Rare earth magnet and method for manufacturing the same

Abstract

The present invention relates to a rare earth magnet and a method for manufacturing the same. The present disclosure is a rare earth magnet having a main phase and a grain boundary phase and a method for manufacturing the same. The overall composition of the rare earth magnet of the present disclosure is represented by the formula (R 1 (1‑x‑y) La x Ce y ) u (Fe (1‑z) Co z ) (100‑u‑w‑v) B w M 1 v (wherein R 1 is a specified rare earth element, M 1 is a specified element, and 0.05 ≤ x ≤ 0.25, 0 ≤ y / (x + y) ≤ 0.50, 13.5 ≤ u ≤ 20.0, 0 ≤ z ≤ 0.100, 5.0 ≤ w ≤ 10.0 and 0 ≤ v ≤ 2.00). The main phase has an R2Fe 14 B-type crystal structure, and the average particle diameter and volume fraction of the main phase are 1.0 to 20.0 μm and 80.0 to 90.0%. The main phase and the grain boundary phase satisfy (the proportion of La present in the grain boundary phase) / (the proportion of La present in the main phase) > 1.30.

Description

Technical Field

[0001] The present disclosure relates to a rare earth magnet and a method for manufacturing the same, and in particular to an R-Fe-B system rare earth magnet (wherein R is a rare earth element) and a method for manufacturing the same. Background Art

[0002] R-Fe-B rare earth magnets have R2Fe 14 The main phase of the B-type crystal structure. High residual magnetization is obtained due to this main phase.

[0003] Among R-Fe-B rare earth magnets, the most common one is Nd-Fe-B rare earth magnet (neodymium rare earth magnet) in which Nd is selected as R due to its excellent balance between performance and price. Therefore, Nd-Fe-B rare earth magnets are rapidly becoming popular, and it is also expected that the use of Nd will increase sharply in the future, and it is possible that the use of Nd will exceed the reserve in the future. Therefore, attempts have been made to replace part or all of Nd with light rare earth elements such as Ce, La, Y and Sc.

[0004] For example, Japanese Patent Application Laid-Open No. 2020-27933 discloses an R—Fe—B-based rare earth magnet in which a portion of Nd is replaced with La and Ce so that La and Ce have a predetermined molar ratio. Summary of the invention

[0005] In R-Fe-B rare earth magnets, when a part of Nd is replaced by a light rare earth element, the magnetic properties generally decrease. In the R-Fe-B rare earth magnet disclosed in Japanese Patent Laid-Open No. 2020-27933, La and Ce are selected as light rare earth elements and their molar ratio is within a specified range, thereby suppressing the decrease in coercive force at high temperature. On the other hand, the inventors have discovered the following problem: it is desirable to produce an R-Fe-B rare earth magnet that minimizes the decrease in residual magnetization at room temperature even when a part of Nd is replaced by a light rare earth element.

[0006] The present disclosure is made to solve the above-mentioned problems and aims to provide an R—Fe—B rare earth magnet in which the decrease of residual magnetization at room temperature is suppressed as much as possible even when a part of Nd is replaced by a light rare earth element, and a method for producing the same.

[0007] In order to achieve the above-mentioned purpose, the inventors have conducted intensive research and completed the rare earth magnet and the method for manufacturing the same disclosed in the present invention. The rare earth magnet and the method for manufacturing the same disclosed in the present invention include the following schemes.

[0008] <1> The rare earth magnet comprises a main phase and a grain boundary phase existing around the main phase, and the overall composition in terms of molar ratio is given by the formula (R 1 (1-x-y) La x Ce y ) u(Fe (1-z) Co z ) (100-u-w-v) B w M 1 v represents, where R 1 is one or more elements selected from Nd, Pr, Gd, Tb, Dy, and Ho, and M 1 is one or more elements selected from Ga, Al, Cu, Au, Ag, Zn, In, and Mn and inevitable impurity elements, and 0.05 ≤ x ≤ 0.25, 0 ≤ y / (x + y) ≤ 0.50, 13.5 ≤ u ≤ 20.0, 0 ≤ z ≤ 0.100, 5.0 ≤ w ≤ 10.0, and 0 ≤ v ≤ 2.00,

[0009] The above main phase has an R2Fe 14 B-type crystal structure, where R is a rare earth element,

[0010] The average particle size of the above main phase is 1.0 to 20.0 μm,

[0011] The volume fraction of the above main phase is 80.0 to 90.0%, and

[0012] Regarding the above main phase and the above grain boundary phase, (the proportion of La present in the above grain boundary phase) / (the proportion of La present in the above main phase) > 1.30 is satisfied.

[0013] <2>The rare earth magnet according to item <1>, wherein the above R 1 is one or more elements selected from Nd and Pr, and the above M 1 is one or more elements selected from Ga, Al, and Cu and inevitable impurity elements.

[0014] <3>The rare earth magnet according to item <1> or <2>, wherein the volume fraction of the above main phase is 80.0 to 86.6%.

[0015] <4>The rare earth magnet according to any one of items <1> to <3>, wherein, regarding the above main phase and the above grain boundary phase, (the proportion of La present in the above grain boundary phase) / (the proportion of La present in the above main phase) ≥ 1.56 is satisfied.

[0016] <5>The manufacturing method of a rare earth magnet, which is the manufacturing method of the rare earth magnet described in item <1>, includes:

[0017] Preparing a molten metal having a formula in molar ratio (R 1 (1-x-y) La x Ce y ) u (Fe(1-z) Co z ) (100-u-w-v) B w M 1 v represents the composition, where R 1 is one or more elements selected from Nd, Pr, Gd, Tb, Dy, and Ho, and M 1 is one or more elements selected from Ga, Al, Cu, Au, Ag, Zn, In, and Mn and inevitable impurity elements, and 0.05 ≤ x ≤ 0.25, 0 ≤ y / (x + y) ≤ 0.50, 13.5 ≤ u ≤ 20.0, 0 ≤ z ≤ 0.100, 5.0 ≤ w ≤ 10.0, and 0 ≤ v ≤ 2.00,

[0018] The above molten metal is cooled at a rate of 1 to 10 4 °C / second to obtain a magnetic alloy,

[0019] The above magnetic alloy is pulverized to obtain magnetic powder, and

[0020] The above magnetic powder is sintered under pressureless conditions to obtain a sintered body.

[0021] <6>According to the method for manufacturing a rare earth magnet described in item <5>, wherein the above magnetic powder is sintered under pressureless conditions at 900 to 1100°C

[0022] <7>According to the method for manufacturing a rare earth magnet described in item <5> or <6>, wherein the sintered body after the above pressureless sintering is cooled at a rate of 1°C / minute or less.

[0023] <8>According to the method for manufacturing a rare earth magnet described in any one of items <5> to <7>, wherein the above R 1 is one or more elements selected from Nd and Pr, and the above M 1 is one or more elements selected from Ga, Al, and Cu and inevitable impurity elements.

[0024] According to the present disclosure, by making the volume fraction of the main phase within a specified range, it is possible to preferentially distribute La in the main phase to the grain boundary phase, and the proportion of La present in the grain boundary phase can be increased compared to that in the main phase. Moreover, instead of La preferentially distributed from the main phase to the grain boundary phase, Nd or the like, such as R 1 in the grain boundary phase can enter the main phase, and La, which is the cause of the decrease in the residual magnetization, can be present in a larger amount in the grain boundary phase that has a small influence on the residual magnetization. As a result, according to the present disclosure, it is possible to provide an R-Fe-B-based rare earth magnet and a method for manufacturing the same that can strongly suppress the decrease in the residual magnetization at room temperature even when a part of Nd is replaced with a light rare earth element. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, where like reference numerals denote like elements, and wherein:

[0026] Figure 1 It is an explanatory diagram schematically showing the structure of the rare earth magnet of the present disclosure.

[0027] Figure 2 It is a coordinate diagram showing an example of predicting the residual magnetization from the overall composition (mixing ratio of raw materials) of rare earth elements.

[0028] Figure 3 It is a coordinate diagram showing the relationship between the measured residual magnetization and the predicted residual magnetization when the molar ratio of La to Ce, La:Ce, is 1.0.

[0029] Figure 4 It is an explanatory diagram schematically showing the cooling device used in the strip casting method.

