Rare earth sintered magnet, method for producing a rare earth sintered magnet, rotor and rotating machine

Abstract

A rare earth sintered magnet (1) includes a main phase (10) satisfying a general formula (Nd, Pr, R)-Fe-B, where R represents one or more rare earth elements selected excluding Nd and Pr, the main phase (10) comprising crystal grains based on a Nd 2 Fe 14 B crystal structure. The main phase (10) includes a core portion and a shell portion covering the core portion. The main phase (10) includes a first main phase (11) that satisfies CNd>CPr and a second main phase (12) that satisfies CNd

Description

Area

[0001] The present disclosure relates to a rare earth sintered magnet which is a permanent magnet obtained by sintering a material containing a rare earth element, a method for producing a rare earth sintered magnet, a rotor and a rotary machine. General state of the art

[0002] RTB-based permanent magnets containing a tetragonal intermetallic R 2 T 14B compound as the main phase are well known. Here, R stands for a rare earth element, T stands for a transition metal element such as Fe (iron) or Fe partially replaced by cobalt (Co), and B stands for boron. RTB-based permanent magnets are used for various components that have high added value, including, for example, industrial motors. In particular, Nd-Fe-B-based sintered magnets, where R stands for neodymium (Nd), are used for various components due to their excellent magnetic properties. In addition, since industrial motors are often used in a high-temperature environment exceeding 100°C, attempts have been made to improve the coercive force by adding heavy rare earth elements such as dysprosium (Dy) to Nd-TB-based sintered magnets.

[0003] In recent years, the production of Nd-Fe-B-based sintered magnets has expanded, and the consumption of Nd and heavy rare earth elements, such as Dy and terbium (Tb), has increased. However, Nd and heavy rare earth elements are expensive and pose a procurement risk due to their highly uneven distribution. In view of this, one possible measure to reduce the consumption of Nd and heavy rare earth elements is to use a magnet that forms a main phase containing a low-content heavy rare earth phase, to use rare earth elements other than R, such as praseodymium (Pr), cerium (Ce), lanthanum (La), samarium (Sm), scandium (Sc), gadolinium (Gd), yttrium (Y), and lutetium (Lu), or to use a special production process, such as applying hot plastic deformation to a sintered body.Hereinafter, in this document, hot plastic deformation applied to a sintered body is referred to as hot deformation. However, adding a heavy rare earth element to the main phase contributes significantly to improving the coercive force, but significantly deteriorates the residual magnetic flux density. Furthermore, replacing Nd in whole or in part with elements such as Pr, Ce, La, Sm, Sc, Gd, Y, and Lu significantly deteriorates the magnetic properties of the residual magnetic flux density and the coercive force. Furthermore, applying hot deformation to the sintered body significantly deteriorates the magnetization of the magnet due to the refinement of the crystal grains. Based on the above, it has been difficult to achieve both saving heavy rare earth elements and achieving excellent magnetic properties and magnetization.Therefore, conventional attempts have been made to develop a technology that enables room-temperature magnetic properties to be improved and prevents the deterioration of magnetic properties associated with temperature rise when using these elements to produce Nd-Fe-B-based sintered magnets. In particular, a rare earth magnet that enables both further reduction of heavy rare earth elements and excellent magnetic properties and magnetization is currently required.

[0004] Patent Literature 1 discloses an RTB-based sintered magnet containing main phase grains consisting of an R 2 T 14B crystal, where R stands for one or more kinds of rare earth elements containing a heavy rare earth element RH as an essential element, T stands for one or more kinds of transition metal elements containing Fe or containing Fe and Co as an essential element, B stands for boron. A part of the main phase grains of the RTB-based sintered magnet includes a plurality of crystal phases with a small amount of heavy rare earth elements therein, and the crystal phase with a small amount of heavy rare earth elements is a phase consisting of an R 2 T 14B crystal and has a relatively low concentration of the heavy rare earth element relative to the concentration of the heavy rare earth element in the entire main phase grains. According to the technique described in Patent Literature 1, it is possible to obtain an RTB-based sintered magnet with improved magnetic properties at low cost.

[0005] Patent Literature 2 discloses a method for producing a rare earth magnet, comprising: a first step of producing a sintered body represented by a composition formula of (R1 1-x R2 x ) a TM b B c M dand having a structure consisting of a main phase and a grain boundary phase; a second step of producing a rare earth magnet precursor by applying hot deformation to the sintered body; and a third step of producing a rare earth magnet from the rare earth magnet precursor by causing a melt of an R3-M modified alloy to spread and penetrate the grain boundary phase of the rare earth magnet precursor.Here, R1 represents one or more rare earth elements, including Y, R2 represents a rare earth element other than R1, TM represents a transition metal, including one or more of Fe, nickel (Ni), and Co, B represents boron, and M represents one or more of titanium (Ti), gallium (Ga), zinc (Zn), silicon (Si), aluminum (Al), niobium (Nb), zirconium (Zr), Ni, Co, manganese (Mn), vanadium (V), tungsten (W), tantalum (Ta), germanium (Ge), copper (Cu), chromium (Cr), hafnium (Hf), molybdenum (Mo), phosphorus (P), carbon (C), magnesium (Mg), mercury (Hg), silver (Ag), and gold (Au). Furthermore, x, a, b, c, and d satisfy 0.01≤x≤1, 12≤a≤20, b=100-acd, 5≤c≤20, and 0≤d≤3, each in at%. R3 represents a rare earth element including R1 and R2.According to the technique described in Patent Literature 2, it is possible to produce a rare earth magnet that is excellent not only in magnetization but also in coercive force performance even when the main phase ratio is high. List of citationsPatent literature Patent literature 1: JP 2018 - 174 313 A Patent literature 2: JP 2015 - 153 813 A Brief description of the inventionProblem to be solved by the invention

[0006] However, in the RTB-based sintered magnet described in Patent Literature 1, a phase containing a heavy rare earth element is present in the main phase, which improves the coercive force, but cannot provide the residual magnetic flux density required for industrial motors or the like, which may lead to deterioration of the magnetic properties. Furthermore, since heavy rare earth elements are used, there is a problem that the procurement risk and cost cannot be reduced. Even if the rare earth magnet produced by the production method described in Patent Literature 2 can reduce heavy rare earth elements and improve the coercive force, the production method involves hot deformation. For this reason, there is a possibility that the residual magnetic flux density and magnetization of the rare earth magnet to be produced will be reduced.

[0007] The present disclosure has been made in view of the foregoing, and an object thereof is to obtain a rare earth sintered magnet capable of improving magnetic properties and magnetization compared with the related art while reducing the use of Nd and heavy rare earth elements compared with the related art. Solution to the problem

[0008] In order to solve the problems described above and to achieve the object, a rare earth sintered magnet according to the present disclosure includes a main phase satisfying a general formula (Nd, Pr, R)-Fe-B, where R represents one or more rare earth elements selected excluding Nd and Pr, the main phase comprising crystal grains based on Nd 2 Fe 14B crystal structure. The main phase includes a core portion and a shell portion covering the core portion. The main phase includes a first main phase satisfying CNd>CPr and a second main phase satisfying CNd <CPr erfüllt, wobei CNd für die Konzentration von Nd im Kernabschnitt steht und CPr für die Konzentration von Pr im Kernabschnitt steht. Die erste Hauptphase und die zweite Hauptphase werden gemischt bereitgestellt. Effects of the invention

[0009] The rare earth sintered magnet according to the present disclosure can achieve the effect of improving magnetic properties and magnetization compared to the related art while reducing the use of Nd and heavy rare earth elements compared to the related art. Short description of the drawings Fig. 1 is a diagram schematically illustrating an exemplary sintered structure of a rare earth sintered magnet according to a first embodiment. Fig. 2 is a diagram schematically illustrating an exemplary sintered structure of a rare earth sintered magnet according to the second embodiment. Fig. 3 is a representation of the atomic sites in a tetragonal Nd 2 Fe 14 B crystal structure illustrated. Fig. 4 is a flowchart illustrating an exemplary process of a method for producing a rare earth sintered magnet alloy according to the second embodiment. Fig. 5 is a flowchart illustrating an exemplary operation of a method for producing a rare earth sintered magnet according to the third embodiment. Fig. 6 is a cross-sectional view schematically illustrating an exemplary configuration of a rotor equipped with a rare earth sintered magnet according to the fourth embodiment. Fig. 7 is a cross-sectional view schematically illustrating an exemplary configuration of a rotary machine according to the fifth embodiment. Fig. 8 is a sketch of a composition image obtained by analyzing a cross section of a rare earth sintered magnet according to Examples 1 to 8 with an FE-EPMA. Fig. Figure 9 is an element map of Nd obtained by analyzing a cross section of a rare earth sintered magnet according to Examples 1 to 8 with an FE-EPMA. Fig. Figure 10 is an elemental map of Pr obtained by analyzing a cross section of a rare earth sintered magnet according to Examples 1 to 8 with an FE-EPMA. Fig. Figure 11 is an element map of O obtained by analyzing a cross section of a rare earth sintered magnet according to Examples 1 to 8 with an FE-EPMA. Fig. Figure 12 is an element map of La obtained by analyzing a cross section of a rare earth sintered magnet according to Examples 1 to 8 with an FE-EPMA. Fig. Figure 13 is an element map of Sm obtained by analyzing a cross section of a rare earth sintered magnet according to Examples 1 to 8 with an FE-EPMA. Description of embodiments

[0010] Next, in this document, a rare earth sintered magnet, a method for producing a rare earth sintered magnet, a rotor, and a rotary machine according to embodiments of the present disclosure will be described in detail with reference to the drawings. First embodiment.

[0011] Fig. 1 is a diagram schematically illustrating an exemplary sintered structure of a rare earth sintered magnet according to the first embodiment. The rare earth sintered magnet 1 according to the first embodiment includes a main phase 10 satisfying a general formula (Nd, Pr, R)-Fe-B and crystal grains based on an Nd 2 Fe 14 B crystal structure, and the main phase 10 includes a core portion and a shell portion covering the core portion. Here, R represents one or more rare earth elements selected excluding Nd and Pr. The shell portion has a composition different from that of the core portion and is provided to cover the core portion. The rare earth sintered magnet 1 further includes a subphase 20 present between the main phase 10 and the main phase 10. The subphase 20 will be described in the second embodiment.

[0012] In the rare earth sintered magnet 1 according to the first embodiment, the main phase 10 includes a first main phase 11 satisfying CNd>CPr and a second main phase 12 satisfying CNd <CPr erfüllt, wobei CNd für die Konzentration von Nd im Kernabschnitt steht und CPr für die Konzentration von Pr im Kernabschnitt steht und die erste Hauptphase 11 und die zweite Hauptphase 12 gemischt bereitgestellt sind. Die erste Hauptphase 11 beinhaltet einen Kernabschnitt 11c und einen Hüllenabschnitt 11s, der eine Zusammensetzung aufweist, die sich von der des Kernabschnitts 11c unterscheidet, und den Kernabschnitt 11c bedeckt. Die zweite Hauptphase 12 beinhaltet einen Kernabschnitt 12c und einen Hüllenabschnitt 12s, der eine Zusammensetzung aufweist, die sich von der des Kernabschnitts 12c unterscheidet, und den Kernabschnitt 12c bedeckt. CNd> CPr is fulfilled in core section 11c of the first main phase 11 and CNd <CPr ist im Kernabschnitt 12c der zweiten Hauptphase 12 erfüllt.

