JP2022147793A - Production method of r-t-b based sintered magnet - Google Patents

Abstract

To provide a production method of an R-T-B based sintered magnet superior in the balance of Br and HcJ while reducing an amount of heavy rare earth RH to be used.SOLUTION: A production method of an R-T-B based sintered magnet comprises: a step of preparing an R-T-B based sintered magnet material (R is a rare earth element, and T represents at least one element selected from a group consisting of Fe, Co, Al, Mn and Si, inevitably including Fe); a step of preparing RL-RH-C-M based alloy; and a diffusion step of depositing at least part of the RL-RH-C-M based alloy to at least part of the surface of the R-T-B based sintered magnet material, followed by heating. In the RL-RH-C-M based alloy, the content of RL is 50 mass% or more and 95 mass% or less; the content of RH is 45 mass% or less (including 0 mass%); the content of C is 0.1 mass% or more and 0.5 mass% or less; and the content of M is 4 mass% or more and 49.9 mass% or less.SELECTED DRAWING: Figure 2

Description

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

RTB-based sintered magnets (R is a rare earth element, T is mainly Fe, and B is boron) are known to have the highest performance among permanent magnets, and are used in hard disk drives. voice coil motors (VCM), motors for electric vehicles (EV, HV, PHV, etc.), motors for industrial equipment, and home appliances. RTB based sintered magnets contribute to energy saving and environmental load reduction through the miniaturization and weight reduction of various motors.

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

RTB based sintered magnets have a problem of irreversible thermal demagnetization due to a decrease in coercive force H _cJ (hereinafter simply referred to as “H _cJ ”) at high temperatures. Therefore, RTB sintered magnets used in motors for electric vehicles in particular are required to have a high H _cJ even at high temperatures, that is, to have a higher H _cJ at room temperature.

It is known that replacing light rare earth elements (mainly Nd, Pr) in the R ₂ T ₁₄ B-type compound phase with heavy rare earth elements (mainly Dy, Tb) improves H _cJ . However, while the H _cJ is improved, the saturation magnetization of the R ₂ T ₁₄ B type compound phase is reduced, which causes a problem that the residual magnetic flux density B _r (hereinafter simply referred to as “B _r ”) is reduced.

Patent Document 1 describes supplying a heavy rare earth element such as Dy to the surface of a sintered magnet made of an RTB alloy and diffusing the heavy rare earth element RH inside the sintered magnet. . The method described in Patent Document 1 diffuses Dy from the surface of the RTB system sintered magnet to the inside, and concentrates Dy only in the outer shell portion of the main phase crystal grains, which is effective for improving _HcJ . As a result, a high _HcJ can be obtained while suppressing a decrease in _Br .

Patent Document 2 discloses that the surface of a sintered RTB magnet is heat-treated by bringing an R-Ga-Cu alloy of a specific composition into contact with the surface of the sintered RTB magnet, thereby reducing the grain boundaries in the sintered RTB magnet. Controlling the composition and thickness of the phases is described to improve the _HcJ .

WO2007/102391 WO2016/133071

However, in recent years, especially in motors for electric vehicles, etc., the amount of expensive heavy rare earth elements used has been reduced, and furthermore, _R that has an excellent balance between Br and _HcJ (high _HcJ while suppressing the decrease in Br) has been used _. It is desired to obtain a -TB system sintered magnet.

Various embodiments of the present disclosure provide methods for producing RTB-based sintered magnets with an excellent balance between B _r and H _cJ while reducing the amount of heavy rare earth elements used.

