alloy, and is selected from Al, Ga, and Cu1. It contains more than one kind of metal element M. As a result, an R ₂ T ₁₇ phase is generated at the grain boundary, and the volume ratio of the transition metal rich phase (R ₆ T _{13 M) formed at the grain boundary from this R 2} T _{17 phase increases, so that H cJ} Is improved.

International Publication No. 2013/0087756

It is noteworthy that the method described in Patent Document 1 can increase the coercive force of the RTB-based sintered magnet while suppressing the content of heavy rare earth elements. However, there is a problem that _{Br is significantly reduced.} Demand for RTB-based sintered magnets is expected to grow significantly in the future, especially for motors for electric vehicles. Therefore, it is necessary not only to reduce heavy rare earth elements but also to diversify the use of rare earth elements. As a specific means, La (in addition to Ce), which has a relatively abundant abundance among rare earth elements, can be used.

Embodiments of the present disclosure, using La, while reducing the content of heavy rare earth elements, to provide a method of manufacturing a R-T-B based sintered magnet having a high B _r and a high H _cJ.

The method for producing an R-TB-based sintered magnet of the present disclosure includes, in an exemplary embodiment, a step of preparing an R1-T1-B-based sintered body, a step of preparing an R2-M-based alloy, and a step of preparing an R2-M alloy. At least a part of the R2-M alloy is brought into contact with at least a part of the surface of the R1-T1-B-based sintered body, and heat treatment is performed at a temperature of 450 ° C. or higher and 850 ° C. or lower in a vacuum or an inert gas atmosphere. In the R1-T1-B-based sintered body, R1 is at least one of rare earth elements, and always contains at least one of Nd and Pr, and the content of R1 is R1-T1-. It is 27 mass% or more and 35 mass% or less of the whole B-based sintered body, T1 is Fe or at least one of Co, Al, Mn, and Si and Fe, and the content of Fe with respect to the whole T1 is 80 mass% or more and B. The mol ratio of T1 to ([T1] / [B]) is more than 14.0 and 15.0 or less, and in the R2-M alloy, R2 is at least one of the rare earth elements and always contains La. The content of R2 is 55 mol% or more and 90 mol% or less of the whole R2-M alloy, and the ratio of La to the whole rare earth element is the ratio of La to the whole rare earth element of the R1-T1-B based sintered body. Higher than, M contains Cu or both Cu and Al, and the content of M is 5 mol% or more and 40 mol% or less of the whole R2-M alloy.
The method for producing an R-TB-based sintered magnet of the present disclosure is a step of preparing an R1-T1-B-based sintered body and a step of preparing an R2-Al-Cu-based alloy in another exemplary embodiment. At least a part of the R2-Al—Cu alloy is brought into contact with at least a part of the surface of the R1-T1-B-based sintered body, and the temperature is 450 ° C. or higher and 850 in a vacuum or an inert gas atmosphere. In the R1-T1-B-based sintered body, which includes a step of performing a heat treatment at a temperature of ° C. or lower, R1 is at least one of rare earth elements, always contains at least one of Nd and Pr, and contains R1. Is 27 mass% or more and 35 mass% or less of the entire R1-T1-B-based sintered body, T1 is Fe or at least one of Co, Al, Mn, and Si and Fe, and the content of Fe with respect to the entire T1 is 80 mass. % Or more, and the mol ratio of T1 to B ([T1] / [B]) is more than 14.0 and 15.0 or less. In the R2-Al—Cu alloy, R2 is at least one of the rare earth elements. And
La is always contained, the content of R2 is 70 mol% or more and 90 mol% or less of the whole R2-Al—Cu alloy, and the ratio of La to the whole rare earth element is the ratio of La to the whole rare earth element of the R1-T1-B based sintered body. It is higher than the ratio of La to the total rare earth elements, and the Al content is 5 mol% or more and 20 mo of the total R2-Al—Cu alloy.
It is l% or less, and the Cu content is 5 mol% or more and 20 mol% or less of the entire R2-Al—Cu based alloy.
In a certain embodiment, La in the R2-Al—Cu based alloy is 50 mol% or more of the total amount of R2.
In certain embodiments, R2 in the R2-Al—Cu based alloy is La (including impurities).
In a certain embodiment, the total content of R2, Al, and Cu in the R2-Al—Cu based alloy is 8.
It is 0 mol% or more.
In a certain embodiment, in the step of preparing the R1-T1-B-based sintered body, the raw material alloy has a particle size D ₅₀ of 3.
This includes pulverizing the material so that the thickness is μm or more and 10 μm or less, and then aligning the material in a magnetic field for sintering.

According to embodiments of the present disclosure, it is possible to use La, while reducing the content of heavy rare earth elements, to provide a method of manufacturing a R-T-B based sintered magnet having a high B _r and a high H _cJ it can.

