JP5710818B2 - Permanent magnet, motor and generator using the same - Google Patents

Description

  Embodiments described herein relate generally to a permanent magnet, and a motor and a generator using the permanent magnet.

  As high performance permanent magnets, rare earth magnets such as Sm-Co magnets and Nd-Fe-B magnets are known. When a permanent magnet is used for a motor of a hybrid vehicle (HEV) or an electric vehicle (EV), the permanent magnet is required to have heat resistance. In HEV and EV motors, permanent magnets are used in which a part of Nd of the Nd—Fe—B magnet is replaced with Dy to improve heat resistance. Since Dy is one of rare elements, there is a demand for a permanent magnet that does not use Dy. As a highly efficient motor and generator, a variable magnetic flux motor and a variable magnetic flux generator using a variable magnet and a fixed magnet are known. In order to improve the performance and efficiency of variable magnetic flux motors and variable magnetic flux generators, it is required to increase the coercive force and magnetic flux density of variable magnets and fixed magnets.

Since the Sm—Co magnet has a high Curie temperature, it is known to exhibit excellent heat resistance in a system that does not use Dy, and it is possible to realize good motor characteristics and the like at high temperatures. Of the Sm—Co magnets, the Sm ₂ Co ₁₇ type magnet can be used as a variable magnet based on its coercive force manifestation mechanism and the like. In Sm-Co magnets, it is required to increase the coercive force and the magnetic flux density. Although increasing the Fe concentration is effective for increasing the magnetic flux density of the Sm—Co-based magnet, the coercive force tends to decrease in the composition region of the high Fe concentration. Therefore, a technique for expressing a large coercive force with an Sm—Co magnet having a high Fe concentration is required.

JP 2010-121167 A

  The problems to be solved by the present invention are a permanent magnet capable of exhibiting a large coercive force with high reproducibility in an Sm-Co magnet having a composition region with a high Fe concentration as a main phase, and a method for producing the same. It is in providing the motor and generator which used this.

The permanent magnet of the embodiment is
_{Formula: R p Fe q M r Cu} s Co 100-pqrs
(In the formula, R is at least one element selected from rare earth elements, M is at least one element selected from Zr, Ti, and Hf, and p, q, r, and s are each in atomic percent, and 10 ≦ (p ≦ 13.5, 28 ≦ q ≦ 40, 0.88 ≦ r ≦ 7.2, 4 ≦ s ≦ 13.5)
And a metal structure having a composition in which 50 atomic% or more of the element R is Sm and the main phase is a composition region in which the Fe concentration is 28 mol% or more. The metal structure includes a Cu-M rich phase having a concentration of element M of 3 mol% or more, and the volume fraction of the Cu-M rich phase with respect to all constituent phases constituting the metal structure is 0.01% or more and 5% or less. Range.

It is a SEM image which expands and shows the metal structure of the permanent magnet of an embodiment. It is a TEM image which expands and shows the fine structure of the main phase of the permanent magnet shown in FIG. It is a SEM image which expands and shows the metal structure of the conventional permanent magnet. It is a TEM image which expands and shows the fine structure of the main phase of the permanent magnet shown in FIG. It is a figure which shows an example of the result of the suggestive thermal analysis of the alloy powder used in the manufacturing process of the permanent magnet by embodiment. It is a figure which shows the other example of the result of the suggestive thermal analysis of the alloy powder used in the manufacturing process of the permanent magnet by embodiment. It is a figure which shows the permanent magnet motor of embodiment. It is a figure which shows the variable magnetic flux motor of embodiment. It is a figure which shows the permanent magnet generator of embodiment.

Hereinafter, the permanent magnet of the embodiment will be described. The permanent magnet of this embodiment is
_{Formula: R p Fe q M r Cu} s Co 100-pqrs ... (1)
(In the formula, R is at least one element selected from rare earth elements, M is at least one element selected from Zr, Ti, and Hf, and p, q, r, and s are each in atomic percent, and 10 ≦ (p ≦ 13.5, 28 ≦ q ≦ 40, 0.88 ≦ r ≦ 7.2, 4 ≦ s ≦ 13.5)
And a metal structure having a main phase in a composition range in which the Fe concentration is 28 mol% or more. The permanent magnet of the embodiment is characterized in that the Cu concentration in the main phase of the metal structure constituting the permanent magnet is 5 mol% or more.

  In the composition formula (1), as the element R, at least one element selected from rare earth elements including yttrium (Y) is used. Any of the elements R provides a large magnetic anisotropy to the permanent magnet and imparts a high coercive force. The element R is preferably at least one selected from samarium (Sm), cerium (Ce), neodymium (Nd), and praseodymium (Pr), and particularly preferably Sm. By setting Sm to 50 atom% or more of the element R, the performance of the permanent magnet, particularly the coercive force, can be improved with good reproducibility. Furthermore, it is desirable that 70 atomic% or more of the element R is Sm.

