JP2005294381A - Magnet and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the manufacturing method of a magnet to obtain the magnet having sufficiently excellent anti-corrosion property. <P>SOLUTION: In the manufacturing method of a magnet, an anode material and a cathode material including a magnetic raw material having conductivity are soaked into the aqueous solution of electrolyte, and a current is applied across these anode and cathode materials. Accordingly, a magnet where a dense protection layer is formed on the surface of the magnet raw material can be obtained. Existence of this protection layer enables the magnet to show sufficiently excellent anti-corrosion property. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a magnet manufacturing method and a magnet.

  In recent years, for example, R—Fe—B magnets (R represents a rare earth element such as Nd) have been developed as permanent magnets exhibiting a high energy product of 25 MGOe or more. More specifically, for example, Patent Document 1 discloses an R—Fe—B magnet formed by sintering, and Patent Document 2 discloses a magnet formed by rapid quenching. However, since R-Fe-B magnets contain rare earth elements and iron that are relatively easily oxidized as main components, their corrosion resistance is relatively low, and as a result, magnets are manufactured and used. As a result, there are problems such as deterioration in performance and / or reliability of manufactured magnets being relatively low. For the purpose of improving the corrosion resistance of such R-Fe-B magnets, various protective films have been applied to the surface of the magnet body as described in, for example, Patent Documents 3 to 9 so far. Proposals to make are made.

  More specifically, for example, in Patent Document 3, R (where R is at least one of rare earth elements including Y) is intended to improve the oxidation resistance of a permanent magnet mainly composed of rare earth, boron, and iron. Species) Oxidation-resistant plating layer is coated on the surface of permanent magnet body consisting mainly of tetragonal phase with 8 to 30 atom%, B2 to 28 atom%, and B42 to 90 atom% as the main component. Permanent magnets have been proposed. Patent Document 3 discloses plating of metal or alloy having oxidation resistance such as Ni, Cu, Zn, or composite plating thereof.

  Patent Document 10 discloses that a wet oxidation method is used on the surface of a metal layer formed on the surface of a magnet body in order to improve the corrosion resistance of a permanent magnet mainly composed of rare earth, boron, and iron. The fact that a film is formed is described.

Further, in Patent Document 11, with the aim of improving the oxidation resistance of a permanent magnet mainly composed of rare earth, boron, and iron, Al ₂ O ₃ , that a protective layer made of a metal oxide such as cr ₂ O ₃ is disclosed.
JP 59-46008 A JP-A-60-9852 JP-A-60-54406 JP-A-60-63901 JP 60-63902 A Japanese Patent Laid-Open No. 61-130453 JP-A-61-166115 JP 61-166116 A JP 61-270308 A JP-A-7-302705 JP-A-61-150201

  However, the present inventors have studied in detail the conventional rare earth magnets containing the rare earth elements including those described in Patent Documents 1 to 11 described above. It was found that it does not have good corrosion resistance. That is, for example, a rare earth magnet provided with the above-described oxidation-resistant plating layer described in Patent Document 3, a rare earth magnet provided with a chromate film described in Patent Document 10, or a metal oxide described in Patent Document 11 The present inventors have found that when a salt spray test specified in JIS-C-0023 is performed on a rare earth magnet provided with a layer made of the above, corrosion is observed in the magnet body of the rare earth magnet. .

  Here, the “salt spray test” means, for example, a 5 ± 1 mass% NaCl aqueous solution (pH = 6.5 to 7.2) under a temperature condition of about 35 ° C. for 24 hours in a fine damp and dense fog state. This is done by contacting the sample and checking the corrosion state of the sample. As a factor in which corrosion is recognized in the magnet body by the salt spray test, it is considered that pinholes are generated in the protective layer (oxidation-resistant plating layer). When a pinhole is generated in the protective layer of the rare earth magnet, a corrosive substance in the atmosphere enters from the pinhole and becomes a factor that corrodes the magnet body. In particular, rare earth magnets corrode very easily due to the presence of a slight amount of corrosive substances. Therefore, conventional rare earth magnets in which corrosion is observed in the magnet body by the salt spray test are also used in actual usage environments. It cannot be said that it is necessarily excellent in corrosion resistance.

