JP7447606B2 - RTB system sintered magnet - Google Patents

Description

The present invention relates to an RTB-based sintered magnet.

RTB system sintered magnets (R is at least one rare earth element, T is mainly Fe, and B is boron) are known as the highest performance permanent magnets. They are 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 boundaries of this main phase. The R ₂ T ₁₄ B compound, which is the main phase, is a ferromagnetic material with high saturation magnetization and anisotropic magnetic field, and is the basis of the characteristics of RTB-based sintered magnets.

RTB-based sintered magnets have a problem in that irreversible thermal demagnetization occurs because the coercive force H _cJ (hereinafter simply referred to as "H _cJ ") decreases at high temperatures. Therefore, RTB-based sintered magnets used particularly in electric vehicle motors are required to have high H _cJ even at high temperatures, that is, to have higher H _cJ at room temperature.

International Publication No. 2007/102391 International Publication No. 2016/133071

It is known that H _cJ is improved when light rare earth elements (mainly Nd and Pr) in the R ₂ T ₁₄ B-type compound phase are replaced with heavy rare earth elements (mainly Dy and Tb). However, while H _cJ is improved, there is a problem in that the saturation magnetization of the R ₂ T ₁₄ B-type compound phase is reduced, so that the residual magnetic flux density B _r (hereinafter simply referred to as "B _r ") is reduced.

Patent Document 1 describes that a heavy rare earth element such as Dy is supplied to the surface of a sintered magnet made of an RTB alloy, and the heavy rare earth element is diffused into the inside of the sintered magnet. The method described in Patent Document 1 diffuses Dy from the surface of the RTB-based sintered magnet into the interior, and concentrates Dy only in the outer shell of the main phase crystal grains, which is effective for improving H _cJ . By doing so, high H _cJ can be obtained while suppressing a decrease in B _r .

Patent Document 2 discloses that the grain boundaries in the RTB sintered magnet are Controlling phase composition and thickness to improve H _cJ has been described.

However, in recent years, there has been a demand for obtaining even higher B _r and higher H _cJ while reducing the amount of heavy rare earth elements used, particularly in electric vehicle motors and the like.

Various embodiments of the present disclosure provide RTB-based sintered magnets with high B _r and high H _cJ while reducing the usage of heavy rare earth elements.

In an exemplary embodiment, the method for manufacturing an RTB-based sintered magnet of the present disclosure includes an RTB-based sintered magnet containing main phase crystal grains and a grain boundary phase, wherein R: 27 .0 mass% or more and 35.0 mass% or less (R consists of RL and RH, RL is at least two types of light rare earth elements and always includes Nd and Pr, RH is at least one type of heavy rare earth elements, and Tb and (Always contains at least one of Dy), B: 0.80 mass% or more and 1.20 mass% or less, Ga: 0.20 mass% or more and 0.80 mass% or less, T: 61.5 mass% or more (T is Fe and Co, , 90 mass% or more of T is Fe), and the molar ratio of Pr to Nd (([Pr]/atomic weight of Pr) in the central part of the main phase crystal grain located at a depth of 300 μm from the magnet surface. /([Nd]/atomic weight of Nd)) is 0 or more and 0.45 or less ([Pr] is the content of Pr expressed in mass%, and [Nd] is the content of Nd expressed in mass%) ), the molar ratio of Pr to Nd (([Pr]/atomic weight of Pr)/([Nd]/atomic weight of Nd)) within the two-grain grain boundary located at a depth of 300 μm from the magnet surface is 2.0 or more. 5.0 or less, including a portion where the RH concentration gradually decreases from the magnet surface toward the inside of the magnet, and includes a portion where the Ga concentration gradually decreases from the magnet surface toward the inside of the magnet.

In an embodiment, [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 holds true.

In one embodiment, the molar ratio of Pr to Nd (([Pr]/atomic weight of Pr)/([Nd]/atomic weight of Nd)) within the two-grain grain boundary located at a depth of 300 μm from the magnet surface is It is 2.0 or more and 4.0 or less.

In one embodiment, the RTB-based sintered magnet contains Cu, and the content of Cu is 0.05 mass% or more and 0.80 mass% or less.

In some embodiments, the Ga content is greater than the Cu content.

According to the embodiments of the present disclosure, it is possible to provide an RTB-based sintered magnet having high _Br and high H _cJ while reducing the amount of heavy rare earth elements used.

FIG. 2 is a cross-sectional view schematically showing an enlarged portion of an RTB-based sintered magnet. FIG. 1B is a further enlarged cross-sectional view schematically showing the inside of the broken line rectangular area in FIG. 1A. 1 is a flowchart illustrating an example of steps in a method for manufacturing an RTB-based sintered magnet according to the present disclosure. 3 is a flowchart showing another example of the steps in the method for manufacturing an RTB-based sintered magnet according to the present disclosure.

First, the basic structure of the RTB-based sintered magnet according to the present disclosure will be explained. RTB-based sintered magnets have a structure in which powder particles of a raw material alloy are bonded together by sintering, and consist of a main phase consisting mainly of R ₂ T ₁₄ B compound particles and a grain boundary portion of this main phase. It consists of a grain boundary phase located at

FIG. 1A is an enlarged schematic cross-sectional view of a part of the RTB-based sintered magnet, and FIG. 1B is a further enlarged schematic cross-sectional view of the rectangular area indicated by the broken line in FIG. 1A. It is. In FIG. 1A, as an example, an arrow having a length of 5 μm is shown as a standard length indicating the size for reference. As shown in FIGS. 1A and 1B, the RTB-based sintered magnet has a main phase 12 mainly composed of R ₂ T ₁₄ B compounds, and a grain boundary phase 14 located at the grain boundary portion of the main phase 12. It is composed of. Further, as shown in FIG. 1B, the grain boundary phase 14 includes a two-grain grain boundary phase 14a in which two R ₂ T ₁₄ B compound particles (grains) are adjacent to each other, and a two-grain boundary phase 14a in which three R ₂ T ₁₄ B compound particles are adjacent to each other. grain boundary triple point 14b. A typical main phase crystal grain size is 3 μm or more and 10 μm or less as an average value of the equivalent circle diameter of the magnet cross section. The R ₂ T ₁₄ B compound, which is the main phase 12, is a ferromagnetic material with high saturation magnetization and an anisotropic magnetic field. Therefore, in the RTB-based sintered magnet, B _r can be improved by increasing the abundance ratio of the R ₂ T ₁₄ B compound, which is the main phase 12. In order to increase the abundance ratio of the R ₂ T ₁₄ B compound, the amount of R, the amount of T, and the amount of B in the raw material alloy are adjusted to the stoichiometric ratio of the R ₂ T ₁₄ B compound (R amount: T amount: B amount = 2:14:1).

In addition, by substituting a part of the light rare earth elements (mainly Nd) of the R ₂ T ₁₄ B compound, which is the main phase, with heavy rare earth elements such as Tb, Dy, and Ho, we can lower the saturation magnetization while increasing the difference in the main phase. It is known that the directional magnetic field can be increased. In particular, the main phase outer shell in contact with the two-grain grain boundary phase is likely to become the starting point of magnetization reversal, so heavy rare earth diffusion technology that can preferentially replace heavy rare earth elements in the main phase outer shell is efficient while suppressing the drop in saturation magnetization. A relatively high H _cJ can be obtained.

