Method for producing rare earth magnet

Abstract

To provide a method for more easily manufacturing a rare earth magnet having high coercive force and high residual magnetic flux density.SOLUTION: A method for producing a rare earth magnet, the method comprising the steps of: preparing a first powder and a second powder each containing grains having an R2X14B phase (R is at least one element selected from rare earths (Sc, Y, and lanthanoids), and X is Fe or Fe partially substituted with Co) as a main phase; and mixing and molding the first powder and the second powder, wherein a difference in total rare earth amount between the first powder and the second powder is 0.4 mass% or more and 1.5 mass% or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing a rare earth magnet. [Background technology]

[0002] The method of manufacturing magnets by mixing two types of alloys has been around for a long time and is known as the two-alloy method. This method involves mixing the main phase of the magnet (R2Fe 14 B) A method of increasing the coercive force of a magnet by mixing alloy powder containing heavy rare earth elements into the powder. Another known method for increasing the coercive force of magnets is the grain boundary diffusion method, in which rare earth elements are diffused from the magnet surface into the magnet's interior through heat treatment, resulting in a rare earth-containing phase coating the magnet's main phase particles, increasing the magnet's coercive force.

[0003] Furthermore, as a conventional method for manufacturing rare earth magnets, for example, Patent Document 1 discloses a method for manufacturing R12X 14 The method for producing a rare earth magnet is described, which is characterized by contacting the surface of a rare earth magnet having crystal grains whose main phase is B phase (where R1 is at least one element selected from rare earth lanthanide elements, X is Fe or Fe partially substituted with Co) and a crystal grain size of 1 μm or less with an R2 metal and / or an R2-based alloy (where R2 is at least one element selected from Dy, Tb, and Ho), and then performing a heat treatment so that the crystal grain size does not exceed 1 μm, thereby diffusing the R2 element into the magnet.

[0004] Patent Document 2 describes a method for producing an RTB sintered magnet containing 28% by mass or more and 33% by mass or less of R (R is a light rare earth element RL and a heavy rare earth element RH, where RL is Nd and / or Pr and RH is Dy), 0.5% by mass or more and 5% by mass or less of RH, 0.5% by mass or more and 2% by mass or less of B, 0.5% by mass or more and 2.5% by mass or less of Co, 0.05% by mass or more and 0.2% by mass or less of Cu, 0.05% by mass or more and 0.2% by mass or less of Ga, and the remainder being Fe and unavoidable impurities. In the method, R1 is 28 mass% or more and 33 mass% or less (R1 consists of a light rare earth element RL or a light rare earth element RL and a heavy rare earth element RH, RL is Nd and / or Pr, and RH is Dy), RH is 4.4 mass% or less (including 0 mass%), B is 0.5 mass% or more and 2 mass% or less, Co is 2 mass% or less (including 0 mass%), Cu is 0.2 mass% or less (including 0 mass%), Ga is 0.2 mass% or less (including 0 mass%), and the balance is Fe and unavoidable impurities the difference between the content (mass%) of R1 in the first alloy powder and the content (mass%) of R2 in the second alloy powder is within 1. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-114200 [Patent Document 2] Patent No. 6044866 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention provides a simpler method for producing rare earth magnets with both high coercivity and high residual magnetic flux density. [Means for solving the problem]

