JP2006019721A - Rare-earth magnet and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rare-earth magnet having sufficient corrosion resistance, and to provide a manufacturing method thereof. <P>SOLUTION: A method of manufacturing a rare-earth magnet of the preferred embodiment is a method of manufacturing a rare-earth magnet for thermally processing a magnet base body 3, containing a rare earth element to form a protective layer 5 on the surface of the magnet base body 3. This method includes a protective layer forming process of thermally processing the magnet base body 3 to form the protective layer 5, while adjusting any one of the following conditions of oxide gas partial pressure; a processing temperature and a processing time in an oxide atmosphere, containing the oxide gas so that the protective layer 5 has a first layer 5a covering the magnet base body and containing the rare-earth element and a second layer 5b covering the first layer 5a and containing less quantity of the rare earth element than that of the first layer 5a; and a resin layer forming process depositing resin on the surface of the protective layer 5, after the protective layer forming process to form a resin layer 7. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a rare earth magnet and a method for producing the same, and more particularly to a rare earth magnet having a protective layer formed on a surface thereof.

    In recent years, so-called rare-earth magnets (R—Fe—B-based magnets; R represents a rare earth element such as neodymium (Nd); the same applies hereinafter) have been developed as permanent magnets having a high energy product of 25 MGOe or more. As such a rare earth magnet, for example, Patent Document 1 discloses a magnet formed by sintering, and Patent Document 2 discloses a magnet formed by rapid quenching.

  Although this rare earth magnet exhibits a high energy product, it has a relatively low corrosion resistance because it contains rare earth elements and iron that are relatively easily oxidized as main components.

In order to improve the corrosion resistance of such rare earth magnets, it has been proposed to form a protective layer. Among these, Patent Document 3 proposes forming a protective layer by heating a rare earth magnet at 200 to 500 ° C. in an oxidizing atmosphere.
JP 59-46008 A JP-A-60-9852 JP-A-5-226129

  However, in Patent Document 3, it is proposed to form a protective layer at a specific temperature in an oxidizing atmosphere. However, in this document, how to adjust the conditions for forming the protective layer is specifically described. It is not disclosed. Therefore, when the rare earth magnet is heat-treated in an oxidizing atmosphere, a satisfactory protective layer cannot be formed to prevent corrosion of the rare earth magnet, and there is a problem that dusting or weight reduction occurs in the corrosion resistance test.

  Therefore, the present invention has been made in view of the above circumstances, and an object thereof is to provide a rare earth magnet having sufficient corrosion resistance and a method for manufacturing the same.

  As a result of diligent research to obtain a rare earth magnet having sufficient corrosion resistance, the present inventors have found that an oxidation formed on the surface of the rare earth magnet when the protective layer is formed by heat treating the rare earth magnet in an oxidizing atmosphere. By using the film configuration as an index, it was found that excessive corrosion of rare earth magnets can be suppressed and that the above problems can be solved, and further that corrosion resistance is further improved by providing a resin layer on the protective layer. The present invention has been completed.

  That is, the present invention is a method of manufacturing a rare earth magnet by heat-treating a magnet element containing a rare earth element to form a protective layer on the surface of the magnet element, the rare earth element containing the magnet element In an oxidizing atmosphere containing an oxidizing gas so that the protective layer has a first layer covering the first layer and a second layer having a rare earth element content less than the first layer. A protective layer forming step of adjusting the at least one of the oxidizing gas partial pressure, the processing temperature, and the processing time to heat-treat the magnet body to form a protective layer; and a protective layer after the protective layer forming step. It is another object of the present invention to provide a method for producing a rare earth magnet comprising a resin layer forming step of depositing a resin on a surface to form a resin layer.

  In the method for producing a rare earth magnet of the present invention, the resin layer is preferably coated with a resin layer forming coating solution containing a resin and dried.

  The method for producing a rare earth magnet of the present invention is a method for producing a rare earth magnet in which a magnet element containing a rare earth element is heat-treated to form a protective layer on the surface of the magnet element. In an oxidizing atmosphere containing an oxidizing gas so that the protective layer has a first layer covering the body and containing a rare earth element and a second layer covering the first layer and substantially free of the rare earth element A protective layer forming step of adjusting the at least one of the oxidizing gas partial pressure, the processing temperature, and the processing time to heat-treat the magnet body to form a protective layer; and a protective layer after the protective layer forming step. And a resin layer forming step of forming a resin layer by applying a resin layer-forming coating solution containing a resin on the surface and drying.

  According to the present invention, using the structure of the oxide film formed on the surface of the rare earth magnet as an index, at least one of the oxidizing gas partial pressure, the processing temperature, and the processing time when the magnet body is heat-treated in an oxidizing atmosphere. By adjusting one condition, it is possible to suppress the occurrence of excessive corrosion in an oxidizing atmosphere in which rare earth magnets easily corrode and to form a protective layer with excellent corrosion resistance, and by providing a resin layer, sufficient corrosion resistance is provided. A rare earth magnet can be obtained.

  In addition, the rare earth magnet obtained by the production method of the present invention has a slight occurrence of rust in the salt spray test, and the deterioration of the magnetic properties due to the test is sufficiently suppressed. Furthermore, since the protective layer is formed as described above in the rare earth magnet obtained by the manufacturing method of the present invention, the surface of the protective layer is formed with minute crystals and fine irregularities are formed. Conceivable. Therefore, an anchor effect is exhibited by this uneven shape, adhesion between the protective layer and the resin layer is improved, peeling and swelling of the resin layer are sufficiently suppressed, and deterioration of magnetic properties is also sufficiently suppressed.

  The present inventors infer the reason why the rare earth magnet obtained by the production method of the present invention has sufficient corrosion resistance as follows.

  That is, the rare earth magnet obtained by the production method of the present invention contains a rare earth element as a constituent element. Such rare earth elements are very easy to oxidize and easily elute into acidic solutions. In the rare earth magnet of the present invention, the protective layer covers the magnet body, the first layer containing the rare earth element, and the rare earth element content (substantially contained) is less than the first layer covering the first layer. No) has a second layer. Therefore, it is considered that the stability of the protective layer is improved and the corrosion resistance is improved because the rare earth magnet is covered with the second layer having a low rare earth element content. Further, the protective layer having the specific configuration has a dense configuration, and as a result, it is considered that the stability of the protective layer is improved and the corrosion resistance is improved. In addition, since the surface of the rare earth magnet of the present invention is coated with a resin layer, it is possible to suppress contact between the metal constituting the rare earth magnet and an oxidizing substance such as water vapor or oxygen existing outside. It is thought that the corrosion resistance was further improved.

