CN115881414A

CN115881414A - Method for producing R-T-B sintered magnet

Info

Publication number: CN115881414A
Application number: CN202211156101.9A
Authority: CN
Inventors: 江口彻; 国吉太
Original assignee: Bomeilicheng Co ltd
Current assignee: Bomeilicheng Co ltd
Priority date: 2021-09-22
Filing date: 2022-09-22
Publication date: 2023-03-31

Abstract

The invention provides a diffusion source using La and having high B _r And high H _cJ The method for producing an R-T-B sintered magnet of (1). The method for producing an R-T-B sintered magnet of the present invention comprises: preparing a R-T-B sintered magnet material; process for preparing R1-M alloy(ii) a And a diffusion step of heating the R-T-B sintered magnet material and the R1-M alloy at a temperature of 700 to 1100 ℃ in a vacuum or an inert gas atmosphere to diffuse R1 and M into the R-T-B sintered magnet material, wherein the R1 content in the R1-M alloy is 70 to 95mass% of the total R1-M alloy, the La content in the R1 is 5 to less than 50%, and the M content is 5 to 30mass% of the total R1-M alloy.

Description

Method for producing R-T-B sintered magnet

Technical Field

The present invention relates to a method for producing an R-T-B sintered magnet.

Background

An R-T-B sintered magnet (R is a rare earth element and must contain at least one element selected from Nd, pr and Ce, T is at least one element selected from Fe, co, al, mn and Si and must contain Fe, B is boron) is constituted by having R ₂ Fe ₁₄ A main phase of a compound having a B-type crystal structure, a grain boundary phase located in a grain boundary portion of the main phase, and a compound phase generated by the influence of a trace amount of an additive element or an impurity. R-T-B sintered magnet exhibiting high residual magnetic flux density B _r (hereinafter, it may be referred to as "B _r ") and a high coercive force H _cJ (hereinafter, it may be referred to as "H") _cJ "), the highest performing magnet among the permanent magnets is known.

Therefore, the R-T-B sintered magnet is used in various motors in the automotive field such as electric vehicles (EV, HV, PHV), the renewable energy field such as wind power generation, the household electrical appliance field, the industrial field, and the like. The R-T-B sintered magnet is an essential material for the motors to be small, light, efficient, and energy-saving (improvement in energy efficiency). The R-T-B sintered magnet is used in a drive motor for an electric vehicle, and the electric vehicle is used in place of an internal combustion engine vehicle, thereby contributing to prevention of global warming due to reduction of greenhouse gases such as carbon dioxide (reduction of fuel and exhaust gas). Thus, the R-T-B sintered magnet makes a great contribution to the realization of a clean energy society.

It is known that in R-T-B sintered magnets, R is replaced with a heavy rare earth element RH (RH is at least one of Tb and Dy) ₂ T ₁₄ H is a part of the light rare earth elements RL (e.g., nd and Pr) contained in R in the B compound _cJ And (4) improving. H with increasing amount of RH replacement _cJ And (4) improving. However, when R is replaced by RH ₂ T ₁₄ R-T-B is H of sintered magnet when RL is in compound B _cJ Increase, on the other hand, the residual magnetic flux density B _r And (4) reducing. In addition, heavy rare earthElements are resource-risky raw materials, and therefore, it is necessary to increase H by reducing or not using the amount thereof _cJ 。

Patent document 1 describes that RH, pr, and Ga are diffused by performing heat treatment in a state where at least a part of an R2 — Ga alloy is in contact with at least a part of the surface of an R-T-B-based sintered magnet material having a specific composition. This can reduce the RH content and can obtain high B content _r And high H _cJ 。

Documents of the prior art

Patent document

Patent document 1: international publication No. 2018/143230

Disclosure of Invention

Technical problems to be solved by the invention

The method described in patent document 1 can obtain high B while suppressing the content of heavy rare earth elements _r And high H _cJ The R-T-B system (2) is of interest in this regard. However, in recent years, the demand for R-T-B sintered magnets, particularly for electric motors for electric vehicles, is expected to increase in the future. Therefore, not only the content of the heavy rare earth element but also other rare earth elements are contained, and it is necessary to use the rare earth element in a well-balanced manner, without being biased toward the use of the heavy rare earth element from the viewpoint of effective use of resources and cost reduction. Specific examples of the case include the use of La (or Ce) which is present in relatively large amounts in rare earth elements. In particular, it is effective to use La or the like in place of Nd or Pr, which are main elements in R-T-B based sintered magnets. However, it is known that when La or the like is used instead of Nd or Pr, the magnetic properties are greatly reduced.

The embodiment of the invention provides a diffusion source using La and capable of maintaining high B _r And high H _cJ The method for producing the R-T-B sintered magnet of (1).

