Anisotropic rare earth magnet and method for producing same

Abstract

An anisotropic rare earth magnet comprising a magnetic phase and a non-magnetic phase, the magnetic phase having a composition represented by R2T14B (wherein R represents one or more rare earth elements containing 50 at% or more of Nd and / or Pr when the total amount thereof is 100 at%; t represents one or more transition metal elements including Fe, or two or more transition metal elements including Fe and Co), the nonmagnetic phase has a composition represented by RCu (wherein R represents one or more rare earth elements including at least 50 at% of Nd and / or Pr when the total amount is 100 at%), and T represents one or more transition metal elements including Fe or two or more transition metal elements including Fe and Co), and the nonmagnetic phase has a composition represented by RCu (wherein R represents one or more rare earth elements including at least 50 at% of Nd and / or Pr when the total amount is 100 at%). Cu is 6 at% to 80 at% inclusive, the proportion of the magnetic phase is 51 vol% or more and less than 69 vol%, and the saturation magnetization is 0.8 T or more.

Description

Technical Field

[0001] The present invention relates to an anisotropic rare earth magnet and a method for manufacturing the same. Background Art

[0002] Rare earth magnets have a high maximum energy product, and thus are used in energy-saving household appliances such as refrigerators and washing machines, motors for driving hybrid vehicles / electric vehicles, which are high fuel consumption vehicles, motors for power steering, etc., and have become an indispensable material in modern society.

[0003] Rare earth magnets are roughly classified into sintered magnets and bonded magnets.

[0004] As a method for obtaining a sintered magnet, for example, the methods of Patent Documents 1 to 3 are proposed.

[0005] Patent Document 1 describes a method for manufacturing a rare earth magnet, wherein the method for manufacturing the rare earth magnet includes: a melting step of preparing an alloy melt of an R-T-B alloy; a first cooling step of cooling the alloy melt to generate crystal nuclei and solidifying at least a part of the alloy melt; and a second cooling step of further cooling the alloy containing the crystal nuclei to obtain an alloy sheet.

[0006] Patent Document 2 describes a method for manufacturing an alloy powder for an R-Fe-B-based rare earth magnet, the manufacturing method including: a first pulverization step of roughly pulverizing a raw material alloy for a rare earth magnet by a hydrogen pulverization method; and a second pulverization step of finely pulverizing the raw material alloy.

[0007] Patent Document 3 describes a method for manufacturing an R-Fe-B-based rare earth magnet, the manufacturing method including: a pressing step of compression molding a rare earth alloy powder by a dry pressing method to produce a molded body; a step of impregnating an oil agent from the surface of the molded body into the molded body; and a step of sintering the molded body.

[0008] As a method for obtaining a bonded magnet, for example, the method of Patent Document 4 is proposed. Patent Document 4 describes a method for manufacturing anisotropic magnet powder, the method for manufacturing the anisotropic magnet powder including a mixing step, a diffusion heat treatment step, and a dehydrogenation step (second degassing step), the mixing step mixing hydride (RFeBH X ) powder of an RFeB-based material with diffusion powder composed of hydrides of simple substances, alloys, and compounds of rare earth elements, the diffusion heat treatment step uniformly diffusing rare earth elements on the surface and inside of the RFeBH X powder after the mixing step, and the dehydrogenation step removing hydrogen from the mixed powder after the diffusion heat treatment step.

[0009] Furthermore, the present inventors reported in Non-Patent Document 1 that an anisotropic cast rare earth magnet composed of an R2T 14 B magnetic phase and an RCu non-magnetic phase (for example, R represents Nd and T represents a transition metal element containing Fe) and having an R2T 14 B magnetic phase of 49 vol% (50 wt%) can be produced by an electromagnetic vibration process.

[0010] Prior Art Documents

[0011] Patent Documents

[0012] Patent Document 1: WO2013-54845;

[0013] Patent Document 2: Japanese Patent Application Laid-Open No. 2002-33206;

[0014] Patent Document 3: Japanese Patent Application Laid-Open No. 2002-170728;

[0015] Patent Document 4: Japanese Patent Application Laid-Open No. 2002-93610.

[0016] Non-Patent Documents

[0017] Non-Patent Document 1: Journal of Alloys and Compounds: 883 (2021) 160915. Summary of the Invention

[0018] Problems to be Solved by the Invention

[0019] However, in the case of the manufacturing methods of Patent Documents 1 to 4, as described above, a very large number of manufacturing steps are required to obtain a rare earth magnet (sintered magnet or bonded magnet).

[0020] On the other hand, in the case of the manufacturing method of Non-Patent Document 1, since only a rare earth magnet having an R2T 14 B magnetic phase content of 49 vol% or less can be produced, the saturation magnetization is less than 0.8 T, and it is difficult to say that it has sufficient functions as a strong magnet.

