JP7452159B2 - Manufacturing method of RTB based sintered magnet - Google Patents

Description

The present invention relates to a method for manufacturing an RTB 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 (VCMs) 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.

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 while supplying a heavy rare earth element such as Dy to the surface of a sintered magnet made of an RTB alloy, the heavy rare earth element RH 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, it is possible to obtain a high H _cJ while reducing the amount of RH used and further 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.

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

However, in recent years, there has been a demand for obtaining higher _Br and higher H _cJ while reducing the amount of expensive heavy rare earth elements used, particularly in motors for electric vehicles.

Various embodiments of the present disclosure provide methods for manufacturing 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 producing an RTB-based sintered magnet of the present disclosure includes producing a sintered body from fine powder having a particle size _D50 of 2.0 μm to 3.5 μm, and - B-based sintered magnet material (R is a rare earth element and always contains at least one selected from the group consisting of Nd, Pr, and Ce, and T is selected from the group consisting of Fe, Co, Al, Mn, and Si) a step of preparing an RL-RH-M alloy (RL is at least one of the light rare earth elements, T always includes Fe, and T always includes Fe); RH is at least one selected from the group consisting of Tb, Dy and Ho, and M is Cu, Ga, Fe, Co, Ni, and Al. and at least a portion of the RL-RH-M alloy on at least a portion of the surface of the RTB sintered magnet material. In the RTB-based sintered magnet material, the content of R is - The content of RL is 27 mass% or more and 35 mass% or less of the entire T-B series sintered magnet material, the content of Fe is 80 mass% or more with respect to the whole T, and the content of RL in the RL-RH-M alloy is: The content of RH is 57 mass% to 82 mass% of the entire RL-RH-M alloy, the content of RH is 13 mass% to 23 mass% of the entire RL-RH-M alloy, and the content of M is RL- 2. The amount of the RL-RH-M alloy attached to the RTB sintered magnet material in the diffusion step is 1 mass% or more and 2. It is 5 mass% or less.

In one embodiment, the amount of the RL-RH-M alloy attached to the RTB sintered magnet material in the diffusion step is 1.5 mass% or more and 2.5 mass% or less.

According to embodiments of the present disclosure, it is possible to provide a method for manufacturing 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 an enlarged cross-sectional view schematically showing a part 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.

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 R in the R ₂ T ₁₄ B compound, which is the main phase, with a heavy rare earth element such as Dy, Tb, or Ho, the anisotropic magnetic field of the main phase can be increased while lowering the saturation magnetization. It has been known. 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.

In the method for manufacturing an RTB-based sintered magnet according to the present disclosure, from the surface of the RTB-based sintered magnet material through the grain boundaries to the inside of the magnet material, together with RH contained in the RL-RH-M-based alloy. , RL and M are spread. As a result of studies by the present inventors, it was found that for RTB-based sintered magnet materials prepared by producing fine powder sintered bodies with a particle size _D50 in the range of 2.0 μm to 3.5 μm, It was discovered that high B _r and high H _cJ can be obtained while reducing expensive RH by performing diffusion treatment with the amount of RL-RH-M alloy deposited and the RH concentration in a narrow specific range. .

As shown in FIG. 2, the method for manufacturing an RTB-based sintered magnet according to the present disclosure includes step S10 of preparing an RTB-based sintered magnet material and preparing an RL-RH-M-based alloy. and step S20. The order of step S10 of preparing the RTB-based sintered magnet material and step S20 of preparing the RL-RH-M alloy is arbitrary.
As shown in FIG. 2, the method for manufacturing an RTB-based sintered magnet according to the present disclosure further includes the addition of an RL-RH-M-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 RL-RH-M alloy attached to the RTB sintered magnet material in the diffusion step S30 is 1 mass% or more and 2.5 mass% or less.

In this disclosure, the RTB-based sintered magnet before and during the diffusion process is referred to as "RTB-based sintered magnet material," and the RTB-based sintered magnet after the diffusion process is referred to as "RTB-based sintered magnet material." The sintered magnet is simply referred to as an "RTB sintered magnet."