Technical solution for solving technical problem

The present invention provides a method for manufacturing an R-T-B sintered magnet, which includes, in an exemplary embodiment: a step for preparing an R-T-B sintered magnet material (wherein R is a rare earth element and must contain at least one element selected from Nd, pr, and Ce, and T is at least one element selected from Fe, co, al, mn, and Si, and must contain Fe); a step of preparing an R1-M alloy (wherein R1 is composed of RH and RL, RH is at least one of Tb and Dy, RL is a rare earth element other than RH, and contains at least one of Nd and Pr and La, and M contains at least one selected from Al, cu, zn, ga, fe, co, and Ni); and a diffusion step of heating the R-T-B-based sintered magnet material and the R1-M-based alloy at a temperature of 700 to 1100 ℃ in a vacuum or inert gas atmosphere to diffuse R1 and M into the R-T-B-based sintered magnet material, wherein the R1 content in the R1-M-based alloy is 70 to 95mass% of the entire R1-M-based alloy, the La content in the R1 is 5 to less than 50%, and the M content is 5 to 30mass% of the entire R1-M-based alloy.

In one embodiment, the content of La in R1 in the R1-M alloy is 5% to 15%.

In one embodiment, the content ratio of RH in R1 in the R1-M alloy is 5% to 20%, and the total content ratio of at least one of Nd and Pr in R1 is 25% to 90%.

In one embodiment, 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.

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

Effects of the invention

According to the embodiment of the present invention, it is possible to provide a diffusion source using La and maintain high B _r And high H _cJ The method for producing the R-T-B sintered magnet of (1).

Drawings

Fig. 1A is an enlarged schematic cross-sectional view of a part of an R-T-B sintered magnet.

Fig. 1B is a cross-sectional view schematically showing a further enlarged view within the dotted-line rectangular area of fig. 1A.

FIG. 2 is a flowchart showing an example of the steps in the method for producing an R-T-B sintered magnet according to the present invention.

Detailed Description

First, the basic structure of the R-T-B sintered magnet of the present invention will be described. The R-T-B sintered magnet has a structure in which powder particles of a raw material alloy are bonded by sintering, and is mainly composed of a main phase containing R and a grain boundary phase ₂ T ₁₄ And B compound particles, the grain boundary phase being located in the grain boundary portion of the main phase.

Fig. 1A is an enlarged cross-sectional view schematically showing a part of an R-T-B sintered magnet, and fig. 1B is a further enlarged cross-sectional view schematically showing a dotted rectangular region of fig. 1A. In fig. 1A, for reference, an arrow having a length of 5 μm is shown as a length of a standard indicating the size. As shown in FIGS. 1A and 1B, the R-T-B sintered magnet is mainly composed of a main phase 12 and a grain boundary phase 14, and the main phase 12 contains R ₂ T ₁₄ B compound, the grain boundary phase 14 is located in the grain boundary part of the main phase 12. In addition, as shown in FIG. 1B, the grain boundary phase 14 includes two R ₂ T ₁₄ Two-particle grain boundary phase 14a in which B compound particles (grains) are adjacent and 3R ₂ T ₁₄ Grain boundary triple points 14B adjacent to the B compound particles. The typical main phase crystal grain size is 2.5 μm or more and 10 μm or less in terms of the average value of the circle equivalent diameter of the magnet cross section. R as the main phase 12 ₂ T ₁₄ The B compound is a ferromagnetic material having high saturation magnetization and an anisotropic magnetic field. Therefore, in the R-T-B system sintered magnet, R as the main phase 12 is increased ₂ T ₁₄ The presence ratio of the compound B can be increased _r . To increase R ₂ T ₁₄ The B compound is present in such a ratio that the amount of R, the amount of T and the amount of B in the raw material alloy are close to R ₂ T ₁₄ The stoichiometric ratio of the B compound (R amount: T amount: B amount = 2.

In addition, it is known that R as a main phase is substituted with a heavy rare earth element such as Dy, tb or Ho ₂ T ₁₄ Part of R of the B compound, lowerLow saturation magnetization and improved anisotropy of the main phase. In particular, the main phase shell in contact with the two-particle grain boundary phase is likely to become the starting point of magnetization reversal, and therefore, the heavy rare earth diffusion technique capable of preferentially replacing the heavy rare earth element in the main phase shell can suppress the decrease in saturation magnetization and efficiently obtain high H _cJ 。

In the method for producing an R-T-B sintered magnet according to the present invention, R1 and M contained in the R1-M alloy are diffused from the surface of the R-T-B sintered magnet material into the magnet material through the grain boundaries.

