JP2002105690A - ELECTROPLATING METHOD FOR R-Fe-B BASED PERMANENT MAGNET - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electroplating method by which R-Fe-B based permanent magnets having plating films exhibiting excellent corrosion resistance even though they are thin can stably be mass-produced. SOLUTION: In this electroplating method in which a plurality of pieces of R-Fe-B based permanent magnets composed of a main phase and a plurality of crystal phases of grain boundary phases having corrosion potential baser than that of the main phase are simultaneously subjected to electroplating, the individual magnets are disposed in a separated state, and film deposition is performed at an average film deposition rate of >=0.1 μm/min from the start of the plating until a plating film with a film thickness of 0.5 μm is deposited on the surfaces of the magnets.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroplating method capable of stably mass-producing an R-Fe-B-based permanent magnet having a plating film exhibiting excellent corrosion resistance even on a thin film.

[0002]

2. Description of the Related Art R-Fe-B permanent magnets represented by Nd-Fe-B permanent magnets have high magnetic properties and are used in various fields today. The magnet contains a metal species (particularly R) that is susceptible to oxidative corrosion in the atmosphere. Therefore, when used without performing surface treatment, corrosion proceeds from the surface due to the influence of a slight acid, alkali, moisture, etc., and rust is generated, which leads to deterioration and variation in magnetic characteristics. Will be. Further, when rust is generated on a magnet incorporated in a device such as a magnetic circuit, the rust may scatter and contaminate peripheral components. In order to avoid these problems, conventionally, a plating film as a corrosion-resistant film is formed on the surface of the magnet by performing electroplating to impart the required corrosion resistance to the magnet. When performing electroplating, a barrel-type electroplating method is widely used from the viewpoint that mass processing is possible.

[0003]

In the barrel type electroplating method, a large number of magnets and media (steel balls, etc.) to be processed are accommodated in a barrel, and the barrel is immersed in a plating bath. While rotating and stirring the magnet and media inside, the magnet is energized from the barrel electrode through the media to form a plating film on the surface of the magnet, which is an excellent method in terms of mass productivity. As described above. By the way, in recent years, miniaturization of parts using magnets has been progressing, and accordingly, surface treatment of magnets is also required to respond to thinning. However, when a thin plating film is formed by the barrel-type electroplating method, there is a problem that the corrosion resistance among the magnets varies widely, and some magnets that rust quickly are found. Therefore, an object of the present invention is to provide an electroplating method capable of stably mass-producing an R-Fe-B-based permanent magnet having a plating film exhibiting excellent corrosion resistance even on a thin film.

[0004]