(Process of preparing RTB-based sintered magnet material)
In the RTB system sintered magnet material, R is a rare earth element and always contains at least one selected from the group consisting of Nd, Pr, and Ce, and the content of R is the same as that of the RTB system. It is 27 mass% or more and 35 mass% or less of the entire sintered magnet material. T is at least one selected from the group consisting of Fe, Co, Al, Mn, and Si, T always contains Fe, and the content of Fe with respect to the entire T is 80 mass% or more.
If R is less than 27 mass%, a liquid phase will not be sufficiently 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.

For example, the RTB-based sintered magnet material has the following composition range.
R: 27-35 mass%,
B: 0.80 to 1.20 mass%,
Ga: 0 to 1.0 mass%,
X: 0 to 2 mass% (X is at least one of Cu, Nb, and Zr),
T: Contains 60 mass% or more.

Preferably, in the RTB-based sintered magnet material, the molar ratio of T to B [T]/[B] is more than 14.0 and less than or equal to 15.0. Higher H _cJ can be obtained. [T]/[B] in the present disclosure refers to each element constituting T (at least one selected from the group consisting of Fe, Co, Al, Mn, and Si; T always includes Fe; Calculate the analytical value (mass%) of the total Fe content (80 mass% or more) divided by the atomic weight of each element, and the sum of these values [T] and the analytical value of B (mass% ) divided by the atomic weight of B [B]. The condition that the molar ratio [T]/[B] exceeds 14.0 indicates that the amount of B is small relative to the amount of T used to form the main phase (R ₂ T ₁₄ B compound). . It is more preferable that the molar ratio [T]/[B] is 14.3 or more and 15.0 or less. Even higher H _cJ can be obtained. The content of B is preferably 0.9 mass% or more and less than 1.0 mass% of the entire RTB-based sintered body.

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 using a jet mill or the like to a particle size _D50 of 2.0 μm or more and 3.5 μm or less, and then molded in a magnetic field at a temperature of 900°C or more. A sintered body can be prepared by sintering at a temperature of 1100° C. or lower. If the particle size _D50 is less than 2.0 μm, productivity may deteriorate significantly, and if it exceeds 3.5 μm, the desired effect may not be obtained even if the diffusion process of the present disclosure is performed. There is sex. This is thought to be because the particle size of the powder is reflected in the crystal grain size of the sintered body, which also affects diffusion. Preferably, the particle size D ₅₀ is 2.5 μm or more and 3.3 μm or less. Higher _Br and higher H _cJ can be obtained while suppressing deterioration in productivity and reducing valuable RH. The above _D50 is a particle size at which the cumulative particle size distribution (volume basis) from the small diameter side is 50% in the particle size distribution obtained by laser diffraction using an air flow dispersion method. Further, _D50 can be measured, for example, using a particle size distribution measuring device "HELOS &RODOS" manufactured by Sympatec under the conditions of dispersion pressure: 4 bar, measurement range: R2, and measurement mode: HRLD.

(Step of preparing RL-RH-M alloy)
In the RL-RH-M alloy, RL is at least one light rare earth element, and always includes at least one selected from the group consisting of Nd, Pr, and Ce, and the content of RL is It is 57 mass% or more and 82 mass% or less of the entire -RH-M alloy. Examples of light rare earth elements include La, Ce, Pr, Nd, Pm, Sm, and Eu. RH is at least one selected from the group consisting of Tb, Dy, and Ho, and the content of RH is 13 mass% or more and 23 mass% or less of the entire RL-RH-M alloy. M is at least one selected from the group consisting of Cu, Ga, Fe, Co, Ni, and Al, and the content of M is 5 mass% or more and 20 mass% or less of the entire RL-RH-M alloy. be. Typical examples of RL-RH-M alloys include TbNdPrCu alloy, TbNdCePrCu alloy, TbNdGa alloy, and TbNdPrGaCu alloy.

