JPH07142246A - Permanent magnet - Google Patents

Abstract

PURPOSE:To enhance a bonding property and an oil-resistant property (especially in an oil containing sulfur) at high temperatures in addition to moistureproofness and a salt-water-spraying-resistant property by a method wherein the surface of an R-T-B system permanent magnet body is provided with an Ni-plating layer and an Sn-plating layer is formed on the Ni-plating layer. CONSTITUTION:A permanent magnet body contains R (where R represents one or more kinds of rare-earth elements including Y), Fe and B. It is preferable that contents of R, Fe and B are set at 5.5atom.%<=R<=30atom.%42 atom.%<=Fe<=-90atom.% and 2atom.%<=B<=28atom.%. A protective layer is formed on the surface of the magnet body by an electroplating operation. When the protective layer is formed by the electroplating operation, it is possible to form a high-performance and corrosion-resistant film whose mass productivity is excellent. It is preferable that the protective layer which is formed in this manner is composed mainly of Ni. An Sn-plated layer is formed on the Ni- plating layer. Thereby, the bonding strength of the magnet body at high temperatures can be enhanced due to the improvement of the high-temperature oil-resistant property (the oil is an oil containing sulfur) and the solderability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a permanent magnet, more specifically, R (where R is at least one of rare earth elements including Y), T (where T is Fe or F).
e and Co) and B, and having a substantially tetragonal main phase.

[0002]

2. Description of the Related Art In recent years, R-Fe such as Nd-Fe-B magnets
A -B type magnet has been developed. Japanese Patent Application Laid-Open No. 59-46008 discloses a sintered magnet, and Japanese Patent Application Laid-Open No. 60-9852 discloses a magnet by a rapid quenching method.

These are high-performance magnets exhibiting a high energy product of 25 MGOe or more, but since they contain iron and a rare earth element which are easily oxidized as main components, they have corrosion resistance (particularly moisture resistance and salt spray resistance). Is low, and as a result, deterioration of performance, variation, etc. are becoming problems.

For the purpose of improving the low corrosion resistance of such RTB magnets, there has been proposed a technique of applying Ni plating, two-layer plating, resin coating, Sn plating or the like on the surface of the magnet. (JP-A-60-54406, JP-A-60-63901, JP-A-2-216802, JP-A-5-29118).

[0005]

By the way, recently,
Due to the high performance of the R-T-B magnets, there is an increasing demand for expansion of applications to industrial machines, automobiles, etc., and accordingly, in addition to conventional moisture resistance and salt spray resistance, adhesiveness at high temperatures, Oil resistance (especially one containing sulfur) has come to be required, but no permanent magnet by conventional treatment satisfies these requirements.

Therefore, the object of the present invention is to provide a permanent magnet excellent in all of the adhesiveness at high temperature and the oil resistance (especially those containing sulfur) in addition to the conventional moisture resistance and salt spray resistance. It is what

[0007]

These objects are achieved by the present invention described in (1) to (7) below. (1) R (wherein R is at least one of rare earth elements including Y), T (where T is Fe or Fe and Co) and B are contained, and a substantially tetragonal main phase is formed. Having a Ni plating layer on the surface of the permanent magnet,
A permanent magnet having an Sn plating layer formed on an i plating layer. (2) The thickness of the Sn plating layer is 0.05 μm or more 10
The permanent magnet according to (1) above, which has a size of not more than μm. (3) The permanent magnet according to (1) or (2) above, wherein the Sn plating layer is formed by a neutral plating bath. (4) The permanent magnet as described in any of (1) to (3) above, wherein the thickness of the Ni plating layer is 3 μm or more and 20 μm or less. (5) The permanent magnet according to any one of (1) to (4) above, wherein an intermetallic compound layer of Ni and Sn is formed on at least an interface between the Ni plating layer and the Sn plating layer. (6) The intermetallic compound of Ni and Sn is Ni ₃ Sn, N
The permanent magnet according to (5) above, which is at least one kind of i ₃ Sn ₂ and Ni ₃ Sn ₄ . (7) The thickness of the intermetallic compound layer of Ni and Sn is 0.0
The permanent magnet as described in (5) or (6) above, which is 1 μm or more.

[0008]

In the present invention, the RTB-based permanent magnet body has a Ni plating layer on the surface thereof, and the Sn plating layer is formed on the Ni plating layer. As a result, in the permanent magnet of the present invention, in addition to the conventional moisture resistance and salt spray resistance, adhesion at high temperature and oil resistance (particularly those containing sulfur) were improved.

