WO2018181580A1

WO2018181580A1 - Permanent magnet and rotating machine

Info

Publication number: WO2018181580A1
Application number: PCT/JP2018/012975
Authority: WO
Inventors: 信宏神宮; 敦古田
Original assignee: Tdk株式会社
Priority date: 2017-03-30
Filing date: 2018-03-28
Publication date: 2018-10-04
Also published as: JP2020095991A

Abstract

Provided are: a permanent magnet that has a large magnetic coercive force among the permanent magnets that contain Ce as a substitutional element for Nd; and a rotating machine equipped with said permanent magnet. This permanent magnet 10 is provided with: a plurality of main phase particles 11 each comprising a rare-earth element R, a transition metal element T, and boron; and a grain boundary phase 9 that is situated between the main phase particles 11, wherein the rare-earth element R includes at least neodymium and cerium, and the transition metal element T includes at least iron, the contained amount of copper in the permanent magnet 10 is 0.1-2 at%, the grain boundary phase 9 includes an R-T phase 3 comprising an intermetallic compound of the rare-earth element R and the transition metal element T, and, when the total contained amount of the rare-earth element R in the R-T phase 3 is [R]L at% and the contained amount of cerium in the R-T phase 3 is [Ce]L at%, 100×[Ce]L/[R]L equals to 75-100.

Description

Permanent magnet and rotating machine

The present invention relates to a permanent magnet and a rotating machine.

An RTB-based permanent magnet containing rare earth element R, transition metal element T, and boron B has excellent magnetic properties. For example, the maximum energy product of an Nd—Fe—B permanent magnet is high. However, Nd is more expensive than transition metals, and the supply amount of Nd is not stable. Therefore, research has been conducted in which a part of Nd is replaced with an inexpensive element such as Y, La, or Ce (see Patent Document 1 below).

JP 2016-115774 A

However, the coercive force HcJ of a permanent magnet in which a part of Nd is replaced with Y, La, Ce, or the like is significantly smaller than that in the case where Nd is not replaced.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a permanent magnet having a large coercive force among permanent magnets containing Ce as an alternative element of Nd, and a rotating machine including the permanent magnet. .

A permanent magnet according to one aspect of the present invention includes a plurality of main phase particles containing a rare earth element R, a transition metal element T, and boron, and a grain boundary phase positioned between the plurality of main phase particles. A magnet in which the rare earth element R includes at least neodymium and cerium, the transition metal element T includes at least iron, the copper content in the permanent magnet is 0.1 to 2 atomic%, and the grain boundary phase is , Including an RT phase containing an intermetallic compound of rare earth element R and transition metal element T, and the total content of rare earth element R in the RT phase is [R] _L atomic%, The cerium content in is [Ce] _L atomic%, and 100 × [Ce] _L / [R] _L is 75-100.

A rotating machine according to one aspect of the present invention includes the permanent magnet.

According to the present invention, a permanent magnet having a large coercive force among permanent magnets containing Ce as an alternative element of Nd, and a rotating machine including the permanent magnet are provided.

(A) in FIG. 1 is a schematic perspective view of a permanent magnet 10 according to an embodiment of the present invention, and (b) in FIG. 1 is a permanent magnet shown in (a) in FIG. FIG. 10 is a schematic diagram of a cross section 10cs of FIG. FIG. 2 is an enlarged view of a part II of the cross section 10cs of the permanent magnet 10 shown in FIG. FIG. 3 is a schematic perspective view of a rotating machine according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings as the case may be. However, the present invention is not limited to the following embodiment. In the drawings, the same or equivalent components are denoted by the same reference numerals. The permanent magnet according to the present invention may be a sintered magnet or a hot-worked magnet. The permanent magnet according to the present invention may be a rare earth magnet.

The whole permanent magnet 10 according to the present embodiment is shown in (a) of FIG. A cross section 10cs of the permanent magnet 10 is shown in FIG. FIG. 2 is an enlarged view of a part II of the cross section 10 cs of the permanent magnet 10. As shown in FIG. 2, the permanent magnet 10 includes a plurality of main phase particles 11 (main phase) and a grain boundary phase 9 located between the plurality of main phase particles 11. For example, the permanent magnet 10 may be a sintered body composed of a large number of main phase particles 11 via the grain boundary phase 9.

The main phase particles 11 contain a rare earth element R, a transition metal element T, and B (boron). The rare earth element R contains at least Nd (neodymium) and Ce (cerium). The transition metal element T contains at least Fe (iron). The Cu content [Cu] in the permanent magnet 10 is 0.1 to 2 atomic%.

The grain boundary phase 9 includes an RT phase 3 containing an intermetallic compound of a rare earth element R and a transition metal element T. The total content of rare earth elements R in the RT phase 3 is expressed as [R] _L atomic%. The Ce content in the RT phase 3 is expressed as [Ce] _L atomic%. 100 × [Ce] _L / [R] _L is 75-100.

The inventors of the present invention have arrived at the present invention based on the following considerations.

