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

Abstract

To provide a rare-earth cobalt permanent magnet with excellent magnetic properties, particularly intrinsic coercivity and prismatic shape. [Solution] A rare earth cobalt permanent magnet according to one aspect of the present disclosure is a rare earth cobalt permanent magnet having a composition in mass percentage of R: 24-27% (wherein R is the sum of Sm and Nd, or Sm, Nd and other rare earth elements), Fe: 22-27%, Cu: 4.0-5.0%, Zr: 1.5-2.5%, Mn: 0.01-2.5%, with the remainder being Co and unavoidable impurities.

Description

[Technical Field]

[0001] This disclosure relates to rare-earth cobalt permanent magnets, methods for manufacturing rare-earth cobalt permanent magnets, and devices. [Background technology]

[0002] One type of permanent magnet is the rare-earth cobalt permanent magnet, such as samarium-cobalt magnets. From various perspectives, including improving magnetic properties, rare-earth cobalt permanent magnets with added elements such as Fe, Cu, and Zr are being investigated.

[0003] For example, Patent Document 1 contains a material that has specific amounts of rare earth elements, Fe, Cu, Co, Zr, Ti, and Hf, and Th2Zn 17 A permanent magnet is disclosed, comprising a structure having crystal grains made up of a main phase containing a type crystal phase and grain boundaries of the crystal grains, wherein the average grain size of the crystal grains is 50 to 100 μm.

[0004] Patent Document 2 contains specific amounts of rare earth elements, Fe, Cu, Co, Zr, Ti, and Hf, and Th2Zn 17 A specific permanent magnet is disclosed, comprising a cell phase having a type crystalline phase and a Cu-rich phase with a higher Cu concentration than the cell phase, wherein the average diameter of the cell phase is 220 nm or less.

[0005] Furthermore, Patent Document 3 describes a material containing specific amounts of rare earth elements R, Fe, Cu, Co, and Zr, and Th2Zn 17 A rare earth cobalt permanent magnet is disclosed, comprising a cell phase having a type crystalline phase and a cell wall containing a crystalline phase with an RCo5 type structure surrounding the cell phase, wherein the concentration of rare earth elements in the cell wall is 25 at% or higher than the concentration of rare earth elements in the cell phase. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2017-168827 [Patent Document 2] International Publication No. 2015 / 140829 [Patent Document 3] Japanese Patent Publication No. 2020-188140 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] This disclosure aims to provide a rare-earth cobalt permanent magnet with excellent magnetic properties, particularly intrinsic coercivity and prismatic shape, a method for manufacturing a rare-earth cobalt permanent magnet, and a device. [Means for solving the problem]

[0008] A rare-earth cobalt permanent magnet according to one aspect of this disclosure has a composition in mass percentage of R: 24-27% (wherein R is the sum of Sm and Nd, or Sm, Nd and other rare earth elements), Fe: 22-27%, Cu: 4.0-5.0%, Zr: 1.5-2.5%, Mn: 0.01-2.5%, with the remainder being Co and unavoidable impurities.

[0009] A device according to one aspect of this disclosure is a device having the above-mentioned rare-earth cobalt permanent magnet.

[0010] A method for manufacturing a rare-earth cobalt permanent magnet according to one aspect of this disclosure is: Step (I) involves preparing an alloy containing each raw material such that, after sintering, the composition by mass percentage includes R: 24-27% (where R is the sum of Sm and Nd, or Sm, Nd and other rare earth elements), Fe: 22-27%, Cu: 4.0-5.0%, Zr: 1.5-2.5%, Mn: 0.01-2.5%, with the remainder being Co and unavoidable impurities. A grinding step (II) in which the aforementioned alloy is reduced to powder, A molding step (III) in which the powder is formed into a molded body, The molded body is subjected to a sintering step (IV) at 1170 to 1215°C, The process (V) involves solution treatment of the sintered molded body at 1110-1165°C for less than 30 hours, A first heat treatment step (VI) of heat-treating the molded body after the solution treatment at 780 to 900 °C for 5 to 50 hours, a first cooling step (VII) of cooling the molded body after the first heat treatment step (VI) to 500 to 700 °C at a cooling rate of 0.1 to 0.5 °C / min, a second heat treatment step (VIII) of heat-treating at 500 to 700 °C, which is the temperature after the first cooling step (VII), for 1 to 10 hours, and a second cooling step (IX) of cooling the molded body after the second heat treatment step (VIII) to 350 °C or lower at a cooling rate of 0.1 to 0.5 °C / min.

Advantages 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 intrinsic coercive force and rectangularity, a method for manufacturing a rare earth cobalt permanent magnet, and a device.

Brief Description of the Drawings

[0012] [Figure 1] It is a schematic diagram showing an example of a cross section of a rare earth cobalt permanent magnet according to an embodiment. [Figure 2] It is a mapping image of the Cu element of the rare earth cobalt permanent magnet according to an embodiment. [Figure 3] It is a graph showing the magnetic properties of Example 8 and Comparative Example 3.

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 this embodiment (hereinafter also referred to as "this permanent magnet") has a composition in mass percentage that includes R: 24-27% (wherein R is the sum of Sm and Nd, or Sm, Nd and other rare-earth elements), Fe: 22-27%, Cu: 4.0-5.0%, Zr: 1.5-2.5%, Mn: 0.01-2.5%, with the remainder being Co and unavoidable impurities.

[0015] In this embodiment, R includes Sm and Nd, or Sm, Nd and other rare earth elements, and the total amount of R is 24-27%, preferably 24-26.5%, and more preferably 24.5-26%. Other rare earth elements include, for example, Y, Pr, Nd, Ce, La, etc. For example, R can be Sm and Nd, Sm, Nd and Y, or Sm, Nd and Pr. In this embodiment, by setting R within the above range, a permanent magnet with high magnetic anisotropy and high intrinsic coercivity can be obtained.