[0021] The present invention has been completed in view of the above circumstances, and an object thereof is to provide a manufacturing method of an anisotropic rare earth magnet capable of obtaining an anisotropic rare earth magnet having excellent magnetization characteristics with fewer steps, and an anisotropic rare earth magnet having a new composition and excellent magnetization characteristics.

[0022] Means for Solving the Problems

[0023] In order to solve the above problems, the following anisotropic rare earth magnets are provided.

[0024] [1]An anisotropic rare earth magnet, which is an anisotropic rare earth magnet composed of a plate-shaped magnetic phase and a non-magnetic phase, characterized in that,

[0025] The magnetic phase has a composition represented by R2T 14 B (wherein, R represents one or more rare earth elements including one or both of Nd and Pr at 50 atomic% or more when the total amount is set to 100 atomic%, and T represents one or more transition metal elements including Fe, or represents two or more transition metal elements including Fe and Co).

[0026] The non-magnetic phase has a composition represented by RCu (wherein, R represents one or more rare earth elements including one or both of Nd and Pr at 50 atomic% or more when the total amount is set to 100 atomic%), and Cu is 6 atomic% or more and 80 atomic% or less.

[0027] The proportion of the magnetic phase is 51% by volume or more and less than 69% by volume.

[0028] The saturation magnetization is 0.8 T or more.

[0029] [2]The anisotropic rare earth magnet according to [1] above, characterized in that,

[0030] The average thickness of the magnetic phase is 7 to 12 μm, and the average plate width is 10 to 35 μm.

[0031] [3]The anisotropic rare earth magnet according to [1] or [2] above, characterized in that,

[0032] The ratio of the average plate width to the average thickness (average plate width / average thickness) of the magnetic phase is 1.5 or more and 15 or less.

[0033] [4]The anisotropic rare earth magnet according to [1] to [3] above, characterized in that,

[0034] The melting point of the magnetic phase is 1000 °C or more and 1300 °C or less, and the melting point of the non-magnetic phase is 400 °C to 900 °C.

[0035] In order to solve the above problems, a manufacturing method of the following anisotropic rare earth magnet is provided.

[0036] [5]A manufacturing method of an anisotropic rare earth magnet, which is a manufacturing method of an anisotropic rare earth magnet with a saturation magnetization of 0.8 T or more, characterized in that,

[0037] The manufacturing method includes a step of performing an orientation treatment on a mixture composed of a plate-like magnetic phase and a non-magnetic phase in a heated state. The magnetic phase has a composition represented by R2T 14 B (wherein, R represents one or more rare earth elements containing 50 atomic% or more of one or both of Nd and Pr when the total amount is set to 100 atomic%, and T represents one or more transition metal elements including Fe, or represents two or more transition metal elements including Fe and Co).

[0038] The non-magnetic phase has a composition represented by RCu (wherein, R represents one or more rare earth elements containing 50 atomic% or more of one or both of Nd and Pr when the total amount is set to 100 atomic%), and Cu is 6 atomic% or more and 80 atomic% or less.

[0039] The proportion of the magnetic phase is 51% by volume or more and less than 69% by volume.

[0040] The heating temperature of the mixture is equal to or higher than the melting point of the non-magnetic phase and equal to or lower than the melting point of the magnetic phase.

[0041] [6] The manufacturing method of the anisotropic rare earth magnet as described in [5] above, characterized in that

[0042] After the orientation treatment, the average thickness of the magnetic phase is 7 to 12 μm, and the average plate width is 10 to 35 μm.

[0043] [7] The manufacturing method of the anisotropic rare earth magnet as described in [5] or [6] above, characterized in that

[0044] After the orientation treatment, the ratio of the average plate width to the average thickness (average plate width / average thickness) of the magnetic phase is 1.5 or more and 15 or less.

[0045] [8] The manufacturing method of the anisotropic rare earth magnet as described in [5] to [7] above, characterized in that

[0046] The melting point of the magnetic phase is 1000 °C or more and 1300 °C or less, and the melting point of the non-magnetic phase is 400 °C to 900 °C.

[0047] Effects of the Invention

[0048] The anisotropic rare earth magnet of the present invention has a new composition and excellent magnetization characteristics. The manufacturing method of the anisotropic rare earth magnet of the present invention can obtain an anisotropic rare earth magnet with excellent magnetization characteristics with fewer processes. Description of the Drawings

[0049] Figure 1is an optical micrograph of a mixture of a magnetic phase (R2T 14 B) and a non-magnetic phase (RCu) produced by casting. The magnetic phase in the mixture is 54 vol%.

[0050] Figure 2 is an optical micrograph of an anisotropic cast rare earth magnet produced by an electromagnetic vibration process. Figure 2 (a) of is such that the proportion of the magnetic phase (R2T 14 B) in the mixture is 49 vol%, Figure 2 (b) of is such that the proportion of the magnetic phase (R2T 14 B) in the mixture is 54 vol%.

