WO2018181592A1

WO2018181592A1 - Permanent magnet and rotating machine

Info

Publication number: WO2018181592A1
Application number: PCT/JP2018/012997
Authority: WO
Inventors: 敦古田; 孝裕諏訪; 信宏神宮
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: JP2020095992A

Abstract

Provided are a permanent magnet having high coercive force and high squareness ratio among permanent magnets including Ce as an alternative element for Nd, and a rotating machine provided with the permanent magnet. The permanent magnet contains a rare-earth element R, a transition metal element T, and boron B, wherein: the rare-earth element R includes at least Nd, Y, and Ce; the transition metal element T includes at least Fe; a total content of the rare-earth element R in the permanent magnet is [R] at%; a total content of the transition metal element T in the permanent magnet is [T] at%; the content of B in the permanent magnet is [B] at%; the content of Y in the permanent magnet is [Y] at%; the content of Ce in the permanent magnet is [Ce] at%; [Y]/[R] is 0.05 to 0.25; [Ce]/[R] is 0.10 to 0.55; and [T]/[B] is 14 to 18.

Description

Permanent magnet and rotating machine

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

An RTB-based permanent magnet containing a rare earth element R, a transition metal element T such as iron (Fe) or cobalt (Co), and boron B has excellent magnetic properties. The main phase of the RTB system permanent magnet contains, for example, a tetragonal R ₂ T ₁₄ B compound. The RTB permanent magnet is a high-performance permanent magnet.

An RTB-based permanent magnet containing Nd, Pr, Dy, Tb, or Ho as the rare earth element R has a large anisotropic magnetic field Ha and is suitable for a permanent magnet. In particular, an Nd—Fe—B permanent magnet containing Nd as the rare earth element R has a good balance between the saturation magnetization Is, the Curie temperature Tc, and the anisotropic magnetic field Ha. In addition, the resource amount of Nd—Fe—B permanent magnets is large. Therefore, Nd—Fe—B permanent magnets are widely used in consumer equipment, industrial equipment, transportation equipment, and the like.

Demand for Nd-Fe-B permanent magnets is expected to increase in the future. Therefore, there is a possibility that the price of Nd will soar. Therefore, an attempt has been made to replace part of Nd contained in the RTB permanent magnet with Ce. Ce prices are low and Ce resources are large. For example, the RTB permanent magnet described in Patent Document 1 has a grain boundary phase containing Ce. This grain boundary phase is formed by a two-alloy method.

Japanese Patent Laying-Open No. 2015-204390

Although the coercive force HcJ of the permanent magnet described in Patent Document 1 is high, the squareness ratio of the hysteresis loop of the permanent magnet is likely to decrease. Therefore, when this permanent magnet is incorporated in a motor (rotating machine), the output of the motor is likely to be reduced.

The present invention has been made in view of the above circumstances, and among permanent magnets containing Ce as a substitute element for Nd, a permanent magnet having both a high coercive force and a high squareness ratio, and a rotating machine including the permanent magnet are provided. The purpose is to provide.

A permanent magnet according to one aspect of the present invention is a permanent magnet containing a rare earth element R, a transition metal element T, and boron B, and the rare earth element R contains at least Nd, Y, and Ce, and the transition metal element T Includes at least Fe, the total content of rare earth elements R in the permanent magnet is [R] atomic%, and the total content of the transition metal elements T in the permanent magnet is [T] atomic%. The content of B in [B] is [B] atomic%, the content of Y in the permanent magnet is [Y] atomic%, the content of Ce in the permanent magnet is [Ce] atomic%, and [Y] / [R] is 0.05 to 0.25, [Ce] / [R] is 0.10 to 0.55, and [T] / [B] is 14 to 18.

In the permanent magnet according to one aspect of the present invention, the C content in the permanent magnet may be 0.00 to 0.25% by mass, and the N content in the permanent magnet is 0.00 to 0.25% by mass. The content of O in the permanent magnet may be 0.00 to 0.25% by mass.

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 high coercive force and a high squareness ratio 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. FIG. 4 is a diagram showing the relationship between [T] / [B] and HcJ in Experiment Group 1. FIG. 5 is a diagram illustrating the relationship between [T] / [B] and the squareness ratio of the experimental group 1. FIG. 6 is a diagram showing the relationship between [Y] / [R] and HcJ for each of the experimental groups 2-1 to 2-4. FIG. 7 is a diagram showing the relationship between [Y] / [R] and the squareness ratio of each of the experimental groups 2-1 to 2-4. FIG. 8 is a diagram showing the relationship between [Ce] / [R] and HcJ in the experimental group 3. FIG. 9 is a diagram showing the relationship between [Ce] / [R] and the squareness ratio in the experimental group 3. FIG. 10 is a diagram showing the relationship between [Y] / [R] and HcJ for each of the experimental groups 4-1 and 4-2. FIG. 11 is a diagram showing the relationship between [Y] / [R] and the squareness ratio of each of the experimental groups 4-1 and 4-2.

