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

Abstract

A rare earth sintered magnet (1) comprises a columnar phase (10) containing crystal grains based on an Nd2Fe14B crystal structure that satisfies the general formula (Nd, Pr, R)-Fe-B when R is one or more rare earth elements selected from Nd and Pr, and a floating phase (20) existing between a plurality of columnar phases (10). The columnar phase (10) has a core portion (11c, 12c) and a shell portion (11s, 12s) covering the core portion (11c, 12c). The columnar phase (10) comprises a first columnar phase (11) in which CNd > CPr when the concentration of Nd in the core portion (11c, 12c) is set to CNd and the concentration of Pr in the core portion (11c, 12c) is set to CPr, and CNd <CPr인 제2 주상(12)을 갖는다. 제1 주상(11)과 제2 주상(12)이 혼재하고 있다. 제1 주상(11) 및 제2 주상(12)에 있어서의 표면의 적어도 일부에 중희토류 원소가 존재한다.

Description

Technology Field

[0001] The present disclosure relates to a rare-earth sintered magnet, which is a permanent magnet sintered from a material containing rare-earth elements, a method for manufacturing a rare-earth sintered magnet, a rotor, and a rotating machine. Background Technology

[0002] Square Equation R2T 14 RTB-type permanent magnets are known to have an intermetallic compound as the main phase. 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. RTB-type permanent magnets are used in various high-value-added components, including industrial motors. In particular, Nd-Fe-B sintered magnets, where R is Nd (neodymium), are used in various components because they possess excellent magnetic properties. Furthermore, since industrial motors are often used in high-temperature environments exceeding 100°C, attempts are being made to improve coercivity by adding heavy rare earth elements such as Dy (dysprosium) to Nd-TB-type sintered magnets.

[0003] In recent years, the production volume of Nd-Fe-B sintered magnets has expanded, and the consumption of heavy rare earth elements such as Nd, Dy, and Tb (terbium) has increased. However, Nd and heavy rare earth elements are expensive and have high regional uneven distribution, posing a procurement risk. Therefore, as a measure to reduce the consumption of Nd and heavy rare earth elements, it is considered to use magnets that form a column containing a low-heavy rare earth phase, to use other rare earth elements such as Pr (praseodymium), Ce (cerium), La (lanthanum), Sm (samarium), Sc (scandium), Gd (gadolinium), Y (yttrium), and Lu (lutetium) in R, or to manufacture using a special manufacturing method that performs hot plastic processing on the sintered body. Hereinafter, the hot plastic processing performed on the sintered body is referred to as hot processing. However, incorporating a significant amount of heavy rare earth elements into the column contributes to the improvement of coercivity but results in a significant decrease in residual magnetic flux density. Furthermore, if all or part of Nd is replaced with elements such as Pr, Ce, La, Sm, Sc, Gd, Y, and Lu, the magnetic properties of residual magnetic flux density and coercivity are significantly reduced. Moreover, if hot working is performed on the sintered body, the magnetization of the magnet is significantly reduced due to the refinement of the crystal grains. For the above reasons, it has been difficult to achieve both the conservation of heavy rare earth elements and excellent magnetic properties and magnetization. Therefore, conventionally, attempts have been made to develop technology that can improve magnetic properties at room temperature and suppress the decrease in magnetic properties accompanying the temperature rise when these elements are used in the manufacture of Nd-Fe-B-based sintered magnets. In particular, under the current conditions, there is a need for rare earth magnets that can achieve both a further reduction of heavy rare earth elements and excellent magnetic properties and magnetization.

[0004] In Patent Document 1, R2T 14An RTB-based sintered magnet comprising a columnar particle formed of B crystal, wherein R is one or more rare earth elements including the heavy rare earth element RH, T is one or more transition metal elements including Fe or Fe and Co, B is boron, and a portion of the columnar particle contains a plurality of low-heavy rare earth element crystal phases therein, and the low-heavy rare earth element crystal phases are R2T 14 An RTB-based sintered magnet is disclosed, characterized by being composed of B crystals and having a phase in which the concentration of heavy rare earth elements is relatively low compared to the concentration of heavy rare earth elements in the entire columnar particle. According to the technology described in Patent Document 1, an RTB-based sintered magnet with improved magnetic properties and low cost is obtained.

[0005] Patent Document 2 describes R being a rare earth element, and R2Fe 14 A rare earth magnet is disclosed having a columnar phase having a B-type crystal structure and a grain boundary phase existing around the columnar phase, wherein the columnar phase has a core portion, a first shell portion existing around the core portion, and a second shell portion existing around the first shell portion. In the rare earth magnet described in Patent Document 2, the abundance ratio of Nd and Pr in the first shell portion is higher than the abundance ratio of Nd and Pr in the core portion and the second shell portion. Furthermore, in the rare earth magnet described in Patent Document 2, the abundance ratio of heavy rare earth elements in the second shell portion is higher than the abundance ratio of heavy rare earth elements in the first shell portion. By doing so, a rare earth magnet with further improved coercivity is obtained. Prior art literature

[0006] Japanese Patent Publication No. 2018-174313 Japanese Patent Publication No. 2021-174818 The problem to be solved

[0007] However, in the RTB-based sintered magnet described in Patent Document 1, since a phase containing heavy rare earth elements exists within the columnar phase, even if coercivity can be improved, the residual magnetic flux density required for industrial motors, etc., cannot be obtained, and there is a possibility that magnetic properties will deteriorate. Furthermore, since heavy rare earth elements are diffused into the columnar particles, the amount of heavy rare earth elements used increases, and there was a problem that procurement risk and cost reduction were not achieved. In addition, in the rare earth magnet described in Patent Document 2, since the columnar phase is of only one type, it does not have a microstructure structure in which the anisotropic magnetic field is sufficiently high, so there was a problem that it is difficult to obtain high magnetic properties. Moreover, in the rare earth magnet described in Patent Document 2, the shell portion of the columnar phase forms a two-layer structure in which the abundance ratio of heavy rare earth elements differs, and since heavy rare earth elements must be placed in both shell portions, there was also a problem that it is difficult to improve magnetic properties with less heavy rare earth elements.

[0008] The present disclosure is made in consideration of the above, and aims to obtain a rare earth sintered magnet capable of improving magnetic properties compared to the conventional while suppressing the use of heavy rare earth elements compared to the conventional. means of solving the problem

[0009] In order to solve the aforementioned problems and achieve the objective, the rare earth sintered magnet according to the present disclosure satisfies the general formula (Nd, Pr, R)-Fe-B when R is one or more rare earth elements selected from Nd and Pr, and Nd2Fe 14It comprises a columnar phase containing crystal grains based on a B crystal structure, and a secondary phase existing between a plurality of columnar phases. The columnar phase has a core portion and a shell portion covering the core portion. The columnar phase comprises a first columnar phase such that CNd > CPr when the concentration of Nd in the core portion is set to CNd and the concentration of Pr in the core portion is set to CPr, and CNd <CPr인 제2 주상을 갖는다. 제1 주상과 제2 주상이 혼재하고 있다. 제1 주상 및 제2 주상에 있어서의 표면의 적어도 일부에 중희토류 원소가 존재한다. Effects of the invention

[0010] The rare earth sintered magnet according to the present disclosure exhibits the effect of improving magnetic properties compared to the conventional while suppressing the use of heavy rare earth elements compared to the conventional. Brief explanation of the drawing

[0011] FIG. 1 is a schematic diagram showing an example of the structure of the sintered state of a rare earth sintered magnet according to Embodiment 1. FIG. 2 is a schematic diagram showing an example of the structure of the sintered state of a rare earth sintered magnet according to Embodiment 2. FIG. 3 is a schematic diagram showing an example of the structure of the sintered state of a rare earth sintered magnet according to Embodiment 3. Figure 4 is an elemental mapping of Sm obtained by analyzing the cross-section of a rare-earth sintered magnet according to Embodiment 3 with FE-EPMA. Figure 5 is an elemental mapping of Tb obtained by analyzing a cross-section of a rare-earth sintered magnet according to Embodiment 3 with FE-EPMA. Figure 6 shows tetragonal Nd2Fe 14 B is a diagram showing atomic sites in the crystal structure. FIG. 7 is a flowchart showing an example of the steps of a method for manufacturing a rare earth sintered magnet according to Embodiment 4. FIG. 8 is a flowchart showing an example of the steps of a rare earth sintered magnet alloy manufacturing process according to Embodiment 4. FIG. 9 is a flowchart showing an example of the steps of a diffusion precursor manufacturing process according to Embodiment 4. FIG. 10 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 5. FIG. 11 is a cross-sectional view schematically showing an example of the configuration of a rotary machine according to embodiment 6. FIG. 12 is a diagram tracing the compositional image obtained by analyzing the cross-section of a rare earth sintered magnet according to Examples 1 to 8 with FE-EPMA. FIG. 13 is an elemental mapping of Nd obtained by analyzing the cross-section of rare earth sintered magnets according to Examples 1 to 8 with FE-EPMA. FIG. 14 is an elemental mapping of Pr obtained by analyzing the cross-section of rare earth sintered magnets according to Examples 1 to 8 with FE-EPMA. FIG. 15 is an elemental mapping of Dy obtained by analyzing the cross-section of rare earth sintered magnets according to Examples 1 to 8 with FE-EPMA. FIG. 16 is an elemental mapping of O obtained by analyzing the cross-section of a rare earth sintered magnet according to Examples 1 to 8 with FE-EPMA. Figure 17 is an elemental mapping of Sm obtained by analyzing the cross-section of rare earth sintered magnets according to Examples 1 to 8 with FE-EPMA. FIG. 18 is an elemental mapping of La obtained by analyzing the cross-section of a rare earth sintered magnet according to Examples 1 to 8 with FE-EPMA. Specific details for implementing 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 based on the drawings.

[0013] Embodiment 1.

[0014] FIG. 1 is a schematic diagram showing an example of the structure of a sintered state of a 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 Nd2Fe 14 The device has a columnar phase (10) containing crystal grains based on a B crystal structure, and the columnar 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 Nd and Pr. The shell portion has a composition different from that of the core portion and is provided to cover the core portion. Additionally, the rare earth sintered magnet (1) further has a float (20) existing between the columnar phases (10), that is, between a plurality of columnar phases (10). The float (20) is a phase based on an oxide phase represented with (Nd, Pr, R)-O as the main component.

[0015] In the rare earth sintered magnet (1) according to embodiment 1, when the concentration of Nd in the core part is set to CNd and the concentration of Pr in the core part is set to CPr, the columnar phase (10) comprises a first columnar phase (11) in which CNd > CPr and CNd <CPr인 제2 주상(12)을 갖고, 제1 주상(11)과 제2 주상(12)이 혼재하고 있다. 제1 주상(11)은, 코어부(11c)와, 코어부(11c)와는 조성이 상이하고, 코어부(11c)를 덮는 셸부(11s)를 갖는다. 제2 주상(12)은, 코어부(12c)와, 코어부(12c)와는 조성이 상이하고, 코어부(12c)를 덮는 셸부(12s)를 갖는다. 제1 주상(11)의 코어부(11c)에서는, CNd> CPr, and in the core part (12c) of the second column (12), CNd <CPr이다.

[0016] That is, in the rare earth sintered magnet (1), there exist two types of pillars (10), a first pillar (11) and a second pillar (12). Focusing on the core portions (11c, 12c) of the two types of pillars (10), it means that in the first pillar (11), the Nd concentration is higher than the Pr concentration, and conversely, in the second pillar (12), the Pr concentration is higher than the Nd concentration. By mixing two types of pillars (10) having different core-shell structures with different anisotropic magnetic fields, i.e., magnetic anisotropies, it is possible to improve residual magnetic flux density and coercivity while maintaining good magnetization properties while reducing Nd and heavy rare earth elements. Furthermore, it contributes to suppressing the degradation of magnetic properties associated with temperature changes. Here, the first pillar (11) where CNd > CPr and CNd <CPr인 제2 주상(12)」에 나타나는 농도차는 전자 프로브 마이크로 애널라이저(Electron Probe Micro Analyzer: EPMA)를 이용한 매핑 분석에 의해, Nd 및 Pr의 검출 강도에 명확하게 차가 나고 있는 것을 의미한다. 구체적으로는, 제1 주상(11)의 경우를 예로서 들면, 코어부(11c)의 Nd의 농도에 대해서는, EPMA의 검출 강도가 Nd의 검출 강도의 평균보다 높고, Pr의 농도에 대해서는, EPMA의 검출 강도가 Pr의 검출 강도의 하한 부근을 나타내고 있다는 것이다. 제2 주상(12)은 제1 주상(11)의 경우와 반대로 되어 있다고 말할 수 있다.