[0030] Figure 5 It is a coordinate diagram showing the relationship between the volume fraction of the main phase, the measured residual magnetization, and the gain for the specimens of Example 2 and Comparative Examples 3 to 5.

[0031] Figure 6 It is a diagram showing the electron beam image and the results of surface analysis of La, Nd, and Fe for the specimen of Example 2.

[0032] Figure 7 It is a diagram schematically showing the structure of a conventional rare earth magnet. Detailed Embodiments

[0033] Hereinafter, embodiments of the rare earth magnet and its manufacturing method of the present disclosure will be described in detail. It should be noted that the embodiments shown below do not limit the rare earth magnet and its manufacturing method of the present disclosure.

[0034] The insights obtained by the present inventors regarding being able to strongly suppress the decrease in the residual magnetization at room temperature even when part of Nd is replaced with a light rare earth element will be described using the accompanying drawings. Figure 1 It is an explanatory diagram schematically showing the structure of the rare earth magnet of the present disclosure. Figure 7 It is a diagram schematically showing the structure of a conventional rare earth magnet.

[0035] The R-Fe-B-based rare earth magnet can suppress the formation of the α-Fe phase by solidifying a molten metal containing more R than the theoretical composition of R2Fe 14 B, and thus can stably obtain a phase having a crystal structure of R2Fe 14 B. It should be noted that regarding R2Fe 14The theoretical composition of B is 11.8 mol% for R, 82.3 mol% for Fe, and 5.9 mol% for B. In the following description, the molten metal containing more R than the theoretical composition of R2Fe 14 B is sometimes referred to as "R-rich molten metal", and the phase having the crystal structure of R2Fe 14 B type is sometimes referred to as "R2Fe 14 B phase".

[0036] When the R-rich molten metal is solidified, as shown in Figure 1 and Figure 7 , a structure having a main phase 10 and a grain boundary phase 20 existing around the main phase 10 is obtained. The main phase 10 is the R2Fe 14 B phase. In addition, in the grain boundary phase 20, various phases having a higher proportion of R than the R2Fe 14 B phase exist integrally. Therefore, such phases in the grain boundary phase 20 are generally collectively referred to as "R-rich phases".

[0037] When R is composed of different rare earth elements R 2 and R 3 , and such an R-rich molten metal is solidified to obtain the main phase 10 and the grain boundary phase 20 as shown in Figure 1 and Figure 7 , R 2 and R 3 are basically equally distributed in the main phase 10 and the grain boundary phase 20 respectively. For example, when an R-rich molten metal having a molar ratio of R 2 and R 3 of 0.70:0.30 is solidified, basically, the molar ratio of R 2 and R 3 is also 0.70:0.30 in either the main phase 10 or the grain boundary phase 20.

[0038] However, when R 2 is a specified rare earth element other than La such as Nd, and R 3 is La, La is more distributed in the grain boundary phase 20 than in the main phase 10 (hereinafter, sometimes referred to as "preferential distribution of La to the grain boundary phase 20"). Moreover, sometimes correspondingly, rare earth elements other than La such as Nd are more distributed in the main phase 10 than in the grain boundary phase 20 (hereinafter, sometimes referred to as "preferential distribution of Nd etc. to the main phase 10").

[0039] Compared with the width of the grain boundary phase 20 of the conventional rare earth magnet 200 shown in Figure 7 , Figure 1The width of the grain boundary phase 20 of the rare earth magnet 100 of the present disclosure shown is wider. This is because the volume fraction of the grain boundary phase 20 of the rare earth magnet 100 of the present disclosure is higher than that of the grain boundary phase 20 of the conventional rare earth magnet 200. That is, the volume fraction of the main phase 10 of the rare earth magnet of the present disclosure is lower than that of the main phase 10 of the conventional rare earth magnet 200. When the volume fraction of the main phase 10 is low as in the rare earth magnet 100 of the present disclosure, the preferential distribution of La to the grain boundary phase 20 is likely to occur. Hereinafter, for example, R 2 is Nd, R 3 is La and R 2 (Nd) and R 3 (La) with a molar ratio of 0.90:0.10 will be described for the case of solidifying the R-rich molten metal.

[0040] In Figure 7 the conventional rare earth magnet 200 shown, for example, the molar ratio of R 2 (Nd) and R 3 (La) in the main phase is 0.90:0.10, and the molar ratio of R 2 (Nd) and R 3 (La) in the grain boundary phase 20 is 0.89:0.11. While in Figure 1 the rare earth magnet 100 of the present disclosure shown, for example, the molar ratio of R 2 (Nd) and R 3 (La) in the main phase is 0.92:0.08, and the molar ratio of R 2 (Nd) and R 3 (La) in the grain boundary phase 20 is 0.82:0.18. Thus, compared with the conventional rare earth magnet 200, in the rare earth magnet 100 of the present disclosure, the preferential distribution of La to the grain boundary phase 20 occurs more significantly. Moreover, correspondingly, in the rare earth magnet 100 of the present disclosure, the preferential distribution of Nd to the main phase occurs more significantly.

[0041] In addition, the remanent magnetization of the rare earth magnet can be calculated by the following formula (1).

[0042] (Remanent magnetization of rare earth magnet) = (Saturation magnetization of main phase) × (Volume fraction of main phase) × (Orientation degree) ··· Formula (1)

[0043] According to formula (1), it can be understood that when the saturation magnetization of the main phase, the volume fraction of the main phase, and the orientation degree increase, the remanent magnetization of the rare earth magnet increases. The orientation degree is an index indicating the degree when anisotropy is imparted to the rare earth magnet. Methods for imparting anisotropy to the rare earth magnet such as molding in a magnetic field have been established, and usually the orientation degree is 94-98%. Thus, in order to increase the remanent magnetization of the rare earth magnet, it is effective to increase the saturation magnetization of the main phase or the volume fraction of the main phase.

[0044] As described above, the main phase 10 is R2Fe 14 B phase. Compared with the saturation magnetization of the R2Fe 14 B phase other than the light rare earth elements (such as Nd2Fe 14 B phase), the saturation magnetization of the R2Fe 14 B phase of the light rare earth elements (such as Ce2Fe 14 B phase) is usually small. In addition, the La2Fe 14 B phase is very unstable, so it is difficult to exist in the form of La2Fe 14 B phase. However, for example, when a part of Nd in the Nd2Fe 14 B phase is replaced by La to form (Nd,La)2Fe 14 B phase, if the replacement amount in terms of La is below a specified value, it is relatively stable. However, in the (Nd,La)2Fe 14 B phase, the saturation magnetization decreases corresponding to the amount of Nd replaced by La.

[0045] Compared with the width of the grain boundary phase 20 of the conventional rare earth magnet 200 (refer to Figure 7 ), the width of the grain boundary phase 20 of the rare earth magnet 100 of the present disclosure (refer to Figure 1 ) is wider. This is because the volume fraction of the grain boundary phase 20 in the rare earth magnet 100 of the present disclosure is higher than that of the grain boundary phase 20 of the conventional rare earth magnet 200. That is, compared with the volume fraction of the main phase of the conventional rare earth magnet 200, the volume fraction of the main phase 10 in the rare earth magnet 100 of the present disclosure is low. Thus, since the remanent magnetization is generated by the main phase 10, it is also considered that according to Equation (1), the remanent magnetization of the rare earth magnet 100 of the present disclosure is smaller than that of the conventional rare earth magnet 200. However, as described above, in the conventional rare earth magnet 200 and the rare earth magnet 100 of the present disclosure, even if the overall compositions of the two are the same, when R 2 is a rare earth element other than La such as Nd, R 3In the case of La, preferential distribution of La to the grain boundary phase 20 also occurs, and correspondingly, preferential distribution of Nd, etc. to the main phase 10 occurs. Moreover, the preferential distribution of La to the grain boundary phase 20 and the preferential distribution of Nd, etc. to the main phase 10 occur significantly when the volume fraction of the main phase 10 is low. Therefore, the saturation magnetization of the main phase 10 of the rare earth magnet 100 of the present disclosure is higher than that of the main phase 10 of the conventional rare earth magnet 200. Accordingly, when the volume fraction of the main phase 10 is within a specified range as in the rare earth magnet 100 of the present disclosure, the proportion of La present in the grain boundary phase 20 exceeds a specified value relative to the proportion of La present in the main phase 10, and correspondingly, the proportion of Nd, etc. present in the main phase 10 exceeds a specified value relative to the proportion of Nd, etc. present in the grain boundary phase 20. As a result, in the rare earth magnet 100 of the present disclosure, the increase in the residual magnetization caused by the preferential distribution of Nd, etc. to the main phase 10 and thus the increase in the proportion of Nd, etc. present in the main phase 10 exceeds the decrease in the residual magnetization caused by the decrease in the volume fraction of the main phase 10. Thereby, it is possible to provide an R-Fe-B-based rare earth magnet that can strongly suppress the decrease in the residual magnetization at room temperature even when a part of Nd is replaced with a light rare earth element.