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 may include 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 permanent magnet 10 contains a rare earth element R, a transition metal element T, and boron B. The main phase particle 11 may contain a rare earth element R, a transition metal element T, and B. The rare earth element R contains at least Nd (neodymium), Y (yttrium), and Ce (cerium). The transition metal element T contains at least Fe (iron). The total content of rare earth elements R in the permanent magnet 10 is expressed as [R] atomic%. The total content of the transition metal element T in the permanent magnet 10 is expressed as [T] atomic%. The B content in the permanent magnet 10 is expressed as [B] atomic%. The Y content in the permanent magnet 10 is expressed as [Y] atomic%. The Ce content in the permanent magnet 10 is expressed as [Ce] atomic%. [Y] / [R] is 0.05 to 0.25. [Ce] / [R] is 0.10 to 0.55. [T] / [B] is 14-18.

The present inventors examined a method for increasing the coercive force of a permanent magnet in which a part of the rare earth element R is replaced with Ce. The main phase particles in the permanent magnet are, for example, tetragonal R ₂ T ₁₄ B compounds. The stoichiometric ratio of T to B in R ₂ T ₁₄ B is 14. The present inventors have found that a high coercive force can be obtained when [T] / [B] is 14 or more and 18 or less, which is the stoichiometric ratio. However, the squareness ratio of the permanent magnet is likely to be lowered only when [T] / [B] is within the above range. When [T] / [B] is 14 or more, the R ₂ T ₁₇ phase is likely to be precipitated in the grain boundary phase, so that the squareness ratio of the permanent magnet is likely to be lowered. When the permanent magnet does not contain Ce, the R ₂ T ₁₇ phase can be modified into the main phase by performing liquid phase sintering at a sufficiently high temperature. However, when a part of the rare earth element R is replaced with Ce, the liquidus temperature of the main phase is lowered, so that the main phase becomes coarse due to abnormal grain growth even when the temperature of the liquid phase sintering is relatively low. Magnetic properties such as magnetic force are reduced. In order to prevent deterioration of the magnetic properties, liquid phase sintering must be performed at a relatively low temperature, and it is considered that the R ₂ T ₁₇ phase cannot be reformed to the main phase. Accordingly, the present inventors have [Y] / [R] of 0.05 to 0.25 and [Ce] / [B] in addition to [T] / [B] of 14 to 18. It was found that when R] is 0.10 to 0.55, both high coercive force and high squareness ratio can be obtained. The present inventors consider that the reason why the coercive force of the permanent magnet 10 is high and the squareness ratio is high is as follows. In the permanent magnet 10, [Y] / [R] is 0.05 to 0.25, and a part of R in the main phase is replaced with Y, so that the liquidus temperature of the main phase increases, The coarsening of the phase particles 11 is suppressed, and liquid phase sintering becomes possible at a relatively high temperature. As a result, the R ₂ T ₁₇ phase can be reformed to the main phase, and the squareness ratio of the permanent magnet 10 is increased. [Ce] / [R] is 0.10 to 0.55, and the substitution amount of Ce in the main phase is not too large, so that the liquidus temperature of the main phase is unlikely to decrease. As a result, since the sintering can be performed at a sufficiently high temperature to modify the R ₂ T ₁₇ phase, the squareness ratio of the permanent magnet 10 is unlikely to decrease. From the above, even if a part of the rare earth element R is replaced with Ce, both a high coercive force and a high squareness ratio can be achieved. The reason why the permanent magnet 10 has a high coercive force and a high squareness ratio is not limited to the above reason.

The rare earth element R may further contain other rare earth elements in addition to Nd, Y, and Ce. Other rare earth elements include, for example, Sc (scandium), La (lanthanum), Pr (praseodymium), Sm (samarium), Eu (europium), Gd (gadolinium), Ho (holmium), Dy (dysprosium) and Tb ( May be at least one selected from the group consisting of terbium). The rare earth element R may consist only of Nd, Y, and Ce. [R] may be 11-18 atomic%. The Nd content [Nd] in the permanent magnet 10 may be 2.2 to 14.4 atomic%. [Y] may be 0.55 to 4.5 atomic%. [Ce] may be 1.1 to 9.9 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. [T] may be 76.5 to 84.3 atomic%. The Fe content [Fe] in the permanent magnet 10 may be 71.5 to 84.3 atomic%. The Co content [Co] in the permanent magnet 10 may be 0 to 5 atomic%.