In an exemplary embodiment of the method for producing an RTB based sintered magnet of the present disclosure, an RTB based sintered magnet material (R is a rare earth element, the group consisting of Nd, Pr and Ce and T is at least one selected from the group consisting of Fe, Co, Al, Mn, and Si, and necessarily includes Fe.); - An RL-RH-C-M alloy (RL is at least one of the light rare earth elements and selected from the group consisting of Nd, Pr and Ce) on at least part of the surface of the TB based sintered magnet material necessarily including at least one selected, RH is at least one selected from the group consisting of Tb, Dy and Ho; C is carbon; M is Cu, Ga, Fe, Co, Ni, At least one selected from the group consisting of Al, Ag, Zn, Si, and Sn.) is deposited and heated at a temperature of 700° C. or higher and 1100° C. or lower in a vacuum or inert gas atmosphere. and a diffusion step, wherein the RTB based sintered magnet material has a molar ratio [T]/[B] of T to B of more than 14.0 and 15.0 or less, and the RL-RH- In the CM alloy, the RL content is 50 mass% or more and 95 mass% or less, the RH content is 45 mass% or less (including 0 mass%), and the C content is 0.10 mass% or more and 0.1 mass% or less. 50 mass% or less, and the content of M is 4 mass% or more and 49.9 mass% or less.

In one embodiment, the molar ratio [T]/[B] of T to B in the RTB based sintered magnet material is more than 14.0 and 15.0 or less.

According to the embodiments of the present disclosure, it is possible to provide a method for manufacturing an RTB based sintered magnet having an excellent balance between B _r and H _cJ while reducing the amount of heavy rare earth elements used.

FIG. 2 is a cross-sectional view schematically showing an enlarged part of an RTB based sintered magnet. FIG. 1B is a schematic cross-sectional view further enlarging the inside of the dashed-line rectangular area of FIG. 1A; 4 is a flow chart showing an example of steps in a method for manufacturing a sintered RTB magnet according to the present disclosure;

First, the basic structure of the RTB based sintered magnet according to the present disclosure will be described. RTB sintered magnets have a structure _in which raw material alloy powder particles _are bonded by sintering. It consists of a grain boundary phase located at

FIG. 1A is a schematic cross-sectional view enlarging a part of the RTB based sintered magnet, and FIG. 1B is a cross-sectional view schematically showing a further enlarged broken-line rectangular area in FIG. 1A. is. In FIG. 1A, as an example, an arrow with a length of 5 μm is shown for reference as a reference length indicating the size. As shown in FIGS. 1A and 1B, the RTB system sintered magnet has a main phase 12 mainly composed of an R ₂ T ₁₄ B compound and a grain boundary phase 14 located at the grain boundary portion of the main phase 12. It consists of In addition, as shown in FIG. 1B, the grain boundary phase 14 includes a two-particle grain boundary phase 14a in which two R ₂ T ₁₄ B compound particles (grains) are adjacent, and a two-particle grain boundary phase 14a in which three R ₂ T ₁₄ B compound particles are adjacent. and the grain boundary triple point 14b. A typical main phase crystal grain size is 3 μm or more and 10 μm or less as the average value of the circle equivalent diameter of the cross section of the magnet. The R ₂ T ₁₄ B compound, which is the main phase 12, is a ferromagnetic material with high saturation magnetization and anisotropic magnetic field. Therefore, in an RTB based sintered magnet, B _r can be improved by increasing the abundance ratio of the R ₂ T ₁₄ B compound that is the main phase 12 . In order to increase the abundance ratio of the R ₂ T ₁₄ B compound, the R amount, T amount, and B amount in the raw material alloy are adjusted to the stoichiometric ratio of the R ₂ T ₁₄ B compound (R amount: T amount: B amount = 2:14:1). Incidentally, part of B in the R ₂ T ₁₄ B compound can be substituted with C.
In addition, by substituting a portion of R in the main phase R ₂ T ₁₄ B compound with a heavy rare earth element such as Dy, Tb, or Ho, the anisotropic magnetic field of the main phase can be increased while reducing the saturation magnetization. It has been known. In particular, the outer shell of the main phase, which is in contact with the grain boundary phase, is likely to become the starting point of magnetization reversal. A relatively high _HcJ is obtained.
On the other hand, it is known that a high _HcJ can be obtained also by controlling the magnetism of the two-grain 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 becomes closer to non-magnetic, thereby reducing the magnetic coupling between the main phases. It can be weakened to suppress magnetization reversal.

