JPH02250221A - Manufacture of multi-conductor oxide superconducting wire - Google Patents

Abstract

PURPOSE:To reduce the amount of covering metal and suppress drop of denseness of the core part due to multi-core construction by wrapping a powder of oxide superconductor tightly with a tap of covering metal. CONSTITUTION:A tape 2 is shaped into U-profile, and a powder 1 of oxide superconductor is supplied onto this tape 2 until its two side edges are closed. The powder 1 is compressed, while overlap of the tape 2 side edges is increased, and wrapped tightly with the tape 2 so as to yield a composite wire. The covering metal constituting tape is not restricted to Ag, but Ag alloy such as Ag-Pd, Ag-Mgu, or a substance not reacting with good electroconductive or oxide superconductive material such as Cu, Au, Ni may be used. The allows reduction of the amount of covering metal 2 when turned into multi-core construction, which enables the electric conducted part to be made in dense construction.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for manufacturing a multifilamentary wire suitable for utilizing an oxide superconductor that can use liquid nitrogen as a refrigerant for energy applications. be.

[Prior Art] Oxide superconductors such as the Y-Ba-Cu-0 system exhibit a critical temperature exceeding the liquid nitrogen temperature (77 K) and are attracting attention as superconductors that can be used at liquid nitrogen temperatures.

Superconducting grades include Y-Ba-Cu-0 series, B1-P
b/5r-Ca-Cu-0 system or Tl-Ba/5r-C
Prototypes of Y-based, old thread, and T1-based oxide superconductors such as the a-Cu-0 system have been made, and critical current densities of 3000 to 12000 Δ/C- (
Jc) is obtained.

Most wire rods have a single-core cross-sectional configuration, but multi-core wires have also been prototyped. The manufacturing method is usually that oxide superconductor powder is filled into a metal such as a silver pipe and subjected to surface-reducing plastic processing, then the required number of pieces are incorporated into a metal such as a silver vibe, subjected to surface-reducing plastic processing, and then sintered. A multifilamentary wire is produced by heat treatment.

In addition, it has been considered to wrap oxide superconductor powder in copper tape and then perform surface-reducing plastic processing to make it into a wire, but there are no reports of wires using the latter method exhibiting superconducting properties.

In the example of a silver-coated tape-shaped wire, in the case of a single core, the Jc value increases as the thickness decreases, but when multi-core,
As the number of multi-core increases, the characteristics deteriorate. This is because when the oxide superconductor part is multi-core, the cross-sectional area ratio of the coating metal increases, which correspondingly deteriorates the densification during area reduction processing, and the oxide superconductor during sintering heat treatment. This is presumed to be due to the core becoming porous because the coating metal is unable to follow the shrinkage of the core.

The present invention has been made with the object of solving the above-mentioned drawbacks of the prior art and providing a multicore metal-coated wire with good characteristics.

[Means for Solving the Problems] The gist of the present invention is to adopt a method of wrapping oxide superconductor powder with a coated metal tape as a method for forming a single-core wire, thereby reducing the amount of coated metal. This reduces the densification of the core due to multi-core structure.

In this case, the method of wrapping the oxide superconductor powder with a coated metal tape is to form the tape into a U-shaped cross section and wrap the oxide superconductor powder on the tape until the both edges are closed. A method is adopted in which the powder is compressed while increasing the overlap of both side edges of the tape to tightly surround the powder with the tape to form a composite wire, and the coated metal constituting the tape is: Not limited to silver, Ag-
Pd.

Silver alloys such as Ag-Mgu, and materials that do not react with insect-type conductors or oxide superconductors such as Cu, u, N1, etc., are used.

In addition, the oxide superconducting materials are not particularly limited, but include Y-Ba-Cu-0, Ln-Ba-Cu-0 based on which Y is replaced with a magnetic element (Ln) such as Er5no, etc.
l3l-Pb/5r-Ca-Cu-0 system, Tl-Ba/
Other oxide superconductors based on 5r-Ca-Cu-0 can be used.

[Example] Below, an example of a silver-coated multifilamentary wire using Y-Ba-Cu-0 powder as a raw material will be described.