[0017] In addition, the rare earth sintered magnet (1) according to embodiment 1 has, when the Nd concentration of the core part (11c) of the first column (11) is set to C1Nd, the Nd concentration of the core part (12c) of the second column (12) is set to C2Nd, the Pr concentration of the core part (11c) of the first column (11) is set to C1Pr, and the Pr concentration of the core part (12c) of the second column (12) is set to C2Pr, C1Nd > C2Nd, C1Pr <C2Pr의 관계식을 만족시킨다. 즉, Nd 농도에 대해서는, 제2 주상(12)의 코어부(12c)에 비해 제1 주상(11)의 코어부(11c) 쪽이 높아져 있고, 반대로 Pr 농도에 대해서는, 제1 주상(11)의 코어부(11c)에 비해 제2 주상(12)의 코어부(12c) 쪽이 높아져 있다. 여기에서의 농도차도 상기의 EPMA를 이용한 매핑 분석에 의한 Nd 및 Pr의 검출 강도에 차가 나고 있는 것을 의미한다. 구체적으로, Nd의 농도의 경우에는, 제1 주상(11)의 코어부(11c)의 Nd의 EPMA의 검출 강도가, Nd의 검출 강도의 평균보다도 높고, 제2 주상(12)의 코어부(12c)의 Nd의 EPMA의 검출 강도가, Nd의 검출 강도의 평균보다도 낮은 상태인 것을 의미하고 있다. Pr의 농도의 경우에는, 제2 주상(12)의 코어부(12c)의 Pr의 EPMA의 검출 강도가, Pr의 검출 강도의 평균보다도 높고, 제1 주상(11)의 코어부(11c)의 Pr의 EPMA의 검출 강도가, Pr의 검출 강도의 평균보다도 낮은 상태가 되어 있는 것을 의미한다. 즉, Nd 농도가 낮은 제2 주상(12)의 코어부(12c)에는 Pr이 많이 존재하고, 반대로, Pr 농도가 낮은 제1 주상(11)의 코어부(11c)에는 Nd가 많이 존재하고 있게 된다. 이와 같은 조직 형태로 제어함으로써, 우수한 자기 특성을 갖는 희토류 소결 자석(1)을 얻는 것이 가능해진다.

[0018] In addition, in the rare earth sintered magnet (1) according to Embodiment 1, CNd<CPr인 제2 주상(12)보다도 CNd> The first columnar phase (11) of CPr is made to exist in large quantities. In other words, Nd2Fe 14 The number of first columnar phases (11) having the compositional formula of B is Pr2Fe 14 This means that there are more than the number of second pillars (12) having the compositional formula of B. This is Nd2Fe 14 The first columnar phase (11) having the compositional formula of B is extended, Pr2Fe 14 This is because superior magnetic properties and temperature properties are obtained compared to increasing the second columnar phase (12) having the compositional formula of B. Furthermore, by controlling the structure in this way, the overall refinement of the crystal grains is suppressed, so it is possible to obtain superior magnetic properties compared to the conventional method while ensuring magnetization.

[0019] In addition, regarding the rare earth sintered magnet (1) according to embodiment 1, focusing on the shell portions (11s, 12s) of the core-shell structure, when the concentration of Nd in the shell portions (11s, 12s) is set to SNd and the concentration of Pr in the shell portions (11s, 12s) is set to SPr, the first columnar phase (11) is such that CNd > SNd, CPr <SPr의 관계식을 만족시키고, 제2 주상(12)은, CNd<SNd, CPr> The relationship of SPr is satisfied. Specifically, the shell portion (11s) of the first column (11) has a lower concentration of Nd but a higher concentration of Pr than the core portion (11c), and the shell portion (12s) of the second column (12) has a lower concentration of Pr but a higher concentration of Nd than the core portion (12c). By forming a column (10) having a shell portion (11s) with a high concentration of Pr, as in the first column (11), the coercivity can be improved. Furthermore, by forming a column (10) having a shell portion (12s) with a high concentration of Nd, as in the second column (12), the decrease in residual magnetic flux density can be suppressed while maintaining the coercivity. By selectively controlling the structure to have such an organization, the rare earth sintered magnet (1) can exhibit superior magnetic properties compared to the conventional one.

[0020] Additionally, the column (10) has a layer (31) containing a heavy rare earth element that contains a heavy rare earth element on at least a portion of its surface. That is, a heavy rare earth element is present on at least a portion of the surface of the column (10), i.e., the first column (11) and the second column (12). More specifically, a heavy rare earth element is present on at least a portion of the outer surface of the shell portion (11s, 12s), and the heavy rare earth element is not penetrated into the core portion (11c, 12c). The heavy rare earth element is one or more elements selected from the group consisting of Dy, Tb, Gd, and Ho (holmium). In this way, the coercivity is increased by introducing heavy rare earth elements into the R sites of the first column (11) and the second column (12), but since the heavy rare earth elements do not penetrate into the core part (11c) inside the first column (11) and the core part (12c) inside the second column (12), a significant decrease in residual magnetic flux density can be suppressed. That is, the decrease in residual magnetic flux density can be suppressed while improving the coercivity. To obtain such an effect, it is preferable that the ratio of heavy rare earth elements in the column (10) be greater than 0 at.% and less than or equal to 10 at.%.

[0021] When comparing the magnetic properties of a rare earth sintered magnet (1) in which heavy rare earth elements are contained within the column (10) and in which heavy rare earth elements are contained on the surface layer, it is known that in order to obtain the same magnetic properties, heavy rare earth elements are contained on the surface layer of the column (10) at a lower concentration than the concentration in which heavy rare earth elements are contained within the column (10). That is, compared to the case in which heavy rare earth elements are contained within the column (10), in the rare earth sintered magnet (1) according to Embodiment 1 in which heavy rare earth elements are contained on the surface layer of the column (10), the amount of heavy rare earth elements used can be reduced.

[0022] Furthermore, it is preferable that the average grain size of the crystal grains of the columnar (10) be 100 μm or less, and more preferable that it be 0.5 μm or more and 50 μm or less for improved magnetic properties. Furthermore, by making it 1 μm or more and 10 μm or less, the grain size becomes different from the microstructure produced by hot working, so good magnetization performance is maintained and it becomes possible to make a rare earth sintered magnet (1) having superior magnetic properties compared to conventional ones.

[0023] The rare earth sintered magnet (1) according to Embodiment 1 may contain an additive element M that further improves magnetic properties. The additive element M is one or more elements selected from the group consisting of Ga (gallium), Cu (copper), Al (aluminum), Co, Zr (zirconium), Ti (titanium), Nb (niobium), and Mn (manganese). Accordingly, the rare earth sintered magnet (1) according to Embodiment 1 has a general formula (Nd) if RH is a heavy rare earth element selected from the group consisting of Dy, Tb, Gd, and Ho, and R is a rare earth element other than Nd, Pr, and the heavy rare earth element RH. a Pr b R c RH d )Fe e B f M g It is expressed as follows. The additive element M is one or more elements selected from the group consisting of Ga, Cu, Al, Co, Zr, Ti, Nb, and Mn. It is preferable that a, b, c, d, e, f, and g satisfy the following relationship.

[0024] 5≤a+b≤20

[0025] 0 <c+d<(a+b)

[0026] 0 <d<10

[0027] 70≤e≤90

[0028] 0.5≤f≤10

[0029] 0≤g≤5

[0030] a+b+c+d+e+f+g=100at.%

[0031] The rare earth sintered magnet (1) according to embodiment 1 satisfies the general formula (Nd, Pr, R)-Fe-B when R is one or more rare earth elements selected from Nd and Pr, and Nd2Fe 14 In a columnar phase (10) comprising crystal grains based on a B crystal structure, there exists a columnar phase (10) having a core portion (11c, 12c) and a shell portion (11s, 12s) covering the core portion (11c, 12c), and the columnar phase (10) comprises a first columnar phase (11) in which CNd > CPr and CNd <CPr인 제2 주상(12)을 갖고, 제1 주상(11)과 제2 주상(12)이 혼재하고 있다. 이와 같은 구성에 의해, Nd 및 중희토류 원소의 사용을 억제하면서, 종래에 비해 자기 특성 및 착자성을 향상시킨 희토류 소결 자석(1)을 얻을 수 있다.

[0032] In addition, the first column (11) and the second column (12) are C1Nd>C2Nd, C1Pr <C2Pr의 관계식을 만족시키도록 했다. 혹은, 제2 주상(12)의 수보다도 제1 주상(11)의 수 쪽이 많아지도록 했다. 혹은, 제1 주상(11)은 CNd> SNd, CPr <SPr의 관계식을 만족시키고, 제2 주상(12)은 CNd<SNd, CPr> The relationship of SPr was made to satisfy. By doing so, a rare earth sintered magnet (1) with improved magnetic properties and magnetization can be obtained while suppressing the use of Nd and heavy rare earth elements.

[0033] Additionally, heavy rare earth elements are present on at least a portion of the surface of the first column (11) and the second column (12), and heavy rare earth elements are not present inside the first column (11) and the second column (12). By doing so, a rare earth sintered magnet (1) can be obtained that suppresses the use of heavy rare earth elements, improves coercivity compared to the conventional method, and suppresses a significant decrease in residual magnetic flux density. In other words, it has the effect of improving the magnetic properties of the rare earth sintered magnet (1) compared to the conventional method.

[0034] In addition, in Embodiment 1, the first column (11) and the second column (12) have a core-shell structure having a single layer of shell portions (11s, 12s), and heavy rare earth elements are present on at least a portion of the surface of the shell portions (11s, 12s). On the other hand, in Patent Document 2, which has a two-layer core-shell structure, heavy rare earth elements must be diffused into the two-layer core-shell portions. Thus, the rare earth sintered magnet (1) of Embodiment 1 also has the effect of being able to suppress the amount of heavy rare earth elements used compared to Patent Document 2.

[0035] Embodiment 2.

[0036] FIG. 2 is a schematic diagram showing an example of the structure of the sintered state of a rare earth sintered magnet according to Embodiment 2. Meanwhile, the same reference numerals are used for components identical to those in Embodiment 1, and their descriptions are omitted. The rare earth sintered magnet (1) according to Embodiment 2 has a columnar structure (10) and a floating structure (20).

[0037] The column (10) has a structure similar to that of Embodiment 1. That is, the column (10) has a first column (11) and a second column (12) having a core-shell structure, and the composition of the core portion (11c, 12c) and the composition of the shell portion (11s, 12s) are the same as those described in Embodiment 1. However, in Embodiment 2, the heavy rare earth element containing layer (31) does not exist on the surface of the column (10).

[0038] The float (20) is a phase based on an oxide phase represented with (Nd, Pr, R)-O as the main component. However, in embodiment 2, the float (20) contains heavy rare earth elements. The heavy rare earth elements are distributed throughout the entire float (20). In one example, the heavy rare earth elements are uniformly distributed within the float (20).

[0039] In this way, in embodiment 2, a float (20) having heavy rare earth elements exists between the column (10) and the column (10). Heavy rare earth elements are uniformly distributed within the float (20), and it can be assumed that heavy rare earth elements penetrate into a part of the surface of the column (10) in contact with the float (20). That is, it is assumed that heavy rare earth elements do not penetrate to the core portion (11c, 12c) of the column (10), but penetrate into a part of the shell portion (11s, 12s). Because of this, as in embodiment 1, the reduction of residual magnetic flux density can be suppressed while improving the coercivity of the rare earth sintered magnet (1).

[0040] As shown in FIG. 2, among the rare earth sintered magnets (1), the column (10) comes into contact with another column (10) without interposing a float (20), or comes into contact with another column (10) with interposing a float (20). That is, at least a portion of the surface of the column (10) is in contact with the float (20). In addition, the float (20) contains heavy rare earth elements. Because of this, at least a portion of the surface of the column (10) is covered by the float (20) containing heavy rare earth elements. When looking at the distribution pattern of the heavy rare earth elements on the column (10), heavy rare earth elements are present on at least a portion of the surface of the column (10). That is, regarding the same rare earth sintered magnet (1), Embodiment 1 shows the distribution of heavy rare earth elements by focusing on the interface between the column (10) and the floating (20), and Embodiment 2 shows the distribution of heavy rare earth elements by focusing on the floating (20). In this way, Embodiment 1 and Embodiment 2 can be said to be the same rare earth sintered magnet (1) viewed from different angles.

[0041] In Embodiment 2, just like in Embodiment 1, a rare earth sintered magnet (1) can be obtained while suppressing the use of heavy rare earth elements, improving coercivity compared to the conventional method, and suppressing a significant decrease in residual magnetic flux density. That is, it has the effect of improving the magnetic properties of the rare earth sintered magnet (1) compared to the conventional method.

[0042] Embodiment 3.

[0043] FIG. 3 is a schematic diagram showing an example of the structure of the sintered state of a rare earth sintered magnet according to Embodiment 3. The rare earth sintered magnet (1) according to Embodiment 3 has a columnar structure (10) and a floating structure (20). The columnar structure (10) includes a first columnar structure (11) and a second columnar structure (12) as described in Embodiment 1, but in FIG. 2, the first columnar structure (11) and the second columnar structure (12) are collectively referred to as the columnar structure (10). The floating structure (20) exists between the columnar structures (10).

[0044] The rare earth sintered magnet (1) according to Embodiment 3 illustrates the case where La and Sm are selected for the rare earth element R. When La and Sm are selected for the rare earth element R, the effect of improving magnetic properties and having superior magnetization properties compared to conventional ones is enhanced while suppressing the use of Nd and heavy rare earth elements. In this example, the columnar structure (10) is (Nd, Pr, La, Sm)2Fe 14 It has the compositional formula of B. Tetragonal R2Fe 14 The reason for making the rare earth element R of the rare earth sintered magnet (1) having a B crystal structure a rare earth element including La and Sm is that, based on the calculation results of magnetic interaction energy using molecular orbital methods, a practical rare earth sintered magnet (1) is obtained in which the degradation of magnetic properties accompanying a rise in temperature can be significantly suppressed by using a composition with added La and Sm. In addition, by intentionally segregating La and Sm to grain boundaries, which are examples of levitation (20), Nd and Pr are relatively diffused into the columnar phase (10), thereby increasing the crystal magnetic anisotropy of the columnar phase (10). As a result, a core-shell structure is formed in which a part with high magnetic anisotropy and a part with low magnetic anisotropy exist within the columnar phase (10), and a first columnar phase (11) in which CNd > CPr and CNd <CPr인 제2 주상(12)이 혼재하는 희토류 소결 자석(1)이 생기기 쉬운 상태를 형성한다.