  The content p of the element R is in the range of 10 atomic% to 13.5 atomic%. When the content p of the element R is less than 10 atomic%, a large amount of the α-Fe phase is precipitated and a sufficient coercive force cannot be obtained. On the other hand, when the content of the element R exceeds 13.5 atomic%, the saturation magnetization is significantly reduced. The content p of the element R is preferably in the range of 10.3 to 13 atomic%, more preferably in the range of 10.5 to 12.5 atomic%.

  Iron (Fe) is an element mainly responsible for the magnetization of the permanent magnet. By containing a large amount of Fe, the saturation magnetization of the permanent magnet can be increased. However, if Fe is contained excessively, the α-Fe phase is precipitated, or a desired two-phase structure described later is difficult to obtain, so that the coercive force may be lowered. For this reason, the content q of Fe is in the range of 28 atomic% to 40 atomic%. The Fe content q is preferably in the range of 29 to 38 atomic%, more preferably in the range of 30 to 36 atomic%.

  As the element M, at least one element selected from titanium (Ti), zirconium (Zr), and hafnium (Hf) is used. By blending the element M, a large coercive force can be expressed with a composition having a high Fe concentration. The content r of the element M is in the range of 0.88 atomic% to 7.2 atomic%. By setting the content r of the element M to 0.88 atomic% or more, a large coercive force can be expressed in a permanent magnet having a high Fe concentration composition. On the other hand, when the content r of the element M exceeds 7.2 atomic%, the magnetization is remarkably lowered and a Cu-M rich phase described later is hardly generated. The content r of the element M is preferably in the range of 1.3 to 4.3 atomic%, and more preferably in the range of 1.5 to 2.6 atomic%.

  The element M may be any of Ti, Zr, and Hf, but preferably contains at least Zr. In particular, the effect of increasing the coercive force of the permanent magnet can be further improved by using 50 atomic% or more of the element M as Zr. On the other hand, since Hf is particularly expensive among the elements M, it is preferable to reduce the amount used even when Hf is used. The Hf content is preferably less than 20 atomic% of the element M.

  Copper (Cu) is an element for causing a permanent magnet to exhibit a high coercive force. The blending amount s of Cu is in the range of 4 atomic% to 13.5 atomic%. When the blending amount s of Cu is less than 4 atomic%, it is difficult to obtain a high coercive force. Furthermore, it becomes difficult to make the Cu concentration in the main phase 5 mol% or more. When the Cu content s is set to 4 atomic% or more, the Cu concentration in the main phase can be set to 5 mol% or more due to generation of a different phase with a small amount of Cu. The same applies to the generation of the Cu-M rich phase. On the other hand, when the Cu content s exceeds 13.5 atomic%, the magnetization decreases significantly. The blending amount s of Cu is preferably in the range of 4.2 to 9 atomic%, and more preferably in the range of 4.5 to 7.2 atomic%.

  Cobalt (Co) is an element necessary for developing a high coercive force while bearing the magnetization of the permanent magnet. Further, when a large amount of Co is contained, the Curie temperature is increased and the thermal stability of the permanent magnet is improved. If the Co content is too small, these effects cannot be obtained sufficiently. However, when the Co content is excessive, the content ratio of Fe is relatively lowered and the magnetization is lowered. Accordingly, the content of Co is set so that the content of Fe satisfies the above range in consideration of the contents of elements R, Zr, element M, and Cu.

  Part of Co is nickel (Ni), vanadium (V), chromium (Cr), manganese (Mn), aluminum (Al), gallium (Ga), niobium (Nb), tantalum (Ta) and tungsten (W). Substitution with at least one element A selected from These substitution elements A contribute to improvement of magnet characteristics, for example, coercive force. However, since excessive substitution of Co with the element A may cause a decrease in magnetization, the substitution amount with the element A is preferably 20 atomic% or less of Co.

The permanent magnet of this embodiment has a composition range in which the Fe concentration is 28 mol% or more as a main phase. Furthermore, the Cu concentration in the main phase is 5 mol% or more. Here, it is known that the coercive force expression mechanism of the Sm—Co magnet is generally a domain wall pinning type. The Sm ₂ Co ₁₇ type magnet has a Th ₂ Zn ₁₇ type crystal phase (a crystal phase having a Th ₂ Zn ₁₇ type structure / 2-17 phase) and a CaCu ₅ type crystal phase (CaCu ₅ type structure) by heat treatment. The domain wall pinning type coercive force expression mechanism is obtained by phase separation into (crystal phase / 1-5 phase). The metal structure after phase separation has a secondary structure called a cell structure. That is, the 1-5 phase (cell wall phase) is precipitated as the grain boundary phase of the 2-17 phase (cell phase), and the cell phase is separated by the cell wall phase.

  The domain wall energy of the 1-5 phase (cell wall phase) precipitated at the grain boundary of the 2-17 phase (cell phase) is larger than the domain wall energy of the 2-17 phase, and this domain wall energy difference is a barrier for domain wall movement. It becomes. That is, it is considered that the domain wall pinning type coercive force is expressed by the 1-5 phase having a large domain wall energy acting as a pinning site. Here, it is considered that the domain wall energy difference is mainly caused by the difference in Cu concentration. If the Cu concentration in the cell wall phase (grain boundary phase) is higher than the Cu concentration in the cell phase, it is considered that sufficient coercive force is developed.

