JPH06124814A - Manufacture of r-tm-b magnet - Google Patents

Abstract

PURPOSE:To improve corrosion-resistance by forming a chromate coating down to the bottom of a pin hole in a plate-film. CONSTITUTION:A plate layer and chromate coating layer are sequentially laminates an the surface of R-TM-B group permanent magnet, consisting of R (here, R is one or more kinds of rare earth elements including Y), TM (here, TM is one or more kinds of transition metal elements) and B (baron), for an R-TM-B magnet to be manufactured. In manufacture of the R-TM-B magnet, supersonic wave vibration is applied at formation of chromate coating layer.

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 coating formed thereon, and in particular to an R-TM-B having a plating layer such as Ni plating and a chromate coating layer sequentially formed.
The present invention relates to a method for manufacturing a B-based permanent magnet.

[0002]

2. Description of the Related Art As electric and electronic equipments have become higher in performance and smaller in size, the same requirement has been increased for a permanent magnet as one component thereof. 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 permanent magnets have emerged (Japanese Patent Laid-Open No. 59-46).
No. 008). Here, R is one kind or a combination of two or more kinds of 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, Ni plating, oxidation resistant resin, Al ion plating, etc. have been proposed. In particular, Ni plating is noted as improving the corrosion resistance of the R-TM-B permanent magnet with a simple treatment. (JP-A-60-544)
06). The Ni plating has the advantage that the surface coating layer has excellent mechanical strength as compared with the oxidation resistant resin, and that the coating layer itself has almost no hygroscopicity. However, unlike the oxidation resistant resin layer, there is a problem that pinholes exist on the surface of the Ni plating film layer. Therefore, regardless of whether or not the coating layer itself has hygroscopicity, there is a problem that moisture permeates through the pinholes into the magnet body with time and causes corrosion deterioration. In order to solve this problem, there have been proposed methods such as two-layer plating in which Ni plating is further applied on the Ni plating layer and filling of pinholes with a film of an oxidation resistant resin (Japanese Patent Laid-Open Publication No. Sho 6-96).
3-110707). However, the method using two-layer plating or an oxidation resistant resin coating is related to the adhesion between the lower Ni plating layer and the upper Ni plating layer or the oxidation resistant resin layer, and the corrosion resistance of the upper Ni plating layer or the oxidation resistant resin layer itself. I had a problem. Therefore, the above-mentioned method cannot sufficiently improve the corrosion resistance, which is a problem. As a means for solving this problem, it has been proposed to provide a Ni plating layer on the surface of the R-TM-B system permanent magnet and further provide a chromate film layer having strong water repellent property thereon.

[0003]

However, according to the conventional technique, the chromate film is formed even on the bottom of the pinhole of the plating film generated due to the surface roughness of the R-TM-B magnet. Is very difficult, and the incomplete chromate film causes a problem that the pinhole serves as a starting point of corrosion and the corrosion progresses throughout the magnet. Then, this invention makes it a subject to provide the manufacturing method of the R-TM-B type | system | group permanent magnet which forms a chromate film to the bottom of the pinhole of a plating film, and improves corrosion resistance.

[0004]

In order to solve the above problems, in the present technology, an ultrasonic oscillator is added to the chromate film forming step after plating. That is, the present invention relates to R (where R is one or more rare earth elements including Y), TM
(Where TM is one or more transition metal elements),
In a method for manufacturing an R-TM-B magnet in which a plating layer and a chromate coating layer are laminated on the surface of an R-TM-B based permanent magnet made of B (boron), ultrasonic vibration is generated when the chromate coating layer is formed. Is given. The present invention enhances the chromate effect inside the pinhole by applying fine vibrations by ultrasonic waves to the object during the chromate treatment regardless of the treatment method such as the chromate treatment by the rack or the chromate treatment by the barrel. As the frequency of ultrasonic waves, 27 KHz or 40 KHz can be used.

In the magnet according to the present invention, a part of TM of Fe, Co, Ni, etc. is Ga, Al, Ti, V, Cr, Mn, Z.
r, Hf, Nb, Ta, Mo, Ge, Sb, Sn, B
It can be replaced with an element such as i. The manufacturing method thereof may be a sintering method, a melt quenching method, or a modification thereof.