[0045] On the other hand, if the addition amounts of La and Sm are excessive, the amounts of Nd and Pr, which are elements with high magnetic anisotropy constants and saturation magnetic polarization, decrease, leading to a deterioration in magnetic properties. For this reason, when the compositional ratios of Nd, Pr, La, and Sm are set to A, B, C, and D, respectively, it is desirable to have (A+B) > (C+D).

[0046] In the rare earth sintered magnet (1) according to Embodiment 3, when R=La and Sm, in addition to the first columnar phase (11) and the second columnar phase (12) of Embodiment 1, a float (20) is provided. The float (20) has a crystalline first float (21) based on an oxide phase with a main component represented as (Nd, Pr, La, Sm)-O, and a crystalline second float (22) with a main component represented as (Nd, Pr, La)-O. The concentration of Sm in the float (20) is characterized in that the first float (21) is higher than that of the second float (22). That is, the first float (21) forms an Sm-enriched portion (41) with a higher Sm concentration than the second float (22). By doing so, it exhibits an effect of suppressing the decrease in magnetic properties accompanying a rise in temperature, as well as magnetic properties at room temperature.

[0047] Here, "the concentration of Sm is higher in the first float (21) than in the second float (22)" means that, based on mapping analysis using EPMA, the detection intensity of Sm in the first float (21) is higher on average than in the second float (22).

[0048] The crystalline phase (20) is a collective term for the crystalline first phase (21) and the crystalline second phase (22), and exists between the main phase (10). The crystalline first phase (21) is represented as (Nd, Pr, La, Sm)-O, and the crystalline second phase (22) is represented as (Nd, Pr, La)-O. Here, (Nd, Pr, La, Sm) means that a portion of Nd and Pr is substituted by La and Sm. Meanwhile, since the elements of the main components are listed in parentheses here, the first phase (21) and the second phase (22) may contain trace amounts of other components in addition to the elements appearing in parentheses. In one example, the second phase (22) represented as (Nd, Pr, La)-O contains a minute amount of Sm.

[0049] In the rare earth sintered magnet (1) according to Embodiment 3, there is a difference in the concentration of La and Sm between the column (10) and the floating (20), and La and Sm are segregated in the floating (20) more than in the column (10). That is, the sum of the concentrations of La in the first floating (21) and the second floating (22) is greater than the concentration of La in the column (10), and the sum of the concentrations of Sm in the first floating (21) and the second floating (22) is greater than the concentration of Sm in the column (10). Specifically, the concentrations of La and Sm in the floating (20) are greater than the concentrations of La and Sm in the column (10). Here, the concentration of La in the column (10) is the sum of the concentration of La in the first column (11) and the concentration of La in the second column (12). That is, the sum of the concentrations of La in the first floating phase (21) and the second floating phase (22) is higher than the sum of the concentrations of La in the first columnar phase (11) and the second columnar phase (12). Also, the concentration of Sm in the columnar phase (10) is the sum of the concentration of Sm in the first columnar phase (11) and the concentration of Sm in the second columnar phase (12). That is, the sum of the concentrations of Sm in the first floating phase (21) and the second floating phase (22) is higher than the sum of the concentrations of Sm in the first columnar phase (11) and the second columnar phase (12).

[0050] Here, when the La concentration included in the main body (10) is set to X, the La concentration included in the first floating body (21) is set to X1, the La concentration included in the second floating body (22) is set to X2, the Sm concentration included in the main body (10) is set to Y, the Sm concentration included in the first floating body (21) is set to Y1, and the Sm concentration included in the second floating body (22) is set to Y2, the relationship of the following equation (1) is satisfied.

[0051] 1<(Y1+Y2) / Y<(X1+X2) / X ····(1)

[0052] Additionally, regarding the concentrations of Nd and Pr included in the main body (10) in terms of improving magnetic properties, the following relationships (2) and (3) are satisfied.

[0053] (CNd+SNd)>(X+Y) ····(2)

[0054] (CPr+SPr)>(X+Y) ····(3)

[0055] Meanwhile, as stated above, the concentration of La in the column (10) is the sum of the concentrations of La in the first column (11) and the second column (12), and the concentration of Sm in the column (10) is the sum of the concentrations of Sm in the first column (11) and the second column (12). This indicates that La and Sm are segregated together in the floating (20) rather than in the column (10). However, when viewed locally, there may be cases where the sum of the respective concentrations of La and Sm in the first column (11) and the second column (12), and the sum of the respective concentrations of La and Sm in the first floating (21) and the second floating (22) do not satisfy the above relationship. For this reason, more specifically, the concentration of La in the column (10) represents the average of the concentrations of La in the first column (11) and the second column (12), and the concentration of Sm in the column (10) represents the average of the concentrations of Sm in the first column (11) and the second column (12). In this case, the concentration of La in the floating (20), that is, the sum of the concentrations of La in the first floating (21) and the second floating (22), means the average of the concentrations of La in the first floating (21) and the second floating (22), and the concentration of Sm in the floating (20), that is, the sum of the concentrations of Sm in the first floating (21) and the second floating (22), means the average of the concentrations of Sm in the first floating (21) and the second floating (22).

[0056] La, by being present in high concentration at the grain boundaries during the manufacturing process, particularly during the heat treatment process, diffuses Nd and Pr into the columnar phase (10) relatively. As a result, in the rare earth sintered magnet (1) of Embodiment 3, Nd and Pr in the columnar phase (10) are not consumed at the grain boundaries, thereby improving the crystal magnetic anisotropy. In the case of Sm, since it is present in high concentration at the floating phase (20), particularly the first floating phase (21), compared to the columnar phase (10), it diffuses Nd into the columnar phase (10) relatively, just like La, thereby improving the crystal magnetic anisotropy.

[0057] As described in Embodiment 2, since the float (20) contains heavy rare earth elements, the first float (21) and the second float (22) contain heavy rare earth elements; however, in Embodiment 3, the distribution of heavy rare earth elements in the first float (21) and the second float (22) is different. In the second float (22), where the Sm concentration is lower than that of the first float (21), the heavy rare earth elements are uniformly distributed within the second float (22). On the other hand, in the first float (21) forming the Sm enrichment portion (41), the heavy rare earth elements are not uniformly distributed within the first float (21), but are selectively distributed between the outer edge of the first float (21) and the Sm enrichment portion (41), that is, in the inner circumference of the outer edge of the first float (21). Specifically, they exist to selectively surround the outer edge of the Sm enrichment portion (41) where the Sm concentration of the first float (21) is high. From this, it can also be said that the first float (21) has an Sm enriched portion (41) and a heavy rare earth element containing portion (32) in which heavy rare earth elements exist, which selectively surrounds the outer edge of the Sm enriched portion (41). The outer edge of the first float (21) is the boundary between the first float (21) and the columnar (10).

[0058] Similar to Embodiment 2, a first float (21) and a second float (22) having heavy rare earth elements exist between the column (10) and the column (10). It can be assumed that heavy rare earth elements penetrate into a part of the surface of the column (10) that is in contact with the first float (21) and the second float (22) having heavy rare earth elements. That is, it is assumed that heavy rare earth elements do not penetrate to the core portion (11c, 12c) of the column (10), but penetrate into a part of the shell portion (11s, 12s). Because of this, similar to Embodiment 1, the reduction of residual magnetic flux density can be suppressed while improving the coercivity of the rare earth sintered magnet (1).

[0059] FIGS. 4 and 5 are elemental mappings obtained by analyzing a cross-section of a rare-earth sintered magnet according to Embodiment 3 using a Field Emission-Electron Probe Micro Analyzer (FE-EPMA). FIG. 4 is an elemental mapping of Sm, and FIG. 5 is an elemental mapping of Tb. In these figures, a floating section (20) is shown existing between the main section (10) and the main section (10). In addition, the floating section (20) includes a first floating section (21) having an Sm enrichment section (41) and a second floating section (22) having a lower Sm concentration than the first floating section (21). In the second floating section (22), as described above, the heavy rare-earth element Tb is uniformly distributed. On the other hand, in the first floating section (21), there is a bias in the distribution of Tb. Referring to FIGS. 4 and 5, a heavy rare earth element containing portion (32) exists to selectively surround the Sm enrichment portion (41) in the first float (21), where the Sm concentration is high. Additionally, there are almost no heavy rare earth elements in the Sm enrichment portion (41). Furthermore, the concentration of heavy rare earth elements selectively distributed around the Sm enrichment portion (41) is higher than the concentration of heavy rare earth elements distributed throughout the interior of the second float (22).

[0060] Next, La and Sm are tetragonal R2Fe 14 It explains which atomic sites of the crystal structure B are substituted. Fig. 6 shows tetragonal Nd2Fe 14 B is a diagram showing atomic sites in a crystal structure. Meanwhile, the crystal structure shown in Fig. 6 is described in FIG. 1 of Reference 1 shown below, as an example. The sites to be substituted are determined by calculating the stabilization energy due to substitution through band calculations and the molecular field approximation of the Heisenberg model, and by the numerical value of that energy.

[0061] (Reference 1) JF 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.

[0062] First, the method for calculating the stabilization energy in La is explained. The stabilization energy in La is Nd8Fe 56 Using a B4 crystal cell, (Nd7La1)Fe 56 B4+Nd and Nd8(Fe 55 It can be determined by the energy difference of La1)B4+Fe. The smaller the energy value, the more stable the substitution of an atom at that site. In other words, La is more likely to be substituted at the atomic site with the lowest energy among all atomic sites. In this calculation, when La substitutes the original atom, the tetragonal R2Fe 14 It is said that the lattice constant in the B crystal structure does not change with differences in atomic radius. Table 1 is a table showing the stabilization energy of La at each substitution site when the ambient temperature is changed.

[0063]

[0064] According to Table 1, the stable substitution site of La is the Nd(f) site at temperatures above 1000K, and the Fe(c) site at temperatures of 293K and 500K. As described below, the rare earth sintered magnet (1) according to Embodiment 3 is formed by heating the raw material of the rare earth sintered magnet (1) to a temperature above 1000K to melt it, and then rapidly cooling it. Because of this, it is believed that the raw material of the rare earth sintered magnet (1) is maintained at a temperature above 1000K, i.e., 727°C, preferably around 1300K, i.e., 1027°C. At that time, it is believed that La is substituted into the Nd(f) site or the Nd(g) site. Here, it is believed that La is preferentially substituted into the energetically stable Nd(f) site, but among the substitution sites of La, substitution into the Nd(g) site, which has a small energy difference, may also occur. For this reason, the Nd(g) site is also being mentioned as a candidate for the substitution site of La.

[0065] Furthermore, when a rare earth sintered magnet (1) is manufactured by the manufacturing method described below, the temperature during sintering is 1000K or higher, but by undergoing a first aging process, a second aging process, and further a third aging process, a fourth aging process, and a cooling process, the Fe(c) sites listed in Table 1 are maintained in an energetically stable temperature range multiple times. In other words, the substitution of La in the Nd sites of the columnar (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 in the Nd sites of the columnar (10), but in the rare earth sintered magnet (1) produced by the manufacturing method described below, by deliberately maintaining the Nd sites of the columnar (10) in an unstable energy state temperature range multiple times, a certain amount of La is selectively released from the Nd sites of the columnar (10), and as a result, La is segregated in the floating (20). As a result, the columnar structure (10) promotes the formation of a characteristic structure called a core-shell structure.

[0066] Next, the method for calculating the stabilization energy for Sm is explained. Regarding the stabilization energy of Sm, (Nd7Sm1)Fe 56 B4+Nd and Nd8(Fe 55 It can be determined by the energy difference of Sm1)B4+Fe. Due to atomic substitution, tetragonal R2Fe 14 Regarding the point that the lattice constant in the B crystal structure does not change, it is the same as in the case of La. Table 2 is a table showing the stabilization energy of Sm at each substitution site when the ambient temperature is changed.

[0067]

[0068] According to Table 2, the stable substitution site of Sm is the Nd(g) site at any temperature, unlike La. Although it is thought that Sm is preferentially substituted to the energetically stable Nd(g) site, there may also be substitution to the Nd(f) site, which has a small energy difference, among the substitution sites of Sm.

[0069] When a rare earth sintered magnet (1) is manufactured by the manufacturing method described below, the substitution of Nd(g) sites in the columnar phase (10) is energetically the most stable. However, as described above, by maintaining the temperature range in which the substitution of La into Nd sites in the columnar phase (10) becomes unstable, some Sm is also released from the Nd sites in the columnar phase (10) along with La and is segregated in the floating phase (20). As a result, there is a difference in concentration between the columnar phase (10) and the floating phase (20) for La and Sm, and the sum of the concentrations of La in the first floating phase (21) and the second floating phase (22) is greater than the concentration of La in the columnar phase (10), and the sum of the concentrations of Sm in the first floating phase (21) and the second floating phase (22) is greater than the concentration of Sm in the columnar phase (10). More specifically, the average concentration of La in the first floating phase (21) and the second floating phase (22) is greater than the average concentration of La in the first columnar phase (11) and the second columnar phase (12), and the average concentration of Sm in the first floating phase (21) and the second floating phase (22) is greater than the average concentration of Sm in the first columnar phase (11) and the second columnar phase (12). That is, it can be said that La and Sm are segregated in the floating phase (20).