  Further, in Patent Document 10, although there is a description that a predetermined resistance is exhibited with respect to the salt spray test, it has been clarified that the corrosion resistance is not necessarily excellent in an actual use environment.

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

  The method of manufacturing a magnet of the present invention that solves the above-mentioned problems involves immersing an anode material containing a conductive magnet body and a cathode material in an aqueous electrolyte solution, and applying a current between the anode material and the cathode material. It is characterized by doing.

  The reason why the magnet obtained by such a manufacturing method is sufficiently excellent in corrosion resistance is not clear in detail, but the present inventors consider as follows. However, the factors are not limited to these.

  The inventors can polarize a magnet (element body) on the surface of an aqueous electrolyte solution containing a salt selected from borate, tungstate, phosphate, oxalate and molybdic acid. It has been found that a new layer is formed and the magnet has sufficient corrosion resistance.

  It is generally considered that the magnet corrosion phenomenon occurs when electrons contained in the metal constituting the magnet are emitted to the outside and oxidized. During this oxidation process, the metal is ionized and eluted into an external solution, or chemically bonded to oxygen, hydroxide ions, etc. to form compounds such as oxides and hydroxides. Therefore, the present inventors consider that it is necessary to prevent or suppress this electron emission in order to prevent the corrosion of the magnet.

  On the other hand, it is generally known that when a metal is polarized in an electrolyte solution and a hardly soluble corrosion product forms a dense surface film, further corrosion reaction can be suppressed. This state is called a passive state (passive state), and a film formed on the metal surface in this state is called a passive state film.

From the above, the present inventors believe that a passive film is formed on the surface of the magnet obtained by the above-described production method of the present invention. The passive film formed at this time is mainly composed of oxides or hydroxides of metals (Fe and Nd) contained in the magnet body (Fe _x Nd _y O _z and Fe (OH) ₃ for the Fe part), Fe (OH) ₂ , α-FeOOH, etc., where the Nd portion is presumed to be Nd ₃ O ₄ or Nd (OH) ₃ ), but it contains a compound that is generated by a chemical reaction with an electrolyte component I think that there is also.

  The manufacturing method of the magnet of the present invention can be applied to a known apparatus used in a so-called versatile technique called anodic oxidation, and is a manufacturing method excellent in mass productivity.

  According to the magnet manufacturing method of the present invention, the size of the obtained magnet is approximately the same as the size of the magnet body. Therefore, it is possible to form a magnet having sufficiently excellent corrosion resistance with high dimensional accuracy.

  Moreover, it is preferable that the manufacturing method of the magnet of this invention uses what contains 1 or more types of salts chosen from the group which consists of tungstate, phosphate, oxalate, and molybdate as electrolyte aqueous solution. In particular, when one containing at least one salt selected from the group consisting of tungstate, phosphate and molybdate is used, the resulting magnet is selected from the group consisting of tungsten, phosphorus and molybdenum on its surface. It is provided with a protective layer made of a passive film containing one or more elements, and is further excellent in corrosion resistance. Although the above-mentioned thing is estimated as the factor, a factor is not limited to this.

  The magnet of the present invention is characterized by comprising a conductive magnet body and a protective layer formed on the surface of the magnet body and containing tungsten. Such a magnet can effectively prevent external corrosion factor substances (oxygen, moisture, salt water, sulfides, etc.) from coming into contact with the magnet body by the protective layer containing tungsten. As a result, the magnet of the present invention is sufficiently excellent in corrosion resistance.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the magnet for obtaining the magnet which has the sufficiently excellent corrosion resistance, and the magnet 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.

  First, a rare earth magnet which is one of the preferred embodiments of a magnet obtained by the magnet manufacturing method of the present invention will be described.

  FIG. 1 is a schematic perspective view showing a rare earth magnet according to this embodiment, and FIG. 2 is a diagram schematically showing a cross section that appears when the rare earth magnet of FIG. 1 is cut along the line II. As is clear from FIGS. 1 and 2, the rare earth magnet 100 is composed of a magnet element body 10 and a protective layer 20 formed by covering the entire surface of the magnet element body 10.

