Rare earth sintered magnet, method for manufacturing rare earth sintered magnet, rotor, and rotating electrical machine

Abstract

A rare earth sintered magnet (1) has a main phase (10) which contains crystal particles having a Nd2Fe14B crystal structure as a base and satisfying a general formula (Nd, Pr, R)-Fe-B, when R is one or more types of rare earth element selected from rare earth elements other than Nd and Pr. The main phase (10) has a core section and a shell section which covers the core section. The main phase (10) has a first main phase (11) in which CNd>CPr and a second main phase (12) in which CNd<CPr, when the concentration of Nd in the core section is CNd and the concentration of Pr in the core section is CPr. The first main phase (11) and the second main phase (12) are mixed with one another.

Description

Technical Field

[0001] The present disclosure relates to a rare earth sintered magnet which is a permanent magnet obtained by sintering a material containing rare earth elements, a method for manufacturing the rare earth sintered magnet, a rotor, and a rotating machine.

Background Art

[0002] Tetragonal R2T 14 R-T-B based permanent magnets having a tetragonal R2T 14 B intermetallic compound as a main phase are known. Here, R is a rare earth element, T is a transition metal element such as Fe (iron) or Fe partially substituted by Co (cobalt), and B is boron. R-T-B based permanent magnets are used in various high-value-added components including industrial motors. In particular, Nd-Fe-B based sintered magnets in which R is Nd (neodymium) are used in various components because of their excellent magnetic properties. In addition, since industrial motors are often used in high-temperature environments exceeding 100°C, attempts have been made to improve the coercive force by adding heavy rare earth elements such as Dy (dysprosium) to Nd-T-B based sintered magnets.

[0003] In recent years, the production volume of Nd-Fe-B sintered magnets has been expanding, and the consumption of heavy rare earth elements such as Nd and Dy, Tb (terbium) has been increasing. However, Nd and heavy rare earth elements are expensive and have a high degree of regional concentration and procurement risks. Therefore, as a measure to reduce the consumption of Nd and heavy rare earth elements, using magnets that form a main phase containing a low heavy rare earth phase, using other rare earth elements such as Pr (praseodymium), Ce (cerium), La (lanthanum), Sm (samarium), Sc (scandium), Gd (gadolinium), Y (yttrium) and Lu (lutetium) for R, manufacturing by a special manufacturing method such as hot plastic working the sintered body, etc. are considered. Hereinafter, the hot plastic working applied to the sintered body is referred to as hot working. However, although incorporating a significant amount of heavy rare earth elements into the main phase contributes to an improvement in coercivity, the residual magnetic flux density significantly decreases. Also, when all or part of Nd is replaced with elements such as Pr, Ce, La, Sm, Sc, Gd, Y and Lu, the magnetic properties of the residual magnetic flux density and coercivity significantly deteriorate. Furthermore, when the sintered body is subjected to hot working, the magnetism of the magnet significantly decreases due to the refinement of crystal grains. From the above, it has been difficult to achieve both reduction of heavy rare earths and excellent magnetic properties and magnetism. Therefore, conventionally, when these elements are used in the manufacture of Nd-Fe-B sintered magnets, attempts have been made to develop technologies that can improve the magnetic properties at room temperature and suppress the deterioration of magnetic properties accompanying temperature rise. In particular, at present, there is a demand for rare earth magnets that can achieve both further reduction of heavy rare earth elements and excellent magnetic properties and magnetism.

[0004] Patent Document 1 discloses an R-T-B sintered magnet containing main phase particles composed of R2T 14 B crystals, where R is one or more rare earth elements including the heavy rare earth element RH as an essential component, T is one or more transition metal elements including Fe or Fe and Co as an essential component, B is boron, and a part of the main phase particles contains a plurality of low heavy rare earth element crystal phases inside, and the low heavy rare earth element crystal phase is R2T 14An R-T-B sintered magnet is disclosed which is composed of B crystals and has a phase in which the concentration of the heavy rare earth element is relatively low with respect to the concentration of the heavy rare earth element in the entire main phase particles. According to the technique described in Patent Document 1, an R-T-B sintered magnet with improved magnetic properties and low cost can be obtained.

[0005] Patent Document 2 discloses a method for manufacturing a sintered body having a structure composed of a main phase and a grain boundary phase, represented by the composition formula of (R1 1-x R2 x ) a TM b B c M d , which comprises a first step of manufacturing a sintered body having a structure composed of a main phase and a grain boundary phase, a second step of subjecting the sintered body to hot working to manufacture a rare earth magnet precursor, and a third step of diffusing and infiltrating a melt of an R3-M modified alloy into the grain boundary phase of the rare earth magnet precursor to manufacture a rare earth magnet. Here, R1 is one or more rare earth elements including Y, R2 is a rare earth element different from R1, TM is a transition metal containing one or more of Fe, Ni (nickel), and Co, B is boron, and M is one or more of Ti (titanium), Ga (gallium), Zn (zinc), Si (silicon), Al (aluminum), Nb (niobium), Zr (zirconium), Ni, Co, Mn (manganese), V (vanadium), W (tungsten), Ta (tantalum), Ge (germanium), Cu (copper), Cr (chromium), Hf (hafnium), Mo (molybdenum), P (phosphorus), C (carbon), Mg (magnesium), Hg (mercury), Ag (silver), and Au (gold). Also, x, a, b, c, d satisfy 0.01 ≦ x ≦ 1, 12 ≦ a ≦ 20, b = 100 - a - c - d, 5 ≦ c ≦ 20, 0 ≦ d ≦ 3, and all are at%. Further, R3 is a rare earth element including R1 and R2. According to the technique described in Patent Document 2, a rare earth magnet excellent not only in magnetization but also in coercive force performance can be manufactured even when the main phase ratio is high.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

[0007] However, in the R-T-B sintered magnet described in Patent Document 1, since the phase containing the heavy rare earth element exists in the main phase, even if the coercive force can be improved, the residual magnetic flux density required for industrial motors and the like cannot be obtained, and the magnetic properties may deteriorate. Furthermore, since heavy rare earth elements are used, there is a problem that procurement risk and cost reduction cannot be achieved. In addition, even if the rare earth magnet manufactured by the manufacturing method described in Patent Document 2 can reduce the heavy rare earth element and improve the coercive force, the hot working is included in the manufacturing method. For this reason, there is a possibility that the residual magnetic flux density and the magnetism of the manufactured rare earth magnet may be reduced.

[0008] The present disclosure has been made in view of the above, and an object thereof is to obtain a rare earth sintered magnet capable of improving magnetic properties and magnetism as compared with the conventional ones while suppressing the use of Nd and heavy rare earth elements as compared with the conventional ones. [Means for Solving the Problems]

[0009] In order to solve the above-described problems and achieve the object, when R is one or more rare earth elements selected from other than Nd and Pr, the rare earth sintered magnet according to the present disclosure satisfies the general formula (Nd, Pr, R)-Fe-B, and has a main phase containing crystal grains based on the Nd2Fe 14 B crystal structure. The main phase has a core part and a shell part covering the core part. The main phase has a first main phase in which the concentration of Nd in the core part is CNd and the concentration of Pr in the core part is CPr, and CNd > CPr, and a second main phase in which CNd < CPr. The first main phase and the second main phase are mixed. [Effects of the Invention]

[0010] The rare earth sintered magnet according to the present disclosure has an effect that it can improve magnetic properties and magnetism-attracting property as compared with the conventional ones while suppressing the use of Nd and heavy rare earth elements as compared with the conventional ones.

Brief Description of the Drawings

[0011]

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Mode for Carrying Out the Invention

[0012] Hereinafter, a rare-earth sintered magnet, a method for manufacturing a rare-earth sintered magnet, a rotor, and a rotating machine according to an embodiment of the present disclosure will be described in detail with reference to the drawings.

[0013] Embodiment 1. FIG. 1 is a diagram schematically showing an example of the structure of the sintered state of the rare-earth sintered magnet according to Embodiment 1. The rare-earth sintered magnet 1 according to Embodiment 1 satisfies the general formula (Nd, Pr, R)-Fe-B and has a main phase 10 containing crystal grains based on the Nd2Fe 14 B crystal structure. The main phase 10 has a core portion and a shell portion covering the core portion. Here, R is one or more rare-earth elements selected from other than Nd and Pr. The shell portion has a composition different from that of the core portion and is provided so as to cover the core portion. Further, the rare-earth sintered magnet 1 further has a secondary phase 20 existing between the main phases 10. The secondary phase 20 will be described in Embodiment 2.

[0014] In the rare-earth sintered magnet 1 according to Embodiment 1, when the concentration of Nd in the core portion is denoted as CNd and the concentration of Pr in the core portion is denoted as CPr, the main phase 10 has a first main phase 11 where CNd > CPr and a second main phase 12 where CNd < CPr, and the first main phase 11 and the second main phase 12 are mixed. The first main phase 11 has a core portion 11c and a shell portion 11s whose composition is different from that of the core portion 11c and covers the core portion 11c. The second main phase 12 has a core portion 12c and a shell portion 12s whose composition is different from that of the core portion 12c and covers the core portion 12c. In the core portion 11c of the first main phase 11, CNd > CPr, and in the core portion 12c of the second main phase 12, CNd < CPr.

[0015] That is, the rare earth sintered magnet 1 has two types of main phases 10, namely, a first main phase 11 and a second main phase 12. Focusing on the core portions 11c and 12c of the two types of main phases 10, it means that in the first main phase 11, the Nd concentration is higher than the Pr concentration, and conversely, in the second main phase 12, the Pr concentration is higher than the Nd concentration. By mixing the two types of main phases 10 having a core-shell structure with different anisotropic magnetic fields, i.e., magnetic anisotropy, it is possible to improve the residual magnetic flux density and coercive force while maintaining good magnetism while reducing Nd and heavy rare earth elements. Furthermore, it also contributes to suppressing the decrease in magnetic properties accompanying temperature changes. Here, the concentration difference shown in "the first main phase 11 where CNd > CPr and the second main phase 12 where CNd < CPr" means that there is a clear difference in the detection intensities of Nd and Pr by mapping analysis using an electron probe micro analyzer (EPMA). Specifically, taking the case of the first main phase 11 as an example, regarding the concentration of Nd in the core portion 11c, the detection intensity of EPMA is higher than the average of the detection intensities of Nd, and regarding the concentration of Pr, the detection intensity of EPMA indicates near the lower limit of the detection intensity of Pr. It can be said that the second main phase 12 is the opposite of the case of the first main phase 11.

