JP3248982B2 - Permanent magnet and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a permanent magnet and a method for producing the same, and more particularly, to R (where R is at least one of rare earth elements including Y), T (where T is Fe The present invention also relates to a permanent magnet containing Fe and Co) and B and having a substantially tetragonal main phase and a method for producing the same.

[0002]

2. Description of the Related Art Rare earth magnets having high performance include Sm-Co magnets manufactured by powder metallurgy and having an energy product of 32M.
GOe is mass-produced.

However, this has a disadvantage that the raw material price of Sm and Co is high. Among the rare earth elements, elements having a small atomic weight, for example, Ce, Pr, and Nd are more abundant and cheaper than Sm. Fe is less expensive than Co. Therefore, in recent years, Nd-Fe-B magnets and Nd-Fe
R-T-B magnets (T is Fe or Fe and Co) such as -Co-B magnets have been developed.
The publication discloses a sintered magnet. In the magnet by the sintering method, the conventional Sm-Co powder metallurgy process (melting → mother alloy ingot casting → ingot coarse grinding → fine grinding →
Molding → sintering → magnet) can be applied, and it is easy to obtain high magnetic properties.

[0004] However, since these materials contain a rare earth element which is easily oxidized and iron as main components, they have low corrosion resistance and have problems such as performance deterioration and variation. For the purpose of improving the low corrosion resistance of the RTB-based magnet, a technique of providing the surface of the magnet with Ni plating has been proposed.

Ni plating is excellent in mass productivity and is useful because it not only improves corrosion resistance but also exerts a reinforcing effect on mechanical strength.

However, due to its chemical stability,
There has been a problem that the bonding strength cannot be secured when performing bonding or resin coating.

As a remedy, a technique called "metal coating + chemical conversion treatment" has been proposed (JP-A-62-602).
12, JP-A-63-110707, JP-A-1-223712, JP-A-4-144101, JP-A-4-276603).

Specifically, the above-mentioned Japanese Patent Application Laid-Open No. 62-60212 is disclosed.
Japanese Patent Application Laid-Open Publication No. Hei 11 (1995) discloses a technique for improving the corrosion resistance by applying an Al plating layer on an Nd magnet, performing a shot peening treatment on the surface thereof, and further performing a chromate treatment thereon. JP-A-63-110707 discloses Nd.
By forming a Ni plating layer on the magnet, performing a chromate treatment on the surface of the Ni plating layer, and forming a resin layer thereon, to improve the corrosion resistance and the adhesion of the resin layer,
A technique for preventing dropout is disclosed. Also, Japanese Patent Application Laid-Open
No. 223712 discloses that the surface of an Nd magnet is treated with a shot blast, and a Zn alloy plating layer is applied to the surface.
Further, a technique has been disclosed in which a resin layer is formed after the plating layer surface is subjected to a chromate treatment, thereby improving salt water resistance and adhesion. Also, Japanese Patent Application Laid-Open No. 4-144101 discloses a technique in which a Ni plating layer is provided on an Nd magnet and a chromate film is formed on the Ni plating layer to improve corrosion resistance. Further, Japanese Patent Application Laid-Open No. 4-276603
Japanese Patent Application Laid-Open Publication No. H11-163873 discloses a technique in which a Ni plating layer is formed on an Nd magnet, and a chromate film having strong water repellency is formed thereon to improve corrosion resistance.

As described above, most of the methods for treating the plating surface relate to "chromate treatment".

The chromate treatment is very excellent as a base treatment for a resin coat, but the coating itself is weak to heat.
By heating around 00 degrees, it gradually dehydrates and becomes insoluble,
It is said that the coating cracks and the repair effect by Cr ⁶⁺ is lost, and the corrosion resistance is reduced. In addition, the chromate film immediately after the treatment shows excellent coating performance and adhesion performance, but the water repellency becomes stronger with the passage of time, which may cause poor coating and poor adhesion. Therefore, it can be said that the chromate treatment is not suitable as a final surface treatment particularly from the viewpoints of adhesiveness and corrosion resistance.

