JP2023046258A - Method for manufacturing r-t-b based sintered magnet - Google Patents

Abstract

To provide a method for manufacturing an R-T-B based sintered magnet that has high Br and high HcJ while using La as a diffusion source.SOLUTION: A method for manufacturing an R-T-B based sintered magnet according to the present disclosure includes: a step of preparing an R-T-B based sintered magnet material; a step of preparing an R1-M based alloy; and a diffusion step of heating the R-T-B based sintered magnet material and the R1-M based alloy at a temperature equal to or higher than 700°C and equal to or lower than 1,100°C in vacuum or an inert gas atmosphere and diffusing R1 and M into the R-T-B based sintered magnet material. A content of R1 in the R1-M based alloy is equal to or more than 70 mass% and equal to or less than 95 mass% of the whole R1-M based alloy, a content ratio of La in R1 is equal to or more than 5% and less than 50%, and a content of M is equal to or more than 5 mass% and equal to or less than 30 mass% of the whole R1-M based alloy.SELECTED DRAWING: Figure 2

Description

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

RTB based sintered magnet (R is a rare earth element, always contains at least one selected from the group consisting of Nd, Pr and Ce, and T consists of Fe, Co, Al, Mn and Si at least one selected from the group and necessarily containing Fe, B is boron) is located in the main phase of the compound having the R ₂ Fe ₁₄ B-type crystal structure and the grain boundary portion of this main phase It is composed of a grain boundary phase and a compound phase generated by the influence of trace elements and impurities. The RTB sintered magnet has a high residual magnetic flux density B _r (hereinafter sometimes simply referred to as “B _r ”) and a high coercive force H _cJ (hereinafter simply referred to as “H _cJ ”). It is known as the magnet with the highest performance among permanent magnets.

For this reason, RTB sintered magnets are used in various motors in the automobile field such as electric vehicles (EV, HV, PHV), renewable energy fields such as wind power generation, home appliances, and industrial fields. ing. RTB based sintered magnets are essential materials for making these motors smaller, lighter, and more efficient and energy saving (improving energy efficiency). RTB sintered magnets are also used in drive motors for electric vehicles.・It also contributes to the prevention of global warming by reducing exhaust gas. In this way, RTB based sintered magnets are greatly contributing to the realization of a clean energy society.

In the RTB system sintered magnet, part of the light rare earth element RL (for example, Nd and Pr) contained in R in the R ₂ T ₁₄ B compound is replaced with the heavy rare earth element RH (RH is Tb and Dy). at least one) is known to improve _HcJ . The _HcJ improves as the amount of RH substitution increases. However, when RH is substituted for RL in the R ₂ T ₁₄ B compound, the H _cJ of the RTB system sintered magnet is improved, but the residual magnetic flux density B _r is lowered. In addition, since heavy rare earth elements are raw materials with high resource risk, it is required to reduce their usage or improve _HcJ without using them.

In Patent Document 1, RH, Pr and Ga are removed by heat-treating in a state in which at least part of an R2-Ga alloy is in contact with at least part of the surface of an RTB based sintered magnet material having a specific composition. It is described to diffuse the As a result, high _Br and high _HcJ can be obtained while reducing the RH content.

WO2018/143230

The method described in Patent Document 1 is noteworthy in that it provides an RTB based sintered magnet with high B _r and high H _cJ while suppressing the content of heavy rare earth elements. However, in recent years, it is expected that the demand for RTB based sintered magnets, especially for use in motors for electric vehicles, will greatly expand in the future. Therefore, not only the content of heavy rare earth elements but also other rare earth elements are used in a well-balanced manner, including other rare earth elements, rather than overlying the use of heavy rare earth elements, from the viewpoint of effective utilization of resources and cost reduction. There is a need to. As a specific means, it is possible to use La (and Ce) which is relatively abundant among rare earth elements. In particular, it is effective to use La instead of Nd and Pr, which are major elements in RTB sintered magnets. However, it is known that the use of La or the like in place of Nd or Pr significantly degrades the magnetic properties.

Embodiments of the present disclosure provide a method for producing a RTB based sintered magnet that maintains high B _r and high H _cJ while using La as a diffusion source.