[0016] Also, in the rare-earth sintered magnet 1 according to Embodiment 1, when the Nd concentration in the core portion 11c of the first main phase 11 is C1Nd, the Nd concentration in the core portion 12c of the second main phase 12 is C2Nd, the Pr concentration in the core portion 11c of the first main phase 11 is C1Pr, and the Pr concentration in the core portion 12c of the second main phase 12 is C2Pr, the relational expressions C1Nd > C2Nd and C1Pr < C2Pr are satisfied. That is, regarding the Nd concentration, the core portion 11c of the first main phase 11 is higher than the core portion 12c of the second main phase 12, and conversely, regarding the Pr concentration, the core portion 12c of the second main phase 12 is higher than the core portion 11c of the first main phase 11. The concentration difference here also means that there is a difference in the detection intensity of Nd and Pr by the mapping analysis using the above EPMA. Specifically, in the case of the Nd concentration, the EPMA detection intensity of Nd in the core portion 11c of the first main phase 11 is higher than the average of the Nd detection intensities, and the EPMA detection intensity of Nd in the core portion 12c of the second main phase 12 is lower than the average of the Nd detection intensities. In the case of the Pr concentration, the EPMA detection intensity of Pr in the core portion 12c of the second main phase 12 is higher than the average of the Pr detection intensities, and the EPMA detection intensity of Pr in the core portion 11c of the first main phase 11 is lower than the average of the Pr detection intensities. That is, there is a large amount of Pr in the core portion 12c of the second main phase 12 where the Nd concentration is low, and conversely, there is a large amount of Nd in the core portion 11c of the first main phase 11 where the Pr concentration is low. By controlling to such a tissue form, it becomes possible to obtain the rare-earth sintered magnet 1 having excellent magnetic characteristics.

[0017] Also, in the rare-earth sintered magnet 1 according to Embodiment 1, the first main phase 11 where CNd > CPr is made to exist in a larger amount than the second main phase 12 where CNd < CPr. In other words, the number of the first main phases 11 having the composition formula of Nd2Fe 14 B is larger than the number of the second main phases 12 having the composition formula of Pr2Fe 14 B. This means that increasing the number of the first main phases 11 having the composition formula of Nd2Fe 14 B is more beneficial than increasing the number of the second main phases 12 having the composition formula of Pr2Fe 14This is because more excellent magnetic properties and temperature characteristics can be obtained than by increasing the second main phase 12 having the composition formula of B. Furthermore, by controlling to such a microstructure, the refinement of the overall crystal grains is also suppressed, so that it is possible to obtain excellent magnetic properties compared to the prior art while ensuring the magnetization.

[0018] Also, in the rare earth sintered magnet 1 according to Embodiment 1, paying attention to the shell portions 11s and 12s of the core-shell structure, when the Nd concentration in the shell portions 11s and 12s is denoted as S Nd and the Pr concentration in the shell portions 11s and 12s is denoted as S Pr, the first main phase 11 satisfies the relational expressions of C Nd > S Nd and C Pr < S Pr, and the second main phase 12 satisfies the relational expressions of C Nd < S Nd and C Pr > S Pr. Specifically, in the shell portion 11s of the first main phase 11, instead of a low Nd concentration, the Pr concentration is higher than that in the core portion 11c, and in the shell portion 12s of the second main phase 12, instead of a low Pr concentration, the Nd concentration is higher than that in the core portion 12c. By forming the main phase 10 having the shell portion 11s with a high Pr concentration like the first main phase 11, the coercivity can be improved. Furthermore, by forming the main phase 10 having the shell portion 12s with a high Nd concentration like the second main phase 12, it is possible to suppress a decrease in the residual magnetic flux density while maintaining the coercivity. By selectively controlling to such a microstructure, the rare earth sintered magnet 1 can exhibit excellent magnetic properties compared to the prior art.

[0019] Furthermore, the average grain diameter of the crystal grains of the main phase 10 is preferably 100 μm or less, and more preferably 0.5 μm or more and 50 μm or less for improving the magnetic properties. Further, by setting it to about 1 μm or more and 10 μm or less, it becomes a grain diameter different from the fine structure manufactured from hot working, and good magnetization performance is maintained, making it possible to obtain a rare earth sintered magnet 1 having excellent magnetic properties compared to the prior art.

[0020] The rare-earth sintered magnet 1 according to Embodiment 1 may contain an additive element M for further improving magnetic properties. The additive element M is 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 Embodiment 1 has a general formula of (Nd a Pr b R c )Fe d B e M f and is represented by, and the additive element M is 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.

[0021] 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 atomic %

[0022] When the rare-earth sintered magnet 1 according to Embodiment 1 uses one or more rare-earth elements selected from other than Nd and Pr as R, it satisfies the general formula (Nd, Pr, R)-Fe-B, and in the main phase 10 containing crystal grains based on the Nd2Fe 14 B crystal structure, there exists a main phase 10 having a core portion and a shell portion covering the core portion. The main phase 10 has a first main phase 11 where CNd > CPr and a second main phase 12 where CNd < CPr, and the first main phase 11 and the second main phase 12 are mixed. With such a configuration, it is possible to obtain the rare-earth sintered magnet 1 with improved magnetic properties and magnetization while suppressing the use of Nd and heavy rare-earth elements as compared with the prior art.

[0023] In addition, the first main phase 11 and the second main phase 12 were made to satisfy the relational expressions of C1Nd > C2Nd and C1Pr < C2Pr. Alternatively, the number of the first main phase 11 was made larger than the number of the second main phase 12. Alternatively, the first main phase 11 was made to satisfy the relational expressions of CNd > SNd and CPr < SPr, and the second main phase 12 was made to satisfy the relational expressions of CNd < SNd and CPr > SPr. Also by this, while suppressing the use of Nd and heavy rare earth elements, the rare earth sintered magnet 1 with improved magnetic properties and adhesion magnetism can be obtained.

[0024] Embodiment 2. FIG. 2 is a diagram schematically showing an example of the structure of the sintered state of the rare earth sintered magnet according to Embodiment 2. The rare earth sintered magnet 1 according to Embodiment 2 has a main phase 10 and a secondary phase 20. The main phase 10 includes the first main phase 11 and the second main phase 12 as described in Embodiment 1, 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 secondary phase 20 exists between the main phases 10.

[0025] In the rare earth sintered magnet 1 according to Embodiment 2, the case where La and Sm are selected for the element R is shown. When La and Sm are selected for the element R, while suppressing the use of Nd and heavy rare earth elements, the effect of improving the magnetic properties and having excellent adhesion magnetism compared to the prior art becomes even greater. In this example, the main phase 10 has a composition formula of (Nd, Pr, La, Sm)2Fe 14 B. The tetragonal R2Fe 14The reason for using rare earth elements containing La and Sm as the element R of the rare earth sintered magnet 1 having a B crystal structure is that, from the calculation results of the magnetic interaction energy using the molecular orbital method, a practical rare earth sintered magnet 1 can be obtained in which the decrease in magnetic properties accompanying the temperature rise can be greatly suppressed by using a composition containing La and Sm. Further, by intentionally segregating La and Sm also at the grain boundary which is an example of the secondary phase 20, Nd and Pr can be relatively diffused into the primary phase 10, and the crystalline magnetic anisotropy of the primary phase 10 can be enhanced. As a result, a core-shell structure in which a portion with high magnetic anisotropy and a portion with low magnetic anisotropy exist within the primary phase 10 is formed, and a state is formed in which it is easy to form the rare earth sintered magnet 1 in which the first primary phase 11 with CNd > CPr and the second primary phase 12 with CNd < CPr are mixed.

[0026] In addition, if the addition amounts of La and Sm are too large, the amounts of Nd and Pr, which are elements with high magnetic anisotropy constant and saturation magnetic polarization, will decrease, leading to a deterioration of the magnetic properties. Therefore, when the composition ratios of Nd, Pr, La, and Sm are A, B, C, and D, respectively, it is preferable that (A + B) > (C + D).

[0027] In the rare earth sintered magnet 1 according to Embodiment 2, when R = La, Sm, in addition to the first primary phase 11 and the second primary phase 12 in Embodiment 1, it has a secondary phase 20. The secondary phase 20 has a crystalline first secondary phase 21 based on an oxide phase whose main component is represented as (Nd, Pr, La, Sm)-O, and a crystalline second secondary phase 22 whose main component is represented as (Nd, Pr, La)-O. The concentration of Sm in the secondary phase 20 is characterized in that it is higher in the first secondary phase 21 than in the second secondary phase 22. Thereby, not only the magnetic properties at room temperature but also the effect of suppressing the decrease in magnetic properties accompanying the temperature rise is exhibited.

[0028] Here, "the concentration of Sm is higher in the first secondary phase 21 than in the second secondary phase 22" means that the detection intensity of Sm is on average higher in the first secondary phase 21 than in the second secondary phase 22 by mapping analysis using EPMA.

[0029] The crystalline secondary phase 20 is a general term for the crystalline first secondary phase 21 and the crystalline second secondary phase 22, and exists between the primary phases 10. The crystalline first secondary phase 21 is represented by (Nd, Pr, La, Sm)-O, and the crystalline second secondary phase 22 is represented by (Nd, Pr, La)-O. Here, (Nd, Pr, La, Sm) means that part of Nd and Pr is substituted by La and Sm. Since the main component elements are described in parentheses here, the first secondary phase 21 and the second secondary phase 22 may contain trace amounts of other components in addition to the elements shown in the parentheses. In one example, the second secondary phase 22 represented by (Nd, Pr, La)-O contains a very small amount of Sm.