If RL is less than 57 mass%, RH and M will be difficult to introduce into the RTB sintered magnet material, and H _cJ may decrease; if RL exceeds 82 mass%, RL-RH-M During the manufacturing process of alloy-based alloys, the alloy powder becomes very active. As a result, significant oxidation or ignition of the alloy powder may occur. Preferably, the content of RL is 70 mass% or more and 80 mass% or less of the entire RL-RH-M alloy. Higher H _cJ can be obtained.

If RH is less than 13 mass%, a high H _cJ improving effect by RH may not be obtained, and if it exceeds 23 mass%, the H _cJ improving effect by RL and M may be reduced. It may not be possible to obtain an RTB-based sintered magnet having high B _r and high H _cJ while reducing the amount used. Preferably, the content of RH is 13 mass% or more and 20 mass% or less of the entire RL-RH-M alloy. Higher B _r and higher H _cJ can be obtained.

If M is less than 5 mass%, it will be difficult for RL and RH to be introduced into the two-grain boundary phase, and H _cJ may not be sufficiently improved. If M is more than 20 mass%, the content of RL and RH will decrease and H _cJ may not be improved sufficiently. Preferably, the content of M is 7 mass% or more and 15 mass% or less of the entire RL-RH-M alloy. Higher H _cJ can be obtained. Furthermore, M preferably contains Ga, and further preferably contains Cu, and higher H _cJ can be obtained.

The method for producing the RL-RH-M 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 prepared RL-RH-M alloy is attached to at least a portion of the surface of the RTB sintered magnet material prepared as described above, and the mixture is heated in vacuum (non-oxidizing atmosphere) or inert gas. A diffusion step of heating is performed in an atmosphere at a temperature of 700° C. or more and 1100° C. or less. As a result, a liquid phase containing RL, RH, and M is generated from the RL-RH-M alloy, and the liquid phase passes from the surface of the sintered material via the grain boundaries in the R-T-B sintered magnet material. It is diffused and introduced into the interior. The amount of RL-RH-M alloy attached to the RTB sintered magnet material in the diffusion process is set to 1 mass% or more and 2.5 mass% or less. Thereby, a high H _cJ improvement effect can be obtained. If the amount of RL-RH-M alloy attached to the RTB sintered magnet material is less than 1 mass%, the amount of RH, RL, and M introduced into the inside of the magnet material is too small, resulting in high H _cJ . Br may not be obtained, and if it exceeds 2.5 mass%, _Br may decrease. Preferably, the amount of the RL-RH-M alloy attached to the RTB sintered magnet material is 1.5 mass% or more and 2.2 mass% or less. Higher H _cJ can be obtained. Further, it is preferable that the amount of RH attached to the RTB sintered magnet material made of the RL-RH-M alloy is 0.1 mass% or more and 0.4 mass% or less. By setting it within this range, it is possible to obtain an RTB based sintered magnet having a high H _cJ while more reliably reducing the amount of heavy rare earth elements used. Note that the amount of RH attached is the amount of RH attached to the RTB series sintered magnet material, and it is the RH concentration in the RL-RH-M series alloy and the R- of the RL-RH-M series alloy. It can be calculated from the amount of adhered TB-based sintered magnet material. The RH adhesion amount is defined by the mass ratio when the mass of the RTB-based sintered magnet material is 100 mass%.

If the heating temperature in the diffusion step is less than 700° C., the amount of liquid phase containing RH, RL, and M may be too small to obtain high H _cJ . On the other hand, if the temperature exceeds 1100°C, H _cJ may decrease significantly. Preferably, the heating temperature in the diffusion step is 800°C or more and 1000°C or less. Higher H _cJ can be obtained. Preferably, the RTB sintered magnet that has been subjected to a diffusion process (700°C or more and 1100°C or less) is cooled from the temperature at which the diffusion process is performed to 300°C at a cooling rate of 15°C/min or more. Cooling is preferable. Higher H _cJ can be obtained.

