JP2018174323A - Permanent magnet and rotary machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a permanent magnet high in flexural strength, and a rotary machine including the permanent magnet.SOLUTION: A permanent magnet 10 comprises: primary-phase grains 11 including a rare earth element R, a transition metal element T and a boron B; and grain boundary phases 9 located among the primary-phase grains 11, wherein R includes at least Nd and Ce; and T includes at least Fe. A total R content in the permanent magnet 10 is [R] atom%, a total T content in the permanent magnet 10 is [T] atom%, a B content in the permanent magnet 10 is [B]atom%, and a Ce content in the permanent magnet 10 is [Ce]atom%, [Ce]/[R] is 0.1-0.6, and [T]/[B] is 14-18. The grain boundary phases 9 comprise R-T phases 3 including an intermetallic compound of R and T. When the area of a unit section of the permanent magnet 10 is A, and the area of the R-T phases 3 in the unit section is Ain total, A/Ais 0.05-0.5.SELECTED DRAWING: Figure 2

Description

  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 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.

  In the future, it is expected that there will be an increasing demand for high-speed rotation of motors (rotating machines) using RTB permanent magnets. Due to the stress applied to the RTB permanent magnet during high-speed rotation of the motor, the RTB permanent magnet is easily cracked. Therefore, it is necessary to increase the bending strength of the RTB permanent magnet. For example, in Patent Document 1, the bending strength in the easy axis direction of a permanent magnet is increased by controlling the thickness of the grain boundary phase in the easy axis direction and the thickness of the grain boundary phase in the hard axis direction. It is described.

JP 2002-246215 A

  In order to increase the reliability at the time of high-speed rotation of the motor, it is required to further increase the bending strength of the permanent magnet.

  This invention is made | formed in view of the said situation, and it aims at providing a rotary machine provided with the permanent magnet with high bending strength, and the said 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 B, and a grain boundary phase positioned between the plurality of main phase particles. A permanent magnet, wherein the rare earth element R includes at least Nd and Ce, the transition metal element T includes at least Fe, and the total content of the rare earth element R in the permanent magnet is [R] atomic%, The total content of transition metal elements T in the magnet is [T] atomic%, the content of B in the permanent magnet is [B] atomic%, and the content of Ce in the permanent magnet is [Ce] atomic%. Yes, [Ce] / [R] is 0.1 to 0.6, [T] / [B] is 14 to 18, and the grain boundary phase is between the rare earth element R and the transition metal element T. The area of the unit cross section of the permanent magnet including the RT phase containing the compound is A ₀ , And the total area of the R-T phases in the unit cross section is _{A L, A L} / _{A 0} is 0.05 to 0.5.

  In the permanent magnet according to one aspect of the present invention, the element X may be at least one selected from the group consisting of Ga, Si, Sn, and Bi, and the total content of the elements X in the permanent magnet is 0. It may be from 0 to 0.4 atomic%.

  In the permanent magnet according to one aspect of the present invention, [Ce] / [R] may be 0.15 to 0.6.

  The Co content in the permanent magnet according to one aspect of the present invention may be 0.0 to 5.0 atomic%.

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

  ADVANTAGE OF THE INVENTION According to this invention, a rotating machine provided with a permanent magnet with high bending strength and the said permanent magnet is 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. 10 is a schematic diagram (a view taken in the direction of the line bb) 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 reflected electron image of a cross section of the permanent magnet of Example 1 taken with a field emission scanning electron microscope (FE-SEM). FIG. 4 is a perspective view schematically showing a rotating machine according to an embodiment of the present invention. FIG. 5 is a diagram showing a relationship between A _L / A ₀ and bending strength of each of experimental groups 1 to 3. FIG. 6 is a diagram showing the relationship between [Ce] / [R] and bending strength of Experimental Group 1. FIG. 7 is a diagram showing the relationship between [T] / [B] and bending strength of Experimental Group 2.

  In the following, 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 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 particle 11 contains 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). 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 Ce content in the permanent magnet 10 is expressed as [Ce] atomic%. [Ce] / [R] is 0.1 to 0.6. [T] / [B] is 14-18.