However, permanent magnets are often used after being bonded to a circuit board or the like by means of an adhesive, and thus it has been desired to improve the adhesiveness of the permanent magnet.

[0012] On the other hand, the report of “phosphate treatment” is described in “Paper No. W3.1 Presented at the Ele” for Nd-based magnets.
0nth International Workshop on Rare-Earth Magnets
andTheir Applications, Pittsburgh, PA, 21-24 Octobe
r, 1990. (Proceedings Book: Carnegie Mellon Universit
y, Pittsburgh, PA 15213, USA).
Further, it describes in detail the conditions and the like of zinc phosphate when performing resin coating. It is also applicable to Ni plating and improves the adhesion and corrosion resistance. However, the description of the zinc phosphate treatment in the case of Ni plating is limited thereto.

As described above, the combination of “metal film + chemical conversion treatment” aims at improving the adhesion between the metal film and the resin and the corrosion resistance when a resin coating is performed on the metal film.

[0014]

In view of the above “Ni plating layer + chromate film layer” from the viewpoint of adhesiveness,
The only improvement is the improvement of the wettability during the formation of the chromate film layer, and there is no structural or morphological effect. Therefore, there is a disadvantage that an adhesive having good affinity must be selected.

Further, the conventional chromate film layer also has the problem of heat resistance as described above, so that it cannot be expected to be particularly effective in applications where the use environment is at a high temperature, and in some cases, it may have an adverse effect. .

It is an object of the present invention to provide a permanent magnet which is superior in heat resistance to chromate and has not only wettability but also structural and morphological effects in adhesiveness, thereby significantly improving adhesiveness. And

[0017]

This and other objects are achieved by the present invention which is defined below as (1) to (5). (1) R (where R is at least one of rare earth elements including Y), T (where T is Fe or Fe and Co) and B, and a substantially tetragonal main phase Having a Ni plating layer on the surface of the permanent magnet body
A permanent magnet having a structure in which a zinc phosphate coating layer is formed on an i-plated layer, and wherein the zinc phosphate coating has a Zn / Ni weight ratio of 8 or more and 30 or less. (2) The thickness of the zinc phosphate coating is 0.1 μm or more and 10 or more.
The permanent magnet according to the above (1), which is not more than μm. (3) The permanent magnet according to (2) or (3), wherein the Ni plating layer is provided by a sulfamic acid bath. (4) The method for producing a permanent magnet according to any one of the above (1) to (3), wherein the surface of the Ni plating layer is treated with an acid containing soluble fluoride before forming the zinc phosphate coating layer. A method for producing a permanent magnet, comprising: (5) The method for producing a permanent magnet according to the above (4), wherein the surface of the permanent magnet body is treated with a treatment solution containing aldonic acid or a salt thereof and nitric acid before forming the Ni plating layer.

[0018]

In the present invention, a Ni-plated layer is provided on the surface of the RTB-based permanent magnet body, and a zinc phosphate coating layer is formed on the Ni-plated layer. By setting Zn / Ni of the zinc phosphate coating to a weight ratio of 8 or more and 30 or less, the adhesion between the constituent layers is improved, and the adhesion using an adhesive is improved. Can be. Moreover, the permanent magnet body of the present invention has improved corrosion resistance and reliability.

[0019]

[Specific Configuration] Hereinafter, a specific configuration of the present invention will be described in detail. In the present invention, before forming the protective layer on the permanent magnet, a pretreatment is performed using a predetermined treatment liquid.

