Method for manufacturing and determining the composition of RTB-type sintered magnets

Abstract

To manufacture an R-T-B sintered magnet having desired magnetic characteristics by adjusting the Ce ratio and the Dy ratio.SOLUTION: On the basis of a target Br=standard Br+coefficient W11×(Ce ratio-standard Ce ratio)+coefficient W12×(Dy ratio-standard Dy ratio) (formula 1), and a target HcJ=standard HcJ+coefficient W21×(Ce ratio-standard Ce ratio)+coefficient W22×(Dy ratio-standard Dy ratio) (formula 2), the Ce ratio and the Dy ratio to obtain the target Br and the target HcJ are determined. The standard Br and the standard HcJ, the standard Ce ratio, and the standard Dy ratio are Br and HcJ of one of at least three R-T-B sintered magnets.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] This disclosure relates to a method for manufacturing and determining the composition of RTB-type sintered magnets. [Background technology]

[0002] RTB-type sintered magnets (where R is a rare earth element and must contain at least one selected from the group consisting of Nd, Pr, and Ce, T is Fe or Fe and Co, and B is boron) are R2Fe 14 RT-B sintered magnets are composed of a main phase of a compound having a type B crystal structure, a grain boundary phase located at the grain boundaries of this main phase, and a compound phase formed by the influence of trace added elements and impurities. r (Hereafter simply "B r (Sometimes it is written as ") and has high coercivity H cJ (Hereafter simply "H cJ It is sometimes described as "a high-performance magnet" and is known as the most powerful magnet among permanent magnets.

[0003] For this reason, RTB-type sintered magnets are used in a variety of motors in fields such as automobiles (EVs, HVs, PHVs), renewable energy (wind power generation, etc.), home appliances, and industrial applications. RTB-type sintered magnets are essential materials for miniaturizing, lightening, and improving the efficiency and energy saving (improving energy efficiency) of these motors. Furthermore, RTB-type sintered magnets are used in drive motors for electric vehicles, and by replacing internal combustion engine vehicles with electric vehicles, they contribute to preventing global warming by reducing greenhouse gases such as carbon dioxide (reduction in fuel and exhaust gases). In this way, RTB-type sintered magnets are making a significant contribution to the realization of a clean energy society.

[0004] In RTB-type sintered magnets, R2T 14 When some of the light rare earth elements RL (e.g., Nd or Pr) in R of compound B are replaced with the heavy rare earth element RH (RH is at least one of Tb and Dy), H cJis known to be improved. As the substitution amount of RH increases, H cJ is improved. However, R2T 14 When RL in the R2T-B compound is substituted with RH, the H of the R-T-B sintered magnet cJ is improved, while the residual magnetic flux density B r decreases. In addition, since heavy rare earth elements are raw materials with high resource risks, it is required to reduce their usage amount or improve H cJ without using them.

[0005] Patent Document 1 describes that by heat-treating at least a part of the surface of an R-T-B sintered magnet material with a specific composition in contact with at least a part of an R2-Ga alloy, RH, Pr, and Ga are diffused. Thereby, while reducing the content of RH, high B r and high H cJ can be obtained.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] The method described in Patent Document 1 suppresses the content of heavy rare earth elements while achieving high B r and high H cJRTB-type sintered magnets are noteworthy because they can be produced using this technology. However, in recent years, demand for RTB-type sintered magnets is expected to expand significantly, particularly for electric vehicle motors. Therefore, from the perspective of efficient resource utilization and cost reduction, it is necessary to use rare earth elements in a balanced manner, including other rare earth elements, rather than relying solely on heavy rare earth elements, in addition to the heavy rare earth element content. One specific measure is to use Ce, which is relatively abundant among rare earth elements. In particular, using Ce instead of Nd and Pr, which are major elements in RTB-type sintered magnets, is effective.

[0008] However, when Ce is added instead of Nd or Pr, the magnetic properties change depending on the amount of Ce added. Predicting this change is difficult. The inventors have found that in certain RTB-type sintered magnets, desired magnetic properties can be achieved by adjusting the amount of Ce added.

[0009] Embodiments of the present disclosure are desired B r and H cJ This invention provides a method for manufacturing and determining the composition of an RTB-type sintered magnet having the following properties. [Means for solving the problem]

[0010] A method for manufacturing an RTB-type sintered magnet, as described in an exemplary embodiment, The content of Ce, Nd, Pr, Dy, and Tb are denoted as [Ce], [Nd], [Pr], [Dy], and [Tb], respectively. Let ([Ce] / ([Nd]+[Pr]+[Ce]+[Dy]+[Tb])) be the Ce ratio. Let ([Dy] / ([Nd]+[Pr]+[Ce]+[Dy]+[Tb])) be the ratio of Dy, Prepare at least three RTB-type sintered magnets with different Ce ratios and Dy ratios, and the B of each RTB-type sintered magnet r and H cJ The process of measuring, B of each RTB system sintered magnet r and H cJThe measured values ​​and the coefficients W shown in Equations 1 and 2 below are used for the Ce ratio and Dy ratio. 11 , W 12 , W 21 , W 22 The process of determining, Goal B r = Criterion B r + coefficient W 11 × (Ce ratio - base Ce ratio) + coefficient W 12 ×(Dy ratio - standard Dy ratio) (Equation 1), Goal H cJ =Reference H cJ + coefficient W 21 × (Ce ratio - base Ce ratio) + coefficient W 22 ×(Dy ratio - standard Dy ratio) (Formula 2) Based on the coefficients determined in Equations 1 and 2 above, target B r and target H cJ A step to determine the Ce ratio and Dy ratio to obtain, The process involves preparing an R1-TB sintered magnet material containing Ce and Dy in the determined Ce and Dy ratios (where R1 is a rare earth element and contains at least one of Nd and Pr and at least one of Ce and Dy, and T is Fe or Fe and Co), The process involves preparing an R2-M diffusion source (where R2 is a rare earth element and must contain at least one of Nd and Pr, and M is at least one selected from the group consisting of Cu, Ga, Fe, Co, Ni, and Al), A diffusion step involves bringing an R2-M diffusion source into contact with the surface of the R1-TB sintered magnet material and performing a heat treatment. Includes, Criterion B r and standard H cJ This refers to the B of one of the RTB-type sintered magnets among the at least three RTB-type sintered magnets. r and H cJ That is the case.

[0011] In one embodiment, the Ce ratio and Dy ratio in one RTB-type sintered magnet are, each, 0% or more and 30% or less.

[0012] In one embodiment, the at least three RTB-type sintered magnets include a first RTB-type sintered magnet and a second RTB-type sintered magnet, each having a Ce ratio of 2 mass% or more and a Dy ratio of 1 mass% or more compared to the single RTB-type sintered magnet.

[0013] In one embodiment, the at least three RTB-type sintered magnets include a first RTB-type sintered magnet and a second RTB-type sintered magnet, each having a Ce ratio of 5 mass% or more and a Dy ratio of 3 mass% or more compared to the first RTB-type sintered magnet.

[0014] In one embodiment, the content of elements other than rare earth elements in each of the at least three RTB-type sintered magnets is a common value, and in the step of preparing an R1-TB-type sintered magnet material containing Ce and Dy at a determined Ce ratio and Dy ratio, the content of rare earth elements other than rare earth elements in the R1-TB-type sintered magnet material is maintained at a predetermined value.

