JP2746273B2 - Insulated wire conductor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductor for a coated electric wire which is insulated and coated with polyethylene or the like, and particularly to a conductor for a coated electric wire which is laid between utility poles or the like.

[Related Art] Hard copper wires made of tough pitch copper or oxygen-free copper have been used as conductors for overhead distribution lines that are wired between utility poles and the like. The assembled plurality of hard copper wires are twisted, and an insulation coating of polyethylene, polyvinyl chloride, or the like is applied on the twisted wires. Further, it is used as a single copper wire, and the single wire is coated with an insulating coating.

[Problem to be Solved by the Invention] When cold drawing is performed on tough pitch copper or oxygen-free copper, residual stress often exists on the surface of the obtained wire. As the residual stress, there is particularly a tensile residual stress. In addition, a twisted wire repulsive force for untwisting is inevitably generated on the surface of each twisted copper wire. This stranded wire repulsion appears as a tensile residual stress on the surface of each copper wire. Furthermore, each copper wire may have a residual stress due to a curl generated when the copper wire is wound on the drum.

In the case of a conventional coated electric wire, a disconnection in which the above-described residual stress is one factor may occur. Therefore,
If rainwater enters the covered electric wire, the inside of the covering layer becomes an environment that is easily corroded, and an oxide film is formed on the surface of the copper wire. When such a corrosive environment and the above-mentioned residual stress affect each other, stress corrosion cracking occurs in the copper wire, and as a result, the wire breaks.

Therefore, an object of the present invention is to provide a conductor for a covered electric wire which does not cause the stress corrosion cracking phenomenon described above.

[Means for Solving the Problems] The present invention relates to a conductor for a covered electric wire in which a plurality of copper wires are assembled into a stranded wire, and a Si coating layer is formed on at least the surface of the copper wire located in the outer layer. It is characterized by being formed.

[Effects of the Invention] Si exhibits stable properties against a corrosive environment. Typically
Although Si is brittle, when a Si thin film is formed on the surface of a ductile metal, the Si thin film can be deformed to some extent according to the deformation of the metal.

When a Si thin film is formed on the surface of a copper strand that constitutes a stranded wire,
Even if rainwater enters the covered electric wire, the presence of the Si thin film can prevent the copper wire from contacting the rainwater. Therefore, disconnection due to stress corrosion cracking as described above does not occur.

The Si coating layer may be formed on the surface of all the copper wires constituting the stranded wire, but the Si coating layer may be formed on the surface of the outer copper wire where stress corrosion cracking easily occurs.

The thickness of the Si coating layer is preferably in the range from 0.1 to 20 μm. When the thickness is less than 0.1 μm, the effect of protecting the internal copper wires is small. On the other hand, if the thickness exceeds 20 μm, cracks are likely to occur in the Si coating layer when the copper wire is bent, and there is a possibility that rainwater and the copper wire may come into contact.

As a method of forming a Si thin film, a thermal CVD method, a reduced pressure CVD method,
There are various CVD methods such as a plasma CVD method and an optical CVD method, a sputtering method, an ion plating method, and a vapor deposition method.
According to the CVD method or the sputtering method, a dense Si thin film can be obtained.

[Example] A copper wire having a diameter of 2.0 mm and heated to 400 ° C is continuously supplied into a CVD reaction vessel supplied with a mixed gas using H ₂ gas as a carrier gas and SiCl ₄ as a source gas. Then 1
When a 3.56 MHz radio wave was applied, a thin film of Si was continuously formed on the surface of the copper wire. Thus, a thickness of 5
A μm Si thin film was formed. Nineteen copper wires thus obtained were assembled into a stranded wire, and a polyethylene coating was applied on the stranded wire.

When a diluted ammonia water was injected into the inside of the coated electric wire to perform a stress corrosion cracking test, no disconnection was observed even after 3 months.

For comparison, nineteen copper wires having a diameter of 2.0 mm and having no Si coating layer were assembled into a stranded wire, and the stranded wire was coated with polyethylene. When a diluted ammonia water was injected into the inside of the covered electric wire, a stress corrosion cracking test was performed.
After a lapse of months, the wire broke due to stress corrosion cracking.

Claims (5)

(57) [Claims] An insulated wire conductor in which a plurality of copper strands are assembled into a stranded wire, wherein at least the copper strand located in the outer layer has a Si coating layer formed on the surface thereof. A conductor for insulated wires. 2. The coated electric wire conductor according to claim 1, wherein the thickness of the Si coating layer is in a range of 0.1 to 20 μm. 3. The insulated wire conductor according to claim 1, wherein an Si coating layer is formed on the surface of all of the copper strands constituting the stranded wire. 4. The conductor for a coated electric wire according to claim 1, wherein said Si coating layer is formed by a CVD method. 5. The conductor for a covered electric wire according to claim 1, wherein said Si covering layer is formed by a sputtering method.