On the other hand, it is known that high H _cJ can also be obtained by controlling the magnetism of the two-grain boundary phase 14a. Specifically, by lowering the concentration of magnetic elements (Fe, Co, Ni, etc.) in the two-grain boundary phase, the two-grain boundary phase is brought closer to non-magnetic properties, thereby reducing the magnetic coupling between the main phases. Magnetization reversal can be suppressed by weakening it.

As a result of study, the present inventor found that, for example, as described in Patent Document 2, when R (mainly Pr and Nd) or Ga is diffused from the magnet surface to the inside of the magnet (in the depth direction), H _cJ is particularly affected. It has been found that H _cJ can be significantly improved by setting the Pr concentration at a possible two-grain boundary to a high specific range. This is considered to be because by increasing the Pr concentration at the two-grain boundary, the width of the two-grain boundary phase becomes easier to spread, and the magnetic interaction between the main phases can be further reduced. Furthermore, if RH (RH is at least one type of heavy rare earth element and always includes at least one of Tb and Dy) is diffused together with Pr and Ga, the anisotropic magnetic field of the main phase outer shell can be improved by diffusion even with a small amount of RH. It was found that H _cJ can be significantly improved while suppressing a decrease in B _r . The thus obtained RTB-based sintered magnet of the present disclosure can have high B _r and high H _cJ . In order to set the Pr concentration at the two-grain grain boundary in a high specific range and to noticeably improve the anisotropic magnetic field of the main phase outer shell due to diffusion even with a small RH, for example, the RH content of the diffusion alloy described below should be reduced. After that, the amount of adhesion to the surface of the RTB sintered magnet material is controlled within a relatively large specific range to diffuse all of Pr, RH, and Ga, as well as the first diffusion process and second diffusion described later. This can be achieved by the method of carrying out the process.

(RTB system sintered magnet)
The RTB-based sintered magnet of the present disclosure includes a main phase crystal grain and a grain boundary phase,
R: 27.0 mass% or more and 35.0 mass% or less (R consists of RL and RH, RL is at least two types of light rare earth elements and always includes Nd and Pr, and RH is at least one type of heavy rare earth elements) (Always includes at least one of Tb and Dy),
B: 0.80 mass% or more and 1.20 mass% or less,
Ga: 0.20 mass% or more and 0.80 mass% or less,
T: Contains 61.5 mass% or more (T is Fe and Co, and 90 mass% or more of T is Fe).

If R is less than 27.0 mass%, a sufficient liquid phase will not be generated during the sintering process, and it may be difficult to sufficiently densify the sintered body. On the other hand, if R exceeds 35 mass%, grain growth may occur during sintering and H _cJ may decrease. It is preferable that R is 28 mass% or more and 33 mass% or less. Higher _Br can be obtained. The RTB-based sintered magnet of the present disclosure can obtain high B _r and high H _cJ while reducing the amount of RH used, so even when higher H _cJ is required, the amount of RH added can be reduced. Typically, the RH content can be 5 mass% or less, preferably the RH content is 3 mass% or less, and most preferably the RH content is 0.1 mass% or more and 1.0 mass% or less. It is.

If B is less than 0.80 mass%, _Br may decrease. On the other hand, if B exceeds 1.20 mass%, high H _cJ may not be obtained. B is preferably 0.87 mass% or more and 0.92 mass% or less, and more preferably 0.88 mass% or more and 0.90 mass% or less. Higher B _r and higher H _cJ can be obtained.

If Ga is less than 0.20 mass%, high H _cJ may not be obtained. On the other hand, if Ga exceeds 0.80 mass%, _Br may decrease. Ga is preferably 0.30 mass% or more and less than 0.70 mass%, more preferably 0.40 mass% or more and 0.60 mass% or less. Higher B _r and higher H _cJ can be obtained.

If T is less than 61.5 mass%, _Br may be significantly reduced. Therefore, the T content is 61.5 mass% or more. If the proportion of Fe in T is less than 90% in mass ratio, there is a risk that _Br may decrease. Therefore, the ratio of Co content to T content is preferably 10% or less of the total T content, and more preferably 2.5% or less.

Preferably, in order to obtain higher H _cJ , in the RTB-based sintered magnet of the present disclosure, [T] is the content of T expressed in mass%, and [B] is the content of B expressed in mass%. When considering the content, [T]/55.85>14×[B]/10.8 holds true. Satisfying this inequality means that the content of B is less than the stoichiometric composition ratio of the R ₂ T ₁₄ B compound, that is, the amount of B used to form the main phase (R ₂ T ₁₄ B compound) is This means that the amount of B is relatively small. Similarly, in order to obtain higher H _cJ , the RTB-based sintered magnet of the present disclosure contains Cu, and the content of Cu is 0.05 mass% or more and 0.80 mass% or less. is preferable, and the content of Ga is preferably greater than the content of Cu.

Furthermore, the RTB-based sintered magnet of the present disclosure is
The molar ratio of Pr to Nd (([Pr]/atomic weight of Pr)/([Nd]/atomic weight of Nd)) in the central part of the main phase crystal grain located at a depth of 300 μm from the magnet surface is 0 or more. .45 or less;
The molar ratio of Pr to Nd (([Pr]/atomic weight of Pr)/([Nd]/atomic weight of Nd)) within the two-grain grain boundary located at a depth of 300 μm from the magnet surface is 2.0 or more5. is less than or equal to 0,
Including a part where the RH concentration gradually decreases from the magnet surface toward the inside of the magnet,
It includes a portion where the Ga concentration gradually decreases from the magnet surface toward the inside of the magnet.

The molar ratio of Pr to Nd (([Pr]/atomic weight of Pr)/([Nd]/atomic weight of Nd)) in the central part of the main phase crystal grain located at a depth of 300 μm from the magnet surface is 0 or more. The fact that it is .45 or less indicates that Nd is the main component of R in the main phase crystal grains. [Pr] is the Pr content expressed in mass%, and [Nd] is the Nd content expressed in mass%. If the above (([Pr]/atomic weight of Pr)/(atomic weight of [Nd]/Nd)) at the center of the main phase crystal grain is outside the range of 0 or more and 0.45 or less, the Pr of the main phase crystal grain The temperature coefficient of H _cJ may decrease.

The molar ratio of Pr to Nd (([Pr]/atomic weight of Pr)/([Nd]/atomic weight of Nd)) within the two-grain grain boundary located at a depth of 300 μm from the magnet surface is 2.0 or more5. The fact that it is 0 or less indicates that R at the two-grain grain boundary is in a specific range where the Pr concentration is higher than Nd. If the above-mentioned (([Pr]/atomic weight of Pr)/(atomic weight of [Nd]/Nd) within the two-grain grain boundary is less than 2.0, a high H _cJ cannot be obtained because the concentration of Pr is low. Moreover, if it exceeds 5.0, the concentration of Pr is too high, resulting in a large amount of Pr being diffused, resulting in a large decrease in _Br . Furthermore, the Pr concentration of the main phase crystal grains adjacent to the two-grain boundary increases, and the temperature coefficient of H _cJ decreases. Preferably, in order to obtain higher H _cJ , the RTB-based sintered magnet of the present disclosure has a mol ratio of Pr to Nd (([ Pr]/atomic weight of Pr)/([Nd]/atomic weight of Nd)) is 2.0 or more and 4.0 or less, more preferably 2.3 or more and 3.5 or less. Most preferably, it is 2.3 or more and 3.0 or less.