[B] may be 4.32 to 5.93 atomic%, or 4.65 to 5.41 atomic%.

[Y] / [R] may be 0.05 to 0.25, or 0.05 to 0.15. When [Y] / [R] is within the above range, the squareness ratio of the permanent magnet 10 tends to be high.

[Ce] / [R] may be 0.10 to 0.55, or 0.1 to 0.4. When [Ce] / [R] is within the above range, even if R in the main phase is replaced with Ce, the coercive force of the permanent magnet 10 is hardly reduced.

[T] / [B] may be 14.0 to 18.0, or 15.5 to 18.0. When [T] / [B] is within the above range, the coercive force of the permanent magnet 10 tends to be high.

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

The C (carbon) content in the permanent magnet 10 may be 0.00 to 0.25% by mass, or 0.00 to 0.10% by mass. The content of N (nitrogen) in the permanent magnet 10 may be 0.00 to 0.25% by mass, or 0.00 to 0.10% by mass. The content of O (oxygen) in the permanent magnet 10 may be 0.00 to 0.25% by mass, or 0.00 to 0.10% by mass. When the contents of C, N, and O are within the above ranges, the Y-OCN phase is hardly generated in the grain boundary phase, and the substitution amount of Y in the main phase is difficult to decrease. As a result, the liquidus temperature of the main phase is likely to be high, and the R ₂ T ₁₇ phase can be reformed to the main phase by liquid phase sintering at a relatively high temperature, so that the squareness ratio of the permanent magnet 10 is increased. easy. The Y-OCN phase may include at least one selected from the group consisting of yttrium oxide, yttrium carbide, and yttrium nitride, for example.

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.

Each main phase particle 11 may include 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), Y (yttrium), and Ce (cerium). That is, a part of Nd is substituted with Y and 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 (B). 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 -xy} Y _x Ce _y Fe _{14 -s} Co _s B _{1 -t} C _t . x + y is greater than 0 and less than 2. x is greater than 0 and less than 2. y 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 an RT phase 3 containing an intermetallic compound of a rare earth element R and a transition metal element T. The grain boundary phase 9 may include 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 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.

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)

(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, an alloy or an oxide. When an oxide is used as a starting material, a reduction process for removing oxygen may be performed at any point in the manufacturing process of the permanent magnet 10. However, in order to easily control the composition of the permanent magnet 10, it is better not to use an oxide as a starting material.

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 on the surface of the roll and solidifies. By crushing the alloy peeled from the roll, a raw material alloy in the form of a thin plate or flakes (scales) is obtained. 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. By performing dehydrogenation of the coarse powder at the temperature and time within the above ranges, the amount of hydrogen remaining in the coarse powder and the molded body described later is likely to increase moderately as compared with the conventional method. Therefore, in the process of obtaining a sintered body by sintering a molded body described later, hydrogen contained in the molded body and each of C, N, and O contained in the molded body are combined to form these elements. Easily released out of the body. As a result, the contents of C, N, and O in the sintered body tend to decrease. When the contents of C, N, and O in the sintered body are small, precipitation of heterogeneous phases such as Y-OCN is suppressed, the amount of substitution of Y in the main phase is likely to increase, and the liquidus temperature of the main phase is increased. It tends to be expensive. Therefore, the R ₂ T ₁₇ phase can be reformed to the main phase by liquid phase sintering at a high temperature, and the squareness ratio of the permanent magnet 10 tends to be high.

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 coarse powders are less likely to agglomerate and the coarse powder is less likely to fuse 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, argon gas or the like. The particle size of the fine powder may be, for example, 0.5 to 10 μm.

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.

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 450 to 950 ° C., for example. The time for aging treatment may be, for example, 0.1 to 100 hours. The aging treatment may be performed in a reduced pressure atmosphere, an inert atmosphere, or the like. By performing the aging treatment, the coercive force of the permanent magnet 10 tends to be higher. The aging treatment may be composed of a one-stage heat treatment process or may be composed of two or more heat treatment processes. 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 be higher.

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.

