JPH0443510A - Oxide superconductive wire material - Google Patents

Abstract

PURPOSE:To prevent a deterioration of superconductive property to a mechanical bending by cladding a tape-like reinforcement metal on one side of a metal-clad oxide superconductive tape-like wire member. CONSTITUTION:A metal-clad oxide superconductive tape-formed wire member and a tape-like reinforcement metal member other than the wire member are clad. As the reinforcement metal member to be clad, a material having a strength at a high temperature such as Ni, a Ni alloy, and SUS is used. The thickness of the reinforcement metal member depends on the thickness of the wire member, making from about half to several times the thickness of the wire member.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to improvements in superconducting wires, particularly metal-coated oxide superconducting tape-shaped wires.

[Prior Art] Currently, most metal-coated oxide superconducting wires are manufactured as follows.

Powder that exhibits superconductivity in advance, such as Y-Ba-Cu
-0 series, Bl -Pb -Sr -Ca -Cu -0
or TI-Ba/Sr-Ca-Cu-0 system powder is filled into a metal vibrator, for example, Ag, and extruded.
After reducing the area by drawing, swaging, etc., it is rolled into a metal-coated tape-like wire, and finally, it is subjected to sintering heat treatment in an oxygen atmosphere at 800 to 900°C to bond the powder particles.

The tape-shaped wire produced by such a method is YBa-Cu at liquid nitrogen temperature (77K) and zero magnetic field.
-0 series, 3000-4000A/cl, Tl-B
a/ 10000 to 1 in Sr-Ca-Cu-0 system
A critical current density (Jc) of 5000 A/c has been obtained.

Furthermore, when looking at the bending characteristics of the tape-shaped wire rod, as shown in FIG. 2, it is observed that Jc decreases as the amount of strain increases.

Figure 2 shows TI-Ba/Sr- with a tape thickness of about 0.2
In the case of a Ca-Cu-0 based silver-coated tape-shaped wire,
The amount of bending strain (ε) was defined as ε−(t/2R) x +OO(%), where the tape thickness was 11 and the bending radius was R.

Further, the characteristics shown in FIG. 2 were evaluated for both (a) where Jc was measured after heat treatment after bending, and (b) where Jc was measured after heat treatment and bending. The vertical axis indicates the value normalized by Jc when the amount of strain is zero.

According to Fig. 2, a decrease in Jc is observed from a strain amount of about 0.2%, and for the former (a), 6096 at ε-0.6%.
A decrease in Jc was observed, and a similar decrease of 25% was observed in the latter (b>).

[Problem to be solved by the invention] The above-mentioned conventional technology has the following problems.

(1) Oxide superconducting wires have significantly lower Je than metal-based wires. Currently, Je at liquid nitrogen temperature (77K) and zero magnetic field is on the order of io'A/c-, but in practice it is 1
05-1o6A/cd is required. Therefore, in order to improve the characteristics, it is necessary to make the core superconductor a dense structure and to improve the weak bond between the crystals.
Improving this and introducing pinning points will be important factors.

(2) The main cause of property deterioration due to bending of oxide superconducting wire is cracks, which exhibit irreversible behavior. Therefore, if the amount of bending strain is large when winding the coil, cracks will occur, lowering the critical current value, and further causing a large drop in Jc due to the magnetic field generated from the coil.

Therefore, a wire rod whose Jc decreases less when mechanically bent is required.

It is an object of the present invention to provide a metal-coated oxide superconducting tape-shaped wire material which eliminates the drawbacks of the prior art described above, whose superconducting properties do not deteriorate due to mechanical bending, and whose critical current density can be greatly increased. Our goal is to provide the following.

[Means for Solving the Problems] The gist of the present invention is to clad a metal-coated oxide superconducting tape-shaped wire with a tape-shaped reinforcing metal material separate from the wire, thereby improving the bending properties. This is an attempt to improve and improve Jc.