[0046] Preferential distribution of Ce to the grain boundary phase 20 and the accompanying preferential distribution of Nd, etc. to the main phase 10 are also observed, although to a lesser extent than the preferential distribution of La to the grain boundary phase 20 and the accompanying preferential distribution of Nd, etc. to the main phase 10. Without being bound by theory, compared with the Nd2Fe 14 B phase, the La2Fe 14 B phase is very unstable, and the Ce2Fe 14 B phase is unstable. Therefore, it is considered that La and Ce are more stable when present in the grain boundary phase 20 than when present in the main phase 10. As a result, it is considered that preferential distribution of La and Ce to the grain boundary phase 20 and the accompanying preferential distribution of Nd, etc. to the main phase 10 occur.

[0047] Since the grain boundary phase 20 is a rare earth-rich phase, in order to reduce the volume fraction of the main phase 10 (increase the volume fraction of the grain boundary phase 20), it is effective to increase the total content ratio of rare earth elements in the entire rare earth magnet. Without being bound by theory, when a part of Nd is replaced by La, the opportunity for preferential distribution of La to the grain boundary phase 20 and the accompanying preferential distribution of Nd, etc. to the main phase increases when the total content ratio of rare earth elements in the entire rare earth magnet is high. Similarly, without being bound by theory, when a part of Nd is optionally replaced by Ce, the opportunity for preferential distribution of Ce to the grain boundary phase 20 and the accompanying preferential distribution of Nd, etc. to the main phase increases when the total content ratio of rare earth elements in the entire rare earth magnet is high. Accordingly, as long as the volume fraction of the main phase 10 is not too low and the residual magnetization of the rare earth magnet does not decrease excessively, it is preferable that the volume fraction of the main phase 10 is low (the volume fraction of the grain boundary phase 20 is high).

[0048] In addition, without being bound by theory, it is considered that the preferential distribution of La in the grain boundary phase 20 and the accompanying preferential distribution of Nd and the like in the main phase 10 occur during the production of the magnetic powder and during the sintering of the magnetic powder. The occurrence during the production of the magnetic powder means that it occurs when the molten metal is cooled to form the main phase 10. The occurrence during the sintering of the magnetic powder means that it occurs when La and Nd and the like are mutually replaced between the main phase 10 and the grain boundary phase 20 after the formation of the main phase 10. In either case, it is considered that the preferential distribution of La in the grain boundary phase 20 and the accompanying preferential distribution of Nd and the like in the main phase 10 require time. Accordingly, it is considered that the cooling rate of the molten metal and the cooling rate of the sintered body after the completion of sintering are preferably slow. Regarding the cooling rate of the molten metal, for example, a rate is considered such that even when the magnetic powder is sintered without pressure, the main phase in the magnetic powder does not coarsen to a degree that would affect the particle size. Regarding the cooling rate of the sintered body after the completion of sintering, for example, a rate is considered that is not as fast as that of active air cooling or other intentional cooling methods.

[0049] As described so far, in the rare earth magnet of the present disclosure, La and Ce, which are the causes of the decrease in the residual magnetization, are mostly distributed in the grain boundary phase, and Nd and the like, which contribute to the increase in the residual magnetization, are distributed in the main phase. Accordingly, it is explained that even when the amount of use of Nd and the like is reduced in the rare earth magnet of the present invention, the decrease in the residual magnetization is suppressed to a certain extent.

[0050] In recent years, materials informatics has developed rapidly. When using materials informatics, if the composition of the main phase (the molar ratio of each element constituting the main phase) is determined, the saturation magnetization of the main phase can be predicted relatively accurately. As described above, if rare earth elements such as La and Ce that are preferentially distributed to the grain boundary phase are not used, each rare earth element is evenly distributed to the main phase and the grain boundary phase.

[0051] The molar ratio of each element in the overall composition of the rare earth magnet is substantially equal to the compounding molar ratio of the raw materials. For example, the overall composition of the rare earth magnet of the present disclosure is represented by the formula (R 1 (1-x-y) La x Ce y ) u (Fe (1 - z) Co z ) (100-u-w-v) B w M 1 vrepresentation. The molar ratio of each element in the overall composition represented by this formula is approximately equal to the compounding molar ratio of the raw materials. Therefore, if La and Ce are not preferentially distributed as described above, the saturation magnetization of the main phase of the resulting rare earth magnet can be predicted at the stage of compounding the raw materials. Then, the residual magnetization of the rare earth magnet obtained using the above formula (1) can be predicted.

[0052] Figure 2 is a coordinate diagram showing an example of predicting the residual magnetization from the overall composition (compounding ratio of raw materials) of rare earth elements. Figure 2 The coordinate diagram of is obtained by predicting the saturation magnetization of the main phase from the overall composition (compounding ratio of raw materials) of rare earth elements and converting it into the residual magnetization using the above formula (1).

[0053] In the rare earth magnet of the present disclosure, La and optionally Ce are used. Therefore, compared with Figure 2 the prediction result of, the residual magnetization is improved. Figure 3 is a coordinate diagram showing the relationship between the measured residual magnetization and the predicted residual magnetization when the molar ratio of La to Ce, La:Ce, is 1:0.

[0054] According to Figure 3 , it can be understood that the measured residual magnetization is higher than the predicted residual magnetization. In this specification, the difference between the measured residual magnetization and the predicted residual magnetization is referred to as "gain". According to Figure 3 , it can be understood that when a part of Nd is replaced with light rare earth elements such as La and Ce to reduce the amount of Nd used, depending on the molar ratio of La and Ce and the manufacturing conditions, Nd and Ce are preferentially distributed as described above, so that the decrease in residual magnetization can be suppressed corresponding to the amount of gain.

[0055] The constituent elements of the rare earth magnet of the present disclosure and its manufacturing method based on these insights will be described below.

[0056] "Rare Earth Magnet"

[0057] First, the constituent elements of the rare earth magnet of the present disclosure will be described.

[0058] As Figure 1 shown, the rare earth magnet 100 of the present disclosure includes a main phase 10 and a grain boundary phase 20. Hereinafter, the overall composition of the rare earth magnet 100 of the present disclosure and the main phase 10 and the grain boundary phase 20 will be described.

[0059] <Overall Composition>

[0060] The overall composition of the rare earth magnet 100 of the present disclosure will be described. The overall composition of the rare earth magnet 100 of the present disclosure refers to the entire composition combining the main phase 10 and the grain boundary phase 20.

[0061] The overall composition of the rare earth magnet of the present disclosure in terms of molar ratio is represented by the formula (R 1 (1-x-y) La x Ce y ). u (Fe (1-z) Co z ). (100-u-w-v) B w M 1 v In this formula, the total of R 1 and La and Ce is u molar parts, the total of Fe and Co is (100 - u - w - v) molar parts, B is w molar parts, and M 1 is v molar parts. Therefore, their total is u molar parts + (100 - u - w - v) molar parts + w molar parts + v molar parts = 100 molar parts.

[0062] In the above formula, R 1 (1-x-y) La x Ce y means that relative to the total of R 1 and La and Ce, in terms of molar ratio, there is (1 - x - y) of R 1 , there is x of La, and there is y of Ce. Similarly, in the above formula, Fe (1-z) Co z means that relative to the total of Fe and Co, in terms of molar ratio, there is (1 - z) of Fe and there is z of Co.