As a result of investigations by the present inventors, the method described in Patent Document 2 can obtain an RTB system sintered magnet having a high _HcJ while reducing the amount of heavy rare earth elements used. It has been found that a decrease in _r may occur. This decrease in Br is thought to be due to the increase in the amount of _R (especially RL) near the magnet surface due to diffusion, which reduces the volume ratio of the main phase near the magnet surface. Based on these findings, the inventor of the present invention conducted further investigations and found that a narrow specific range of C was introduced into the magnet material from the surface of the RTB sintered magnet material through the grain boundary, together with specific ranges of RL and M. It was found that by diffusing it, it becomes possible to suppress a decrease in the volume ratio of the main phase near the surface of the magnet. As a result, it is possible to suppress the decrease in Br due to diffusion, so that it is possible to obtain an _RTB -based sintered magnet having an excellent balance between _{Br and HcJ while} reducing the amount of heavy rare earth elements used. can. It is believed that this is because Fe present at the grain boundaries near the surface of the magnet and RL introduced by diffusion form the main phase with C (C that can replace B) also introduced by diffusion.

As shown in FIG. 2, the method for producing an RTB based sintered magnet according to the present disclosure comprises a step S10 of preparing an RTB based sintered magnet material and an RL-RH-CM based alloy. and a step S20 of preparing. The order of the step S10 of preparing the RTB based sintered magnet material and the step S20 of preparing the RL-RH-CM based alloy is arbitrary.
As shown in FIG. 2, in the method for producing an RTB based sintered magnet according to the present disclosure, an RL-RH-CM based material is further added to at least a part of the surface of the RTB based sintered magnet material. A diffusion step S30 is included in which at least part of the alloy is deposited and heated at a temperature of 700° C. or higher and 1100° C. or lower in a vacuum or inert gas atmosphere.

In the present disclosure, the RTB system sintered magnet before and during the diffusion process is referred to as "RTB system sintered magnet material", and the RTB system sintered magnet after the diffusion process. A magnet is simply called an "RTB system sintered magnet".

(Step of preparing RTB based sintered magnet material)
In the RTB 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 Fe, Co, Al, Mn and Si. is at least one selected from the group consisting of and necessarily contains Fe. The content of R is, for example, 27 mass % or more and 35 mass % or less of the entire RTB based sintered magnet material. It is preferable that the content of Fe with respect to the entire T is 80 mass% or more.
If R is less than 27% by mass, the liquid phase is not sufficiently formed in the sintering process, and it may become difficult to sufficiently densify the sintered body. On the other hand, if R exceeds 35 mass%, grain growth may occur during sintering and _HcJ may decrease. R is preferably 28 mass% or more and 33 mass% or less.

The RTB based sintered magnet material has, for example, the following composition range.
R: 27 to 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: 60 mass% or more.

Preferably, in the RTB based sintered magnet material, the molar ratio [T]/[B] of T to B is more than 14.0 and 15.0 or less. A higher _HcJ can be obtained. [T] / [B] in the present disclosure is each element constituting T (at least one selected from the group consisting of Fe, Co, Al, Mn and Si, T always contains Fe, T Fe content in the whole is 80 mass% or more) analysis value (mass%) was divided by the atomic weight of each element, and the sum of those values [T] and the analysis value of B (mass% ) divided by the atomic weight of B to [B]. The condition that the mol ratio [T]/[B] exceeds 14.0 indicates that the amount of B is relatively small with respect to the amount of T used to form the main phase (R ₂ T ₁₄ B compound). . More preferably, the molar ratio [T]/[B] is 14.3 or more and 15.0 or less. Even higher _HcJ 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 general method for manufacturing RTB based sintered magnets typified by Nd—Fe—B based sintered magnets. As an 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 5.0 μm or less, and then molded in a magnetic field and heated to 900 ° C. or more. A sintered body can be prepared by sintering at a temperature of 1100° C. or less. High magnetic properties can be obtained by pulverizing to a particle size _D50 of 2.0 μm or more and 5 μm or less. Preferably, the particle size _D50 is between 2.5 μm and 4.0 μm. It is possible to obtain an RTB based sintered magnet having a better balance between B _r and H _cJ while suppressing deterioration of productivity and reducing valuable RH. The _D50 is the 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 the laser diffraction method based on the air dispersion method. In addition, _D50 can be measured, for example, using a particle size distribution analyzer "HELOS &RODOS" manufactured by Sympatec under conditions of dispersion pressure: 4 bar, measurement range: R2, and measurement mode: HRLD.