It is a flowchart which shows the example of the process in the manufacturing method of the RTB system sintered magnet by this disclosure. It is a schematic diagram which shows the main phase and the grain boundary phase of the RTB-based sintered magnet. It is a schematic diagram which further enlarged the inside of the broken line rectangular area of FIG. 2A. It is explanatory drawing which shows typically the example of the arrangement form of the R1-T1-B-based sintered body and the R2-Al-Cu-based alloy in the heat treatment step.

In the present disclosure, rare earth elements may be collectively referred to as "R". When referring to a specific element or group of rare earth elements R, for example, the symbols "R1" and "R2" are used to distinguish them from other rare earth elements. Further, in the present disclosure, the entire transition metal element including Fe is referred to as "T". When both a specific element or element group of the transition metal element T and a specific element or element group other than the transition metal element that is easily replaced with the Fe site of the main phase are included, the reference numeral "T1" is used. Distinguish from other transition metal elements.
As shown in FIG. 1, the method for producing an R-TB-based sintered magnet according to the present disclosure includes a step S10 for preparing an R1-T1-B-based sintered body and an R2-M-based alloy (preferably R2). The step S20 for preparing the −Al—Cu based alloy) is included. The order of the step S10 for preparing the R1-T1-B-based sintered body and the step S20 for preparing the R2-M-based alloy (preferably R2-Al—Cu-based alloy) is arbitrary, and each has a different location. The R1-T1-B-based sintered body and the R2-M-based alloy (preferably R2-Al—Cu-based alloy) produced in the above may be used.

In the present disclosure, the R-TB-based sintered magnet before and during the heat treatment is referred to as an R1-T1-B-based sintered body, and the R1-T1-B-based sintered body after the heat treatment is simply RT-. It is called a B-based sintered magnet.

In the R1-T1-B-based sintered body, the following (1) to (3) are established.
(1) R1 is at least one of rare earth elements and always contains at least one of Nd and Pr, and the content of R1 is 27 mass% or more and 35 mass% or less of the entire R1-T1-B-based sintered body.
(2) T1 is Fe or at least one of Co, Al, Mn, and Si and Fe, and the content of Fe with respect to the whole T1 is 80 mass% or more.
(3) The mol ratio of T1 to B ([T1] / [B]) is more than 14.0 and 15.0 or less.
The mol ratio of T1 to B ([T1] / [B]) in the present disclosure is an analytical value (mass%) of each element (at least one of Fe or Co, Al, Mn, Si and Fe) constituting T1. Was divided by the atomic weight of each element, and the ratio (a /) of the sum of those values (a) and the analytical value of B (mass%) divided by the atomic weight of B (b). b).
Mol ratio of T1 for B ([T1] / [B ]) that is greater than 14.0, the content ratio of B is meant that less than the stoichiometric composition ratio of _R 2 _{T 14} B compound There is. In other words, the R1-T1-B based sintered body, relative B amount relative to the amount of T1 to be used in the formation of the main phase _{(R 2 T 14} B compound) is small.

In the R2-M alloy, the following (4) and (5) are established.
(4) R2 is at least one of rare earth elements and always contains La, and the content of R2 is 55 mol% or more and 90 mol% or less of the whole R-2M alloy, and the ratio of La to the whole rare earth element. However, it is higher than the ratio of La to the total rare earth elements of the R1-T1-B based sintered body.
(5) M contains Cu or both Cu and Al, and the content of M is 5 mol% or more and 40 mol% or less of the entire R2-M alloy.
Further, as a preferable alloy form of the R2-M based alloy, an R2-Al—Cu based alloy can be mentioned.
In the R2-Al—Cu based alloy, the following (6) to (8) are preferably established.
(6) R2 is at least one of the rare earth elements and always contains La, and the content of R2 is 70 mol% or more and 90 mol% or less of the whole R2-Al—Cu alloy, and La with respect to the whole rare earth element. Is higher than the ratio of La to the total rare earth elements of the R1-T1-B based sintered body.
(7) The Al content is 5 mol% or more and 20 mol% or less of the entire R2-Al—Cu based alloy.
(8) The Cu content is 5 mol% or more and 20 mol% or less of the entire R2-Al—Cu based alloy.

Method for producing R-T-B based sintered magnet according to the present disclosure, the main phase (R 2 _T 14 _B compound) relatively reduced in a stoichiometric ratio to the amount of T that are used in forming, and the particular An R2-M alloy (preferably an R2-Al—Cu alloy) is brought into contact with at least a part of the surface of the R1-T1-B sintered body containing a B amount in the range, and as shown in FIG. Step S30 of performing the heat treatment at a temperature of 450 ° C. or higher and 850 ° C. or lower in a vacuum or an inert gas atmosphere is performed. Thus, it is possible to obtain the R-T-B based sintered magnet having a high _{B r} and a high _{H cJ.}