The inventors of the present invention have studied in detail an R1-M alloy and a method of diffusing the alloy by heat treatment on the surface of an R-T-B sintered magnet. As a result, it was found that when R1 of the R1 — M alloy is made to contain RH and R1 and M are diffused, the RL in R1 can suppress the decrease in magnetic properties due to the addition of La even if La is contained in a specific range instead of Nd or Pr. As shown in examples described later, this effect cannot be obtained when Ce is used instead of La. Further, as a more preferable mode, it was found that the magnetic properties are hardly deteriorated by narrowing the specific range of La in the R1 — M alloy. In this way, it is considered that the reason why the decrease in magnetic properties can be suppressed or the magnetic properties hardly decrease even if La is contained instead of Nd or Pr is that: la that enters the interior of the magnet in the diffusion step is less likely to be contained in R than Nd or Pr ₂ T ₁₄ B is mainly present on the grain boundary phase side, and therefore, R is not bonded to B ₂ T ₁₄ The magnetic properties of the B compound have a large influence. Thus, la having a high B content can be used as a diffusion source _r And high H _cJ The R-T-B sintered magnet of (1).

As shown in FIG. 2, the method for producing an R-T-B sintered magnet according to the present invention includes a step S10 of preparing an R-T-B sintered magnet material and a step S20 of preparing an R1-M alloy. The sequence of the step S10 of preparing the R-T-B sintered magnet material and the step S20 of preparing the R1-M alloy is arbitrary.

As shown in FIG. 2, the method for producing an R-T-B sintered magnet according to the present invention further includes a diffusion step S30 of heating the R-T-B sintered magnet material and the R1-M alloy at a temperature of 700 ℃ to 1100 ℃ in a vacuum or inert gas atmosphere to diffuse R1 and M into the R-T-B sintered magnet material.

In the present invention, the R-T-B sintered magnet before and during the diffusion step is referred to as "R-T-B sintered magnet raw material", and the R-T-B sintered magnet after the diffusion step is simply referred to as "R-T-B sintered magnet".

(step of preparing R-T-B based sintered magnet Material)

In the R-T-B sintered magnet material, R is a rare earth element and must contain at least one element selected from Nd, pr and Ce, and the content of R is, for example, 27mass% or more and 35mass% or less of the entire R-T-B sintered magnet material. T is at least one selected from the group consisting of Fe, co, al, mn and Si, and T is essentially Fe, and the content of Fe in the entire T is 80mass% or more.

If R is less than 27mass%, a liquid phase may not be sufficiently generated during sintering, and it may be difficult to sufficiently densify the sintered body. On the other hand, when R exceeds 35mass%, grain growth is caused at the time of sintering, H _cJ May be reduced. In order to obtain higher B _r Preferably, R is 28% to 33% by mass.

The R-T-B sintered magnet material has, for example, the following composition range.

R：27～35mass％，

B：0.80～1.20mass％，

Ga：0～1.0mass％，

X:0 to 2mass% (X is at least one of Cu, nb and Al),

t: contains more than 60mass percent.

Preferably, in the R-T-B sintered magnet material, the mol ratio of T to B [ T [ ]]/[B]More than 14.0 and 15.0 or less. Higher H can be obtained _cJ . [ T ] of the invention]/[B]Is as follows [ T]And [ B ]]Ratio of [ C ] with respect to [ T]Each element (at least one selected from the group consisting of Fe, co, al, mn and Si) constituting T, T necessarily contains Fe, and the content of Fe relative to the whole T is 80mass% or more) Is divided by the atomic weight of each element, and the value obtained by summing these values is defined as [ T ]]About [ B ]]The value obtained by dividing the analysis value (mass%) of B by the atomic weight of B is defined as [ B%]. mol ratio [ T]/[B]The condition that it exceeds 14.0 indicates that the amount of B is relative to the main phase (R) ₂ T ₁₄ Compound B) is formed using a relatively small amount of T. mol ratio [ T]/[B]More preferably from 14.3 to 15.0. Higher H can be obtained _cJ . The content of B is preferably 0.9mass% or more and less than 1.0mass% of the entire R-T-B sintered body.

The R-T-B sintered magnet material can be prepared by using a general method for producing an R-T-B sintered magnet represented by an Nd-Fe-B sintered magnet. For example, a raw material alloy produced by a strip casting method or the like is pulverized into a particle diameter D using a jet mill or the like ₅₀ Is 2.0 to 4.5 μm, is molded in a magnetic field, and is sintered at a temperature of 900 to 1100 ℃ to prepare a sintered body. By particle diameter D ₅₀ Pulverizing into 2.0-4.5 μm powder to obtain high B content _r And high H _cJ . Particle diameter D ₅₀ Preferably 2.5 μm to 3.5 μm. Can reduce the precious RH while suppressing the deterioration of productivity, and can obtain higher B _r And higher H _cJ . Further, the particle diameter D ₅₀ The particle size distribution obtained by the laser diffraction method of the air dispersion method is a particle size in which the cumulative particle size distribution (volume basis) from the smaller diameter side is 50%. Further, the particle diameter D ₅₀ For example, a particle size distribution measuring apparatus "HELOS" manufactured by Sympatec corporation can be used&RODOS ", under dispersion pressure: 4bar, measurement Range: r2, measurement mode: measured under HRLD conditions. The step of preparing the R-T-B-based sintered magnet material is a step of obtaining the R-T-B-based sintered magnet material supplied to the diffusion step, and includes a method of obtaining a separately produced R-T-B-based sintered magnet material in addition to a method of self-production before the diffusion step.