[0013] This means that the rare earth sintered magnet 1 has two main phases 10, namely, the first main phase 11 and the second main phase 12. Focusing on the core portions 11c and 12c of the two main phases 10, the Nd concentration in the first main phase 11 is higher than the Pr concentration, and conversely, the Pr concentration in the second main phase 12 is higher than the Nd concentration. As described above, by mixing two main phases 10 that have core-shell structures that differ in anisotropic magnetic field, i.e., magnetic anisotropy, it is possible to reduce Nd and heavy rare earth elements, and also improve the residual magnetic flux density and coercive force while maintaining good magnetization. Furthermore, it also contributes to preventing deterioration of magnetic properties associated with temperature changes.Here, the concentration difference caused by “the first main phase 11, which satisfies CNd>CPr, and the second main phase 12, which satisfies CNd <CPr erfüllt“ angegeben wird, dass es eine klare Differenz in der Erfassungsintensität von Nd und Pr durch eine Abbildungsanalyse unter Verwendung eines Elektronenstrahlmikrosondenanalysegeräts (electronic probe microanalyzer - EPMA) gibt. Unter Bezugnahme auf den Fall der ersten Hauptphase 11 als Beispiel ist konkret die EPMA-Erfassungsintensität der Konzentration von Nd in dem Kernabschnitt 11c höher als der Durchschnitt der Erfassungsintensität von Nd und die EPMA-Erfassungsintensität der Konzentration von Pr gibt ungefähr den unteren Grenzwert der Erfassungsintensität von Pr an. Der Fall in der zweiten Hauptphase 12 ist das Gegenteil des Falls in der ersten Hauptphase 11.

[0014] The rare earth sintered magnet 1 according to the first embodiment satisfies relational expressions of C1Nd>C2Nd and C1Pr <C2Pr, wobei C1Nd für die Nd-Konzentration des Kernabschnitts 11c der ersten Hauptphase 11 steht, C2Nd für die Nd-Konzentration des Kernabschnitts 12c der zweiten Hauptphase 12 steht, C1Pr für die Pr-Konzentration des Kernabschnitts 11c der ersten Hauptphase 11 steht und C2Pr für die Pr-Konzentration des Kernabschnitts 12c der zweiten Hauptphase 12 steht. Das heißt, die Nd-Konzentration ist in dem Kernabschnitt 11c der ersten Hauptphase 11 höher als in dem Kernabschnitt 12c der zweiten Hauptphase 12 und umgekehrt ist die Pr-Konzentration in dem Kernabschnitt 12c der zweiten Hauptphase 12 höher als in dem Kernabschnitt 11c der ersten Hauptphase 11. Die Konzentrationsdifferenz bedeutet hier ebenfalls, dass es eine Differenz bei der Erfassungsintensität von Nd und Pr durch die Abbildungsanalyse unter Verwendung des EPMA gibt.Specifically, in the case of the concentration of Nd, this means that the EPMA detection intensity of Nd in the core portion 11c of the first main phase 11 is higher than the average detection intensity of Nd, and the EPMA detection intensity of Nd in the core portion 12c of the second main phase 12 is lower than the average detection intensity of Nd. In the case of the concentration of Pr, this means that the EPMA detection intensity of Pr in the core portion 12c of the second main phase 12 is higher than the average detection intensity of Pr, and the EPMA detection intensity of Pr in the core portion 11c of the first main phase 11 is lower than the average detection intensity of Pr.That is, a large amount of Pr is present in the core portion 12c of the second main phase 12, which has a low Nd concentration, and conversely, a large amount of Nd is present in the core portion 11c of the first main phase 11, which has a low Pr concentration. Control to achieve such a structural shape leads to obtaining the rare earth sintered magnet 1 having excellent magnetic properties.

[0015] In the rare earth sintered magnet 1 according to the first embodiment, the first main phases 11 each satisfying CNd>CPr are more present than the second main phase 12 each satisfying CNd <CPr erfüllt. Mit anderen Worten bedeutet dies, dass die Anzahl der ersten Hauptphasen 11, die die Zusammensetzungsformel von Nd 2 Fe 14 B is greater than the number of second main phases 12, which have the composition formula of Pr 2 Fe 14B. This is due to the fact that increasing the first main phase 11, which is the composition formula of Nd 2 Fe 14 B, leads to more outstanding magnetic properties and temperature properties than increasing the second main phase 12, which has the composition formula of Pr 2 Fe 14 B. In addition, the control to achieve such a structural shape also prevents refinement of the crystal grains as a whole, so that it is possible to obtain excellent magnetic properties compared with the prior art while ensuring magnetization.

[0016] In the rare earth sintered magnet 1 according to the first embodiment, focusing on the shell portions 11s and 12s of the core-shell structures, the first main phase 11 satisfies the relational expressions of CNd>SNd and CPr <SPr und erfüllt die zweite Hauptphase 12 die relationalen Ausdrücke von CNd<SNd und CPr> SPr, where SNd represents the concentration of Nd in the shell portions 11s and 12s, and SPr represents the concentration of Pr in the shell portions 11s and 12s. Specifically, the shell portion 11s of the first main phase 11 has a higher concentration of Pr than the core portion 11c, rather than having a lower concentration of Nd, and the shell portion 12s of the second main phase 12 has a higher concentration of Nd than the core portion 12c, rather than having a lower concentration of Pr.By forming the first main phase 11 including the shell portion 11s having a high concentration of Pr in the main phase 10, the coercive force can be improved. Furthermore, by forming the second main phase 12 including the shell portion 12s having a high concentration of Nd in the main phase 10, it is possible to prevent deterioration of the residual magnetic flux density while maintaining the coercive force. By selectively controlling to achieve such a structural shape, the rare earth sintered magnet 1 can exhibit excellent magnetic properties compared to the related art.

[0017] Furthermore, the average grain size of the crystal grains of the main phase 10 is preferably 100 μm or less, and more preferably 0.5 μm to 50 μm to improve the magnetic properties. Furthermore, setting the average grain size to about 1 μm to 10 μm results in a grain size different from the microstructure produced by hot working, resulting in the rare earth sintered magnet 1 that maintains good magnetization ability and exhibits excellent magnetic properties compared to the related art.

[0018] The rare earth sintered magnet 1 according to the first embodiment may contain an additional element M that further improves the magnetic properties. The additional element M represents one or more elements selected from the group consisting of Ga, Cu, Al, Co, Zr, Ti, Nb, Dy, Tb, Mn, Gd, and Ho (holmium). Therefore, the rare earth sintered magnet 1 according to the first embodiment is represented by the general formula (Nd a Pr b R c ) Fe d B e M f described, where the additional element M stands for one or more elements selected from the group consisting of Ga, Cu, Al, Co, Zr, Ti, Nb, Dy, Tb, Mn, Gd and Ho. It is desirable that a, b, c, d, e and f satisfy the following relational expressions. 5≤a+b≤20 0 <c<(a+b) 70≤d≤90 0.5≤e≤10 0≤f≤5 a+b+c+d+e+f=100 atom−%

[0019] The rare earth sintered magnet 1 according to the first embodiment includes the main phase 10 satisfying a general formula (Nd, Pr, R)-Fe-B, where R represents one or more rare earth elements selected excluding Nd and Pr, the main phase 10 crystal grains based on a Nd 2 Fe 14 B crystal structure, wherein the main phase 10 includes a core portion and a shell portion covering the core portion, wherein the main phase 10 includes the first main phase 11 satisfying CNd>CPr and the second main phase 12 satisfying CNd <CPr erfüllt, beinhaltet und die erste Hauptphase 11 und die zweite Hauptphase 12 gemischt bereitgestellt werden. Mit einer solchen Konfiguration ist es möglich, den Seltenerd-Sintermagneten 1 zu erlangen, bei dem magnetische Eigenschaften und Magnetisierung im Vergleich zum einschlägigen Stand der Technik verbessert sind, während die Verwendung von Nd und schweren Seltenerd-Elementen reduziert ist.

[0020] The first main phase 11 and the second main phase 12 satisfy the relational expressions of C1Nd>C2Nd and C1Pr <C2Pr. Alternativ ist die Anzahl der ersten Hauptphasen 11 größer als die Anzahl der zweiten Hauptphasen 12. Alternativ erfüllt die erste Hauptphase 11 die relationalen Ausdrücke von CNd> SNd and CPr <SPr und erfüllt die zweite Hauptphase 12 die relationalen Ausdrücke von CNd<SNd und CPr> SPr. This also makes it possible to obtain the rare earth sintered magnet 1, in which magnetic properties and magnetization are improved while the use of Nd and heavy rare earth elements is reduced. Second embodiment.

[0021] Fig. Fig. 2 is a diagram schematically illustrating an exemplary sintered structure of a rare earth sintered magnet according to the second embodiment. The rare earth sintered magnet 1 according to the second embodiment includes the main phase 10 and the subphase 20. The main phase 10 includes the first main phase 11 and the second main phase 12 as described in the first embodiment, but in Fig. 2, the first main phase 11 and the second main phase 12 are collectively referred to as the main phase 10. The subphase 20 exists between the main phases 10.

[0022] In the rare earth sintered magnet 1 according to the second embodiment, a case will be described where La and Sm are selected as the element R. In a case where La and Sm are selected as the element R, the effect of improving the magnetic properties and having excellent magnetization is further enhanced compared to the related art, while the use of Nd and heavy rare earth elements is reduced. In this example, the main phase 10 has the composition formula (Nd, Pr, La, Sm). 2 Fe 14 B. The reason why the element R of the rare earth sintered magnet 1, which has a tetragonal R 2 Fe 14B crystal structure, represents rare earth elements including La and Sm. Magnetic interaction energy calculation using a molecular orbital method shows that a composition in which La and Sm are added can produce the rare earth sintered magnet 1 suitable for practical use in that deterioration of magnetic properties associated with a temperature increase can be significantly prevented. Furthermore, by intentionally segregating La and Sm even in the grain boundary, which is an example of subphase 20, it is possible to cause Nd and Pr to be relatively widespread in the main phase 10, resulting in enhanced magnetocrystalline anisotropy of the main phase 10.As a result, a core-shell structure in which a portion having high magnetic anisotropy and a portion having low magnetic anisotropy exist in the main phase 10 is formed, as well as a state in which the rare earth sintered magnet 1 in which the first main phase 11 satisfies CNd>CPr and the second main phase 12 satisfies CNd <CPr erfüllt, gemischt bereitgestellt werden, leicht gebildet wird.

[0023] It should be noted that excessive addition of La and Sm will cause a decrease in the amount of Nd and Pr, which are elements with high magnetic anisotropy constants and high magnetic saturation polarization, leading to a deterioration of magnetic properties. Therefore, (A+B)>(C+D) is preferably satisfied, where A, B, C, and D represent the composition ratios of Nd, Pr, La, and Sm, respectively.