[0016] In this embodiment, the ratio Ra of Nd, or Nd and other rare earth elements in R, is preferably 14% or less, more preferably 12% or less, and even more preferably 10% or less. For example, if R is Sm and Nd, then Ra = Nd / (Sm+Nd). If R is Sm, Nd and Y, then Ra = (Nd+Y) / (Sm+Nd+Y). If R is Sm, Nd and Pr, then Ra = (Nd+Pr) / (Sm+Nd+Pr). In this embodiment, by setting Ra within the above range, a permanent magnet with high magnetic anisotropy and high intrinsic coercivity can be obtained.

[0017] This permanent magnet contains 22-27% Fe, preferably 23-27%, and more preferably 23-26.5%. A Fe content of 22% or more improves saturation magnetization. Furthermore, a Fe content of 27% or less results in a permanent magnet with high intrinsic coercivity.

[0018] This permanent magnet contains 4.0 to 5.0% of copper (Cu), preferably 4.2 to 4.7%. A Cu content of 4.0% or more results in a permanent magnet with high intrinsic coercivity. Furthermore, a Cu content of 5.0% or less suppresses the decrease in magnetization.

[0019] This permanent magnet contains 1.5 to 2.5%, preferably 1.9 to 2.3%, of Zr. By including 1.5 to 2.5% Zr, a permanent magnet with a high maximum energy product (BH)m, which is the maximum magnetic static energy that the magnet can hold, can be obtained.

[0020] This permanent magnet contains 0.01 to 2.5% Mn, preferably 0.05 to 1.5%. Including 0.01 wt% or more Mn increases the concentration of Cu at the grain boundaries. Furthermore, including Mn within the above range makes it easier to obtain a crystalline structure with relatively large grain sizes and uniform grain size, improving the angularity ratio. On the other hand, exceeding 2.5% Mn tends to result in smaller grain sizes.

[0021] It is presumed that the presence of 0.01% or more of Mn lowers the melting point, leading to the appearance of a large amount of liquid phase during sintering and the formation of a concentration distribution in Cu, etc. Furthermore, it is presumed that the appearance of a large amount of liquid phase leads to an increase in the grain size. In addition, it is presumed that Mn contributes to the demagnetization of the grain boundaries, and that the generation of reverse magnetic domains at the grain boundaries is suppressed.

[0022] Furthermore, the remainder of this permanent magnet consists of Co and unavoidable impurities. The inclusion of Co improves the thermal stability of the permanent magnet. On the other hand, if the Co content is excessive, the relative proportion of Fe decreases. Unavoidable impurities are elements that are inevitably mixed in from the raw materials or manufacturing process, and specifically include, but are not limited to, C, N, P, S, Al, Ti, Cr, Ni, Hf, Sn, and W. In this permanent magnet, the total proportion of unavoidable impurities is preferably 5% or less, more preferably 1% or less, and even more preferably 0.1% or less, based on the total amount of the permanent magnet. The local proportion of each element in the permanent magnet can be measured, for example, using energy dispersive X-ray spectrometry (EDX).

[0023] Next, the structure of this permanent magnet will be explained using Figure 1. Figure 1 is a schematic diagram showing an example of a cross-section of a rare-earth cobalt permanent magnet according to this embodiment. As shown in the example in Figure 1, this permanent magnet 10 has a plurality of crystal grains 1 (regions enclosed by solid lines in the figure), and grain boundaries 2 (solid lines in the figure) are present between the crystal grains 1. Each crystal grain 1 contains Th2Zn 17 The structure includes a cell phase 3 (indicated by a dotted line only or by a dotted and solid line in the figure) containing a crystalline phase of type RCo5 structure (hereinafter also referred to as phase 2-17), and a cell wall 4 (indicated by a dotted line in the figure) containing a crystalline phase of type RCo5 structure (hereinafter also referred to as phase 1-5). In this embodiment, the cell structure refers to a combination of one cell phase 3 and the cell wall 4 surrounding it, and is the smallest unit that constitutes a crystal grain 1.

[0024] This permanent magnet is made of Th2Zn as described above. 17 It has a cell phase 3 whose main phase is a crystalline phase with a type structure. 17The type structure is a crystal structure having an R-3m type space group. In this permanent magnet, the Th portion is occupied by rare earth elements and Zr, and the Zn portion is occupied by Co, Cu, Fe, and Zr. Furthermore, as described above, it has a cell wall 4 containing a crystal phase of the RCo5 type structure. In this RCo5 type crystal phase, the R portion is occupied by rare earth elements and Zr, and the Co portion is occupied by Co, Cu, and Fe. In this permanent magnet 10, the size of the cell structure refers to the length of the cell wall 4 (length of the crystal phase of the RCo5 type structure: long side). In this permanent magnet, from the viewpoint of magnetic properties, the size of the cell structure constituting the crystal grain 1 is preferably 300 to 700 nm, more preferably 400 to 700 nm, and even more preferably 500 to 700 nm. By setting the size of the cell structure within this range, a magnet with good prismatic properties (Hk / Hcj) can be obtained.

[0025] As described above, this permanent magnet has multiple crystal grains 1 and grain boundaries 2, and the crystal grains 1 are made of Th2Zn 17 The cell comprises a cell phase 3 containing phases 2-17 of type structure and a cell wall 4 containing phases 1-5 of type RCo5 structure. In this case, the average Cu concentration in phases 1-5 (cell wall 4) is preferably 30 at% or more, more preferably 40 at% or more, and even more preferably 50 at% or more.