(step of preparing R1-M alloy)

In the above R1-M alloy, R1 is composed of RH and RL, and RH is Tb orAt least one of Dy, RL is a rare earth element other than RH, at least one of Nd and Pr, and La are required to be contained, and M is required to contain at least one selected from Al, cu, zn, ga, fe, co, and Ni. The content of R1 is 70 to 95mass% of the entire R1-M alloy. Thereby, high magnetic characteristics can be obtained. The La content in R1 is 5% or more and less than 50%. Here, the "La content ratio in R1" in the present invention is a value obtained by calculating the La ratio by mass% (mass%) of R1. As described above, when R1 and M are diffused by adding RH to R1 in the R1-M alloy, the RL containing not less than 5% and less than 50% of La instead of Nd or Pr can suppress the deterioration of magnetic properties, and therefore, a high B content can be obtained _r And high H _cJ The R-T-B sintered magnet of (1). To obtain a catalyst having a higher H _cJ The R-T-B sintered magnet of (2) is preferably 5% to 35%. Further, the La content in R1 is most preferably 5% to 15%. If the amount is within this range, the magnetic properties are hardly degraded even if La is added. In addition, to obtain a composition having a higher B content _r And higher H _cJ The content ratio of RH in R1 is preferably 5% to 20%, and the total content ratio of at least one of Nd and Pr in R1 is preferably 25% to 90%. In addition, to obtain a composition having a higher H _cJ In the R-T-B sintered magnet according to (1), preferably, R1 of the R1-M alloy should contain Pr, and the proportion of Pr contained in the R1 is 25% to 90%. In addition, in order to more reliably obtain a high B _r And high H _cJ In the R-T-B sintered magnet of (1), the total content of RH, pr and La in R1 is more preferably 50% or more.

Further, M is at least one selected from the group consisting of Al, cu, zn, ga, fe, co and Ni. The content of M is 5mass% or more and 30mass% or less of the entire R1-M alloy. The content of M is preferably 7 to 15mass% of the entire R1-M alloy. Higher H can be obtained _cJ . Further, 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%The above. By containing Cu and Ga, higher H can be obtained _cJ 。

Typical examples of the R1-M alloy include TbNdPrLaCu alloy, tbNdLaGa alloy, tbPrLaGa alloy, and the like. In addition to the above elements, a small amount of an element such as an unavoidable impurity such as Mn, O, C, N, or the like may be contained.

The method for producing the R1-M alloy is not particularly limited. The metal alloy can be produced by a roll quenching method or a casting method. Further, these alloys may be pulverized to prepare alloy powder. The coating composition can also be prepared by a known atomization method such as a centrifugal atomization method, a rotary electrode method, a gas atomization method, and a plasma atomization method. The step of preparing the R1-M alloy is a step of obtaining the R1-M alloy supplied to the diffusion step, and includes a method of obtaining a separately produced R1-M alloy in addition to a method of producing the R1-M alloy by itself before the diffusion step.

(diffusion step)

The following diffusion step was performed: the R-T-B sintered magnet material and the R1-M alloy prepared by the above method are heated at a temperature of 700 to 1100 ℃ in a vacuum or an inert gas atmosphere, and R1 and M are diffused into the R-T-B sintered magnet material. As a result, a liquid phase containing R1 and M is generated from the R1-M alloy, and this liquid phase is introduced by diffusion from the surface of the sintered material to the inside thereof via the grain boundary in the R-T-B sintered magnet material.

When the heating temperature in the diffusion step is less than 700 ℃, the amount of the liquid phase containing R1 and M is too small, and high H may not be obtained _cJ . On the other hand, when it exceeds 1100 deg.C, H _cJ May be significantly reduced. The heating temperature in the diffusion step is preferably 800 ℃ to 1000 ℃. Higher H can be obtained _cJ . It is preferable that the R-T-B sintered magnet subjected to the diffusion step (700 ℃ C. To 1100 ℃ C.) is cooled from the temperature at which the diffusion step is performed to 300 ℃ at a cooling rate of 15 ℃/min or more. Can obtain higher H _cJ 。

