Rare-earth cobalt permanent magnet, method for manufacturing rare-earth cobalt permanent magnet, and device

Abstract

To provide a rare earth cobalt permanent magnet having excellent magnetic properties which are particularly coercive force and squareness.SOLUTION: A rare earth cobalt permanent magnet is a sintered body having a composition which contains R: 24 to 27 wt% (note that R denotes the total of rare earth elements including Sm), Fe: 23 to 27 wt%, Cu: 4.0 to 5.0 wt%, Zr: 1.5 to 2.5 wt%, and Mn: 0.1 to 2.5 wt%, and the balance consists of Co and inevitable impurities, where the body has a plurality of crystal grains and grain boundary phases, an average Mn concentration on the grain boundary phases is 0.5 to 1.5 times for an average Mn concentration on the crystal grains, the crystal grains have 2-17 phase of a Th2Zn17 type structure and 1-5 phase of a RCo5 type structure, and an average Mn concentration on the 1-5 phase is 0.4 to 1.5 times for an average Mn concentration on the 2-17 phase.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to rare earth cobalt permanent magnets, methods for manufacturing rare earth cobalt permanent magnets, and devices.

Background Art

[0002] As one of the permanent magnets, rare earth cobalt permanent magnets such as samarium cobalt magnets are known. For rare earth cobalt permanent magnets, those added with, for example, Fe, Cu, Zr, etc. have been studied from various viewpoints such as improving magnetic properties.

[0003] For example, in Patent Document 1, there is disclosed a permanent magnet having a specific amount of rare earth elements, Fe, Cu, Co, Zr, Ti, Hf, and comprising crystal grains composed of a main phase containing a Th2Zn 17 type crystal phase, and a structure having grain boundaries of the crystal grains, wherein the average grain diameter of the crystal grains is 50 to 100 μm.

[0004] In Patent Document 2, there is disclosed a specific permanent magnet containing a cell phase having a Th2Zn 17 type crystal phase and a Cu-rich phase having a higher Cu concentration than the cell phase, wherein the average diameter of the cell phase is 220 nm or less.

[0005] Also, in Patent Document 3, there is disclosed a rare earth cobalt permanent magnet having a specific amount of rare earth element R, Fe, Cu, Co, Zr, and comprising a cell phase having a Th2Zn 17 type crystal phase and a cell wall containing a crystal phase having an RCo5 type structure surrounding the cell phase, wherein the concentration of the rare earth element in the cell wall is 25 at% or more higher than the concentration of the rare earth element in the cell phase.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

[0007] The present disclosure aims to provide a rare earth cobalt permanent magnet excellent in magnetic properties, particularly coercivity and rectangularity, a method for manufacturing a rare earth cobalt permanent magnet, and a device. [Means for Solving the Problems]

[0008] The rare earth cobalt permanent magnet according to one aspect of the present disclosure is a sintered body having a composition containing R: 24 to 27 wt% (where R is the total of rare earth elements including at least Sm), Fe: 23 to 27 wt%, Cu: 4.0 to 5.0 wt%, Zr: 1.5 to 2.5 wt%, Mn: 0.1 to 2.5 wt%, and the balance being composed of Co and unavoidable impurities, having a plurality of crystal grains and a grain boundary phase, the average Mn concentration in the grain boundary phase being 0.5 to 1.5 times the average Mn concentration in the crystal grains, and the crystal grains having a 2-17 phase of a Th2Zn 17 type structure and a 1-5 phase of an RCo5 type structure, and the average Mn concentration in the 1-5 phase being 0.4 to 1.5 times the average Mn concentration in the 2-17 phase.

[0009] The device according to one aspect of the present disclosure is a device having the above-described rare earth cobalt permanent magnet.

[0010] The method for manufacturing a rare earth cobalt permanent magnet according to one aspect of the present disclosure includes, after sintering, R: 24 to 27 wt% (where R is the total of rare earth elements including at least Sm), Fe: 23 to 27 wt%, Cu: 4.0 to 5.0 wt%, Zr: 1.5 to 2.5 wt%, Mn: 0.1 to 2.5 wt%, and the balance consists of Co and unavoidable impurities. A step (I) of preparing an ingot containing each raw material, a pulverization step (II) of pulverizing the ingot into powder, a pressure molding step (III) of forming the powder into a molded body, a sintering step (IV) of heating the molded body to form a sintered body, a solution treatment step (V) of heating the sintered body to perform solution treatment, a quenching step (VI) of quenching the sintered body after the solution treatment step (V), and Th2Zn 17 An aging treatment step (VII) of forming a 2-17 phase having a Th2Zn type structure and a 1-5 phase having an RCo5 type structure. The step (I) of preparing the ingot includes a first ingot heat treatment step of treating a mixture of the respective raw materials at a first ingot heat treatment temperature, and a second ingot heat treatment step of treating the mixture at a second ingot heat treatment temperature after the first ingot heat treatment step. When the sintering temperature of the molded body is S1 and the temperature of the solution treatment is S2, the first ingot heat treatment temperature T1 satisfies S1 - 50 ≤ T1 ≤ S1 (however, when the temperature difference between S1 and S2 is within 50°C, S2 < T1 ≤ S1), and the second ingot heat treatment temperature T2 satisfies S2 - 30 ≤ T2 ≤ S2.

Effects of the Invention

[0011] According to the present disclosure, it is possible to provide a rare earth cobalt permanent magnet excellent in magnetic properties, particularly coercivity and rectangularity, a method for manufacturing a rare earth cobalt permanent magnet, and a device.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments will be described with reference to the drawings. Note that "~" indicating a numerical range includes the lower limit value and the upper limit value thereof unless otherwise specified.

[0014] <Rare Earth Cobalt Permanent Magnet> The rare earth cobalt permanent magnet according to the present embodiment (hereinafter, also referred to as the present permanent magnet) contains R: 24 to 27 wt% (where R is the total of rare earth elements including at least Sm), Fe: 23 to 27 wt%, Cu: 4.0 to 5.0 wt%, Zr: 1.5 to 2.5 wt%, Mn: 0.1 to 2.5 wt%, and the balance is composed of Co and unavoidable impurities, and is a sintered body having a plurality of crystal grains and a grain boundary phase, and the average Mn concentration in the grain boundary phase is 0.5 to 1.5 times that in the crystal grains, and the crystal grains have a 2-17 phase of Th2Zn 17 type structure and a 1-5 phase of RCo5 type structure, and the average Mn concentration in the 1-5 phase is 0.4 to 1.5 times that in the 2-17 phase.

[0015] In this embodiment, the rare earth element R is a general term for Sc, Y, and lanthanoids (elements with atomic numbers 57 to 71), and at least Sm is included as the rare earth element R. The rare earth element R may be used alone as only Sm, or may be a combination of Sm and one or more other rare earth elements. From the viewpoint of magnetic properties, among others, Pr, Nd, Ce, and La are preferable as the other rare earth elements. Also, from the viewpoint of magnetic properties, Sm is preferably 80 wt% or more, more preferably 90 wt% or more, and still more preferably 95 wt% or more with respect to the whole rare earth element R. In this permanent magnet, the rare earth element R is contained in an amount of 24 to 27 wt%, preferably 24 to 26 wt%. By containing the rare earth element R in the above ratio, a permanent magnet having high magnetic anisotropy and high coercive force can be obtained.