[0063] In the above formula, R 1 is one or more elements selected from Nd, Pr, Gd, Tb, Dy, and Ho. Nd is neodymium, Pr is praseodymium, Gd is gadolinium, Tb is terbium, Dy is dysprosium, and Ho is holmium. Fe is iron. Co is cobalt. B is boron. M 1 is one or more elements selected from Ga, Al, Cu, Au, Ag, Zn, In, and Mn and inevitable impurity elements. Ga is gallium, Al is aluminum, Cu is copper, Au is gold, Ag is silver, Zn is zinc, In is indium, and Mn is manganese.

[0064] In this specification, unless otherwise specified, rare earth elements are composed of 17 elements: Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. Among them, unless otherwise specified, Sc, Y, La, and Ce are light rare earth elements. In addition, unless otherwise specified, Pr, Nd, Pm, Sm, and Eu are medium rare earth elements. Moreover, unless otherwise specified, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu are heavy rare earth elements. It should be noted that generally, heavy rare earth elements are more rare, while light rare earth elements are less rare. The rarity of medium rare earth elements is between that of heavy rare earth elements and light rare earth elements. It should be noted that Sc is scandium, Y is yttrium, La is lanthanum, Ce is cerium, Pr is praseodymium, Nd is neodymium, Pm is promethium, Sm is samarium, Eu is europium, Gd is gadolinium, Tb is terbium, Dy is dysprosium, Ho is holmium, Er is erbium, Tm is thulium, Yb is ytterbium, and Lu is lutetium.

[0065] The constituent elements of the rare earth magnet of the present disclosure represented by the above formula are described below.

[0066] <R 1 >

[0067] R 1 is an essential component for the rare earth magnet of the present disclosure. As described above, R 1 is one or more elements selected from Nd, Pr, Gd, Tb, Dy, and Ho. R 1 is a constituent element of the main phase (the phase having an R2Fe 14 B-type crystal structure (R2Fe 14 B phase)). From the viewpoint of the balance between the remanence, coercivity, and price, R 1 is preferably one or more elements selected from Nd and Pr. When Nd and Pr coexist as R 1 neodymium praseodymium can be used.

[0068] <la>

[0069] La is an essential component in the rare earth magnet of the present disclosure. By replacing a part of R 1 with La, the preferential distribution of La in the grain boundary phase occurs, and along with it, the preferential distribution of R 1 in the main phase occurs.

[0070] <ce>

[0071] is an optional component in the rare earth magnet of the present disclosure. By replacing a part of R 1 with Ce, the preferential distribution of Ce in the grain boundary phase occurs, and concomitantly, the preferential distribution of R 1 in the main phase occurs.

[0072] <R 1 and the molar ratio of La and Ce>

[0073] As described above, in the rare earth magnet of the present disclosure, R 1 and La and Ce exist in a ratio of (1 - x - y):x:y in terms of molar ratio. Since (1 - x - y)+x + y = 1, it means that a part of R 1 is replaced by Nd, and optionally a part of R 1 is replaced by Ce.

[0074] In the rare earth magnet of the present disclosure, as described above, La preferentially distributes in the grain boundary phase, and concomitantly, R 1 preferentially distributes in the main phase. If x is 0.05 or more, its effect is practically confirmed. From this viewpoint, x can be 0.07 or more, 0.10 or more, or 0.12 or more. On the other hand, if x is 0.25 or less, the main phase (R2Fe 14 B phase) will not become unstable. From this viewpoint, x can be 0.23 or less, 0.20 or less, or 0.15 or less.

[0075] In the rare earth magnet of the present disclosure, in the case of optionally containing Ce, Ce preferentially distributes in the grain boundary phase, and concomitantly, R 1 preferentially distributes in the main phase. Corresponding to the molar number of La and Ce preferentially distributed in the grain boundary phase, R 1 preferentially distributes in the main phase. As described above, compared with the preferential distribution of Ce in the grain boundary phase, the preferential distribution of La in the grain boundary phase is significant. If the content ratio of La is increased, more R 1 preferentially distributes in the main phase, and as a result, the remanence magnetization is further increased. From this viewpoint, regarding y / (x + y) representing the ratio of the molar number of Ce to the total molar number of La and Ce, it can be 0 or more, 0.10 or more, or 0.20 or more, and can be 0.50 or less, 0.40 or less, or 0.30 or less. It should be noted that y / (x + y)=0 means that Ce is substantially not contained.

[0076] <R 1 and the total content ratio of La and Ce>

[0077] In the above formula, R 1 The total content ratio of La and Ce is represented by u and satisfies 13.5 ≤ u ≤ 20.0. It should be noted that the value of u is the content ratio with respect to the rare earth magnet of the present disclosure and is equivalent to mol% (atomic%).

[0078] If u is 13.5 or more, not only does the α-Fe phase no longer exist in large quantities, but also the volume fraction of the grain boundary phase becomes higher (the volume fraction of the main phase becomes lower) compared with conventional rare earth magnets, and the preferential distribution of La in the grain boundary phase and the accompanying preferential distribution of R 1 in the main phase are promoted. From this viewpoint, u can be 14.0 or more, 14.5 or more, 15.0 or more, 15.5 or more, or 16.0 or more. On the other hand, if u is 20.0 or less, the grain boundary phase is not excessive, and thus the residual magnetization does not decrease excessively. From this viewpoint, u can be 19.0 or less, 18.0 or less, or 17.0 or less.

[0079]

[0080] Composition B Figure 1 forms the main phase 10 (R2Fe 14 B phase), which affects the proportion (volume ratio) of the main phase 10 and the grain boundary phase 20 present.

[0081] In the above formula, the content ratio of B is represented by w. The value of w is the content ratio relative to the rare earth magnet of the present disclosure and is equivalent to mol% (atomic%). If w is 10.0 or less, a rare earth magnet in which the main phase and the grain boundary phase are appropriately present can be obtained. From this viewpoint, w can be 9.0 or less, 8.0 or less, 7.0 or less, or 6.0 or less. On the other hand, if w is 5.0 or more, the formation of the R2Fe 14 B phase is less likely to be hindered. From this viewpoint, w can be 5.1 or more, 5.2 or more, or 5.3 or more.

[0082] <M 1 >

[0083] M 1 is an element that can be contained within the range that does not impair the characteristics of the rare earth magnet of the present disclosure. M 1 may include inevitable impurity elements. In the present specification, the so-called inevitable impurity elements refer to impurity elements contained in the raw materials of the rare earth magnet or impurity elements mixed in during the manufacturing process, etc., impurity elements that cannot be avoided or whose inclusion would cause a significant increase in manufacturing costs in order to avoid their inclusion. Impurity elements mixed in during the manufacturing process, etc., contain elements contained within a range that does not affect the magnetic properties due to manufacturing reasons. In addition, the inevitable impurity elements include rare earth elements other than the rare earth elements selected as R 1 and La and Ce, which are inevitably mixed due to the above reasons, etc.

[0084] As the element M within the range that does not impair the effects of the rare earth magnet of the present disclosure and its manufacturing method 1 , one or more elements selected from Ga, Al, Cu, Au, Ag, Zn, In, and Mn can be cited. As long as these elements are present below the upper limit of the content of M 1 , these elements do not substantially affect the magnetic properties. Therefore, these elements can be treated equivalently to the inevitable impurity elements. In addition, in addition to these elements, inevitable impurity elements can also be contained as M 1 . As M 1 , one or more selected from Ga, Al, and Cu and inevitable impurity elements are preferred.

[0085] In the above formula, M 1 The content ratio is represented by v. The value of v is the content ratio relative to the rare earth magnet of the present disclosure, equivalent to mol% (atomic%). If the value of v is 2.00 or less, the magnetic properties of the rare earth magnet of the present disclosure are not impaired. From this viewpoint, v can be 1.70 or less, 1.60 or less, 1.55 or less, 1.56 or less, 1.00 or less, 0.65 or less, 0.60 or less, or 0.50 or less.

[0086] As M 1 , since it is impossible to completely eliminate Ga, Al, Cu, Au, Ag, Zn, In, and Mn and inevitable impurity elements, even if the lower limit of v is 0.05, 0.10, 0.20, 0.30, or 0.40, there is no practical problem.

[0087] <fe>

[0088] Fe is combined with R 1 , La, Ce, and B, and Co described later to form the main components of the main phase (R2Fe 14 B phase). A part of Fe can be replaced by Co.

