JPH042008A - Superconductive wire and manufacture thereof - Google Patents

Abstract

PURPOSE: To form a superconductive material into a wire or a cable by forming a gutter of a metallic strip, filling the gutter with superconductive powder, and then, pressing the powder. CONSTITUTION: A proper metallic/alloy strip 12 is bent so as to be formed into a gutter. The gutter is bent and closed so as to be formed into a tube provided with a seam, after the gutter is filled with superconductive powder. Subsequently, the tube with its filler is passed through a die or a roller, which is provided with a gradually reducing diameter of a required hole outline, so as to be extruded until a thin wire with a required cross sectional dimension is obtained. When a required diameter for a wire 10 is provided, the wire 10 is wound into a coil on a solenoid, or the wire 10 is used in the straight form directly or in a required final form, and then, the wire 10 is heated to a temperature required for providing a crystalline characteristic to a ceramic conductor.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a wire or cable that is superconducting to electric current and a method for manufacturing the same.

BACKGROUND OF THE INVENTION Wires and cables used to conduct electricity are made of conductive metals in a wide variety of diameters and cross-sectional shapes.

The wire is surrounded by one or more layers of non-conducting material as an insulating layer, which may also be surrounded by wire mesh or a solid metal shield. The shield may also be surrounded by a protective coating of rubber or polymer. Such a layer assembly around multiple strands of wire is commonly referred to as a cable.

Special types of wire conductors are used as heating elements in kitchen ranges and ovens. A metal conductor, usually made of a high melting point, higher resistivity alloy, is housed in a hollow tube of a high temperature and corrosion resistant alloy. The space between the wire and the tube is filled with a powdered refractory material, such as magnesium oxide, which is a non-conductor at all operating temperatures. Such an assembly is sealed at both ends and then pultruded through a die of the desired size and shape to make the tube and its contents thinner and longer. The drawing action is repeated until the tube is reduced to the desired diameter and cross-sectional shape. The result is a rigid "shield" wire in which the central conductive wire is embedded in highly compressed insulation and the entire assembly is protected by a metal sheath.

This wire can be cut into several pieces and these pieces can be bent into the desired shape. The conductive core can be connected at its ends to current-conducting contacts to complete the electrical circuit.

It has long been known that materials formed at sufficiently low temperatures become superconductors of electrical current with very low (or no) electrical resistance. Much research is being focused on finding materials that become superconducting at temperatures above the atmospheric boiling point of liquid nitrogen. So far, these materials are known to be ceramic-based materials. Ceramics are compositions of hard, brittle metal elements and oxygen. Such materials are well described in extensive specialized literature.

Superconductors in the form of wires or cables are most useful for transmitting electrical energy. However, due to the hard and brittle nature of ceramic materials, ceramic superconductors are naturally not easily suited for such applications.

It is therefore an object of the present invention to provide a means by which superconducting materials can be formed into wires and cables.

[Means to solve the problem]

To obtain a wire of superconducting material according to the invention, a suitable metal or alloy strip is bent into a gutter. The gutter is filled with superconducting powder and then closed by bending the gutter into a seamed tube. This seam may or may not be sealed by welding or brazing. This tube, along with its contents, is then drawn through rollers through a die of decreasing diameter and desired hole profile until a thin wire of the desired cross-sectional dimensions is obtained. When the desired diameter of the wire is obtained, this wire can be coiled into a solenoid or used as is or in any desired final shape and then used to give the ceramic superconductor the desired crystalline properties. Heat to the specified temperature.

〔Example〕

In one embodiment of the invention that is suitable for continuous operation, unlimited lengths of wire of any desired diameter can be produced. In this continuous method, metal or alloy strips of appropriate width and length are supplied in rolled form. If a continuous state of length is required, the starting section of the 20th line should be replaced with the 10th line.
You can weld it to the end of the cable. A metal strip is curved across its width between rollers in a U-shaped cross section to form a gutter. Injecting superconducting powder or a precursor thereof into the U-shaped portion of the gutter so formed and forcing the gutter through an O-shaped opening that may be formed with a roller or die, thereby forming the gutter and contents into a closed tube. do. Seal the beginning of the gutter with a conductive metal plug. When so formed, the closure tube has a seam which may be left in place or sealed by continuous welding or brazing if deemed advantageous. This tube can be filled even more with powder by vibration. The tube so formed can be drawn through a die or rollers to compact the powder and form the tube to any desired cross-sectional shape and diameter.

The formed tube can be provided with layered concentric tubes that define the cavity surrounding it. To provide a larger concentric tube, a wider metal strip can be formed in the tube around the fill tube to direct the coolant around the superconducting wire. The second concentric tube may be of a different alloy than the first strip, for example for magnetic shielding, or the second strip may be of the same material as the first strip to improve the properties of the first strip. Good too.