[0016] This permanent magnet contains 23 to 27 wt%, preferably 23 to 26.5 wt% of Fe. By containing 23 wt% or more of Fe, the saturation magnetization is improved. Also, since the content of Fe is 27 wt% or less, a permanent magnet having high coercive force is obtained.

[0017] This permanent magnet contains 4.0 to 5.0 wt%, preferably 4.0 to 4.7 wt% of Cu. By containing 4.0 wt% or more of Cu, a permanent magnet having high coercive force is obtained. Also, since the content of Cu is 5.0 wt% or less, a decrease in magnetization is suppressed.

[0018] This permanent magnet contains 0.1 to 2.5 wt%, preferably 0.15 to 1.5 wt% of Mn. By containing 0.1 wt% or more of Mn, the concentration of Cu in the grain boundary phase can be increased. Also, by containing Mn within the above range, a crystal structure having relatively large grain size and uniform grain size crystals is easily obtained, and the aspect ratio is improved. On the other hand, when Mn exceeds 2.5 wt%, the grain size tends to become smaller instead.

[0019] It is presumed that the inclusion of 0.1 wt% or more of Mn lowers the melting point, and a large amount of liquid phase appears during sintering, resulting in a concentration distribution in Cu, etc. It is also presumed that the large amount of liquid phase increases the grain size of the crystal grains. It is also presumed that Mn contributes to the demagnetization of the grain boundary phase, suppressing the generation of reverse magnetic domains in the grain boundary phase.

[0020] The permanent magnet contains 1.5 to 2.5 wt%, and preferably 1.9 to 2.3 wt%, of Zr. By containing 1.5 to 2.5 wt% Zr, a permanent magnet with a high maximum energy product (BH)m, which is the maximum magnetostatic energy that a magnet can hold, can be obtained.

[0021] The remainder of the permanent magnet is composed of Co and inevitable impurities. The inclusion of Co improves the thermal stability of the permanent magnet. On the other hand, if the content of Co becomes excessive, the content of Fe decreases relatively. The inevitable impurities are elements that are inevitably mixed in from the raw materials or manufacturing process, and specific examples include, but are not limited to, C, N, P, S, Al, Ti, Cr, Ni, Hf, Sn, and W. In the permanent magnet, the content of inevitable impurities is preferably 5 wt% or less in total, more preferably 1 wt% or less, and even more preferably 0.1 wt% or less, based on the total amount of the permanent magnet. The local content of each element in the permanent magnet can be measured, for example, using energy dispersive X-ray spectrometry (EDX).

[0022] The metallographic structure of the permanent magnet will be described with reference to Figures 1 and 2. Figure 1 is a schematic diagram showing an example of a cross section of a rare earth cobalt permanent magnet according to this embodiment, and Figure 2 is a schematic diagram showing an enlarged view of part A (a part of crystal grains 10) in Figure 1. As shown in the example of Figure 1, the rare earth cobalt permanent magnet 100 according to this embodiment has a plurality of crystal grains 10 and a grain boundary phase 20 present between the crystal grains 10. Also, as shown in the example of Figure 2, the crystal grains 10 are composed of Th2Zn 17It has a phase 11 of the Th2Zn17 type structure (hereinafter sometimes referred to as the 2-17 phase 11) and a phase 12 of the RCo5 type structure (hereinafter sometimes referred to as the 1-5 phase 12), and has a structure (hereinafter sometimes referred to as the cell structure) in which the 2-17 phase is the main phase (volume ratio is 50% or more). Note that the crystal grain 10 may further have a crystal phase of the TbCu7 type structure (hereinafter sometimes referred to as the 1-7 phase) (not shown).

[0023] Th2Zn 17 The phase 11 of the Th2Zn17 type structure is a crystal structure having a space group of the R-3m type. In this permanent magnet, usually, the Th site is occupied by a rare earth element and Zr, and the Zn site is occupied by Co, Cu, Fe, and Zr. Further, in the phase 12 of the RCo5 type structure, usually, the R site is occupied by a rare earth element and Zr, and the Co site is occupied by Co, Cu, and Fe. Further, in the crystal phase of the TbCu7 type structure, usually, the Tb site is occupied by a rare earth element and Zr, and the Cu site is occupied by Co, Cu, and Fe. The crystal structure can be determined by the X-ray diffraction method.

[0024] As described above, in this permanent magnet, the average Mn concentration in the grain boundary phase 20 is 0.5 to 1.5 times that in the crystal grain 10. Further, the average Mn concentration in the 1-5 phase 12 is 0.4 to 1.5 times that in the 2-17 phase 11. Therefore, a rare earth cobalt permanent magnet excellent in magnetic properties, particularly coercivity and rectangularity, can be obtained.

[0025] In this permanent magnet, the average Mn concentration in the grain boundary phase 20 is preferably 0.8 to 1.2 times that in the crystal grain 10. Further, the average concentrations of Cu and Zr in the grain boundary phase 20 may be 2 times or more, preferably 4 times or more higher than the average concentrations of Cu and Zr in the crystal grain 10. Further, the average Mn concentration in the 1-5 phase 12 is preferably 0.8 to 1.0 times that in the 2-17 phase 11. In this embodiment, by setting each value within such a range, a rare earth cobalt permanent magnet having further excellent magnetic properties can be obtained.

[0026] FIG. 3 is an electron micrograph of the rare earth cobalt permanent magnet according to the present embodiment, showing crystal grains 10 and grain boundary phase 20. FIG. 4 is a graph showing the composition analysis results of the rare earth cobalt permanent magnet according to the present embodiment, showing the composition analysis results near the crystal grains 10 and the grain boundary phase 20. That is, the graph shown in FIG. 4 is the composition analysis result starting from the crystal grain 10, passing through the grain boundary phase 20, and ending at another crystal grain 10.

[0027] As shown in the electron micrograph of FIG. 3, there is a grain boundary phase 20 between the crystal grains 10. Also, as shown in the composition analysis results of FIG. 4, the composition of each element in the grain boundary phase 20 varies compared to the composition of each element in the crystal grain 10. Specifically, in the grain boundary phase 20, the amounts of Fe and Co are reduced compared to the crystal grain 10, while the amounts of Cu and Zr are increased. Further, in the present embodiment, the average concentrations of Cu and Zr in the grain boundary phase 20 are preferably at least twice as high as the average concentrations of Cu and Zr in the crystal grain 10, and more preferably at least four times as high. Also, the average Mn concentration in the grain boundary phase 20 is preferably 0.5 to 1.5 times, and more preferably 0.8 to 1.2 times, that of the average Mn concentration in the crystal grain 10. That is, in the present embodiment, in the crystal grains 10 and the grain boundary phase 20, Mn is uniformly dispersed compared to Cu and Zr.

[0028] FIG. 5 is an electron micrograph of the rare earth cobalt permanent magnet according to the present embodiment, showing the 2-17 phase 11 and the 1-5 phase 12 in the crystal grains. FIG. 6 is a graph showing the composition analysis results of the rare earth cobalt permanent magnet according to the present embodiment, showing the composition analysis results of the 2-17 phase 11 and the 1-5 phase 12. That is, the graph shown in FIG. 6 is the composition analysis result starting from the 2-17 phase 11, passing through the 1-5 phase 12, and ending at another 2-17 phase 11.

