WO2025009051A1 - 希土類焼結磁石、希土類焼結磁石の製造方法、回転子および回転機 - Google Patents

希土類焼結磁石、希土類焼結磁石の製造方法、回転子および回転機 Download PDF

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Publication number
WO2025009051A1
WO2025009051A1 PCT/JP2023/024736 JP2023024736W WO2025009051A1 WO 2025009051 A1 WO2025009051 A1 WO 2025009051A1 JP 2023024736 W JP2023024736 W JP 2023024736W WO 2025009051 A1 WO2025009051 A1 WO 2025009051A1
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Prior art keywords
rare earth
main phase
sintered magnet
concentration
subphase
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PCT/JP2023/024736
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English (en)
French (fr)
Japanese (ja)
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亮人 岩▲崎▼
泰貴 中村
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Mitsubishi Electric Corp
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Mitsubishi Electric Corp
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Priority to PCT/JP2023/024736 priority Critical patent/WO2025009051A1/ja
Priority to CN202380099677.2A priority patent/CN121444182A/zh
Priority to KR1020257042628A priority patent/KR20260014615A/ko
Priority to JP2025530847A priority patent/JP7843934B2/ja
Publication of WO2025009051A1 publication Critical patent/WO2025009051A1/ja
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
    • H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
    • H01F1/047—Alloys characterised by their composition
    • H01F1/053—Alloys characterised by their composition containing rare earth metals
    • H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
    • H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
    • H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
    • H01F1/0575—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together
    • H01F1/0577—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together sintered
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
    • H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
    • H01F1/047—Alloys characterised by their composition
    • H01F1/053—Alloys characterised by their composition containing rare earth metals
    • H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
    • H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
    • H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
    • H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
    • H01F41/0253—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets
    • H01F41/0293—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets diffusion of rare earth elements, e.g. Tb, Dy or Ho, into permanent magnets

Definitions

  • This disclosure relates to rare earth sintered magnets, which are permanent magnets made by sintering materials containing rare earth elements, methods for manufacturing rare earth sintered magnets, rotors, and rotating machines.
  • R-T-B system permanent magnets are known that have a tetragonal R 2 T 14 B intermetallic compound as the main phase.
  • R is a rare earth element
  • T is a transition metal element such as Fe (iron) or Fe partially substituted with Co (cobalt)
  • B is boron.
  • R-T-B system permanent magnets are used in various high-value-added parts, including industrial motors.
  • Nd-Fe-B system sintered magnets in which R is Nd (neodymium), are used in various parts because of their excellent magnetic properties.
  • industrial motors are often used in high-temperature environments exceeding 100°C, attempts have been made to improve the coercive force by adding heavy rare earth elements such as Dy (dysprosium) to Nd-T-B system sintered magnets.
  • Nd-Fe-B sintered magnets have expanded, and the consumption of Nd and heavy rare earth elements such as Dy and Tb (terbium) has increased.
  • Nd and heavy rare earth elements are expensive and are unevenly distributed around the world, which poses procurement risks. For this reason, research is being conducted into technologies to reduce the consumption of Nd and heavy rare earth elements.
  • Patent Document 1 discloses an R-T-B system sintered magnet including main phase particles made of R 2 T 14 B crystals, where R is one or more rare earth elements essentially including a heavy rare earth element RH, T is one or more transition metal elements essentially including Fe or Fe and Co, and B is boron, and a part of the main phase particles includes a plurality of low heavy rare earth element crystal phases and a plurality of nonmagnetic R-rich phases.
  • the low heavy rare earth element crystal phase is made of R 2 T 14 B crystals and is a phase in which the concentration of the heavy rare earth element is relatively low compared to the concentration of the heavy rare earth element in the entire main phase particle.
  • the nonmagnetic R-rich phase is a phase in which the content of R is 70 at.
  • a part of the main phase particles has one type of core-shell structure having a core portion and a shell portion surrounding the periphery of the core portion and having a total heavy rare earth element concentration lower than that of the core portion. According to the technique described in Patent Document 1, it is possible to obtain a low-cost RTB based sintered magnet that has improved coercive force.
  • Patent Document 2 discloses a method for producing a rare earth magnet , which comprises a first step of producing a sintered body having a structure represented by the composition formula (R11 -xR2x ) aTMbBcMd and consisting of a main phase and a grain boundary phase, a second step of subjecting the sintered body to hot plastic working to produce a rare earth magnet precursor, and a third step of diffusing and infiltrating a melt of an R3-M modifier alloy into the grain boundary phase of the rare earth magnet precursor to produce a rare earth magnet.
  • R1 is one or more rare earth elements including Y (yttrium), R2 is a rare earth element different from R1, TM is a transition metal including one or more of Fe, Ni (nickel), and Co, B is boron, and M is one or more of Ti (titanium), Ga (gallium), Zn (zinc), Si (silicon), Al (aluminum), Nb (niobium), Zr (zirconium), Ni, Co, Mn (manganese), V (vanadium), W (tungsten), Ta (tantalum), Ge (germanium), Cu (copper), Cr (chromium), Hf (hafnium), Mo (molybdenum), P (phosphorus), C (carbon), Mg (magnesium), Hg (mercury), Ag (silver), and Au (gold).
  • TM is a transition metal including one or more of Fe, Ni (nickel), and Co
  • B is boron
  • M is one or more of Ti (titanium),
  • R3 is a rare earth element including R1 and R2.
  • hot processing According to the technology described in Patent Document 2, it is possible to reduce the heavy rare earth element and produce a rare earth magnet that is excellent not only in magnetization but also in coercivity performance, even when the main phase ratio is high.
  • the R-T-B based sintered magnet described in Patent Document 1 can improve its coercive force because a phase containing heavy rare earth elements is present in the main phase, the structural structure of the R-T-B based sintered magnet described in Patent Document 1 does not provide the residual magnetic flux density required for industrial motors and the like, and there is a possibility that the magnetic properties will deteriorate due to thermal load.
  • rare earth magnets manufactured using the manufacturing method described in Patent Document 2 can reduce the heavy rare earth elements and improve their coercive force, but because the manufacturing method includes hot working, the grain size of the main phase becomes small, resulting in a problem of deteriorated magnetization performance.
  • the present disclosure has been made in light of the above, and aims to obtain a rare earth sintered magnet that can improve coercivity without reducing residual magnetic flux density and magnetization performance compared to conventional magnets.
  • the rare earth sintered magnet according to the present disclosure has a main phase that satisfies the general formula (Nd, Pr, RH, R)-Fe-B and includes crystal grains based on the Nd 2 Fe 14 B crystal structure, where RH is a heavy rare earth element including at least one of Dy and Tb, and R is one or more rare earth elements selected from among Nd, Pr (praseodymium), Dy, and Tb.
  • the main phase has a core portion and a shell portion that covers the core portion.
  • the main phase has a first main phase in which CNd>CPr and a second main phase in which CNd ⁇ CPr, where CNd is the concentration of Nd in the core portion and CPr is the concentration of Pr in the core portion.
  • the concentration of the heavy rare earth element RH in the core portion of the first main phase is higher than the concentration of the heavy rare earth element RH in the core portion of the second main phase.
  • the first main phase and the second main phase are mixed together.
  • the rare earth sintered magnet disclosed herein has the advantage of being able to improve coercivity without reducing residual magnetic flux density and magnetization performance compared to conventional magnets.
  • FIG. 1 is a schematic diagram showing an example of the structure of a rare earth sintered magnet in a sintered state according to the first embodiment
  • FIG. 13 is a schematic diagram showing an example of the structure of a rare earth sintered magnet in a sintered state according to the second embodiment
  • FIG. 13 is a cross-sectional view showing a schematic example of the configuration of a rotor equipped with a rare earth sintered magnet according to a fourth embodiment.
  • FIG. 13 is a cross-sectional view showing a schematic example of a configuration of a rotating machine according to a fifth embodiment.
  • FIG. 1 is a trace of composition images obtained by analyzing cross sections of the rare earth sintered magnets of Examples 1 to 8 with FE-EPMA.
  • rare earth sintered magnet manufacturing method for rare earth sintered magnet, rotor, and rotating machine according to the embodiments of the present disclosure are described in detail with reference to the drawings.
  • FIG. 1 is a diagram showing a schematic example of the structure of the rare earth sintered magnet according to the first embodiment in a sintered state.
  • the rare earth sintered magnet 1 according to the first embodiment has a main phase 10 that satisfies the general formula (Nd, Pr, RH, R)-Fe-B and includes crystal grains based on the Nd 2 Fe 14 B crystal structure, and the main phase 10 has a core portion and a shell portion that covers the core portion.
  • RH is a heavy rare earth element, and in one example, it is Dy, Tb, Gd (gadolinium), or Ho (holmium), and preferably, RH is a heavy rare earth element containing at least one of Dy and Tb.
  • R is one or more rare earth elements selected from among Nd, Pr, and RH.
  • the shell portion has a different composition from the core portion and is provided so as to cover the core portion.
  • the rare earth sintered magnet 1 further has a subphase 20 that exists between the main phase 10 and the main phase 10, but the subphase 20 will be described in the second embodiment.
  • the main phase 10 when the concentration of Nd in the core portions 11c and 12c is CNd and the concentration of Pr in the core portions 11c and 12c is CPr, the main phase 10 has a first main phase 11 where CNd>CPr and a second main phase 12 where CNd ⁇ CPr, and the first main phase 11 and the second main phase 12 are mixed. Also, the concentration of the heavy rare earth element RH in the core portion 11c of the first main phase 11 is higher than the concentration of the heavy rare earth element RH in the core portion 12c of the second main phase 12.
  • the concentration of the heavy rare earth element RH in the core portion 11c of the first main phase 11 is C1RH and the concentration of the heavy rare earth element RH in the core portion 12c of the second main phase 12 is C2RH, C1RH>C2RH.
  • the first main phase 11 has a core portion 11c and a shell portion 11s that has a different composition from the core portion 11c and covers the core portion 11c.