[0015] A method for determining the composition of an RTB-type sintered magnet in this disclosure is, in an exemplary embodiment, The content of Ce, Nd, Pr, Dy, and Tb are denoted as [Ce], [Nd], [Pr], [Dy], and [Tb], respectively. Let ([Ce] / ([Nd]+[Pr]+[Ce]+[Dy]+[Tb])) be the Ce ratio. Let ([Dy] / ([Nd]+[Pr]+[Ce]+[Dy]+[Tb])) be the ratio of Dy, Prepare at least three RTB-type sintered magnets with different Ce ratios and Dy ratios, and the B of each RTB-type sintered magnet r and H cJ The process of measuring, B of each RTB system sintered magnet r and H cJ The measured values ​​and the coefficients W shown in Equations 1 and 2 below are used for the Ce ratio and Dy ratio. 11 , W 12 , W 21 , W 22 The process of determining, Goal B r = Criterion B r + coefficient W 11 × (Ce ratio - base Ce ratio) + coefficient W 12 ×(Dy ratio - standard Dy ratio) (Equation 1), Goal H cJ =Reference H cJ + coefficient W 21 × (Ce ratio - base Ce ratio) + coefficient W 22 ×(Dy ratio - standard Dy ratio) (Formula 2) Based on the coefficients determined in Equations 1 and 2 above, target B r and target H cJ A step to determine the Ce ratio and Dy ratio to obtain, Includes, Criterion B r and standard H cJ This refers to the B of one of the at least three RTB-type sintered magnets. r and H cJ That is the case.

[0016] In one embodiment, the Ce ratio and Dy ratio in one RTB-type sintered magnet are, each, 0% or more and 30% or less.

[0017] In one embodiment, the RTB-type sintered magnets include the RTB-type sintered magnets according to claim 1 or 2, wherein the at least three RTB-type sintered magnets include a first RTB-type sintered magnet and a second RTB-type sintered magnet, the first having a Ce ratio of 2 mass% or more and a Dy ratio of 1 mass% or more compared to the first RTB-type sintered magnet.

[0018] In one embodiment, the at least three RTB-type sintered magnets include a first RTB-type sintered magnet and a second RTB-type sintered magnet, each having a Ce ratio of 5 mass% or more and a Dy ratio of 3 mass% or more compared to the single RTB-type sintered magnet.

[0019] In one embodiment, the content of elements other than rare earth elements in each of the at least three RTB-type sintered magnets is a common value. [Effects of the Invention]

[0020] According to embodiments of this disclosure, it becomes possible to manufacture RTB-based sintered magnets having desired magnetic properties by adjusting the Ce ratio and Dy ratio. [Brief explanation of the drawing]

[0021] [Figure 1A] This is a schematic cross-sectional view showing a magnified portion of an RTB-type sintered magnet. [Figure 1B] This is a schematic cross-sectional view showing a further enlargement of the area within the dashed rectangular region in Figure 1A. [Figure 2] This graph schematically shows the relationship between Br and HcJ in RTB-type sintered magnets with different Ce and Dy ratios. [Figure 3] This flowchart shows an example of the process in the manufacturing method of RTB-type sintered magnets according to this disclosure. [Figure 4] This flowchart shows examples of other steps in the manufacturing method of RTB-type sintered magnets according to this disclosure. [Figure 5] This graph shows the magnetic properties of the comparative example. [Figure 6] This is a graph showing the magnetic properties of Example 1. [Figure 7] This is a graph showing the magnetic properties of Example 2. [Figure 8] This is a graph showing the magnetic properties of Example 3. [Figure 9] This is a graph showing the magnetic properties of Example 4. [Figure 10] This is a graph showing the magnetic properties of Example 5. [Modes for carrying out the invention]

[0022] First, the basic structure of the RTB-type sintered magnet according to this disclosure will be explained. The RTB-type sintered magnet has a structure in which powder particles of raw material alloy are bonded together by sintering, and is mainly R2T 14 It is composed of a main phase consisting of B compound particles and a grain boundary phase located at the grain boundaries of this main phase.

[0023] Figure 1A is a schematic cross-sectional view showing a magnified portion of an RTB-type sintered magnet, and Figure 1B is a schematic cross-sectional view showing a further magnified portion within the dashed rectangular area of ​​Figure 1A. In Figure 1A, an arrow with a length of 5 μm is included as an example to indicate the size as a reference length. As shown in Figures 1A and 1B, RTB-type sintered magnets are mainly R2T 14 The structure consists of a main phase 12 made of compound B and a grain boundary phase 14 located at the grain boundaries of the main phase 12. Furthermore, as shown in Figure 1B, the grain boundary phase 14 has two R2T 14 B compound particles (grains) are adjacent to a two-particle grain boundary phase 14a and three R2T 14 The B compound particles contain adjacent grain boundary triple points 14b. The typical main phase grain size is between 2.5 μm and 10 μm, based on the average equivalent diameter of the magnet cross-section. The main phase 12 is R2T. 14 Compound B is a ferromagnetic material with high saturation magnetization and anisotropic magnetic field. Therefore, in RTB-type sintered magnets, the main phase 12 is R2T. 14 By increasing the proportion of compound B, r This can improve R2T 14 To increase the proportion of B compound, the amounts of R, T, and B in the raw alloy should be R2T 14 The goal is to approximate the stoichiometric ratio of compound B (amount of R:amount of T:amount of B = 2:14:1).

[0024] Furthermore, the main phase is R2T 14It is known that by substituting part of R in the B compound with heavy rare earth elements such as Dy, Tb, Ho, etc., the saturation magnetization can be lowered while increasing the anisotropy magnetic field of the main phase. In particular, since the main phase outer shell in contact with the two-particle grain boundary phase is likely to be the starting point of magnetization reversal, the heavy rare earth diffusion technique that can preferentially substitute the heavy rare earth elements in the main phase outer shell can efficiently increase the high H while suppressing the decrease in saturation magnetization. cJ can be obtained.

[0025] In the method for manufacturing an R-T-B sintered magnet according to the present disclosure, R2 and M contained in the R2-M alloy are diffused from the surface of the R-T-B sintered magnet material through the grain boundaries into the magnet material interior.

[0026] The inventors of the present invention have studied in detail a method of heating an R1-T-B sintered magnet material and an R2-M alloy to diffuse R2 and M into the interior of the R1-T-B sintered magnet material. As a result, in a specific R-T-B sintered magnet, it has been found that each of B r and H cJ can be very well approximated by a linear combination of the Ce ratio and the Dy ratio. The specific R-T-B sintered magnet having this property is an R-T-B sintered magnet that has been subjected to a diffusion process in which an R2-M diffusion source (R2 is a rare earth element, which necessarily includes at least one of Nd and Pr, and M is at least one selected from the group consisting of Cu, Ga, Fe, Co, Ni, and Al) is brought into contact with the surface of the R1-T-B sintered magnet material and heat-treated.

[0027] Hereinafter, embodiments of the method for manufacturing an R-T-B sintered magnet according to the present disclosure will be described.

[0028] <Method for Manufacturing R-T-B Sintered Magnet> In the present disclosure, the contents (mass ratios) of Ce, Nd, Pr, Dy, and Tb in the R-T-B sintered magnet are denoted as [Ce], [Nd], [Pr], [Dy], and [Tb], respectively. And, ([Ce] / ([Nd]+[Pr]+[Ce]+[Dy]+[Tb])) is defined as the Ce ratio. Also, ([Dy] / ([Nd]+[Pr]+[Ce]+[Dy]+[Tb])) is defined as the Dy ratio.

[0029] According to the experiments of the present inventors, in specific R-T-B sintered magnets with different Ce ratios and Dy ratios, as shown in FIG. 2, B r and H cJが were found to change linearly according to the Ce ratio and the Dy ratio.

[0030] FIG. 2 is a graph schematically showing the relationship between B r and H cJ of R-T-B sintered magnets with different Ce ratios and Dy ratios. In the graph of FIG. 2, the horizontal axis is H cJ , and the vertical axis is B r .