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); system alloy (R1 consists of RH and RL, RH is at least one of Tb and Dy, RL is a rare earth element other than RH, at least one of Nd and Pr and La, M is Al, at least one selected from the group consisting of Cu, Zn, Ga, Fe, Co, and Ni); a diffusion step of heating at a temperature of 700° C. or more and 1100° C. or less in a vacuum or inert gas atmosphere to diffuse R1 and M into the RTB system sintered magnet material, In the alloy, the content of R1 is 70 mass% or more and 95 mass% or less of the entire R1-M system alloy, the content of La in R1 is 5% or more and less than 50%, and the content of M is R1-M system It is 5 mass% or more and 30 mass% or less of the entire alloy.

In one embodiment, the content of La in R1 in the R1-M alloy is 5% or more and 15% or less.

In one embodiment, in the R1-M alloy, the content of RH in R1 is 5% or more and 20% or less, and the total content of at least one of Nd and Pr in R1 is 25% or more and 90%. It is below.

In one embodiment, M in the R1-M alloy must contain at least one of Cu and Ga, and the total content of Cu and Ga in M is 80% or more.

In one embodiment, R1 of the R1-M alloy must contain Pr, and the content of Pr in R1 is 25% or more and 90% or less.

According to the embodiments of the present disclosure, it is possible to provide a method for manufacturing an RTB based sintered magnet in which high B _r and high H _cJ are maintained while using La as a diffusion source.

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 2.5 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).

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.

In the manufacturing method of the RTB system sintered magnet according to the present disclosure, R1 and M contained in the R1-M system alloy are introduced from the surface of the RTB system sintered magnet material into the magnet material through the grain boundary. I am spreading it.
The present inventors have studied in detail the method of heat-treating and diffusing the surfaces of R1-M alloy and RTB-based sintered magnets. As a result, when RH is contained in R1 of the R1-M alloy and then R1 and M are diffused, even if La is contained in a specific range instead of Nd or Pr as RL in R1, La It was found that the deterioration of the magnetic properties due to the addition of was able to be suppressed. As shown in the examples below, this effect cannot be obtained when Ce is used instead of La. Further, as a more preferable embodiment, the inventors have found that the magnetic properties are hardly degraded by setting La in the R1-M alloy to a specific narrow range. In this way, even if La is contained instead of Nd or Pr, the deterioration of the magnetic properties is suppressed, or the magnetic properties hardly deteriorate. It is thought that this is because it is less likely to be contained in the R ₂ T ₁₄ B compound compared to , and is present mainly on the grain boundary phase side, so that it does not significantly affect the magnetic properties of the R ₂ T ₁₄ B compound. This makes it possible to obtain an RTB based sintered magnet having high B _r and high H _cJ while using La as a diffusion source.

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 step S20 of preparing an R1-M based alloy. including. The order of the step S10 of preparing the RTB based sintered magnet material and the step S20 of preparing the R1-M based alloy is arbitrary.
As shown in FIG. 2, the method for producing an RTB based sintered magnet according to the present disclosure further comprises the step of placing the RTB based sintered magnet material and the R1-M based alloy in a vacuum or inert gas atmosphere. Medium includes a diffusion step S30 of heating at a temperature of 700° C. or more and 1100° C. or less to diffuse R1 and M inside the RTB based sintered magnet material.

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 the content of R is, for example, RT- It is 27 mass % or more and 35 mass % or less of the entire B-based 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 relative 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. In order to obtain a higher _Br , 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 Al),
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. To give 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 4.5 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 _Br and high _HcJ can be obtained by pulverizing to a particle size _D50 of 2.0 μm or more and 4.5 μm or less. Preferably, the particle size _D50 is between 2.5 μm and 3.5 μm. Higher _Br and higher _HcJ can be obtained while suppressing deterioration of productivity and reducing valuable RH. The particle size _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. Further, the particle size _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. The step of preparing the RTB based sintered magnet material is a step of obtaining the RTB based sintered magnet material to be subjected to the diffusion process. It also includes a mode in which a separately manufactured RTB based sintered magnet material is obtained.