Means for Solving the Problems The present inventor has obtained the following knowledge by analyzing why the above-mentioned problems occur when a thin plating film is formed by a barrel type electroplating method. (1) First, among the magnets coated by the barrel-type electroplating method, there are many pinholes in the coating of the magnet having poor corrosion resistance, which causes the variation of the corrosion resistance between the magnets. I have. (2) Since magnets and media exist in the barrel as an aggregate, the magnets outside the aggregate are well energized and are easily plated, but the magnets inside are immersed in the plating solution. It is only present and is in a state of being easily corroded. Of course, the magnet and the media are agitated, but the thinner the plating film that is formed, the greater the effect of the magnet being simply immersed in the plating solution, which causes pinholes in the plating film. Become. Furthermore, once the magnet is corroded, the plating solution remains in the corroded portion during plating,
Even after the film is formed, the plating solution remaining inside causes the corrosion of the magnet to proceed. (3) In particular, the grain boundary phase having a less noble corrosion potential than the main phase as a main phase _(Nd 2 _{Fe 1 4} B phase) as the sintered magnet of Nd-Fe-B permanent magnets (Nd-rich phase) In a magnet composed of a plurality of crystal phases, the grain boundary phase is essentially a phase with a very low corrosion potential and, in addition, has a large corrosion potential difference from the main phase. This hinders the formation of a uniform plating film and causes pinholes. Such corrosion of the magnet greatly affects the corrosion resistance even when performing multilayer plating for the purpose of improving the corrosion resistance. (4) The Nd-Fe-B permanent magnet has a strong tendency to cause deterioration of magnetic properties and decrease in adhesion to a plating film, particularly when the grain boundary phase absorbs hydrogen generated during plating. Therefore, when plating, it is necessary to reduce the current density in order to suppress the generation of hydrogen. In the case of the barrel-type electroplating method, since the metal ion concentration in the barrel tends to be small, hydrogen is more likely to be generated, and the hydrogen generated inside the aggregate is likely to stay at the place, In order to minimize hydrogen generation, it is necessary to set the current density to a lower value. for that reason,
The average film forming rate naturally becomes slow, and the time during which the magnet is immersed in the plating solution becomes longer, which further promotes the corrosion of the magnet. (5) Further, as described in (2), the magnets with good energization are limited to those existing outside the assembly, and the actual current densities of the individual magnets with respect to the set current density vary. There is. A large amount of hydrogen is generated in a portion where a current density higher than the set current density is applied (4).
Causes problems as described in
The current density must be set in consideration of the variation, and the value naturally becomes low. As a result, variations in corrosion resistance due to corrosion of the magnet by the plating solution are promoted. (6) Further, since the number of magnets existing outside the aggregate is limited by the presence of the media, there is a tendency that the corrosion of the magnets and the generation of pinholes in the formed film are more likely to occur. As a means for suppressing the corrosion of the magnet as much as possible, a method of increasing the stirring speed of the magnet and the media inside the barrel by increasing the rotation speed of the barrel can be considered, but if this method is adopted, collision between magnets or The collision between the magnet and the medium frequently occurs or occurs due to a strong impact force, and as a result, a large number of cracks or chips are generated in the magnet, which is not preferable. (7) Then, due to such corrosion of the magnet, metal components constituting the magnet, such as Nd and Fe, are eluted into the plating solution. For example, when Ni plating is performed, of the eluted metal components, Fe is eutectoid with Ni and forms a film having poor corrosion resistance when the current density is low. Nd inhibits stable precipitation of Ni by an ion adsorption phenomenon, and causes poor adhesion of the coating. In the barrel electroplating method, the current density must be set to a low value because the energization state of individual magnets varies as described above, and thus, it is necessary to suppress the deposition of a film having poor corrosion resistance. It is difficult. Therefore, in mass production, it is difficult to form a high-quality and uniform film, which causes variation in quality between lots.

As a result of various studies based on the above findings, the present inventor has found that in order to stably mass-produce rare earth permanent magnets having a plated film exhibiting excellent corrosion resistance even on a thin film, a barrel-type permanent magnet is required. I realized that it is important not to use the electroplating method and to form a plating film quickly at the early stage of plating. The present invention has been made under the circumstances as described above, and the electroplating method of the present invention has a main phase and a grain boundary phase having a lower corrosion potential than the main phase. R-Fe- consisting of multiple crystal phases
In a method of electroplating a plurality of B-based permanent magnets simultaneously, the individual magnets are separated from each other,
In addition, a film is formed at an average film forming rate of 0.1 μm / min or more from the start of plating until a plating film having a thickness of 0.5 μm is formed on the magnet surface. The electroplating method according to claim 2 is characterized in that, in the electroplating method according to claim 1, a film is formed under the condition that the current density is 20 A / dm ² or less. The electroplating method according to claim 3 is characterized in that, in the electroplating method according to claim 1 or 2, the plating is any one of Ni plating, Zn plating, and Cu plating. Further, the electroplating method according to claim 4 is a method according to claims 1 to 3.
Wherein the thickness of the plating film is 1 μm to 25 μm.
Further, R-Fe-B having a plating film on the surface of the present invention.
As described in claim 5, the system-based permanent magnet is obtained by the electroplating method according to any one of claims 1 to 4.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The electroplating method of the present invention comprises a plurality of R-Fe-B-based permanent magnets comprising a plurality of crystal phases of a main phase and a grain boundary phase having a lower corrosion potential than the main phase. In the plating method, the individual magnets are set in a state where the magnets are separated from each other, and the film thickness is 0.5 mm from the start of plating.
0.1μm until a μm plating film is formed on the magnet surface
The film is formed at an average film forming speed of at least m / min. That is, in the electroplating method of the present invention, the magnets are separated from each other without gathering so that a plurality of magnets do not form an aggregate, and the average film forming speed in the initial plating is set to a certain value or more. By immersing the magnet in the plating solution, a uniform plating film is quickly formed on all the magnets, so that various problems with the barrel-type electroplating method, that is, corrosion of the magnet and its origin Generation of pinholes, deterioration of the magnetic properties of the magnet due to occlusion of hydrogen, and reduction in adhesion to the plating film can be eliminated.