[0030] In the rare earth sintered magnet 1 according to Embodiment 2, there is a concentration difference of La and Sm between the primary phase 10 and the secondary phase 20, and La and Sm are segregated in the secondary phase 20 rather than in the primary phase 10. That is, the sum of the La concentrations in the first secondary phase 21 and the second secondary phase 22 is equal to or higher than the La concentration in the primary phase 10, and the sum of the Sm concentrations in the first secondary phase 21 and the second secondary phase 22 is equal to or higher than the Sm concentration in the primary phase 10. Specifically, the La and Sm concentrations in the secondary phase 20 are equal to or higher than the La and Sm concentrations in the primary phase 10. The La concentration in the primary phase 10 here is the sum of the La concentrations in the first primary phase 11 and the second primary phase 12. That is, the sum of the La concentrations in the first secondary phase 21 and the second secondary phase 22 is higher than the sum of the La concentrations in the first primary phase 11 and the second primary phase 12. Also, the Sm concentration in the primary phase 10 is the sum of the Sm concentrations in the first primary phase 11 and the second primary phase 12. That is, the sum of the Sm concentrations in the first secondary phase 21 and the second secondary phase 22 is higher than the sum of the Sm concentrations in the first primary phase 11 and the second primary phase 12.

[0031] Here, when the La concentration contained in the primary phase 10 is X, the La concentration contained in the first secondary phase 21 is X1, the La concentration contained in the second secondary phase 22 is X2, the Sm concentration contained in the primary phase 10 is Y, the Sm concentration contained in the first secondary phase 21 is Y1, and the Sm concentration contained in the second secondary phase 22 is Y2, the relationship of the following formula (1) is satisfied.

[0032] 1 < (Y1 + Y2) / Y < (X1 + X2) / X ····(1)

[0033] Furthermore, from the viewpoint of improving magnetic properties, with respect to the concentrations of Nd and Pr contained in the main phase 10, the relationships of the following formulas (2) and (3) are satisfied.

[0034] (CNd + SNd) > (X + Y) ····(2) (CPr + SPr) > (X + Y) ····(3)

[0035] 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 segregated to the secondary phase 20 rather than the main phase 10. However, when viewed locally, the sum of the respective concentrations of La and Sm in the first main phase 11 and the second main phase 12 and the sum of the respective concentrations of La and Sm in the first secondary phase 21 and the second secondary phase 22 may not satisfy the above-described relationship. Therefore, more specifically, the concentration of La in the main phase 10 indicates 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 indicates 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 secondary phase 20, that is, the sum of the concentrations of La in the first secondary phase 21 and the second secondary phase 22, means the average of the concentrations of La in the first secondary phase 21 and the second secondary phase 22, and the concentration of Sm in the secondary phase 20, that is, the sum of the concentrations of Sm in the first secondary phase 21 and the second secondary phase 22, means the average of the concentrations of Sm in the first secondary phase 21 and the second secondary phase 22.

[0036] La is present at a high concentration at grain boundaries during the manufacturing process, particularly the heat treatment process, and thus relatively diffuses Nd and Pr into the main phase 10. As a result, in the rare earth sintered magnet 1 in Embodiment 2, the Nd and Pr in the main phase 10 are not consumed at the grain boundaries, and the crystalline magnetic anisotropy is improved. Also in the case of Sm, since it is present at a high concentration in the secondary phase 20, particularly the first secondary phase 21, compared to the main phase 10, it relatively diffuses Nd into the main phase 10 in the same manner as La, improving the crystalline magnetic anisotropy.

[0037] Next, it will be described at which atomic site in the tetragonal R2Fe 14 B crystal structure La and Sm are substituted. FIG. 3 is a diagram showing the atomic sites in the tetragonal Nd2Fe 14 B crystal structure. Note that the crystal structure shown in FIG. 3 is an example and is described in FIG. 1 of Reference 1 shown below. The site to be substituted is determined by calculating the stabilization energy due to substitution by band calculation and the molecular field approximation of the Heisenberg model, and by the numerical value of that energy. (Reference 1) J.F. Herbst et al. “Relationships between crystal structure and magnetic properties in Nd2Fe 14 B”. PHYSICAL REVIEW B. 1984, Vol.29, No.7, p. 4176 - 4178.

[0038] First, the method for calculating the stabilization energy in La will be described. The stabilization energy in La can be obtained from the energy difference between (Nd7La1)Fe 56 B4 + Nd and Nd8(Fe 56 La1)B4 + Fe using the Nd8Fe 55 B4 crystal cell. The smaller the energy value, the more stable it is when an atom is substituted at that site. That is, La is likely to be substituted at the atomic site where the energy is the smallest among the atomic sites. In this calculation, when La is substituted for the original atom, the tetragonal R2Fe 14The lattice constant in the B crystal structure is assumed not to change due to the difference in atomic radius. Table 1 shows the stabilization energy of La at each substitution site when the environmental temperature is changed.

[0039]

Table 1

[0040] According to Table 1, the stable substitution site of La is the Nd(f) site at temperatures of 1000 K or higher, and the Fe(c) site at temperatures of 293 K and 500 K. As will be described later, the rare earth sintered magnet 1 according to Embodiment 2 is heated and melted at a temperature of 1000 K or higher, and then rapidly cooled. Therefore, it is considered that the raw material of the rare earth sintered magnet 1 is maintained at a state of 1000 K or higher, that is, 727 °C or higher, preferably about 1300 K, that is, 1027 °C. At that time, it is considered that La is substituted at the Nd(f) site or the Nd(g) site. Here, it is considered that La is preferentially substituted at the energetically stable Nd(f) site, but substitution at the Nd(g) site with a small energy difference among the substitution sites of La is also possible. Therefore, the Nd(g) site is also cited as a candidate for the substitution site of La.

[0041] Furthermore, when the rare earth sintered magnet 1 is manufactured by the manufacturing method described later, although the temperature is 1000 K or higher during sintering, through the first aging process, the second aging process, and further the third aging process, the fourth aging process and the cooling process, the Fe(c) sites described in Table 1 are repeatedly maintained in the temperature range where they are energetically stable. In other words, the substitution of La at the Nd sites in the main phase 10 is maintained in an unstable energy state. That is, in the raw material stage of the rare earth sintered magnet 1, La was mainly substituted at the Nd sites of the main phase 10, but in the rare earth sintered magnet 1 manufactured by the manufacturing method described later, for the Nd sites of the main phase 10, by repeatedly maintaining them in the temperature range of the unstable energy state, as a result, a certain amount of La is selectively released from the Nd sites of the main phase 10, and La segregates to the secondary phase 20. As a result, the main phase 10 promotes the formation of a characteristic core-shell structure.

[0042] Next, the calculation method of the stabilization energy in Sm will be described. Regarding the stabilization energy of Sm, it can be obtained from the energy difference between (Nd7Sm1)Fe 56 B4 + Nd and Nd8(Fe 55 Sm1)B4 + Fe. Regarding the point that the lattice constant in the tetragonal R2Fe 14 B crystal structure does not change due to the substitution of atoms, it is the same as the case of La. Table 2 is a table showing the stabilization energy of Sm at each substitution site when the environmental temperature is changed.

[0043]

Table 2

[0044] According to Table 2, unlike La, the stable substitution site of Sm is the Nd(g) site at any temperature. Also in the case of Sm, it is considered that it is preferentially substituted at the Nd(g) site that is energetically stable, but substitution at the Nd(f) site with a small energy difference among the substitution sites of Sm is also possible.

[0045] When the rare-earth sintered magnet 1 is manufactured by the manufacturing method described below, substitution of Nd(g) sites in the main phase 10 is the most stable energetically. However, as described above, by holding in the temperature range where substitution of Nd sites in the main phase 10 becomes unstable in La, part of Sm is also released from the Nd sites in the main phase 10 together with La and segregates into the secondary phase 20. As a result, there is a concentration difference between the main phase 10 and the secondary phase 20 in the concentrations of La and Sm, and the sum of the concentrations of La in the first secondary phase 21 and the second secondary phase 22 is equal to or higher than the concentration of La in the main phase 10, and the sum of the concentrations of Sm in the first secondary phase 21 and the second secondary phase 22 is equal to or higher than the concentration of Sm in the main phase 10. More specifically, the average concentration of La in the first secondary phase 21 and the second secondary phase 22 is equal to or higher than the average concentration of La in the first main phase 11 and the second main phase 12, and the average concentration of Sm in the first secondary phase 21 and the second secondary phase 22 is equal to or higher than the average concentration of Sm in the first main phase 11 and the second main phase 12. That is, it can be said that La and Sm segregate into the secondary phase 20.

[0046] Comparing with La and Sm, from an energetic point of view, it can be seen that La held in the temperature range of an unstable energy state is much more likely to segregate into the secondary phase 20. Thereby, in the case of the rare-earth sintered magnet 1 in which the concentrations of La and Sm are adjusted to the same degree, the segregation ratio of La into the secondary phase 20 is larger than that of Sm in the rare-earth sintered magnet 1. By being held repeatedly in this temperature region, a concentration difference of Sm with a small segregation ratio is generated in the secondary phase 20, and the first secondary phase 21 and the second secondary phase 22 are formed. Thereby, the formation of the core-shell structure in the main phase 10 is promoted.

[0047] This time, as shown in FIG. 3, a typical explanation will be given for Nd. However, as represented by Di (dysprosium), since Nd and Pr are produced as a mixture, it is considered that the energy levels of Nd and Pr are close. Therefore, the same can be said even when Nd is replaced with Pr. By having two types of Nd and Pr, the main phase 10 having two types of core-shell structures can be formed.