[0089] <co>

[0090] Co is an element that can replace Fe in the main phase and the grain boundary phase. In this specification, when it is described as Fe, it means that a part of Fe can be replaced by Co. For example, R2Fe 14 A part of Fe in the B phase is replaced by Co, becoming R2(Fe,Co) 14 B phase.

[0091] By replacing a part of Fe with Co, R2Fe 14 The B phase becomes R2(Fe,Co) 14 B phase, and the corrosion resistance and Curie temperature of the rare earth magnet of the present disclosure are improved. When the improvement of corrosion resistance and Curie temperature is not desired, Co may not be contained, and the inclusion of Co is not essential.

[0092] <Molar ratio of Fe and Co>

[0093] Even when the rare earth magnet of the present disclosure contains Co, its content is small, so the main corrosion resistance is improved. Even when containing Co in a small amount, an improvement in corrosion resistance has been confirmed. When z is 0.010 or more, 0.012 or more, or 0.014 or more, an improvement in corrosion resistance is more clearly confirmed. On the other hand, since Co is of high price, from the viewpoint of economy, z can be 0.100 or less, 0.080 or less, 0.060 or less, 0.040 or less, or 0.020 or less.

[0094] <Total content ratio of Fe and Co>

[0095] Fe and Co are the balance (remaining part) of R 1 , La, Ce, B, and M 1 described so far, and their total content ratio is represented by (100 - u - w - v). As described above, the values of u, w, and v are the content ratios with respect to the rare earth magnet of the present disclosure, so (100 - u - w - v) corresponds to mol% (atomic%). When u, w, and v are within the ranges described so far, the main phase 10 and the grain boundary phase 20 as shown in Figure 1 are obtained.

[0096] As Figure 1 shown, the rare earth magnet 100 of the present disclosure includes a main phase 10 and a grain boundary phase 20. Hereinafter, the main phase 10 and the grain boundary phase 20 will be described.

[0097] <Main phase>

[0098] The main phase has an R2Fe 14 B-type crystal structure. R is a rare earth element. Using R2Fe 14 The reason for the "type B" is that in the main phase (crystal structure), elements other than R, Fe, and B can be included in a substitutional and / or interstitial type. For example, in the rare earth magnet of the present disclosure, in the main phase, a part of Fe is replaced by Co. Co can also exist in the main phase in an interstitial type. Further, in the rare earth magnet of the present disclosure, in the main phase, a part of any one of the elements R, Fe, Co, and B can be replaced by M 1 substituted. Or, for example, M 1 can exist in the main phase in an interstitial type. Hereinafter, the average particle diameter and volume fraction of the main phase will be described.

[0099] <Average particle diameter of the main phase>

[0100] The average particle diameter of the main phase of the rare earth magnet of the present disclosure is 1.0 to 20.0 μm. The rare earth magnet of the present disclosure is obtained by pressureless sintering. If the average particle diameter of the main phase is 1.0 μm or more, coarsening of the main phase can be suppressed during pressureless sintering. Further, if the molten metal is cooled at a rate such that the average particle diameter of the main phase becomes 1.0 μm or more during the production of the magnetic powder, it is possible to expect the time required to ensure the preferential distribution of La in the grain boundary phase and the accompanying preferential distribution of Nd etc. in the main phase during the formation of the main phase. From this viewpoint, the average particle diameter of the main phase can be 2.0 μm or more, 3.0 μm or more, 4.0 μm or more, 5.0 μm or more, 5.5 μm or more, or 6.0 μm or more. On the other hand, if the average particle diameter of the main phase is 20.0 μm or less, a decrease in the residual magnetization and coercive force can be suppressed. From this viewpoint, the average particle diameter of the main phase can be 15.0 μm or less, 10.0 μm or less, 8.0 μm or less, 7.7 μm or less, 7.5 μm or less, 7.0 μm or less, 6.5 μm or less, or 6.2 μm or less.

[0101] The "average particle diameter" is measured as follows. In a scanning electron microscope image or a transmission electron microscope image, a certain region is defined as observed from the perpendicular direction of the easy magnetization axis, and a plurality of lines are drawn in the perpendicular direction of the easy magnetization axis with respect to the main phase existing in the certain region, and the size (length) of the main phase is calculated from the distance between the points intersecting within the particles of the main phase (sectioning method). When the cross section of the main phase is close to a circle, it is converted to the equivalent diameter of the projected area. When the cross section of the main phase is close to a rectangle, it is converted to an approximate rectangular parallelepiped. The D 50 value of the obtained size (length) distribution (particle size distribution) is the average particle diameter.

[0102] <Volume fraction of the main phase>

[0103] The volume fraction of the main phase of the rare earth magnet of the present disclosure is 80.0 to 90.0%. When the volume fraction of the main phase is low, the preferential distribution of R associated with the preferential distribution of La and Ce in the grain boundary phase promotes the preferential distribution of R in the main phase, increasing the saturation magnetization of the main phase, but reducing the component of the main phase that contributes to the manifestation of magnetization. On the other hand, when the volume fraction of the main phase is high, the preferential distribution of R associated with the preferential distribution of La and Ce in the grain boundary phase is difficult to occur, making it difficult to increase the saturation magnetization of the main phase, but increasing the component of the main phase that contributes to the manifestation of magnetization. Accordingly, if the volume fraction of the main phase is 80.0% or more, the increase in the residual magnetization caused by the higher proportion of R in the main phase due to the preferential distribution of R associated with the preferential distribution of La and Ce in the grain boundary phase exceeds the decrease in the residual magnetization caused by the lower volume fraction of the main phase. From this perspective, the volume fraction of the main phase can be 81.0% or more, 82.0% or more, or 83.0% or more. On the other hand, if the volume fraction of the main phase is 90.0% or less, the preferential distribution of La and Ce in the grain boundary phase and the preferential distribution of R in the main phase are promoted. From this perspective, the volume fraction of the main phase can be 89.0% or less, 88.0% or less, 87.0% or less, or 86.6% or less. 1 When the volume fraction of the main phase is low, the preferential distribution of R associated with the preferential distribution of La and Ce in the grain boundary phase promotes the preferential distribution of R in the main phase, increasing the saturation magnetization of the main phase, but reducing the component of the main phase that contributes to the manifestation of magnetization. On the other hand, when the volume fraction of the main phase is high, the preferential distribution of R associated with the preferential distribution of La and Ce in the grain boundary phase is difficult to occur, making it difficult to increase the saturation magnetization of the main phase, but increasing the component of the main phase that contributes to the manifestation of magnetization. 1 Accordingly, if the volume fraction of the main phase is 80.0% or more, the increase in the residual magnetization caused by the higher proportion of R in the main phase due to the preferential distribution of R associated with the preferential distribution of La and Ce in the grain boundary phase exceeds the decrease in the residual magnetization caused by the lower volume fraction of the main phase. From this perspective, the volume fraction of the main phase can be 81.0% or more, 82.0% or more, or 83.0% or more. On the other hand, if the volume fraction of the main phase is 90.0% or less, the preferential distribution of La and Ce in the grain boundary phase and the preferential distribution of R in the main phase are promoted. From this perspective, the volume fraction of the main phase can be 89.0% or less, 88.0% or less, 87.0% or less, or 86.6% or less. 1 preferential distribution in the main phase, the R 1 in the main phase results in an increase in the residual magnetization that exceeds the decrease in the residual magnetization caused by the lower volume fraction of the main phase. From this perspective, the volume fraction of the main phase can be 81.0% or more, 82.0% or more, or 83.0% or more. On the other hand, if the volume fraction of the main phase is 90.0% or less, the preferential distribution of La and Ce in the grain boundary phase and the preferential distribution of R 1 in the main phase are promoted. From this perspective, the volume fraction of the main phase can be 89.0% or less, 88.0% or less, 87.0% or less, or 86.6% or less.

[0104] The volume fraction of the main phase is determined by measuring the overall composition of the rare earth magnet using high-frequency inductively coupled plasma atomic emission spectroscopy (ICP-AES: Inductively Coupled Plasma Atomic Emission Spectroscopy), and calculating the volume fraction of the main phase from the measured values assuming that the rare earth magnet is phase-separated into a main phase (R2Fe 14 B phase) and an R-rich phase.

