JP2002353057A - Rare earth permanent magnet having superior oxidataion resistance, and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an oxidation resistive film, having superior reliability on a surface of a rare earth permanent magnet made of Nd2 Fe14 B-based alloy as a typical material. SOLUTION: Electrolysis is carried out in an electrolytic solution, having a triazone dithiol derivative dissolved into an organic solvent with use of a rare earth permanent magnet as an anode to form a film obtained by the electrolysis of the composition on the surface of the magnet, an oxidation resistive film is formed by metal plating on the obtained oxidation resistive film, and further a film obtained by the triazone dithiol derivative is formed thereon. Water, which causes rust, is not used for the formation of the film using triazone dithiol derivative, the formed film is water repellent but is not oriented. Thus the film is higher in reliability than a prior art oxidation resistive film. Since films made by metal plating and using triazone dithiol derivative are further formed on the above film, the reliability to oxidation is improved significantly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention is represented by Nd ₂ Fe ₁₄ B-based alloy, rare earth elements: and R, a transition metal: relates R ₂ T ₁₄ B system intermetallic compound magnet comprising a T, particularly acid TECHNICAL FIELD The present invention relates to an R ₂ T ₁₄ B-based rare-earth permanent magnet having improved chemical properties and a method for producing the same.

[0002]

2. Description of the Related Art R-Fe- represented by Nd-Fe-B
The B-based magnet has higher magnetic characteristics than a conventional rare-earth permanent magnet, Sm-Co-based magnet. However, such a magnetic alloy contains Nd-
Since it contains an Fe alloy phase and R ₂ Fe ₁₄ B is also easily oxidized, deterioration and variation in magnetic properties due to oxidation of the magnet are greater than Sm—Co.

[0003] Further, when incorporated in a device such as a magnetic circuit, there is a possibility that contamination of peripheral components may be caused by scattering of oxides generated from the magnet.

As a method for solving this problem, Japanese Patent Laid-Open Publication No.
JP-A-54406 and JP-A-60-63903 have been proposed. However, the oxidation-resistant coatings proposed in these publications use a large amount of water during the coating formation process, so that the magnet material is oxidized during the treatment process,
Even after the treatment, a small amount of moisture remains often causes oxidation, and it is hard to say that the oxidation resistance is sufficient.

[0005] In the coating method, which is a general method of surface treatment for rust prevention of metal, since the base material of the coating is an organic polymer,
Insufficient affinity for metal, which easily causes cracking and peeling during the process of forming and using magnet parts.Especially in the case of reaction-curable coatings, changes over time of traces of unreacted functional groups It may cause rusting, and in particular, the reliability of such an alloy system is insufficient, and the application is currently limited.

Further, the oxidation prevention method by forming a metal film using sputtering or ion vapor deposition is difficult because it is difficult to uniformly coat the entire magnet and the coating layer structure has directionality in the direction perpendicular to the underlying surface. In addition, there is a problem that minute gaps are formed in the coating layer and sufficient oxidation resistance cannot be expected.

[0007]

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a rare earth permanent magnet having better oxidation resistance and a method for producing the same in view of the above-mentioned drawbacks.

[0008]

SUMMARY OF THE INVENTION The present invention provides a conventional coating,
By using electrolytic plating, sputtering, ion deposition, etc., and completely different from these methods,
This is a result of studying a method of forming a stronger oxidation-resistant film on an R ₂ T ₁₄ B-based rare earth permanent magnet.

That is, the present invention comprises RTB as a main component.
R_TwoT₁₄B-based alloy [R: rare earth containing yttrium (Y)
At least one or more of the earth elements, T: transition metal,
B: boron] on the surface of the sintered rare earth permanent magnet
Any of positions 2, 4, and 6 of 1,3,5-triazine
Is -R, the remainder is -SM [R is SH or NR₁R_TwoAnd R
₁, R_TwoIs any of hydrogen, an alkyl group and a phenyl group, M
Is hydrogen, alkali metal, or alkaline earth metal,
S is sulfur, N is nitrogen]
Formed by at least one electrolysis of
A first oxidation resistant coating, and a first oxidation resistant coating formed on the first oxidation resistant coating.
Second oxidation-resistant coating made of plated coating formed
And a first oxidation-resistant film formed on the second oxidation-resistant film.
A third oxidation-resistant coating having the same configuration as the oxidation-resistant coating;
It is a rare earth permanent magnet characterized by having.