The residual magnetic flux density of the permanent magnet tends to decrease as the amount of Nd replaced increases. In order to increase the coercive force of the permanent magnet, the amount of the grain boundary phase in the permanent magnet and the magnetism of the grain boundary phase are important. When the content of the grain boundary phase increases, the content of the main phase decreases, so that the residual magnetic flux density of the permanent magnet tends to be small. As a method of increasing the coercive force of the permanent magnet, there is a method of making the main phase particles fine as follows. For example, the particle size of the main phase particles is reduced to 1 μm or less by the melt span method or HDDR (Hydrogenation Decomposition Decomposition Recombination) method. Then, an alloy having a low co-crystal point such as Nd—Ga or Nd—Cu is diffused and infiltrated into the sintered body from the surface of the sintered body, and the concentration of Nd on the surface of the main phase particles is changed to another rare earth element R. Higher than. As a result, the coercive force of the permanent magnet obtained from the sintered body tends to increase. The smaller the particle size of the main phase particles, the higher the specific surface area of the main phase particles and the easier it is to obtain a modification effect due to the increased Nd concentration on the surface of the particles. However, in the sintering process, it is necessary to perform the sintering process at a low temperature in order to maintain a fine main phase crystal structure of 1 μm or less. Therefore, the conventional high-temperature sintering method cannot be used, and it is necessary to use a method such as warm working or hot working, and the manufacturing cost of the permanent magnet tends to increase. Furthermore, since the depth at which an alloy having a low eutectic point can be diffused and penetrated from the surface of the sintered body is limited, the shape of the permanent magnet to which the above method can be applied is limited. Therefore, a method for increasing the coercive force of the permanent magnet is required without depending on the particle size of the main phase particles.

The present inventors have found that an RT phase exists in the grain boundary phase of a permanent magnet containing Ce. The RT phase may be, for example, an RFe ₂ phase. By SEM-EDS analysis using an energy dispersive X-ray spectrometer (EDS) attached to a scanning electron microscope (SEM), each content of Nd and Ce in the rare earth element R in the RFe ₂ phase (unit: atomic%) ) Was measured. As a result, the Nd content was, for example, 30%. The Ce content was, for example, 70%. The CeFe ₂ phase exists in the binary phase diagram of Ce and Fe, but the NdFe ₂ phase does not exist in the binary phase diagram of Nd and Fe. That, NdFe ₂ phase is energetically stable than the CeFe ₂ phase, hardly the CeFe ₂ phase is easily formed in the grain boundary phase, NdFe ₂ phase is formed in the grain boundary phase. As the Ce content in the RT phase increases, the magnetization of the RT phase decreases and the magnetization of the grain boundary phase decreases. Therefore, as Nd in the grain boundary phase is replaced with Ce, the magnetization of the grain boundary phase decreases, and magnetic separation between main phase grains tends to occur. As a result, the coercive force of the permanent magnet increases. Thus, if the method of controlling the magnetization of the grain boundary phase by replacing Nd with Ce, the coercive force of the permanent magnet can be increased at a low manufacturing cost regardless of the particle size of the main phase particles. Based on the above consideration, the present inventors have found the permanent magnet 10 according to the present embodiment.

That is, the present inventors consider that the reason why the coercive force of the permanent magnet 10 is large is as follows. The magnetism of the RT phase 3 changes according to the type of rare earth element R contained in the RT phase 3. There is a positive correlation between the Nd content in the RT phase 3 and the magnetization of the RT phase 3, and the Ce content in the RT phase 3 and the RT phase 3 There is a negative correlation with magnetization. When Cu is added to the raw material of the permanent magnet 10, Cu contained in the grain boundary phase 9 and Nd contained in the RT phase 3 form an Nd—Cu phase in the process of producing the permanent magnet 10. The magnetization of the Nd—Cu phase is very small. The Nd—Cu phase is formed outside the RT phase 3 by, for example, sucking Nd contained in the RT phase 3 (RFe ₂ phase) by Cu. Also, Cu diffuses into the RT phase 3 (RFe ₂ phase), and the T site is replaced with Cu, whereby an Nd-Cu phase is formed in the RT phase 3, and the Nd-Cu phase is Separate from RT phase 3. The atomic radius of Cu is approximately equal to the atomic radius of Fe and is 1.17Å. Therefore, the Fe site of the RFe ₂ phase is easily replaced with Cu. By separating the Nd—Cu phase from the RT phase 3, the content of Nd in the RT phase 3 is reduced, and 100 × [Ce] _L / [R] _L becomes 75 to 100. Due to the decrease in the Nd content in the RT phase 3 and the generation of the Nd—Cu phase, the magnetization of the grain boundary phase 9 becomes small. As a result, magnetic separation between the main phase particles 11 easily occurs, and the coercive force of the permanent magnet 10 increases. If the Cu content [Cu] in the permanent magnet 10 is too small, the amount of Nd—Cu phase generated is not sufficient, and sufficient coercive force cannot be obtained. When there is too much [Cu], Nd contained in the main phase particle 11 and Cu contained in the grain boundary phase 9 form an Nd—Cu phase in addition to Nd contained in the RT phase 3. Therefore, Fe is generated from the main phase particles 11 in the grain boundary phase 9, Fe is precipitated in the grain boundary phase, and a different phase (αFe) is generated in the grain boundary phase 9. αFe has a small coercive force and αFe has a large magnetization. As a result, magnetic separation between the main phase particles 11 hardly occurs, and the coercive force of the permanent magnet 10 becomes small. When [Cu] is 0.1 to 2 atomic%, a sufficient amount of Nd—Cu phase is formed, and αFe is hardly generated, so that the coercive force of the permanent magnet 10 is increased. The Nd—Cu phase may include an intermetallic compound of Nd and Cu. The Nd—Cu phase may include, for example, NdCu ₂ . The reason why the coercive force of the permanent magnet 10 is large is not limited to the above reason.