[0007] The present invention includes the following (1) to (4). (1) R2X 14 a preparation step of preparing a first powder and a second powder containing crystal grains whose main phase is a B phase (R is at least one element selected from rare earths (Sc, Y, and lanthanides), and X is Fe or Fe partially substituted with Co); a processing step of mixing and molding the first powder and the second powder; Equipped with A method for producing a rare earth magnet, wherein the difference between the total rare earth content of the first powder and the total rare earth content of the second powder is 0.4% by mass or more and 1.5% by mass or less. (2) The method for producing a rare earth magnet according to (1) above, wherein in the processing step, the first powder and the second powder are mixed and then hot-molded. (3) The method for producing a rare earth magnet according to (1) or (2) above, wherein the first powder and / or the second powder contains at least one element selected from the group consisting of Cu, Al, Ga, Ge, Sn, In, Si, P, Zr, Nb, Ti, Ta, and W. (4) A method for producing a rare earth magnet according to any one of (1) to (3) above, wherein the first powder and the second powder are substantially free of the heavy rare earth elements Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a method for more simply producing a rare earth magnet having both high coercivity and high residual magnetic flux density. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a graph showing the relationship between remanence (RT-Br(T)) and coercivity (150° C.-Hcj(kA / m)) in Experiment 1. [Figure 2] 10 is a graph showing the relationship between remanence (RT-Br(T)) and coercivity (150° C.-Hcj(kA / m)) in Experiment 2. [Figure 3] 10 is a graph showing the relationship between remanence (RT-Br(T)) and coercivity (150° C.-Hcj(kA / m)) in Experiment 3. [Figure 4] 10 is a graph showing the relationship between remanence (RT-Br(T)) and coercivity (150° C.-Hcj(kA / m)) in Experiment 4. [Figure 5] 10 is a graph showing the relationship between remanence (RT-Br(T)) and coercivity (150° C.-Hcj(kA / m)) in Experiment 5. [Figure 6] 10 is a graph showing the relationship between remanence (RT-Br(T)) and coercivity (150° C.-Hcj(kA / m)) in Experiment 6. [Figure 7] 10 is a graph showing the relationship between remanence (RT-Br(T)) and coercivity (150° C.-Hcj(kA / m)) in Experiment 7. [Figure 8] 10 is a graph showing the relationship between remanence (RT-Br(T)) and coercivity (150° C.-Hcj(kA / m)) in Experiment 8. [Figure 9] 10 is a graph showing the relationship between remanence (RT-Br(T)) and coercivity (150° C.-Hcj(kA / m)) in Experiment 9. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will now be described. The present invention is R2X 14This method for producing a rare earth magnet includes a preparation step of preparing a first powder and a second powder containing crystal grains whose main phase is B phase (R is at least one element selected from rare earths (Sc, Y, and lanthanides), and X is Fe or Fe partially substituted with Co), and a processing step of mixing and molding the first powder and the second powder, wherein the difference in total rare earth content between the first powder and the second powder is 0.4% by mass or more and 1.5% by mass or less. Such a method for producing a rare earth magnet is hereinafter also referred to as the "production method of the present invention."

[0011] <Preparation process> The preparation steps in the manufacturing method of the present invention will be described. In the preparation step, a first powder and a second powder are prepared. Both the first powder and the second powder are R2X. 14 It contains crystal grains with B phase as the main phase.

[0012] The first powder and the second powder are observed at 20,000 to 100,000 magnifications using an SEM, and the crystal structure is determined by X-ray diffraction. The components contained therein are determined by ICP analysis. 14 It can be seen that the R2X contains crystal grains with the B phase as the main phase. 14 The crystal grains having the B phase as the main phase are usually several nm to 300 nm in size, and a grain boundary phase may exist surrounding this main phase.

[0013] The components contained in the first powder and the second powder are determined by ICP analysis.

[0014] Here, R is at least one element selected from the rare earths. In the production method of the present invention, the rare earth elements mean Sc, Y and lanthanoids. The lanthanides are La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. Thus, R means at least one selected from the group consisting of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu.

[0015] Preferably, R contains Nd and / or Pr. In the first powder and / or the second powder, the total mass of Nd+Pr relative to the total mass of R (Sc+Y+La+Ce+Pr+Nd+Pm+Sm+Eu+Gd+Tb+Dy+Ho+Er+Tm+Yb+Lu) is preferably 50% or more.

[0016] It is preferable that the first powder and the second powder are substantially free of heavy rare earth elements. Because heavy rare earth elements are expensive, if the first powder and the second powder are substantially free of heavy rare earth elements, production costs can be reduced. Furthermore, because heavy rare earth elements are highly unevenly distributed and more than 90% are mined in China, if the first powder and the second powder are substantially free of heavy rare earth elements, resource procurement risks can be reduced.