[0007] In the electroplating method of the present invention, it is an important requirement that the individual magnets be separated from each other. By setting the individual magnets in this state, the set current density can be applied uniformly to all magnets, so that hydrogen generation can be suppressed even at a high current density setting, and hydrogen can be reduced. Even if it occurs, the effect on the magnetic properties of the magnet and the effect on the adhesion between the magnet and the plating film can be avoided as much as possible. Accordingly, it is possible to increase the average density of the plating film by increasing the current density, and it is possible to quickly form a uniform plating film on the surface of the magnet before the corrosion of the magnet starts.

Here, the "separated state" means a state in which the possibility that the individual magnets come into contact with each other is eliminated. Such a state is achieved, for example, by a rack-type electroplating method, that is, using a plating jig provided with a large number of conductive support members that support a magnet as an object to be processed and supply a plating current to the magnet. The method can be realized by adopting a method of forming a plating film on the surface of a magnet by directly supporting a magnet through a supporting member in a plating solution by independently supporting the magnets.

There are various types of jigs used in the rack-type electroplating method.
It is desirable to use a jig provided with a mechanism that does not leave any. As such a jig, for example, a jig provided with a mechanism in which a magnet supporting position of a conductive supporting member that supports a magnet and supplies a plating current to the magnet relatively changes in relation to the magnet and the member. Utensils. FIG. 1 shows a specific example of such a jig described in Japanese Patent Application No. 11-91585.

FIG. 1 shows a structure in which at least one of the members supporting the magnet is replaced with another member at a constant period, and the replaced member supports the magnet, so that the magnet support position is changed. Is a jig on which a member for supporting is arranged. That is, the jig is used for the inner magnet support members 4-a, 4-a.
b and outer magnet supporting members 5-a and 5-b. Both members are made of metal. The inner magnet support member is attached to a metal support frame 1 and the outer magnet support member is attached to a metal support frame 2. Both members and both support frames are coated with an insulating coating at desired locations as required. The support frame 1 and the support frame 2 are connected to a switching device 7 for supplying a plating current only to members supporting the magnet. The switching device 7 suppresses unnecessary plating thickening of members and the support frame. An electric actuator 6 is attached to the support frame 2 via an insulator 8 so that the outer magnet support members 5-a and 5-b move up and down at regular intervals as shown by arrows. . The operations of the electric actuator 6 and the switching device 7 are controlled by the control unit 9. FIG.
The outer magnet support members 5-a and 5-b support the magnet 3, and the switching device 7 supplies a plating current only to the members. When the outer magnet supporting member is lowered by the electric actuator 6, the magnets are alternately supported by the inner magnet supporting members 4-a and 4-b, and the switching device 7 supplies plating current only to the member. Become. In this way, the members supporting the magnets 3 are changed at regular intervals into the inner magnet support members 4-a and 4-b and the outer magnet support members 5-a.
By switching between a and 5-b, the support position of the magnet supported by the member is not fixed, so that a plating film having no trace of support can be formed on the magnet surface.

Other than the jig described in Japanese Patent Application No. 11-91585, a preferable jig having a mechanism that does not leave a support mark on the magnet is a jig suitable for plating a ring-shaped magnet. There is a jig provided with a mechanism capable of moving a supporting position by plating while rotating a magnet. As a specific example of such a jig, Japanese Patent Application No. Hei.
A conductive support member that supports a ring-shaped magnet having a cylindrical inner peripheral surface described in the specification of Japanese Patent Application Publication No. 1-290571 from the inner peripheral surface side and imparts a rotating operation to the magnet is provided, and the magnet is pressed against the support member. Jig provided with loading member, Japanese Patent Application No. 20
No. 00-174537, which has an anode inserted into a hollow portion of a ring-shaped magnet and a conductive support member for rotating the magnet around its central axis and supplying a plating current to the magnet. Jig, Japanese Patent Application 2000-2
No. 69986, a conductive support member for revolving around a rotation axis is provided, and this support member rotatably supports a ring-shaped magnet having a cylindrical inner peripheral surface from the inner peripheral surface side. Jig and the like. Also, Japanese Patent Application No. 11-
As described in Japanese Patent Application No. 265400 and Japanese Patent Application No. 2000-213427, one magnet is housed in each compartment of a conductive support member having a large number of cage compartments, and the support member is rotated. A jig that performs plating while performing the plating, and an apparatus that performs plating while carrying a magnet on a plurality of conductive rollers described in Japanese Patent Application No. 2000-64237 are also preferably used.