(Step of preparing RL-RH-C-M alloy)
In the RL-RH-C-M alloy, RL is at least one light rare earth element and must contain at least one selected from the group consisting of Nd, Pr and Ce, and RH is Tb, at least one selected from the group consisting of Dy and Ho, C is carbon, and M is selected from the group consisting of Cu, Ga, Fe, Co, Ni, Al, Ag, Zn, Si, Sn at least one. The content of RL is 50 mass% or more and 95 mass% or less of the entire RL-RH-CM alloy. Light rare earth elements include La, Ce, Pr, Nd, Pm, Sm, and Eu. The content of RH is 45 mass% or less (including 0 mass%) of the entire RL-RH-CM alloy. That is, RH may not be contained. The content of C is 0.10 mass% or more and 0.50 mass% or less of the entire RL-RH-CM alloy. The content of M is 4 mass% or more and 49.9 mass% or less of the entire RL-RH-CM alloy. Typical examples of RL-RH-CM system alloys are TbNdPrCCu alloy, TbNdCePCCu alloy, TbNdPrCCuFe alloy, TbNdCGa alloy, TbNdPrCGaCu alloy, TbNdCGaCuFe alloy, NdPrTbCCuGaAl alloy and the like. In addition to the above elements, a small amount of elements such as unavoidable impurities such as Mn, O, and N may be contained.

If RL+RH is less than 50 mass%, RH, C, and M are less likely to be introduced into the RTB sintered magnet material, and H _cJ may decrease. If it exceeds 95 mass%, RL-RH - The alloy powder becomes very active during the manufacturing process of the CM system alloy. As a result, the alloy powder may be significantly oxidized or ignited. Preferably, the content of RL+RH is 70 mass% or more and 80 mass% or less of the entire RL-RH-CM alloy. A higher _HcJ can be obtained.

If the RH exceeds 45 mass %, it is not possible to obtain an RTB based sintered magnet having an excellent balance between B _r and H _cJ while reducing the amount of heavy rare earth elements, which are rare elements. Preferably, the content of RH is 20 mass% or less of the entire RL-RH-CM alloy. Further, the total content of RL and RH in the RL-RH-CM alloy is preferably 55 mass% or more of the entire RL-RH-CM alloy. Thereby, a high _HcJ can be obtained. Further, when the RL content (mass%) in the RL-RH-CM alloy is [RL] and the RH content is [RH], the relationship [RL] > 1.5 × [RH] is preferably satisfied. As a result, it is possible to obtain an RTB-based sintered magnet having an excellent balance between B _r and H _cJ while reducing the amount of heavy rare earth elements used.

If C is less than 0.10 mass%, it may not be possible to suppress the decrease in the volume ratio of the main phase near the magnet surface near the magnet surface, and if it exceeds 0.50 mass%, the effect of improving H _cJ by RL and B. may decline. Preferably, the content of C is 0.20 mass% or more and 0.50 mass% or less of the entire RL-RH-CM alloy. An RTB based sintered magnet having a better balance between B _r and H _cJ can be obtained.

When M is less than 4 mass%, RL, B, and RH are difficult to introduce into the two-grain grain boundary phase, and H _cJ may not be sufficiently improved. may decrease and H _cJ may not improve sufficiently. Preferably, the content of M is 7 mass% or more and 15 mass% or less of the entire RL-RH-CM alloy. A higher _HcJ can be obtained. Preferably, M in the RL-RH-CM alloy always contains at least one of Cu, Ga, and Fe, and the content of Cu, Ga, and Fe in M is 80% or more. A high _HcJ can be obtained.