The diffusion step can be performed by placing an RL-RH-M alloy in an arbitrary shape 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 RL-RH-M alloy, and then the diffusion process can be performed. For example, a coating step of applying the adhesive to the surface to be coated and a step of attaching the RL-RH-M 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. In addition, for example, after applying a slurry in which the RL-RH-M alloy is dispersed in a dispersion medium to the surface of the RTB sintered magnet material, the dispersion medium is evaporated to form the RL-RH-M alloy and the RTB-based sintered magnet material. -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. In addition, as long as at least a part of the RL-RH-M alloy is attached to at least a part of the RTB-based sintered magnet material, its placement position is not particularly limited; however, it is preferable that the RL-RH-M alloy -M 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 RL, RH and M can be more efficiently diffused into the magnet from the surface thereof. In this case, even if the RL-RH-M alloy is attached only in the orientation direction of the RTB-based sintered magnet material, the RL-RH-M 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.

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

Experimental example 1
[Process of preparing R-T-B sintered magnet material]
Each element was weighed so as to have the composition of the RTB sintered magnet material shown in No. 1 in Table 1, and a raw material alloy was produced by a strip casting method. Each of the obtained alloys was coarsely pulverized by a hydrogen pulverization method to obtain coarsely pulverized powder. Next, 0.035 mass % of zinc stearate was added as a lubricant to the coarsely pulverized powder based on 100 mass % of the coarse powder and mixed. The coarsely pulverized powder containing a lubricant was pulverized using a jet mill under conditions A and B described below.
Under condition A, fine powder having a particle size D ₅₀ of 4.2 μm and a particle size D ₉₉ of 12.5 μm was obtained by pulverization. In addition, D ₅₀ and D ₉₉ are the particle size at which the integrated particle size distribution (volume basis) from the small diameter side is 50% in the particle size distribution obtained by laser diffraction method using air flow dispersion method, and the particle size from the small particle size side, respectively. This is the particle size at which the integrated particle size distribution (volume basis) is 99%. Further, _D50 and _D99 were measured using a particle size distribution measuring device "HELOS&RODOS" manufactured by Sympatec under the conditions of dispersion pressure: 4 bar, measurement range: R2, and measurement mode: HRLD.
Condition B was to perform fine pulverization so that the particle size D ₅₀ was 3.3 μm and the particle size D ₉₉ was 8.5 μm.

To each of the obtained finely pulverized powders under conditions A and B, zinc stearate was added as a lubricant in an amount of 0.05 mass% based on 100 mass% of the finely pulverized powders, and after mixing, the mixture was 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 for 4 hours (a temperature was selected to ensure sufficient densification due to sintering), and then rapidly cooled to obtain an RTB-based sintered magnet material. The density of the obtained RTB-based sintered magnet material was 7.5 Mg/m ³ or more.
In order to determine the components of the RTB-based sintered magnet material obtained under conditions A and B, the contents of Nd, Pr, Fe, Co, Al, Si, Ga, Cu, Zr, and B were determined by high-frequency induction. Measured by coupled plasma optical emission spectroscopy (ICP-OES). In addition, the oxygen content of the RTB sintered magnet material was measured using a gas analyzer using the gas melting-infrared absorption method, the nitrogen content using the gas melting-thermal conduction method, and the carbon content using the sintering-infrared absorption method. It was measured using Both Condition A and Condition B had the same composition. The results of the analysis are shown in Table 1. Note that the total components of the RTB-based sintered magnet material may not be 100 mass%. This is because the measurement methods are different as described above, and because other elements may be contained as unavoidable impurities.

[Process of preparing RL-RH-M alloy]
Each element is weighed and the raw materials are melted so as to have the composition of the RL-RH-M alloy shown in Nos. 1-A and 1-B in Table 2. An alloy of Table 2 shows the composition of the obtained RL-RH-M alloy. In addition, each component in Table 2 was measured using high frequency inductively coupled plasma emission spectrometry.

[Diffusion process]
The RTB-based sintered magnet material with reference numeral 1 in Table 1 was cut and machined into a cube of 7.2 mm x 7.2 mm x 7.2 mm. After processing, PVA was applied as an adhesive over the entire surface of the RTB magnet material using a dipping method. Next, an RL-RH-M alloy was deposited on the entire surface of the RTB sintered magnet material coated with an adhesive under the manufacturing conditions shown in Table 3. The amount of RL-RH-M alloy deposited was determined by crushing the RL-RH-M alloy in a mortar in an argon atmosphere and then passing it through several types of sieves with openings of 45 to 1000 μm. Adjustment was made by using a -RH-M alloy. Then, using a vacuum heat treatment furnace, the RL-RH-M alloy and RTB-based sintered magnet material were heated under the conditions shown in the diffusion process in Table 3 in a reduced-pressure argon atmosphere controlled at 100 Pa. , cooled.

[Process of heat treatment]
The RTB-based sintered magnet material heated in the diffusion step was heat-treated at 500° C. in a vacuum heat treatment furnace controlled at 100 Pa in reduced pressure argon. The entire surface of each sample after heat treatment was cut using a surface grinder to obtain a 7.0 mm x 7.0 mm x 7.0 mm cube-shaped sample (RTB-based sintered magnet). . In addition, the heating temperature of the RL-RH-M alloy and the RTB-based sintered magnet material in the diffusion process, and the heating temperature of the RTB-based sintered magnet in the process of performing heat treatment after the diffusion process. The temperature was measured using a thermocouple.

[Sample evaluation]
The residual magnetic flux density B _r and coercive force H _cJ of the obtained sample were measured using a BH tracer. In addition, the difference (ΔH _cJ ) between the H _cJ of the RTB sintered magnet material and the H _cJ of the RTB sintered magnet after the diffusion process and the heat treatment process was determined. The results are shown in Table 3. In addition, in the experimental example, the amount of adhesion of the RL-RH-M alloy to the RTB-based sintered magnet material was 2.5 mass% or less, and the obtained RTB-based sintered magnet The magnetic properties of B _r : 1.35 T or more and H _cJ : 1925 kA/m or more were evaluated as examples of the present invention. As shown in Table 3, using the RTB-based sintered magnet material obtained from the finely pulverized powder under the above condition B, the RL-RH with the composition shown in the numbers 1-A and 1-B in Table 2 was used. - Sample No. of the present invention example using M-based alloy. It can be seen that samples 1-4 to 1-6 can obtain high B _r and high H _cJ , and also have high ΔH _cJ . On the other hand, using the RTB-based sintered magnet material obtained from the finely pulverized powder crushed under the above condition A, RL-RH-M with the composition shown in codes 1-A and 1-B in Table 2 was used. Sample No. using alloy based on In Examples 1-1 to 1-3, H _cJ is lower than that of the examples of the present invention, and ΔH _cJ , which indicates the effect of the diffusion process and heat treatment process, is also low.

Experimental example 2
[Process of preparing R-T-B sintered magnet material]
Each element was weighed so as to have the composition of the RTB-based sintered magnet material shown in numeral 2 in Table 4, and a raw material alloy was produced by a strip casting method. Each of the obtained alloys was coarsely pulverized by a hydrogen pulverization method to obtain coarsely pulverized powder. Next, 0.035 mass % of zinc stearate as a lubricant was added to the coarsely pulverized powder based on 100 mass % of the coarse powder and mixed to obtain a lubricant-containing finely pulverized powder. The obtained lubricant-containing coarsely pulverized powder was pulverized using a jet mill to obtain finely pulverized powder having a particle size D ₅₀ of 3.3 μm and a D ₉₉ of 8.5 μm.
To the obtained finely pulverized powder, zinc stearate was added as a lubricant 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 a vacuum for 4 hours (a temperature was selected to ensure sufficient densification due to sintering), and then rapidly cooled to obtain a sintered magnet material. The density of the obtained RTB-based sintered magnet material was 7.5 Mg/m ³ or more.
Table 4 shows the results of the obtained RTB-based sintered magnet material. Note that each component in Table 4 was measured in the same manner as in Experimental Example 1.

[Process of preparing RL-RH-M alloy]
Each element is weighed and the raw materials are melted to obtain the composition of the RL-RH-M alloy shown in 2-A, 2-B, and 2-C in Table 5, and then the single-roll ultra-quenching method is used. A ribbon or flake-like alloy was obtained. Table 5 shows the composition of the obtained RL-RH-M alloy. In addition, each component in Table 5 was measured using high frequency inductively coupled plasma emission spectrometry.

[Diffusion process]
The RTB-based sintered magnet material numbered 2 in Table 4 was cut and machined into a cube of 7.2 mm x 7.2 mm x 7.2 mm. After processing, PVA was applied as an adhesive over the entire surface of the RTB magnet material using a dipping method. Next, the RL-RH-M alloy was adhered to the entire surface of the RTB sintered magnet material coated with an adhesive under the manufacturing conditions shown in Table 6. The amount of the RL-RH-M alloy deposited is determined by crushing the RL-RH-M alloy in an argon atmosphere using a mortar, passing it through several types of sieves with openings of 45 to 1000 μm, and determining the particle size. Adjustments were made by using different RL-RH-M alloys. and. After heating the RL-RH-M alloy and RTB-based sintered magnet material under the conditions shown in the diffusion process in Table 6 in a reduced-pressure argon atmosphere controlled to 100 Pa using a vacuum heat treatment furnace, Cooled.

[Process of heat treatment]
After the diffusion step, the RTB-based sintered magnet material was heat-treated at 490° C. in a vacuum heat treatment furnace controlled to 100 Pa in reduced pressure argon. The entire surface of each sample after heat treatment was cut using a surface grinder to obtain a 7.0 mm x 7.0 mm x 7.0 mm cube-shaped sample (RTB-based sintered magnet). . In addition, the heating temperature of the RL-RH-M alloy and the RTB-based sintered magnet material in the process of performing the diffusion process, and the heating temperature of the RTB-based alloy in the process of performing the heat treatment after the diffusion process. The heating temperature of each sintered magnet was measured using a thermocouple. The heating temperature of the RL-RH-M alloy and the RTB sintered magnet material in the diffusion step was 900° C. x 10 hours, as in Experimental Example 1.

[Sample evaluation]
As shown in Table 6, sample no. In 2-1 to 2-4, B _r and H _cJ were compared in a range where the amount of RL-RH-M alloy deposited was less than 1.6 mass%. Sample No. in which the RH amount of the RL-RH-M alloy is less than 13 mass%. In 2-1, a high B _r was obtained, but a high H _cJ was not obtained. On the other hand, sample No. which is an example of the present invention. In samples 2-2 to 2-4, both high B _r and high H _cJ were obtained.

Claims (2)

A sintered body is produced from a fine powder with a particle size _D50 of 2.0 μm to 3.5 μm, and an RTB-based sintered magnet material (R is a rare earth element selected from the group consisting of Nd, Pr, and Ce) is produced. and T is at least one selected from the group consisting of Fe, Co, Al, Mn, and Si, and T always contains Fe.
RL-RH-M alloy (RL is at least one light rare earth element and always contains at least one selected from the group consisting of Nd, Pr and Ce, RH is selected from Tb, Dy and Ho) and M is at least one selected from the group consisting of Cu, Ga, Fe, Co, Ni, and Al.
At least a portion of the RL-RH-M alloy is adhered to at least a portion of the surface of the RTB-based sintered magnet material, and heated at a temperature of 700° C. or more and 1100° C. or less in a vacuum or an inert gas atmosphere. a diffusion process of heating at a temperature;
including;
In the RTB-based sintered magnet material, the R content is 27 mass% or more and 35 mass% or less of the entire RTB-based sintered magnet material, and the Fe content is 80 mass% with respect to the entire T. That's all,
In the RL-RH-M alloy, the RL content is 70 mass% or more and 82 mass% or less of the entire RL-RH-M alloy, and the RH content is 13 mass% or more and 23 mass% or less, and the M content is 5 mass% or more and 9.9 mass% or less of the entire RL-RH-M alloy,
The amount of the RL-RH-M alloy attached to the RTB sintered magnet material in the diffusion step is 1 mass% or more and 2.5 mass% or less,
A method for manufacturing an RTB-based sintered magnet. R- according to claim 1, wherein the amount of the RL-RH-M alloy attached to the RTB sintered magnet material in the diffusion step is 1.5 mass% or more and 2.5 mass% or less. A method for manufacturing a TB-based sintered magnet.

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