[0031] In FIG. 2, the R-T-B sintered magnet having the reference B r and the reference H cJ is the "reference magnet", which is indicated by the reference numeral "Ref_0". In the example of FIG. 2, the reference magnet Ref_0 has a low value where the Ce ratio and the Dy ratio can be approximated to 0 or substantially 0. On the other hand, the R-T-B sintered magnet indicated by the reference numeral "Ref_1" in FIG. 2 is the first reference magnet. On the other hand, the R-T-B sintered magnet indicated by the reference numeral "Ref_2" in FIG. 2 is the second reference magnet. The first reference magnet Ref_1 has, for example, a low value where the Dy ratio can be approximated to 0 or substantially 0, and the Ce ratio has a relatively high value. On the contrary, the second reference magnet Ref_2 has, for example, a low value where the Ce ratio can be approximated to 0 or substantially 0, and the Dy ratio has a relatively high value.

[0032] In the graph of FIG. 2, the magnetic properties (H cJ , B r ) of the reference magnet Ref_0 and the magnetic properties (H cJ , B r ) of the first reference magnet Ref_1 are located on the straight line 10. On the other hand, the magnetic properties (H cJ , B r ) of the reference magnet Ref_0 and the magnetic properties (H cJ , B r ) of the second reference magnet Ref_2 are located on the straight line 20.

[0033] As described below, the following was found from the experiments of the present inventors. That is, in the case of a specific R-T-B sintered magnet, when the Ce ratio is increased without increasing the Dy ratio of the reference magnet Ref_0, the magnetic properties (H cJ , B r ) move from the point indicating the magnetic properties of the reference magnet Ref_0 toward the point indicating the magnetic properties of the first reference magnet Ref_1 along the straight line 10. Further, when the Dy ratio is increased without increasing the Ce ratio of the reference magnet Ref_0, the magnetic properties (H cJ , B r ) move from the point indicating the magnetic properties of the reference magnet Ref_0 toward the point indicating the magnetic properties of the second reference magnet Ref_2 along the straight line 20.

[0034] Furthermore, when both the Ce ratio and the Dy ratio are increased from the Ce ratio and the Dy ratio in the reference magnet Ref_0, the magnetic properties (H cJ , B r ) at the intersection of two straight lines (dotted line and broken line) parallel to the respective straight lines 10 and 20, which are determined according to the increased Ce ratio and Dy ratio, are also realized. The present invention has been completed based on such findings.

[0035] Incidentally, when the R-T-B sintered magnet having the lowest Ce ratio and Dy ratio is tentatively defined as the "reference magnet Ref_0", the Ce ratio and the Dy ratio in the reference magnet Ref_0 may each be 0% or more and 50% or less. Preferably, they are 0% or more and 10% or less, and more preferably 0% or more and 5% or less.

[0036] According to the study of the present inventors, both the Ce ratio and the Dy ratio of the reference magnet Ref_0 do not necessarily have the smallest values compared to the three magnets. As long as the Ce ratio or the Dy ratio is at least one of the three magnets, any one of them can function as the reference magnet Ref_0.

[0037] In one embodiment, the first reference magnet Ref_1 may have a Ce ratio of 10 times or more and a Dy ratio of 2 times or less compared to the reference magnet Ref_0. Similarly, the second reference magnet Ref_2 may have a Ce ratio of 2 times or less and a Dy ratio of 10 times or more compared to the reference magnet Ref_0. The magnetic properties (H) are determined among the three magnets Ref_0, Ref_1, and Ref_2. cJ B r The greater the range of change in ), the easier it becomes to determine lines 10 and 20 with high accuracy.

[0038] However, the present invention is not limited to such cases. If the first reference magnet Ref_1 and the second reference magnet Ref_2 differ from each other in either their Ce ratio or Dy ratio, and the Ce ratio is 2 mass% or more higher and the Dy ratio is 1 mass% or more higher than that of the reference magnet Ref_0, then the coefficients described later can be calculated. It is more preferable if the Ce ratio is 5 mass% or more higher and the Dy ratio is 3 mass% or more higher for the first reference magnet Ref_1 and the second reference magnet Ref_2 compared to that of the reference magnet Ref_0.

[0039] The following describes embodiments of the method for manufacturing RTB-type sintered magnets according to this disclosure.

[0040] The manufacturing method in this embodiment involves preparing at least three RTB-type sintered magnets with different Ce ratios and Dy ratios, as shown in Figure 3, and then measuring the B of each RTB-type sintered magnet. r and H cJ Step S1 is performed to measure the reference B. r and standard H cJ This refers to the B of one of the RTB sintered magnets among at least three RTB sintered magnets. r and H cJ That is the case.

[0041] Next, the B of each RTB-type sintered magnet r and H cJ The measured values ​​and the coefficients W shown in Equations 1 and 2 below are used for the Ce ratio and Dy ratio. 11 , W 12 , W21 , W 22 The process S2 is executed to determine the outcome. Goal B r = Criterion B r + coefficient W 11 × (Ce ratio - base Ce ratio) + coefficient W 12 ×(Dy ratio - standard Dy ratio) (Equation 1), Goal H cJ =Reference H cJ + coefficient W 21 × (Ce ratio - base Ce ratio) + coefficient W 22 ×(Dy ratio - standard Dy ratio) (Formula 2) Here, the reference Ce ratio and reference Dy ratio are the Ce ratio and Dy ratio of the RTB-type sintered magnet selected as the reference magnet.

[0042] As will be explained in detail in the examples described later, the present invention relates to a specific RTB-type sintered magnet, B r and H cJ This is based on the discovery that each of these can be approximated very well by a linear combination of the Ce ratio and the Dy ratio. Such an approximation does not hold for typical RTB sintered magnets. The reason the approximation does not hold is that in typical RTB sintered magnets, B r and H cJ This is because each of these properties does not depend linearly on the Ce ratio. It is presumed that this is because the location of Ce contained in RTB-type sintered magnets is not necessarily limited to locations that contribute to changes in magnetic properties, and therefore the magnetic properties do not show a linear change depending on the Ce ratio.

[0043] In the above formula, criterion B r and standard H cJ As mentioned above, B is measured from a single RTB-type sintered magnet. r and H cJThis is the case. We will refer to such a standard RTB-type sintered magnet as the "reference magnet." The above-mentioned three RTB-type sintered magnets include, in addition to the "reference magnet," a first RTB-type sintered magnet and a second RTB-type sintered magnet, each having different Ce and Dy ratios. For simplicity, here we will refer to the first RTB-type sintered magnet as "reference magnet 1" and the second RTB-type sintered magnet as "reference magnet 2." Reference magnet 1 does not need to have the magnetic properties indicated by the reference symbol "Ref_1" in Figure 2. Similarly, reference magnet 2 does not need to have the magnetic properties indicated by the reference symbol "Ref_2" in Figure 2.

[0044] From reference magnet 1, B of reference magnet 1 r The Ce ratio and Dy ratio are obtained by measurement. Similarly, from reference magnet 2, the B of reference magnet 2 is obtained. r The Ce ratio and Dy ratio are obtained by measurement from the reference magnet. r , criterion H cJ The standard Ce ratio and standard Dy ratio are obtained by measurement.

[0045] In this embodiment, the B of the reference magnet 1 r The measured value is the target B on the left side of Equation 1. r Substitute the values ​​into the equation, and then substitute the measured values ​​of the Ce ratio and Dy ratio into the Ce ratio and Dy ratio on the right-hand side of Equation 1. As a result, the unknown coefficient W 11 and coefficient W 12 An equation containing this is obtained. Similarly, B of reference magnet 2 r The measured value is the target B on the left side of Equation 1. r Substituting the measured values ​​of the Ce ratio and Dy ratio into the Ce ratio and Dy ratio on the right-hand side of Equation 1, the unknown coefficient W 11 and coefficient W 12 Another equation containing the coefficient W is obtained. By solving these two simultaneous equations, the coefficient W is obtained. 11 and coefficient W 12 This can be determined. When the number of reference magnets being measured is 3 or more, the number of equations becomes excessive, so the coefficient W 11 and coefficient W 12The value is calculated as an approximate estimate using methods such as the least squares method.