Commercially available reagents Y203, BaCOz and C were used as raw materials.
uO was prepared, weighed accurately so as to have a composition of Y 1Ba2CU30 , mixed well in a ball mill, and then molded into a predetermined shape. Next, it was calcined in an oxygen atmosphere at 950°C for 10 hours, and then pulverized using a ball mill, and then molded, calcined, and pulverized again to obtain a superconducting powder with a predetermined particle size. When the superconducting properties of this powder were confirmed by the alternating current magnetic susceptibility method, the critical temperature was found to be Tc=92.

Next, as shown in FIG. 1, the powder was wrapped with a silver tape 2 to form a silver-coated single-core wire 3. As shown in FIG. 2, this wire 3 is made by bending a silver tape 2 with a thickness of 50 μm inward to form a U-shaped cross section. of superconducting powder 1 is supplied, and by passing the tape 2 through the first and second dies 4 and 5, the overlap of both side edges of the tape 2 is increased, and the powder 1 is compressed to have an outer diameter of 2.0 mm. Single core wire 3 was used. Thereafter, the wire rod 3 was drawn to an outer diameter of 1.6 mm by die drawing to increase the overlap of both side edges of the tape 2, and 1 part of the powder was further compressed to form a solid.

Next, 37 silver-coated single-core wires 3 cut to a predetermined length were assembled into a silver vibe with an outer diameter of 1.0 mm and a wall thickness of 0.5 mm, and then the outer diameter was 2.0
Plastic working to reduce the surface area and further reduce the thickness by rolling 1. On
A tape-shaped wire rod with a width of 4.01 m and a width of 4.01 m was produced.

Finally, after a sintering heat treatment in an oxygen atmosphere at 920° C. for 20 hours, oxygen annealing was performed to obtain a multicore silver-coated oxide superconducting wire.

In the case of the multicore wire rod (37 cores) produced in this way,
The cross-sectional area ratio of the superconducting portion in the entire wire was about 70%, which was much larger than the 20-40% obtained by the conventional multicore method. This means that even if the critical current density (Jc) is constant, the current that can be passed through the wire in the superconducting state can be increased to about twice as much if the wire size is constant. Furthermore, since the cross-sectional area ratio of silver, which is the coating metal, is small, the shrinkage characteristics during sintering heat treatment are good, resulting in a dense oxide superconductor and improved Jc characteristics itself.

Specifically, in the conventional multi-core method, J e = 420 OA/c can be achieved at most, while J e = 420 OA/c at zero magnetic field of 77. did it.

In addition, although the example of 37 cores was shown above, this does not limit the number of multiple cores, and it is possible to increase or decrease the number of cores, such as 6 cores or 1330 cores. Although the case where a tube material is used as a covering material in multi-core construction is shown, a tape or a sheet material may also be used.

Further, the degree of overlapping of the side edges of the tape in the single-core wire may be a little larger, and depending on the case, the overlapping position may be shifted and the tape may be wound twice.

[Effects of the Invention] As is clear from the above, according to the present invention, it is possible to reduce the amount of coating metal when making a multi-core wire, so it is possible to make the superconductor part denser, and it is possible to increase the density of the multi-core wire. The critical current density can be improved, which is a great advantage when applied to magnets, etc. Furthermore, the present invention has the advantage of being easy to manufacture and providing a wire rod with good characteristics.

[Brief explanation of drawings]

FIG. 1 is an enlarged cross-sectional view of a single-core wire in an embodiment of the method according to the present invention, and FIG. 2 is an explanatory diagram showing a method for forming the single-core wire. 1: Superconducting powder, 2: Silver tape, 3: Single core wire, 4 and 5: Dice.

Claims (1)

[Claims] (1) Powder of oxide superconductor is supplied onto a coated metal tape formed into a U-shaped cross section until both side edges of the tape close, and while increasing the overlap of both side edges of the tape, A single-core wire is obtained by compressing powder and tightly surrounding the powder with the tape, and a plurality of the single-core wires are collectively subjected to area-reducing plastic processing, and then subjected to sintering heat treatment. A method for producing a cored oxide superconducting wire.