The acid used for the plating pretreatment is hydrochloric acid,
A non-oxidizing acid such as sulfuric acid is often used. However, particularly when the permanent magnet contains a rare earth element, when the treatment is performed using these acids, hydrogen generated by the acids becomes
It is occluded on the surface of the permanent magnet, the occluded site is embrittled, and a large amount of undissolved powder is generated. Since this powdery undissolved substance causes a defect in the protective layer or causes a decrease in adhesion, it is preferable that these non-oxidizing acids are not contained in the treatment liquid if possible. Therefore, it is preferable to use nitric acid, which is an oxidizing acid that generates little hydrogen, as the acid to be used. By using nitric acid, the surface of the magnet is chemically etched by its oxidizing action, and a fine uneven structure that cannot be visually confirmed is formed.

In the present invention, in addition to this nitric acid,
Contains aldonic acid or a salt thereof.

When this aldonic acid or a salt thereof is contained, the Fe ion eluted by nitric acid and the aldonic acid salt form a stable chelate compound, and dissolution by substitution reaction with free Fe ion of Nd having a higher ionization tendency than Fe. Can be suppressed. Therefore, by adding aldonic acid or its salt, the chemical etching that occurs locally and suddenly with nitric acid alone proceeds more gently, and there is a uniform, locally sharply deep recess on the magnet surface. No, a fine and uniform uneven structure is formed, and the adhesion of the protective layer can be improved.

Such an improvement in adhesion can be selectively realized by aldonic acid or a salt thereof, and cannot be realized by other chelating agents such as citric acid and tartaric acid.

The amount of dissolution of the magnet body by such pretreatment is preferably 5 μm or more, more preferably 10 to 15 μm in average thickness from the surface. If the amount of dissolution is less than 5 μm, a deteriorated layer and an oxidized layer due to the processing of the magnet body surface cannot be completely removed, so that sufficient adhesion cannot be obtained.

The average depth of the unevenness (the depth from the valley to the peak) is preferably about 1 to 5 μm. The average pitch of the unevenness is preferably about 10 to 50 μm. These improve the adhesion.

It is desirable that the concentration of nitric acid in the treatment liquid used for such pretreatment is 1 N or lower, particularly 0.6 N or lower, more preferably 0.5 N or lower. When the nitric acid concentration exceeds 1N, the dissolution rate of the magnet body becomes extremely fast, and it is difficult to control the amount of dissolution, so that a product having desired dimensional accuracy cannot be obtained. Further, in the case of a large amount of processing such as barrel processing, the dispersion of the processing state becomes large. In addition, when the nitric acid concentration is low, the amount of the solution becomes too large, and the amount of dissolution becomes insufficient. For this reason, the nitric acid concentration is desirably 1 normal or less, particularly preferably 0.05 to 0.5 normal or less.

The amount of aldonic acid or a salt thereof added to the treatment solution is preferably at least equimolar to Fe dissolved during the treatment. If the amount of the aldonic acid or salt thereof is less than the equimolar amount of Fe dissolved in the treatment liquid at the end of the treatment, the effect of forming irregularities is not sufficient, and the adhesion is undesirably low.

The amount of Fe dissolved at the end of the treatment is about 1 to 10 g / liter. Thus, aldonic acid or a salt thereof is
Generally, about 0.02 to 0.2 mol / liter is contained. That is, the dissolution treatment is performed by batch processing, and when the Fe dissolution amount is reached, the treatment liquid may be discarded.

Aldonic acid or a salt thereof is HOCH ₂ (C
HOH) nCOOY (Y is H or a cation), and may be, for example, any of gluconic acid, arabonic acid, mannonic acid, galactonic acid, heptonic acid and the like in which n = 3 to 5. In this case, these alkali metal salts are preferable because a highly pure reagent can be obtained.

Of these, sodium gluconate, potassium gluconate, sodium heptanoate and the like can be most preferably used, and uniform and fine irregularities can be formed without increasing powdery undissolved matter. .

In addition to aldonic acid and salts thereof, for example, salts of hydroxycarboxylic acids such as citric acid, tartaric acid and oxyacetic acid may be added to the acid treatment solution. The effect of forming fine irregularities, which is observed when the salt is added, cannot be obtained, and the improvement in adhesion as in the present invention cannot be achieved. In addition, the amount of powdery undissolved matter also increases.