  In addition, as resin contained in a resin layer, since a desired characteristic can be exhibited also in a high temperature environment (for example, 150 degreeC or more), a thermosetting resin is preferable. Among these, as the resin, at least one resin selected from the group consisting of a phenol resin, a melamine resin, a polyamideimide resin, a polyparaxylylene resin, a polyurea resin, and an epoxy silicone resin is preferable.

  Thus, since the rare earth magnet obtained by the production method of the present invention has sufficient corrosion resistance, it is suitable for use as a part for automobiles, industrial machines, etc., and particularly suitable for use as a motor for hybrid cars. is there.

  Thus, the rare earth magnet obtained by the production method of the present invention is formed on the surface of the magnet body, the protective layer formed on the surface of the magnet body, the magnet body containing the rare earth element. And a resin layer containing a resin, the protective layer covering the magnet body and containing a rare earth element, and the second layer covering the first layer and substantially free of rare earth elements Formed by heat-treating the magnet body in an oxidizing atmosphere containing an oxidizing gas by adjusting at least one of the oxidizing gas partial pressure, the processing temperature and the processing time. It has been done.

  The rare earth magnet of the present invention includes a magnet element containing a rare earth element, a first layer covering the magnet element and containing a rare earth element, and a rare earth element covering the first layer than the first layer. It is good also as providing the protective layer which has a 2nd layer with little content of, and the resin layer which is formed on the surface of a protective layer and contains resin. In particular, the rare earth element content in the second layer is preferably less than or equal to half the rare earth element content in the first layer.

  The rare earth magnet of the present invention has sufficient corrosion resistance, and the protective layer in such rare earth magnet has a uniform film thickness and excellent dimensional accuracy. In addition, since the specific protective layer and the resin layer are formed in the rare earth magnet of the present invention, deterioration in performance during production and use can be suppressed, and the reliability of the produced magnet can be improved. It becomes possible.

  The rare earth magnet of the present invention includes a magnet element containing a rare earth element and a rare earth element formed on the surface of the magnet element, containing oxygen and an element derived from the magnet element, covering the magnet element And a protective layer having a second layer that covers the first layer and substantially does not contain a rare earth element, and a resin layer that is formed on the surface of the protective layer and contains a resin, It is good also as providing.

  Furthermore, the second layer in the rare earth magnet of the present invention preferably contains a transition element and oxygen. More specifically, the magnet body contains a rare earth element and a transition element other than the rare earth element, the first layer contains oxygen, a rare earth element and a transition element other than the rare earth element, and the second layer It is preferable to contain transition elements other than oxygen and rare earth elements. In particular, the magnet body includes a rare earth element and a transition element other than the rare earth element, the first layer is mainly composed of the rare earth element, the transition element, and oxygen, and the second layer is composed of the transition element and oxygen. Is preferably the main component. Here, the “main component” means a case where the total mass of each component constituting the component occupies 90% by mass or more.

  In such a rare earth magnet, at least one of the rare earth element in the first layer, the transition element in the first layer, and the transition element in the second layer, more preferably all the elements are magnet elements. The element constituting the main phase of the body is more preferable. In such a rare earth magnet of the present invention, the rare earth element is preferably neodymium, and the second layer is more preferably substantially free of neodymium. Furthermore, iron and / or cobalt is preferable as the transition element other than the rare earth element.

  Furthermore, the resin constituting the resin layer is preferably a thermosetting resin, and is at least one selected from the group consisting of a phenol resin, a melamine resin, a polyamideimide resin, a polyparaxylylene resin, a polyurea resin, and an epoxy silicone resin. A resin is more preferable.

  Furthermore, in the rare earth magnet of the present invention, the total film thickness of the first layer and the second layer (the sum of the film thickness of the first layer and the film thickness of the second layer) is 0.1. It is preferably ˜20 μm, more preferably 0.1 to 5 μm.

  As described above, the protective layer in the rare earth magnet obtained by the manufacturing method of the present invention has at least one of the oxidizing gas partial pressure, the processing temperature, and the processing time in the oxidizing atmosphere so as to have the specific configuration. It is formed by heat-treating the magnet body by adjusting one condition.

  According to the method for producing a rare earth magnet of the present invention, a protective layer can be formed very easily and at low cost, and a protective layer having a uniform film thickness can be formed, producing a rare earth magnet having excellent dimensional accuracy. can do.

  In the method for producing a rare earth magnet of the present invention, it is preferable to heat-treat the magnet body by adjusting the oxidizing gas partial pressure, the treatment temperature and the treatment time during the heat treatment. By adjusting the above three conditions, it is possible to obtain a rare earth magnet that is easier and surely has sufficient corrosion resistance.

  In the method for producing a rare earth magnet of the present invention, it is preferable that the magnet body is acid-washed before the heat treatment. In the pre-stage of the heat treatment described above, by washing the magnet body with an acid, it is possible to remove a deteriorated layer and an oxide layer by processing formed on the surface of the magnet body during or after the manufacture of the magnet body. The oxide film can be formed with higher accuracy.

  ADVANTAGE OF THE INVENTION According to this invention, the rare earth magnet which has sufficient corrosion resistance, and its manufacturing method can be provided.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings as necessary. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. Further, the positional relationship such as up, down, left and right is based on the positional relationship shown in the drawings unless otherwise specified. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios.

  FIG. 1 is a schematic perspective view showing an embodiment of the rare earth magnet of the present invention, and FIG. 2 is a diagram schematically showing a cross section that appears when the rare earth magnet of FIG. 1 is cut along line II. . As is apparent from FIGS. 1 and 2, the rare earth magnet 1 of the present embodiment includes a magnet body 3, a protective layer 5 formed by covering the entire surface of the magnet body 3, and the surface of the protective layer 5. The resin layer 7 is formed so as to cover the whole.

(Magnet body)
The magnet body 3 is a permanent magnet containing a rare earth element. In this case, rare earth elements refer to scandium (Sc), yttrium (Y), and lanthanoid elements belonging to Group 3 of the long-period periodic table. Examples of the lanthanoid element include lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium. (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu) and the like are included.