[0029] As shown in the electron micrograph of Fig. 5, 2-17 phase 11 and 1-5 phase 12 exist in the crystal grains. Also, as shown in the composition analysis results of Fig. 6, the composition of each element in 1-5 phase 12 varies compared to the composition of each element in 2-17 phase 11. Specifically, in 1-5 phase 12, the amounts of Fe, Co, and Zr are reduced compared to 2-17 phase 11, while the amounts of Cu and Sm are increased. Further, in the present embodiment, the average Mn concentration in 1-5 phase 12 is preferably 0.4 to 1.5 times, more preferably 0.8 to 1.0 times, the average Mn concentration in 2-17 phase 11. That is, in the present embodiment, within the crystal grains, Mn is uniformly dispersed compared to Cu and Zr. In other words, in 2-17 phase 11 and 1-5 phase 12, Mn is uniformly dispersed compared to Cu and Zr.

[0030] In the present embodiment, the "average concentration" of each element is the arithmetic mean concentration at the analysis points of each phase.

[0031] Note that the electron micrographs and composition analysis results shown in Figs. 3 to 6 can be measured using the following method. First, the sample is physically polished with water-resistant abrasive paper or the like. Then, the surface is processed using a focused ion beam (FIB) or ion milling so that no unevenness appears on the surface. The target location is observed for the thus-processed sample using a transmission electron microscope (TEM). The observation magnification at this time may be 3000 to 5000 times for the grain boundary phase and 10000 to 30000 times for the cell structure within the crystal grains. Also, energy dispersive X-ray spectroscopy (EDX) is used to perform composition analysis on the observed location as it is. The composition analysis is preferably performed at 5 to 20 nm for the grain boundary phase and 0.5 to 2.0 nm for the cell structure.

[0032] This permanent magnet preferably has a sintered body density of 8.20 to 8.45 g / cm3, more preferably 8.25 to 8.40 g / cm3. By setting the sintered body density within this range, the residual magnetic flux density (Br) and squareness ratio can be made particularly good.

[0033] This permanent magnet is characterized in that the structure is homogenized by heat treatment such as sintering and solutionizing followed by rapid cooling, and further aging is performed to develop the characteristics of the permanent magnet.

[0034] The remanence (Br) of this permanent magnet is 11.8 kG or more, preferably 12.0 kG or more. Also, the coercive force (Hcj) is 20 kOe or more, preferably 22 kOe or more. Further, the maximum energy product (BH)m is 260 kJ / m 3 or more, preferably 265 kJ / m 3 or more. Here, the maximum energy product (BH)m is the maximum static magnetic energy that the magnetic material can hold, and represents the maximum value of the product of the magnetic flux density B and the magnetic field H on the B-H decay curve in the second quadrant (decay curve) of the magnetization curve (B-H curve).

[0035] The squareness ratio represented by the ratio (Hk / Hcj) of the magnetic field (Hk) to the coercive force (Hcj) of this permanent magnet is 65% or more, preferably 70% or more. Here, the magnetic field (Hk) is defined as the magnetic field at 90% magnetization of the remanent magnetization.

[0036] It is considered that the coercive force of this permanent magnet is developed by pinning the magnetic wall between the 2-17 phase and the 1-5 phase during magnetic wall movement. Also, when the two-phase separation occurs, Fe and Cu are concentrated in the 2-17 phase and the 1-5 phase respectively, thereby improving the squareness ratio and increasing the maximum energy product (BH)m. Furthermore, the better the composition ratio of the 2-17 phase and the 1-5 phase is constant throughout the sample, the better the magnetic properties can be obtained.

[0037] When measuring the magnetic properties, first process the sample into a predetermined shape. When using a DC B-H tracer, magnetize by applying a magnetic field about 3 to 4 times higher than the predicted Hcj, and then measure according to the usage method of the device. When using a pulse type B-H tracer, magnetization is not necessary.

[0038] <Manufacturing method of rare earth cobalt permanent magnet> Next, a method for manufacturing a rare earth cobalt permanent magnet according to the present embodiment will be described. The method for manufacturing this permanent magnet includes, after sintering, R: 24 to 27 wt% (where R is the total of rare earth elements including at least Sm), Fe: 23 to 27 wt%, Cu: 4.0 to 5.0 wt%, Zr: 1.5 to 2.5 wt%, Mn: 0.1 to 2.5 wt%, and the balance consists of Co and unavoidable impurities. A step (I) of preparing an ingot containing each raw material, a pulverization step (II) of pulverizing the ingot into powder, a pressure molding step (III) of forming the powder into a molded body, a sintering step (IV) of heating the molded body to form a sintered body, a solution treatment step (V) of heating the sintered body to perform solution treatment, a quenching step (VI) of quenching the sintered body after the solution treatment step (V), and Th2Zn 17 An aging treatment step (VII) of forming a 2-17 phase of a Th2Zn type structure and a 1-5 phase of an RCo5 type structure. The step (I) of preparing the ingot includes a first ingot heat treatment step of treating a mixture of the respective raw materials at a first ingot heat treatment temperature, and a second ingot heat treatment step of treating the mixture at a second ingot heat treatment temperature after the first ingot heat treatment step. When the sintering temperature of the molded body is S1 and the temperature of the solution treatment is S2, the first ingot heat treatment temperature T1 satisfies S1 - 50 ≤ T1 ≤ S1 (however, when the temperature difference between S1 and S2 is within 50 °C, S2 < T1 ≤ S1), and the second ingot heat treatment temperature T2 satisfies S2 - 30 ≤ T2 ≤ S2.

[0039] Hereinafter, the method for manufacturing this permanent magnet will be described in detail.

[0040] In step (I) of preparing an ingot containing each raw material, as the raw materials, those based on Sm, rare earth elements such as Nd, Pr, Ce, Fe, Cu, Co, and further master alloys such as FeZr or CuZr are used. Here, it is preferable to select a master alloy having a composition with a low eutectic temperature from the viewpoint of facilitating the compositional homogenization of the alloy ingot. For example, FeZr or CuZr is preferable. In the case of FeZr, those around Fe 80% and Zr 20% by weight ratio, and in the case of CuZr, those of Cu 50% and Zr 50% are suitable for this embodiment. These raw materials are blended to have a predetermined composition, placed in a crucible such as alumina, and melted by a high-frequency melting furnace in a vacuum of 1×10 -2 torr or less or in an inert gas atmosphere, and then cast into a mold to obtain an alloy ingot.

[0041] Considering the manufacturing cost, it is better to use the obtained alloy ingot as it is. However, in this embodiment, heat treatment is performed to further homogenize the structure and improve the magnetic properties. Specifically, in order to eliminate and homogenize the phases formed during casting, a first ingot heat treatment step of treating at the first ingot heat treatment temperature and a second ingot heat treatment step of treating at the second ingot heat treatment temperature are carried out.