As described above, Cu is an essential element for allowing the Sm ₂ Co ₁₇ type magnet to exhibit a high coercive force. That is, it is considered that Cu is enriched in the cell wall phase (grain boundary phase) generated by the heat treatment, whereby the cell wall phase acts as a pinning site of the domain wall, thereby developing a coercive force. However, when the Fe concentration of the Sm ₂ Co _17- type magnet is increased, such a coercive force tends to be hardly exhibited. As a cause thereof, it is considered that when the Fe concentration is increased, phase separation of the main phase into the 2-17 phase and the 1-5 phase does not proceed sufficiently during the heat treatment (during aging treatment).

As a result of intensive studies on this cause, the present inventors have found that the Cu concentration in the main phase of the sintered magnet tends to be lower than the prepared Cu concentration in the composition region where the Fe concentration is high. That is, it has been found that even when Cu is added for the purpose of improving the coercive force, Cu is not sufficiently contained in the main phase. In the Sm ₂ Co ₁₇ type magnet, if a sufficient Cu concentration difference does not appear between the cell phase and the cell wall phase formed during the aging treatment, the cell wall phase may not function sufficiently as a domain wall pinning site. Conceivable. If a sufficient amount of Cu is not secured in the main phase, it is difficult to obtain a sufficient Cu concentration between the cell phase and the cell wall phase, or the phase separation itself is less likely to occur. It is thought that it is preventing.

  As a result of intensive studies and studies on this point, it was found that a sufficient coercive force can be obtained by setting the Cu concentration in the main phase to 5 mol% or more. That is, in a permanent magnet having a composition region having a high Fe concentration as a main phase, particularly a permanent magnet having a composition region having a Fe concentration of 28 mol% or more as a main phase, a different phase rich in Cu and element M (Cu concentration is 5%). The hetero-phase / Cu-M rich phase in which the concentration is not less than mol% and the concentration of the element M is not less than 3 mol% and the balance is the elements R, Fe and Co) is likely to precipitate. It is considered that the Cu concentration in the main phase is reduced by enriching Cu in this Cu-M rich phase (different phase). That is, the Cu concentration in the main phase can be maintained at 5 mol% or more by suppressing the formation of the Cu-M rich phase.

  As described above, the permanent magnet of this embodiment can maintain the Cu concentration in the main phase having an Fe concentration of 28 mol% or more at 5 mol% or more by suppressing the formation of the Cu-M rich phase. It is a thing. According to the main phase having a Cu concentration of 5 mol% or more, the phase separation into the cell phase (2-17 phase) and the cell wall phase (1-5 phase, etc.) proceeds sufficiently during the aging treatment, and the cell phase and the cell A sufficient Cu concentration difference can be generated between the wall phase and the wall phase. Therefore, it is possible to give a sufficient coercive force based on the above-described domain wall pinning type coercive force expression mechanism to the Sm—Co magnet whose magnetization is improved based on the main phase having an Fe concentration of 28 mol% or more. Become.

The Cu-M rich phase (heterogeneous phase) is considered to be generated starting from a phase rich in element M, particularly Zr, produced during the production of the alloy ingot. Since the M-rich phase generated at the time of producing the alloy ingot has a low melting point, when the alloy ingot containing such a phase is pulverized by a jet mill, a ball mill, or the like, the pulverized powder contains an M-rich low melting point fine powder. . When this low melting point M-rich phase becomes a liquid phase during sintering, Cu tends to concentrate in the liquid phase, so a Cu-M rich phase is produced in the sintered body, and the Cu concentration in the main phase Is thought to decline. Therefore, by sintering the green compact of the alloy powder at a temperature lower than the melting start temperature T _{M of the} low melting M rich phase, the amount of Cu-M rich phase generated in the sintered body can be reduced. . The sintering temperature of the green compact of the alloy powder will be described in detail later.

  FIG. 3 is an SEM image (scanning electron microscope image) showing an enlarged metal structure of a conventional Sm—Co magnet. As is apparent from FIG. 3, the conventional Sm—Co-based magnet contains a relatively large amount of Cu—M rich phase (Cu—Zr rich phase) in addition to the main phase having an Fe concentration of 28 mol% or more. I understand. For this reason, the Cu concentration in the main phase decreases. 4 is an enlarged TEM image (transmission electron microscope image) showing the microstructure of the main phase of the permanent magnet shown in FIG. As can be seen from FIG. 4, when the sintered body containing a large amount of the Cu-M rich phase is subjected to heat treatment, the two-phase separation is insufficient. For this reason, sufficient coercive force cannot be obtained.

  FIG. 1 is an SEM image showing an enlarged metal structure of the Sm—Co magnet of this embodiment. As is apparent from FIG. 1, by controlling the sintering temperature of the green compact, for example, it is possible to suppress the precipitation of the Cu—M rich phase (Cu—Zr rich phase). As a result, the Cu concentration in the main phase can be 5 mol% or more. FIG. 2 is a TEM image showing an enlarged microstructure of the main phase of the permanent magnet shown in FIG. As can be seen from FIG. 2, when heat treatment is performed on the sintered body in which the precipitation of the Cu-M rich phase is suppressed, the two-phase separation of the main phase proceeds sufficiently. Therefore, a large coercive force can be imparted to the Sm—Co magnet.