[0009]

Specific Structure The specific structure of the present invention will be described in detail below.

[Pretreatment] In the present invention, before the protective layer is formed on the permanent magnet, pretreatment is performed using a predetermined treatment liquid.

The acid used for the pretreatment of plating is hydrochloric acid,
Non-oxidizing acids such as sulfuric acid are often used. However, particularly when the permanent magnet contains a rare earth element, when treatment is performed using these acids, hydrogen generated by the acids is
It is occluded on the surface of the permanent magnet and the occluded site becomes brittle, and a large amount of powdery undissolved material is generated. Since this powdery undissolved substance causes defects 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 less hydrogen, as the acid used. By using nitric acid, the surface of the magnet is chemically etched by its oxidizing action, and a fine concavo-convex structure that is invisible to the naked eye is formed.

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

When this aldonic acid or its salt is contained, Fe ions eluted by nitric acid and aldonic acid salts form a stable chelate compound, and Nd, which has a greater ionization tendency than Fe, is dissolved by the substitution reaction with free Fe ions. Can be suppressed. Therefore, by adding aldonic acid or its salt, chemical etching, which occurs locally and suddenly only with nitric acid, proceeds more gently, and there is a uniform and locally deep 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 improvement in adhesion is selectively realized by aldonic acid or a salt thereof, and is not realized by other chelating agents such as citric acid and tartaric acid.

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

The average depth of the irregularities (the depth from the valleys to the peaks) is preferably about 1 to 5 μm. The average pitch of the irregularities 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 less, particularly 0.6 N or less, and more preferably 0.5 N or less. When the nitric acid concentration exceeds 1 N, the dissolution rate of the magnet body becomes extremely high, and it is difficult to control the amount of dissolution, so that a product with desired dimensional accuracy cannot be obtained. In addition, when a large amount of processing such as barrel processing is performed, variations in processing state become large. Further, when the nitric acid concentration is low, the amount of liquid becomes too large, and the amount of dissolution becomes insufficient. Therefore, the nitric acid concentration is preferably 1 N or less, particularly preferably 0.05 to 0.5 N.

The addition amount of aldonic acid or its salt added to the treatment liquid is preferably equimolar or more to Fe dissolved during the treatment. If the addition amount of aldonic acid or its salt is less than the equimolar amount of Fe dissolved in the treatment liquid at the end of treatment, the effect of forming irregularities is insufficient and the adhesiveness is lowered, which is not preferable.

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

Aldonic acid or its salt is HOCH ₂ (C
HOH) nCOOY (Y is H or a cation), and may be any of gluconic acid, arabonic acid, mannonic acid, galactonic acid, heptonic acid, etc., having n = 3 to 5, for example. In this case, these alkali metal salts are preferable from the viewpoint that a reagent having a particularly high purity can be obtained.

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

In addition to aldonic acid and its salts, salts of hydroxycarboxylic acids such as citric acid, tartaric acid and oxyacetic acid may be added to the acid treatment liquid. When the salt is added, 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 material also increases.

Further, a surfactant such as sodium lauryl sulfate or polyoxyethylene nonylphenyl ether may be added to the acid treatment liquid, but when these are added to the treatment liquid of the present invention, a powdery form is obtained. 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, which adversely reduces the adhesion.

The treatment temperature with the treatment liquid is 40 ° C. or lower, particularly 30 ° C. or lower, and more preferably 20 ° C. or lower. If the treatment temperature exceeds 40 ° C, the action of nitric acid to dissolve the magnet body becomes predominant, and the effect of adding the aldonate disappears, 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 it 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 magnet body thus pretreated, it is preferable to carry out cleaning using ultrasonic waves. This ultrasonic cleaning is preferably 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 for the purpose of neutralizing the residual acid is dissolved. If chlorine ions are contained in the cleaning liquid, it may cause rust 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. Furthermore, before performing the pretreatment, mechanical polishing treatment and dipping or electrolytic degreasing treatment or alkali derusting treatment usually performed as plating pretreatment may be performed depending on 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 become too large.

[Ni Plating Layer] A protective layer is formed on the cleaned magnet surface by electroplating. By forming the protective film by electroplating, it is possible to form a high-performance corrosion resistant film having excellent mass productivity.

The protective 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 antirust 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 borofluoride bath, a nickel bromide bath, and the like. However, in this case, since the dissolution of the anode is reduced, it is necessary to replenish the bath with nickel ions. This nickel ion is preferably supplemented as a solution of nickel sulfate or nickel bromide.