Furthermore, surfactants such as sodium lauryl sulfate and polyoxyethylene nonyl phenyl ether may be added to the acid treatment liquid, but when these are added to the treatment liquid of the present invention, powdery substances may be added. This is not desirable because it causes an increase in undissolved substances and also causes adsorption to the surface of the magnet body after the treatment, thereby deteriorating the adhesion.

The processing temperature with the processing solution is preferably 40 ° C. or lower, particularly 30 ° C. or lower, more preferably 20 ° C. or lower. If the treatment temperature exceeds 40 ° C., the dissolving action of the magnet by the nitric acid becomes dominant, and the effect of adding the aldone salt is lost, which is not preferable. The treatment time may be appropriately adjusted depending on the composition of the treatment liquid, the temperature, and the desired etching amount, but is usually preferably 1 to 20 minutes.

In order to completely remove a small amount of undissolved substances and residual acid components from the surface of the pretreated magnet body, it is preferable to perform cleaning using ultrasonic waves. This ultrasonic cleaning is desirably performed in water having a low chlorine ion content, such as ion-exchanged water, or a solution in which a small amount of a basic compound is dissolved for the purpose of neutralizing the residual acid. If chloride ions are contained in the cleaning solution, rust may be generated on the magnet surface.

If necessary, the same immersion cleaning with water or a basic aqueous solution may be performed before and after the ultrasonic cleaning. Further, before performing the pretreatment, mechanical polishing and immersion or electrolytic degreasing or alkali derusting, which are usually performed as plating pretreatment, may be performed according to the processing method and storage state of the magnet body. .

In the pretreatment, it is preferable not to apply ultrasonic waves. This is because the unevenness may be too large.

A protective layer is formed on the cleaned magnet surface by electroplating. By forming the protective film by electroplating, a high-performance corrosion-resistant film having excellent mass productivity can be formed.

The protection layer thus formed preferably contains Ni as a main component.

By using Ni as the protective layer, the strength of the protective layer can be increased and an excellent rust prevention effect can be obtained. Examples of the plating bath used for the electroplating of Ni include a Watt bath containing no nickel chloride component, a sulfamic acid bath, a fluorinated bath, and a nickel bromide bath. However, in this case, since the dissolution of the anode is reduced, it is necessary to replenish the bath with nickel ions. The nickel ions are preferably replenished as a solution of nickel sulfate or nickel bromide.

For example, among these, it is preferable to use a sulfamic acid bath exhibiting higher peel strength.
The following composition is mentioned.

Ni (NH ₂ SO ₃ ) ₂ .4H ₂ O 150-600 g / l NiBr ₂ .6H ₂ O 0-30 g / l Boric acid 30-60 g / l

At this time, the water in the bath preferably does not contain chlorine, and the chlorine content in the bath is preferably 100 ppm or less. As described above, by removing the chlorine component from the plating bath, it is possible to prevent blisters mainly due to aging.

The plating conditions are pH 3 to 6, particularly preferably 4.0 to 5.0, temperature 30 to 70 ° C., and current density 0.1 to 0.1.
It may be about 10 A / m ² . If the pH is lower than this range, the magnet body will be dissolved, and if the pH is higher than this range, nickel hydroxide precipitates and the plating film becomes brittle. If the current density is less than this range, impurities such as Cu, Co and the like in the plating film are often folded, resulting in a film having poor appearance and low corrosion resistance. Hydrogen generation in the vicinity increases and is absorbed by the magnetic material, causing a decrease in adhesion.

In the present invention, if necessary, the improvement of the corrosion resistance of known double nickel plating, trinickel plating and the like having different natural potentials as described on page 115 of the plating technique guidebook (published by Tokyo Plating Materials Cooperative Union). Multi-layer plating for the purpose can also be preferably used. In addition, even when a normal watt bath or a sulfamine bath containing a chloride is used, the effects of improving the adhesion and the corrosion resistance of the present invention can be obtained.