[0042] In the first ingot heat treatment step, from the viewpoint of suppressing the evaporation of Sm, the first ingot heat treatment temperature is preferably lower than the sintering temperature and 50°C higher than the solutionizing temperature. However, when the difference between the sintering temperature and the solutionizing temperature is within 50°C, the first ingot heat treatment temperature is preferably equal to or lower than the sintering temperature and higher than the solutionizing temperature. Specifically, when the sintering temperature of the compact is S1 and the temperature of the solutionizing treatment (solutionizing temperature) is S2, the first ingot heat treatment temperature T1 is preferably set to satisfy S1 - 50 ≤ T1 ≤ S1 (however, when the temperature difference between S1 and S2 is within 50°C, S2 < T1 ≤ S1). In addition, in the present embodiment, the first ingot heat treatment temperature T1 is more preferably set to satisfy S1 - 30 ≤ T1 ≤ S1 (however, when the temperature difference between S1 and S2 is within 30°C, S2 < T1 ≤ S1). The heat treatment time in the first ingot heat treatment step is preferably 0.5 to 3 hours, and more preferably 1 to 2 hours. By setting the heat treatment temperature and the heat treatment time within this range, it is possible to suppress the evaporation of Sm and eliminate the dendrite phase and other unintended phases.

[0043] In addition, in the second ingot heat treatment step, from the viewpoint of promoting homogenization, the second ingot heat treatment temperature is preferably equal to or lower than the solutionizing temperature and higher than a temperature 30 degrees lower than the solutionizing temperature. Specifically, the second ingot heat treatment temperature T2 is preferably set to satisfy S2 - 30 ≤ T2 ≤ S2. In addition, in the present embodiment, the second ingot heat treatment temperature T2 is more preferably set to satisfy S2 - 20 ≤ T2 ≤ S2. The heat treatment time in the second ingot heat treatment step is preferably 1 to 10 hours, and more preferably 3 to 8 hours. By setting the heat treatment time within this range, it is possible to suppress the evaporation of Sm and homogenize the structure.

[0044] When shifting from the first ingot heat treatment temperature T1 to the second ingot heat treatment temperature T2, from the viewpoints of suppressing the evaporation of Sm and promoting homogenization, it is preferable to lower the temperature at a rate of 0.1 to 20 °C / min, and more preferably at a rate of 1 to 10 °C / min. Note that in this embodiment, the ingot heat treatment process is not limited to two steps, and the ingot heat treatment process may be three steps or more. Further, instead of casting into a mold, a method called strip casting may be used, in which a molten metal is dropped onto a copper roll to obtain a flake-like alloy having a thickness of about 1 mm.

[0045] Next, the ingot produced as described above is pulverized into a powder (pulverization step (II)). First, the ingot is roughly pulverized to obtain a powder having an average size of about 100 to 500 μm. Then, the roughly pulverized powder is finely pulverized by a ball mill, a jet mill, or the like to obtain a powder having an average of about 1 μm or more and 10 μm or less. By setting such an average particle size, it is possible to shorten the sintering time in the sintering step described later, and a uniform permanent magnet can be manufactured. Further, in this embodiment, from the viewpoint of improving the sinterability, the particle size distribution of the finely pulverized powder is such that D10, which is the particle size value of 10% or less of the whole, is less than 4 μm, the median diameter D50 (the particle size value of 50% or less of the whole) is 5 to 8 μm, and D90, which is the particle size value of 90% or less of the whole, is less than 16 μm. It is more preferable that D10 is less than 3 μm, D50 is 5 to 7 μm, and D90 is less than 15 μm. By setting such a particle size distribution, a sintered body having a density of 8.20 g / cm 3 or more can be obtained.

[0046] Next, the powder obtained as described above is pressure-molded to produce a molded body (pressure molding step (III)). In the present embodiment, from the viewpoint of improving magnetic properties by aligning the crystal orientations of the powder, it is preferable to perform pressure molding in a constant magnetic field. The relationship between the direction of the magnetic field and the pressing direction is not particularly limited and may be appropriately selected according to the shape of the product, etc. For example, when manufacturing a ring magnet or a thin plate-shaped magnet, it can be a parallel magnetic field press that applies a magnetic field in a parallel direction with respect to the pressing direction. On the other hand, from the viewpoint of excellent magnetic properties, it is preferable to use a perpendicular magnetic field press that applies a magnetic field perpendicular to the pressing direction.

[0047] The magnitude of the magnetic field is not particularly limited and may be, for example, a magnetic field of 15 kOe or less or a magnetic field of 15 kOe or more according to the use of the product, etc. Among them, from the viewpoint of excellent magnetic properties, it is preferable to perform pressure molding in a magnetic field of 15 kOe or more. Also, the pressure during pressure molding may be appropriately adjusted according to the size, shape, etc. of the product. As an example, the pressure can be set to 0.5 to 2.0 ton / cm 2 of pressure.

[0048] Next, the molded body obtained as described above is heated to obtain a sintered body (sintering step (IV)). In the present embodiment, the sintering conditions only need to ensure sufficient densification of the obtained sintered body and can be known conditions. From the viewpoint of densification of the sintered body, the sintering temperature is preferably 1170 to 1215 °C, more preferably 1180 to 1210 °C. By setting it to 1215 °C or lower, evaporation of rare earth elements, particularly Sm, is suppressed, and a permanent magnet with excellent magnetic properties can be manufactured. Also, in the present embodiment, since having Mn tends to lower the melting point, sufficient sintering is possible at 1215 °C or lower.

[0049] Regarding the heating rate conditions in the sintering process, from the perspective of removing adsorbed gas contained in the green compact, it is preferable to first start evacuation at room temperature and heat at a rate of 1 to 10 °C / min. In this heating process, a hydrogen atmosphere may be used instead of evacuation. Also in this case, it is preferable to switch to a vacuum atmosphere within the range of 1150 °C or lower. The sintering time is preferably 20 to 210 minutes, more preferably 30 to 150 minutes, from the point of sufficiently achieving densification while suppressing the evaporation of Sm. Also, from the perspective of suppressing oxidation, the above sintering process is preferably carried out in a vacuum of 1000 Pa or lower or in an inert gas atmosphere, and more preferably carried out in a vacuum of 100 Pa or lower from the point of increasing the density of the sintered body.

[0050] Next, the sintered body is heated to perform a solution treatment (solution treatment step (V)). The solution treatment is a process for forming a 1-7 phase (TbCu7-type structure), which is a precursor for separating into 2-17 phases and 1-5 phases. From the perspective of the production process, it is preferable to continue the solution treatment without cooling to room temperature after sintering. Here, when transitioning from the sintering temperature to the solution temperature, it is preferable to cool at a rate of 0.1 to 10 °C / min, more preferably at a rate of 0.2 to 2.5 °C / min, from the perspective of suppressing the evaporation of Sm and promoting homogenization. The solution treatment is carried out at a temperature of 1110 to 1165 °C in a vacuum of 1000 Pa or lower or in an inert gas atmosphere. Since the optimum solution temperature varies depending on the composition, it is preferable to perform solution treatment at a temperature suitable for each. If the solution temperature is too high, a liquid phase remains and homogenization cannot be achieved, and if it is too low, it takes time for homogenization. Therefore, the solution treatment is preferably carried out at 1120 to 1160 °C. Also, the solution treatment time is preferably 5 to 150 hours, more preferably 10 to 100 hours. If the solution treatment time is too short, homogenization into the 1-7 phase is insufficient, and if the solution treatment time is too long, Sm evaporates and good magnetic properties cannot be obtained. Therefore, the solution treatment time is preferably within the above range.