[0048] As described above, when R is one or more rare earth elements selected from elements other than Nd and Pr, the rare earth sintered magnet 1 of Embodiment 2 satisfies the general formula (Nd, Pr, R)-Fe-B, and Nd2Fe 14 It has a main phase 10 containing crystal grains based on the Nd2Fe14B crystal structure. The main phase 10 has a core part and a shell part covering the core part. When R = La or Sm, in addition to the first main phase 11 and the second main phase 12 in Embodiment 1, it has a secondary phase 20. The secondary phase 20 has a crystalline first secondary phase 21 based on an oxide phase whose main component is represented by (Nd, Pr, La, Sm)-O, and a crystalline second secondary phase 22 whose main component is represented by (Nd, Pr, La)-O. Regarding the concentration of Sm, the first secondary phase 21 has a higher concentration than the second secondary phase 22. That is, two types of main phases 10 and two types of secondary phases 20 are made to exist. Thereby, it becomes possible to provide a rare earth sintered magnet 1 having excellent magnetic properties such as temperature characteristics of magnetic properties as compared with the conventional ones. Further, by setting R to La or Sm, the main phase 10 is in a state where a first main phase 11 with CNd > CPr and a second main phase 12 with CNd < CPr are mixed. In other words, the rare earth sintered magnet 1 has a main phase 10 having two types of first main phases 11 and second main phases 12. Focusing on the core parts of the two types of main phases 10, in the first main phase 11, the Nd concentration is higher than the Pr concentration, and conversely, in the second main phase 12, the Pr concentration is higher than the Nd concentration, so that a main phase 10 having two types of core-shell structures is likely to occur. As a result, while suppressing the use of Nd and heavy rare earth elements, the magnetic properties can be improved, and the effect of having excellent magnetism as compared with the conventional ones can be further enhanced.

[0049] Embodiment 3. In Embodiment 3, regarding the method for manufacturing the rare earth sintered magnet 1 described in Embodiment 1 or Embodiment 2, it will be separately described as a method for manufacturing a rare earth sintered magnet alloy that is a raw material for the rare earth sintered magnet 1 and a method for manufacturing the rare earth sintered magnet 1 using the rare earth sintered magnet alloy.

[0050] FIG. 4 is a flowchart showing an example of the procedure of a method for manufacturing a rare earth sintered magnet alloy according to Embodiment 3. First, as shown in FIG. 4, the method for manufacturing a rare earth sintered magnet alloy that is a raw material of the rare earth sintered magnet 1 includes a melting step (step S1) of heating and melting a raw material of the rare earth sintered magnet alloy containing the elements constituting the rare earth sintered magnet 1 at a temperature of 1000 K or higher, a first cooling step (step S2) of cooling the molten raw material on a rotating body to obtain a solidified alloy, and a second cooling step (step S3) of further cooling the solidified alloy in a container. Thereby, a rare earth sintered magnet alloy can be manufactured. Hereinafter, each step will be described.

[0051] In the melting step of step S1, the raw material of the rare earth sintered magnet alloy is heated and melted in a crucible at a temperature of 1000 K or higher in an atmosphere containing an inert gas such as Ar (argon) or in a vacuum. Thereby, a molten alloy of the rare earth sintered magnet alloy is prepared. As the raw materials, Nd, Pr, La, Sm, Fe, and B can be used. Also, FeB may be used instead of B as the raw material. At this time, one or more elements selected from the group of Al, Co, Zr, Ti, Nb, Dy, Tb, Mn, Gd, and Ho may be included in the raw materials as the additive element M.

[0052] Next, in the first cooling step of step S2, the molten alloy prepared in the melting step is poured into a tundish and then poured onto a single roll which is a rotating body. Thereby, the molten alloy is rapidly cooled on the rotating single roll in a defined direction, and a solidified alloy thinner than the ingot alloy is prepared on the single roll. Here, a single roll is used as the rotating body, but the present invention is not limited thereto, and it may be rapidly cooled by contacting a double roll, a rotating disk, a rotating cylindrical mold, or the like. From the viewpoint of efficiently obtaining a thin solidified alloy, the cooling rate in the first cooling step is preferably 10 °C / second or more and 10 7 °C / second or less, and 10 3 °C / second or more and 10 4It is more preferable that it is at or below ℃ / second. The thickness of the solidified alloy is in the range of 0.03 mm or more and 10 mm or less. The molten alloy starts to solidify from the portion in contact with the single roll, and crystals grow columnarly or acicularly in the thickness direction from the contact surface with the single roll.

[0053] Thereafter, in the secondary cooling step of step S3, the thin solidified alloy prepared in the primary cooling step is put into a tray container and cooled. When the thin solidified alloy enters the tray container, it breaks into flaky rare earth sintered magnet alloy and is cooled. Depending on the cooling rate, a ribbon-shaped rare earth sintered magnet alloy may be obtained, and it is not limited to being flaky. From the viewpoint of obtaining a rare earth sintered magnet alloy having a microstructure with good temperature characteristics of magnetic properties, the cooling rate in the secondary cooling step is 10 -2 ℃ / second or more and 10 5 ℃ / second or less is preferable, and 10 -1 ℃ / second or more and 10 2 ℃ / second or less is more preferable.

[0054] The rare earth sintered magnet alloy obtained through these steps has a short-axis direction size of 3 μm or more and 10 μm or less, and a long-axis direction size of 10 μm or more and 300 μm or less. In the case of Embodiment 2, it has a fine crystal structure containing an (Nd,Pr,La,Sm)-Fe-B crystal phase and a crystalline secondary phase 20 of an oxide represented by (Nd,Pr,La,Sm)-O. Hereinafter, the crystalline secondary phase 20 of the oxide 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 composed of an oxide with a relatively high concentration of rare earth elements. The thickness of the (Nd,Pr,La,Sm)-O phase corresponds to the width of the grain boundary and is 10 μm or less. Since the rare earth sintered magnet alloy manufactured by the above manufacturing method has undergone a step of being rapidly cooled, its structure is refined compared to the rare earth sintered magnet alloy obtained by the mold casting method.

[0055] Next, a method for manufacturing the rare earth sintered magnet 1 using a rare earth sintered magnet alloy will be described. FIG. 5 is a flowchart showing an example of the procedure of the method for manufacturing a rare earth sintered magnet according to Embodiment 3. As shown in FIG. 5, the method for manufacturing the rare earth sintered magnet 1 includes a pulverizing step (step S21) of pulverizing a rare earth sintered magnet alloy having a (Nd, Pr, La, Sm)-Fe-B crystal phase and a (Nd, Pr, La, Sm)-O phase, a molding step (step S22) of preparing a molded body by molding the powder of the pulverized rare earth sintered magnet alloy, a sintering step (step S23) of sintering the molded body at a sintering temperature which is a determined temperature to obtain a sintered body, an aging step (step S24) of aging the sintered body to enhance magnetic properties such as the coercive force of the rare earth sintered magnet 1, and a cooling step (step S25) of cooling the aged sintered body. Hereinafter, each step will be described.

[0056] In the pulverizing step of step S21, a rare earth sintered magnet alloy satisfying (Nd, Pr, R)-Fe-B manufactured according to the method for manufacturing a rare earth sintered magnet alloy of FIG. 4 is pulverized to obtain rare earth sintered magnet alloy powder having a particle size of 200 μm or less, preferably 0.5 μm or more and 100 μm or less, and further preferably about 1 μm or more and 10 μm or less in consideration of the magnetization performance. In one example, 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 particular, when reducing the particle 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, the incorporation of oxygen into the powder can be suppressed. However, if the atmosphere during pulverization does not affect the magnetic properties of the magnet, the pulverization of the rare earth sintered magnet alloy may be performed in the air.

[0057] In the molding step of step S22, the powder of the rare earth sintered magnet alloy is compression-molded in a mold with a magnetic field applied thereto to prepare a molded body. Here, the magnetic field to be applied can be set to 2 T in one example. Note that the molding may be performed without applying a magnetic field instead of in a magnetic field.

[0058] In the sintering process of step S23, the sintered body is obtained by holding the compression-molded green body at a sintering temperature in the range of 950°C or higher and 1300°C or lower, preferably in the range of 1000°C or higher and less than 1150°C, for a time in the range of 0.1 hour or longer and 10 hours or shorter, preferably 1.0 hour or longer and 6.0 hours or shorter. Sintering is preferably carried out in an atmosphere containing an inert gas or in a vacuum for suppressing oxidation. Sintering may be carried out while applying a magnetic field.

[0059] In the aging process of step S24, in the case of FIG. 5, it includes the first aging process of step S24-1, the second aging process of step S24-2, the third aging process of step S24-3, and the fourth aging process of step S24-4. Aging is preferably carried out in an atmosphere containing an inert gas or in a vacuum for suppressing oxidation.

[0060] The conditions of the first aging process of step S24-1 are to hold the obtained sintered body at a first aging temperature which is a temperature lower than the sintering temperature, specifically in the range of 700°C or higher and less than 950°C, for 0.1 hour or longer and 10 hours or shorter, preferably 0.5 hour or longer and 5 hours or shorter.

[0061] The conditions of the second aging process of step S24-2 are, after the first aging process, to hold the sintered body held in the first aging process at a second aging temperature which is a temperature lower than the first aging temperature, specifically in the range of 450°C or higher and less than 700°C, for 0.1 hour or longer and 10 hours or shorter, preferably 1.0 hour or longer and 7 hours or shorter.

[0062] The conditions of the third aging process of step S24-3 are, after the second aging process, to raise the temperature of the sintered body held in the second aging process to the first aging temperature again, specifically to a temperature in the range of 700°C or higher and less than 950°C, and hold it at the first aging temperature for 0.1 hour or longer and 10 hours or shorter, preferably 0.5 hour or longer and 5 hours or shorter.

[0063] The conditions of the fourth aging process in step S24-4 are such that after the third aging process, the sintered body retained in the third aging process is again held within the range of the second aging temperature, specifically 450°C or more and less than 700°C, for 0.1 hour or more and 10 hours or less, preferably within the range of 1.0 hour or more and 7 hours or less.

[0064] Finally, in the cooling process of step S25, the sintered body retained in the fourth aging process is held at a temperature lower than the second aging temperature, specifically within the range of 200°C or more and less than 450°C, for 0.1 hour or more and 5 hours or less. Thereafter, by cooling to room temperature, the rare earth sintered magnet 1 is completed. Cooling is preferably performed in an atmosphere containing an inert gas or in a vacuum for suppressing oxidation.