(Step of preparing R1-M alloy)
In the R1-M alloy, R1 consists of RH and RL, RH is at least one of Tb and Dy, RL is a rare earth element other than RH, and always contains at least one of Nd and Pr and La. , M necessarily include at least one selected from the group consisting of Al, Cu, Zn, Ga, Fe, Co, and Ni. The content of R1 is 70 mass% or more and 95 mass% or less of the entire R1-M alloy. This makes it possible to obtain high magnetic properties. Moreover, the content ratio of La in R1 is 5% or more and less than 50%. Here, the "content ratio of La in R1" in the present disclosure is a value obtained by calculating the ratio of La relative to mass% (mass%) in R1. After RH is contained in R1 of the R1-M alloy as described above, when R1 and M are diffused, 5% or more and less than 50% of La is contained in R1 instead of Nd or Pr as RL. Since the deterioration of the magnetic properties is suppressed even when the content is reduced, it is possible to obtain an RTB based sintered magnet having high B _r and high H _cJ . In order to obtain an RTB based sintered magnet having a higher _HcJ , the content is preferably 5% or more and 35% or less. Most preferably, the content of La in R1 is 5% or more and 15% or less. Within this range, even if La is added, the magnetic properties hardly deteriorate. In order to obtain a RTB based sintered magnet having higher B _r and higher H _cJ , the content of RH in R1 is preferably 5% or more and 20% or less. The total content of at least one of is preferably 25% or more and 90% or less. In addition, in order to obtain an RTB sintered magnet having a higher _HcJ , R1 of the R1-M alloy must contain Pr, and the content of Pr in R1 must be 25% or more. It is preferably 90% or less. In order to more reliably obtain a RTB based sintered magnet having high _Br and high _HcJ , the total content of RH, Pr and La in R1 should be 50% or more. More preferred.

Also, M is at least one selected from the group consisting of Al, Cu, Zn, Ga, Fe, Co, and Ni. The content of M is 5 mass% or more and 30 mass% or less of the entire R1-M alloy. Preferably, the content of M is 7 mass% or more and 15 mass% or less of the entire R1-M alloy. A higher _HcJ can be obtained. Moreover, M preferably contains at least one of Cu and Ga, and more preferably contains both Cu and Ga. The total content of Cu and Ga in M is preferably 80% or more. A higher _HcJ can be obtained by containing Cu and Ga.
Typical examples of R1-M alloys are TbNdPrLaCu alloys, TbNdLaGa alloys, TbPrLaGa alloys, and the like. In addition to the above elements, a small amount of elements such as unavoidable impurities such as Mn, O, C, and N may be contained.

The method for producing the R1-M 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. In addition, the step of preparing the R1-M alloy is a step of obtaining the R1-M alloy to be subjected to the diffusion step. It also includes a mode of obtaining.

(Diffusion process)
The RTB based sintered magnet material and the R1-M based alloy prepared by the method described above are heated in a vacuum or inert gas atmosphere at a temperature of 700° C. or higher and 1100° C. or lower to convert R1 and M into R - Perform a diffusion step of diffusing into the inside of the TB based sintered magnet material. As a result, a liquid phase containing R1 and M is generated from the R1-M alloy, and the liquid phase diffuses from the surface of the sintered material to the interior via the grain boundaries in the RTB sintered magnet material. be introduced.

If the heating temperature in the diffusion step is less than 700°C, the amount of the liquid phase containing R1 and M may be too small 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 treatment step may be carried out by placing an arbitrary shaped R1-M alloy 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 an R1-M alloy powder layer and heat treated. For example, after a slurry in which an R1-M alloy is dispersed in a dispersion medium is applied to the surface of an RTB sintered magnet material, the dispersion medium is evaporated to obtain an R1-M alloy and an RTB system. It may be brought into contact with the sintered magnet material. In this case, the amount of the R1-M alloy attached to the RTB sintered magnet material in the diffusion step is preferably 1 mass% or more and 6 mass% or less, and more preferably, the RTB sintered magnet material. The adhesion amount of the R1-M alloy to is 1.5 mass% or more and 3 mass% or less. A higher _HcJ can be obtained. Examples of dispersion media include alcohols (ethanol, etc.), aldehydes, and ketones. In addition, the heavy rare earth element RH is obtained not only from the R1-M alloy, but also from the R1-M alloy and the fluoride, oxide, acid fluoride, etc. of the heavy rare earth element RH on the surface of the RTB system sintered magnet. The heavy rare earth element RH may be introduced by arranging. That is, any method can be used as long as the heavy rare earth element RH and the light rare earth elements RL and M can be diffused simultaneously. Examples of fluorides, oxides, and acid fluorides of the heavy rare earth element RH include TbF ₃ , DyF ₃ , Tb ₂ O ₃ , Dy ₂ O ₃ , Tb ₄ OF, and Dy ₄ OF.