  The magnet body 10 contains R, iron (Fe), and boron (B). R represents one or more rare earth elements, specifically, one or more selected from the group consisting of scandium (Sc), yttrium (Y) and lanthanoids belonging to Group 3 of the long-period periodic table. Indicates an element. Here, the lanthanoid is 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) and lutetium (Lu).

  The composition of the above-described elements in the magnet body 10 is preferably as described below when the magnet body 10 is manufactured by a sintering method.

  R preferably includes one or more elements of Nd, Pr, Ho, and Tb among those described above, and further includes 1 of La, Sm, Ce, Gd, Er, Eu, Tm, Yb, and Y. It is also preferable to include more than one element.

  The content ratio of R in the magnet body 10 is preferably 8 to 40 atomic% with respect to the total amount of atoms constituting the magnet body 10. When the content ratio of R is less than 8 atomic%, the crystal structure has a cubic structure having the same structure as that of α-iron. Therefore, the rare earth magnet 100 having a high coercive force (iHc) tends not to be obtained. Further, when the content ratio of R exceeds 30 atomic%, the R-rich nonmagnetic phase increases, and the residual magnetic flux density (Br) of the rare earth magnet 100 tends to decrease.

  The content ratio of Fe in the magnet body 10 is preferably 42 to 90 atomic% with respect to the total amount of atoms constituting the magnet body 10. If the Fe content is less than 42 atomic%, the Br of the rare earth magnet 100 tends to decrease, and if it exceeds 90 atomic%, the iHc of the rare earth magnet 100 tends to decrease.

  The content ratio of B in the magnet body 10 is preferably 2 to 28 atomic% with respect to the total amount of atoms constituting the magnet body 10. If the B content is less than 2 atomic%, the crystal structure has a rhombohedral structure, so the iHc of the rare earth magnet 100 tends to be insufficient. If it exceeds 28 atomic%, there are many B-rich nonmagnetic phases. Therefore, the Br of the rare earth magnet 100 tends to decrease.

  Further, the magnet body 10 may be configured by replacing part of Fe with cobalt (Co). By adopting such a configuration, the temperature characteristics tend to be improved without impairing the magnetic characteristics of the rare earth magnet 100. In this case, the content ratio of Fe and Co after substitution is preferably such that Co / (Fe + Co) is 0.5 or less on an atomic basis. If the amount of substitution of Co is larger than this, the magnetic properties of the rare earth magnet 100 tend to deteriorate.

  Furthermore, even if a part of B is replaced with one or more elements selected from the group consisting of carbon (C), phosphorus (P), sulfur (S), and copper (Cu), the magnet body 10 is configured. Good. By adopting such a configuration, the productivity of the rare earth magnet 100 is improved and the production cost tends to be reduced. In this case, the content of C, P, S and / or Cu is preferably 4 atom% or less with respect to the amount of all atoms constituting the magnet body 10. When the content of C, P, S and / or Cu is more than 4 atomic%, the magnetic properties of the rare earth magnet 100 tend to deteriorate.

  Further, from the viewpoint of improving the coercive force of the rare earth magnet 100, improving productivity, and reducing the cost, 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 ( The magnet body 10 may be configured by adding one or more elements of Si), gallium (Ga), copper (Cu), and / or hafnium (Hf). In this case, it is preferable that the addition amount of the element is 10 atomic% or less with respect to the total amount of atoms constituting the magnet body 10. When the addition amount of these elements exceeds 10 atomic%, the magnetic properties of the rare earth magnet 100 tend to deteriorate.

  In the magnet body 10, oxygen (O), nitrogen (N), carbon (C), and / or calcium (Ca), etc. as unavoidable impurities are included in the amount of all atoms constituting the magnet body 10. And may be contained within a range of 3 atomic% or less.

  As shown in FIG. 3, the magnet body 10 includes a main phase 50 having a substantially tetragonal crystal structure, a rare earth-rich phase 60 containing a relatively large amount of rare earth elements, and a boron rich material containing a relatively large amount of boron. And the phase 70 is formed. The particle size of the main phase 50 which is a magnetic phase is preferably about 1 to 100 μm. The rare earth-rich phase 60 and the boron-rich phase 70 are nonmagnetic phases and exist mainly at the grain boundaries of the main phase 50. These nonmagnetic phases 60 and 70 are usually contained in the magnet body 10 by about 0.5 volume% to 50 volume%.