  Examples of the constituent material of the magnet body 3 include a material containing the rare earth element and a transition element other than the rare earth element in combination. In this case, the rare earth element is preferably at least one element selected from the group consisting of Nd, Sm, Dy, Pr, Ho, and Tb. These elements include La, Ce, Gd, Er, Eu, Tm, Yb, and More preferably, it further contains at least one element selected from the group consisting of Y.

  As transition elements other than rare earth elements, iron (Fe), cobalt (Co), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), nickel (Ni), copper (Cu) At least one element selected from the group consisting of zirconium (Zr), niobium (Nb), molybdenum (Mo), hafnium (Hf), tantalum (Ta) and tungsten (W) is preferable, and Fe and / or Co are more preferable. preferable.

  More specifically, examples of the constituent material of the magnet body 3 include R—Fe—B and R—Co materials. In the former constituent material, R is preferably a rare earth element mainly composed of Nd, and in the latter constituent material, R is preferably a rare earth element mainly composed of Sm.

  As the constituent material of the magnet element body 3, an R—Fe—B based constituent material is particularly preferable. Such a material has a main phase having a substantially tetragonal crystal structure, and a rare earth-rich phase having a high rare earth element content in the grain boundary portion of the main phase, and a boron atom content ratio. Has a high boron-rich phase. These rare earth-rich phase and boron-rich phase are nonmagnetic phases that do not have magnetism, and such a nonmagnetic phase is usually contained in an amount of 0.5 to 50% by volume in the magnet constituting material. Moreover, the particle size of the main phase is usually about 1 to 100 μm.

  In such R—Fe—B-based constituent materials, the rare earth element content is preferably 8 to 40 atomic%. When the rare earth element content is less than 8 atomic%, the crystal structure of the main phase becomes almost the same as that of α-iron, and the coercive force (iHc) tends to decrease. On the other hand, if it exceeds 40 atomic%, a rare earth-rich phase is excessively formed, and the residual magnetic flux density (Br) tends to be small.

  The Fe content is preferably 42 to 90 atomic%. When the Fe content is less than 42 atomic%, the residual magnetic flux density decreases, and when it exceeds 90 atomic%, the coercive force tends to decrease. Furthermore, the B content is preferably 2 to 28 atomic%. If the B content is less than 2 atomic%, a rhombohedral structure is likely to be formed, and this tends to reduce the holding force. If it exceeds 28 atomic%, a boron-rich phase is excessively formed. Therefore, the residual magnetic flux density tends to be small.

  In the constituent materials described above, a part of Fe in the R—Fe—B system may be substituted with Co. Thus, if a part of Fe is replaced by Co, the temperature characteristics can be improved without deteriorating the magnetic characteristics. In this case, it is desirable that the amount of substitution of Co not be larger than the content of Fe. When the Co content exceeds the Fe content, the magnetic properties of the magnet body 3 tend to deteriorate.

  A part of B in the constituent material may be substituted with an element such as carbon (C), phosphorus (P), sulfur (S) or copper (Cu). By replacing a part of B in this way, the magnet body can be easily manufactured and the manufacturing cost can be reduced. At this time, the substitution amount of these elements is desirably an amount that does not substantially affect the magnetic properties, and is preferably 4 atomic% or less with respect to the total amount of constituent atoms.

  Further, from the viewpoint of improving the holding power and reducing the manufacturing cost, in addition to the above-described structure, aluminum (Al), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), bismuth (Bi ), Niobium (Nb), tantalum (Ta), molybdenum (Mo), tungsten (W), antimony (Sb), germanium (Ge), tin (Sn), zirconium (Zr), nickel (Ni), silicon (Si) ), Gallium (Ga), copper (Cu), hafnium (Hf), or other elements may be added. These addition amounts are also preferably in a range that does not affect the magnetic properties, and are preferably 10 atomic% or less with respect to the total amount of constituent atoms. In addition, oxygen (O), nitrogen (N), carbon (C), calcium (Ca), and the like are conceivable as other components that are inevitably mixed. It may be contained in an amount of.

The magnet body 3 having such a configuration can be manufactured by powder metallurgy. In this method, first, an alloy having a desired composition is produced by a known alloy production process such as a casting method or a strip casting method. Next, this alloy was pulverized to a particle size of 10 to 100 μm using a coarse pulverizer such as a jaw crusher, a brown mill, or a stamp mill, and then further pulverized by a fine pulverizer such as a jet mill or an attritor. The particle size is 5 to 5 μm. The powder thus obtained is preferably molded at a pressure of 0.5 to ⁵ t / cm ² in a magnetic field having a magnetic field strength of 600 kA / m or more.

  Thereafter, the obtained compact is preferably sintered in an inert gas atmosphere or under vacuum at 1000 to 1200 ° C. for 0.5 to 10 hours and then rapidly cooled. Furthermore, this sintered body is subjected to heat treatment at 500 to 900 ° C. for 1 to 5 hours in an inert gas atmosphere or vacuum, and if necessary, the sintered body is processed into a desired shape (practical shape). A magnet body 3 is obtained.

  The thus obtained magnet body 3 is preferably further subjected to acid cleaning. That is, it is preferable that the surface of the magnet body 3 is subjected to acid cleaning in the previous stage of heat treatment to be described later.

  Nitric acid is preferably used as the acid used in the acid cleaning. When plating a general steel material, non-oxidizing acids such as hydrochloric acid and sulfuric acid are often used. However, when the magnet body 3 contains a rare earth element like the magnet body 3 in the present embodiment, hydrogen generated by the acid is removed from the magnet body 3 by performing treatment using these acids. Occluded on the surface, the occlusion site becomes brittle and a large amount of powdery undissolved material is generated. Since this powdery undissolved material causes surface roughness, defects, and poor adhesion after the surface treatment, it is preferable not to include the above-described non-oxidizing acid in the acid cleaning solution. Therefore, it is preferable to use nitric acid, which is an oxidizing acid that generates little hydrogen.

  The amount of dissolution of the surface of the magnet body 3 by such acid cleaning is preferably 5 μm or more, preferably 10 to 15 μm in average thickness from the surface. By completely removing the altered layer or oxide layer by processing the surface of the magnet body 3, a desired oxide film can be formed with higher accuracy by heat treatment described later.

  The concentration of nitric acid in the treatment solution used for the acid cleaning is preferably 1 N or less, particularly preferably 0.5 N or less. If the nitric acid concentration is too high, the dissolution rate of the magnet body 3 is extremely fast, and it becomes difficult to control the amount of dissolution. In particular, large-scale processing such as barrel processing has a large variation, making it difficult to maintain the dimensional accuracy of the product. Tend. Moreover, when the nitric acid concentration is too low, the dissolved amount tends to be insufficient. For this reason, the nitric acid concentration is preferably 1 N or less, and particularly preferably 0.5 to 0.05 N. The amount of Fe dissolved at the end of the treatment is about 1 to 10 g / l.