Further, the present invention provides an R ₂ T ₁₄ B-based alloy containing R—T—B as a main component [R: at least one or more rare earth elements including yttrium (Y);
B: Boron] sintered rare earth permanent magnet
-R any position 2,4,6 triazine, is -SM [R a balance with SH or _{NR 1 R 2, R 1,} R 2 is hydrogen, an alkyl group, or a phenyl group, M is Any one of hydrogen, an alkali metal and an alkaline earth metal, S is sulfur, and N is nitrogen]. A first oxidation-resistant film is formed on the surface, and a second oxidation-resistant film made of a plating film is formed on the first oxidation-resistant film by at least one of electrolytic plating and electroless plating. And forming a third oxidation-resistant coating on the second oxidation-resistant coating in the same procedure as in the case of the first oxidation-resistant coating. It is.

The present invention also provides a method for producing a rare earth permanent magnet as described above, wherein the solvent of the solution is an organic solvent.

The present invention also provides a method for producing a rare-earth permanent magnet, wherein the temperature of the solution is 0 to 80 ° C.

Further, according to the present invention, in the above-mentioned method for producing a rare earth permanent magnet, the electrolytic treatment for obtaining the first oxidation-resistant film and the third oxidation-resistant film is performed by applying a voltage of 20 V or less (0
), And the current density is 10 mA / dm ² to 10 A / d
A method for producing a rare earth permanent magnet, characterized in that the method is performed in the range of m ² .

Further, according to the present invention, in the above-mentioned method for producing a rare earth permanent magnet, the electrolytic treatment time for obtaining the first oxidation-resistant film and the third oxidation-resistant film is 0.1 seconds to 10 minutes. A method for manufacturing a rare earth permanent magnet.

[0015]

According to the method for forming an oxidation-resistant coating of the present invention, the triazinedithiol derivative is ionized in the electrolytic solution to generate negative ions. The negative ions provided by are electrodeposited to form a film.

Further, by forming a metal film by plating on the oxidation-resistant film obtained from the triazinethiol derivative, and further forming an oxidation-resistant film obtained from the triazinethiol derivative on the oxidation-resistant film, the oxidation-resistant film is formed. And a rare earth permanent magnet having extremely high oxidation resistance can be obtained.

The film formed on the magnet surface from the triazinedithiol derivative has extremely excellent corrosion resistance and durability and has a large bonding force with the metal surface as compared with conventional conversion films. Furthermore, since water repellency and lubricity are provided, it is possible to prevent water landing, icing, and the like. In addition, a thin film that is difficult to peel off can be formed inexpensively in a short time.

The electrolytic solution can be prepared by dissolving the triazinedithiol derivative in an organic solvent.
The reason for using an organic compound as the solvent is that when water is used as the solvent, rust on the surface of the magnet cannot be completely prevented due to water remaining in the coating.

The organic solvent is not particularly limited as long as it is a liquid having a low viscosity in a temperature range of 0 to 80 ° C., and most of them can be used. For example, alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, and ethyl cellosolve, ketones such as acetone and methyl ethyl ketone, amides such as dimethylformamide, esters such as ethyl acetate, furans such as tetrahydrofuran, benzene, and toluene And the like can be used. The concentration of the solution is from 1 × 10 ⁻¹ to 1 × of the triazonedithiol compound.
10 ⁻⁶ mol / l, preferably 5 × 10 ^{−2 to} 5 × 10
^-4 mol / l.

In addition, an insoluble material is used for the cathode in order to prevent a substance eluted from the cathode from being mixed into the coating. Such materials include, for example, platinum, titanium, stainless steel, carbon, graphite, and the like.

In the electrolysis, the temperature of the solution is adjusted to 0 to 80 ° C., the voltage is 20 V or less, and the current density is 10 mA / dm ² to 10
Electrolyze at A / dm ² for 0.1 second to 10 minutes. The reason for limiting the temperature of the solution is that if the temperature is lower than 0 ° C., it takes a long time to form the coating, and if it is higher than 80 ° C., it becomes difficult to control the thickness of the coating. .

The reason for limiting the voltage is that the voltage is
If it is higher than V, the formation of the coating on the magnet surface becomes non-uniform. Furthermore, the reason for limiting the current density is that
If the current density is less than 10 mA / dm ² , no film is formed, and if the current density is more than 10 A / dm ² , the film formation becomes non-uniform.

The reason why the electrolysis time is limited is that if the electrolysis time is less than 0.1 second, a coating cannot be formed on the entire magnet surface even if the current density is 10 A / dm ² , and the electrolysis time exceeds 10 minutes. This is because the coating functions as an insulator, so that electrolysis is substantially impossible.

In general, a salt or the like which is hardly subjected to oxidation and reduction at an electrode is added to a solution used for electrolysis as a supporting electrolyte in order to improve the conductivity of the solution or to reduce the electrophoretic current. The addition of the supporting electrolyte exhibits a certain effect.

The oxidation-resistant plating film formed on the oxidation-resistant film made of the triazinethiol derivative includes:
An oxidation-resistant metal or alloy such as Ni, Cu, or Zn is used, and composite plating of these metals is also applicable.
Plating methods include electroless plating, electrolytic plating,
Alternatively, these may be used in combination.

If the thickness of the plating film exceeds 25 μm, the strength of the plating film deteriorates, it becomes difficult to secure the dimensional accuracy of the product, and it takes a long time for the plating process. From the viewpoint of manufacturing cost, the thickness of the plating film is preferably 25 μm or less.

[0027]

The present invention will be described below with reference to specific examples.

(Example 1) Nd with a purity of 99% or more, electrolytic iron with a purity of 99%, and a ferroboron alloy were weighed in required amounts, melted by high frequency heating in an argon atmosphere and cast, and 64.9 wt% Fe- An ingot of 34% by weight Nd-1.1% by weight B was obtained. Next, the ingot was roughly pulverized with a disk mill and further finely pulverized with a ball mill to obtain a raw material powder having an average particle diameter of 3 μm.

This raw material powder was molded at a pressure of 10 kPa in a magnetic field of 1600 kA / m. The obtained molded body is
After vacuum sintering at 050 to 1100 ° C for 2 hours, the resultant was furnace-cooled to obtain a sintered body. This sintered body was heat-treated at 500 to 600 ° C for 1 hour and then rapidly cooled. The rare earth permanent magnet thus obtained was cut into a cubic shape with one side of 10 mm, and used as a test piece for evaluating oxidation resistance.

Next, as a triazine dithiol derivative, 2-dibutylamino-4,6-dithiol-triazine shown in Chemical Formula 1 was used as a supporting electrolyte so as to have a concentration of 5 × 10 ^-2 mol / l. Lithium oxide (LiCl
O ₄ ) was dissolved in ethyl alcohol at a ^{concentration} of 5 × 10 ⁻⁴ mol / l to prepare an electrolytic solution.

[0031]

Embedded image

Next, using the electrolytic solution, the test piece washed with acetone was placed on the anode, stainless steel (SUS30).
4) Using a steel plate as a cathode, electrolysis was performed at a solution temperature of 25 to 30 ° C. and a current density of 1.0 to 2.0 A / dm ² for 10 to 240 seconds to obtain a first oxidation-resistant coating.

Thereafter, the test piece was subjected to a current density of 2.0 A using a Watt bath having a solution temperature set at 50 ° C. as a plating bath.
/ Dm ² to change the processing time, the thickness is 3, 5, 10 μm
A second oxidation-resistant film made of nickel plating was formed. In addition, another test piece was prepared by changing the treatment time at a current density of 2.0 A / dm ² using a bluing bath having a solution temperature of room temperature as a plating bath, and changing the copper plating of 3, 5, and 10 μm in thickness. A second oxidation resistant coating was formed. Further, with respect to another test piece, zinc plating having a thickness of 3, 5, and 10 μm was performed by changing the treatment time at a current density of 2.0 A / dm ² using a bluing bath having a solution temperature of 30 ° C. as a plating bath. A second oxidation-resistant film was formed.

Further, a test piece on which a second oxidation-resistant film made of these platings was formed was coated with the above-mentioned electrolytic solution containing 2-dibutylamino-4,6-dithiol-triazine and lithium perchlorate. A third oxidation-resistant film was formed under exactly the same conditions as described above.

For comparison, the first condition was the same under the same conditions as above.
On the test piece on which the oxidation-resistant coating was formed, only the plating layer of nickel, copper, and zinc was formed using the plating bath described above.
Test pieces formed to have thicknesses of 5, 10, and 15 μm, respectively, were prepared. These test pieces were subjected to a test of spraying a 5% saline solution for 72 hours and a grid test. Table 1 shows the results of the test pieces having three oxidation-resistant films formed thereon, and Table 2 shows the results of the test pieces having two oxidation-resistant films formed thereon.

[0036]

[Table 1]

[0037]

[Table 2]

Example 2 As a triazine dithiol derivative, 2-oleylamino-4,6-dimercapto-triazine monosodium shown in Chemical formula 2 was used at a concentration of 5 ×.
Lithium fluoroborate (LiBF ₄ ) was used as a supporting electrolyte at a concentration of 5 × 1 so as to be 10 ⁻⁴ mol / l.
Each was dissolved in ethyl alcohol so as to be 0 ⁻⁴ / l to prepare an electrolytic solution. Using this electrolytic solution, electrolysis was performed on the rare-earth permanent magnet prepared under the same conditions as in Example 1 in the same manner as in Example 1 to form a first oxidation-resistant film.

[0039]

Embedded image

Thereafter, a current density of 2.0 A was applied to the test piece using a Watt bath in which a solution temperature was set to 50 ° C. as a plating bath.
/ Dm ² to change the processing time, the thickness is 3, 5, 10 μm
A second oxidation-resistant film made of nickel plating was formed. As for another test piece, a bluing bath in which the solution temperature was set to room temperature was used as a plating bath, and the current density was 2.0 A / d.
The treatment time was changed by m ² to form a second oxidation-resistant film made of copper plating having a thickness of 3, 5, or 10 μm. Further, for another test piece, the solution temperature was set to 30 ° C. in the plating bath.
Using a bluing bath set as described above, the treatment time was changed at a current density of 2.0 A / dm ² , and a second oxidation-resistant coating made of zinc plating having a thickness of 3, 5, or 10 μm was formed.

Further, the test piece on which the plating layer was formed,
Using the electrolyte containing 2-oleylamino-4,6-dimercapto-triazine monosodium and lithium fluoroborate, a third oxidation-resistant film was formed under exactly the same conditions as above.

For comparison, the first condition was the same under the same conditions as above.
On the test piece on which the oxidation-resistant coating was formed, only the plating layer of nickel, copper, and zinc was formed using the plating bath described above.
Test pieces formed to have thicknesses of 5, 10, and 15 μm, respectively, were prepared. These test pieces were subjected to a test of spraying a 5% saline solution for 72 hours and a grid test. Table 3 shows the results of the test pieces on which the three oxidation-resistant films were formed, and Table 4 shows the results of the test pieces on which the two oxidation-resistant films were formed.

[0043]

[Table 3]

[0044]

[Table 4]

As shown in Tables 1 and 3, the test pieces having the three oxidation-resistant coatings formed on the surface by the method of the present invention show no rust or the like and show no change in appearance. Not observed. On the other hand, as shown in Tables 2 and 4, in the test pieces having no third acid-resistant coating formed thereon, even if the thickness of the metal plating layer was the same, significant corrosion was observed, and The effect of the three-layer oxidation resistant coating was apparent.

[0046]

As described above, according to the present invention, an oxidation-resistant coating obtained by electrolysis of a triazinethiol derivative, an oxidation-resistant coating made of a metal plating layer, and an acid-resistant coating obtained by electrolysis of a triazinethiol derivative. Thus, a rare earth permanent magnet having an oxidation-resistant coating having a three-layer structure obtained by sequentially laminating and coating the oxidizable coating is obtained. These coatings are thinner than conventional coatings, exhibit excellent corrosion resistance, and can significantly improve the reliability and durability of rare earth permanent magnets.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C25D 13/12 C25D 13/12 Z H01F 1/053 H01F 7/02 E 7/02 1/04 HF term (Reference) 4K018 AA27 FA23 FA25 FA27 KA45 4K024 AA03 AA05 AA09 AA14 AA17 AB03 AB15 BA01 BB14 BC07 GA04 4K044 AA02 AB08 AB10 BA06 BA10 BA21 BB04 BC02 CA15 CA17 CA18 CA53 5E040 AA04 BC01 BC08 BD02 CA01 HB14CG

Claims (6)

[Claims] 1. An R having RTB as a main component._TwoT₁₄B type
Alloy [R: Of rare earth elements containing yttrium (Y)
At least one or more, T: transition metal, B: boron]
The surface of a sintered rare earth permanent magnet
-R at any of positions 2, 4, and 6 of azine, and-
SM [R is SH or NR₁R_TwoAnd R ₁, R_TwoIs hydrogen,
Any of a alkyl group or a phenyl group, M is hydrogen or an alkali
Either metal or alkaline earth metal, S is sulfur, N is
Nitrogen] substituted triazinedithiol derivatives
First oxidation resistance formed by one kind of electrolysis
A film formed on the first oxidation-resistant film.
A second oxidation-resistant coating comprising a coating film and a second oxidation-resistant coating
The same as the first oxidation resistant coating formed on the coating
Having a third oxidation-resistant coating having the configuration
Rare earth permanent magnet. _2. An R ₂ T ₁₄ B-based alloy mainly composed of RTB [R: at least one or more rare earth elements including yttrium (Y), T: transition metal, B: boron] Sintered rare earth permanent magnets were replaced with 1,3,5-triazine 2,
One of positions 4 and 6 is -R, and the remainder is -SM [R is S
H or NR ₁ R ₂ , where R ₁ and R ₂ are hydrogen, any of an alkyl group and a phenyl group, M is hydrogen, any of an alkali metal or an alkaline earth metal, S is sulfur, and N is nitrogen] Electrolytic treatment in at least one solution of the prepared triazinedithiol derivative to form a first oxidation-resistant film on the surface of the sintered rare-earth permanent magnet, and on the first oxidation-resistant film Forming a second oxidation-resistant film made of a plating film by at least one of electrolytic plating and electroless plating, and forming the first oxidation-resistant film on the second oxidation-resistant film.
The method for producing a rare-earth permanent magnet according to claim 1, wherein the third oxidation-resistant film is formed in the same procedure as in the case of the oxidation-resistant film described in (1). 3. The method for producing a rare earth permanent magnet according to claim 2, wherein the solvent of the solution is an organic solvent. 4. The method for producing a rare earth permanent magnet according to claim 2, wherein the temperature of the solution is 0 to 80 ° C. 5. The method for producing a rare earth permanent magnet according to claim 2, wherein the electrolytic treatment for obtaining the first oxidation-resistant film and the third oxidation-resistant film is performed by:
Voltage 20V or less (excluding 0), current density 10mA
A method for producing a rare earth permanent magnet, wherein the method is performed in the range of / Am / dm ^{2 to} 10 A / dm ² . 6. The method for producing a rare earth permanent magnet according to claim 2, wherein the electrolytic treatment time for obtaining the first oxidation-resistant film and the third oxidation-resistant film is set to 0. . A method for producing a rare earth permanent magnet, wherein the time is from 1 second to 10 minutes.