[0026] Figure 2 shows a mapping image of the Cu element in a rare-earth cobalt permanent magnet according to this embodiment. In this embodiment, as shown in Figure 2, the Cu concentration in phases 1-5 (cell wall 4) is configured to be higher than the Cu concentration in phases 2-17 (cell phase 3). By concentrating Cu in phases 1-5 (cell wall 4) in this way, the movement of the magnetic domain wall can be effectively pinned at the cell wall 4 (phases 1-5), thereby increasing the intrinsic coercivity (Hcj) and angularity.

[0027] The mapping image shown in Fig. 2 can be measured using the following method. First, the sample is physically polished with waterproof abrasive paper or the like. Then, the surface is processed using a focused ion beam (FIB) or ion milling so that no irregularities are formed on the surface. The target location is observed for the thus processed sample using a transmission electron microscope (TEM). The magnification for observation at this time may be 3000 - 5000 times at the grain boundary and 10000 - 30000 times for the cell structure within the crystal grains. Further, energy dispersive X-ray spectroscopy (EDX) is used to perform composition analysis directly on the observed location. The composition analysis may be performed at 5 - 20 nm at the grain boundary and 0.5 - 2.0 nm for the cell structure.

[0028] This permanent magnet preferably has a sintered body density of 8.20 - 8.45 g / cm3, more preferably 8.25 - 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.

[0029] This permanent magnet is characterized in that the properties of the permanent magnet are manifested by achieving homogenization of the structure through sintering and solution treatment followed by aging treatment, that is, the first heat treatment step (VI), the first cooling step (VII), the second heat treatment step (VIII), and the second cooling step (IX) described below.

[0030] The residual magnetic flux density (Br) of this permanent magnet is 1.18 T or more, preferably 1.19 T or more, more preferably 1.20 T or more. Also, the intrinsic coercive force (Hcj) is 1600 kA / m or more, preferably 1650 kA / m or more, more preferably 1700 kA / m or more. Further, the maximum energy product (BH)m is 260 kJ / m 3 or more, preferably 265 kJ / m 3 or more, more preferably 270 kJ / m 3That concludes the explanation. Here, the maximum energy product (BH)m is the maximum magnetostatic energy that a magnetic material can hold, and represents the maximum value of the product of magnetic flux density B and magnetic field H on the BH decay curve in the second quadrant (decay curve) of the magnetization curve (BH curve).

[0031] Furthermore, in this permanent magnet, when the magnetic flux density is 90% of the remanent magnetic flux density (Br), the reverse magnetic field Hk is defined as the ratio of Hk to the intrinsic coercivity (Hcj) (Hk / Hcj), and the angular ratio is 65% or more, preferably 68% or more, and more preferably 70% or more.

[0032] This permanent magnet is thought to exhibit intrinsic coercivity due to pinning of the magnetic domain walls between the 2-17 phase and the 1-5 phase during domain wall movement. Furthermore, the concentration of Fe and Cu in the 2-17 and 1-5 phases, respectively, during phase separation improves the angular ratio and increases the maximum energy product (BH)m. Moreover, the more constant the composition ratio of the 2-17 phase and the 1-5 phase is throughout the sample, the better the magnetic properties can be obtained.

[0033] When measuring magnetic properties, first prepare the sample into the desired shape. When using a DC BH tracer, magnetize the sample by applying a magnetic field approximately 3 to 4 times higher than the predicted HcJ, and then measure according to the instrument's instructions. Magnetization is not necessary when using a pulsed BH tracer.

[0034] <Method for manufacturing rare-earth cobalt permanent magnets> Next, a method for manufacturing a rare-earth cobalt permanent magnet according to this embodiment will be described. The manufacturing method of this permanent magnet is Step (I) involves preparing an alloy containing each raw material such that, after sintering, the composition by mass percentage includes R: 24-27% (where R is the sum of Sm and Nd, or Sm, Nd and other rare earth elements), Fe: 22-27%, Cu: 4.0-5.0%, Zr: 1.5-2.5%, Mn: 0.01-2.5%, with the remainder being Co and unavoidable impurities. A grinding step (II) in which the aforementioned alloy is reduced to powder, A molding step (III) in which the powder is formed into a molded body, The molded body is subjected to a sintering step (IV) at 1170 to 1215°C, The process (V) involves solution treatment of the sintered molded body at 1110-1165°C for less than 30 hours, The first heat treatment step (VI) involves heat-treating the molded body after solution treatment at 780-900°C for 5-50 hours, A first cooling step (VII) is performed to cool the molded body after the first heat treatment step (VI) to 500 to 700°C at a cooling rate of 0.1 to 0.5°C / min, The second heat treatment step (VIII) involves heat treatment at a temperature of 500-700°C for 1-10 hours, which is the temperature after the first cooling step (VII), The process includes a second cooling step (IX) in which the molded body after the second heat treatment step (VIII) is cooled to 350°C or below at a cooling rate of 0.1 to 0.5°C / min.

[0035] The manufacturing method of this permanent magnet will be described in detail below.

[0036] First, after sintering, an alloy is prepared containing each raw material such that, in terms of mass percentage composition, it contains R: 24-27% (where R is the sum of Sm and Nd, or Sm, Nd and other rare earth elements), Fe: 22-27%, Cu: 4.0-5.0%, Zr: 1.5-2.5%, Mn: 0.01-2.5%, with the remainder being Co and unavoidable impurities (Step (I)). The method of preparing the alloy is not particularly limited; it may be prepared by obtaining a commercially available alloy with the desired composition, or by blending each element to achieve the desired composition. The following describes specific examples of blending each element, but this manufacturing method is not limited to this method.