In addition, the present inventors have found that the coercive force of the permanent magnet 10 tends to increase when an aging treatment is performed on the sintered body described later at a predetermined temperature in the process of manufacturing the permanent magnet 10. The temperature of the aging treatment may be 900 to 970 ° C., or 900 to 950 ° C. The present inventors consider that the reason why the coercive force tends to increase when the temperature of the aging treatment is within the above range is as follows. If the temperature of the aging treatment is too low, the amount of the liquid phase generated from the RT phase 3 is small. Therefore, Nd migration in the RT phase 3 and diffusion of Cu into the RT phase 3 hardly occur. When the temperature of the aging treatment is too high, an Nd—Cu phase derived from Nd contained in the main phase particles 11 is easily formed. If the temperature of the aging treatment is within the above range, the amount of the liquid phase generated from the RT phase 3 tends to increase, and the Nd—Cu phase derived from Nd contained in the RT phase 3 is the main phase particle. As compared with the Nd—Cu phase derived from Nd contained in No. 11, it is easily formed. As a result, the coercive force of the permanent magnet 10 tends to increase. The reason why the coercive force of the permanent magnet 10 tends to increase is not limited to the above reason.

Each main phase particle 11 includes at least a rare earth element R, a transition metal element T, and boron (B). The rare earth element R contains at least Nd (neodymium) and Ce (cerium). That is, a part of Nd is replaced with Ce. The transition metal element T contains at least Fe (iron). The transition metal element T may contain Fe and Co (cobalt). That is, a part of the Fe may be replaced with Co. Each main phase particle 11 may contain carbon (C) in addition to boron. That is, a part of the above B may be replaced with C. The main phase particle 11 may contain R ₂ T ₁₄ M as a main phase. The element M may be only B. The element M may be B and C. In other words, R ₂ T ₁₄ M may be represented as Nd _2−x Ce _x Fe _14−s Co _s B _1−t C _t . x is greater than 0 and less than 2. s is 0 or more and less than 14. t is 0 or more and less than 1. For example, the main phase particles 11 may contain Nd ₂ Fe ₁₄ B. For example, the main phase particles 11 may include Y ₂ Fe ₁₄ B. For example, the main phase particles 11 may include Ce ₂ Fe ₁₄ B.

As shown in FIG. 2, the grain boundary phase 9 may include, in addition to the RT phase 3, an R rich phase 5, a heterogeneous phase 7, an R ₆ T ₁₃ E phase, and the like. The element E may be at least one selected from the group consisting of Ga, Si, Sn, and Bi. The definitions of RT phase 3, R rich phase 5, heterogeneous phase 7, and R ₆ T ₁₃ E phase may be as follows.

The content of C in the RT phase 3 is expressed as [C] _L atomic%. The N content in the RT phase 3 is expressed as [N] _L atomic%. The content of O in the RT phase 3 is expressed as [O] _L atomic%. The total content of rare earth elements R in the RT phase 3 is expressed as [R] _L atomic%. The total content of the transition metal element T in the RT phase 3 is expressed as [T] _L atomic%. The total content of the element E in the RT phase 3 is expressed as [E] _L atomic%. The RT phase 3 may be a phase that satisfies all of the following inequalities (1), (2), and (3).
0 ≦ [C] _L + [N] _L + [O] _L <30 (1)
0.26 ≦ [R] _L / ([R] _L + [T] _L ) ≦ 0.40 (2)
0.00 ≦ [E] _L / ([R] _L + [T] _L + [E] _L ) ≦ 0.03 (3)

The RT phase 3 may include, for example, an RT ₂ phase. That is, the intermetallic compound contained in the RT phase 3 may be, for example, RT _2. RT ₂ may be represented as Nd _1-γ Ce _γ Fe _2-δ Co _δ . γ is 0 or more and 1 or less. δ is 0 or more and 2 or less. RT ₂ may be, for example, NdFe ₂ or CeFe ₂ . The RT phase 3 may contain trace elements other than R and T in addition to R and T intermetallic compounds. The RT phase 3 may be a Laves phase. The crystal structure of RT phase 3 may be C15 type. The RT phase 3 may be specified based on the diffraction angle 2θ of the diffraction peak derived from the lattice plane (hkl) using an X-ray diffraction (XRD) pattern. For example, when CuKα rays are used for measurement of the XRD pattern, 2θ derived from the lattice plane (220) of the RT phase 3 may be 34.0 to 34.73 °. Further, when CuKα rays are used for measurement of the XRD pattern, 2θ derived from the lattice plane (311) of the RT phase 3 may be 40.10 to 40.97 °. The 2θ may vary within the above range depending on the type of rare earth element R contained in the RT phase 3.