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. Area of the unit section of the permanent magnet 10 is represented as A _0. Total area of the R-T phase 3 in the unit section is represented as A _L. A _L / A ₀ is 0.05 to 0.5.

The present inventors consider that the reason why the bending strength of the permanent magnet 10 is high is as follows. When [Ce] / [R] is 0.1 to 0.6 and [T] / [B] is 14 to 18, the RT phase 3 is easily generated in the grain boundary phase. RT phase 3 has high toughness. In the permanent magnet 10, A _L / A ₀ is 0.05 or more and the content of the RT phase 3 is large, so that a high bending strength can be obtained. The reason why the bending strength of the permanent magnet 10 is high 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 (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 expressed 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 X phase, and the like. The element X may be at least one selected from the group consisting of Ga, Si, Sn, and Bi. The definitions of the RT phase 3, the R-rich phase 5, the heterogeneous phase 7, and the R ₆ T ₁₃ X 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 X in the RT phase 3 is expressed as [X] _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 ≦ [X] _L / ([R] _L + [T] _L + [X] _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 °. 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 X phase is expressed as [C] _A atomic%. The N content in the R ₆ T ₁₃ X phase is expressed as [N] _A atomic%. The content of O in the R ₆ T ₁₃ M phase is expressed as [O] _A atomic%. The total content of rare earth elements R in the R ₆ T ₁₃ X phase is expressed as [R] _A atomic%. The total content of the transition metal element T in the R ₆ T ₁₃ X phase is expressed as [T] _A atomic%. The total content of the element X in the R ₆ T ₁₃ X phase is expressed as [X] _A atomic%. The R ₆ T ₁₃ X 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 <[X] _A / ([R] _A + [T] _A + [X] _A ) ≦ 1.00 (9)

A _L / A ₀ may be 0.05 to 0.5, or 0.1 to 0.25. When A _L / A ₀ is within the above range, the bending strength of the permanent magnet 10 is likely to be high, and the residual magnetic flux density Br of the permanent magnet 10 is likely to be high.

A _L / A ₀ may be determined by the following method, for example. The cross section of the permanent magnet 10 is polished using polishing paper, buffs, diamond abrasive grains, or the like. The polished cross section is subjected to ion milling to remove oxide film, nitride film and the like on the cross section. The cross section after the ion milling process is photographed using an FE-SEM, and a reflected electron image of the cross section of the permanent magnet 10 is obtained. In the reflected electron image, the region where the content of the rare earth element R is high appears white, and the region where the content of the rare earth element R is low appears black. For example, FIG. 3 is a reflected electron image of a cross section of the permanent magnet 10 of Example 1 taken with an FE-SEM. In FIG. 3, the main phase particles 11 appear black. R-rich phase 5 appears white. RT phase 3 appears gray. That is, the radiation efficiency of the reflected electrons in the RT phase 3 is an intermediate value between the radiation efficiency of the reflected electrons in the main phase particle 11 and the radiation efficiency of the reflected electrons in the R-rich phase 5. A predetermined region in the reflected electron image is defined as a unit cross section. The dimension of the unit cross section may be, for example, 50 μm × 50 μm. The unit cross section is subjected to point analysis using an energy dispersive X-ray spectrometer (EDS) attached to the FE-SEM to confirm that the gray region in the unit cross section is the RT phase 3. In the gray region of the reflected electron image, the ratio of the content of the rare earth element R and the content of the transition metal element T may be 1: 2. Only the RT phase 3 is extracted by providing a threshold value for the density of the reflected electron image. The image analysis method, and the area A ₀ of the unit cross section, and the area A _L of R-T phase 3 is calculated in the unit section. A _L / A ₀ is obtained from A ₀ and A _L.