[0037] First, the raw materials are prepared, including rare earth elements such as Sm, Nd, Y, Pr, and Ce, and metallic elements such as Fe, Cu, Mn, and Co, along with a master alloy. Here, it is preferable to select a master alloy with a low eutectic temperature composition, as this makes it easier to achieve a homogenized composition in the resulting alloy. In this manufacturing method, it is preferable to select and use FeZr or CuZr as the master alloy. As an example, a FeZr alloy with approximately 20% Fe and 80% Zr is suitable. As an example, a CuZr alloy with approximately 50% Cu and 50% Zr is suitable. Note that Nd and Pr have a larger magnetic moment than Sm, and therefore have the effect of increasing magnetization.

[0038] These raw materials are mixed to achieve the desired composition and placed in a crucible made of alumina or similar material, 1 × 10 -2 A homogenized alloy can be obtained by melting the alloy in a high-frequency induction furnace in a vacuum below torr or in an inert gas atmosphere. Furthermore, this manufacturing method may include a step of casting the molten alloy using a mold to form an alloy ingot. Alternatively, the molten alloy may be dropped onto a copper roll to produce a flake-like alloy about 1 mm thick (strip casting method). In this invention, the method of melting in a furnace is preferred because it makes it easier to obtain permanent magnets with high intrinsic coercivity and a high square ratio.

[0039] When an alloy ingot is produced by the aforementioned casting, it is preferable to use the resulting alloy ingot as is, considering the manufacturing cost. However, heat treatment may be performed to make the structure more uniform and improve the magnetic properties. Heat treatment conditions include holding at a constant temperature for a certain period of time, followed by rapid cooling. For example, heat treatment may be performed by holding at 1150°C for 5 hours and then rapidly cooling. Depending on the purpose, the heat treatment may also be divided into multiple stages. For example, heat treatment may be performed by holding at 1200°C for 1 hour, then cooling to 1150°C, and then holding for 3 hours.

[0040] Next, the ingot prepared as described above is crushed into powder (crushing step (II)). First, the ingot is coarsely crushed to obtain powder with an average size of approximately 100 to 500 μm. Then, this coarsely crushed powder is finely crushed using a ball mill or jet mill to obtain powder with an average size of approximately 1 μm to 10 μm. By achieving such an average particle size, it is possible to shorten the sintering time in the sintering step described later and to manufacture a uniform permanent magnet. Furthermore, in this embodiment, in order to improve sinterability, it is preferable that the particle size distribution of the finely crushed powder be such that D10 (the particle size value of 10% or less of the total) is less than 4 μm, the median diameter D50 (the particle size value of 50% or less of the total) is 5 to 8 μm, and D90 (the particle size value of 90% or less of the total) is less than 16 μm. It is even more preferable that D10 be less than 3 μm, D50 be 5 to 7 μm, and D90 be less than 15 μm. With such a particle size distribution, 8.20 g / cm³ 3 A sintered body having the above density can be obtained.

[0041] Next, the powder obtained as described above is pressure-molded to produce a molded body (molding step (III)). In this embodiment, it is preferable to pressure-mold in a constant magnetic field in order to align the crystal orientation of the powder and improve its magnetic properties. The relationship between the direction of the magnetic field and the pressing direction is not particularly limited and can be appropriately selected according to the shape of the product, etc. For example, when manufacturing ring magnets or thin plate magnets, a parallel magnetic field press can be used, in which the magnetic field is applied in a direction parallel to the pressing direction. On the other hand, in terms of superior magnetic properties, it is preferable to use a right-angle magnetic field press, in which the magnetic field is applied perpendicular to the pressing direction.

[0042] The magnitude of the magnetic field is not particularly limited and may be 15 kOe or less, or 15 kOe or more, depending on the product's application. Among these, pressure molding in a magnetic field of 15 kOe or more is preferable due to its superior magnetic properties. The pressure applied during pressure molding should be adjusted appropriately according to the size and shape of the product. For example, 0.5 to 2.0 ton / cm perpendicular to the magnetic field. 2 It can be molded under pressure.

[0043] Next, the molded body obtained as described above is heated to form a sintered body (sintering step (IV)). In this embodiment, the sintering conditions only need to be such that the resulting sintered body is sufficiently densified, and known conditions can be used. From the viewpoint of densifying the sintered body, the sintering temperature is preferably 1170 to 1215°C, and more preferably 1180 to 1210°C. By setting the temperature to 1215°C or lower, the evaporation of rare earth elements, especially Sm, is suppressed, and a permanent magnet with excellent magnetic properties can be manufactured. In addition, in this embodiment, the presence of Mn tends to lower the melting point, so sufficient sintering is possible at 1215°C or lower.

[0044] In the sintering process, the heating conditions are preferably such that vacuum is first started at room temperature and the temperature is raised at a rate of 1 to 10°C / min, from the viewpoint of removing adsorbed gases contained in the molded body. Instead of vacuum, a hydrogen atmosphere may be used during this heating process. In this case as well, it is preferable to switch to a vacuum atmosphere in the range of 1150°C or lower. The sintering time is preferably 20 to 210 minutes, and more preferably 30 to 150 minutes, from the viewpoint of suppressing evaporation of Sm while ensuring sufficient densification. Furthermore, from the viewpoint of suppressing oxidation, the sintering process is preferably carried out in a vacuum of 1000 Pa or less or in an inert gas atmosphere, and more preferably in a vacuum of 100 Pa or less from the viewpoint of increasing the density of the sintered body.