[0046] Also, the H of reference magnet 1 cJ The measured value of the target H on the left side of Equation 2 cJ Substituting the measured values ​​of the Ce ratio and Dy ratio into the Ce ratio and Dy on the right-hand side of Equation 2, we obtain the unknown coefficient W. 21 and coefficient W 22 An equation containing the following is obtained. Similarly, the H of reference magnet 2 cJ The measured value of the target H on the left side of Equation 2 cJ Substituting the measured values ​​of the Ce ratio and Dy ratio into the Ce ratio and Dy on the right-hand side of Equation 2, we obtain the unknown coefficient W. 21 and coefficient W 22 Another equation containing the coefficient W is obtained. By solving these two simultaneous equations, the coefficient W is obtained. 21 and coefficient W 22 This can be determined. When the number of reference magnets being measured is 3 or more, the number of equations becomes excessive, so the coefficient W 21 and coefficient W 22 The value of is also calculated as an approximate estimate using methods such as the least squares method.

[0047] In embodiments of this disclosure, based on the coefficients determined by Equations 1 and 2 above, target B r and target H cJ Step S3 is performed to determine the Ce ratio and Dy ratio to obtain the desired result.

[0048] Next, refer to Figure 4.

[0049] The process shown in Figure 4 includes a step S10 for preparing an R1-TB sintered magnet material, a step S20 for preparing an R2-M diffusion source, and a diffusion step S30.

[0050] In the R1-TB sintered magnet material, R1 is a rare earth element containing at least one of Nd and Pr and at least one of Ce and Dy, and T is Fe or Fe and Co. In the R2-M diffusion source, R2 is a rare earth element containing at least one of Nd and Pr, and M is at least one selected from the group consisting of Cu, Ga, Fe, Co, Ni, and Al. In the diffusion step S30, the R2-M diffusion source is brought into contact with the surface of the R1-TB sintered magnet material and heat treatment is performed. This heat treatment is carried out in a vacuum or inert gas atmosphere at a temperature of 700°C to 1100°C to diffuse R2 and M into the interior of the R1-TB sintered magnet material. In this disclosure, the RTB sintered magnet before and during the diffusion step is referred to as the "RTB sintered magnet material," and the RTB sintered magnet after the diffusion step is simply referred to as the "RTB sintered magnet." Each of these steps will be described in more detail below.

[0051] (Process for preparing R1-TB sintered magnet material) In this embodiment, an R1-TB sintered magnet material containing Ce and Dy in the Ce ratio and Dy ratio determined by the method described above is prepared (R1 is a rare earth element and contains at least one of Nd and Pr and at least one of Ce and Dy, and T is Fe or Fe and Co).

[0052] First, we will explain the preferred composition range for R1-TB sintered magnet materials.

[0053] R1 contains Ce and / or Dy. The Ce content in R1 is in the range of 0 mass% to 25 mass%, and the Dy content in R1 is in the range of 0 mass% to 10 mass%. The specific content is determined by the Ce ratio and Dy ratio that satisfy Equations 1 and 2.

[0054] In one preferred embodiment, the R1, oxygen content, carbon content, etc., contained in the R1-TB sintered magnet material are adjusted to satisfy the relationship 25.8 mass% ≤ ([Nd] + [Pr] + [Ce] + [Dy] + [Tb] - (9 × [O] + 12 × [C]) ≤ 27.3 mass% and the relationship 0.08 mass% ≤ [O] ≤ 0.30 mass%. Preferably, an R1-TB sintered magnet material is prepared that satisfies the relationship 0.05 mass% ≤ [C] ≤ 0.18 mass%. By performing the diffusion process described later on such an R1-TB sintered magnet material, it becomes possible to appropriately promote the diffusion of R2 and M inside the R1-TB magnet material.

[0055] The R1-TB sintered magnet material prepared in this process has, for example, the following composition. R1: 26.6 mass% or more and 31.5 mass% or less (R1 is a rare earth element, containing at least one of Nd and Pr, and at least one of Ce and Dy). B: 0.8 mass% to 1.0 mass%, preferably 0.88 mass% to 0.97 mass% of the total R1-TB sintered magnet material. M: 0 mass% to 1.0 mass% (M is at least one element selected from the group consisting of Ga, Cu, Zn, and Si), M1: 0 mass% to 2.0 mass% (M1 is at least one element selected from the group consisting of Al, Ti, V, Cr, Mn, Ni, Zr, Nb, Mo, Ag, In, Sn, Hf, Ta, W, Pb, and Bi) The remainder consists of T (where T is Fe or Fe and Co) and unavoidable impurities. Furthermore, the Nd content in R1 is preferably 50 mass% or more.

[0056] Next, we will explain the preparation method for R1-TB type sintered magnet material.

[0057] First, an alloy for RTB-type sintered magnets is prepared, and then this alloy is coarsely ground, for example, by a hydrogen pulverization method.

[0058] Examples of methods for manufacturing alloys for RTB-type sintered magnets are provided. Alloy ingots can be obtained by an ingot casting method, in which a metal or alloy pre-adjusted to the above-mentioned composition is melted and solidified in a mold. Alternatively, the alloy may be produced by a strip casting method, in which molten metal or alloy pre-adjusted to the above-mentioned composition is rapidly cooled by contacting it with a single roll, double roll, rotating disk, or rotating cylindrical mold, etc., to produce a rapidly solidified alloy. Flake-shaped alloys may also be produced by other rapid cooling methods, such as centrifugal casting.

[0059] In the embodiments of this disclosure, alloys manufactured by either the ingot method or the quenching method can be used, but it is preferable to use alloys manufactured by the quenching method, such as the strip casting method. The thickness of alloys produced by the quenching method is usually in the range of 0.03 mm to 1 mm and is in flake shape. By hydrogen pulverizing the obtained alloy, the size of the hydrogen pulverized powder (coarse pulverized powder) can be made, for example, 1.0 mm or less. The coarse pulverized powder thus obtained is then pulverized with a jet mill.

[0060] Jet milling is performed in an inert atmosphere such as nitrogen. Alternatively, the grinding may be carried out in a jet mill under a humidified atmosphere.

[0061] The fine powder used to produce the R1-TB sintered magnet material may be made from a single raw material alloy (single raw material alloy) or by a method of mixing two or more raw material alloys (blending method), provided that the above conditions are met.

[0062] In a preferred embodiment, a powder molded body is produced from the above-mentioned fine powder by pressing in a magnetic field, and then this powder molded body is sintered. In pressing in a magnetic field, it is preferable to form the powder molded body by pressing in an inert gas atmosphere or by wet pressing from the viewpoint of suppressing oxidation. In particular, with wet pressing, the surface of the particles constituting the powder molded body is coated with a dispersant such as an oil, and contact with oxygen and water vapor in the atmosphere is suppressed. Therefore, oxidation of the particles by the atmosphere before, during, or after the pressing process can be prevented or suppressed. For this reason, it is easy to control the oxygen content within a predetermined range. When performing wet pressing in a magnetic field, a slurry is prepared by mixing fine powder with a dispersion medium, and it is supplied to the cavity of the mold of the wet pressing apparatus and press-molded in a magnetic field.

[0063] Next, the molded body is sintered to obtain an R1-TB sintered magnet material. The molded body is sintered at a temperature in the range of 950°C to 1150°C. To prevent oxidation due to sintering, residual gases in the atmosphere may be replaced with inert gases such as helium or argon. The obtained sintered body (R1-TB sintered magnet material) may be subjected to heat treatment. Known conditions can be used for heat treatment conditions such as heat treatment temperature and heat treatment time.

