JP2017022375A - permanent magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a permanent magnet capable of preventing reduction of output of a rotary electric machine which performs variable speed drive from a low speed rotation to a high speed operation.SOLUTION: The permanent magnet has a composition containing at least one element selected from rare-earth elements. The residual magnetization is 1.16T or more. The coercive force Hcj on an M-H curved line is 1000 kA/m or more. The recoil permeability on a B-H curved line is 1.1 or more.SELECTED DRAWING: Figure 1

Description

  The invention of the embodiments relates to a permanent magnet.

  In automobiles, railway vehicles, and the like, it is known to use rotating electrical machines such as motors and generators equipped with Nd—Fe—B magnets in order to increase efficiency. The Nd—Fe—B magnet has a high magnetic flux density. Therefore, high torque can be obtained by using an Nd—Fe—B based sintered magnet for a rotating electrical machine.

  In motors for automobiles and railway vehicles, variable speed driving from low speed rotation to high speed rotation is performed. At this time, in the motor having the conventional Nd—Fe—B based sintered magnet, a high torque can be obtained on the low speed rotation side, but the output is reduced due to the induction voltage (back electromotive force) generated on the high speed rotation side. To do.

  In permanent magnets such as Nd—Fe—B sintered magnets, the flux linkage is always generated with a constant strength. At this time, the induced voltage by the permanent magnet increases in proportion to the rotation speed. For this reason, the motor voltage reaches the upper limit of the power supply voltage at high speed rotation, and the current required for output does not flow. As a result, the output is greatly reduced, and further, it cannot be driven in the range of high-speed rotation.

  As a method for suppressing the influence of the induced voltage in high-speed rotation, for example, a field weakening control method can be cited. The field weakening control method is a method of reducing the magnetic flux density by generating a reverse magnetic field and reducing the number of flux linkages. However, a permanent magnet having a high magnetic flux density such as an Nd—Fe—B based sintered magnet cannot sufficiently reduce the magnetic flux density during high-speed rotation.

JP 2012-175738 A

IEEJ Transactions Industry Applications, 2013, Vol. 133, NO. 9, pp.943-951

  A problem to be solved by the present invention is to suppress a decrease in output in a rotating electrical machine that performs variable speed driving from low speed rotation to high speed rotation.

  The permanent magnet of the embodiment has a composition containing at least one element selected from rare earth elements. The residual magnetization is 1.16T or more. The coercive force Hcj on the MH curve is 1000 kA / m or more. The recoil permeability on the BH curve is 1.1 or more.

It is a figure which shows the example of a magnetic characteristic of the permanent magnet of this embodiment. It is a figure which shows the example of a magnetic characteristic of the permanent magnet of a comparative example. It is a figure which shows an example of the bright field image by STEM-EDX. It is a figure which shows the mapping image of Sm by STEM-EDX. It is a figure which shows the mapping image of oxygen by STEM-EDX. It is a figure which shows a motor.

  Hereinafter, embodiments will be described with reference to the drawings. The drawings are schematic, and for example, the relationship between the thickness and the planar dimensions, the ratio of the thickness of each layer, and the like may be different from the actual ones. In the embodiments, substantially the same constituent elements are denoted by the same reference numerals and description thereof is omitted.

(First embodiment)
In the present embodiment, an example of a permanent magnet that can be applied to a motor that performs variable speed driving from low speed to high speed will be described. FIG. 1 is a diagram illustrating an example of magnetic characteristics of a permanent magnet according to the present embodiment, and FIG. 2 is a diagram illustrating an example of magnetic characteristics of a permanent magnet according to a comparative example. 1 and 2, the horizontal axis represents the magnetic field H, and the vertical axis represents the magnetic flux density B or the magnetization M.

  The curve 1a shown in FIG. 1 shows the MH curve of the permanent magnet of this embodiment, and the curve 1b shows the BH curve of the permanent magnet of this embodiment. The permanent magnet of this embodiment has high magnetization in the BH curve. Further, when a reverse magnetic field is applied by the field weakening control method, the magnetization decrease width when changing from the operating point a on the BH curve to the operating point b is large. That is, the permanent magnet of this embodiment has a high recoil permeability on the BH curve.

Recoil permeability is defined as follows. The sintered magnet is magnetized by a magnetizer or a pulsed magnetic field. Magnetization measurement is performed on this magnet to obtain a BH curve. The slope is obtained by performing a linear fit on the BH curve. The value obtained by dividing this inclination by the vacuum magnetic permeability of 1.26 × 10 ⁻⁶ is taken as the recoil permeability.

  Moreover, the permanent magnet of this embodiment has a characteristic that a nick point does not occur on the BH curve. A knick point is a change point where the gradient changes and the magnetic flux density rapidly decreases when the magnetic flux density is lowered by an external magnetic field.

  The curve 2a shown in FIG. 2 shows the MH curve of a neodymium sintered magnet, and the curve 2b shows the BH curve of a neodymium sintered magnet. In the case of a neodymium sintered magnet, as shown in FIG. 2, the magnetization reduction width when changing from the operating point a to the operating point b is smaller than that of the permanent magnet of this embodiment. That is, with a neodymium sintered magnet, it is difficult to lower the magnetic flux density even if the field-weakening control method is used. In the field weakening, the magnetic flux is canceled out by the magnetic flux generated by the field weakening current. However, the spatial waveforms of the magnetic flux and the magnet magnetic flux due to the field weakening current are different from each other. For this reason, even if the magnetic flux of the spatial fundamental wave component can be canceled out, the spatial harmonic component is not canceled out and expands in some cases.

  Spatial harmonic components cause iron loss and magnet eddy current loss during high-speed rotation. Furthermore, magnet temperature rises due to magnet eddy current loss, and thermal demagnetization tends to occur. In particular, in the embedded magnet type, the magnetic flux is close to a rectangular wave and includes many spatial harmonics. Moreover, since the gap length is short and the spatial harmonic of the slot ripple component is large, the problem is great. One reason is that the low-order spatial harmonics that remain without being canceled out are modulated by slot ripple to become high-order spatial harmonics.

  As a method of reducing the magnetic flux density, for example, it is conceivable to use a bonded magnet. Curve 3a in FIG. 2 is a diagram showing an MH curve of a neodymium bonded magnet, and curve 3b is a diagram showing a BH curve of a neodymium bonded magnet. As shown in FIG. 2, the neodymium bonded magnet has a larger magnetization reduction width when changing from the operating point a to the operating point b than the neodymium sintered magnet, that is, the recoil permeability is high. However, since the remanent magnetization is low and the coercive force Hcj is small, it is difficult to obtain high torque at low speed rotation when variable speed driving from low speed to high speed is performed with a motor equipped with the magnet.

  In addition to neodymium bonded magnets, examples of magnets with high recoil permeability include incompletely magnetized Al—Ni—Co based magnets. However, an Al—Ni—Co magnet in an incompletely magnetized state has a small residual magnetization like a neodymium bonded magnet, and thus it is difficult to obtain a high torque at a low speed. Further, neodymium magnets and samarium magnets have high magnetization and high torque can be obtained, but the recoil permeability of these magnets is generally about 1, and it is difficult to obtain characteristics with large recoil permeability.

  On the other hand, in the permanent magnet of this embodiment, the residual magnetization is 1.16 or more, the coercive force Hcj on the MH curve is 1000 kA / m or more, and the recoil permeability is 1.15 or more. The remanent magnetization is more preferably 1.2 or more. The coercive force is more preferably 1200 kA / m or more. The recoil permeability is more preferably 1.2 or more. Thus, the permanent magnet of this embodiment has high recoil permeability in addition to high magnetization and high coercivity. Therefore, it is possible to suppress a decrease in output in a motor that performs variable speed driving from low speed to high speed.