When the protective layer is formed by electroplating, a rack plating method or a barrel plating method is appropriately applied according to the size and shape of the magnet body.

In general, a magnet body having a large size which is processed by the rack plating method requires a large area requiring a defect-free protective layer. Therefore, it is necessary to increase the thickness of the protective layer. The preferred thickness is 20-30
μm. On the other hand, the desirable protective layer thickness by electroplating only for a magnet body having a small surface area such as being processed in large quantities by barrel plating and having a weight of several tens g or less is 10 to 2 g.
0 μm.

[Pretreatment of Zinc Phosphate Treatment] Since the Ni plating itself is very stable (because of low reactivity), the pretreatment of the zinc phosphate coating is important. Therefore, after the oxide film on the Ni plating surface is removed and activated by the activating acid immersion treatment, the surface is adjusted and zinc phosphate treatment is performed to obtain a film having good adhesion. The treatment solution to be used may be a general activation treatment agent for plating, but is preferably an acid containing a soluble fluoride. This is because the general purpose of the activated acid treatment agent is to mainly activate the oxidized Ni surface, but in actuality, the brightening agent of the plating bath component adheres to the outermost surface of the plating after the completion of the Ni plating, and this is the subsequent phenomenon. Since the possibility of causing poor adhesion to the coating is great, an acid containing a soluble fluoride is suitable for removing such organic substances and the like. However,
When an organic substance is not used as a brightener or the like of a plating bath component, the activation treatment is unnecessary. The surface adjustment is desirably performed because the crystal growth of zinc phosphate is assisted and the crystal can be made dense and fine, and a treatment agent containing alkaline colloidal titanium is more preferable.

[Zinc phosphate coating] The components of the treatment liquid used in the present invention include zinc ions, phosphate ions, simple fluorides, complex fluorides, active fluorides and film formation accelerators. As the film formation accelerator, at least one selected from nitrite ions, m-nitrobenzenesulfonic acid ions, and hydrogen peroxide is used. These preferred concentrations (more preferred concentrations in parentheses) are, for example, as follows.

Zinc ion: 0.15 to 3.0 (0.4
5 to 3.0) g / l phosphate ion: 7.5 to 60 (15 to 45) g / l nitrite ion: 0.015 to 0.75 (0.015 to 15)
0.6) g / l m-nitrobenzenesulfonic acid ion: 0.075 to
7.5 (0.15~6) g / l of hydrogen peroxide (H ₂ O ₂ 100% conversion): 0.75 to 15
(1.5-12) g / l

It is preferable to adjust the free acidity (FA) in the range of 1.0 to 4.0.

If the zinc ion concentration is less than 0.15 g / l, a uniform zinc phosphate film is not formed on the nickel surface, and the scale may increase. The zinc ion concentration was 3.0 g /
If it exceeds l, a uniform zinc phosphate coating will be formed, but the Zn / Ni ratio in the coating will be too high and the adhesion between the Ni plating and the zinc phosphate coating will be insufficient.

If the phosphate ion concentration is less than 7.5 g / l, a non-uniform film is easily formed, and if it exceeds 60 g / l, no improvement in the effect can be expected.

When the concentration of the film formation promoting agent is lower than the above range, sufficient film formation cannot be performed on the nickel surface, and when the concentration exceeds the above range, passivation of nickel is caused and no film is formed.

FA is 0.1 N-Na required to neutralize 10 ml of the treatment solution using bromophenol blue as an indicator.
It is defined by the number of consumed OH ml. If it is less than 0.1, a uniform zinc phosphate film is not formed on the nickel surface.
If it exceeds 0, the ratio of Zn / Ni in the coating becomes too low, so that a good zinc phosphate coating cannot be obtained. (Scaly flake-like crystals cannot be obtained, and sufficient structural and morphological effects on the adhesiveness cannot be obtained.)