First, the basic structure of the RTB-based sintered magnet will be described.
R-T-B based sintered magnet, the powder particles of the raw material alloy has a structure bonded by sintering, mainly a main phase consisting of R _{2 T} 14 _B compound, the grain boundary portion of the main phase It is composed of the located grain boundary phase.
FIG. 2A is a schematic view showing the main phase and the grain boundary phase of the RTB-based sintered magnet, and FIG. 2B is a schematic view further enlarging the inside of the broken line rectangular region of FIG. 2A. In FIG. 2A, as an example, an arrow having a length of 5 μm is shown for reference as a reference length indicating the size. As shown in FIGS. 2A and 2B, R-T-B based sintered magnet includes a main phase 12 mainly composed of _R 2 _{T 14} B compound, the grain boundary phase located grain boundary of the main phase 12 14 It is composed of and. Further, as shown in FIG. 2B, the grain boundary phase 14 is _{a two-particle grain boundary phase 14a in which two R 2} T ₁₄ B compound particles (grains) are adjacent to each other, and three or more R ₂ T ₁₄ B compound particles. Includes adjacent grain boundary triple points 14b.
_{The R 2} T ₁₄ B compound, which is the main phase 12, is a ferromagnetic phase 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 changed to the stoichiometric ratio of the R 2} T ₁₄ B compound (R amount: T amount: B amount = It should be close to 2:14: 1). When the _{amount of B or R for forming the R 2} T ₁₄ B compound is less than the stoichiometric ratio, generally, _{a ferromagnet such as Fe phase or R 2} T ₁₇ phase is generated in the grain boundary phase 14. , H _cJ drops sharply. However, as in the method described in Patent Document 1, the B amount is less than the stoichiometric ratio of R _{2 T} 14 _B compound, and, Al, Ga, of one or more selected among Cu the inclusion of the metal element M, can be obtained a high H _cJ in the grain boundary to the transition metal-rich phase from the R ₂ T ₁₇ phase (e.g. R-T-M phase) is generated. However, with the method described in Patent Document 1, _Br is significantly reduced.

In the method for producing an RTB-based sintered magnet of the present disclosure, a rare earth element is formed on at least a part of the surface of an R1-T1-B-based sintered body having a low B composition and containing a specific B amount. Among them, R2-M alloys (preferably R2-Al—Cu alloys) containing La, which is relatively abundant in abundance, as R2 are brought into contact with each other to perform heat treatment, whereby R2 and M (preferably Al and M) containing La are subjected to heat treatment. Cu) is diffused inside the magnet. As a result of examination by the inventors, the content of R2 in the R2-M alloy (preferably R2-Al—Cu based alloy) is such that the ratio of La to the whole rare earth element is the ratio of the R1-T1-B based sintered magnet body. It should be higher than the ratio of La to the total rare earth elements. Then, when La is present in R2 at such a ratio and heat treatment is performed at a specific temperature (450 ° C. or higher and 850 ° C. or lower), grain boundary diffusion is promoted and thick two-particle grain boundaries are sintered. It was found that it can be easily formed even inside the body. Thus using La, while reducing the content of heavy rare earth elements, it is possible to obtain a high B _r and high H _cJ. That is, the present disclosure, R2 and M comprising La (preferably Al and Cu) by diffusing into the sintered body of the specific composition subjected to heat treatment the alloy containing at certain temperatures, a high B _r and high H _cJ It was found that the above can be realized.

(Step of preparing R1-T1-B-based sintered body)
First, the composition of the sintered body in the step of preparing the R1-T1-B-based sintered body (hereinafter, may be simply referred to as “sintered body”) will be described.
R1 is at least one of rare earth elements and always contains at least one of Nd and Pr. _{In order to improve the HcJ} of the R1-T1-B-based sintered body, a small amount of commonly used heavy rare earth elements such as Dy, Tb, Gd, and Ho may be contained. However, according to the production method according to the present disclosure, a sufficiently high _HcJ can be obtained without using a large amount of heavy rare earth elements. Therefore, the content of the heavy rare earth element is preferably 1 mass% or less, more preferably 0.5 mass% or less, and not contained (substantially 0 mass%) of the R1-T1-B-based sintered body. ) Is even more preferable.

The content of R1 is 27 mass% or more and 35 mass% or less of the entire R1-T1-B-based sintered body. If the content of R1 is less than 27 mass%, a liquid phase is not sufficiently formed in the sintering process, and it becomes difficult to sufficiently densify the R1-T1-B-based sintered body. On the other hand, although the effect of the present disclosure can be obtained even if the content of R1 exceeds 35 mass%, the alloy powder in the manufacturing process of the R1-T1-B-based sintered body becomes very active. As a result, significant oxidation or ignition of the alloy powder may occur, so 35 mass% or less is preferable. The content of R1 is more preferably 27.5 mass% or more and 33 mass% or less, and further preferably 28 mass% or more and 32 mass% or less.

