JP2757575B2 - Method for manufacturing high-temperature superconducting wire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a bismuth-based oxide superconductor.

[0002]

2. Description of the Related Art In recent years, ceramic superconducting materials, that is, oxide superconducting materials, have attracted attention as superconducting materials exhibiting higher critical temperatures.

For example, a bismuth-based oxide superconducting material has a high critical temperature of about 110 K, and is expected to be put to practical use.

[0004] Bismuth-based superconductors have a critical temperature of 11
It is known that there are those having a temperature of 0K and those having critical temperatures of 80K and 10K.

Further, in a bismuth-based oxide superconductor, (Bi, Pb) -Sr-Ca-C in which 110B phase, Bi: Sr: Ca: Cu or Bi is partially substituted by Pb.
u has a 2223 composition in the composition of
It is known that the K phase has a 2212 composition with the same constituent elements.

In a method of manufacturing an oxide superconductor, a method in which a raw material in a metal sheath is converted into a superconductor by performing plastic working and heat treatment in a state where the raw material of the oxide superconductor is filled in a metal sheath. There is. This method can be advantageously applied, for example, when manufacturing a long superconducting wire.

[0007]

When a superconductor is applied to a cable, a magnet, or the like, the superconductor has a high critical temperature, a high critical current density, and a critical current density of a wire over a long length. Must be uniform.

As described above, in the manufacturing process, plastic working and heat treatment are performed. During this heat treatment, gas is generated from the raw material filled in the metal sheath, and the wire is expanded. Due to this expansion, cracks occur in the superconductor portion, and a problem arises in that the critical current density of the wire decreases.

In order to heat-treat a long wire in a furnace in which the uniform range of the heating distribution is limited, it is necessary to heat-treat the long wire in a more compact state.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a long superconducting wire capable of obtaining a uniform critical current density in the longitudinal direction, preventing expansion of the wire during heat treatment, and maintaining a compact state. An object of the present invention is to provide a method for producing a high-temperature superconducting wire capable of heat-treating a long wire.

[0011]

In the method for producing a high-temperature superconducting wire according to the present invention, a step of filling a high-temperature superconductor or its raw material with a powder prepared by repeating heat treatment and subsequent pulverization a plurality of times into a metal pipe; Performing a first plastic working on the filled metal pipe to produce a wire having a metal coating formed from the metal pipe, and a first tape material that is not joined to the metal coating of the wire during heat treatment. The first heat treatment is performed by attaching the wire to the wire in a state where the wire is spirally wound and laminated, and the thermal expansion of the wire in which the second tape having a smaller thermal expansion coefficient than the metal coating is suppressed is suppressed. Applying, performing a second plastic working on the wire after the first heat treatment, and performing a second heat treatment on the wire after the second plastic working.

In the present invention, at the time of the first heat treatment,
As the first tape material to be interposed when the wires are spirally wound and laminated, a material that is not bonded to the metal coating of the wires during heat treatment is used. Such materials include Si
A glass tape or the like containing as a main component can be used.

In the first heat treatment, a tape material having a smaller coefficient of thermal expansion than a metal coating is used as a tape material attached to the wire material in a state where thermal expansion of the laminated wire material is suppressed. The coefficient of thermal expansion here is, for example, the coefficient of thermal expansion in a temperature range of 0 ° C. to 900 ° C.

As such a second tape material, Si is used.
And the like. Therefore, in the present invention, the first tape material and the second tape material may be made of the same material.

Further, in the present invention, for example, silver or a silver alloy can be used as the metal pipe.

[0016]

In the present invention, when performing the first heat treatment,
The wire is spirally wound and laminated with the first tape interposed, and the second tape is wound around the outer periphery of the laminated wire. In the first heat treatment of the conventional manufacturing method, gas was partially generated from the filled powder, and a phenomenon was observed in which the metal coating surrounding the filled powder expanded by several cm every several tens of cm. Due to this partial expansion, in the subsequent second plastic working, uneven working was performed, and the critical current density was reduced.

In the present invention, since the first tape material is interposed and the outer periphery of the laminated wire material is wound by the second tape material, such expansion is averaged over the entire wire material, and deterioration due to the wire expansion is achieved. Can be prevented.

In the present invention, since the wires are laminated and subjected to the first heat treatment with the first tape material interposed therebetween,
The wires are not joined together, and the long wires can be heat-treated in a more compact state.

[0019]

According to the present invention, a high-temperature superconducting wire having a high critical current density can be manufactured, and a long wire can be heat-treated in a heat treatment furnace in a compact state.

[0020]

EXAMPLES Bi ₂ O ₃ , PbO, SrCO ₃ , and C
Using uO, Bi: Pb: Sr: Ca: Cu = 1.
A powder having a composition ratio of 8: 0.4: 2: 2.2: 3 was prepared.