[0024] In the rare earth sintered magnet 1 according to the second embodiment, when R=La and / or Sm in the first embodiment, the rare earth sintered magnet 1 includes the subphase 20 in addition to the first main phase 11 and the second main phase 12. The subphase 20 includes a crystalline first subphase 21 based on an oxide phase having a main component represented by (Nd, Pr, La, Sm)-O, and a crystalline second subphase 22 having a main component represented by (Nd, Pr, La)-O. The concentration of Sm in the subphase 20 is higher in the first subphase 21 than in the second subphase 22. This achieves the effect of not only preventing deterioration of the magnetic properties at room temperature but also preventing deterioration of the magnetic properties associated with a temperature rise.

[0025] Here, “the concentration of Sm is higher in the first subphase 21 than in the second subphase 22” means that the detection intensity of Sm by imaging analysis using an EPMA is on average higher in the first subphase 21 than in the second subphase 22.

[0026] The crystalline subphase 20 is a generic term for the crystalline first subphase 21 and the crystalline second subphase 22 and is present between the main phases 10. The crystalline first subphase 21 is represented by (Nd, Pr, La, Sm)-O, and the crystalline second subphase 22 is represented by (Nd, Pr, La)-O. Here, (Nd, Pr, La, Sm) means that part of Nd and Pr is replaced by La and Sm. Note that the elements of the main components are described in parentheses; therefore, the first subphase 21 and the second subphase 22 may contain a small amount of another component in addition to the elements indicated in parentheses. In one example, the second subphase 22, represented by (Nd, Pr, La)-O, contains an extremely small amount of Sm.

[0027] In the rare earth sintered magnet 1 according to the second embodiment, there is a concentration difference of La and Sm between the main phase 10 and the subphase 20, and La and Sm are more segregated in the subphase 20 than in the main phase 10. That is, the sum of the concentrations of La in the first subphase 21 and the second subphase 22 is equal to or greater than the concentration of La in the main phase 10, and the sum of the concentrations of Sm in the first subphase 21 and the second subphase 22 is equal to or greater than the concentration of Sm in the main phase 10. Specifically, the concentrations of La and Sm in the subphase 20 are equal to or higher than the concentrations of La and Sm in the main phase 10. Here, the concentration of La of the main phase 10 is the sum of the concentration of La in the first main phase 11 and the concentration of La in the second main phase 12.That is, the sum of the concentrations of La in the first subphase 21 and the second subphase 22 is higher than the sum of the concentrations of La in the first main phase 11 and the second main phase 12. Here, the concentration of Sm of the main phase 10 is the sum of the concentration of Sm in the first main phase 11 and the concentration of Sm in the second main phase 12. That is, the sum of the concentrations of Sm in the first subphase 21 and the second subphase 22 is higher than the sum of the concentrations of Sm in the first main phase 11 and the second main phase 12.

[0028] If X represents the concentration of La contained in the main phase 10, X 1 represents the concentration of La contained in the first subphase 21, X 2 represents the concentration of La contained in the second subphase 22, Y represents the concentration of Sm contained in the main phase 10, Y 1represents the concentration of Sm contained in the first subphase 21 and Y 2 represents the concentration of Sm contained in the second subphase 22, the relationship of the following formula (1) is satisfied here. 1<(Y1+Y2) / Y<(X1+X2) / X

[0029] In addition, in view of improving the magnetic properties, the relationships of the following formulas (2) and (3) are satisfied with respect to the concentrations of Nd and Pr contained in the main phase 10. (CNd+SNd)>(X+Y) (CPr+SPr)>(X+Y)

[0030] In the above description, the concentration of La in the main phase 10 is the sum of the concentrations of La in the first main phase 11 and the second main phase 12, and the concentration of Sm in the main phase 10 is the sum of the concentrations of Sm in the first main phase 11 and the second main phase 12. This indicates that both La and Sm are more segregated in the subphase 20 than in the main phase 10. However, when viewed locally, each of the sum of the concentrations of La and Sm in the first main phase 11 and the second main phase 12 and each of the sum of the concentrations of La and Sm in the first subphase 21 and the second subphase 22 may not satisfy the above relationship.Therefore, more specifically, the concentration of La in the main phase 10 represents the average of the concentrations of La in the first main phase 11 and the second main phase 12, and the concentration of Sm in the main phase 10 represents the average of the concentrations of Sm in the first main phase 11 and the second main phase 12. In this case, the concentration of La in the subphase 20, that is, the sum of the concentrations of La in the first subphase 21 and the second subphase 22, represents the average of the concentrations of La in the first subphase 21 and the second subphase 22, and the concentration of Sm in the subphase 20, that is, the sum of the concentrations of Sm in the first subphase 21 and the second subphase 22, represents the average of the concentrations of Sm in the first subphase 21 and the second subphase 22.

[0031] La is present in a high concentration in the grain boundary during the production process, especially during heat treatment, whereby Nd and Pr are relatively dispersed throughout the main phase 10. As a result, in the rare earth sintered magnet 1 according to the second embodiment, Nd and Pr in the main phase 10 are not consumed at the grain boundary, resulting in improved magnetocrystalline anisotropy. Sm is also present in the subphase 20, especially in the first subphase 21, at a higher concentration than in the main phase 10, resulting in Nd being relatively dispersed throughout the main phase 10, as in the case of La, resulting in improved magnetocrystalline anisotropy.

[0032] Next, it is described at which atomic sites of the tetragonal R 2 Fe 14 B crystal structure La and Sm are substituted. Fig. 3 is a representation of the atomic sites in a tetragonal Nd 2 Fe 14B crystal structure. It should be noted that the Fig. 3 illustrated crystal structure in an example in Fig. 1 of the reference literature shown below. The substitution sites are determined based on the numerical value of the stabilization energy associated with the substitution, which is calculated using the band calculation and the molecular field approximation based on the Heisenberg model.

[0033] (Reference literature 1): JF Herbst et al., “Relationships between crystal structure and magnetic properties in Nd 2 Fe 14 B", PHYSICAL REVIEW B. 1984, Vol. 29, No. 7, pp. 4176-4178.

[0034] First, a method for calculating the stabilization energy in La is described. The stabilization energy in La can be defined as the energy difference between (Nd 7 La 1 ) Fe 56 B 4 +Nd and Nd 8 (FessLa 1 ) B 4+Fe using Nd 8 Fez 56 B 4 -crystal cells. The smaller the energy value, the more stable it is when the atom is substituted at that site. This means that La is likely to be substituted at an atomic site that has the lowest energy among the atomic sites. This calculation assumes that substituting La for the original atom changes the lattice constant in the tetragonal R 2 Fe 14 B crystal structure does not change due to the difference in atomic radius. Table 1 shows the stabilization energy of La at each substitution site at different ambient temperatures. [Table 1] (Table 1) Substitutionsplätze für La Temperatur 293K 500K 1000K 1300K 1400K 1500K Nd(f) -136.372 -84.943 -48.524 -40.132 -38.132 -35.451 Nd(g) -132.613 -82.740 -47.442 -38.211 -36.358 -34.753 Fe(k1) -135.939 -80.596 -41.428 -32.390 -30.237 -17.095 Fe(k2) -127.480 -75.638 -38.948 -30.482 -28.466 -26.719 Fe(j1) -124.248 -73.076 -38.003 -29.754 -27.791 -26.089 Fe(j2) -117.148 -71.400 -35.923 -28.5316 -26.917 -25.271 Fe(e) -130.814 -77.593 -39.926 -31.235 -29.164 -27.371 Fe(c) -148.317 -87.850 -45.055 -35.179 -32.828 -30.789 Einheit: eV

[0035] Table 1 indicates that the stable substitution sites for La are Nd(f) sites at temperatures of 1000 K and above, and Fe(c) sites at temperatures of 293 K and 500 K. As described later, the raw material of the rare earth sintered magnet 1 according to the second embodiment is heated and melted at a temperature of 1000 K or above, and then rapidly cooled. Therefore, it is considered that the raw material of the rare earth sintered magnet 1 is maintained in a state of 1000 K or above, that is, 727 °C or above, and more preferably about 1300 K, that is, 1027 °C. In this case, it is assumed that La is substituted at Nd(f) sites or Nd(g) sites. It is assumed that La is preferentially substituted at energetically stable Nd(f) sites, but it can be substituted at Nd(g) sites that have a small energy difference between the substitution sites for La.For this reason, Nd(g) sites are also mentioned as candidates for the substitution sites for La.

[0036] Furthermore, when the rare earth sintered magnet 1 is produced using the production method described later, the temperature at the time of sintering is 1000 K or more, but the Fe(c) sites described in Table 1 are repeatedly maintained in an energetically stable temperature zone through the primary aging step, the secondary aging step, the tertiary aging step, the quaternary aging step, and the cooling step. In other words, the substitution of La at Nd sites of the main phase 10 is maintained in an unstable energy state.That is, La is mainly substituted at Nd sites of the main phase 10 in the raw material stage of the rare earth sintered magnet 1; however, in the rare earth sintered magnet 1 produced by the production method described later, by repeatedly intentionally maintaining the Nd sites of the main phase 10 in an unstable energy state within a temperature range, a certain amount of La is selectively released from the Nd sites of the main phase 10, and as a result, La is segregated in the subphase 20. As a result, the main phase 10 promotes the formation of the characteristic structure, namely the core-shell structure.

[0037] Next, a method for calculating the stabilization energy in Sm is described. The stabilization energy of Sm can be expressed as the energy difference between (Nd 7 SM 1 ) Fe 56 B 4 +Nd and Nd 8 (Fe 55 Sm 1 ) B 4+Fe. Similar to the case of La, atom substitution changes the lattice constant in the tetragonal R 2 Fe 14 B crystal structure. Table 2 shows the stabilization energy of Sm at each substitution site at different ambient temperatures. [Table 2] (Table 2) Substitutionsplätze für Sm Temperatur 293K 500K 1000K 1300K 1400K 1500K Nd(f) -164.960 -101.695 -56.921 -46.589 -44.128 -41.976 Nd(g) -168.180 -103.583 -57.865 -47.315 -44.803 -42.626 Fe(k1) -136.797 -81.098 -41.679 -32.583 -17.350 -16.343 Fe(k2) -127.769 -75.808 -38.482 -29.603 -28.528 -25.696 Fe(j1) -122.726 -73.304 -37.783 -28.392 -26.525 -24.681 Fe(j2) 124.483 -73.883 -38.072 -28.483 -26.610 -24.985 Fe(e) 125.937 72.525 35.301 26.633 24.450 22.782 Fe(c) -155.804 -94.457 -48.359 -37.720 -35.187 -32.992 Einheit: eV

[0038] Table 2 indicates that, unlike in the case of La, stable substitution sites for Sm are Nd(g) sites at any temperature. Sm is assumed to be preferentially substituted at energetically stable Nd(g) sites, but it can be substituted at Nd(f) sites that exhibit a small energy difference between the substitution sites for Sm.

[0039] When the rare earth sintered magnet 1 is produced using the production method described later, the substitution at Nd(g) sites of the main phase 10 is the most stable in terms of energy. As described above, maintaining it in a temperature range where the substitution of La at Nd sites of the main phase 10 is unstable causes some Sm to be released from the Nd sites of the main phase 10 along with La and segregated in the subphase 20. As a result, the concentrations of La and Sm differ between the main phase 10 and the subphase 20: the sum of the concentrations of La in the first subphase 21 and the second subphase 22 is equal to or greater than the concentration of La in the main phase 10, and the sum of the concentrations of Sm in the first subphase 21 and the second subphase 22 is equal to or greater than the concentration of Sm in the main phase 10.More specifically, the average of the concentrations of La in the first subphase 21 and the second subphase 22 is equal to or greater than the average of the concentrations of La in the first main phase 11 and the second main phase 12, and the average of the concentrations of Sm in the first subphase 21 and the second subphase 22 is equal to or greater than the average of the concentrations of Sm in the first main phase 11 and the second main phase 12. That is, La and Sm can be said to be segregated in the subphase 20.

