Permanent magnets, rotating electrical machines, vehicles, and aircraft

Abstract

To provide a permanent magnet that achieves both high remnant magnetization and coercive force at a high temperature, and a rotatory electric machine, a vehicle and an aircraft using the permanent magnet.SOLUTION: According to an embodiment, a permanent magnet is provided that comprises: a composition represented by a compositional formula: RpFeqMrCutCo100-p-q-r-t (in the formula, R denotes one element selected from rare earth elements, M denotes one element selected from Zr, Ti, and Hf, p denotes a number that satisfies 10.0 atom%≤p≤14.5 atom%, r denotes a number that satisfies 1.5 atom%≤r≤4.2 atom%, t denotes a number that satisfies 0.5 atom%≤t≤9.0 atom%, q denotes a number that satisfies 17 atom%≤q≤26 atom%); and a metallographic structure that includes a cell phase having a Th2Zn17 type crystal phase, a cell wall phase formed so as to demarcate the Th2Zn17 type crystal phase, and a platelet phase formed so as to intersect an axis c of the Th2Zn17 type crystal phase, a mean distance between platelet phases being 10 nm to 30 nm inclusive.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a permanent magnet, a rotating electric machine, a vehicle, and an aircraft. [Background technology]

[0002] Permanent magnets are used in a wide range of products, including rotating electrical machines such as motors and generators, electrical equipment such as speakers and measuring instruments, and vehicles such as automobiles and railway cars. In particular, in recent years, the electrification of various mobile objects such as automobiles, aircraft, and ships has progressed, and the drive motors used in these vehicles are required to be smaller, lighter, and have higher output. Aiming to reduce size and weight while maintaining high output increases the heat density, making the motor more susceptible to temperature increases. In particular, when permanent magnets become too hot, thermal demagnetization occurs, resulting in a decrease in motor output. Therefore, in order to achieve both smaller, lighter, and higher output motors, it is necessary to improve the heat resistance of permanent magnets and suppress thermal demagnetization.

[0003] Known examples of high-performance permanent magnets include rare earth magnets such as Sm-Co magnets and Nd-Fe-B magnets. For example, permanent magnets are used in which part of the Nd in Nd-Fe-B magnets is replaced with Dy to improve heat resistance. As Dy is a rare element, there is a demand for permanent magnets that do not use Dy. Sm-Co magnets have a high Curie temperature, so they are known to exhibit excellent heat resistance even in systems that do not use Dy. Sm-Co magnets are attracting attention as permanent magnets that can achieve good motor characteristics at high temperatures.

[0004] Increasing the magnetic flux density of permanent magnets is an effective way to increase motor output. In Sm-Co magnets, replacing some of the Co with Fe and increasing the Fe concentration are effective ways to increase the magnetic flux density. However, in composition regions with high Fe concentrations, the coercive force decreases, making them susceptible to thermal demagnetization. Therefore, there is a need for permanent magnets that combine high magnetic flux density and high coercive force. Thermal demagnetization is likely to occur at high temperatures, for example, above 200°C. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5586648 specification Summary of the Invention [Problem to be solved by the invention]

[0006] The problem to be solved by the present invention is to provide a permanent magnet that achieves both high residual magnetization and high coercive force at high temperatures, and a rotating electric machine, vehicle, and aircraft that use such a permanent magnet. [Means for solving the problem]

[0007] The permanent magnet of this embodiment has a composition represented by the formula: RpFeqMrCutCo100-pqrt (wherein R is at least one element selected from rare earth elements, M is at least one element selected from Zr, Ti, and Hf, p is a number satisfying 10.0 atomic %≦p≦14.5 atomic %, r is a number satisfying 1.5 atomic %≦r≦4.2 atomic %, t is a number satisfying 0.5 atomic %≦t≦9.0 atomic %, and q is a number satisfying 17 atomic %≦q≦26 atomic %), a cell phase having a Th2Zn17-type crystal phase, a cell wall phase formed so as to separate the Th2Zn17-type crystal phase, and a phase formed so as to intersect with the c-axis of the Th2Zn17-type crystal phase. , the concentration of element M is high in the cell phase The permanent magnet has a metal structure including a platelet phase, and the average distance between the platelet phases is 10 nm or more and 30 nm or less. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 3 is a cross-sectional view schematically showing a part of a cross section of a sintered body. [Figure 2] FIG. 2 is a diagram showing a method for measuring the distance between platelet phases in a sintered body. [Figure 3] FIG. 1 is a cross-sectional view showing a permanent magnet motor. [Figure 4] FIG. 1 is a schematic diagram showing a part of a cross section of a permanent magnet motor. [Figure 5]Schematic diagram showing a generator. [Figure 6] FIG. 1 is a schematic diagram showing an example of a railway vehicle. [Figure 7] FIG. 1 is a schematic diagram showing an example of an automobile. [Figure 8] FIG. 1 is a schematic diagram showing an example of an aircraft. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments will be described with reference to the drawings. Note that the drawings are schematic, and for example, the relationship between thickness and planar dimensions, the thickness ratio of each layer, etc. may differ from the actual. Furthermore, in the embodiments, substantially identical components are assigned the same reference numerals, and descriptions thereof will be omitted.