(Step of performing heat treatment)
Preferably, the RTB sintered magnet subjected to the diffusion step is heated in a vacuum or inert gas atmosphere at a temperature of 400° C. or higher and 750° C. or lower and lower than the temperature of the diffusion step. heat treatment at high temperature. Higher _HcJ can be obtained by heat treatment.

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

Example 1
[Step of preparing RTB sintered magnet material]
Each element was weighed so as to obtain the composition of the RTB based sintered magnet material shown in Table 1, and a raw material alloy was produced by strip casting. Each of the obtained alloys was coarsely pulverized by a hydrogen pulverization method to obtain a coarsely pulverized powder. Next, 0.035 parts by mass of zinc stearate as a lubricant was added to the coarsely pulverized powder and mixed with 100 parts by mass of the coarse powder. Coarsely pulverized powder containing a lubricant was finely pulverized by a jet mill. A fine powder having a particle size D ₅₀ of 3.5 μm was obtained by pulverization. _D50 was measured using a Sympatec particle size distribution analyzer "HELOS&RODOS" under conditions of dispersion pressure: 4 bar, measurement range: R2, and measurement mode: HRLD.

0.05% by mass of zinc stearate as a lubricant was added to 100% by mass of the finely pulverized powder, mixed, and 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 compact thus obtained was sintered in vacuum for 4 hours (a temperature at which sintering causes sufficient densification was selected) 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 obtained RTB based sintered magnet material, the contents of Nd, Pr, Fe, Co, Al, Ga, Cu, Zr, and B were analyzed by high frequency inductively coupled plasma atomic emission spectrometry ( ICP-OES). The oxygen content of the RTB sintered magnet material was measured using a gas fusion-infrared absorption method, the nitrogen content was measured by a gas fusion-heat conduction method, and the carbon content was measured by a sintering-infrared absorption method using a gas analyzer. measured by In some cases, the total composition of the RTB based sintered magnet material does not reach 100 mass%. This is because the measurement method is different as described above and because other elements may be contained as unavoidable impurities. Note that TRE is the total value of Nd and Pr.

[Step of preparing R1-M alloy]
No. in Table 2. Each element is weighed so that the composition of the R1-M alloy is as shown in 1-A to 1-H, the raw materials are melted, and a ribbon or flake-shaped alloy is formed by a single roll ultra-quenching method. Obtained. Table 2 shows the composition of the obtained R1-M alloy. Each component in Table 2 was measured using high frequency inductively coupled plasma atomic emission spectrometry. Table 2 also shows the content ratio (mass%) of La in R1.

[Diffusion process]
No. in Table 1. 1 to 3 RTB based sintered magnet materials were cut and machined into 7.2 mm square cubes. After processing, PVA as an adhesive was applied to the entire surface of the RTB magnet material by a dipping method. Next, under the manufacturing conditions shown in Table 3, the R1-M alloy was adhered to the entire surface of the RTB sintered magnet material coated with the adhesive. The amount of the R1-M alloy deposited was determined by pulverizing the R1-M alloy in an argon atmosphere using a mortar and passing it through several types of sieves with an opening of 45 to 1000 μm. was adjusted by using The adhesion amount was around 2 mass %. Then, using a vacuum heat treatment furnace, in a reduced pressure argon atmosphere controlled at 100 Pa, the R1-M alloy and RTB sintered magnet materials were heated under the conditions shown in the diffusion process in Table 3, and then cooled. bottom.

[Step of performing heat treatment]
The RTB based sintered magnet material heated in the diffusion step was subjected to heat treatment at 500° C. in reduced pressure argon controlled at 100 Pa using a vacuum heat treatment furnace. Using a surface grinder, the entire surface of each sample after heat treatment was cut to obtain a cubic sample (RTB sintered magnet) of 7.0 mm × 7.0 mm × 7.0 mm. . The heating temperature of the R1-M alloy and RTB sintered magnet material in the diffusion process, and the heating temperature of the RTB sintered magnet in the process of performing heat treatment after the diffusion process are , respectively, were measured using thermocouples.

