JPH02189817A - Manufacturing method of oxide superconducting tape-shaped wire - Google Patents

Abstract

PURPOSE:To enable the manufacture of an elaborate wire rod by filling a pipe with metal and an oxide superconductor which are to be made a base material for a tape-state wire rod, making the pipe in a tape-state with cold working applied, and applying heat treatment after an outer peripheral pipe is removed. CONSTITUTION:The inside of a silver or copper pipe (outer diameter of 15mm, inner diameter of 10mm) is filled with a silver rod (outer diameter of 9.5mm) cut out half in a longitudinal direction and oxide superconductive powder, and the pipe is made in a flat plate state with drawing processing and rolling processing applied. Then the silver or copper pipe is etchingly removed and heat-treated in an oxygen atmosphere to obtain a tape-state wire rod.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing an oxide-based superconducting tape-shaped wire, and in particular to superconducting wires for use in linear motor cars, superconducting propulsion vessels, nuclear magnetic resonance tomography devices, etc. This invention relates to a method for manufacturing oxide superconducting tape-shaped wires that are applied to conductive magnets, power transmission cables, etc.

[Conventional technology]

Oxide superconductors have higher critical temperatures Tc and upper critical magnetic fields IC2 than conventional superconductors, and are expected to be applied to superconducting magnets, power transmission cables, and the like. To achieve this, it is essential to make the oxide superconductor into a wire, which involves filling a metal sheath with oxide and then stretching it, or attaching the oxide to a tape-shaped base material by screen printing, plasma spraying, etc. Attempts have been made to make wire rods using methods such as the following.

As an oxide superconductor with a high critical temperature Tc, Y
-Ba-Cu-0 system (Tc=90K), B1-3r
-Ca-CuO system (Tc=80~ll0K), Tl
-Ba-Ca-Cu-0 system (Tc=120K) etc. are known. In the Y-Ba-Cu-0 system, the composition of the superconductor is generally indicated as YBazC+g07-δ, but oxygen is indicated as 7-δ because the amount of oxygen contained in this oxide depends on the temperature etc. indicates that they are different.

In YBazCu30t-δ, the superconductor has δ-,
-0.1, but it has been reported that δyO09 at the temperature required for sintering, around 900°C. In order for this material to become superconducting, it must be furnace cooled after sintering to absorb oxygen, and δ 0
．． It is necessary to set it to 1. Also, B1-3r-Ca
- Among the Cu-0 and Tl-Ba-Ca-Cu-0 systems, the Y-Ba-Cu-0 system does not release or absorb any oxygen, but the superconducting properties are better when the furnace is cooled after sintering. There are also experimental results showing that oxygen absorption is necessary.

Applications of superconductors include power storage and transmission using zero resistance and perfect diamagnetism, linear motor vehicles, electromagnetic ships, etc., but in order to apply them to these applications, it is essential to make superconductors into wires. It is.

[Problem to be solved by the invention]

When making wires from oxide superconductors, the critical current density J
Densification and orientation are required for the purpose of improving c.
A tape-like shape is desired to shorten the diffusion distance of oxygen. Screen printing method,
A plasma spray method or the like is applied, but the former has problems such as difficulty in densification, and the latter makes it difficult to control the composition of the oxide. On the other hand, a method in which the sheath is filled with an oxide superconductor and then subjected to drawing processing has the advantage that composition control and densification are facilitated, and tape-shaped wire rods can also be easily obtained by performing rolling processing. However, oxide superconductors ultimately require heat treatment at high temperatures (700-950°C), and at this time oxygen is released from the oxide, so heat treatment at low temperatures is required for a long time after heat treatment at high temperatures. The problem was that it was necessary. Furthermore, if the sheath was removed from the processed wire to facilitate oxygen diffusion, there were problems in handling due to the brittleness of the oxide.

In view of the above-mentioned state of the art, the present invention aims to provide a method for producing a dense oxide superconductor without the problems encountered in the prior art.