The diffusion treatment step may be performed by disposing R1-M-based bonds of arbitrary shapes on the surface of the R-T-B-based sintered magnet materialGold was carried out using a known heat treatment apparatus. For example, the surface of the R-T-B sintered magnet material may be covered with a powder layer of an R1-M alloy and heat-treated. For example, a slurry obtained by dispersing the R1-M alloy in a dispersion medium may be applied to the surface of the R-T-B sintered magnet material, and then the dispersion medium may be evaporated to bring the R1-M alloy into contact with the R-T-B sintered magnet material. In this case, the amount of adhesion of the R1-M alloy to the R-T-B sintered magnet material in the diffusion step is preferably 1 to 6mass%, and the amount of adhesion of the R1-M alloy to the R-T-B sintered magnet material is more preferably 1.5 to 3 mass%. Higher H can be obtained _cJ . Further, as the dispersion medium, alcohols (ethanol and the like), aldehydes, and ketones can be exemplified. The heavy rare earth element RH may be introduced not only from the R1-M alloy but also by disposing a fluoride, an oxide, an oxyfluoride, or the like of the heavy rare earth element RH on the surface of the R-T-B sintered magnet together with the R1-M alloy. That is, if the light rare earth elements RL and M can be diffused simultaneously together with the heavy rare earth element RH, the method thereof is not particularly limited. Examples of the fluoride, oxide and oxyfluoride of the heavy rare earth element RH include TbF ₃ 、DyF ₃ 、Tb ₂ O ₃ 、Dy ₂ O ₃ 、Tb ₄ OF、Dy ₄ OF。

(Process for carrying out Heat treatment)

The R-T-B sintered magnet subjected to the diffusion step is preferably heat-treated at a temperature of 400 ℃ to 750 ℃ in a vacuum or inert gas atmosphere and at a temperature lower than the temperature applied in the diffusion step. By performing the heat treatment, higher H can be obtained _cJ 。

Examples

The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1

[ Process for preparing R-T-B sintered magnet Material ]

So as to be R-T-B sintered magnets shown in Table 1The elements were weighed in the form of composition of raw materials, 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, zinc stearate as a lubricant was added to and mixed with the coarse pulverized powder in an amount of 0.035 parts by mass relative to 100 parts by mass of the coarse pulverized powder. The coarsely pulverized powder containing the lubricant is finely pulverized by a jet mill. By crushing, the particle diameter D is obtained ₅₀ :3.5 μm in size. The particle size distribution measuring apparatus "HELOS" manufactured by Sympatec Inc. was used&RODOS ", at dispersion pressure: 4bar, measurement range: r2, measurement mode: measurement of D under HRLD conditions ₅₀ 。

To the obtained fine powder was added zinc stearate as a lubricant in an amount of 0.05mass% relative to 100mass% of the fine powder, and the mixture was molded in a magnetic field to obtain a molded article. In addition, a so-called perpendicular magnetic field forming device (transverse magnetic field forming device) in which the magnetic field application direction and the pressing direction are orthogonal to each other is used as the forming device. The obtained compact was sintered in vacuum for 4 hours (the temperature was selected to sufficiently cause densification by sintering), and then quenched to obtain an R-T-B-based sintered magnet material. The density of the R-T-B sintered magnet material obtained was 7.5Mg/m ³ The above.

In order to obtain the composition of the obtained R-T-B-based sintered magnet material, the contents of Nd, pr, fe, co, al, ga, cu, zr, and B were measured by high-frequency inductively coupled plasma optical emission spectrometry (ICP-OES). Further, the oxygen amount of the R-T-B based sintered magnet material was measured by using a gas analyzer based on a gas melting-infrared absorption method, the nitrogen amount was measured by using a gas analyzer based on a gas melting-heat conduction method, and the carbon amount was measured by using a gas analyzer based on a sintering-infrared absorption method. In addition, the total amount of the components of the R-T-B sintered magnet material may not be 100mass%. This is because, as described above, the measurement method is different and other elements may be contained as inevitable impurities. TRE is the total value of Nd and Pr.

TABLE 1

[ Process for preparing R1-M based alloy ]

The elements were weighed so as to have the compositions of R1-M alloys shown in Nos. 1-A to 1-H of Table 2, and these raw materials were melted to obtain a ribbon-like or sheet-like alloy by a single-roll super-quenching method. The composition of the obtained R1-M alloy is shown in table 2. The components in table 2 were measured by high-frequency inductively coupled plasma emission spectrometry. The content ratio (mass%) of La in R1 is also shown in Table 2.

TABLE 2

[ diffusion step ]

The R-T-B sintered magnet materials of Nos. 1 to 3 in Table 1 were cut and machined into a 7.2mm square cube. The processed R-T-B-based magnet material was coated with PVA as a binder over the entire surface of the R-T-B-based magnet material by a dip coating method. Next, under the production conditions shown in Table 3, the R1-M alloy was adhered to the entire surface of the R-T-B sintered magnet material coated with the binder. The amount of the R1-M alloy deposited was adjusted by pulverizing the R1-M alloy in an argon atmosphere using a mortar, passing the pulverized alloy through various sieves having a mesh size of 45 to 1000. Mu.m, and using R1-M alloys having different particle sizes. The amount of adhesion was set to about 2 mass%. Then, the R1-M alloy and the R-T-B sintered magnet material were heated in a vacuum heat treatment furnace under a reduced pressure argon atmosphere controlled to 100Pa under the conditions shown in the diffusion step in Table 3, and then cooled.