  In the motor, a rotor is provided by arranging a plurality of magnetic poles in the rotor core. A stator is disposed on the outer periphery of the rotor via an air gap. Further, armature windings are provided on the stator. The magnetic flux generated by the armature winding can reversibly change the amount of magnetic flux of the permanent magnet that constitutes the magnetic pole of the rotor. However, since two or more kinds of magnets are required, the structure is complicated, and the number of manufacturing steps increases.

  On the other hand, the permanent magnet of this embodiment has both the characteristics of high magnetization and high recoil permeability with a single magnet, so the structure of the motor can be simplified, and the number of manufacturing steps Can be suppressed.

Further, an example of a permanent magnet having the above characteristics will be described. Permanent magnet of this embodiment, the composition _{formula: R p Fe q M r Cu} t Co 100-p-q-r-t ( wherein, at least one element R selected from rare earth elements, M is Zr, Ti And at least one element selected from the group consisting of Hf, p is a number satisfying 10.8 ≦ p ≦ 12.5 atomic%, q is a number satisfying 25 ≦ q ≦ 40 atomic%, and r is 0.8. A number satisfying 88 ≦ r ≦ 3.5 atomic%, and t is a number satisfying 3.5 ≦ t ≦ 13.5 atomic%).

  R in the above compositional formula is an element that can bring great magnetic anisotropy to the magnet material. As the R element, for example, one or more elements selected from rare earth elements including yttrium (Y) can be used. For example, samarium (Sm), cerium (Ce), neodymium (Nd), praseodymium (Pr) In particular, it is preferable to use Sm. For example, when a plurality of elements including Sm are used as the R element, the performance of the magnet material, for example, the coercive force, can be increased by setting the Sm concentration to 50 atomic% or more of the total elements applicable as the R element. Note that it is more preferable that Sm is 70 atomic% or more, more preferably 90% or more of the element applicable as the R element.

  The coercive force can be increased by setting the concentration of the element applicable as the R element to, for example, 10.8 atomic% or more and 12.5 atomic% or less. When the concentration of the element applicable as the R element is less than 10.8 atomic%, a large amount of alpha-Fe is precipitated to reduce the coercive force, and the concentration of the element applicable as the R element is 12.5 atomic%. When exceeding, saturation magnetization falls. The concentration of the element applicable as the R element is more preferably 10.9 atomic% or more and 12.1 atomic% or less, and further preferably 11.0 atomic% or more and 12.0 atomic% or less.

  M in the above composition formula is an element that can develop a large coercive force with a composition having a high Fe concentration. As the M element, for example, one or more elements selected from the group consisting of titanium (Ti), zirconium (Zr), and hafnium (Hf) are used. When the content r of the M element exceeds 4.3 atomic%, a heterogeneous phase containing an excessive amount of the M element is likely to be generated, and both the coercive force and the magnetization are likely to be reduced. Further, when the content r of the M element is less than 0.88 atomic%, the effect of increasing the Fe concentration tends to be small. That is, the content r of the M element is preferably 0.88 atomic% or more and 3.5 atomic% or less. The content r of the element M is more preferably 1.14 atomic% or more and 3.4 atomic% or less, further larger than 1.49 atomic% and not more than 2.24 atomic%, and further 1.55 atomic%. It is preferable that it is above 2.23 atomic%.

  The M element preferably contains at least Zr. In particular, the coercive force of the permanent magnet can be increased by using 50 atomic% or more of the M element as Zr. On the other hand, since Hf is particularly expensive among the M elements, it is preferable that the amount used is small even when Hf is used. For example, the Hf content is preferably less than 20 atomic% of the M element.

  Cu is an element that can exhibit a high coercive force in a magnet material. The Cu content is preferably, for example, 3.5 atomic% or more and 13.5 atomic% or less. When the amount is larger than this, the magnetization is remarkably lowered, and when the amount is smaller than this, it is difficult to obtain a high coercive force and a good squareness ratio. The Cu content t is more preferably 3.9 atomic% or more and 10.0 atomic% or less, and further preferably 4.1 atomic% or more and 5.8 atomic% or less.

  Fe is an element mainly responsible for the magnetization of the magnet material. The saturation magnetization of the magnet material can be increased by blending a large amount of Fe, but if it is blended excessively, it becomes difficult to obtain a desired crystal phase due to precipitation of alpha-Fe and phase separation, which may reduce the coercive force. is there. Therefore, the Fe content q is preferably 25 atomic% or more and 40 atomic% or less. The Fe content q is more preferably 26 atom% or more and 36 atom% or less, and further preferably 30 atom% or more and 33 atom% or less.

  Co is an element that bears the magnetization of the magnet material and can develop a high coercive force. Further, when a large amount of Co is blended, a high Curie temperature is obtained, and the thermal stability of the magnet characteristics can be improved. If the amount of Co is small, these effects are reduced. However, if Co is added excessively, the proportion of Fe is relatively reduced, and there is a possibility that the magnetization is lowered. Further, by substituting 20 atomic% or less of Co with one or more elements selected from the group consisting of Ni, V, Cr, Mn, Al, Si, Ga, Nb, Ta, and W, magnet characteristics, for example, retention. Magnetic force can be increased.

The permanent magnet of this embodiment includes a main phase having a hexagonal Th ₂ Zn ₁₇ type crystal phase (2-17 type crystal phase), and a grain boundary phase provided between crystal grains constituting the main phase. , Including a two-dimensional metal structure. Further, the main phase includes a cell phase having a 2-17 type crystal phase, a Cu rich phase having a hexagonal CaCu ₅ type crystal phase (1-5 type crystal phase), and a platelet phase.

The Cu rich phase is preferably formed so as to surround the cell phase. The above structure is also called a cell structure. The Cu rich phase also includes a cell wall phase that divides the cell phase. It is preferable that the c-axis of the Th ₂ Zn _17- type crystal phase exists parallel to the easy magnetization axis. Note that “parallel” may include a state within ± 10 degrees from the parallel direction (substantially parallel).

The Cu rich phase is a phase having a high Cu concentration. The Cu concentration of the Cu rich phase is higher than the Cu concentration of the Th ₂ Zn ₁₇ type crystal phase. For example, the Cu concentration in the Cu-rich phase is preferably 1.2 times or more the Cu concentration in the Th ₂ Zn ₁₇ type crystal phase. The Cu-rich phase exists, for example, in the form of a line or a plate in the cross section including the c-axis in the Th ₂ Zn ₁₇ type crystal phase. The structure of the Cu rich phase is not particularly limited, and examples thereof include a hexagonal CaCu ₅ type crystal phase (1-5 type crystal phase). Moreover, the permanent magnet may have a plurality of Cu-rich phases having different phases.

The domain wall energy of the Cu-rich phase is higher than the domain wall energy of the Th ₂ Zn ₁₇ type crystal phase, and this domain wall energy difference becomes a barrier for domain wall movement. That is, when the Cu rich phase functions as a pinning site, domain wall movement between a plurality of cell phases can be suppressed. In particular, the effect of suppressing the domain wall motion is enhanced by forming the cell structure. This is also called a domain wall pinning effect. Therefore, it is more preferable that the Cu rich phase is formed so as to surround the cell phase. A permanent magnet having such a structure is also referred to as a pinning-type permanent magnet.

  In the Sm—Co magnet containing 25 atomic% or more of Fe, the Cu concentration of the Cu rich phase is preferably 10 atomic% or more and 60 atomic% or less. The coercive force and the squareness ratio can be increased by increasing the Cu concentration of the Cu-rich phase. In the region where the Fe concentration is high, the Cu concentration of the Cu-rich phase is likely to vary. For example, a Cu-rich phase having a large domain wall pinning effect and a Cu-rich phase having a small domain wall pinning effect occur, and the coercive force and the squareness ratio are low. descend.