[0045] Next, the sintered body is heated and subjected to solution treatment (solution treatment step (V)). Solution treatment is a process for forming the 1-7 phase (TbCu7 type structure), which is a precursor for separating the 2-17 phase and the 1-5 phase. From the viewpoint of the production process, it is preferable to continue the solution treatment immediately after sintering without cooling to room temperature. When transitioning from the sintering temperature to the solution treatment temperature, it is preferable to cool at a rate of 0.1 to 10°C / min, and more preferably at a rate of 0.2 to 2.5°C / min, from the viewpoint 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 less, or in an inert atmosphere. Since the optimal solution treatment temperature varies depending on the composition, it is preferable to perform the solution treatment at a temperature suitable for each. If the solution temperature is too high, the liquid phase remains and homogenization cannot be achieved, and if it is too low, homogenization takes too long. Therefore, the solution temperature is preferably 1120 to 1160°C. If the solution time is too short, homogenization to phases 1-7 will be insufficient, and if it is too long, in addition to the evaporation of Sm, productivity will decrease. Therefore, the solution time is preferably 5 to 29 hours, and more preferably 10 to 29 hours.

[0046] Next, the sintered body is rapidly cooled after the solution treatment (rapid cooling step). Rapid cooling is a process to preserve phases 1-7 obtained in the solution treatment, and if the rapid cooling is insufficient, the structure will change during cooling. The important temperature range for effective rapid cooling is from the solution temperature to 600°C. In order to preserve phases 1-7, a rapid cooling rate of 60°C / min or higher is required within the above range, and a rapid cooling rate of 80°C / min or higher is preferable.

[0047] Next, the molded body after the rapid cooling process is subjected to aging treatment to form phases 2-17 and 1-5. In this embodiment, it is preferable to perform isothermal heat treatment in two or more stages as the aging treatment. By dividing the isothermal heat treatment in two or more stages in this way, the structure can be made more uniform, and a rare-earth cobalt permanent magnet with excellent magnetic properties, especially intrinsic coercivity and prismatic shape, can be obtained. For example, it is preferable that the second isothermal heat treatment be performed at a lower temperature and for a shorter time than the first isothermal heat treatment. Also, it is preferable not to introduce rapid cooling in the aging treatment. For example, in this embodiment, the heat treatment (aging treatment) process consists of a first heat treatment step (VI), a first cooling step (VII), a second heat treatment step (VIII), and a second cooling step (IX).

[0048] Specifically, the first heat treatment step (VI) is performed by heat-treating the molded body after solution treatment (or after rapid cooling if a rapid cooling step is performed) at 780-900°C for 5-50 hours, more preferably at 800-880°C for 10-40 hours. By setting the heat treatment temperature in the first heat treatment step (VI) within this range, a permanent magnet with good magnetic properties can be obtained. Furthermore, by setting the heat treatment time in the first heat treatment step (VI) within this range, the cell phase (phases 2-17) can be formed uniformly, and the precipitation of different phases can be suppressed.

[0049] Next, the molded body after the first heat treatment step (VI) is cooled to 500-700°C at a cooling rate of 0.1-0.5°C / min to perform the first cooling step (VII). By setting the cooling rate of the first cooling step (VII) within this range, Cu can be concentrated into phases 1-5 while improving productivity.

[0050] Next, the second heat treatment step (VIII) is carried out by heat treatment at 500-700°C for 1-10 hours, preferably 550-650°C for 2-7 hours, which is the temperature after the first cooling step (VII). The heat treatment temperature and time of the second heat treatment step (VIII) are preferably lower and shorter than those of the first heat treatment step (VI). By setting the heat treatment temperature of the second heat treatment step (VIII) within this range, the concentration of Cu into phases 1-5 can be promoted. Furthermore, by setting the heat treatment time of the second heat treatment step (VIII) within this range, the concentration of Cu into phases 1-5 can be promoted while improving productivity.

[0051] Next, the molded body after the second heat treatment step (VIII) is cooled to below 350°C at a cooling rate of 0.1 to 0.5°C / min to perform the second cooling step (IX). By setting the cooling rate of the second cooling step (IX) within this range, Cu can be concentrated into phases 1 to 5 while improving productivity. Below 350°C, it does not contribute to the formation of the cell structure, so it may be rapidly cooled thereafter, or it may be furnace-cooled as is.

[0052] By performing a heat treatment (aging process) that divides this isothermal heat treatment into two or more stages, it is possible to form a permanent magnet that homogeneously contains phases 2-17 and 1-5.

[0053] By using the method for manufacturing rare-earth cobalt permanent magnets according to this embodiment described above, it is possible to manufacture rare-earth cobalt permanent magnets having the above-mentioned properties.

[0054] <device> This embodiment can further provide a device having the rare-earth cobalt permanent magnet described above. Specific examples of such devices include, for example, clocks, electric motors, various instruments, communication devices, computer terminals, speakers, video discs, and sensors. Furthermore, because the rare-earth cobalt permanent magnet according to this embodiment has excellent heat resistance and does not easily degrade in magnetic force even at high ambient temperatures, it can be suitably used in angle sensors used in the engine compartment of automobiles, ignition coils, drive motors for HEVs (Hybrid electric vehicles), etc. In particular, as mentioned above, because it has a high residual magnetic flux density, high coercivity, and a high aspect ratio, it can be suitably applied to variable magnetic field motors, and a variable magnetic field motor that achieves high efficiency from low speed to high speed can be obtained.

[0055] The embodiments described above provide a rare-earth cobalt permanent magnet with excellent magnetic properties, particularly coercivity and prismatic shape, a method for manufacturing a rare-earth cobalt permanent magnet, and a device. [Examples]

[0056] The present invention will be specifically described below with reference to examples and comparative examples. However, this description is not intended to limit the present invention.