[0051] Figure 3 is an optical micrograph showing the structure of an anisotropic cast rare earth magnet after pressing (orientation treatment). Figure 3 (a) of is a cross-sectional photograph of the oriented plate-like magnetic phase observed from the lateral direction (thickness direction), Figure 2 (b) of is a cross-sectional photograph of the oriented plate-like magnetic phase observed from above (front).

[0052] Figure 4 is a graph showing the JH curve representing the characteristics of the magnets of the specimens of Examples 1-3.

[0053] Figure 5 is a diagram illustrating the form of pressing (orientation treatment) of a rod-shaped mixture using a mold in Example 4.

[0054] Figure 6 is a graph showing the JH curve representing the characteristics of the magnet of the specimen of Example 4. Detailed Description of the Invention

[0055] An embodiment of the anisotropic rare earth magnet of the present invention and its manufacturing method will be described.

[0056] (Manufacturing Method of Anisotropic Rare Earth Magnet)

[0057] The manufacturing method of the present invention is a method for manufacturing an anisotropic rare earth magnet having a saturation magnetization of 0.8 T or more.

[0058] This manufacturing method includes a step of subjecting a mixture composed of a magnetic phase and a non-magnetic phase to an orientation treatment in a heated state.

[0059] The magnetic phase has a composition represented by R2T 14 B.

[0060] Here, R represents one or more rare earth elements that, when their total amount is set to 100 atomic %, contain one or both of Nd and Pr at 50 atomic % or more. More specifically, R is one or both of Nd and Pr, and can be 50 atomic % or more, 60 atomic % or more, 70 atomic % or more, 80 atomic % or more, 90 atomic % or more, or can be 100 atomic %.

[0061] T is one or more transition metal elements including Fe, or two or more transition metal elements including Fe and Co. That is, the magnetic phase (R2T 14 B phase) contains, for example, a form having a composition of R2Fe 14 B or R2(Fe, Co) 14 B.

[0062] More specifically, examples of the magnetic phase (R2T 14 B phase) include Nd-Fe-B-based alloys, Pr-Fe-B-based alloys, Nd-Pr-Fe-B-based alloys, Nd-Ce-Fe-B-based alloys, Nd-Pr-Ce-Fe-B-based alloys, substances obtained by replacing a part of Fe in them with other transition metals such as Co and Ni, and the like.

[0063] The proportion (volume ratio) of the magnetic phase (R2T 14 B phase) in the mixture is 51 volume % or more and less than 69 volume %. In addition, from the viewpoint of achieving excellent saturation magnetization, the lower limit value of the proportion of the magnetic phase (R2T 14 B phase) in the mixture is preferably 54 volume % or more, 59 volume % or more, 64 volume % or more. The upper limit value of the proportion of the magnetic phase (R2T 14 B phase) in the mixture can be 68 volume % or less. If the proportion of the magnetic phase (R2T 14 B phase) in the mixture is within this range, the magnetic phase (R2T 14 B phase) is oriented by the orientation treatment described later, and a sufficient saturation magnetization (0.8 T or more) as a permanent magnet is achieved.

[0064] In addition, the shape of the magnetic phase (R2T 14 B phase) is plate-like. The average thickness of the magnetic phase (R2T 14 B phase) is preferably 7 to 12 μm, and the average plate width is preferably 10 to 35 μm.

[0065] The melting point of the magnetic phase (R2T 14 B phase) is preferably 1000 °C or more and 1300 °C or less, more preferably 1100 °C or more and 1300 °C or less. The magnetic phase (R2T 14 B phase) has the above composition, and thus shows the melting point as described above.

[0066] The non-magnetic phase has a composition represented by RCu. Similar to the magnetic phase, R represents one or more rare earth elements that contain 50 atomic% or more of one or both of Nd and Pr when the total amount thereof is set to 100 atomic%. R is one or both of Nd and Pr, and can be 50 atomic% or more, 60 atomic% or more, 70 atomic% or more, 80 atomic% or more, 90 atomic% or more, or can be 100 atomic%.

[0067] Cu in the non-magnetic phase (RCu phase) is 6 atomic% or more and 80 atomic% or less, preferably 20 atomic% or more and 53 atomic%. If Cu in the non-magnetic phase is within this range, the magnetic phase is oriented by the orientation treatment, and a sufficient saturation magnetization (0.8 T or more) as a permanent magnet is obtained.

[0068] The melting point of the non-magnetic phase (RCu phase) is preferably 400 to 900 °C, more preferably 400 to 700 °C.

