JP4835407B2 - Rare earth magnet and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rare earth magnet which can be formed by a simple method and has a protective layer having a superior electrical insulation property. <P>SOLUTION: The preferred rare earth magnet 1 includes a magnet body 2 containing a metallic element including at least a rare earth element, and the protective layer 4 formed on the surface of the magnet body 2. The protective layer 4 has inorganic particles 14, and an inter-particle phase 24 including a compound of a metallic element that is equivalent to at least one type of a metallic element among metallic elements contained in the magnet body 2. The magnet body 2 has a surface arithmetic mean roughness (Ra) of 0.08 to 0.8 &mu;m. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a rare earth magnet and a method for manufacturing the same.

  Although a rare earth magnet containing a rare earth element has an excellent magnetic force, it contains a rare earth element that is easily oxidized as a main component, and therefore tends to have low corrosion resistance. Therefore, rare earth magnets are often configured such that a protective layer made of resin, plating, or the like is provided on the surface of a magnet body containing a rare earth element. In recent years, in rare earth magnets, when the corrosion resistance of the magnet body itself has been improved, or when it is used for applications that do not require the corrosion resistance as in the past, it is easier and less expensive than before, to a certain extent In some cases, it is required to be able to form a protective layer capable of exhibiting the above corrosion resistance.

As a method for forming such a protective layer, a method is known in which a colloidal solution composed of inorganic fine particles (SiO ₂ ) is applied to the surface of a magnet body and heated and solidified (see Patent Document 1). According to such a method, since the protective layer can be formed simply by applying a colloidal solution to the magnet body and then heating it, it is possible to obtain a rare earth magnet having the protective layer on the surface at a relatively simple and low cost. It becomes.
JP-A 63-301506

  By the way, in recent years, rare earth magnets are increasingly applied to applications such as motors. In this case, in addition to sufficient corrosion resistance, rare earth magnets can prevent eddy currents generated in the rare earth magnets. It is required to have characteristics. For this purpose, it is preferable that the protective layer has excellent electrical insulation, but the protective layer described in Patent Document 1 does not necessarily have sufficient electrical insulation for applications such as motors. It could not be granted.

  Therefore, the present invention has been made in view of such circumstances, and an object thereof is to provide a rare earth magnet that can be formed by a simple method and includes a protective layer having excellent electrical insulation.

  In order to achieve the above object, a rare earth magnet of the present invention comprises a magnet body containing a metal element containing at least a rare earth element, and a protective layer formed on the surface of the magnet body. Inorganic particles and a compound of the same metal element as at least one of the metal elements contained in the magnet body, and the magnet body has an arithmetic average roughness (Ra) of the surface of 0.08. It is -0.8 micrometer. Here, the arithmetic average roughness (Ra) refers to the arithmetic average roughness according to JIS B 0601: 1994.

  The protective layer in the rare earth magnet of the present invention having the above-described structure contains, in addition to the inorganic particles, the same metal element compound (hereinafter abbreviated as “metal compound”) contained in the magnet element body. The protective layer has a structure in which the metal compound is present between the inorganic particles, in other words, the gap between the inorganic particles is filled with the metal compound.

  Here, since the protective layer as described in Patent Document 1 is only agglomerated of the inorganic particles, moisture or the like is likely to enter the gaps between the inorganic particles, which tends to lower the insulating properties. It was a thing. On the other hand, the protective layer in the rare earth magnet of the present invention has a metal compound between the inorganic particles as described above, so that the gaps between the inorganic particles are not easily absorbed by the protective layer. .

  In particular, in the rare earth magnet having the above-described configuration, the inventors have extremely excellent insulating properties when the surface roughness (Ra) of the magnet body is in a specific range (0.08 to 0.8 μm). It was found that can be obtained. Although it is not necessarily clear about such a factor, the present inventors presume as follows.

  That is, if the protective layer has a portion where the thickness is partially small, a conductive path is likely to be formed in that portion, and as a result, the overall insulation is also lowered. Therefore, the protective layer tends to have better insulation as the thickness variation is smaller. In the rare earth magnet of the present invention, since the surface roughness of the magnet body on which the protective layer is formed is relatively small, there is a high probability that the variation in the thickness of the protective layer will be smaller than when the surface roughness is large. . As a result, it is considered that the protective layer in the rare earth magnet of the present invention can exhibit excellent insulating properties.

  However, as a result of the study by the present inventors, even if the surface roughness of the magnet body is too small, the protective layer is easily peeled off from the magnet body, so that a conductive path is formed by peeling of the protective layer. In addition, the inventors have found that the insulating properties tend to decrease due to the intrusion of moisture and the like from the peeled portion. On the other hand, in the present invention, the occurrence of peeling as described above can be suppressed by not reducing the surface roughness of the magnet body too much, and as a result, excellent insulation can be maintained. In the present invention, the surface roughness of the magnet body is set in a specific range (0.08 to 0.8 μm), so that it is possible to remarkably suppress a decrease in insulation based on the two factors described above. As a result, it is presumed that excellent insulation is obtained.

  In the rare earth magnet of the present invention, since the protective layer has a dense structure composed of inorganic particles and a metal compound, corrosive components such as moisture and corrosive ions adhere to the magnet body through the protective layer. As a result, excellent corrosion resistance can be obtained. Furthermore, since the protective layer in the rare earth magnet of the present invention contains the same metal as the magnet element body, it has high adhesion to the magnet element body, which also contributes to excellent insulation and corrosion resistance. It is thought that.

  The rare earth magnet of the present invention includes a magnet body containing a metal element containing at least a rare earth element, and a protective layer formed on the surface of the magnet body. The protective layer includes silicon, oxygen, and The magnet element contains the same metal element as at least one of the metal elements contained in the magnet element, and the magnet element has an arithmetic mean roughness (Ra) of the surface of 0.08 to 0.8 μm. This may be a feature.