  When the domain wall deviating from the pinning site moves, the magnetization is reversed by the amount of movement, so that the magnetization is lowered. If the domain wall is deviated from the pinning site all at once in a certain magnetic field when an external magnetic field is applied, the magnetization is less likely to be reduced by the application of the magnetic field, and a good squareness ratio is obtained. In other words, when a magnetic field is applied, if the pinning site deviates with a magnetic field lower than the coercive force and the domain wall moves, magnetization is reduced by the amount of movement, leading to deterioration of the squareness ratio.

Platelet _phase, the concentration of the element M such as Zr than Th 2 _{Zn 17} crystal phase is a high M-rich platelet phase _is c-axis perpendicular to the formation of Th 2 _{Zn 17} crystal phase. For example, when the Zr concentration of the platelet phase is higher than the Th ₂ Zn ₁₇ type crystal phase, the platelet phase is also referred to as a Zr rich platelet phase.

As described above, the permanent magnet of this embodiment has a composition containing at least a rare earth element. Since the magnet has a high Curie point, it is possible to achieve good motor characteristics at high temperatures. The neodymium magnet is a new creation type permanent magnet, whereas the magnet is a pinning type permanent magnet. In the neodymium magnet, when the reverse axis is generated, the domain walls are simultaneously reversed. On the other hand, in the permanent magnet of this embodiment, the domain wall movement is suppressed by the Cu-rich phase, and the domain wall movement (magnetization reversal) proceeds by deviating from the pinning site. In other words, the domain wall motion can be suppressed by the size of the cell structure constituted by the Th ₂ Zn ₁₇ type crystal phase, the Cu rich phase, and the platelet phase and the composition of each phase.

  The cell structure becomes dense when the concentration of the R element is high, and becomes rough when the concentration is low. Further, when compared with sintered bodies having the same composition, the volume fraction of the cell wall phase is high in a sample having a dense cell structure and low in a coarse sample. When the Cu concentration in the cell wall phase is compared, the denser the cell structure, the lower the Cu concentration.

  The Cu rich phase affects the pinning force of the domain wall. When the Cu concentration is low, the pinning force is weak and the coercive force is small. On the other hand, when the cell structure is rough and the Cu concentration in the Cu-rich phase is high, the coercive force increases because the pinning force of each Cu-rich phase is high. If two or more different characteristics can be realized with a single sintered body, there are locations where the domain wall is easy to move (magnetization reversal) and locations where magnetization reversal is difficult to occur with one magnet, and the distribution of coercive force. Can be generated. As a result, the slope of the magnetization curve becomes steep and the recoil permeability increases. Furthermore, since the coercive force is large, the knick point exists on the high magnetic field side, and irreversible demagnetization does not occur even when a large magnetic field is applied.

  Control of the concentration of R element is important for realizing the magnet. In the permanent magnet of the present invention, the concentration of the R element is controlled by utilizing the oxidation phenomenon. In the permanent magnet of the present embodiment, the sintered body has a phase containing a rare earth element oxide provided so as to be exposed on the surface of the sintered body. The thickness of the phase containing the rare earth element oxide is not less than 50 micrometers and not more than 800 micrometers.

  The permanent magnet of this embodiment has a region rich in the R element and a region rich in the R element. For example, an R element oxide is formed by oxidizing R-Co powder. At this time, since the R element of the main phase is consumed, as a result, the concentration of the R element of the main phase decreases. Therefore, the coercive force of the surface portion is larger than that of the central portion where the influence of oxidation is small. That is, a coercive force distribution is formed by a single magnet. In such a magnet, the oxygen concentration in the surface portion is higher than in the central portion. When the oxygen concentration in the surface portion is twice or more that in the central portion, the effect of increasing the recoil permeability becomes significant.

The oxygen concentration in the surface portion is defined as follows. The sintered body sample is cut so that the cut surface includes the vicinity of the center. Next, EDX (Energy Dispersive X-ray Spectroscopy: EDX) surface analysis is performed in a measurement region of 20 micrometers × 20 micrometers in a region located within a depth of 100 micrometers from the sample surface on the cut surface. This measurement is performed five times at an arbitrary position on one sample, and this average value is defined as the oxygen concentration O _surface of the surface portion.

The oxygen concentration at the center is defined as follows. An EDX plane analysis of an area of 20 micrometers × 20 micrometers is performed in an area located at least 500 micrometers or more from the sample surface in the sintered body on the cut surface. This measurement is performed five times at an arbitrary position for one sample, and this average value is defined as the oxygen concentration O _{center at the center} .

When the ratio of the oxygen concentration O _surface of the surface portion to the oxygen concentration O _center of the _center portion (O _surface / O _center ) is 2 or more and the thickness of the phase containing the oxide of the R element is 50 micrometers or more, the recoil permeability The improvement in magnetic susceptibility is significant. However, when the thickness exceeds 800 micrometers, the influence of a decrease in remanent magnetization and a decrease in coercive force due to the generation of an excessive Sm poor region increases. More preferably, the thickness of the phase containing the oxide of R element is 100 micrometers or more and 500 micrometers or less.

  Since the permanent magnet contains a low coercive force component, the recoil permeability is large. The coercive force Hcb on the BH curve is 800 kA / m or less. However, since a high coercive force component is also included, a nick point on the BH curve does not occur on the high magnetic field side exceeding 1000 kA / m as shown in FIG. In order not to cause a nick point in the BH curve, the coercive force Hcj on the MH curve is preferably 1000 kA / m or more. Furthermore, in the permanent magnet of this embodiment, the ratio of the magnetic field Hk90 when the magnetization is 90% of the residual magnetization to the coercive force Hcj is 70 or less. Thus, the permanent magnet of this embodiment has a favorable squareness ratio.

  The composition of the permanent magnet is, for example, ICP (Inductively Coupled Plasma) emission spectroscopy, SEM-EDX (scanning electron microscope-energy dispersive X-ray spectroscopy: SEM-Energy Dispersive X-ray Spectroscopy), TEM. -EDX (Transmission Electron Microscope-Energy Dispersive X-ray Spectroscopy: Transmission Electron Microscope-EDX) or the like. The volume ratio of each phase is comprehensively determined by combining observation with an electron microscope or an optical microscope and X-ray diffraction, etc., but can be obtained by area analysis of an electron micrograph obtained by photographing a cross section of a permanent magnet. it can. As the cross section of the permanent magnet, a cross section at a substantially central portion of the surface having the maximum area of the sample is used.

_Also, Th 2 _{Zn 17} type crystal phase, the metal structure of the Cu-rich phase or the like, for example, be certified as follows. First, the sample is observed with a scanning transmission electron microscope (STEM). At this time, the location of the grain boundary phase is specified by observing the sample with an SEM, and the observation is performed by processing the sample so that the grain boundary phase enters the field of view using a focused ion beam (FIB). Efficiency can be increased. The sample is a sample after aging treatment. At this time, the sample is preferably an unmagnetized product.

  Next, the density | concentration of each element, such as a cell phase and Cu rich phase, is measured using the energy dispersive X ray spectroscopy (STEM-Energy Dispersive X-ray Spectroscopy: STEM-EDX) using STEM, for example.

  When measuring the concentration of each element with STEM-EDX, a sample for measurement is cut out from the inside of 1 mm or more of the surface of the sample. Further, the observation is performed at an observation magnification of 100 k with respect to a plane parallel to the easy magnetization axis (c-axis). An example of the STEM bright field image obtained in this way is shown in FIG. Further, FIG. 4 shows a mapping image of Sm in the same visual field, and FIG. 5 shows a mapping image of oxygen.