[Sample evaluation]
The residual magnetic flux density B _r and coercive force H _cJ of the obtained sample were measured by a BH tracer. Table 3 shows the results. As shown in Table 3, comparative examples in which Ce was added to the R1-M alloy (Samples No. 1-12 to 1-13 are sample No. 1 using the R1-M alloy to which La and Ce are not added. -11 (Criterion 3), the H _cJ decreased greatly as the amount of Ce added increased.In contrast, the present invention examples (No. 1-10) are samples No. 1-1 (reference 1) and No. 1-6 (reference 2) using R1-M alloys to which La and Ce are not added, and No. of the example of the present invention In 1-2, 1-3, 1-7, and 1-8, there was no decrease in _Br , and the amount of decrease in _HcJ was less than 4% of the standard characteristics, and the addition of La hardly decreased the magnetic characteristics. In addition, when comparing Nos. 1-4, 1-5, 1-9 and 1-10 of the present invention with comparative examples (Nos. 1-12 to 1-13) in which Ce was added, Ce Even if the addition amount of La is larger than that of La, the deterioration of the magnetic properties is greatly suppressed.

Example 2
[Step of preparing RTB sintered magnet material]
An R—T—B based sintered magnet material was prepared in the same manner as in [Step of preparing R—T—B based sintered magnet material] in Example 1, except that the composition was different. Table 4 shows the composition of the produced sintered magnet.

[Step of preparing R1-M alloy]
No. in Table 5. Each element is weighed so as to obtain the composition of the R1-M alloy as shown in 2-A to 2-D, the raw materials are melted, and a ribbon or flake-shaped alloy is formed by a single roll super quenching method. Obtained. Table 5 shows the composition of the obtained R1-M alloy. Each component in Table 5 was measured using high frequency inductively coupled plasma atomic emission spectrometry.

[Diffusion process]
The RTB based sintered magnet material of No. 4 in Table 4 was cut and machined into a 7.2 mm square cube. After processing, PVA as an adhesive was applied to the entire surface of the RTB magnet material by a dipping method. Next, under the manufacturing conditions shown in Table 6, the R1-M alloy was adhered to the entire surface of the RTB sintered magnet material coated with the adhesive. The amount of the R1-M alloy deposited was determined by pulverizing the R1-M alloy in an argon atmosphere using a mortar and passing it through several types of sieves with an opening of 45 to 1000 μm. was adjusted by using The adhesion amount was around 2 mass %. Then, using a vacuum heat treatment furnace, in a reduced pressure argon atmosphere controlled at 100 Pa, the R1-M alloy and RTB sintered magnet materials were heated under the conditions shown in the diffusion process in Table 6, and then cooled. bottom.

[Step of performing heat treatment]
The RTB based sintered magnet material heated in the diffusion step was subjected to heat treatment at 500° C. in reduced pressure argon controlled at 100 Pa using a vacuum heat treatment furnace. Using a surface grinder, the entire surface of each sample after heat treatment was cut to obtain a cubic sample (RTB sintered magnet) of 7.0 mm × 7.0 mm × 7.0 mm. . The heating temperature of the R1-M alloy and RTB sintered magnet material in the diffusion process, and the heating temperature of the RTB sintered magnet in the process of performing heat treatment after the diffusion process are , respectively, were measured using thermocouples.

[Sample evaluation]
The residual magnetic flux density B _r and coercive force H _cJ of the obtained sample were measured by a BH tracer. Table 6 shows the results. As shown in Table 6, sample no. Compared to 2-1 (reference), the present invention examples (No. 2-2, 2-3) have no decrease in _Br , and the amount of decrease in H _cJ is less than 4% of the reference characteristics. has not declined. On the other hand, in a comparative example (Sample No. 2-4) using an R1-M alloy with an excessive La concentration in R1, _Br did not decrease, but _HcJ decreased significantly.

Example 3
Step of preparing RTB based sintered magnet material]
Each element was weighed so as to obtain the composition of the RTB based sintered magnet material shown in Table 7, and a raw material alloy was produced by strip casting. Each of the obtained alloys was coarsely pulverized by a hydrogen pulverization method to obtain a coarsely pulverized powder. Next, 0.035% by mass of zinc stearate as a lubricant was added to the coarsely pulverized powder with respect to 100% by mass of the coarsely pulverized powder and mixed. Coarsely pulverized powder containing a lubricant was finely pulverized by a jet mill. A fine powder having a particle size D ₅₀ of 3.0 μm was obtained by pulverization. _D50 was measured using a Sympatec particle size distribution analyzer "HELOS&RODOS" under conditions of dispersion pressure: 4 bar, measurement range: R2, and measurement mode: HRLD.

