JPH0582320A - R-tm-b series permanent magnet having improved corrosion resistance and film thickness uniformity - Google Patents

Abstract

PURPOSE:To remarkably improve corrosion resistance and film thickness uniformity insufficient in conventional plating in a magnet containing rare earth elements and iron as main ingredients. CONSTITUTION:An R-TM-B series permanent magnet having improved corrosion resistance and film thickness uniformity comprises double layers formed of an electrolytic Cu-plated layer and an electrolytic Ni-plated layer on the surface of the R-TM-B series permanent magnet substantially containing by weight 5-40% of R (R is a combination of one or more types of rare earth elements including Y), 50-90% of TM (TM is transition metal containing Fe as a main ingredient) and 0.2-8% of B (boron).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an R-TM-B type permanent magnet having a corrosion-resistant and film-thickness remarkably improved by providing a Cu plating layer by electrolysis in a magnet body.

[0002]

2. Description of the Related Art As electric and electronic devices have become more sophisticated and smaller in size, the same requirements have been increased for a permanent magnet, which is one of the components. That is, the strongest permanent magnet before was a rare earth / cobalt (R-Co) system, but in recent years, a stronger R-co
TM-B system permanent magnets have emerged (Japanese Patent Laid-Open No. 59-46).
No. 008). Here, R is one or a combination of two or more rare earth elements including Y, TM is a transition metal center such as Fe or Co, and a part thereof is replaced with another metal element or non-metal element, B is boron. However, R-TM-B
The system permanent magnet has a problem that it is extremely rusty. Therefore, in order to improve the corrosion resistance, a measure has been taken to provide an oxidation resistant coating layer on the surface of the permanent magnet body. As the type of coating layer, electrolytic Ni plating, oxidation resistant resin, Al ion plating, etc. have been proposed.
The i-plating has been attracting attention because it improves the corrosion resistance of the R-TM-B type permanent magnet with a simple treatment (Japanese Patent Laid-Open No. 60-
54406). Electrolytic Ni plating has the advantage that the surface coating layer is superior in mechanical strength to the oxidation resistant resin, and that the coating layer itself has almost no hygroscopicity.

[0003]

However, the electrolytic N
In the method using i-plating, the plating current tends to concentrate on the peripheral parts such as the corners of the magnet body, and the film thickness on the peripheral parts becomes thicker. There was a tendency that the film thickness of the part became thin. Therefore, it is not possible to achieve a sufficient film thickness homogeneity with electrolytic Ni plating, and in particular for irregularly shaped products such as cylinders, the Ni plating layer can hardly be coated on the inner diameter portion, which poses a problem in terms of corrosion resistance. Was becoming. Therefore, an object of the present invention is to improve the corrosion resistance and the film thickness uniformity with high reliability.
-To provide a TM-B system permanent magnet.

[0004]

In the present invention, the weight ratio of R (where R is one or a combination of two or more rare earth elements including Y) is 5 to 40%, TM (here, TM is mainly Fe). In the R-TM-B based permanent magnet composed of 50 to 90% of transition metal) and 0.2 to 8% of B (boron), as a base plating of an electrolytic Ni plating layer provided for the purpose of improving corrosion resistance,
It is an R-TM-B system permanent magnet with improved corrosion resistance and film thickness uniformity, characterized by providing a Cu plating layer by electrolysis, and a method for producing the same. Further, the present invention is characterized in that, when performing the above-mentioned electrolytic Cu plating, electrolytic Ni strike plating is performed as a pretreatment. Cu is easily discolored in the air, but unlike Al and Zn, it is electrochemically noble and less corrosive, and is therefore an important metal for rust prevention. Further, since Cu is excellent in electric conductivity and rich in flexibility and spreadability, it has an advantage that the film throwing power is good even by an electroplating method. This tendency is particularly noticeable in alkaline baths, and it is thought that this enables uniform coating of the plating regardless of the inner and outer diameters even for irregularly shaped products such as cylinders where it was difficult to make the film thickness uniform by Ni electrolytic plating. Be done. The present invention improves the corrosion resistance and film thickness uniformity of the R-TM-B based permanent magnet by performing Cu plating by electrolysis as described above. In the present invention, F
Elements such as e, Co, and Ni that partially replace TM are Ga, Al, Ti, V, Cr, and M depending on the purpose of addition.
n, Zr, Hf, Nb, Ta, Mo, Ge, Sb, S
n, Bi, Ni, etc. can be added to the present invention, and any RT
It can also be applied to MB magnets. Further, the manufacturing method thereof may be a sintering method, a molten metal quenching method, or a modification thereof. Regarding the pre-plating treatment, it is preferable to use an acidic solution in order to remove the work-affected layer and activate the pre-plating. A strong acid such as sulfuric acid or hydrochloric acid is effective for pre-plating activation, but in order to avoid the influence of pre-plating treatment on the material as much as possible, the first etching with 2 to 10 vol% nitric acid, and then 5 to 10 vol. %, Acetic acid 10
The second etching with a mixed acid of ˜30 vol% is most desirable. Then, Ni strike plating treatment by electrolysis is performed. It is more preferable to perform electrolytic Ni strike plating before performing electrolytic Cu plating. This is because when the R-TM-B system permanent magnet is directly immersed in the electrolytic plating solution, a very thin Cu displacement plating film is formed on the surface of the magnet body, and the adhesion between the plating film and the surface of the magnet body deteriorates. is there. Therefore, it is more desirable to prevent displacement plating by providing a Ni strike plating layer by electrolysis in order to improve adhesion. Electrolysis N
The type of i plating may be a Watt bath, a sulfamic acid bath, or an ammonium bath. The current density is 1 to
10 A / dm ² is good, and the thickness of the Ni plating layer is 0.5-
5 μm is preferable. Next, after the electrolytic Ni strike plating treatment is followed by washing with water, electrolytic Cu plating treatment is performed. As a bath for electrolytic Cu plating, an alkaline bath is preferable from the viewpoint of good turning property of the film as described above, and a Cu pyrophosphate bath is particularly preferable. The current density is 1 to 5 A / d
m ^{2 is} good, and the thickness of the Cu plating layer is 5 to 15 μm, preferably 10 to 15 μm. Then Ni by electrolysis
Perform plating process. It is preferable to perform electrolytic Ni plating treatment after washing with water after electrolytic Cu plating treatment. If the Cu plating is left as it is, the discoloration in the air is easy as described above, and thus surface oxidation is likely to occur, which is not preferable. Further, by coating an electrochemically base Ni plating layer on the Cu plating layer, it is possible to expect an effect of a corrosion prevention mechanism by characteristic plating of both lower Cu layer and upper Ni layer. After that, it is desirable to perform electrolytic Ni plating treatment. The type of electrolytic Ni plating may be a Watt bath, a sulfamic acid bath, or an ammonium bath. The current density is 1 to
5A / dm ² is good, and the thickness of the Ni plating layer is 5-15μ
m, preferably 5 to 10 μm. The total thickness of the plated layer is preferably 15 to 25 μm.