[0105] <Grain boundary phase>

[0106] As Figure 1 shown, the rare earth magnet 100 of the present disclosure includes a main phase 10 and a grain boundary phase 20 existing around the main phase 10. As described above, the main phase 10 includes a magnetic phase (R2Fe 14 B-type crystal structure (R2Fe 14 B phase). On the other hand, the grain boundary phase 20 includes a phase having a crystal structure other than the R2Fe 14 B-type crystal structure and a phase with an unclear crystal structure. The so-called "unclear phase", without being bound by theory, refers to a phase (state) in which at least a part of the phase has an incomplete crystal structure and they exist disorderly. Among the phases existing in the grain boundary phase 20, those having R2Fe 14 The proportion of R in any of the phases with crystal structures other than the B-type and the phases with unclear crystal structures is higher than that in the phase with the R2Fe 14 phase having a B-type crystal structure. Accordingly, as described above, the grain boundary phase 20 is sometimes referred to as the "R-rich phase".

[0107] <(The proportion of La present in the grain boundary phase) / (The proportion of La present in the main phase)>

[0108] In the rare earth magnet of the present disclosure, La is preferentially distributed in the grain boundary phase, and concomitantly, R 1 is preferentially distributed in the main phase. The degree of preferential distribution of La in the grain boundary phase can be evaluated by (The proportion of La present in the grain boundary phase) / (The proportion of La present in the main phase). The proportion of La present in the grain boundary phase is the ratio of the number of moles of La in the grain boundary phase to the total number of moles of all rare earth elements in the grain boundary phase. The proportion of La present in the main phase is the ratio of the number of moles of La in the main phase to the total number of moles of all rare earth elements in the main phase. It should be noted that the number of moles of each element containing La in the main phase and the grain boundary phase can be determined by analysis using SEM-EDX (Scanning Electron Microscope / Energy Dispersive X-ray).

[0109] If (The proportion of La present in the grain boundary phase) / (The proportion of La present in the main phase) exceeds 1.30, then due to the preferential distribution of R 1 in the main phase accompanying the preferential distribution of La in the grain boundary phase, the increase in the remanent magnetization caused by the increase in the proportion of R 1 in the main phase exceeds the decrease in the remanent magnetization caused by the decrease in the volume fraction of the main phase. From this viewpoint, (The proportion of La present in the grain boundary phase) / (The proportion of La present in the main phase) can be 1.33 or more, 1.50 or more, 1.55 or more, 1.56 or more, 1.60 or more, 1.70 or more, 1.75 or more, 1.80 or more, or 2.00 or more. The upper limit of (The proportion of La present in the grain boundary phase) / (The proportion of La present in the main phase) is not particularly limited, and is approximately 3.00 to 4.00 as the upper limit.

[0110] Even in the preferential distribution of R 1 in the main phase accompanying the preferential distribution of Ce in the grain boundary phase, the proportion of R 1 in the main phase also increases, contributing to the increase in the remanent magnetization. Compared with the preferential distribution of R 1 in the main phase accompanying the preferential distribution of Ce in the grain boundary phase, the preferential distribution of R 1 The preferential distribution in the main phase is sufficiently large, so it can be represented by (the proportion of La present in the grain boundary phase) / (the proportion of La present in the main phase).

[0111] "Manufacturing Method"

[0112] Next, the manufacturing method of the rare earth magnet of the present disclosure will be described.

[0113] The manufacturing method of the rare earth magnet of the present disclosure includes processes of molten metal preparation, molten metal cooling, pulverization, and pressureless sintering. Hereinafter, each process will be described.

[0114] <Molten Metal Preparation Process>

[0115] Prepare a molten metal having a composition represented by the formula (R 1 (1-x-y) La x Ce y )(Fe u (Fe (1-z) Co z ) (100-u-w-v) B w M 1 v In this formula, regarding R 1 , La, Ce, Fe, Co, B, and M 1 and x, y, z, u, w, and v, it is as described in "Rare Earth Magnet". Regarding the elements that will be consumed in the subsequent processes, their consumption amounts can be estimated.

[0116] <Molten Metal Cooling>

[0117] Cool the molten metal having the above composition at a rate of 1 to ×10 4 °C / second. By cooling at such a rate, a magnetic alloy having a main phase with an average particle size of 1 to 20 μm is obtained. From the viewpoint of obtaining a main phase with an average particle size of 1 μm or more, the molten metal can be cooled at a rate of 5×10 3 °C / second or less, 10 3 °C / second or less, 5°C×10 2 °C / second or less. On the other hand, from the viewpoint of obtaining a main phase with an average particle size of 20 μm or less, the molten metal can be cooled at a rate of 5°C / second or more, 10°C / second or more, or 10 2 °C / second or more. In addition, the main phase is a phase having an R2Fe 14 B-type crystal structure, and a grain boundary phase exists around the main phase. Then, by cooling the molten metal at a rate within the above range, in the manufacture of the magnetic alloy, that is, in the formation of the main phase (R2Fe 14 When it is the B phase), it is expected that La and Ce are preferentially distributed in the grain boundary phase. From the viewpoint of the preferential distribution of La and Ce in the grain boundary phase, regarding the cooling rate of the molten metal, it is preferably 5×10 3 ℃ / second or less, more preferably 10 3 ℃ / second or less, and even more preferably 5℃×10 2 ℃ / second or less.

[0118] As long as the molten metal can be cooled at the above-mentioned rate, the method is not particularly limited, and typically, an arc melting method, a method using a book-shaped mold, a strip casting method, etc. can be cited. From the viewpoint of being able to stably obtain the above-mentioned rate and being able to continuously cool a large amount of molten metal, the strip casting method is preferred. From the viewpoint of further promoting the preferential distribution of La and Ce in the grain boundary phase, the arc melting method is preferred.

[0119] The arc melting method is to load the raw materials into a container, typically inside a crucible, and arc-melt the raw materials in the container or crucible to obtain molten metal. Thereafter, the arc discharge is stopped, and the molten metal is cooled in the container or crucible to obtain a magnetic alloy in the form of a casting.

[0120] A book-shaped mold is a casting mold having a flat cavity. The thickness of the cavity can be appropriately determined so as to obtain the above-mentioned cooling rate. The thickness of the cavity can be, for example, 0.5 mm or more, 1 mm or more, 2 mm or more, 3 mm or more, 4 mm or more, or 5 mm or more, and can be 20 mm or less, 15 mm or less, 10 mm or less, 9 mm or less, 8 mm or less, 7 mm or less, or 6 mm or less.

[0121] Next, the strip casting method will be described with reference to the drawings. Figure 4 It is an explanatory diagram schematically showing a cooling device used in the strip casting method.

[0122] The cooling device 70 includes a melting furnace 71, a tundish 73, and a cooling roll 74. In the melting furnace 71, the raw materials are melted to prepare molten metal 72 having the above composition. The molten metal 72 is supplied to the tundish 73 at a certain supply amount. The molten metal 72 supplied to the tundish 73 is supplied to the cooling roll 74 from the end of the tundish 73 by its own weight.

[0123] The tundish 73 is made of ceramics or the like, temporarily stores the molten metal 72 continuously supplied from the melting furnace 71 at a specified flow rate, and can rectify the flow of the molten metal 72 to the cooling roll 74. In addition, the tundish 73 also has a function of adjusting the temperature of the molten metal 72 just before reaching the cooling roll 74.

[0124] The cooling roll 74 is formed of a material with high thermal conductivity such as copper or chromium, and the surface of the cooling roll 74 is chrome-plated or the like to prevent erosion (corrosion) by the high-temperature molten metal. The cooling roll 74 can be rotated in the arrow direction at a prescribed rotational speed by a drive device (not shown).

[0125] In order to obtain the above cooling rate, the peripheral speed (circumferential speed) of the cooling roll 74 can be 0.5 m / s or more, 1.0 m / s or more, or 1.5 m / s or more, and can be 5.0 m / s or less, 4.5 m / s or less, 4.0 m / s or less, 3.5 m / s or less, 3.0 m / s or less, 2.5 m / s or less, or 2.0 m / s or less.

[0126] When supplying from the end of the tundish 73 to the cooling roll 74, the temperature of the molten metal can be 1350 °C or more, 1400 °C or more, or 1450 °C or more, and can be 1600 °C or less, 1550 °C or less, or 1500 °C or less.