[0051] Next, the sintered body is rapidly cooled after the solution treatment (rapid cooling step (VI)). Rapid cooling is a treatment for maintaining the 1-7 phase obtained by the solution treatment. If the rapid cooling is insufficient, the structure will change during cooling. In particular, the important temperature range for effective rapid cooling is the solution temperature to 600°C. To retain the 1-7 phase, a rapid cooling rate of 60°C / min or more is required in the above range, and a rapid cooling rate of 80°C / min or more is preferable.

[0052] Next, the formed body after the rapid cooling step is subjected to an aging treatment to form a 2-17 phase and a 1-5 phase (aging treatment step (VII)). The aging temperature is not particularly limited. However, in order to obtain a permanent magnet having the 2-17 phase as the main phase and having the 2-17 phase and the 1-5 phase homogeneously, it is preferably held at a temperature of 700 to 900°C for 2 to 20 hours, and then the cooling rate is set to 2°C / min or less until it is cooled to at least 400°C. By holding at a temperature of 700°C to 900°C for 2 to 20 hours, the 2-17 phase and the 1-5 phase can be formed homogeneously. Among them, it is preferable to perform the aging treatment in the temperature range of 800 to 850°C. Also, from the viewpoint of obtaining good magnetic properties, the cooling rate is preferably 2°C / min or less, and more preferably 0.5°C / min or less.

[0053] By using the method for manufacturing a rare earth cobalt permanent magnet according to the embodiment described above, a rare earth cobalt permanent magnet having the above-described characteristics can be manufactured. That is, a rare earth cobalt permanent magnet having a plurality of crystal grains and a grain boundary phase, wherein the average Mn concentration in the grain boundary phase is 0.5 to 1.5 times that in the crystal grains, and the crystal grains have a 2-17 phase with a Th2Zn 17 type structure and a 1-5 phase with an RCo5 type structure, and the average Mn concentration in the 1-5 phase is 0.4 to 1.5 times that in the 2-17 phase can be manufactured.

[0054] <Device> This embodiment can further provide a device having the above-described rare earth cobalt permanent magnet. Specific examples of such devices include, for example, watches, electric motors, various instruments, communication devices, computer terminals, speakers, video disks, sensors, and the like. Further, the rare earth cobalt permanent magnet according to this embodiment has excellent heat resistance and is less likely to deteriorate in magnetic force even at a high environmental temperature. Therefore, it can also be suitably used for angle sensors, ignition coils, drive motors of HEVs (Hybrid electric vehicles), etc. used in the engine room of automobiles. Among them, as described above, since it has a high residual magnetic flux density, a high coercive force, and a high squareness ratio, it can be suitably applied to a variable magnetic field motor, and a variable magnetic field motor that realizes high efficiency from low speed to high speed can be obtained.

[0055] According to the embodiment described above, it is possible to provide a rare earth cobalt permanent magnet excellent in magnetic properties, particularly coercive force and rectangularity, a method for manufacturing a rare earth cobalt permanent magnet, and a device.

Examples

[0056] Hereinafter, the present invention will be specifically described with reference to examples and comparative examples. Note that the present invention is not limited by these descriptions.

[0057] (Examples 1 to 3) The master alloy of Fe20%Zr80% and each raw material were adjusted to have the compositions of Examples 1 to 3 in Table 1-1, melted in a high-frequency melting furnace, and cast to obtain alloy ingots, respectively. Each of the obtained alloy ingots was heat-treated at 1155 °C (Example 1), 1180 °C (Example 2), and 1205 °C (Example 3) for 2 hours, and then heat-treated at 1125 °C for 5 hours. Thereafter, each heat-treated alloy ingot was coarsely pulverized in an inert gas to an average of about 100 to 500 μm, and then finely pulverized in an inert gas using a ball mill so that D10 was about 2.5 μm, D50 was about 6 μm, and D90 was about 13.5 μm. These powders were each placed in a magnetic field of 15 kOe at 1 ton / cm 2A molded body was obtained by pressing at the pressure of

[0058] This molded body was sintered at 1205 °C for 1 hour in a vacuum of less than 1000 Pa, and then solution heat treatment was performed at 1130 °C for 30 hours. Subsequently, it was quenched from 1000 to 600 °C at a cooling rate of 80 °C / min. After quenching, it was held at 825 °C for 25 hours, and then aged under the condition of slow cooling to 350 °C at a cooling rate of 0.5 °C / min to obtain a permanent magnet. Note that in Table 1-1, ΔT1 is the difference between the sintering temperature (S1) and the first ingot heat treatment temperature (T1), ΔT2 is the difference between the solution heat treatment temperature (S2) and the second ingot heat treatment temperature (T2), and S1 - S2 is the difference between the sintering temperature (S1) and the solution heat treatment temperature (S2). The same applies to other tables.

[0059] The magnetic properties of this permanent magnet were measured as a molded body. The magnetic properties of the permanent magnet were measured using a B-H tracer. In addition, the necessary processing was performed on the permanent magnet, and microstructure observation and composition analysis were carried out using TEM / EDX. The residual magnetic flux density (Br), coercive force (Hcj), squareness ratio (Hk / Hcj), ratio of the grain boundary phase to the crystal grains of the average Mn concentration, ratio of the 1-5 phase to the 2-17 phase in the crystal grains (within the cell structure) of the average Mn concentration, ratio of the grain boundary phase to the crystal grains of the average Cu concentration, and ratio of the grain boundary phase to the crystal grains of the average Zr concentration of this permanent magnet are shown in Table 1-2.

[0060] (Comparative Examples 1-2) Permanent magnets according to Comparative Examples 1-2 were obtained in the same manner as in Examples 1-3 except that the first ingot heat treatment temperature (T1) was changed as in Comparative Examples 1-2 of Table 1-1.

[0061]

Table 1

[0062] As shown in Table 1-1 and Table 1-2, in Examples 1 to 3, the average Mn concentration in the grain boundary phase was in the range of 0.5 to 1.5 times that in the crystal grains. Also, in Examples 1 to 3, the average Mn concentration in the 1-5 phase was in the range of 0.4 to 1.2 times that in the 2-17 phase. Further, in Examples 1 to 3, the average concentrations of Cu and Zr in the grain boundary phase were more than twice as high as those in the crystal grains. For this reason, in Examples 1 to 3, the residual magnetic flux density (Br), coercive force (Hcj), and squareness ratio (Hk / Hcj) had good values.

[0063] (Examples 4 to 6) The master alloy of Fe20%Zr80% and each raw material were adjusted to have the compositions of Examples 4 to 6 in Table 2-1, melted by a high-frequency melting furnace, and cast to obtain alloy ingots respectively. Each of the obtained alloy ingots was heat-treated at 1170°C for 1 hour, and then heat-treated at 1110°C (Example 4), 1125°C (Example 5), and 1140°C (Example 6) for 5 hours. Then, each heat-treated alloy ingot was roughly pulverized in an inert gas to an average of about 100 to 500 μm, and then finely pulverized in an inert gas using a ball mill so that D10 was about 2.5 μm, D50 was about 6 μm, and D90 was about 13.5 μm. These powders were each pressed in a magnetic field of 15 kOe at a pressure of 1 ton / cm 2 to obtain a compact.