The method for producing the RL-RH-CM alloy is not particularly limited. It may be produced by a roll quenching method or may be produced by a casting method. Alternatively, these alloys may be pulverized 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 part of the prepared RL-RH-C-M alloy is attached to at least part of the surface of the RTB-based sintered magnet material prepared as described above, and is placed in a vacuum or inert gas atmosphere. , a diffusion step of heating at a temperature of 700° C. or more and 1100° C. or less. As a result, a liquid phase containing RL, C, (RH) and M is generated from the RL-RH-CM alloy, and the liquid phase passes through the grain boundaries in the RTB sintered magnet material. As a result, it diffuses into the interior from the surface of the sintered material. The amount of the RL-RH-CM alloy attached to the RTB sintered magnet material is preferably 1 mass % or more and 8 mass % or less, more preferably 1 mass % or more and 5 mass % or less. By setting the content within this range, it is possible to obtain an RTB based sintered magnet having a high _HcJ while reducing the amount of the heavy rare earth element to be used more reliably.

If the heating temperature in the diffusion step is less than 700° C., it may not be possible to obtain a high _HcJ . On the other hand, if the temperature exceeds 1100°C, the _HcJ may drop significantly. Preferably, the heating temperature in the diffusion step is 800° C. or higher and 1000° C. or lower. A higher _HcJ can be obtained. Further, preferably, the RTB sintered magnet subjected to the diffusion step (700° C. or higher and 1100° C. or lower) is cooled from the temperature at which the diffusion step is performed to 300° C. at a cooling rate of 15° C./min or higher. Cooling is preferred. A higher _HcJ can be obtained.

The diffusion process can be performed by placing an RL-RH-CM alloy in an arbitrary shape on the surface of the RTB sintered magnet material and using a known heat treatment apparatus. For example, the surface of an RTB based sintered magnet material can be covered with a powder layer of an RL-RH-CM based alloy to carry out the diffusion process. For example, an application step of applying an adhesive to the surface of the object to be applied and a step of adhering the RL-RH-CM alloy to the area to which the adhesive is applied may be performed. Examples of adhesives include PVA (polyvinyl alcohol), PVB (polyvinyl butyral), PVP (polyvinylpyrrolidone), and the like. When the adhesive is a water-based adhesive, the RTB-based sintered magnet material may be preliminarily heated before application. The purpose of preheating is to remove the excess solvent, control the adhesive force, and evenly adhere the adhesive. The heating temperature is preferably 60 to 200°C. This step may be omitted in the case of highly volatile organic solvent-based pressure-sensitive adhesives. Alternatively, for example, a slurry in which an RL-RH-CM alloy is dispersed in a dispersion medium is applied to the surface of the RTB-based sintered magnet material, and then the dispersion medium is evaporated to obtain an RL-RH-CM A system alloy and an RTB system sintered magnet material may be adhered. Examples of dispersion media include alcohols (ethanol, etc.), aldehydes, and ketones.
Further, as long as at least part of the RL-RH-CM alloy adheres to at least part of the RTB-based sintered magnet material, the arrangement position is not particularly limited.

(Heat treatment process)
Preferably, as shown in FIG. 2, the RTB sintered magnet subjected to the diffusion step is subjected to the diffusion step at 400° C. or higher and 900° C. or lower in a vacuum or inert gas atmosphere. The heat treatment is performed at a temperature lower than the temperature performed in . Heat treatment may be performed multiple times. Higher _HcJ can be obtained by heat treatment.

(RTB system sintered magnet)
The RTB based sintered magnet obtained by the manufacturing method of the present disclosure contains R (R is a rare earth element and always contains at least one selected from the group consisting of Nd, Pr and Ce), containing T (T is at least one selected from the group consisting of Fe, Co, Al, Mn, and Si, and necessarily includes Fe), B and C, and Cu, Ga, Ni, Ag, It contains at least one selected from the group consisting of Zn and Sn.