T1 is Fe or at least one of Co, Al, Mn, and Si and Fe, and the content of Fe with respect to the whole T1 is 80 mass% or more. That is, T1 may be Fe alone, or may be composed of at least one of Co, Al, Mn, and Si and Fe. However, the content of Fe with respect to the whole T1 is 80 mass% or more. When the content of Fe is less than 80 mass%, _{B r} and _{H cJ} may be reduced. Here, "the content of Fe with respect to the whole T1 is 80 mass% or more" means, for example, when the content of T1 in the R1-T1-B-based sintered body is 70 mass%, the R1-T1-B-based sintered body. It means that 56 mass% or more of the body is Fe. Preferably, the Fe content with respect to the whole T1 is 90 mass% or more. This is because it is possible to obtain a higher _{B r} and a high _{H cJ.} When Co, Al, Mn, and Si are contained, the preferable contents of Co are 5.0 mass% or less, Al is 1.5 mass% or less, and Mn and Si are 0.2 mass% or less, respectively.

The mol ratio of T1 to B ([T1] / [B]) is more than 14.0 and 15.0 or less.
If the mol ratio of T1 to B ([T1] / [B]) is 14.0 or less, a high H _cJ cannot be obtained. On the other hand, mol ratio of T1 for B ([T1] / [B ]) can not be obtained beyond the high _{B r} and high _{H cJ} 15.0. The mol ratio of T1 to B ([T1] / [B]) is preferably 14.3 or more and 15.0 or less. This is because it is possible to obtain a higher _{B r} and a high _{H cJ.} The B content is preferably 0.85 mass% or more and less than 0.95 mass% of the entire R1-T1-B-based sintered body.

In addition to the above elements, the R1-T1-B-based sintered body includes Ga, Cu, Ag, Zn, In, Sn, Zr, Nb, Ti, Ni, Hf, Ta, W, Ge, Mo, V, Y, La, Ce, Sm, Ca, Mg, Cr, H, F, P, S, Cl, O, N, C and the like may be contained. The contents of Ga, Cu, Ag, Zn, In, Sn, Zr, Nb, and Ti are 0.5 mass% or less, respectively, and Ni, Hf, Ta, W, Ge, Mo, V, Y, La, Ce, It is preferable that Sm, Ca, Mg and Cr are 0.2 mass% or less, H, F, P, S and Cl are 500 ppm or less, O is 6000 ppm or less, N is 1000 ppm or less, and C is 1500 ppm or less. The total content of these elements is preferably 5 mass% or less of the entire R1-T1-B-based sintered body. The total content of these elements may not be able to obtain the high _{B r} and high _{H cJ} exceeds 5 mass% of the total R1-T1-B based sintered body.

Next, a step of preparing the R1-T1-B-based sintered body will be described. The step of preparing the R1-T1-B-based sintered body can be prepared by using a general manufacturing method typified by the R-TB-based sintered magnet. In the R1-T1-B-based sintered body, the raw material alloy is _{crushed so that the particle size D 50} (volume center value obtained by measurement by the air flow dispersion laser diffraction method = D ₅₀ ) is 3 μm or more and 10 μm or less, and then the raw material alloy is crushed. It is preferable to perform sintering by orienting in a magnetic field. As an example, a raw material alloy produced by a strip casting method _{or the like is pulverized using a jet mill device or the like so that the particle size D 50} is 3 μm or more and 10 μm or less, and then molded in a magnetic field at 900 ° C. or higher. It can be prepared by sintering at a temperature of 1100 ° C. or lower. If the particle size D _{50 of the} raw material alloy is less than 3 μm, it is very difficult to produce a pulverized powder, and the production efficiency is significantly reduced, which is not preferable. On the other hand, if the particle size D ₅₀ exceeds 10 μm, the crystal particle size of the finally obtained R1-T1-B-based sintered body becomes too large, and it becomes difficult to obtain _{a high H cJ, which is not preferable.} The particle size D ₅₀ is preferably 3 μm or more and 5 μm or less.

The R1-T1-B-based sintered body may be produced from one kind of raw material alloy (single raw material alloy) as long as each of the above conditions is satisfied, or two or more kinds of raw material alloys are used for them. May be produced by a method of mixing (blending method). Further, the obtained R1-T1-B-based sintered body may be subjected to known machining such as cutting or cutting if necessary, and then heat treatment described later may be performed.

(R2-M alloy (preferably the step of preparing R2-Al—Cu alloy))
First, the compositions of the R2-M alloy and the R2-Al—Cu alloy in the step of preparing the R2-M alloy (preferably R2-Al—Cu alloy) will be described. The following description of the R2-M alloy includes the R2-Al—Cu alloy as a preferable form. By containing R2 and M in a specific range described later, R2 and M in the R2-M alloy can be introduced into the R1-T1-B-based sintered body in the step of performing the heat treatment described later. ..
R2 is at least one of rare earth elements and always contains La, and the content of R2 is 55 mol% (preferably 70 mol%) or more and 90 mol% or less of the whole R2-M alloy. If the R2 content is less than 55 mol%, diffusion may not proceed sufficiently by the heat treatment described later. On the other hand, although the effect of the present disclosure can be obtained even if the content of R2 exceeds 90 mol%, the alloy powder in the manufacturing process of the R2-M alloy becomes very active. As a result, the alloy powder may be significantly oxidized or ignited. Therefore, the R2 content is preferably 90 mol% or less of the total R2-M alloy. The content of R2 is more preferably 75 mol% or more and 85 mol% or less. This is because a higher H _cJ can be obtained. Further, as described above, while there is a concern that the supply of Nd will be insufficient, it is preferable that La in the R2-M alloy is 80 mol% or more of the total amount of R2 from the viewpoint of diversification of the use of rare earth elements, which is more preferable. R2 in the R2-M alloy is La (including impurities).