To avoid contamination of the powder with the material of the IJ tube during heating operations for crystallization of the superconductor, the strip on the side forming the inner surface of the tube is coated with a suitable metal, e.g. silver or other noble metal. The barrier may be provided by coating, plating, or depositing with a lining of glass gob, glass nonwoven, quartz flake, or other suitable non-metallic material. This barrier may be attached to the strip, or the strip of barrier material may be fastened to the metal strip with a volatile adhesive such as collodion that evaporates without leaving a residue at brazing, welding or recrystallization temperatures. It's okay.

Once the desired length of superconducting powder-filled tube has been created, the tube is closed with a conductive metal plug or camp to produce a terminal electrical contact.

The thickness of the outer metal layer and the size of the superconducting wire are determined by the dimensions and amount of superconducting material of the initial strip, any inner coating, plating layer or deposit layer, and the number of reductions. The strip is soft! If made of magnetic material, the metal thickness would be greater and the resulting magnetic shielding of the superconducting wire can be imagined.

As the superconducting filler powder, various compositions well known in the art can be used.

All of these ceramic superconductors suffer from the same conventional drawbacks. That is, these superconductors can be formed by conventionally known methods into wires of unlimited length with sufficient mechanical strength to withstand the strong magnetic forces that tend to disturb the action of any magnetic coils using the wires. I haven't passed it through. The wire manufactured according to the invention can be used if the metal shielding action of the tube or the second additional shielding tube is strong enough to withstand the above-mentioned forces.
Eliminate the above drawbacks.

The present invention also provides support for non-metallic materials such as glass and/or
Alternatively, a method for manufacturing a superconductor wire having an insulating cover material is provided. To obtain a glass-coated superconductor wire, a metal tube is lined with the desired glass-coated material and then the lined tube is filled with superconductor material. After manufacturing the superconductor wire to the desired length and bending or coiling the wire into a shape suitable for the desired application, the superconductor is heat treated to achieve the desired state of superconductivity. At this time, the heat treatment fuses the glass of the liner to the superconductor. The metal tubing can then be removed by etching leaving the glass coated superconductor wire. This glass-covered wire can be mechanically further strengthened by coating with a synthetic resin.

In yet another embodiment, which is a continuous process, the deposited metal strip or metal strip and the glass felt or nonwoven strip are wrapped around a mandrel such that the deposited layer or glass layer is between the metal strip and the mandrel. do. Preferably, the mandrel should be hollow and serve as a funnel for injecting the superconducting powder.

As the winding operation progresses, cylinders are continuously formed and the mandrel is slid out of the cylinders at the same rate as the cylinders are formed and the superconducting powder is filled into the cylinders. The cylinder so formed has a longitudinal or helical seam, which can be closed by welding, brazing or soldering. Alternatively, other tubes can be soldered around the assembly to seal the seams. Once the end of the tube is reached, the tube is closed with a camp or plug as an electrical terminal, its diameter is reduced as described above, and then heat treated to crystallize the superconductor.

10-3 illustrate a wire 10 of the present invention in which a superconductor 14 is encased in metal 12.

In FIG. 3, an intermediate encasing layer 18, such as glass, is shown. Although the illustrated cross-sectional shape is circular or hexagonal,
Any desired cross-sectional shape can be formed, including squares, rectangles, or any other desired polygons.

FIG. 4 shows the formation of a U-shaped gutter of metal strips with an inner surface coating or second layer of material.

FIG. 5 shows a funnel-like device for closing the gutter of FIG. 4 after loading semiconductor material into the gutter to form a tube. FIG. 6 illustrates the operation of reducing the diameter of the tube formed in FIG.

In the superconducting state of the wire core, very high currents can be transmitted in the superconducting wire without significant voltage drops across the ends of the wire. Therefore, almost no current flows through the metal tube itself). Thus,
Metal tube; acts as a protective insulator for the superconductor. However, the superconductivity of the core may be reduced for some reasons.
Once lost, the core becomes a relatively poor conductor and the voltage across the ends of the wire increases to a high unity value, sustaining current through the wire. Such high -1 voltages can cause high currents to flow through the metal sheath, which can overheat and destroy the wire assembly. For this reason, it is necessary to connect fast-acting disconnect relays to both ends of the superconductor wire to electrically jibring the wire assembly. When some resistance rises and current begins to flow within the metal sheath between the ends, this relay immediately breaks the connection between the wire and the rest of the electrical circuit, thus causing Joule heating of the metal sheath. prevent.

Having fully described the superconducting wire of the present invention, the following examples further illustrate certain features of the invention and are not intended to be limiting.