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

[0032] _{Ni (NH 2 SO 3) 2} · 4H 2 O 150~600g / l NiBr ₂ · 6H ₂ O 0~30g / l boric acid 30 to 60 g / l

At this time, it is preferable that the water in the bath also does not contain chlorine, and the amount of chlorine 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 mainly prevent the generation of blisters over time.

The plating conditions are pH 3-6, particularly preferably 4-5, temperature 30-70 ° C., current density 0.1-10 A /
It should be about dm ² . If the pH is below this range, the magnet body will dissolve, and if the pH exceeds this range, nickel hydroxide precipitates and the plating film becomes brittle. Further, if the current density is less than this range, impurities such as Cu and Co often co-fold in the plated film, resulting in a film with poor appearance and low corrosion resistance. Hydrogen generation in the vicinity increases and is absorbed by the magnetic material, which causes a decrease in adhesion.

In the present invention, the thickness of the Ni plating layer is set to about 3 to 20 μm, preferably about 10 to 20 μm. When the film thickness is in this range, the function as a protective layer is sufficient and the magnetic characteristics are not deteriorated.

In the present invention, if necessary, corrosion resistance improvement such as known double nickel plating and tri-nickel plating having different natural potentials as described in page 115 of the plating technology guidebook (published by Tokyo Plating Materials Cooperative Association). Multilayer plating for the purpose can also be preferably used. Even when a normal Watts bath or a sulfamine bath containing chloride is used, the effect of improving the adhesion and the corrosion resistance of the present invention can be obtained.

When forming the protective layer by electroplating, a rack plating method or a barrel plating method is appropriately applied depending on the size and shape of the magnet body.

Generally, in a magnet body having a large size which is processed by the rack plating method, a protective layer which is defect-free has a large area, so that it is necessary to increase the thickness of the protective layer, while the barrel plating method is used. A desirable protective layer thickness by only electroplating in a magnet body having a small surface area that can be processed in a large amount and having a weight of several tens g or less may be relatively thin.

[Sn Plating Layer] In the present invention, a Sn plating layer is formed on the Ni plating layer.

This Sn plating layer is formed by an electroplating method using a conventionally known neutral bath of pyrophosphoric acid, organic carboxylic acid, etc., acid bath of sulfuric acid, etc.

For example, among these, it is preferable to use a neutral bath which exhibits higher compressive shear strength in the soldering test, and one of them is the composition of the neutral pyrophosphate bath.

SnSO ₄ 35-60 g / liter K ₄ P ₂ O ₇ 125-200 g / liter Organic additive 0.1-10 g / liter

The plating conditions may be pH 7.5 to 9.0, temperature 25 to 55 ° C., and current density 0.1 to 5 A / dm ² . If the temperature is lower than this range, the gloss will be good, but the uniform electrodeposition property and current efficiency will decrease. If the temperature exceeds this range, the uniform electrodeposition property and current efficiency will decrease due to poor gloss and an increase in tetravalent tin. Invite. On the other hand, if the current density is less than this range, eutectoids of impurities such as Ni, Cu, Pb in the plated film become too much, resulting in a film with poor appearance and corrosion resistance. When it exceeds, the current efficiency is lowered, hydrogen generation near the cathode is increased, and hydrogen is absorbed by the magnetic material through the Ni plating film, which causes a decrease in adhesion.

In the present invention, the thickness of the Sn plating layer is
It is desirable to set it to 0.05 to 10 μm, preferably 0.1 to 5 μm, and particularly 0.1 to 1 μm. When the thickness of the Sn plating layer is less than this range, it is difficult to control the film thickness, and salt spray resistance and oil resistance become insufficient. When it exceeds this range, the difference in film stress becomes remarkable, and adhesion with Ni plating This is because the appearance is changed from gloss to matte (gray), the surface morphology of the coating is changed, and the salt water spray resistance is reduced.

In the Sn plating layer of the present invention,
Impurities such as Pb, Sb, Cu and Fe may be contained in the range of less than 5 wt%.

[Ni—Sn Intermetallic Compound] In the present invention, a Ni—Sn intermetallic compound layer, particularly stable Ni ₃ S, is provided at least at the interface between the Ni plating layer and the Sn plating layer.
It is desirable that there is a layer in which at least one of n, Ni ₃ Sn ₂ and Ni ₃ Sn ₄ is formed.