In R2, the ratio of La to the whole rare earth element is higher than the ratio of La to the whole rare earth element of the R1-T1-B-based sintered body. As a result, grain boundary diffusion is promoted, and Al and Cu can be diffused inside the magnet. If the ratio of La is lower than the ratio of La to the entire rare earth element of the R1-T1-B-based sintered body, the intergranular diffusion is not promoted and the diffusion of Al and Cu may stay near the surface of the sintered body. is there. Therefore, the introduction amount to the inside from the magnet surface of Al or Cu is insufficient, there is a possibility that it is impossible to obtain a R-T-B based sintered magnet having a high B _r and high H _cJ. Preferably, when [La] / [R1] in the R1-T1-B-based sintered body is α and [La] / [R2] in the R2-Al—Cu-based alloy is β, β / α ≧ 1.5.

M contains Cu or both Cu and Al. That is, M is either Cu alone or contains both Al and Cu. Preferably, it is an R2-Al—Cu based alloy containing both Al and Cu, which will be described later.
The M content is 5 mol% or more and 40 mol% or less of the entire R2-M alloy. When the M content is less than 5 mol%, M in the R2-M alloy is R1 in the step of performing the heat treatment described later. It becomes difficult to introduce it into the −T1-B based sintered body, and high _HcJ cannot be obtained. On the other hand, if M is a 40 mol% excess, _{B r} may be lowered significantly.
Next, a preferable composition of Al and Cu in the case of an R2-Al—Cu based alloy in which M contains both Al and Cu will be described.
Al is 5 mol% or more and 20 mol% or less of the entire R2-Al—Cu based alloy. If Al is less than 5 mol%, it becomes difficult for Al and Cu in the R2-Al—Cu-based alloy to be introduced into the R1-T1-B-based sintered body in the step of performing the heat treatment described later, and high _HcJ is obtained. I can't. On the other hand, when the Al is a 20 mol% excess, _{B r} may be lowered significantly. Al is more preferably 10 mol% or more and 20 mol% or less. This is because it is possible to obtain a higher _{B r} and a high _{H cJ.}

Cu is contained in an amount of 5 mol% or more and 20 mol% or less of the entire R2-Al—Cu based alloy. If it is less than 5 mol%, _{it may not be possible to obtain high H cJ} , and if Cu exceeds 20 mol%, the abundance ratio of Al at the grain boundary may decrease. Therefore, 20 mol% or less is preferable.

In addition to the above elements, the R2-M alloy includes Co, Ga, Ag, Zn, Si, In, Sn, Zr, Nb, Ti, Ni, Hf, Ta, W, Ge, Mo, V, Y, Ce, and Sm. , Ca, Mg, Mn, Cr, H, F, P, S, Cl, O, N, C and the like.
Co may be contained in an amount of 0.5 mol% or more and 10 mol% or less in order to improve corrosion resistance. Ga is less than 5 mol%, Ag, Zn, Si, In, Sn, Zr, Nb, and Ti are 0.5 mol% or less, respectively, Ni, Hf, Ta, W, Ge, Mo, V, Y, La, Ce, Sm, Ca, Mg, Mn, Cr are 0.2 mol% or less, H, F, P, S, Cl are 500 ppm or less, O is 6000 ppm or less, N is 1000 ppm or less, and C is 1500 ppm or less. preferable. However, when the total content of these elements exceeds 20 mol%, R2 and M in R2-M alloy (preferably Al and Cu) then the amount of, to obtain a high _{B r} and high _{H cJ} It may not be possible. Therefore, the total content of R2 and M (preferably Al and Cu) in the R2-M alloy is preferably 80 mol% or more, more preferably 90 mol% or more.

Next, the process of preparing the R2-M alloy will be described. The R2-M alloy is a raw material alloy manufacturing method used in a general manufacturing method represented by an Nd-Fe-B-based sintered magnet, for example, a mold casting method, a strip casting method, or a single roll ultra-quenching method. It can be prepared by using a method (melt spinning method) or an atomizing method. Further, the R2-M alloy may be an alloy obtained by pulverizing the alloy obtained above by a known pulverizing means such as a pin mill. Further, in order to improve the pulverizability of the alloy obtained as described above, pulverization may be performed after heat treatment at 700 ° C. or lower is performed in a hydrogen atmosphere to contain hydrogen.