[0064] This compact was sintered at 1200°C for 1.5 hours in a vacuum of less than 1000 Pa, and then solution-treated at 1140°C for 100 hours. Next, it was rapidly cooled from 1000 to 600°C at a cooling rate of 80°C / min. After rapid cooling, it was held at 825°C for 25 hours, and then aged under the condition of slow cooling to 350°C at a cooling rate of 0.5°C / min to obtain a permanent magnet.

[0065] The magnetic properties of this permanent magnet were measured as a compact. The magnetic properties of the permanent magnet were measured using a B-H tracer. Further, the necessary processing was performed on the permanent magnet, and microstructure observation and composition analysis were carried out using TEM / EDX. Table 2-2 shows the residual magnetic flux density (Br), coercive force (Hcj), squareness ratio (Hk / Hcj), ratio of the grain boundary phase to the crystal grains in terms of the average Mn concentration, ratio of the 1-5 phase to the 2-17 phase in the crystal grains (within the cell structure) in terms of the average Mn concentration, ratio of the grain boundary phase to the crystal grains in terms of the average Cu concentration, and ratio of the grain boundary phase to the crystal grains in terms of the average Zr concentration of this permanent magnet.

[0066] (Comparative Examples 3 to 4) Permanent magnets according to Comparative Examples 3 to 4 were obtained in the same manner as in Examples 4 to 6, except that the second ingot heat treatment temperature (T2) was changed as in Comparative Examples 3 to 4 of Table 2-1.

[0067] [Table 2]

[0068] As shown in Table 2-1 and Table 2-2, in Examples 4 to 6, the average Mn concentration in the grain boundary phase was in the range of 0.5 to 0.9 times that in the crystal grains. Also, in Examples 4 to 6, the average Mn concentration in the 1-5 phase was in the range of 0.6 to 0.8 times that in the 2-17 phase. Further, in Examples 4 to 6, the average concentrations of Cu and Zr in the grain boundary phase were 2 times or more higher than those in the crystal grains. For this reason, in Examples 4 to 6, the residual magnetic flux density (Br), coercive force (Hcj), and squareness ratio (Hk / Hcj) became good values.

[0069] (Examples 7 to 12) The master alloy of Fe 20% Zr 80% and each raw material were adjusted to have the compositions of Examples 7 to 12 in Table 3-1, melted in a high-frequency melting furnace, and cast to obtain alloy ingots, respectively. In Example 7, the obtained alloy ingot was heat-treated at 1170 °C for 1 hour and then at 1135 °C for 6 hours. In Example 8, the obtained alloy ingot was heat-treated at 1170 °C for 1 hour and then at 1130 °C for 6 hours. In Example 9, the obtained alloy ingot was heat-treated at 1185 °C for 1 hour and then at 1135 °C for 6 hours. In Example 10, the obtained alloy ingot was heat-treated at 1185 °C for 1 hour and then at 1130 °C for 6 hours. In Example 11, the obtained alloy ingot was heat-treated at 1210 °C for 1 hour and then at 1135 °C for 6 hours. In Example 12, the obtained alloy ingot was heat-treated at 1210 °C for 1 hour and then at 1130 °C for 6 hours.

[0070] Each of the heat-treated alloy ingots was roughly pulverized in an inert gas to an average of about 100 to 500 μm, and then finely pulverized in an inert gas using a ball mill so that D10 was about 2.5 μm, D50 was about 6 μm, and D90 was about 13.5 μm. These powders were each pressed in a magnetic field of 15 kOe at a pressure of 1 ton / cm 2 to obtain a compact.

[0071] In Examples 7, 9, and 11, this compact was sintered at 1210 °C for 0.5 hour in a vacuum of less than 1000 Pa and then solution-treated at 1165 °C for 50 hours. In Examples 8, 10, and 12, this compact was sintered at 1210 °C for 0.5 hour in a vacuum of less than 1000 Pa and then solution-treated at 1160 °C for 50 hours. Then, it was quenched from 1000 to 600 °C at a cooling rate of 80 °C / min. After quenching, it was held at 825 °C for 25 hours and then aged under the condition of slow cooling to 350 °C at a cooling rate of 0.5 °C / min to obtain a permanent magnet.

[0072] The magnetic properties of this permanent magnet were measured as a compact. The magnetic properties of the permanent magnet were measured using a B-H tracer. Further, the necessary processing was performed on the permanent magnet, and microstructure observation and composition analysis were carried out using TEM / EDX. The residual magnetic flux density (Br), coercive force (Hcj), squareness ratio (Hk / Hcj), ratio of the grain boundary phase to the crystal grains in terms of the average Mn concentration, ratio of the 1-5 phase to the 2-17 phase in the crystal grains (within the cell structure) in terms of the average Mn concentration, ratio of the grain boundary phase to the crystal grains in terms of the average Cu concentration, and ratio of the grain boundary phase to the crystal grains in terms of the average Zr concentration of this permanent magnet are shown in Table 3-2.

[0073] (Comparative Examples 5 to 8) Permanent magnets according to Comparative Examples 5 to 8 were obtained in the same manner as in Examples 7 to 12, except that the heat treatment conditions, sintering conditions, and solution treatment conditions of the alloy ingot were changed as follows.

[0074] In Comparative Example 5, the obtained alloy ingot was heat-treated at 1160°C for 1 hour and then heat-treated at 1135°C for 6 hours. In Comparative Example 6, the obtained alloy ingot was heat-treated at 1160°C for 1 hour and then heat-treated at 1130°C for 6 hours. In Comparative Example 7, the obtained alloy ingot was heat-treated at 1215°C for 1 hour and then heat-treated at 1135°C for 6 hours. In Comparative Example 8, the obtained alloy ingot was heat-treated at 1215°C for 1 hour and then heat-treated at 1130°C for 6 hours.

[0075] Also, in Comparative Examples 5 and 7, the compact was sintered at 1210°C for 1 hour in a vacuum of less than 1000 Pa and then solution-treated at 1165°C for 6 hours. In Comparative Examples 6 and 8, the compact was sintered at 1210°C for 1 hour in a vacuum of less than 1000 Pa and then solution-treated at 1160°C for 6 hours.

[0076] [Table 3]

[0077] As shown in Table 3-1 and Table 3-2, in Examples 7 to 12, the average Mn concentration in the grain boundary phase was in the range of 0.5 to 0.8 times that in the crystal grains. Also, in Examples 7 to 12, the average Mn concentration in the 1-5 phase was in the range of 0.4 to 0.8 times that in the 2-17 phase. Further, in Examples 7 to 12, the average concentrations of Cu and Zr in the grain boundary phase were more than twice as high as those in the crystal grains. For this reason, in Examples 7 to 12, the residual magnetic flux density (Br), coercive force (Hcj), and squareness ratio (Hk / Hcj) had good values.

[0078] (Examples 13 to 20) The master alloy of Fe20%Zr80% and each raw material were adjusted to have the compositions of Examples 13 to 20 in Table 4-1, melted by a high-frequency melting furnace, and cast to obtain alloy ingots respectively. In Example 13, the obtained alloy ingot was heat-treated at 1185°C for 1 hour and then at 1130°C for 6 hours. In Example 14, the obtained alloy ingot was heat-treated at 1160°C for 1 hour and then at 1100°C for 10 hours. In Examples 15 to 16, the obtained alloy ingot was heat-treated at 1180°C for 2 hours and then at 1120°C for 8 hours. In Examples 17 to 18, the obtained alloy ingot was heat-treated at 1175°C for 3 hours and then at 1125°C for 4 hours. In Examples 19 to 20, the obtained alloy ingot was heat-treated at 1195°C for 1.5 hours and then at 1115°C for 9 hours.