[ Process for carrying out Heat treatment ]

The R-T-B sintered magnet material heated in the diffusion step was subjected to a heat treatment of heating at 500 ℃ in a vacuum heat treatment furnace under reduced pressure argon controlled at 100 Pa. The entire surface of each of the heat-treated samples was cut with a surface grinding disk to obtain a cubic sample (R-T-B sintered magnet) of 7.0 mm. Times.7.0 mm. The heating temperatures of the R1-M alloy and the R-T-B sintered magnet material in the diffusion step and the R-T-B sintered magnet material in the heat treatment step after the diffusion step were measured by thermocouples.

TABLE 3

[ sample evaluation ]

Determination of the residual magnetic flux density B on the samples obtained by means of a B-H tracer _r And coercive force H _cJ . The results are shown in table 3. As shown in Table 3, in the comparative examples (samples Nos. 1-12 to 1-13) in which Ce was added to the R1-M alloy, H increased with the amount of Ce added as compared with sample No.1-11 (reference 3) in which the R1-M alloy to which La and Ce were not added was used _cJ Greatly reducing the cost. On the other hand, in the inventive examples (Nos. 1-2 to 1-5 and 1-7 to 1-10) in which La was added, B did not occur in the inventive examples Nos. 1-2, 1-3, 1-7 and 1-8, as compared with the inventive examples Nos. 1-1 (Standard 1) and 1-6 (Standard 2) in which the R1-M alloy to which La and Ce were not added was used _r Reduction of (D), H _cJ The amount of decrease in (b) is less than 4% of the reference characteristic, and the magnetic characteristic hardly decreases even if La is added. Further, comparison of the inventive examples Nos. 1-4, 1-5, 1-9, and 1-10 with the comparative examples (Nos. 1-12 to 1-13) in which Ce was added revealed that even when the amount of La added was larger than the amount of Ce added, the deterioration of the magnetic properties was greatly suppressed.

Example 2

[ Process for preparing R-T-B 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 changed. The composition of the sintered magnet thus produced is shown in table 4.

TABLE 4

[ Process for preparing R1-M based alloy ]

The elements were weighed so as to have the compositions of R1-M alloys shown in Nos. 2-A to 2-D of Table 5, and these raw materials were melted to obtain a ribbon-like or sheet-like alloy by a single-roll super-quenching method. The compositions of the obtained R1-M alloys are shown in table 5. The components in table 5 were measured by high-frequency inductively coupled plasma emission spectrometry.

TABLE 5

[ diffusion Process ]

The R-T-B sintered magnet material of No.4 in Table 4 was cut and machined into a 7.2mm square cube. PVA as a binder was applied to the entire surface of the R-T-B magnet material by dip coating. Next, under the production conditions shown in Table 6, an R1-M alloy was applied to the entire surface of the R-T-B sintered magnet material coated with the binder. The amount of the R1 — M alloy deposited is adjusted as follows: the R1-M alloy was pulverized in an argon atmosphere using a mortar, and then passed through various sieves having a mesh size of 45 to 1000. Mu.m, and R1-M alloys having different particle sizes were used. The amount of adhesion was set to about 2 mass%. Then, the R1-M alloy and the R-T-B sintered magnet material were heated in a vacuum heat treatment furnace in a reduced-pressure argon atmosphere controlled to 100Pa under the conditions shown in the diffusion step in Table 6, and then cooled.

[ Process for carrying out Heat treatment ]

The R-T-B sintered magnet material heated in the diffusion step was subjected to a heat treatment of heating at 500 ℃ in a vacuum argon atmosphere controlled to 100Pa using a vacuum heat treatment furnace. The entire surface of each sample after the heat treatment was cut with a surface grinding disk to obtain a cubic sample (R-T-B sintered magnet) of 7.0 mm. Times.7.0 mm. The heating temperatures of the R1-M alloy and the R-T-B sintered magnet material in the diffusion step and the R-T-B sintered magnet material in the heat treatment step after the diffusion step were measured by thermocouples.

TABLE 6

[ sample evaluation ]

Determination of the residual magnetic flux density B on the samples obtained by means of a B-H tracer _r And coercive force H _cJ . The results are shown in table 6. As shown in Table 6, in the inventive examples (Nos. 2-2 and 2-3), B did not occur in comparison with the sample No.2-1 (reference) using the R1-M alloy not containing La and Ga _r Reduction of (D), H _cJ The amount of decrease in (b) is less than 4% of the reference characteristic, and the magnetic characteristic is hardly decreased. On the other hand, in the comparative example (sample No. 2-4) using the R1-M alloy in which the La content in R1 is excessive, B does not occur _r Is reduced, however H _cJ Greatly reducing the cost.