(Step of performing heat treatment)
At least a part of the R2-M alloy is brought into contact with at least a part of the surface of the R1-T1-B-based sintered body prepared as described above, and the temperature is 450 ° C. in a vacuum (non-oxidizing atmosphere) or an inert gas atmosphere. The heat treatment is performed at a temperature of 850 ° C. or lower. As a result, a liquid phase containing R2 and M (preferably Al and Cu) containing La is generated from the R2-M alloy, and the liquid phase is baked via the grain boundaries of the R1-T1-B-based sintered body. It is diffusely introduced from the surface of the alloy to the inside, and the RTM phase is generated at the grain boundaries. If the heat treatment temperature is lower than 450 ° C., (preferably Al and Cu) R2 and M containing La is too small, amount of liquid phase containing, may not be able to obtain a high B _r and high H _cJ .. On the other hand, if the temperature exceeds 850 ° C., the diffusion of the R2-M alloy into the R1-T1-B-based sintered body may be inhibited and a high _HcJ may not be obtained. The heat treatment may be performed at a relatively low temperature (450 ° C. or higher and 600 ° C. or lower) only (one-stage heat treatment), or after the heat treatment is performed at a relatively high temperature (700 ° C. or higher and 850 ° C. or lower), comparison is performed. Heat treatment (two-stage heat treatment) may be performed at a target low temperature (450 ° C. or higher and 600 ° C. or lower). The heat treatment time is set to an appropriate value depending on the composition and dimensions of the R1-T1-B-based sintered body and the R2-M alloy, the heat treatment temperature, etc., but is preferably 5 minutes or more and 24 hours or less, and 10 minutes or more and 20 hours or less. Is more preferable, and 30 minutes or more and 16 hours or less is further preferable. Further, it is preferable to prepare the R2-M alloy in an amount of 2 mass% or more and 30 mass% or less with respect to the weight of the R1-T1-B-based sintered body. If the R2-M alloy is less than 2 mass% with respect to the weight of the R1-T1-B-based sintered body, high _HcJ may not be obtained. On the other hand, there is a possibility _{that B r} exceeds 30 mass% is greatly reduced.

The heat treatment can be performed by arranging an R2-M alloy having an arbitrary shape on the surface of the R1-T1-B-based sintered body and using a known heat treatment apparatus. For example, the surface of the R1-T1-B-based sintered body can be covered with a powder layer of R2-M alloy and heat-treated. For example, a slurry in which an R2-M alloy is dispersed in a dispersion medium is applied to the surface of an R1-T1-B-based sintered body, and then the dispersion medium is evaporated to form an R2-M alloy and an R1-T1-B-based sintered body. It may be in contact with the body. Further, as shown in an experimental example described later, it is preferable that the R2-M alloy is arranged so as to be in contact with a surface perpendicular to the orientation direction of at least the R1-T1-B-based sintered body. Examples of the dispersion medium include alcohol (ethanol and the like), NMP (N-methylpyrrolidone), aldehyde and ketone. Further, the R1-T1-B-based sintered body that has been heat-treated may be subjected to known machining such as cutting or cutting.

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

Experimental Example 1
[Preparation of R1-T1-B-based sintered body]
Using Nd metal, ferrobolon alloy, and electrolytic iron (all metals have a purity of 99% or more), the sintered body is blended so as to have a composition of reference numeral 1-A shown in Table 1, and the raw materials thereof are dissolved. The raw material alloy was cast by a strip casting method to obtain a flaky raw material alloy having a thickness of 0.2 to 0.4 mm. The obtained flaky raw material alloy was pulverized with hydrogen, and then subjected to a dehydrogenation treatment of heating to 550 ° C. in a vacuum and then cooling to obtain a coarsely pulverized powder. Next, zinc stearate as a lubricant was added to the obtained coarsely pulverized powder in an amount of 0.04 mass% with respect to 100 mass% of the coarsely pulverized powder, mixed, and then nitrogen was used using an airflow type pulverizer (jet mill device). Dry pulverization was performed in an air stream to obtain a finely pulverized powder (alloy powder) having _{a pulverized particle size D 50 of 4 μm.} The pulverized particle size D ₅₀ is a volume center value (volume-based median diameter) obtained by a laser diffraction method based on an air flow dispersion method.

Zinc stearate as a lubricant was added to the finely pulverized powder in an amount of 0.05 mass% based on 100 mass% of the finely pulverized powder, mixed, and then molded in a magnetic field to obtain a molded product. As the molding apparatus, a so-called right-angled magnetic field forming apparatus (transverse magnetic field forming apparatus) in which the magnetic field application direction and the pressurizing direction are orthogonal to each other was used.