  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. [R] may be 11.0 to 18.0 atomic%. The Nd content [Nd] in the permanent magnet 10 may be 4.4 to 16.2 atomic%, or 6.2 to 14.0 atomic%. [Ce] may be 1.1 to 10.8 atomic%, or 1.6 to 9.3 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 76.5-84.3 atomic%. The Fe content [Fe] in the permanent magnet 10 may be 71.5 to 84.3 atomic%, or 77.3 to 79.3 atomic%. The Co content [Co] in the permanent magnet 10 may be 0.0 to 5.0 atomic% or 0.0 to 0.5 atomic%. When [Co] is 5.0 atomic% or less, since the main transition metal element T in the RT phase 3 is Fe, the RT phase 3 tends to have high toughness, and the permanent magnet 10 The bending strength is likely to increase. As [Co] is smaller, the RT phase 3 tends to have higher toughness, and the bending strength of the permanent magnet 10 is likely to increase. On the other hand, when [Co] exceeds 5.0 atomic%, the main transition metal element T in the RT phase 3 tends to be Co, the toughness of the RT phase 3 is reduced, and the resistance of the permanent magnet 10 is reduced. Folding strength tends to decrease.

  [B] may be 4.32 to 5.93 atomic%, or 4.4 to 5.6 atomic%.

  [Ce] / [R] may be 0.1 to 0.6, 0.15 to 0.6, or 0.15 to 0.30. When [Ce] / [R] is within the above range, the bending strength of the permanent magnet 10 tends to be high.

  [T] / [B] may be 14.0 to 18.0, or 15.5 to 17.0. When [T] / [B] is within the above range, the formation of the RT phase 3 is promoted and the bending strength of the permanent magnet 10 is likely to be increased.

  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 element X may be at least one selected from the group consisting of Ga, Si, Sn, and Bi. The total content [X] of the element X in the permanent magnet 10 may be 0.0 to 0.4 atomic%, 0.0 to 0.2 atomic%, or 0.0 to 0.1 atomic%. . When [X] is 0.4 atomic% or more, the R rich phase mainly composed of Nd is easily reformed to the R ₆ T ₁₃ X phase. The hardness of the R ₆ T ₁₃ X phase is high. As a result, the hardness of the grain boundary phase of the permanent magnet 10 is increased, and when the permanent magnet 10 is processed into a predetermined shape, a part of the permanent magnet 10 is chipped and chipped (fragment, fragment) from the permanent magnet 10. ) Is likely to occur. When [X] is within the above range, the R-rich phase is difficult to be reformed to the R ₆ T ₁₃ X phase having a high hardness, so that when the permanent magnet 10 is processed into a predetermined shape, Is unlikely to occur.

  The composition of the permanent magnet 10 includes: 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.

(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.

  A 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, or 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.

  The raw material alloy obtained by the above melting and rapid cooling is pulverized 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 alloy is occluded with 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 400-600 ° C. The dehydrogenation time may be 0.5 to 20 hours.

  The coarse powder is pulverized to obtain a 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 or the like. The particle size of the fine powder may be, for example, 0.5 to 10 μm.

  The fine powder is put into a molding space (cavity) of a molding machine, and the fine powder is pressurized 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 to 1600 kA / m. The pressure applied to the fine powder may be, for example, 10 to 500 MPa.

  The molded body is sintered to obtain a sintered body. The sintering temperature may be 900 to 960 ° C., for example. The sintering time may be, for example, 10 to 50 hours. The green body may be sintered in a reduced pressure atmosphere, an inert atmosphere, or the like. When the sintering temperature and time are within the above ranges, Ce contained in the main phase particles 11 is easily released to the grain boundary phase 9 during the liquid phase sintering, and the RT phase 3 is added to the grain boundary phase 9. Is easy to generate. On the other hand, when sintered at a high sintering temperature (for example, 1000 ° C. or higher), the ratio of coarse particles in the main phase is likely to increase, and the amount of RT phase 3 is likely to decrease. The bending strength of the permanent magnet tends to decrease.

  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 an aging treatment may be 450-950 degreeC, 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 (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.

  As mentioned above, although preferred embodiment of this invention was described, this invention is not necessarily limited to embodiment mentioned above. 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, Co, FeB, 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 14.0 atomic% Nd-1.6 atomic% Ce-78.1 atomic% Fe-0.5 atomic% Co-5.6 atomic% B-0.2 atomic% Al-0.1 Each starting material was weighed and mixed so as to be atomic% Cu to prepare a mixed 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.

  A 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 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 molded body was sintered to obtain a sintered body. The sintering temperature was 960 ° C. The sintering time was 16 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, and the permanent magnet of Example 1 was obtained. The temperature of the aging treatment was 700 ° C. The time for aging treatment was 1 hour.