Note that the concentrations of Pr and Nd are determined as follows, for example. First, crystal grains (main phase crystal grains) and two-grain grain boundaries in a magnet cross section of an RTB-based sintered magnet are observed using a transmission electron microscope (TEM). The main phase crystal grains and the two-grain grain boundaries are observed at arbitrary magnet cross sections at 300 μm from the surface of the RTB sintered magnet. Next, the concentration of Pr (mass%) and the concentration of Nd (mass%) contained in the central part of the main phase grain and the two-grain boundary (any place within the two-grain boundary) are measured using energy dispersive X-rays. The composition is analyzed by spectroscopy (EDX). The molar ratio of Pr to Nd (([Pr]/atomic weight of Pr)/([Nd]/atomic weight of Nd)) is calculated by dividing the Pr concentration (mass%) by the Pr atomic weight (a). , is the ratio (a/b) of the Nd concentration (mass%) divided by the atomic weight of Nd (b).

In addition, "The molar ratio of Pr to Nd (([Pr]/atomic weight of Pr)/([Nd]/atomic weight of Nd)" in the central part of the main phase crystal grain located at a depth of 300 μm from the magnet surface is 0 or more and 0.45 or less, and the molar ratio of Pr to Nd within the two-grain boundary located at a depth of 300 μm from the magnet surface (([Pr]/atomic weight of Pr)/([Nd]/atomic weight of Nd) )) is 2.0 or more and 5.0 or less" does not necessarily have to be satisfied in all the main phase crystal grains and within the two-grain boundary at a depth of 300 μm from the magnet surface over the entire magnet surface. It is sufficient that only a part of the above conditions are satisfied. This is useful if the location where high B _r and high H _cJ need to be obtained is not necessarily the entire magnet, but may be a portion of the magnet (for example, if the magnet is used in a motor, high B _r and high This is because there are cases where _HcJ is required).

``Includes a portion where the RH concentration gradually decreases from the magnet surface toward the inside of the magnet'' and ``includes a portion where the Ga concentration gradually decreases from the magnet surface toward the inside of the magnet'' means that RH and Ga are distributed from the magnet surface to the inside of the magnet. This means that it is in a state of being diffused. "Includes a portion where the RH concentration gradually decreases from the magnet surface toward the inside of the magnet" and "includes a portion where the Ga concentration gradually decreases from the magnet surface toward the inside of the magnet" refers to, for example, an RTB based sintered magnet. This can be confirmed by performing line analysis from the magnet surface to the vicinity of the magnet center in any cross section using energy dispersive X-ray spectroscopy (EDX). The RH and Ga concentrations can be determined by measuring the main phase crystal grains (R ₂ T ₁₄ B compound particles) or grain boundaries, the R1-T-B sintered magnet material before diffusion, or the RH and Ga produced during diffusion. The concentrations of RH and Ga may locally decrease or increase depending on the type and presence or absence of compounds contained. However, the overall RH and Ga concentrations gradually decrease (gradually become lower) as they go inside the magnet. Therefore, even if the concentration locally decreases or increases, as long as the RH and Ga amounts gradually decrease overall at a depth of at least 200 μm from the magnet surface to the inside of the magnet, the magnet can be removed from the magnet surface of the present disclosure. It is assumed that the inside includes a portion where the RH and Ga concentrations gradually decrease. Note that for diffusion of RH from the magnet surface to the inside of the magnet, it is preferable that RH be Tb. That is, it is preferable to include a portion where the Tb concentration gradually decreases from the magnet surface toward the inside of the magnet. Higher H _cJ can be obtained.

In the RTB sintered magnet of the present disclosure, for example, RL1, RH contained in the RL1-RH-M1 alloy is and can be obtained by diffusing M1. As a result of studies by the present inventors, the molar ratio of Pr to Nd (([Pr]/atomic weight of Pr)/([Nd]/Nd of In order to obtain the RTB based sintered magnet of the present disclosure having an atomic weight)) of 2.0 or more and 5.0 or less, for example, the RH in the RL1-RH-M1 based alloy must be It has been found that an effective method is to reduce the content of RL1, RH, and M1 and to control the amount of adhesion to the surface of the RTB sintered magnet material within a relatively large specific range, thereby diffusing all of RL1, RH, and M1. Understood. Further, for example, after adhering and diffusing the RTB-based sintered magnet material and the RL1-RH-M1-based alloy (first diffusion step), the R -By attaching the TB-based sintered magnet material and the RL2-M2-based alloy and performing heat treatment, RL2 and M2 are further diffused from the magnet surface into the inside of the magnet material (second diffusion step). It has been found that the RTB based sintered magnet of the present disclosure can be reliably obtained. However, the RTB-based sintered magnet of the present disclosure is not limited to these methods. Any method may be used as long as RL1, RL2, RH, M1, and M2 can be diffused from the surface of the magnet into the interior so as to obtain the RTB-based sintered magnet of the present disclosure.

(Method for manufacturing RTB-based sintered magnet)
In an embodiment, the method for manufacturing an RTB-based sintered magnet according to the present disclosure includes a step S10 of preparing an RTB-based sintered magnet material, and RL1-RH-M1, as shown in FIG. and step S20 of preparing a system alloy. The order of step S10 of preparing an RTB-based sintered magnet material and step S20 of preparing an RL1-RH-M1 alloy is arbitrary, and each A magnet material and RL1-RH-M1 alloy may also be used.
As shown in FIG. 2, the method for manufacturing an RTB-based sintered magnet according to the present disclosure further includes an RL1-RH-M1-based alloy on at least a portion of the surface of the RTB-based sintered magnet material. It includes a diffusion step S30 in which at least a portion is attached and heated at a temperature of 700° C. or more and 1100° C. or less in a vacuum or an inert gas atmosphere. The amount of the RL1-RH-M1 alloy attached to the RTB sintered magnet material in the diffusion step S30 is preferably 4 mass% or more and 15 mass% or less.

In the present disclosure, the RTB-based sintered magnet before the diffusion process and during the diffusion process (in another embodiment described below, before the second diffusion process and during the second diffusion process) is referred to as "RTB". -B series sintered magnet material", and the RTB series sintered magnet after the diffusion process (in another embodiment described later, after the second diffusion process) is simply called "RTB series sintered magnet material. It is called "condensation magnet".

(Process of preparing RTB-based sintered magnet material)
For example, the RTB-based sintered magnet material has the following composition range.
R: 27.0 to 35.0 mass%,
B: 0.80 to 1.20 mass%,
Ga: 0 to 0.80 mass%,
T: Contains 61.5 mass% or more.

The RTB-based sintered magnet material can be prepared using a common manufacturing method for RTB-based sintered magnets, typified by Nd-Fe-B-based sintered magnets. For example, a raw material alloy produced by a strip casting method or the like is pulverized to 3 μm or more and 10 μm or less using a jet mill, etc., then molded in a magnetic field, and sintered at a temperature of 900° C. or more and 1100° C. or less. You can prepare by doing this.