[0057] <Examples 1-17> Each raw material was prepared to have the composition described in Examples 1 to 17 of Table 1, and melted in a high-frequency induction furnace to obtain an ingot to be the master alloy (Alloy preparation step (I)). For this melting, a master alloy of Fe 20% and Zr 80% was used. The obtained master alloy was heat-treated at 1185°C for 1 hour, and then at 1120°C for 6 hours. The heat-treated master alloy was coarsely ground in an inert gas to an average size of approximately 100 μm, and then finely ground using a ball mill in an inert gas to a size of approximately 2.5 μm for D10, approximately 6 μm for D50, and approximately 13.5 μm for D90 (Ground grinding step (II)). This powder was ground in a magnetic field of 15 kOe at a rate of 1 ton / cm². 2 A molded body was obtained by pressing with the specified pressure (molding process (III)).

[0058] The molded body was sintered at 1205°C for 1 hour in a vacuum of less than 1000 Pa (sintering step (IV)), then solution treatment was performed at the solution temperature and time shown in Table 1 (solution treatment step (V)), and subsequently, it was rapidly cooled at the rapid cooling rates shown in Table 1 (rapid cooling rates from 1000 to 600°C). After rapid cooling, the heat treatment (aging treatment) steps of the first heat treatment step (VI), the first cooling step (VII), the second heat treatment step (VIII), and the second cooling step (IX) were carried out.

[0059] Specifically, the first heat treatment step (VI) was performed by heat-treating the molded body at the heat treatment temperature and time shown in Table 1. Subsequently, the first cooling step (VII) was performed by cooling the molded body to the heat treatment temperature of the next step, the second heat treatment step (VIII), at the cooling rate shown in Table 1. After that, the second heat treatment step (VIII) was performed by heat-treating the molded body at the heat treatment temperature and time shown in Table 1. Subsequently, the second cooling step (IX) was performed by cooling the molded body to 350°C or below at the cooling rate shown in Table 1. Permanent magnets according to Examples 1 to 17 were manufactured using this method.

[0060] The magnetic properties of the permanent magnets obtained in this way were measured in their molded state. The magnetic properties of the permanent magnets were measured using a BH tracer. Furthermore, after the necessary processing was performed on the permanent magnets, microstructure observation and compositional analysis were carried out using TEM / EDX. The residual magnetic flux density (Br), maximum energy product (BH)m, intrinsic coercivity (Hcj), aspect ratio (Hk / Hcj), cell structure size (length of cell wall 4, referred to as "long side of the cell"), and average Cu concentration (at%) within phases 1-5 (cell wall 4) are shown in Table 2.

[0061] <Comparative Examples 1-11> Each raw material was prepared to have the composition described in Comparative Examples 1-11 of Table 1, and melted in a high-frequency induction furnace to obtain ingots for the master alloy. For this melting, a master alloy of Fe 20% and Zr 80% was used. The obtained master alloy was heat-treated at 1185°C for 1 hour, and then at 1120°C for 6 hours. The heat-treated master alloy was coarsely ground in an inert gas to an average size of approximately 100 μm, and then finely ground using a ball mill in an inert gas to a size of approximately 2.5 μm for D10, approximately 6 μm for D50, and approximately 13.5 μm for D90. This powder was ground in a magnetic field of 15 kOe at a rate of 1 ton / cm². 2 A molded body was obtained by pressing it with pressure.

[0062] The molded body was sintered at 1205°C for 1 hour in a vacuum of less than 1000 Pa (sintering step (IV)), then solution treatment was performed at the solution temperature and time shown in Table 1 (solution treatment step (V)), and subsequently, it was rapidly cooled at the rapid cooling rates shown in Table 1 (rapid cooling rates from 1000 to 600°C). After rapid cooling, the heat treatment (aging treatment) steps of the first heat treatment step (VI), the first cooling step (VII), the second heat treatment step (VIII), and the second cooling step (IX) were carried out.

[0063] Specifically, the first heat treatment step (VI) was performed by heat-treating the molded body at the heat treatment temperature and time shown in Table 1. Subsequently, the first cooling step (VII) was performed by cooling the molded body to the heat treatment temperature of the next step, the second heat treatment step (VIII), at the cooling rate shown in Table 1. After that, the second heat treatment step (VIII) was performed by heat-treating the molded body at the heat treatment temperature and time shown in Table 1. Subsequently, the second cooling step (IX) was performed by cooling the molded body to 350°C or below at the cooling rate shown in Table 1. Permanent magnets according to Comparative Examples 1 to 11 were manufactured using this method.

[0064] The magnetic properties of the permanent magnets obtained in this way were measured in their molded state. The magnetic properties of the permanent magnets were measured using a BH tracer. Furthermore, after the necessary processing was performed on the permanent magnets, microstructure observation and compositional analysis were carried out using TEM / EDX. The residual magnetic flux density (Br), maximum energy product (BH)m, intrinsic coercivity (Hcj), aspect ratio (Hk / Hcj), cell structure size (length of cell wall 4, referred to as "long side of the cell"), and average Cu concentration (at%) within phases 1-5 (cell wall 4) are shown in Table 2.

[0065] <Examples 18-21, Comparative Examples 12-17> The raw materials were adjusted to the compositions described in Examples 18-21 and Comparative Examples 12-17 in Table 3, and melted in a high-frequency induction furnace to obtain ingots for the master alloy (Alloy Preparation Step (I)). For this melting, a master alloy of Fe 20% and Zr 80% was used. The obtained master alloy was heat-treated at 1185°C for 1 hour, and then at 1120°C for 6 hours. The heat-treated master alloy was coarsely ground in an inert gas to an average size of approximately 100 μm, and then finely ground using a ball mill in an inert gas to a size of approximately 2.5 μm for D10, approximately 6 μm for D50, and approximately 13.5 μm for D90 (Grinding Step (II)). This powder was ground in a magnetic field of 15 kOe at a rate of 1 ton / cm². 2 A molded body was obtained by pressing with the specified pressure (molding process (III)).