The plating is performed after degreasing with an organic solvent, the current density is preferably 1 to ^{2 A} / dm ² , and the thickness of the plating layer is preferably 5 to 20 μm. 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 on the material of the pre-plating treatment as much as possible, the first etching with 2 to 10% by volume of nitric acid and then hydrogen peroxide 5 -10vol
%, And the second etching with a mixed acid of 10 to 30 vol% acetic acid is most desirable. Next, a plating process is performed. The type of plating is not limited, but Ni plating is most preferable as described above. In this case, any of the Watts bath, the sulfamic acid bath, and the ammonium bath may be used, but bright plating is preferable. Matte plating is not preferable because it has a columnar crystal structure. However, since it has good adhesion and little stress, it is effective as a base for multilayer plating. The plating layer is not limited to one layer and may be a multilayer plating layer having two or more layers.

Finally, chromate treatment is performed to form a chromate film. In the present invention, ultrasonic waves are applied at this time so that even if there are pinholes in the plating layer, the treatment liquid reaches the bottom of the pinhole. Infiltrate. The chromate treatment conditions are as follows. After washing with water after the plating treatment, a dipping treatment is performed in a chromic acid solution. The chromate temperature is preferably 20 to 80 ° C., and the immersion time is preferably 1 to 10 minutes.
As the type of chromic acid solution, it is preferable to use chromic anhydride or dichromic acid having high acidity. The Cr concentration is preferably 0.01 mol / l or more. Chromate treatment using chromic acid having a low acidity is not preferable because a chromate film having no water repellent property is formed. Also, in order to activate the dipping treatment, it is preferable to use chromic acid having a high acidity as the type of chromic acid solution. Furthermore, it is desirable to use a chromic acid solution that does not contain a strong acid such as sulfuric acid, hydrochloric acid or nitric acid. The inclusion of a strong acid in the chromic acid solution in the chromate treatment of the present invention causes excessive activation of the chromic acid solution, which causes dissolution of Ni, which is the film quality, and is preferable for the adhesion of the chromate film. Absent. Further, when the strong acid penetrates into the magnet body through the pinhole on the Ni plating, the magnet body may be corroded. Therefore, it is desirable to use a chromic acid solution without strong acid for the dipping treatment. After the immersion process, wash with water,
Dry. The drying temperature is preferably 20 to 120 degrees. The drying temperature should not exceed 120 degrees because excessive heating causes deterioration of the corrosion resistance of the chromate coating.

[0008]

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.
Fine pulverization with a pulverized particle size of 3.5 μm (FSSS) was carried out by pulverizing with a jet mill using N ₂ gas as the pulverizing medium.
The obtained raw material powder was subjected to transverse magnetic field molding in a magnetic field of 15 KOe. The molding pressure was ² Ton / cm ² . The compact was sintered in vacuum at 1090 ° C for 2 hours. 18 × sintered body
Cut out to a size of 10 × 6 mm, then heat and hold in an argon atmosphere at 900 ° C. for 2 hours and then rapidly cool to a temperature of 6
It was kept for 1 hour in an atmosphere of argon kept at 00 ° C. The sample thus obtained was subjected to the following surface treatment.
The obtained sample was degreased with IPA, then HNO ₃ 2vol%, etched with a solution for 1 minute, and then washed with water to obtain acetic acid 20vol.
%, Hydrogen peroxide solution 5 vol% mixed acid for 30 seconds, washed with water, and then plated. A Watt bath was used as the Ni plating solution, and saccharin or the like was added as a brightening agent. The film thickness was 15 μm. After plating, chemical conversion treatment was performed under the working conditions shown in Table 1. 7g / l Cr as chemical conversion treatment liquid
An O ₃ solution was used. (Temperature 60 ° C)

[0009]

[Table 1] The number of samples was 100 each. Table 2 shows the results of the corrosion resistance test. In the corrosion resistance test, the sample was left in a state of 119.6 ° C. × 2 atm and 100% for a prescribed time (judged by the presence of surface blisters).

[0010]

[Table 2]

[0011]

According to the present invention, a coating layer composed of metal plating and a chromate coating layer is made more complete by applying vibration by an ultrasonic oscillator during formation of the chromate coating layer, -It significantly improved the corrosion resistance of the TM-B magnet.

Claims (1)

[Claims] 1. From R (where R is one or more kinds of rare earth elements including Y), TM (where TM is one or more kinds of transition metal elements), and B (boron) R-TM
In a method for producing an R-TM-B magnet in which a plating layer and a chromate coating layer are sequentially laminated on the surface of a -B permanent magnet,
A method for producing an R-TM-B based permanent magnet, which comprises applying ultrasonic vibration during formation of a chromate coating layer.