  The magnet body 10 is prepared, for example, by being manufactured by a sintering method as described below. First, a desired composition containing the elements described above is cast to obtain an ingot. Subsequently, the obtained ingot is roughly pulverized to a particle size of about 10 to 100 μm using a stamp mill or the like, and then finely pulverized to a particle size of about 0.5 to 5 μm using a ball mill or the like to obtain a powder. .

Next, the obtained powder is preferably molded in a magnetic field to obtain a molded body. In this case, the magnetic field strength in the magnetic field is preferably 10 kOe or more, and the molding pressure is preferably about 1 to 5 ton / cm ² .

  Subsequently, the obtained molded body is sintered at 1000 to 1200 ° C. for about 0.5 to 5 hours and rapidly cooled. The sintering atmosphere is preferably an inert gas atmosphere such as Ar gas. And preferably, the magnet body 10 as described above is obtained by performing heat treatment (aging treatment) at 500 to 900 ° C. for 1 to 5 hours in an inert gas atmosphere.

  In addition to the above, the magnet body 10 can be prepared by, for example, a well-known super rapid cooling method, a warm brittle processing method, a casting method, or a mechanical alloying method. Further, a commercially available magnet body 10 may be prepared.

  The protective layer 20 is obtained by a rare earth magnet manufacturing method described below. The protective layer 20 may contain a metal component contained in the electrolyte solution. The thickness of the protective layer 20 is preferably 0.5 μm or more.

  Next, a method for manufacturing a magnet according to a preferred embodiment of the present invention will be described. In the magnet manufacturing method of the present embodiment, an anode material including a magnet element body 10 having conductivity and containing a rare earth element and a cathode material are immersed in an aqueous electrolyte solution, and the gap between the anode material and the cathode material is immersed. The current is passed through.

  The electrolyte solution (electrolytic solution) used in the present embodiment is preferably a metal acid salt aqueous solution or an organic acid salt aqueous solution. Examples of the metal salt aqueous solution include aqueous solutions of tungstate, borate, phosphate, vanadate, tantalate, zirconate, molybdate, and the like. Examples of the organic acid salt aqueous solution include aqueous solutions of oxalate, maleate and fumarate.

Among these, the electrolyte solution used in the present embodiment is preferably one containing molybdate, tungstate, phosphate, or oxalate. These salts have, for example, sodium molybdate, sodium tungstate and sodium oxalate having polarization resistances of 1.35 × 10 ⁴ Ω · cm ² , 2.86 × 10 ³ Ω · cm ² and 1.72 × 10 respectively. Since it is relatively large at ³ Ω · cm ² , magnets obtained using these salts can further exhibit the effects of the present invention. In particular, it is more preferable to use a tungstate aqueous solution as the electrolyte solution because it is possible to form a magnet that exhibits much better corrosion resistance than conventional magnets.

  The cation contained in these electrolyte solutions is not particularly limited, and examples thereof include sodium (Na), potassium (K), lithium (Li), magnesium (Mg), and calcium (Ca).

  The pH in the electrolyte solution is preferably adjusted to 7 or higher. If the pH of the electrolyte solution is less than 7, rare earth elements and the like contained in the magnet body 10 are likely to be actively dissolved on the electrolyte solution side, and this tends to reduce the corrosion resistance of the obtained magnet. is there. The present inventors speculate that this is due to the fact that the protective layer 20 such as an oxide film is hardly formed on the surface of the magnet body 10 due to active dissolution of rare earth elements and the like contained in the magnet body 10. However, the factor is not limited to this.

  In this embodiment, the magnet body 10 whose corrosion resistance is to be improved is used as the anode material. Since the R-Fe-B magnet body 10 containing rare earth elements as described above has conductivity, it can be used as an anode material without any particular limitation.