  In FIG. 4, a region 11 is a region including the main phase. Further, a relatively white area is an area having a high Sm concentration, and a relatively white area in FIG. 5 is an area having a high oxygen concentration. At this time, a region where both the Sm concentration and the oxygen concentration are high when FIGS. 4 and 5 are overlapped corresponds to a phase (region 12) containing an oxide of R element. Further, a region 13 having a low Sm concentration and a low oxygen concentration is provided between the region 11 and the region 12. From this, it can be seen that in the sintered body, both a region where the R element is high and a region where the R element is low are formed. When the mapping image of FIG. 4 and the mapping image of FIG. 5 are compared, the density of the white region is different, but this is a problem in image processing, and the density does not necessarily represent the relative concentration of each element. Absent.

  Note that a three-dimensional atom probe (3-DAP) may be used for measuring the concentration of each phase element. The analysis method using 3DAP is an analysis method in which an observation sample is field-evaporated by applying a voltage, and an atomic arrangement is specified by detecting a field-evaporated ion with a two-dimensional detector. By identifying the ion species from the time of flight until reaching the two-dimensional detector, continuously detecting the individually detected ions in the depth direction, and arranging (reconstructing) the ions in the detected order A three-dimensional atomic distribution can be obtained. Compared with TEM-EDX concentration measurement, each element concentration in each crystal phase can be measured more accurately.

  The element concentration in each phase is measured by 3DAP according to the following procedure. First, a sample is sliced by dicing, and a needle-like sample for a pick-up atom probe (AP) is produced therefrom by FIB.

  The measurement by 3DAP is performed on the inside of the sintered body. The measurement inside the sintered body is as follows. 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 a corner of the first reference line drawn to the end perpendicular to the side and extending to the end, starting from a position 1/2 of each side, and the center of each corner. And a second reference line drawn inward toward the end at a position that is 1/2 of the inner angle of the first angle, and the length of the reference line from the start point of the first reference line and the second reference line The 1% position is defined as the surface portion, and the 40% position is defined as the interior. 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 quadrangle, the reference line is a total of eight lines, each of the first reference line and the second reference line, and the measurement points are on the surface and inside. There are 8 places each. In the present embodiment, it is preferable that all of the eight portions in the surface portion and inside are within the above-described composition range, but it is sufficient that at least four portions in 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. Observation is performed after the observation surface inside the sintered body thus defined is polished and smoothed. For example, the observation location of TEM-EDX in the concentration measurement is 20 arbitrary points in each phase, and the average value of the measurement values obtained by removing the maximum value and the minimum value from the measurement values at these points is obtained. Is the concentration of each element. The measurement of 3DAP is based on this.

  In the measurement result of the concentration in the Cu rich phase using 3DAP described above, it is preferable that the Cu concentration profile in the Cu rich phase is sharper. Specifically, the full width at half maximum (FWHM) of the Cu concentration profile is preferably 5 nm or less, and a higher coercive force can be obtained in such a case. This is because when the distribution of Cu in the Cu-rich phase is sharp, a domain wall energy difference between the cell phase and the Cu-rich phase is abruptly generated, and the domain wall is more easily pinned.

  The full width at half maximum (FWHM) of the Cu concentration profile in the Cu-rich phase is obtained as follows. Based on the above-described method, the highest Cu concentration (PCu) is obtained from the 3DAP Cu profile, and the peak width at which the value is half the value (PCu / 2), that is, the half width (FWHM) is obtained. . Such measurement is performed on 10 peaks, and the average value of these values is defined as the half width (FWHM) of the Cu profile. When the full width at half maximum (FWHM) of the Cu profile is 3 nm or less, the effect of further increasing the coercive force is improved, and in the case of 2 nm or less, a more excellent coercive force improving effect can be obtained.

The squareness ratio is defined as follows. First, DC magnetization characteristics at room temperature are measured with a DC BH tracer. Next, determine the measurement result from the basic characteristics of the magnet from the BH curve obtained residual magnetization _{M r} and the coercive force Hcj and the maximum energy product (BH) max. At this time, the theoretical maximum value by using the _{M r} (BH) max is obtained by the following equation (1).
(BH) max (theoretical ^{_{value) = M r 2 / 4μ 0}} ··· (1)

The squareness ratio is evaluated by the ratio of (BH) max and (BH) max (theoretical value) obtained by measurement, and is obtained by the following formula (2).
(BH) max (actual value) / (BH) max (theoretical value) × 100 (2)

  Next, an example of a method for manufacturing a permanent magnet will be described. First, an alloy powder containing a predetermined element necessary for the synthesis of a permanent magnet is prepared. Next, an alloy powder is filled in a mold placed in an electromagnet, and a green compact having a crystal axis oriented is manufactured by pressure forming while applying a magnetic field.

  For example, an alloy powder can be prepared by pulverizing an alloy ingot obtained by casting a molten metal by an arc melting method or a high frequency melting method. The alloy powder may have a desired composition by mixing a plurality of powders having different compositions. Further, the alloy powder may be prepared using a mechanical alloying method, a mechanical grinding method, a gas atomizing method, a reducing diffusion method, or the like. In the production of an alloy ribbon using the strip cast method, an alloy powder is prepared by producing a flake-like alloy ribbon and then pulverizing the alloy ribbon. For example, a thin ribbon that is continuously solidified to a thickness of 1 mm or less can be produced by pouring the molten alloy into a cooling roll that rotates at a peripheral speed of 0.1 m / second or more and 20 m / second or less. When the peripheral speed is less than 0.1 m / second, composition variations tend to occur in the ribbon. In addition, when the peripheral speed exceeds 20 m / sec, the magnetic properties may be deteriorated, for example, crystal grains are excessively refined. The peripheral speed of the cooling roll is 0.3 m / second or more and 15 m / second or less, more preferably 0.5 m / second or more and 12 m / second or less.

  Furthermore, it is possible to homogenize the material by subjecting the alloy powder or the material of the alloy before grinding to a heat treatment. For example, the material can be pulverized using a jet mill, a ball mill, or the like. Note that the powder can be prevented from being oxidized by grinding the material in an inert gas atmosphere or an organic solvent.

  In the pulverized powder, the degree of orientation is such that the average particle size is 2 micrometers or more and 5 micrometers or less, and the proportion of the powder having a particle diameter of 2 micrometers or more and 10 micrometers or less is 80% or more of the whole powder. The coercive force increases. In order to realize this, pulverization by a jet mill is preferable.

For example, when pulverizing with a ball mill, even if the average particle size of the powder is 2 micrometers or more and 5 micrometers or less, a large amount of fine powder having a particle size of submicron level is contained. When this fine powder aggregates, the c-axis of the crystal in the TbCu ₇ phase is difficult to align in the direction of the easy magnetization axis during magnetic field orientation during pressing, and the degree of orientation tends to deteriorate. Further, such fine powder may increase the amount of oxide in the sintered body and reduce the coercive force. In particular, when the Fe concentration is 25 atomic% or more, it is desirable that the proportion of the powder having a particle diameter of 10 micrometers or more in the pulverized powder is 10% or less of the whole powder. When the Fe concentration is 25 atomic% or more, the amount of different phases in the ingot as a raw material increases. In this heterogeneous phase, not only the amount of powder increases but also the particle size tends to increase, and the particle size may be 20 micrometers or more.

  When such an ingot is pulverized, for example, a powder having a particle diameter of 15 micrometers or more may be directly converted into a different-phase powder. When the pulverized powder containing such a heterogeneous coarse powder is pressed in a magnetic field to form a sintered body, the heterogeneous phase remains, causing a decrease in coercive force, a decrease in magnetization, a decrease in squareness, and the like. When the squareness decreases, magnetization becomes difficult. In particular, it is difficult to magnetize the rotor after assembly. As described above, the coercive force is increased while suppressing a decrease in the squareness ratio in a high Fe concentration composition containing 25 atomic% or more of Fe by setting the powder having a particle diameter of 10 micrometers or more to 10% or less of the whole. be able to.

