JPH09134625A - Manufacture of insulated superconducting wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an insualting layer whose film thickness is uniform and by which a pinhole is hardly generated by depositing paint on a normal conductor surface by carrying an electric current to a conductor by passing it through into insulating water paint by using the conductor where a normal conductor is arranged on a superconductor as a postive electrode. SOLUTION: An insulated superconducting wire is composed of a superconductor 1 composed of a metallic or oxide superconducting material, a normal conductor layer 2 composed of Cu and Ag or the like and an insulating layer 3 formed by electrodeposition painting. A conductor where the normal conductor layer 2 is arranged on the superconductor 1 is used as a positive electrode, and an electric current is carried to the conductor while passing it through into insulating water paint, and the paint is deposited on a normal conductor surface. Afterwards, it is baked and hardened, and the insulating layer 3 is formed on the layer 2.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for manufacturing an insulated superconducting wire.

[0002]

2. Description of the Related Art A superconducting wire using a superconducting material made of an alloy-based or compound-based (ceramic-based) superconducting material as a core wire is usually provided with copper or silver around the superconductor 1 as shown in FIG. Etc., a normal conductor layer 2 is provided, an insulating layer 3 is applied on the normal conductor layer 2, and the whole is covered with insulation. Generally, the insulating layer 3 is formed by dip coating used for coating the wire material. As is well known, the dip coating is a coating method in which an object to be coated is immersed in a paint and pulled up, and then the paint is baked and dried, and a polyvinyl formal paint is often used as a paint for forming an insulating layer. .

[0003]

The thickness of the insulating layer is generally required to be around 20 μm, depending on the type and application of the superconducting wire. Therefore, the coating is usually repeated until a predetermined layer thickness is obtained. However, the thin film insulating layer formed by the dip coating is not uniform in film thickness because of the dip coating, pinholes are often generated, and insulation failure often occurs. It is conceivable to increase the thickness of the insulating layer in order to deal with poor insulation, but increasing the thickness of the insulating layer lowers the thermal conductivity of the superconducting wire. In order to maintain the superconducting wire in the superconducting state, the superconducting wire usually has to be cooled below the critical temperature, and in that sense it is better to make the insulating layer as thin as possible to improve the thermal conductivity. is there. Especially recently
Considering that various electric devices are becoming smaller and lighter, a small space factor (space factor) is required for the superconducting wire which is one element of the device. The appearance is expected.

Therefore, in view of the above points, an object of the present invention is to provide a superconducting wire having an insulating layer having a uniform film thickness and a small number of pinholes even though the film is as thin as possible. is there.

[0005]

Means for Solving the Problems As a result of intensive research for achieving the above-mentioned object, the present inventors have found that if an insulating layer is formed by electrodeposition coating, a uniform coating film is formed, The inventors have found that the occurrence of pinholes is extremely small, and have completed the present invention. That is, the manufacturing method of the insulated superconducting wire in the present invention, by using the core wire provided with the normal conductor layer on the superconductor as an anode, by energizing the core wire while passing it through the insulating water-based paint. A coating material is deposited on the surface of the normal conductor layer.

[0006] As is well known, the electrodeposition coating is a coating in which an electrode is inserted into an aqueous paint and a direct current is passed to move paint particles having a negative charge toward the anode to deposit it on the anode plate. Is the way. In general, an object to be coated is used as an anode, and a current is applied between it and a cathode placed at a certain distance to deposit the paint on the surface of the object to be coated on the anode, and then take it out to complete baking coating.

Also in the present invention, the core wire provided with the normal conductor layer on the superconductor is used as an anode, and current is passed through the normal conductor layer by passing current through the insulating water-based paint. It will flow, thus depositing paint on the surface of the normal conductor layer. After that, the insulating layer is formed by baking and then introducing it into a furnace and baking and curing. According to such an insulating layer forming method, not only an insulating layer having a thickness of about 10 μm or less (for example, about 1 to 7 μm) can be obtained in one coating step, but pinholes are extremely few as compared with dip coating. Is obtained.

Examples of the insulating coating used for electrodeposition coating include water-dispersible epoxy-acrylic resin varnish, water-soluble polyimide resin varnish, water-dispersible polyurethane resin varnish, and non-hydrogen polyimide dispersion varnish. Among these, the superconducting wire in which the insulating layer is formed using the water-dispersible epoxy / acrylic resin varnish is not inferior to the polyvinyl formal varnish in the characteristics of the film other than the pinhole even at the liquid helium temperature, Water-dispersible epoxy-acrylic resin varnish is preferred. The material of the superconductor to be the core wire is not particularly limited, and existing materials may be used, but there are metal-based and oxide-based superconducting materials. Metal-based superconducting materials include niobium / titanium and niobium / tin, and oxide-based superconducting materials include barium / yttrium / copper / oxygen, barium / lanthanum / copper / oxygen,
Strontium / lanthanum / copper / oxygen, barium / scandium / copper / oxygen, and compounds containing calcium / lanthanum / copper / oxygen.

The core wire used in the present invention has a normal conductor layer made of copper or silver formed on the surface of a superconductor. This normal conductor layer is often used, for example, in the production of oxide-based superconductors in order to compensate for the brittle and poor flexibility properties of superconductors (particularly superconductors made of oxide-based superconducting materials). It is formed by filling a hollow pipe made of copper or silver with a superconducting material and drawing it.
Therefore, by providing the normal conductor layer, a current flows in the normal conductor layer when the superconducting wire is not in the superconducting state, which is convenient for actual application.

[0010]

EXAMPLES The present invention will be described below based on examples.
The insulated superconducting wire to be manufactured by the present invention is formed by, for example, as shown in FIG. 1, a superconductor 1 made of a metal-based or oxide-based superconducting material, a normal conductor layer 2 made of copper or silver, and electrodeposition coating. The insulating layer 3 is formed.

Examples 1 to 5 and Comparative Examples 1 to 4 Next, in the insulated superconducting wire obtained from the present invention, it is made clear by the examples how small the amount of pinholes is generated in the insulating layer. As examples and comparative examples, a superconducting wire having a diameter of 1.0 mm formed of a twisted wire made of a superconductor made of a niobium-titanium superconducting material and a normal conductor layer made of copper provided on the surface of the twisted wire On the normal conductor layer,
The insulating layer was formed by electrodeposition coating in Examples and immersion coating in Comparative Examples. The number of pinholes generated in the insulating layer of the obtained superconducting wire was examined, and the results are shown in Table 1. However,
In the examples, the above-mentioned insulating paint was used, and in the comparative examples, polyvinyl formal varnish (concentration 20%) was used, and ordinary dip coating was performed to form an insulating layer.

[0012]

[Table 1]

[0013]

As described above, in the insulated superconducting wire obtained by the method of the present invention, since the insulating layer is formed by electrodeposition coating, the thickness of the insulating layer is thinner than the conventional dip coating, and The amount of pinholes generated in the insulating layer is extremely small, and the insulation is excellent. In addition, the space factor becomes smaller (same as above) as the insulating layer becomes thinner. In addition, since the insulating layer is a thin film, the thermal conductivity of the superconducting wire is further improved, and the cooling property for maintaining the superconducting wire in the superconducting state is improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of an insulated superconducting wire obtained from the present invention.

[Explanation of symbols]

 1 superconductor 2 normal conductor layer 3 insulating layer

Claims (1)

[Claims] 1. A normal conductor layer is provided on a surface of the normal conductor layer, wherein a core wire having a normal conductor layer formed on a superconductor is used as an anode, and the core wire is energized while passing through the insulating water-based paint. A method for producing an insulated superconducting wire, characterized in that paint is deposited on the surface.