[0069] In addition, within the range not impairing the effects of the present invention, the non-magnetic phase (RCu phase) may also contain other elements. That is, as long as it is a substance that does not exhibit magnetism (non-magnetic), specifically, for example, elements such as Al, Mg, C, and O can be exemplified.

[0070] The mixing of the magnetic phase (R2T 14 B phase) and the non-magnetic phase (RCu phase) is not particularly limited, and known methods such as casting and powder metallurgy techniques can be adopted. For example, in the case of casting, the raw materials of the magnetic phase (R2T 14 B phase) and the non-magnetic phase (RCu phase) are all put into a crucible, and a mixture can be produced by melting / casting in an inert environment. As another method, for example, the magnetic phase (R2T 14 B phase) and the non-magnetic phase (RCu phase) are separately melted / cast, and then pulverized, mixed, pressed powder, etc., so that a mixture can be produced. At this time, as described above, the proportion of the magnetic phase in the mixture can be adjusted to 51% by volume or more and less than 69% by volume.

[0071] The method of the orientation treatment is not particularly limited, and hot working (pressing, rolling, forging, extrusion processing, etc.) can be exemplified. The easy magnetization axis direction is oriented (anisotropized) by the orientation treatment.

[0072] Moreover, in the manufacturing method of the present invention, the temperature during the orientation treatment (heating temperature of the mixture of the magnetic phase and the non-magnetic phase) is above the melting point of the non-magnetic phase (RCu phase) and is the magnetic phase (R2T 14below the melting point of the B phase. Further, preferably, the temperature during the orientation treatment is above the melting point of the non-magnetic phase (RCu phase) and below the temperature at which melting of the magnetic phase (R2T 14 B phase) starts. That is, in this manufacturing method, during the orientation treatment, the magnetic phase (R2T 14 B phase) is in a solid state (including a solid-liquid coexistence state), and the non-magnetic phase (RCu phase) is in a liquid state. By performing the orientation treatment on the mixture of the magnetic phase (R2T 14 B phase) and the non-magnetic phase (RCu phase) in this solid-liquid coexistence state, it is easy to orient the magnetic phase (R2T 14 B phase) to achieve a sufficient saturation magnetization (0.8 T or more) as a strong magnet.

[0073] Specifically, the temperature of the orientation treatment (heating temperature of the mixture of the magnetic phase and the non-magnetic phase) depends on the compositions of the magnetic phase (R2T 14 B phase) and the non-magnetic phase (RCu phase). For example, the lower limit value can be 400 °C or more, and the upper limit value can be 1100 °C or less, 1000 °C or less, 900 °C or less, 700 °C or less. Considering the energy during the orientation treatment and the mold life, preferably, the composition of the mixture is prepared such that it becomes a solid-liquid coexistence state at 400 - 700 °C, and the orientation treatment is performed at this temperature.

[0074] In addition, when the orientation treatment is a hot working process, the pressure applied to the mixture can be, for example, 50 MPa or more, 100 MPa or more, 200 MPa or more, 500 MPa or more.

[0075] In addition, preferably, after the orientation treatment, the magnetic phase (R2T 14 B phase) is plate-shaped, with an average thickness of 7 - 12 μm and an average plate width of 10 - 35 μm. If the average thickness and average plate width of the magnetic phase (R2T 14 B phase) are within this range, a sufficient saturation magnetization (0.8 T or more) as a strong magnet can be achieved. The measurement method for the average thickness and average plate width of the magnetic phase (R2T 14 B phase) can be a known method. For example, it can be calculated based on the average region width and average region length of the magnetic phase (R2T 14 B phase) according to the measurement method described in the following examples.

[0076] In addition, the average plate width of the magnetic phase (R2T 14 B phase) does not necessarily need to be 10 - 35 μm in the state before the orientation treatment. During the orientation treatment such as hot working, the magnetic phase (R2T 14 B phase) is easily broken, and the average plate width can be adjusted to 10 - 35 μm. On the other hand, for the magnetic phase (R2T14 The average thickness of the B phase is preferably 7 to 12 μm in the state before the orientation treatment.

[0077] Furthermore, the magnetic phase (R2T 14 The ratio of the average plate width to the average thickness (average plate width / average thickness) of the B phase is preferably 1.5 or more and 15 or less. If the ratio of the average plate width to the average thickness (average plate width / average thickness) of the magnetic phase (R2T 14 B phase) is within this range, a sufficient saturation magnetization (0.8 T or more) as a permanent magnet is achieved.