[0040] When comparing La and Sm, La, which is maintained in an unstable energy state within a temperature range, is overwhelmingly more likely to be segregated in subphase 20 in terms of energy. Consequently, in the case of the rare earth sintered magnet 1 manufactured with nearly equal concentrations of La and Sm, when comparing La and Sm present in the rare earth sintered magnet 1, La has a larger segregation ratio to subphase 20. By repeatedly maintaining it in this temperature range, subphase 20 generates a concentration difference of Sm having a small segregation ratio, and the first subphase 21 and the second subphase 22 are formed. This promotes the formation of the core-shell structure in the main phase 10.

[0041] Here Nd is representative as in Fig. 3, but Nd and Pr are produced as a mixture, as represented by didymium (Di), and the energy levels of Nd and Pr are therefore considered to be close to each other. Accordingly, the same applies to a case where Nd is replaced by Pr. Since the two types of Nd and Pr are present, the main phase 10, which has two types of core-shell structures, can be formed.

[0042] As described above, the rare earth sintered magnet 1 according to the second embodiment includes the main phase 10 satisfying a general formula (Nd, Pr, R)-Fe-B, where R represents one or more rare earth elements selected excluding Nd and Pr, the main phase 10 crystal grains based on an Nd 2 Fe 14B crystal structure, wherein the main phase 10 includes a core portion and a shell portion covering the core portion, and when R=La and / or Sm, the rare earth sintered magnet 1 includes the subphase 20 in addition to the first main phase 11 and the second main phase 12 described in the first embodiment. The subphase 20 includes the crystalline first subphase 21 having a main component based on an oxide phase represented by (Nd, Pr, La, Sm)-O, and the crystalline second subphase 22 having a main component represented by (Nd, Pr, La)-O, and the concentration of Sm is higher in the first subphase 21 than in the second subphase 22. That is, the two types of main phases 10 and the two types of subphases 20 are present.As a result, it is possible to provide the rare earth sintered magnet 1 that has excellent magnetic properties, such as temperature characteristics of magnetic properties, compared with the related art. In addition, by setting R to La and Sm, the main phase 10 is in a state where the first main phase 11 satisfies CNd>CPr and the second main phase 12 satisfies CNd>CPr. <CPr erfüllt, gemischt bereitgestellt werden.In other words, in the rare earth sintered magnet 1, the main phase 10 having the two types of the first main phase 11 and the second main phase 12 are present. Focusing on the core portions of the two types of main phases 10, the main phase 10 having the two types of core-shell structures is easily generated, where the Nd concentration in the first main phase 11 is higher than the Pr concentration, and conversely, the Pr concentration in the second main phase 12 is higher than the Nd concentration. As a result, the effect of improving the magnetic properties and having excellent magnetization can be further enhanced compared to the related art while reducing the use of Nd and heavy rare earth elements. Third embodiment.

[0043] In the third embodiment, a method for producing the rare earth sintered magnet 1 described in the first or second embodiment is described separately as a method for producing a rare earth sintered magnet alloy which is the raw material of the rare earth sintered magnet 1 and a method for producing the rare earth sintered magnet 1 using the rare earth sintered magnet alloy.

[0044] Fig. 4 is a flowchart illustrating an exemplary process of a method for producing a rare earth sintered magnet alloy according to the third embodiment. As shown in Fig. As illustrated in Fig. 4, the method for producing a rare earth sintered magnet alloy, which is the raw material of the rare earth sintered magnet 1, first includes a melting step (step S1) for heating and melting the raw material of the rare earth sintered magnet alloy containing an element constituting the rare earth sintered magnet 1 at a temperature of 1000 K or higher, a primary cooling step (step S2) for cooling the molten raw material on a rotating body capable of rotation to obtain a solidified alloy, and a secondary cooling step (step S3) for further cooling the solidified alloy in a container. Thus, a rare earth sintered magnet alloy can be produced. Each step will be described below.

[0045] In the melting step S1, the raw material of the rare earth sintered magnet alloy is heated and melted at a temperature of 1000 K or higher in a crucible in an atmosphere containing an inert gas such as argon (Ar) or in a vacuum. Consequently, the rare earth sintered magnet alloy melts into a molten alloy. Nd, Pr, La, Sm, Fe, and B can be used as the raw material. FeB can be used instead of B as the raw material. At this time, one or more elements selected from the group consisting of Al, Co, Zr, Ti, Nb, Dy, Tb, Mn, Gd, and Ho can be contained in the raw material as the additive element M.

[0046] Next, in the primary cooling step S2, the molten alloy produced in the melting step is supplied to a tundish and then supplied to a single roller, which is a rotating body. Consequently, the molten alloy is rapidly cooled on the single roller rotating in a predetermined direction, and a solidified alloy thinner than the ingot alloy is produced from the molten alloy on the single roller. In this example, the single roller is used as the rotating body, but the present disclosure is not limited thereto, and twin rollers, a rotating disk, a rotating cylindrical mold, or the like may be used for rapid contact cooling. From the viewpoint of efficiently obtaining the thin solidified alloy, the cooling rate in the primary cooling step is preferably in the range of 10 °C / s to 10 7°C / s and more preferably in the range of 10 3 °C / s to 10 4 °C / s. The thickness of the solidified alloy ranges from 0.03 mm to 10 mm. The molten alloy begins to solidify at the portion in contact with the single roller, and crystals grow columnar or needle-shaped in the thickness direction from the contact surface with the single roller.

[0047] Thereafter, in the secondary cooling step S3, the thin solidified alloy produced in the primary cooling step is placed in a tray container and cooled. Upon entering the tray container, the thin solidified alloy is crushed into scaly (or flake) pieces of the rare earth sintered magnet alloy and cooled. Depending on the cooling rate, instead of scaly pieces, ribbon-shaped pieces of the rare earth sintered magnet alloy can also be obtained. From the viewpoint of obtaining the rare earth sintered magnet alloy having a structure with favorable temperature characteristics of the magnetic properties, the cooling rate in the secondary cooling step is preferably in the range of 10 -2 °C / s to 10 5 °C / s and more preferably in the range of 10 -1 °C / s to 10 2 °C / s

[0048] The rare earth sintered magnet alloy obtained through these steps has a size in the minor axis direction of 3 µm to 10 µm and a size in the major axis direction of 10 µm to 300 µm. In the case of the second embodiment, the rare earth sintered magnet alloy has a fine crystal structure including a (Nd, Pr, La, Sm)-Fe-B crystal phase and the crystalline oxide subphase 20 represented by (Nd, Pr, La, Sm)-O. Hereinafter, in this document, the crystalline oxide subphase 20 represented by (Nd, Pr, La, Sm)-O is referred to as the (Nd, Pr, La, Sm)-O phase. The (Nd, Pr, La, Sm)-O phase is a non-magnetic phase consisting of an oxide having a relatively high concentration of rare earth elements. The thickness of the (Nd, Pr, La, Sm)-O phase is 10 µm or less, which corresponds to the width of the grain boundary.After the rapid cooling step, the rare earth sintered magnet alloy produced by the above production method has a refined structure compared with the rare earth sintered magnet alloy obtained by die casting.

[0049] Next, a method for producing the rare earth sintered magnet 1 using the rare earth sintered magnet alloy will be described. Fig. 5 is a flowchart illustrating an exemplary process of a method for producing a rare earth sintered magnet according to the third embodiment. As shown in Fig. 5, the method for producing the rare earth sintered magnet 1 includes a pulverization step (step S21) for pulverizing the rare earth magnet alloy having the (Nd, Pr, La, Sm)-Fe-B crystal phase and the (Nd, Pr, La, Sm)-O phase, a molding step (step S22) for producing a molded body by molding the pulverized rare earth sintered magnet alloy, a sintering step (step S23) for obtaining a sintered body by sintering the molded body at a sintering temperature that is a predetermined temperature, and an aging step (step S24) for aging the sintered body to improve the magnetic properties, such as the coercive force, of the rare earth sintered magnet 1, and a cooling step (step S25) for cooling the sintered body that has undergone the aging process. Each step will be described below.

[0050] In the pulverization step in step S21, the rare earth sintered magnet alloy satisfying (Nd, Pr, R)-Fe-B obtained according to the method for producing a rare earth sintered magnet alloy in Fig. 4 is pulverized into rare earth sintered magnet alloy powder having a grain size of 200 µm or less, preferably 0.5 µm to 100 µm, and more preferably about 1 µm to 10 µm, taking magnetization ability into consideration. The pulverization of the rare earth sintered magnet alloy is performed using an agate mortar, a stamp mill, a jaw crusher, or a jet mill in one example. In particular, in order to reduce the grain size of the powder, it is preferable to pulverize the rare earth sintered magnet alloy in an atmosphere containing an inert gas. By pulverizing the rare earth sintered magnet alloy in an atmosphere containing an inert gas, it is possible to prevent oxygen from mixing into the powder. As long as the pulverization atmosphere does not impair the magnetic properties of the magnet, the rare earth sintered magnet alloy can be pulverized in the air.

[0051] In the molding step S22, the rare earth sintered magnet alloy powder is molded in a mold under a magnetic field to produce a molded article. Here, the applied magnetic field may be 2 T in one example. Note that molding may be performed without applying a magnetic field.

[0052] In the sintering step S23, the molded body produced by compression molding is held at a sintering temperature in the range of 950°C to 1300°C, preferably 1000°C or higher but lower than 1150°C, for a period of time ranging from 0.1 hour to 10 hours, preferably 1.0 hour to 6.0 hours, thereby obtaining a sintered body. Sintering is preferably carried out in an atmosphere containing an inert gas or in a vacuum to prevent oxidation. Sintering may be carried out under the application of a magnetic field.

[0053] In the case of Fig. 5, the aging step S24 includes a primary aging step S24-1, a secondary aging step S24-2, a tertiary aging step S24-3, and a quaternary aging step S24-4. Aging is preferably performed in an atmosphere containing an inert gas or in a vacuum to prevent oxidation.

[0054] The condition of the primary aging step in step S24-1 is that the obtained sintered body is kept for 0.1 hour to 10 hours, preferably 0.1 hour to 10 hours at a primary aging temperature which is a temperature lower than the sintering temperature, specifically at a temperature of 700 °C or higher but lower than 950 °C.

[0055] The condition of the secondary aging step in step S24-2 is that after the primary aging step, the sintered body held in the primary aging step is held for 0.1 to 10 hours, preferably 1.0 hour to 7 hours, at a secondary aging temperature which is a temperature lower than the primary aging temperature, specifically at a temperature of 450 °C or higher but lower than 700 °C.

[0056] The condition of the tertiary aging step in step S24-3 is that after the secondary aging step, the sintered body held in the secondary aging step is heated again to the primary aging temperature, specifically, a temperature of 700 °C or higher but lower than 950 °C, and held at the primary aging temperature for 0.1 to 10 hours, preferably 0.5 hours to 5 hours.