  In the manufacturing method of the permanent magnet of this embodiment, an oxidation process is performed with respect to the compacting body obtained by pressure molding. By performing the oxidation treatment, oxygen molecules can be adsorbed on the surface of the green compact before sintering. The oxidation treatment has little effect even if it is performed on the final product. This is because only the sample surface is oxidized in the final product. The thickness of the phase containing the R element oxide must be at least 50 micrometers or more. In order to make it 50 micrometers or more, it is necessary to perform an oxidation treatment before sintering. However, if it is oxidized more than necessary, the entire magnet is oxidized, and adverse effects such as a decrease in magnetization and coercive force are caused.

  In the method for producing a permanent magnet according to the present embodiment, a compacted body is formed at a temperature of 15 ° C. or more and 35 ° C. or less and a time of 2 hours or more and less than 24 hours in an atmosphere composed of air having a humidity of 20% or more and 50% or less. Oxidation treatment is performed by leaving

  When oxidation treatment is performed under conditions including at least one of a humidity of less than 20%, a temperature of less than 15 ° C., a time of less than 2 hours, and an atmosphere of an inert gas, oxygen molecules are not sufficiently adsorbed to the sintered body. . At this time, the thickness of the phase containing the oxide of R element is less than 50 micrometers, and the recoil permeability is less than 1.1. Further, when the oxidation treatment is performed under conditions including at least one of humidity exceeding 50%, temperature exceeding 35 ° C., and time longer than 24 hours, oxygen molecules are excessively adsorbed on the sintered body. At this time, the thickness of the phase containing the oxide of R element exceeds 800 micrometers, and the reduction of magnetization and coercive force becomes remarkable. In the oxidation treatment, the humidity is more preferably 23% or more and 45% or less. The temperature is more preferably 20 ° C. or higher and 30 ° C. or lower. The time is more preferably 6 hours or more and less than 12 hours.

  Next, sintering is performed. In sintering, the green compact is heat-treated by holding at 1180 ° C. or higher and 1220 ° C. or lower for 1 hour or longer and 15 hours or shorter. For example, when the holding temperature is less than 1180 ° C., the density of the produced sintered body tends to be low. On the other hand, when the temperature is higher than 1220 ° C., the magnetic characteristics may be deteriorated due to excessive evaporation of R element such as Sm in the powder. A more preferable holding temperature is 1190 ° C. or higher and 1210 ° C. or lower. On the other hand, when the holding time is less than 1 hour, the density tends to be non-uniform, and the magnetization is likely to decrease. Further, the crystal grain size of the sintered body is reduced, and the grain boundary phase ratio is increased. Is prone to decline. On the other hand, if the heat treatment time exceeds 15 hours, evaporation of the R element in the powder becomes excessive, and the magnetic properties may be deteriorated. A more preferable holding time is 2 hours or more and 13 hours or less, and further preferably 3 hours or more and 10 hours or less. Note that oxidation can be suppressed by performing heat treatment in vacuum or argon gas. Also, the vacuum can be maintained until the temperature is close to the holding temperature, for example, 1100 ° C. or more and 1200 ° C. or less, and then the sintered body density can be improved by switching to an Ar atmosphere and holding it isothermally.

  In the method for producing a permanent magnet according to the present embodiment, a green compact formed by adsorbing oxygen molecules by oxidation treatment is sintered to form a phase containing an R element oxide having a thickness of 50 micrometers or more. be able to. Conventionally, sintering is performed as soon as possible after forming the green compact, or the green compact is stored in an inert gas atmosphere. On the other hand, in the permanent magnet of this embodiment, a phase including an oxide of R element is formed by sintering a green compact that has adsorbed oxygen molecules by oxidation treatment.

  According to the manufacturing method, a phase including an oxide of R element can be formed in a necessary range in the surface portion rather than the central portion. Further, the thickness of the phase containing the oxide of R element can be set to 50 micrometers or more and 800 micrometers or less.

  Next, high quality processing is performed. In the high-quality treatment, the heat treatment is performed by holding at a temperature lower by 10 ° C. or more than the heat treatment temperature during sintering and at a temperature higher by 10 ° C. or more than the heat treatment temperature during solution treatment for 2 hours or more and 12 hours or less. Do. If the heat treatment is not performed at a temperature lower by 10 ° C. or more than the heat treatment temperature at the time of sintering, the heterogeneous phase derived from the liquid phase generated during the sintering cannot be sufficiently removed. The orientation of this hetero phase is often low, and when the hetero phase is present, the crystal orientation of the crystal grains tends to shift with respect to the easy axis of magnetization, and not only the squareness ratio but also the magnetization tends to decrease. In the solution treatment, the temperature is low, and it is difficult to sufficiently remove the heterogeneous phase generated during the sintering from the viewpoint of element diffusion rate. Further, the grain growth rate is slow, and there is a possibility that a sufficient crystal grain size cannot be obtained, and improvement in the squareness ratio cannot be expected. On the other hand, by performing the high-quality treatment at a temperature higher by 10 ° C. than the holding temperature at the time of the solution treatment, the heterogeneous phase can be sufficiently removed and the crystal grains constituting the main phase can be enlarged.

  The holding temperature during the high-quality treatment is preferably, for example, 1130 ° C. or higher and 1190 ° C. or lower. When the temperature is lower than 1130 ° C or higher than 1190 ° C, the squareness ratio may be lowered. When the heat treatment time is less than 2 hours, the diffusion is insufficient, the heterogeneous phase is not sufficiently removed, and the effect of improving the squareness ratio is small. Further, when it exceeds 12 hours, there is a possibility that R elements such as Sm evaporate and good magnetic properties cannot be obtained. Note that the heat treatment time in the high-quality treatment is more preferably 4 hours or longer and 10 hours or shorter, and further preferably 6 hours or longer and 8 hours or shorter. In order to prevent oxidation, it is preferable to perform the high-quality treatment in a vacuum or an inert atmosphere such as argon gas.

  At this time, the effect of suppressing the generation of a heterogeneous phase is enhanced by setting the pressure in the chamber in the high-quality treatment to a positive pressure. Therefore, since excessive evaporation of the R element can be suppressed, a decrease in coercive force can be suppressed. The pressure in the chamber is, for example, preferably 0.15 MPa or more and 15 MPa or less, more preferably 0.2 MPa or more and 10 MPa or less, and further preferably 1.0 MPa or more and 5.0 MPa or less.

Next, a solution treatment is performed. The solution treatment is a process for forming a TbCu _7- type crystal phase (1-7-type crystal phase) that becomes a precursor of a phase-separated structure. In the solution treatment, heat treatment is performed by holding at a temperature of 1090 ° C. or higher and lower than 1170 ° C. for 3 hours or longer and 28 hours or shorter.

When the holding temperature during the solution treatment is less than 1090 ° C. or 1170 ° C. or more, the proportion of the TbCu _7- type crystal phase present in the sample after the solution treatment is small, and the magnetic properties may be deteriorated. The holding temperature is preferably 1100 ° C. or higher and 1165 ° C. or lower. Also, when the retention time during the solution treatment is less than 3 hours, the constituent phases tend to be non-uniform, the coercive force tends to decrease, the crystal grain size of the metal structure tends to be small, and the grain boundary phase ratio is high. Therefore, the magnetization tends to decrease. Moreover, when the holding temperature at the time of solution treatment exceeds 28 hours, there is a possibility that the magnetic properties may be deteriorated due to evaporation of the R element in the sintered body. The holding time is preferably 4 hours or longer and 24 hours or shorter, and more preferably 10 hours or longer and 18 hours or shorter. Note that oxidation of the powder can be suppressed by performing a solution treatment in a vacuum or an inert atmosphere such as argon gas.

  Next, an aging treatment is performed on the sintered body after rapid cooling. The aging treatment is a treatment for increasing the coercive force of the magnet by controlling the metal structure, and aims to phase-separate the metal structure of the magnet into a plurality of phases.