The RTB based sintered magnet of the present disclosure may have, for example, the following composition.

R: 26.8 mass% or more and 31.5 mass% or less,
B: 0.90 mass% or more and 0.97 mass% or less,
C: 0.08 mass% or more and 0.30 mass% or less,
M: 0.05 mass% or more and 1.0 mass% or less (M is at least one selected from the group consisting of Ga, Cu, Zn and Si),
M1: 0 mass% or more and 2.0 mass% or less (M1 consists of Al, Ti, V, Cr, Mn, Ni, Zr, Nb, Mo, Ag, In, Sn, Hf, Ta, W, Pb, and Bi at least one species selected from the group)
The remainder consists of T (T is Fe or Fe and Co) and unavoidable impurities.
The present disclosure can provide RTB based sintered magnets with excellent balance between B _r and H _cJ while reducing the amount of heavy rare earth elements used. Therefore, in particular, Tb is preferably 5 mass% or less (including 0 mass%), more preferably 1 mass% or less, further preferably 0.5 mass% or less of the entire RTB based sintered magnet.

Further, the RTB based sintered magnet of the present disclosure may include a portion in which the RH (eg, Tb) concentration gradually decreases from the surface of the magnet toward the inside of the magnet. The RTB system sintered magnet includes a portion where the RH concentration gradually decreases from the surface of the magnet toward the inside of the magnet, which means that at least one of the RH is in a state of being diffused from the surface of the magnet into the inside of the magnet. is doing.

The present invention will be explained in more detail by examples, but the present invention is not limited to them.

Experimental example 1
[Step of preparing RTB-based sintered magnet material (magnet material)]
Each element was weighed so as to obtain the composition of the magnet material indicated by reference numeral 1-A in Table 1, and the material was cast by a strip casting method to obtain a raw material alloy in the form of flakes with a thickness of 0.2 to 0.4 mm. After hydrogen pulverization of the resulting flaky raw material alloy, a dehydrogenation treatment was performed by heating to 550° C. in vacuum and then cooling to obtain a coarsely pulverized powder. Next, the obtained coarsely pulverized powder was pulverized using an air flow type pulverizer (jet mill apparatus) to obtain a finely pulverized powder (alloy powder) having a particle size D50 of 3 μm. The particle diameter D50 is the volume center value (volume-based median diameter) obtained by the laser diffraction method based on the air dispersion method.

The finely pulverized powder was compacted in a magnetic field to obtain a compact. As the forming apparatus, a so-called orthogonal magnetic field forming apparatus (transverse magnetic field forming apparatus) in which the magnetic field application direction and the pressurizing direction are perpendicular to each other was used.

The resulting molded body was sintered in vacuum for 4 hours (a temperature was selected for each sample at which sufficient densification by sintering occurred) 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. Each component in Table 1 was measured using high frequency inductively coupled plasma optical emission spectrometry (ICP-OES). As a result of measuring the oxygen content of the magnet material by the gas fusion-infrared absorption method, it was confirmed that all of them were around 0.2 mass %. Further, C (carbon content) was confirmed to be around 0.1 mass% as a result of measurement using a gas analyzer based on combustion-infrared absorption method. "[T]/[B]" in Table 1 is obtained by dividing the analysis value (mass%) of each element (here, Fe, Al, Si, Mn) constituting T by the atomic weight of the element. It is the ratio (a/b) of (a) obtained by summing these values and (b) obtained by dividing the analytical value of B (mass%) by the atomic weight of B. The same is true for all tables below. The sum of each composition, oxygen content, and carbon content in Table 1 does not equal 100 mass%. This is because impurity elements other than the elements listed in the table are included. The same applies to other tables.

[Step of preparing RL-RH-C-M alloy]
Each element is weighed and the raw materials are melted so that the composition of the RL-RH-C-M alloy shown in symbols 1-a to 1-e in Table 2 is obtained, and a single roll super quenching method (melt spinning A ribbon- or flake-shaped alloy was obtained by the method). The obtained alloy was pulverized in an argon atmosphere using a mortar to prepare an RL-RH-CM alloy. Table 2 shows the composition of the obtained RL-RH-CM alloy.

[Diffusion process]
An RTB based sintered magnet material indicated by reference numeral 1-A in Table 1 was cut and processed into a cube of 7.2 mm×7.2 mm×7.2 mm. Next, an adhesive containing a sugar alcohol was applied to the entire surface of the RTB sintered magnet material by a dipping method. 3 mass % of RL-RH-CM system alloy powder was attached to the RTB system sintered magnet material coated with the adhesive with respect to the mass of the RTB system sintered magnet material. Next, using a vacuum heat treatment furnace, the RL-RH-C-M system alloy and the RTB system sintered magnet material are heated under conditions of 900° C. for 10 hours to carry out a diffusion process, cooled. Thereafter, heat treatment was performed using a vacuum heat treatment furnace at 470° C. or higher and 530° C. or lower for 3 hours, and then cooled.

[sample test]
B _r and H _cJ of each sample were measured with a BH tracer for the RTB system sintered magnet materials and the obtained samples (RTB system sintered magnets after heat treatment). From the measurement results of B _r and H _cJ of the RTB system sintered magnet and the B _r value (B _r after diffusion) of the RTB system sintered magnet, the RTB system sintered magnet Table 3 shows the value obtained by subtracting the B _r value of the magnet material (B _r before diffusion) as ΔB _r . In addition, Table 4 shows the results of measuring the components of the samples using high frequency inductively coupled plasma optical emission spectrometry (ICP-OES). As shown in Table 3, sample No. 3, which is an RTB based sintered magnet material, was used. Sample No. 1-1 was used to diffuse the RL-RH-CM alloy. In Examples 1-3 to 1-4, it can be seen that not only a high H _cJ was obtained in the diffusion process, but also a decrease in _Br was small. Therefore, an RTB based sintered magnet with an excellent balance between B _r and H _cJ (high H _cJ while suppressing a decrease in B _r ) is obtained. On the other hand, sample no. It can be seen that Comparative Example 1-2 has a high H _cJ in the diffusion process, but a large decrease in Br _. Also, sample No. in which an RL-RH-CM alloy with a C content above the appropriate range was diffused. It can be seen that Comparative Examples 1-5 and 1-6 show little decrease in _{Br, but do not provide sufficient HcJ .}

Experimental example 2
[Step of preparing RTB-based sintered magnet material (magnet material)]
Each element was weighed and cast by a strip casting method so as to have the composition of the magnet material indicated by symbols 2-A and 2-B in Table 5, to obtain a flake-shaped raw material alloy with a thickness of 0.2 to 0.4 mm. rice field. After hydrogen pulverization of the resulting flaky raw material alloy, a dehydrogenation treatment was performed by heating to 550° C. in vacuum and then cooling to obtain a coarsely pulverized powder. Next, the obtained coarsely pulverized powder was pulverized using an air flow type pulverizer (jet mill apparatus) to obtain a finely pulverized powder (alloy powder) having a particle size D50 of 3 μm. The particle diameter D50 is the volume center value (volume-based median diameter) obtained by the laser diffraction method based on the air dispersion method.

The finely pulverized powder was compacted in a magnetic field to obtain a compact. As the forming apparatus, a so-called orthogonal magnetic field forming apparatus (transverse magnetic field forming apparatus) in which the magnetic field application direction and the pressurizing direction are perpendicular to each other was used.

The resulting compact was sintered in vacuum at 1000° C. or higher and 1050° C. or lower (a temperature at which sintering causes sufficient densification was selected for each sample) for 10 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 5 shows the results of the components of the obtained magnet material. Each component in Table 5 was measured using high frequency inductively coupled plasma optical emission spectroscopy (ICP-OES). As a result of measuring the oxygen content of the magnet materials by the gas fusion-infrared absorption method, it was confirmed that all of them were around 0.2 mass %. Further, C (carbon content) was confirmed to be around 0.1 mass% as a result of measurement using a gas analyzer based on combustion-infrared absorption method.