[0010] (First embodiment) The permanent magnet of this embodiment has a composition represented by the composition formula: RpFeqMrCutCo100-pqrt (wherein R is at least one element selected from rare earth elements, M is at least one element selected from Zr, Ti, and Hf, p is a number satisfying 10.0 atomic %≦p≦14.5 atomic %, r is a number satisfying 1.5 atomic %≦r≦5.0 atomic %, t is a number satisfying 0.5 atomic %≦t≦9.0 atomic %, and q is a number satisfying 17 atomic %≦q≦26 atomic %), a cell phase having a Th2Zn17-type crystal phase, a cell wall phase formed so as to separate the Th2Zn17-type crystal phase, and a phase formed so as to intersect with the c-axis of the Th2Zn17-type crystal phase. , the concentration of element M is high in the cell phase The permanent magnet has a metal structure including a platelet phase, and the average distance between the platelet phases is 10 nm or more and 30 nm or less.

[0011] The R element provides a permanent magnet with large magnetic anisotropy and high coercivity. One or more rare earth elements are used as the R element. It is more preferable to use at least one element selected from yttrium (Y), samarium (Sm), cerium (Ce), neodymium (Nd), and praseodymium (Pr), with Sm being particularly preferable. By making 50 atomic % or more of the R element Sm, the performance of the permanent magnet, particularly the coercivity, can be improved with good reproducibility. Furthermore, it is more preferable that 70 atomic % or more, and even 90 atomic % or more of the R element be Sm.

[0012] The content of R element is, for example, the composition formula: R p Fe q M r Cu t Co 100-p-q-r-t In this case, the number p satisfies 10.0 atomic %≦p≦14.5 atomic %. If the content of the R element is less than 10.0 atomic %, a large amount of α-Fe phase precipitates in the permanent magnet, making it impossible to obtain sufficient coercivity. On the other hand, if the content of the R element exceeds 14.5 atomic %, the saturation magnetization decreases significantly. The content of the R element is preferably 10.3 atomic % to 14 atomic %, and more preferably 10.5 atomic % to 13.5 atomic %.

[0013] The M element is at least one element selected from titanium (Ti), zirconium (Zr), and hafnium (Hf). By incorporating the M element, it is possible to develop a large coercive force even when using a composition with a high Fe concentration. The content of the M element can be determined, for example, by the composition formula: R p Fe q M r Cu t Co 100-p-q-r-tIn the formula, r is a number satisfying 1.5 atomic %≦r≦4.2 atomic %. If the content r of the M element is less than 1.5 atomic %, the effect of increasing the coercive force is small, and if r exceeds 4.2 atomic %, a phase containing an excess of the M element is generated, which tends to deteriorate the magnetic properties. The content of the M element is preferably 1.6 atomic % to 4.1 atomic %, more preferably 1.7 atomic % to 4.0 atomic %, even more preferably 2.0 atomic % to 3.9 atomic %, and even more preferably 2.5 atomic % to 3.8 atomic %.

[0014] The M element may be any of Ti, Zr, and Hf, but preferably contains at least Zr. In other words, the M element is preferably Zr alone, or a combination of three elements: Zr and Ti, Zr and Hf, and Zr, or Ti and Hf. In particular, by making 50 atomic % or more of the M element Zr, the effect of increasing the coercive force of the permanent magnet can be further improved. On the other hand, since Hf is particularly expensive among the M elements, it is preferable to use a small amount of Hf, even when using Hf.

[0015] Copper (Cu) gives permanent magnets high coercivity. The Cu content is determined by the composition formula R p Fe q M r Cu t Co 100-p-q-r-t In this case, 0.5 atomic %≦t≦9.0 atomic %. Because Cu is a non-magnetic element, if the Cu content exceeds 9.0 atomic %, the magnetization decreases significantly. On the other hand, if the Cu content is less than 0.5 atomic %, it becomes difficult to obtain high coercivity. The Cu content is preferably 0.6 atomic % to 8.9 atomic %, more preferably 0.7 atomic % to 8.8 atomic %, more preferably 0.8 atomic % to 8.7 atomic %, more preferably 0.9 atomic % to 8.6 atomic %, and even more preferably 1.0 atomic % to 8.5 atomic %.

[0016] Iron (Fe) is primarily responsible for the magnetization of permanent magnets. By including a large amount of Fe, the saturation magnetization of permanent magnets can be increased. However, if the Fe content is too high, the coercive force decreases due to factors such as the inability to form an appropriate cellular structure. The Fe content is determined by the composition formula R p Fe q M r Cu t Co 100-p-q-r-t In this case, q is a number that satisfies 17 atomic %≦q≦26 atomic %. The Fe content is more preferably 17.5 atomic % to 25.8 atomic % both inclusive, more preferably 18 atomic % to 25.6 atomic % both inclusive, even more preferably 18.5 atomic % to 25.4 atomic % both inclusive, still more preferably 19.0 atomic % to 25.2 atomic % both inclusive, even more preferably 19.5 atomic % to 25 atomic % both inclusive, and still more preferably 20 atomic % to 24.8 atomic % both inclusive.

[0017] Cobalt (Co) is responsible for the magnetization of permanent magnets and is an element necessary for developing high coercive force. Furthermore, a high Co content increases the Curie temperature and improves the thermal stability of the permanent magnet. These effects are reduced if the Co content is low. However, if a permanent magnet contains too much Co, the Fe content decreases relatively, which may result in a decrease in magnetization. The Co content is within the range defined by p, q, r, and t (100-pqrt).

[0018] A portion of Co may be substituted with at least one element A selected from nickel (Ni), vanadium (V), chromium (Cr), manganese (Mn), aluminum (Al), silicon (Si), gallium (Ga), niobium (Nb), tantalum (Ta), and tungsten (W). These substitution elements contribute to improving magnetic properties, such as coercivity. p Fe q M r Cu t Co 100-p-q-r-tIn the above, 20% or less of the atomic % of Co can be substituted with the above-mentioned element A. If more than 20% of the atomic % of Co is substituted with element A, excessive substitution of Co with element A may result in a decrease in magnetization.

[0019] The composition of a permanent magnet can be measured by, for example, inductively coupled plasma (ICP) optical emission spectroscopy, scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX), transmission electron microscope-energy dispersive X-ray spectroscopy (TEM-EDX), scanning transmission electron microscope-energy dispersive X-ray spectroscopy (STEM-EDX), etc. To measure the composition of a permanent magnet, it is sufficient to select and carry out one of these methods. The composition of a permanent magnet obtained by these measurement methods means the average composition of the entire permanent magnet.

[0020] 1 is a cross-sectional view showing a part of a cross section of a permanent magnet. The permanent magnet of this embodiment uses a high-temperature phase, TbCu7-type crystalline phase (a crystalline phase having a TbCu7-type structure, hereinafter referred to as the 1-7 phase), as a precursor, and is formed by aging treatment or the like to form a phase-separated structure, namely, Th2Zn 17 The cell phase 50 having the above-mentioned Th2Zn 17 The cell wall phase 51 formed to separate the crystalline phase and the Th2Zn 17 The metal structure includes a platelet phase 52 formed so as to intersect with the c-axis of the crystalline phase. The platelet phase 52 is a Th2Zn 17It is preferable that the cell wall phase 51 intersects perpendicularly with the c-axis of the 2-17 type crystal phase, and in this case, "perpendicular" may also include a state within ±10 degrees from the perpendicular direction (approximately perpendicular). Each phase is also characterized in terms of composition, with the cell wall phase 51 having a higher Cu concentration than the cell phase 50 (main phase), and the platelet phase 52 having a higher concentration of element M, such as Zr, than the cell phase 50 (main phase). Note that the metal structure of the permanent magnet may include crystalline phases and amorphous phases other than the cell phase 50 consisting of the 2-17 phase, the cell wall phase 51, and the platelet phase 52.

[0021] The cell wall phase 51 may be, for example, a 1-5 phase, but is not necessarily limited to this. Examples of the cell wall phase 51 other than the 1-5 phase include the 1-7 phase, which is a high-temperature phase (a structure before phase separation), and a precursor phase of the 1-5 phase that occurs in the early stage of phase separation of the 1-7 phase.

[0022] The platelet phase 52 is a plate-like phase containing the M element that exists across the crystal grains composed of the cell phase 50 and the cell wall phase 51, and exists perpendicular to the c-axis direction of the cell phase 50. Therefore, the platelet phases 52 are observed parallel to each other within one observation field.

[0023] Each phase of the metal structure is comprehensively determined by, for example, a combination of observation using an electron microscope and electron diffraction analysis, X-ray diffraction analysis, etc. For example, by combining a STEM observation image with an element mapping image obtained by STEM-EDX, the cell phase 50, the cell wall phase 51, and the platelet phase 52 can be identified.

[0024] The domain wall energy of the cell wall phase precipitated at the grain boundaries of the cell phase is larger than that of the cell phase itself, and this difference in domain wall energy acts as a barrier to domain wall motion. 17 In this type of magnet, the cell wall phase with large domain wall energy acts as a pinning site, which is thought to be the reason for the domain wall pinning type coercivity. Here, the difference in domain wall energy is mainly caused by the difference in Cu concentration.

[0025] Here, for example, if a Cu concentration distribution occurs in the cell wall phase, resulting in a cell wall phase with a large domain wall pinning effect and a cell wall phase with a small domain wall pinning effect, the coercivity will decrease. Therefore, it is desirable that the Cu concentration difference between the cell phase and the cell wall phase is large and that the Cu concentration distribution in the cell wall phase is small.

[0026] The difference in Cu concentration between the cell phase and the cell wall phase occurs when the TbCu7-type crystal phase separates into the cell phase, cell wall phase, and platelet phase, and Cu diffuses between the cell phase and the cell wall phase through the platelet phase. Therefore, when the platelet phase is densely formed, for example, the difference in Cu concentration between the cell phase and the cell wall phase is large, and the Cu concentration distribution within the cell wall phase is narrow, resulting in improved coercivity.

[0027] The concentration of Cu element contained in the cell wall phase is preferably 5 to 25 times the concentration of Cu element contained in the cell phase, more preferably 8 to 22 times, and even more preferably 10 to 20 times. If the Cu concentration in the cell wall phase is less than 5 times the Cu concentration in the cell phase, the effect of increasing the coercive force is weak. If it exceeds 25 times, it becomes difficult to maintain a stable crystal structure.

[0028] The Cu concentration in the cell wall phase and cell phase can be measured, for example, by compositional analysis using STEM-EDX, TEM-EDX, or a three-dimensional atom probe. For example, STEM-EDX is used to observe an area of ​​800 nm × 1200 nm to 900 μm × 1300 μm at 100kx magnification. The acceleration voltage is preferably 200 kV. The cell wall phase and cell phase are identified in the observation image by STEM-EDX, and the composition is measured at 10 or more arbitrary locations for each. The Cu concentration in the cell wall phase and cell phase in a single observation image is calculated by averaging the results. Observation is performed at 10 or more non-overlapping locations, and the average value is calculated by excluding the maximum and minimum values ​​of the average composition calculated for each image. This value is used as the average Cu concentration in the cell wall phase and cell phase. For the cross section of the permanent magnet, the sample cross section is divided into three equal parts in the vertical and horizontal directions, and the center portions in both the vertical and horizontal directions are used.

[0029] The average distance between the platelet phases is, for example, 10 nm or more and 30 nm or less. If the average distance between the platelet phases exceeds 30 nm, the platelet phases are sparsely present within the permanent magnet, increasing the proportion of the cell wall phase with a low Cu concentration and resulting in a decrease in coercivity. If the average distance between the platelet phases is less than 10 nm, the platelet phases are densely present within the permanent magnet, reducing the proportion of the cell phase and cell wall phase present in the permanent magnet and significantly reducing magnetization. The average distance between the platelet phases is preferably 12 nm or more and 28 nm or less, more preferably 15 nm or more and 27 nm or less, and even more preferably 20 nm or more and 26 nm or less.

[0030] <Method for measuring the average distance between platelet phases> The average distance between the platelet phases is measured from a structural observation image of the cross section of the permanent magnet using, for example, STEM, transmission electron microscope (TEM), or three-dimensional atom probe. The cross section of the permanent magnet is taken from substantially the center of the surface having the largest area of ​​the sample. With STEM, for example, a region of 800 nm × 1200 nm to 900 μm × 1300 μm is observed at a magnification of 100k. The acceleration voltage is preferably 200 kV. The width direction of the STEM image is perpendicular to the platelet phase, i.e., the same direction as the c-axis. Note that "perpendicular" may also include a state within ±10 degrees of the perpendicular direction (approximately perpendicular).

[0031] Here, we will explain the method for measuring the average distance between platelet phases using Figure 2. In the observed STEM image, the area is divided into six equal parts along the a-axis or b-axis, and five lines of the same length as the c-axis direction of the STEM image are drawn at equal intervals. The intersections of the aforementioned c-axis lines and the platelet phases are counted. For example, in Figure 2, the leftmost line in the image has 13 intersections. The average distance between the platelet phases for each of these lines is calculated by dividing the length of the c-axis direction of the STEM image by the intersection point (c-axis length of the STEM image / intersection point). The distances between the platelet phases along the five lines are then averaged to obtain the average distance between the platelet phases in a single observation image. Observations are performed at 10 or more non-overlapping locations, and the maximum and minimum values ​​of the calculated average distances are subtracted from each other to calculate the average distance between the platelet phases. This value is used as the average distance between the platelet phases.

[0032] <Methods for measuring magnetic properties such as coercive force and residual magnetization of permanent magnets> The magnetic properties of permanent magnets, such as coercive force and residual magnetization, are calculated using, for example, a DC magnetometer (BH tracer) or a vibrating sample magnetometer (VSM). The measurement temperature can be controlled by incorporating a heating mechanism such as a heater or by incorporating a thermostatic bath.

[0033] Next, an example of a method for manufacturing a permanent magnet will be described.

[0034] <Manufacturing method of permanent magnets> First, an alloy powder containing the predetermined elements necessary for synthesizing a permanent magnet is prepared. For example, the alloy powder can be prepared by pulverizing an alloy ingot obtained by casting a molten metal by arc melting or high-frequency melting. The alloy powder may also be prepared by mixing multiple powders with different compositions to obtain the desired composition.

[0035] Other examples of alloy powder preparation methods include mechanical alloying, mechanical grinding, gas atomization, and reduction-diffusion. The strip casting method can improve the uniformity of the alloy powder. Furthermore, the alloy powder or the alloy material before pulverization can be heat-treated to homogenize the material. For example, the material can be pulverized using a jet mill, a ball mill, or the like. Furthermore, pulverizing the material in an inert gas atmosphere or an organic solvent can prevent oxidation of the powder.

[0036] The average particle size of the powder after pulverization is preferably 1 μm or more and 10 μm or less. The average particle size of the powder after pulverization is more preferably 3 μm or more and 8 μm or less, and even more preferably 4 μm or more and 7 μm or less. By making the proportion of particles with a particle size of 1 μm or less 1% by volume or less, the amount of oxides can be suppressed. By making the proportion of particles with a particle size of 10 μm or more 2% by volume or less, the porosity of the sintered body produced after sintering is reduced, and sufficient density can be achieved.

[0037] The average particle size of a powder is defined as the particle size (median diameter: d50) at which the cumulative distribution is 50% in the particle size distribution measured by laser diffraction, etc. A jet mill is suitable for producing such powder.

[0038] Next, the above-mentioned green compact is sintered by heat treatment at 1180°C to 1250°C for 0.5 to 15 hours. If the heat treatment temperature is less than 1180°C, the sintered compact will not be sufficiently densified. If the heat treatment temperature is more than 1250°C, the R elements such as Sm in the powder will evaporate excessively, resulting in a deterioration in magnetic properties. The heat treatment temperature is preferably, for example, 1180°C to 1220°C, and more preferably, 1190°C to 1210°C.

[0039] If the heat treatment time is less than 0.5 hours, the sintered body will not be sufficiently densified. If the heat treatment time exceeds 15 hours, the R element in the powder will evaporate excessively, resulting in a deterioration of magnetic properties. The heat treatment time is preferably 1 hour to 10 hours, and more preferably 1 hour to 7 hours. In the sintering process, the heat treatment is preferably performed in a vacuum or in an inert atmosphere such as argon gas to suppress oxidation.

[0040] The obtained sintered body is subjected to solution heat treatment, followed by rapid cooling. By performing solution heat treatment, the precursor phase, TbCu7-type crystal phase (1-7 phase), can be converted into a single phase. The heat treatment is preferably performed in a vacuum or an inert atmosphere such as argon gas. The solution heat treatment temperature is preferably 1170°C or higher and lower than 1220°C, and the solution heat treatment time is preferably 10 hours or higher and 50 hours or lower. If the solution heat treatment temperature is lower than 1170°C or shorter than 10 hours, the platelet phase is sparsely formed, resulting in a low effect of improving coercivity. If the solution heat treatment temperature is higher than 1220°C or longer than 50 hours, the coercivity decreases due to excessive evaporation of R elements.

[0041] The temperature of the solution heat treatment is, for example, more preferably 1180° C. or higher, and even more preferably 1190° C. or higher. Also, it is more preferably 1210° C. or lower, and even more preferably 1200° C. or lower. The time of the solution heat treatment is more preferably 4 hours or longer and 30 hours or shorter.

[0042] Before the solution heat treatment, a quality improvement heat treatment may be performed. For example, the heat treatment is performed by holding the material at a temperature 10°C or more lower than the heat treatment temperature during sintering and 10°C or more higher than the heat treatment temperature during the solution heat treatment for 4 to 30 hours. The quality improvement heat treatment causes, for example, coarsening and homogenization of the crystal grains, improving the squareness of the magnetic properties.

[0043] The temperature of the quality improvement heat treatment is preferably 1180°C or higher and 1220°C or lower. If the temperature is higher than the heat treatment temperature during sintering, a different phase may be generated from the liquid phase, which may deteriorate the magnetic properties and may also cause the R element to evaporate. If the temperature of the quality improvement heat treatment is too low, the diffusion will not proceed sufficiently and the effect will not be obtained.

[0044] By rapidly cooling to room temperature after solution heat treatment, the TbCu7 type crystal phase can be stabilized, making it easier to develop coercive force. If the cooling rate is slow, the Ce2Ni7 type crystal phase and Th2Zn 17 The crystalline phase is more likely to be formed.

[0045] Next, the sintered body after the solution heat treatment is subjected to aging treatment to form a phase-separated structure. The aging treatment is preferably performed by heat treating at a temperature of 700°C to 900°C for 10 to 100 hours, followed by slow cooling at a rate of 0.1°C / min to 5°C / min to a temperature of 20°C to 600°C, and then cooling to room temperature (e.g., 25°C). By performing the aging treatment under these conditions, it is possible to improve the coercivity of the permanent magnet having the phase-separated structure. To prevent oxidation, the aging treatment is preferably performed in a vacuum or in an inert gas atmosphere such as argon gas.

[0046] If the aging temperature is less than 700°C or more than 900°C, a homogeneous mixed structure of the cell phase and the cell wall phase cannot be obtained, and the magnetic properties of the permanent magnet may be deteriorated. The aging temperature is preferably 750°C or higher and 880°C or lower, and more preferably 780°C or higher and 850°C or lower.

[0047] If the aging treatment time is less than 10 hours, the cell wall phase may not be sufficiently formed or the element diffusion may be insufficient. On the other hand, if the holding time exceeds 100 hours, the cell wall phase may become thicker, reducing the volume fraction of the cell phase and potentially preventing good magnetic properties. The aging treatment time is preferably 10 to 90 hours, and even more preferably 20 to 80 hours.

[0048] If the cooling rate during slow cooling is less than 0.1°C / min, productivity may decrease and costs may increase. If the cooling rate during slow cooling exceeds 5°C / min, a homogeneous mixed structure of the cell phase and cell wall phase may not be obtained, and the magnetic properties of the permanent magnet may deteriorate. The cooling rate after aging treatment is preferably 0.3°C / min or more and 4°C / min or less, and more preferably 0.5°C / min or more and 3°C / min or less.

[0049] Prior to the aging treatment, a pre-aging treatment may be performed at a temperature lower than the aging heat treatment temperature. The pre-aging treatment is preferably performed at a temperature of 500°C to 900°C for 0.5 to 10 hours, followed by slow cooling at a rate of 0.1°C / min to 5°C / min to a temperature of 20°C to 450°C. Pre-aging treatment can improve the squareness of the magnetic properties.

[0050] From the above, the permanent magnet according to this embodiment has the composition formula: R p Fe q M r Cu t Co 100-p-q-r-t (wherein R is at least one element selected from rare earth elements, M is at least one element selected from Zr, Ti, and Hf, p is a number satisfying 10.0 atomic %≦p≦14.5 atomic %, r is a number satisfying 1.5 atomic %≦r≦5.0 atomic %, t is a number satisfying 0.5 atomic %≦t≦9.0 atomic %, and q is a number satisfying 17 atomic %≦q≦26 atomic %), and 17 Cellular phase with a type crystalline phase and Th2Zn 17 The cell wall phase formed to separate the crystalline phase and the Th2Zn 17 The permanent magnet has a metal structure including platelet phases formed so as to intersect with the c-axis of the crystalline phase, and the average distance between the platelet phases in the structure of the permanent magnet is 10 nm or more and 30 nm or less. This allows the permanent magnet to have both high remanence and coercive force at high temperatures.

[0051] (Second embodiment) The permanent magnet of the first embodiment can be used in rotating electrical machines such as various motors and generators installed in automobiles, railway vehicles, aircraft, etc. It can also be used as a fixed magnet or variable magnet in variable magnetic flux motors and variable magnetic flux generators. Various motors and generators can be configured using the permanent magnet of the first embodiment. When the permanent magnet of the first embodiment is applied to a variable magnetic flux motor, known techniques can be applied as appropriate to the configuration of the variable magnetic flux motor and its drive system.

[0052] A rotating electric machine having a permanent magnet according to the first embodiment, a vehicle equipped with the rotating electric machine, and an aircraft will be described below. The rotating electric machine is, for example, a permanent magnet motor or a generator.

[0053] [A] Permanent magnet motor In the permanent magnet motor 11 shown in FIG. 3, a rotor 13 is disposed within a stator 12. A permanent magnet 15, which is the permanent magnet of the first embodiment, is disposed within an iron core 14 of the rotor 13. By using the permanent magnet of the first embodiment, it is possible to achieve high efficiency, miniaturization, and cost reduction of the permanent magnet motor 11 based on the characteristics of each permanent magnet. Furthermore, the permanent magnet can also be inserted into the flux barrier portion of a synchronous reluctance motor. This can increase the power factor of the synchronous reluctance motor.

[0054] Fig. 4 is a schematic diagram showing a portion of a cross section of a permanent magnet motor according to this embodiment. The permanent magnet motor according to this embodiment includes a stator 32 and a rotor 33, and the stator 32 or rotor 33 has the permanent magnet according to the first embodiment. In the permanent magnet motor 31 shown in Fig. 4, a rotor 33 is disposed within the stator 32. A permanent magnet 35, which is the permanent magnet according to the first embodiment, is disposed on the surface of an iron core 34 of the rotor 33. A housing 36 and cooling fins 37 are disposed outside the stator 32.

[0055] By having the permanent magnet according to the first embodiment in the permanent magnet motor, the heat resistance of the permanent magnet is improved, and by adopting an air-cooling method, the motor system can be made smaller and lighter.

[0056] [B] Generator FIG. 5 is a schematic diagram showing a generator according to this embodiment. The generator 41 shown in FIG. 5 includes a stator 42 using the above-described permanent magnet. A rotor 43 arranged inside the stator 42 is connected to a turbine 44 provided at one end of the generator 41 via a shaft 45. The turbine 44 is rotated, for example, by a fluid supplied from the outside. Note that instead of the turbine 44 being rotated by a fluid, the shaft 45 can also be rotated by transmitting dynamic rotation such as regenerative energy from a vehicle such as an automobile. Various known configurations can be employed for the stator 42 and the rotor 43.

[0057] The shaft 45 is in contact with a commutator (not shown) arranged on the opposite side of the rotor 43 from the turbine 44, and the electromotive force generated by the rotation of the rotor 43 is boosted to a system voltage as the output of the generator 41 via a phase separation bus and a main transformer (not shown) and transmitted. The generator 41 may be either a normal generator or a variable magnetic flux generator. The rotor 43 is charged by static electricity from the turbine 44 and by an axial current accompanying power generation. For this reason, the generator 41 is provided with brushes 46 for discharging the charge on the rotor 43.

[0058] As described above, by applying the permanent magnet to a generator, it is possible to obtain effects such as high efficiency, miniaturization, and cost reduction.

[0059] [C] Railway Vehicles The rotating electric machine may be mounted on, for example, a railway vehicle (an example of a vehicle) used for rail transportation. FIG. 6 is a schematic diagram showing an example of a railway vehicle 100 equipped with a rotating electric machine 101. The motor of FIG. 3 or the generator of FIG. 5 may be used as the rotating electric machine 101. When the rotating electric machine is mounted as the railway vehicle 101, the rotating electric machine 101 may be used as an electric motor (motor) that outputs driving force by utilizing power supplied from an overhead line or power supplied from a secondary battery mounted on the railway vehicle 100, or may be used as a generator that converts kinetic energy into electric power and supplies the power to various loads in the railway vehicle 100. By using a highly efficient rotating electric machine such as the rotating electric machine of the embodiment, the railway vehicle can be run with reduced energy.

[0060] [D] Automobile The rotating electric machine may be mounted on an automobile (another example of a vehicle), such as a hybrid automobile or an electric automobile. Fig. 7 is a schematic diagram showing an example of an automobile 200 equipped with a rotating electric machine 201. The motor of Fig. 3 or the generator of Fig. 5 may be used as the rotating electric machine 201. When the rotating electric machine is mounted as the rotating electric machine 201, the rotating electric machine 201 may be used as an electric motor that outputs driving force for the automobile 200, or as a generator that converts kinetic energy of the automobile 200 while it is running into electric power.

[0061] [E] Aircraft The rotating electric machine may be mounted on an aircraft. FIG. 8 is a schematic diagram showing an example of an aircraft 300 equipped with a rotating electric machine 301. The rotating electric machine 301 arranged in the tail of the fuselage drives a fan 302, increasing the airflow speed of the aircraft behind the fuselage, thereby improving the propulsion efficiency of the aircraft. The motor shown in FIG. 3 above can be used for the rotating electric machine 301 for driving the fan. The generator shown in FIG. 4 above can be used for the rotating electric machine 301 for supplying power to the motor. The motor shown in FIG. 3 above may be used instead of an engine. The rotating electric machine may also be mounted on, for example, industrial equipment (industrial motors), air conditioning equipment (air conditioner / water heater compressor motors), wind power generators, or elevators (hoists).

[0062] (Example) Examples will be described below, but the embodiments are not limited to the examples described below.

[0063] Examples 1 to 9 The raw materials were weighed in the prescribed proportions to obtain a permanent magnet with the desired composition, and then an alloy ingot was produced by high-frequency melting. The alloy ingot was coarsely crushed and then finely crushed in a jet mill to produce alloy powder with an average particle size of 4 μm.

[0064] The resulting fine powder was pressed under a pressure of 1 T in a magnetic field of 1 T to form a green compact. The green compact was then sintered by heating it to 1210°C in an Ar atmosphere and holding it there for 3 hours.

[0065] Next, the alloy was subjected to solution heat treatment by being held at a temperature of 1190°C for 16 hours in an Ar atmosphere, and then gas cooled to room temperature.

[0066] Next, the sintered body after the solution heat treatment was subjected to an aging treatment at 830°C for 40 hours in an Ar atmosphere, and then slowly cooled to 300°C at a cooling rate of 0.3°C / min, and further cooled to room temperature. A permanent magnet was obtained through these steps.

[0067] Example 10 A permanent magnet was obtained in the same manner as in Examples 1 to 9, except that the sintering temperature of the green compact was raised to 1200°C, sintering was performed, solution heat treatment was performed at 1170°C, and the aging temperature of the sintered compact was set to 840°C.

[0068] Example 11 A permanent magnet was obtained in the same manner as in Examples 1 to 9, except that the solution heat treatment was carried out at 1210°C and the temperature for the aging treatment of the sintered body was changed to 840°C.

[0069] Example 12 A permanent magnet was obtained in the same manner as in Examples 1 to 9, except that the solution heat treatment was carried out at a temperature of 1190° C. for 50 hours.

[0070] Example 13 A permanent magnet was obtained in the same manner as in Examples 1 to 9, except that the composition was changed as shown in Table 1.

[0071] (Comparative Example 1) Each raw material was weighed in a predetermined ratio so as to obtain a permanent magnet of the desired composition formula, and a permanent magnet was obtained in the same manner as in Examples 1-9.

[0072] (Comparative Example 2) Each raw material was weighed in a predetermined ratio so as to obtain a permanent magnet of the desired composition formula, and a permanent magnet was obtained in the same manner as in Examples 1-9.

[0073] (Comparative Example 3) A permanent magnet was obtained in the same manner as in Example 1, except that the sintering temperature of the green compact was raised to 1240°C and the solution heat treatment was carried out at 1220°C.

[0074] Comparative Example 4 A permanent magnet was obtained in the same manner as in Example 1, except that the solution heat treatment was carried out at a temperature of 1150°C.

[0075] The compositions of the permanent magnets of Examples 1 to 13 and Comparative Examples 1 to 4 were evaluated using ICP. The results of the above measurements are shown in Table 1. [Table 1]

[0076] The remanence and coercivity of the permanent magnets of Examples 1 to 13 and Comparative Examples 1 to 4 were evaluated using a BH tracer. Measurements were carried out at 300° C. The average distance between the platelet phases was measured from STEM images using the following method.

[0077] The average distance between the platelet phases was measured from STEM structural observation images. The cross section of the permanent magnet was taken from essentially the center of the surface with the largest area of ​​the sample. An 800 nm × 1200 nm area was observed with STEM at a magnification of 100k. The acceleration voltage was 200 kV. The width direction of the STEM image was perpendicular to the platelet phase, i.e., the same direction as the c-axis. Note that "perpendicular" also includes a state within ±10 degrees of the perpendicular direction (approximately perpendicular).

[0078] In the observed STEM image, five lines were drawn at equal intervals along the a-axis, dividing the area into six equal parts along the a-axis. Each line had the same length as the c-axis direction of the STEM image, and the intersections between the c-axis lines and the platelet phases were counted. The average distance between the platelet phases for each line was calculated by dividing the length of the c-axis direction of the STEM image by the intersection point (c-axis length of the STEM image / intersection point). The distances between the platelet phases along the five lines were then averaged to obtain the average distance between the platelet phases for a single observation image. Observations were performed at 10 non-overlapping locations, and the maximum and minimum values ​​of the calculated average distances were removed to calculate the average distance between the platelet phases. The results obtained using the above method are shown in Table 2.

[0079] The Cu concentrations in the cell wall phase and cell phase of the permanent magnets of Examples 1 to 13 and Comparative Examples 1 to 4 were measured by the following method.

[0080] The Cu concentrations in the cell wall and cell phases were measured by compositional analysis using STEM-EDX. STEM-EDX observations were performed on an 800 nm × 1200 nm area at 100kx magnification. The accelerating voltage was 200 kV. The cell wall and cell phases were identified in the observed image using STEM-EDX, and the compositions of each were measured at 10 random locations. The Cu concentrations in the cell wall and cell phases for a single image were calculated by averaging the results. Observations were performed at 10 non-overlapping locations, and the average values ​​calculated for each image were calculated by excluding the maximum and minimum values. This value was used as the average Cu concentration in the cell wall and cell phases. The cross section of the permanent magnet was divided into three equal parts in both the vertical and horizontal directions, and the center sections in both the vertical and horizontal directions were used. Table 2 shows the results obtained using the above method. [Table 2]

[0081] As is clear from Table 2, in Examples 1 to 13, the average distance between the platelet phases is 10 nm or more and 30 nm or less, and both the remanence and coercivity are higher than in Comparative Examples 1 to 4. It can be seen that when the average distance between the platelet phases exceeds 30 nm, the coercivity decreases significantly. It can also be seen that when the average distance between the platelet phases is less than 10 nm, the remanence decreases significantly. Furthermore, in Examples 1 to 12, the concentration of Cu element contained in the cell wall phase is 5 to 25 times the concentration of Cu element contained in the cell phase, which further increases the coercivity. Furthermore, by keeping the concentration within the above range, the crystal structure can be stably maintained, resulting in high remanence.

[0082] The permanent magnet according to this embodiment has the composition formula: p Fe q M r Cu t Co 100-p-q-r-t(wherein R is at least one element selected from rare earth elements, M is at least one element selected from Zr, Ti, and Hf, p is a number satisfying 10.0 atomic %≦p≦14.5 atomic %, r is a number satisfying 1.5 atomic %≦r≦5.0 atomic %, t is a number satisfying 0.5 atomic %≦t≦9.0 atomic %, and q is a number satisfying 17 atomic %≦q≦26 atomic %), and 17 Cellular phase with a type crystalline phase and Th2Zn 17 The cell wall phase formed to separate the crystalline phase and the Th2Zn 17 The permanent magnet has a metal structure including platelet phases formed so as to intersect with the c-axis of the crystalline phase, and the average distance between the platelet phases is 10 nm to 30 nm, which allows for both high remanence and coercive force at high temperatures.

[0083] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments may be embodied in various other forms, and various omissions, substitutions, and modifications may be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the inventions and their equivalents as defined in the claims.

[0084] The invention according to the embodiment will be described below.

[0085] [1] Composition formula: R p Fe q M r Cu t Co 100-p-q-r-t (wherein R is at least one element selected from rare earth elements, M is at least one element selected from Zr, Ti, and Hf, p is a number satisfying 10.0≦p≦14.5 atomic %, r is a number satisfying 1.5≦r≦4.2 atomic %, t is a number satisfying 0.5≦t≦9.0 atomic %, and q is a number satisfying 17≦q≦26 atomic %), and Th2Zn 17 a cellular phase having a crystalline phase; Th2Zn 17 a cell wall phase formed to separate the crystalline phase; Th2Zn 17 A permanent magnet having a metal structure including a platelet phase formed so as to intersect with the c-axis of a crystalline phase, A permanent magnet in which the average distance between the platelet phases is 10 nm or more and 30 nm or less.

[0086] [2] The permanent magnet according to [1], wherein 50 atomic % or more of the R elements in the composition formula are Sm.

[0087] [3] The permanent magnet according to [1] or [2], wherein 20% or less of the atomic percentage of Co in the composition formula is substituted with at least one element selected from the group consisting of Ni, V, Cr, Mn, Al, Si, Ga, Nb, Ta, and W.

[0088] [4] The permanent magnet according to any one of [1] to [3], wherein 50 atomic % or more of the M element in the composition formula is Zr.

[0089] [5] The permanent magnet according to any one of [1] to [4], wherein the concentration of Cu element contained in the cell wall phase is 5 to 25 times the concentration of Cu element contained in the cell phase.

[0090] [6] a stator; a rotor; A rotating electric machine, wherein the stator or the rotor has the permanent magnet according to any one of [1] to [5].

[0091] [7] The rotating electric machine according to [6], which is provided with cooling fins.

[0092] [8] The rotating electric machine according to [6] or [7], wherein the rotor is connected to the turbine via a shaft.

[0093] [9] A vehicle comprising the rotating electric machine according to any one of [6] to [8].

[0094]

[10] The rotor is connected to a shaft; [9] The vehicle described in [9], wherein rotation is transmitted to the shaft.

[0095]

[11] An aircraft comprising the rotating electric machine according to any one of [6] to [8]. [Explanation of symbols]

[0096] 11...rotating shaft, 12...rotor core, 13 permanent magnet, 14...fixed member, 15...air gap layer, 16...coil, 17...stator core, 18...q-axis center, 19...d-axis center, 31...permanent magnet motor, 32...stator, 33...rotor, 34...iron core, 35...permanent magnet, 36...casing, 37...cooling fin, 41...generator, 42...stator, 43...rotor, 44...turbine, 45...shaft, 46...brush, 100...railroad vehicle, 101...rotating electric machine, 200...automobile, 201...rotating electric machine, 300...aircraft, 301...rotating electric machine, 302...fan

Claims

1. a composition represented by the composition formula: RpFeqMrCutCo100-p-q-r-t (wherein R is at least one element selected from rare earth elements, M is at least one element selected from Zr, Ti, and Hf, p is a number satisfying 10.0 atomic %≦p≦14.5 atomic %, r is a number satisfying 1.5 atomic %≦r≦4.2 atomic %, t is a number satisfying 0.5 atomic %≦t≦9.0 atomic %, and q is a number satisfying 17 atomic %≦q≦26 atomic %); A cell phase having a Th2Zn17 type crystalline phase; a cell wall phase formed so as to separate the Th2Zn17 type crystalline phase; A permanent magnet having a metal structure including a platelet phase formed so as to intersect with the c-axis of the Th2Zn17 type crystalline phase and having a higher concentration of element M than the cell phase, A permanent magnet in which the average distance between the platelet phases is 10 nm or more and 30 nm or less.

2. 2. The permanent magnet according to claim 1, wherein 50 atomic % or more of the R elements in the composition formula are Sm.

3. 3. The permanent magnet according to claim 1 or 2, wherein 20% or less of the atomic percent of Co in the composition formula is substituted with at least one element selected from the group consisting of Ni, V, Cr, Mn, Al, Si, Ga, Nb, Ta, and W.

4. 2. The permanent magnet according to claim 1, wherein 50 atomic % or more of the M element in the composition formula is Zr.

5. 2. The permanent magnet according to claim 1, wherein the concentration of Cu element contained in the cell wall phase is 5 to 25 times the concentration of Cu element contained in the cell phase.

6. a stator; a rotor; The rotating electric machine according to claim 1 , wherein the stator or the rotor has the permanent magnet.

7. The rotating electrical machine according to claim 6, further comprising cooling fins.

8. The rotating electric machine according to claim 6 , wherein the rotor is connected to a turbine via a shaft.

9. A vehicle comprising the rotating electric machine according to claim 6 or 7.

10. The rotor is connected to a shaft; The vehicle of claim 9 , wherein rotation is transmitted to the shaft.

11. An aircraft comprising the rotating electric machine according to claim 6 or 7.

12. A permanent magnet as described in claim 1, wherein q in the composition formula satisfies 17 atomic %≦q≦23.6 atomic %.

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