  In the aging treatment, the temperature is raised to a temperature of 760 ° C. or higher and 850 ° C. or lower, and then held at that temperature for 20 hours or longer and 60 hours or shorter (first holding). Next, after slow cooling to a temperature of 350 ° C. or more and 650 ° C. or less at a cooling rate of 0.2 ° C./min or more and 2.0 ° C./min or less, the temperature is maintained for 0.5 hours or more and 8 hours or less. Heat treatment is performed by (second holding). Then, it cools to room temperature. A sintered magnet can be obtained as described above.

  In the first holding, when the holding temperature is higher than 850 ° C., the cell phase becomes coarse and the squareness ratio tends to decrease. On the other hand, when the holding temperature is less than 760 ° C., the cell structure is not sufficiently obtained, and it becomes difficult to develop the coercivity. The holding temperature in the first holding is more preferably 780 ° C. or higher and 840 ° C. or lower, for example. In the first holding, when the holding time is less than 20 hours, the cell structure becomes insufficient, and the coercive force is difficult to be expressed. When the holding time is longer than 60 hours, the cell wall phase becomes excessively thick, and the squareness ratio may be deteriorated. The holding time in the first holding is more preferably 25 hours or more and 40 hours or less, for example.

  When the cooling rate at the time of slow cooling is less than 0.2 ° C./min, the cell wall phase becomes excessively thick and the magnetization tends to decrease. Moreover, when it exceeds 2.0 degree-C / min, the difference of Cu concentration of a cell phase and a cell wall phase is not fully obtained, and a coercive force tends to fall. The cooling rate during slow cooling is, for example, 0.4 ° C./min or more and 1.5 ° C./min or less, more preferably 0.5 ° C./min or more and 1.3 ° C./min or less. Moreover, when it cools slowly to less than 350 degreeC, the low temperature heterogeneous phase as mentioned above is easy to be generated. Moreover, when it cools to the temperature exceeding 650 degreeC, Cu density | concentration in a Cu rich phase may not become high enough, and sufficient coercive force may not be obtained. In addition, when the holding time in the second holding exceeds 8 hours, a low temperature heterogeneous phase is generated, and sufficient magnetic properties may not be obtained.

  In the aging treatment, the temperature may be maintained at a predetermined temperature for a certain time during the slow cooling, and then gradually cooled. Further, the above aging treatment is set as the main aging treatment, and the preliminary aging treatment is performed by holding the aging treatment at a temperature lower than the holding temperature in the first holding before the main aging treatment and in a time shorter than the holding time in the first holding. May be performed. The squareness ratio can be further increased by the holding during the slow cooling and the pre-aging treatment.

(Second Embodiment)
The permanent magnet of the first embodiment can be used for rotating electrical machines such as various motors and generators. It can also be used as a fixed magnet or a variable magnet of a variable magnetic flux motor. Various motors are configured by using the permanent magnet of the first embodiment. When the permanent magnet of the first embodiment is applied to a variable magnetic flux motor, the configuration and drive system of the variable magnetic flux motor are disclosed in, for example, Japanese Patent Application Laid-Open Nos. 2008-29148 and 2008-43172. Can be applied.

  Next, a motor having the permanent magnet will be described with reference to the drawings. FIG. 6 is a diagram showing a permanent magnet motor in the present embodiment. In the permanent magnet motor 100 shown in FIG. 6, a rotor (rotor) 103 is disposed in a stator (stator) 102. In the iron core 104 of the rotor 103, the permanent magnet 105 which is the permanent magnet of the first embodiment is arranged. The magnetic flux density (magnetic flux amount) of the permanent magnet 105 can be varied. Since the magnetization direction of the permanent magnet 105 is orthogonal to the Q-axis direction, the permanent magnet 105 can be magnetized by the D-axis current without being affected by the Q-axis current. The rotor 103 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 permanent magnet 105.

  As the permanent magnet 105, the permanent magnet of the first embodiment can be used. Thereby, even when variable speed driving from low speed to high speed is performed, it is possible to suppress a decrease in output during high speed rotation.

  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.

  In this embodiment, a specific example of a permanent magnet will be described.

(Example 1, Example 2)
Each raw material used for the permanent magnet was weighed and mixed at a predetermined ratio, and then melted in an Ar gas atmosphere to produce an alloy ingot. The alloy ingot was held at 1160 ° C. for 19 hours for heat treatment, and then the alloy ingot was coarsely pulverized and pulverized by a jet mill to prepare an alloy powder as a magnet raw material powder. The obtained alloy powder was press-molded in a magnetic field to produce a compression molded body.

  Next, as shown in Table 2, an oxidation treatment was performed by leaving the compression molded body at 30% humidity, a temperature of 23 ° C., and a time of 2.5 hours. Furthermore, the compression molded body of the alloy powder is placed in a sintering furnace chamber, and after the inside of the chamber is evacuated, the temperature is raised to 1175 ° C. and held at the ultimate temperature for 30 minutes, after which Ar gas is introduced, and Ar atmosphere The temperature was raised to 1200 ° C., and the sintering was carried out at the ultimate temperature for 6 hours. Next, in the Ar atmosphere, the pressure inside the chamber was set to 0.5 MPa, and the quality was improved by holding at 1185 ° C. for 3 hours. Next, it was gradually cooled to 1170 ° C. at a cooling rate of 5.0 ° C./min, held at the ultimate temperature for 12 hours for solution treatment, and then cooled to room temperature. The cooling rate after the solution treatment was 180 ° C./min.

  Next, the sintered body after the solution treatment was heated to 750 ° C., held at the ultimate temperature for 1 hour, and then gradually cooled to 350 ° C. at a cooling rate of 1.5 ° C./min. Next, as an aging treatment, the temperature was raised to 835 ° C. and held at the ultimate temperature for 35 hours. Thereafter, it was gradually cooled to 400 ° C. at a cooling rate of 1.0 ° C./min, and held at the ultimate temperature for 1 hour. Then, the magnet was obtained by furnace-cooling to room temperature.

  In addition, the composition analysis of the magnet was performed by an inductively coupled plasma (ICP) method. The composition analysis by ICP method was performed according to the following procedure. First, a sample collected from the described measurement location was pulverized with a mortar, and a certain amount of the pulverized sample was weighed and placed in a quartz beaker. Further, mixed acid (acid containing nitric acid and hydrochloric acid) was put into the beaker and heated to about 140 ° C. on a hot plate to completely dissolve the sample in the beaker. After further cooling, it was transferred to a PFA volumetric flask and the volume was adjusted to obtain a sample solution.

Furthermore, the components contained in the sample solution were quantified by a calibration curve method using an ICP emission spectroscopic analyzer. As an ICP emission spectroscopic analyzer, SPS4000 manufactured by SII Nano Technology was used. The composition of the obtained magnet is as shown in Table 1. The oxygen concentration _{O center} of the central portion, the surface portion of oxygen concentration _{O Surface,} the thickness of the phase containing an oxide of R element, recoil permeability, coercive force Hcj, and residual magnetization was measured. The results are shown in Table 3. In each example and comparative example, HD2300 manufactured by Hitachi High-Tech was used as a measuring device.

(Example 3, Example 4, Example 5)
Each raw material was weighed and mixed at a predetermined ratio, and then melted at a high frequency in an Ar gas atmosphere to prepare an alloy ingot. After subjecting the alloy ingot to coarse pulverization, heat treatment was performed at 1160 ° C. for 2 hours, followed by rapid cooling to cool to room temperature. Further, coarse pulverization and pulverization with a jet mill were carried out to prepare an alloy powder as a raw material powder for the magnet. Further, the alloy powder was press-molded in a magnetic field to produce a compression molded body.