[0070] When comparing La and Sm, it can be seen that, from an energetic perspective, La, which is maintained in the temperature range of an unstable energy state, is overwhelmingly more likely to be segregated in the float (20). Accordingly, in the case of a rare earth sintered magnet (1) prepared with the same concentration of La and Sm, among the La and Sm present in the rare earth sintered magnet (1), the segregation ratio for the float (20) is larger for La. By maintaining it in this temperature range multiple times, a difference in the concentration of Sm, which has a lower segregation ratio in the float (20), is created, and the first float (21) and the second float (22) are formed. This promotes the formation of a core-shell structure in the columnar structure (10).

[0071] This time, as shown in FIG. 6, the explanation is given with respect to Nd as a representative example. However, as represented by Di (didymium), Nd and Pr are produced as a mixture, so the energy levels of Nd and Pr are considered to be close. For this reason, the same can be said even if Nd is substituted with Pr. By having two types of Nd and Pr, a columnar phase (10) having two types of core-shell structures can be formed.

[0072] As described above, the rare earth sintered magnet (1) of embodiment 3 satisfies the general formula (Nd, Pr, R)-Fe-B when R is one or more rare earth elements selected from Nd and Pr, and Nd2Fe 14A columnar phase (10) comprising crystal grains based on a B crystal structure is provided, and the columnar phase (10) has a core portion (11c, 12c) and a shell portion (11s, 12s) covering the core portion (11c, 12c). When R=La and Sm, in addition to the first columnar phase (11) and the second columnar phase (12) in Embodiment 1, a floating phase (20) is provided. The floating phase (20) has a crystalline first floating phase (21) based on an oxide phase with a main component represented as (Nd, Pr, La, Sm)-O, and a crystalline second floating phase (22) with a main component represented as (Nd, Pr, La)-O. The concentration of Sm is higher in the first floating phase (21) than in the second floating phase (22). That is, two types of columnar phases (10) and two types of floating phases (20) are provided. From this, it becomes possible to provide a rare-earth sintered magnet (1) with magnetic properties, such as temperature characteristics of magnetic properties, that are superior to those of the conventional type. Additionally, by making R La and Sm, the columnar phase (10) comprises a first columnar phase (11) in which CNd > CPr and CNd <CPr인 제2 주상(12)이 혼재하고 있는 상태가 된다. 바꾸어 말하면, 희토류 소결 자석(1)에는 2종류의 제1 주상(11) 및 제2 주상(12)을 갖는 주상(10)이 존재하고, 2종류의 주상(10)의 코어부(11c, 12c)에 착안하면, 제1 주상(11)에서는 Nd 농도가 Pr 농도보다 높고, 반대로 제2 주상(12)에서는 Pr 농도가 Nd 농도보다 높아지는, 2종류의 코어 셸 구조를 갖는 주상(10)이 생기기 쉬워진다. 이 결과, Nd 및 중희토류 원소의 사용을 억제하면서, 자기 특성을 향상시키고, 종래에 비해 우수한 착자성을 갖는다는 효과를 더 높일 수 있다.

[0073] In addition, in embodiment 3, just like in embodiment 1, a rare earth sintered magnet (1) can be obtained while suppressing the use of heavy rare earth elements, improving the coercivity compared to the conventional method, and suppressing a significant decrease in residual magnetic flux density. That is, it has the effect of improving the magnetic properties of the rare earth sintered magnet (1) compared to the conventional method.

[0074] Embodiment 4.

[0075] In Embodiment 4, a method for manufacturing a rare earth sintered magnet (1) as described in Embodiments 1, 2, or 3 is described. FIG. 7 is a flowchart showing an example of the steps of a method for manufacturing a rare earth sintered magnet according to Embodiment 4. As shown in FIG. 7, the method for manufacturing a rare earth sintered magnet (1) includes a rare earth sintered magnet alloy manufacturing process (step S10) for manufacturing a rare earth sintered magnet alloy that serves as a raw material for a diffusion precursor, which is a sintered body before diffusing heavy rare earth elements into the rare earth sintered magnet (1); a diffusion precursor manufacturing process (step S20) for forming a diffusion precursor; a grain boundary diffusion process (step S30) for diffusing heavy rare earth elements into the diffusion precursor; and a cooling process (step S40) for cooling the diffusion precursor in which heavy rare earth elements have been diffused to obtain a rare earth sintered magnet (1).

[0076] First, details of the manufacturing process of the rare earth sintered magnet alloy in Step S10 will be described. FIG. 8 is a flowchart illustrating an example of the sequence of the manufacturing process of the rare earth sintered magnet alloy according to Embodiment 4. First, as shown in FIG. 8, the manufacturing process of the rare earth sintered magnet alloy, which serves as the raw material for the diffusion precursor, comprises a melting process (Step S11) in which the raw material for the rare earth sintered magnet alloy containing elements constituting the diffusion precursor is heated to a temperature of 1000K or higher to melt it, a first cooling process (Step S12) in which the molten raw material is cooled on a rotating body to obtain a solidified alloy, and a second cooling process (Step S13) in which the solidified alloy is further cooled in a container. By doing so, the rare earth sintered magnet alloy can be manufactured. Each process will be described below.

[0077] In the melting process of Step S11, the raw material of the diffusion precursor is heated to a temperature of 1000K or higher in an atmosphere containing an inert gas such as Ar (argon) or in a vacuum and melted. By doing so, a molten alloy in which the rare earth sintered magnet alloy is melted is prepared. When manufacturing the rare earth sintered magnet (1) of Embodiments 1 and 2, Nd, Pr, Fe, and B may be used as raw materials. When manufacturing the rare earth sintered magnet (1) of Embodiment 3, Nd, Pr, La, Sm, Fe, and B may be used as raw materials. In addition, FeB may be used instead of B as a raw material. At this time, one or more elements selected from the group consisting of Al, Co, Zr, Ti, Nb, and Mn may be included in the raw material as the additive element M.

[0078] Next, in the first cooling process of Step S12, the molten alloy prepared in the melting process is flowed into a tundish and subsequently flowed onto a single roll, which is a rotating body. As a result, the molten alloy is rapidly cooled on the single roll rotating in a predetermined direction, and a solidified alloy thinner than the ingot alloy is prepared from the molten alloy on the single roll. Here, a single roll was used as the rotating body, but it is not limited thereto; rapid cooling may also be achieved by contacting a twin roll, a rotating disk, a rotating cylindrical mold, etc. From the perspective of efficiently obtaining a thin solidified alloy, the cooling rate in the first cooling process is 10°C / second or higher, 10 7 It is desirable to keep it at ℃ / sec or less, and 10 3 10 ℃ / sec or more 4 It is more desirable to keep it at ℃ / sec or lower. The thickness of the solidified alloy is in the range of 0.03 mm or more and 10 mm or less. Solidification of the molten alloy begins from the part in contact with the single roll, and crystals grow in a columnar or needle shape in the thickness direction from the contact surface with the single roll. The first cooling process of step S12 corresponds to the first alloy cooling process.

[0079] Subsequently, in the second cooling process of Step S13, the thin solidified alloy prepared in the first cooling process is placed into a tray container and cooled. As the thin solidified alloy enters the tray container, it breaks into a flake-like rare-earth sintered magnet alloy and cools. Depending on the cooling rate, a ribbon-like rare-earth sintered magnet alloy may also be obtained, so it is not limited to the flake-like form. From the perspective of obtaining a rare-earth sintered magnet alloy having a microstructure with good temperature characteristics of magnetic properties, the cooling rate in the second cooling process is 10 -2 10 ℃ / sec or more 5 It is desirable to keep it at ℃ / sec or less, and 10 -1 10 ℃ / sec or more 2It is more desirable to keep it at ℃ / sec or less. The second cooling process of step S13 corresponds to the second alloy cooling process.

[0080] The rare earth sintered magnet alloy obtained through these processes has a size in the minor axis direction of 3 μm or more and 10 μm or less, and a size in the major axis direction of 10 μm or more and 300 μm or less. When manufacturing the rare earth sintered magnet (1) of Embodiment 3, it has a fine crystalline structure containing a (Nd, Pr, La, Sm)-Fe-B crystalline phase and a crystalline phase (20) of an oxide represented as (Nd, Pr, La, Sm)-O. Hereinafter, the crystalline phase (20) of an oxide represented as (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 is 10 μm or less, corresponding to the width of the grain boundary. The rare earth sintered magnet alloy produced by the above manufacturing process undergoes a rapid cooling process, so compared to the rare earth sintered magnet alloy obtained by the mold casting method, the microstructure is refined.

[0081] Next, the diffusion precursor manufacturing process of step S20 of FIG. 7 will be described. FIG. 9 is a flowchart showing an example of the sequence of the diffusion precursor manufacturing process according to Embodiment 4. Below, the case of manufacturing the rare earth sintered magnet (1) of Embodiment 3 will be described as an example, but the rare earth sintered magnets (1) of Embodiments 1 and 2 can be manufactured by changing the raw material of the rare earth sintered magnet alloy used. As shown in FIG. 9, the diffusion precursor manufacturing process comprises a grinding process (step S21) for grinding 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 process (step S22) for forming a molded body by molding the powder of the ground rare earth sintered magnet alloy; a sintering process (step S23) for obtaining a sintered body by sintering the molded body at a sintering temperature that is a predetermined temperature; an aging process (step S24) for aging the sintered body to increase magnetic properties such as coercivity of the rare earth sintered magnet (1); and a sintered body cooling process (step S25) for cooling the aged sintered body. Each process will be described below.

[0082] In the grinding process of step S21, a rare earth sintered magnet alloy satisfying (Nd, Pr, R)-Fe-B, manufactured according to the rare earth sintered magnet alloy manufacturing process of FIG. 8, is ground to obtain a 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 furthermore, 1 μm or more and 10 μm or less when considering magnetization performance. The grinding of the rare earth sintered magnet alloy is performed, for example, using a mortar and pestle, a stamp mill, a jaw crusher, or a jet mill. In particular, when reducing the particle size of the powder, it is preferable to perform the grinding of the rare earth sintered magnet alloy in an atmosphere containing an inert gas. By performing the grinding of 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 grinding does not affect the magnetic properties of the magnet, the grinding of the rare-earth sintered magnet alloy may be performed in the atmosphere.

[0083] In the forming process of step S22, powder of a rare-earth sintered magnet alloy is compression molded in a mold to which a magnetic field is applied to form a molded body. Here, the applied magnetic field can be 2T, for example. Meanwhile, forming may be performed without applying a magnetic field, rather than in a magnetic field.

[0084] In the sintering process of step S23, a compression-molded body is obtained by maintaining it 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 hours or higher and 10 hours or lower, preferably in the range of 1.0 hours or higher and 6.0 hours or lower. To inhibit oxidation, it is preferable to perform the sintering in an atmosphere containing an inert gas or in a vacuum. The sintering may also be performed while applying a magnetic field.

[0085] The aging process of step S24, in the case of FIG. 9, 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. It is preferable that the aging be performed in an atmosphere containing an inert gas or in a vacuum to inhibit oxidation.

[0086] The condition of the first aging process of Step S24-1 is to maintain the obtained sintered body at a first aging temperature, which is a temperature lower than the sintering temperature, for a time within the range of 0.1 hours or more and 10 hours or less, preferably 0.5 hours or more and 5 hours or less. Specifically, the first aging temperature is a temperature within the range of 700°C or more and less than 950°C, and is a temperature lower than the sintering temperature.

[0087] The condition of the second aging process of Step S24-2 is that, after the first aging process, the sintered body maintained in the first aging process is maintained at a second aging temperature, which is a temperature lower than the first aging temperature, for a period of time ranging from 0.1 hours to 10 hours, preferably from 1.0 hour to 7 hours. Specifically, the second aging temperature is a temperature within the range of 450°C to less than 700°C, and is a temperature lower than the first aging temperature.

[0088] The condition of the third aging process of Step S24-3 is that, after the second aging process, the sintered body maintained in the second aging process is again heated to the first aging temperature, specifically within the range of 700°C or higher and less than 950°C, and maintained at the first aging temperature for a time within the range of 0.1 hours or more and 10 hours or less, preferably 0.5 hours or more and 5 hours or less.

[0089] The condition of the fourth aging process of step S24-4 is that, after the third aging process, the sintered body maintained in the third aging process is again maintained at a second aging temperature, specifically at a temperature within the range of 450°C or higher and less than 700°C, for a time of 0.1 hours or more and 10 hours or less, preferably within the range of 1.0 hours or more and 7 hours or less.

[0090] Finally, in the cooling process of the sintered body in step S25, the sintered body maintained in the fourth aging process is maintained at a cooling temperature within the range of 200°C or higher and less than 450°C for a time within the range of 0.1 hours or more and 5 hours or less. After that, by cooling to room temperature, a diffusion precursor of the rare earth sintered magnet (1) is produced. To suppress oxidation, it is preferable that the cooling be carried out in an atmosphere containing an inert gas or in a vacuum.

[0091] In this way, a diffusion precursor, which is a sintered body having the shape of a final rare earth sintered magnet (1), is formed.