The thickness of the Ni-Sn intermetallic compound layer is
It is desirable that the interface between the Ni plating layer and the Sn plating layer be 0.01 μm or more, and the entire Sn plating layer may be a Ni—Sn intermetallic compound. Therefore, the upper limit of the thickness of the Ni-Sn intermetallic compound layer does not exist, but in view of economical efficiency such as heat treatment, it may be about 2 to 3 µm.

The thickness of the Ni-Sn intermetallic compound layer is
If it is less than 0.01 μm, it is Ni-Sn by X-ray diffraction.
The level of intermetallic compounds was not detected, and no improvement in adhesive strength due to soldering was observed.

The Ni—Sn intermetallic compound layer is formed by applying a Ni plating layer and a Sn plating layer on the magnet body, and
It is formed by performing heat treatment for 30 minutes to 20 hours in an atmosphere of 0 to 200 ° C. This treatment may be performed in the atmosphere. If the temperature is less than this range, it is difficult to form an intermetallic compound, and if the temperature exceeds this range, excessive heat treatment causes excessive discoloration, and the adhesion between the Ni plating and the magnet body decreases.

If the time is less than this range, the actual temperature may not be reached due to the shape of the object to be treated and the heat treatment will be insufficient. On the other hand, when it exceeds 20 hours, the effect of heat treatment does not change and the productivity is remarkably reduced.

Here, FIG. 1 shows a specific example of the formation of the Ni—Sn intermetallic compound by heat treatment.

[Permanent Magnet Body] In the present invention, the permanent magnet body having the protective layer formed on the surface thereof contains R (where R is at least one rare earth element including Y), Fe and B. is there.

The contents of R, Fe and B are 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 a sintering method, the following composition is preferable.

As the rare earth element R, Nd, Pr, H
at least one of o and 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 of misch metal or the like can be used as a raw material.

The content of R is 5.5 to 30 as described above.
At% is preferable, and the reason is that if it is less than 5.5 at%, a high coercive force (iHc) cannot be obtained because the crystal structure has a cubic crystal structure having the same structure as α-iron, and 30% by This is because if it exceeds, the R-rich nonmagnetic phase increases and the residual magnetic flux density (Br) decreases.

The Fe content is 42 to 90 as described above.
It is preferably at% because the Fe content is 42 at
If it is less than%, Br decreases, and if it exceeds 90 at%, iH
This is because c decreases.

The content of B is 2 to 28 at% as described above.
The reason is that if B is less than 2 at%, a rhombohedral structure is formed, so that iHc is insufficient.
If it exceeds 8 at%, the B-rich nonmagnetic phase increases,
This is because Br decreases.

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

Further, in addition to R, Fe and B, Ni, Si, Al, Cu, Ca, etc. are inevitably contained in the total 3 as inevitable impurities.
It may be contained at at% or less.

Furthermore, by substituting a part of B with at least one of C, P, S, and Cu, it is possible to improve the productivity and reduce the cost. In this case, the substitution amount is preferably 4 at% or less of the whole. In order to improve coercive force, productivity, and cost reduction, Al, Ti,
V, Cr, Mn, Bi, Nb, Ta, Mo, W, Sb,
You may add 1 or more types, such as Ge, Sn, Zr, Ni, Si, and Hf. In this case, the total addition amount is preferably 10 at% or less.

The permanent magnet body of 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% by volume of a non-magnetic phase.

Such a permanent magnet body is disclosed in JP-A-61-1.
No. 85910 is disclosed.

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

The powder obtained is preferably shaped 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 is heated to 1000 to 1200 ° C.
Sinter for 0.5-5 hours and quench. The sintering atmosphere is preferably an inert gas atmosphere such as Ar gas. After this, preferably in an inert gas atmosphere, 500
Aging treatment is performed at ˜900 ° C. for 1 to 5 hours.

[0068]

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

27.4 Nd prepared by the powder metallurgy method
A sintered body having a composition of −3.0Dy−1.0B−the balance of Fe (the numbers are% by weight) was used in an argon atmosphere at 600 ° C.
A permanent magnet was obtained by subjecting to a time aging treatment, processing into a disk shape having a diameter of 23.5 mm and a thickness of 3.4 mm, and further chamfering by barrel polishing treatment.

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

After ultrasonically cleaning the above treated sample in ion-exchanged water, Ni plating was carried out by a barrel method using a Watt bath and a sulfamic acid bath having the following composition and conditions.