  • the second main phase 12 has a core portion 12c and a shell portion 12s that has a different composition from the core portion 12c and covers the core portion 12c.
  • the main phase 10 when the sum of the concentration of Nd and the concentration of the heavy rare earth element RH in the core portions 11c, 12c is C(Nd, RH), the main phase 10 has a first main phase 11 where C(Nd, RH)>CPr and a second main phase 12 where C(Nd, RH) ⁇ CPr, and it can be said that the first main phase 11 and the second main phase 12 are mixed together.
  • the rare earth sintered magnet 1 has two main phases 10, the first main phase 11 and the second main phase 12. Focusing on the cores 11c and 12c of the two main phases 10, the sum of the Nd concentration and the heavy rare earth element RH concentration is higher than the Pr concentration in the first main phase 11, and conversely, the Pr concentration is higher than the sum of the Nd concentration and the heavy rare earth element RH concentration in the second main phase 12.
  • the concentration difference shown by "C1RH>C2RH” means that a mapping analysis using an electron probe microanalyzer (EPMA) has revealed a clear difference in the detection intensity of the heavy rare earth element RH in the core portion 11c of the first main phase 11 and the core portion 12c of the second main phase 12.
  • the detection intensity of the heavy rare earth element RH in the core portion 11c of the first main phase 11 by EPMA is higher than the average detection intensity of the heavy rare earth element RH
  • the detection intensity of the heavy rare earth element RH in the core portion 12c of the second main phase 12 by EPMA is near the lower limit of the detection intensity of the heavy rare earth element RH.
  • the heavy rare earth element RH is contained in the core portion 11c of the first main phase 11, but is hardly contained in the core portion 12c of the second main phase 12.
  • the concentration difference shown in "the first main phase 11 where C(Nd, RH)>CPr and the second main phase 12 where C(Nd, RH) ⁇ CPr" means that a clear difference has been found between the detection intensity of Nd and the heavy rare earth element RH and the detection intensity of Pr by mapping analysis using EPMA.
  • the detection intensity by EPMA for the concentration of Nd and the heavy rare earth element RH in the core portion 11c is higher than the average detection intensity of Nd and the heavy rare earth element RH, and for the concentration of Pr, the detection intensity by EPMA indicates the vicinity of the lower limit of the detection intensity of Pr.
  • the second main phase 12 is the opposite of the case of the first main phase 11.
  • the rare earth sintered magnet 1 according to the first embodiment satisfies the relational expressions C1Nd>C2Nd, C1Pr ⁇ C2Pr when the Nd concentration in the core portion 11c of the first main phase 11 is C1Nd, the Nd concentration in the core portion 12c of the second main phase 12 is C2Nd, the Pr concentration in the core portion 11c of the first main phase 11 is C1Pr, and the Pr concentration in the core portion 12c of the second main phase 12 is C2Pr.
  • the Nd concentration is higher in the core portion 11c of the first main phase 11 than in the core portion 12c of the second main phase 12, and conversely, the Pr concentration is higher in the core portion 12c of the second main phase 12 than in the core portion 11c of the first main phase 11.
  • This concentration difference also means that there is a difference in the detection intensity of Nd and Pr by the mapping analysis using the EPMA described above.
  • the EPMA detection strength of Nd in the core portion 11c of the first main phase 11 is higher than the average Nd detection strength
  • the EPMA detection strength of Nd in the core portion 12c of the second main phase 12 is lower than the average Nd detection strength.
  • the first main phases 11 having C(Nd, RH)>CPr are more present than the second main phases 12 having C(Nd, RH) ⁇ CPr.
  • the number of the first main phases 11 having the composition formula of (Nd, RH) 2Fe14B is greater than the number of the second main phases 12 having the composition formula of Pr2Fe14B .
  • the overall crystal grains are also suppressed from becoming finer, so that it is possible to obtain magnetic properties that are superior to those of the prior art while ensuring magnetization.
  • 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 SNd, the concentration of Pr in the shell portions 11s, 12s is SPr, and the concentration of the heavy rare earth element RH in the shell portions 11s, 12s is SRH, the first main phase 11 satisfies the relational expressions CNd>SNd, CPr ⁇ SPr, CRH>SRH, and the second main phase 12 satisfies the relational expressions CNd ⁇ SNd, CPr>SPr, CRH ⁇ SRH.
  • the concentrations of Nd and the heavy rare earth element RH are lower than in the core portion 11c, but the concentration of Pr is higher than in the core portion 11c.
  • the shell portion 12s of the second main phase 12 has a lower concentration of Pr than the core portion 12c, but the concentrations of Nd and the heavy rare earth element RH are higher than those of the core portion 12c.
  • the rare earth sintered magnet 1 focusing on the shell portions 11s, 12s of the core-shell structure, when the sum of the Nd concentration and the heavy rare earth element RH concentration in the shell portions 11s, 12s is S(Nd, RH) and the Pr concentration in the shell portions 11s, 12s is SPr, the first main phase 11 satisfies the relational expression C(Nd, RH)>S(Nd, RH), CPr ⁇ SPr, and the second main phase 12 satisfies the relational expression C(Nd, RH) ⁇ S(Nd, RH), CPr>SPr.
  • the sum of the Nd concentration and the heavy rare earth element RH concentration is smaller than that in the core portion 11c, but the Pr concentration is higher than that in the core portion 11c.
  • the concentration of Pr is smaller than that in the core portion 12c, but the sum of the concentration of Nd and the concentration of the heavy rare earth element RH is higher than that in the core portion 12c.
  • a main phase 10 having a shell portion 11s with a high concentration of Pr like the first main phase 11, it is possible to improve the coercive force. Furthermore, by forming a main phase 10 having a shell portion 12s with a high concentration of Nd and the sum of the heavy rare earth element RH, like the second main phase 12, it is possible to suppress the decrease in residual magnetic flux density while maintaining the coercive force. By selectively controlling to obtain such a structural form, the rare earth sintered magnet 1 is able to exhibit superior magnetic properties compared to conventional magnets.
  • the average grain size of the crystal grains of the main phase 10 is preferably 100 ⁇ m or less, and more preferably 0.5 ⁇ m to 50 ⁇ m to improve the magnetic properties. Furthermore, by making it approximately 1 ⁇ m to 10 ⁇ m, the grain size will be different from the microstructure produced by hot working, good magnetization performance will be maintained, and it will be possible to produce a rare earth sintered magnet 1 with superior magnetic properties compared to conventional magnets.
  • the rare earth sintered magnet 1 according to the first embodiment may contain an additive element M that further improves the magnetic properties.
  • the additive element M is one or more elements selected from the group of Ga, Cu, Al, Co, Zr, Ti, Nb, and Mn. Therefore, the rare earth sintered magnet 1 according to the first embodiment is expressed by the general formula (Nd a Pr b R c RH d ) Fe e B f M g , where RH is one or more heavy rare earth elements selected from the group of Dy, Tb , Gd, and Ho, and R is a rare earth element other than Nd, Pr , and the heavy rare earth element RH . It is desirable that a, b, c, d, e, f , and g satisfy the following relational expressions.
  • the rare earth sintered magnet 1 satisfies the general formula (Nd, Pr, RH, R)-Fe-B, where R is one or more rare earth elements selected from the group consisting of Nd, Pr, and a heavy rare earth element RH.
  • the main phase 10 including crystal grains based on the Nd2Fe14B crystal structure, the main phase 10 has core portions 11c, 12c and shell portions 11s, 12s covering the core portions 11c, 12c.
  • the main phase 10 has a first main phase 11 in which CNd>CPr and a second main phase 12 in which CNd ⁇ CPr.
  • the concentration of the heavy rare earth element RH in the first main phase 11 is higher than the concentration of the heavy rare earth element RH in the second main phase 12, and the first main phase 11 and the second main phase 12 are mixed together. With this configuration, it is possible to obtain a rare earth sintered magnet 1 that has improved magnetic properties and magnetization compared to conventional magnets, while reducing the amount of Nd and the heavy rare earth element RH used.
  • the R-T-B system sintered magnet described in Patent Document 1 is compared with the rare earth sintered magnet 1 according to the first embodiment.
  • the R-T-B system sintered magnet described in Patent Document 1 has one or more rare earth elements, with the heavy rare earth element RH being essential, and has one type of main phase particle composed of a core portion and a shell portion.
  • all main phase particles in the R-T-B system sintered magnet contain the heavy rare earth element RH.
  • the main phase 10 has a first main phase 11 and a second main phase 12, and the concentration of the heavy rare earth element RH is lower in the second main phase 12 than in the first main phase 11.
  • the core portion 11c of the first main phase 11 contains the heavy rare earth element RH, but the core portion 12c of the second main phase 12 contains almost no heavy rare earth element RH.
  • the heavy rare earth element RH is selectively arranged in the main phase 10.
  • the rare earth sintered magnet 1 according to embodiment 1 which includes a main phase 10 having a first main phase 11 and a second main phase 12 in which the concentration of the heavy rare earth element RH is lower than that of the first main phase 11, can reduce the amount of heavy rare earth element RH used.
  • the heavy rare earth element RH is selectively disposed, and the amount of heavy rare earth element RH used can be reduced compared to the R-T-B based sintered magnet described in Patent Document 1.
  • the rare earth sintered magnet 1 according to embodiment 1 Compare the rare earth magnet manufactured by the technique described in Patent Document 2 with the rare earth sintered magnet 1 according to embodiment 1.
  • a larger amount of heavy rare earth element RH must be added compared to the rare earth sintered magnet 1 according to embodiment 1, as shown in the examples described later.
  • the rare earth sintered magnet 1 according to embodiment 1 can reduce the amount of heavy rare earth element RH used compared to the technique described in Patent Document 2.
  • the magnetic properties of the rare earth magnet manufactured by the technique described in Patent Document 2 will be lower than the magnetic properties of the rare earth sintered magnet 1 according to embodiments 1 and 2.
  • the first main phase 11 and the second main phase 12 are made to satisfy the relational expressions C1Nd>C2Nd, C1Pr ⁇ C2Pr.