[0092] Returning to FIG. 7, in the grain boundary diffusion process of Step S30, heat treatment is performed under conditions where the diffusion precursor formed in Step S25 and heavy rare earth elements are present, thereby diffusing the heavy rare earth elements into the diffusion precursor at the grain boundaries. In one example, a heat treatment is performed in which the diffusion precursor is maintained at a temperature lower than the sintering temperature in the sintering process of Step S23. The grain boundary diffusion process may be performed simultaneously with the aging process of Step S24. In the grain boundary diffusion process, the heavy rare earth elements are selectively diffused into at least a portion of the outer edge of the Sm enrichment portion (41) of the first floating portion (21) and are uniformly diffused into the second floating portion (22). Known grain boundary diffusion methods can be used for the treatment in the grain boundary diffusion process. Various techniques for grain boundary diffusion methods have been proposed depending on the form of supply of the heavy rare earth elements, and coating diffusion, sputter diffusion, and vapor diffusion are representative methods. These representative grain boundary diffusion methods will be explained below.

[0093] <Application Diffusion Method>

[0094] In the coating diffusion method, the grain boundary diffusion process includes a diffusion element attachment process in which a heavy rare earth element supply portion, which is a material containing heavy rare earth elements and serves as a source of heavy rare earth elements to the diffusion precursor, is attached, and a diffusion heat treatment process in which heat treatment is performed to diffuse heavy rare earth elements from the heavy rare earth element supply portion to the diffusion precursor. In the diffusion element attachment process, a slurry in which a powdered mixture of heavy rare earth elements is mixed with water or an organic solvent, etc., is attached to the surface of the diffusion precursor. The slurry attached to the surface of the diffusion precursor becomes the heavy rare earth element supply portion. The attachment of the slurry can be performed by spraying, dip coating, spin coating, screen printing, electrodeposition, etc. In the diffusion heat treatment process, the diffusion precursor with the attached heavy rare earth element supply portion is heat-treated at a diffusion temperature lower than the sintering temperature in the sintering process of Step S23, thereby diffusing heavy rare earth elements into the interior of the diffusion precursor. The heat treatment conditions are set at a diffusion temperature below the sintering temperature for a time within the range of 0.1 hours to 100 hours. In one example, the diffusion temperature is a temperature within the range of 300°C to 1000°C and is lower than the sintering temperature. To inhibit oxidation, it is preferable to perform the heat treatment in an atmosphere containing an inert gas or in a vacuum.

[0095] Sputter Diffusion Method

[0096] In the sputter diffusion method, similar to the coating diffusion method, the grain boundary diffusion process includes a diffusion element attachment process and a diffusion heat treatment process. In the diffusion element attachment process, a thin film of a single metal or alloy composition of a heavy rare earth element is formed on the surface of the diffusion precursor under a dry environment. The thin film formed on the surface of the diffusion precursor serves as a supply of heavy rare earth elements. In one example, the thin film is formed by the sputter method. In the diffusion heat treatment process, the diffusion precursor with the supply of heavy rare earth elements formed thereon is heat-treated at a diffusion temperature lower than the sintering temperature in the sintering process of Step S23, thereby diffusing the heavy rare earth elements into the interior of the diffusion precursor. The conditions for the heat treatment are set to a time within the range of 0.1 hours to 100 hours at a diffusion temperature lower than the sintering temperature. In one example, the diffusion temperature is a temperature within the range of 300°C to 1000°C and is lower than the sintering temperature. To inhibit oxidation, it is preferable to perform the heat treatment in an atmosphere containing an inert gas or in a vacuum.

[0097] Vapor Diffusion Method

[0098] In the vapor diffusion method, after installing a diffusion precursor and a source of heavy rare earth elements in a vacuum furnace, a heat treatment is performed to diffuse heavy rare earth elements into the interior of the diffusion precursor by heat treating the diffusion precursor in the vacuum furnace at a temperature lower than the sintering temperature in the sintering process of Step S23. In the heat treatment, the source of heavy rare earth elements is turned into a gaseous state by vacuum heating, and the heavy rare earth elements are supplied to the diffusion precursor through the gaseous state. The conditions for the heat treatment are set to a time within the range of 0.1 hours to 100 hours at a diffusion temperature lower than the sintering temperature. For example, the diffusion temperature is a temperature within the range of 600°C to 900°C and is lower than the sintering temperature. Furthermore, in the vapor diffusion method, unlike the coating diffusion method and the sputter diffusion method, there is no need to attach the source of heavy rare earth elements to the diffusion precursor, so the diffusion element attachment process can be omitted, thereby shortening the time of the grain boundary diffusion process.

[0099] Returning to FIG. 7, in the cooling process of the final step S40, the diffusion precursor in which heavy rare earth elements are diffused in the grain boundary diffusion process is maintained at a temperature of less than 200°C for a time within the range of 0.1 hours to 5 hours. After that, by cooling to room temperature, the rare earth sintered magnet (1) shown in embodiments 1 to 3 is formed. In the case of embodiment 1, a rare earth sintered magnet (1) is formed in which heavy rare earth elements are present on at least a part of the surface of the column (10); in the case of embodiment 2, a rare earth sintered magnet (1) in which heavy rare earth elements are diffused on the float (20) is formed; and in the case of embodiment 3, a rare earth sintered magnet (1) is formed in which heavy rare earth elements are diffused to selectively surround the outer edge of the Sm enrichment portion (41) of the first float (21) and are uniformly diffused on the second float (22). To inhibit oxidation, it is preferable to perform cooling in an atmosphere containing an inert gas or in a vacuum.

[0100] As described above, a rare earth sintered magnet (1) of a desired shape is obtained by diffusing a heavy rare earth element into a diffusion precursor having the shape of a final rare earth sintered magnet (1) at the grain boundaries.

[0101] As described above, by controlling the temperature and time during the sintering process, aging process, and sintered body cooling process, the sintered body is maintained multiple times in a temperature range of unstable energy states. As a result, a first columnar phase (11) consisting of CNd > CPr and CNd <CPr로 이루어지는 제2 주상(12)을 혼재시키는 것이 가능해진다. 바꾸어 말하면, 희토류 소결 자석(1)에는 제1 주상(11) 및 제2 주상(12)의 2종류의 주상(10)이 존재하고, 2종류의 주상(10)의 코어부(11c, 12c)에 착안하면, 제1 주상(11)은 Nd 농도가 Pr 농도보다 높고, 반대로 제2 주상(12)은 Pr 농도가 Nd 농도보다 높다는 특징을 갖는 희토류 소결 자석(1)을 제조할 수 있다.

[0102] Additionally, in addition to the first phase (11) and second phase (12) of embodiment 1, a rare earth sintered magnet (1) can be manufactured having a crystalline first phase (21) based on an oxide phase with a main component represented as (Nd, Pr, La, Sm)-O and a crystalline second phase (22) with a main component represented as (Nd, Pr, La)-O, wherein the concentration of Sm is higher in the first phase (21) than in the second phase (22).

[0103] By doing so, it is possible to provide a rare earth sintered magnet (1) having superior magnetization performance and magnetic properties compared to conventional ones while suppressing the use of Nd and heavy rare earth elements.

[0104] In Embodiment 4, a rare earth sintered magnet alloy powder is formed by crushing a rare earth sintered magnet alloy having a (Nd, Pr, La, Sm)-Fe-B crystal phase and a (Nd, Pr, La, Sm)-O phase, and the formed molded body is sintered to form a sintered body, and then the sintered body is aged to manufacture a rare earth sintered magnet (1). By doing so, a rare earth sintered magnet (1) according to Embodiment 3 can be manufactured.

[0105] In addition, in the first aging process, the obtained sintered body is maintained at a first aging temperature, which is a temperature below the sintering temperature, for a range of 0.1 hours or more and 10 hours or less, preferably 0.5 hours or more and 5 hours or less. In the second aging process, the sintered body is maintained at a second aging temperature, which is a temperature below the first aging temperature, for a range of 0.1 hours or more and 10 hours or less, preferably 1.0 hours or more and 7 hours or less. In the third aging process, the temperature is raised again to the first aging temperature, and the sintered body is maintained at the first aging temperature for a range of 0.1 hours or more and 10 hours or less, preferably 0.5 hours or more and 5 hours or less. In the fourth aging process, the sintered body is maintained again at the second aging temperature for a range of 0.1 hours or more and 10 hours or less, preferably 1.0 hours or more and 7 hours or less. In this way, by controlling the temperature and time to perform two sets of the first aging process and the second aging process, a state is created in which the sintered body is maintained multiple times in a temperature range of unstable energy states. As a result, a first columnar phase (11) consisting of CNd > CPr and CNd <CPr로 이루어지는 제2 주상(12)이 혼재하고 있는 희토류 소결 자석(1)을 얻을 수 있다. 바꾸어 말하면, 희토류 소결 자석(1)은, 제1 주상(11) 및 제2 주상(12)의 2종류의 주상(10)이 존재하고, 2종류의 주상(10)의 코어부(11c, 12c)에 착안하면, 제1 주상(11)은 Nd 농도가 Pr 농도보다도 높고, 반대로 제2 주상(12)은 Pr 농도가 Nd 농도보다도 높아지는 희토류 소결 자석(1)을 선택적으로 제조할 수 있다.

[0106] Additionally, by the above manufacturing process, a rare earth sintered magnet (1) having a characteristic structural structure having a crystalline first phase (21) based on an oxide phase represented by (Nd, Pr, La, Sm)-O and a crystalline second phase (22) represented by (Nd, Pr, La)-O, wherein the concentration of Sm is higher in the first phase (21) than in the second phase (22) can be selectively manufactured.

[0107] In addition, in the method for manufacturing a rare earth sintered magnet (1) according to Embodiment 4, a R-Fe-B system rare earth sintered magnet alloy containing a rare earth element R including Nd and Pr is crushed, a molded body of the powder of the R-Fe-B system rare earth sintered magnet alloy is sintered, and an aging treatment is performed to form a diffusion precursor having a first columnar phase (11) and a second columnar phase (12). In the method for manufacturing a rare earth sintered magnet (1) according to Embodiment 4, a rare earth sintered magnet (1) in which a heavy rare earth element exists on a part of the surface of the first columnar phase (11) and the second columnar phase (12), or a rare earth sintered magnet (1) in which a heavy rare earth element exists on the floating phase (20), can be produced by heat treatment in which a heavy rare earth element is diffused into the diffusion precursor at the grain boundaries. By doing so, a rare earth sintered magnet (1) can be obtained that suppresses the use of heavy rare earth elements compared to conventional methods, suppresses the deterioration of magnetic properties, and improves magnetic properties compared to conventional methods.

[0108] Additionally, in the method for manufacturing a rare earth sintered magnet (1) according to embodiment 4, an R-Fe-B system rare earth sintered magnet alloy containing rare earth elements R including Nd, Pr, La and Sm is crushed, a molded body of powder of the R-Fe-B system rare earth sintered magnet alloy is sintered, and an aging treatment is performed to form a diffusion precursor having a first phase (21) having an Sm-enriched portion (41) in addition to the first phase (11) and the second phase (12), and a second phase (22) having a lower Sm concentration than the first phase (21). In the method for manufacturing a rare earth sintered magnet (1) according to Embodiment 4, by heat treatment in which a heavy rare earth element is diffused into a diffusion precursor at the grain boundaries, a rare earth sintered magnet (1) can be produced in which the heavy rare earth element selectively surrounds the outer edge of the Sm enrichment portion (41) in the first floating portion (21) and the heavy rare earth element is uniformly distributed in the second floating portion (22). By doing so, a rare earth sintered magnet (1) can be obtained that suppresses the use of heavy rare earth elements compared to the conventional method, suppresses the deterioration of magnetic properties, and improves magnetic properties compared to the conventional method.

[0109] Embodiment 5.

[0110] In Embodiment 5, a rotor using a rare earth sintered magnet (1) in Embodiments 1, 2, and 3, manufactured by the manufacturing method of Embodiment 4, is described. FIG. 10 is a schematic cross-sectional view showing an example of the configuration of a rotor equipped with a rare earth sintered magnet according to Embodiment 5. FIG. 10 shows a cross-section in a direction perpendicular to the rotation axis (RA) of the rotor (100).

[0111] The rotor (100) can rotate about a rotation axis (RA). The rotor (100) is equipped with a rotor core (101) and a rare earth sintered magnet (1) that is inserted into a magnet insertion hole (102) provided in the rotor core (101) along the circumferential direction of the rotor (100). FIG. 10 shows an example 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 magnet insertion holes (102) and rare earth sintered magnets (1) may be changed according to the design of the rotor (100). The rotor core (101) is formed by stacking multiple disc-shaped electromagnetic steel plates in the axial direction of the rotation axis (RA).

[0112] The rare earth sintered magnet (1) is manufactured according to the manufacturing method described in Embodiment 4. Four rare earth sintered magnets (1) are each inserted into corresponding magnet insertion holes (102). The four rare earth sintered magnets (1) are each magnetized such that the magnetic poles of the rare earth sintered magnets (1) on the outer side of the radial direction of the rotor (100) are different from those of neighboring rare earth sintered magnets (1).

[0113] Thus, the rotor (100) according to embodiment 5 is equipped with a rare earth sintered magnet (1) according to embodiment 1, embodiment 2, or embodiment 3, which can realize an improvement in magnetic properties at room temperature and suppression of the deterioration of magnetic properties accompanying a rise in temperature. Thus, since the rare earth sintered magnet (1) can suppress the deterioration of magnetic properties accompanying a rise in temperature while maintaining high residual magnetic flux density and coercivity and suppressing the use of heavy rare earth elements compared to the conventional method, the deterioration of magnetic properties is suppressed even in a high-temperature environment exceeding 100°C. As a result, Nd and heavy rare earth elements, which are expensive and have a procurement risk due to high regional unevenness, can be replaced with inexpensive rare earth elements, while improving magnetic properties and magnetization, and stabilizing the operation of the rotor (100) even in a high-temperature environment exceeding 100°C. Additionally, since the rare earth sintered magnet (1) according to embodiment 1, embodiment 2, or embodiment 3 has superior magnetization performance compared to conventional magnets, magnetization in an assembly state in which the rare earth sintered magnet (1) is set on the rotor (100) is also possible, making the handling of the manufacturing process easier. Furthermore, since a magnetization process with reduced voltage can be realized, it contributes to energy saving.