[0066] The molded body was sintered at 1205°C for 1 hour in a vacuum of less than 1000 Pa (sintering step (IV)), then solution treatment was performed at the solution temperature and time shown in Table 3 (solution treatment step (V)), and subsequently, it was rapidly cooled at the rapid cooling rates shown in Table 3 (rapid cooling rates from 1000 to 600°C). After rapid cooling, the first heat treatment step (VI), the first cooling step (VII), the second heat treatment step (VIII), and the second cooling step (IX) were carried out under the conditions described in Table 3. Permanent magnets according to Examples 18-21 and Comparative Examples 12-17 were manufactured using this method.

[0067] The magnetic properties of the permanent magnets obtained in this manner were measured in their molded state. The magnetic properties of the permanent magnets were measured using a BH tracer. Furthermore, after the necessary processing was performed on the permanent magnets, microstructure observation and compositional analysis were carried out using TEM / EDX. The residual magnetic flux density (Br), maximum energy product (BH)m, intrinsic coercivity (Hcj), aspect ratio (Hk / Hcj), cell structure size (length of cell wall 4, referred to as "long side of the cell"), and average Cu concentration (at%) within phases 1-5 (cell wall 4) are shown in Table 4.

[0068] <Result> As shown in Table 2, in all permanent magnets used in Examples 1 to 17, the residual magnetic flux density (Br) was 1.18 T or higher, and the maximum energy product (BH) m was 260 kJ / m. 3 In summary, the intrinsic coercivity (Hcj) was 1600 kA / m or higher, and the aspect ratio (Hk / Hcj) was 65% or higher, indicating good magnetic properties. Furthermore, the cell structure size (longest side of the cell) was 300-700, and the average Cu concentration within phases 1-5 was 30 at% or higher.

[0069] In other words, the permanent magnets according to Examples 1 to 17 have a composition (the composition of the present invention) in terms of mass percentage, containing R: 24-27% (wherein R is the sum of Sm and Nd, or Sm, Nd and other rare earth elements), Fe: 22-27%, Cu: 4.0-5.0%, Zr: 1.5-2.5%, Mn: 0.01-2.5%, with the remainder being Co and unavoidable impurities. As a result, each measured value falls within the above range, and the magnetic properties are good.

[0070] On the other hand, in Comparative Examples 1 to 11, there were no samples that met all of the above criteria for magnetic properties. In other words, in Comparative Examples 1 and 2, the sum of Sm and Nd was outside the composition range of the present invention; in Comparative Examples 3 and 4, Fe was outside the composition range of the present invention; in Comparative Examples 5 and 6, Cu was outside the composition range of the present invention; in Comparative Examples 7 and 8, Zr was outside the composition range of the present invention; in Comparative Examples 9 and 10, Mn was outside the composition range of the present invention; and in Comparative Example 11, Nd was not added, so there were no samples that met all of the above criteria for magnetic properties.

[0071] Figure 3 is a graph showing the magnetic properties of Example 8 and Comparative Example 3. Figure 3 shows the demagnetization curves of the permanent magnets of Example 8 and Comparative Example 3. As shown in Figure 3, the permanent magnet of Example 8 has superior intrinsic coercivity and prismaticity compared to the permanent magnet of Comparative Example 3.

[0072] Table 4 shows the magnetic properties of samples with the same composition but varying the aging conditions, i.e., the conditions for the first heat treatment step (VI), the first cooling step (VII), the second heat treatment step (VIII), and the second cooling step (IX) (see Table 3).

[0073] As shown in Table 4, in all permanent magnets used in Examples 18-21, the residual magnetic flux density (Br) was 1.18T or higher, and the maximum energy product (BH)m was 260kJ / m². 3 In summary, the intrinsic coercivity (Hcj) was 1600 kA / m or higher, and the aspect ratio (Hk / Hcj) was 65% or higher, indicating good magnetic properties. Furthermore, the cell structure size (longest side of the cell) was 300-700, and the average Cu concentration within phases 1-5 was 30 at% or higher.

[0074] In other words, as shown in Table 3, the permanent magnets of Examples 18 to 21 were subjected to the following conditions: the first heat treatment step (VI) was performed at a heat treatment temperature of 780 to 900°C for a heat treatment time of 5 to 50 hours, the first cooling step (VII) was performed at a cooling rate of 0.1 to 0.5°C / min, the second heat treatment step (VIII) was performed at a heat treatment temperature of 500 to 700°C for a heat treatment time of 1 to 10 hours, and the second cooling step (IX) was performed at a cooling rate of 0.1 to 0.5°C / min. As a result, each measured value fell within the above range, and the magnetic properties were good.

[0075] On the other hand, in Comparative Examples 12 to 17, none of the samples met all of the above criteria for magnetic properties. In other words, as shown in Table 3, in Comparative Example 12, the heat treatment temperature of the first heat treatment step (VI) was 775°C, which is lower than the heat treatment temperature range of 780 to 900°C for the first heat treatment step (VI) of the present invention. Also, in Comparative Example 13, the heat treatment time of the first heat treatment step (VI) was 4 hours, which is shorter than the heat treatment time range of 5 to 50 hours for the first heat treatment step (VI) of the present invention. Also, in Comparative Example 14, the cooling rate of the first cooling step (VII) was 1.0°C / min, which is faster than the cooling rate range of 0.1 to 0.5°C / min for the first cooling step (VII) of the present invention. Also, in Comparative Example 15, the heat treatment temperature of the second heat treatment step (VIII) was 450°C, which is lower than the heat treatment temperature range of 500 to 700°C for the second heat treatment step (VIII) of the present invention. Furthermore, in Comparative Example 16, the heat treatment time for the second heat treatment step (VIII) was 0.5 hours, which is shorter than the heat treatment time range of 1 to 10 hours for the second heat treatment step (VIII) of the present invention. Also, in Comparative Example 17, the cooling rate for the second cooling step (IX) was 1.0°C / min, which is faster than the cooling rate range of 0.1 to 0.5°C / min for the second cooling step (IX) of the present invention. For these reasons, none of the samples in Comparative Examples 12 to 17 met all of the above criteria values ​​for magnetic properties.