  In such a rare earth magnet of the present invention, the protective layer is considered to be in a state in which silicon and oxygen (specifically, a compound containing these) are strongly bonded to the metal element. And by such a protective layer, the rare earth magnet of the present invention has low hygroscopicity, and as a result, it can maintain excellent insulation and also has excellent corrosion resistance. Moreover, since the magnet body has a predetermined surface Ra (0.08 to 0.8 μm), it is possible to exhibit even better insulation. About this, the reason similar to the case of the other rare earth magnet of this invention mentioned above can be considered.

  In each of the rare earth magnets of the present invention, it is preferable that Ra on the surface of the protective layer is smaller than Ra on the surface of the magnet body. In this way, it becomes easier to reduce the variation in the thickness of the protective layer, and a better insulating property can be obtained.

  The concentration of at least one of the metal elements contained in the protective layer is preferably increased from the surface side of the protective layer toward the magnet body side. In this case, the content ratio of the metal element at the interface portion between the protective layer and the magnet body is the highest, thereby further increasing the adhesion between the two, and it is difficult for stress to occur in the protective layer. Cracks are less likely to occur. As a result, the insulation and corrosion resistance by the protective layer are further improved. It is more preferable that the metal element in the protective layer is contained at least on the surface side from the center in the thickness direction of the protective layer.

  In addition, the method for producing a rare earth magnet of the present invention includes the surface of a magnet body containing a metal element containing at least a rare earth element and having an arithmetic average roughness (Ra) of the surface of 0.08 to 0.8 μm. Then, an acidic aqueous solution containing inorganic particles is contacted to form a protective layer containing a compound of the same metal element as that of at least one metal element contained in the magnet body and inorganic particles on the surface. It has the process.

  In the manufacturing method of the present invention, by bringing the aqueous solution into contact with the magnet body, the inorganic particles adhere to the surface of the magnet body, and the metal compound formed from the metal generated by dissolving the magnet body is inorganic. It is considered that the particles are deposited so as to fill the gaps between the particles. That is, in this manufacturing method, since the protective layer is formed only by bringing the treatment liquid into contact with the magnet body, a rare earth magnet having a protective layer can be obtained easily. Since the protective layer thus formed has the same structure as the protective layer in the rare earth magnet of the present invention, it can exhibit excellent corrosion resistance.

  Another method for producing a rare earth magnet according to the present invention includes a magnet element containing a metal element containing at least a rare earth element, and having an arithmetic average roughness (Ra) of the surface of 0.08 to 0.8 μm. The surface of the substrate is brought into contact with an acidic aqueous solution containing a compound containing silicon and oxygen, and on this surface, the same metal element as at least one of the metal elements contained in silicon, oxygen and the magnet body is formed. It may be characterized by having a step of forming a protective layer containing a compound.

  According to the manufacturing method of the present invention, silicon, oxygen, and magnet element are formed by the compound containing silicon and oxygen in the treatment liquid and the metal compound formed from the metal generated by dissolving the magnet element body. A protective layer containing at least three elements of the same metal element as at least one of the metal elements contained in the body is formed. Such a protective layer can be easily formed only by contact with the treatment liquid, and can exhibit excellent corrosion resistance for the same reason as described above.

  And especially according to the manufacturing method of the two rare earth magnets mentioned above, the rare earth magnet which is extremely excellent in insulation can be obtained. This is because the surface roughness of the magnet body is in the specific range described above, so that it is relatively smooth so that the thickness variation is sufficiently small, and a protective layer that does not easily peel off from the magnet body can be obtained. In addition, since the surface of the magnet body is smooth, it can be considered that the variation in the concentration of the metal compound in the obtained protective layer can be reduced.

  Here, when the surface of the magnet body has a large Ra, that is, the surface is rough, the metal compound tends to precipitate in the concave portions of the surface in the above-described protective layer forming step. For this reason, the protective layer formed on the convex portion of the magnet body tends to have a smaller metal compound content than the protective layer formed on the concave portion. And in a protective layer, since a conductive path is easy to be formed, so that the content rate of a metal compound is low, the protective layer with a large dispersion | variation in the content rate of a metal compound tends to become low as a whole. On the other hand, in the manufacturing method of the present invention, since a magnet body having a surface roughness in a certain range is used, the metal compound can be deposited relatively uniformly. It is considered that a protective layer having excellent insulating properties can be formed.

  In the production method of the present invention, it is preferable to further carry out a step of washing the protective layer in a state where the treatment liquid adheres after the treatment liquid is brought into contact. As a result, it is possible to remove excess processing liquid adhering to the protective layer, and to form a protective layer having a more uniform thickness. In addition, if the acidic treatment liquid remains attached, the rare earth magnet (magnet body) may be deteriorated earlier, but the risk of such deterioration is reduced by removing the treatment liquid after forming the protective layer. You can also In addition, in the method of simply attaching inorganic fine particles as in the above-mentioned prior art, even the inorganic fine particles forming the protective layer may be removed by washing, so that such washing is performed. Is usually difficult.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the rare earth magnet provided with the protective layer which can be formed by a simple method and has the outstanding electrical insulation, and its manufacturing method.

Hereinafter, preferred embodiments of the present invention will be described.
[Rare earth magnet]

  FIG. 1 is a diagram showing a rare earth magnet according to a preferred embodiment of the present invention. Moreover, FIG. 2 is a figure which shows typically the cross-sectional structure which follows the II-II line | wire of the rare earth magnet shown in FIG. As illustrated, the rare earth magnet 1 is composed of a magnet body 2 and a protective layer 4 formed on the surface thereof.

(Magnet body)
First, the configuration of the magnet body 2 will be described. The magnet body 2 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 lanthanoid elements include lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), and 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 2 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.

  As a constituent material of the magnet body 2, an R—Fe—B constituent material is particularly preferable. When the magnet body 2 is of the R—Fe—B type, excellent magnet characteristics can be obtained, and the effect of improving the corrosion resistance due to the formation of the protective layer 4 can be obtained more favorably.