[0078] As described above, in this manufacturing method, the magnetic phase (R2T 14 B phase) and the non-magnetic phase (RCu phase) have a specified composition, and the proportion of the magnetic phase (R2T 14 B phase) is 51% by volume or more and less than 69% by volume. And, by performing an orientation treatment such as heat treatment on the mixture of the magnetic phase (R2T 14 B phase) and the non-magnetic phase (RCu phase) only under the condition that the temperature is above the melting point of the non-magnetic phase (RCu phase) and below the melting point of the magnetic phase (R2T 14 B phase), the magnetic phase (R2T 14 B phase) is oriented. Therefore, an anisotropic rare earth magnet having excellent magnetization characteristics can be easily obtained. That is, in this manufacturing method, there is no need for the complicated processes required in the conventional methods, and an anisotropic rare earth magnet having excellent magnetization characteristics (saturation magnetization of 0.8 T or more) can be obtained through the orientation treatment process based on the above conditions.

[0079] (Anisotropic rare earth magnet)

[0080] The anisotropic rare earth magnet of the present invention can be obtained by the manufacturing method of the anisotropic rare earth magnet of the present invention described above. Regarding the anisotropic rare earth magnet of the present invention, a part of the description is omitted for the content that duplicates the content described in the above manufacturing method.

[0081] The anisotropic rare earth magnet of the present invention is composed of a magnetic phase and a non-magnetic phase, and the magnetic phase is oriented in one direction.

[0082] The magnetic phase has a composition represented by R2T 14 B.

[0083] Here, R is at least any one of Nd and Pr, that is, one or both of Nd and Pr are one or more rare earth elements of 50 atomic% or more. More specifically, for R, one or both of Nd and Pr can be 50 atomic% or more, 60 atomic% or more, 70 atomic% or more, 80 atomic% or more, 90 atomic% or more, or can be 100 atomic%.

[0084] T is one or more transition metal elements including Fe, or two or more transition metal elements including Fe and Co. That is, the magnetic phase includes a form having a composition of R2Fe 14 B or R2(Fe, Co) 14 B.

[0085] In the anisotropic rare earth magnet, the proportion (volume ratio) of the magnetic phase (R2T 14 B phase) is 51% by volume or more and less than 69% by volume. For the lower limit value of the proportion of the magnetic phase (R2T 14 B phase), in order of preference, 51% by volume or more, 54% by volume or more, 59% by volume or more, 64% by volume or more can be cited. As the upper limit value of the proportion of the magnetic phase (R2T 14 B phase), 68% by volume or less can be cited. If the proportion of the magnetic phase in the anisotropic rare earth magnet is within this range, a sufficient saturation magnetization (0.8 T or more) as a strong magnet is achieved.

[0086] In addition, for the proportion (volume ratio) of the magnetic phase (R2T 14 B phase) of the anisotropic rare earth magnet, for example, the average area ratio (area%) of the magnetic phase in a plurality of observation surfaces of at least 3 fields of view that can observe a cross section parallel to the pressing direction of the orientation treatment (hot working such as pressing) can be set as the volume ratio (volume%).

[0087] By the proportion of the magnetic phase (R2T 14 B phase) in the anisotropic rare earth magnet being within this range, a sufficient saturation magnetization (0.8 T or more) as a strong magnet is achieved.

[0088] In addition, the magnetic phase (R2T 14 B phase) is plate-shaped. Specifically, the average thickness of the magnetic phase in the anisotropic rare earth magnet is preferably 7 to 12 μm, and the average plate width is preferably 10 to 35 μm. If the average thickness and average plate width of the magnetic phase (R2T 14 B phase) are within this range, the anisotropic rare earth magnet achieves a sufficient saturation magnetization (0.8 T or more) as a strong magnet.

[0089] Furthermore, the ratio of the average plate width to the average thickness (average plate width / average thickness) of the magnetic phase (R2T 14 B phase) is preferably 1.5 or more and 15 or less. If the ratio of the average plate width to the average thickness (average plate width / average thickness) of the magnetic phase (R2T 14 B phase) is within this range, the anisotropic rare earth magnet achieves a sufficient saturation magnetization (0.8 T or more) as a strong magnet.

[0090] The melting point of the magnetic phase (R2T 14 B phase) is preferably 1000 °C or higher and 1300 °C or lower, more preferably 1100 °C or higher and 1300 °C or lower.

[0091] Furthermore, within the range not impairing the effects of the present invention, the magnetic phase may also contain elements other than R, T, and B.

[0092] The non-magnetic phase has a composition represented by RCu. Similar to the magnetic phase (R2T 14 B phase), R represents one or both of Nd and Pr, which are one or more rare earth elements containing 50 atomic% or more of one or both of them when the total amount is set to 100 atomic%. For R, one or both of Nd and Pr may be 50 atomic% or more, 60 atomic% or more, 70 atomic% or more, 80 atomic% or more, 90 atomic% or more, or may be 100 atomic%.

[0093] Cu in the non-magnetic phase (RCu phase) is 6 atomic% or more and 80 atomic% or less, preferably 20 atomic% or more and 53 atomic%. If the content of Cu in the non-magnetic phase is within this range, a sufficient saturation magnetization (0.8 T or more) as a permanent magnet is achieved.