[0017] Here, heavy rare earth elements mean Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu.

[0018] Furthermore, when the content of heavy rare earth elements in each of the first powder and the second powder is 0.1 mass % or less, this means that each of the first powder and the second powder does not substantially contain heavy rare earth elements.

[0019] When the total amount of rare earth elements (total content of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) in each of the first powder and the second powder is TRE[1] and TRE[2], the difference between TRE[1] and TRE[2] is 0.4 mass% or more and 1.5 mass% or less. In this case, the inventors have found that when the coercivity and remanence of a rare earth magnet obtained using only the first powder are compared with the coercivity and remanence of a rare earth magnet obtained using only the second powder, calculated taking into account the respective mixing ratios, the rare earth magnet obtained using the manufacturing method of the present invention has a higher coercivity and a substantially equivalent remanence. From the perspective of increasing the coercivity and remanence, the difference between TRE[1] and TRE[2] may be 0.5% by mass or more, or 0.8% by mass or more. For the same reason, the upper limit of this difference is set to 1.5% by mass or less. The manufacturing method of the present invention is a simple method in which powders of different compositions are mixed before compaction, and does not require grinding of the magnet surface after diffusion treatment as in the grain boundary diffusion method, making net shaping possible.

[0020] In addition, in the preparation process, R2X 14 Three or more types of powder containing crystal grains with the B phase as the main phase may be prepared, and these three or more types of powder may be mixed and molded in the processing step. In this case, among the three or more types of powder, the one having the largest total amount of rare earth elements and the one having the smallest total amount of rare earth elements are designated as the first powder and the second powder.

[0021] The first powder and / or the second powder may contain at least one element selected from the group consisting of Cu, Al, Ga, Ge, Sn, In, Si, P, Zr, Nb, Ti, Ta and W. The content of these is preferably 5% by mass or less, more preferably 2% by mass or less, and even more preferably 0.5% by mass or less.

[0022] X is Fe or Fe partially substituted with Co.

[0023] In each of the first powder and the second powder, the content of the rare earth element is preferably 28 to 33 mass %. In each of the first powder and the second powder, the total content of Fe and Co is preferably 64 to 71 mass %. In each of the first powder and the second powder, the B content is preferably 0.8 to 1.0 mass %. In each of the first powder and the second powder, the content of elements other than rare earth elements, Fe, Co, and B is preferably 0 to 2 mass %.

[0024] The average particle size of the first powder and the second powder is preferably 50 to 500 μm, and more preferably 100 to 300 μm. The average particle sizes of the first powder and the second powder refer to values ​​measured using a laser diffraction / scattering particle size distribution measuring device.

[0025] The first and second powders can be prepared by a rapid cooling method. Specifically, an R1-XB alloy having a predetermined composition, such as an Nd-Fe-B alloy, an Nd-Fe-Co-B alloy, a Pr-Fe-B alloy, a Pr-Fe-Co-B alloy, or a (Nd,Pr)-Fe-B alloy, is melted at 1300°C or higher in a vacuum or in an inert gas atmosphere such as argon. The molten metal is then injected through an orifice onto a rotating roll (e.g., a copper rotating roll) with high heat dissipation properties and rapidly cooled (e.g., at a peripheral roll speed of 10 m / s to 30 m / s). This produces a flaky powder measuring several millimeters to several tens of millimeters in length and approximately 18 to 50 μm thick, with an interior composed of fine crystal grains of approximately 10 to 50 nm and a portion of amorphous material. This flaky powder is then crushed using an impact airflow crusher or the like, and if necessary, sieved to have a long side of approximately 300 μm or less, to produce R2X. 14 It is possible to obtain a first powder and a second powder containing crystal grains whose main phase is phase B. The first powder and the second powder (rapidly cooled powders) produced in this manner are magnetically isotropic powders.