Next, as shown in Table 2, an oxidation treatment was performed by leaving the compression molded body at 36% humidity, 18 ° C., and 20 hours. Furthermore, the compression molded body of the alloy powder was placed in the chamber of the sintering furnace, the inside of the chamber was evacuated to 8.8 × 10 ⁻³ Pa, then the temperature was raised to 1175 ° C., and the temperature was maintained for 60 minutes. Thereafter, Ar gas was introduced into the chamber. The temperature in the chamber in the Ar atmosphere was raised to 1195 ° C. and held at the ultimate temperature for 5 hours for sintering. Next, in the Ar atmosphere, the pressure inside the chamber was set to 0.2 MPa, and the high-quality treatment was performed by holding at 1160 ° C. for 2 hours. Next, it was gradually cooled to 1130 ° C. at a cooling rate of 5.0 ° C./min, held at the ultimate temperature for 20 hours for solution treatment, and then cooled to room temperature. The cooling rate after the solution treatment was 150 ° C./min.

  Next, the temperature of the sintered body after the solution treatment is raised to 700 ° C. and held at the ultimate temperature for 0.5 hours, and subsequently, as an aging treatment, the temperature is raised to 850 ° C. and held at the ultimate temperature for 50 hours. did. Thereafter, it was gradually cooled to 450 ° C. at a cooling rate of 0.75 ° C./min, and held at the ultimate temperature for 4 hours. Then, it was gradually cooled to 380 ° C. at a cooling rate of 0.5 ° C./min, and held at the ultimate temperature for 1 hour. Then, the magnet was obtained by furnace-cooling to room temperature.

Further, the components contained in the sample solution were quantified by a calibration curve method using the ICP emission spectroscopic analyzer. The composition of the obtained magnet is as shown in Table 1. Further, as in the other examples, the central portion oxygen concentration O _center , the surface portion oxygen concentration O _surface , the thickness of the phase including the oxide of the R element, the recoil permeability, the coercive force Hcj, and the residual magnetization are measured. did. The results are shown in Table 3.

(Example 6, Example 7)
Each raw material was weighed and mixed at a predetermined ratio, and then melted at a high frequency in an Ar gas atmosphere to prepare an alloy ingot. After roughly pulverizing the alloy ingot, heat treatment was performed at 1170 ° C. for 10 hours, followed by rapid cooling to cool to room temperature. Further, coarse pulverization and pulverization with a jet mill were carried out to prepare an alloy powder as a raw material powder for the magnet. Further, the alloy powder was press-molded in a magnetic field to produce a compression molded body.

Next, as shown in Table 2, an oxidation treatment was performed by leaving the compression molded body to stand at a humidity of 24%, a temperature of 28 ° C., and a time of 12 hours. Next, the compression molded body is placed in a chamber of a sintering furnace, the inside of the chamber is brought to a vacuum state of 7.5 × 10 ⁻³ Pa, the temperature is raised to 1165 ° C., and held at the ultimate temperature for 10 minutes, Ar gas was introduced into the chamber. Sintering was performed by raising the temperature in the chamber in an Ar atmosphere to 1185 ° C. and holding at the ultimate temperature for 5 hours. Next, in the Ar atmosphere, the pressure inside the chamber was set to 0.7 MPa, and the high-quality treatment was performed by holding at 1160 ° C. for 10 hours. Next, it was gradually cooled to 1115 ° C. at a cooling rate of 5.0 ° C./min, held at the ultimate temperature for 12 hours for solution treatment, and then cooled to room temperature. The cooling rate after the solution treatment was 220 ° C./min.

  Next, the sintered body after the solution treatment was heated to 660 ° C., held at the ultimate temperature for 1 hour, and subsequently heated to 840 ° C. as an aging treatment, and held at the ultimate temperature for 50 hours. Thereafter, it was gradually cooled to 500 ° C. at a cooling rate of 0.6 ° C./min, and held at the ultimate temperature for 1 hour. Thereafter, it was gradually cooled to 400 ° C. at a cooling rate of 0.5 ° C./min, and held at the ultimate temperature for 1 hour. Then, the magnet was obtained by furnace-cooling to room temperature.

As in other examples, the composition of each magnet was confirmed by the ICP method. The composition of the obtained magnet is as shown in Table 1. Further, as in the other examples, the central portion oxygen concentration O _center , the surface portion oxygen concentration O _surface , the thickness of the phase including the oxide of the R element, the recoil permeability, the coercive force Hcj, and the residual magnetization are measured. did. The results are shown in Table 3.

(Example 8)
Each raw material was weighed and mixed at a predetermined ratio, and then melted at a high frequency in an Ar gas atmosphere to prepare an alloy ingot. The alloy ingot was coarsely pulverized, then subjected to heat treatment at 1160 ° C. for 12 hours, and cooled rapidly to room temperature. Further, an alloy powder was prepared as a raw material powder for the magnet by coarse pulverization and pulverization by a jet mill. Further, the alloy powder was press-molded in a magnetic field to produce a compression molded body.

Next, as shown in Table 2, an oxidation treatment was performed by leaving the compression molded body to stand at a humidity of 26%, a temperature of 23 ° C., and a time of 8 hours. Further, the compression molded body of the alloy powder was placed in the chamber of the sintering furnace, the inside of the chamber was evacuated to 7.5 × 10 ⁻³ Pa, then the temperature was raised to 1165 ° C., and held at the ultimate temperature for 60 minutes. Thereafter, Ar gas was introduced into the chamber. The temperature in the chamber in the Ar atmosphere was raised to 1195 ° C. and held at the ultimate temperature for 5 hours for sintering. Next, in the Ar atmosphere, the pressure inside the chamber was set to 0.5 MPa, and the quality was increased by holding at 1170 ° C. for 6 hours. Next, it was gradually cooled to 1140 ° C. at a cooling rate of 5.0 ° C./min, held at the ultimate temperature for 8 hours for solution treatment, and then cooled to room temperature. The cooling rate after the solution treatment was 190 ° C./min.

  Next, the sintered body after the solution treatment was heated to 690 ° C. and held at the ultimate temperature for 2 hours, and subsequently, as an aging treatment, the temperature was raised to 830 ° C. and held at the ultimate temperature for 45 hours. Thereafter, it was gradually cooled to 600 ° C. at a cooling rate of 0.7 ° C./min, and held at the ultimate temperature for 2 hours. Thereafter, it was gradually cooled to 400 ° C. at a cooling rate of 0.5 ° C./min and held at the ultimate temperature for 1 hour. Then, the magnet was obtained by furnace-cooling to room temperature.

As in other examples, the composition of each magnet was confirmed by the ICP method. The composition of the obtained magnet is as shown in Table 1. Further, as in the other examples, the central portion oxygen concentration O _center , the surface portion oxygen concentration O _surface , the thickness of the phase including the oxide of the R element, the recoil permeability, the coercive force Hcj, and the residual magnetization are measured. did. The results are shown in Table 3.

(Examples 9 to 14)
An alloy powder having the same composition as that of Example 8 was used as a raw material, and press-molded in a magnetic field by the same method to produce a compression molded body.

  Next, oxidation treatment was performed. As shown in Table 2, in Example 9, the oxidation treatment was performed by leaving the compression molded body at 26% humidity, 23 ° C., and 4 hours. In Example 10, the oxidation treatment was performed by leaving the compression-molded body at a humidity of 26%, a temperature of 23 ° C., and a time of 22 hours. In Example 11, the oxidation treatment was performed by leaving the compression molded body at 26% humidity, 17 ° C., and 8 hours. In Example 12, the oxidation treatment was performed by leaving the compression-molded body at a humidity of 26%, a temperature of 32 ° C., and a time of 8 hours. In Example 13, the oxidation treatment was performed by leaving the compression molded body at 22% humidity, 23 ° C., and 8 hours. In Example 14, the oxidation treatment was performed by leaving the compression molded product at a humidity of 44%, a temperature of 22 ° C., and a time of 8 hours.