This powder is heat-treated at 800 ° C. for 8 hours,
This was crushed for 2 hours using an automatic mortar to make the powder. The powder obtained by the pulverization was heat-treated at 860 ° C. for 8 hours and pulverized again in the same manner as described above.

While heating under reduced pressure, the powder was filled in a silver pipe having an outer diameter of 15 mm and an inner diameter of 10 mm, and then drawn and rolled to obtain a tape-shaped wire rod having a thickness of 0.18 mm.

FIG. 1 is a perspective view showing a wire state at the time of the first heat treatment in the present invention. Referring to FIG. 1, a wire 1 is configured by providing a silver coating 3 around a superconductor layer 2. Such wires 1 are stacked in a plurality of layers via a first tape material 4, the outer periphery of the stacked wires 1 is wound around with a second tape material 5, and a first heat treatment is performed in this state.

The tape-shaped wire obtained as described above is spirally wound in a plurality of layers with a glass tape serving as a first tape interposed therebetween to form a wire bundle 10 as shown in FIG. The outer periphery of the wire bundle 10 was wound with a glass tape as the second tape material 11, and a first heat treatment was performed in this state. This is referred to as Example 1.

Further, a plurality of tape-shaped wires are stacked with a glass tape as a first tape material interposed therebetween, and the periphery thereof is wound with a glass tape as a second tape material 21 as shown in FIG. The wire bundle 20 is used.
Were spirally laminated. The first heat treatment was performed in such a state as shown in FIG. This is Example 2.

FIG. 4 further shows, as a comparative example, a wire 30 as shown in FIG. 4 arranged spirally without being stacked as shown in FIG. 5 without laminating with a first tape material interposed therebetween. Then, a first heat treatment was performed in this state. This is a comparative example.

A first heat treatment was performed in the state of Examples 1 and 2 and Comparative Example. The first heat treatment is 84
Heat treatment was performed in the air at 5 ° C. for 50 hours, and then the mixture was gradually cooled.

After the first heat treatment, the wire was taken out, rolled to 0.14 mm, and then subjected to a second heat treatment at 840 ° C. for 50 hours.

The critical current density of the obtained wire was measured by changing the length of the wire. Table 1 shows the results.
Table 1 also shows whether or not the wire has expanded during the first heat treatment. Table 1 also shows the volume occupied by the first heat treatment.

[0030]

[Table 1]

In the case of the wire rod of the comparative example, 1 for about 50 cm
While expansion of about 2 cm was observed, no expansion phenomenon was observed in the first heat treatment in the wires of Examples 1 and 2.

In Examples 1 and 2 produced according to the present invention, good wires having a higher critical current density and higher uniformity in the length direction were obtained as compared with those of Comparative Examples.

Further, it can be seen that the volume of the wire bundle at the time of the heat treatment, that is, the occupied volume, is much smaller in Examples 1 and 2 than in Comparative Example.

In the above embodiment, the second tape material is wound around the outer periphery of the laminated wire to suppress the thermal expansion at the time of the first heat treatment. However, the thermal expansion may be suppressed by other methods. Good. For example, when a material having a small coefficient of thermal expansion is used as the first tape material, the end of the first tape material is fixed so that the bundled wires do not expand during the first heat treatment. Thereby, it may function as the second tape material. In this case, the second tape material and the first tape material are the same.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a wire state during a first heat treatment in the present invention.

FIG. 2 is a plan view showing Embodiment 1 according to the present invention.

FIG. 3 is a plan view showing a second embodiment according to the present invention.

FIG. 4 is a perspective view showing a state of a wire during a first heat treatment in a comparative example.

FIG. 5 is a plan view showing a comparative example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 wire 2 superconductor layer 3 silver coating 4 first tape 5 second tape 10 wire bundle 11 second tape 20 wire bundle 21 second tape

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Kenichi Sato 1-3-1, Shimaya, Konohana-ku, Osaka-shi Sumitomo Electric Industries, Ltd. Osaka Works (56) References JP-A-2-207422 (JP, A) ( 58) Field surveyed (Int.Cl. ⁶ , DB name) H01B 13/00 565 H01B 12/10 ZAA

Claims (1)

(57) [Claims] A step of filling a prepared metal powder with a powder prepared by repeating heat treatment and subsequent pulverization of the high-temperature superconductor or its raw material a plurality of times, and subjecting the filled metal pipe to a first plastic working; Producing a wire having a metal coating formed from the metal pipe,
A second tape having a smaller coefficient of thermal expansion than the metal coating, while spirally winding and laminating the wire with a first tape material of a material that is not bonded to the metal coating of the wire during heat treatment interposed therebetween. Attaching a wire to the wire in a state in which thermal expansion of the laminated wire is suppressed and performing a first heat treatment; applying a second plastic working to the wire after the first heat treatment; Subjecting the wire after plastic working to a second heat treatment.