  The R-Fe-B-based magnet element body 2 has a main phase with 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 boron It has a structure having a boron-rich phase with a high proportion of atoms. These rare earth-rich phase and boron-rich phase are nonmagnetic phases that do not have magnetism. 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 the R—Fe—B-based constituent material, 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 coercive force. On the other hand, if it exceeds 28 atomic%, a boron-rich phase is excessively formed, and this tends to reduce the residual magnetic flux density.

  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. If the Co content exceeds the Fe content, the magnetic properties of the magnet body 2 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 coercive force and reducing the manufacturing cost, the magnet body 2 is made of aluminum (Al), titanium (Ti), vanadium (V), chromium (Cr), manganese (in addition to the above elements). 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) and the like may further be contained. Especially, it is suitable that the magnet body 2 further contains Al and / or Cu. These contents are also preferably in a range that does not affect the magnetic properties, and preferably 10 atomic% or less with respect to the total amount of constituent atoms. In addition, oxygen (O), nitrogen (N), carbon (C), calcium (Ca), etc. are conceivable as components that are inevitably mixed. These may be contained in an amount of about 3 atom% or less with respect to the total amount of constituent atoms.

  The magnet body 2 made of the above-described material has an arithmetic average roughness (Ra) of 0.08 to 0.8 μm, preferably 0.08 to 0.7 μm, and preferably 0.08 to 0.8. More preferably, it is 35 μm. When the Ra of the magnet body 2 is 0.8 μm or less, the effect of particularly improving the insulation can be exhibited. However, when this Ra is less than 0.08 μm, the magnet body and the protective layer are easily peeled off, and an insulating path is formed by forming a conductive path in the peeled portion or intrusion of moisture from the peeled portion. The property tends to decrease. The surface smoothing of the magnet body 2 has a technical limit, and for this reason, the lower limit of Ra is about 0.08 μm.

  Further, the magnet body 2 may have a cylindrical shape or other shapes in addition to the flat plate shape as illustrated. When the magnet body 2 is a polyhedron, the magnet body 2 only needs to satisfy the above-described Ra conditions only on the surface where good insulation is required. It is preferable that the whole surface is satisfy | filled from a viewpoint especially maintained suitably.

(Protective layer: 1st form)
Next, the configuration of the protective layer 4 according to the first embodiment will be described. The protective layer 4 is a layer containing inorganic particles and a compound (metal compound) containing a metal element and oxygen contained in the magnet body. Here, the suitable structure of the protective layer 4 is demonstrated in detail with reference to FIG. FIG. 3 is an enlarged schematic view showing a cross-sectional configuration near the surface of the protective layer.

  As shown in FIG. 3, the protective layer 4 has a structure in which inorganic particles 14 are mainly aggregated and an interparticle phase 24 is formed between the inorganic particles 14. Examples of the inorganic particles 14 include those composed of a metal compound containing a metal. As this metal, silicon (Si), aluminum (Al), titanium (Ti), zirconium (Zr), iron (Fe) or tin (Sn) is preferable. Among these, Si, Al, or Ti is more preferable, and Si is particularly preferable. In this specification, Si is included in the metal.

  The inorganic particles 14 are preferably composed of metal oxide, metal hydroxide, or metal nitride, more preferably composed of metal oxide or metal hydroxide, and composed of metal oxide. More preferred. Examples of the inorganic particles 14 made of a metal oxide include particles of silica, alumina (including boehmite), titania, zirconia, and the like, and silica particles are particularly preferable.

  The inorganic particles 14 included in the protective layer 4 preferably have an average particle size of 200 nm or less, and more preferably 5 to 100 nm. Here, as the average particle diameter, a value measured by a method such as BET method, X-ray small angle scattering method, dynamic light scattering method, observation with a transmission electron microscope can be adopted. When the average particle diameter of the inorganic particles 14 exceeds 200 nm, the gap between the inorganic particles 14 becomes too large, and this gap may not be sufficiently filled with the interparticle phase 24. In addition, when the average particle diameter of the inorganic particles 14 is less than 5 nm, the shrinkage stress is increased when the protective layer 4 is formed, and cracks may easily occur in the layer.

  The interparticle phase 24 is mainly composed of a compound (metal compound) of the same metal element as at least one of the metal elements contained in the magnet body 2. As such a metal compound, a compound containing a metal element and oxygen is suitable, and specifically, a metal oxide or a metal hydroxide can be mentioned. A suitable magnet body 2 includes a plurality of types of metal elements such as rare earth elements and other transition elements as described above. In this case, the interparticle phase 24 is a single type of metal element in the magnet body 2. Or a compound of a plurality of types of metal elements.

  As the metal compound contained in the interparticle phase 24, when the magnet body 2 contains Fe, an Fe compound, particularly an Fe oxide is preferable. Thus, when the intergranular phase 24 contains a Fe compound, the inorganic particles 14 in the protective layer 4 are further bonded to each other, and the corrosion resistance of the rare earth magnet 1 is further improved. In addition, since Fe can function as a curing catalyst for anaerobic adhesive, the protective layer 4 (interparticle phase 24) contains an Fe compound, so that the anaerobic adhesive can be used for the rare earth magnet 1 as another member. It tends to provide excellent adhesion when used for adhesion.

  Furthermore, when the magnet body 2 contains Al and / or Cu, the interparticle phase 24 preferably contains Al and / or Cu in the same form as Fe. When the protective layer 4 contains Al, further excellent insulation and corrosion resistance can be obtained due to the high affinity of Al for the inorganic particles 14 and the like. Moreover, since Cu can function as a curing catalyst for anaerobic adhesives similarly to Fe, the rare earth magnet 1 including the protective layer 4 further containing Cu is bonded to other members using an anaerobic adhesive. When it does, it comes to be able to exhibit the outstanding adhesiveness.

  Furthermore, when the magnet body 2 further contains a metal element other than the above metal elements, the interparticle phase 24 may further contain a compound of these metal elements.