[0065] As described above, by controlling the temperature and time in the sintering process, aging process, and cooling process, the sintered body is held several times in the temperature range of the unstable energy state. As a result, it becomes possible to mix the first main phase 11 composed of CNd > CPr and the second main phase 12 composed of CNd < CPr. In other words, in the rare earth sintered magnet 1, there are two types of main phases 10, namely the first main phase 11 and the second main phase 12. Focusing on the core portions of the two types of main phases 10, the first main phase 11 has a higher Nd concentration than the Pr concentration, and conversely, the second main phase 12 has a higher Pr concentration than the Nd concentration, and a rare earth sintered magnet 1 can be manufactured.

[0066] Furthermore, in addition to the first main phase 11 and the second main phase 12 in Embodiment 1, there are a crystalline first sub-phase 21 based on an oxide phase whose main component is represented by (Nd, Pr, La, Sm)-O, and a crystalline second sub-phase 22 whose main component is represented by (Nd, Pr, La)-O, and a rare earth sintered magnet 1 can be manufactured in which the Sm concentration is higher in the first sub-phase 21 than in the second sub-phase 22.

[0067] This makes it possible to provide a rare earth sintered magnet 1 that has excellent magnetization performance and magnetic properties compared to the prior art while suppressing the use of Nd and heavy rare earth elements.

[0068] In Embodiment 3, a rare earth sintered magnet alloy powder obtained by pulverizing a rare earth sintered magnet alloy having a (Nd, Pr, La, Sm)-Fe-B crystal phase and a (Nd, Pr, La, Sm)-O phase is molded, and the molded body is sintered to form a sintered body. After that, the sintered body is aged to produce the rare earth sintered magnet 1. Thereby, the rare earth sintered magnet 1 according to Embodiment 2 can be manufactured.

[0069] Also, in the first aging step, the obtained sintered body is held at a first aging temperature which is a temperature lower than the sintering temperature, specifically in the range of 700°C or higher and lower than 950°C for 0.1 hour or more and 10 hours or less, preferably in the range of 0.5 hour or more and 5 hours or less. In the second aging step, the sintered body is held at a second aging temperature which is a temperature lower than the first aging temperature, specifically in the range of 450°C or higher and lower than 700°C for 0.1 hour or more and 10 hours or less, preferably in the range of 1.0 hour or more and 7 hours or less. In the third aging step, the temperature is raised again to the first aging temperature, specifically in the range of 700°C or higher and lower than 950°C, and the sintered body is held at the first aging temperature for 0.1 hour or more and 10 hours or less, preferably in the range of 0.5 hour or more and 5 hours or less. In the fourth aging step, the sintered body is held again at the second aging temperature, specifically in the range of 450°C or higher and lower than 700°C for 0.1 hour or more and 10 hours or less, preferably in the range of 1.0 hour or more and 7 hours or less. In this way, by controlling the temperature and time so that two sets of the first aging step and the second aging step are carried out, a state is created in which the sintered body is held several times in the temperature range of the unstable energy state. As a result, a rare earth sintered magnet 1 in which a first main phase 11 composed of CNd > CPr and a second main phase 12 composed of CNd < CPr are mixed can be obtained. In other words, the rare earth sintered magnet 1 has two types of main phases 10, namely the first main phase 11 and the second main phase 12. Focusing on the core parts of the two types of main phases 10, the first main phase 11 has a higher Nd concentration than the Pr concentration, and conversely, the second main phase 12 has a higher Pr concentration than the Nd concentration, and the rare earth sintered magnet 1 can be selectively manufactured.

[0070] Furthermore, by the above manufacturing process, a crystalline first secondary phase 21 based on an oxide phase whose main component is represented by (Nd, Pr, La, Sm)-O and a crystalline second secondary phase 22 whose main component is represented by (Nd, Pr, La)-O are obtained, and the rare-earth sintered magnet 1 having a characteristic microstructure in which the concentration of Sm is higher in the first secondary phase 21 than in the second secondary phase 22 can be selectively manufactured.

[0071] Embodiment 4. In Embodiment 4, a rotor using the rare-earth sintered magnet 1 in Embodiment 1 or Embodiment 2 manufactured by the manufacturing method of Embodiment 3 will be described. FIG. 6 is a cross-sectional view schematically showing an example of the configuration of a rotor equipped with a rare-earth sintered magnet according to Embodiment 4. In FIG. 6, a cross-section in a direction perpendicular to the rotation axis RA of the rotor 100 is shown.

[0072] The rotor 100 is rotatable about the rotation axis RA. The rotor 100 includes a rotor core 101 and a 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. In FIG. 6, an example is shown in which four magnet insertion holes 102 are provided in the rotor core 101 and four rare-earth sintered magnets 1 are inserted into the magnet insertion holes 102, but the number of the magnet insertion holes 102 and the rare-earth sintered magnets 1 may be changed according to the design of the rotor 100. The rotor core 101 is formed by laminating a plurality of disk-shaped electromagnetic steel sheets in the axial direction of the rotation axis RA.

[0073] The rare-earth sintered magnet 1 is manufactured according to the manufacturing method described in Embodiment 3. The four rare-earth sintered magnets 1 are respectively inserted into the corresponding magnet insertion holes 102. The four rare-earth sintered magnets 1 are magnetized such that the magnetic poles of the rare-earth sintered magnets 1 on the outer side in the radial direction of the rotor 100 are different from those of the adjacent rare-earth sintered magnets 1.

[0074] 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 can improve the magnetic properties at room temperature and suppress the deterioration of the magnetic properties due to temperature rise. Thus, since the rare earth sintered magnet 1 can suppress the deterioration of the magnetic properties even in a high-temperature environment exceeding 100°C while maintaining a high residual magnetic flux density and coercive force, the deterioration of the magnetic properties is suppressed. As a result, while replacing expensive Nd and heavy rare earth elements with high regional concentration and procurement risks with inexpensive rare earth elements, the magnetic properties and magnetism are improved, and the operation of the rotor 100 can be stabilized even in a high-temperature environment exceeding 100°C. Further, since the rare earth sintered magnet 1 according to the first embodiment or the second embodiment has excellent magnetization performance compared with the prior art, magnetization can be performed in an assembled state in which the rare earth sintered magnet 1 is set in the rotor 100, which facilitates handling in the manufacturing process. Further, since a magnetization process with suppressed voltage can be realized, it also contributes to energy saving.

[0075] Embodiment 5. In Embodiment 5, a rotating machine equipped with the rotor 100 in Embodiment 4 will be described. FIG. 7 is a cross-sectional view schematically showing an example of the configuration of the rotating machine according to Embodiment 5. In FIG. 7, a cross-section in a direction perpendicular to the rotation axis RA of the rotor 100 is shown.

[0076] The rotating machine 120 includes a rotor 100 that is rotatable about a rotation axis RA and described in Embodiment 4, and an annular stator 130 that is provided coaxially with the rotor 100 and disposed opposite to the rotor 100. The stator 130 is formed by laminating a plurality of electromagnetic steel sheets in the axial direction of the rotation axis RA. The configuration of the stator 130 is not limited to this, and an existing configuration can also be adopted. The stator 130 is provided with teeth 131 protruding toward the rotor 100 along the inner surface of the stator 130. Windings 132 are provided on the teeth 131. As an example, the winding method of the windings 132 may be concentrated winding or distributed winding. That is, the stator 130 has windings 132 provided on teeth 131 protruding toward the rotor 100 on the inner surface on the side where the rotor 100 is disposed, and has an annular structure disposed opposite to the rotor 100. The number of magnetic poles of the rotor 100 in the rotating machine 120 is two or more, that is, the rare earth sintered magnet 1 may be two or more. Further, in FIG. 7, an example of the magnet-embedded type rotor 100 is shown, but a surface magnet type rotor 100 in which the rare earth sintered magnet 1 is fixed to the outer peripheral portion with an adhesive may also be used.

[0077] As described above, the rotating machine 120 in Embodiment 5 includes the rare earth sintered magnet 1 according to Embodiment 1 or Embodiment 2 that can improve the magnetic properties at room temperature and suppress the decrease in magnetic properties accompanying the temperature rise. Thus, since it is the rare earth sintered magnet 1 that can suppress the decrease in magnetic properties accompanying the temperature rise while maintaining a high residual magnetic flux density and coercive force, the decrease in magnetic properties is suppressed even in a high temperature environment exceeding 100°C. As a result, while replacing expensive Nd and heavy rare earth elements with high regional concentration and procurement risks with inexpensive rare earth elements, the magnetic properties and magnetism are improved, and even in a high temperature environment exceeding 100°C, the rotor 100 can be stably driven and the operation of the rotating machine 120 can be stabilized.

Example

[0078] Hereinafter, the details of the rare earth sintered magnet 1 of the present disclosure will be described by way of examples and comparative examples.

[0079] In Examples 1 to 8, the rare-earth sintered magnet 1 is manufactured by the method shown in Embodiment 3 using samples of (Nd, Pr, La, Sm)-Fe-B of a plurality of rare-earth sintered magnet alloys having different compositions. In Examples 1 to 8, the rare-earth sintered magnet 1 is manufactured using a rare-earth sintered magnet alloy in which the contents of Nd, Pr, La, and Sm are changed. That is, in Examples 1 to 8, the rare-earth sintered magnet 1 is manufactured using the manufacturing method shown in Embodiment 3 with a rare-earth sintered magnet alloy represented by (Nd, Pr, La, Sm)-Fe-B.

[0080] In Comparative Examples 1 to 12, the rare-earth sintered magnet 1 is experimentally manufactured by the general method for manufacturing rare-earth magnets shown in Patent Document 1 or Patent Document 2 using samples of rare-earth sintered magnet alloys R-Fe-B having different compositions. In the samples of the rare-earth sintered magnet 1 according to Comparative Examples 1 to 12, the portion of R is changed.

[0081] In Comparative Examples 1 to 6, the rare-earth sintered magnet 1 is manufactured using the manufacturing method shown in Patent Document 1 with a rare-earth sintered magnet alloy in which R contains Nd and a heavy rare-earth element Dy, or any one of Pr, La, and Sm.

[0082] In Comparative Examples 7 to 12, the rare-earth sintered magnet 1 is manufactured using the manufacturing method shown in Patent Document 2 with a rare-earth sintered magnet alloy in which R contains Nd and a heavy rare-earth element Dy, or any one of Pr, La, and Sm.