  • the number of first main phases 11 is made greater than the number of second main phases 12.
  • the first main phase 11 is made to satisfy the relational expressions CNd>SNd, CPr ⁇ SPr, CRH>SRH
  • the second main phase 12 is made to satisfy the relational expressions CNd ⁇ SNd, CPr>SPr, CRH ⁇ SRH. This also makes it possible to obtain a rare earth sintered magnet 1 with improved magnetic properties and magnetization while limiting the use of Nd and the heavy rare earth element RH.
  • the main phase 10 contains the heavy rare earth element RH
  • a rare earth sintered magnet 1 with significantly improved coercivity compared to conventional magnets is obtained.
  • a rare earth sintered magnet 1 with a better temperature coefficient of coercivity compared to conventional magnets is obtained. Therefore, even when a thermal load is applied to the rare earth sintered magnet 1, the coercivity is greater than conventional magnets, and the decrease in coercivity due to temperature rise is also more gradual than conventional magnets.
  • the coercivity is significantly improved compared to conventional rare earth sintered magnets, the magnetic properties when a thermal load is applied to the rare earth sintered magnet 1 are also better than conventional magnets.
  • Fig. 2 is a diagram showing a schematic diagram of an example of the structure of a rare earth sintered magnet in a sintered state according to embodiment 2.
  • the rare earth sintered magnet 1 according to embodiment 2 has a main phase 10 and a subphase 20.
  • the main phase 10 includes a first main phase 11 and a second main phase 12, but in Fig. 2, the first main phase 11 and the second main phase 12 are collectively referred to as the main phase 10.
  • the subphase 20 exists between the main phases 10.
  • the rare earth sintered magnet 1 In the rare earth sintered magnet 1 according to the second embodiment, La and Sm are selected as the rare earth element R.
  • La and Sm are selected as the rare earth element R, the effect of improving the magnetic properties and having a better magnetization than the conventional magnet while suppressing the use of Nd and the heavy rare earth element RH is further enhanced.
  • the main phase 10 has a composition formula of (Nd, Pr, RH, La, Sm) 2 Fe 14 B.
  • the rare earth element R of the rare earth sintered magnet 1 having a tetragonal R 2 Fe 14 B crystal structure is a rare earth element containing La and Sm
  • a practical rare earth sintered magnet 1 that can significantly suppress the deterioration of the magnetic properties associated with an increase in temperature can be obtained by adding La and Sm to the composition, based on the results of calculations of the magnetic interaction energy using the molecular orbital method.
  • Nd and Pr can be relatively diffused into main phase 10, thereby increasing the magnetocrystalline anisotropy of main phase 10.
  • a core-shell structure is formed in main phase 10, in which parts with high magnetic anisotropy and parts with low magnetic anisotropy exist, and a first main phase 11 in which CNd>CPr and a second main phase 12 in which CNd ⁇ CPr coexist, creating a state in which rare earth sintered magnet 1 is easily produced in which the concentration of heavy rare earth element RH in core portion 11c of first main phase 11 is higher than the concentration of heavy rare earth element RH in core portion 12c of second main phase 12.
  • the subphase 20 has a crystalline first subphase 21 based on an oxide phase whose main component is expressed as (Nd, Pr, RH, La, Sm)-O, and a crystalline second subphase 22 whose main component is expressed as (Nd, Pr, RH, La)-O.
  • O is oxygen.
  • the first subphase 21 has a higher Sm concentration in the subphase 20 than the second subphase 22.
  • the first subphase 21 forms an Sm-enriched portion 41 whose Sm concentration is higher than that of the second subphase 22. This not only improves the magnetic properties at room temperature, but also suppresses the deterioration of the magnetic properties as the temperature increases.
  • the concentration of Sm is higher in the first subphase 21 than in the second subphase 22
  • the detection intensity of Sm is, on average, higher in the first subphase 21 than in the second subphase 22.
  • the crystalline subphase 20 is a collective term for the crystalline first subphase 21 and the crystalline second subphase 22, and exists between the main phase 10.
  • the crystalline first subphase 21 is represented by (Nd, Pr, RH, La, Sm)-O
  • the crystalline second subphase 22 is represented by (Nd, Pr, RH, La)-O.
  • (Nd, Pr, RH, La, Sm) means that a part of Nd and Pr is replaced by the heavy rare earth elements RH, La, and Sm.
  • the first subphase 21 and the second subphase 22 may contain trace amounts of other components in addition to the elements shown in parentheses.
  • the second subphase 22 represented by (Nd, Pr, RH, La)-O contains a very small amount of Sm.
  • the rare earth sintered magnet 1 there is a difference in the concentrations of La and Sm between the main phase 10 and the subphase 20, and La and Sm are segregated more in the subphase 20 than in the main phase 10.
  • the sum of the concentrations of La in the first subphase 21 and the second subphase 22 is greater than or equal to the concentration of La in the main phase 10
  • the sum of the concentrations of Sm in the first subphase 21 and the second subphase 22 is greater than or equal to the concentration of Sm in the main phase 10.
  • the concentrations of La and Sm in the subphase 20 are greater than or equal to the concentrations of La and Sm in the main phase 10.
  • the concentration of La in the main phase 10 here is the sum of the concentration of La in the first main phase 11 and the concentration of La in the second main phase 12. That is, the sum of the La concentrations in the first subphase 21 and the second subphase 22 is higher than the sum of the La concentrations in the first main phase 11 and the second main phase 12.
  • the Sm concentration in the main phase 10 is the sum of the Sm concentration in the first main phase 11 and the Sm concentration in the second main phase 12. That is, the sum of the Sm concentrations in the first subphase 21 and the second subphase 22 is higher than the sum of the Sm concentrations in the first main phase 11 and the second main phase 12.
  • the La concentration contained in the main phase 10 is X
  • the La concentration contained in the first subphase 21 is X1
  • the La concentration contained in the second subphase 22 is X2
  • the Sm concentration contained in the main phase 10 is Y
  • the Sm concentration contained in the first subphase 21 is Y1
  • the Sm concentration contained in the second subphase 22 is Y2
  • the concentrations of Nd and Pr contained in the main phase 10 satisfy the relationship of the following equations (2) and (3).
  • the La concentration in the main phase 10 is the sum of the La concentrations in the first main phase 11 and the second main phase 12
  • the Sm concentration in the main phase 10 is the sum of the Sm concentrations in the first main phase 11 and the second main phase 12.
  • the La concentration in the main phase 10 indicates the average of the La concentrations in the first main phase 11 and the second main phase 12
  • the Sm concentration in the main phase 10 indicates the average of the Sm concentrations in the first main phase 11 and the second main phase 12.
  • the La concentration in the subphase 20, i.e., the sum of the La concentrations in the first subphase 21 and the second subphase 22 means the average La concentration in the first subphase 21 and the second subphase 22
  • the Sm concentration in the subphase 20 i.e., the sum of the Sm concentrations in the first subphase 21 and the second subphase 22 means the average Sm concentration in the first subphase 21 and the second subphase 22.
  • La is present in high concentrations at the grain boundaries during the manufacturing process, particularly during heat treatment, and thus diffuses Nd and Pr relatively into the main phase 10.
  • Nd and Pr in the main phase 10 are not consumed at the grain boundaries, improving the crystalline magnetic anisotropy.
  • Sm is also present in high concentrations in the subphase 20, particularly the first subphase 21, compared to the main phase 10, and thus, like La, diffuses Nd relatively into the main phase 10, improving the crystalline magnetic anisotropy.
  • the subphase 20 contains the heavy rare earth element RH, and therefore the first subphase 21 and the second subphase 22 also contain the heavy rare earth element RH, but the distribution of the heavy rare earth element RH differs between the first subphase 21 and the second subphase 22.
  • the heavy rare earth element RH is distributed uniformly within the second subphase 22.
  • the heavy rare earth element RH is not distributed uniformly within the first subphase 21, but is selectively distributed between the outer periphery of the first subphase 21 and the Sm-enriched portion 41, i.e., in the inner periphery of the outer periphery of the first subphase 21.
  • the heavy rare earth element RH is present so as to selectively surround the outer periphery of the Sm-enriched portion 41, which has a high Sm concentration in the first subphase 21.
  • the first subphase 21 has an Sm-enriched portion 41 and a heavy rare earth element-containing portion 42 in which the heavy rare earth element RH is present and which selectively surrounds the outer periphery of the Sm-enriched portion 41.
  • the outer periphery of the first subphase 21 is the boundary between the first subphase 21 and the main phase 10.
  • the first subphase 21 and the second subphase 22 containing the heavy rare earth element RH are present between the main phases 10. Therefore, it can be considered that the heavy rare earth element RH penetrates into a portion of the surface of the main phase 10 that contacts the first subphase 21 and the second subphase 22 containing the heavy rare earth element RH.
  • the second embodiment can also suppress a decrease in the residual magnetic flux density while improving the coercive force of the rare earth sintered magnet 1.
  • Fig. 3 is a diagram showing atomic sites in the tetragonal Nd2Fe14B crystal structure.
  • the crystal structure shown in Fig. 3 is, for example, shown in Fig. 1 of Reference Technical Document 1 below.
  • the substituted site is determined by the value of the stabilization energy due to the substitution, which is calculated by band calculation and molecular field approximation of the Heisenberg model. (Reference 1) JFHerbst et al. “Relationships between crystal structure and magnetic properties in Nd2Fe14B ”. PHYSICAL REVIEW B. 1984, Vol.29, No.7, p.4176-4178.
  • the stabilization energy of La can be calculated by the energy difference between (Nd7La1 )Fe56B4 + Nd and Nd8 ( Fe55La1 ) B4 + Fe using a Nd8Fe56B4 crystal cell.
  • Table 1 shows the stabilization energy of La at each substitution site when the environmental temperature is changed.
  • the stable substitution site of La is the Nd(f) site at temperatures of 1000K or higher, and the Fe(c) site at temperatures of 293K and 500K.
  • the rare earth sintered magnet 1 according to the second embodiment is produced by heating the raw material of the rare earth sintered magnet 1 to a temperature of 1000K or higher, melting it, and then quenching it. For this reason, it is considered that the raw material of the rare earth sintered magnet 1 is maintained at a temperature of 1000K or higher, i.e., 727°C or higher, and preferably at about 1300K, i.e., 1027°C. At that time, it is considered that La is substituted at the Nd(f) site or Nd(g) site.
  • La is preferentially substituted at the energetically stable Nd(f) site, but it is also possible that La is substituted at the Nd(g) site, which has a small energy difference among the substitution sites of La. For this reason, the Nd(g) site is also listed as a candidate for the substitution site of La.
  • the rare earth sintered magnet 1 is manufactured by the manufacturing method described later, although the temperature is 1000K or more during sintering, the Fe(c) site described in Table 1 is repeatedly maintained in an energetically stable temperature range by going through the first aging process, the second aging process, the third aging process, the fourth aging process, and the cooling process described later. In other words, the substitution of La at the Nd site of the main phase 10 is maintained in an unstable energy state.
  • the rare earth sintered magnet 1 in the raw material stage of the rare earth sintered magnet 1, La is mainly substituted at the Nd site of the main phase 10, but in the manufacturing method described later, the rare earth sintered magnet 1 is repeatedly held in a temperature range that is intentionally in an unstable energy state with respect to the Nd site of the main phase 10, and as a result, a certain amount of La is selectively released from the Nd site of the main phase 10, and La segregates into the subphase 20. As a result, the main phase 10 promotes the formation of a characteristic structure called a core-shell structure.
  • the stabilization energy of Sm can be calculated from the energy difference between ( Nd7Sm1 ) Fe56B4 +Nd and Nd8 ( Fe55Sm1 ) B4 + Fe.
  • the lattice constant in the tetragonal R2Fe14B crystal structure does not change due to the substitution of atoms.
  • Table 2 shows the stabilization energy of Sm at each substitution site when the environmental temperature is changed.
  • the stable substitution site for Sm is the Nd(g) site at all temperatures. It is thought that Sm is preferentially substituted at the energetically stable Nd(g) site, but substitution at the Nd(f) site, which has a small energy difference among the substitution sites for Sm, is also possible.
  • rare earth sintered magnet 1 When rare earth sintered magnet 1 is manufactured by the manufacturing method described below, substitution at the Nd(g) site of main phase 10 is the most stable in terms of energy. However, as described above, by maintaining the temperature range in which substitution of La at the Nd site of main phase 10 becomes unstable, some Sm is also released from the Nd site of main phase 10 together with La and segregates into subphase 20. As a result, there is a difference in the concentrations of La and Sm between main phase 10 and subphase 20, and the sum of the concentrations of La in first subphase 21 and second subphase 22 is equal to or greater than the concentration of La in main phase 10, and the sum of the concentrations of Sm in first subphase 21 and second subphase 22 is equal to or greater than the concentration of Sm in main phase 10.
  • the average concentration of La in the first subphase 21 and the second subphase 22 is equal to or greater than the average concentration of La in the first main phase 11 and the second main phase 12
  • the average concentration of Sm in the first subphase 21 and the second subphase 22 is equal to or greater than the average concentration of Sm in the first main phase 11 and the second main phase 12.
  • Nd is a representative example, as shown in Figure 3, but since Nd and Pr are produced as a mixture, as typified by Di (didymium), it is thought that the energy levels of Nd and Pr are close. Therefore, the same can be said when Nd is replaced with Pr.
  • Di didymium
  • the subphase 20 has a crystalline first subphase 21 based on an oxide phase whose main component is represented by (Nd, Pr, RH, La, Sm)-O, and a crystalline second subphase 22 whose main component is represented by (Nd, Pr, RH, La)-O.
  • the first subphase 21 has a higher Sm concentration than the second subphase 22, and the first subphase 21 has an Sm-enriched portion 41 in which Sm is selectively distributed.
  • two types of main phases 10 and two types of subphases 20 are present. This makes it possible to provide a rare earth sintered magnet 1 whose magnetic properties, such as temperature characteristics of the magnetic properties, are superior to those of the conventional magnets.
  • the main phase 10 is in a state in which the first main phase 11 in which C(Nd, RH)>CPr and the second main phase 12 in which C(Nd, RH) ⁇ CPr are mixed.
  • the rare earth sintered magnet 1 has a main phase 10 having two types of first and second main phases 11 and 12, and when focusing on the cores 11c, 12c of the two types of main phases 10, it is easy to produce a main phase 10 having two types of core-shell structures, in which the Nd concentration is higher than the Pr concentration in the first main phase 11 and, conversely, the Pr concentration is higher than the Nd concentration in the second main phase 12, and the concentration of the heavy rare earth element RH in the first main phase 11 is higher than the concentration of the heavy rare earth element RH in the second main phase 12.
  • Embodiment 3 the method for manufacturing the rare earth sintered magnet 1 described in embodiments 1 and 2 will be explained separately as a method for manufacturing a rare earth sintered magnet alloy that is the raw material for the rare earth sintered magnet 1, and a method for manufacturing the rare earth sintered magnet 1 using the rare earth sintered magnet alloy.
  • FIG. 4 is a flow chart showing an example of the steps of the method for producing a rare earth sintered magnet alloy according to the third embodiment.
  • the method for producing a rare earth sintered magnet alloy which is the raw material for the rare earth sintered magnet 1
  • a melting step S1 in which the raw material for the rare earth sintered magnet alloy, which contains the elements that make up the rare earth sintered magnet 1 is heated to a temperature of 1000K or higher to melt it
  • step S2 a first cooling step
  • step S3 in which the molten raw material is cooled on a rotating body to obtain
  • the raw material of the rare earth sintered magnet alloy is heated to a temperature of 1000K or higher in a crucible in an atmosphere containing an inert gas such as Ar (argon) or in a vacuum to melt it.
  • the raw materials can be Nd, Pr, RH, R, Fe, and B.
  • R is La and Sm. Examples of RH include Dy and Tb.
  • FeB can be used as a raw material instead of B.
  • the raw material can contain one or more elements selected from the group of Ga, Cu, Al, Co, Zr, Ti, Nb, and Mn as the additive element M.
  • the molten alloy prepared in the melting step is poured into a tundish and then onto a single roll, which is a rotating body.
  • the molten alloy is rapidly cooled on the single roll rotating in a specified direction, and a solidified alloy having a thickness thinner than the ingot alloy is prepared from the molten alloy on the single roll.
  • a single roll is used as the rotating body, but this is not limited thereto, and the molten alloy may be rapidly cooled by contacting it with a twin roll, a rotating disk, a rotating cylindrical mold, or the like.
  • the cooling rate in the first cooling step is preferably 10° C./sec or more and 10 7 ° C./sec or less, and more preferably 10 3 ° C./sec or more and 10 4 ° C./sec or less.
  • the thickness of the solidified alloy is in the range of 0.03 mm or more and 10 mm or less.
  • the thin solidified alloy prepared in the first cooling step is put into a tray container and cooled.
  • the thin solidified alloy is broken into flake-like rare earth sintered magnet alloy when it enters the tray container and cooled.
  • a ribbon-like rare earth sintered magnet alloy may be obtained, and is not limited to flake-like.
  • the cooling rate in the second cooling step is preferably 10-2 °C/s or more and 105 °C/s or less, and more preferably 10-1 °C/s or more and 102 °C/s or less.
  • the rare earth sintered magnet alloy obtained through these processes has a minor axis size of 3 ⁇ m to 10 ⁇ m and a major axis size of 10 ⁇ m to 300 ⁇ m.
  • it has a fine crystal structure containing a (Nd, Pr, RH, La, Sm)-Fe-B crystal phase and a crystalline subphase 20 of an oxide represented by (Nd, Pr, RH, La, Sm)-O.
  • the crystalline subphase 20 of an oxide represented by (Nd, Pr, RH, La, Sm)-O is referred to as the (Nd, Pr, RH, La, Sm)-O phase.
  • the (Nd, Pr, RH, La, Sm)-O phase is a non-magnetic phase consisting of an oxide with a relatively high concentration of rare earth elements.
  • the thickness of the (Nd, Pr, RH, La, Sm)-O phase corresponds to the width of the grain boundary and is 10 ⁇ m or less.
  • the rare earth sintered magnet alloys produced by the above manufacturing method have a finer structure than those produced by mold casting because they go through a rapid cooling process.
  • FIG. 5 is a flow chart showing an example of the procedure of the method for manufacturing the rare earth sintered magnet according to the third embodiment.
  • the method for manufacturing the rare earth sintered magnet 1 includes a crushing step (step S21) for crushing a rare earth sintered magnet alloy having a (Nd, Pr, RH, La, Sm)-Fe-B crystal phase and a (Nd, Pr, RH, La, Sm)-O phase, a molding step (step S22) for preparing a compact by molding the powder of the crushed rare earth sintered magnet alloy, a sintering step (step S23) for sintering the compact at a sintering temperature that is a set temperature to obtain a sintered body, an aging step (step S24) for aging the sintered body to enhance the magnetic properties such as the coercive force of the rare earth sintered magnet 1, and a cooling step (step S21) for crushing a rare earth sintered magnet alloy having a (Nd, Pr, RH, La, Sm)-
  • the rare earth sintered magnet alloy having the (Nd, Pr, RH, La, Sm)-Fe-B crystal phase and the (Nd, Pr, RH, La, Sm)-O phase manufactured according to the manufacturing method of the rare earth sintered magnet alloy of FIG. 4 is pulverized to obtain a rare earth sintered magnet alloy powder having a particle size of 200 ⁇ m or less, preferably 0.5 ⁇ m to 100 ⁇ m, and further, when considering magnetization performance, about 1 ⁇ m to 10 ⁇ m.
  • the rare earth sintered magnet alloy is pulverized using an agate mortar, a stamp mill, a jaw crusher, or a jet mill.
  • the rare earth sintered magnet alloy when the particle size of the powder is to be reduced, it is preferable to pulverize the rare earth sintered magnet alloy in an atmosphere containing an inert gas.
  • the rare earth sintered magnet alloy By pulverizing the rare earth sintered magnet alloy in an atmosphere containing an inert gas, the inclusion of oxygen in the powder can be suppressed.
  • the atmosphere during pulverization does not affect the magnetic properties of the magnet, the rare earth sintered magnet alloy may be pulverized in air.
  • the La and Sm of the rare earth sintered magnet alloy used in manufacturing the rare earth sintered magnet 1 of embodiment 2 can be replaced with a rare earth element R other than Nd, Pr and the heavy rare earth element RH.
  • a rare earth sintered magnet alloy having a (Nd, Pr, RH, R)-Fe-B crystal phase and a (Nd, Pr, RH, R)-O phase may be pulverized.
  • the rare earth sintered magnet alloy powder is compression molded in a die to which a magnetic field is applied to prepare a molded body.
  • the magnetic field applied can be 2 T, for example. Note that molding can also be performed without applying a magnetic field, rather than in a magnetic field.
  • the compression-molded body is held at a sintering temperature in the range of 950°C to 1300°C, preferably 1000°C to less than 1150°C, for a time in the range of 0.1 to 10 hours, preferably 1.0 to 6.0 hours, to obtain a sintered body.
  • Sintering is preferably performed in an atmosphere containing an inert gas or in a vacuum to suppress oxidation. Sintering may be performed while a magnetic field is applied.
  • the aging process of step S24 includes a first aging process of step S24-1, a second aging process of step S24-2, a third aging process of step S24-3, and a fourth aging process of step S24-4.
  • Aging is preferably performed in an atmosphere containing an inert gas or in a vacuum to suppress oxidation.
  • the obtained sintered body is held at a first aging temperature, which is a temperature lower than the sintering temperature, specifically within the range of 700°C or higher and lower than 950°C, for 0.1 to 10 hours, preferably 0.5 to 5 hours.
  • a first aging temperature which is a temperature lower than the sintering temperature, specifically within the range of 700°C or higher and lower than 950°C, for 0.1 to 10 hours, preferably 0.5 to 5 hours.
  • the sintered body held in the first aging step is held at a second aging temperature that is lower than the first aging temperature, specifically within the range of 450°C or higher and lower than 700°C, for 0.1 to 10 hours, preferably 1.0 to 7 hours.
  • the sintered body held in the second aging process is heated again to the first aging temperature, specifically to a temperature in the range of 700°C or higher and lower than 950°C, and held at the first aging temperature for 0.1 hours to 10 hours, preferably 0.5 hours to 5 hours.
  • the sintered body held in the third aging process is again held at the second aging temperature, specifically, at a temperature in the range of 450°C or higher and lower than 700°C for 0.1 to 10 hours, preferably 1.0 to 7 hours.
  • the sintered body held in the fourth aging step is held at a temperature lower than the second aging temperature, specifically, in the range of 200°C or higher and lower than 450°C for 0.1 to 5 hours.
  • the rare earth sintered magnet 1 is then completed by cooling to room temperature. It is preferable that the cooling is also performed in an atmosphere containing an inert gas or in a vacuum to suppress oxidation.
  • the sintered body is repeatedly maintained in the temperature range of the unstable energy state.
  • the first main phase 11 consisting of CNd>CPr
  • the second main phase 12 consisting of CNd ⁇ CPr
  • the rare earth sintered magnet 1 has two main phases 10, the first main phase 11 and the second main phase 12, and when focusing on the cores 11c and 12c of the two main phases 10, it is possible to manufacture a rare earth sintered magnet 1 having the characteristics that the sum of the Nd concentration and the heavy rare earth element RH concentration in the first main phase 11 is higher than the Pr concentration, and conversely, the Pr concentration in the second main phase 12 is higher than the sum of the Nd concentration and the heavy rare earth element RH concentration.
  • a rare earth sintered magnet 1 can be manufactured that has a crystalline first subphase 21 based on an oxide phase whose main component is expressed as (Nd, Pr, RH, La, Sm)-O, and a crystalline second subphase 22 whose main component is expressed as (Nd, Pr, RH, La)-O, in which the concentration of Sm is higher in the first subphase 21 than in the second subphase 22, and in which Sm-enriched portions 41 are formed in the first subphase 21.
  • a rare earth sintered magnet alloy having a (Nd, Pr, RH, La, Sm)-Fe-B crystal phase and a (Nd, Pr, RH, La, Sm)-O phase is pulverized to form a rare earth sintered magnet alloy powder, the shaped compact is sintered to form a sintered body, and the sintered body is aged to manufacture the rare earth sintered magnet 1.
  • the heavy rare earth element is adjusted to a desired concentration before the rare earth sintered magnet alloy is manufactured, and the rare earth sintered magnet 1 is manufactured using this rare earth sintered magnet alloy, so that the heavy rare earth element RH can easily enter the inside of the main phase 10.
  • the temperature and time in the sintering step, the aging step, and the sintered body cooling step are controlled.
  • the obtained sintered body is held at the first aging temperature, which is a temperature lower than the sintering temperature, specifically within the range of 700°C to 950°C, for 0.1 to 10 hours, preferably 0.5 to 5 hours.
  • the sintered body is held at the second aging temperature, which is a temperature lower than the first aging temperature, specifically within the range of 450°C to 700°C, for 0.1 to 10 hours, preferably 1.0 to 7 hours.
  • the temperature is raised again to the first aging temperature, specifically within the range of 700°C to 950°C, and the sintered body is held at the first aging temperature for 0.1 to 10 hours, preferably 0.5 to 5 hours.
  • the sintered body is again held at the second aging temperature, specifically, within a range of 450°C to 700°C for 0.1 to 10 hours, preferably 1.0 to 7 hours. In this way, the temperature and time are controlled so that the first aging step and the second aging step are performed in two sets. This creates a state in which the sintered body is repeatedly held in a temperature range of an unstable energy state.
  • the rare earth sintered magnet 1 has two types of main phases 10, a first main phase 11 and a second main phase 12.
  • the above manufacturing process makes it possible to selectively manufacture rare earth sintered magnets 1 having a characteristic structure in which the first subphase 21 is a crystalline phase based on an oxide phase whose main component is represented by (Nd, Pr, RH, La, Sm)-O, the second subphase 22 is a crystalline phase whose main component is represented by (Nd, Pr, RH, La)-O, the first subphase 21 has a higher Sm concentration than the second subphase 22, and Sm-enriched portions 41 are formed in the first subphase 21.
  • the R-T-B system sintered magnet described in Patent Document 1 has one or more rare earth elements, with the heavy rare earth element RH being essential, and has one type of main phase particle composed of a core portion and a shell portion.
  • all main phase particles contain the heavy rare earth element RH.
  • the main phase 10 of the rare earth sintered magnet 1 according to embodiment 1 is a mixture of a first main phase 11 in which the heavy rare earth element RH is contained in the core portion 11c, and a second main phase 12 in which the heavy rare earth element RH is hardly contained in the core portion 12c.
  • the heavy rare earth element RH is selectively arranged in the first main phase 11, which is one of the two types of main phases 10.
  • the rare earth sintered magnet 1 according to embodiment 1, in which the heavy rare earth element RH only needs to be contained in the first main phase 11 of the two types of main phases 10, can reduce the amount of heavy rare earth element RH used.
  • the ratio of the volume of the subphase 20 to the total volume of the rare earth sintered magnet 1 is extremely small, even if the heavy rare earth element RH is diffused and present in the subphase 20, the amount of heavy rare earth element RH used can be reduced compared to the technology of Patent Document 1.
  • FIG. 6 is a cross-sectional view showing a schematic example of the configuration of a rotor equipped with a rare earth sintered magnet according to embodiment 4.
  • Fig. 6 shows a cross section in a direction perpendicular to the rotation axis RA of the rotor 100.
  • the rotor 100 is rotatable about the rotation axis RA.
  • the rotor 100 includes a rotor core 101 and rare earth sintered magnets 1 that are inserted into magnet insertion holes 102 provided in the rotor core 101 along the circumferential direction of the rotor 100.
  • FIG. 6 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 depending on the design of the rotor 100.
  • the rotor core 101 is formed by stacking multiple disk-shaped electromagnetic steel plates in the axial direction of the rotation axis RA.
  • the rare earth sintered magnets 1 are manufactured according to the manufacturing method described in embodiment 3.
  • the four rare earth sintered magnets 1 are inserted into the corresponding magnet insertion holes 102.
  • the four rare earth sintered magnets 1 are each magnetized so that the magnetic poles of the rare earth sintered magnets 1 on the radial outside of the rotor 100 are different between adjacent rare earth sintered magnets 1.
  • the rotor 100 according to embodiment 4 includes the rare earth sintered magnet 1 according to embodiment 1 or 2, which can improve the magnetic properties at room temperature and suppress the deterioration of the magnetic properties with increasing temperature.
  • the rare earth sintered magnet 1 suppresses the use of heavy rare earth elements RH compared to the conventional method, and can suppress the deterioration of the magnetic properties with increasing temperature while maintaining high residual magnetic flux density and coercive force, so that the deterioration of the magnetic properties is suppressed even in high-temperature environments exceeding 100°C.
  • the magnetic properties and magnetization allows the magnetic properties and magnetization to be improved while replacing Nd and heavy rare earth elements RH, which are expensive, highly unevenly distributed in different regions, and have procurement risks, with inexpensive rare earth elements, and the operation of the rotor 100 can be stabilized even in high-temperature environments exceeding 100°C.
  • the rare earth sintered magnet 1 according to embodiment 1 or 2 has superior magnetization performance compared to the conventional method, it is possible to magnetize the rotor 100 in an assembled state with the rare earth sintered magnet 1 set thereon, which makes it easier to handle the manufacturing process.
  • the magnetization process can be performed with reduced voltage, which contributes to energy savings.
  • FIG. 7 is a cross-sectional view showing a schematic example of a configuration of a rotating machine according to the fifth embodiment.
  • Fig. 7 shows a cross section in a direction perpendicular to the rotation axis RA of the rotor 100.
  • the rotating machine 120 includes the rotor 100 described in the fourth embodiment, which is rotatable around the rotation axis RA, and the annular stator 130, which is arranged coaxially with the rotor 100 and faces the rotor 100.
  • the stator 130 is formed by laminating a plurality of electromagnetic steel sheets in the axial direction of the rotation axis RA.
  • the configuration of the stator 130 is not limited to this, and an existing configuration can also be adopted.
  • the stator 130 has teeth 131 protruding toward the rotor 100 and provided along the inner surface of the stator 130.
  • the teeth 131 are provided with windings 132.
  • the windings 132 may be wound in a concentrated winding or a distributed winding, for example.
  • the stator 130 has windings 132 attached to the teeth 131 protruding toward the rotor 100 on the inner surface on the side where the rotor 100 is arranged, and has an annular structure arranged facing the rotor 100.
  • the number of magnetic poles of the rotor 100 in the rotating machine 120 must be two or more, that is, the number of rare earth sintered magnets 1 must be two or more.
  • FIG. 7 shows an example of a rotor 100 with embedded magnets
  • the rotor 100 may be a surface magnet type rotor in which the rare earth sintered magnets 1 are fixed to the outer periphery with adhesive.
  • the rotating machine 120 in embodiment 5 includes the rare earth sintered magnet 1 according to embodiment 1 or 2, which can improve the magnetic properties at room temperature and suppress the deterioration of the magnetic properties with increasing temperature.
  • the rare earth sintered magnet 1 suppresses the use of heavy rare earth elements compared to conventional methods, and can suppress the deterioration of the magnetic properties with increasing temperature while maintaining high residual magnetic flux density and coercive force, so that the deterioration of the magnetic properties is suppressed even in high temperature environments exceeding 100°C.
  • the magnetic properties and magnetization are improved while replacing Nd and heavy rare earth elements, which are expensive, highly unevenly distributed around the region, and have procurement risks, with inexpensive rare earth elements, and the rotor 100 can be stably driven and the operation of the rotating machine 120 can be stabilized even in high temperature environments exceeding 100°C.
  • rare earth sintered magnet 1 is manufactured by the method shown in embodiment 3 using a sample of multiple rare earth sintered magnet alloys with different compositions represented by (Nd, Pr, Tb, La, Sm)-Fe-B.
  • rare earth sintered magnet 1 is manufactured by using a rare earth sintered magnet alloy with a changed content of Nd, Pr, Tb, La and Sm.
  • rare earth sintered magnet 1 is manufactured by using a rare earth sintered magnet alloy represented by (Nd, Pr, Tb, La, Sm)-Fe-B and the manufacturing method shown in embodiment 3.
  • rare earth sintered magnet 1 is experimentally manufactured using samples of multiple rare earth sintered magnet alloys R-Fe-B with different compositions, according to a general method for manufacturing rare earth magnets as shown in Patent Document 1 or Patent Document 2. In the samples of rare earth sintered magnet 1 according to Comparative Examples 1 to 14, the R portion is changed.
  • rare earth sintered magnet 1 is manufactured using the manufacturing method shown in Patent Document 1 from a rare earth sintered magnet alloy in which R is Nd, or a rare earth sintered magnet alloy in which R contains Nd and one or more elements selected from the group of Tb, Pr, La, and Sm.
  • a rare earth sintered magnet 1 is manufactured using a rare earth sintered magnet alloy in which R is Nd, or a rare earth sintered magnet alloy in which R contains Nd and one or more elements selected from the group of Tb, Pr, La, and Sm, by the manufacturing method shown in Patent Document 2.
  • the manufacturing method shown in Patent Document 2 includes a step of performing hot working on the sintered body.
  • Table 3 shows the general formula of the rare earth sintered magnets of the examples and comparative examples, the content of the elements that make up R, the analysis results of the structural morphology, and the evaluation results of the magnetic properties and magnetization performance.
  • Table 3 shows the general formula of the main phase 10 of each sample, which is the rare earth sintered magnet 1 of Examples 1 to 8 and Comparative Examples 1 to 14.
  • the structure of the rare earth sintered magnet 1 is determined by elemental analysis using a scanning electron microscope (SEM) and an EPMA.
  • SEM scanning electron microscope
  • EPMA Field Emission-Electron Probe Micro Analyzer
  • FE-EPMA Field Emission-Electron Probe Micro Analyzer
  • the elemental analysis conditions are an acceleration voltage of 15.0 kV, an irradiation current of 2.271e -008 A, an irradiation time of 130 ms, a pixel count of 512 pixels x 512 pixels, a magnification of 5000 times, and an accumulation count of 1 time.
  • the magnetic properties are evaluated by measuring the coercive force of multiple samples using a pulse excitation type BH tracer.
  • the maximum magnetic field applied by the BH tracer is 6 T or more, at which the rare earth sintered magnet 1 is fully magnetized.
  • a DC magnetic flux meter also called a DC type BH tracer
  • VSM vibrating sample magnetometer
  • MPMS magnetic property measurement system
  • PPMS physical property measurement system
  • the measurement is performed in an atmosphere containing an inert gas such as nitrogen.
  • the magnetic properties of each sample are measured by detecting the magnetization picked up by a search coil or a magnetic sensor of the rare earth sintered magnet 1 magnetized by the applied magnetic field.
  • the magnetic properties are measured from the J-H curve or B-H curve, which is the measured magnetic hysteresis.
  • the magnetic properties of each sample are measured at a first measurement temperature T1 and a second measurement temperature T2, which are different from each other.
  • the temperature coefficient ⁇ [%/°C] of the residual magnetic flux density is the ratio of the difference between the residual magnetic flux density at the first measurement temperature T1 and the residual magnetic flux density at the second measurement temperature T2 to the residual magnetic flux density at the first measurement temperature T1, divided by the temperature difference (T2-T1).
  • the temperature coefficient ⁇ [%/°C] of the coercive force is the ratio of the difference between the coercive force at the first measurement temperature T1 and the coercive force at the second measurement temperature T2 to the coercive force at the first measurement temperature T1, divided by the temperature difference (T2-T1). Therefore, the smaller the absolute values
  • magnetization performance can be measured by calculating the magnetization rate from the ratio of the magnetic flux density measured from the magnetic hysteresis drawn by applying an arbitrary magnetic field at a constant permeance coefficient to the magnetic flux density measured from the magnetic hysteresis drawn by applying a saturating magnetic field. If a high magnetization rate can be obtained even in a weaker magnetic field, it can be said that the magnetization performance is high.
  • FIG. 8 is a trace of the composition image obtained by analyzing the cross section of the rare earth sintered magnet according to Examples 1 to 8 by FE-EPMA.
  • FIG. 9 to FIG. 14 are elemental mappings obtained by analyzing the cross section of the rare earth sintered magnet according to Examples 1 to 8 by FE-EPMA.
  • FIG. 9 is an elemental mapping of Nd
  • FIG. 10 is an elemental mapping of Pr
  • FIG. 11 is an elemental mapping of Tb
  • FIG. 12 is an elemental mapping of O
  • FIG. 13 is an elemental mapping of Sm
  • FIG. 14 is an elemental mapping of La. Note that FIG. 9 to FIG.
  • FIG. 8 to FIG. 14 show representative examples of Examples 1 to 8. Furthermore, the same components as those in FIG. 1 and FIG. 2 are given the same reference numerals.
  • RH is Tb
  • R is one or more rare earth elements selected from among Nd, Pr, and RH
  • the general formula (Nd, Pr, Tb, R)-Fe-B is satisfied
  • the main phase 10 including crystal grains based on the Nd 2 Fe 14 B crystal structure has core parts 11c, 12c and shell parts 11s, 12s covering the core parts 11c, 12c.
  • the main phase 10 includes a first main phase 11 in which CNd>CPr and a second main phase 12 in which CNd ⁇ CPr are mixed.
  • concentration of Tb in the first main phase 11 is C1Tb
  • the concentration of Tb in the second main phase 12 is C2Tb, C1Tb>C2Tb.
  • the concentration difference shown here between "the first main phase 11 where CNd>CPr and the second main phase 12 where CNd ⁇ CPr” means that a clear difference has been found between the detection intensity of Nd and the detection intensity of Pr by mapping analysis using EPMA.
  • the Nd concentration in the core portion 11c has a higher than average detection intensity by EPMA, while the Pr concentration shows an EPMA detection intensity close to the lower limit.
  • the second main phase 12 is the opposite of the first main phase 11.
  • the average EPMA Nd detection level is 89, and the average Pr detection level is 46.
  • the first main phase 11 CNd is higher than 89, and CPr is near the lower limit, indicating a clear concentration difference.
  • the second main phase 12 is the opposite of the first main phase 11, and therefore CPr is higher than 46, and CNd is near the lower limit, indicating a clear concentration difference.
  • the concentration difference shown by "C1Tb>C2Tb” means that mapping analysis using EPMA has revealed a clear difference between the detection intensity of Tb in the first main phase 11 and the detection intensity of Tb in the second main phase 12. Specifically, the EPMA detection intensity of the Tb concentration in the first main phase 11 is higher than the average, and the EPMA detection intensity of the Tb concentration in the second main phase 12 is near the lower limit.
  • the average EPMA Tb detection level is 44.
  • CTb is higher than 44, but in the case of the second main phase 12, CTb is near the lower limit, and a clear concentration difference occurs.
  • the rare earth sintered magnet 1 has, in addition to the first main phase 11 and second main phase 12 in embodiment 1, a crystalline first subphase 21 based on an oxide phase whose main component is expressed as (Nd, Pr, Tb, La, Sm)-O, and a crystalline second subphase 22 whose main component is expressed as (Nd, Pr, Tb, La)-O. It can also be seen that the concentration of Sm is higher in the first subphase 21 than in the second subphase 22.
  • the concentration of Nd and the concentration of Tb indicate that the detection intensity by EPMA is higher than the average, and the concentration of Pr indicates that the detection intensity by EPMA is near the lower limit.