  In the protective layer 4, the metal element contained in the interparticle phase 24 is preferably contained at least from the interface portion with the magnet body 2 to the surface side from the center in the thickness direction of the protective layer 4, It is more preferable that the surface of the protective layer 4 is included. In this case, in the protective layer 4, it is more preferable that the concentration of the metal element increases from the surface side toward the magnet body 2 side. When the protective layer 4 has such a configuration, the adhesion between the protective layer 4 and the magnet body 2 is further improved. Moreover, it becomes difficult to generate stress in the protective layer 4 and the generation of cracks is reduced. As a result, the insulation and corrosion resistance of the rare earth magnet 1 are further improved. The concentration of the metal element in the protective layer 4 can be measured by, for example, Auger electron spectroscopy. The concentration in this case refers to the ratio of the corresponding metal element to the total amount of metal element measured by such a measurement method.

  Further, the protective layer 4 may contain a metal element other than that contained in the magnet body 2. Examples of such metal elements include titanium (Ti), zirconium (Zr), vanadium (V), molybdenum (Mo), tungsten (W), and manganese (Mn). These may be contained in either the inorganic particles 14 or the interparticle phase 24, but are preferably contained in the interparticle phase 24. When the protective layer 4 contains these elements, the corrosion resistance of the rare earth magnet 1 tends to be further improved.

  Since the protective layer 4 is formed on the surface of the magnet element body 2, when the magnet element body 2 has irregularities, the surface of the protective layer 4 on the magnet element body 2 side has the surface shape of the magnet element body 2. Will have unevenness along. Therefore, the thickness of the protective layer 4 corresponds to the distance from the surface of the magnet body 2 to the outer surface of the protective layer 4 (surface opposite to the magnet body 2). Here, the protective layer 4 may have irregularities on the outer surface thereof. In this case, the surface Ra of the protective layer 4 is preferably smaller than Ra of the magnet body. If it carries out like this, since the dispersion | variation in the thickness of the protective layer 4 becomes easier to be reduced, it exists in the tendency for the outstanding insulation to become easy to be obtained.

(Protective layer: second form)
Next, the structure of the protective layer 4 which concerns on a 2nd form is demonstrated. The protective layer 4 according to the second embodiment is a layer having a composition containing silicon (Si), oxygen (O) and at least one of the metal elements contained in the magnet body 2 and the same kind of metal element. In such a protective layer 4, the compound containing silicon and oxygen may constitute inorganic particles as in the first embodiment.

The protective layer 4 of the second form has the following structure, for example. That is, the protective layer 4 contains a silicate represented by the general formula MO _x · nSiO ₂ (M is the same metal element as the magnet body 2). These silicates are considered to be ionic crystals having a structure in which regular tetrahedrons of SiO ₄ are regularly linked and arranged, and metal ions represented by M are contained in the gaps. In addition to these silicates, the protective layer 4 may further contain silicon dioxide, metal element oxides, hydroxides, carbonates, etc. in the magnet body 2.

  In the protective layer 4, at least one of the same kind of metal elements as the magnet body 2 has a concentration from the surface side of the protective layer 4 (the surface side opposite to the magnet body 2) toward the magnet body 2 side. It is preferable that it is large. The protective layer 4 having such a configuration has a composition close to that of the magnet body 2 in the vicinity of the interface with the magnet body 2 as compared with the case where all the metal elements are contained substantially uniformly. The adhesion to the element body 2 is very good. In addition, the protective layer 4 containing a metal element in this way is less prone to stress, and therefore is less likely to crack. Therefore, the rare earth magnet 1 provided with the protective layer 4 is less deteriorated due to the occurrence of cracks or the like in the protective layer 4. As a result, excellent corrosion resistance and insulation can be exhibited. The concentration of the metal element in the protective layer 4 can be measured in the same manner as the concentration of the metal element contained in the interparticle phase 24 in the protective layer 4 of the first embodiment.

  Moreover, it is preferable that the protective layer 4 includes a portion in which the concentration of the same metal element as that of the magnet element body 2 is higher than the concentration of the metal element in the magnet element body 2. Thereby, the denseness of the protective layer 4 and the adhesion to the magnet body 2 are further improved, and the corrosion resistance of the rare earth magnet 1 is further improved. It is more preferable that the concentration of such a metal element increases in the protective layer 4 as it approaches the magnet body as described above. Furthermore, the metal element of the same type as the magnet body 2 included in the protective layer 4 is at least included in a region from the interface portion with the magnet body 2 to the surface side from the center in the thickness direction of the protective layer 4. It is preferable that the protective layer 4 is included up to the surface portion.

  Further, the protective layer 4 of the second form is composed of one or more metal elements of Fe and Al as the same kind of metal element as that of the magnet body 2 as in the case of the protective layer 4 of the first form described above. It is preferably contained as a metal compound such as a metal oxide or a metal hydroxide. In addition to these, it is more preferable that Cu is contained as a metal simple substance or a metal compound. By including these metal elements, the same effect as in the first embodiment can be obtained. Further, when the magnet body 2 further contains a metal element other than Fe, Al, and Cu, the protective layer 4 may contain such a metal element, and further include a metal element that is not included in the magnet body 2. You may contain.

Furthermore, the protective layer 4 according to the second embodiment may also have irregularities on the outer surface (the surface on the opposite side to the magnet body 2), as in the first embodiment. In this case, Ra on the outer surface of the protective layer 4 is preferably smaller than Ra of the magnet body. If it carries out like this, since the dispersion | variation in the thickness of the protective layer 4 becomes easier to be reduced, it exists in the tendency for the outstanding insulation to become easy to be obtained.
[Rare earth magnet manufacturing method]

  Next, a preferred embodiment of a method for producing a rare earth magnet will be described.

First, the magnet body 2 can be manufactured by a powder metallurgy method. In this method, first, an alloy having a desired composition is manufactured by a known alloy manufacturing process such as a casting method or a strip casting method. Next, this alloy is 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. Thereafter, the particle size is further adjusted to 0.5 to 5 μm by a fine pulverizer such as a jet mill or an attritor. 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.

  Then, 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. Further, the sintered body is subjected to heat treatment at 500 to 900 ° C. for 1 to 5 hours in an inert gas atmosphere or in vacuum, and the sintered body is processed into a desired shape (practical shape) as necessary. Element body 2 is obtained.

  Thereafter, the magnet body 2 is preferably subjected to acid cleaning. The acid cleaning can be performed using a treatment liquid containing an acid (hereinafter referred to as “acid treatment liquid”). Nitric acid is preferred as the acid used in this acid cleaning. Usually, when a steel material or the like is subjected to a plating treatment, a non-oxidizing acid having no oxidizing property such as hydrochloric acid or sulfuric acid is often used. However, when a rare earth element is included as in the magnet body 2 in the present embodiment, when processing is performed using these acids, hydrogen generated by the acid is easily occluded on the surface of the magnet body 2, The occlusion site may become brittle and a large amount of powdery undissolved material may be generated. This powdery undissolved product may cause surface roughness, defects and poor adhesion after the surface treatment. Therefore, in the acid cleaning, it is preferable to use an oxidizing acid with little generation of hydrogen, for example, nitric acid, and this makes it easier to obtain the magnet body 2 having a smooth (small Ra) surface.

  Further, it is more preferable that the acid treatment liquid further contains a compound having a buffering ability such as boric acid or borate. Usually, when an acid comes into contact with a magnet body, the grain boundary portion tends to be selectively eluted. Here, when an oxidizing acid such as nitric acid as described above is used, the dissolution of the main phase portion may also occur, so that the selective elution of the grain boundary portion is reduced. Since the portion is slightly easier to elute, a depression may be formed in this portion. Once such a depression is formed, the pH of the depression is lower than that of the surrounding area. As a result, even when an oxidizing acid is used, the grain boundary portion may be etched in the depth direction from the surroundings. On the other hand, by making the acid treatment liquid contain a compound having a buffering capacity, a decrease in pH in the recessed portion as described above can be suppressed. As a result, it is considered that the etching at the grain boundary portion is further suppressed and the surface of the magnet body is etched more uniformly. Therefore, when the acid treatment liquid contains a compound having a buffering capacity as described above, it is easy to obtain the magnet body 2 having a smoother surface (small Ra).

  The amount of dissolution of the surface of the magnet body 2 by such acid cleaning is preferably 5 μm or more, preferably 10 to 15 μm in average thickness from the surface. By so doing, the altered layer and the oxidized layer due to the processing of the surface of the magnet body 2 can be almost completely removed, and the protective layer 4 described later can be formed satisfactorily.

  The concentration of nitric acid used in the acid treatment liquid 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 2 will be extremely fast, and it will be difficult to control the amount of dissolution. In particular, it will be difficult to maintain the dimensional accuracy of the product due to large variations in mass processing such as barrel processing. Tend to be. 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.

  After the acid cleaning, in order to remove undissolved substances and residual acid components adhering to the surface of the magnet body 2, it is preferable to further clean the magnet body 2, preferably 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 2. Further, before and after the washing and in each process of the treatment with the acid treatment liquid, washing with water may be performed as necessary.

  The magnet body 2 formed by the above-described process has an arithmetic average roughness (Ra) of 0.08 to 0.8 μm, preferably 0, before performing the process of forming the protective layer 4 described later. 0.08 to 0.7 μm, more preferably 0.08 to 0.35 μm. When this Ra is within the range of the predetermined value, excellent insulation and corrosion resistance tend to be easily obtained. Examples of a method for reducing the Ra of the magnet body 2 include a method in which the above-described acid cleaning is performed under conditions that allow desired Ra to be obtained. Specifically, the acid cleaning is preferably performed using an acid treatment solution containing an oxidizing acid such as nitric acid as described above, and further contains a compound having a buffer capacity such as boric acid or borate. More preferably, the acid treatment solution is used. At this time, in the acid cleaning, the concentration, treatment time, and the like are adjusted so that the surface Ra of the magnet body 2 does not become less than the lower limit. If the surface Ra of the magnet body 2 is less than the lower limit, peeling of the protective layer 4 formed on the surface tends to occur, and sufficient insulating properties tend not to be obtained.

  The surface Ra of the magnet body 2 can also be adjusted by polishing the surface of the magnet body 2 such as buffing or chemical mechanical polishing. Further, acid cleaning and polishing may be combined. In addition, from the viewpoint of removing the deteriorated layer and the oxide layer on the surface of the magnet body 2, it is preferable to perform the above-described acid cleaning. However, when these removals are not necessary, the magnet body is not subjected to acid cleaning. 2 may be adjusted to adjust Ra of the magnet body 2.

  Then, when forming the protective layer 4 of a 1st form, the aqueous solution (processing liquid) which contains an inorganic particle and has acidity is made to contact the surface of the magnet body 2, and an inorganic particle and a magnet are contacted on this surface. A protective layer containing a compound of the same metal element as at least one of the metal elements contained in the element body is formed.

  The treatment liquid is preferably an aqueous sol in which inorganic particles composed of the above-described metal compound or the like are uniformly dispersed. Examples of such aqueous sols include Snowtex (manufactured by Nissan Chemical Industries, Ltd.), Quattron (manufactured by Fuso Chemical Industries, Ltd.), alumina sol (manufactured by Nissan Chemical Industries, Ltd.), titania sol STS (manufactured by Ishihara Sangyo Co., Ltd.), and the like. It can be illustrated.

  On the other hand, in the second embodiment, when silicon and oxygen do not constitute inorganic particles, the protective layer 4 is, for example, a compound containing silicon and oxygen (for example, silicate ions) on the surface of the magnet body 2. And an acidic aqueous solution (treatment liquid) is brought into contact, and the protective layer 4 is deposited on the surface.

The treatment liquid containing silicate ions, which is an example of the treatment liquid, is obtained, for example, by dissolving silicate in the treatment liquid. Examples of the silicate include alkali metal salts represented by nA ₂ O · mSiO ₂ (A is an alkali metal element) and ammonium salts such as ammonium silicate. Among these, alkali metal silicates are preferable because a protective layer can be easily formed. Examples of the alkali metal silicate include lithium silicate, sodium silicate, potassium silicate, cesium silicate, and the like. The concentration of silicate ions in the treatment solution is preferably a 0.01~4mol / L in terms of SiO _2.

  The processing liquid has acidity as described above. Specifically, the pH of the treatment liquid is preferably 0 to 6, and more preferably 1 to 5. If the pH of the treatment liquid is too low, the magnet body 2 may be excessively dissolved and it may be difficult to obtain a rare earth magnet having a desired shape. On the other hand, if the pH exceeds 5, the stability of the treatment liquid when coming into contact with the magnet body 2 tends to be low, and the protective layer 4 having a uniform thickness tends to be difficult to be formed.

  The acidity of the treatment liquid can be adjusted by adding an acid to an aqueous solution containing inorganic particles such as the aqueous sol described above. The acid is not particularly limited, and inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid, and organic acids such as malic acid, malonic acid, citric acid, and succinic acid can be applied. By adjusting the concentration of this acid, the pH of the treatment liquid can be adjusted to the preferred range as described above.

  More preferably, the treatment liquid contains an acid having an oxidizing property as an acid. Examples of the oxidizing acid include those further containing an oxidizing agent in addition to the above-described acids. Examples of the oxidizing agent include nitric acid or nitrate, nitrous acid or nitrite, hydrogen peroxide, permanganate and the like. When the treatment liquid contains an acid having an oxidizing property, the main phase of the magnet body 2 is well dissolved, and the protective layer 4 having a uniform thickness is formed. In addition, during the treatment with the acidic treatment liquid, there may be a problem of embrittlement of the magnet body 2 by hydrogen as in the case of the above-described acid cleaning. This makes it possible to reduce problems.

  In particular, the treatment liquid preferably contains nitric acid, perchloric acid, or chromic acid as an acid having an oxidizing property. These can function alone as both acids and oxidants. Therefore, by containing these, the treatment liquid has good acidity and oxidizability without containing an oxidizing agent. Of these, nitric acid is particularly preferable as the acid having oxidizing properties because it has both the properties of an acid and an oxidizing agent. In addition, even if it is a case where a process liquid contains the acid which functions as an acid and an oxidizing agent alone, it may further contain an oxidizing agent. Furthermore, it is preferable that the treatment liquid further contains a compound having a buffer capacity such as boric acid or borate. When such a compound is contained, the protective layer is more easily formed on the entire surface of the magnet, so that the variation in the thickness of the protective layer can be easily reduced.

  Further, in the treatment liquid, for example, a metal salt other than those contained in the magnet body 2 as described above may be further added to the protective layer 4 in order to contain a metal salt thereof. . Examples of such metals include compounds of Ti, Zr, V, Mo, W, or Mn. Examples of the metal salt added to the treatment liquid include titanium sulfate, zirconium sulfate, zirconium chloride oxide, zirconium nitrate oxide, sodium vanadate, potassium vanadate, ammonium vanadate, sodium molybdate, potassium molybdate, ammonium molybdate, Examples thereof include sodium tungstate, potassium tungstate, ammonium tungstate, manganese sulfate, manganese nitrate, manganese formate, and potassium permanganate. The blending amount of these metal salts is preferably 0.01 mol / L to 0.5 mol / L in the treatment liquid.

  Examples of the method of bringing the treatment liquid into contact with the magnet body 2 include an immersion method in which the magnet body 2 is immersed in the treatment liquid, and a spray method in which the treatment liquid is sprayed onto the magnet body 2. Especially, the immersion method which can make a process liquid adhere simply to the whole surface of the magnet element | base_body 2 is suitable. The temperature of the treatment liquid during the treatment is preferably 0 to 90 ° C, and more preferably 10 to 60 ° C. In the case of the immersion method, the time for immersing the magnet body 2 in the treatment liquid is preferably 10 seconds to 30 minutes. These conditions can be appropriately changed according to the desired thickness of the protective layer 4 and the like.

  The mechanism by which the protective layer 4 is formed by the contact of the treatment liquid described above is not necessarily clear. For example, when the protective layer 4 of the first form is formed, the following (1) and (2) are assumed. Is done. That is, when an acidic aqueous solution (treatment liquid) comes into contact with the magnet body 2, first, the magnet body 2 in that portion is dissolved. (1) When the dissolution of the magnet body 2 occurs in this manner, the acidity of the treatment liquid in that portion is weakened by this reaction (pH increases). If it becomes like this, the dispersibility of inorganic particles will fall in the part in which the acidity in a process liquid weakened, and, thereby, an inorganic particle adheres to the surface of the magnet element | base_body 2. FIG. At this time, the metal element eluted from the magnet body 2 reacts with the components in the treatment liquid to form the metal compound as described above, and the surface of the magnet body 2 so as to fill the gaps between the inorganic particles. It is thought to deposit on top.

  Further, (2) when the magnet element body 2 is dissolved by the contact of the treatment liquid, metal ions derived from the metal elements constituting the magnet element body 2 are dispersed in the treatment liquid in the vicinity of the magnet element body 2. The metal ions and the like adhere to the surface of the inorganic particles by adsorption or the like in the treatment liquid. Inorganic particles to which metal ions are attached tend to aggregate because the zeta potential of the surface changes. Therefore, the inorganic particles are aggregated in the vicinity of the surface of the magnet body 2 and the aggregated inorganic particles adhere to the surface of the magnet body. At this time, metal ions or the like attached to the inorganic particles react with components in the treatment liquid to form the metal compound and deposit on the surface of the magnet body 2 so as to fill the gaps between the inorganic particles. Conceivable. However, the formation mechanism of the protective layer 4 is not necessarily limited to these.

  After the formation of the protective layer 4, the surface of the protective layer 4 is washed with water in order to remove the treatment liquid adhering to the surface of the protective layer 4, by-products after the reaction, components dissolved from the magnet body 2, and the like. It is preferable. Thereby, excess processing liquid is removed and unevenness in the thickness of the protective layer 4 due to the flow of the processing liquid or the like is reduced. In addition, since the treatment liquid has acidity and tends to corrode the rare earth magnet 1, the corrosion of the rare earth magnet 1 due to the remaining treatment liquid can be reliably prevented by washing with water. More preferably, after the protective layer 4 is washed with water, the protective layer 4 is dried by warm air drying or natural drying.

  Further, the protective layer 4 may be further subjected to heat treatment. It is conceivable that, for example, condensation of the metal compound constituting the intergranular phase 24 proceeds by the heat treatment, which may improve the insulation and corrosion resistance of the rare earth magnet 1. The heat treatment can be performed by heating the rare earth magnet 1 after the protective layer 4 is formed. The heating temperature in this case can be 50-450 degreeC, for example.

  By such a manufacturing method, the rare earth magnet 1 including the protective layer 4 on the surface of the magnet body 2 is obtained. In this manufacturing method, as described above, since the magnet body 2 before the formation of the protective layer 4 is one having a surface Ra in a predetermined range, the magnet body 2 of the obtained rare earth magnet 1 is also used. Have substantially the same Ra. This is because the treatment liquid for forming the protective layer 4 causes the elution of the magnet body 2 but does not change the surface Ra, but the surface of the magnet body 2 before the formation of the protective layer 4 is maintained as it is. It is thought that it is because it is done. Therefore, when manufacturing the rare earth magnet 1 including the magnet body 2 having a predetermined range of Ra, the Ra of the magnet body 2 before forming the protective layer 4 may be set to the predetermined range. According to the method, the desired rare earth magnet 1 can be obtained by a simple method.

  According to the manufacturing method of this embodiment, since the Ra of the magnet body 2 is in the predetermined range, the metal compound is uniformly deposited when the protective layer 4 is formed. The protective layer 4 having a small variation in the ratio is formed. The rare earth magnet 1 thus obtained has a very small insulation and corrosion resistance because it has a protective layer 4 on the surface that has a small variation in thickness and mixing ratio of the metal compound and hardly peels off from the magnet body 2. It will have.

  As mentioned above, although preferred embodiment of the rare earth magnet of this invention and its manufacturing method was described, this invention is not necessarily limited to embodiment mentioned above. For example, first, in the protective layer 4 of the first form in the rare earth magnet 1, the interparticle phase 24 does not necessarily have to completely fill the gaps between the inorganic particles 14 as described above. A form in which the same metal compound as that of the interparticle phase 24 is attached to the surface may be used. In addition, the inorganic particles 14 and the metal compound need not be separated in the protective layer 4, and the metal compound may be contained in the inorganic particles 14.

  The rare earth magnet 1 may further include a layer for protecting the rare earth magnet 1 on the surface of the protective layer 4. As such a layer, what is normally formed as a layer which protects the surface of a rare earth magnet can be applied without a restriction | limiting, A resin layer, an inorganic compound layer, a metal layer, etc. are mentioned. Thereby, the corrosion resistance of the rare earth magnet 1 can be further improved.

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
First, an ingot having a composition of 27.6Nd-4.9Dy-0.5Co-0.4Al-0.07Cu-1.0B-remaining Fe (numbers represent weight percentage) is produced by powder metallurgy. 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 20 mm × 10 mm × 2 mm and processed to obtain a magnet body.

  Next, the obtained magnet body is subjected to acid cleaning by immersing in an acidic aqueous solution having a nitric acid concentration of 0.4 mol / L and a boric acid concentration of 0.4 mol / L for 2 minutes, and then ultrasonic cleaning is performed. Surface treatment was performed, thereby producing a magnet body having a predetermined surface roughness.

  Further, as a treatment liquid for forming a protective layer, a liquid in which a silica particle dispersed aqueous solution (Snowtex C manufactured by Nissan Chemical Industries, Ltd.) is adjusted to a particle concentration of 6%, and nitric acid is added to adjust the pH to 2.3. Produced. Then, the magnet body obtained above was immersed in this treatment liquid for 2 minutes to form a protective layer of about 2 μm on the surface of the magnet body, thereby obtaining a rare earth magnet. After pulling up the rare earth magnet from the treatment liquid, it was sufficiently washed with water before the treatment liquid was dried, and further subjected to a heat treatment at 180 ° C. for 20 minutes. Thus, a rare earth magnet having a protective layer on the surface of the magnet body was completed.

(Example 2)
A rare earth magnet was produced in the same manner as in Example 1, except that acid cleaning was performed using an acidic aqueous solution having a nitric acid concentration of 0.4 mol / L in the surface treatment of the magnet body.

(Example 3)
A rare earth magnet was produced in the same manner as in Example 1 except that in the surface treatment of the magnet body, buffing was performed on the processed magnet body instead of acid cleaning.

(Example 4)
In the surface treatment of the magnet body, CMP (chemical mechanical polishing) was performed before the acid cleaning, and then the acid cleaning was performed by immersing in an acidic aqueous solution having a nitric acid concentration of 0.4 mol / L for 10 seconds. Except for this, a rare earth magnet was produced in the same manner as in Example 1.

(Example 5)
As a treatment liquid for forming a protective layer, silica particle-dispersed aqueous solution (Snowtex C manufactured by Nissan Chemical Industries, Ltd.) was adjusted to a particle concentration of 6%, boric acid was added at 0.4 mol / L, and nitric acid was added. Thus, a rare earth magnet was produced in the same manner as in Example 1 except that a solution having a pH of 2.3 was used.

(Comparative Example 1)
In the surface treatment of the magnet body, the rare earth magnet was prepared in the same manner as in Example 1 except that acid cleaning was performed using an acidic aqueous solution having a nitric acid concentration of 0.4 mol / L and an acetic acid concentration of 0.02 mol / L. Produced.