  In order to completely remove a small amount of undissolved substances and residual acid components from the surface of the magnet body 3 that has been subjected to acid cleaning, it is preferable to perform cleaning using ultrasonic waves. This ultrasonic cleaning is preferably performed in pure water with very few chlorine ions that generate rust on the surface of the magnet body 3. Moreover, you may perform the same water washing before and after the said ultrasonic cleaning, and in each process of acid cleaning as needed.

(Protective layer)
The protective layer 5 contains an element derived from the magnet element body 3 and oxygen, covers the magnet element body 3 and contains the rare earth element, and covers the first layer 5a. And a second layer 5b having a rare earth element content less than 5a. Here, “the rare earth element content is lower than that of the first layer 5a” means that the rare earth element content in the second layer 5b is smaller than the rare earth element content in the first layer 5a. It means that. Here, the “rare earth element content” is the ratio (mass%) of the mass of the rare earth element contained in each layer to the total mass of each layer. The second layer 5b preferably has a rare earth element content (content) that is less than or equal to half the rare earth element content (content ratio) in the first layer 5a, and does not substantially contain a rare earth element. Is particularly preferred. The element derived from the magnet body 3 is a constituent material of the magnet body 3 and includes at least a rare earth element and a transition element other than the rare earth element, and further includes B, Bi, Si, Al, and the like. is there. The protective layer 5 is not coated or pasted on the magnet element body 3, but is made of an element that appears on the magnet element body 3 when the magnet element body 3 itself changes due to oxidation or the like. Therefore, the protective layer 5 does not contain a new metal element that does not constitute a magnet body, but may contain a nonmetallic element such as oxygen or nitrogen.

  The first layer 5a contains oxygen and elements derived from the magnet body 3 including rare earth elements, and more specifically contains oxygen, transition elements other than rare earth elements and rare earth elements. When the constituent material of the magnet body 3 is R-Fe-B, the transition element is mainly composed of Fe, and may contain Co or the like depending on the composition of the constituent material.

  The second layer 5b contains an element derived from the magnet body 3 and oxygen, but does not substantially contain a rare earth element. More specifically, the second layer 5b contains a transition element other than oxygen and rare earth elements. When the constituent material of the magnet body 3 is R-Fe-B, the transition element is mainly composed of Fe, and may contain Co or the like depending on the composition of the constituent material.

  The content of each constituent material of the first layer 5a and the second layer 5b is EPMA (X-ray microanalyzer method), XPS (X-ray photoelectron spectroscopy), AES (Auger electron spectroscopy) or EDS (energy dispersion). This can be confirmed using a known composition analysis method such as X-ray fluorescence X-ray spectroscopy.

  Here, as an aspect which does not contain a rare earth element substantially, the aspect in which a rare earth element is not detected by EDS mentioned above can be considered.

  The protective layer 5 adjusts at least one of the oxidizing gas partial pressure, the processing temperature, and the processing time so that the protective layer 5 has the above-described configuration in an oxidizing atmosphere containing an oxidizing gas. The magnet body 3 is formed by heat treatment (heating) (protective layer forming step). In this heat treatment, it is preferable to adjust three conditions of oxidizing gas partial pressure, treatment temperature, and treatment time.

  Here, the oxidizing atmosphere is not particularly limited as long as it contains an oxidizing gas. For example, the atmosphere, oxygen atmosphere (preferably oxygen partial pressure adjustment atmosphere), water vapor atmosphere (preferably water vapor partial pressure adjustment atmosphere) ) And the like. The oxidizing gas is not particularly limited, and examples thereof include oxygen and water vapor. For example, the oxygen atmosphere is an atmosphere having an oxygen concentration of 0.1% or more, and an inert gas coexists with oxygen in the atmosphere. Such inert gas includes nitrogen. That is, as an aspect of the oxygen atmosphere, there is an atmosphere composed of oxygen and an inert gas. For example, the water vapor atmosphere is an atmosphere having a water vapor partial pressure of 10 hPa or more, and an inert gas coexists with the water vapor in the atmosphere. An example of such an inert gas is nitrogen, and an embodiment of a water vapor atmosphere is an atmosphere composed of water vapor and an inert gas. It is preferable that the oxidizing atmosphere is a water vapor atmosphere because the protective layer can be more easily formed. Furthermore, examples of the oxidizing atmosphere include an atmosphere containing oxygen, water vapor, and an inert gas.

  When adjusting the above conditions, first, a correlation between the configuration of the protective layer 5 and at least one of the oxidizing gas partial pressure, the processing temperature, and the processing time is obtained. Next, based on the correlation, at least one of the oxidizing gas partial pressure, the processing temperature, and the processing time is adjusted during the heat treatment so that the protective layer 5 has the specific configuration.

  At this time, it is preferable to adjust processing temperature from the range of 200-550 degreeC, and it is more preferable to adjust from the range of 250-500 degreeC. If the processing temperature exceeds the upper limit, the magnetic properties tend to deteriorate, and if it is lower than the lower limit, it tends to be difficult to form a desired oxide film.

  The treatment time is preferably adjusted from the range of 1 minute to 24 hours, and more preferably adjusted from the range of 5 minutes to 10 hours. When the processing time exceeds the above upper limit value, the magnetic properties tend to deteriorate, and when the processing time is less than the lower limit value, it tends to be difficult to form a desired oxide film.

  When the oxidizing atmosphere is a water vapor atmosphere, first, the correlation between the configuration of the protective layer 5 and the water vapor partial pressure, the treatment temperature, and the treatment time is obtained. Next, based on the correlation, at least one of the water vapor partial pressure, the processing temperature, and the processing time is adjusted during the heat treatment so that the protective layer 5 has the specific configuration.

  In this case, it is preferable that the processing temperature and the processing time are adjusted from the above-described ranges. Moreover, it is preferable that water vapor partial pressure is adjusted from the range of 10-2000 hPa. When the water vapor partial pressure is less than 10 hPa, the protective layer 5 tends not to have a two-layer structure as described above. On the other hand, when the pressure exceeds 2000 hPa, the apparatus configuration is complicated due to the high pressure, and workability tends to be deteriorated, such as condensation is likely to occur.