[0079] Each heat-treated alloy ingot was roughly crushed in an inert gas to an average of about 100 to 500 μm, and then finely crushed in an inert gas using a ball mill so that D10 was about 2.5 μm, D50 was about 6 μm, and D90 was about 13.5 μm. These powders were each pressed in a magnetic field of 15 kOe at a pressure of 1 ton / cm 2 to obtain a compact.

[0080] In Example 13, this molded body was sintered at 1215 °C for 1.5 hours in a vacuum of less than 1000 Pa, and then solution heat treatment was performed at 1140 °C for 30 hours. In Example 14, this molded body was sintered at 1170 °C for 2.5 hours in a vacuum of less than 1000 Pa, and then solution heat treatment was performed at 1110 °C for 40 hours. In Examples 15 to 16, this molded body was sintered at 1185 °C for 2.0 hours in a vacuum of less than 1000 Pa, and then solution heat treatment was performed at 1125 °C for 50 hours. In Examples 17 to 18, this molded body was sintered at 1195 °C for 1.0 hour in a vacuum of less than 1000 Pa, and then solution heat treatment was performed at 1140 °C for 60 hours. In Examples 19 to 20, this molded body was sintered at 1200 °C for 1.0 hour in a vacuum of less than 1000 Pa, and then solution heat treatment was performed at 1130 °C for 50 hours.

[0081] Subsequently, it was rapidly cooled from 1000 to 600 °C at a cooling rate of 80 °C / min. After rapid cooling, it was held at 825 °C for 25 hours, and then aged under the condition of slow cooling to 350 °C at a cooling rate of 0.5 °C / min to obtain a permanent magnet.

[0082] The magnetic properties of this permanent magnet were measured as a molded body. The magnetic properties of the permanent magnet were measured using a B-H tracer. In addition, the necessary processing was performed on the permanent magnet, and microstructure observation and composition analysis were performed using TEM / EDX. Table 4-2 shows the residual magnetic flux density (Br), coercive force (Hcj), squareness ratio (Hk / Hcj), ratio of the average Mn concentration in the grain boundary phase to the crystal grains, ratio of the 1-5 phase to the 2-17 phase in the crystal grains (within the cell structure) of the average Mn concentration, ratio of the average Cu concentration in the grain boundary phase to the crystal grains, and ratio of the average Zr concentration in the grain boundary phase to the crystal grains of this permanent magnet.

[0083] (Comparative Examples 9 to 18) The master alloy of Fe 20% Zr 80% and each raw material were adjusted to have the compositions of Comparative Examples 9 to 18 in Table 4-1, melted in a high-frequency melting furnace, and cast to obtain alloy ingots respectively. In Comparative Examples 9 to 10, the obtained alloy ingots were heat-treated at 1185 °C for 1 hour and then at 1130 °C for 6 hours. In Comparative Examples 11 to 12, the obtained alloy ingots were heat-treated at 1160 °C for 1 hour and then at 1100 °C for 10 hours. In Comparative Examples 13 to 14, the obtained alloy ingots were heat-treated at 1180 °C for 2 hours and then at 1120 °C for 8 hours. In Comparative Examples 15 to 16, the obtained alloy ingots were heat-treated at 1175 °C for 3 hours and then at 1125 °C for 4 hours. In Comparative Examples 17 to 18, the obtained alloy ingots were heat-treated at 1195 °C for 1.5 hours and then at 1115 °C for 9 hours.

[0084] Each of the heat-treated alloy ingots was roughly pulverized in an inert gas to an average of about 100 to 500 μm, and then finely pulverized in an inert gas using a ball mill so that D10 was about 2.5 μm, D50 was about 6 μm, and D90 was about 13.5 μm. These powders were each pressed at a pressure of 1 ton / cm 2 in a magnetic field of 15 kOe to obtain a compact.

[0085] In Comparative Examples 9 to 10, this compact was sintered at 1215 °C for 1.5 hours in a vacuum of less than 1000 Pa and then solution-treated at 1140 °C for 30 hours. In Comparative Examples 11 to 12, this compact was sintered at 1170 °C for 2.5 hours in a vacuum of less than 1000 Pa and then solution-treated at 1110 °C for 40 hours. In Comparative Examples 13 to 14, this compact was sintered at 1185 °C for 2.0 hours in a vacuum of less than 1000 Pa and then solution-treated at 1125 °C for 50 hours. In Comparative Examples 15 to 16, this compact was sintered at 1195 °C for 1.0 hour in a vacuum of less than 1000 Pa and then solution-treated at 1140 °C for 60 hours. In Comparative Examples 17 to 18, this compact was sintered at 1200 °C for 1.0 hour in a vacuum of less than 1000 Pa and then solution-treated at 1130 °C for 50 hours.

[0086] Subsequently, it was quenched from 1000 to 600 °C at a cooling rate of 80 °C / min. After quenching, it was held at 825 °C for 25 hours, and then aged under the condition of slow cooling to 350 °C at a cooling rate of 0.5 °C / min to obtain a permanent magnet.

[0087] The magnetic properties of this permanent magnet were measured as a molded body. The magnetic properties of the permanent magnet were measured using a B-H tracer. In addition, the necessary processing was performed on the permanent magnet, and microstructure observation and composition analysis were carried out using TEM / EDX. Table 3-2 shows the residual magnetic flux density (Br), coercive force (Hcj), squareness ratio (Hk / Hcj), ratio of the grain boundary phase to the crystal grains of the average Mn concentration, ratio of the 1-5 phase to the 2-17 phase in the crystal grains (within the cell structure) of the average Mn concentration, ratio of the grain boundary phase to the crystal grains of the average Cu concentration, and ratio of the grain boundary phase to the crystal grains of the average Zr concentration of this permanent magnet.

[0088]

Table 4

[0089]

Table 5

[0090] As shown in Table 4-1 and Table 4-2, in Example 13 and Comparative Examples 9 to 10, the composition of Sm, which is a rare earth element, was changed. From the results of Example 13 and Comparative Examples 9 to 10, when the composition range of Sm was 24 to 27 wt%, the residual magnetic flux density (Br), coercive force (Hcj), and squareness ratio (Hk / Hcj) became good values. In Example 14 and Comparative Examples 11 to 12, the composition of Fe was changed. From the results of Example 14 and Comparative Examples 11 to 12, when the composition range of Fe was 23 to 27 wt%, the residual magnetic flux density (Br), coercive force (Hcj), and squareness ratio (Hk / Hcj) became good values. In Examples 15 to 16 and Comparative Examples 13 to 14, the composition of Cu was changed. From the results of Examples 15 to 16 and Comparative Examples 13 to 14, when the composition of Cu was 4.0 to 5.0 wt%, the residual magnetic flux density (Br), coercive force (Hcj), and squareness ratio (Hk / Hcj) became good values.