(Comparative Example 2)
In the surface treatment of the magnet body, the rare earth magnet was prepared in the same manner as in Example 1 except that acid cleaning was performed using an acidic aqueous solution having a nitric acid concentration of 0.4 mol / L and an acetic acid concentration of 0.1 mol / L. Produced.

(Comparative Example 3)
In the surface treatment of the magnet body, a rare earth magnet was prepared in the same manner as in Example 1 except that acid cleaning was performed using an acidic aqueous solution having a nitric acid concentration of 0.4 mol / L and an acetic acid concentration of 0.5 mol / L. Produced.
[Characteristic evaluation]

  Using the rare earth magnets manufactured in Examples 1 to 5 and Comparative Examples 1 to 3, the following characteristics evaluation was performed. The results obtained are summarized in Table 1.

(Measurement of surface roughness)
First, in the manufacturing process of the rare earth magnets of Examples 1 to 5 and Comparative Examples 1 to 3, the arithmetic average roughness (Ra) of the surface of the magnet body before forming the protective layer was measured using a laser microscope (VK-9500 manufactured by Keyence). It measured using. This is defined as “Ra on the element surface”. Further, the surface of each example or comparative example after completion of the rare earth magnet, that is, the Ra of the protective layer surface was measured in the same manner. This is defined as “Ra on the surface of the protective layer”.

(Insulation test)
The insulating properties of the rare earth magnets obtained in Examples 1 to 5 and Comparative Examples 1 to 3 were measured by the following method. That is, two rare earth magnet pieces were placed between two copper foils, and the resistance value between the copper foils when a load was applied thereto was measured using a simple tester. At this time, the load was applied by applying a pressure of 1 MPa with a press machine insulated with a Teflon (registered trademark) sheet. The higher the obtained resistance value, the higher the insulating property of the rare earth magnet.

  From Table 1, the rare earth magnets of Examples 1 to 6 whose Ra on the element body surface was 0.08 to 0.8 μm had a higher resistance value than Comparative Examples 1 to 3 that exceeded 0.8 μm. It was confirmed that it has excellent insulating properties. Further, comparing the rare earth magnets of Example 2 and Example 5 in which the Ra on the element body surface was the same, the rare earth magnet of Example 5 in which the Ra on the surface of the protective layer was smaller than the surface of the element body. It was found that the insulation is remarkably excellent.

(Observation of protective layer)
Regarding the rare earth magnets obtained in Examples 1 to 5, the constituent elements of the protective layer and their distribution were observed. First, the surface composition of each rare earth magnet was analyzed by fluorescent X-ray analysis (ZSX-100e; manufactured by Rigaku Corporation). As a result, it was confirmed that Si, Al and Cu were deposited on the surface of each rare earth magnet.

  Moreover, about each rare earth magnet, the profile of the depth direction of the element contained in a protective layer was analyzed with the Auger electron spectroscopy (SAM680 by ULVAC-PHI). As a result, it was confirmed that the protective layer further contained Fe and O. Furthermore, the change in the intensity of each element with respect to the depth from the surface of the rare earth magnet was observed by analysis by Auger electron spectroscopy. As a result, it was confirmed that the concentration of Fe and Al gradually increased from the surface of the protective layer toward the interface with the magnet body in all rare earth magnets. Further, it was confirmed that the Al concentration in the protective layer was larger than the Al concentration inside the magnet body, and in particular, increased in the vicinity of the interface with the magnet body.

It is a figure which shows the rare earth magnet of suitable embodiment. It is a figure which shows typically the cross-sectional structure which follows the II-II line | wire of the rare earth magnet shown in FIG. It is a schematic diagram which expands and shows the cross-sectional structure of a protective layer.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Rare earth magnet, 2 ... Magnet body, 4 ... Protective layer, 14 ... Inorganic particle, 24 ... Interparticle phase.

Claims (6)

A magnet body containing a metal element including at least a rare earth element, and a protective layer formed on the surface of the magnet body,
The protective layer, inorganic particles, and, seen containing a compound of the same metal element and at least one of metal element contained in the magnet body,
The magnet body has an arithmetic mean roughness of the (Ra) of the surface is, Ri 0.08~0.8μm der, and,
The concentration of at least one of the metal elements contained in the protective layer increases from the surface side of the protective layer toward the magnet body side.
Rare earth magnet characterized by that. A magnet body containing a metal element including at least a rare earth element, and a protective layer formed on the surface of the magnet body,
The protective layer may be silicon, oxygen, and, looking containing the same metal element and at least one of metal element contained in the magnet body,
The magnet body has an arithmetic mean roughness of the (Ra) of the surface is, Ri 0.08~0.8μm der, and,
The concentration of at least one of the metal elements contained in the protective layer increases from the surface side of the protective layer toward the magnet body side.
Rare earth magnet characterized by that.   The rare earth magnet according to claim 1, wherein Ra on the surface of the protective layer is smaller than Ra on the surface of the magnet body. An aqueous solution containing inorganic particles and having acidity is brought into contact with the surface of a magnet body containing at least a metal element including a rare earth element and having an arithmetic average roughness (Ra) of 0.08 to 0.8 μm on the surface. by, on the surface, it has a step of forming a protective layer containing the compound and the inorganic particles of the same metal element and at least one of metal element contained in the magnet body, and,
The method for producing a rare earth magnet , wherein the concentration of at least one of the metal elements contained in the protective layer increases from the surface side of the protective layer toward the magnet body side . It contains a metal element containing at least a rare earth element, and the surface of the magnet body having an arithmetic average roughness (Ra) of 0.08 to 0.8 μm on its surface contains a compound containing silicon and oxygen. the in aqueous solution by contacting with, on the surface, and organic silicon, oxygen and forming a protective layer containing a compound of the same metal element and at least one of metal element contained in the magnet body, and,
The method for producing a rare earth magnet , wherein the concentration of at least one of the metal elements contained in the protective layer increases from the surface side of the protective layer toward the magnet body side . The method for producing a rare earth magnet according to claim 4 , further comprising a step of washing the protective layer in a state where the aqueous solution is adhered after the aqueous solution is contacted.

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