  The total film thickness of the first layer 5a and the second layer 5b is preferably larger than 0.1 μm, and more preferably 1 μm or more. If the total film thickness is 0.1 μm or less, it tends to be difficult to form a protective layer having a two-layer structure. On the other hand, the total film thickness of the first layer 5a and the second layer 5b is preferably less than 20 μm, and more preferably 5 μm or less. When the total film thickness is 20 μm or more, it tends to be difficult to form an oxide film or to deteriorate magnetic properties.

  The film thickness of the second layer 5b is preferably 5 nm or more. If the film thickness is less than 5 nm, the film thickness becomes too thin, and the effect of inhibiting corrosion tends to be insufficient.

(Resin layer)
The resin layer 7 is configured to contain a resin. Such a resin may be a synthetic resin or a natural resin, but is preferably a synthetic resin, and more preferably a thermosetting resin. Such thermosetting resins include phenolic resins, epoxy resins, urethane resins, silicone resins, melamine resins, epoxy melamine resins, thermosetting acrylic resins, polyimide resins, polyamideimide resins, polyparaxylylene resins, polyureas. Resins, epoxy silicone resins, acrylic silicone resins and the like can be mentioned. Moreover, as a thermoplastic resin, the vinyl resin which uses vinyl compounds, such as acrylic acid, ethylene, styrene, vinyl chloride, vinyl acetate, as a raw material is mentioned. The resin layer 7 may contain metal particles, oxide particles, carbon particles, and the like.

  Especially, the resin layer 7 is preferable in it being a layer containing a phenol resin, an epoxy resin, an epoxy silicone resin, or a melamine resin. In particular, a layer containing a combination of a phenol resin, an epoxy silicone resin or an epoxy resin and a melamine resin is preferable. An epoxy-modified silicone resin such as an epoxy silicone resin is excellent in corrosion resistance as compared with an unmodified silicone resin, and thus can be suitably used in the same manner as a phenol resin or the like.

  Examples of the phenol resin that can form the resin layer 7 include alkyl phenol resins and alkyl polyhydric phenol resins, such as those obtained by curing alkyl phenol, alkyl polyhydric phenol monomers, oligomers, and mixtures thereof. it can. Curing can be carried out, for example, by reacting the above-described monomer or the like with formaldehyde to form a resole, and then polymerizing the obtained resole or by polymerizing urushiol and water.

Examples of the alkylphenol or the alkyl polyhydric phenol include compounds represented by the following general formula (1).

In the formula, R ¹¹ and R ¹² represent a hydroxyl group or an alkyl group, and at least one of R ¹¹ and R ¹² is an alkyl group. Among these, an alkyl polyhydric phenol having a hydroxy group at the ortho position of the hydroxy group in the formula and having an alkyl group at the meta position or para position is preferable. As such an alkyl polyhydric phenol, a component generally contained in a lacquer coating is suitable. Specifically, urushiol having a —C ₁₇ H ₂₅ group at the meta position, and a —C ₁₇ H ₃₃ group at the para position. And thiol having a —C ₁₇ H ₃₁ group at the meta position.

  Since the above alkylphenol or alkylpolyphenol can act as a reducing agent, even if it is exposed to a high temperature during curing, the magnet body 3 will be covered in a strong reducing atmosphere, and due to the progress of oxidation. Deterioration of the magnet body 3 can be greatly reduced.

  The epoxy resin is not particularly limited, and for example, epoxy compounds such as bisphenol type, polyol glycidyl ether type, polyacid glycidyl ester type, polyamine glycidyl amine type, and alicyclic epoxy type can be applied. Moreover, it is preferable that an epoxy resin further contains the hardening | curing agent which can harden the said compound in addition to the epoxy compound mentioned above. Examples of the curing agent include polyamines, polyamine epoxy resin adducts, polyamidoamines, polyamide resins, and the like. Specific examples include metaxylenediamine, isophoronediamine, diethylenetriamine, triethylenetetramine, diaminodiphenylmethane, and the like. It can be illustrated.

  Further, the melamine resin is a resin obtained by reacting melamine (2,4,6-triamino-1,3,5-triazine) with formaldehyde to obtain methylolmelamine and then curing it. Although such a melamine resin may form the resin layer 7 independently, it is more preferable to use it in combination with the phenol resin or epoxy resin mentioned above, for example. Since the melamine resin can form many cross-linked structures in the phenol resin or the epoxy resin, the resin layer 7 containing a combination of these has extremely excellent heat resistance and strength. As a result, the corrosion resistance and heat resistance of the rare earth magnet 1 are further improved.

  The resin layer 7 is formed using each resin mentioned above. For example, the resin layer 7 can be formed by dissolving the above-described resins in an organic solvent to prepare a coating solution for forming a resin layer, applying the coating solution on the surface of the protective layer 5 and drying it. (Resin layer forming step).

  Here, the coating method for forming the resin layer 7 is not particularly limited, and examples thereof include a dip coating method, a dip spin coating method, and a spray coating method. The resin layer 7 may be formed by applying the coating solution for forming the resin layer once, or may be formed by applying a plurality of times. In addition, when the resin layer 7 is formed by applying the coating liquid a plurality of times, an uncoated portion is unlikely to occur.

  As a method for forming the resin layer 7, a chemical vapor deposition method (CVD method) can be applied in addition to the above-described application. Among these, the vapor deposition polymerization method in which the vaporized monomer is vapor-deposited on the surface of the protective layer 5 and simultaneously polymerized to form the resin layer 7 is preferable. According to such a vapor deposition polymerization method, the resin layer 7 having good followability to the surface shape of the protective layer 5 is formed, and the adhesion between the protective layer 5 and the resin layer 7 tends to be improved. As a result, the effect of improving the corrosion resistance by the resin layer 7 is further improved.

  Specifically, for example, when the resin layer 7 made of polyparaxylylene is formed, first, a dimer of p-xylylene is prepared and introduced into an evaporation furnace to be 200 ° C. or lower and 1 Torr or lower. The gaseous p-xylylene obtained by evaporation is introduced into a decomposition furnace and thermally decomposed at 700 ° C. or lower and 0.5 Torr or lower. Next, the decomposed gas is guided to a vapor deposition chamber in which the magnet body 3 on which the protective layer 5 is formed is disposed, and is vapor-deposited on the surface of the protective layer 5 under conditions of normal temperature and 0.01 to 0.2 Torr. At the same time, polymerization of p-xylylene is caused to form a resin layer 7 made of polyparaxylylene.