[0091] In Examples 17 - 18 and Comparative Examples 15 - 16, the composition of Zr was changed. From the results of Examples 17 - 18 and Comparative Examples 15 - 16, when the composition range of Zr was 1.5 - 2.5 wt%, the remanent magnetic flux density (Br), coercive force (Hcj), and squareness ratio (Hk / Hcj) became good values. In Examples 19 - 20 and Comparative Examples 17 - 18, the composition of Mn was changed. From the results of Examples 19 - 20 and Comparative Examples 17 - 18, when the composition range of Mn was 0.1 - 2.5 wt%, the remanent magnetic flux density (Br), coercive force (Hcj), and squareness ratio (Hk / Hcj) became good values.

[0092] As shown in Examples 1 - 20 above, when samples were prepared under predetermined conditions, the average Mn concentration in the grain boundary phase was in the range of 0.5 - 1.5 times that in the crystal grains (Condition A). Also, the average Mn concentration in the 1 - 5 phases was in the range of 0.4 - 1.5 times that in the 2 - 17 phases (Condition B). Also, the average concentrations of Cu and Zr in the grain boundary phase were 2 times or more higher than those in the crystal grains (Condition C). Also, the remanent magnetic flux density (Br) was 11.8 kG or more, the coercive force (Hcj) was 20 kOe, and the squareness ratio (Hk / Hcj) was 65% or more.

[0093] On the other hand, in samples where the heat treatment conditions of the ingot deviated from the predetermined range or the composition deviated from the predetermined range (i.e., Comparative Examples 1 - 18), some or all of the above Conditions A - C were not satisfied. Also, in Comparative Examples 1 - 18, the conditions that the remanent magnetic flux density (Br) was 11.8 kG or more, the coercive force (Hcj) was 20 kOe, and the squareness ratio (Hk / Hcj) was 65% or more were also not satisfied in part or in whole.

[0094] As described above, the present invention has been described in accordance with the above embodiments, but the present invention is not limited only to the configurations of the above embodiments, and of course includes various deformations, modifications, and combinations that those skilled in the art can make within the scope of the invention of the claims in the scope of the present patent application.

Explanation of Reference Numerals

[0095] 10 Crystal grains 11 2 - 17 phases 12 1 - 5 phases 20 grain boundary phase 100 rare earth cobalt permanent magnet

Claims

1. R: 24 to 27 wt% (wherein R is the total of rare earth elements including at least Sm), Fe: 23 to 27 wt%, Cu: 4.0 to 5.0 wt%, Zr: 1.5 to 2.5 wt%, Mn: 0.1 to 2.5 wt%, and the balance consists of Co and inevitable impurities, and it is a sintered body having a plurality of crystal grains and a grain boundary phase, and the average Mn concentration in the grain boundary phase is 0.5 to 1.5 times that in the crystal grains, and the crystal grains have a 2-17 phase of a Th Zn type structure and an RCo ２ Zn １７ type structure of 1-5 phase, and the average Mn concentration in the 1-5 phase is 0.4 to 1.5 times that in the 2-17 phase, a rare earth cobalt permanent magnet. ５

2. The rare earth cobalt permanent magnet according to claim 1, wherein the average concentrations of Cu and Zr in the grain boundary phase are 2 times or more higher than the average concentrations of Cu and Zr in the crystal grains.

3. The rare earth cobalt permanent magnet according to claim 1 or 2, wherein the average Mn concentration in the grain boundary phase is 0.8 to 1.2 times that in the crystal grains.

4. The rare earth cobalt permanent magnet according to claim 1 or 2, wherein the average Mn concentration in the 1-5 phase is 0.8 to 1.0 times that in the 2-17 phase.

5. The rare earth cobalt permanent magnet according to claim 1 or 2, wherein the average concentrations of Cu and Zr in the grain boundary phase are 4 times or more higher than the average concentrations of Cu and Zr in the crystal grains.

6. The rare earth cobalt permanent magnet according to claim 1 or 2, wherein the residual magnetic flux density (Br) is 11.8 kG or more.

7. The rare earth cobalt permanent magnet according to claim 1 or 2, wherein the coercive force (Hcj) is 20 kOe or more.

8. The rare earth cobalt permanent magnet according to claim 1 or 2, wherein the squareness ratio represented by the ratio (Hk / Hcj) of the magnetic field (Hk) to the coercive force (Hcj) is 65% or more.

9. A device comprising the rare earth cobalt permanent magnet according to claim 1 or 2.

10. Step (I) of preparing an ingot containing each raw material so that, after sintering, it has a composition containing R: 24 to 27 wt% (where R is the total of rare earth elements including at least Sm), Fe: 23 to 27 wt%, Cu: 4.0 to 5.0 wt%, Zr: 1.5 to 2.5 wt%, Mn: 0.1 to 2.5 wt%, and the balance consisting of Co and unavoidable impurities; A pulverizing step (II) of pulverizing the ingot into powder; A pressure molding step (III) of molding the powder into a molded body; A sintering step (IV) of heating the molded body to form a sintered body; A solution treatment step (V) of heating the sintered body to perform solution treatment; A quenching step (VI) of rapidly cooling the sintered body after the solution treatment step (V); Th ２ Zn １７ A aging treatment step (VII) of forming a 2-17 phase of a ThZn type structure and a 1-5 phase of an RCo type structure; and ５ The step (I) of preparing the ingot includes A first ingot heat treatment step of treating the mixture of the raw materials at a first ingot heat treatment temperature; After the first ingot heat treatment step, a second ingot heat treatment step of treating the mixture at a second ingot heat treatment temperature; and when the sintering temperature of the molded body is S1 and the temperature of the solution treatment is S2, the first ingot heat treatment temperature T1 satisfies S1 - 50 ≤ T1 ≤ S1 (however, when the temperature difference between S1 and S2 is within 50°C, S2 < T1 ≤ S1), and the second ingot heat treatment temperature T2 satisfies S2 - 30 ≤ T2 ≤ S2 - 5. ​​ The heat treatment time of the first ingot heat treatment step is 0.5 hours or more and 3.0 hours or less, and the heat treatment time of the second ingot heat treatment step is 1.0 hours or more and 10.0 hours or less. A method for manufacturing a rare earth cobalt permanent magnet.

11. The sintering step (IV) is a step of heating the green compact at a temperature of 1170 ° C or more and 1215 ° C or less for 20 minutes or more and 210 minutes or less. The solution heat treatment step (V) is a step of heating the sintered body at 1110 ° C or more and 1165 ° C or less for 5 hours or more and 150 hours or less. The rapid cooling step (VI) is a step of cooling the solution heat treated body at a cooling rate of 60 ° C / min or more from at least the solution heat treatment temperature to 600 ° C. The method for manufacturing a rare earth cobalt permanent magnet according to claim 10.

12. In the pulverization step (II), the ingot is pulverized so that the particle size D10 is less than 4 μm, the particle size D50 is 5 μm or more and 8 μm or less, and the particle size D90 is less than 16 μm. The method for manufacturing a rare earth cobalt permanent magnet according to claim 10.

13. The rare earth cobalt permanent magnet has a plurality of crystal grains and a grain boundary phase, and the average Mn concentration in the grain boundary phase is 0.5 to 1.5 times that in the crystal grains. The crystal grains are Th ２ Zn １７ type structure 2-17 phase and RCo ５ type structure 1-5 phase, and the average Mn concentration in the 1-5 phase is 0.4 to 1.5 times that in the 2-17 phase. The method for manufacturing a rare earth cobalt permanent magnet according to claim 10.

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