[0083] Table 3 is a table showing the general formula of the rare-earth sintered magnet according to the examples and comparative examples, the content of the elements constituting R, the analysis results of the tissue form, and the determination results of the magnetic properties and the magnetization performance. In Table 3, the general formula of the main phase 10 of each sample of the rare-earth sintered magnet 1 of Examples 1 to 8 and Comparative Examples 1 to 12 is shown.

[0084]

Table 3

[0085] Next, a method for analyzing the microstructure of the rare-earth sintered magnets 1 of Examples 1 to 8 and Comparative Examples 1 to 12 will be described. The microstructure 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, as the SEM and EPMA, a field emission-electron probe microanalyzer (FE-EPMA) (manufactured by JEOL Ltd., product name: JXA-8530F) is used. The conditions for elemental analysis are as follows: the acceleration voltage is 15.0 kV, the irradiation current is 2.271e -008 A, the irradiation time is 130 ms, the number of pixels is 512 pixels × 512 pixels, the magnification is 5000 times, and the number of integrations is 1 time.

[0086] Next, a method for evaluating the magnetic properties of the rare-earth sintered magnets 1 of 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 excitation type BH tracer. The maximum applied magnetic field by the BH tracer is 6 T or more in a state where the rare-earth sintered magnet 1 is fully magnetized. In addition to the pulse excitation type BH tracer, if a maximum applied magnetic field of 6 T or more can be generated, a DC self-recording fluxmeter, also called a DC type BH tracer, a vibrating sample magnetometer (VSM), a magnetic property measurement system (MPMS), a physical property measurement system (PPMS), etc. may be used. The measurement is performed in an atmosphere containing an inert gas such as nitrogen. The magnetic properties of each sample are measured by detecting the magnetization picked up by a search coil or a magnetic sensor from the rare-earth sintered magnet 1 magnetized by an applied magnetic field. The magnetic properties are measured from the measured magnetic hysteresis, the J-H curve or the B-H curve. Also, the magnetic properties of each sample are measured at respective temperatures of a first measurement temperature T1 and a second measurement temperature T2 that are different from each other. The temperature coefficient α [% / °C] of the residual magnetic flux density is a value obtained by dividing 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 by the residual magnetic flux density at the first measurement temperature T1, and then dividing by the temperature difference (T2 - T1). Also, the temperature coefficient β [% / °C] of the coercive force is a value obtained by dividing the difference between the coercive force at the first measurement temperature T1 and the coercive force at the second measurement temperature T2 by the coercive force at the first measurement temperature T1, and then dividing by the temperature difference (T2 - T1). Therefore, the smaller the absolute values |α| and |β| of the temperature coefficients of the magnetic properties, the more the decrease in the magnetic properties of the magnet due to temperature rise is suppressed.

[0087] Furthermore, regarding the measurement of magnetization performance, the magnetization rate is obtained by calculating the ratio between the magnetic flux density measured from the magnetic hysteresis depicted by applying an arbitrary magnetic field and the magnetic flux density measured from the magnetic hysteresis depicted by applying a saturating magnetic field at a certain permeability coefficient. If a high magnetization rate can be obtained even at a lower magnetic field, it can be said that the magnetization performance is high.

[0088] First, the analysis results of each sample according to Examples 1 to 8 and Comparative Examples 1 to 12 will be described. FIG. 8 is a diagram tracing the composition image obtained by analyzing the cross-section of the rare-earth sintered magnet according to Examples 1 to 8 by FE-EPMA. FIGS. 9 to 13 are element mappings obtained by analyzing the cross-section of the rare-earth sintered magnet according to Examples 1 to 8 by FE-EPMA. FIG. 9 is the element mapping of Nd, FIG. 10 is the element mapping of Pr, FIG. 11 is the element mapping of O, FIG. 12 is the element mapping of La, and FIG. 13 is the element mapping of Sm. Note that FIGS. 9 to 13 are the element mappings of the region shown in FIG. 8. Also, since the rare-earth sintered magnets 1 according to Examples 1 to 8 all show the same results, FIGS. 8 to 13 show a representative example among Examples 1 to 8. Furthermore, the same reference numerals are assigned to the same components as in FIGS. 1 and 2.

[0089] As shown in FIGS. 9 and 10, in each sample of Examples 1 to 8, R is one or more rare-earth elements selected from other than Nd and Pr, satisfying the general formula (Nd, Pr, R)-Fe-B, and in the main phase 10 containing crystal grains based on the Nd2Fe 14 B crystal structure, there exists a main phase 10 having a core portion and a shell portion covering the core portion. Also, it can be confirmed that in the main phase 10, the first main phase 11 where CNd > CPr and the second main phase 12 where CNd < CPr are mixed.

[0090] Here, the concentration difference shown by "the first main phase 11 where CNd > CPr and the second main phase 12 where CNd < CPr" means that there is a clear difference in the detection intensities of Nd and Pr by mapping analysis using EPMA. Specifically, taking the case of the first main phase 11 as an example, the concentration of Nd in the core part 11c has a detection intensity of EPMA higher than the average, and the concentration of Pr shows a detection intensity of EPMA near the lower limit. It can be said that the second main phase 12 is the reverse of the first main phase 11.

[0091] More specifically, taking the Nd mapping diagram in FIG. 9 and the Pr mapping diagram in FIG. 10 as examples, the average value of the detection level of EPMA for Nd is 32.0, and the average value of the detection level of EPMA for Pr is 45. In the case of the first main phase 11, CNd is higher than 32.0, and CPr is near the lower limit value, and there is a clear concentration difference. Also, since the second main phase 12 is the reverse of the first main phase 11, CPr is higher than 45.0, and CNd is near the lower limit value, and there is a clear concentration difference.

[0092] As shown in FIGS. 11 to 13, when R = La, Sm, the rare earth sintered magnet 1 has, in addition to the first main phase 11 and the second main phase 12 in Embodiment 1, a crystalline first sub-phase 21 based on an oxide phase whose main component is represented as (Nd, Pr, La, Sm)-O, and a crystalline second sub-phase 22 whose main component is represented as (Nd, Pr, La)-O. It can also be confirmed that the concentration of Sm is higher in the first sub-phase 21 than in the second sub-phase 22.

[0093] In Table 3, for the samples in which the states of the first main phase 11 with CNd > CPr and the second main phase 12 with CNd < CPr could be confirmed, "〇" was entered in the columns of the first main phase 11 and the second main phase 12, respectively, and for the samples in which the states could not be confirmed, "×" was entered in the columns of the first main phase 11 and the second main phase 12, respectively. The concentration difference of the inequality sign means that there is a clear difference in the detection intensities of Nd and Pr. Specifically, in one example, in the case of the first main phase 11, the concentration of Nd has a detection intensity by EPMA higher than the average, and the concentration of Pr has a detection intensity by EPMA near the lower limit value. In the case of the second main phase 12, it can be said that it is the opposite of the case of the first main phase 11. When only CNd < CPr such as the second main phase 12 was confirmed, "〇" was entered only in the column of the second main phase 12, and "×" was entered in the column of the first main phase 11.

[0094] Furthermore, in Table 3, there are a crystalline first secondary phase 21 based on an oxide phase whose main components are represented as (Nd, Pr, La, Sm)-O, and a crystalline second secondary phase 22 whose main components are represented as (Nd, Pr, La)-O. For the samples in which it was confirmed that the first secondary phase 21 has a higher Sm concentration than the second secondary phase 22, "〇" was entered in each of the columns of the first secondary phase 21 and the second secondary phase 22, and for the samples in which it could not be confirmed, "×" was entered in each of the columns of the first secondary phase 21 and the second secondary phase 22. Also, for those in which only one secondary phase 20 exists, or in which there is no Sm concentration difference between the secondary phases 20, assuming that only the first secondary phase 21 exists, "〇" was entered only in the column of the first secondary phase 21, and "×" was entered in the column of the second secondary phase 22. The concentration difference between the first secondary phase 21 and the second secondary phase 22 means that the detection intensity of Sm in the first secondary phase 21 is on average higher than that in the second secondary phase 22 by mapping analysis using EPMA. Specifically, taking the Sm mapping diagram in Fig. 13 as an example, the average value of the detection level of Sm by EPMA is 5.4, the first secondary phase 21 is higher than 5.4, and the second secondary phase 22 is lower than 5.4, that is, it is in a state where detection is not possible in an aggregated state.

[0095] Also, it can be confirmed that the number of the first main phase 11 where CNd > CPr is larger than the number of the second main phase 12 where CNd < CPr, from the intensity ratio of the element mapping obtained by FE-EPMA analysis. When focusing on the shell part of the core-shell structure, it can also be confirmed that the first main phase 11 satisfies the relational expressions of CNd > SNd and CPr < SPr, and the second main phase 12 satisfies the relational expressions of CNd < SNd and CPr > SPr.

[0096] Next, the measurement results of the magnetic properties in each sample according to Examples 1 to 8 and Comparative Examples 1 to 12 will be described. The shape of each sample for magnetic measurement is a block shape with a length, width, and height all 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 possible temperature as the environment during the operation of automotive motors and industrial motors.

[0097] First, the determination of the residual magnetic flux density and coercive force in each sample according to Examples 1 to 8 and Comparative Examples 2 to 12 is performed in comparison with Comparative Example 1. When the values of the residual magnetic flux density and coercive force at 23°C of each sample show values within 1% considered to be the measurement error compared with the values in Comparative Example 1, it is determined as "equivalent". When the values are 1% or higher, it is determined as "good". When the values are 1% or lower, it is determined as "bad".

[0098] 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. Also, 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. For each sample, when the value is within ±1% considered to be the measurement error compared to 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 according to Comparative Example 1, it is determined as "equivalent", when the value is lower than -1%, it is determined as "good", and when the value is higher than +1%, it is determined as "bad". For the samples determined as "good", since the temperature coefficient is smaller, the decrease in magnetic properties due to temperature rise is suppressed, and a rare earth sintered magnet 1 having stable magnetic properties can be provided even in a high-temperature environment.