(Process of preparing RL1-RH-M1 alloy)
In the RL1-RH-M1 alloy, for example, RL1 is at least one light rare earth element and always contains Pr, and the content of Pr with respect to the entire RL1 is 55 mass% or more. The content of Pr with respect to the entire RL1 is more preferably 70 mass% or more. The content of RL1 is 60 mass% or more and 97 mass% or less of the entire RL1-RH-M1 alloy. The content of RH (RH is at least one heavy rare earth element and always includes at least one of Tb and Dy) is 1 mass% or more and 8 mass% or less of the entire RL1-RH-M1 alloy. M1 is at least one selected from the group consisting of Ga, Cu, Fe, Co, Ni, and Al, M1 always contains Ga, and the content of Ga with respect to the entire M1 is 50 mass% or more. The content of M1 is 2 mass% or more and 39 mass% or less of the entire RL1-RH-M1 alloy. Typical examples of RL1-RH-M1 alloys include TbNdPrCu alloy, DyNdCePrCu alloy, and TbNdPrGaCu alloy. Further, RH fluoride, oxide, oxyfluoride, etc. may be prepared together with the RL1-M1 alloy. Examples of the RH fluoride, oxide, and acid fluoride include TbF ₃ , DyF ₃ , Tb ₂ O ₃ , Dy ₂ O ₃ , Tb ₄ OF, and Dy ₄ OF. The RL1-RH-M1 alloy contains a small amount (for example, about 2 mass% in total) of elements other than the above-mentioned elements (for example, Si, Mn, etc.) by adjusting the contents of RL1, RH, and M1. Good too.

The method for producing the RL1-RH-M1 alloy is not particularly limited. It may be produced by a roll quenching method or by a casting method. Alternatively, these alloys may be ground into alloy powder. It may be produced by a known atomization method such as a centrifugal atomization method, a rotating electrode method, a gas atomization method, or a plasma atomization method.

(diffusion process)
At least a portion of the RL1-RH-M1 alloy prepared above was attached to at least a portion of the surface of the RTB sintered magnet material prepared above, and then heated for 700 minutes in a vacuum or inert gas atmosphere. A diffusion step of heating at a temperature of 1100° C. or higher is performed. As a result, a liquid phase containing RL1, RH, and M1 is generated from the RL1-RH-M1 alloy, and the liquid phase passes from the surface of the sintered material via the grain boundaries in the RTB-based sintered magnet material. It is diffused and introduced into the interior. The adhesion amount of the RL1-RH-M1 alloy to the RTB sintered magnet material in the diffusion step is 4 mass% or more and 15 mass% or less, and the R- It is preferable that the amount of RH attached to the TB-based sintered magnet material is 0.1 mass% or more and 0.6 mass% or less. As a result, the RTB-based sintered magnet of the present disclosure can be obtained, and high _Br and high H _cJ can be obtained. If the amount of RL1-RH-M1 alloy attached to the RTB sintered magnet material is less than 4 mass%, RH, RL1 (especially Pr) and M1 (especially Ga) will be introduced into the magnet material. If the amount is too small, it may be impossible to obtain high H _cJ , and if it exceeds 15 mass%, the amount of RH, RL1, and M1 introduced may be too large, resulting in a significant decrease in _Br , or the use of heavy rare earth elements. Not only will the amount increase too much, but the RL-RH-M alloy that has not fully diffused into the magnet may remain on the magnet surface, causing other problems such as corrosion resistance and workability. Preferably, the amount of the RL1-RH-M1 alloy attached to the RTB sintered magnet material is 5 mass% or more and 10 mass% or less. Higher H _cJ can be obtained. Furthermore, if the amount of RH attached to the RTB sintered magnet material by the RL1-RH-M1 alloy is less than 0.1 mass%, there is a possibility that the H _cJ improvement effect due to RH cannot be obtained. If it exceeds 0.6 mass%, it is impossible to obtain an RTB based sintered magnet having a high H _cJ while reducing the amount of heavy rare earth elements used. Preferably, the amount of RH adhered to the RTB sintered magnet material by the RL1-RH-M1 alloy is 0.1 mass% or more and 0.5 mass% or less. Here, the adhesion amount of RH is the amount of RH contained in the RL1-RH-M1 alloy adhering to the RTB sintered magnet material. It is defined by the mass ratio when the mass of is set to 100 mass%.

The diffusion step can be performed by placing an arbitrary shaped RL1-RH-M1 alloy on the surface of the RTB-based sintered magnet material and using a known heat treatment device. For example, the surface of the RTB-based sintered magnet material can be covered with a powder layer of RL1-RH-M1 alloy, and then the diffusion process can be performed. For example, a coating step of applying an adhesive to the surface to be coated and a step of adhering the RL1-RH-M1 alloy to the area coated with the adhesive may be performed. Examples of the adhesive include PVA (polyvinyl alcohol), PVB (polyvinyl butyral), and PVP (polyvinylpyrrolidone). If the adhesive is a water-based adhesive, the RTB sintered magnet material may be preliminarily heated before application. The purpose of preheating is to remove excess solvent, control adhesive strength, and uniformly adhere the adhesive. The heating temperature is preferably 60 to 200°C. In the case of a highly volatile organic solvent-based adhesive, this step may be omitted. Further, for example, after applying a slurry in which the RL1-RH-M1 alloy is dispersed in a dispersion medium to the surface of the RTB-based sintered magnet material, the dispersion medium is evaporated, and the RL1-RH-M1 alloy and the RTB -B-based sintered magnet material may be attached. In addition, alcohol (ethanol etc.), an aldehyde, and a ketone can be illustrated as a dispersion medium. Further, RH may be introduced by placing RH fluoride, oxide, oxyfluoride, etc. on the surface of the RTB-based sintered magnet material together with the RL1-M1 alloy. That is, as long as RL1 and M1 can be diffused simultaneously with RH, the method is not particularly limited.

Further, as long as at least a part of the RL1-RH-M1 alloy is attached to at least a part of the RTB-based sintered magnet material, its position is not particularly limited, but it is preferable that the RL1-RH- The M1 alloy is arranged so as to be attached to at least the surface perpendicular to the orientation direction of the RTB based sintered magnet material. The liquid phase containing RL1, RH, and M1 can be more efficiently diffused into the magnet from the surface thereof. In this case, even if the RL1-RH-M1 alloy is attached only in the orientation direction of the RTB-based sintered magnet material, the RL1-RH-M1 alloy can be applied to the entire surface of the RTB-based sintered magnet material. It may also be attached.

(Step of performing heat treatment)
Preferably, the RTB-based sintered magnet subjected to the diffusion step is heated at a temperature of 400° C. or more and 750° C. or less and lower than the temperature at which the diffusion step was performed in a vacuum or an inert gas atmosphere. Perform heat treatment at temperature. By performing heat treatment, higher H _cJ can be obtained.

In another embodiment, the method for manufacturing an RTB-based sintered magnet according to the present disclosure includes step S50 of preparing an RTB-based sintered magnet material, and RL1-RH- It includes a step S60 of preparing an M1 alloy and a step S61 of preparing an RL2-M2 alloy. The order of the step S50 of preparing the RTB-based sintered magnet material, the step S60 of preparing the RL1-RH-M1 alloy, and the step S61 of preparing the RL1-M2 alloy is arbitrary, and they are performed at different locations. The manufactured RTB-based sintered magnet materials, RL1-RH-M1-based alloys, and RL2-M2-based alloys may be used. As shown in FIG. 3, the method for manufacturing an RTB-based sintered magnet according to the present disclosure further includes an RL1-RH-M1-based alloy on at least a portion of the surface of the RTB-based sintered magnet material. R-T-B based sintered magnet material subjected to the first diffusion step S70 of attaching at least a portion and heating at a temperature of 700°C or higher and 1100°C or lower in a vacuum or inert gas atmosphere and the first diffusion step. includes a second diffusion step S71 in which at least a portion of the RL2-M2 alloy is attached to at least a portion of the surface of the RL2-M2 alloy and heated at a temperature of 400° C. or more and 600° C. or less in a vacuum or an inert gas atmosphere.