[Analysis of composition]
The contents (unit: atomic%) of Nd, Ce, Fe, Co, Al, and Cu in the permanent magnet of Example 1 were measured by X-ray fluorescence analysis. The B content (unit: atomic%) in the permanent magnet of Example 1 was measured by ICP emission analysis. The content [Nd] of Nd and the content [Ce] of Ce were totaled to obtain the total content [R] of the rare earth element R. The Fe content [Fe] and the Co content [Co] were totaled to obtain the total content [T] of the transition metal element T. [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. The results are shown in Table 1. At% in the following table means atomic%. TRE means [R].

[ _AL / _A0 ]
The permanent magnet of Example 1 was cut. The permanent magnet after cutting was embedded in an epoxy resin so that the cut surface was exposed. The permanent magnet was polished while changing the count of the abrasive paper from low to high. Each abrasive paper was a commercially available abrasive paper. Finally, the cross section of the permanent magnet was polished using a buff and diamond abrasive grains. In polishing using buffs and diamond abrasive grains, no liquid such as water was used in order to avoid corrosion of grain boundary phase components.

Ion milling was performed on the cross section of the polished permanent magnet to remove the oxide film and nitride film on the cross section. Then, the backscattered electron image of the cross section of a permanent magnet was image | photographed using FE-SEM. FIG. 3 shows a reflected electron image of a cross section of the permanent magnet of Example 1 taken with an FE-SEM. Based on the contrast of the reflected electron image, it was confirmed that the unit cross section in the reflected electron image contained a plurality of grain boundary phase components. The dimension of the unit cross section was 50 μm × 50 μm. Point analysis by EDS was performed on the unit cross section. In the point analysis by EDS, the element of the starting material used for the production of the raw material alloy was the object of analysis. From the ratio of R and T calculated by point analysis by EDS, it was confirmed that the RT phase (RT ₂ phase) was included in the grain boundary phase in the unit cross section.

The RT phase (RT ₂ phase) in the unit cross section was extracted by providing a threshold value in the shade of the reflected electron image. The image analysis method, and the area A ₀ of the unit cross section was determined area A _L of R-T phase in a unit cross section. A _L / A ₀ was determined from A ₀ and A _L. The results are shown in Table 1.

[Folding strength]
The permanent magnet of Example 1 was processed to obtain 10 samples for measurement. The shape of each sample was a rectangular parallelepiped. The size of each sample was 16.0 mm × 4.5 mm × thickness 2.0 mm. The thickness direction of each sample coincided with the magnetic field anisotropy direction. Each sample is not subjected to surface treatment. The bending strength test was individually performed for each sample. In the bending strength test, a three-point bending test was performed using a universal testing machine. In the three-point bending test, a bending strength (unit: MPa) was measured by applying a load in the thickness direction at the center of the surface of the sample. The measurement conditions were as follows. The average value of the bending strength of 10 samples was determined. The results are shown in Table 1. The bending strength is preferably 350 MPa or more, and more preferably 400 MPa or more.
Load II (load): 500kgf
Loaded speed: 0.5 mm / min or less Distance between fulcrums: 15 mm

[Free drop test]
The permanent magnet of Example 1 was processed by inner peripheral edge processing to obtain ten test samples. The size of each sample was 10.0 mm × 10.0 mm × 10.0 mm. The mass M ₀ of each sample before the test was measured. Each sample was individually dropped from a height of 1000 mm and collided with a flat concrete surface. The mass M ₁ of each sample after the test was measured. The mass change 100 × (M ₀ -M ₁ ) / M ₀ (unit:%) of each sample was determined. Table 1 shows the number of samples in which 100 × (M ₀ −M ₁ ) / M ₀ was 0.1 or less.

(Examples 2-19, Comparative Examples 1-5)
Each starting material of each of Examples 2 to 19 and Comparative Examples 1 to 5 was weighed so that the composition of the permanent magnet was as shown in Tables 1 to 4. According to the following procedure, the sintered body appropriately sintered (the sintered bodies of Examples 2 to 19 and Comparative Examples 1 to 5) was 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 900 ° C. to 960 ° 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, permanent magnets of Examples 2 to 19 and Comparative Examples 1 to 5 were individually manufactured by the same method as in Example 1. In Examples 7 to 19, Ga, Si, Sn, or Bi was further used as a starting material (single or alloy).