[0127] The molten metal 72 cooled and solidified on the outer periphery of the cooling roll 74 becomes the magnetic alloy 75, peels off from the cooling roll 74, and is recovered by a recovery device (not shown). The form of the magnetic alloy 75 is typically a thin strip or a thin sheet.

[0128] In any of the molten metal cooling methods, in order to prevent oxidation of the molten metal, etc., melting of the raw material and cooling of the molten metal are preferably carried out in an inert gas atmosphere. The inert gas atmosphere includes a nitrogen atmosphere.

[0129] <Crushing>

[0130] The magnetic alloy obtained as described above is crushed to obtain magnetic powder. The crushing method is not particularly limited, and examples thereof include the following methods: after coarsely crushing the magnetic powder, further crushing is carried out using a jet mill and / or a cutting mill, etc. As the method for coarse crushing, for example, a method using a hammer mill and a method of hydrogen embrittlement crushing of the magnetic alloy, etc. can be cited. These methods can be combined.

[0131] The particle size of the crushed magnetic powder is not particularly limited as long as the magnetic powder can be sintered, and it is preferable that there is one main phase in one particle of the magnetic powder. The particle size of the magnetic powder is, for example, D 50 The gauge can be 1 μm or more, 5 μm or more, or 10 μm or more, and can be 3000 μm or less, 2000 μm or less, 1000 μm or less, 900 μm or less, 800 μm or less, 700 μm or less, 600 μm or less, 500 μm or less, 400 μm or less, 300 μm or less, 200 μm or less, 100 μm or less, 50 μm or less, 40 μm or less, 30 μm or less, 20 μm or less, or 15 μm or less. In order for there to be one main phase in one particle of the magnetic powder, it is preferable that the particle size of the magnetic powder is, for example, D 50 The gauge is 1 μm or more, 5 μm or more, or 10 μm or more, and is 20 μm or less, 15 μm or less, or 12 μm or less. By setting it in this way, the sinterability is improved.

[0132] <Homogenization heat treatment>

[0133] Optionally, in order to homogenize the magnetic alloy before pulverization, the ingot can be heat-treated (hereinafter, such heat treatment is sometimes referred to as "homogenization heat treatment"). As a result, the composition of each example of the magnetic powder after pulverization of the magnetic alloy becomes substantially uniform.

[0134] The temperature of the homogenization heat treatment can be, for example, 1000 °C or more, 1050 °C or more, or 1100 °C or more, and is 1300 °C or less, 1250 °C or less, 1200 °C or less, or 1150 °C or less. The homogenization heat treatment time can be, for example, 6 hours or more, 12 hours or more, 18 hours or more, or 24 hours or more, and is 48 hours or less, 42 hours or less, 36 hours or less, or 30 hours or less.

[0135] In order to suppress the oxidation of the magnetic alloy, the homogenization heat treatment is preferably carried out in an inert gas atmosphere. The inert gas atmosphere includes a nitrogen atmosphere.

[0136] <Pressureless sintering>

[0137] The magnetic powder is pressurelessly sintered to obtain a sintered body. Compared with pressure sintering, in pressureless sintering, without applying a pressure, the magnetic powder is sintered at a high temperature for a long time to increase the density of the sintered body.

[0138] The sintering temperature can be, for example, 900 °C or higher, 950 °C or higher, 1000 °C or higher, 1020 °C or higher, 1030 °C or higher, 1040 °C or higher, 1050 °C or higher, 1060 °C or higher, or 1070 °C or higher, and can be 1100 °C or lower, 1090 °C or lower, or 1080 °C or lower. The sintering time can be, for example, 1 hour or longer, 2 hours or longer, 3 hours or longer, or 4 hours or longer, and can be 24 hours or shorter, 18 hours or shorter, 12 hours or shorter, or 6 hours or shorter. In order to suppress the oxidation of the magnetic powder during sintering, the sintering atmosphere is preferably an inert atmosphere. The inert gas atmosphere includes a nitrogen atmosphere.

[0139] In order to promote the preferential distribution of La and Ce in the grain boundary phase and, concomitantly, R 1 In order to promote the preferential distribution of La and Ce in the grain boundary phase and, concomitantly, R to preferentially distribute in the main phase, preferably in pressureless sintering, not only the grain boundary phase but also the vicinity of the surface of the main phase becomes a liquid phase. Therefore, the sintering temperature is preferably 1040 °C or higher, 1050 °C or higher, 1060 °C or higher, or 1070 °C or higher and 1100 °C or lower, 1090 °C or lower, or 1080 °C or lower.

[0140] In order to promote the preferential distribution of La and Ce in the grain boundary phase and, concomitantly, R 1 In order to promote the preferential distribution of La and Ce in the grain boundary phase and, concomitantly, R to preferentially distribute in the main phase, it is preferable to slowly cool the part that has become a liquid phase. Therefore, the sintered body after pressureless sintering is preferably cooled at 1 °C / minute or lower, 0.5 °C / minute or lower, 0.1 °C / minute or lower, 0.05 °C / minute or lower, or 0.01 °C / minute or lower. There is no particular limitation on the lower limit of the cooling rate of the sintered body after pressureless sintering. From the viewpoint of productivity, the lower limit of the cooling rate is approximately 0.001 - 0.005 °C / minute.

[0141] <Magnetic field cold compaction>

[0142] In order to increase the density of the sintered body, optionally, the magnetic powder can be pre-compacted before sintering, and its compacted body (green compact) is sintered. The molding pressure during compaction is, for example, 50 MPa or higher, 100 MPa or higher, 200 MPa or higher, or 300 MPa or higher, and can be 1000 MPa or lower, 800 MPa or lower, or 600 MPa or lower. In order to impart anisotropy to the sintered body, the magnetic powder can be compacted while applying a magnetic field. The applied magnetic field can be 0.1 T or higher, 0.5 T or higher, 1.0 T or higher, 1.5 T or higher, or 2.0 T or higher, and can be 10.0 T or lower, 8.0 T or lower, 6.0 T or lower, or 4.0 T or lower.

[0143] <Heat treatment>

[0144] Optionally, the sintered body can be heat-treated under specified conditions (hereinafter, such heat treatment may sometimes be referred to as "specific heat treatment"). By the specific heat treatment, it is possible to make the contact surface between the main phase and the grain boundary phase a facet interface, thereby increasing the coercivity, particularly the coercivity at high temperatures.

[0145] Examples of the conditions for the specific heat treatment include holding the sintered body at 850 to 1000 °C for 50 to 300 minutes and then cooling it at a rate of 0.1 to 5.0 °C / minute to 450 to 700 °C. As the specific heat treatment, after the above heat treatment, it is possible to further hold it at 450 to 650 °C for 30 to 180 minutes and then cool it to room temperature at a rate of 10 to 2000 °C / minute. That is, the heat treatment can be performed in two stages.

[0146] In order to suppress the oxidation of the sintered body during the specific heat treatment, the specific heat treatment atmosphere is preferably an inert gas atmosphere. The inert gas atmosphere includes a nitrogen atmosphere.

[0147] <Modification>

[0148] In addition to what has been described so far, the rare earth magnet and its manufacturing method of the present disclosure can also be variously modified within the scope of the content described in the patent claims. For example, the rare earth magnet of the present disclosure can be used as a precursor, and a modifying material can be diffused and infiltrated into the precursor to increase the coercivity. As a method for diffusing and infiltrating the modifying material, a known method can be adopted.

[0149] Examples of the method for diffusing and infiltrating the modifying material include the following: a gas phase method in which the precursor is exposed to a gas atmosphere of a specified rare earth element such as Nd, a solid phase method in which a fluoride of a specified rare earth element such as Nd is brought into contact with the precursor and heated, and a liquid phase method in which a melt of a low melting point alloy of a specified rare earth element such as Nd and a transition metal such as Cu is brought into contact with the precursor. They can be combined. As the rare earth element such as Nd, typically one or more elements selected from Nd, Pr, Gd, Tb, Dy, and Ho can be cited. As the transition metal element such as Cu, typically one or more elements selected from Cu, Al, Co, and Fe can be cited.