[0064] (Process for preparing R2-M alloys) First, the composition of the R2-M alloy will be described. In the R2-M alloy, R2 is a rare earth element and must contain at least one of Nd and Pr, and M is at least one selected from the group consisting of Cu, Ga, Fe, Co, Ni, and Al. Preferably, R2 is 65 mass% to 97 mass% of the total R2-M alloy, and M is 3 mass% to 35 mass% of the total R2-M alloy. More preferably, R2 is 85 mass% to 95 mass% of the total R2-M alloy, and M is 5 mass% to 15 mass% of the total R2-M alloy. cJThis can be obtained. The content of Tb and Dy in R2 is preferably 3 mass% to 24 mass% of the total R2-M alloy. Also, the content of Pr in R2 is preferably 65 mass% to 86 mass% of the total R2-M alloy. Furthermore, M preferably always contains at least one of Ga and Cu. Higher H cJ This can be obtained. Preferably, the Pr content of the R2-M alloy is 50 mass% or more of the total R2, and more preferably, R2 consists only of Pr and Tb. The presence of Pr facilitates diffusion in the grain boundary phase, making it possible to diffuse Tb more efficiently and obtain higher H cJ You can obtain this.

[0065] The shape and size of R2-M alloys are not particularly limited and are arbitrary. R2-M alloys can take the form of films, foils, powders, blocks, particles, etc.

[0066] Next, we will explain the method for producing R2-M alloys.

[0067] R2-M alloys can be prepared using raw material alloy manufacturing methods employed in general RTB sintered magnet manufacturing methods, such as die casting, strip casting, single-roll ultra-rapid cooling (melt spinning), and atomization. Alternatively, the R2-M alloy may be obtained by grinding the alloy using known grinding methods such as a pin mill.

[0068] (Diffusion process) The R1-TB sintered magnet material and the R2-M alloy prepared by the method described above are heated in a vacuum or inert gas atmosphere at a temperature of 700°C to 1100°C to perform a diffusion process in which R2 and M are diffused into the interior of the R1-TB sintered magnet material. As a result, a liquid phase containing R2 and M is generated from the R2-M alloy, and this liquid phase is diffused into the interior of the sintered body from the surface via the grain boundaries in the R1-TB sintered magnet material. At this time, it is preferable to increase the content of heavy rare earth element RH (preferably Tb) contained in the R1-TB sintered magnet material in an extremely small range of 0.05 mass% to 0.30 mass%. This suppresses the consumption of heavy rare earth element RH while providing an extremely high H cJ An improvement effect can be obtained. Various conditions such as the amount of R2-M alloy, the heating temperature during processing, the particle size (if the R2-M alloy is particulate), and the processing time can be adjusted to increase the RH content in the R1-TB sintered magnet material by 0.05 mass% to 0.30 mass%. Among these, the amount of heavy rare earth element RH introduced (increase) can be controlled relatively easily by adjusting the amount of R2-M alloy and the heating temperature during processing.

[0069] In this specification, for example, "increasing the Tb content by 0.05 mass% or more and 0.30 mass% or less" means that the mass% value of the content increases by 0.05 or more and 0.30 or less. For example, if the Tb content of the R1-TB sintered magnet material before the diffusion process was 0.50 mass% and the Tb content of the RTB sintered magnet after the diffusion process was 0.60 mass%, then the diffusion process increased the Tb content by 0.10 mass%. Furthermore, whether the content of at least one of Tb and Dy (RH content) has increased by 0.05 mass% to 0.30 mass% can be calculated by measuring the RH content of the R1-TB sintered magnet material before the diffusion process and the RTB sintered magnet (total) after the diffusion process, and determining how much the RH content increased before and after diffusion. In addition, if there is a concentrated area of ​​the R2-M alloy on the surface of the RTB sintered magnet after diffusion, it is desirable to remove the concentrated area by cutting or other means before measuring the RH content.

[0070] If the heating temperature is below 700°C, for example, the amount of liquid phase containing Tb, Pr, and M is too small, resulting in high H₂ cJ It is not possible to obtain this. On the other hand, if the temperature exceeds 1100℃, H cJ The temperature may decrease. Preferably, it is between 850°C and 980°C. cJ You can obtain this.

[0071] The diffusion treatment process may be carried out by placing an R2-M alloy of any shape on the surface of the R1-TB sintered magnet material and using a known heat treatment apparatus. For example, the surface of the R1-TB sintered magnet material can be covered with a powder layer of the R2-M alloy and then heat treated. Alternatively, a slurry in which the R2-M alloy is dispersed in a dispersion medium may be applied to the surface of the R1-TB sintered magnet material, and then the dispersion medium may be evaporated to bring the R2-M alloy into contact with the R1-TB sintered magnet material. Examples of dispersion mediums include alcohols (ethanol, etc.), aldehydes, and ketones. Furthermore, heavy rare earth elements RH may be introduced not only from the R2-M alloy, but also by placing fluorides, oxides, acid fluorides, etc. of heavy rare earth elements RH on the RTB sintered magnet surface together with the R2-M alloy. In other words, as long as the light rare earth elements RL and M can be diffused simultaneously with the heavy rare earth elements RH, the method is not particularly limited. Examples of fluorides, oxides, and acid fluorides of heavy rare earth elements RH include TbF3, DyF3, Tb2O3, Dy2O3, Tb4OF, and Dy4OF.

[0072] (Heat treatment process) The RTB-type sintered magnet after the diffusion treatment process may be subjected to heat treatment in a vacuum or inert gas atmosphere at a temperature of 400°C to 750°C, and at a temperature lower than that used in the diffusion treatment. By performing heat treatment, high H cJ You can obtain this. [Examples]

[0073] The present invention will be described in more detail by reference to examples, but the present invention is not limited thereto.

[0074] Experimental Example 1 [Process for preparing R1-T-B type sintered magnet material] Each element was weighed to obtain the composition of the R1-TB sintered magnet material shown in Table 1, No. A to N, and raw alloys were prepared by the strip casting method. Each of the obtained alloys was coarsely ground by hydrogen pulverization to obtain coarse powder. Next, B-29 was added as a lubricant at a concentration of 0.2 mass% per 100 mass% of the coarse powder, mixed, and then ground in a nitrogen stream using an air-jet mill to obtain a particle size D 50 A finely ground powder with a particle size of 3.3 μm was obtained.

[0075] The obtained finely ground powder was mixed with a dispersion medium to prepare a slurry. The slurry was molded in a magnetic field to obtain a molded body. A so-called right-angle magnetic field molding apparatus (or transverse magnetic field molding apparatus) was used as the molding apparatus, in which the direction of magnetic field application and the direction of pressure are perpendicular.

[0076] The obtained molded body was sintered in a vacuum at a temperature of 1000°C or higher and 1100°C or lower (a temperature was selected to ensure sufficient densification by sintering), and then rapidly cooled to obtain an R1-TB sintered magnet material. The density of the obtained R1-TB sintered magnet material was 7.5 Mg / m³. 3 The above was the result. The composition of the obtained RTB-based sintered magnet material is shown in Table 1. The content of Nd, Pr, Ce, Dy, B, Co, Al, Cu, Ga, and Tb was measured using inductively coupled plasma atomic emission spectroscopy (ICP-OES), and the content of O, N, and C was measured using a gas analyzer by gas fusion-infrared absorption spectroscopy.

[0077] [Table 1]

[0078] [Material sample evaluation] For R1-TB sintered magnet materials No. A to N, heat treatment was performed at 800°C for 2 hours in a reduced-pressure argon environment controlled at 50 Pa, followed by cooling to room temperature. Then, heat treatment was performed again at 480°C to 520°C for 1 hour in a reduced-pressure argon environment controlled at 50 Pa, followed by cooling to room temperature. After these processes, each sample was machined using a surface grinder to obtain cubic samples measuring 7.0 mm × 7.0 mm × 7.0 mm.

[0079] The obtained sample was analyzed using a BH tracer to determine the residual magnetic flux density B r and coercivity H cJ The following measurements were taken. The obtained experimental values ​​and the Ce ratio ([Ce] / ([Nd]+[Pr]+[Ce]+[Dy]+[Tb])) and Dy ratio ([Dy] / ([Nd]+[Pr]+[Ce]+[Dy]+[Tb])) in R1 of the R1-TB sintered magnet material are shown in Table 2.