Example 3

[ Process for preparing R-T-B sintered magnet Material ]

The elements were weighed so as to have the compositions of the R-T-B-based sintered magnet raw materials shown in table 7, and raw material alloys were 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, zinc stearate was added to the coarse pulverized powder and mixed as a lubricant in an amount of 0.035mass% relative to 100mass% of the coarse powder. The coarsely pulverized powder containing the lubricant is finely pulverized by a jet mill. By crushing to obtain particle diameter D ₅₀ :3.0 μm in size. The particle size distribution measuring apparatus "HELOS" manufactured by Sympatec Inc. was used&RODOS ", under dispersion pressure: 4bar, measurement range: r2, measurement mode: measurement of D under HRLD conditions ₅₀ 。

Adding a fine powder to the obtained fine powderAfter zinc stearate having a pulverized powder content of 100mass% to 0.05mass% was used as a lubricant, the resultant was molded in a magnetic field to obtain a molded article. In addition, a so-called perpendicular magnetic field forming apparatus (transverse magnetic field forming apparatus) in which the magnetic field application direction is orthogonal to the pressing direction is used as the forming apparatus. The obtained compact was sintered in vacuum for 4 hours (the temperature was selected to sufficiently cause densification by sintering), and then quenched to obtain an R-T-B-based sintered magnet material. The density of the R-T-B sintered magnet material obtained was 7.5Mg/m ³ As described above.

In order to determine the components of the R-T-B sintered magnet material obtained, the contents of Nd, pr, fe, dy, tb, co, al, ga, cu, zr, and B were measured by high-frequency inductively coupled plasma optical emission spectrometry (ICP-OES). Further, the oxygen amount of the R-T-B based sintered magnet material was measured by using a gas analyzer based on a gas melting-infrared absorption method, the nitrogen amount was measured by using a gas analyzer based on a gas melting-heat conduction method, and the carbon amount was measured by using a gas analyzer based on a sintering-infrared absorption method. In addition, the total amount of the components of the R-T-B-based sintered magnet material may not be 100mass%. This is because, as described above, the measurement method is different, and other elements may be contained as inevitable impurities. TRE is the total value of Nd, pr and Dy.

TABLE 7

[ Process for preparing R1-M based alloy ]

The elements were weighed so as to have the compositions of R1-M alloys shown in Nos. 3-A to 3-D of Table 8, and these raw materials were melted to obtain a ribbon-like or sheet-like alloy by a single-roll super-quenching method. The compositions of the obtained R1 — M alloys are shown in table 8. Further, each component in table 8 was measured by a high-frequency inductively coupled plasma emission spectrometry.

TABLE 8

[ diffusion Process ]

The R-T-B sintered magnet material of No.5 in Table 7 was cut and machined into a 7.2mm square cube. PVA as a binder was applied to the entire surface of the R-T-B magnet material by a dip coating method after processing. Next, under the production conditions shown in Table 9, an R1-M alloy was applied to the entire surface of the R-T-B sintered magnet material coated with the binder. The amount of the R1-M alloy deposited was adjusted as follows: the R1-M alloy was pulverized in an argon atmosphere using a mortar, and then passed through various sieves having a mesh size of 45 to 1000. Mu.m, thereby using R1-M alloys having different particle sizes. The amount of adhesion was set to about 2 mass%. Then, the R1-M alloy and the R-T-B sintered magnet material were heated in a vacuum heat treatment furnace under a reduced pressure argon atmosphere controlled to 100Pa under the conditions shown in the diffusion step in Table 9, and then cooled.

[ Process for carrying out Heat treatment ]

TABLE 9

[ sample evaluation ]

Determination of the residual magnetic flux density B of the resulting sample by means of a B-H tracer _r And coercive force H _cJ . Will be provided withThe results are shown in Table 9. As shown in Table 9, in the inventive examples (Nos. 3-2 and 3-3), B was not generated in comparison with the sample No.3-1 (reference) using the R1-M alloy not containing La _r Reduction of (A) H _cJ The amount of decrease in (b) is less than 4% of the reference characteristic, and the magnetic characteristic is hardly decreased. On the other hand, in the comparative example (sample No. 3-4) using the R1-M alloy in which the La content in R1 is excessive, B does not occur _r Is reduced, however H _cJ Greatly reducing the cost.

Example 4

[ Process for preparing R-T-B sintered magnet Material ]

An R-T-B sintered magnet material was prepared in the same manner as in example 3. The composition of the sintered magnet was the same as that in table 7.

[ Process for preparing R1-M based alloy ]

Each element was weighed so as to have the composition of R1-M alloy shown in Nos. 4-A to 4-D of Table 10, and these raw materials were melted to obtain a ribbon-like or sheet-like alloy by a single-roll super-quenching method. The compositions of the obtained R1 — M alloys are shown in table 10. The components in table 10 were measured by high-frequency inductively coupled plasma emission spectrometry.