[0150] The composition of the above low melting point alloy is, for example, represented by the molar ratio formula R’ (1-s) M’ s (where s is 0.05 to 0.40). R' can be, for example, a rare earth element such as Nd described above. M' can be, for example, a transition metal element such as Cu described above, and M' may contain inevitable impurity elements. The so-called inevitable impurity elements refer to impurity elements contained in the raw materials or impurity elements mixed in during the manufacturing process, etc., which cannot be avoided or will cause a significant increase in manufacturing costs in order to avoid their inclusion. The impurity elements mixed in during the manufacturing process include elements contained within a range that does not affect the magnetic properties due to manufacturing reasons. In addition, the inevitable impurity elements include rare earth elements inevitably mixed in for reasons such as those described above, in addition to the rare earth elements selected as R'.

[0151] Using the rare earth magnet of the present disclosure as a precursor, and diffusing a modifying material having a composition represented by the formula of the above molar ratio of R' (1-s) M' s into the precursor, the overall composition of the rare earth magnet after modification can be represented by (R 1 (1-x-y) La x Ce y ) u (Fe (1-z) Co z ) (100-u-w-v) B w M 1 v ·R' (1-s) M' s represent.

[0152] Hereinafter, the rare earth magnet and its manufacturing method of the present disclosure will be further specifically described by way of examples and comparative examples. It should be noted that the rare earth magnet and its manufacturing method of the present disclosure are not limited to the conditions used in the following examples.

[0153] 《Preparation of Specimens》

[0154] Specimens of Examples 1 to 5 and Comparative Examples 1 to 6 were prepared in the following order.

[0155] The raw materials were arc melted and solidified to obtain a magnetic alloy so as to have the composition shown in Table 1. The cooling rate of the molten metal was 50 °C / second. The magnetic alloy was subjected to homogenization heat treatment at 1100 °C for 24 hours.

[0156] The magnetic alloy after homogenization heat treatment was pulverized by the method shown in Table 1 to obtain magnetic powder. Then, the magnetic powder was compacted in a magnetic field of 1.0 T to obtain a compact (green compact). The pressure during compaction was 100 MPa.

[0157] The compact was sintered without pressure under the conditions shown in Table 1. The sintered body after sintering was cooled at the speed shown in Table 1 to prepare each specimen.

[0158] "Evaluation"

[0159] Using a vibrating sample magnetometer (VSM), the magnetic properties of each sample were measured at 27°C.

[0160] Each sample was observed by SEM (Scanning Electron Microscope) to determine the average particle size of the main phase. In addition, for each sample, the volume fraction of the main phase was measured by the method described in "Rare Earth Magnets". Moreover, for each sample, SEM-EDX (Scanning Electron Microscope / Energy Dispersive X-ray) was used to analyze the R in the main phase and the grain boundary phase respectively 1 and the molar ratio of La and Ce, and (the proportion of La in the grain boundary phase) / (the proportion of La in the main phase) was calculated.

[0161] The results are shown in Table 1-1 and Table 1-2 and Figure 5 and Figure 6 . In Table 1-1 and Table 1-2, the residual magnetization (predicted residual magnetization) of each sample predicted from the overall composition of the rare earth magnet of the present disclosure is also shown. In addition, in Table 1, for each sample, the difference between the predicted residual magnetization and the measured residual magnetization, that is, the gain, is also shown. Figure 5 Regarding the samples of Example 2 and Comparative Examples 3 to 5, the relationship between the volume fraction of the main phase and the measured residual magnetization and the gain is shown. Figure 6 Regarding the sample of Example 2, an electron beam image and the results of surface analysis of La, Nd, and Fe are shown.

[0162]

Table 1-1

[0163]

[0164]

Table 1-2

[0165]

[0166] From Table 1-1 and Table 1-2, it can be understood that the samples of the examples all have the volume fraction of the main phase within a specified range and satisfy (the proportion of La in the grain boundary phase) / (the proportion of La in the main phase)>1.30. Moreover, according to Figure 5 and Table 1-1 and Table 1-2, it can be understood that in the samples of the examples, not only is the gain 0.003 T or more, but also the measured residual magnetization is 1.26 T or more, compared with R 1 Compared with the residual magnetization of 1.333 T of the sample of Comparative Example 1 in which a part of (Nd and Pr) is not replaced by light rare earth elements, the decrease in residual magnetization can be strongly suppressed. In addition, according to Figure 6 , it can be understood that in the sample of Example 2, the proportion of La present in the grain boundary phase is higher than the proportion of La present in the main phase.

[0167] Based on the above results, the effects of the rare earth magnet and the method for manufacturing the same according to the present disclosure can be confirmed.< / co> < / fe> < / ce> < / la>

Claims

1. A rare earth magnet having a main phase and a grain boundary phase existing around the main phase, and the overall composition in terms of molar ratio is represented by the formula (R 1 (1-x-y) La x Ce y ) u (Fe (1-z) Co z ) (100-u-w-v) B w M 1 v wherein R 1 is one or more elements selected from Nd, Pr, Gd, Tb, Dy, and Ho, M 1 is one or more elements selected from Ga, Al, Cu, Au, Ag, Zn, In, and Mn and inevitable impurity elements, and 0.05 ≤ x ≤ 0.25, 0 ≤ y / (x + y) ≤ 0.50, 13.5 ≤ u ≤ 20.0, 0 ≤ z ≤ 0.100, 5.0 ≤ w ≤ 10.0, and 0 ≤ v ≤ 2.00, The above-mentioned main phase has an R2Fe 14 B-type crystal structure, where R is a rare earth element, The average particle diameter of the above-mentioned main phase is 6.0 to 8.0 μm, the volume fraction of the above-mentioned main phase is 80.0 to 90.0%, and with respect to the above-mentioned main phase and the above-mentioned grain boundary phase, 1.30 < (the proportion of La present in the above-mentioned grain boundary phase) / (the proportion of La present in the above-mentioned main phase) ≤ 3.00 is satisfied.

2. The rare earth magnet according to claim 1, wherein, The above-mentioned R 1 is one or more elements selected from Nd and Pr, and the above-mentioned M 1 is one or more elements selected from Ga, Al, and Cu and inevitable impurity elements.

3. The rare earth magnet according to claim 1 or 2, wherein, The volume fraction of the above-mentioned main phase is 80.0 to 86.6%.

4. The rare earth magnet according to claim 1 or 2, wherein, With respect to the above-mentioned main phase and the above-mentioned grain boundary phase, (the proportion of La present in the above-mentioned grain boundary phase) / (the proportion of La present in the above-mentioned main phase) ≥ 1.56 is satisfied.

5. A method for manufacturing a rare earth magnet, which is the method for manufacturing the rare earth magnet according to claim 1, comprising: Prepare a molten metal having a composition represented by the formula (R 1 (1-x-y) La x Ce y ) u (Fe (1-z) Co z ) (100-u-w-v) B w M 1 v wherein R 1 is one or more elements selected from Nd, Pr, Gd, Tb, Dy, and Ho, M 1 is one or more elements selected from Ga, Al, Cu, Au, Ag, Zn, In, and Mn and inevitable impurity elements, and 0.05 ≤ x ≤ 0.25, 0 ≤ y / (x + y) ≤ 0.50, 13.5 ≤ u ≤ 20.0, 0 ≤ z ≤ 0.100, 5.0 ≤ w ≤ 10.0, and 0 ≤ v ≤ 2.00, Cool the above molten metal at a rate of 1 to 10 4 °C per second to obtain a magnetic alloy, crushing the above-mentioned magnetic alloy to obtain magnetic powder, and performing pressureless sintering on the above-mentioned magnetic powder to obtain a sintered body.

6. The method for manufacturing a rare earth magnet according to claim 5, wherein, Performing pressureless sintering on the above-mentioned magnetic powder at 900 to 1100 °C.

7. The method for manufacturing a rare earth magnet according to claim 5 or 6, wherein, Cooling the above-mentioned sintered body after the pressureless sintering at a rate of 1 °C / minute or less.

8. The method for manufacturing a rare earth magnet according to claim 5 or 6, wherein, The above-mentioned R 1 is one or more elements selected from Nd and Pr, and the above-mentioned M 1 is one or more elements selected from Ga, Al and Cu and inevitable impurity elements.

Images