  As described above, the precipitation of the Cu-M rich phase (heterogeneous phase) in the metal structure of the Sm-Co magnet should be avoided in order to maintain the Cu concentration in the main phase. However, a small amount of Cu-M rich phase is preferably included as long as the Fe concentration of the main phase of the sintered body is in the range of 28 mol% or more and the Cu concentration is 5 mol% or more. Due to the existence of the Cu-M rich phase at the grain boundary of the cell phase, the coarsening of the crystal grain size is prevented, and because the Cu-M rich phase works as a pinning site of the domain wall, etc. May bring improvements. From this point, the metal structure of the Sm—Co-based magnet is composed entirely of a Cu—M rich phase having a Cu concentration of 5 mol% or more and an element M concentration of 3 mol% or more. It is preferable that the volume fraction of the Cu-M rich phase with respect to the phase is 0.01% or more and 5% or less.

  When the volume fraction of the Cu-M rich phase with respect to all the constituent phases constituting the metal structure exceeds 5%, the decrease in the Cu concentration in the main phase becomes significant, and the coercive force is reduced for the reason described above. On the other hand, when the volume fraction of the Cu-M rich phase is less than 0.01%, the effect of suppressing the coarsening of the crystal grain size and the effect of improving the coercive force by acting as a pinning site of the domain wall are sufficiently obtained. Can't get to. The volume fraction of the Cu-M rich phase with respect to all the constituent phases constituting the metal structure is more preferably in the range of 0.5% to 3.5%.

As described above, the metal structure (sintered body structure) of the Sm—Co magnet has a composition region in which the Fe concentration is 28 mol% or more and the Cu concentration is 5 mol% or more as a main phase, and other than that, Cu -It includes heterogeneous phases such as M-rich phase. The metal structure of the Sm—Co based magnet may contain a different phase other than the Cu—M rich phase. The different phase refers to a phase other than the main phase among all the constituent phases constituting the metal structure. Examples of the different phases other than the Cu-M rich phase include Sm ₂ (Co, Fe, Zr, Cu) ₇ phase, Sm (Co, Fe, Zr, Cu) ₃ phase, Zr ₂ (Fe, Co, Cu) ₁₁ phase, and the like. Can be mentioned. However, if the amount of the different phase including the Cu-M rich phase is too large, the amount of the main phase is relatively decreased, and there is a possibility that the magnet characteristics such as magnetization and coercive force may be lowered. The rate is preferably 10% or less.

  As described above, the permanent magnet of this embodiment has a two-phase separation structure in which the main phase is a cell phase (2-17 phase) and a cell wall phase (1-5 phase or the like) after aging treatment. The cell wall phase preferably has a Cu concentration of 1.2 times or more of the Cu concentration of the 2-17 phase which is the cell phase. Thereby, the cell wall phase can sufficiently function as a pinning site of the domain wall. In other words, by setting the Cu concentration in the main phase to 5 mol% or more, the Cu concentration in the cell wall phase can be 1.2 times or more of the cell phase with good reproducibility. However, if the Cu concentration in the cell wall phase is too high, the amount of Cu-M rich phase produced becomes too small as described above, so the Cu concentration in the cell wall phase is 14 times or less, and further 10 times the Cu concentration in the cell phase. The following is preferable.

As a typical example of the cell wall phase (grain boundary phase) existing at the grain boundary of the cell phase, the above-described 1-5 phase can be mentioned, but it is not necessarily limited thereto. When the cell wall phase has a Cu concentration that is 1.2 times or more the Cu concentration of the cell phase, the cell wall phase can sufficiently function as a pinning site of the domain wall. Therefore, the cell wall phase may be such a Cu-rich phase. Cell wall phases other than the 1-5 phase include a TbCu ₇ type crystal phase (crystal phase having a TbCu ₇ type structure / 1-7 phase) which is a high temperature phase (structure before phase separation), a 1-7 phase Examples thereof include a 1-5 phase precursor phase generated in the initial stage of two-phase separation.

  In the permanent magnet of this embodiment, Fe concentration and Cu concentration in the main phase, and Cu concentration and M concentration (Zr concentration, etc.) in the Cu-M rich phase are SEM-EDX (energy dispersive X-ray spectroscopy). Can be measured. SEM-EDX observation is performed on the inside of the sintered body. The measurement inside the sintered body is as shown below. First, in the central part of the longest side in the surface having the maximum area, the composition is measured at the surface part and inside of the cross section cut perpendicularly to the side (in the case of a curve, perpendicular to the tangent to the central part).