The treatment liquid used in the present invention may contain manganese ions and nickel ions in addition to the above components.

The processing temperature is preferably 20 to 70 ° C.
35-60 degreeC is more preferable. If it is lower than this range, the film-forming property is poor and a long-time treatment is required. On the other hand, if it is higher than this range, the balance of the processing solution tends to be lost due to decomposition of the film formation accelerator and precipitation of the processing solution, and it is difficult to obtain a good film.

The weight ratio of Zn / Ni in the zinc phosphate coating is preferably from 8 to 30, more preferably from 10 to 20. If the weight ratio is less than 8, the ratio of Ni is high and the ratio of Zn is too low, so that a uniform and good coating cannot be obtained (F
A is the same as when A exceeds 4.0). When the weight ratio exceeds 30, a uniform zinc phosphate film is formed,
When the ratio of i is too low, the adhesion between Ni plating and zinc phosphate becomes insufficient.

Next, regarding the relationship between the processing time and the film thickness, the processing time is 3 to 30 minutes, more preferably 5 to 15 minutes, with the bath composition in the above range. If the time is less than 3 minutes, a uniform zinc phosphate film cannot be obtained, and if the time exceeds 30 minutes, the film becomes too thick and the adhesion is reduced.

Accordingly, the film thickness is preferably from 0.1 to 10 μm, more preferably from 0.5 to 5 μm.

In the present invention, the permanent magnet body on which the protective layer is provided on the surface contains R (where R is one or more rare earth elements including Y), Fe and B.

The content of R, Fe and B is preferably 5.5 at% ≦ R ≦ 30 at% 42 at% ≦ Fe ≦ 90 at% 2 at% ≦ B ≦ 28 at%.

In particular, when the permanent magnet body is manufactured by the sintering method, the following composition is preferable.

As the rare earth element R, Nd, Pr, H
o, at least one of Tb, or L
a, Sm, Ce, Gd, Er, Eu, Pm, Tm, Y
Those containing at least one of b and Y are preferable.

When two or more elements are used as R, a mixture such as misch metal can be used as a raw material.

The R content is preferably 8 to 30 at%.

If the content is less than 8 at%, a high coercive force (iHc) cannot be obtained since the crystal structure becomes a cubic structure having the same structure as that of α-iron, and if it exceeds 30 at%, many R-rich nonmagnetic phases are formed. And the residual magnetic flux density (Br) decreases.

The content of Fe is preferably 42 to 90 at%.

When Fe is less than 42 at%, Br decreases, and when it exceeds 90 at%, iHc decreases.

The B content is preferably 2 to 28 at%.

If B is less than 2 at%, a rhombohedral structure is formed, resulting in insufficient iHc. If B exceeds 28 at%, the B-rich non-magnetic phase increases and Br decreases.

By replacing part of Fe with Co, the temperature characteristics can be improved without impairing the magnetic characteristics. In this case, if the amount of Co substitution exceeds 50% of Fe, the magnetic properties deteriorate, so the amount of Co substitution is preferably set to 50% or less.

In addition to R, Fe and B, Ni, Si, Al, Cu, Ca, etc.
at% or less may be contained.

Further, by substituting a part of B with one or more of C, P, S and Cu, it is possible to improve productivity and reduce costs. In this case, the substitution amount is preferably 4 at% or less of the whole. In order to improve coercive force, improve productivity, and reduce cost, Al, Ti,
V, Cr, Mn, Bi, Nb, Ta, Mo, W, Sb,
One or more of Ge, Sn, Zr, Ni, Si, Hf and the like may be added. In this case, it is preferable that the total amount is 10 at% or less.

The permanent magnet according to the present invention has a main phase having a substantially tetragonal crystal structure. The particle size of this main phase is
It is preferably about 1 to 100 μm. And it usually contains 1 to 50% of a non-magnetic phase by volume ratio.