(Process of preparing RTB-based sintered magnet material)
For example, the RTB-based sintered magnet material has the following composition range.
R: 27.0 to 35.0 mass%,
B: 0.80 to 1.20 mass%,
Ga: 0 to 0.80 mass%,
T:61.5mass% or more

The RTB-based sintered magnet material can be prepared using a common manufacturing method for RTB-based sintered magnets, typified by Nd-Fe-B-based sintered magnets. For example, a raw material alloy produced by a strip casting method or the like is pulverized to 3 μm or more and 10 μm or less using a jet mill, etc., then molded in a magnetic field, and sintered at a temperature of 900° C. or more and 1100° C. or less. You can prepare by doing this.

(Process of preparing RL1-RH-M1 alloy)
In the RL1-RH-M1 alloy, for example, RL1 is at least one light rare earth element and always contains Pr, and the content of Pr with respect to the entire RL1 is 55 mass% or more. The content of Pr with respect to the entire RL1 is more preferably 70 mass% or more. The content of RL1 is 60 mass% or more and 97 mass% or less of the entire RL1-RH-M1 alloy. The content of RH (RH is at least one heavy rare earth element and always includes at least one of Tb and Dy) is 1 mass% or more and 8 mass% or less of the entire RL1-RH-M1 alloy. M1 is at least one selected from the group consisting of Ga, Cu, Fe, Co, Ni, and Al, M1 always contains Ga, and the content of Ga with respect to the entire M1 is 50 mass% or more. The content of M1 is 2 mass% or more and 39 mass% or less of the entire RL1-RH-M1 alloy. Typical examples of RL1-RH-M1 alloys include TbNdPrCu alloy, TbNdCePrCu alloy, and TbNdPrGaCu alloy. Furthermore, RH fluoride, oxide, oxyfluoride, etc. may be prepared together with the RL1-M1 alloy. Examples of the RH fluoride, oxide, and acid fluoride include TbF ₃ , DyF ₃ , Tb ₂ O ₃ , Dy ₂ O ₃ , Tb ₄ OF, and Dy ₄ OF.

The RL1-RH-M1 alloy contains a small amount (for example, about 2 mass% in total) of elements other than the above-mentioned elements (for example, Si, Mn, etc.) by adjusting the contents of RL1, RH, and M1. Good too.

The method for producing the RL1-RH-M1 alloy is not particularly limited. It may be produced by a roll quenching method or by a casting method. Alternatively, these alloys may be ground into alloy powder. It may be produced by a known atomization method such as a centrifugal atomization method, a rotating electrode method, a gas atomization method, or a plasma atomization method.

(Process of preparing RL2-M2 alloy)
In the RL2-M2 alloy, for example, RL2 is at least one light rare earth element and always contains Pr, and the content of Pr with respect to the entire RL2 is 55 mass% or more. The content of Pr with respect to the entire RL2 is more preferably 70 mass% or more. The content of RL2 is 60 mass% or more and 97 mass% or less of the entire RL2-M2 alloy, and M2 is at least one selected from the group consisting of Ga, Cu, Fe, Co, Ni, and Al, M2 always contains Ga, and the content of Ga with respect to the entire M2 is 50 mass% or more. The content of M2 is 3 mass% or more and 40 mass% or less of the entire RL2-M2 alloy. Typical examples of RL2-M2 alloys include NdPrCu alloy, NdCePrCu alloy, and NdPrGaCu alloy.

The RL2-M2 alloy may contain a small amount (for example, about 2 mass% in total) of elements other than the above-mentioned elements (for example, Si, Mn, etc.) by adjusting the respective contents of RL2 and M2.

The method for producing the RL2-M2 alloy is not particularly limited. It may be produced by a roll quenching method or by a casting method. Alternatively, these alloys may be ground into alloy powder. It may be produced by a known atomization method such as a centrifugal atomization method, a rotating electrode method, a gas atomization method, or a plasma atomization method.

(First diffusion step)
At least a portion of the RL1-RH-M1 alloy prepared above was attached to at least a portion of the surface of the RTB sintered magnet material prepared above, and then heated for 700 minutes in a vacuum or inert gas atmosphere. A first diffusion step of heating at a temperature of 1100°C or higher is performed. As a result, a liquid phase containing RL1, RH, and M1 is generated from the RL1-RH-M1 alloy, and the liquid phase passes from the surface of the sintered material via the grain boundaries in the RTB-based sintered magnet material. It is diffused and introduced into the interior. The adhesion amount of the RL1-RH-M1 alloy to the RTB sintered magnet material in the first diffusion step is 4 mass% or more and 15 mass% or less, and the RL1-RH-M1 alloy is The amount of RH attached to the RTB-based sintered magnet material is set to 0.1 mass% or more and 0.6 mass% or less. Preferably, the amount of the RL1-RH-M1 alloy attached to the RTB sintered magnet material is 5 mass% or more and 10 mass% or less, and the RTB based on the RL1-RH-M1 alloy -The amount of RH attached to the B-based sintered magnet material is 0.1 mass% or more and 0.5 mass% or less. Higher H _cJ can be obtained.

The first diffusion step can be performed by placing the RL1-RH-M1 alloy in an arbitrary shape on the surface of the RTB-based sintered magnet material and using a known heat treatment device.

(Second diffusion step)
At least a portion of the RL2-M2 alloy is attached to at least a portion of the surface of the RTB sintered magnet material on which the first diffusion step has been performed, and the RL2-M2 alloy is heated for 400 minutes in a vacuum or inert gas atmosphere. A second diffusion step of heating at a temperature of .degree. C. or more and 600.degree. C. or less is performed. As a result, a liquid phase containing RL2 and M2 is generated from the RL2-M2 alloy, and the liquid phase is diffused into the inside from the surface of the sintered material via the grain boundaries in the RTB sintered magnet material. be done. The amount of the RL2-M2 alloy attached to the RTB sintered magnet material in the second diffusion step is 1 mass% or more and 15 mass% or less. Thereby, the RTB-based sintered magnet of the present disclosure can be obtained more reliably, and high B _r and high H _cJ can be obtained. If the amount of adhesion is less than 1 mass%, the amount of RL2 and M2 introduced into the inside of the magnet material may be too small to obtain a high H _cJ . On the other hand, if the amount of adhesion exceeds 15 mass%, the amount of RL2 and M2 introduced will be too large, resulting in a significant drop in _Br , and the RL2-M2 alloy that cannot be diffused into the magnet will remain on the magnet surface, resulting in poor corrosion resistance. Other problems such as workability may occur. Preferably, the amount of the RL2-M2 alloy attached to the RTB sintered magnet material is 2 mass% or more and 10 mass% or less. Higher H _cJ can be obtained.