[0005]

EXAMPLES Nd (Fe _0.7 Co _0.2 B _0.07 Ga _0.03 ) _6.5
An alloy having the following composition was produced by arc melting, and the obtained ingot was roughly crushed by a stamp mill and a disc mill.
N ₂ gas was used as the grinding medium to carry out fine grinding with a jet mill to obtain fine grinding having a grinding particle size of 3.5 μm (FSSS). The obtained raw material powder was oriented in a magnetic field of 15 kOe, and 2
It was molded into a cylinder at a pressure of ton / cm ² . The compact was sintered in vacuum at 1090 ° C for 2 hours. Outer diameter of the sintered body is 20
It was cut out into a cylinder having dimensions of inner diameter 16 × height 10 mm and then heated and held in an argon atmosphere at 900 ° C. for 2 hours and then rapidly cooled and held in an argon atmosphere in which the temperature was kept at 600 ° C. for 1 hour. For the sample thus obtained, the first etching with 5 vol% nitric acid was performed as a pretreatment for plating, followed by 10 vol% hydrogen peroxide and 25 vol% acetic acid.
The second etching was performed using the mixed acid of. Then Table 1
Under the conditions shown in Table 1, various surface treatments were performed so that the thickness of the plating layer on the outer diameter portion of the cylindrical body would be the value shown in Table 1.

[0006]

[Table 1]

With respect to the samples shown in Table 1, the thickness of the plating layer on the inner diameter of the cylinder was measured and was 119.6 ° C. and 100% RH.
Corrosion resistance test at 2 atm for 100 hours and 80 ° C 90% R
A humidity resistance test was conducted at H for 500 hours. The results are shown in Table 2.

[0008]

[Table 2]

In Table 2, the corrosion resistance test results and the humidity resistance test results show changes in the appearance of the samples. From Table 2,
It can be seen that the permanent magnet according to the present invention can significantly improve the corrosion resistance and the film thickness uniformity as compared with the conventional magnet.

[0010]

According to the present invention, in a magnet mainly composed of rare earth and iron, the corrosion resistance and the film thickness uniformity, which were insufficient by the conventional plating, were remarkably improved.

Claims (2)

[Claims] 1. A weight ratio of R (where R is one or a combination of two or more rare earth elements including Y) 5 to 40%, TM
(Here, TM is a transition metal mainly composed of Fe) 50 to 90
%, B (boron) 0.2 to 8%, which is substantially R-TM
-Electrolytic Cu plating layer and electrolytic N on the surface of the B-based permanent magnet
An R-TM-B system permanent magnet having a double layer composed of an i-plated layer and having improved corrosion resistance and film thickness uniformity. 2. A weight ratio of R (where R is one or a combination of two or more rare earth elements containing Y) 5 to 40%, TM
(Here, TM is a transition metal mainly composed of Fe) 50 to 90
%, B (boron) 0.2-8% R-TM practically
-Electrolytic Ni strike plating layer on the surface of B type permanent magnet,
R-TM-B having a triple layer consisting of an electrolytic Cu plating layer and an electrolytic Ni plating layer and having improved corrosion resistance and film thickness uniformity
System permanent magnet.