[0114] Embodiment 6.

[0115] In Embodiment 6, a rotary machine equipped with the rotor (100) of Embodiment 5 is described. FIG. 11 is a cross-sectional view schematically showing an example of the configuration of the rotary machine according to Embodiment 6. FIG. 11 shows a cross-section in a direction perpendicular to the rotation axis (RA) of the rotor (100).

[0116] The rotating machine (120) comprises a rotor (100) described in Embodiment 5, which is rotatable about a rotation axis (RA), and an annular stator (130) that is arranged coaxially with the rotor (100) and positioned opposite the rotor (100). The stator (130) is formed by stacking multiple electrical steel sheets in the axial direction of the rotation axis (RA). The configuration of the stator (130) is not limited thereto and may adopt a conventional configuration. In the stator (130), a tooth (131) protruding toward the rotor (100) is provided along the inner surface of the stator (130). A winding (132) is provided on the tooth (131). The winding method of the winding (132) may, for example, be a concentrated winding or a distributed winding. That is, the stator (130) has a winding (132) that is placed on a tooth (131) protruding toward the rotor (100) on the inner surface of the side where the rotor (100) is placed, and has an annular structure that is positioned opposite the rotor (100). The number of poles of the rotor (100) in the rotor (120) is 2 poles or more, that is, the rare earth sintered magnet (1) can be 2 or more. Also, although FIG. 11 shows an example of a magnet-embedded type rotor (100), it may be a surface magnet type rotor (100) in which the rare earth sintered magnet (1) is fixed to the outer periphery with adhesive.

[0117] In this way, the rotor (120) in embodiment 6 is equipped with a rare earth sintered magnet (1) according to embodiment 1, embodiment 2, or embodiment 3, which can realize an improvement in magnetic properties at room temperature and suppression of the deterioration of magnetic properties accompanying a rise in temperature. As such, the use of heavy rare earth elements is suppressed compared to the conventional method, and since the rare earth sintered magnet (1) is capable of suppressing the deterioration of magnetic properties accompanying a rise in temperature while maintaining high residual magnetic flux density and coercivity, the deterioration of magnetic properties is suppressed even in a high-temperature environment exceeding 100°C. As a result, Nd and heavy rare earth elements, which are expensive and have high regional unevenness and procurement risk, are replaced with inexpensive rare earth elements, while improving magnetic properties and magnetization, and stably driving the rotor (100) even in a high-temperature environment exceeding 100°C, thereby stabilizing the operation of the rotor (120).

[0118] Examples

[0119] Below, details of the rare earth sintered magnet (1) of the present disclosure are described by way of examples and comparative examples.

[0120] In Examples 1 to 8, a rare earth sintered magnet (1) is manufactured by the method shown in Example 4 using a sample of a plurality of rare earth sintered magnet alloys with different compositions, which is represented as (Nd, Pr, La, Sm)-Fe-B. In Examples 1 to 8, a diffusion precursor is formed using a rare earth sintered magnet alloy with varying content of Nd, Pr, La, and Sm, and Dy is diffused into the diffusion precursor at the grain boundaries so that the heavy rare earth element Dy is 0.10 at.%, thereby manufacturing a rare earth sintered magnet (1). That is, in Examples 1 to 8, a rare earth sintered magnet (1) in which the heavy rare earth element Dy is diffused at 0.10 at.% is manufactured from a rare earth sintered magnet alloy represented as (Nd, Pr, La, Sm)-Fe-B using the manufacturing method shown in Example 4.

[0121] In Comparative Examples 1 to 12, a rare earth sintered magnet (1) containing heavy rare earth elements is experimentally manufactured by the general method of manufacturing a rare earth magnet according to Patent Document 1 or Patent Document 2, using a sample represented by a plurality of rare earth sintered magnet alloys R-Fe-B with different compositions. In the samples of the rare earth sintered magnet (1) according to Comparative Examples 1 to 12, the R portion is changed.

[0122] In Comparative Examples 1 to 6, a rare earth sintered magnet (1) is manufactured from a rare earth sintered magnet alloy in which R contains Nd and one or more elements among Dy, Pr, La, and Sm, using the manufacturing method shown in Patent Document 1, in which the heavy rare earth element Dy is diffused at 0.15 at.%.

[0123] In Comparative Examples 7 to 12, a rare earth sintered magnet (1) is manufactured from a rare earth sintered magnet alloy in which R contains Nd and one or more elements among Dy, Pr, La, and Sm, using the manufacturing method shown in Patent Document 2, in which the heavy rare earth element Dy is diffused at 0.15 at.%.

[0124] 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 element constituting R, the results of the analysis of the microstructure, and the results of the determination of magnetic properties. Table 3 shows the general formula of the columnar structure (10) of each sample, which is the rare earth sintered magnet (1) of Examples 1 to 8 and Comparative Examples 1 to 12.

[0125]

[0126] 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 magnets (1) is determined by elemental analysis using a Scanning Electron Microscope (SEM) and EPMA. Here, FE-EPMA (manufactured by Nihon Electronics Co., Ltd., product name: JXA-8530F) is used as the SEM and EPMA. The conditions for elemental analysis are an acceleration voltage of 15.0 kV and an irradiation current of 2.271 e -008 A, the irradiation time is 130ms, the pixel count is 512 pixels × 512 pixels, the magnification is 5000x, and the number of accumulated cycles is 1.

[0127] 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 magnetic properties is performed by measuring the coercivity of a plurality of samples using a pulse-excited BH tracer. The maximum applied magnetic field by the BH tracer is 6T or higher, which is the state in which the rare earth sintered magnet (1) is fully magnetized. In addition to the pulse-excited BH tracer, a DC magnetic fluxmeter, also called a DC BH tracer, a vibrating sample magnetometer (VSM), a magnetic property measurement system (MPMS), a physical property measurement system (PPMS), etc., may be used as long as they can generate a maximum applied magnetic field of 6T or higher. 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 magnetic sensor of a rare-earth sintered magnet (1) magnetized by an applied magnetic field. The magnetic properties are measured from the measured magnetic hysteresis, which is the JH curve or BH curve. Additionally, the magnetic properties of each sample are measured at different temperatures, a first measurement temperature T1 and a second measurement temperature T2. The temperature coefficient α [% / ℃] of the residual magnetic flux density is the value obtained by dividing the ratio of the residual magnetic flux density at the first measurement temperature T1 to the difference between the residual magnetic flux density at the second measurement temperature T2 and the residual magnetic flux density at the first measurement temperature T1 by the temperature difference (T2-T1). Additionally, the temperature coefficient β [% / ℃] of the coercivity is the value obtained by dividing the ratio of the coercivity at the first measurement temperature T1 to the difference between the coercivity at the first measurement temperature T1 and the coercivity at the second measurement temperature T2 by the temperature difference (T2-T1).Therefore, as the absolute values ​​|α| and |β| of the temperature coefficients of magnetic properties become smaller, the degradation of the magnet's magnetic properties with respect to temperature increase is suppressed.

[0128] First, the analysis results for each sample according to Examples 1 to 8 and Comparative Examples 1 to 12 will be described. FIG. 12 is a diagram tracing the compositional phase obtained by analyzing the cross-section of the rare earth sintered magnet according to Examples 1 to 8 using FE-EPMA. FIG. 13 to 18 are elemental mappings obtained by analyzing the cross-section of the rare earth sintered magnet according to Examples 1 to 8 using FE-EPMA. FIG. 13 is an elemental mapping of Nd, FIG. 14 is an elemental mapping of Pr, FIG. 15 is an elemental mapping of Dy, FIG. 16 is an elemental mapping of O, FIG. 17 is an elemental mapping of Sm, and FIG. 18 is an elemental mapping of La. Meanwhile, FIG. 13 to 18 are elemental mappings of the region shown in FIG. 12. In addition, since the rare earth sintered magnets (1) according to Examples 1 to 8 all show similar results, FIGS. 12 to 18 show representative examples among Examples 1 to 8. Furthermore, the same reference numerals are used for components identical to those in FIGS. 1 and FIGS. 3.

[0129] As shown in FIGS. 13 and 14, in each sample of Examples 1 to 8, R is one or more rare earth elements selected from Nd and Pr, satisfying the general formula (Nd, Pr, R)-Fe-B, and Nd2Fe 14 In a columnar phase (10) comprising crystal grains based on a B crystal structure, there exists a columnar phase (10) having a core portion (11c, 12c) and a shell portion (11s, 12s) covering the core portion (11c, 12c). Additionally, the columnar phase (10) includes a first columnar phase (11) in which CNd > CPr, and CNd <CPr인 제2 주상(12)이 혼재하고 있는 것을 확인할 수 있다.

[0130] Here, the first column (11) where CNd > CPr and CNd <CPr인 제2 주상(12)」에 나타나는 농도차는, EPMA를 이용한 매핑 분석에 의해, Nd 및 Pr의 검출 강도에 명확하게 차가 나고 있는 것을 의미한다. 구체적으로는, 제1 주상(11)의 경우를 예로서 들면, 코어부(11c)의 Nd의 농도는 EPMA의 검출 강도가 평균보다 높고, Pr의 농도는 EPMA의 검출 강도가 하한 부근을 나타내고 있다는 것이다. 제2 주상(12)은 제1 주상(11)이 반대로 되어 있다고 말할 수 있다.

[0131] More specifically, taking the mapping of Nd in FIG. 13 and the mapping of Pr in FIG. 14 as examples, the average detection level of Nd in EPMA is 92, and the average detection level of Pr is 135. In the case of the first main phase (11), CNd is higher than 92 and CPr is near the lower limit, so there is a clear difference in concentration. Also, since the second main phase (12) is the opposite of the first main phase (11), CPr is higher than 135 and CNd is near the lower limit, so there is a clear difference in concentration.

[0132] As shown in FIGS. 16 to 18, when R=La and Sm, the rare earth sintered magnet (1) has, in addition to the first columnar phase (11) and the second columnar phase (12) of Embodiment 1, a crystalline first phase (21) based on an oxide phase with a main component represented as (Nd, Pr, La, Sm)-O and a crystalline second phase (22) with a main component represented as (Nd, Pr, La)-O. Thus, it can be confirmed that the concentration of Sm is higher in the first phase (21) than in the second phase (22).

[0133] Table 3 shows the first columnar phase (11) where CNd > CPr, and CNd <CPr인 제2 주상(12)의 상태를 확인할 수 있었던 시료에 대해서는, 각각 제1 주상(11) 및 제2 주상(12)의 난에 「○」가 입력되고, 확인할 수 없었던 시료에 대해서는, 각각 제1 주상(11) 및 제2 주상(12)의 난에 「×」가 입력되어 있다. 부등호의 농도차에 대해서는, Nd 및 Pr의 검출 강도에 명확하게 차가 나고 있는 것을 의미한다. 구체적으로는, 일례에서는 제1 주상(11)의 경우에 있어서는, Nd의 농도는 EPMA의 검출 강도가 평균보다 높고, Pr의 농도는 EPMA의 검출 강도가 하한치 부근이라는 것이다. 제2 주상(12)의 경우에 있어서는 제1 주상(11)의 경우와는 반대로 되어 있다고 말할 수 있다. 제2 주상(12)과 같은 CNd<CPr밖에 확인되지 않았던 경우는, 제2 주상(12)의 난에만 「○」가 입력되고, 제1 주상(11)의 난에는 「×」가 입력되어 있다.

[0134] Additionally, in Table 3, there is a crystalline first phase (21) based on an oxide phase with a main component represented as (Nd, Pr, La, Sm)-O, and a crystalline second phase (22) with a main component represented as (Nd, Pr, La)-O. For samples where it was confirmed that the concentration of Sm is higher in the first phase (21) than in the second phase (22), "○" is entered in the columns for the first phase (21) and the second phase (22), respectively, and for samples where it was not confirmed, "×" is entered in the columns for the first phase (21) and the second phase (22), respectively. Furthermore, for samples where there is only one phase (20) or where there is no difference in the concentration of Sm between the phases (20), "○" is entered only in the column for the first phase (21) and "×" is entered in the column for the second phase (22), as it is said that only the first phase (21) exists. Meanwhile, the difference in concentration between the first floating (21) and the second floating (22) means that, by mapping analysis using EPMA, the detection intensity of Sm in the first floating (21) is on average higher than that in the second floating (22). Specifically, taking the mapping diagram of Sm in FIG. 17 as an example, with respect to the average value of the detection level of Sm in EPMA being 15.9, the first floating (21) is higher than 15.9 and the second floating (22) is lower than 15.9, that is, it is a state where it is not detected in an aggregated state.

[0135] In addition, from the intensity ratio of the elemental mapping obtained by FE-EPMA analysis, CNd<CPr인 제2 주상(12)의 수보다도 CNd> It can also be confirmed that there are many first pillars (11) of CPr. When considering the shell parts (11s, 12s) of the core-shell structure, the first pillars (11) are CNd > SNd, CPr <SPr의 관계식을 만족시키고, 제2 주상(12)은 CNd<SNd, CPr> It can also be confirmed that the relationship of SPr is satisfied.

[0136] Next, the measurement results of magnetic properties for 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 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. The 200°C of the second measurement temperature T2 is a temperature that can occur as an environment during the operation of automotive motors and industrial motors.

[0137] First, the determination of residual magnetic flux density and coercivity in each sample according to Examples 1 to 8 and Comparative Examples 2 to 12 is performed by comparison with Comparative Example 1. If the values ​​of residual magnetic flux density and coercivity at 23°C of each sample show a value within 1% of the measurement error compared to the value in Comparative Example 1, it is determined to be "equivalent"; if it shows a value 1% or higher, it is determined to be "good"; and if it shows a value 1% or lower, it is determined to be "poor".

[0138] Next, the temperature coefficient α of the residual magnetic flux density is calculated using the residual magnetic flux density at 23°C at the first measurement temperature T1 and the residual magnetic flux density at 200°C at the second measurement temperature T2. Additionally, the temperature coefficient β of the coercivity is calculated using the coercivity at 23°C at the first measurement temperature T1 and the coercivity at 200°C at the second measurement temperature T2. The temperature coefficients of the residual magnetic flux density and the temperature coefficients of the coercivity for each sample according to Examples 1 to 8 and Comparative Examples 2 to 12 are determined by comparison with Comparative Example 1. For each sample, the absolute value |α| of the temperature coefficient of the residual magnetic flux density in the sample according to Comparative Example 1 When compared with the absolute value |β| of the temperature coefficient of coercivity, if a value within ±1% of the measurement error is shown, it is judged as "equivalent"; if a value lower than -1% is shown, it is judged as "good"; and if a value higher than +1% is shown, it is judged as "defective". For samples judged as "good," the temperature coefficient is smaller, so the deterioration of magnetic properties accompanying the rise in temperature is suppressed, and a rare earth sintered magnet (1) having stable magnetic properties can be provided even under high temperature environments.

[0139] The results of determining the above residual magnetic flux density, coercivity, temperature coefficient of residual magnetic flux density, and temperature coefficient of coercivity are shown in Table 3.

[0140] Comparative Example 1 is a sample of a rare earth sintered magnet (1) with 0.15 at.% Dy diffused therein, manufactured according to the manufacturing method described in Patent Document 1 using Nd, Fe, and FeB as raw materials to form Nd-Fe-B. When observing the microstructure of this sample according to the method described above, since Pr, La, and Sm are not added, the core-shell structure in the columnar phase (10) cannot be confirmed, and the concentration of Sm in the float (20) cannot be confirmed to be higher in the first float (21) than in the second float (22). Furthermore, when evaluating the magnetic properties of this sample according to the method described above, the residual magnetic flux density is 1.3 T and the coercivity is 1250 kA / m. The temperature coefficients of the residual magnetic flux density and coercivity are |α|=0.191% / ℃ and |β|=0.460% / ℃, respectively. These values ​​of Comparative Example 1 are used as a reference.

[0141] Comparative Example 2 is a sample of a rare earth sintered magnet (1) with 0.15 at.% Dy diffused therein, manufactured according to the manufacturing method described in Patent Document 1 using Nd, Dy, Fe, and FeB as raw materials to form (Nd, Dy)-Fe-B. When observing the microstructure of this sample according to the method described above, since Pr, La, and Sm are not added, the core-shell structure in the columnar phase (10) cannot be confirmed, and the concentration of Sm in the floating phase (20) cannot be confirmed to be higher in the first floating phase (21) than in the second floating phase (22). Furthermore, when evaluating the magnetic properties of this sample according to the method described above, the residual magnetic flux density becomes "poor," the coercivity becomes "good," the temperature coefficient of the residual magnetic flux density becomes "equivalent," and the temperature coefficient of the coercivity becomes "equivalent." This is a result reflecting that the coercivity is improved as Dy, which has high crystal magnetic anisotropy, is substituted for a part of Nd. Furthermore, since magnetic properties depend on the organizational structure of the diffusion precursor, the magnetic properties do not improve even if Dy, a heavy rare earth element, is diffused into such a diffusion precursor.

[0142] Comparative Example 3 is a sample of a rare earth sintered magnet (1) with 0.15 at.% Dy diffused therein, manufactured according to the manufacturing method described in Patent Document 1 using Nd, Pr, Fe, and FeB as raw materials to form (Nd, Pr)-Fe-B. When observing the microstructure of this sample according to the method described above, a columnar phase (10) in which Nd and Pr are mixed together can be confirmed due to the addition of Pr, but it does not form a core-shell structure. Also, since La and Sm are not added, it cannot be confirmed that the concentration of Sm in the float (20) is higher in the first float (21) than in the second float (22). When evaluating the magnetic properties of this sample according to the method described above, the residual magnetic flux density is "equivalent" and the coercivity is "good," the temperature coefficient of the residual magnetic flux density is "equivalent" and the temperature coefficient of the coercivity is "poor." This result reflects that although the addition of Pr increases the magnetic anisotropy of the columnar phase (10) and improves the coercivity, it is not an optimal structural form for the columnar phase (10) and the floating phase (20). Furthermore, since magnetic properties depend on the structural structure of the diffusion precursor, which is the base material, even if Dy, a heavy rare earth element, is diffused into such a diffusion precursor, the magnetic properties do not improve.

[0143] Comparative Example 4 is a sample of a rare earth sintered magnet (1) with 0.15 at.% Dy diffused therein, manufactured according to the manufacturing method described in Patent Document 1 using Nd, La, Sm, Fe, and FeB as raw materials to form (Nd, La, Sm)-Fe-B. When observing the microstructure of this sample according to the method described above, the core-shell structure of the columnar structure (10) cannot be confirmed because Pr is not added. Furthermore, because La and Sm are added, the concentration of Sm is segregated in one float (20) along with the segregation of La, but the second float (22) does not exist. Moreover, it cannot be confirmed that the concentration of Sm is higher in the first float (21) than in the second float (22). Furthermore, when the magnetic properties of this sample are evaluated according to the method described above, the residual magnetic flux density becomes "equivalent," the coercivity becomes "equivalent," the temperature coefficient of the residual magnetic flux density becomes "positive," and the temperature coefficient of the coercivity becomes "positive." This indicates that, due to the presence of La and Sm in the columnar (10) or floating (20), the temperature coefficient of the magnetic properties shows good results, but the magnetic properties at room temperature are not improved, reflecting the fact that the columnar (10) and floating (20) are not in an optimal structural form. Additionally, since magnetic properties depend on the structural structure of the diffusion precursor that is the base material, even if Dy, a heavy rare earth element, is diffused into such a diffusion precursor, the magnetic properties do not improve.

[0144] Comparative Example 5 is a sample of a rare earth sintered magnet (1) with 0.15 at.% Dy diffused therein, manufactured according to the manufacturing method described in Patent Document 1 using Nd, La, Sm, Fe, and FeB as raw materials to form (Nd, La, Sm)-Fe-B. The compositional ratio of Nd, La, and Sm is different from that of Comparative Example 4. When observing the microstructure of this sample according to the method described above, the core-shell structure of the columnar structure (10) cannot be confirmed because Pr is not added. Furthermore, because La and Sm are added, the concentration of Sm is segregated in one floating phase (20) along with the segregation of La, but the second floating phase (22) does not exist. Moreover, it cannot be confirmed that the concentration of Sm is higher in the first floating phase (21) than in the second floating phase (22). In addition, when the magnetic properties of this sample are evaluated according to the method described above, the residual magnetic flux density becomes "equivalent," the coercivity becomes "equivalent," the temperature coefficient of the residual magnetic flux density becomes "positive," and the temperature coefficient of the coercivity becomes "positive." This is because, due to the presence of La and Sm in the columnar (10) or floating (20), the temperature coefficient of the magnetic properties shows good results, but the magnetic properties at room temperature are not improved, and this reflects the fact that the structure is not optimal in the columnar (10) and floating (20), and even if the composition ratio of Nd, La, and Sm is changed, results almost identical to Comparative Example 4 are obtained. Furthermore, since magnetic properties depend on the structural structure of the diffusion precursor that is the base material, even if Dy, a heavy rare earth element, is diffused into such a diffusion precursor, the magnetic properties are not improved.

[0145] Comparative Example 6 is a sample of a rare earth sintered magnet (1) with 0.15 at.% Dy diffused therein, manufactured according to the manufacturing method described in Patent Document 1 using Nd, Pr, La, Sm, Fe, and FeB as raw materials to form (Nd, Pr, La, Sm)-Fe-B. When observing the microstructure of this sample according to the method described above, a columnar phase (10) in which Nd and Pr are mixed together can be confirmed due to the addition of Pr, but it does not form a core-shell structure. Furthermore, due to the addition of La and Sm, the concentration of Sm is segregated in one float (20) along with the segregation of La, but a second float (22) does not exist. Moreover, it cannot be confirmed that the concentration of Sm is higher in the first float (21) than in the second float (22). Furthermore, when the magnetic properties of this sample are evaluated according to the method described above, the residual magnetic flux density becomes "equivalent," the coercivity becomes "positive," the temperature coefficient of the residual magnetic flux density becomes "positive," and the temperature coefficient of the coercivity becomes "equivalent." This indicates that, while the addition of Pr increases the magnetic anisotropy of the columnar phase (10) and improves the coercivity, the presence of La and Sm in the columnar phase (10) or the floating phase (20) results in an improvement in the temperature coefficient of the magnetic properties, particularly the temperature coefficient of the coercivity, but this result reflects that the structure is not optimal for the columnar phase (10) and the floating phase (20). Additionally, since magnetic properties depend on the structural organization of the diffusion precursor, which is the base material, even if Dy, a heavy rare earth element, is diffused into such a diffusion precursor, the magnetic properties do not improve.

[0146] Comparative Example 7 is a sample of a rare earth sintered magnet (1) with 0.15 at.% Dy diffused therein, manufactured according to a manufacturing method including the hot working method described in Patent Document 2, using Nd, Fe, and FeB as raw materials to form Nd-Fe-B. When observing the microstructure of this sample according to the method described above, since Pr, La, and Sm are not added, the core-shell structure in the columnar phase (10) cannot be confirmed, and the concentration of Sm in the floating phase (20) cannot be confirmed to be higher in the first floating phase (21) than in the second floating phase (22). However, microstructure refinement, which is a characteristic of magnets produced by the hot working method, is confirmed. When evaluating the magnetic properties of this sample according to the method described above, the residual magnetic flux density is "poor," the coercivity is "good," the temperature coefficient of the residual magnetic flux density is "equivalent," and the temperature coefficient of the coercivity is "equivalent." This result reflects the decrease in residual magnetic flux density, although coercivity is improved due to the microstructure refinement by the hot working method. Furthermore, since magnetic properties depend on the microstructure of the diffusion precursor in the base material, magnetic properties do not improve even if Dy, a heavy rare earth element, is diffused into such a diffusion precursor.

[0147] Comparative Example 8 is a sample of a rare earth sintered magnet (1) with 0.15 at.% Dy diffused therein, manufactured according to a manufacturing method including the hot working method described in Patent Document 2 using Nd, Dy, Fe, and FeB as raw materials to form (Nd, Dy)-Fe-B. When observing the microstructure of this sample according to the method described above, since Pr, La, and Sm are not added, the core-shell structure in the columnar phase (10) cannot be confirmed, and the concentration of Sm in the floating phase (20) cannot be confirmed to be higher in the first floating phase (21) than in the second floating phase (22). Furthermore, when evaluating the magnetic properties of this sample according to the method described above, the residual magnetic flux density becomes "poor," the coercivity becomes "good," the temperature coefficient of the residual magnetic flux density becomes "equivalent," and the temperature coefficient of the coercivity becomes "equivalent." In addition to being produced by hot working, the coercivity is significantly improved by the substitution of some Nd with Dy, which has high crystal magnetic anisotropy; however, other properties are a result of microstructure refinement. Furthermore, since magnetic properties depend on the microstructure of the diffusion precursor in the base material, magnetic properties do not improve even if Dy, a heavy rare earth element, is diffused into such a diffusion precursor.

[0148] Comparative Example 9 is a sample of a rare earth sintered magnet (1) with 0.15 at.% Dy diffused therein, manufactured according to a manufacturing method including the hot working method described in Patent Document 2 using Nd, Pr, Fe, and FeB as raw materials to form (Nd, Pr)-Fe-B. When observing the microstructure of this sample according to the method described above, a core-shell structure is confirmed by hot working in addition to the addition of Pr, but there is only one type of columnar structure (10) with a high Pr concentration in the core part. Also, since La and Sm are not added, it cannot be confirmed that the concentration of Sm in the floating part (20) is higher in the first floating part (21) than in the second floating part (22). When evaluating the magnetic properties of this sample according to the method described above, the residual magnetic flux density is "poor," the coercivity is "good," the temperature coefficient of the residual magnetic flux density is "equivalent," and the temperature coefficient of the coercivity is "equivalent." This means that the coercivity is greatly improved to the level of a rare earth sintered magnet (1) with Dy added by forming a core-shell structure with a high Pr concentration in the core part, but other properties are the result of reflecting the microstructure refinement. Also, since magnetic properties depend on the microstructure of the diffusion precursor that is the base material, even if Dy, a heavy rare earth element, is diffused into such a diffusion precursor, the magnetic properties are not improved.

[0149] Comparative Example 10 is a sample of a rare earth sintered magnet (1) with 0.15 at.% Dy diffused therein, manufactured according to a manufacturing method including the hot working method described in Patent Document 2, using Nd, La, Sm, Fe, and FeB as raw materials to form (Nd, La, Sm)-Fe-B. When observing the microstructure of this sample according to the method described above, the core-shell structure of the columnar structure (10) cannot be confirmed because Pr is not added. Furthermore, because La and Sm are added, the concentration of Sm is segregated in one floating phase (20) along with the segregation of La, but the second floating phase (22) does not exist. Moreover, it cannot be confirmed that the concentration of Sm is higher in the first floating phase (21) than in the second floating phase (22). Furthermore, when the magnetic properties of this sample are evaluated according to the method described above, the residual magnetic flux density becomes "poor," the coercivity becomes "good," the temperature coefficient of the residual magnetic flux density becomes "good," and the temperature coefficient of the coercivity becomes "good." This is because, due to the presence of La and Sm in the columnar (10) or floating (20), the temperature coefficient of the magnetic properties shows good results, but the residual magnetic flux density at room temperature is not improved, and this result reflects that the columnar (10) and floating (20) are not in an optimal structural form. Additionally, since magnetic properties depend on the structural structure of the diffusion precursor that is the base material, even if Dy, a heavy rare earth element, is diffused into such a diffusion precursor, the magnetic properties do not improve.

[0150] Comparative Example 11 is a sample of a rare earth sintered magnet (1) with 0.15 at.% Dy diffused therein, manufactured according to a manufacturing method including the hot working method described in Patent Document 2, using Nd, La, Sm, Fe, and FeB as raw materials to form (Nd, La, Sm)-Fe-B. The compositional ratio of Nd, La, and Sm is different from that of Comparative Example 10. When observing the microstructure of this sample according to the method described above, the core-shell structure of the columnar structure (10) cannot be confirmed because Pr is not added. Furthermore, because La and Sm are added, the concentration of Sm is segregated in one floating phase (20) along with the segregation of La, but the second floating phase (22) does not exist. Moreover, it cannot be confirmed that the concentration of Sm is higher in the first floating phase (21) than in the second floating phase (22). In addition, when the magnetic properties of this sample are evaluated according to the method described above, the residual magnetic flux density becomes "poor," the coercivity becomes "good," the temperature coefficient of the residual magnetic flux density becomes "good," and the temperature coefficient of the coercivity becomes "good." This is because, due to the presence of La and Sm in the columnar (10) or floating (20), the temperature coefficient of the magnetic properties shows good results, but the residual magnetic flux density at room temperature is not improved, and this result reflects that the structure is not optimal in the columnar (10) and floating (20). Even if the composition ratio of Nd, La, and Sm is changed, results almost identical to Comparative Example 10 are obtained. Furthermore, since magnetic properties depend on the structural structure of the diffusion precursor that is the base material, even if Dy, a heavy rare earth element, is diffused into such a diffusion precursor, the magnetic properties are not improved.

[0151] Comparative Example 12 is a sample of a rare earth sintered magnet (1) with 0.15 at.% Dy diffused therein, manufactured according to a manufacturing method including the hot working method described in Patent Document 2, using Nd, Pr, La, Sm, Fe, and FeB as raw materials to form (Nd, Pr, La, Sm)-Fe-B. When the microstructure of this sample is observed according to the method described above, a core-shell structure is confirmed by hot working in addition to the addition of Pr, but there is only one type of columnar phase (10) with a high Pr concentration in the core part. Furthermore, as La and Sm are added, the concentration of Sm is segregated in one phase (20) along with the segregation of La, but a second phase (22) does not exist. Moreover, it cannot be confirmed that the concentration of Sm is higher in the first phase (21) than in the second phase (22). In addition, when the magnetic properties of this sample are evaluated according to the method described above, the residual magnetic flux density becomes "poor," the coercivity becomes "good," the temperature coefficient of the residual magnetic flux density becomes "good," and the temperature coefficient of the coercivity becomes "good." This is because, by forming a core-shell structure with a high Pr concentration in the core part, the coercivity is greatly improved to the level of a rare-earth sintered magnet (1) with added Dy, and by having La and Sm in the columnar (10) or floating (20), the temperature coefficient of the magnetic properties, especially the temperature coefficient of the coercivity, shows good results. However, the residual magnetic flux density at room temperature is not improved, and this is also a result reflecting that the structure is not optimal in the columnar (10) and floating (20). Furthermore, since magnetic properties depend on the structure of the diffusion precursor which is the base material, even if Dy, a heavy rare-earth element, is diffused into such a diffusion precursor, the magnetic properties are not improved.

[0152] The samples of Examples 1 to 8 are in which R is one or more rare earth elements selected from Nd and Pr, satisfying the general formula (Nd, Pr, R)-Fe-B, and Nd2Fe 14A columnar phase (10) comprising crystal grains based on a B crystal structure, wherein the columnar phase (10) has a core portion (11c, 12c) and a shell portion (11s, 12s) covering the core portion (11c, 12c), and the columnar phase (10) comprises a first columnar phase (11) in which CNd > CPr and CNd <CPr인 제2 주상(12)이 혼재하고 있는 희토류 소결 자석(1)이다. 또한, R=La, Sm으로 한 경우이고, 제1 주상(11) 및 제2 주상(12)에 더하여, 주성분이 (Nd, Pr, La, Sm)-O로서 표시되는 산화물상을 기본으로 하는 결정성의 제1 부상(21)과, 주성분이 (Nd, Pr, La)-O로서 표시되는 결정성의 제2 부상(22)을 갖고, Sm의 농도는, 제2 부상(22)에 비해 제1 부상(21) 쪽이 높은 것을 특징으로 하고 있다. 실시예 1 내지 8의 시료의 자기 특성을 전술한 방법에 따라 평가하면, 잔류 자속 밀도는 「양」이 되고, 보자력은 「양」이 되고, 잔류 자속 밀도의 온도 계수는 「양」이 되고, 보자력의 온도 계수는 「양」이 된다. 이 결과, 이들 희토류 소결 자석(1)은, 고가이고 또한 지역 편재성이 높아 조달 리스크가 있는 Nd 및 중희토류 원소의 사용을 억제하면서, 종래에 비해 우수한 자기 특성을 갖는다는 효과를 발휘한다. 또한, 자기 특성은, 모재인 확산 전구체의 조직 구조에 의존하고 있기 때문에, 자기 특성이 양호한 확산 전구체에 중희토류 원소인 Dy를 확산시키면, 자기 특성이 더 향상된다. 또한, 실시예 1 내지 8에서는, 비교예 1 내지 12에서의 Dy의 확산량인 0.15at.%보다도 낮은 0.10at.%의 확산량으로, 자기 특성이 양호한 희토류 소결 자석(1)을 얻을 수 있다. 즉, 비교예 1 내지 12에 비해, 중희토류 원소의 사용량을 억제하면서, 잔류 자속 밀도를 저감시키지 않고, 보자력을 크게 향상시킬 수 있는 희토류 소결 자석(1)을 얻을 수 있다.

[0153] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, and embodiments may be combined with each other. Furthermore, parts of the configuration may be omitted or modified without departing from the gist of the invention. Explanation of the symbols

[0154] 1 Rare earth sintered magnet, 10 columnar, 11 first columnar, 11c, 12c core part, 11s, 12s shell part, 12 second columnar, 20 float, 21 first float, 22 second float, 31 heavy rare earth element containing layer, 32 heavy rare earth element containing part, 41 Sm enriched part, 100 rotor, 101 rotor core, 102 magnet insertion hole, 120 rotor, 130 stator, 131 teeth, 132 winding.

Claims

Claim 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 Nd2Fe 14 It has a main phase including crystal grains based on the Nd2FeB crystal structure, and a secondary phase existing between a plurality of the main phases. The main phase has a core part and a shell part covering the core part. The main phase has a first main phase where 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 where CNd < CPr. The first main phase and the second main phase are mixed, and a heavy rare earth element exists on at least a part of the surface in the first main phase and the second main phase. A rare earth sintered magnet characterized by this. Claim 2 When R is one or more rare earth elements selected from elements other than Nd and Pr, it satisfies the general formula (Nd, Pr, R)-Fe-B and Nd2Fe 14 A columnar phase comprising crystal grains based on a B crystal structure, and a phase existing between a plurality of said columnar phases, wherein the columnar phase has a core portion and a shell portion covering the core portion, and the columnar phase comprises a first columnar phase such that CNd > CPr when the concentration of Nd in the core portion is CNd and the concentration of Pr in the core portion is CPr, and CNd <CPr인 제2 주상을 갖고,상기 제1 주상과 상기 제2 주상이 혼재하고,상기 부상에 중희토류 원소가 존재하는 것을 특징으로 하는 희토류 소결 자석. Claim 3 A rare earth sintered magnet according to claim 1, characterized in that the number of the first column is greater than the number of the second column. Claim 4 A rare earth sintered magnet according to claim 2, characterized in that the number of the first column is greater than the number of the second column. Claim 5 In claim 1, when the concentration of Nd in the shell portion is set to SNd and the concentration of Pr in the shell portion is set to SPr, the first columnar phase is CNd > SNd, CPr <SPr의 관계식을 만족시키고, 상기 제2 주상은 CNd<SNd, CPr> A rare earth sintered magnet characterized by satisfying the relationship of SPr. Claim 6 In paragraph 2, when the concentration of Nd in the shell portion is set to SNd and the concentration of Pr in the shell portion is set to SPr, the first columnar phase is CNd > SNd, CPr <SPr의 관계식을 만족시키고, 상기 제2 주상은 CNd<SNd, CPr> A rare earth sintered magnet characterized by satisfying the relationship of SPr. Claim 7 A rare earth sintered magnet according to claim 1, wherein the phase comprises a crystalline first phase based on an oxide phase represented as (Nd, Pr, La, Sm)-O when R is La and Sm, and a crystalline second phase represented as (Nd, Pr, La)-O, wherein the concentration of Sm is higher in the first phase than in the second phase. Claim 8 A rare earth sintered magnet according to claim 2, wherein the above-mentioned phase comprises a crystalline first phase based on an oxide phase in which the main component is represented as (Nd, Pr, La, Sm)-O when R is La and Sm, and a crystalline second phase in which the main component is represented as (Nd, Pr, La)-O, and the first phase forms an Sm-enriched portion in which the concentration of Sm is higher than that of the second phase. Claim 9 A rare earth sintered magnet according to claim 8, characterized in that the heavy rare earth element exists to surround the outer edge of the Sm enrichment portion in the first float. Claim 10 A method for manufacturing a rare earth sintered magnet as described in any one of claims 1 to 9, comprising: a rare earth sintered magnet alloy manufacturing process for manufacturing a rare earth sintered magnet alloy that serves as a raw material for a diffusion precursor before diffusing the heavy rare earth element into the rare earth sintered magnet; a diffusion precursor manufacturing process for manufacturing the diffusion precursor; a diffusion process for diffusing the heavy rare earth element into the diffusion precursor; and a cooling process for cooling the diffusion precursor in which the heavy rare earth element has been diffused. The rare earth sintered magnet alloy manufacturing process comprises: a melting process for melting a raw material for a rare earth sintered magnet alloy containing an element constituting the diffusion precursor; a first alloy cooling process for obtaining a solidified alloy by cooling the raw material in a molten state in the melting process; and a second alloy cooling process for obtaining a rare earth sintered magnet alloy by further cooling the solidified alloy. The diffusion precursor manufacturing process comprises: a grinding process for grinding the rare earth sintered magnet alloy satisfying (Nd, Pr, R)-Fe-B; and A molding process for preparing a molded body by molding the powder of the rare earth sintered magnet alloy crushed in a crushing process; a sintering process for obtaining a sintered body by maintaining the molded body at a sintering temperature within the range of 950°C to 1300°C for a time within the range of 0.1 hours to 10 hours; a first aging process for maintaining the sintered body at a first aging temperature within the range of 700°C to 950°C, which is lower than the sintering temperature, for a time within the range of 0.1 hours to 10 hours; a second aging process for maintaining the sintered body maintained in the first aging process at a second aging temperature within the range of 450°C to 700°C, which is lower than the first aging temperature, for a time within the range of 0.1 hours to 10 hours; and the sintered body maintained in the second aging process again at the first aging temperature.A method for manufacturing a rare earth sintered magnet, comprising: a third aging process for maintaining the sintered body maintained in the third aging process for a period of time within the range of 1 hour or more and 10 hours or less; a fourth aging process for maintaining the sintered body maintained in the third aging process at the second aging temperature for a period of time within the range of 0.1 hours or more and 10 hours or less; and a sintered body cooling process for maintaining the sintered body maintained in the fourth aging process at a cooling temperature within the range of 200°C or more and less than 450°C for a period of time within the range of 0.1 hours or more and 5 hours or less, and then cooling to room temperature to obtain the diffusion precursor; wherein in the diffusion process, under conditions in which the diffusion precursor and the heavy rare earth element are present, the diffusion precursor is heat-treated at a temperature below the sintering temperature and within the range of 300°C or more and 1000°C for a period of time within the range of 0.1 hours or more and 10 hours or less. Claim 11 A rotor characterized by having a rotor core and a rare earth sintered magnet described in any one of claims 1 to 9 provided in the rotor core. Claim 12 A rotor characterized by having a rotor described in claim 11, a winding disposed on a tooth protruding toward the rotor on the inner surface of the side on which the rotor is disposed, and an annular stator disposed opposite the rotor.

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