Next, in the electroplating method of the present invention, a film is formed at an average film forming rate of 0.1 μm / min or more from the start of plating until a plating film having a thickness of 0.5 μm is formed on the magnet surface. Is an important requirement. Even if each magnet is set in a state in which the magnets are separated from each other, the film thickness is not more than 0.
If a plating film of 5 μm is not formed on the magnet surface within 5 minutes from the start of plating, corrosion of the magnet starts in the plating solution, which causes pinholes in the film or deteriorates the plating solution. .

[0013] The plating in the present invention may be any plating, but Ni plating, Ni plating, and the like are preferred because they are films that provide excellent adhesion to the magnet surface and can be formed at low cost. Zn plating and Cu plating are desirable.
The thickness of such plating is 0.5 μm from the start of plating.
0.1μm / until the plating film of
Min, preferably at an average deposition rate of 0.2 μm / min or more. Such a speed is achieved by setting the current density to an appropriate value as a result of allowing each magnet to be in a state where the magnets are separated from each other, so that the current density can be uniformly applied to each magnet. Can be achieved.
Even if an attempt is made to form a film at such an average film forming rate in the barrel-type electroplating method, since the current densities of the individual magnets vary, the above-described various problems occur, and all magnets have problems. However, a uniform film cannot be formed on the surface.

The average film forming rate of 0.1 μm / min or more is usually set to a current density of 0.5 A / dm when performing Ni plating, Zn plating, or Cu plating using divalent metal ions.
^By setting the current density to ² or more, or when performing Cu plating using monovalent Cu ions such as copper cyanide, it can be achieved by setting the current density to 0.25 A / dm ² or more. It is desirable that the current density is set to 20 A / dm ² or less to form a film. If the current density is set to exceed this value, the problem of hydrogen generation becomes apparent, and there is a risk of causing deterioration in characteristics due to hydrogen absorption of the magnet and reduction in adhesion to the plating film. 20 A / d current density
By forming is set to m ² or less, the amount of hydrogen in the magnet surface 100ppm or less, preferably it is possible to suppress less than 50ppm.

The final thickness of the plating film formed on the magnet surface is desirably 1 μm or more. The average film forming rate may be fixed and maintained at an average film forming rate of 0.1 μm / min or more from the plating start place, or may be changed at a certain time. Although the upper limit of the thickness of the plating film that can be formed on the magnet surface by the electroplating method of the present invention is not particularly limited, the electroplating method of the present invention
In view of the demand for miniaturization of the magnet itself, it is suitable for stably mass-producing R-Fe-B-based permanent magnets having a plating film having a thickness of 25 μm or less, preferably 20 μm or less, more preferably 10 μm or less. In recent years, it has been required to stably mass-produce a thin film and a plating film exhibiting high corrosion resistance by a simple process, but the electroplating method of the present invention is a method capable of meeting the needs of such an era. is there.

The plating solution used in the present invention is not particularly limited, and various plating solutions that have been marketed or proposed can be used, but from the viewpoint of minimizing the generation of hydrogen. It is desirable to use a plating solution having a property of electrodeposition efficiency of 90% or more. Also,
Generally, when a low-pH plating solution is used, pinholes may be generated in the plating film or the plating solution may be deteriorated due to elution of metal components constituting the magnet. When used, hydroxides may precipitate on the magnet surface and a uniform plating film may not be formed.
Therefore, it is desirable to use a plating solution having a pH of 5 to 13, and more desirably a plating solution having a pH of 6 to 12.