[0057] The condition of the quaternary aging step in step S24-4 is that after the tertiary aging step, the sintered body held in the tertiary aging step is held again at the secondary aging temperature, specifically, a temperature of 450 °C or higher but lower than 700 °C, for 0.1 hour to 10 hours, preferably 1.0 hour to 7 hours.

[0058] Finally, in the cooling step in step S25, the sintered body held in the quaternary aging step is held for 0.1 hour to 5 hours at a temperature lower than the secondary aging temperature, specifically, at a temperature of 200°C or higher but lower than 450°C. Thereafter, the rare earth sintered magnet 1 is finished by cooling it to room temperature. The cooling is also preferably performed in an atmosphere containing an inert gas or in a vacuum to prevent oxidation.

[0059] As described above, by controlling the temperature and time in the sintering step, the aging step, and the cooling step, the sintered body is repeatedly maintained in an unstable energy state within a temperature range. As a result, the first main phase 11 consisting of CNd>CPr and the second main phase 12 consisting of CNd <CPr besteht, gemischt werden. Mit anderen Worten weist der Seltenerd-Sintermagnet 1 zwei Arten von Hauptphasen 10 auf, nämlich die erste Hauptphase 11 und die zweite Hauptphase 12, und mit Fokus auf die Kernabschnitte der zwei Arten von Hauptphasen 10 ist es möglich, den Seltenerd-Sintermagneten 1 zu produzieren, der dadurch gekennzeichnet ist, dass in der ersten Hauptphase 11 die Nd-Konzentration höher als die Pr-Konzentration ist und umgekehrt in der zweiten Hauptphase 12 die Pr-Konzentration höher als die Nd-Konzentration ist.

[0060] Furthermore, it is possible to produce the rare earth sintered magnet 1 comprising, in addition to the first main phase 11 and the second main phase 12 described in the first embodiment, the crystalline first subphase 21 having a main component based on an oxide phase represented by (Nd, Pr, La, Sm)-O and the crystalline second subphase 22 having a main component represented by (Nd, Pr, La)-O, wherein the concentration of Sm in the first subphase 21 is higher than in the second subphase 22.

[0061] Therefore, it is possible to provide the rare earth sintered magnet 1 which has excellent magnetization ability and excellent magnetic properties compared with the related art while reducing the use of Nd and heavy rare earth elements.

[0062] In the third embodiment, the rare earth magnet alloy containing the (Nd, Pr, La, Sm)-Fe-B crystal phase and the (Nd, Pr, La, Sm)-O phase is pulverized into rare earth sintered magnet alloy powder, which is then molded. Thereafter, the molded body is sintered to form a sintered body, and the sintered body is aged to become the rare earth sintered magnet 1. Thus, the rare earth sintered magnet 1 according to the second embodiment can be produced.

[0063] In the primary aging step, the obtained sintered body is kept for 0.1 hour to 10 hours, preferably 0.5 hour to 5 hours at the primary aging temperature, which is a temperature lower than the sintering temperature, specifically at a temperature of 700 °C or higher but lower than 950 °C. In the secondary aging step, the sintered body is kept for 0.1 hour to 10 hours, preferably 1.0 hour to 7 hours at the secondary aging temperature, which is a temperature lower than the primary aging temperature, specifically at a temperature of 450 °C or higher but lower than 700 °C. In the tertiary aging step, the sintered body is heated again to the primary aging temperature, specifically a temperature of 700 °C or higher but lower than 950 °C, and kept at the primary aging temperature for 0.1 to 10 hours, preferably 0.5 hours to 5 hours.In the quaternary aging step, the sintered body is again held at the secondary aging temperature, specifically at a temperature of 450°C or higher but lower than 700°C, for 0.1 hour to 10 hours, preferably 1.0 hour to 7 hours. In this way, by controlling the temperature and time to perform two sets of the primary aging step and the secondary aging step, a state is created in which the sintered body is repeatedly held in an unstable energy state within a temperature range. As a result, it is possible to obtain the rare earth sintered magnet 1 in which the first main phase 11 consisting of CNd>CPr and the second main phase 12 consisting of CNd <CPr besteht, gemischt bereitgestellt werden.In other words, the rare earth sintered magnet 1 has two kinds of main phases 10, namely the first main phase 11 and the second main phase 12, and by focusing on the core portions of the two kinds of main phases 10, it is possible to selectively produce the rare earth sintered magnet 1 in which the Nd concentration is higher than the Pr concentration in the first main phase 11 and conversely, the Pr concentration is higher than the Nd concentration in the second main phase 12.

[0064] Furthermore, by the above production process, it is possible to selectively produce the rare earth sintered magnet 1 comprising the crystalline first subphase 21 having a main component based on an oxide phase represented by (Nd, Pr, La, Sm)-O and the crystalline second subphase 22 having a main component represented by (Nd, Pr, La)-O, wherein the concentration of Sm in the first subphase 21 is higher than in the second subphase 22. Fourth embodiment.

[0065] In the fourth embodiment, a rotor using the rare earth sintered magnet 1 according to the first embodiment or the second embodiment manufactured by the production method according to the third embodiment will be described. Fig. 6 is a cross-sectional view schematically illustrating an exemplary configuration of a rotor equipped with a rare earth sintered magnet according to the fourth embodiment. Fig. 6 shows a cross section in a direction perpendicular to a rotation axis RA of a rotor 100.

[0066] The rotor 100 is rotatable about the rotation axis RA. The rotor 100 includes a rotor core 101 and the rare earth sintered magnet 1 inserted into a magnet insertion hole 102 provided in the rotor core 101 along the circumferential direction of the rotor 100. Fig. 6 illustrates an example in which the four magnet insertion holes 102 are provided in the rotor core 101 and the four rare earth sintered magnets 1 are inserted into the magnet insertion holes 102, but the number of magnet insertion holes 102 and the number of rare earth sintered magnets 1 can be changed according to the configuration of the rotor 100. The rotor core 101 is formed by a plurality of disc-shaped electromagnetic steel sheets stacked in the axial direction of the rotation axis RA.

[0067] The rare earth sintered magnets 1 are produced using the production method described in the third embodiment. Each of the four rare earth sintered magnets 1 is inserted into the corresponding magnet insertion hole 102. The four rare earth sintered magnets 1 are magnetized such that the magnetic poles of the rare earth sintered magnets 1 on the radially outer side of the rotor 100 are different from each other between adjacent rare earth sintered magnets 1.

[0068] As described above, the rotor 100 according to the fourth embodiment includes the rare earth sintered magnet 1 according to the first embodiment or the second embodiment, which is capable of improving magnetic properties at room temperature and preventing deterioration of magnetic properties associated with a temperature rise. Thus, due to the rare earth sintered magnet 1, which is capable of preventing deterioration of magnetic properties associated with a temperature rise while maintaining high residual magnetic flux density and coercive force, deterioration of magnetic properties is prevented even in a high-temperature environment exceeding 100°C.As a result, it is possible to improve magnetic properties and magnetization while substituting inexpensive rare earth elements for Nd and heavy rare earth elements, which are expensive and have a procurement risk due to high distribution irregularities, and to stabilize the operation of the rotor 100 even in a high-temperature environment exceeding 100°C. Furthermore, since the rare earth sintered magnet 1 according to the first embodiment or the second embodiment has excellent magnetization ability compared to the related art, magnetization is possible in an assembled state in which the rare earth sintered magnet 1 is placed on the rotor 100, thus facilitating handling in the production process. Furthermore, the magnetization process can be implemented with reduced voltage, contributing to energy saving. Fifth embodiment.

[0069] In the fifth embodiment, a rotary machine equipped with the rotor 100 according to the fourth embodiment will be described. Fig. 7 is a cross-sectional view schematically illustrating an exemplary configuration of a rotary machine according to the fifth embodiment. Fig. 7 represents a cross-section in a direction perpendicular to the rotation axis RA of the rotor 100.

[0070] The rotary machine 120 includes the rotor 100 described in the fourth embodiment, which is rotatable about the rotation axis RA, and an annular stator 130 provided coaxially with the rotor 100 and facing the rotor 100. The stator 130 is formed by stacking a plurality of electromagnetic steel sheets in the axial direction of the rotation axis RA. Instead of the described configuration, another existing configuration may be adopted as the configuration of the stator 130. In the stator 130, teeth 131 are provided along the inner surface of the stator 130, which protrude toward the rotor 100. Coils 132 are provided on the teeth 131. The winding type of the coils 132 may be a concentrated winding or a distributed winding, in one example.That is, the annular stator 130 has an annular structure facing the rotor 100 and includes, on an inner surface on a side where the rotor 100 is placed, the teeth 131 protruding toward the rotor 100 and the windings 132 provided on the teeth 131. The number of magnetic poles of the rotor 100 in the rotary machine 120 should be not less than two, that is, the number of rare earth sintered magnets 1 should be not less than two. Although in . Fig. 7 illustrates an example of the rotor 100 of the inner magnet type, the rotor 100 may be of the surface magnet type in which the rare earth sintered magnets 1 are fixed to the outer circumference with an adhesive.

[0071] As described above, the rotary machine 120 according to the fourth embodiment includes the rare earth sintered magnet 1 according to the first embodiment or the second embodiment, which is capable of improving magnetic properties at room temperature and preventing deterioration of magnetic properties associated with a temperature rise. Thus, due to the rare earth sintered magnet 1 capable of preventing deterioration of magnetic properties associated with a temperature rise while maintaining high residual magnetic flux density and coercive force, deterioration of magnetic properties is prevented even in a high-temperature environment exceeding 100°C.As a result, it is possible to improve magnetic properties and magnetization while substituting low-cost rare earth elements for Nd and heavy rare earth elements, which are expensive and have a procurement risk due to high distribution irregularities, and to stably drive the rotor 100 and stabilize the operation of the rotary machine 120 even in a high-temperature environment exceeding 100 °C. [Examples]

[0072] Hereinafter, the rare earth sintered magnet 1 according to the present disclosure will be described in detail with reference to examples and comparative examples.

[0073] In Examples 1 to 8, the rare earth sintered magnet 1 is produced by the method described in the third embodiment using (Nd, Pr, La, Sm)-Fe-B-based samples of a plurality of rare earth sintered magnet alloys that differ in composition. In Examples 1 to 8, the rare earth sintered magnet 1 is produced using the rare earth sintered magnet alloys that differ in the contents of Nd, Pr, La, and Sm. That is, in Examples 1 to 8, the rare earth sintered magnet 1 is produced using the rare earth sintered magnet alloy represented by (Nd, Pr, La, Sm)-Fe-B by the production method described in the third embodiment.

[0074] In Comparative Examples 1 to 12, the rare earth sintered magnet 1 is experimentally produced using R-Fe-B-based samples of a variety of rare earth sintered magnet alloys differing in composition by a general rare earth magnet production method disclosed in Patent Literature 1 or Patent Literature 2. The samples of the rare earth sintered magnets 1 according to Comparative Examples 1 to 12 differ in R.

[0075] In Comparative Examples 1 to 6, the rare earth sintered magnet 1 is produced by using a rare earth sintered magnet alloy in which R includes Nd and a heavy rare earth element Dy or R includes Nd and any of the rare earth elements Pr, La, and Sm, by the production method disclosed in Patent Literature 1.