  In the cross section, the measurement point is the reference line 1 drawn from the position of 1/2 of each side to the end perpendicular to the side to the end, and the inner angle of the corner starting from the center of each corner. A reference line 2 drawn to the end toward the inside at a position of 1/2 of the angle is provided, and the position of 1% of the length of the reference line from the starting point of these reference lines 1 and 2 is the surface portion, 40% Define the position as internal. In addition, when a corner | angular part has a curvature by chamfering etc., let the intersection which extended the adjacent edge | side be an edge part (center of a corner | angular part). In this case, the measurement location is not from the intersection point but from the portion in contact with the reference line.

  By making the measurement points as described above, for example, when the cross section is a square, the reference line is a total of eight reference lines 1 and 2, and the measurement points are 8 on the surface and inside, respectively. Become. In this embodiment, it is preferable that all eight locations are within the above-described composition range on the surface portion and inside, but it is sufficient that at least four locations on the surface portion and inside each are within the above-described composition range. In this case, the relationship between the surface portion and the inside at one reference line is not defined. After the observation surface inside the sintered body thus defined is polished and smoothed, SEM observation is performed at a magnification of 2500 times. The acceleration voltage is preferably 20 kV. The observation place of SEM-EDX is arbitrary 10 to 20 points in the crystal grain, and measurement is performed at each point to obtain an average value, and this average value is set as the concentration of each element.

  The volume fraction of the Cu-M rich phase can be defined by the area ratio of the Cu-M rich phase in the visual field of EPMA observation. The area ratio of the Cu-M rich phase can be obtained as follows. First, a 2500 × BSE image is taken with a field emission (FE) type EPMA. A commercially available image analysis software or the like performs specific contrast extraction on the captured image using two threshold values, and then calculates the area. In contrast extraction, two “threshold values” are provided for the luminance (brightness) of each pixel of an image. If it is greater than or equal to A and less than or equal to the threshold value B, the region is identified as “1”. As the threshold value, a value at which the luminance to be extracted is minimum on both sides of the distribution is used, and the region is selected. When different contrast and luminance distributions overlap, a value that minimizes the luminance of both is used as a threshold value, and that region is selected.

  The permanent magnet of this embodiment is produced as follows, for example. First, an alloy powder containing a predetermined amount of element is prepared. The alloy powder is prepared by, for example, producing a flake-like alloy ribbon by a strip casting method and then pulverizing it. In the strip casting method, it is preferable to obtain a thin ribbon that is solidified continuously to a thickness of 1 mm or less by pouring the molten alloy onto a cooling roll rotating at a peripheral speed of 0.1 to 20 m / sec. If the peripheral speed of the cooling roll is less than 0.1 m / sec, composition variations are likely to occur in the ribbon, and if the peripheral speed exceeds 20 m / sec, the crystal grains are refined to a single domain size or less, and good magnetic properties. Cannot be obtained. The peripheral speed of the cooling roll is more preferably in the range of 0.3 to 15 m / sec, and still more preferably in the range of 0.5 to 12 m / sec.

  The alloy powder may be prepared by pulverizing an alloy ingot obtained by casting a molten metal by an arc melting method or a high frequency melting method. Other methods for preparing the alloy powder include a mechanical alloying method, a mechanical grinding method, a gas atomizing method, a reduction diffusion method, and the like, and an alloy powder prepared by these methods may be used. The alloy powder thus obtained or the alloy before pulverization may be homogenized by performing a heat treatment as necessary. Flakes and ingots are pulverized using a jet mill, a ball mill or the like. The pulverization is preferably performed in an inert gas atmosphere or an organic solvent in order to prevent oxidation of the alloy powder.

Next, an alloy powder is filled in a metal mold placed in an electromagnet or the like, and pressure forming is performed while applying a magnetic field, thereby producing a green compact with the crystal axis oriented. By sintering this green compact under appropriate conditions, a sintered body having a large coercive force can be obtained. That is, a sintered compact with a small amount of different phases can be obtained by sintering the green compact at a temperature T _S lower than the melting start temperature T _M of the low melting M rich phase. However, since the sintering temperature T _S can not be sufficiently enhanced relative density too low a sintered body, the magnetization of the permanent magnets is reduced.

For this reason, the sintering temperature T _S of the green compact is preferably set to a temperature exceeding the temperature (T _M −50 ° C.) lower by 50 ° C. than the melting start temperature T _M of the low melting M rich phase. Practically, the density of the sintered body constituting the permanent magnet is preferably 8.2 g / cm ³ or more. The sintering temperature T _S of the green compact exceeds the temperature (T _M −50 ° C.) lower than the melting start temperature T _M of the M-rich phase (T _M −50 ° C.) and less than the melting start temperature T _M of the M-rich phase (T _{By making M-} 50 <T _S <T _M (° C.), it is possible to obtain a sintered body with a small amount of heterogeneous phase such as a Cu-M rich phase with good reproducibility while realizing the above density. It becomes possible. The sintering temperature T _S is more preferable to (T _M -40 ℃) temperatures above _{(T M -40 ≦ T S)} , further (T _M -20 ℃) temperatures above (T _M -20 ≦ T _S ) is desirable.