0.05% by mass of zinc stearate as a lubricant was added to 100% by mass of the finely pulverized powder, mixed, and 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 compact thus obtained was sintered in vacuum for 4 hours (a temperature at which sintering causes sufficient densification was selected) 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 obtained RTB based sintered magnet material, the contents of Nd, Pr, Fe, Dy, Tb, Co, Al, Ga, Cu, Zr, and B were measured by high-frequency inductively coupled plasma emission. Measured by spectrophotometry (ICP-OES). The oxygen content of the RTB sintered magnet material was measured using a gas fusion-infrared absorption method, the nitrogen content was measured by a gas fusion-heat conduction method, and the carbon content was measured by a sintering-infrared absorption method using a gas analyzer. measured by In some cases, the total composition of the RTB based sintered magnet material does not reach 100 mass%. This is because the measurement method is different as described above and because other elements may be contained as unavoidable impurities. Note that TRE is the sum of Nd, Pr, and Dy.

[Step of preparing R1-M alloy]
No. in Table 8. Each element is weighed so as to obtain the composition of the R1-M alloy as shown in 3-A to 3-D, the raw materials are melted, and the ribbon or flake-shaped alloy is produced by the single roll super quenching method. Obtained. Table 8 shows the compositions of the obtained R1-M alloys. Each component in Table 8 was measured using high frequency inductively coupled plasma atomic emission spectrometry.

[Diffusion process]
The RTB based sintered magnet material of No. 5 in Table 7 was cut and machined into a 7.2 mm square cube. After processing, PVA as an adhesive was applied to the entire surface of the RTB magnet material by a dipping method. Next, under the manufacturing conditions shown in Table 9, the R1-M alloy was adhered to the entire surface of the RTB sintered magnet material coated with the adhesive. The amount of the R1-M alloy deposited was determined by pulverizing the R1-M alloy in an argon atmosphere using a mortar and passing it through several types of sieves with an opening of 45 to 1000 μm. was adjusted by using The adhesion amount was around 2 mass %. Then, using a vacuum heat treatment furnace, in a reduced pressure argon atmosphere controlled at 100 Pa, the R1-M alloy and RTB sintered magnet materials were heated under the conditions shown in the diffusion process in Table 9, and then cooled. bottom.

[Step of performing heat treatment]
The RTB based sintered magnet material heated in the diffusion step was subjected to heat treatment at 500° C. in reduced pressure argon controlled at 100 Pa using a vacuum heat treatment furnace. Using a surface grinder, the entire surface of each sample after heat treatment was cut to obtain a cubic sample (RTB sintered magnet) of 7.0 mm × 7.0 mm × 7.0 mm. . The heating temperature of the R1-M alloy and RTB sintered magnet material in the diffusion process, and the heating temperature of the RTB sintered magnet in the process of performing heat treatment after the diffusion process are , respectively, were measured using thermocouples.

[Sample evaluation]
The residual magnetic flux density B _r and coercive force H _cJ of the obtained sample were measured by a BH tracer. Table 9 shows the results. As shown in Table 9, sample no. Compared to 3-1 (reference), the present invention examples (No. 3-2, 3-3) have no decrease in _Br , and the amount of decrease in H _cJ is less than 4% of the reference characteristics, almost magnetic characteristics has not declined. On the other hand, in a comparative example (Sample No. 3-4) using an R1-M alloy with an excessive La concentration in R1, _Br did not decrease, but _HcJ decreased significantly.

Example 4
[Step of preparing RTB sintered magnet material]
An RTB based sintered magnet material was prepared in the same manner as in Example 3. The composition of the produced sintered magnet is the same as in Table 7.

[Step of preparing R1-M alloy]
No. in Table 10 Each element is weighed so that the composition of the R1-M alloy is as shown in 4-A to 4-D, the raw materials are melted, and a ribbon or flake-shaped alloy is formed by a single roll super quenching method. Obtained. Table 10 shows the composition of the obtained R1-M alloy. Each component in Table 10 was measured using high frequency inductively coupled plasma atomic emission spectrometry.

[Diffusion process]
The RTB based sintered magnet material of No. 5 in Table 7 was cut and machined into a 7.2 mm square cube. After processing, PVA as an adhesive was applied to the entire surface of the RTB magnet material by a dipping method. Next, under the manufacturing conditions shown in Table 11, the R1-M alloy was adhered to the entire surface of the RTB sintered magnet material coated with the adhesive. The amount of the R1-M alloy deposited was determined by pulverizing the R1-M alloy in an argon atmosphere using a mortar and passing it through several types of sieves with an opening of 45 to 1000 μm. was adjusted by using The adhesion amount was around 2 mass %. Then, using a vacuum heat treatment furnace, in a reduced pressure argon atmosphere controlled at 100 Pa, the R1-M alloy and RTB sintered magnet materials were heated under the conditions shown in the diffusion process in Table 11, and then cooled. bottom.