100 × [Ce] _L / [R] _L may be 76-84. When 100 × [Ce] _L / [R] _L is within the above range, the coercive force of the permanent magnet 10 tends to increase. [Ce] _L and [R] _L may be measured by SEM-EDS analysis. When the content of rare earth element R in the permanent magnet 10 is small and it is necessary to analyze the fine RT phase 3, TEM-EDS analysis using EDS attached to a transmission electron microscope (TEM), or It may be measured by three-dimensional atom probe (3DAP) analysis. 100 × [Ce] _L / [R] _L may be calculated from the measured [Ce] _L and [R] _L.

The content of C in the R-rich phase 5 is expressed as [C] _R atomic%. The N content in the R-rich phase 5 is expressed as [N] _R atomic%. The content of O in the R-rich phase 5 is expressed as [O] _R atomic%. The total content of rare earth elements R in the R-rich phase 5 is expressed as [R] _R atomic%. The total content of the transition metal element T in the R-rich phase 5 is expressed as [T] _R atomic%. The R-rich phase 5 may be a phase that satisfies the following inequalities (4) and (5).
0 ≦ [C] _R + [N] _R + [O] _R <30 (4)
0.50 ≦ [R] _R / ([R] _R + [T] _R ) ≦ 1.00 (5)

The content of C in the heterogeneous phase 7 is expressed as [C] _D atomic%. The N content in the different phase 7 is expressed as [N] _D atomic%. The content of O in the heterogeneous phase 7 is expressed as [O] _D atomic%. The hetero phase 7 may be a phase in which the sum of [C] _D , [N] _D, and [O] _D [C] _D + [N] _D + [O] _D is 30 or more and less than 100. That is, the different phase 7 may be a phase satisfying the following inequality (6). The hetero phase 7 may include, for example, at least one selected from the group consisting of an oxide of R, a carbide of R, and a nitride of R.
30 ≦ [C] _D + [N] _D + [O] _D <100 (6)

The content of C in the R ₆ T ₁₃ E phase is expressed as [C] _A atomic%. The content of N in the R ₆ T ₁₃ E phase is expressed as [N] _A atomic%. The content of O in the R ₆ T ₁₃ E phase is expressed as [O] _A atomic%. The total content of rare earth elements R in the R ₆ T ₁₃ E phase is expressed as [R] _A atomic%. The total content of the transition metal element T in the R ₆ T ₁₃ E phase is expressed as [T] _A atomic%. The total content of the element E in the R ₆ T ₁₃ E phase is expressed as [E] _A atomic%. The R ₆ T ₁₃ E phase may be a phase that satisfies all of the following inequalities (7), (8), and (9).
0 ≦ [C] _A + [N] _A + [O] _A <30 (7)
0.26 ≦ [R] _A / ([R] _A + [T] _A ) ≦ 0.40 (8)
0.03 <[E] _A / ([R] _A + [T] _A + [E] _A ) ≦ 1.00 (9)

The rare earth element R may further contain other rare earth elements in addition to Nd and Ce. Other rare earth elements include, for example, Sc (scandium), Y (yttrium), La (lanthanum), Pr (praseodymium), Sm (samarium), Eu (europium), Gd (gadolinium), Ho (holmium), Dy ( It may be at least one selected from the group consisting of dysprosium) and Tb (terbium). The rare earth element R may consist only of Nd and Ce. The total content [R] of the rare earth element R in the permanent magnet 10 may be 14 to 18 atomic%. The Nd content [Nd] in the permanent magnet 10 may be 7 to 13 atomic%, or 9 to 11 atomic%. The Ce content [Ce] in the permanent magnet 10 may be 4 to 8 atomic%.

The transition metal element T may further contain Co (cobalt) in addition to Fe, and may further contain other transition metal elements. The other transition metal element may be, for example, Ni (nickel). The transition metal element T may consist only of Fe and Co. The total content [T] of the transition metal element T in the permanent magnet 10 may be 76 to 84 atomic%. The Fe content [Fe] in the permanent magnet 10 may be 72 to 84 atomic%. The Co content [Co] in the permanent magnet 10 may be 0 to 5 atomic%.

The B content [B] in the permanent magnet 10 may be 4.2 to 5.8 atomic%.