Here, the melting start temperature T _M of the low melting point of M-rich phase can be determined by differential thermal analysis. The sample shape used for the differential thermal analysis is not necessarily a powder shape. That is, since it is considered that the low melting point M-rich phase and the main phase are produced at the time of producing the alloy, a flake-like alloy ribbon obtained by strip casting, an alloy ingot produced by arc melting, or the like may be used.

FIG. 5 shows an example of the suggested thermal analysis result of the alloy powder used for producing the permanent magnet in this embodiment. In FIG. 5, the largest endothermic peak is the endothermic peak due to melting of the main phase. A peak smaller than the peak of the endothermic reaction of the main phase is observed on the lower temperature side than the peak due to the endothermic reaction of the main phase. This is an endothermic peak due to melting of the M-rich phase. In the vicinity of the peak temperature of this peak, melting of the low melting point M-rich phase becomes prominent. The peak temperature of the rapid heating peak due to the melting of the M-rich phase is defined as the melting start temperature T _M of the M-rich phase.

Depending on the alloy composition, the melting point of the main phase and the melting point of the M-rich phase (low melting point phase) are close, and a clear endothermic reaction peak of the low melting point phase may not be detected. In such a case, the intersection of the rising tangent of the largest endothermic peak (L1 in FIG. 6) and the background tangent (L2 in FIG. 6) is regarded as the melting start temperature T _M of the M-rich phase. be able to. The endothermic peak due to melting of the main phase and the endothermic peak due to melting of the M-rich phase (such as Zr-rich phase) are usually in the temperature range of 1000 ° C to 1300 ° C.

  The sintering time at the above temperature is preferably 0.5 to 15 hours. As a result, a dense sintered body can be obtained. When the sintering time is less than 0.5 hour, non-uniformity occurs in the density of the sintered body. On the other hand, if the sintering time exceeds 15 hours, Sm and the like in the alloy powder may evaporate, so that good magnetic properties may not be obtained. A more preferable sintering time is 1 to 10 hours, and further preferably 1 to 4 hours. The green compact is preferably sintered in vacuum or in an inert gas atmosphere such as argon gas in order to prevent oxidation.

  Next, a solution treatment and an aging treatment are performed on the obtained sintered body to control the crystal structure. In order to obtain the 1-7 phase which is a precursor of a phase-separated structure, the solution treatment is preferably heat-treated at a temperature in the range of 1100 to 1200 ° C. for 0.5 to 8 hours. At temperatures below 1100 ° C. and temperatures above 1200 ° C., the proportion of the 1-7 phase in the sample after solution treatment is small, and good magnetic properties cannot be obtained. The solution treatment temperature is more preferably in the range of 1120 to 1180 ° C, still more preferably in the range of 1120 to 1170 ° C.

  When the solution treatment time is less than 0.5 hours, the constituent phases tend to be non-uniform. If the solution treatment is performed for more than 8 hours, rare earth elements such as Sm in the sintered body may evaporate, and good magnetic properties may not be obtained. The solution treatment time is more preferably in the range of 1 to 8 hours, and still more preferably in the range of 1 to 4 hours. The solution treatment is preferably performed in vacuum or in an inert atmosphere such as argon gas in order to prevent oxidation.

  Next, an aging treatment is performed on the sintered body after the solution treatment. The aging treatment is a treatment for controlling the crystal structure and increasing the coercive force of the magnet. The aging treatment is held at a temperature of 700 to 900 ° C. for 0.5 to 80 hours, and then gradually cooled to a temperature of 400 to 650 ° C. at a cooling rate of 0.2 to 2 ° C./min, and subsequently cooled to room temperature. It is preferable. The aging treatment may be performed by a two-stage heat treatment. That is, it is preferable that the above heat treatment is the first stage, and after that, the second stage heat treatment is held at a predetermined temperature for a certain time, and subsequently cooled to room temperature by furnace cooling. The aging treatment is preferably performed in vacuum or in an inert gas atmosphere such as argon gas in order to prevent oxidation.

  When the aging treatment 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 treatment temperature is more preferably 750 to 880 ° C, and further preferably 780 to 850 ° C. When the aging treatment time is less than 0.5 hour, the cell wall phase may not be sufficiently precipitated from the 1-7 phase. On the other hand, when the holding time exceeds 80 hours, the cell wall volume increases in thickness, and the volume fraction of the cell phase decreases or the crystal grains become coarse, resulting in good magnet characteristics. May not be obtained. The aging treatment time is more preferably 4 to 60 hours, and further preferably 8 to 40 hours.

  In addition, when the cooling rate after aging heat treatment is less than 0.2 ° C./min, the cell wall volume increases in thickness and the volume fraction of the cell phase decreases or the crystal grains become coarse. As a result, good magnetic properties may not be obtained. If the cooling rate after the aging heat treatment exceeds 2 ° C./min, 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 cooling rate after the aging heat treatment is more preferably in the range of 0.4 to 1.5 ° C./min, and still more preferably in the range of 0.5 to 1.3 ° C./min.