Similar to the first diffusion step, in the second diffusion step, an RL2-M2 alloy of an arbitrary shape is placed on the surface of the RTB-based sintered magnet material on which the first diffusion step has been carried out, and the well-known heat treatment is performed. This can be done using a device. Further, as in the first diffusion step, as long as at least a portion of the RL2-M2 alloy is attached to at least a portion of the RTB sintered magnet material, the placement position is not particularly limited, but preferably , RL2-M2 alloy is arranged so as to be attached to at least a surface perpendicular to the orientation direction of the RTB based sintered magnet material. The liquid phase containing RL2 and M2 can be more efficiently diffused into the magnet from the surface thereof. In this case, the RL2-M2 alloy may be attached only to the orientation direction of the RTB-based sintered magnet material, or the RL2-M2 alloy may be attached to the entire surface of the RTB-based sintered magnet material. good.

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

(Example 1)
[Process of preparing RTB-based sintered magnet material (magnet material)]
Each element was weighed and cast using a strip casting method to obtain a flaky raw material alloy with a thickness of 0.2 to 0.4 mm. The obtained flake-like raw material alloy was hydrogen-pulverized and then subjected to dehydrogenation treatment in which it was heated to 550° C. in vacuum and then cooled to obtain coarsely pulverized powder. Next, 0.04 mass% of zinc stearate was added as a lubricant to the obtained coarsely pulverized powder based on 100 mass% of the coarsely pulverized powder, and the mixture was mixed. Dry pulverization was performed in an air stream to obtain finely pulverized powder (alloy powder) with a particle size _D50 of 4 μm. Note that the particle size D ₅₀ is a volume center value (volume-based median diameter) obtained by a laser diffraction method using an air flow dispersion method.

Zinc stearate was added as a lubricant to the finely pulverized powder in an amount of 0.05 mass% based on 100 mass% of the finely pulverized powder, and the mixture was mixed and then molded in a magnetic field to obtain a molded body. The forming apparatus used was a so-called right-angle magnetic field forming apparatus (transverse magnetic field forming apparatus) in which the magnetic field application direction and the pressing direction were perpendicular to each other.

The obtained molded body was sintered in vacuum at 1040° C. (a temperature at which sufficient densification by sintering would occur) was sintered for 4 hours, and then rapidly cooled to obtain a magnet material. The density of the obtained magnet material was 7.5 Mg/m ³ or more. Table 1 shows the results of the components of the obtained magnet material. Note that each component in Table 1 was measured using high frequency inductively coupled plasma optical emission spectroscopy (ICP-OES). In addition, as a result of measuring the oxygen content of the magnet material by gas melting-infrared absorption method, it was confirmed that all of the oxygen content was around 0.1 mass%. Further, as a result of measuring C (carbon content) using a gas analyzer using combustion-infrared absorption method, it was confirmed that C (carbon content) was around 0.1 mass%. "[T]/[B]" in Table 1 is the analytical value (mass%) divided by the atomic weight of each element that constitutes T (here, Fe, Al, Si, Mn). It is the ratio (a/b) between the sum of these values (a) and the analytical value (mass%) of B divided by the atomic weight of B (b). The same applies to all tables below. In addition, even if the respective compositions, oxygen amounts, and carbon amounts in Table 1 are totaled, they do not add up to 100 mass%. This is because, as mentioned above, the analysis method differs depending on each component. The same applies to other tables.

[Process of preparing RL1-RH-M1 alloy]
Each element is weighed and the raw materials are melted so as to have the composition of the RL1-RH-M1 alloy shown in code 1-a1 in Table 2, and then formed into ribbons or flakes by a single roll ultra-quenching method (melt spinning method). A shaped alloy was obtained. After crushing the obtained alloy in an argon atmosphere using a mortar, it was passed through several types of sieves with openings of 38 to 1000 μm to change the amount of adhesion to the RTB sintered magnet material. RL1-RH-M1 alloys with different particle sizes were prepared. Table 2 shows the composition of the obtained RL1-RH-M1 alloy. Note that each component in Table 2 was measured using high frequency inductively coupled plasma optical emission spectroscopy (ICP-OES).

[First diffusion step]
The RTB-based sintered magnet material labeled 1-A in Table 1 was cut and machined to form a cube of 7.2 mm x 7.2 mm x 7.2 mm. Next, PVA was applied as an adhesive over the entire surface of the RTB-based sintered magnet material by a dipping method. RL1-RH-M1 alloy powders of five different particle sizes were adhered to RTB sintered magnet materials coated with adhesive. RL1-RH-M1 alloy powder was spread in a processing container and adhered to the entire surface of an RTB sintered magnet material coated with an adhesive. Next, using a vacuum heat treatment furnace, the RL1-RH-M1 based alloy and the RTB based sintered magnet material were heated at 900°C for 10 hours in reduced pressure argon controlled at 200 Pa. After carrying out the diffusion step, it was cooled.

[Process of preparing RL2-M2 alloy]
Each element is weighed and the raw materials are melted so that the composition of the RL2-M2 alloy shown in code 1-a2 in Table 3 is obtained, and then ribbon or flake-like Obtained alloy. The obtained alloy was ground in an argon atmosphere using a mortar and then passed through several types of sieves with openings of 38 to 1000 μm to prepare RL2-M2 alloys. Table 3 shows the composition of the obtained RL2-M2 alloy. Note that each component in Table 3 was measured using high frequency inductively coupled plasma optical emission spectroscopy (ICP-OES).

[Second diffusion step]
After the first diffusion step, PVA was again applied to the entire surface of the sample as an adhesive by dipping. Thereafter, the RL2-M2 alloy powder was spread in a processing container and adhered to the entire surface of the sample coated with the adhesive. Next, the RL2-M2 alloy and the RTB sintered magnet material are heated and diffused at 500°C for 3 hours in reduced pressure argon controlled at 200 Pa using a vacuum heat treatment furnace. After carrying out the process, it was cooled. After heat treatment, the entire surface of each sample was cut using a surface grinder to obtain a cubic sample (RTB-based sintered magnet) of 7.0 mm x 7.0 mm x 7.0 mm. Obtained. In addition, the heating temperature of the RL1-RH-M1 series alloy and the RTB series sintered magnet material in the process of implementing the first diffusion process, and the heating temperature of the RL2-RH-M2 series alloy and R in the process of implementing the second diffusion process. -The heating temperature of the TB-based sintered magnet material was measured by attaching a thermocouple to each.