[0099] Next, the magnetization performance is calculated from the ratio between the magnetic flux density at the intersection of 1 of the magnetic hysteresis of the applied magnetic field of 20 kOe and the permeability coefficient Pc and the magnetic flux density at the intersection of 1 of the magnetic hysteresis of the applied magnetic field of 80 kOe in the saturation magnetization state and the permeability coefficient Pc. The magnetization performance 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, when the value is -1% or more considered to be the measurement error compared to the magnetization ratio in the sample according to Comparative Example 1, it is determined as "equivalent or better", and when the value is lower than -1%, it is determined as "bad". For the samples determined as "equivalent or better", a rare earth sintered magnet 1 with high magnetization performance can be provided.

[0100] The determination results of the above residual magnetic flux density, coercive force, temperature coefficient of the residual magnetic flux density, temperature coefficient of the coercive force, and magnetization performance are shown in Table 3.

[0101] Comparative Example 1 is a sample of the rare earth sintered magnet 1 produced according to the manufacturing method described in Patent Document 1 using Nd, Fe, and FeB as raw materials so as to be Nd-Fe-B. When the microstructure of this sample was observed according to the method described above, since Pr, La, and Sm were not added, the core-shell structure in the main phase 10 could not be confirmed, and it could not be confirmed that the concentration of Sm in the secondary phase 20 was higher in the first secondary phase 21 than in the second secondary phase 22. Further, when the magnetic properties of this sample were evaluated according to the method described above, the residual magnetic flux density was 1.3 T, and the coercive force was 1000 kA / m. The temperature coefficients of the residual magnetic flux density and the coercive force were |α| = 0.191% / °C and |β| = 0.460% / °C, respectively. The magnetization rate was 98.6%. These values of Comparative Example 1 are used as a reference.

[0102] Comparative Example 2 is a sample of the rare earth sintered magnet 1 produced according to the manufacturing method described in Patent Document 1 using Nd, Dy, Fe, and FeB as raw materials so as to be (Nd, Dy)-Fe-B. When the microstructure of this sample was observed according to the method described above, since Pr, La, and Sm were not added, the core-shell structure in the main phase 10 could not be confirmed, and it could not be confirmed that the concentration of Sm in the secondary phase 20 was higher in the first secondary phase 21 than in the second secondary phase 22. Further, when the magnetic properties of this sample were evaluated according to the method described above, the residual magnetic flux density was "poor", the coercive force was "good", the temperature coefficient of the residual magnetic flux density was "equivalent", the temperature coefficient of the coercive force was "equivalent", and the magnetization performance was "equal or better". This is the result reflecting that the coercive force is improved by substituting a part of Nd with Dy having high crystalline magnetic anisotropy.

[0103] Comparative Example 3 is a sample of the rare earth sintered magnet 1 produced according to the production method described in Patent Document 1 using Nd, Pr, Fe, and FeB as raw materials so as to be (Nd, Pr)-Fe-B. When observing the microstructure of this sample according to the method described above, although the main phase 10 in which Nd and Pr were mixed could be confirmed due to the addition of Pr, the core-shell structure was not formed. Also, since La and Sm were not added, it could not be confirmed that the concentration of Sm in the secondary phase 20 was higher in the first secondary phase 21 than in the second secondary phase 22. When evaluating the magnetic properties of this sample according to the method described above, the residual magnetic flux density was "equivalent", the coercive force was "good", the temperature coefficient of the residual magnetic flux density was "equivalent", the temperature coefficient of the coercive force was "poor", and the magnetization performance was "equivalent or better". This is a result reflecting that although the magnetic anisotropy of the main phase 10 is increased by the addition of Pr and the coercive force is improved, the optimal microstructures in the main phase 10 and the secondary phase 20 are not obtained.

[0104] Comparative Example 4 is a sample of the rare earth sintered magnet 1 produced according to the production method described in Patent Document 1 using Nd, La, Sm, Fe, and FeB as raw materials so as to be (Nd, La, Sm)-Fe-B. When observing the microstructure of this sample according to the method described above, the core-shell structure of the main phase 10 could not be confirmed because Pr was not added. Also, since La and Sm were added, although the concentration of Sm was segregated into one secondary phase 20 along with the segregation of La, the second secondary phase 22 did not exist. Furthermore, it could not be confirmed that the concentration of Sm was higher in the first secondary phase 21 than in the second secondary phase 22. Also, when evaluating the magnetic properties of this sample according to the method described above, the residual magnetic flux density was "equivalent", the coercive force was "equivalent", the temperature coefficient of the residual magnetic flux density was "good", the temperature coefficient of the coercive force was "good", and the magnetization performance was "equivalent or better". This is a result reflecting that although the temperature coefficients of the magnetic properties show good results due to the presence of La and Sm in the main phase 10 or the secondary phase 20, the magnetic properties at room temperature are not improved and the optimal microstructures in the main phase 10 and the secondary phase 20 are not obtained.

[0105] Comparative Example 5 is a sample of the rare-earth sintered magnet 1 produced according to the production method described in Patent Document 1 using Nd, La, Sm, Fe, and FeB as raw materials so as to be (Nd, La, Sm)-Fe-B. The composition ratio of Nd, La, and Sm is different from that of Comparative Example 4. When the microstructure of this sample is observed according to the method described above, since Pr is not added, the core-shell structure of the main phase 10 cannot be confirmed. Further, since La and Sm are added, although the concentration of Sm segregates to one secondary phase 20 along with the segregation of La, the second secondary phase 22 does not exist. Furthermore, it cannot be confirmed that the concentration of Sm is higher in the first secondary phase 21 than in the second secondary phase 22. Also, when the magnetic properties of this sample are evaluated according to the method described above, the residual magnetic flux density is "equivalent", the coercive force is "equivalent", the temperature coefficient of the residual magnetic flux density is "good", the temperature coefficient of the coercive force is "good", and the magnetization performance is "equivalent or better". This indicates that although the temperature coefficient of the magnetic properties shows good results due to the presence of La and Sm in the main phase 10 or the secondary phase 20, the magnetic properties at room temperature are not improved, which reflects that the microstructure in the main phase 10 and the secondary phase 20 is not the optimal form. Even if the composition ratio of Nd, La, and Sm is changed, results almost the same as those of Comparative Example 4 can be obtained.

[0106] Comparative Example 6 is a sample of a rare earth sintered magnet 1 produced according to the production method described in Patent Document 1 using Nd, Pr, La, Sm, Fe, and FeB as raw materials so as to be (Nd, Pr, La, Sm)-Fe-B. When the microstructure of this sample was observed according to the method described above, although the main phase 10 in which Nd and Pr were mixed could be confirmed because Pr was added, the core-shell structure was not formed. Further, because La and Sm were added, although the concentration of Sm was segregated into one secondary phase 20 along with the segregation of La, the second secondary phase 22 did not exist. Furthermore, it could not be confirmed that the concentration of Sm was higher in the first secondary phase 21 than in the second secondary phase 22. When the magnetic properties of this sample were evaluated according to the method described above, the residual magnetic flux density was "equivalent", the coercive force was "good", the temperature coefficient of the residual magnetic flux density was "good", the temperature coefficient of the coercive force was "equivalent", and the magnetization performance was "equal or higher". This indicates that the addition of Pr increases the magnetic anisotropy of the main phase 10, improving the coercive force, and the presence of La and Sm in the main phase 10 or the secondary phase 20 improves the temperature coefficient of the magnetic properties, particularly the temperature coefficient of the coercive force. However, this is the result reflecting that the microstructure in the main phase 10 and the secondary phase 20 is not the optimal form.

[0107] Comparative Example 7 is a sample of a rare earth sintered magnet 1 produced according to the production method including a hot working method described in Patent Document 2 using Nd, Fe, and FeB as raw materials so as to be Nd-Fe-B. When the microstructure of this sample was observed according to the method described above, since Pr, La, and Sm were not added, the core-shell structure in the main phase 10 could not be confirmed, and it could not be confirmed that the concentration of Sm in the secondary phase 20 was higher in the first secondary phase 21 than in the second secondary phase 22. However, the refinement of the microstructure, which is a characteristic of a magnet produced by the hot working method, was confirmed. When the magnetic properties of this sample were evaluated according to the method described above, the residual magnetic flux density was "poor", the coercive force was "good", the temperature coefficient of the residual magnetic flux density was "equivalent", the temperature coefficient of the coercive force was "equivalent", and the magnetization performance was "poor". This is the result reflecting that although the coercive force is improved with the refinement of the microstructure by the hot working method, the residual magnetic flux density decreases and the magnetization performance deteriorates.

[0108] Comparative Example 8 is a sample of the rare earth sintered magnet 1 produced according to the manufacturing method including the hot working method described in Patent Document 2 using Nd, Dy, Fe, and FeB as raw materials so as to be (Nd, Dy)-Fe-B. When the microstructure of this sample was observed according to the method described above, since Pr, La, and Sm were not added, the core-shell structure in the main phase 10 could not be confirmed, and it could not be confirmed that the concentration of Sm in the secondary phase 20 was higher in the first secondary phase 21 than in the second secondary phase 22. Further, when the magnetic properties of this sample were evaluated according to the method described above, the residual magnetic flux density was "poor", the coercive force was "good", the temperature coefficient of the residual magnetic flux density was "equivalent", the temperature coefficient of the coercive force was "equivalent", and the magnetization performance was "poor". This is because, in addition to being produced by hot working, although the coercive force is significantly improved by substituting highly magnetocrystalline anisotropic Dy for a part of Nd, the other properties are the results reflecting the refinement of the microstructure.

[0109] Comparative Example 9 is a sample of the rare earth sintered magnet 1 produced according to the manufacturing method including the hot working method described in Patent Document 2 using Nd, Pr, Fe, and FeB as raw materials so as to be (Nd, Pr)-Fe-B. When the microstructure of this sample was observed according to the method described above, in addition to the addition of Pr, a core-shell structure was confirmed by hot working, but there was only one type of main phase 10 with a high Pr concentration in the core part. Further, since La and Sm were not added, it could not be confirmed that the concentration of Sm in the secondary phase 20 was higher in the first secondary phase 21 than in the second secondary phase 22. When the magnetic properties of this sample were evaluated according to the method described above, the residual magnetic flux density was "poor", the coercive force was "good", the temperature coefficient of the residual magnetic flux density was "equivalent", the temperature coefficient of the coercive force was "equivalent", and the magnetization performance was "poor". This is because, due to the formation of the core-shell structure with a high Pr concentration in the core part, although the coercive force is significantly improved to the level of the rare earth sintered magnet 1 containing Dy, the other properties are the results reflecting the refinement of the microstructure.