Such a permanent magnet body is disclosed in the aforementioned Japanese Patent Application Laid-Open No. 61-185910.

The above-described permanent magnet body is preferably manufactured by a sintering method as described below. First,
An alloy having a desired composition is cast to obtain an ingot. The obtained ingot is subjected to a particle size of 10 to 10 using a stamp mill or the like.
The material is roughly pulverized to about 0 μm and then finely pulverized by a ball mill or the like to a particle size of about 0.5 to 5 μm.

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

The obtained molded body was heated at 1000 to 1200 ° C.
And quenched for 0.5-5 hours. The sintering atmosphere is preferably an inert gas atmosphere such as Ar gas. After that, preferably in an inert gas atmosphere,
Perform aging treatment at ~ 900 ° C for 1-5 hours.

[0079]

EXAMPLES Hereinafter, the present invention will be described in more detail by showing specific examples of the present invention.

27.4 Nd prepared by powder metallurgy
-3.0Dy-1.0B-bal. A sintered body having a composition of Fe (the number is% by weight) was heated at 600 ° C. in an argon atmosphere.
Aging treatment for 2 hours, diameter 23.5mm, thickness 3.
A permanent magnet was obtained by processing into a disk having a size of 4 mm and chamfering by barrel polishing.

The above 100 samples were subjected to nitric acid concentration: 0.5N,
Sodium gluconate concentration: The surface layer was dissolved by immersion in 50 liters of a treatment solution having a concentration of 0.025 mol / liter at 10 ° C. for 3 minutes. The average amount dissolved was 6 μm.

The treated sample was subjected to ultrasonic cleaning in ion-exchanged water, and then Ni plating was performed by a barrel method using a sulfamic acid plating bath having the following composition and conditions.

Ni (NH ₂ SO ₃ ) ₂ .4H ₂ O 180 g / l NiBr ₂ .6H ₂ O 5 g / l Boric acid 45 g / l LiNH ₂ SO ₃ 200 g / l Bath temperature 50 ° C. pH 4.5

The average cathode current density was 0.3 A / dm ² , and the average thickness of the plating film was 10 μm.

Further, at 45 ° C. using an alkaline degreasing agent,
After immersion treatment for 0 minutes, the solution was treated with an acid containing a soluble fluoride (specifically, Metex Acid Salt M-629, manufactured by Nippon MacDermid Co., 120 g / l).
After immersion at 5 ° C. for 5 minutes to activate the surface of the Ni plating layer, immersion treatment was performed for 1 minute at room temperature with a surface conditioner containing alkaline colloidal titanium.

Next, treatment was carried out using a zinc phosphate treatment bath having the following composition and conditions.

Zinc ion 1.5 g / l Phosphate ion 25 g / l Nitrite ion 0.3 g / l Simple fluoride HF 0.25 g / l Complex fluoride H ₂ SiF ₆ 1.2 g / l (manganese ion : 0.8 g / l, nickel ion: 0.
8g / l) Total acidity (TA): 34, free acidity (FA): 2.5, bath temperature: 45 ° C, treatment time: 10 minutes

Then, drying was performed at 80 ° C. for 10 minutes.
Thus, a sample of Example 1 was produced.

Further, the samples of Examples 2 to 7 and the samples of Comparative Examples 1 to 3 were prepared by changing the zinc phosphate treatment conditions variously as shown in Table 1.

[0090]

[Table 1]

A sample of Example 8 was prepared in the same manner as in Example 1 except that Ni plating was performed by a barrel method using a Watt bath having the following composition and conditions.

NiSO ₄ .6H ₂ O 280 g / l NiCl ₂ .6H ₂ O 50 g / l Boric acid 45 g / l Commercial brightener (organic) 15 ml / l Bath temperature 50 ° C. pH 4.5

The average cathode current density was 0.3 A / dm ² , and the average thickness of the plating film was 10 μm.