[0094] The melting point of the non-magnetic phase (RCu phase) is preferably 400 - 900 °C, more preferably 400 - 700 °C.

[0095] In addition, within the range not impairing the effects of the present invention, the non-magnetic phase (RCu phase) may also contain other elements. That is, as long as it is a non-magnetic substance (non-magnetic), specifically, for example, elements such as Al, Mg, C, and O can be cited.

[0096] The anisotropic rare earth magnet of the present invention is composed of a magnetic phase (R2T 14 B phase) and a non-magnetic phase (RCu phase) having the above-described composition, and has excellent magnetic properties. Specifically, the saturation magnetization of the anisotropic rare earth magnet of the present invention is 0.8 T or more, preferably 0.9 T or more, more preferably 1.0 T or more.

[0097] The anisotropic rare earth magnet of the present invention and its manufacturing method are not limited to the above embodiments. For example, the manufacturing method of the anisotropic rare earth magnet of the present invention may also include known processes other than the above. In addition, for example, inevitable impurities generated during the manufacturing process may also be contained in the anisotropic rare earth magnet of the present invention.

[0098] Examples

[0099] Hereinafter, the anisotropic rare earth magnet and its manufacturing method of the present invention will be described together with examples. The anisotropic rare earth magnet and its manufacturing method of the present invention are not limited by any of the following examples.

[0100] <Reference Example>

[0101] According to the description in Non-Patent Document 1, an anisotropic rare earth magnet was produced by an electromagnetic vibration process.

[0102] Specifically, Nd2Fe 14 B was selected as the magnetic phase, and a Nd-30 atomic% Cu alloy was selected as the non-magnetic phase. The master alloys constituting the magnetic phase and the non-magnetic phase were weighed so that the proportion of the magnetic phase became 49 vol% and 54 vol%. By melting in an inert environment at high frequency (molten liquid temperature 1600 °C), it was poured into a carbon steel mold coated with a thick BN release agent, thereby producing a rod-shaped mixture.

[0103] The optical micrograph of this mixture (magnetic phase (Nd2Fe 14 B): 54 vol%, non-magnetic phase (Nd-30 atomic% Cu alloy)) is shown in Figure 1 . The white phase is the magnetic phase (Nd2Fe 14 B), and the other phases are non-magnetic phases (Nd-30 atomic% Cu alloy).

[0104] After cutting this rod-shaped mixture into 15 mm, it was set in a superconducting magnet. Under an Ar gas flow, the magnetic field was raised to 10 T and the sample temperature was heated to 700 °C. It was carried out by an electromagnetic vibration process in two stages, the first stage: applying an alternating current of 250 Hz and 90 A for 120 s; the second stage: applying an alternating current of 1000 Hz and 90 A for 120 s, air-cooling to 400 °C (about 200 s), and reducing the magnetic field to 0 T.

[0105] As a result, when the proportion of the magnetic phase (Nd2Fe 14 B) in the mixture was 49 vol%, it was possible to completely orient as in Figure 2 (a), but the saturation magnetization was less than 0.8 T (0.79 T), and it was confirmed that it did not have sufficient function as a strong magnet. On the other hand, when the proportion of the magnetic phase (Nd2Fe 14 B) in the mixture was 54 vol%, as in Figure 2 (b), most of them could not be crushed, and it was confirmed that they could not function as magnets.

[0106] <Examples 1-3, Comparative Example 1>

[0107] As the magnetic phase (R2T 14B) Select Nd2Fe 14 B, as the non-magnetic phase (RCu), select a Nd-30 atomic% Cu alloy. Weigh the master alloy so that the ratio of the magnetic phase (Nd2Fe 14 B) and the non-magnetic phase (Nd-30 atomic%) becomes a specified ratio (Example 1: magnetic phase 54% by volume, Example 2: magnetic phase 59% by volume, Example 3: magnetic phase 64% by volume, Comparative Example 1: magnetic phase 69% by volume). By melting in an inert environment at high frequency (molten liquid temperature 1600 °C), pour it into a carbon steel mold coated with a thick BN release agent to fabricate a mixed body round bar. Through this casting, prepare a round bar-shaped mixture composed of the magnetic phase (Nd2Fe 14 B) and the non-magnetic phase (Nd-30 atomic% Cu).

[0108] After cutting the round bar-shaped mixture into lengths of 5 mm, heat it to 700 °C in the atmosphere and press the round bar into a plate shape (orientation treatment) by placing a 11 kg weight. It should be noted that among them, the specimen of Comparative Example 1 with a magnetic phase (Nd2Fe 14 B) of 69% by volume cannot be pressed.