  Furthermore, the film thickness of the resin layer 7 is preferably 0.1 to 100 μm, and more preferably 1 to 50 μm.

EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to these Examples.
[Manufacture of rare earth magnets]

Example 1
An ingot having a composition of 13.2Nd-1.5Dy-77.6Fe-1.6Co-6.1B (the number represents an atomic percentage) was prepared by powder metallurgy, and this was coarsely pulverized. Thereafter, jet milling with an inert gas was performed to obtain a fine powder having an average particle size of about 3.5 μm. The obtained fine powder was filled in a mold and molded in a magnetic field. Next, after sintering in vacuum, heat treatment was performed to obtain a sintered body. The obtained sintered body was cut into a size of 35 mm × 19 mm × 6.5 mm and processed to obtain a magnet body processed into a practical shape.

Next, the obtained magnet body was immersed in a 2% HNO ₃ aqueous solution for 2 minutes and then subjected to ultrasonic water washing.

  The magnet body that has been subjected to acid cleaning (acid treatment) as described above is heat-treated at 400 ° C. for 8 minutes in an oxygen-nitrogen mixed atmosphere with an oxygen partial pressure of 70 hPa (oxygen concentration 7%) to form a protective layer. did.

  The rare earth magnet having the protective layer formed on the surface of the magnet body as described above was sliced using a focused ion beam processing apparatus, and the film structure near the surface was observed with a transmission electron microscope. Note that JEM-3010 manufactured by JEOL Ltd. was used for the transmission electron microscope. FIG. 3 shows the obtained electron micrograph, and FIG. 4 shows an enlarged view of a part of the electron micrograph of FIG.

  3 and 4, the rightmost black layer is a platinum-palladium film, and the white layer adjacent to the black layer is a second layer that does not contain neodymium in the protective layer of the rare earth magnet, The average film thickness was confirmed to be 50 nm. In addition, the gray layer adjacent to the second layer (the layer whose color gradually increases from the white boundary toward the magnet body side) is the first layer containing neodymium, and its average film thickness is It was confirmed to be 1 μm. As can be seen from FIGS. 3 and 4, it was confirmed that the first layer was formed on the magnet body and the second layer was formed on the first layer.

  Furthermore, the rare earth magnet was thinned using a focused ion beam processing apparatus, and the film structure near the surface was observed with a transmission electron microscope (JEM-3010, manufactured by JEOL) and included in the first layer and the second layer. These elements were analyzed using EDS (Voyager III manufactured by Noraan Instruments). As a result, Nd, Fe, and O were detected as main components from the first layer, Fe and O were detected from the second layer, and Nd was not detected.

  A phenol resin coating was further applied by dip spin coating to the rare earth magnet thus formed with the protective layer, and heated at 150 ° C. for 20 minutes. This process was repeated twice to form a resin layer of about 3 μm, and the rare earth magnet of Example 1 was obtained.

(Example 2)
A sintered body was produced in the same manner as in Example 1, and the obtained sintered body was cut into a size of 30 mm × 19 mm × 6.5 mm to obtain a magnet body processed into a practical shape. Next, acid cleaning was performed in the same manner as in Example 1, heat treatment was performed, and a protective layer was formed. In the obtained rare earth magnet, it was confirmed that the first layer was formed on the magnet body and the second layer was formed on the first layer.

  The rare earth magnet thus formed with the protective layer was further coated with a phenol resin paint by spray coating and heated at 150 ° C. for 20 minutes. In this way, a resin layer of about 5 μm was formed, and the rare earth magnet of Example 2 was obtained.

Example 3
A sintered body was produced in the same manner as in Example 1, and the obtained sintered body was cut into a size of 20 mm × 10 mm × 2 mm to obtain a magnet body processed into a practical shape. Next, acid cleaning was performed in the same manner as in Example 1, heat treatment was performed, and a protective layer was formed. In the obtained rare earth magnet, it was confirmed that the first layer was formed on the magnet body and the second layer was formed on the first layer.

  Thus, the epoxy resin paint was further applied by spray coating to the rare earth magnet on which the protective layer was formed, and heated at 150 ° C. for 20 minutes. In this way, a resin layer of about 5 μm was formed, and the rare earth magnet of Example 3 was obtained.

Example 4
A rare earth magnet of Example 4 was obtained in the same manner as in Example 3 except that a silicone resin paint was used instead of the epoxy resin paint.

(Example 5)
A rare earth magnet of Example 5 was obtained in the same manner as Example 3 except that a polyimide resin paint was used instead of the epoxy resin paint and the heating conditions were 250 ° C. and 20 minutes.

(Example 6)
After obtaining a rare earth magnet on which a protective layer was formed in the same manner as in Example 3, this was subjected to vapor deposition polymerization in which monochloroparaxylylene dimer was thermally decomposed and polymerized, and about 5 μm comprising a polyparaxylylene film. Thus, a rare earth magnet of Example 6 was obtained.

(Example 7)
First, in the same manner as in Example 1, a magnet body was formed and subjected to acid cleaning. The obtained magnet body after acid cleaning was heat-treated at 450 ° C. for 10 minutes in a nitrogen atmosphere having a water vapor partial pressure of 475 hPa to form a protective layer. As a result of observing the film structure near the surface of the magnet body on which the protective layer was formed in the same manner as in Example 1, the thickness of the first layer was 3 μm, and the thickness of the second layer was 100 nm. there were.

  Next, a phenol resin paint was applied to the magnet body having this protective layer by spray coating, and then heated at 150 ° C. for 20 minutes to form a resin layer of about 5 μm. Thus, the rare earth magnet of Example 7 was obtained. It was.

(Example 8)
Heat treatment was performed under conditions of oxygen concentration 7%, 350 ° C. for 13 minutes, and a protective layer having a first layer having a thickness of 0.9 μm and a second layer having a thickness of 50 nm was formed. A rare earth magnet of Example 8 was obtained in the same manner as Example 7 except for the above.

Example 9
Heat treatment is performed at an oxygen concentration of 0.5% and 410 ° C. for 10 minutes, and a protective layer having a first layer having a thickness of 1.5 μm and a second layer having a thickness of 50 nm is formed. Except that, a rare earth magnet of Example 9 was obtained in the same manner as Example 7.

(Example 10)
Heat treatment was performed at an oxygen concentration of 21% and 410 ° C. for 10 minutes, and a protective layer having a first layer having a thickness of 2.1 μm and a second layer having a thickness of 100 nm was formed. A rare earth magnet of Example 10 was obtained in the same manner as Example 7 except for the above.

(Example 11)
Heat treatment was performed under conditions of oxygen concentration of 7% and 500 ° C. for 10 minutes, except that a protective layer having a first layer having a thickness of 5 μm and a second layer having a thickness of 300 nm was formed. In the same manner as in Example 7, a rare earth magnet of Example 11 was obtained.

(Example 12)
The heat treatment is performed under conditions of oxygen concentration of 0.5%, water vapor partial pressure of 74 hPa, and 390 ° C. for 10 minutes, and the protective layer includes a first layer having a thickness of 1.7 μm and a second layer having a thickness of 100 nm. A rare earth magnet of Example 12 was obtained in the same manner as in Example 7 except that a material having the following was formed.

(Example 13)
Heat treatment is performed under the conditions of oxygen concentration of 0.5%, water vapor partial pressure of 12 hPa, and 390 ° C. for 10 minutes, and the protective layer includes a first layer having a thickness of 1.4 μm and a second layer having a thickness of 80 nm. A rare earth magnet of Example 13 was obtained in the same manner as in Example 7 except that a material having a slag was formed.

(Example 14)
The heat treatment was performed under conditions of a water vapor partial pressure of 2000 hPa and 400 ° C. for 10 minutes, and a protective layer having a first layer having a thickness of 1.8 μm and a second layer having a thickness of 120 nm was formed. A rare earth magnet of Example 14 was obtained in the same manner as Example 7 except for the above.

(Example 15)
First, in the same manner as in Example 1, a magnet body was formed and subjected to acid cleaning. The obtained magnet body after the acid cleaning was heat-treated at an oxygen concentration of 7% and at 330 ° C. for 10 minutes to form a protective layer. The film structure near the surface of the magnet body on which this protective layer was formed was analyzed by depth direction analysis by Auger electron spectroscopy (AES). For Auger electron spectroscopy, SAM680 manufactured by ULVAC-PHI was used. As a result, it was confirmed that the second layer was formed at a depth of 16 nm from the surface, and the first layer was formed on the lower 0.4 μm of the second layer.

  Next, a phenol resin paint was applied by spray coating to the magnet body having this protective layer, and then heated at 150 ° C. for 20 minutes to form a resin layer of about 5 μm, whereby the rare earth magnet of Example 15 was obtained. It was.

(Example 16)
Heat treatment was performed at an oxygen concentration of 21% and 290 ° C. for 10 minutes, and a protective layer having a first layer having a thickness of 1.1 μm and a second layer having a thickness of 10 nm was formed. A rare earth magnet of Example 16 was obtained in the same manner as Example 15 except for the above.

(Example 17)
A rare earth magnet of Example 17 was obtained in the same manner as Example 3 except that an epoxy silicone resin paint was used instead of the epoxy resin paint.

(Comparative Example 1)
A magnet body was prepared in the same manner as in Example 1, and acid cleaning with a 2% HNO ₃ aqueous solution was performed to obtain a rare earth magnet of Comparative Example 1. With respect to such a magnet body, a processed cross section was prepared using a focused ion beam processing apparatus, and observed with a scanning electron microscope (S-4700, manufactured by Hitachi, Ltd.). FIG. 5 shows the obtained electron micrograph, and FIG. 6 shows an enlarged view of a part of the electron micrograph of FIG. 5 and 6, the white layer is a platinum-palladium film for analysis, and a magnet body was confirmed below the white layer.

(Comparative Example 2)
A magnet body was prepared in the same manner as in Example 1, and acid cleaning with a 2% HNO ₃ aqueous solution was performed. Next, heat treatment was performed in the same manner as in Example 1 to form a protective layer, and a rare earth magnet of Comparative Example 2 was obtained. In addition, the rare earth magnet of the comparative example 2 is a thing in which the resin layer is not formed. Further, the rare earth magnet of Comparative Example 2 was observed with a transmission electron microscope in the same manner as in Example 1. As a result, even in the rare earth magnet of Comparative Example 2, the protective layer is a second layer having an average film thickness of 50 nm on the outermost surface of the rare earth magnet, and a first layer having an average film thickness of 1 μm below the second layer. It was confirmed that it was composed of

(Comparative Example 3)
A magnet body was prepared in the same manner as in Example 1, and acid cleaning with a 2% HNO 3 aqueous solution was performed. Next, without forming a protective layer by heat treatment, a phenol resin paint was applied by spray coating and heated at 150 ° C. for 20 minutes. In this way, a resin layer of about 5 μm was formed, and the rare earth magnet of Comparative Example 3 was obtained.

(Salt spray test)
The rare earth magnets of Examples 1 to 17 and Comparative Examples 1 to 3 were subjected to a salt spray test for 96 hours at 35 ° C. using 5% salt water in accordance with JIS K5600-7-1.

  First, when the rare earth magnet magnetic fluxes of Examples 1 to 17 and Comparative Examples 1 to 3 after the salt spray test were measured, the magnetic flux decrease compared to that before the test was 0.4% in Example 1, and Comparative Example 1 Was 2.7% and Comparative Example 2 was 2.0%. In Examples 2 to 17 and Comparative Example 3, no decrease in magnetic flux was observed.

  Moreover, the rust generation | occurrence | production situation of Examples 1-17 by the salt spray test and the rare earth magnets of Comparative Examples 1-3 was compared.

  First, rust did not occur in any rare earth magnet before the salt spray test. As an example, a photograph of the rare earth magnet of Example 2 before the salt spray test is shown in FIG. 7, a photograph of the rare earth magnet of Comparative Example 1 is shown in FIG. 9, and a photograph of the rare earth magnet of Comparative Example 2 is shown in FIG.

  At 24 hours from the start of the salt spray test, the occurrence of rust was partial and slight in Example 1, and no rust was found in Example 2. In contrast, in Comparative Examples 1 and 2, the entire magnet was covered with rust, and particularly in Comparative Example 1, the occurrence of rust was significant. FIG. 8 shows a photograph of the rare earth magnet of Example 2 at 24 hours from the start of the salt spray test, FIG. 10 shows a photograph of the rare earth magnet of Comparative Example 1, and FIG. 12 shows a photograph of the rare earth magnet of Comparative Example 2. Each is shown.

  Moreover, even after 96 hours from the start of the salt spray test, the occurrence of rust in each rare earth magnet was compared. As a result, in Comparative Examples 1 and 2, the rust was so thick that the rust was peeled off from the magnet surface, and the rust layer remained on the surface without being wiped off even when the rust was wiped off. On the other hand, in Example 1, the resin layer such as the corner of the magnet generated from an incomplete part of the rust covered about half of the magnet surface, but when the rust was wiped off, the rust layer was removed, It was confirmed that the generation of rust was slight. Moreover, when the cross section was confirmed, in Comparative Example 2, rust was generated at a thickness of about 50 μm from the magnet surface. On the other hand, in Example 1, rust was not observed in the cross section. Moreover, in Example 2, generation | occurrence | production of rust was not seen.

  Furthermore, the occurrence of rust was similarly observed for the rare-earth magnets of Examples 3 to 17 and Comparative Example 3, and no rust was observed.

(Pressure cooker test)
A pressure cooker test was performed on the rare earth magnets of Examples 1 to 17 and Comparative Example 3. The test conditions were left at 100 ° C., 0.2 MPa, 100% RH for 100 hours. As a result, in Examples 1 to 17, no change in appearance such as exfoliation of the resin layer, swelling, and generation of rust was observed. On the other hand, in the rare earth magnet of Comparative Example 3, peeling of the resin layer was observed at the end after the test.

  Moreover, when the change of the magnetic flux before and after the test of these rare earth magnets was measured, all of the rare earth magnets of Examples 1 to 17 had a very small change in magnetic flux, and the rare earth magnet after the test was sufficiently practical. On the other hand, the rare earth magnet of Comparative Example 3 was greatly deteriorated in magnetic flux. Table 1 summarizes changes in magnetic flux caused by the rare earth magnets of Examples 1 to 17 and Comparative Example 3.

It is a schematic perspective view which shows one Embodiment of the rare earth magnet of this invention. It is a schematic sectional drawing which shows one Embodiment of the rare earth magnet of this invention. 2 is an electron micrograph of a rare earth magnet of Example 1. It is the electron micrograph which expanded a part of FIG. 4 is an electron micrograph of a rare earth magnet of Comparative Example 1. It is the electron micrograph which expanded a part of FIG. It is a photograph of the rare earth magnet of Example 2 before the salt spray test. It is a photograph of the rare earth magnet of Example 2 at 24 hours from the start of the salt spray test. It is a photograph of the rare earth magnet of Comparative Example 1 before the salt spray test. It is a photograph of the rare earth magnet of Comparative Example 1 at 24 hours from the start of the salt spray test. It is a photograph of the rare earth magnet of Comparative Example 2 before the salt spray test. It is a photograph of the rare earth magnet of Comparative Example 2 at the point of 24 hours from the start of the salt spray test.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Rare earth magnet, 3 ... Magnet base body, 5 ... Protective layer, 5a ... 1st layer, 5b ... 2nd layer, 7 ... Resin layer.

Claims (14)

A method for producing a rare earth magnet by heat treating a magnet body containing a rare earth element to form a protective layer on the surface of the magnet body,
The protective layer has a first layer covering the magnet body and containing a rare earth element, and a second layer covering the first layer and having a rare earth element content less than the first layer. In addition, in the oxidizing atmosphere containing the oxidizing gas, at least one of the oxidizing gas partial pressure, the processing temperature, and the processing time is adjusted to heat-treat the magnet body to form a protective layer A layer forming step;
A resin layer forming step of forming a resin layer by depositing a resin on the surface of the protective layer after the protective layer forming step;
A method for producing a rare earth magnet, comprising:   The method for producing a rare earth magnet according to claim 1, wherein the resin layer is formed by applying a resin layer-forming coating solution containing a resin and drying. A method for producing a rare earth magnet by heat treating a magnet body containing a rare earth element to form a protective layer on the surface of the magnet body,
Contains an oxidizing gas so that the protective layer has a first layer covering the magnet body and containing a rare earth element and a second layer covering the first layer and substantially free of the rare earth element. A protective layer forming step in which at least one of an oxidizing gas partial pressure, a processing temperature, and a processing time is adjusted in an oxidizing atmosphere to heat-treat the magnet body to form a protective layer;
On the surface of the protective layer after the protective layer forming step, a resin layer forming step of applying a resin layer-forming coating solution containing a resin and drying to form a resin layer;
A method for producing a rare earth magnet, comprising: A magnet body containing a rare earth element;
A first layer that covers the magnet body and contains a rare earth element; and a protective layer that covers the first layer and has a second layer that contains less rare earth element than the first layer;
A resin layer formed on the surface of the protective layer and containing a resin;
A rare earth magnet comprising:   5. The rare earth magnet according to claim 4, wherein the rare earth element content in the second layer is not more than half of the rare earth element content in the first layer. A magnet body containing a rare earth element;
A first layer formed on the surface of the magnet body, containing oxygen and an element derived from the magnet body, covering the magnet body, containing a rare earth element, and covering the first layer, A protective layer having a second layer not contained
A resin layer formed on the surface of the protective layer and containing a resin;
A rare earth magnet comprising:   The rare earth magnet according to claim 4, wherein the second layer contains a transition element and oxygen. The magnet body includes a rare earth element and a transition element other than the rare earth element,
The first layer contains the rare earth element, the transition element and oxygen,
The rare earth magnet according to any one of claims 4 to 7, wherein the second layer contains the transition element and oxygen. The magnet body includes a rare earth element and a transition element other than the rare earth element,
The first layer is mainly composed of the rare earth element, the transition element and oxygen,
The rare earth magnet according to any one of claims 4 to 8, wherein the second layer contains the transition element and oxygen as main components.   At least one of the rare earth element in the first layer, the transition element in the first layer, and the transition element in the second layer constitutes the main phase of the magnet body. The rare earth magnet according to claim 8 or 9, wherein the rare earth magnet is an element.   The rare earth element in the first layer, the transition element in the first layer, and the transition element in the second layer are elements constituting a main phase of the magnet body. The rare earth magnet according to any one of claims 8 to 10.   The rare earth magnet according to any one of claims 4 to 11, wherein the rare earth element is neodymium.   The rare earth magnet according to claim 4, wherein the resin is a thermosetting resin. 14. The resin according to claim 4, wherein the resin is at least one resin selected from the group consisting of a phenol resin, a melamine resin, a polyamideimide resin, a polyparaxylylene resin, a polyurea resin, and an epoxy silicone resin. The rare earth magnet according to any one of the above.

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