  Further, as the anode material, a material other than the magnet body 10 that is desired to improve the corrosion resistance, such as a nickel-plated iron ball (2 to 10Φ), may be used. When such an anode material is used in combination with the magnet body 10, the element bodies tend to overlap each other, thereby preventing an unprocessed region from existing in the element body. This effect can be obtained particularly significantly in the case of a flat body.

  The cathode material used in the present embodiment is not particularly limited as long as it is a conductive material that can function as a cathode in relation to the magnet body 10 for which corrosion resistance is desired to be improved. As such a cathode material, various metals such as platinum-plated titanium, or conductive oxides can be used.

  In the magnet manufacturing method of the present embodiment, first, an electrolyte solution is filled in a container included in a rotating barrel device, a vibration barrel device, and the like, and the above-described anode material (magnet body 10) and cathode are placed in the electrolyte solution. Immerse the material. The anode material and the cathode material are electrically connected via a DC power source or an AC power source.

  Then, by turning on the power source and applying (flowing) a current between the anode material and the cathode material, the magnet body 10 that is the anode material is forcibly subjected to electrical processing to obtain a magnet. When the power source is a DC power source, the negative electrode side of the power source may be connected to the anode material, and the positive electrode side may be connected to the cathode material. Moreover, even when the power source is an AC power source, the magnet obtained by this manufacturing method has improved corrosion resistance compared to the magnet body before the electrical treatment.

The current density and application time of the current applied at this time are not particularly limited, but their product (that is, current density × application time) so that the thickness of the protective layer 20 to be formed is 0.5 μm or more. Is preferably set. Thereby, it exists in the tendency which the corrosion resistance of the magnet obtained improves further. Specifically, preferably the current density is 0.001~1A / dm ^2, and more preferably a 0.01~0.1A / dm ^2. The application time is preferably 10 to 60 minutes.

  Although the temperature of the electrolyte solution at the time of applying an electric current is not specifically limited, It is preferable in it being 20-90 degreeC. If this temperature is below 20 ° C., the curing of the protective layer tends to proceed excessively and tends to show high brittleness, and if it exceeds 90 ° C., the protective layer formation rate increases, making management difficult and the protective layer in a desired state. Tend to be difficult to obtain.

  In addition, it is preferable to perform the current application process before magnetizing the R—Fe—B magnet because it is easy to obtain desired magnetic characteristics.

  The R-Fe-B magnet obtained in this way is provided with the protective layer 20 on the surface thereof, but the protective layer 20 may contain a component derived from the electrolyte solution. For example, when a metal acid salt aqueous solution is used for the electrolyte solution, the metal constituting the metal acid salt may be contained in the protective layer 20. Therefore, when a tungstic acid aqueous solution capable of imparting particularly excellent corrosion resistance to the magnet is used as the electrolyte solution, tungsten can be contained in the protective layer 20 of the obtained magnet. As a result, the magnet obtained by the above-described manufacturing method and including the protective layer 20 containing tungsten tends to exhibit higher corrosion resistance.

  According to the magnet manufacturing method of the present embodiment described above, a protective layer is formed on the surface of the magnet element body, which is an anode material, and the protective layer is rich in density. The -B magnet is sufficiently excellent in corrosion resistance.

  Further, even if the protective layer is formed in this way, the magnetic properties (residual magnetic flux density, coercive force, etc.) of the obtained magnet are unlikely to deteriorate from those of the magnet body. Therefore, the magnet has sufficiently excellent magnetic properties.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment. For example, the magnet element may be a magnet element having conductivity even if it is other than the R-Fe-B magnet element. For example, Fe may be completely substituted with another transition metal, such as an R-TM magnet element ("TM" indicates a transition metal, such as an Sm-Co magnet element) or R-TM-N. Other rare earth magnet elements such as a magnet element may be used. In this case, specific examples of TM include Co, Fe—Ni, Fe—Co—Ni and the like in addition to Fe. Further, it may be a metal-based magnet element such as an Fe—Cr—Co magnet element.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

(Example 1)
A sintered body having a composition of 14Nd-1Dy-7B-78Fe (numbers are atomic ratio) prepared by powder metallurgy is heat-treated at 600 ° C. for 2 hours in an argon gas atmosphere, and then 35 × 35 × 5 (mm ), Processed to a size of about 1 kg, and further chamfered by barrel polishing to obtain a magnet body.

  Subsequently, the obtained magnet body was immersed in 3% nitric acid for 5 minutes, washed with ultrasonic water and pretreated.

  Next, a 0.1 M aqueous solution of sodium oxalate (pH = 7.1) was prepared as an electrolyte solution by a conventional method, and this aqueous solution was placed in a container of a rotating barrel device (bottom cylindrical shape, diameter 300 mm, length 400 mm). Filled. Furthermore, a platinum-coated titanium mesh (400 mm × 500 mm × 2 mm) as a cathode material is immersed in the electrolyte aqueous solution in the container, and the magnet body and nickel-plated iron ball (3Φ sphere, 4 kg) as an anode material. Soaked.

The rotational speed of the rotating barrel device is set to 6 times / minute, and a current is passed between the anode material and the cathode material in a room temperature environment so that the average current density is 0.03 A / dm ^2. Was magnetized for 10 minutes to obtain the magnet of Example 1.

  When the obtained magnet was washed with water and dried, a humidified high-temperature test (PCT test, 120 ° C., 2 atm, 100 hours) was performed, and no abnormal appearance and weight reduction were observed in the magnet.

(Example 2)
A magnet of Example 2 was obtained in the same manner as Example 1 except that a 0.1 M sodium tungstate aqueous solution (pH = 8.4) was used as the electrolyte solution and the average current density was 1 A / dm ² . When the obtained magnet was washed with water and dried, a humidified high-temperature test (PCT test, 120 ° C., 2 atm, 100 hours) was performed, and no abnormal appearance and weight reduction were observed in the magnet.

(Example 3)
A magnet of Example 3 was obtained in the same manner as in Example 1 except that a 0.1 M aqueous sodium phosphate solution (pH = 6.75) was used as the electrolyte solution and the average current density was 0.02 A / dm ^2. It was. When the obtained magnet was washed with water and dried, a humidified high-temperature test (PCT test, 120 ° C., 2 atm, 100 hours) was performed, and no abnormal appearance and weight reduction were observed in the magnet.

Example 4
A magnet of Example 4 is obtained in the same manner as in Example 1 except that a 0.1 M sodium molybdate aqueous solution (pH = 7.3) is used as the electrolyte solution and the average current density is 0.02 A / dm ^2. It was. When the obtained magnet was washed with water and dried, a humidified high-temperature test (PCT test, 120 ° C., 2 atm, 100 hours) was performed, and no abnormal appearance and weight reduction were observed in the magnet.

(Comparative Example 1)
Comparison in which the magnet body obtained in the same manner as in Example 1 was immersed in a chemical conversion treatment solution (pH = 5.0) containing phosphate and molybdate at 50 ° C. for 10 minutes for chemical conversion treatment. The magnet of Example 1 was obtained. The obtained magnet was washed with water and dried, and then a humidified high temperature test (PCT test, 120 ° C., 2 atm, 100 hours) was performed. As a result, abnormal appearance (rusting) was observed in the magnet.

It is a schematic perspective view which shows the rare earth magnet obtained by the manufacturing method of the rare earth magnet which concerns on embodiment of this invention. It is a schematic sectional drawing which shows the rare earth magnet obtained by the manufacturing method of the rare earth magnet which concerns on embodiment of this invention. It is a model enlarged view which shows the phase structure of a R-Fe-B type magnet.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Magnet body, 20 ... Protective layer, 100 ... Magnet.

Claims (3)

  A method for producing a magnet, comprising immersing an anode material containing a conductive magnet body and a cathode material in an aqueous electrolyte solution, and applying a current between the anode material and the cathode material.   The method for producing a magnet according to claim 1, wherein the aqueous electrolyte solution contains one or more salts selected from the group consisting of tungstate, phosphate, oxalate and molybdate. . A magnet body having conductivity;
A protective layer formed on the surface of the magnet body and containing one or more elements selected from the group consisting of tungsten, phosphorus and molybdenum;
A magnet comprising:

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