Further, in Example 1, a sample of Example 9 was prepared by applying a zinc phosphate coating layer without performing the activation treatment on the surface of the Ni plating layer. The sample of Example 10 was produced by applying a zinc phosphate coating layer without performing the activation treatment of.

The thickness of the zinc phosphate coating layer, the Zn / Ni ratio, and the initial compressive shear strength of the samples of the above Examples and Comparative Examples were measured. The results are shown in Table 2.

[0096]

[Table 2]

In the measurement of the film thickness, a part of the zinc phosphate film layer of the sample was scraped off, and the level difference was measured using a surface roughness meter, and this was taken as the film thickness of the zinc phosphate film. The Zn / Ni ratio in the coating was determined by scraping off a part of the zinc phosphate coating layer and performing non-standard quantification by SEM-EDX to determine the weight% ratio of zinc to nickel.

Further, the following tests were specifically conducted for the initial compressive shear strength indicating the adhesive strength.
Note that, for example, Ni / element in the column of the peeled portion is Ni
It means that peeling occurred between the plating layer and the element body.

[Adhesive]: ThreeBond 3062 (anaerobic, UV-curable adhesive)

[Adhesion method]: After applying the adhesive to the sample, the sample was sufficiently pressed against an Al block as a body, irradiated with UV (4 kW, 200 mV / cm ² ) for 5 minutes, and left standing at room temperature for 72 hours to cure. Was.

[Adhesion test]: The compression shear strength was measured at n = 5 at a compression speed of 5 mm / min.

Note that the pressure cooker test (120 ° C., 10
When 100 hours were performed at 0% RH) n = 50, no abnormalities were observed in the appearance in all cases.

On the other hand, a sample of Comparative Example 4 was formed by forming only the Ni plating layer using the sulfamic acid plating bath of Example 1 and not performing the zinc phosphate treatment.

Further, Comparative Example 5 was obtained by applying only the Ni plating layer in the Watt bath of Example 8 and not performing the zinc phosphate treatment.

The sample of Comparative Example 5 was added at 20 g / l.
-Chromate treatment was performed by immersion in a chromic anhydride solution at 30 ° C for 5 minutes, and a chromate film layer was formed on the Ni plating layer to obtain a sample of Comparative Example 6.

The samples of Comparative Examples 5 and 6 were also subjected to the same compressive shear strength test as described above. The results are also shown in Table 2.

From the above table, the effect of the present invention is clear. That is, in the permanent magnet of the present invention, when the permanent magnet is adhered onto the element body using an adhesive, the adhesive strength and the adhesive strength are as large as 60 kgf / m ² or more. Then, the maximum was as small as 40 kgf / m ² .

As is clear from the above, according to the present invention, it is possible to obtain a permanent magnet having a high adhesive strength by an adhesive.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01F 1/032-1/117 H01F 41/02 B22F 3/24

Claims (5)

(57) [Claims] Claims 1. R (where R is at least one of rare earth elements including Y), T (where T is Fe or Fe and Co) and B, and a substantially tetragonal system A Ni plating layer on the surface of the permanent magnet body having a phase, a zinc phosphate coating layer formed on the Ni plating layer, and Zn / Ni of the zinc phosphate coating.
Wherein the weight ratio is 8 or more and 30 or less. 2. The film thickness of the zinc phosphate coating is 0.1 μm.
2. The permanent magnet according to claim 1, which is not less than 10 μm. 3. The permanent magnet according to claim 2, wherein the Ni plating layer is provided by a sulfamic acid bath. 4. The method for producing a permanent magnet according to claim 1, wherein the surface of the Ni plating layer is treated with an acid containing soluble fluoride before forming the zinc phosphate coating layer. A method for producing a permanent magnet, comprising: 5. The method for producing a permanent magnet according to claim 4, wherein the surface of the permanent magnet body is treated with a treatment solution containing aldonic acid or a salt thereof and nitric acid before forming the Ni plating layer.