[Step of preparing RL-RH-C-M alloy]
Each element was weighed and the raw materials were melted so that the composition of the RL-RH-C-M alloy and the composition of the alloy not containing B shown in 2-a to 2-e in Table 6 were obtained. A ribbon- or flake-like alloy was obtained by a single-roll ultra-quenching method (melt spinning method). The obtained alloy was pulverized in an argon atmosphere using a mortar to prepare an RL-RH-CM alloy. Table 6 shows the composition of the obtained RL-RH-CM alloy.

[Diffusion process]
The RTB based sintered magnet materials 2-A to 2-B in Table 5 were cut and cut into cubes of 7.2 mm×7.2 mm×7.2 mm. Next, an adhesive containing a sugar alcohol was applied to the entire surface of the RTB sintered magnet material by a dipping method. 3 mass % of RL-RH-CM system alloy powder was attached to the RTB system sintered magnet material coated with the adhesive with respect to the mass of the RTB system sintered magnet material. Next, using a vacuum heat treatment furnace, the RL-RH-C-M system alloy and the RTB system sintered magnet material are heated under conditions of 900° C. for 10 hours to carry out a diffusion process, cooled. Thereafter, heat treatment was performed using a vacuum heat treatment furnace at 470° C. or higher and 530° C. or lower for 1 hour, and then cooled.

[sample test]
B _r and H _cJ of each sample were measured with a BH tracer for the RTB system sintered magnet materials and the obtained samples (RTB system sintered magnets after heat treatment). From the measurement results of B _r and H _cJ of the RTB system sintered magnet and the B _r value (B _r after diffusion) of the RTB system sintered magnet, the RTB system sintered magnet Table 7 shows the value obtained by subtracting the B _r value of the magnet material (B _r before diffusion) as ΔB _r . As shown in Table 7, sample No. 1, which is an RTB based sintered magnet material, was used. 2-1, sample No. Sample No. 2-7 was used to diffuse the RL-RH-CM alloy. 2-3 to 2-5, sample No. In Examples 2-9 to 2-10, it can be seen that not only a high H _cJ was obtained in the diffusion process, but also a decrease in B _r was small. Therefore, an RTB based sintered magnet with an excellent balance of B _r and H _cJ is obtained. On the other hand, sample no. 2-2, No. In Comparative Example 2-8, a high H _cJ was obtained in the diffusion process, but the Br was greatly decreased _. 2-6, sample no. It can be seen that Comparative Example 2-11 does not provide a sufficient _HcJ , although the decrease in _Br is small.

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

Claims (2)

RTB 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, T is Fe, Co, Al, Mn and Si at least one selected from the group consisting of and necessarily containing Fe);
An RL-RH-C-M alloy (RL is at least one of light rare earth elements and consists of Nd, Pr and Ce) is applied to at least part of the surface of the RTB sintered magnet material. RH is at least one selected from the group consisting of Tb, Dy and Ho, C is carbon, M is Cu, Ga, Fe, Co, At least one selected from the group consisting of Ni, Al, Ag, Zn, Si, and Sn.) is deposited, and at a temperature of 700 ° C. or higher and 1100 ° C. or lower in a vacuum or inert gas atmosphere. a diffusion step of heating,
The RTB based sintered magnet material has a molar ratio [T]/[B] of T to B of more than 14.0 and 15.0 or less,
In the RL-RH-CM alloy, the RL content is 50 mass% or more and 95 mass% or less, the RH content is 45 mass% or less (including 0 mass%), and the C content is 0.5 mass% or less. A method for producing an RTB based sintered magnet, wherein the content of M is 10 mass% or more and 0.50 mass% or less, and the M content is 4 mass% or more and 49.9 mass% or less. The RTB system according to claim 1, wherein the molar ratio of T to B in the RTB system sintered magnet material [T]/[B] is more than 14.0 and 15.0 or less. A method for producing a sintered magnet.

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