[Means to solve the problem]

That is, the present invention provides (1) after filling a pipe with the metal and oxide superconductor that will serve as the base material of the tape-shaped wire, cold working it into a tape shape, then removing the outer peripheral pipe, and then heat-treating it. A method for manufacturing an oxide superconducting tape-shaped wire (first invention), characterized in that (2) a pipe is filled with a metal serving as a base material of the tape-shaped wire and an oxide superconductor, and then cold working is performed. A method for producing an oxide superconducting tape-shaped wire material (second invention), characterized in that the outer circumferential pipe is removed after heat treatment and (3) in (1) and (2) above. A method for manufacturing a tape-shaped wire (third invention), characterized in that the obtained tape-shaped wire is subjected to pressure processing and heat treatment one or more times.

[Effect]

First, the reason why the pipe is filled with the oxide superconductor and the metal serving as the base material of the tape-like wire at the same time is to facilitate handling of the superconductor when the sheath is removed after processing. The base metal may include materials that do not easily react with the oxide superconductor, such as gold, silver, and platinum, but silver is particularly preferred from the viewpoint of economy and reactivity.

As the oxide superconductor, (RE)-Ba-Cu-0 system B1-3r-Ca-Cu-0 system, B1-Pb-5r-
Examples include Ca-Cu-0 type and Tl-BaCa-Cu-0 type, and each can be filled as a raw material powder mixture, a precursor after heat treatment, or a final product.

At this time, the heat treatment temperature after removing the pipe of the first invention and the second invention
The heat treatment temperature before pipe removal in the invention varies depending on the type of oxide, and is 850 to 940° for the (RE)-Ba-Cu-0 system.
C, Bj-5r-Ca-Co-0 system, B1-Pb-3
r-Ca-Cu-0 system: 750-890°C, Tl
-Ba-Ca-Cu-0 system is 800 to 940°C. Here, the reason for specifying each temperature range is that sintering is insufficient below the lower limit temperature, and (RE)-Ba-C
The upper limit temperature of 940"C in the u-0 system and the Tl-Ba-Ca-1co-0 system is hereinafter referred to as the base metal,
For example, melting of silver becomes a problem. Also B1-5
r-Ca-Cu-0 system and B1-Pb-3r-CaCu
The upper limit temperature of 890°C in the -0 system is because the oxide melts above this temperature.

Secondly, the heat treatment in the first invention and the second invention facilitates the diffusion of oxygen into the oxide and improves the superconducting properties. If silver is used as the pipe, this heat treatment may be performed either before or after removing the pipe (that is, it can be adopted in either the first invention or the second invention), but if copper or stainless steel is used as the pipe, Heat treatment must be performed after pipe removal in consideration of reaction with oxides.

(In other words, the first invention cannot be carried out, the second invention must be carried out.) The obtained wire rod (according to the first invention or the second invention) may be annealed in an oxygen atmosphere as necessary to undergo oxidation. It is preferable to promote the diffusion of oxygen into the object.

Thirdly, the tape-shaped wire rod obtained in the above manner is subjected to pressure processing and heat treatment once.''-B1-5r-C
This is to orient plate-like particles, which are particularly noticeable in a-Cu-0 superconductors.

[Example 1] As shown in Fig. 1, a silver rod with an outer diameter of 9.5 mm was cut in half in the longitudinal direction and a silver pipe with an outer diameter of 15 mm and an inner diameter of 10 mm was placed inside the copper pipe. , Y--Ba--CuO based superconducting powder was filled, and stretched and rolled to form a flat plate as shown in FIG.

Next, the silver pipe and copper pipe were removed by etching, heat treated at 900°C for 14 hours in an oxygen atmosphere, and then heated at 3°C.
The temperature was lowered at a cooling rate of /min.

Figure 3 shows the results of measuring the superconducting transition curve of a superconductor obtained using a silver pipe by the induction method. It can be seen from FIG. 3 that a 90-grade superconductor exists in a single phase. Also, zero resistance was confirmed at 92 using the DC four terminal method.

Also, regarding superconductors obtained using copper pipes,
Results similar to those above were obtained.

[Example 2] The flat wire rod processed using the silver pipe in Example 1 was heat treated at 900°C for 14 hours before removing the silver pipe, and then heated at 400°C after etching and removing the silver pipe.
Oxygen annealing was performed at °C for 10 hours. The obtained tape-shaped wire was evaluated for superconducting properties in the same manner as in Example 1,
It was confirmed that the superconducting phase was single-phase and that the zero resistance was 92.

