JP3126215B2 - Manufacturing method of corrosion resistant rare earth permanent magnet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a high corrosion resistant rare earth permanent magnet by jig plating.

[0002]

2. Description of the Related Art Rare-earth permanent magnets are widely used in the field of electric and electronic equipment because of their excellent magnetic properties and economical efficiency. Of these, Nd-based rare earth permanent magnets are particularly inexpensive in raw material costs and excellent in magnetic properties as compared with Sm-based rare earth permanent magnets, and are therefore being applied to wider fields than ever before. However, Nd-based rare earth alloys generally have the disadvantage that they are easily oxidized in humid air in a very short time. This oxidation involves not only surface oxidation in which an oxide is formed on the magnet surface, but also intergranular corrosion, in which oxidation proceeds from the surface to the inside. This phenomenon is particularly remarkable in the case of Nd-based magnets. If corrosion proceeds during use, the performance of the device incorporating the magnet is degraded, and problems such as contamination of the periphery of the device occur. Such rare earth permanent magnets,
In particular, various surface treatment methods have been proposed to overcome the disadvantages of Nd-based magnets.
i-plating is excellent in corrosion resistance, productivity, cost, stability and the like, and is currently the mainstream of surface treatment for Nd-based magnets.

[0003]

Generally, Ni plating can be roughly classified into a barrel type and a jig type according to the technique. Barrel plating is a method in which a magnet is placed in a barrel-shaped basket and plating is performed while rotating the basket in a plating solution.
The jig method is a method in which magnets are fixed one by one with a jig and plated. The barrel type has an advantage that, unlike the jig type, there is no trace of a jig contact or a trace of an electric contact (hereinafter, referred to as a contact trace collectively in the present invention) on the product surface, but it rotates in a basket. Since the magnets are sometimes plated while contacting and colliding with each other, they are used only for small magnets that do not crack or chip even when contacting or colliding. For this reason, jig-type plating that leaves traces of contacts is adopted for large magnets, but the traces of the contacts are not plated, and oxidation corrosion progresses from the traces of the contacts as they are. Therefore, in order to impart corrosion resistance to the contact marks having a diameter of 0.1 to 1 mm, which are usually left in two to several places per product, resin coating such as a paint or an adhesive has been performed. In the case of computer peripherals, etc., where magnets are used in a relatively good environment, there was no problem with resin coating.However, with the expanding use of Nd-based magnets, the use of magnets in harsh atmospheres of high temperature and humidity has recently increased. It has been demanded that jig-type plated contact marks have at least the same corrosion resistance as resin coating, preferably Ni plating. The purpose of the present invention is
In the resin coating, the problem of moisture absorption and water permeability of the resin itself cannot be avoided, and high corrosion resistance cannot be obtained. Therefore, an object of the present invention is to provide a jig-type Ni plating method which is excellent in corrosion resistance by high corrosion resistance coating other than resin coating.

[0004]

Means for Solving the Problems In order to solve the above problems, the present inventors have studied various methods of improving the corrosion resistance of contact traces after jig plating by using a metal system from the viewpoint of water absorption. As a result, they have found that a brazing method with good workability at a relatively low temperature is effective, and have completed the present invention. That is, the gist of the present invention is characterized in that, in a method for manufacturing a rare earth-iron-boron-based sintered permanent magnet, a jig-type plating is performed on the surface of the sintered magnet body, and then a contact trace is soft-brazed. And a method for producing a corrosion-resistant rare earth permanent magnet. The soft solder is preferably Sn-Pb.

Hereinafter, the present invention will be described in detail. First, a rare earth sintered permanent magnet formed and sintered is plated by a known jig method. The process is alkaline degreasing, activation,
Desmutting, electric Ni plating, and solvent degreasing are performed in this order. Finally, contact mark processing is performed to obtain a product.

The most important feature of the present invention resides in that the contact marks of the jig-plated magnet are treated by brazing. The magnet is removed from the jig, and solvent degreasing is performed to remove stains such as oils and fats adhering to the contact traces and the vicinity thereof, and residual plating solution that cannot be completely cleaned. This is performed by immersion or wiping in a solvent such as trichloroethylene, perchlorethylene, trichloroethane, or chlorofluorocarbon. Brazing is then applied to coat the contact marks.