The obtained molded product was sintered in vacuum at 1020 ° C. for 4 hours and then rapidly cooled to obtain an R1-T1-B-based sintered body. The density of the obtained sintered body was 7.5 Mg / m ³ or more. The composition of the obtained sintered body is shown in Table 1. Each component in Table 1 was measured using high frequency inductively coupled plasma emission spectroscopy (ICP-OES). As a result of measuring the amount of oxygen in the sintered body by the gas melting-infrared absorption method, it was confirmed that it was around 0.4 mass%. “[T1] / [B]” in Table 1 indicates the analytical value (mass%) of each element constituting T1 (including unavoidable impurities, Fe, Al, Si, Mn in this experimental example). Divided by the atomic weight of the element, the sum of those values (a) and the analytical value of B (mass%) divided by the atomic weight of B (mass%) divided by the atomic weight of B (b) The ratio with (a / b).

[Preparation of R2-M alloy (R2-Al—Cu alloy)]
Using La metal, Pr metal, Al metal, and Cu metal (all metals have a purity of 99% or more), the alloys are blended so as to have a composition of reference numerals 1-a to 1-d shown in Table 2. The raw materials of the above were melted to obtain a ribbon or flake-shaped alloy by a single-roll ultra-quenching method (melt spinning method). The obtained alloy was pulverized in an argon atmosphere using a mortar and then passed through a sieve having a mesh size of 425 μm to prepare an R2-Al—Cu based alloy. The composition of the obtained R2-Al—Cu based alloy is shown in Table 2.

[Heat treatment]
The R1-T1-B-based sintered body of reference numeral 1-A in Table 1 was cut and machined to obtain a rectangular parallelepiped of 4.4 mm × 4.4 mm × 4.4 mm (orientation direction). Next, as shown in FIG. 3, in the processing container 3 made of niobium foil, the plane perpendicular to the orientation direction (arrow direction in the figure) of the R1-T1-B-based sintered body 1 is mainly R2-. The R2-Al-Cu alloys of reference numerals 1-a to 1-d shown in Table 2 were combined with the R1-T1-B-based sintered bodies of reference numerals 1-A so as to come into contact with the Al—Cu based alloy 2. Placed above and below.

Then, using a tubular air-flow furnace, heat treatment was performed at the heat treatment temperature and time shown in Table 3 in reduced pressure argon controlled at 200 Pa, and then cooled. In order to remove the concentrated portion of the R2-Al—Cu alloy existing near the surface of each sample after heat treatment, the entire surface of each sample is cut by 0.2 mm using a surface grinding machine, and 4.0 mm × A cubic sample (RTB-based sintered magnet) having a size of 4.0 mm × 4.0 mm was obtained.

[sample test]
Residual magnetic flux density of the sample obtained by the BH tracer _{(B r)} and coercivity _{(H cJ)} were measured. The measurement results are shown in Table 3. As shown in Table 3, the R1-T1-B-based sintered body, the R2-Al-Cu-based alloy, and the heat treatment temperature are within the scope of the present disclosure. 1-2,1-4,1-5,1-7 and 1-9, high _{B r} and high _{H cJ} than the comparative example is obtained.

Experimental Example 2
[Preparation of R2-M alloys (R2-Cu alloys and R2-Al—Cu alloys)]
Using La metal, Al metal, and Cu metal (all metals have a purity of 99% or more), the alloys are blended so as to have a composition of reference numerals 2-a to 2-d shown in Table 4, and the raw materials thereof are mixed. It was melted to obtain a ribbon or flake-shaped alloy by a single-roll ultra-quenching method (melt spinning method). The obtained alloy was pulverized in an argon atmosphere using a mortar and then passed through a sieve having a mesh size of 425 μm to prepare an R2-Cu alloy and an R2-Al—Cu alloy. Table 2 shows the compositions of the obtained R2-Cu alloy and R2-Al—Cu alloy.

[Heat treatment]
The R1-T1-B-based sintered body of reference numeral 1-A in Table 1 was prepared in the same manner as in Experimental Example 1. The R1-T1-B-based sintered body of reference numeral 1-A was cut and machined to obtain a rectangular parallelepiped having a size of 4.4 mm × 4.4 mm × 4.4 mm (orientation direction). Next, as shown in FIG. 3, in the processing container 3 made of niobium foil, the plane perpendicular to the orientation direction (arrow direction in the figure) of the R1-T1-B-based sintered body 1 is mainly R2-. R2-Cu-based alloys or R2-Al- of reference numerals 1-b shown in Table 1 and codes 2-a to 2-d shown in Table 4 so as to come into contact with the Cu-based alloy or R2-Al-Cu-based alloy 2. Cu-based alloys were placed above and below each of the R1-T1-B-based sintered bodies of reference numeral 1-A.

Then, using a tubular air-flow furnace, heat treatment was performed at the heat treatment temperature and time shown in Table 5 in reduced pressure argon controlled at 200 Pa, and then cooled. In order to remove the concentrated portion of the R2-Cu alloy or R2-Al—Cu alloy existing near the surface of each sample after the heat treatment, the entire surface of each sample is cut by 0.2 mm using a surface grinding machine. Then, a cubic sample (RTB-based sintered magnet) having a size of 4.0 mm × 4.0 mm × 4.0 mm was obtained.