[Step of performing heat treatment]
The RTB based sintered magnet material heated in the diffusion step was subjected to heat treatment at 500° C. in reduced pressure argon controlled at 100 Pa using a vacuum heat treatment furnace. Using a surface grinder, the entire surface of each sample after heat treatment was cut to obtain a cubic sample (RTB sintered magnet) of 7.0 mm × 7.0 mm × 7.0 mm. . The heating temperature of the R1-M alloy and RTB sintered magnet material in the diffusion process, and the heating temperature of the RTB sintered magnet in the process of performing heat treatment after the diffusion process are , respectively, were measured using thermocouples.

[Sample evaluation]
The residual magnetic flux density B _r and the coercive force H _cJ of the obtained sample were measured under room temperature, 150° C. and 180° C. conditions using a BH tracer. Table 11 shows the magnetic measurement results, and Table 12 shows the calculated temperature coefficients of _Br and _HcJ .

As shown in Table 11, sample No. using R1-M alloy containing no La. Compared to 4-1 (reference), the present invention examples (No. 4-2 and 4-3) show no decrease in _Br , and the amount of decrease in H _cJ is less than 4% of the reference. not decreased. On the other hand, in a comparative example (Sample No. 4-4) using an R1-M alloy with an excessive La concentration in R1, _Br did not decrease, but _HcJ greatly decreased. Also, sample No. 1 was obtained by diffusion-treating an R1-M alloy to which Ce was added. As for 4-5 and 4-6, H _cJ decreased by 4% or more compared to the standard (Sample No. 4-1). Further, as shown in Tables 11 and 12, the magnetic properties at temperatures of 150° C. and 180° C. show that sample No. 4-1 of this example is superior to the standard (sample No. 4-1). In 4-2 and 4-3, there is no significant decrease in magnetic properties for both B _r and H _cJ . The temperature coefficient α of B _r and the temperature coefficient β of H _cJ were superior to the standard in 4-2 and comparable to the standard in 4-3. On the other hand, sample No. with excessive La concentration in R1-M. In 4-4, the temperature coefficients α and β showed higher values than the standard, but the values of _HcJ were greatly reduced at 150°C and 180°C. In addition, in samples No. 4-5 and 4-6 using the R1-M alloy with Ce added, H _cJ at 150 ° C. and 180 ° C. decreased significantly, and the temperature coefficients α and β also decreased. was

Claims (5)

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);
R1-M alloy (R1 consists of RH and RL, RH is at least one of Tb and Dy, RL is a rare earth element other than RH, and always contains at least one of Nd and Pr and La, M necessarily includes at least one selected from the group consisting of Al, Cu, Zn, Ga, Fe, Co, Ni);
The RTB sintered magnet material and the R1-M alloy are heated in a vacuum or inert gas atmosphere at a temperature of 700° C. or more and 1100° C. or less, and R1 and M are RTB sintered. a diffusion step of diffusing into the magnet material,
In the R1-M alloy, the content of R1 is 70 mass% or more and 95 mass% or less of the entire R1-M alloy, the content of La in R1 is 5% or more and less than 50%, and the content of M is 5 mass% or more and 30 mass% or less of the entire R1-M alloy,
A method for producing an RTB-based sintered magnet. The content of La in R1 in the R1-M alloy is 5% or more and 15% or less,
The method for producing an RTB based sintered magnet according to claim 1. In the R1-M alloy, the content of RH in R1 is 5% or more and 20% or less, and the total content of at least one of Nd and Pr in R1 is 25% or more and 90% or less. Item 1. A method for producing an RTB based sintered magnet according to item 1. M of the R1-M alloy must contain at least one of Cu and Ga, and the total content of Cu and Ga in M is 80% or more, RT- according to claim 1 or 2 A method for producing a B-based sintered magnet. R1 of the R1-M alloy must contain Pr, and the content of Pr in R1 is 25% or more and 90% or less, RT- according to any one of claims 1 to 3 A method for producing a B-based sintered magnet.

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