[0026] <Processing process> The processing steps in the manufacturing method of the present invention will be described. In the processing step, the first powder and the second powder prepared in the preparation step are mixed together. The product obtained by mixing the first powder and the second powder will hereinafter also be referred to as a mixture. The mixture may include more than just the first powder and the second powder.

[0027] The mixing ratio (mass ratio) of the first powder to the second powder is preferably 2:8 to 8:2, and more preferably 2:3 to 3:2. Since the first powder and the second powder have relatively large average particle sizes, the powders themselves are less likely to be oxidized during mixing, which has the advantage that they can be mixed in air without significant control over the atmosphere.

[0028] In the processing step, the mixture obtained by mixing the first powder and the second powder is molded. Here, the forming is preferably carried out in a hot state, and more preferably, cold forming is followed by hot forming.

[0029] When the mixture is cold-molded, for example, the mixture can be molded using a cold press. The mixture is filled into a mold of the cold press and then pressed to form a cold-molded body having various shapes such as a cylinder, a column, or a plate. The true density of the cold-formed body is preferably 40 to 70%, more preferably 50 to 70%, from the viewpoints of strength during handling, press pressure, die life, and the like. The compression molding pressure during cold molding is 2 to 4 ton / cm 2 It can be about. The pressure holding time during cold forming can be about 1 to 10 seconds. Generally, since oxidation hardly progresses at room temperature, cold forming may be carried out in an air atmosphere, but forming may also be carried out in an inert gas atmosphere such as nitrogen or argon.

[0030] It is preferable to hot form the cold-formed body obtained by the above-mentioned cold forming. Specifically, a graphite-based lubricant or the like may be applied to the surface of the obtained cold-formed body, which may then be loaded into a hot press, and the mold may be heated in an inert gas atmosphere such as argon, in a vacuum, or in the air to compress and densify the cold-formed body. Alternatively, a graphite-based lubricant or the like may be applied to the inner surface of the hot press, and the obtained cold-formed body may then be loaded into the hot press, and the mold may be heated in an inert gas atmosphere such as argon, in a vacuum, or in the air to compress and densify the cold-formed body. In addition to hot forming using such a hot press machine, SPS (spark plasma sintering) can also be applied, which involves applying heat, pressure, and a high current to promote densification.

[0031] The heating temperature during hot forming is preferably 600 to 900°C, more preferably 700 to 850°C, from the viewpoint of the balance between densification and the effect of inhibiting grain growth. The compression molding pressure during hot molding is 2 to 4 ton / cm 2 It can be about. The pressure holding time during hot forming can be about 5 to 20 seconds. The density of the hot-formed body after hot-forming is preferably 97 to 100% of the true density, more preferably 98 to 100%, and even more preferably 99.5 to 100%. [Example]

[0032] The present invention will be described with reference to examples, but the present invention is not limited to the examples described below.

[0033] Seventeen types of powdered raw materials (raw materials 1 to 17) were prepared, each having the following composition (the remainder being Fe or a portion of Fe substituted with Co and unavoidable impurities). The following compositions indicate the contents (mass %) of light rare earth elements (RL: La, Ce, Pr, Nd, Pm, Sm, Eu) that are the main components, and B. The compositions may also contain at least one element selected from the group consisting of Cu, Al, Ga, Ge, Sn, In, Si, P, Zr, Nb, Ti, Ta, and W in an amount of 5 mass % or less, 2 mass % or less, or 0.5 mass % or less. The average particle size of each is within the range of 100 to 300 μm. ·Raw material 1:30.1RL-0.97B ·Raw material 2:30.9RL-0.93B ·Raw material 3:30.5RL-0.95B ·Raw material 4:31.0RL-0.93B ·Raw material 5:29.4RL-0.93B ·Raw material 6:30.1RL-0.95B ·Raw material 7:29.0RL-0.95B ·Raw material 8:30.5RL-0.94B ·Raw material 9:31.0RL-0.93B ·Raw material 10:31.0RL-0.93B ·Raw material 11:30.7RL-0.95B ·Raw material 12:30.62RL-0.94B ·Raw material 13:30.97RL-0.94B ·Raw material 14:30.2RL-0.93B ·Raw material 15:30.4RL-0.93B ·Raw material 16:31.5RL-0.91B ·Raw material 17:29.8RL-0.93B

[0034] Next, for each experiment, two types of raw materials were selected from the above 17 types of raw materials and used as the first powder or the second powder, respectively. Furthermore, neither of them substantially contains heavy rare earth elements Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu.