[0007] There are two types of brazing: soft brazing and hard brazing. With a melting point of 450 ° C, a low melting brazing is called a soft brazing and a high melting brazing is called a hard brazing. In the present invention, high corrosion resistance can be obtained by using any of them, but it is preferable to use a soft solder having a low melting point because hard brazing may adversely affect the magnet properties and the corrosion resistance of plating. An example using a soft solder will be described below. As a kind of soft solder, there is a tin-lead alloy, which is usually called solder, and tin mainly plays a role of bonding because it is easy to form an alloy with iron and copper, and lead lowers melting point and increases strength Used for The composition is Sn 19 to 96% by weight, Pb 4 to 81
% By weight, and Sb, Cd, Bi,
One or more of As and Ag are contained in an amount of 30% by weight or less, and the melting point is 180 to 300 ° C. In addition, it is preferable that the brazing is contained in the brazing because the brazing has a good elongation and the workability is improved, but if the brazing remains after brazing, there is a possibility that the brazing may corrode. Required.

[0008] The brazing operation is performed using a brazing iron.
A wax heated to 0 ° C. to 300 ° C. is poured into the contact mark and its vicinity. When the magnet is large, it is preferable to heat the magnet body to 40 ° C. to 200 ° C. in advance to improve the flow of the wax. After brazing, the surface of the braze is polished and finished.

[0009]

EXAMPLES Hereinafter, specific embodiments of the present invention will be described with reference to examples, but the present invention is not limited thereto. [Example] 32.0 Nd-2.0 by high frequency melting in an Ar atmosphere
Tb-1.1B-58.4Fe-5.0Co-1.0A
An ingot consisting of 1-0.5Ga in each weight% was prepared. This ingot is coarsely crushed with a jaw crusher,
The powder was further pulverized by a jet mill using N ₂ gas to obtain a fine powder having an average particle size of 3.5 μm. Next, this fine powder was
98. Fill the mold with a magnetic field of 000 Oe applied.
Molding was performed under a pressure of 07 MPa (1.0 t / cm ² ). Then, it is sintered at 1,090 ° C. for 2 hours in vacuum, and further 550 ° C.
For 1 hour to obtain a permanent magnet. A test piece of 50 mm × 30 mm × 10 mmt was cut out from the obtained permanent magnet, and the axis of easy magnetization was made to coincide with the thickness direction. This test piece is subjected to the following surface treatment. (1) Alkaline degreasing: An alkaline degreasing solution having the following composition was added to 50
Soak at 30 ° C for 30 minutes. Liquid composition: sodium hydroxide 30 g / l, sodium carbonate 20 g / l, sodium orthosilicate 50 g / l, surfactant 2 g / l. (2) Activation treatment: Immersion in an activation treatment solution having the following composition for 1 minute. Bath composition: acetic acid 2% (V / V), hydrochloric acid 2% (V / V), sulfuric acid 2% (V / V), sodium laurate 1 g / liter. (3) Smut removal: Ultrasonic washing is performed for 30 seconds. (4) Electric Ni plating: 20 μm plating is performed by a jig at a temperature of 50 ° C. in a Ni plating solution having the following composition. Liquid composition: nickel sulfate 280 g / l, nickel chloride 45 g / l, boric acid 40 g / l, brightener 3 cc / l. (5) Solvent degreasing: The organic oil at the contact trace and its surroundings is removed with trichloroethylene. (6) Brazing treatment: A solder having the following composition is applied to the contact trace of plating at 2.0 mmφ × 1.0 mmt. Solder composition: 63% by weight of tin, 37% by weight of lead.

After completion of the above brazing surface treatment, a corrosion resistance test was conducted under the following conditions, and the results are shown in Table 1. [Corrosion resistance test] 120 ° C, 202.6 kPa (2 atm), 100% R
H was subjected to an autoclave test to check for the appearance of abnormalities such as rusting and blistering. Evaluation: ：: No abnormality. ×: rusting from the electrode contact coating.

[Comparative Example] For comparison, a magnet similar to that of the embodiment except that the contact mark was coated with an epoxy resin was subjected to electric Ni plating.
Table 1 shows the results of the corrosion resistance test.

[0012]

[Table 1]

[0013]

According to the present invention, the trace of the contact point of a jig-type plated product of a rare earth-iron-boron permanent magnet is brazed with a soft solder so that the corrosion resistance is excellent and the deterioration of magnetic properties with time is small. Thus, a rare earth permanent magnet having a long life and high reliability is obtained, and its industrial value is extremely high.

Claims (2)

(57) [Claims] 1. A rare earth - iron - The method of manufacturing a boron-based sintered permanent magnets, after the jig type plating sintered magnet body surface, characterized in that it 軟Ro cormorants with handle contact traces Manufacturing method of corrosion resistant rare earth permanent magnet. 2. The method according to claim 1, wherein the soft solder is Sn-Pb.
2. Production of a corrosion-resistant rare earth permanent magnet according to claim 1.
Method.