[0076] In Comparative Examples 7 to 12, the rare earth sintered magnet 1 is produced by using a rare earth sintered magnet alloy in which R includes Nd and a heavy rare earth element Dy or R includes Nd and any of the rare earth elements Pr, La, and Sm, by the production method disclosed in Patent Literature 2.

[0077] Table 3 shows the general formulas of the rare earth sintered magnets according to Examples and Comparative Examples, the content of elements constituting R, the results of structural analysis, and the results of determining magnetic properties and magnetization ability. Table 3 shows the general formula of the main phase 10 of each sample, which is the rare earth sintered magnet 1 according to Examples 1 to 8 and Comparative Examples 1 to 12. [Table 3]

[0078] Next, a method for analyzing the structure of the rare earth sintered magnet 1 according to Examples 1 to 8 and Comparative Examples 1 to 12 will be described. The structural shape of the rare earth sintered magnet 1 is determined by elemental analysis using a scanning electron microscope (SEM) and an electron probe microanalyzer (EPMA). Here, a field emission electron probe microanalyzer (FE-EPMA) (JEOL Ltd., product name: JXA-8530F) was used as the SEM and EPMA. The conditions for elemental analysis are as follows: acceleration voltage: 15.0 kV, irradiation current: 2.271 e -008 A, Irradiation time: 130 ms, number of pixels: 512 pixels × 512 pixels, magnification: 5000x, number of integrations: one.

[0079] Next, a method for evaluating the magnetic properties of the rare earth sintered magnet 1 according to Examples 1 to 8 and Comparative Examples 1 to 12 will be described. The evaluation of the magnetic properties is performed by measuring the coercive force of a plurality of samples using a pulse-excited BH tracer. The maximum applied magnetic field obtained by the BH tracer is equal to or greater than 6 T, and the rare earth sintered magnet alloy 1 is fully magnetized.The pulse-excited BH tracer can be replaced with a self-registering DC magnetometer, also called a DC BH tracer, a vibrating sample magnetometer (VSM), a magnetic property measurement system (MPMS), a physical property measurement system (PPMS), or the like, as long as a maximum applied magnetic field of 6 T or more can be generated. The measurement is performed in an atmosphere containing an inert gas such as nitrogen. The magnetic properties of each sample are measured by detecting a magnetization received by a search coil or a magnetic sensor on the rare-earth sintered magnet 1, which is magnetized by an applied magnetic field.Magnetic properties are measured using a JH curve or a BH curve, which is the measured magnetic hysteresis. The magnetic properties of each sample are measured at a first measurement temperature T1 and a second measurement temperature T2, which are different from each other. The temperature coefficient α [% / °C] of the residual magnetic flux density is a value obtained by calculating the ratio of the difference between the residual magnetic flux density at the first measurement temperature T1 and the residual magnetic flux density at the second measurement temperature T2 to the residual magnetic flux density at the first measurement temperature T1 and dividing the ratio by the temperature difference (T2-T1).The temperature coefficient β [% / °C] of the coercive force is a value obtained by calculating the ratio of the difference between the coercive force at the first measurement temperature T1 and the coercive force at the second measurement temperature T2 to the coercive force at the first measurement temperature T1 and dividing the ratio by the temperature difference (T2-T1). Therefore, the smaller the absolute values ​​|α| and |β| of the temperature coefficients of the magnetic properties are, the more effectively the deterioration of the magnetic properties of the magnet with respect to temperature rise is prevented.

[0080] Furthermore, the measurement of magnetization capability is obtained by calculating the magnetization rate based on the ratio between the magnetic flux density measured by the magnetic hysteresis plotted by applying an arbitrary magnetic field and the magnetic flux density measured by the magnetic hysteresis plotted by applying a saturated magnetic field at a constant permeance coefficient. If a higher magnetization rate is obtained with a lower magnetic field, the magnetization capability can be said to be high.

[0081] First, the results of the analysis of the samples according to Examples 1 to 8 and Comparative Examples 1 to 12 are described. Fig. Figure 8 is a sketch of a composition image obtained by analyzing a cross section of a rare earth sintered magnet according to Examples 1 to 8 with an FE-EPMA. Fig. 9 to 13 are element maps obtained by analyzing a cross section of a rare earth sintered magnet according to Examples 1 to 8 with the FE-EPMA. Fig. 9 is an element map of Nd, Fig. 10 is an element map of Pr, Fig. 11 is an element map of O, Fig. 12 is an element map of La and Fig. 13 is an element card of Sm. It should be noted that the Fig. 9 to 13 are the element cards that the Fig. 8. Since the rare earth sintered magnets 1 according to Examples 1 to 8 all produce similar results, the Fig. 8 to 13 are representative of Examples 1 to 8. In addition, components that meet the requirements Fig. 1 and Fig. 2, are marked with the same reference numerals.

[0082] As in the Fig. 9 and Fig. 10, each of the samples of Examples 1 to 8 includes the main phase 10 satisfying a general formula (Nd, Pr, R)-Fe-B, where R represents one or more rare earth elements selected excluding Nd and Pr, the main phase 10 crystal grains based on a Nd 2 Fe 14 B crystal structure, where the main phase 10 includes a core portion and a shell portion covering the core portion. It is also confirmed that in the main phase 10, the first main phase 11, which satisfies CNd>CPr, and the second main phase 12, which satisfies CNd <CPr erfüllt, gemischt bereitgestellt werden.

[0083] Here, the concentration difference caused by “the first main phase 11, which satisfies CNd>CPr, and the second main phase 12, which satisfies CNd <CPr erfüllt“ angegeben wird, dass es eine klare Differenz in den Erfassungsintensitäten von Nd und Pr durch eine Abbildungsanalyse unter Verwendung eines EPMA gibt. Unter Bezugnahme auf den Fall der ersten Hauptphase 11 als Beispiel ist konkret die EPMA-Erfassungsintensität der Konzentration von Nd in dem Kernabschnitt 11c höher als der Durchschnitt und die EPMA-Erfassungsintensität der Konzentration von Pr gibt ungefähr den unteren Grenzwert an. Die zweite Hauptphase 12 ist das Gegenteil der ersten Hauptphase 11.

[0084] Referring to the imaging representation of Nd in Fig. 9 and the mapping of Pr in Fig. 10 as examples, the average detection level of Nd with EPMA is 32.0, and the average detection level of Pr is 45. In the case of the first main phase 11, CNd is higher than 32.0, CPr is approximately at the lower limit, and a clear concentration difference exists. Since the second main phase 12 is the opposite of the first main phase 11, CPr is higher than 45.0, CNd is approximately at the lower limit, and a clear concentration difference exists.

[0085] As in the Fig. As illustrated in FIGS. 11 to 13, when R=La and / or Sm, the rare earth sintered magnet 1 includes the first subphase 21, which is crystalline and has a main component based on an oxide phase represented by (Nd, Pr, La, Sm)-O, and the second subphase 22, which is crystalline and has a main component represented by (Nd, Pr, La)-O, in addition to the first main phase 11 and the second main phase 12 in the first embodiment. It is confirmed that the concentration of Sm in the first subphase 21 is higher than in the second subphase 22.

[0086] In Table 3, “◯” is entered in the columns of the first main phase 11 and the second main phase 12 for the samples in which the states of the first main phase 11, which satisfies CNd>CPr, and the second main phase 12, which satisfies CNd <CPr erfüllt, bestätigt sind und „ד ist in die Spalten der ersten Hauptphase 11 und der zweiten Hauptphase 12 für die Proben eingetragen, in denen solche Zustände nicht bestätigt sind. Die Konzentrationsdifferenz von Ungleichheitszeichen bedeutet hier, dass es eine klare Differenz bei den Erfassungsintensitäten von Nd und Pr gibt. Konkret ist in einem Beispiel im Fall der ersten Hauptphase 11 die EPMA-Erfassungsintensität der Konzentration von Nd höher als der Durchschnitt und liegt die EPMA-Erfassungsintensität der Konzentration von Pr ungefähr beim unteren Grenzwert. Der Fall in der zweiten Hauptphase 12 ist das Gegenteil des Falls in der ersten Hauptphase 11.If only CNd <CPr, wie in der zweiten Hauptphase 12 bestätigt ist, wird „◯“ nur in die Spalte der zweiten Hauptphase 12 eingetragen und wird „ד in die Spalte der ersten Hauptphase 11 eingetragen.

[0087] Further, for samples confirmed to have the crystalline first subphase 21 based on an oxide phase having a main component represented by (Nd, Pr, La, Sm)-O and the crystalline second subphase 22 having a main component represented by (Nd, Pr, La)-O, and confirmed that the concentration of Sm in the first subphase 21 is higher than that in the second subphase 22, in Table 3, “◯” is entered in each of the columns of the first subphase 21 and the second subphase 22, and for samples not confirmed, “×” is entered in each of the columns of the first subphase 21 and the second subphase 22.In addition, in a case where there is only one subphase 20 or there is no Sm concentration difference between the subphases 20, "◯" is entered only in the column of the first subphase 21 and "×" is entered in the column of the second subphase 22, assuming that only the first subphase 21 exists. It should be noted that the concentration difference between the first subphase 21 and the second subphase 22 means that the detection intensity of Sm in an imaging analysis using EPMA is, on average, higher in the first subphase 21 than in the second subphase 22. Referring to the imaging representation of Sm in . Fig. 13 as an example, more specifically, the average value of the detection levels of Sm with EPMA is 5.4 and the first subphase 21 is higher than 5.4, whereas the second subphase 22 is lower than 5.4, indicating that detection in an aggregation state cannot be performed.

[0088] Furthermore, based on the intensity ratio of the element map obtained by FE-EPMA analysis, it is further confirmed that the number of first main phases 11, which are CNd>CPr, is larger than the number of second main phases 12, which are CNd <CPr sind. Mit Fokus auf den Hüllenabschnitt der Kern-Hülle-Struktur wird zudem bestätigt, dass die erste Hauptphase 11 die relationalen Ausdrücke von CNd> SNd and CPr <SPr erfüllt und die zweite Hauptphase 12 die relationalen Ausdrücke von CNd<SNd und CPr> SPr fulfilled.

[0089] Next, the results of measuring the magnetic properties of each sample according to Examples 1 to 8 and Comparative Examples 1 to 12 are described. The shape of each sample subject to magnetic measurement is a block shape with a length, width, and height of 7 mm. The first measurement temperature T1 is 23°C, and the second measurement temperature T2 is 200°C. 23°C is room temperature. 200°C of the second measurement temperature T2 is a temperature that can be encountered as an environment in which automobile engines and industrial engines operate.

[0090] First, the residual magnetic flux density and coercive force in each sample according to Examples 1 to 8 and Comparative Examples 2 to 12 were determined compared to Comparative Example 1. If the residual magnetic flux density and coercive force values ​​of each sample at 23°C are within a 1% allowable measurement error compared to the values ​​of Comparative Example 1, the values ​​are classified as "equivalent." Values ​​1% or more above are classified as "good," and values ​​1% or more below are classified as "poor."