  Next, the compression-molded body of the alloy powder is placed in the chamber of the sintering furnace, and the steps up to sintering are performed under the same conditions as in Example 8. Thereafter, the high-quality treatment and solution are performed under the same conditions as in Example 8. A magnet was obtained by performing aging treatment and aging treatment.

As in other examples, the composition of each magnet was confirmed by the ICP method. The composition of the obtained magnet is as shown in Table 1. Further, as in the other examples, the central portion oxygen concentration O _center , the surface portion oxygen concentration O _surface , the thickness of the phase including the oxide of the R element, the recoil permeability, the coercive force Hcj, and the residual magnetization are measured. did. The results are shown in Table 3.

(Comparative Example 1)
Magnets having the compositions shown in Table 1 were produced in the same manner as in Example 1. The oxygen concentration O _{center at the center} , the oxygen concentration O _{surface at the surface} , the thickness of the oxide region, the coercive force Hcj, and the remanent magnetization were measured in the same manner as in the example. The results are shown in Table 3. The recoil permeability could not be measured because the coercive force was less than 1000 kA / m and a nick point was generated in the BH curve. The same applies to Comparative Examples 4, 6, and 8.

(Comparative Example 2)
Magnets having the compositions shown in Table 1 were produced in the same manner as in Example 4. Oxygen concentration _{O center} examples as well as the center, of the surface portion of oxygen concentration _{O Surface,} the thickness of the phase containing an oxide of R element, recoil permeability, coercive force Hcj, and residual magnetization was measured. The results are shown in Table 3.

(Comparative Examples 3 to 8)
An alloy powder having the same composition as that of Example 8 was used as a raw material, and press-molded in a magnetic field by the same method to produce a compression molded body.

  Next, oxidation treatment was performed. As shown in Table 2, in Comparative Example 3, the oxidation treatment was performed by leaving the compression-molded body at a humidity of 26%, a temperature of 23 ° C., and a time of 0.5 hours. In Comparative Example 4, the oxidation treatment was performed by leaving the compression molded body at a humidity of 26%, a temperature of 23 ° C., and a time of 36 hours. In Comparative Example 5, the oxidation treatment was performed by leaving the compression molded body at 26% humidity, 10 ° C., and 8 hours. In Comparative Example 6, the oxidation treatment was performed by leaving the compression molded body at 26% humidity, 46 ° C., and 8 hours. In Comparative Example 7, the oxidation treatment was performed by leaving the compression molded product at 15% humidity, 23 ° C., and 8 hours. In Comparative Example 8, the oxidation treatment was performed by leaving the compression molded product at 80% humidity, 23 ° C., and 8 hours.

  Next, the compression-molded body of the alloy powder is placed in the chamber of the sintering furnace, and the steps up to sintering are performed under the same conditions as in Example 8. Thereafter, the high-quality treatment and solution are performed under the same conditions as in Example 8. A magnet was obtained by performing aging treatment and aging treatment.

As in the examples, the composition of each magnet was confirmed by the ICP method. The composition of the obtained magnet is as shown in Table 1. Further, as in the other examples, the central portion oxygen concentration O _center , the surface portion oxygen concentration O _surface , the thickness of the phase including the oxide of the R element, the recoil permeability, the coercive force Hcj, and the residual magnetization are measured. did. The results are shown in Table 3.

  As is apparent from Tables 1 to 3, the permanent magnets of Examples 1 to 14 have a higher recoil permeability than those of Comparative Example 1 having a high Sm concentration and Comparative Example 2 having a high Zr concentration. It exhibits magnetic susceptibility, high coercive force, and high magnetization. From this, it can be seen that the magnet characteristics can be improved by adjusting the amount of each element constituting the permanent magnet.

  The permanent magnets of Examples 8 to 14 are higher than, for example, the permanent magnet of Comparative Example 3 in which the oxidation treatment time is less than 2 hours and the permanent magnet of Comparative Example 4 in which the oxidation treatment time is more than 24 hours. It exhibits recoil permeability, high coercivity, and high magnetization. From this, it is understood that the magnet characteristics can be improved by performing the oxidation treatment for a predetermined time.

  The permanent magnets of Examples 8 to 14 are higher than, for example, the permanent magnet of Comparative Example 5 in which the oxidation treatment temperature is less than 15 ° C. and the permanent magnet of Comparative Example 6 in which the oxidation treatment temperature exceeds 35 ° C. It exhibits recoil permeability, high coercivity, and high magnetization. From this, it is understood that the magnet characteristics can be enhanced by performing the oxidation treatment at a predetermined temperature.

  In the permanent magnets of Examples 8 to 14, for example, the recoil permeability is higher than the permanent magnet of Comparative Example 7 in which the humidity of oxidation treatment is less than 20% and the permanent magnet of Comparative Example 8 in which the leaving humidity exceeds 50%. It exhibits magnetic susceptibility, high coercive force, and high magnetization. From this, it is understood that the magnet characteristics can be enhanced by performing the oxidation treatment at a predetermined temperature.

As described above, in the permanent magnet of Example 1 to Example 14, the control in the main phase, the oxygen concentration _{O center} of the central portion, the oxygen concentration _{O Surface} of the surface portion, the thickness of the phase containing an oxide of R element By doing so, high recoil permeability, high coercive force, and high magnetization are expressed. From this, it can be seen that the permanent magnets of Examples 1 to 14 have excellent magnet characteristics. Further, when the field weakening control method at high speed rotation is used for a rotating electric machine such as a motor, current by the field weakening control method becomes unnecessary, and loss can be reduced and efficiency can be improved.

  DESCRIPTION OF SYMBOLS 1a ... Curve, 1b ... Curve, 2a ... Curve, 2b ... Curve, 3a ... Curve, 3b ... Curve, 11 ... Area, 12 ... Area, 13 ... Area, 100 ... Permanent magnet motor, 103 ... Rotor, 104 ... Iron core, 105: Permanent magnet, a: Operating point, b: Operating point.

Claims (7)

A permanent magnet having a composition containing at least one element selected from rare earth elements,
A permanent magnet having a remanent magnetization of 1.16 T or more, a coercive force Hcj on an MH curve of 1000 kA / m or more, and a recoil permeability on a BH curve of 1.1 or more. The coercive force Hcb on the BH curve is 800 kA / m or less,
2. The permanent magnet according to claim 1, wherein the ratio of the magnetic field Hk90 to the coercive force Hcj when the magnetization is 90% of the residual magnetization is 70 or less. Comprising a sintered body having the composition,
The sintered body has a phase containing an oxide of the rare earth element provided so as to be exposed on the surface of the sintered body,
3. The permanent magnet according to claim 1, wherein a thickness of the phase containing the rare earth element oxide is not less than 50 μm and not more than 800 μm.   The oxygen concentration in the first region located at a depth within 100 micrometers from the surface of the sintered body is the oxygen concentration in the second region located at a depth of 500 micrometers or more from the surface of the sintered body. The permanent magnet according to claim 3, wherein the permanent magnet is at least twice as long. The sintered body includes a metal structure including a main phase having a Th ₂ Zn ₁₇ type crystal phase,
5. The permanent magnet according to claim 3, wherein the main phase includes a cell phase having the Th ₂ Zn ₁₇ type crystal phase and a Cu rich phase having a Cu concentration higher than that of the cell phase. The composition is
_{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 the group consisting of Zr, Ti, and Hf, and p satisfies 10.8 ≦ p ≦ 12.5 atomic%) Q is a number that satisfies 25 ≦ q ≦ 40 atomic%, r is a number that satisfies 0.88 ≦ r ≦ 3.5 atomic%, and t is 3.5 ≦ t ≦ 13.5 atomic% Is the number to do)
The permanent magnet as described in any one of Claims 1 thru | or 5 represented by these. 50 atomic% or more of the element R in the composition formula is Sm,
The permanent magnet according to claim 6, wherein 50 atomic% or more of the element M in the composition formula is Zr.

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