[0035] Next, the first powder alone, the second powder alone, and the mixture obtained by mixing them were each cold-molded in air using a conventionally known cold press to obtain a cold-molded body. The true density of the cold-formed body was set to be within the range of 40 to 70%. The compression molding pressure during cold molding is 2 to 4 ton / cm 2 It was made to be within the range of. The pressure holding time during cold forming was set to be within the range of 1 to 10 seconds.

[0036] Next, each of the obtained cold-formed bodies was hot-formed in an air atmosphere using a conventionally known hot press at a hot extrusion speed and forming temperature described below. Note that since the first powder and the second powder have a relatively large average particle size, the powders themselves are not easily oxidized, which is advantageous in that they can be formed in air without significant control of the atmosphere. The density of the hot-formed body after hot-forming was set within the range of 97 to 100% of the true density.

[0037] The residual magnetic flux density (RT-Br(T)) and coercive force (150°C-Hcj(kA / m)) of each of the hot-molded bodies obtained using only the first powder, the hot-molded body using only the second powder, and the hot-molded body using the mixture were measured at 23°C and 150°C using a DC magnetic flux meter (manufactured by Toei Kogyo Co., Ltd., model number: TRF-5BH-25auto).

[0038] <Experiment 1> Raw material 1 was used as the first powder, and raw material 2 was used as the second powder. In this case, the difference in total rare earth element content (TRE) was 0.4 mass% or more. These were mixed in a mass ratio of 1:1 to obtain a mixture. Then, for each powder, cold compacts were obtained as described above, followed by hot compaction. The remanence (RT-Br) and coercivity (150°C-Hcj (kA / m)) of the obtained hot compacts were measured. Table 1 shows the measurement results of the residual magnetic flux density at 23°C (RT-Br(T)) and the coercive force at 150°C (150°C-Hcj(kA / m)). The relationship between the residual magnetic flux density at 23°C (RT-Br(T)) and the coercive force at 150°C (150°C-Hcj(kA / m)) is shown in Figure 1. As shown in Figure 1, it was found that the compacts obtained from the mixture tended to have relatively high residual magnetic flux density and coercive force compared to raw material 1 alone and raw material 2 alone. In addition, the weighted average values ​​(based on the mass ratio of the first powder to the second powder (1:1 in Experiment 1)) of the remanence and coercivity of the hot-compacted compacts obtained at the same compacting temperature using only the first powder and the hot-compacted compacts obtained using only the second powder were calculated. The plots based on these values ​​are shown in Figure 1 as crosses, along with an approximate straight line based on these plots. Figure 1 also shows an approximate straight line for the plots (black circles) of the remanence and coercivity of the hot-compacted compacts made from the mixture. It can be seen from Figure 1 that the plots (black circles) of the remanence and coercivity of the hot-compacted compacts made from the mixture are located to the upper right of the cross plots. This indicates that the coercivity of the hot-compacted compacts obtained by the manufacturing method of the present invention is higher than the coercivity value predicted from the mixing ratio (mass ratio) of the two raw materials. It can also be seen that the remanence of the hot-compacted compacts obtained by the manufacturing method of the present invention is approximately equal to the remanence predicted from the mixing ratio (mass ratio) of the two raw materials. The same applies to Experiments 2, 3, and 4 below.