[0109] For the specimens of Examples 1-3, the optical microscope photos of the pressed specimens are shown in Figure 3 . Figure 3 The (a) in Figure 3 is a cross-sectional photo of the oriented plate-shaped magnetic phase observed from the side (thickness direction (a)), and

[0110] The average thickness, average plate width, and average plate width / average thickness values of the magnetic phase (Nd2Fe 14 B) measured at various parts of the specimens of Examples 1-3 are shown in Table 1.

[0111] In addition, the measurement methods for the average thickness and average plate width are as follows. First, the specimen is cut in a way that a cross-section parallel to the pressing direction can be observed, and then polished. Using an optical microscope, an optical microscope photograph of an arbitrary part of the polished observation surface is taken in such a way that 1 pixel of the image is 0.564×0.564 μm and the image becomes 1280×960 pixels. At this time, the photograph is taken in such a way that the pressing direction becomes the vertical axis of the image. The taken image is measured by Image-Pro Premier Ver9.3. First, in the "Morphology" tab, filtering is performed by "Shrink, Shape 2×2 square, Times 4". Then, binarization is performed in such a way that only the magnetic phase is selected, and the average area length and average area width are measured. However, objects with a region width value of 2 pixels (1.128 μm) or less are excluded. The value obtained by adding the reduction amount 4.512 μm corresponding to the shrink filter to their values, i.e., (average area length + 4.512 μm), is the average plate width, and (average area width + 4.512 μm) is the average thickness. In addition, the average value of the ratio of the average plate width to the average thickness (average plate width / average thickness) is a value calculated using the average plate width and average thickness of one taken image. In Example 1, 25 images are processed, in Example 2, 27 images are processed, and in Example 3, 35 images are processed. The ranges of these values are shown in Table 1.

[0112] In addition, the proportion (volume ratio) of the magnetic phase (R2T 14 B phase) of the pressed specimen is calculated from the average area ratio (area %) of the magnetic phase in a plurality of observation surfaces of at least 3 fields or more that can observe a cross-section parallel to the pressing direction. For the proportion (volume ratio) of the magnetic phase (R2T 14 B phase) of the pressed specimen, the specimen of Example 1 is 54 vol%, the specimen of Example 2 is 59 vol%, and the specimen of Example 3 is 64 vol%.

[0113] Table 1

[0114]

[0115] It was confirmed that in the specimens of Examples 1 - 3, the average thickness was 7 - 12 μm and the average plate width was within 10 - 35 μm. In addition, it was confirmed that the ratio of the average plate width to the average thickness (average plate width / average thickness) was 1.5 or more.

[0116] The JH curves showing the characteristics of the magnets of the specimens of Examples 1 - 3 are shown in Figure 4It was confirmed that Example 1 (magnetic phase: 54 vol%), Example 2 (magnetic phase: 59 vol%), and Example 3 (magnetic phase: 64 vol%) became anisotropic magnets having high residual magnetization, exhibiting coercive force, and having a saturation magnetization of 0.8 T or more.

[0117] <Example 4>

[0118] As the magnetic phase (R2T 14 B), Nd2Fe 14 B was selected, and as the non-magnetic phase (RCu), a Nd-30 atomic% Cu alloy was selected. The master alloy was weighed so that the ratio of the magnetic phase (Nd2Fe 14 B) and the non-magnetic phase (Nd-30 atomic%) became 64 vol% of the magnetic phase. Then, it was melted by high-frequency melting (molten liquid temperature: 1600 °C) in an inert environment and poured into a carbon steel mold coated with a thick BN release agent, thereby producing a rod-shaped mixture. By this casting, a rod-shaped mixture composed of the magnetic phase (Nd2Fe 14 B) and the non-magnetic phase (Nd-30 atomic% Cu) was prepared.

[0119] After cutting the rod-shaped mixture into a length of 5 mm, it was heated to 620 °C in the atmosphere and pressed into a 1-mm-thick plate (orientation treatment) using the Figure 5 mold shown in the figure under a load of 450 MPa. The part used as the magnet was the part with a bottom diameter of 6 mm.

[0120] The ratio (volume ratio) of the magnetic phase (R2T 14 B phase) of the pressed specimen was calculated from the average area ratio (area%) of the magnetic phase in three fields of view of the observation surface that could observe a cross section parallel to the pressing direction. The ratio (volume ratio) of the magnetic phase (R2T 14 B phase) of the pressed specimen was 67.6 vol%.

[0121] The average thickness, average plate width, and average plate width / average thickness values of the magnetic phase (Nd2Fe 14 B) measured at each part of the specimen in Example 4 are shown in Table 2.