[0080] Here, from the experimental values ​​of No. A and B, where the Dy ratio is equal and the Ce ratio is different, we can see that B per Ce ratio is different for No. A. r and H cJ The coefficient W 11 , W 21 We can find W 11 -0.37T, W 21 This becomes -897kA / m. Similarly, from the experimental values ​​of No. A and C, which have the same Ce ratio but different Dy ratios, the B per Dy ratio for No. A is r and H cJ The coefficient W 12 , W 22 To find W 12 -0.80T, W 22 This becomes 4614 kA / m. Here, the standard B of No. A r and standard H cJ B per Ce and Dy ratio obtained from the standard Ce and Dy ratios r and H cJ The coefficient W 11 , W 21、 W 12 , W 22 Target B calculated using r and target H cJ The values ​​are shown in Table 2. The calculation formula in this case is as follows. Goal B r =1.492-0.37×(Ce ratio-standard Ce ratio)-0.80×(Dy ratio-standard Dy ratio) Goal H cJ =1098-897×(Ce ratio-standard Ce ratio)+4614×(Dy ratio-standard Dy ratio)

[0081] [Table 2]

[0082] [Process for preparing R2-M alloys] Each element was weighed to obtain the alloy composition shown in Table 3, No. a., and these raw materials were melted to obtain alloy powder by disk atomization or ultra-rapid quenching. The composition of the obtained alloy powder is shown in Table 3. Note that each component in Table 3 was measured using high-frequency inductively coupled plasma atomic emission spectroscopy.

[0083] [Table 3]

[0084] [R2-M alloy dispersion process] The R1-TB sintered magnet materials No. A to J in Table 1 were cut and machined to form cubes of 7.2 mm × 7.2 mm × 7.2 mm. Next, 3 mass% of R2-M alloy (No. a) was scattered over 100 mass% of the aforementioned R1-TB sintered magnet materials No. A to N.

[0085] [Heat treatment process] The R1-TB sintered magnet material heated in the diffusion step was subjected to heat treatment at 900°C for 10 hours in a vacuum argon chamber controlled at 50 Pa, and then cooled to room temperature. This yielded an RTB sintered magnet that had undergone the first heat treatment. Furthermore, the heat-treated RTB sintered magnet was subjected to heat treatment at 480°C to 520°C for 1 hour in a vacuum argon chamber controlled at 50 Pa, and then cooled to room temperature to produce R1-TB sintered magnets (No. 1 to 14). The compositions of the obtained RTB sintered magnets, measured by high-frequency inductively coupled plasma atomic emission spectroscopy, are shown in Table 4.

[0086] [Table 4]

[0087] [Sample Evaluation] Each heat-treated sample was machined using a surface grinder to obtain a cubic sample measuring 7.0 mm × 7.0 mm × 7.0 mm. The residual magnetic flux density B of the obtained samples was determined using a BH tracer. r and coercivity H cJ We measured it.

[0088] Table 5 shows the experimental values ​​obtained and the Ce ratio ([Ce] / ([Nd]+[Pr]+[Ce]+[Dy]+[Tb])) and Dy ratio ([Dy] / ([Nd]+[Pr]+[Ce]+[Dy]+[Tb])) in R of the RTB-type sintered magnet material.

[0089] Furthermore, from the experimental values ​​of No. 1 and No. 2, where the Dy ratio is the same but the Ce ratio is different, the B per Ce ratio for No. 1 r and H cJ The coefficient W 11 , W 21 We can find W 11 -0.31T, W 21 This becomes -1178 kA / m. Similarly, from the experimental values ​​of No. 1 and 3, where the Ce ratio is the same and the Dy ratio is different, the coefficients W of Br and HcJ per Dy ratio for No. 1 are 12 , W 22 To find W 12 -0.77T, W 22 This becomes 5276 kA / m. Here, the standard B of No. 1 r and standard H cJ B per Ce and Dy ratio obtained from the standard Ce and Dy ratios r and H cJ The coefficient W 11 , W 21 , W 12 , W 22 Target B calculated using r and target H cJ The values ​​are shown in Table 5. The calculation formula in this case is as follows. Goal B r =1.454-0.31×(Ce ratio-standard Ce ratio)-0.77×(Dy ratio-standard Dy ratio) Goal H cJ=2061-1178×(Ce ratio-standard Ce ratio)+5276×(Dy ratio-standard Dy ratio)

[0090] [Table 5]

[0091] Experimental Example 2 For the R1-TB sintered magnet material prepared in Example 1, each element was weighed to obtain the alloy composition shown in No. b of Table 6. These raw materials were melted, and the newly obtained R2-M alloy was prepared by the disc atomization method or ultra-rapid cooling method. The R2-M alloy was then scattered and heat-treated in the same procedure as in Example 1 to produce RTB sintered magnets (No. 15-28). The composition of the obtained R2-M alloy powder is shown in Table 6, and the composition of the obtained RTB sintered magnets is shown in Table 7.

[0092] [Table 6]

[0093] [Table 7]

[0094] [Sample Evaluation] Table 8 shows the experimental values ​​obtained by evaluation in the same manner as in Example 1, as well as the Ce ratio and Dy ratio in R of the RTB-type sintered magnet material.

[0095] Furthermore, from the experimental values ​​of No. 15 and 16, where the Dy ratio is the same but the Ce ratio is different, the B per Ce ratio for No. 15 r and H cJ The coefficient W 11 , W 21 To find W 11 -0.30T, W 21 This becomes -744kA / m, and similarly, from the experimental values ​​of No. 15 and 17, which have the same Ce ratio but different Dy ratios, the B per Dy ratio for No. 15 r and H cJ The coefficient W12 , W 22 To find W 12 -0.71T, W 22 This becomes 4492 kA / m. Here, the standard B of No. 15 r and standard H cJ B per Ce and Dy ratio obtained from the standard Ce and Dy ratios r and H cJ The coefficient W 11 , W 21 , W 12 , W 22 Target B calculated using r and target H cJ The values ​​are shown in Table 8. The calculation formula in this case is as follows: Goal B r =1.438-0.30×(Ce ratio-standard Ce ratio)-0.71×(Dy ratio-standard Dy ratio) Goal H cJ =1944-744×(Ce ratio-standard Ce ratio)+4492×(Dy ratio-standard Dy ratio)

[0096] [Table 8]

[0097] Experimental Example 3 For the R1-TB sintered magnet material prepared in Example 1, each element was weighed to obtain the alloy composition shown in No. c of Table 9. These raw materials were melted, and the newly obtained R2-M alloy was prepared by the disc atomization method or ultra-rapid cooling method. The R2-M alloy was then scattered and heat-treated in the same procedure as in Example 1 to produce RTB sintered magnets (No. 29-42). The composition of the obtained R2-M alloy powder is shown in Table 9, and the composition of the obtained RTB sintered magnets is shown in Table 10.

[0098] [Table 9]

[0099] [Table 10]

[0100] [Sample Evaluation] Table 11 shows the experimental values ​​obtained by evaluation in the same manner as in Example 1, as well as the Ce ratio and Dy ratio in R of the RTB-type sintered magnet material.