[0039] [Table 1]

[0040] <Experiment 2> Raw material 3 was used as the first powder, and raw material 4 was used as the second powder. In this case, the difference in total rare earth element content (TRE) was 0.4 mass% or more. These were mixed in a mass ratio of 2:3 to obtain a mixture. Then, for each, cold compacts were obtained as described above, and then hot compacted. The remanence (RT-Br) and coercivity (150°C-Hcj (kA / m)) of the obtained hot compacts were measured. Table 2 shows the measurement results of the residual magnetic flux density at 23°C (RT-Br(T)) and the coercive force at 150°C (150°C-Hcj(kA / m)). FIG. 2 shows the relationship between the residual magnetic flux density at 23° C. (RT-Br(T)) and the coercive force at 150° C. (150° C.-Hcj(kA / m)).

[0041] [Table 2]

[0042] <Experiment 3> Raw material 5 was used as the first powder, and raw material 6 was used as the second powder. In this case, the difference in total rare earth element content (TRE) was 0.4 mass% or more. These were mixed in a mass ratio of 1:1 to obtain a mixture. Then, for each powder, cold compacts were obtained as described above, followed by hot compaction. The remanence (RT-Br) and coercivity (150°C-Hcj (kA / m)) of the obtained hot compacts were measured. Table 3 shows the measurement results of the residual magnetic flux density at 23°C (RT-Br(T)) and the coercive force at 150°C (150°C-Hcj(kA / m)). FIG. 3 shows the relationship between the residual magnetic flux density at 23° C. (RT-Br(T)) and the coercive force at 150° C. (150° C.-Hcj(kA / m)).

[0043] [Table 3]

[0044] <Experiment 4> Raw material 7 was used as the first powder, and raw material 8 was used as the second powder. In this case, the difference in total rare earth element content (TRE) was 0.4 mass% or more. These were mixed in a mass ratio of 1:1 to obtain a mixture. Then, for each, cold compacts were obtained as described above, and then hot compacted. The remanence (RT-Br) and coercivity (150°C-Hcj (kA / m)) of the obtained hot compacts were measured. Table 4 shows the measurement results of the residual magnetic flux density at 23°C (RT-Br(T)) and the coercive force at 150°C (150°C-Hcj(kA / m)). FIG. 4 shows the relationship between the residual magnetic flux density at 23° C. (RT-Br(T)) and the coercive force at 150° C. (150° C.-Hcj(kA / m)).

[0045] [Table 4]

[0046] <Experiment 5> Raw material 9 was used as the first powder, and raw material 4 was used as the second powder. In this case, the difference in total rare earth element (TRE) content was less than 0.4% by mass. These were mixed in a 1:1 mass ratio to obtain a mixture. Then, for each powder, cold compacts were obtained as described above, followed by hot compaction. The remanence (RT-Br) and coercivity (150°C-Hcj (kA / m)) of the obtained hot compacts were measured. Table 5 shows the measurement results of the residual magnetic flux density at 23°C (RT-Br(T)) and the coercive force at 150°C (150°C-Hcj(kA / m)). FIG. 5 shows the relationship between the residual magnetic flux density at 23° C. (RT-Br(T)) and the coercive force at 150° C. (150° C.-Hcj(kA / m)).

[0047] [Table 5]

[0048] <Experiment 6> Raw material 10 was used as the first powder, and raw material 11 was used as the second powder. In this case, the difference in total rare earth element (TRE) content was less than 0.4% by mass. These were mixed in a 1:1 mass ratio to obtain a mixture. Then, for each powder, cold compacts were obtained as described above, followed by hot compaction. The remanence (RT-Br) and coercivity (150°C-Hcj (kA / m)) of the obtained hot compacts were measured. Table 6 shows the measurement results of the residual magnetic flux density at 23°C (RT-Br(T)) and the coercive force at 150°C (150°C-Hcj(kA / m)). FIG. 6 shows the relationship between the residual magnetic flux density at 23° C. (RT-Br(T)) and the coercive force at 150° C. (150° C.-Hcj(kA / m)).