[0072] dull Watts bath _{NiSO 4 · 6H 2 O 280g /} l NiCl 2 · 6H 2 O 45g / l boric acid 40 g / l bath temperature 50 ° C. pH 4.5 average cathode current density of 0.3 A / dm ² plating film Thickness 15 μm

Watt 2-layer The first layer of semi-bright watt Ni plating was performed using a plating bath having the composition and conditions shown below.

NiSO ₄ .6H ₂ O 280 g / l NiCl ₂ .6H ₂ O 45 g / l Boric acid 40 g / l Commercial semi-brightening agent (no sulfur) 1.5 ml / l Bath temperature 50 ° C. pH 4.5 Average cathode Current density 0.3A / dm ² Plating film thickness 10μm

Further, bright watt Ni plating was performed using a plating bath having the following composition and conditions to obtain a two-layer plating.

[0076] _{NiSO 4 · 6H 2 O 280g /} l NiCl 2 · 6H 2 O 50g / l boric acid 45 g / l commercial brightener (sulfur-based) 15 ml / l bath temperature 50 ° C. pH 4.5 Average cathodic current density 0. 3A / dm ² plating film thickness 5μm

[0077] sulfamic acid bath _{Ni (NH 2 SO 3) 2} · 4H 2 O 180g / l NiBr 2 · 6H 2 O 5g / l boric acid _{45g / l LiNH 2 SO 3 200g} / l bath temperature 50 ° C. pH 4.5 Average cathode current density 0.3A / dm ²

Next, Sn plating was carried out by a barrel method using a neutral pyrophosphoric acid bath and an acidic matte sulfuric acid bath having the following composition and conditions.

Neutral pyrophosphate bath SnSO ₄ 45 g / l K ₄ P ₂ O ₇ 165 g / l Organic additive 2 g / l Bath temperature 30 ° C. pH 8.0 Average cathode current density 0.5 A / dm ²

Acid matte sulfuric acid bath SnSO ₄ 50 g / l H ₂ SO ₄ 100 g / l Cresolsulfonic acid 100 g / l β-naphthol 1 g / l Gelatin 2 g / l Bath temperature 20 ° C. Average cathode current density 1.5 A / dm ²

Samples of Examples 1 to 9 were prepared by changing the film thickness shown in Table 1 depending on the treatment time of Ni plating and Sn plating. It should be noted that the samples of these examples were not subjected to heat treatment and therefore Ni-S
There was also no n intermetallic compound layer.

[0082]

[Table 1]

Next, using the sample of Example 5 above, the heat treatment conditions were changed to form a Ni—Sn intermetallic compound at the interface between the Ni plating layer and the Sn plating layer, and Example 10 as shown in Table 2 was used. ~ 16 samples were made.

Of the above samples, the structure of the interface between the Ni group and the Sn group was examined by X-ray diffraction for Example 5 not subjected to heat treatment and Example 15 subjected to heat treatment. As shown in (a) of FIG. 1, the presence of the Ni—Sn intermetallic compound was not recognized, but in Example 15, (b) of FIG.
Ni ₃ Sn, Ni ₃ S ₂ , Ni ₃
The presence of a Ni—Sn intermetallic compound which is Sn ₄ was observed. The film thickness of the Ni—Sn intermetallic compound layer was measured by oblique polishing SEM observation.

[0085]

[Table 2]

For comparison, surface treatments of Ni plating only, Sn plating only, two-layer plating of Ni and electroless Ni-P, spray coating only, electrodeposition coating only, Ni plating + electrodeposition coating were performed, and Samples of Comparative Examples 1 to 10 as shown in 3 were prepared.

[0087]

[Table 3]

The samples of the above Examples and Comparative Examples were evaluated as follows, and the results are shown in Tables 4, 5 and 6.

[0089]

[Table 4]

[0090]

[Table 5]

[0091]

[Table 6]

[Moisture resistance test] Pressure cooker test (120 ° C., 100% RH, 2 atm) for 40 hours and 1
The results of appearance evaluation (number: 20) at 00 hours are shown by the cumulative number of defective occurrences at each evaluation time.

[Salt Spray Test] Salt spray test (35 ° C.,
5 wt% -NaCl] Appearance evaluation (number: 10) at 24 hours and 48 hours was shown by rating numbers at each evaluation time.

[SO ₂ Gas Test] SO ₂ gas test (40
SE at 96 ° C., 75% RH, 5 ppm-SO ₂ )
Regarding the evaluation results of M-EDX observation (number: 1), those in which no morphological change was observed are indicated by ◯, and those in which morphological change was observed are indicated by x.