[Sample evaluation]
B _r and H _cJ of each sample were measured using a BH tracer. The measurement results are shown in Table 4. Further, Table 5 shows the results of measuring the components of the sample using high frequency inductively coupled plasma optical emission spectroscopy (ICP-OES). In addition, for any RTB-based sintered magnet, [T] is the content of T expressed in mass%, and [B] is the content of B expressed in mass%, [T]/55 It was confirmed that .85>14×[B]/10.8 holds true. Also, "molar ratio of Pr to Nd (([Pr]/atomic weight of Pr)/([Nd]/atomic weight of Nd)) in the central part of the main phase crystal grain located at a depth of 300 μm from the magnet surface" And "molar ratio of Pr to Nd (([Pr]/atomic weight of Pr)/([Nd]/atomic weight of Nd)) in the two-grain grain boundary located at a depth of 300 μm from the magnet surface" was determined. Furthermore, it was also confirmed whether there was a part where the RH and Ga concentrations gradually decreased from the magnet surface toward the inside of the magnet. Specifically, it was performed as follows. No. Crystal grains (main phase crystal grains) and two-grain boundaries at 300 μm from the magnet surface (here, the plane perpendicular to the magnetization direction) of 1-1 to 1-5 were observed using a transmission electron microscope (TEM). The concentration (mass%) of Nd and Pr contained in the central part of the main phase grain and the two-grain boundary (any location on the two-grain boundary) was measured using dispersive X-ray spectroscopy (EDX). . Ratio (a/b) of the measured concentration of Pr (mass%) divided by the atomic weight of Pr (a) and the measured concentration of Nd (mass%) divided by the atomic weight of Nd (b) were calculated respectively. The measurement results and calculation results are shown in Table 4. Table 4 shows the results of the molar ratio of Pr to Nd (([Pr]/atomic weight of Pr)/(atomic weight of Nd)/(atomic weight of Nd)) at the center of the main phase grain. [Pr]/[Nd]'' and the molar ratio of Pr to Nd within the two-particle grain boundary (([Pr]/atomic weight of Pr)/([Nd]/atomic weight of Nd)). "Inside grain boundaries [Pr]/[Nd]". The same applies to subsequent tables. Furthermore, No. Line analysis (line analysis) is performed using the EDX from the magnet surface to the vicinity of the magnet center in the magnet cross sections 1-1 to 1-5, and whether the RH and Ga concentrations are gradually decreasing from the magnet surface to the magnet center (gradually Check whether the concentration is low. In Table 4, if the RH and Ga concentrations are gradually decreasing, they are marked as ○, and when they are not gradually decreasing, they are marked as ×.

As shown in Table 4, sample No. It can be seen that in all of the invention examples 1-2 to 1-4, a high B _r of 1.34 T or more and a high H _cJ of 1800 kA/m or more were obtained. On the other hand, sample No. 2 has ([Pr]/[Nd]) less than 2.0 in the two-grain grain boundary and does not include a portion where the Ga concentration gradually decreases from the magnet surface toward the inside of the magnet. 1-1 did not provide high H _cJ . Furthermore, sample No. 2 in which ([Pr]/[Nd]) within the two-grain grain boundary was more than 5.0. 1-5 could not obtain high _Br .

(Example 2)
[Process of preparing RTB-based sintered magnet material (magnet material)]
Each element was weighed and cast by the strip casting method to obtain a raw material alloy in the form of flakes with a thickness of 0.2 to 0.4 mm so as to have the composition of the magnet material shown in 2-A in Table 6. The obtained flake-like raw material alloy was hydrogen-pulverized and then subjected to dehydrogenation treatment in which it was heated to 550° C. in vacuum and then cooled to obtain coarsely pulverized powder. Next, 0.04 mass% of zinc stearate was added as a lubricant to the obtained coarsely pulverized powder based on 100 mass% of the coarsely pulverized powder, and the mixture was mixed. Dry pulverization was performed in an air stream to obtain finely pulverized powder (alloy powder) with a particle size _D50 of 4 μm. Note that the particle size D ₅₀ is a volume center value (volume-based median diameter) obtained by a laser diffraction method using an air flow dispersion method.

Zinc stearate was added as a lubricant to the finely pulverized powder in an amount of 0.05 mass% based on 100 mass% of the finely pulverized powder, and the mixture was mixed and then molded in a magnetic field to obtain a molded body. The forming apparatus used was a so-called right-angle magnetic field forming apparatus (transverse magnetic field forming apparatus) in which the magnetic field application direction and the pressing direction were perpendicular to each other.

The obtained compact was sintered in vacuum at 1030° C. (a temperature at which sufficient densification by sintering occurred for each sample was selected) for 4 hours, and then rapidly cooled to obtain a magnet material. The density of the obtained magnet material was 7.5 Mg/m ³ or more. Table 6 shows the results of the components of the obtained magnet material. Note that each component in Table 6 was measured using high frequency inductively coupled plasma optical emission spectroscopy (ICP-OES). In addition, as a result of measuring the oxygen content of the magnet material by gas melting-infrared absorption method, it was confirmed that all of the oxygen content was around 0.1 mass%. Further, as a result of measuring C (carbon content) using a gas analyzer using combustion-infrared absorption method, it was confirmed that C (carbon content) was around 0.1 mass%.

[Process of preparing RL1-RH-M1 alloy]
Each element is weighed and the raw materials are melted so as to have the composition of the RL1-RH-M1 alloy shown in code 2-a1 in Table 7, and then formed into ribbons or flakes by a single roll ultra-quenching method (melt spinning method). A shaped alloy was obtained. The obtained alloy was crushed in an argon atmosphere using a mortar, and then passed through several types of sieves with openings of 38 to 1000 μm to change the amount of adhesion to the RTB sintered magnet material. RL1-RH-M1 alloys with different particle sizes were prepared. Table 7 shows the composition of the obtained RL1-RH-M1 alloy. Note that each component in Table 7 was measured using high frequency inductively coupled plasma optical emission spectroscopy (ICP-OES).

[Diffusion process]
The RTB-based sintered magnet material labeled 2-A in Table 6 was cut and machined to form a cube of 7.2 mm x 7.2 mm x 7.2 mm. Next, PVA was applied as an adhesive over the entire surface of the RTB-based sintered magnet material by a dipping method. RL1-RH-M1 alloy powders of three different particle sizes were adhered to RTB sintered magnet material coated with an adhesive. RL1-RH-M1 alloy powder was spread in a processing container and adhered to the entire surface of an RTB sintered magnet material coated with an adhesive. Next, using a vacuum heat treatment furnace, the RL1-RH-M1 based alloy and the RTB based sintered magnet material were heated at 900°C for 10 hours in reduced pressure argon controlled at 200 Pa. After carrying out the diffusion step, it was cooled. Next, the RTB-based sintered magnet material after the diffusion process was heated in a reduced pressure argon controlled at 200 Pa at 500° C. for 3 hours using a vacuum heat treatment furnace, and then cooled. The heating temperatures of the RL1-RH-M1 alloy and the RTB sintered magnet material in the diffusion step and the subsequent heat treatment step were each measured by attaching thermocouples.

[Sample evaluation]
B _r and H _cJ of each sample were measured using a BH tracer. The measurement results are shown in Table 8. Further, Table 9 shows the results of measuring the components of the sample using high frequency inductively coupled plasma optical emission spectroscopy (ICP-OES). In addition, for any RTB-based sintered magnet, [T] is the content of T expressed in mass%, and [B] is the content of B expressed in mass%, [T]/55 It was confirmed that .85>14×[B]/10.8 holds true. Furthermore, in the same manner as in Example 1, the concentrations of Nd and Pr contained in the central part of the main phase crystal grain and the two-grain boundary (any location on the two-grain boundary) were measured, and the concentrations of Nd and Pr contained in the central part of the main phase crystal grain and [Pr]/[Nd] at the two-particle grain boundary was determined. Furthermore, it was confirmed in the same manner as in Example 1 whether or not there was a portion where the RH and Ga concentrations gradually decreased from the magnet surface toward the inside of the magnet. Table 8 shows the measurement results and calculation results. As shown in Table 8, sample No. It can be seen that in all of the invention examples 2-1 to 2-3, high B _r of 1.35 T or more and high H _cJ of 1900 kA/m or more were obtained.