[0110] Comparative Example 10 is a sample of a rare-earth sintered magnet 1 produced according to a manufacturing method including a hot working method described in Patent Document 2 using Nd, La, Sm, Fe, and FeB as raw materials so as to be (Nd, La, Sm)-Fe-B. When the microstructure of this sample was observed according to the method described above, since Pr was not added, the core-shell structure of the main phase 10 could not be confirmed. Further, since La and Sm were added, although the concentration of Sm was segregated to one secondary phase 20 along with the segregation of La, the second secondary phase 22 did not exist. Furthermore, it could not be confirmed that the concentration of Sm was higher in the first secondary phase 21 than in the second secondary phase 22. Also, when the magnetic properties of this sample were evaluated according to the method described above, the residual magnetic flux density was "poor", the coercive force was "good", the temperature coefficient of the residual magnetic flux density was "good", the temperature coefficient of the coercive force was "good", and the magnetization performance was "poor". This is because although the temperature coefficient of the magnetic properties shows good results due to the presence of La and Sm in the main phase 10 or the secondary phase 20, the residual magnetic flux density and the magnetization performance at room temperature do not improve, reflecting that the microstructure in the main phase 10 and the secondary phase 20 is not optimal.

[0111] Comparative Example 11 is a sample of the rare-earth sintered magnet 1 produced according to the manufacturing method including the hot working method described in Patent Document 2 using Nd, La, Sm, Fe, and FeB as raw materials so as to be (Nd, La, Sm)-Fe-B. The composition ratio of Nd, La, and Sm is different from that of Comparative Example 10. When the microstructure of this sample is observed according to the method described above, the core-shell structure of the main phase 10 cannot be confirmed because Pr is not added. Further, since La and Sm are added, although the concentration of Sm segregates to one secondary phase 20 along with the segregation of La, the second secondary phase 22 does not exist. Furthermore, it cannot be confirmed that the concentration of Sm is higher in the first secondary phase 21 than in the second secondary phase 22. When the magnetic properties of this sample are evaluated according to the method described above, 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 magnetization performance is "poor". This is because although the temperature coefficient of the magnetic properties shows good results due to the presence of La and Sm in the main phase 10 or the secondary phase 20, the residual magnetic flux density and the magnetization performance at room temperature do not improve, which reflects that the microstructure in the main phase 10 and the secondary phase 20 is not the optimal form. Even if the composition ratio of Nd, La, and Sm is changed, results almost the same as those of Comparative Example 10 are obtained.

[0112] Comparative Example 12 is a sample of a rare earth sintered magnet 1 produced according to a manufacturing method including a hot working method described in Patent Document 2 using Nd, Pr, La, Sm, Fe, and FeB as raw materials so as to be (Nd, Pr, La, Sm)-Fe-B. When the microstructure of this sample is observed according to the method described above, in addition to the addition of Pr, a core-shell structure is confirmed by hot working, but there is only one main phase 10 with a high Pr concentration in the core part. Further, since La and Sm are added, although the concentration of Sm segregates to one secondary phase 20 along with the segregation of La, the second secondary phase 22 does not exist. Furthermore, it cannot be confirmed that the concentration of Sm is higher in the first secondary phase 21 than in the second secondary phase 22. Also, when the magnetic properties of this sample are evaluated according to the method described above, 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 magnetization performance is "poor". This is because the formation of a core-shell structure with a high Pr concentration in the core part significantly improves the coercive force to the level of the rare earth sintered magnet 1 to which Dy is added, and the presence of La and Sm in the main phase 10 or the secondary phase 20 shows good results for the temperature coefficient of the magnetic properties, particularly the temperature coefficient of the coercive force. However, the residual magnetic flux density and the magnetization performance at room temperature do not improve, which also reflects that the microstructure in the main phase 10 and the secondary phase 20 is not optimal.

[0113] The samples of Examples 1 to 8 use R as one or more rare earth elements selected from other than Nd and Pr, satisfy the general formula (Nd, Pr, R)-Fe-B, and Nd2Fe 14The rare-earth sintered magnet 1 has a main phase 10 containing crystal grains based on the B crystal structure. The main phase 10 has a core part and a shell part covering the core part. The main phase 10 is a mixture of a first main phase 11 where CNd > CPr and a second main phase 12 where CNd < CPr. Also, when R = La, Sm, in addition to the first main phase 11 and the second main phase 12, it has a crystalline first sub-phase 21 based on an oxide phase whose main component is represented as (Nd, Pr, La, Sm)-O, and a crystalline second sub-phase 22 whose main component is represented as (Nd, Pr, La)-O. The concentration of Sm is higher in the first sub-phase 21 than in the second sub-phase 22. When the magnetic properties of the samples of Examples 1 to 8 are evaluated according to the above-described method, 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 performance is "equal to or better than". As a result, these rare-earth sintered magnets 1 exhibit the effect of having excellent magnetic properties and magnetizability compared to the conventional ones while suppressing the use of Nd and heavy rare-earth elements, which are expensive and have a high regional distribution and procurement risk.

[0114] The configurations shown in the above embodiments are examples, and it is possible to combine them with other known technologies, combine the embodiments with each other, and omit or change a part of the configuration without departing from the gist.

Explanation of Signs

[0115] 1 Rare-earth sintered magnet, 10 Main phase, 11 First main phase, 11c, 12c Core part, 11s, 12s Shell part, 12 Second main phase, 20 Sub-phase, 21 First sub-phase, 22 Second sub-phase, 100 Rotor, 101 Rotor core, 102 Magnet insertion hole, 120 Rotating machine, 130 Stator, 131 Teeth, 132 Winding.

Claims

1. When R is one or more rare earth elements selected from other than Nd and Pr, it satisfies the general formula (Nd, Pr, R)-Fe-B, and Nd 2 Fe 14 has a main phase containing crystal grains based on the B crystal structure, The main phase has a core part and a shell part covering the core part, when the concentration of Nd in the core part of the main phase is CNd and the concentration of Pr in the core part of the main phase is CPr, the main phase has a first main phase where CNd > CPr and a second main phase where CNd < CPr, The rare earth sintered magnet is characterized in that the first main phase and the second main phase are mixed.

2. When the Nd concentration in the core part of the first main phase is C1Nd, the Nd concentration in the core part of the second main phase is C2Nd, the Pr concentration in the core part of the first main phase is C1Pr, and the Pr concentration in the core part of the second main phase is C2Pr, the rare earth sintered magnet according to Claim 1, characterized in that the relational expressions C1Nd > C2Nd and C1Pr < C2Pr are satisfied.

3. The rare earth sintered magnet according to Claim 1, characterized in that the number of the first main phases is larger than the number of the second main phases.

4. When the concentration of Nd in the shell part is SNd and the concentration of Pr in the shell part is Spr, the first main phase satisfies the relational expressions CNd > SNd and CPr < Spr, and the second main phase satisfies the relational expressions CNd < SNd and CPr > Spr. The rare earth sintered magnet according to Claim 1, characterized in that.

5. When R = La, Sm, it further has a crystalline first sub-phase based on an oxide phase represented by the main component as (Nd, Pr, La, Sm) - O, and a crystalline second sub-phase represented by the main component as (Nd, Pr, La) - O, The rare earth sintered magnet according to Claim 1, characterized in that the concentration of Sm is higher in the first sub-phase than in the second sub-phase.

6. Let the La concentration contained in the main phase be X, and the La concentration contained in the first secondary phase be X 1 and the La concentration contained in the second secondary phase be X 2 Let the Sm concentration contained in the main phase be Y, and the Sm concentration contained in the first secondary phase be Y 1 and the Sm concentration contained in the second secondary phase be Y 2 When this is the case, 1 < (Y 1 + Y 2 ) / Y < (X 1 + X 2 ) / X, and the rare earth sintered magnet according to claim 5 is characterized in that

7. The concentrations of Nd and Pr contained in the first main phase satisfy the relational expression (CNd + SNd) > (X + Y), The rare earth sintered magnet according to Claim 4, characterized in that the concentrations of Nd and Pr contained in the second main phase satisfy the relational expression (CPr + Spr) > (X + Y).

8. A method for manufacturing a rare earth sintered magnet according to any one of Claims 1 to 7, a melting step of melting a raw material of a rare earth sintered magnet alloy containing elements constituting the rare earth sintered magnet, a first cooling step of cooling the raw material in a molten state in the melting step to obtain a solidified alloy, a second cooling step of further cooling the solidified alloy to obtain a rare earth sintered magnet alloy, a pulverizing step of pulverizing the rare earth sintered magnet alloy satisfying (Nd, Pr, R) - Fe - B A molding step of preparing a molded body by molding the powder of the rare earth sintered magnet alloy pulverized in the pulverization step; A sintering step of sintering the molded body at a sintering temperature which is a determined temperature to obtain a sintered body; A first aging step of holding the sintered body at a first aging temperature which is a temperature lower than the sintering temperature; A second aging step of holding the sintered body held in the first aging step at a second aging temperature which is a temperature lower than the first aging temperature; A third aging step of holding the sintered body held in the second aging step at the first aging temperature again; A fourth aging step of holding the sintered body held in the third aging step at the second aging temperature; A cooling step of cooling the sintered body held in the fourth aging step; A method for manufacturing a rare earth sintered magnet, characterized by including the above steps.

9. A rotor core; The rare earth sintered magnet according to any one of Claims 1 to 7 provided on the rotor core; A rotor characterized by comprising the above components.

10. The rotor according to Claim 9; An annular stator having windings attached to teeth protruding toward the rotor on the inner surface on the side where the rotor is disposed and disposed opposite to the rotor; An electric machine characterized by comprising the above components.

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