The Cu content [Cu] in the permanent magnet 10 may be 0.1 to 2 atomic%, or 0.3 to 1.0 atomic%. When [Cu] is within the above range, the coercive force of the permanent magnet 10 tends to increase.

The permanent magnet 10 is made of Al (aluminum), Mn (manganese), Nb (niobium), Ta (tantalum), Zr (zirconium), Ti (titanium), W (tungsten), Mo (molybdenum), V (vanadium), You may further contain elements, such as Ag (silver), Ge (germanium), Zn (zinc), Ga (gallium), Si (silicon), Sn (tin), and Bi (bismuth).

When the element E is defined as at least one selected from the group consisting of Si, Sn, Ga, and Bi, the total content [E] of the element E in the permanent magnet 10 is 0 to 1 atomic%. It's okay. When [E] is within the above range, the coercive force of the permanent magnet 10 tends to increase. The present inventors consider that the reason why the coercive force of the permanent magnet 10 tends to increase when [E] is within the above range is as follows. When the permanent magnet 10 contains the element E, an R ₆ T ₁₃ E phase is easily generated in the grain boundary phase 9 in the process of manufacturing the permanent magnet 10. By generating the R ₆ T ₁₃ E phase in the grain boundary phase 9, the content of Nd in the RT phase 3 is reduced, and the magnetization of the grain boundary phase 9 is reduced. As a result, magnetic separation between the main phase particles 11 easily occurs, and the coercive force of the permanent magnet 10 tends to increase. On the other hand, when [E] is less than or equal to the above upper limit value, the transition metal element T is unlikely to precipitate in the grain boundary phase 9 because the RE phase not containing the transition metal element T is hardly generated in the grain boundary phase 9. . As a result, magnetic separation between the main phase particles 11 easily occurs, and the coercive force of the permanent magnet 10 tends to increase. The R ₆ T ₁₃ E phase may be, for example, an R ₆ Fe ₁₃ E phase. The content of Nd in the R ₆ T ₁₃ E phase is expressed as [Nd] _A atomic%. The total content of R in the R ₆ T ₁₃ E phase is expressed as [R] _A atomic%. 100 × [Nd] _A / [R] _A is large, and may be, for example, 70 or more. The reason why the coercive force tends to increase is not limited to the above reason.

The composition of the permanent magnet 10 is X-ray fluorescence analysis, ICP (Inductively Coupled Plasma) emission analysis, inert gas melting-non-dispersive infrared absorption method, combustion in oxygen stream-infrared absorption method, inert gas melting- It may be specified by a thermal conductivity method or the like.

The average particle diameter (D50) of the main phase particles 11 may be 2 to 10 μm, 2.4 to 10 μm, or 3 to 6 μm. If the D50 of the main phase particles 11 is too small, the production of the main phase particles 11 tends to be difficult. When D50 of the main phase particles 11 is too large, the volume of the main phase particles 11 increases, so that the demagnetizing field tends to increase. As a result, magnetization reversal is likely to occur, and the coercive force of the permanent magnet 10 is likely to decrease. When the D50 of the main phase particle 11 is within the above range, the coercive force of the permanent magnet 10 tends to increase. However, even if D50 of the main phase particle 11 is out of the above range, the effects of the present invention can be obtained. In order to pulverize the raw material of the main phase particles 11 so that the D50 of the main phase particles 11 is less than 2 μm by the airflow pulverization method, a compressor for generating a high-speed airflow or cooling of a hard ceramic plate is used. Etc. are necessary. Therefore, the operation cost tends to be high. In addition, since the velocity of the airflow is not sufficient, not all of the raw materials charged into the pulverizer can be recovered as fine powder of less than 2 μm, and the utilization rate of the raw materials tends to be low. Since the raw material that could not be recovered is lost, the manufacturing cost of the permanent magnet 10 tends to increase. When the D50 of the main phase particle 11 is equal to or higher than the lower limit, the utilization rate of the raw material is likely to be high, and the manufacturing cost of the permanent magnet 10 is likely to be low.

(Permanent magnet manufacturing method)
The manufacturing method of the permanent magnet 10 may be as follows. The starting materials are weighed to match the desired permanent magnet 10 composition. The starting material can be, for example, a metal or an alloy.

The raw material alloy may be produced from the above starting materials by the following strip casting method, high frequency induction melting method, arc melting method, and other melting methods. A raw material alloy may be produced from a starting material by a reduction diffusion method. In order to suppress oxidation of the raw material alloy, a melting method such as a strip casting method may be performed in a non-oxidizing atmosphere. The non-oxidizing atmosphere may be, for example, a vacuum or an inert gas such as Ar (argon).

In the strip casting method, the starting material is melted in a non-oxidizing atmosphere to produce a molten metal (melting material alloy). The molten metal is poured onto the surface of a rotating roll in a non-oxidizing atmosphere. Since the metal roll is cooled by water cooling or the like, the molten metal is rapidly cooled and solidified on the surface of the roll to obtain a thin plate or flake (scale piece) of the raw material alloy. The roll may be made of copper, for example.

Crushed the raw material alloy obtained by the above melting and quenching to obtain a coarse powder. The raw material alloy may be pulverized by, for example, hydrogen pulverization. In hydrogen pulverization, the raw material alloy is placed in a hydrogen atmosphere, and the raw material alloy is made to store hydrogen. When the raw material alloy occludes hydrogen, the volume of the raw material alloy expands. Moreover, the hydrogenation reaction of the metal contained in the raw material alloy occurs, and the raw material alloy becomes brittle. As a result, cracks occur in the raw material alloy, and the raw material alloy is pulverized. The particle size of the coarse powder may be, for example, 10 to 1000 μm.

The coarse powder may be dehydrogenated by heating the coarse powder. The dehydrogenation temperature may be 300-400 ° C. The dehydrogenation time may be 0.5 to 20 hours.

Crushed coarse powder to obtain fine powder. Before pulverizing the coarse powder, a lubricant may be added to the coarse powder. By adding a lubricant to the coarse powder, when the coarse powder is pulverized, the powders are less likely to agglomerate and the powder is less likely to be fused to the inner wall of the pulverizer. The lubricant may be, for example, an ester organic material or an amide organic material. The amide-based organic substance may be, for example, oleic acid amide. The coarse powder may be pulverized by an airflow pulverizer (jet mill) or the like. In pulverization by a jet mill, coarse powder is accelerated by an inert gas stream and then pulverized by colliding with a hard ceramic plate. The obtained fine powder is recovered from the particle collecting part (cyclone) of the jet mill. The inert gas may be nitrogen gas or the like. The average particle diameter (D50) of the fine powder may be, for example, 2 to 10 μm. If D50 of the fine powder is too small, coarse particles are likely to be generated in the main phase when an aging treatment described later is applied to the sintered body. As a result, the coercive force of the permanent magnet 10 tends to be small. If D50 of the fine powder is too large, the main phase particles 11 are likely to be large. As a result, the coercive force of the permanent magnet 10 tends to be small. When the D50 of the fine powder is within the above range, the coercive force of the permanent magnet 10 tends to increase.

入れ Place the fine powder into the molding space (cavity) of the molding machine and press the fine powder in a magnetic field to obtain a compact. The pressing direction may be a direction perpendicular to the magnetic field direction. The strength of the magnetic field may be, for example, 960-1600 kA / m. The pressure applied to the fine powder may be, for example, 10 to 500 MPa.

Sintering the molded body to obtain a sintered body. The sintering temperature may be 1000 to 1200 ° C., for example. The sintering time may be, for example, 0.1 to 100 hours. The green body may be sintered in a reduced pressure atmosphere, an inert atmosphere, or the like. While the green body is sintered, the grain boundary phase 9 may be in a molten state, and the RT phase 3 may not be formed. The grain boundary phase 9 in the sintered body may include the RT phase 3 or the like.

The permanent magnet 10 is obtained by subjecting the sintered body to an aging treatment. In the aging treatment, the sintered body is heated. The temperature of the aging treatment may be as described above. The time for aging treatment may be, for example, 1 to 100 hours. The aging treatment may be performed in a reduced pressure atmosphere, an inert atmosphere, or the like. The aging treatment may be composed of one stage of heat treatment or may be composed of two or more stages of heat treatment. For example, after heating at a relatively high temperature, it may be heated at a relatively low temperature. In this case, the coercive force of the permanent magnet 10 tends to increase. The average particle diameter (D50) of the sintered body after the aging treatment may be the same as the average particle diameter (D50) of the main phase particles 11 described above.

If necessary, the obtained permanent magnet 10 may be processed into a predetermined shape. The processing method may be, for example, shape processing such as cutting and grinding, or chamfering processing such as barrel polishing. For example, in order to accurately measure the magnetic characteristics, the surface of the permanent magnet 10 serving as a measurement sample may be processed flat. Due to the flat surface, the exact dimensions of the measurement sample can be obtained. The method for processing the surface to be flat may be, for example, a wet method, a dry method, or the like. The wet method is preferable because the processing time is short and the processing cost is low.

(Rotating machine)
The rotating machine according to the present embodiment includes the permanent magnet 10a. An example of the internal structure of the rotating machine is shown in FIG. The rotating machine 200 according to the present embodiment is a permanent magnet synchronous rotating machine (SPM rotating machine). The rotating machine 200 includes a cylindrical rotor 50 and a stator 30 disposed inside the rotor 50. The rotor 50 includes a cylindrical core 52 and a plurality of permanent magnets 10 a arranged along the inner peripheral surface of the core 52. The plurality of permanent magnets 10 a are arranged so that N poles and S poles are alternately arranged along the inner peripheral surface of the core 52. The stator 30 has a plurality of coils 32 provided along the outer peripheral surface thereof. The coil 32 and the permanent magnet 10a are arranged so as to face each other.