[0049] [Table 6]

[0050] <Experiment 7> Raw material 12 was used as the first powder, and raw material 13 was used as the second powder. In this case, the difference in total rare earth content (TRE) was less than 0.4 mass%. These were mixed in a mass ratio of 1:1 to obtain a mixture. Then, for each, cold compacts were obtained as described above, and then hot compaction was performed. The remanence (RT-Br) and coercivity (150°C-Hcj (kA / m)) of the obtained hot compacts were measured. Table 7 shows the measurement results of the residual magnetic flux density at 23°C (RT-Br(T)) and the coercive force at 150°C (150°C-Hcj(kA / m)). FIG. 7 shows the relationship between the residual magnetic flux density at 23° C. (RT-Br(T)) and the coercive force at 150° C. (150° C.-Hcj(kA / m)).

[0051] [Table 7]

[0052] <Experiment 8> Raw material 14 was used as the first powder, and raw material 15 was used as the second powder. In this case, the difference in total rare earth content (TRE) was less than 0.4 mass%. These were mixed in a mass ratio of 1:1 to obtain a mixture. Then, for each, cold compacts were obtained as described above, and then hot compaction was performed. The remanence (RT-Br) and coercivity (150°C-Hcj (kA / m)) of the obtained hot compacts were measured. Table 8 shows the measurement results of the residual magnetic flux density at 23°C (RT-Br(T)) and the coercive force at 150°C (150°C-Hcj(kA / m)). FIG. 8 shows the relationship between the residual magnetic flux density at 23° C. (RT-Br(T)) and the coercive force at 150° C. (150° C.-Hcj(kA / m)).

[0053] [Table 8]

[0054] <Experiment 9> Raw material 16 was used as the first powder, and raw material 17 was used as the second powder. In this case, the difference in total rare earth element content (TRE) was more than 1.5 mass%. These were mixed in a 1:1 mass ratio to obtain a mixture. Then, for each, cold compacts were obtained as described above, and then hot compacted. The remanence (RT-Br) and coercivity (150°C-Hcj (kA / m)) of the obtained hot compacts were measured. Table 9 shows the measurement results of the residual magnetic flux density at 23°C (RT-Br(T)) and the coercive force at 150°C (150°C-Hcj(kA / m)). FIG. 9 shows the relationship between the residual magnetic flux density at 23° C. (RT-Br(T)) and the coercive force at 150° C. (150° C.-Hcj(kA / m)).

[0055] [Table 9]

[0056] In Examples 1 to 4, where the difference in total rare earth content (TRE) between the first powder and the second powder was 0.4 mass% or more and 1.5 mass% or less, as shown in Figures 1 to 4, the measured values ​​of the residual magnetic flux density (RT-Br) and coercive force (150°C-Hcj (kA / m)) of the hot-molded body when the mixture was used were higher than the calculated values ​​of the residual magnetic flux density (RT-Br) and coercive force (150°C-Hcj (kA / m)) of the hot-molded body when the mixture was used, calculated from the hot-molded body when only the first powder was used and the hot-molded body when only the second powder was used, taking into account the mixing ratio.

Claims

1. R 2 X 14 a preparation step of preparing a first powder and a second powder containing crystal grains whose main phase is a B phase (R is at least one element selected from rare earths (Sc, Y, and lanthanoids), and X is Fe or Fe partially substituted with Co); a processing step of mixing and molding the first powder and the second powder; Equipped with A method for producing a rare earth magnet, wherein the difference between the total rare earth content of the first powder and the total rare earth content of the second powder is 0.4 mass % or more and 1.5 mass % or less.

2. 2. The method for producing a rare earth magnet according to claim 1, wherein in the processing step, the first powder and the second powder are mixed and then hot-molded.

3. 3. The method for producing a rare earth magnet according to claim 1, wherein the first powder and / or the second powder contains at least one element selected from the group consisting of Cu, Al, Ga, Ge, Sn, In, Si, P, Zr, Nb, Ti, Ta, and W.

4. 3. The method for producing a rare earth magnet according to claim 1, wherein the first powder and the second powder are substantially free of heavy rare earth elements Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

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