[Comparative Example] After processing was performed in the same manner as in Example 1 except that copper was used as the pipe material, heat treatment was performed in the same manner as in Example 1 without removing the pipe.

The results of measuring the superconducting transition curve of the superconductor thus obtained by the induction method are also shown in FIG. Although there is also a superconducting phase of 90-degrees, the main superconducting phase is 60-degrees.
It is thought that oxygen diffusion is insufficient. The temperature at which resistance reached zero was 65.

[Example 3] Y of the Y-Ba-Cu-0 superconductor was replaced with other rare earth elements (
La, Nd, Sm, Eu, Gd, Dy, H
The same procedure as in Example I was carried out except that the substitution was made with (o, Er, Tm, Yb). Table 1 shows the critical temperature at which resistance becomes zero, measured by the DC four-probe method. Both were shown at high critical temperatures. Furthermore, in the induction method, it was confirmed that all of them had a single phase.

Table 1 [Example 4] Old-Pb-3r-Ca-Cu-0 as oxide superconductor
Raw material mixed powder of superconductor (Bi:Pb:Sr:Ca:
Processing and etching removal of the pipe were performed in the same manner as in Example 1 except that Cu=2:0.5:2:2:3 (molar ratio) was used, and heat treatment was performed at 850° C. for 100 hours.

Figure 4 shows the superconducting transition curve obtained by the DC four-terminal method. The zero resistance is 105 and the critical current density is 1508/
c+].

[Example 5] Old-Pb-5r-Ca-Cu-0 as oxide superconductor
Raw material mixed powder of superconductor (Bi:Pb:Sr:Ca:
Cu=2:0.5:2:2:3 (molar ratio)) 820
Processing and etching removal of the sheath were carried out in the same manner as in Example 1, except that a precursor heat-treated for 20 hours was used, and the heat treatment was carried out at 850°C for 80 hours. Zero resistance is Example 4
Similarly to 105, the critical current density is 280A/c
It was J.

[Example 6] The oxide superconducting wire obtained in Example 4 was rolled and heat treated at 870"C for 10 hours. In the critical temperature measurement using the DC four-terminal method, the temperature at which zero resistance was reached was that of Example 4, the critical current density was 105, but the critical current density was 1100
A/cJ improved. This is thought to be due to the orientation of the plate-like particles due to rolling.

[Example 7] Processing and etching removal of the pipe were performed in the same manner as in Example 1 except that a Tl-Ba-Ca-Cu-0 based superconductor was used as the oxide superconductor, and heat treatment was performed at 920 °C. I went for 30 minutes. Zero resistance was at 120.

[Effects of the Invention] As described above, according to the present invention, it is possible to produce an oxide superconductor that releases and absorbs a large amount of oxygen and a dense tape-shaped wire of the oxide superconductor that has the form of plate-like particles. This also makes it possible to improve superconducting properties through orientation.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a wire rod before processing according to an embodiment of the present invention;
FIG. 2 is a cross-sectional view of a processed wire according to an embodiment of the present invention;
FIG. 3 is a chart showing superconducting transition curves according to Example 1 and Comparative Example 1 of the present invention, and FIG. 4 is a chart showing superconducting transition curves according to Example 4 of the present invention.

Claims (3)

[Claims] (1) A pipe is filled with the metal and oxide superconductor that will serve as the base material of the tape-shaped wire, and then cold-worked to form a tape, and then the outer pipe is removed and then heat-treated. A method for producing oxide superconducting tape-shaped wire. (2) A pipe is filled with the metal and oxide superconductor that will serve as the base material of the tape-shaped wire, and then subjected to cold working to form a tape, heat-treated, and then the outer circumferential pipe is removed. A method for producing oxide superconducting tape-shaped wire. (3) The tape-like wire obtained by the method for producing an oxide superconducting tape-like wire according to claim (1) or claim (2) is subjected to pressure processing and heat treatment one or more times. A method for producing an oxide superconducting tape-shaped wire.