If necessary, a protective layer may be formed on the surface of the sintered body. The protective layer may be, for example, a resin layer or an inorganic layer (for example, a metal layer or an oxide layer). The method for forming the protective layer may be, for example, a plating method, a coating method, a vapor deposition polymerization method, a gas phase method, or a chemical conversion treatment method.

(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, Y, Ce, Fe, FeB, Co, Cu, and Al 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 13.60 atomic% Nd-0.80 atomic% Y-1.60 atomic% Ce-7.62 atomic% Fe-0.50 atomic% Co-5.58 atomic% B-0.20. Each starting material was weighed and mixed so as to be atomic% Al-0.10 atomic% Cu to prepare a mixed raw material. An alloy flake was obtained by quenching and crushing the melt of the mixed raw material on the surface of the roll by the strip casting method.

The flakes were pulverized by hydrogen pulverization to obtain a coarse powder. By heating the coarse powder, the coarse powder was dehydrogenated. The dehydrogenation temperature was 300 ° C. The dehydrogenation time was 5 hours.

Lubricant was added to the coarse powder after dehydrogenation. 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 argon gas atmosphere to obtain a fine powder.

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 1030 ° C. The sintering time was 6 hours. The sintered body was processed into a rectangular parallelepiped shape by inner peripheral cutting. The volume and weight of the sintered body after processing were measured, and the relative density was calculated. As a result, it was confirmed that the relative density of the sintered body was 99.0% or more. The fracture surface of the sintered body was observed with an optical microscope. As a result, coarse particles were not confirmed. From the observation of the relative density of the sintered body and the cross-sectional structure of the sintered body, it was confirmed that the molded body could be sintered under an appropriate temperature condition.

By heating the sintered body, the sintered body was subjected to an aging treatment to obtain the permanent magnet of Example 1. The temperature of the aging treatment was 700 ° C. The time for aging treatment was 1 hour.

[Analysis of composition]
Each content (unit: atomic%) of Nd, Y, Ce, Fe, Co, Al, and Cu in the permanent magnet of Example 1 was measured by fluorescent X-ray analysis. The B content [B] (unit: atomic%) in the permanent magnet of Example 1 was measured by ICP emission analysis. The Nd content [Nd], the Y content [Y], and the Ce content [Ce] were summed to obtain the total rare earth element R content [R]. The Fe content [Fe] and the Co content [Co] were totaled to obtain the total content [T] of the transition metal element T. [Y] / [R], [Ce] / [R], and [T] / [B] were determined. In addition, each said content was computed on the basis of the total of 100 atomic% of content of all the elements measured above. Table 2 shows the results. At% in the following table means atomic%.

The content (unit: mass%) of O in the permanent magnet of Example 1 was measured by an inert gas melting-non-dispersive infrared absorption method. The C content (unit: mass%) in the permanent magnet of Example 1 was measured by combustion in an oxygen stream-infrared absorption method. The N content (unit: mass%) in the permanent magnet of Example 1 was measured by an inert gas melting-thermal conductivity method. Table 2 shows the results.

[Measurement of magnetic properties]
The coercive force HcJ (unit: kA / m) of the permanent magnet of Example 1 was measured using a BH tracer. Further, the external magnetic field Hk applied to the permanent magnet when the magnetic flux density of 90% of the residual magnetic flux density Br was obtained was obtained. The squareness ratio 100 × Hk / HcJ (unit:%) of the permanent magnet of Example 1 was determined from HcJ and Hk. Table 2 shows the HcJ and the squareness ratio of Example 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. The squareness ratio is preferably 85% or more, and more preferably 90% or more.

(Examples 2 to 9, Comparative Examples 1 to 24, Reference Example 1)
Each starting material of Examples 2 to 9, Comparative Examples 1 to 24 and Reference Example 1 was weighed so that the composition of the permanent magnet was as shown in Tables 1 to 5. According to the following procedure, appropriately sintered sintered bodies (the sintered bodies of Examples 2 to 9, Comparative Examples 1 to 24, and Reference Example 1) were obtained. A plurality of molded bodies were individually produced by the same method as in Example 1. A plurality of sintered bodies were individually manufactured by changing the sintering temperature from 950 ° C. to 1100 ° C. in increments of 10 ° C. The relative density of each sintered body was measured by the same method as in Example 1, and the cross-sectional structure of each sintered body was observed. A sintered body in which the relative density of the sintered body was 99.0% or more and coarse particles were not confirmed on the fracture surface of the sintered body was determined to be an appropriately sintered sintered body.