[0091] Next, the temperature coefficient α of the residual magnetic flux density is calculated using the residual magnetic flux density at the first measurement temperature T1 of 23 °C and the residual magnetic flux density at the second measurement temperature T2 of 200 °C. The temperature coefficient β of the coercive force is calculated using the coercive force at the first measurement temperature T1 of 23 °C and the coercive force at the second measurement temperature T2 of 200 °C. The temperature coefficient of the residual magnetic flux density and the temperature coefficient of the coercive force in each sample according to Examples 1 to 8 and Comparative Examples 2 to 12 are determined in comparison with Comparative Example 1.If the values ​​of each sample are within an allowable measurement error of ±1% compared with the absolute value |α| of the temperature coefficient of the residual magnetic flux density and the absolute value |β| of the temperature coefficient of the coercive force in the sample of Comparative Example 1, the values ​​are classified as "equivalent." Values ​​of -1% or more below are classified as "good," and values ​​of +1% or more above are classified as "poor." Since the samples determined as "good" have a smaller temperature coefficient, it is possible to provide the rare earth sintered magnet 1 that exhibits stable magnetic properties even in a high-temperature environment while preventing deterioration of magnetic properties associated with a temperature rise.

[0092] Next, regarding the magnetization ability, the magnetization rate is calculated from the ratio of the magnetic flux density, which is an intersection of the magnetic hysteresis of the applied magnetic field of 20 kOe and the permeance coefficient Pc, and the magnetic flux density, which is an intersection of the magnetic hysteresis of the applied magnetic field of 80 kOe in the saturation magnetization state and the permeance coefficient Pc. The magnetization ability in each sample according to Examples 1 to 8 and Comparative Examples 2 to 12 is determined in comparison with Comparative Example 1. That is, for each sample, compared with the magnetization rate in the sample according to Comparative Example 1, values ​​of -1% or more above, which is considered a measurement error, are evaluated as "equivalent or better," and values ​​of -1% or more below are evaluated as "poor."It is possible to provide the rare earth sintered magnet 1, which has a high magnetization ability, for samples classified as “equivalent or better”.

[0093] The results of determining the residual magnetic flux density, coercive force, temperature coefficient of residual magnetic flux density, temperature coefficient of coercive force and magnetizing ability are shown in Table 3.

[0094] Comparative Example 1 is a sample of the rare earth sintered magnet 1 produced in the form of Nd-Fe-B by the production method described in Patent Literature 1 using Nd, Fe, and FeB as raw materials. From the observation of the structural shape of this sample by the above-described method, it is not confirmed that there is no core-shell structure in the main phase 10 due to the absence of Pr, La, and Sm, and it is not confirmed that the concentration of Sm in the subphase 20 is higher in the first subphase 21 than in the second subphase 22. Evaluation of the magnetic properties of this sample by the above-described method shows that the residual magnetic flux density is 1.3 T and the coercive force is 1000 kA / m. The temperature coefficients of the residual magnetic flux density and the coercive force are |α|=0.191% / °C and |β|=0.460% / °C, respectively. The magnetization rate is 98.6%.These values ​​from Comparative Example 1 are used as a reference.

[0095] Comparative Example 2 is a sample of the rare earth sintered magnet 1 produced in the form of (Nd, Dy)-Fe-B by the production method described in Patent Literature 1 using Nd, Dy, Fe, and FeB as raw materials. From the observation of the structural shape of this sample by the above-described method, it is confirmed that there is no core-shell structure in the main phase 10 due to the absence of Pr, La, and Sm, and it is not confirmed that the concentration of Sm in the subphase 20 is higher in the first subphase 21 than in the second subphase 22. The evaluation of the magnetic properties of this sample by the above-described method shows that the residual magnetic flux density is "poor," the coercive force is "good," the temperature coefficient of the residual magnetic flux density is "equivalent," the temperature coefficient of the coercive force is "equivalent," and the magnetization ability is "equivalent or better."This result reflects the fact that the coercivity is improved by substituting Dy, which has high magnetocrystalline anisotropy, for part of Nd.

[0096] Comparative Example 3 is a sample of the rare earth sintered magnet 1 produced in the form of (Nd, Pr)-Fe-B by the production method described in Patent Literature 1 using Nd, Pr, Fe, and FeB as raw materials. From the observation of the structural form of this sample by the method described above, the main phase 10 in which Nd and Pr are mixed is confirmed due to the addition of Pr, but no core-shell structure is formed. Furthermore, due to the absence of La and Sm, it is not confirmed that the concentration of Sm in the subphase 20 is higher in the first subphase 21 than in the second subphase 22.Evaluation of the magnetic properties of this sample using the method described above shows that the residual magnetic flux density is "equivalent," the coercivity is "good," the temperature coefficient of the residual magnetic flux density is "equivalent," the temperature coefficient of the coercivity is "poor," and the magnetization ability is "equivalent or better." This result reflects the fact that the addition of Pr increases the magnetic anisotropy of the main phase 10 and improves the coercivity, but the structural shape is suboptimal in the main phase 10 and subphase 20.

[0097] Comparative Example 4 is a sample of the rare earth sintered magnet 1 produced in the form of (Nd, La, Sm)-Fe-B by the production method described in Patent Literature 1 using Nd, La, Sm, Fe, and FeB as raw materials. From the observation of the structural shape of this sample by the method described above, it is confirmed that no core-shell structure exists in the main phase 10 due to the absence of Pr. In addition, due to the addition of La and Sm, the concentration of Sm is segregated in a subphase 20 along with the segregation of La, but the second subphase 22 does not exist. Furthermore, it is not confirmed that the concentration of Sm is higher in the first subphase 21 than in the second subphase 22.Evaluation of the magnetic properties of this sample using the method described above shows that the residual magnetic flux density is "equivalent," the coercivity is "equivalent," the temperature coefficient of the residual magnetic flux density is "good," the temperature coefficient of the coercivity is "good," and the magnetization ability is "equivalent or better." This result reflects the fact that the presence of La and Sm in the main phase 10 or subphase 20 produces a good result in the temperature coefficient of the magnetic properties, but the magnetic properties at room temperature are not improved, and the structural shape in the main phase 10 and subphase 20 is not optimal.

[0098] Comparative Example 5 is a sample of the rare earth sintered magnet 1 produced in the form of (Nd, La, Sm)-Fe-B by the production method described in Patent Literature 1 using Nd, La, Sm, Fe, and FeB as raw materials. The composition ratio of Nd, La, and Sm is different from that of Comparative Example 4. From the observation of the structural shape of this sample by the method described above, it is confirmed that no core-shell structure exists in the main phase 10 due to the absence of Pr. In addition, due to the addition of La and Sm, the concentration of Sm is segregated in a subphase 20 along with the segregation of La, but the second subphase 22 does not exist. Furthermore, it is not confirmed that the concentration of Sm is higher in the first subphase 21 than in the second subphase 22.Evaluation of the magnetic properties of this sample using the method described above shows that the residual magnetic flux density is "equivalent," the coercivity is "equivalent," the temperature coefficient of the residual magnetic flux density is "good," the temperature coefficient of the coercivity is "good," and the magnetization ability is "equivalent or better." This result reflects the fact that the presence of La and Sm in the main phase 10 or subphase 20 produces a good result in the temperature coefficient of the magnetic properties, but the magnetic properties at room temperature are not improved, and the structural shape in the main phase 10 and subphase 20 is not optimal: changing the composition ratio of Nd, La, and Sm leads to almost the same result as Comparative Example 4.

[0099] Comparative Example 6 is a sample of the rare earth sintered magnet 1 produced in the form of (Nd, Pr, La, Sm)-Fe-B by the production method described in Patent Literature 1 using Nd, Pr, La, Sm, Fe, and FeB as raw materials. From the observation of the structural form of this sample by the method described above, the main phase 10 in which Nd and Pr are provided in a mixed manner is confirmed due to the addition of Pr, but no core-shell structure is formed. In addition, due to the addition of La and Sm, the concentration of Sm is segregated in a subphase 20 along with the segregation of La, but the second subphase 22 does not exist. Furthermore, it is not confirmed that the concentration of Sm in the first subphase 21 is higher than that in the second subphase 22.Evaluation of the magnetic properties of this sample using the method described above shows that the residual magnetic flux density is "equivalent," the coercivity is "good," the temperature coefficient of the residual magnetic flux density is "good," the temperature coefficient of the coercivity is "equivalent," and the magnetizing ability is "equivalent or better." This result reflects the fact that the addition of Pr increases the magnetic anisotropy of the main phase 10 to improve the coercivity, and the presence of La and Sm in the main phase 10 or subphase 20 improves the temperature coefficient of the magnetic properties, especially the temperature coefficient of the coercivity, but the structural shape is not optimal in the main phase 10 and subphase 20.

[0100] Comparative Example 7 is a sample of the rare earth sintered magnet 1 produced in the form of Nd-Fe-B by the production method including the hot working method described in Patent Literature 2, using Nd, Fe, and FeB as raw materials. From the observation of the structural shape of this sample by the method described above, no core-shell structure is confirmed in the main phase 10 due to the absence of Pr, La, and Sm, and it is not confirmed that the concentration of Sm in the subphase 20 is higher in the first subphase 21 than in the second subphase 22. However, the refinement of the structure, which is a characteristic of a magnet produced by the hot working method, is confirmed.Evaluation of the magnetic properties of this sample using the method described above shows that the residual magnetic flux density is "poor," the coercivity is "good," the temperature coefficient of the residual magnetic flux density is "equivalent," the temperature coefficient of the coercivity is "equivalent," and the magnetization ability is "poor." This result reflects the decrease in the residual magnetic flux density and the deterioration of the magnetization ability, despite the improvement in the coercivity associated with the structural refinement by the hot deformation process.

[0101] Comparative Example 8 is a sample of the rare earth sintered magnet 1 produced in the form of (Nd, Dy)-Fe-B by the production method including the hot working method described in Patent Literature 2, using Nd, Dy, Fe, and FeB as raw materials. From the observation of the structural shape of this sample by the method described above, it is not confirmed that a core-shell structure exists in the main phase 10 due to the absence of Pr, La, and Sm, and it is not confirmed that the concentration of Sm in the subphase 20 is higher in the first subphase 21 than in the second subphase 22.Evaluation of the magnetic properties of this sample using the method described above shows that the residual magnetic flux density is "poor," the coercivity is "good," the temperature coefficient of the residual magnetic flux density is "equivalent," the temperature coefficient of the coercivity is "equivalent," and the magnetization ability is "poor." This indicates that the coercivity is significantly improved by substituting Dy, which has high magnetocrystalline anisotropy, for part of Nd in addition to hot deformation preparation, but the other properties reflect structural refinement.

[0102] Comparative Example 9 is a sample of the rare earth sintered magnet 1 produced in the form of (Nd, Pr)-Fe-B by the production method including the hot deformation method described in Patent Literature 2, using Nd, Pr, Fe, and FeB as raw materials. From the observation of the structural shape of this sample by the method described above, the core-shell structure is confirmed by hot deformation in addition to the addition of Pr, but there is only one type of main phase 10, which has a high Pr concentration in the core portion. In addition, due to the absence of La and Sm, it is not confirmed that the concentration of Sm in the subphase 20 is higher in the first subphase 21 than in the second subphase 22.Evaluation of the magnetic properties of this sample using the method described above shows that the residual magnetic flux density is "poor," the coercivity is "good," the temperature coefficient of the residual magnetic flux density is "equivalent," the temperature coefficient of the coercivity is "equivalent," and the magnetization ability is "poor." This indicates that the coercivity is significantly improved to the level of the rare earth sintered magnet 1 containing Dy due to the formation of the core-shell structure, which has a high Pr concentration in the core portion, but the other properties reflect structural refinement.