  By the same method as Example 1, the composition of each permanent magnet of Examples 2-19 and Comparative Examples 1-5 was analyzed. The elements used for the starting material were analyzed. The results are shown in Tables 1-4.

By the same method as Example 1, A _L / A ₀ of each of the permanent magnets of Examples 2 to 19 and Comparative Examples 1 to 5 was measured. The results are shown in Tables 1-4.

  By the same method as Example 1, the bending strength of each permanent magnet of Examples 2-19 and Comparative Examples 1-5 was measured. The results are shown in Tables 1-4.

  By the method similar to Example 1, the free drop test of each of Examples 2 to 19 and Comparative Examples 1 to 5 was performed. The results are shown in Tables 1-4.

FIG. 5 shows the relationship between A _L / A ₀ and bending strength of each of experimental groups 1 to 3 shown in Tables 1 to 3. FIG. 6 shows the relationship between [Ce] / [R] and bending strength of Experimental Group 1. FIG. 7 shows the relationship between [T] / [B] and bending strength of Experimental Group 2.

  As shown in Tables 1 to 4, the bending strengths of all examples were 350 MPa or more. On the other hand, there was no comparative example having a bending strength of 350 MPa or more. According to the present invention, it has been confirmed that a permanent magnet having high bending strength is provided.

  In Comparative Example 1, since the RT phase was not generated, it is considered that the bending strength was low.

  In Comparative Example 2, it was considered that the bending strength was low because the amount of RT phase produced was small.

  In Comparative Example 3, since the amount of Ce was large, a large amount of Ce-rich R-rich phase was generated, the generation rate of RT phase was decreased, and the bending strength was considered to be reduced.

  In Comparative Example 4, since the content of B in the permanent magnet was large, the production amount of the RT phase as the grain boundary phase was small. Therefore, it is considered that the bending strength was low.

In Comparative Example 5, it is considered that R ₂ T ₁₇ phase particles containing more transition metal element T than the RT phase (RT ₂ phase) became the starting point of cracking, and the bending strength was low.

In Examples 7 to 16, when the permanent magnet contained the element X, a part of the R-rich phase mainly composed of Nd was easily reformed to the R ₆ T ₁₃ X phase. As a result, it is considered that the hardness of the grain boundary phase is increased, and there is a tendency that chipping easily occurs in the free drop test. On the other hand, even if the permanent magnet contains the element X, the RT phase (RT ₂ phase) is not modified, so that A _L / A ₀ is considered not to change. Therefore, even if the permanent magnet contains the element X, it is considered that the bending strength of the permanent magnet does not decrease.

  The permanent magnet according to the present invention is used in, for example, 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 ... Cross section of permanent magnet, 11 ... Main phase particle, 30 ... Stator, 32 ... Coil 52 ... Core, 200 ... Rotating machine.

Claims (5)

A plurality of main phase particles containing a rare earth element R, a transition metal element T, and boron B;
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 Nd 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 Ce content in the permanent magnet is [Ce] atomic%,
[Ce] / [R] is 0.1 to 0.6,
[T] / [B] is 14-18,
The grain boundary phase includes an RT phase containing an intermetallic compound of the rare earth element R and the transition metal element T;
Area of the unit section of the permanent magnet is A _0,
Total area of the R-T phase in said unit cross section is A _L,
A _L / A ₀ is 0.05 to 0.5,
permanent magnet. The element X is at least one selected from the group consisting of Ga, Si, Sn, and Bi;
The total content of the element X in the permanent magnet is 0.0 to 0.4 atomic%.
The permanent magnet according to claim 1. [Ce] / [R] is 0.15 to 0.6.
The permanent magnet according to claim 1 or 2. The Co content in the permanent magnet is 0.0 to 5.0 atomic%.
The permanent magnet as described in any one of Claims 1-3.   A rotating machine provided with the permanent magnet as described in any one of Claims 1-4.