The chlorine ion concentration in the plating solution, which is a major factor in the corrosion of the magnet, is preferably adjusted to 20 g / L or less, and more preferably to 10 g / L or less. From this viewpoint, when performing Zn plating or Cu plating, it is desirable to use an alkali bath using a complexing agent such as a cyanation bath or a pyrophosphate bath that does not contain chloride ions. In particular, when performing Cu plating, use of such an alkaline bath is also desirable in that the substitution reaction between Cu and R, which is a metal component constituting the magnet on the magnet surface, can be suppressed. .

The plating solution is used to reliably supply metal ions to the surface of the magnet to maintain the average film forming rate, to suppress hydrogen generation as much as possible, and to quickly generate hydrogen even if hydrogen is generated. It is desirable to stir to remove hydrogen generated from the surface. Also, it is desirable to provide anodes in at least two different directions for each magnet so that a uniform plating film is formed on the entire surface of the magnet.

The rare earth element (R) in the R—Fe—B permanent magnet applied to the present invention is Nd, Pr, Dy, H
at least one of o, Tb, and Sm, or La, Ce, Gd, Er, Eu, Tm, Yb, and L
Those containing at least one of u and Y are desirable. Usually, one kind of R is sufficient, but in practice, 2 kinds are preferred.
Mixtures of more than one species (such as misch metal or dymium) can also be used for reasons such as availability. Further, Al, Ti, V, Cr, Mn, Bi, Nb, T
a, Mo, W, Sb, Ge, Sn, Zr, Ni, Si,
By adding at least one of Zn, Hf, and Ga, the coercive force and the squareness of the demagnetization curve can be improved, the productivity can be improved,
It is possible to reduce the price. Further, by substituting a part of Fe with Co, the temperature characteristics can be improved without impairing the magnetic characteristics of the obtained magnet.

The same type of plating film or a different type of plating film may be laminated on the plating film formed on the magnet surface by the electroplating method of the present invention, or another type of film such as a chemical conversion treatment film may be laminated. It may be formed. By adopting such a configuration, the characteristics of the plating film formed by the electroplating method of the present invention can be enhanced or supplemented, or further functionality can be imparted. Even when such a multilayer coating is formed, the plating coating formed by the electroplating method of the present invention sufficiently exhibits its effect, and exhibits excellent corrosion resistance even if the overall thickness (total thickness) is small. Demonstrate. Note that such a total film thickness is desirably 1 μm to 25 μm.

[0021]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following description.

(1) R-Fe-B permanent magnet used:
For example, US Pat. No. 4,770,723 and US Pat.
As described in JP-A-92368, 14Nd-7 obtained by pulverizing a known casting ingot, performing pulverization, followed by molding, sintering, heat treatment and surface processing.
15mm × 25mm × 9Fe-6B-1Co composition
A sintered magnet having a height of 7 mm was used.

(2) Plating jig to be used: (a) The plating jig suitably used in the electroplating method of the present invention is provided with a mechanism shown in FIG. 1 and can process 100 magnets simultaneously. A jig (10 rows × 10 columns) was used (hereinafter abbreviated as a rack jig). (B) A general plastic jig having a cross section of a regular hexagon having a side of 150 mm and a length of 300 mm used in a barrel-type electroplating method and having 100 magnets and a diameter of 2 mm.
2 kg of steel balls were used and rotated at a rotation speed of 5 rpm.

(3) Pretreatment of plating: JP-A-6-574
The test was performed according to the method described in JP-A-80-80. That is, after a magnet is set on a plating jig, this is fixed to a sodium nitrate solution.
Liquid temperature 30 ° C consisting of 2 mol / L, 1.5 vol% sulfuric acid
After immersion in the treatment solution for 4 minutes, the substrate was immediately ultrasonically washed with ion exchanged water of 1 μS / cm or less for 30 seconds, and then plating was started immediately.