A strip of soft pure iron sheet (1 m long in this example) with a thickness of 11 and a width of 31.42 n is fully silver plated on one side. This strip is passed between rollers to form a gutter with the silver plating layer on the inside. This gutter has a diameter of L
The gutter is pressed down through a forming funnel with an oam end opening, thereby forming the gutter into a 10 outside diameter tube with a 2.8 fl wide seam. As the tube exits the funnel, braze the seam with silver solder. The starting end of this tube is closed with a silver plug. After forming a pipe of about 100 m5,
A commercially available powdered superconductor of the Y-Ba-Cu-0 system (also known as the "12-3-system"), which has a slightly biased stoichiometry to fix the field in the superconductor, was Fill the tube. The superconductor powder filling is compressed by vibration of the tube. After filling a sufficient length of tube, the diameter of the tube is reduced by several sets of rollers moving from the newly filled section towards the beginning of the tube which is plugged with an end camp. This compacts the powder, reducing the diameter of the fill tube or wire and increasing its length. During size reduction, the filled tube is heated to 400°C to soften the work hardened iron. The end of the tube is also capped with a silver cap to form an end contact. The end of the fill tube is rolled by a reduction roller to compress the powder against the plug.

The reduced diameter wire is coiled around a metal mandrel to form an electromagnetic coil, which is heated in a furnace in an inert atmosphere or vacuum to conditions determined by the powder feeder. Since the powder is packed in a closed tube, no oxygen is lost during heat treatment.

The silver plating layer acts as a barrier to keep the powder from reacting with the iron of the tube. Before testing the coil in liquid nitrogen, the turns and ends of the coil should be secured to prevent the coil from being unwound by the forces of its own magnetic field. This iron tube shields the superconductor from magnetic fields that tend to minimize the effective conduction path up to the saturation magnetization of the iron.

[Brief explanation of drawings]

FIG. 1 shows a section of the inventive wire with a circular cross-section; FIG. 2 shows the inventive wire with a hexagonal cross-section; FIG. 3 shows the inventive wire with two layers around the superconductor. FIG. 4 shows the formation of a U-shaped metal gutter during the manufacture of the wire of the invention; FIG. FIG. 6 is a diagram illustrating the operation of reducing the diameter of the filling tube by means of rollers and a size reduction die. DESCRIPTION OF SYMBOLS 10... Wire, 12... Metal, 14... Superconductor, 18... Intermediate encasing layer.

Claims (1)

Claims: 1. A wire form of crystalline superconducting material encased in an unlimited length of material of lower electrical conductivity, and at least two means for making electrical contact to said superconducting material. A complex characterized by: 2. Composite according to claim 1, characterized in that at least one material with lower electrical conductivity is a metallic material. 3. A composite according to claim 1, characterized in that the one material with lower electrical conductivity is glass. 4. The composite according to claim 3, further comprising a glass layer between the wire of the crystalline superconducting material and the metal material. 5. The metal material is protected from electrical overload by means for detecting a current passing therethrough and by means for interrupting the circuit when a current passing through the metal material is detected. complex. 6. A method for producing a composite of wires of superconducting material, comprising: a) filling a hollow metal tube with one end sealed with a conductive metal with a superconducting material, and then sealing the other end of the filled tube with a conductive metal; b) passing at least a portion of the filled tube through at least one size reduction device, thereby reducing the diameter of the tube and its contents to the dimensions of the wire, and c) heat treating the resulting wire to make it superconducting. 1. A method characterized by crystallizing a material. 7. The method of claim 6, wherein the hollow metal tube has an inner coating of a protective material that is substantially inert to both the tube and the superconducting material. 8. A method according to claim 6, characterized in that the hollow metal tube is lined with a metallization layer. 9. A method according to claim 6, characterized in that the hollow metal tube is lined with a glass material before being filled with the superconducting material. 10. A method according to claim 9, characterized in that after the heat treatment (c), the outer metal surface of the drawn wire is removed. 11. The method according to claim 10, characterized in that, after removal of the outer surface metal, the superconductor wire is coated with a support material which is a synthetic resin. 12. A method according to claim 6, characterized in that the cross section of the drawn wire is square, rectangular, round or hexagonal. 13. A method for continuous production of a composite of superconducting wires housed in a metal tube, comprising: a) forming a metal strip into a U-shaped gutter or wrapping the strip around a mandrel to form a cylinder; b) filling said gutter or cylinder with a powder of superconductor material; c) sealing said gutter to form a tube to contain superconductor material; d) sealing said gutter or cylinder formed; A method comprising: forming a wire through at least one size reduction device; and e) heat treating the formed wire. 14. Claim 8, characterized in that the tube formed from the gutter and the forming cylinder have a longitudinal joint, the joint being sealed by welding, brazing or soldering.
Method described. 15. The method of claim 8, wherein the hollow metal tube or cylinder has an inner coating of a protective material that is substantially inert to both the tube and the superconducting material. 16. The method according to claim 13, characterized in that the cross section of the drawn wire is square, rectangular, round or hexagonal. 17. The method according to claim 13, characterized in that, after the heat treatment (c), the superconductor wire is coated with a support material which is a synthetic resin. 18. A method according to claim 17, characterized in that, after removal of the outer surface metal, the superconductor wire is coated with a support material which is a synthetic resin. 19. The method according to claim 13, characterized in that after being accommodated in the metal cylinder (b) or metal tube (c), the metal tube or cylinder is housed in a second metal tube or cylinder.