Watch 10

[ diffusion Process ]

The R-T-B sintered magnet material of No.5 in Table 7 was cut and machined into a 7.2mm square cube. PVA as a binder was applied to the entire surface of the R-T-B magnet material by dip coating after processing. Next, under the production conditions shown in Table 11, the R1-M alloy was adhered to the entire surface of the R-T-B sintered magnet material coated with the binder. The amount of the R1-M alloy deposited was adjusted as follows: the R1-M alloy was pulverized in an argon atmosphere using a mortar, and then passed through various sieves having a mesh size of 45 to 1000. Mu.m, thereby using R1-M alloys having different particle sizes. The amount of adhesion was set to about 2 mass%. Then, the R1-M alloy and the R-T-B sintered magnet material were heated in a vacuum heat treatment furnace under a reduced pressure argon atmosphere controlled to 100Pa under the conditions shown in the diffusion step in Table 11, and then cooled.

[ Process for carrying out Heat treatment ]

The R-T-B sintered magnet material heated in the diffusion step was subjected to a heat treatment of heating at 500 ℃ in a vacuum heat treatment furnace under reduced pressure argon controlled at 100 Pa. The entire surface of each sample after the heat treatment was cut with a surface grinding disk to obtain a cubic sample (R-T-B sintered magnet) of 7.0 mm. Times.7.0 mm. The heating temperatures of the R1-M alloy and the R-T-B sintered magnet material in the diffusion step and the R-T-B sintered magnet material in the heat treatment step after the diffusion step were measured by thermocouples.

[ sample evaluation ]

The residual magnetic flux density B of the obtained sample was measured at room temperature, 150 ℃ and 180 ℃ with a B-H tracer _r And coercive force H _cJ . The results of the magnetic measurements are shown in Table 11, and B is calculated _r And H _cJ The results obtained for each temperature coefficient are shown in table 12.

TABLE 11

TABLE 12

As shown in Table 11, in the inventive examples (Nos. 4-2 and 4-3), B did not occur in comparison with the sample No.4-1 (reference) using the R1-M alloy containing no La _r Reduction of (A) H _cJ The amount of decrease in (b) is also less than 4% of the reference value, and the magnetic properties are hardly degraded. On the other hand, la in the case of using R1 contains richIn the comparative example (sample No. 4-4) of the excessive R1-M based alloy, B did not occur _r Is reduced, but H _cJ Greatly reducing the cost. Further, samples Nos. 4-5 and 4-6 obtained by diffusion-treating the R1-M alloy to which Ce was added were H relative to the reference (sample No. 4-1) _cJ The reduction is more than 4 percent. In addition, as shown in tables 11 and 12, in the magnetic characteristics at the temperatures of 150 ℃ and 180 ℃, in samples Nos. 4-2 and 4-3 of this example, B is the same as that of the reference (sample No. 4-1) _r And H _cJ No significant decrease in magnetic properties occurred. With respect to B _r Temperature coefficients of alpha and H _cJ The temperature coefficient beta, 4-2 of (a) is more excellent than the reference value, and 4-3 is about the same as the reference value. On the other hand, in sample No.4-4 in which the La concentration in R1-M was excessive, the temperature coefficients α and β were higher than the reference values, but at the temperatures of 150 ℃ and 180 ℃, H was observed _cJ The value of (2) is greatly reduced. In addition, in sample Nos. 4-5 and 4-6 using the R1-M alloy to which Ce was added, H was added at a temperature of 150 ℃ and 180 DEG C _cJ The temperature coefficient alpha and beta are also reduced.

Claims

1. A method for producing an R-T-B sintered magnet, comprising:

a step for preparing a R-T-B sintered magnet material, wherein R is a rare earth element and must contain at least one element selected from Nd, pr, and Ce, and T is at least one element selected from Fe, co, al, mn, and Si and must contain Fe;

a step of preparing an R1-M alloy, wherein R1 is composed of RH and RL, RH is at least one of Tb and Dy, RL is a rare-earth element other than RH and necessarily contains La and at least one of Nd and Pr, and M is at least one member selected from Al, cu, zn, ga, fe, co and Ni; and

a diffusion step of heating the R-T-B sintered magnet material and the R1-M alloy at a temperature of 700 ℃ to 1100 ℃ in a vacuum or an inert gas atmosphere to diffuse R1 and M into the R-T-B sintered magnet material,

the content of R1 in the R1-M alloy is 70 to 95mass% of the entire R1-M alloy, the content of La in R1 is 5 to less than 50%, and the content of M in the R1-M alloy is 5 to 30mass% of the entire R1-M alloy.

2. The method for producing an R-T-B sintered magnet according to claim 1, wherein:

the content of La in R1 in the R1-M alloy is 5% to 15%.

3. The method for producing an R-T-B sintered magnet according to claim 1, wherein:

the content ratio of RH in R1 in the R1-M alloy is 5% to 20%, and the total content ratio of at least one of Nd and Pr in R1 is 25% to 90%.

4. The method of manufacturing an R-T-B sintered magnet according to claim 1 or 2, wherein:

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

5. The method for producing an R-T-B sintered magnet according to any one of claims 1 to 3, wherein:

r1 of the R1-M alloy must contain Pr, and the proportion of Pr contained in the R1 is 25% to 90%.