[sample test]
Residual magnetic flux density of the sample obtained by the BH tracer _{(B r)} and coercivity _{(H cJ)} were measured. The measurement results are shown in Table 5. As shown in Table 5, any R1-T1-B-based sintered body, R2-Cu-based alloy or R2-Al-Cu-based alloy, and any R-TB-based sintered body whose heat treatment temperature is within the range of the present disclosure. even in the magnet, a high _{B r} and high _{H cJ} are achieved.

The RTB-based sintered magnets obtained according to the embodiment of the present invention include voice coil motors (VCMs) for hard disk drives, motors for electric vehicles (EV, HV, PHV, etc.), motors for industrial equipment, and the like. It can be suitably used for various motors and home appliances.

1 R1-T1-B-based sintered body 2 R2-Al-Cu-based alloy 3 Processing container

Claims (9)

The process of preparing the R1-T1-B-based sintered body and
The process of preparing R2-M alloy and
At least a part of the R2-M alloy is brought into contact with at least a part of the surface of the R1-T1-B-based sintered body, and heat-treated at a temperature of 450 ° C. or higher and 850 ° C. or lower in a vacuum or an inert gas atmosphere. Including the process of carrying out
In the R1-T1-B-based sintered body,
R1 is at least one of rare earth elements and always contains at least one of Nd and Pr, and the content of R1 is 27 mass% or more and 35 mass% or less of the entire R1-T1-B-based sintered body.
T1 is Fe or at least one of Co, Al, Mn, and Si and Fe, and the content of Fe with respect to the whole T1 is 80 mass% or more.
The mol ratio of T1 to B ([T1] / [B]) is more than 14.0 and 15.0 or less.
In the R2-M alloy,
R2 is at least one of the rare earth elements and always contains La, the content of R2 is 55 mol% or more and 90 mol% or less of the whole R2-M alloy, and the ratio of La to the whole rare earth element is R1. Higher than the ratio of La to the total rare earth elements of the -T1-B based sintered body,
M contains Cu or both Cu and Al,
A method for producing an RTB-based sintered magnet, wherein the content of M is 5 mol% or more and 40 mol% or less of the entire R2-M-based alloy. The method for producing an RTB-based sintered magnet according to claim 1, wherein La in the R2-M-based alloy is 80 mol% or more of the total amount of R2. The method for producing an RTB-based sintered magnet according to claim 1, wherein R2 in the R2-M-based alloy is La (including impurities). The method for producing an RTB-based sintered magnet according to any one of claims 1 to 3, wherein the total content of R2, Al, and Cu in the R2-M-based alloy is 80 mol% or more. The process of preparing the R1-T1-B-based sintered body and
The process of preparing R2-Al-Cu alloy and
At least a part of the R2-Al—Cu alloy is brought into contact with at least a part of the surface of the R1-T1-B-based sintered body, and the temperature is 450 ° C. or higher and 850 ° C. or lower in a vacuum or an inert gas atmosphere. Including the process of performing heat treatment in
In the R1-T1-B-based sintered body,
R1 is at least one of rare earth elements and always contains at least one of Nd and Pr, and the content of R1 is 27 mass% or more and 35 mass% or less of the entire R1-T1-B-based sintered body.
T1 is Fe or at least one of Co, Al, Mn, and Si and Fe, and the content of Fe with respect to the whole T1 is 80 mass% or more.
The mol ratio of T1 to B ([T1] / [B]) is more than 14.0 and 15.0 or less.
In the R2-Al—Cu based alloy,
R2 is at least one of the rare earth elements and always contains La, the content of R2 is 70 mol% or more and 90 mol% or less of the whole R2-Al—Cu alloy, and the ratio of La to the whole rare earth element is , Higher than the ratio of La to the total rare earth elements of the R1-T1-B based sintered body,
The Al content is 5 mol% or more and 20 mol% or less of the entire R2-Al—Cu based alloy.
A method for producing an RTB-based sintered magnet, wherein the Cu content is 5 mol% or more and 20 mol% or less of the entire R2-Al—Cu-based alloy. The method for producing an RTB-based sintered magnet according to claim 5, wherein La in the R2-Al—Cu-based alloy is 80 mol% or more of the total amount of R2. The method for producing an RTB-based sintered magnet according to claim 5, wherein R2 in the R2-Al—Cu-based alloy is La (including impurities). The method for producing an RTB-based sintered magnet according to any one of claims 5 to 7, wherein the total content of R2, Al, and Cu in the R2-Al—Cu-based alloy is 80 mol% or more. The step of preparing the R1-T1-B-based sintered body _{includes crushing the raw material alloy so that the particle size D 50} is 3 μm or more and 10 μm or less, and then aligning and sintering in a magnetic field. The method for manufacturing an RTB-based sintered magnet according to any one of claims 1 to 8.

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