The rotating machine 200 may be an electric motor. The electric motor converts electrical energy into mechanical energy by the interaction between the field generated by the electromagnet generated by energizing the coil 32 and the field generated by the permanent magnet 10a. The rotating machine 200 may be a generator. The generator converts mechanical energy into electrical energy by the interaction (electromagnetic induction) between the field and the coil 32 by the permanent magnet 10a.

The rotating machine 200 that functions as an electric motor (motor) may be, for example, a permanent magnet DC motor, a linear synchronous motor, a permanent magnet synchronous motor (SPM motor, IPM motor), or a reciprocating motor. The motor that functions as the reciprocating motor may be, for example, a voice coil motor or a vibration motor. The rotating machine 200 that functions as a generator may be, for example, a permanent magnet synchronous generator, a permanent magnet commutator generator, or a permanent magnet AC generator. The rotating machine 200 may be used for automobiles, industrial machines, household appliances, and the like.

The preferred embodiment of the present invention has been described above, but the present invention is not necessarily limited to the above-described embodiment. Various modifications of the present invention are possible without departing from the spirit of the present invention, and these modified examples are also included in the present invention. For example, the permanent magnet according to the present invention may be manufactured by a hot working method, a film forming method, a spark plasma sintering method, or the like.

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples.

Example 1
A permanent magnet was produced by the method described below. Nd, Ce, Fe, FeB, Al, Co, and Cu were prepared as starting materials (single or alloy) for the permanent magnet. The purity of each starting material was 99.9% by mass. The composition of the permanent magnet is 9.6 atomic% Nd-6.4 atomic% Ce-77.8 atomic% Fe-5.0 atomic% B-0.5 atomic% Al-0.6 atomic% Co-0.1 Each starting material was weighed and mixed so as to be atomic% Cu to prepare a mixed material. An alloy thin plate was obtained by quenching the melt of the mixed raw material on the surface of the roll by strip casting.

The thin plate was pulverized by hydrogen pulverization to obtain a coarse powder.

Lubricant was added to the coarse powder. The lubricant was oleic amide. The content of the lubricant in the coarse powder was 0.1% by mass. The coarse powder to which the lubricant was added was pulverized by a jet mill in a high-pressure nitrogen gas atmosphere to obtain a fine powder. The average particle diameter (D50) of the fine powder was 3 μm.

The fine powder was put into a molding space (cavity) in the molding machine. A fine powder was pressed in a magnetic field and molded to obtain a molded body. The pressing direction was a direction perpendicular to the magnetic field direction. The strength of the magnetic field was 15 × (10 ³ / 4π) kA / m. The pressure applied to the fine powder was 140 MPa.

The sintered body was sintered to obtain a sintered body. The sintering temperature was 1000 ° C. The sintering time was 4 hours.

The sintered body was subjected to an aging treatment by heating the sintered body. The temperature of the aging treatment was 950 ° C. The time for aging treatment was 12 hours. The average particle size (D50) of the sintered body after the aging treatment was 3.2 μm.

The surface of the sintered body after the aging treatment was processed flat by a wet method to obtain the permanent magnet of Example 1.

[Measurement of magnetic properties]
Using a BH tracer, the demagnetization curve of the permanent magnet of Example 1 was measured, and the coercive force HcJ (unit: kA / m) of the permanent magnet of Example 1 was determined. The maximum applied magnetic field in the measurement of the demagnetization curve was 3T. HcJ of Example 1 is shown in Table 1. The unit (kOe) of the coercive force HcJ in the following table is equivalent to “× (10 ³ / 4π) × (kA / m)”. HcJ is preferably 12 × (10 ³ / 4π) kA / m or more.

[Analysis of composition]
The permanent magnet of Example 1 after measuring the magnetic properties was heated in an inert gas atmosphere, whereby the permanent magnet was thermally demagnetized. The contents (unit: atomic%) of Nd, Ce, Fe, B, Al, Co, and Cu in the permanent magnet after thermal demagnetization were measured by ICP emission analysis. In addition, each content was computed on the basis of the total of 100 atomic% of content of all the elements measured above. The results are shown in Table 1.

[100 × [Ce] _L / [R] _L ]
For the permanent magnet of Example 1, the Nd content [Nd] _L in the RT phase and the Ce content [Ce] _L in the RT phase were measured by SEM-EDS analysis. [Nd] _L and [Ce] _L were summed to determine the total content [R] _L of R in the RT phase. From [Ce] _L and [R] _L , 100 × [Ce] _L / [R] _L was determined. The results are shown in Table 1.

(Examples 2 to 5)
In Examples 2 to 5, each starting material was weighed so that the composition of the permanent magnet was as shown in Table 1. Except for this point, permanent magnets of Examples 2 to 5 were individually manufactured by the same method as in Example 1. Table 1 shows D50 of each fine powder of Examples 2 to 5 and D50 of the sintered body after aging treatment.

The magnetic properties of the permanent magnets of Examples 2 to 5 were analyzed in the same manner as in Example 1. The compositions of the permanent magnets of Examples 2 to 5 were analyzed in the same manner as in Example 1. In the same manner as in Example 1, 100 × [Ce] _L / [R] _L of each of Examples 2 to 5 was determined. The results are shown in Table 1.