[0076] [Table 1]

[0077] [Table 2]

[0078] [Table 3]

[0079] [Table 4]

[0080] Although the present invention has been described above in accordance with the above embodiments, the present invention is not limited to the configuration of the above embodiments, and of course includes various modifications, alterations, and combinations that can be made by a person skilled in the art within the scope of the claims of the present patent application. [Explanation of Symbols]

[0081] 1 crystal grain 2 Grain boundaries 3-cell phase 4 Cell Wall 10. Rare Earth Cobalt Permanent Magnets

Claims

1. A rare-earth cobalt permanent magnet having a composition in mass percentage of R: 24-27% (where R is the sum of Sm and Nd, or Sm, Nd and other rare earth elements), Fe: 22-27%, Cu: 4.0-5.0%, Zr: 1.5-2.5%, Mn: 0.01-2.5%, with the remainder being Co and unavoidable impurities.

2. A rare earth cobalt permanent magnet according to claim 1, wherein the proportion of Nd, or Nd and other rare earth elements in R, is 14% or less (Ra).

3. The aforementioned rare-earth cobalt permanent magnet has multiple crystal grains and grain boundaries, The aforementioned crystal grains are Th ２ Zn １７ The 2-17 phase of the type structure and RCo ５ It has a 1-5 phase structure, and the average Cu concentration in the 1-5 phases is 30 at% or more. A rare-earth cobalt permanent magnet according to claim 1 or 2.

4. The rare earth cobalt permanent magnet according to claim 3, wherein the size of the cell structure constituting the crystal grains is 300 to 700 nm.

5. A rare-earth cobalt permanent magnet according to claim 1 or 2, wherein the residual magnetic flux density (Br) is 1.18 T or higher.

6. A rare-earth cobalt permanent magnet according to claim 1 or 2, wherein the intrinsic coercivity (Hcj) is 1600 kA / m or more.

7. The maximum energy product (BH) m is 260 kJ / m ３ The rare earth cobalt permanent magnet according to claim 1 or 2.

8. A rare-earth cobalt permanent magnet according to claim 1 or 2, wherein when the reverse magnetic field Hk is the magnetic field at which the magnetic flux density becomes 90% of the remanent magnetic flux density (Br), the angular ratio expressed as the ratio of Hk to the intrinsic coercivity (Hcj) (Hk / Hcj) is 65% or more.

9. A device having a rare-earth cobalt permanent magnet according to claim 1 or 2.

10. Step (I) is to prepare an alloy containing each raw material such that, after sintering, the composition by mass percentage is R: 24-27% (where R is the sum of Sm and Nd, or Sm, Nd and other rare earth elements), Fe: 22-27%, Cu: 4.0-5.0%, Zr: 1.5-2.5%, Mn: 0.01-2.5%, with the remainder being Co and unavoidable impurities. A grinding step (II) in which the alloy is reduced to powder, A molding step (III) in which the powder is formed into a molded body, The molded body is subjected to a sintering step (IV) at 1170 to 1215°C, Step (V) involves solution treatment of the sintered molded body at 1110-1165°C for less than 30 hours, The first heat treatment step (VI) involves heat-treating the molded body after solution treatment at 780-900°C for 5-50 hours, A first cooling step (VII) is performed to cool the molded body after the first heat treatment step (VI) to 500 to 700°C at a cooling rate of 0.1 to 0.5°C / min, A second heat treatment step (VIII) is performed at a temperature of 500 to 700°C, which is the temperature after the first cooling step (VII), for 1 to 10 hours. The process includes a second cooling step (IX) in which the molded body after the second heat treatment step (VIII) is cooled to 350°C or below at a cooling rate of 0.1 to 0.5°C / min. A method for manufacturing rare-earth cobalt permanent magnets.

11. The method for producing a rare earth cobalt permanent magnet according to claim 10, wherein in step (I) above, an alloy is prepared in which Nd, or Nd and other rare earth elements, with Ra being 14% or less of the ratio of Ra to R, is prepared.

12. A method for manufacturing a rare earth cobalt permanent magnet according to claim 10 or 11, wherein the first heat treatment step (VI) is a step of heat treatment at a temperature of 800 to 880°C for 10 to 40 hours.

13. The method for producing a rare earth cobalt permanent magnet according to claim 10 or 11, wherein the second heat treatment step (VIII) is a step of heat treatment at a temperature of 550 to 650°C for 2 to 7 hours.

14. The rare-earth cobalt permanent magnet after the second cooling step (IX) has a plurality of crystal grains and grain boundaries, The aforementioned crystal grains are Th ２ Zn １７ The 2-17 phase of the type structure and RCo ５ It has a 1-5 phase structure, and the average Cu concentration in the 1-5 phases is 30 at% or more. A method for manufacturing a rare earth cobalt permanent magnet according to claim 10 or 11.

15. A method for manufacturing a rare earth cobalt permanent magnet according to claim 14, wherein the size of the cell structure constituting the crystal grains is 300 to 700 nm.

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