(Example 3)
[Process of preparing RTB-based sintered magnet material (magnet material)]
Each element was weighed and cast using a strip casting method to obtain a flaky raw material alloy with a thickness of 0.2 to 0.4 mm. The obtained flake-like raw material alloy was hydrogen-pulverized and then subjected to dehydrogenation treatment in which it was heated to 550° C. in vacuum and then cooled to obtain coarsely pulverized powder. Next, 0.04 mass% of zinc stearate was added as a lubricant to the obtained coarsely pulverized powder based on 100 mass% of the coarsely pulverized powder, and the mixture was mixed. Dry pulverization was performed in an air stream to obtain finely pulverized powder (alloy powder) with a particle size _D50 of 4 μm. Note that the particle size D ₅₀ is a volume center value (volume-based median diameter) obtained by a laser diffraction method using an air flow dispersion method.

Zinc stearate was added as a lubricant to the finely pulverized powder in an amount of 0.05 mass% based on 100 mass% of the finely pulverized powder, and the mixture was mixed and then molded in a magnetic field to obtain a molded body. The forming apparatus used was a so-called right-angle magnetic field forming apparatus (transverse magnetic field forming apparatus) in which the magnetic field application direction and the pressing direction were perpendicular to each other.

The obtained molded body was sintered in vacuum at 1000° C. to 1030° C. (a temperature at which sufficient densification by sintering occurred was selected for each sample) for 4 hours, and then rapidly cooled to obtain a magnet material. The density of the obtained magnet material was 7.5 Mg/m ³ or more. Table 10 shows the results of the components of the obtained magnet material. Note that each component in Table 10 was measured using high frequency inductively coupled plasma optical emission spectroscopy (ICP-OES). In addition, as a result of measuring the oxygen content of the magnet material by gas melting-infrared absorption method, it was confirmed that all of the oxygen content was around 0.1 mass%. Further, as a result of measuring C (carbon content) using a gas analyzer using combustion-infrared absorption method, it was confirmed that C (carbon content) was around 0.1 mass%.

[Process of preparing RL1-RH-M1 alloy]
Each element is weighed and the raw materials are melted so that the composition of the RL1-RH-M1 alloy shown in 3-a1 to 3-c1 in Table 11 is obtained, and the single-roll ultra-quenching method (melt spinning method) is used. A ribbon or flake-like alloy was obtained. The obtained alloy was crushed in an argon atmosphere using a mortar, and then passed through several types of sieves with openings of 38 to 1000 μm to change the amount of adhesion to the RTB sintered magnet material. RL1-RH-M1 alloys with different particle sizes were prepared. Table 7 shows the composition of the obtained RL1-RH-M1 alloy. Note that each component in Table 7 was measured using high frequency inductively coupled plasma optical emission spectroscopy (ICP-OES).

[Diffusion process]
The RTB-based sintered magnet materials numbered 3-A to 3-M in Table 10 were cut and machined into cubes of 7.2 mm x 7.2 mm x 7.2 mm. Next, PVA was applied as an adhesive over the entire surface of the RTB-based sintered magnet material by a dipping method. RL1-RH-M1 alloy powders of three different particle sizes were adhered to RTB sintered magnet material coated with an adhesive. RL1-RH-M1 alloy powder was spread in a processing container and adhered to the entire surface of an RTB sintered magnet material coated with an adhesive. Next, using a vacuum heat treatment furnace, the RL1-RH-M1 based alloy and the RTB based sintered magnet material were heated at 900°C for 10 hours in reduced pressure argon controlled at 200 Pa. After carrying out the diffusion step, it was cooled. Next, the RTB-based sintered magnet material after the diffusion process was heated in a reduced pressure argon controlled at 200 Pa at 500° C. for 3 hours using a vacuum heat treatment furnace, and then cooled. The heating temperatures of the RL1-RH-M1 alloy and the RTB sintered magnet material in the diffusion step and the subsequent heat treatment step were each measured by attaching thermocouples.

[Sample evaluation]
B _r and H _cJ of each sample were measured using a BH tracer. The measurement results are shown in Table 12. Further, Table 13 shows the results of measuring the components of the sample using high frequency inductively coupled plasma optical emission spectroscopy (ICP-OES). In addition, for any RTB-based sintered magnet, [T] is the content of T expressed in mass%, and [B] is the content of B expressed in mass%, [T]/55 It was confirmed that .85>14×[B]/10.8 holds true. Furthermore, in the same manner as in Example 1, the concentrations of Nd and Pr contained in the central part of the main phase crystal grain and the two-grain boundary (any location on the two-grain boundary) were measured, and the concentrations of Nd and Pr contained in the central part of the main phase crystal grain and [Pr]/[Nd] at the two-particle grain boundary was determined. Furthermore, it was confirmed in the same manner as in Example 1 whether or not there was a portion where the RH and Ga concentrations gradually decreased from the magnet surface toward the inside of the magnet. Table 12 shows the measurement results and calculation results. As shown in Table 12, sample No. It can be seen that in all of the invention examples 3-1 to 3-14, a high B _r of 1.36 T or more and a high H _cJ of 1900 kA/m or more were obtained.

According to the present disclosure, an RTB-based sintered magnet with high residual magnetic flux density and high coercive force can be manufactured. The sintered magnet of the present disclosure is suitable for various motors such as hybrid vehicle motors and home appliances that are exposed to high temperatures.

12...Main phase consisting of R2T14B compound, 14...Grain boundary phase, 14a...Two-grain grain boundary phase, 14b...Grain boundary triple point

Claims (5)

An RTB-based sintered magnet containing main phase crystal grains and a grain boundary phase,
R: 27.0 mass% or more and 35.0 mass% or less (R consists of RL and RH, RL is at least two types of light rare earth elements and always includes Nd and Pr, and RH is at least one type of heavy rare earth elements) (Always includes at least one of Tb and Dy),
B: 0.80 mass% or more and 1.20 mass% or less,
Ga: 0.20 mass% or more and 0.80 mass% or less,
T: Contains 61.5 mass% or more (T is Fe and Co, and 90 mass% or more of T is Fe),
The molar ratio of Pr to Nd (([Pr]/atomic weight of Pr)/([Nd]/atomic weight of Nd)) in the central part of the main phase crystal grain located at a depth of 300 μm from the magnet surface is 0 or more. .45 or less ([Pr] is the content of Pr expressed in mass%, [Nd] is the content of Nd expressed in mass%),
The molar ratio of Pr to Nd (([Pr]/atomic weight of Pr)/([Nd]/atomic weight of Nd)) within the two-grain grain boundary located at a depth of 300 μm from the magnet surface is 2.3 or more5. is less than or equal to 0,
Including a part where the RH concentration gradually decreases from the magnet surface toward the inside of the magnet,
Including a part where the Ga concentration gradually decreases from the magnet surface toward the inside of the magnet,
RTB series sintered magnet. When [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 holds true. The RTB based sintered magnet according to claim 1. The molar ratio of Pr to Nd (([Pr]/atomic weight of Pr)/([Nd]/atomic weight of Nd)) within the two-grain grain boundary located at a depth of 300 μm from the magnet surface is 2.3 or more 4 The RTB-based sintered magnet according to claim 1 or 2, wherein the RTB-based sintered magnet is .0 or less. R- according to any one of claims 1 to 3, wherein the RTB-based sintered magnet contains Cu, and the content of Cu is 0.05 mass% or more and 0.80 mass% or less. T-B series sintered magnet. The RTB-based sintered magnet according to claim 4, wherein the Ga content is greater than the Cu content.

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