  • the concentration of Pr indicates that the detection intensity by EPMA is near the lower limit.
  • C(Nd, RH) ⁇ CPr as in the case of the second main phase 12, is confirmed, then " ⁇ " is entered only in the column for the second main phase 12, and " ⁇ " is entered in the column for the first main phase 11.
  • the concentration difference between the first subphase 21 and the second subphase 22 means that, by mapping analysis using EPMA, the detection intensity of Sm is higher on average in the first subphase 21 than in the second subphase 22.
  • the average EPMA detection level of Sm is 15.0
  • the first subphase 21 is higher than 15.0
  • the second subphase 22 is lower than 15.0, that is, the Sm is in an aggregated state and cannot be detected.
  • the intensity ratio of the element mapping obtained by the FE-EPMA analysis it can be confirmed that there are more first main phases 11 where C(Nd, RH)>CPr than the number of second main phases 12 where C(Nd, RH) ⁇ CPr.
  • the first main phase 11 satisfies the relational expressions CNd>SNd, CPr ⁇ SPr, CTb>STb
  • the second main phase 12 satisfies the relational expressions CNd ⁇ SNd, CPr>SPr, CTb ⁇ STb.
  • the shape of each sample used for magnetic measurement is a block shape with length, width and height all being 7 mm.
  • the first measurement temperature T1 is 23°C
  • the second measurement temperature T2 is 200°C.
  • 23°C is room temperature.
  • the second measurement temperature T2 of 200°C is a temperature that can occur in the operating environment of automotive motors and industrial motors.
  • the residual magnetic flux density and coercivity of each sample from Examples 1 to 8 and Comparative Examples 2 to 14 are judged in comparison with Comparative Example 1. If the residual magnetic flux density and coercivity values at 23°C of each sample are within 1%, which is considered to be a measurement error, compared to the values in Comparative Example 1, they are judged as "same.” If they are 1% or more higher, they are judged as “good.” If they are 1% or less lower, they are judged as "poor.”
  • the temperature coefficient ⁇ of the residual magnetic flux density is calculated using the residual magnetic flux density at the first measurement temperature T1 of 23°C and the residual magnetic flux density at the second measurement temperature T2 of 200°C.
  • the temperature coefficient ⁇ of the coercivity is calculated using the coercivity at the first measurement temperature T1 of 23°C and the coercivity at the second measurement temperature T2 of 200°C.
  • the temperature coefficients of the residual magnetic flux density and the temperature coefficients of the coercivity in each sample according to Examples 1 to 8 and Comparative Examples 2 to 14 are judged by comparing with Comparative Example 1.
  • the magnetization performance is calculated from the ratio of the magnetic flux density at the intersection of the magnetic hysteresis and the permeance coefficient Pc of an applied magnetic field of 20 kOe to the magnetic flux density at the intersection of the magnetic hysteresis and the permeance coefficient Pc of an applied magnetic field of 80 kOe, which is the saturated magnetization state.
  • the magnetization performance of each sample from Examples 1 to 8 and Comparative Examples 2 to 14 is judged by comparing it with Comparative Example 1.
  • Comparative Example 1 is a sample of rare earth sintered magnet 1 produced according to the manufacturing method described in Patent Document 1 using Nd, Tb, Fe, and FeB as raw materials so as to obtain (Nd, Tb)-Fe-B.
  • Nd, Tb a core-shell structure in the main phase 10 cannot be confirmed, and it cannot be confirmed that the concentration of Sm in the subphase 20 is higher in the first subphase 21 than in the second subphase 22.
  • the residual magnetic flux density B r is 1.25 T and the coercive force H cJ is 1600 kA/m.
  • the temperature coefficients of the residual magnetic flux density and the coercive force are
  • 0.185%/°C and
  • 0.455%/°C, respectively.
  • the magnetization rate is 98.6%.
  • Comparative Example 2 is a sample of rare earth sintered magnet 1 produced according to the manufacturing method described in Patent Document 1 using Nd, Fe, and FeB as raw materials to produce Nd-Fe-B.
  • Comparative example 3 is a sample of rare earth sintered magnet 1 produced according to the manufacturing method described in Patent Document 1 using Nd, Pr, Fe, and FeB as raw materials so as to obtain (Nd, Pr)-Fe-B.
  • Pr was added, resulting in a main phase 10 in which Nd and Pr were mixed, but no core-shell structure was formed.
  • La and Sm were not added, it was not confirmed that the concentration of Sm in the subphase 20 was higher in the first subphase 21 than in the second subphase 22.
  • Comparative example 4 is a sample of rare earth sintered magnet 1 produced according to the manufacturing method described in Patent Document 1 using Nd, Pr, Tb, Fe, and FeB as raw materials so as to obtain (Nd, Pr, Tb)-Fe-B.
  • Nd, Pr, Tb, Fe, and FeB as raw materials so as to obtain (Nd, Pr, Tb)-Fe-B.
  • the main phase 10 in which Nd and Pr are mixed can be confirmed, but a core-shell structure is not formed.
  • La and Sm are not added, it cannot be confirmed that the concentration of Sm in the subphase 20 is higher in the first subphase 21 than in the second subphase 22.
  • the magnetization performance is “equal or better.”
  • the temperature coefficient of residual magnetic flux density is “equal.” This reflects the fact that although the addition of Tb and Pr increases the magnetic anisotropy of the main phase 10 and improves the coercive force, it is not the optimal structure of the main phase 10 and subphase 20.
  • Comparative Example 5 is a sample of rare earth sintered magnet 1 produced according to the manufacturing method described in Patent Document 1 using Nd, La, Sm, Fe, and FeB as raw materials so as to obtain (Nd, La, Sm)-Fe-B.
  • the core-shell structure of the main phase 10 cannot be confirmed because Pr is not added.
  • the concentration of Sm is segregated to one subphase 20 due to the segregation of La, but the second subphase 22 does not exist. Furthermore, it cannot be confirmed that the concentration of Sm is higher in the first subphase 21 than in the second subphase 22.
  • the residual magnetic flux density is "good” and the coercivity is “poor” because Tb, which is a heavy rare earth element RH, is not included.
  • the temperature coefficient of coercivity becomes “good”. Since the manufacturing method does not include hot working, the magnetization performance is "equal or better.”
  • the temperature coefficient of the residual magnetic flux density is "equal.” This is because the presence of La and Sm in the main phase 10 or subphase 20 shows good results in the temperature coefficient of coercivity, but the magnetic properties at room temperature do not improve, reflecting the fact that the main phase 10 and subphase 20 are not in an optimal structural form.
  • Comparative Example 6 is a sample of rare earth sintered magnet 1 produced according to the manufacturing method described in Patent Document 1 using Nd, La, Sm, Fe, and FeB as raw materials so as to be (Nd, La, Sm)-Fe-B.
  • the composition ratio of Nd, La, and Sm is different from that of Comparative Example 5.
  • the core-shell structure of the main phase 10 cannot be confirmed because Pr is not added.
  • the concentration of Sm is segregated to one subphase 20 due to the segregation of La, but the second subphase 22 does not exist.
  • the concentration of Sm is higher in the first subphase 21 than in the second subphase 22. Furthermore, when the magnetic properties of this sample are evaluated according to the above-mentioned method, the residual magnetic flux density is "good” and the coercivity is "poor” because Tb, which is a heavy rare earth element RH, is not included. In addition, by optimizing the amount of La and Sm added, the temperature coefficient of the residual magnetic flux density becomes “good” and the temperature coefficient of the coercivity becomes “good”. Since the manufacturing method does not include hot working, the magnetization performance is "equal to or better than".
  • Comparative Example 6 the temperature coefficient of the magnetic properties shows good results by optimizing the amount of La and Sm added, but since Tb, which is a heavy rare earth element RH, is not added to the base material, the magnetic properties at room temperature do not improve, and this reflects the fact that the structure of the main phase 10 and subphase 20 is not optimal. Even if the composition ratio of Nd, La, and Sm is changed, almost the same results as Comparative Example 5 are obtained.
  • Comparative Example 7 is a sample of rare earth sintered magnet 1 produced according to the manufacturing method described in Patent Document 1 using Nd, Pr, La, Sm, Fe, and FeB as raw materials to obtain (Nd, Pr, La, Sm)-Fe-B.
  • Nd, Pr, La, Sm rare earth sintered magnet 1
  • the concentration of Sm is higher in the first subphase 21 than in the second subphase 22. Furthermore, when the magnetic properties of this sample are evaluated according to the above-mentioned method, the residual magnetic flux density is "good” and the coercivity is "poor” because Tb, which is a heavy rare earth element RH, is not included. In addition, by optimizing the amount of La and Sm added, the temperature coefficient of residual magnetic flux density and the temperature coefficient of coercivity should be "good,” but by adding Pr, only the temperature coefficient of coercivity has decreased to "the same.” Since the manufacturing method does not include hot working, the magnetization performance is "the same or better.”
  • Comparative Example 8 is a sample of rare earth sintered magnet 1 produced according to the manufacturing method including hot processing described in Patent Document 2 using Nd, Tb, Fe, and FeB as raw materials to obtain (Nd, Tb)-Fe-B.
  • the fine magnetic powder results in a "good” coercive force and an "equivalent” temperature coefficient of coercive force. Furthermore, since the magnetic moment is difficult to align, the residual magnetic flux density and magnetization performance are “poor”. The temperature coefficient of residual magnetic flux density is "equivalent”. This is because, although the absolute value of the coercive force and the temperature coefficient of coercive force have improved as a result of the finer magnetic powder produced by hot working, the magnetic moment is less likely to be uniform, resulting in a decrease in residual magnetic flux density and a deterioration in magnetization performance.
  • Comparative Example 9 is a sample of rare earth sintered magnet 1 produced according to the manufacturing method including hot processing described in Patent Document 2 using Nd, Fe, and FeB as raw materials to obtain Nd-Fe-B.
  • Nd, Fe, and FeB as raw materials to obtain Nd-Fe-B.