[0101] Furthermore, from the experimental values ​​of No. 29 and 30, where the Dy ratio is the same but the Ce ratio is different, the B per Ce ratio for No. 29 r and H cJ The coefficient W 11 , W 21 To find W 11 -0.26T, W 21 This becomes -1203 kA / m. Similarly, from the experimental values ​​of No. 29 and 31, which have the same Ce ratio but different Dy ratios, the B per Dy ratio for No. 29 is r and H cJ The coefficient W 12 , W 22 To find W 12 -0.63T, W 22 This becomes 4604 kA / m. Here, the standard B of No. 29 r and standard H cJ B per Ce and Dy ratio obtained from the standard Ce and Dy ratios r and H cJ The coefficient W 11 , W 21 , W 12 , W 22 Target B calculated using r and target H cJ The values ​​are shown in Table 11. The calculation formula in this case is as follows: Goal B r =1.438-0.26×(Ce ratio-standard Ce ratio)-0.63×(Dy ratio-standard Dy ratio) Goal H cJ =1931-1203×(Ce ratio-standard Ce ratio)+4604×(Dy ratio-standard Dy ratio)

[0102] [Table 11]

[0103] Experimental Example 4 For the R1-TB sintered magnet material prepared in Example 1, each element was weighed to obtain the alloy composition shown in No. d of Table 12. These raw materials were melted, and the newly obtained R2-M alloy was prepared by the disc atomization method or ultra-rapid cooling method. The R2-M alloy was then scattered and heat-treated in the same procedure as in Example 1 to produce RTB sintered magnets (No. 43-56). The composition of the obtained R2-M alloy powder is shown in Table 12, and the composition of the obtained RTB sintered magnets is shown in Table 13.

[0104] [Table 12]

[0105] [Table 13]

[0106] [Sample Evaluation] Table 14 shows the experimental values ​​obtained by evaluation in the same manner as in Example 1, as well as the Ce ratio and Dy ratio in R of the RTB-type sintered magnet material.

[0107] Furthermore, from the experimental values ​​of No. 43 and 44, where the Dy ratio is the same but the Ce ratio is different, the B per Ce ratio for No. 43 r and H cJ The coefficient W 11 , W 21 To find W 11 -0.25T, W 21 This becomes -1373kA / m. Similarly, from the experimental values ​​of No. 43 and 45, which have the same Ce ratio but different Dy ratios, the B per Dy ratio for No. 43 is r and H cJ The coefficient W 12 , W 22 To find W 12 -0.68T, W 22 This becomes 4012 kA / m. Here, standard B of No. 43 r and standard H cJB per Ce and Dy ratio obtained from the standard Ce and Dy ratios r and H cJ The coefficient W 11 , W 21 , W 12 , W 22 Target B calculated using r and target H cJ The values ​​are shown in Table 14. The calculation formula in this case is as follows: Goal B r =1.436-0.25×(Ce ratio-standard Ce ratio)-0.68×(Dy ratio-standard Dy ratio) Goal H cJ =1628-1373×(Ce ratio-standard Ce ratio)+4012×(Dy ratio-standard Dy ratio)

[0108] [Table 14]

[0109] Experimental Example 5 For the R1-TB sintered magnet material prepared in Example 1, each element was weighed to obtain the alloy composition shown in Table 15, No. e. These raw materials were melted, and the newly obtained R2-M alloy was prepared by the disc atomization method or ultra-rapid cooling method. The R2-M alloy was then scattered and heat-treated in the same procedure as in Example 1 to produce RTB sintered magnets (No. 57-70). The composition of the obtained R2-M alloy powder is shown in Table 15, and the composition of the obtained RTB sintered magnets is shown in Table 16.

[0110] [Table 15]

[0111] [Table 16]

[0112] [Sample Evaluation] Table 17 shows the experimental values ​​obtained by evaluation in the same manner as in Example 1, as well as the Ce ratio and Dy ratio in R of the RTB-type sintered magnet material.

[0113] Furthermore, from the experimental values ​​of No. 57 and 58, where the Dy ratio is the same but the Ce ratio is different, the B per Ce ratio for No. 57 r and H cJ The coefficient W 11 , W 21 To find W 11 -0.32T, W 21 This becomes -544kA / m. Similarly, from the experimental values ​​of No. 57 and 59, which have the same Ce ratio but different Dy ratios, the B per Dy ratio for No. 57 is r and H cJ The coefficient W 12 , W 22 To find W 12 -0.67T, W 22 This becomes 4523 kA / m. Here, the standard B of No. 57 r and standard H cJ B per Ce and Dy ratio obtained from the standard Ce and Dy ratios r and H cJ The coefficient W 11 , W 21 , W 12 , W 22 Target B calculated using r and target H cJ The values ​​are shown in Table 17. The calculation formula in this case is as follows: Goal B r =1.438-0.32×(Ce ratio-standard Ce ratio)-0.67×(Dy ratio-standard Dy ratio) Goal H cJ =1465-544×(Ce ratio-standard Ce ratio)+4523×(Dy ratio-standard Dy ratio)

[0114] [Table 17]

[0115] Table 18 shows B in Examples 1-5. r and H cJThe mean and standard deviation of the difference between the experimental value and the target value ((experimental value) - (target value)) are shown. The standard deviation was calculated in each of Examples 1 to 5 using the following formulas. Standard deviation = ((Difference between experimental value and target value) - (Mean of experimental value and target value)) / (Number of samples)

[0116] A smaller standard deviation value indicates less variation in the difference between experimental and target values. Considering the accuracy of the measurement, B r and H cJ The standard deviation is B r 0.005T, H cJ If the current is 20 kA / m or less, the magnetic properties are determined by the Ce and Dy ratio and the coefficient W. 11 ~W 22 By using this method, it can be determined that the calculations are accurate, meaning that it is possible to manufacture sintered magnets with arbitrary magnetic properties simply by adjusting the Ce and Dy ratio.

[0117] Table 18 shows B r The standard deviation of is 0.005T or less and H cJ For samples where the standard deviation is 20 kA / m or less, we have determined that the prediction calculation was successful and have marked it with "○". For all other samples, we have determined that the prediction calculation was not successful and have marked it with "×".

[0118] In the R1-T-B sintered magnet material of Example 1, H cJ The standard deviation is as high as 40 kA / m, which is significantly different from the calculated value. In contrast, in the RT-B sintered magnets of Examples 1 to 5, all of them were B r and H cJ We confirmed that the standard deviation is small and that it can be predicted by calculation.

[0119] [Table 18]

[0120] Thus, only in RT-B sintered magnets after diffusion, the magnetic properties are determined by the Ce ratio, Dy ratio, and coefficient W. 11 ~W 22The reason why accurate calculations can be performed using this method is thought to be as follows: Specifically, by scattering the R2-M alloy and heat-treating it, the influence of Ce contained in the grain boundary phase of the R1-T-B sintered magnet material on the magnetic properties can be suppressed. Ce is known to be an element that does not readily form main phase particles compared to Dy. In an R1-T-B sintered magnet material containing Ce and Dy, it is expected that Dy preferentially forms the main phase particles, and some of the Ce is left behind in the grain boundary phase. The magnetic properties are a combination of the influence of Ce and Dy contained in the main phase, as well as the influence of Ce contained in the grain boundary phase.

[0121] Furthermore, in multiple R1-T-B sintered magnet materials with different Ce and Dy ratios, the amount of Ce contained in the grain boundary phase of each R1-T-B sintered magnet material differs, so the degree to which the Ce contained in the main phase and grain boundary phase influences the overall magnetic properties changes. Therefore, H in Table 2 cJ As shown, there is a large difference between most experimental values ​​and target values. Also, as shown in Table 18, H cJ The standard deviation is a large value of 40 kA / m, indicating significant variability and that the prediction calculation is not accurate.

[0122] On the other hand, in RT-B sintered magnets that have been heat-treated with scattered R2-M alloy, the elements of the R2-M alloy diffuse into the grain boundary phase, which is thought to reduce the concentration of Ce in the grain boundary phase. Since the influence of Ce in the grain boundary phase on the magnetic properties is suppressed, only the influence of Ce and Dy contained in the main phase particles contributes to the magnetic properties. As a result, it is thought that the magnetic properties after diffusion could be accurately calculated. In fact, the difference between the experimental values ​​and the target values ​​is small in each of Tables 5, 8, 11, 14, and 17. The standard deviation values ​​in Table 18 are all below the level of variation of the measurement accuracy, indicating that the magnetic properties can be accurately predicted and calculated.

