JPH01318209A - Surface treatment of permanent magnet - Google Patents

Abstract

PURPOSE:To obtain a protective coating with resistance to weather by a method wherein the surface of a magnet consisting of a rare-earth element, a transition metal and boron is covered with an oxide film of a specific thickness which mainly consists of a dense rare-earth element. CONSTITUTION:An oxidation film on the surface of a magnet is in powder form at room temperature and under atmospheric pressure and corrosion progresses at a lapse of time. However, if oxygen partial pressure is made lower and is subject to heat-treating at a temperature 200-400 deg.C, an oxide film which mainly consists of a rare-earth is formed and corrosion does not progress any more. It is difficult for this oxide film to be formed uniformly on the surface of the magnet if it measures 0.01mum or less and the metal surface is exposed due to slight friction and the adherence and corrosion resistance are not sufficient. On the other hand, when an oxide film exceeding 10mum in thickness is formed, no dense film is formed. Thus, the thickness of the oxide film should be 0.01-10mum. Thus, an oxide film with resistance to climate can be easily produced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to surface treatment of permanent magnets whose basic components are rare earth elements, transition metals, and boron.

[Prior Art] Permanent magnets are widely used in various electrical appliances in general households and peripheral devices of large computers. ! It is one of the important electrical and electronic materials used in a wide range of fields, including devices. With the recent demand for smaller size and higher efficiency of electrical products, permanent magnets are also required to have increasingly higher performance. Typical permanent magnets currently in use are alnico, hard ferrite, and rare earth-transition metal magnets. In particular, R-Go permanent magnets, which are rare earth (hereinafter abbreviated as R)-transferred metal B (hereinafter abbreviated as TM) magnets, and R-Fe-B permanent magnets have high magnetic performance. Therefore, much research and development has been carried out since then.

Since this R-TM-B permanent magnet is very active, there are problems with corrosion such as oxidation and rust of the magnet. Especially R-F e-
In B-type magnets, the surface of the magnet is severely oxidized, making it difficult to use as a stand-alone magnet, and some type of surface treatment must be applied to prevent oxidation. Metal plating was done by vapor deposition or sputtering, or coating with epoxy or other resins.

[Problems to be Solved by the Invention] However, such surface treatment methods have problems such as a thick protective film, poor adhesion to magnets, water absorption, and the need for expensive equipment. are doing.

The present invention is intended to solve the above problems, and its purpose is to apply a strong, dense, and weather-resistant protective coating to R-T M-B permanent magnets by a simple method. be.

[Means for Solving the Problems] The surface treatment method according to the present invention provides a permanent magnet whose basic components are rare earth elements (including yttrium), transition metals, and boron. Dense rare earth-based oxide film with at least 0.01
This is a surface treatment method for permanent magnets characterized by being coated with a thickness of μm to 10 μm.

[Function] The present inventor found that by heat-treating an R-T M-B magnet alloy in an oxidizing atmosphere, an oxide film containing rare earth elements as a main component is formed on the surface of the R-T M-B magnet alloy. It has been found that by controlling this, it is possible to form a dense film with good adhesion to the magnet.

At room temperature and atmospheric pressure, the oxide film on the magnet surface layer is powder-like, and corrosion progresses over time. However, by lowering the oxygen partial pressure and performing heat treatment at a temperature between 200° C. and 400° C., a black, dense oxide film mainly composed of rare earth elements is formed, and corrosion does not progress any further. This oxide film is 0.0
If the thickness is 1 μm or less, it is difficult to uniformly form the magnet surface, and the metal surface is exposed due to slight friction, resulting in insufficient adhesion and corrosion resistance. On the contrary 1
When an oxide film with a thickness of 0 μm or more is formed, a dense film is not formed, and a problem still remains in corrosion resistance. Furthermore, it is clear that it is better to minimize the amount of substances other than the magnetic phase in the magnet itself, and the thickness of this oxide film should be 0.01 to 10
A value between μm is suitable.

Next, examples of the present invention will be described.

[Example 1] Table 1 shows the composition of the alloy used in this example.

Rare earth elements, transition metal elements,
and boron are weighed and melted and cast in a high frequency melting furnace under an argon gas atmosphere.

Alloys with symbol a are processed by the sintering method as shown in JP-A No. 59-46008, and others are processed by casting-hot working-heat treatment as shown in JP-A-62-276803. A magnet was created.

Each of the created magnets was cut out to an appropriate size and subjected to surface treatment under the following conditions.

Surface treatment conditions = 1 Argon + oxygen gas, oxygen partial pressure 0.01 atm temperature
After surface treatment at 250°C for 10 minutes, the formation of a black oxide film with a thickness of 2 to 5 μm was observed on each magnet.Table 2 shows the weather resistance test.
When left in a thermostat at 45°C and 95% humidity for 24 hours,
The degree of rust on the magnet surface is shown (O: No rust observed, Δ: Partial rust observed, ×: Significant oxidation) As a comparative example, a magnet without surface treatment is also shown in the same manner.

Table 2 [Example 2] Surface treatment was performed in the same manner as in Example 1 under the following conditions 2. The results of the weather resistance test are shown in Table 3.

Surface treatment conditions = 2 Argon + oxygen gas, oxygen partial pressure 0.01 atm temperature
350° C. Time: 1.5.20 minutes The film thickness for each treatment time was as follows for each magnet.

1 minute ~ 0.1 μm 5 minutes 2 ~ 5 μm 20 minutes 10 ~ 20 μm Table 3 As is clear from the above results, according to the surface treatment according to the present invention, the R-T M-B magnet surface has weather resistance. It can be seen that the oxide film can be created by a simple method.

[Effects of the Invention] As described above, according to the present invention, a certain oxide film on the surface of the R-TM''''B magnet can be created by a simple method. It is possible to solve the problem of weather resistance, which is a major drawback of R-T M-B magnets, without increasing costs, and furthermore, it has the effect of greatly expanding the applications of R-T M-B magnets.

that's all Applicant: Seiko Epson Corporation

Claims (1)

[Claims] In a permanent magnet whose basic components are rare earth elements (including yttrium), transition metals, and boron, the surface of the magnet made of the basic components has a dense oxide film mainly composed of rare earths of at least 0.01 μm to 10 μm. A method for surface treatment of a permanent magnet, characterized by forming a permanent magnet.