  • Pr, La, and Sm are not added, a core-shell structure in the main phase 10 cannot be confirmed, and it cannot be confirmed that the concentration of Sm in the subphase 20 is higher in the first subphase 21 than in the second subphase 22.
  • the fine structure which is a characteristic of magnets produced by hot processing, is confirmed.
  • the fine magnetic powder results in a "good” coercive force and an "equivalent” temperature coefficient of coercive force. Furthermore, since the magnetic moment is difficult to align, the residual magnetic flux density and magnetization performance are “poor”. The temperature coefficient of residual magnetic flux density is "equivalent”. This reflects the fact that although the coercive force improves as the magnetic powder becomes finer through hot working, the magnetic moment is less uniform, resulting in a decrease in residual magnetic flux density and a deterioration in magnetization performance.
  • Comparative example 10 is a sample of rare earth sintered magnet 1 produced according to the manufacturing method including hot processing described in Patent Document 2 using Nd, Pr, Fe, and FeB as raw materials to obtain (Nd, Pr)-Fe-B.
  • a core-shell structure is confirmed due to the addition of Pr and hot processing, but the core-shell structure is confirmed only in one type of main phase 10 with a high Pr concentration in the core part.
  • La and Sm are not added, it cannot be confirmed that the concentration of Sm in the subphase 20 is higher in the first subphase 21 than in the second subphase 22.
  • the coercivity is "good” due to the fineness of the magnetic powder, and the temperature coefficient of the coercivity is “same”.
  • the residual magnetic flux density and magnetization performance are “poor”.
  • the temperature coefficient of the residual magnetic flux density is "same”. This is because the formation of a core-shell structure with a high Pr concentration in the core significantly improves the coercivity to the level of rare earth sintered magnet 1 with added Tb, but other properties reflect the refinement of the structure due to hot working.
  • Comparative example 11 is a sample of rare earth sintered magnet 1 produced according to the manufacturing method including hot processing described in Patent Document 2 using Nd, Pr, Tb, Fe, and FeB as raw materials to obtain (Nd, Pr, Tb)-Fe-B.
  • a core-shell structure is confirmed due to the addition of Pr and hot processing, but the core-shell structure is confirmed only in one type of main phase 10 with a high Pr concentration in the core part.
  • La and Sm are not added, it cannot be confirmed that the concentration of Sm in the subphase 20 is higher in the first subphase 21 than in the second subphase 22.
  • the coercive force is "good” due to the fineness of the magnetic powder, and the temperature coefficient of the coercive force is "same".
  • the residual magnetic flux density and magnetization performance are “poor”.
  • the temperature coefficient of the residual magnetic flux density is "same”. This is because it is produced by hot working, and the coercive force is greatly improved by substituting part of the Nd with Tb, which has high crystalline magnetic anisotropy, but other properties reflect the refinement of the structure by hot working.
  • Comparative Example 12 is a sample of rare earth sintered magnet 1 produced according to the manufacturing method including hot processing described in Patent Document 2 using Nd, La, Sm, Fe, and FeB as raw materials to obtain (Nd, La, Sm)-Fe-B.
  • the core-shell structure of the main phase 10 cannot be confirmed because Pr is not added.
  • the concentration of Sm is segregated to one subphase 20 due to the segregation of La, but the second subphase 22 does not exist. Furthermore, it cannot be confirmed that the concentration of Sm is higher in the first subphase 21 than in the second subphase 22.
  • the coercive force and the temperature coefficient of coercive force are "good” due to the fineness of the magnetic powder. Furthermore, because the magnetic moment is difficult to align, the residual magnetic flux density and magnetization performance are "poor”. The temperature coefficient of the residual magnetic flux density is "good.” This is because the presence of La and Sm in the main phase 10 or subphase 20 results in a good temperature coefficient of the magnetic properties, but the magnetic moment is not easily aligned, so the residual magnetic flux density and magnetization performance at room temperature do not improve, and this reflects the fact that the main phase 10 and subphase 20 are not in an optimal structure.
  • Comparative Example 13 is a sample of rare earth sintered magnet 1 produced according to the manufacturing method including hot processing described in Patent Document 2 using Nd, La, Sm, Fe, and FeB as raw materials to obtain (Nd, La, Sm)-Fe-B.
  • the composition ratio of Nd, La, and Sm is different from that of Comparative Example 12.
  • the core-shell structure of the main phase 10 cannot be confirmed because Pr is not added.
  • the concentration of Sm is segregated to one subphase 20 due to the segregation of La, but the second subphase 22 does not exist.
  • the concentration of Sm is higher in the first subphase 21 than in the second subphase 22. Furthermore, when the magnetic properties of this sample are evaluated according to the above-mentioned method, the coercive force and the temperature coefficient of coercive force are "good” due to the fineness of the magnetic powder.
  • the residual magnetic flux density and magnetization performance are “poor.”
  • the temperature coefficient of the residual magnetic flux density is "good.” This is because, although the temperature coefficient of the magnetic properties shows good results due to the presence of La and Sm in the main phase 10 or subphase 20, the magnetic moment is difficult to align, so the residual magnetic flux density and magnetization performance at room temperature do not improve, and this reflects the fact that the main phase 10 and subphase 20 are not in an optimal structural form. Even if the composition ratio of Nd, La, and Sm is changed, almost the same results as Comparative Example 12 are obtained.
  • Comparative Example 14 is a sample of rare earth sintered magnet 1 produced according to the manufacturing method including hot processing described in Patent Document 2 using Nd, Pr, La, Sm, Fe, and FeB as raw materials to obtain (Nd, Pr, La, Sm)-Fe-B.
  • Nd, Pr, La, Sm, Fe, and FeB as raw materials to obtain (Nd, Pr, La, Sm)-Fe-B.
  • a core-shell structure is confirmed due to the addition of Pr and hot processing, but the core-shell structure is confirmed only in one type of main phase 10 where the Pr concentration is high in the core part.
  • the concentration of Sm is segregated to one subphase 20 due to the segregation of La, but the second subphase 22 does not exist.
  • the concentration of Sm is higher in the first subphase 21 than in the second subphase 22. Furthermore, when the magnetic properties of this sample are evaluated according to the above-mentioned method, the coercive force and the temperature coefficient of coercive force are "good” due to the fineness of the magnetic powder.
  • the residual magnetic flux density and magnetization performance are “poor.”
  • the temperature coefficient of the residual magnetic flux density is “good.” This is because the formation of a core-shell structure with a high Pr concentration in the core portion significantly improves the coercivity to the level of rare earth sintered magnet 1 to which Tb is added, and because La and Sm are present in the main phase 10 or subphase 20, the temperature coefficient of the magnetic properties, especially the temperature coefficient of the coercivity, shows good results.
  • the magnetic moments are difficult to align, the residual magnetic flux density and magnetization performance at room temperature do not improve, which also reflects the fact that the main phase 10 and subphase 20 are not in an optimal structural form.
  • the samples of Examples 1 to 8 are rare earth sintered magnets 1 in which the heavy rare earth element RH is Tb, R is one or more rare earth elements selected from among Nd, Pr, and Tb, satisfies the general formula (Nd, Pr, Tb, R)-Fe-B, and has a main phase 10 including crystal grains based on the Nd2Fe14B crystal structure, the main phase 10 having core portions 11c, 12c and shell portions 11s, 12s covering the core portions 11c, 12c, the main phase 10 being a mixture of a first main phase 11 in which CNd>CPr and a second main phase 12 in which CNd ⁇ CPr, and the concentration of Tb, which is the heavy rare earth element RH, in the core portion 11c of the first main phase 11 is higher than the concentration of Tb in the core portion 12c of the second main phase 12.
  • the heavy rare earth element RH is Tb
  • R is one or more rare earth elements selected from among Nd, Pr, and Tb, satisfies
  • these rare earth sintered magnets 1 have the advantage of exhibiting superior magnetic properties and magnetizability compared to conventional magnets, while limiting the use of Nd and the heavy rare earth element RH, which are expensive, highly unevenly distributed around different regions, and therefore pose a procurement risk.
  • the samples of Examples 1 to 8 have a lower content of Tb, which is the heavy rare earth element RH, compared to the samples of Comparative Examples 1, 4, 8, and 11, but the magnetic properties are superior to those of the samples of Comparative Examples 1 to 14.
  • Tb which is the heavy rare earth element
  • the samples of Comparative Examples 8 and 11 manufactured by the manufacturing method of Patent Document 2 are to have magnetic properties equivalent to those of the samples of Examples 1 to 8, Tb must be further added. Therefore, the rare earth sintered magnet 1 according to the first and second embodiments has the effect of being able to reduce the amount of heavy rare earth element RH used compared to the technology of Patent Document 2.
  • the magnetic properties of the rare earth magnet manufactured by the manufacturing method of Patent Document 2 will be lower than those of the rare earth sintered magnet 1 according to the first and second embodiments.
  • Table 3 also shows that, compared to the samples of Comparative Examples 1 and 4 manufactured by the manufacturing method of Patent Document 1, the samples of Examples 1 to 8 can improve magnetic properties while reducing the content of Tb, which is a heavy rare earth element RH.
  • 1 rare earth sintered magnet 10 main phase, 11 first main phase, 11c, 12c core portion, 11s, 12s shell portion, 12 second main phase, 20 subphase, 21 first subphase, 22 second subphase, 41 Sm-enriched portion, 42 heavy rare earth element-containing portion, 100 rotor, 101 rotor core, 102 magnet insertion hole, 120 rotating machine, 130 stator, 131 teeth, 132 winding.

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JP2022054231A (ja) * 2020-09-25 2022-04-06 トヨタ自動車株式会社 磁性材料及びその製造方法
WO2022107221A1 (ja) * 2020-11-17 2022-05-27 三菱電機株式会社 希土類焼結磁石、希土類焼結磁石の製造方法、回転子および回転機
WO2023012929A1 (ja) * 2021-08-04 2023-02-09 三菱電機株式会社 希土類焼結磁石および希土類焼結磁石の製造方法、回転子並びに回転機

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