[High temperature oil resistance test (oil containing sulfur)] High temperature oil resistance test (150 ° C., transmission oil (containing sulfur)) SEM-ED at 300 hours and 600 hours
The results of X observation (number: 2) are indicated by ◯ when no morphological change is observed (see the photograph in FIG. 2), and those in which the morphological change was observed (see the photograph in FIG. 3) or oil on the film. What was observed was the x mark.

2 and 3 show the S of the surface of the sample of Example 13 before and after the high temperature oil resistance test for 600 hours.
4 and 5 are SEM photographs of Comparative Example 2 before and after the 300-hour high temperature oil resistance test. In addition,
The test for 600 hours was not carried out for those in which a morphological change was observed in the test for 300 hours.

[Soldering Test] Sn-plated S45C
The sample was soldered to the plate using a solder paste (225 ° C., 1 hour), and the solderability at that time and the compressive shear strength (number: 3) at high temperature (150 ° C.) In the evaluation, those having good solderability are indicated by ◯, those which can be soldered are indicated by Δ, and those which cannot be soldered are indicated by ×. Further, the measured value of the compressive shear strength at high temperature is shown by the average value of n = 3. As a matter of course, the compressive shear strength test was not carried out for those that could not be soldered.

[Adhesion Test] Compressive shear strength (number: 3) at high temperature (150 ° C.) when the sample is bonded to the S45C plate using the following two kinds of adhesives: a) Normal type : 3M S / W-2214 (Curing conditions:
120 ° C., 60 minutes) b) Heat resistant type: Araldite XN1244SR (Curing condition: 120 ° C., 60 minutes) The evaluation result is that the measured value of compressive shear strength at high temperature is n = 3.
The average value of

The effects of the present invention are apparent from the above table. That is, in the permanent magnet having the protective layer of the present invention, not only the moisture resistance and the salt spray resistance are good, but also the high temperature oil resistance (including sulfur), the solder, as compared with the permanent magnet having the conventional protective layer. The adhesive strength at high temperature was improved due to the improved adhesiveness.

As is apparent from the above, according to the present invention, it is possible to obtain a permanent magnet which has excellent characteristics in various fields and can be preferably used for parts of industrial machines and automobiles.

[Brief description of drawings]

FIG. 1 is an X-ray diffraction pattern of a coating surface for a sample of Example 5 of the present invention and a sample of Example 15.

2 is a photograph as a substitute for a drawing, which is an SEM photograph of a surface of a sample of Example 13 of the present invention before the high temperature oil resistance test (including sulfur) for 600 hours. FIG.

FIG. 3 is a photograph as a substitute for a drawing, which is an SEM photograph of a surface of a sample of Example 13 of the present invention after a high temperature oil resistance test (including sulfur) for 600 hours.

FIG. 4 is a drawing-substitute photograph, which is a SEM photograph of the surface of a sample of Comparative Example 2 of the present invention before the high temperature oil resistance test (including sulfur) for 300 hours.

5 is a drawing-substitute photograph, which is an SEM photograph of the surface of the sample of Comparative Example 2 of the present invention after the high temperature oil resistance test (including sulfur) for 300 hours.

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[Procedure amendment]

[Submission date] February 2, 1994

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Claims (7)

[Claims] 1. R (provided that R is at least one of rare earth elements including Y), T (provided that T is Fe or Fe and Co) and B, and is substantially tetragonal A permanent magnet having a Ni plating layer on the surface of a permanent magnet body having a phase, and an Sn plating layer formed on the Ni plating layer. 2. The thickness of the Sn plating layer is 0.05 μm
The permanent magnet according to claim 1, having a size of not less than 10 μm. 3. The permanent magnet according to claim 1, wherein the Sn plating layer is formed by a neutral plating bath. 4. The thickness of the Ni plating layer is 3 μm or more 2
The permanent magnet according to any one of claims 1 to 3, which has a diameter of 0 µm or less. 5. The permanent magnet according to claim 1, wherein an intermetallic compound layer of Ni and Sn is formed on at least an interface between the Ni plating layer and the Sn plating layer. 6. The intermetallic compound of Ni and Sn is Ni ₃
The permanent magnet according to claim 5, which is at least one kind of Sn, Ni ₃ Sn ₂ and Ni ₃ Sn ₄ . 7. The permanent magnet according to claim 5, wherein the thickness of the intermetallic compound layer of Ni and Sn is 0.01 μm or more.