  The aging treatment is not limited to the two-stage heat treatment, and may be a multi-stage heat treatment, and it is also effective to perform multi-stage cooling. It is also effective to perform a preliminary aging treatment (preliminary aging treatment) at a temperature lower than that of the aging treatment and for a short time as a pretreatment of the aging treatment. This is expected to improve the squareness of the magnetization curve. Specifically, the temperature of the preliminary aging treatment is 600 to 750 ° C., the treatment time is 0.5 to 4 hours, and the slow cooling rate after the aging treatment is 0.5 to 1.5 ° C./min. Improvement in the squareness of the magnet is expected.

  The permanent magnet of this embodiment can be used for various motors and generators. Further, it can be used as a fixed magnet or a variable magnet of a variable magnetic flux motor or a variable magnetic flux generator. Various motors and generators are configured by using the permanent magnet of this embodiment. When the permanent magnet of this embodiment is applied to a variable magnetic flux motor, the technology disclosed in Japanese Patent Application Laid-Open Nos. 2008-29148 and 2008-43172 is applied to the configuration and drive system of the variable magnetic flux motor. be able to.

  Next, the motor and the generator of the embodiment will be described with reference to the drawings. FIG. 7 shows a permanent magnet motor according to the embodiment. In the permanent magnet motor 1 shown in FIG. 7, a rotor (rotor) 3 is disposed in a stator (stator) 2. In the iron core 4 of the rotor 3, the permanent magnet 5 of the embodiment is arranged. Based on the characteristics of the permanent magnet according to the embodiment, the permanent magnet motor 1 can be improved in efficiency, size, cost, and the like.

  FIG. 8 shows a variable magnetic flux motor according to the embodiment. In the variable magnetic flux motor 11 shown in FIG. 8, a rotor (rotor) 13 is disposed in a stator (stator) 12. In the iron core 14 of the rotor 13, the permanent magnets of the embodiment are arranged as a fixed magnet 15 and a variable magnet 16. The magnetic flux density (magnetic flux amount) of the variable magnet 16 can be varied. Since the magnetization direction of the variable magnet 16 is orthogonal to the Q-axis direction, it is not affected by the Q-axis current and can be magnetized by the D-axis current. The rotor 13 is provided with a magnetized winding (not shown). By passing a current from the magnetization circuit through the magnetization winding, the magnetic field directly acts on the variable magnet 16.

  According to the permanent magnet of the embodiment, by changing the various conditions of the manufacturing method described above, for example, a fixed magnet 15 having a coercive force exceeding 500 kA / m and a variable magnet 16 having a coercive force of 500 kA / m or less are obtained. Can do. In the variable magnetic flux motor 11 shown in FIG. 8, the permanent magnet of the embodiment can be used for both the fixed magnet 15 and the variable magnet 16, but the permanent magnet of the embodiment is used for one of the magnets. It may be used. Since the variable magnetic flux motor 11 can output a large torque with a small device size, the variable magnetic flux motor 11 is suitable for a motor such as a hybrid vehicle or an electric vehicle that requires high output and miniaturization of the motor.

  FIG. 9 shows a generator according to the embodiment. A generator 21 shown in FIG. 9 includes a stator (stator) 22 using the permanent magnet of the embodiment. A rotor (rotor) 23 disposed inside the stator (stator) 22 is connected to a turbine 24 provided at one end of the generator 21 via a shaft 25. The turbine 24 is rotated by fluid supplied from the outside, for example. Note that the shaft 25 can be rotated by transmitting dynamic rotation such as regenerative energy of an automobile instead of the turbine 24 rotated by a fluid. Various known configurations can be employed for the stator 22 and the rotor 23.

  The shaft 25 is in contact with a commutator (not shown) disposed on the side opposite to the turbine 24 with respect to the rotor 23, and an electromotive force generated by the rotation of the rotor 23 is used as an output of the generator 21 as a phase separation bus. The power is boosted to the system voltage and transmitted through a main transformer (not shown). The generator 21 may be either a normal generator or a variable magnetic flux generator. Note that the rotor 23 is charged by static electricity from the turbine 2 or a shaft current accompanying power generation. Therefore, the generator 21 is provided with a brush 26 for discharging the charge of the rotor 23.

  Next, examples and evaluation results thereof will be described.

(Examples 1-3)
Each raw material was weighed so as to have the composition shown in Table 1, and then arc-melted in an Ar gas atmosphere to prepare an alloy ingot. Performs differential thermal analysis on alloy ingot was determined melting start temperature T _M of Zr rich phases in accordance with the method described above. For the measurement, a suggestion thermal analyzer TGD7000 manufactured by ULVAC-RIKO was used, the measurement temperature range was from room temperature to 1650 ° C., the heating rate was 10 ° C./min, and the atmosphere was Ar gas (flow rate: 100 mL / min). . The amount of the sample was about 300 mg, alumina was used for the container, and alumina was used for the reference. Table 2 shows the temperature T _M of the alloy ingot thus determined.

Next, the above alloy ingot was coarsely pulverized and further finely pulverized with a jet mill to prepare an alloy powder. The alloy powder is pressed into a green compact in a magnetic field, sintered in an Ar gas atmosphere at the temperature T _S shown in Table 2 for 2 hours, and subsequently heat treated at 1130 ° C. for 3 hours (solution treatment). Thus, a sintered body was produced. The obtained sintered body was held at 790 ° C. for 40 hours, and then cooled to room temperature to obtain the intended sintered magnet. The composition of the sintered magnet is as shown in Table 1. The composition of each magnet was confirmed by the ICP method. Further, according to the method described above, the Fe concentration and Cu concentration in the main phase, and the volume fraction of the Cu-M rich phase were measured. Further, the magnetic characteristics of the sintered magnet were evaluated with a BH tracer, and the coercive force and the remanent magnetization were measured. These results are shown in Table 2.

(Examples 4 to 7)
A sintered magnet was produced in the same manner as in Example 1 except that the composition shown in Table 1 was applied. The sintering temperature T _S of each example was set after obtaining the melting start temperature T _M of the Zr rich phase in the same manner as in Example 1. According to the method described above, the Fe concentration and Cu concentration in the main phase, and the volume fraction of the Cu-M rich phase were measured. Further, the magnetic characteristics of the sintered magnet were evaluated with a BH tracer, and the coercive force and the remanent magnetization were measured. These results are shown in Table 2.

(Comparative Example 1)
Except for changing the sintering temperature to the temperature shown in Table 2, an alloy powder having the same composition as in Example 1 was used, and a sintered magnet was produced under the same conditions. Comparative Example 1 is obtained by setting the sintering temperature T _S in the melting start temperature T _M above the temperature of the Zr-rich phase. According to the method described above, the Fe concentration and Cu concentration in the main phase, and the volume fraction of the Cu-M rich phase were measured. Further, the magnetic characteristics of the sintered magnet were evaluated with a BH tracer, and the coercive force and the remanent magnetization were measured. These results are shown in Table 2.

(Comparative Examples 2 and 3)
A sintered magnet was produced in the same manner as in Example 1 except that the composition shown in Table 1 was applied. In Comparative Example 2, the Fe concentration in the alloy composition is less than 28 atomic%, and in Comparative Example 3, the Sm concentration in the alloy composition is less than 10 atomic%. According to the method described above, the Fe concentration and Cu concentration in the main phase, and the volume fraction of the Cu-M rich phase were measured. Further, the magnetic characteristics of the sintered magnet were evaluated with a BH tracer, and the coercive force and the remanent magnetization were measured. These results are shown in Table 2.

  As is clear from Table 2, it can be seen that the sintered magnets of Examples 1 to 7 all have high magnetization and high coercive force, and are excellent in magnet characteristics. From comparison between Examples 1 and 2 and Example 3, it can be seen that the volume fraction of the Cu-M rich phase is preferably 5% or less. Since the sintered magnet of Comparative Example 1 has a low Cu concentration in the main phase, a sufficient coercive force is not obtained. Further, it can be seen that Comparative Example 2 has a low magnetization due to a low Fe concentration, and Comparative Example 3 has a low Sm concentration, and thus both the coercive force and the magnetization are low.

  In addition, although several embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... Permanent magnet motor, 2 ... Stator, 3 ... Rotor, 4 ... Iron core, 5 ... Permanent magnet, 11 ... Variable magnetic flux motor, 12 ... Stator, 13 ... Rotor, 14 ... Iron core, 15 ... Fixed magnet, 16 ... Variable magnet , 21 ... variable magnetic flux generator, 22 ... stator, 23 ... rotor, 24 ... turbine, 25 ... shaft, 26 ... brush.

Claims (7)

_{Formula: R p Fe q M r Cu} s Co 100-pqrs
(In the formula, R is at least one element selected from rare earth elements, M is at least one element selected from Zr, Ti, and Hf, and p, q, r, and s are each in atomic percent, and 10 ≦ (p ≦ 13.5, 28 ≦ q ≦ 40, 0.88 ≦ r ≦ 7.2, 4 ≦ s ≦ 13.5)
A permanent magnet having a metal structure having a composition in which 50 atomic% or more of the element R is Sm and an Fe concentration is 28 mol% or more as a main phase,
The metal structure includes a Cu-M rich phase having an element M concentration of 3 mol% or more,
A permanent magnet having a volume fraction of the Cu-M rich phase with respect to all constituent phases constituting the metal structure in a range of 0.01% to 5%. The permanent magnet according to claim 1,
The Cu-M rich phase has a Cu concentration of 5 mol% or more, and is a permanent magnet. The permanent magnet according to claim 1 or 2,
The main phase includes a Th ₂ Zn ₁₇ type crystal phase and a grain boundary phase having a Cu concentration of 1.2 times or more of the Cu concentration in the Th ₂ Zn ₁₇ type crystal phase. . The permanent magnet according to any one of claims 1 to 3,
50% or more of the element M in the composition formula is Zr. The permanent magnet according to any one of claims 1 to 4,
A permanent magnet in which 20 atomic% or less of Co in the composition formula is substituted with at least one element A selected from Ni, V, Cr, Mn, Al, Ga, Nb, Ta, and W .   A motor comprising the permanent magnet according to any one of claims 1 to 5.   A generator comprising the permanent magnet according to any one of claims 1 to 5.

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