Example A: Ni plating (1) Nickel sulfate hexahydrate 250 g / L, nickel chloride
Using a plating bath composed of 45 g / L of hexahydrate and 30 g / L of boric acid and adjusted to pH 5.5 with nickel carbonate at a liquid temperature of 50 ° C., and shown in Table 1 (a) from 5 minutes after the start of plating (B) average film formation rate (n)
= Measured value of 10: X-ray fluorescence film thickness meter SFT-7000 (manufactured by Seiko Denshi) is used. same as below. ), (C) a film thickness of 10 at the current density set 5 minutes after the start of plating.
A μm Ni plating film was formed on the magnet surface. The average film thickness of the formed plating film (actual measurement value of n = 10: using a fluorescent X-ray film thickness meter SFT-7000 (manufactured by Seiko Instruments Inc.)).
same as below. ) And pressure cooker test (12
Table 1 shows the results of the corrosion resistance evaluation based on 0 ° C. × 100% RH × 2 atm × 72 hours). From Table 1, using a rack jig, the individual magnets were placed in a state where the magnets were separated from each other.
In addition, it was found that by forming a film at an average film forming rate of 0.1 μm / min or more for 5 minutes from the start of plating, a magnet having a plating film having excellent corrosion resistance on its surface can be stably mass-produced. Further, for one of the magnets having a plating film on the surface obtained in Example 2, the plating film was peeled off from the magnet, and the amount of hydrogen on the magnet surface was measured by glow discharge emission spectrometry (GDS: GDLS-5017: Shimadzu Corporation). (Manufactured by the company) and found to be very low at 42 ppm.

[0026]

[Table 1]

Example B: Ni Plating (Part 2) Nickel sulfate hexahydrate 130 g / L, ammonium citrate 30 g / L, boric acid 15 g / L, ammonium chloride 8 g / L, saccharin 8 g / L, Using a plating bath at a solution temperature of 50 ° C. adjusted to pH 6.5 with ammonia water, (a) the current density set up to 5 minutes after the start of plating and (b) the average film forming rate during that time shown in Table 2 n = 10
(Measured value), (c) A Ni plating film having a film thickness of 10 μm was formed on the magnet surface at a current density set 5 minutes after the start of plating. Average film thickness (n
Table 2 shows the results of the evaluation of corrosion resistance by the pressure cooker test (120 ° C. × 100% RH × 2 atm × 72 hours). From Table 2, using a rack jig, the individual magnets were separated from each other, and a film was formed at an average film forming rate of 0.1 μm / min or more for 5 minutes from the start of plating. Thus, it was found that a magnet having a plating film having excellent corrosion resistance on the surface can be stably mass-produced.

[0028]

[Table 2]

Example C: Two-layer Ni plating Step 1: Using the same plating bath as that used in Example B, (a) the current density set up to 5 minutes after the start of plating shown in Table 3; (B) Average film forming rate during that time (n =
(Measured value of 10), (c) A Ni plating film having a thickness of 4 μm was formed on the magnet surface at a current density set 5 minutes after the start of plating. Table 3 shows the average film thickness (actually measured value of n = 10) of the formed plating film.

[0030]

[Table 3]

Step 2: 240 g of nickel sulfate hexahydrate
/ L, nickel chloride hexahydrate 45g / L, boric acid 30
g / L, sodium 1,5-naphthalenedisulfonic acid 8
g / L, gelatin 0.01 g / L, pH 4.2
And a current density of 0.7 A /
A Ni plating film having a thickness of 16 μm was formed on the surface of the Ni plating film formed in Step 1 at dm ² . The total average film thickness of the plating films formed in step 1 and step 2 (n = 10
Measured value) and neutral salt spray test (5% NaCl × 35 ° C.)
× 168 hours) are shown in Table 4. From Table 4, in step 1, using a rack jig, the individual magnets were brought into a state where the magnets were separated from each other, and at an average deposition rate of 0.1 μm / min or more for 5 minutes from the start of plating. It was found that the effect was exhibited even when multilayer plating was performed by forming the film.

[0032]

[Table 4]

Example D: Influence of Deterioration of Plating Solution During Mass Production Table 5 shows the results of the 50th cycle when Ni plating under the conditions of Example A was repeated using one plating bath.
Table 6 shows the results of the 50th cycle when Ni plating under the conditions of Example B was repeatedly performed using one plating bath. From Tables 5 and 6, the electroplating method of the present invention effectively suppresses the deterioration of the plating solution due to the elution of the metal components constituting the magnet, and is excellent even when one plating bath is used 50 times. Stable production of magnets with plated coatings showing excellent corrosion resistance on the surface.
It turned out that 6 or more was better.