(Examples 6 to 8)
In Examples 6 to 8, the coarse powder was pulverized using a jet mill so that the D50 of the fine powder became the value shown in Table 1. Except for this point, permanent magnets of Examples 6 to 8 were individually manufactured by the same method as in Example 1. Table 1 shows D50 of the sintered bodies after the aging treatment in Examples 6 to 8.

The magnetic properties of the permanent magnets of Examples 6 to 8 were analyzed by the same method as in Example 1. The compositions of the permanent magnets of Examples 6 to 8 were analyzed in the same manner as in Example 1. In the same manner as in Example 1, 100 × [Ce] _L / [R] _L of each of Examples 6 to 8 was determined. The results are shown in Table 1.

(Comparative Examples 1 and 2)
In Comparative Examples 1 and 2, each starting material was weighed so that the composition of the permanent magnet was the composition shown in Table 1. Except for this point, the permanent magnets of Comparative Examples 1 and 2 were individually produced by the same method as in Example 1. Table 1 shows D50 of each fine powder of Comparative Examples 1 and 2 and D50 of the sintered body after aging treatment.

In the same manner as in Example 1, the magnetic properties of the permanent magnets of Comparative Examples 1 and 2 were analyzed. The compositions of the permanent magnets of Comparative Examples 1 and 2 were analyzed by the same method as in Example 1. In the same manner as in Example 1, 100 × [Ce] _L / [R] _L of each of Comparative Examples 1 and 2 was determined. The results are shown in Table 1.

(Comparative Example 3)
The temperature of the aging treatment in Comparative Example 3 was 800 ° C. Except for this point, a permanent magnet of Comparative Example 3 was produced in the same manner as in Example 1. Table 1 shows D50 of the fine powder of Comparative Example 3 and D50 of the sintered body after the aging treatment.

The magnetic properties of the permanent magnet of Comparative Example 3 were analyzed by the same method as in Example 1. The composition of the permanent magnet of Comparative Example 3 was analyzed by the same method as in Example 1. 100 × [Ce] _L / [R] _L of Comparative Example 3 was determined by the same method as in Example 1. The results are shown in Table 1.

The temperature of the aging treatment is denoted by the following Table 1, T _A. 100 × [Ce] _L / [R] _L is expressed as Ce / R in Table 1 below.

As shown in Table 1, the coercive force of all the examples was 12 kOe or more (955 kA / m or more). On the other hand, there was no comparative example having a coercive force of 12 kOe or more. According to the present invention, it has been confirmed that a permanent magnet having a large coercive force among the permanent magnets containing Ce as an alternative element of Nd is provided.

D50 of the fine powder of Example 6 was smaller than that of Example 1. As a result, it is considered that the coercive force of Example 6 was larger than that of Example 1.

The D50 of the fine powder of Example 7 was larger than that of Example 1. As a result, it is considered that the coercive force of Example 7 was smaller than that of Example 1.

D50 of the fine powder of Example 8 was larger than that of Example 1. As a result, it is considered that the coercive force of Example 8 was smaller than that of Example 1.

The permanent magnet of Comparative Example 1 did not contain Cu. As a result, in Comparative Example 1, it is considered that 100 × [Ce] _L / [R] _L was low and the coercive force was small.

In Comparative Example 2, since there was much [Cu], 100 × [Ce] _L / [R] _L was large. However, due to the increase in the Nd—Cu phase, Nd was insufficient in the main phase, and a heterogeneous phase (αFe) was precipitated. As a result, it is thought that the coercive force was small.

In Comparative Example 3, the temperature of the aging treatment was low. As a result, it is considered that 100 × [Ce] _L / [R] _L was low and the coercive force was small.

The permanent magnet according to the present invention is used, for example, in a rotating machine.

DESCRIPTION OF SYMBOLS 3 ... RT phase, 5 ... R rich phase, 7 ... Different phase, 9 ... Grain boundary phase, 10, 10a ... Permanent magnet, 10cs ... Permanent magnet cross section, 11 ... Main phase particle, 30 ... Stator, 32 ... Coil 52 ... Core, 200 ... Rotating machine.

Claims

A plurality of main phase particles containing a rare earth element R, a transition metal element T, and boron;
A grain boundary phase located between the plurality of main phase particles, and a permanent magnet comprising:
The rare earth element R includes at least neodymium and cerium,
The transition metal element T includes at least iron;
The copper content in the permanent magnet is 0.1 to 2 atomic%,
The grain boundary phase includes an RT phase containing an intermetallic compound of the rare earth element R and the transition metal element T;
The total content of the rare earth element R in the RT phase is [R] L atomic%,
The cerium content in the RT phase is [Ce] L atomic%,
100 × [Ce] L / [R] L is 75-100,
permanent magnet.
A rotating machine comprising the permanent magnet according to claim 1.