Except for the above points, permanent magnets of Examples 2 to 9, Comparative Examples 1 to 24, and Reference Example 1 were individually produced in the same manner as in Example 1.

The compositions of the permanent magnets of Examples 2 to 9, Comparative Examples 1 to 24, and Reference Example 1 were analyzed in the same manner as in Example 1. The results are shown in Tables 1-5.

The magnetic properties of the permanent magnets of Examples 2 to 9, Comparative Examples 1 to 24 and Reference Example 1 were measured in the same manner as in Example 1. The results are shown in Tables 1-5.

(Examples 10 to 15)
In Examples 10 and 11, the contents of C, N, and O in the permanent magnet were adjusted to the values shown in Table 5 by adjusting the amount of oleic amide added to the coarse powder. Except for this point, the permanent magnets of Examples 10 and 11 were individually manufactured by the same method as in Example 4. When obtaining the fine powders of Examples 12 and 13, the contents of C, N and O in the permanent magnet were adjusted to the values shown in Table 5 by using a mixed gas of argon and nitrogen instead of argon gas. did. Except for this point, permanent magnets of Examples 12 and 13 were individually produced by the same method as in Example 4. When obtaining the fine powders of Examples 14 and 15, the contents of C, N and O in the permanent magnet were adjusted to the values shown in Table 5 by using a mixed gas of argon and oxygen instead of argon gas. did. Except for this point, permanent magnets of Examples 14 and 15 were individually manufactured by the same method as in Example 4.

The compositions of the permanent magnets of Examples 10 to 15 were analyzed in the same manner as in Example 1. The results are shown in Table 5.

The magnetic properties of the permanent magnets of Examples 10 to 15 were measured in the same manner as in Example 1. The results are shown in Table 5.

FIG. 4 shows the relationship between [T] / [B] and HcJ in the experimental group 1 shown in Table 1. FIG. 5 shows the relationship between [T] / [B] and the squareness ratio in Experimental Group 1. [T] / [B] of the experimental group 2-1 shown in Table 2 is 14. [T] / [B] in the experimental group 2-2 is 18. [T] / [B] is 12 in the experimental group 2-3. [T] / [B] in the experimental group 2-4 is 20. FIG. 6 shows the relationship between [Y] / [R] and HcJ in each of the experimental groups 2-1 to 2-4. FIG. 7 shows the relationship between [Y] / [R] and the squareness ratio in each of the experimental groups 2-1 to 2-4. FIG. 8 shows the relationship between [Ce] / [R] and HcJ in the experimental group 3 shown in Table 3. FIG. 9 shows the relationship between [Ce] / [R] and the squareness ratio in Experimental Group 3. [Ce] / [R] of the experimental group 4-1 shown in Table 4 is 0.55. In the experimental group 4-2, [Ce] / [R] is 0.65. FIG. 10 shows the relationship between [Y] / [R] and HcJ in each of the experimental groups 4-1 and 4-2. FIG. 11 shows the relationship between [Y] / [R] and the squareness ratio in each of the experimental groups 4-1 and 4-2. In the experimental group 5 shown in Table 5, the C content, the N content, or the O content in the permanent magnets are different from each other.

As shown in Tables 1 to 5, HcJ of all examples was 12 kOe or more, and the squareness ratio of all examples was 85% or more. On the other hand, there was no comparative example in which HcJ was 12 kOe or more and the squareness ratio was 85% or more. According to the present invention, it has been confirmed that a permanent magnet having both a high coercive force and a high squareness ratio among the permanent magnets containing Ce as an alternative element of Nd is provided.

From the results of the experimental group 1, in each of the permanent magnets of Comparative Examples 1 to 5, since the liquidus temperature of the main phase was low and liquid phase sintering could not be performed at a sufficiently high temperature, the R ₂ T ₁₇ phase was used as the main phase. It is considered that the squareness ratio was lowered due to the inability to improve.

From the results of the experimental group 2-1, since the liquid phase temperature of the main phase was low in the permanent magnet of Comparative Example 2 and liquid phase sintering could not be performed at a sufficiently high temperature, the R ₂ T ₁₇ phase was used as the main phase. It is considered that the squareness ratio was lowered due to the inability to modify. In the permanent magnet of Comparative Example 6, it is considered that the coercive force was lowered because the amount of substitution of Y in the main phase increased and the anisotropic magnetic field Ha of the main phase decreased.

From the results of Experimental Group 2-2, the permanent magnet of Comparative Example 4 had a low liquidus temperature of the main phase and could not perform liquid phase sintering at a sufficiently high temperature. Therefore, the R ₂ T ₁₇ phase was used as the main phase. It is considered that the squareness ratio was lowered due to the inability to modify. In the permanent magnet of Comparative Example 7, the amount of substitution of Y in the main phase increased, and the anisotropy magnetic field Ha of the main phase decreased.

From the results of the experimental group 2-3, since the liquid phase temperature of the main phase was low in the permanent magnet of Comparative Example 1 and liquid phase sintering could not be performed at a sufficiently high temperature, the R ₂ T ₁₇ phase was used as the main phase. It is considered that the squareness ratio was lowered due to the inability to modify. In each of the permanent magnets of Comparative Examples 8 to 10, it was considered that the coercive force decreased because the B content in the permanent magnet was large. In the permanent magnet of Comparative Example 11, the amount of substitution of Y in the main phase increased and the anisotropy magnetic field Ha of the main phase decreased, so it is considered that the coercive force decreased.

From the results of the experimental group 2-4, it is considered that in each of the permanent magnets of Comparative Examples 5 and 12 to 14, the squareness ratio was low because the B content in the permanent magnet was small. In the permanent magnet of Comparative Example 15, the amount of substitution of Y in the main phase increased, the anisotropy magnetic field Ha of the main phase decreased, the coercive force decreased, and the content of B in the permanent magnet was small. It is considered that the R ₂ T ₁₇ phase could not be completely modified and the squareness ratio was low.

As shown in Table 3, the permanent magnet of Reference Example 1 had a coercive force of 12 kOe or more and a squareness ratio of 85% or more. In the permanent magnet of Reference Example 1, the squareness ratio did not decrease even when part of the rare earth element R was replaced with Ce. However, in the permanent magnet of Reference Example 1, since the Ce content in the permanent magnet is small, there is almost no effect of making the permanent magnet inexpensive. From the results of the experimental group 3, the permanent magnets each Comparative Example 4, and 16-19, the main phase of the liquid phase temperature is low, because it could not implement the liquid-phase sintering at a sufficiently high temperature, the R ₂ T ₁₇ phase It is considered that the squareness ratio was lowered because the main phase could not be modified.

From the results of the experimental group 4-1, the permanent magnet of Comparative Example 4 had a low liquidus temperature of the main phase and could not perform liquid phase sintering at a sufficiently high temperature, so the R ₂ T ₁₇ phase was the main phase. It is considered that the squareness ratio was lowered due to the inability to modify. In the permanent magnet of Comparative Example 20, the amount of substitution of Y in the main phase was increased, and the anisotropic magnetic field Ha of the main phase was decreased.

From the results of the experimental group 4-2, in each of the permanent magnets of Comparative Examples 19 and 21 to 24, the liquidus temperature of the main phase was low, and liquid phase sintering at a sufficiently high temperature could not be performed. Therefore, R ₂ T ₁₇ It is thought that the squareness ratio was lowered because the phase could not be reformed to the main phase.

As shown in Table 5, in each of the permanent magnets of Examples 11, 13 and 15, the squareness ratio was lower than that of each of the permanent magnets of Examples 4, 10, 12 and 14. From the results of the experimental group 5, in each of the permanent magnets of Examples 11, 13, and 15, the Y-OCN phase was precipitated in the grain boundary phase of the permanent magnet, and the amount of substitution of Y in the main phase was reduced. Sintering could not be performed at a sufficiently high temperature. As a result, it is considered that the R ₂ T ₁₇ phase could not be reformed to the main phase and the squareness ratio was lowered.

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 permanent magnet containing a rare earth element R, a transition metal element T, and boron B,
The rare earth element R includes at least Nd, Y and Ce;
The transition metal element T contains at least Fe;
The total content of the rare earth element R in the permanent magnet is [R] atomic%,
The total content of the transition metal element T in the permanent magnet is [T] atomic%,
The content of B in the permanent magnet is [B] atomic%,
The Y content in the permanent magnet is [Y] atomic%,
The Ce content in the permanent magnet is [Ce] atomic%,
[Y] / [R] is 0.05 to 0.25,
[Ce] / [R] is 0.10 to 0.55,
[T] / [B] is 14 to 18,
permanent magnet.
The content of C in the permanent magnet is 0.00 to 0.25% by mass;
The N content in the permanent magnet is 0.00 to 0.25% by mass;
The content of O in the permanent magnet is 0.00 to 0.25% by mass.
The permanent magnet according to claim 1.
A rotating machine comprising the permanent magnet according to claim 1 or 2.