[0103] Comparative Example 10 is a sample of the rare earth sintered magnet 1 produced in the form of (Nd, La, Sm)-Fe-B by the production method including the hot working method described in Patent Literature 2, using Nd, La, Sm, Fe, and FeB as raw materials. From the observation of the structural shape of this sample by the method described above, it is confirmed that no core-shell structure exists in the main phase 10 due to the absence of Pr. In addition, due to the addition of La and Sm, the concentration of Sm is segregated in a subphase 20 along with the segregation of La, but the second subphase 22 does not exist. Furthermore, it is not confirmed that the concentration of Sm is higher in the first subphase 21 than in the second subphase 22.Evaluation of the magnetic properties of this sample using the method described above shows that the residual magnetic flux density is "poor," the coercivity is "good," the temperature coefficient of the residual magnetic flux density is "good," the temperature coefficient of the coercivity is "good," and the magnetization ability is "poor." This result reflects the fact that the presence of La and Sm in the main phase 10 or subphase 20 produces a good result in the temperature coefficient of the magnetic properties, but the residual magnetic flux density and magnetization ability are not improved at room temperature, and the structural shape in the main phase 10 and subphase 20 is suboptimal.

[0104] Comparative Example 11 is a sample of the rare earth sintered magnet 1 produced in the form of (Nd, La, Sm)-Fe-B by the production method including the hot working method described in Patent Literature 2, using Nd, La, Sm, Fe, and FeB as raw materials. The composition ratio of Nd, La, and Sm is different from that of Comparative Example 10. From the observation of the structural shape of this sample by the method described above, it is confirmed that no core-shell structure exists in the main phase 10 due to the absence of Pr. In addition, due to the addition of La and Sm, the concentration of Sm is segregated in a subphase 20 along with the segregation of La, but the second subphase 22 does not exist. Furthermore, it is not confirmed that the concentration of Sm is higher in the first subphase 21 than in the second subphase 22.Evaluation of the magnetic properties of this sample using the method described above shows that the residual magnetic flux density is "poor," the coercive force is "good," the temperature coefficient of the residual magnetic flux density is "good," the temperature coefficient of the coercive force is "good," and the magnetizing ability is "poor." This result reflects the fact that the presence of La and Sm in the main phase 10 or subphase 20 produces a good result in the temperature coefficient of the magnetic properties, but the residual magnetic flux density and magnetizing ability are not improved at room temperature, and the structural shape in the main phase 10 and subphase 20 is suboptimal. Changing the composition ratio of Nd, La, and Sm leads to almost the same result as in Comparative Example 10.

[0105] Comparative Example 12 is a sample of the rare earth sintered magnet 1 produced in the form of (Nd, Pr, La, Sm)-Fe-B by the production method including the hot deformation method described in Patent Literature 2, using Nd, Pr, La, Sm, Fe, and FeB as raw materials. From the observation of the structural shape of this sample by the method described above, the core-shell structure is confirmed by hot deformation in addition to the addition of Pr, but there is only one type of main phase 10, which has a high Pr concentration in the core portion. In addition, due to the addition of La and Sm, the concentration of Sm is segregated in a subphase 20 along with the segregation of La, but the second subphase 22 does not exist. Furthermore, it is not confirmed that the concentration of Sm in the first subphase 21 is higher than that in the second subphase 22.Evaluation of the magnetic properties of this sample using the method described above shows that the residual magnetic flux density is "poor," the coercivity is "good," the temperature coefficient of the residual magnetic flux density is "good," the temperature coefficient of the coercivity is "good," and the magnetization ability is "poor." This indicates that the coercivity is significantly improved to the level of the rare earth sintered magnet 1 containing Dy due to the formation of the core-shell structure having a high Pr concentration in the core portion, and the presence of La and Sm in the main phase 10 or subphase 20 improves the temperature coefficient of the magnetic properties, especially the temperature coefficient of the coercivity.

[0106] However, the result also reflects the fact that the residual magnetic flux density and magnetization ability are not improved at room temperature and the structural shape in the main phase 10 and subphase 20 is not optimal.

[0107] The samples of Examples 1 to 8 are the rare earth sintered magnet 1, which includes the main phase 10 satisfying a general formula (Nd, Pr, R)-Fe-B, where R represents one or more rare earth elements selected excluding Nd and Pr, the main phase 10 crystal grains based on a Nd 2 Fe 14B crystal structure, wherein the main phase 10 includes a core portion and a shell portion covering the core portion, wherein the main phase 10 includes the first main phase 11 satisfying CNd>CPr and the second main phase 12 satisfying CNd <CPr erfüllt, beinhaltet und die erste Hauptphase 11 und die zweite Hauptphase 12 gemischt bereitgestellt werden. Wenn R=La und / oder Sm, sind die erste Subphase 21, die kristallin ist und eine Hauptkomponente auf Grundlage einer Oxidphase aufweist, die durch (Nd, Pr, La, Sm)-O dargestellt wird, und die zweite Subphase 22, die kristallin ist und eine Hauptkomponente aufweist, die durch (Nd, Pr, La)-O dargestellt wird, zusätzlich zu der ersten Hauptphase 11 und der zweiten Hauptphase 12 beinhaltet, und die Konzentration von Sm ist in der ersten Subphase 21 höher als in der zweiten Subphase 22.Evaluation of the magnetic properties of the samples according to Examples 1 to 8 using the method described above shows that the residual magnetic flux density is "good," the coercive force is "good," the temperature coefficient of the residual magnetic flux density is "good," the temperature coefficient of the coercive force is "good," and the magnetization ability is "equivalent to or better." As a result, these rare earth sintered magnets 1 achieve the effect of having excellent magnetic properties and excellent magnetization compared with the related art, while reducing the use of Nd and heavy rare earth elements, which are expensive and have a procurement risk due to high distribution irregularities.

[0108] The configurations described in the above-mentioned embodiments are examples. The embodiments can be combined with other well-known techniques and with each other, and some of the configurations may be omitted or changed within a range that does not deviate from the essence. List of reference symbols

[0109] 1 rare earth sintered magnet; 10 main phase; 11 first main phase; 11c, 12c core section; 11s, 12s shell section; 12 second main phase; 20 subphase; 21 first subphase; 22 second subphase; 100 rotor; 101 rotor core; 102 magnet insertion hole; 120 lathe; 130 stator; 131 teeth; 132 windings. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2018 - 174 313 A

[0005] JP 2015 - 153 813 A

[0005] Cited non-patent literature

[0000] JF Herbst et al., “Relationships between crystal structure and magnetic properties in Nd 2 Fe 14 B", PHYSICAL REVIEW B. 1984, Vol. 29, No. 7, pp. 4176-4178

[0033]

Claims

[1] A rare earth sintered magnet comprising a main phase satisfying a general formula (Nd, Pr, R)-Fe-B, where R represents one or more rare earth elements selected excluding Nd and Pr, the main phase comprising crystal grains based on a Nd2Fe 14 B-crystal structure, where the main phase includes a core section and a shell section covering the core section, the main phase a first main phase that satisfies CNd>CPr and a second main phase that satisfies CNd <CPr erfüllt, beinhaltet, wobei CNd für die Konzentration von Nd im Kernabschnitt steht und CPr für die Konzentration von Pr im Kernabschnitt steht, und the first main phase and the second main phase are provided mixed. [2] Rare earth sintered magnet according to claim 1, wherein relational expressions of C1Nd>C2Nd and C1Pr <C2Pr erfüllt sind, wobei C1Nd für eine Nd-Konzentration des Kernabschnitts der ersten Hauptphase steht, C2Nd für eine Nd-Konzentration des Kernabschnitts der zweiten Hauptphase steht, C1Pr für eine Pr-Konzentration des Kernabschnitts der ersten Hauptphase steht und C2Pr für eine Pr-Konzentration des Kernabschnitts der zweiten Hauptphase steht. [3] A rare earth sintered magnet according to claim 1, wherein the number of the first main phases is greater than the number of the second main phases. [4] A rare earth sintered magnet according to claim 1, wherein the first main phase has relational expressions of CNd>SNd and CPr <SPr erfüllt und die zweite Hauptphase relationale Ausdrücke von CNd<SNd und CPr> SPr, where SNd is the concentration of Nd in the shell portion and SPr is the concentration of Pr in the shell portion. [5] The rare earth sintered magnet according to claim 1, further comprising, when R=La and / or Sm, a first subphase which is crystalline and has a main component based on an oxide phase represented by (Nd, Pr, La, Sm)-O, and a second subphase which is crystalline and has a main component represented by (Nd, Pr, La)-O, wherein a concentration of Sm in the first subphase is higher than in the second subphase. [6] A rare earth sintered magnet according to claim 5, wherein 1<(Y1+Y2) / Y<(X1+X2) / X is satisfied, where X represents the concentration of La contained in the main phase, X1 represents the concentration of La contained in the first subphase, X2 represents the concentration of La contained in the second subphase, Y represents the concentration of Sm contained in the main phase, Y1 represents the concentration of Sm contained in the first subphase, and Y2 represents the concentration of Sm contained in the second subphase. [7] Rare earth sintered magnet according to claim 4, wherein Concentrations of Nd and Pr contained in the first main phase satisfy a relational expression of (CNd+SNd)>(X+Y) and Concentrations of Nd and Pr contained in the second main phase satisfy a relational expression of (CPr+SPr)>(X+Y). [8] A method for producing the rare earth sintered magnet according to any one of claims 1 to 7, the method comprising: a melting step of melting a raw material of a rare earth sintered magnet alloy containing an element constituting the rare earth sintered magnet; a primary cooling step for cooling the raw material melted in the melting step to obtain a solidified alloy; a secondary cooling step for further cooling the solidified alloy to obtain a rare earth sintered magnet alloy; a pulverization step of pulverizing the rare earth sintered magnet alloy satisfying (Nd, Pr, R)-Fe-B; a molding step of producing a molded article by molding a powder of the rare earth sintered magnet alloy pulverized in the pulverizing step; a sintering step of obtaining a sintered body by sintering the molded body at a sintering temperature which is a predetermined temperature; a primary aging step of maintaining the sintered body at a primary aging temperature which is a temperature lower than the sintering temperature; a secondary aging step of holding the sintered body held in the primary aging step at a secondary aging temperature which is a temperature lower than the primary aging temperature; a tertiary aging step for again holding the sintered body held in the secondary aging step at the primary aging temperature; a quaternary aging step for again holding the sintered body held in the tertiary aging step at the secondary aging temperature; and a cooling step for cooling the sintered body held in the quaternary aging step. [9] Rotor, comprising: a rotor core; and the rare earth sintered magnet according to any one of claims 1 to 7, which is provided in the rotor core. [10] Rotary machine, comprising: the rotor according to claim 9; and an annular stator facing the rotor and including, on an inner surface on a side where the rotor is placed, windings provided on teeth projecting toward the rotor.

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