[0122] In addition, the measuring methods for the average thickness and average plate width are as follows. First, the specimen is cut in such a way that a cross-section parallel to the pressing direction can be observed, and then polished. An SEM photograph of an arbitrary part of the mirror-polished observation surface is taken by means of a reflected electron image of a scanning electron microscope with an image of 1 pixel being 0.1×0.1 μm and having 1280×960 pixels. At this time, the photograph is taken with the pressing direction being the vertical axis of the image. The photographed image is measured by Image-Pro Premier Ver9.3. First, in the "Morphology" tab, filtering is performed by "Dilation, Shape 2×2 square, 4 times". Then, binarization is carried out in such a way that only the magnetic phase is selected, and the average area length and average area width are measured. However, objects with a region width value of 2 pixels (0.2 μm) or less are excluded. The value obtained by adding the reduction amount of 0.8 μm corresponding to the dilation filter to their values, i.e., (average area length + 0.8 μm), is the average plate width, and (average area width + 0.8 μm) is the average thickness. In addition, the average value of the ratio of the average plate width to the average thickness (average plate width / average thickness) is a value calculated using the average plate width and average thickness of one photographed image. After processing 20 images, the ranges of these values are shown in Table 2.

[0123] Table 2

[0124]

[0125] It was confirmed that in the specimen of Example 4, the average thickness was 7 to 12 μm and the average plate width was within 10 to 35 μm. In addition, it was confirmed that the ratio of the average plate width to the average thickness (average plate width / average thickness) was 1.5 or more.

[0126] The JH curve showing the characteristics of the magnet of the specimen of Example 4 is shown in Figure 6 . It was confirmed that Example 4 (magnetic phase 67.6 vol%) was an anisotropic magnet having high residual magnetization, showing coercivity, and a saturation magnetization of 0.8 T or more.

Claims

1. An anisotropic rare earth magnet, which is an anisotropic rare earth magnet composed of a plate-shaped magnetic phase and a non-magnetic phase, characterized in that, The magnetic phase has a composition represented by R2T 14 B, where R represents one or more rare earth elements containing one or both of Nd and Pr at 50 atomic% or more when the total amount thereof is set to 100 atomic%, and T represents one or more transition metal elements including Fe, or represents two or more transition metal elements including Fe and Co the non-magnetic phase has a composition represented by RCu, and Cu is 6 atomic% or more and 80 atomic% or less, where R represents one or both of Nd and Pr containing 50 atomic% or more when the total amount is set to 100 atomic% One or more rare earth elements, the proportion of the magnetic phase is 51% by volume or more and less than 69% by volume, the saturation magnetization of the anisotropic rare earth magnet is 0.8 T or more.

2. The anisotropic rare earth magnet according to claim 1, characterized in that, the average thickness of the magnetic phase is 7 to 12 μm, and the average plate width is 10 to 35 μm.

3. The anisotropic rare earth magnet according to claim 1, characterized in that, the ratio of the average plate width to the average thickness of the magnetic phase, that is, average plate width / average thickness, is 1.5 or more and 15 or less.

4. The anisotropic rare earth magnet according to claim 1, characterized in that, the melting point of the magnetic phase is 1000 °C or more and 1300 °C or less, and the melting point of the non-magnetic phase is 400 °C to 900 °C.

5. A method for manufacturing an anisotropic rare earth magnet, which is a method for manufacturing an anisotropic rare earth magnet with a saturation magnetization of 0.8 T or more, characterized in that, the manufacturing method includes a step of performing an orientation treatment on a mixture composed of a plate-shaped magnetic phase and a non-magnetic phase in a heated state, The magnetic phase has a composition represented by R2T 14 B, where R represents one or more rare earth elements containing one or both of Nd and Pr at 50 atomic % or more when the total amount thereof is 100 atomic %, T represents one or more transition metal elements including Fe, or represents two or more transition metal elements including Fe and Co the non-magnetic phase has a composition represented by RCu, and Cu is 6 atomic% or more and 80 atomic% or less, where R represents one or both of Nd and Pr containing 50 atomic% or more when the total amount is set to 100 atomic% One or more rare earth elements, the proportion of the magnetic phase is 51% by volume or more and less than 69% by volume, the heating temperature of the mixture is above the melting point of the non-magnetic phase and below the melting point of the magnetic phase.

6. The method for manufacturing an anisotropic rare earth magnet according to claim 5, characterized in that, after the orientation treatment, the average thickness of the magnetic phase is 7 to 12 μm, and the average plate width is 10 to 35 μm.

7. The method for manufacturing an anisotropic rare earth magnet according to claim 5, characterized in that, after the orientation treatment, the ratio of the average plate width to the average thickness of the magnetic phase, that is, average plate width / average thickness, is 1.5 or more and 15 or less.

8. The method for manufacturing an anisotropic rare earth magnet according to claim 5, characterized in that, the melting point of the magnetic phase is 1000 °C or more and 1300 °C or less, and the melting point of the non-magnetic phase is 400 °C to 900 °C.

Images