[0123] Figures 5, 6, 7, 8, 9, and 10 are graphs showing the magnetic properties of Table 2 (Comparative Example), Table 5 (Example 1), Table 8 (Example 2), Table 11 (Example 3), Table 14 (Example 4), and Table 17 (Example 5), respectively. As shown in Figure 5, in the R1-TB sintered magnet material before diffusion, the magnetic properties of No. E deviate significantly from the line connecting the magnetic properties of No. A and No. B. However, as shown in Figures 6 to 9, a linear approximation as shown in Figure 2 holds true in the examples. [Explanation of symbols]

[0124] 12...main phase, 14...grain boundary phase, 14a...two-grain grain boundary phase, 14b...grain boundary triple point

Claims

1. The contents of Ce, Nd, Pr, Dy, and Tb are denoted as [Ce], [Nd], [Pr], [Dy], and [Tb], respectively. Let ([Ce] / ([Nd]+[Pr]+[Ce]+[Dy]+[Tb])) be the Ce ratio. ([Dy] / ([Nd]+[Pr]+[Ce]+[Dy]+[Tb])) is used as the ratio of Dy, Prepare at least three R-T-B sintered magnets with different Ce ratios and Dy ratios, and then determine the B of each R-T-B sintered magnet. ｒ and H ｃＪ The process of measuring, B of each R-T-B system sintered magnet ｒ and H ｃＪ The measured values ​​and the coefficients W shown in Equations 1 and 2 below are used for the Ce ratio and Dy ratio. １１ , W １２ , W ２１ , W ２２ The process of determining, Target B ｒ = Reference B ｒ + Coefficient W １１ × (Ce ratio - Reference Ce ratio) + Coefficient W １２ × (Dy ratio - Reference Dy ratio) (Equation 1) Goal H ｃＪ = Standard H ｃＪ + coefficient W ２１ × (Ce ratio - base Ce ratio) + coefficient W ２２ × (Dy ratio - standard Dy ratio) (Formula 2) Based on the coefficients determined by the above equations 1 and 2, the target B of the R-T-B sintered magnet to be manufactured is ｒ and target H ｃＪ A step of determining the Ce ratio and Dy ratio to obtain, The process involves preparing an R1-T-B sintered magnet material (where R1 is a rare earth element and includes at least one of Nd and Pr and at least one of Ce and Dy, and T is Fe or Fe and Co), The process involves preparing an R2-M diffusion source (where R2 is a rare earth element, and must contain at least one of Nd and Pr, but not Ce, and M is at least one selected from the group consisting of Cu, Ga, Fe, Co, Ni, and Al), A diffusion step involves bringing an R2-M diffusion source into contact with the surface of the R1-T-B sintered magnet material and performing a heat treatment. Includes, The R1-T-B sintered magnet material contains Ce and Dy in a Ce ratio and Dy ratio that yields the Ce ratio and Dy ratio of the R1-T-B sintered magnet to be produced. Criterion B mentioned above ｒ and standard H ｃＪ This refers to the B of one of the R-T-B sintered magnets among the at least three R-T-B sintered magnets. ｒ and H ｃＪ And, A method for manufacturing R-T-B sintered magnets, wherein the at least three R-T-B sintered magnets are obtained by subjecting an R1-T-B sintered magnet material to a diffusion process in which an R2-M diffusion source is brought into contact with the surface of the R1-T-B sintered magnet material and heat treatment is performed.

2. The method for manufacturing an R-T-B sintered magnet according to claim 1, wherein the Ce ratio and Dy ratio in the aforementioned R-T-B sintered magnet are, each, 0% or more and 30% or less.

3. The aforementioned at least three R-T-B sintered magnets are A method for manufacturing an R-T-B sintered magnet according to claim 1 or 2, comprising a first R-T-B sintered magnet and a second R-T-B sintered magnet having a Ce ratio of 2 mass% or more and a Dy ratio of 1 mass% or more compared to the aforementioned single R-T-B sintered magnet.

4. The aforementioned at least three R-T-B sintered magnets are A method for manufacturing an R-T-B sintered magnet according to claim 1 or 2, comprising a first R-T-B sintered magnet and a second R-T-B sintered magnet having a Ce ratio of 5 mass% or more and a Dy ratio of 3 mass% or more compared to the aforementioned R-T-B sintered magnet.

5. The content of elements other than rare earth elements in each of the three R-T-B sintered magnets is a common value. A method for manufacturing an R-T-B sintered magnet according to any one of claims 1 to 4, wherein in the step of preparing the R1-T-B sintered magnet material, the content of rare earth elements other than rare earth elements in the R1-T-B sintered magnet material is maintained at a predetermined value.

6. The contents of Ce, Nd, Pr, Dy, and Tb are denoted as [Ce], [Nd], [Pr], [Dy], and [Tb], respectively. Let ([Ce] / ([Nd]+[Pr]+[Ce]+[Dy]+[Tb])) be the Ce ratio. ([Dy] / ([Nd]+[Pr]+[Ce]+[Dy]+[Tb])) is used as the ratio of Dy, Prepare at least three R-T-B sintered magnets with different Ce ratios and Dy ratios, and then determine the B of each R-T-B sintered magnet. ｒ and H ｃＪ The process of measuring, B of each R-T-B system sintered magnet ｒ and H ｃＪ The measured values ​​and the coefficients W shown in Equations 1 and 2 below are used for the Ce ratio and Dy ratio. １１ , W １２ , W ２１ , W ２２ The process of determining, Goal B ｒ = Standard B ｒ + coefficient W １１ × (Ce ratio - base Ce ratio) + coefficient W １２ × (Dy ratio - standard Dy ratio) (Formula 1), Goal H ｃＪ = Standard H ｃＪ + coefficient W ２１ × (Ce ratio - base Ce ratio) + coefficient W ２２ × (Dy ratio - standard Dy ratio) (Formula 2) Based on the coefficients determined by the above equations 1 and 2, the target B of the R-T-B sintered magnet to be manufactured is ｒ and target H ｃＪ A step of determining the Ce ratio and Dy ratio to obtain, Includes, Criterion B mentioned above ｒ and standard H ｃＪ This refers to the B of one of the R-T-B sintered magnets among the at least three R-T-B sintered magnets. ｒ and H ｃＪ And, A method for determining the composition of an R-T-B sintered magnet, wherein the at least three R-T-B sintered magnets are obtained by subjecting a diffusion step to heat treatment by contacting an R2-M diffusion source (R2 is a rare earth element, always containing at least one of Nd and Pr, but not Ce, and M is at least one selected from the group consisting of Cu, Ga, Fe, Co, Ni, and Al) to the surface of an R1-T-B sintered magnet material (R1 is a rare earth element, containing at least one of Nd and Pr, but not Ce, and M is at least one selected from the group consisting of Cu, Ga, Fe, Co, Ni, and Al).

7. The method for determining the composition of an R-T-B sintered magnet according to claim 6, wherein the Ce ratio and Dy ratio in the aforementioned R-T-B sintered magnet are, each, 0% or more and 30% or less.

8. The aforementioned at least three R-T-B sintered magnets are A method for determining the composition of an R-T-B sintered magnet according to claim 6 or 7, comprising a first R-T-B sintered magnet and a second R-T-B sintered magnet having a Ce ratio of 2 mass% or more and a Dy ratio of 1 mass% or more compared to the aforementioned single R-T-B sintered magnet.

9. The aforementioned at least three R-T-B sintered magnets are A method for determining the composition of an R-T-B sintered magnet according to claim 6 or 7, comprising a first R-T-B sintered magnet and a second R-T-B sintered magnet having a Ce ratio of 5 mass% or more and a Dy ratio of 3 mass% or more compared to the aforementioned single R-T-B sintered magnet.

10. The method for determining the composition of an R-T-B sintered magnet according to any one of claims 6 to 9, wherein the content of elements other than rare earth elements in each of the at least three R-T-B sintered magnets is a common value.

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