[0034]

[Table 5]

[0035]

[Table 6]

Example E: Zn Plating A plating bath composed of 70 g / L of zinc chloride, 200 g / L of potassium chloride, and 25 g / L of boric acid and having a pH of 5.8 and a temperature of 25 ° C. was used. ) The current density set up to 5 minutes after the start of plating, (b) the average film forming rate during that time (actually measured value of n = 10), and (c) the film density at the current density set 5 minutes after the start of plating. A Zn plating film having a thickness of 15 μm was formed on the magnet surface. Table 7 shows the average thickness (measured value of n = 10) of the formed plating film and the corrosion resistance evaluation result by a pressure cooker test (120 ° C. × 100% RH × 2 atm × 72 hours). From Table 7, using a rack jig, the individual magnets were placed in a state where the magnets were separated from each other, and 0.1 mm was used for 5 minutes from the start of plating.
It was found that by forming a film at an average film forming rate of μm / min or more, a magnet having a plating film exhibiting excellent corrosion resistance on its surface can be stably mass-produced.

[0037]

[Table 7]

Example F: Cu plating A plating bath composed of 220 g / L of copper sulfate pentahydrate, 50 g / L of sulfuric acid, and 120 mg / L of copper chloride dihydrate was used. Table 8 shows (a) current density set up to 5 minutes after the start of plating, (b) average film formation rate (measured value of n = 10), (c) 5 minutes after the start of plating The film thickness is 10μ at the current density set thereafter.
m Cu plating film was formed on the magnet surface. The average thickness of the formed plating film (actual value of n = 10) and the pressure cooker test (120 ° C. × 100% RH × 2)
Table 8 shows the results of the corrosion resistance evaluation according to (atmospheric pressure × 72 hours).
From Table 8, using the rack jig, the individual magnets were separated from each other by magnets, and 5 mm from the start of plating.
It was found that by forming a film at an average film forming rate of 0.1 μm / min or more for a minute, a magnet having a plating film having excellent corrosion resistance on its surface can be stably mass-produced.

[0039]

[Table 8]

[0040]

According to the electroplating method of the present invention, a plurality of R-Fe-B permanent magnets consisting of a main phase and a plurality of crystal phases of a grain boundary phase having a corrosion potential lower than that of the main phase are simultaneously formed. In the plating method, the individual magnets are set in a state where the magnets are separated from each other, and the film thickness is 0.5 mm from the start of plating.
0.1μm until a μm plating film is formed on the magnet surface
By immersing the magnet in the plating solution by forming a film at an average film forming speed of m / min or more, a uniform plating film is quickly formed on all the magnets, thereby obtaining various types of barrel-type electroplating methods. The problem is that the corrosion of the magnet and the occurrence of pinholes due to it, the deterioration of the magnetic properties of the magnet due to the occlusion of hydrogen, and the decrease in the adhesion with the plating film are eliminated, and the plating film showing excellent corrosion resistance even with a thin film R-Fe with
-B-type permanent magnets can be stably mass-produced.

[Brief description of the drawings]

FIG. 1 is a schematic view of a plating jig suitably used in the electroplating method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 2 Support frame 3 Magnet 4-a, 4-b Inner magnet support member 5-a, 5-b Outer magnet support member 6 Electric actuator 7 Switching device 8 Insulator 9 Control part

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01F 41/02 H01F 1/04 H

Claims (5)

[Claims] 1. A method for simultaneously electroplating a plurality of R—Fe—B permanent magnets comprising a main phase and a plurality of crystal phases of a grain boundary phase having a lower corrosion potential than the main phase, wherein each of the magnets comprises: The method is characterized in that the magnets are separated from each other, and a film is formed at an average film forming rate of 0.1 μm / min or more from the start of plating until a plating film having a thickness of 0.5 μm is formed on the magnet surface. Electroplating method. 2. The electroplating method according to claim 1, wherein the film is formed under the condition that the current density is 20 A / dm ² or less. 3. The electroplating method according to claim 1, wherein the plating is any one selected from Ni plating, Zn plating, and Cu plating. 4. The electroplating method according to claim 1, wherein the thickness of the plating film is 1 μm to 25 μm. 5. An R—Fe—B permanent magnet having a plating film on a surface, obtained by the electroplating method according to claim 1. Description: