JPH06244011A - Corrosion-resistant rare earth magnet and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a corrosion-resistant rare-earth magnet whose surface is chemically stable in various kinds of atmosphere. CONSTITUTION:A rare-earth magnet is subjected to fluorinating treatment in a fluorine group gas atmosphere or a fluorine gas-contained atmosphere, thereby forming a mixture which comprises an RF3 compound which is stabilized to corrosion resistance or ROxFy compound or both compounds on a front surface layer of the rare-earth magnet. It is also possible to enhance the corrosion resistance of a raw-material of the rare-earth magnet dramatically by performing a specified heat treatment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rare earth magnet having high magnetic properties and excellent corrosion resistance, and by subjecting the surface of the magnet body to a fluorination treatment, the surface layer of the magnet is exposed to various atmospheres. The present invention relates to a rare earth magnet in which a stable compound of rare earth and fluorine is formed to remarkably improve the corrosion resistance of the raw material of the rare earth magnet, and a manufacturing method thereof.

[0002]

2. Description of the Related Art Today, R is a typical high-performance permanent magnet.
(At least one or more rare earth elements including Y) -Fe-
B-based permanent magnets (Japanese Patent Publication No. 61-34242, etc.) exhibit high magnet characteristics in a structure having a main phase of a ternary tetragonal compound and an R-rich phase, iHc of 25 kOe or more, (BH)
Even when compared with the conventional high-performance rare earth cobalt magnet with a max of 45 MGOe or more, it exhibits remarkably high magnet characteristics.
Further, R-Fe-B based permanent magnets of various compositions have been proposed so as to exhibit various selected magnet characteristics according to the application.

However, the R-Fe-B based permanent magnet having the above-mentioned excellent magnetic characteristics contains a rare earth element and a rare earth element which are easily oxidized or hydroxylated in the air as a main component to easily generate an oxide or a hydroxide. Since it contains iron, R-
When an Fe-B system permanent magnet is incorporated in a magnetic circuit, an oxide or hydroxide generated on the surface of the magnet causes a decrease in output of the magnetic circuit and a variation in magnetism between the magnetic circuits.
Further, there is a problem that peripheral devices are contaminated due to the oxides formed on the surface falling off.

Particularly, in the case of an R-Fe-B system sintered permanent magnet, its constituent layers are composed of R ₂ Fe ₁₄ B phase, R rich phase, B rich phase, etc., among which R ₂ Fe ₁₄ B
Since the R-rich phase existing in the grain boundary portion of the phase is a phase containing a large amount of R, it is extremely apt to be oxidized or hydroxylated, and absorbs moisture in the atmosphere in the magnet surface layer to cause volume expansion and R ₂ There was a problem that the particles of Fe ₁₄ B phase from the magnet surface layer and the hydroxide itself fell off.

Therefore, in order to improve the corrosion resistance of the above R-Fe-B permanent magnet, the surface of the magnet is coated with a corrosion-resistant metal plating layer by electroless plating or electrolytic plating (Japanese Patent Laid-Open No. 60-54406). No.), a corrosion resistant resin is coated by a dipping method or a coating method (Japanese Patent Laid-Open No. 60-63).
No. 901), a corrosion resistant metal such as Al or an alloy film is formed by a vapor deposition method (JP-A-61-150201), or a resin layer containing a corrosion-resistant metal thin film is deposited (JP-A-61-150201). 6
No. 3-166944), and further, a technique of providing a corrosion-resistant coating such as stacking different types of corrosion-resistant coatings (JP-A-1-152602) has been proposed.

[0006]

However, in the electroless plating method or the electrolytic plating method, since the R-Fe-B system permanent magnet is treated in an acidic or alkaline solution, the surface of the magnet is corroded and the magnetic characteristics are deteriorated. In addition to variations, pinholes are present in the plating film, so sufficient corrosion resistance cannot be obtained for severe tests such as salt spray tests. In particular, in an R-Fe-B system sintered permanent magnet containing an R-rich phase that is easily oxidized as a constituent phase, it is used at the time of plating in the so-called wet plating method such as the above-mentioned electroless plating method or electrolytic plating method. The R-rich phase is preferentially corroded by the acidic solvent or the alkaline solvent, and the solvent penetrates into the magnet body from the corroded portion. Therefore, even if the magnet body surface is coated with the plating layer, There is a problem that the residual solvent continues to corrode the R-rich phase, and eventually the internal corrosion causes the magnet itself to collapse.

On the other hand, when a corrosion-resistant resin is coated by a dipping method, a coating method, or an electrodeposition method, no pinholes are present, but sufficient water resistance of the resin film is larger than that of the metal film, so that sufficient corrosion resistance cannot be obtained. There was a problem. That is, in the conventional surface treatment such as the corrosion resistant coating, the above-mentioned problems are caused because the corrosion resistance of the base magnet material is not considered so much. Therefore, a method of improving the corrosion resistance of the magnet material itself by adding various additive elements to the magnet material in advance, such as Co, Ni, and Al, which have excellent corrosion resistance, is also proposed before performing the various surface treatments as described above. However, in order to obtain the effect of corrosion resistance, it is necessary to add a large amount of the above-mentioned additional elements, which causes problems such as deterioration of magnetic characteristics and high cost.

In order to solve the above-mentioned various problems, the present invention specifically has a chemically stable surface in various atmospheres and improves the corrosion resistance of the rare earth magnet material itself. It is an object of the present invention to provide a rare earth magnet having excellent corrosion resistance and a manufacturing method thereof.

[0009]

Means for Solving the Problems The inventor has investigated a magnet surface layer for improving the corrosion resistance of various rare earth magnet materials having a known composition, and paid attention to changing the magnet surface layer to a compound that is stable in various atmospheres. As a result of various studies on the surface treatment method, a compound of rare earth (R) and fluorine (F) by the fluorination treatment, that is, RF on the surface layer part of the magnet
It was found that it is possible to remarkably improve the corrosion resistance of the magnet material itself by forming a ₃ compound or a RO _X F _Y compound or a mixture of both compounds, and completed the present invention. That is, the present invention is a rare earth magnet having excellent corrosion resistance, which comprises an RF ₃ compound or a RO _X F _Y compound or a mixture of both compounds in the surface layer portion of the rare earth magnet.

Further, according to the present invention, a rare earth magnet (containing at least one kind of rare earth element R) is fluorinated in a fluorine-containing gas atmosphere or an atmosphere containing a fluorine-containing gas to obtain a surface layer portion of the magnet. RF ₃ compound or RO _X
Forming a F _Y compound or a mixture of both compounds,
Alternatively, it is a method for producing a rare earth magnet having excellent corrosion resistance, which is characterized by performing heat treatment at a temperature of 200 ° C to 1200 ° C.

Rare Earth Magnet In the present invention, as the rare earth magnet, any rare earth magnet having a known composition containing at least one or more rare earth element R containing Y is targeted, and the magnet form includes a known sintered magnet. The present invention can be applied to all forms such as cast magnets, rolled magnets, and bonded magnets, or can be applied to magnets obtained by any composition and manufacturing method such as raw material powder for bonded magnets, or raw material powders thereof. In particular, when the rare earth magnet is an R—Fe—B permanent magnet material containing R, Fe (a part of Fe can be replaced with a transition metal element such as Co), and B (boron) as a main component, The effect of the present invention is remarkably obtained. That is, a rare earth magnet having at least R ₂ T ₁₄ B phase in the constituent phases constituting the above various rare earth magnets,
Alternatively, in the case of a rare earth magnet having at least R ₂ T ₁₄ B phase and R rich phase, the effect of improving the corrosion resistance can be expected by performing the fluorination treatment of the present invention. In addition,
The R-rich phase is a compound of a rare earth element and a transition metal element, or a compound in which the rare earth element and the transition metal element partially include a metalloid element, and the amount of the rare earth element is other than the rare earth element such as the transition metal element. It is said to be contained in a larger amount than the amount. The compounds effective for the fluorination treatment according to the present invention include R ₃ TM, RTM ₅ , R ₂ TM ₇ , RTM ₃ and RT.
M ₂ , R ₂ TM ₃ , R ₂ TM ₁₇ , R ₅ TM ₁₉ , Dy ₆ Fe ₂ ,
RTM, R ₂ TM ₁₄ B, R _1.11 TM ₄ B ₄ (TM is at least one of transition metal elements) and the like.

Surface Layer Compound In the present invention, R formed on the surface layer portion of the rare earth magnet is used.
The F ₃ compound, the RO _X F _Y compound, or a mixture of both compounds are extremely stable compounds, and R in each compound does not easily react with water or the like. In addition,
In the above RO _X F _Y , each value of X and Y is 0 <X <1.5.
And a compound satisfying 2X + Y = 3. The above compound forms an RF ₃ compound, a RO _X F _Y compound, or a mixture of both compounds by subjecting the R ₂ T ₁₄ B phase and the R rich phase constituting the rare earth magnet to a fluorination treatment described later. In the present invention, the formation thickness of the RF ₃ compound or the RO _X F _Y compound or the mixture of both compounds formed on the surface layer portion of the rare earth magnet is as follows:
It can be freely controlled by changing the fluorination treatment time, fluorination treatment temperature, heat treatment conditions after fluorination treatment, etc. Even if the thickness is extremely small, an effect on corrosion resistance can be expected, but a thick formation thickness As the fluorination process takes longer, the mass productivity on an industrial scale tends to decrease, and the magnetic properties tend to deteriorate. Therefore, the compound formation thickness is preferably 500 μm or less. Considering the reliability of corrosion resistance and corrosion resistance, 1 μm to 100 μm is a more preferable range.

The rare earth magnet having the RF ₃ compound or the RO _X F _Y compound or the mixture of both compounds in the surface layer according to the present invention has sufficient corrosion resistance by itself.
For example, when even higher corrosion resistance is required, such as when the present rare earth magnet is used in an extremely harsh environment, the rare earth magnet may be coated with a metal, an alloy, a resin, etc. by a known surface treatment method. it can. Known surface treatment methods include metals, alloys, resins, etc., and those mixed with various additives, such as electrolytic plating method, electroless plating method, electrodeposition coating method, spray coating method, dipping method, and vapor coating method. The coating is performed by a phase film forming method or the like. In addition, for example, after coating a metal or the like by a plating method, further coating with a resin, or by depositing a metal by a vapor phase film forming method, and then performing chromate treatment, known surface treatment materials and surfaces Coating can be performed by combining various treatment methods.

Fluorination Treatment In the present invention, the fluorination treatment can be carried out by a simple method, for example, by exposing the rare earth magnet to a fluorine-containing gas atmosphere or an atmosphere containing a fluorine-containing gas. In order to accelerate the reaction, a rare earth magnet whose surface is previously processed or subjected to heat treatment after processing is put in a container capable of sucking and exhausting, and the inside of the container is once evacuated, and then a fluorine-based gas is supplied to the container. The fluorination treatment can be carried out by introducing a pressure up to a predetermined pressure and maintaining it at a predetermined temperature for a required time, or by inserting a rare earth magnet in a container in which a fluorine-based gas is made to flow. Further, fluorination treatment by plasma treatment can also be performed. For example, a method of performing plasma treatment in a fluorine-based gas atmosphere or an atmosphere containing a fluorine-based gas (mixed gas of inert gas and fluorine-based gas), oxygen. Method of plasma treatment in mixed gas atmosphere of fluorine and fluorine gas, method of plasma treatment in oxygen atmosphere and then plasma treatment in fluorine gas atmosphere, plasma treatment in fluorine gas atmosphere Any of the methods of performing plasma treatment in a post oxygen atmosphere can be performed. In the present invention, the fluorine-based gas used for the fluorination treatment includes F ₂ , NF ₃ ,
N ₂ F ₄ , N ₂ F ₂ , NOF, NO ₂ F, HF, CF ₄ , CH
F ₃ , CH ₂ F ₂ , C ₂ F ₆ , C ₃ F ₈ , SiF ₄ , SF ₆ , O
F ₂ , BF ₃ , PF ₃ , PF ₅ , ClF ₃ , WF ₆ , MoF ₆
Etc., and a mixed gas of a fluorine-based gas and another gas, for example, a fluorine-based gas and a nitrogen gas,
Alternatively, a gas in which a fluorine-based gas and oxygen gas are mixed is also effective. The fluorination treatment according to the present invention can be performed at room temperature, but heating the rare earth magnet to a required temperature is also an effective means for promoting the reaction between the rare earth magnet and the fluorine-based gas. However, if the fluorination temperature is too high, the reaction between the rare earth magnet and the fluorine-based gas will proceed too rapidly, and RF ₃ formed on the surface layer of the rare earth magnet will be generated.
The fluorination treatment is preferably performed at about 600 ° C. or lower because the formation thickness of the compound or the RO _X F _Y compound or the mixture of both compounds cannot be controlled. In the fluorination treatment of the present invention, the pressure of the fluorine-based gas varies depending on the type of the fluorine-based gas used, but the partial pressure is 10 ⁻⁸ mmH.
An atmosphere of about g or more is preferable, and a fluorination treatment time of about 1 second or more is sufficient, but the pressure of the fluorinated gas and the fluorination treatment time depend on the type of the fluorinated gas and the gas. Since it greatly varies depending on the concentration of fluorine contained, the fluorination temperature, the composition and morphology of the rare earth magnet to be treated, and the thickness of the compound to be formed, it is desirable to appropriately select the optimum conditions.

The fluorination treatment according to the present invention is characterized in that all the steps are performed by dry treatment. That is, in the fluorination treatment by the wet treatment method, elution of the magnet material is inevitable, but in the fluorination treatment by the dry treatment method,
Gas phase of fluorinated gas (gas phase) and rare earth magnet (solid phase)
Since it is a solid-phase reaction, there is almost no elution of the magnet material, and the corrosion resistance of the magnet material itself can be improved. In addition, as with conventional corrosion-resistant coatings by so-called wet treatment such as electroplating and electroless plating, it is possible to eliminate problems such as corrosion from inside the magnet due to residual acidic solvent or alkaline solvent used for pretreatment during treatment. It can exhibit extremely excellent corrosion resistance compared to conventional surface treatments. Further, by changing the atmosphere of the fluorine-based gas, the fluorination treatment time, the fluorination treatment temperature, the heat treatment condition after the fluorination treatment, etc., the RF formed on the surface layer of the rare earth magnet.
The formation thickness of the ₃ compound or the RO _X F _Y compound or a mixture of both compounds can be freely controlled. The fluorination treatment in the present invention is most preferably carried out by a dry treatment such as a method of exposing the rare earth magnet to an atmosphere containing a fluorine-based gas or an atmosphere containing a fluorine-based gas or a plasma treatment as described above. Fluorination can also be performed by so-called wet treatment such as immersing the rare earth magnet in a solvent or a solution containing a fluorine-based solvent. However, in wet fluorination treatment, the magnet material is slightly eluted.Therefore, it is possible to keep the concentration of the fluorinated solvent or the solution containing the fluorinated solvent at the optimum concentration to minimize the elution of the magnet material. desirable.

Heat Treatment In the present invention, the mechanism of the heat treatment is unknown by performing the required heat treatment after the fluorination treatment, but densification and stability of the RF ₃ compound or the RO _X F _Y compound or a mixture of both compounds, etc. This is effective because it contributes to the realization and can further improve the corrosion resistance of the rare earth magnet. If the heat treatment temperature is 200 ° C. or lower, it takes a long time to promote the densification and stabilization of the RF ₃ compound, the RO _X F _Y compound, or the mixture of both compounds, and 1200 ° C.
If it exceeds, the rare earth magnet will be melted, so that the preferable heat treatment temperature is 200 ° C to 1200 ° C, and it is preferable that the heat treatment time and the heat treatment atmosphere are appropriately selected and performed. When the above heat treatment is applied to a permanent magnet that has been subjected to an aging treatment in advance, it is preferable to perform the heat treatment within a range of 200 ° C. to the aging treatment temperature. This is because when the heat treatment exceeds the aging treatment temperature, the aging treatment effect applied in advance disappears and the magnetic properties deteriorate. Further, it is possible to perform the aging treatment after performing the heat treatment at the aging treatment temperature or higher, or to perform the aging treatment at the same time as the heat treatment.

[0017]

According to the present invention, the rare earth magnet is exposed to a fluorine-containing gas atmosphere or an atmosphere containing a fluorine-containing gas for fluorination treatment, whereby the RF ₃ compound or the RO _X F _Y compound or both of them is formed on the surface layer of the rare earth magnet. By forming a stable compound composed of a mixture of compounds or further subjecting it to a required heat treatment, the densification and stabilization of the compound can be further promoted, and the corrosion resistance of the rare earth magnet can be remarkably improved. Further, since the fluorination treatment according to the present invention is a gas-solid reaction between a fluorine-based gas (gas phase) and a rare earth magnet (solid phase), there is almost no elution of the magnet material during the treatment, and further electrolysis Since the problem of residual acidic solvent or alkaline solvent due to so-called wet treatment such as plating or electroless plating can be solved, excellent corrosion resistance can be obtained without performing surface treatment, and also as a surface treatment during surface treatment. Shows excellent effects.

[0018]

【Example】

Example 1 As a sample, the composition was Nd _31.5 B _1.15 balance Fe (% by weight)
A sample obtained by subjecting the R-T-B system sintered permanent magnet consisting of 10 to the whole surface grinding process is inserted into a container capable of sucking and exhausting, and the inside of the container is evacuated to 10 ^-5 mmHg or less, then F ₂ and N _2. A mixed gas of ₂ (10% F ₂ , 90% N ₂ , purity 99.9%) was introduced into a 10 ^-2 mmHg container, and the sample was left for 10 minutes for fluorination treatment, and the magnet surface layer was exposed to RF. A magnet according to the present invention was obtained in which a ₃ compound and a RO _X F _Y compound or a mixture of both compounds were formed (Sample No. 1). When the thickness of the compound formed in the above sample was measured by EPMA, the formed thickness of the compound was about 10 μm.
In addition, the P. C. A T test (temperature 125 ° C., humidity 85%, pressure 2 atm) was performed for 12 hours and 120 hours, and corrosion resistance was evaluated by comparing the amount of weight change due to oxidation after the test. The test results are shown in Table 1.

Example 2 A sample obtained by processing an RTB based sintered permanent magnet having the same composition as in Example 1 was subjected to the same fluorination treatment as in Example 1, and then 10 ^-5 mmHg or less. After evacuation to vacuum, the container was heated to a temperature of 400 ° C. and held for 60 minutes, and then the magnet according to the present invention was formed with the RF ₃ compound and the RO _X F _Y compound or a mixture of both compounds on the surface layer of the magnet. Obtained (Sample No. 2). When the thickness of the compound formed in the above sample was measured by EPMA, the formed thickness of the compound was about 10 μm. In addition, the same P.I. C. Table 1 shows the results of evaluating the corrosion resistance by performing a T test and comparing the amount of weight change due to oxidation after the test.

Example 3 A sample obtained by processing an RTB sintered permanent magnet having the same composition as in Example 1 was inserted into a container capable of sucking and discharging, and the inside of the container was controlled to 10 ⁻⁵ mmHg or less. After evacuation, the container is heated to a temperature of 200 ° C., NF ₃ (nitrogen trifluoride: purity 99.9%) is further introduced into the 10 ⁻⁴ mmHg container, and the sample is left for 30 minutes. After the chemical treatment, it is heated at 400 ° C. in a vacuum atmosphere of 10 ⁻⁵ mmHg or less for 6
Heat treatment for 0 minutes was performed to obtain a magnet according to the present invention in which the RF ₃ compound and the RO _X F _Y compound or a mixture of both compounds were formed on the surface layer of the magnet (Sample No. 3). When the thickness of the compound formed on the above sample was measured by EPMA, the formed thickness of the compound was about 5 μm. In addition, the same P.I. C. The T test was performed and the test results are shown in Table 1.

Example 4 A sample obtained by processing an R-T-B system sintered permanent magnet having the same composition as in Example 1 was inserted into a container capable of sucking and discharging, and the inside of the container was controlled to 10 ^-5 mmHg or less. After evacuation, the inside of the container is heated to a temperature of 400 ° C., CF ₄ (tetrafluoromethane: purity 99.9%) is further introduced into the 10 mmHg container, and the sample is allowed to stand for 10 minutes for fluorination. Thus, a magnet according to the present invention was obtained in which the RF ₃ compound and the RO _X F _Y compound or a mixture of both compounds were formed on the surface layer of the magnet (Sample No. 4). When the thickness of the compound formed in the above sample was measured by EPMA, the formed thickness of the compound was about 20 μm. In addition, the same P.I. C. The T test was performed and the test results are shown in Table 1.

Example 5 An R-T-B system sintered permanent magnet having the same composition as in Example 1 was processed, and then a sample aged at 500 ° C. for 60 minutes was placed in a container capable of sucking and discharging. Insert and put 10 ^-5 m inside the container
After evacuation to mHg or less, HF (hydrogen fluoride:
(Purity 99.9%) The sample was left for 1 minute in the flowing atmosphere, then fluorinated, and then heat-treated at 500 ° C. for 60 minutes in a vacuum atmosphere of 10 ⁻⁵ mmHg or less to give a magnet. A magnet according to the present invention was obtained in which the RF ₃ compound and the RO _X F _Y compound or a mixture of both compounds were formed on the surface layer (Sample No. 5). When the thickness of the compound formed in the above sample was measured by EPMA, the formed thickness of the compound was about 100 μm. In addition, the same P.I. C. T test was conducted and the test results are shown in Table 1.
Shown in.

Comparative Example An RTB-based sintered permanent magnet having the same composition as that of the example was processed only after sintering but not subjected to fluorination (sample No. 6), and the composition. Is Nd _31.5 B _1.15 Co
_{5.0 The} balance consists of Fe (wt%) and Co is added to the RTB sintered permanent magnet to improve the corrosion resistance of the material in advance.
There was obtained a sample (Sample No. 7) which was processed after sintering but not subjected to fluorination at all. For the sample of the above comparative example, the same P.I. C. The T test was performed and the test results are shown in Table 1.

[0024]

[Table 1]

As is apparent from Table 1, the magnet not subjected to the fluorination treatment (Sample No. 6) was manufactured by P.P. C. Under a harsh environment such as the T test, the oxidation significantly progresses with the passage of time, and the weight changes drastically. In addition, a magnet in which the corrosion resistance of the material has been previously improved by adding Co (Sample No. 7)
Even then, oxidation is progressing over time,
Inferior corrosion resistance. On the other hand, the rare earth magnets (Sample Nos. 1 to 5) according to the present invention which have been subjected to the fluorination treatment, even those which are desired to be subjected to the fluorination treatment under various conditions, are oxidized under extremely severe conditions. It can be seen that it has excellent corrosion resistance. In particular, magnets that were heat treated after being fluorinated (Sample Nos. 2, 3,
5) is a P. C. It can be seen that there is no change in weight due to the T test and that it has extremely excellent corrosion resistance. This is because the RF ₃ compound and the RO _X F _Y compound, or a mixture of both compounds, which are extremely stable against moisture and the like, are formed on the surface layer of the fluorinated rare earth magnet according to the present invention. .

Further, according to the first embodiment, the magnet fluorinated in the atmosphere containing the fluorine-based gas (Sample N
o. For each of the magnets (Sample No. 2) which had been subjected to fluorination treatment in an atmosphere containing a fluorine-based gas according to Example 1) and Example 2 and further heat treatment, X-ray diffraction (target) Cu-kα was used). The result of X-ray diffraction is shown in FIG.
Shown in. In addition, A of FIG. Example 2 magnet of No. 2, B is sample No. 1 shows the result of X-ray diffraction of an untreated magnet (Sample No. 6). As is clear from FIG. 1, regarding the untreated magnet (Sample No. 6) which was not subjected to the fluorination treatment, N which is the constituent layer of the magnet was used.
It can be seen that d ₂ Fe ₁₄ B and Nd are present. As described above, these Nd ₂ Fe ₁₄ B and Nd are very easily oxidized, and once an oxide is formed, these oxides are hygroscopic, so that the surface of the magnet is easily exposed to the atmosphere. Reacts with water to cause volume expansion and R ₂ F
This causes the particles constituting the magnet phase, including the e ₁₄ B phase, to shed and fall off. On the other hand, regarding the one subjected to the fluorination treatment (Sample No. 1) and the one subjected to the heat treatment after the fluorination treatment (Sample No. 2), the above-mentioned Nd of the magnet surface layer portion was used.
It can be seen that a compound of a rare earth element and fluorine mainly containing NdF ₃ and NdOF or a mixture of both compounds is present. As described above, by subjecting the rare earth magnet to fluorination treatment, or by subjecting the rare earth magnet to further heat treatment, the rare earth magnet constituent phases, such as rare earth elements and their oxides, which adversely affect the corrosion resistance, can be removed. _A compound of rare earth element and fluorine mainly composed of ₃ or NdOF or a mixture of both compounds can be used, and the corrosion resistance of the material itself of the rare earth magnet can be greatly improved.

[0027]

INDUSTRIAL APPLICABILITY According to the present invention, a rare earth magnet is subjected to a fluorination treatment in a fluorine-based gas atmosphere or in an atmosphere containing a fluorine-based gas, and the surface layer of the rare earth magnet is provided with an RF ₃ compound which is stable to corrosion resistance or By forming a RO _X F _Y compound or a mixture of both compounds, or by further subjecting it to a required heat treatment, the corrosion resistance of the raw material of the rare earth magnet itself can be greatly improved. Further, the fluorination treatment according to the present invention is very easy to perform, and since it is a gas-solid reaction between the fluorine-based gas (gas phase) and the rare earth magnet (solid phase), the magnet during the treatment is processed. Almost no elution of the material, furthermore, acidic solvent by so-called wet treatment such as electrolytic plating and electroless plating,
In addition to solving the problem of residual alkaline solvent and improving the corrosion resistance of the rare earth magnet material itself, it exhibits an excellent effect as a surface treatment during surface treatment, and even without any particular surface treatment, It is possible to use the rare earth magnet in a harsh environment.

[Brief description of drawings]

FIG. 1 is a diffraction pattern diagram showing an X-ray diffraction result of a magnet surface layer portion, where A is sample No. Example 2 magnet of No. 2, B is sample No. Example 1 of 1 magnet, C is an untreated magnet (Sample N
o. The result of X-ray diffraction of 6) is shown.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication location H01F 7/02 Z (72) Inventor Akinori Tasaka 14-14, Katsuyama-cho, Ohara Nogami-sato, Nishikyo-ku, Kyoto Prefecture 9

Claims (3)

[Claims] 1. A rare earth magnet (containing at least one kind of rare earth element R) has an RF ₃ compound or RO _{X on} a surface layer portion thereof.
A rare earth magnet having excellent corrosion resistance, which comprises an F _Y compound or a mixture of both compounds. 2. A rare earth magnet (containing at least one kind of rare earth element R) is fluorinated in a fluorine gas atmosphere or an atmosphere containing a fluorine gas, and an RF ₃ compound is added to the surface layer of the magnet. Alternatively, a method for producing a rare earth magnet having excellent corrosion resistance, which comprises forming a RO _X F _Y compound or a mixture of both compounds. 3. A rare earth magnet (containing at least one kind of rare earth element R) is fluorinated in a fluorine-containing gas atmosphere or an atmosphere containing a fluorine-containing gas to form an RF ₃ compound on the surface layer portion of the magnet. Alternatively, after forming a RO _X F _Y compound or a mixture of both compounds, an additional 20
A method for producing a rare earth magnet having excellent corrosion resistance, which comprises performing heat treatment at a temperature of 0 ° C to 1200 ° C.