In the case of the present invention, various oxide superconductors such as those described above can be used, but the metals covering the superconductor include Ag (silver), Au (gold), Cu (copper).
Good conductors such as and alloys thereof are used. Of course, the superconductor portion coated with a good conductor need not be a single core, but may be a multicore divided into a plurality of parts. In addition, the reinforcing metal materials to be clad include N1 (nickel), Ni
Materials that are strong at high temperatures, such as alloys and SUS, are used.

The thickness of this reinforcing metal material depends on the thickness of the wire, but
It is desirable that the thickness be about half to several times that of the wire.

[Function] The mechanism for improving Jc by the cladding structure has the following points, and its effects are advantageous for manufacturing a coil using an oxide superconductor.

(1> By using reinforcing materials such as SO3 or Ni, which are strong at high temperatures, there is a restraining force on the oxide superconductor at high temperatures, and as a result, good sintering progresses during heat treatment, resulting in a dense oxide superconductor. structure is obtained, and the weak bonds between crystals are improved.

(2) Due to the presence of a metal reinforcing material on one side, when bending deformation is applied so that the reinforcing material is on the outside, that is, the outer periphery,
Since the neutral line where the amount of strain is zero moves outward, compressive stress is applied to much of the inner superconductor, and its processing limits are greatly improved.

[Example] The present invention will be explained in detail below.

A chain tube with an outer diameter of 6.0 mm and a wall thickness of 0 and 1 mm, and a TI2. o Bat, b Sro, 4
A superconducting powder having a composition of Ca2Cu30* was prepared, and the superconducting powder was filled into a chain tube, and then subjected to surface reduction processing by swaging to obtain a wire rod with an outer diameter of 2.8 mm. Next, this wire rod is rolled to a thickness of 1. On+m, 0.5m
It was made into a 1,000-tube-shaped wire rod with a diameter of 0.3 mm. After that, for each tape-shaped wire, Nl tape with the same thickness as the tape-shaped wire was layered on one side, and each tape-shaped wire was processed into a tape-shaped wire with a cross-sectional configuration as shown in Fig. 1 through one rolling process. .

In this case, the thickness of each silver-coated superconducting tape wire portion is 0.
．． It was processed to have a length of 1 m. As a result, the thickness of each clad wire including the N1 layer was 0.8 mm (sample A
), 0.3 m11 (sample B), and 0.21 m1 (sample C) were obtained.

In FIG. 1, 1 indicates a silver coating as a stabilizing material, 2 indicates an oxide superconductor, and 3 indicates a Nl reinforcing material layer.

Finally, each sample was subjected to sintering heat treatment in an oxygen atmosphere at 860° C. for 2 hours, and then subjected to characteristic evaluation.

The liquid nitrogen temperature (77K) of the three types of clad wires obtained was
), the Jc values in zero magnetic field are shown in Table 1 together with the values of the conventional tape-shaped wire without the Ni reinforcing material layer 3 (tape thickness: 0.1 mm).

The Jc value in this case is the current value when a voltage of 1 μV is generated divided by the cross-sectional area of the superconducting portion.

Further, Table 2 shows the bending properties of Sample A after heat treatment in comparison with a tape-shaped wire rod (tape thickness 0.1 mm) made by a conventional method.

In this case, the bending test is performed between two support points at a predetermined interval.
A method was adopted in which a sample of the heat-treated wire was placed with the Ni reinforcing material layer 3 on the lower side, and the sample was pressed with a die from approximately above the center of the support point and bent.

As is clear from Tables 1 and 2, the Jc characteristic of the wire rod made by the conventional method is 10,000 to 15,000 A/c, whereas the Jc characteristic of the wire rod made by the present invention is twice that, 25,000 to 3
5000 A/c- was obtained, and the characteristics were greatly improved. In addition, by creating a cladding structure with N1, the amount of strain can be reduced to 1.
．． It was also observed that there was no decrease in Jc at 0% or less.

Table 1 [Effects of the Invention] As is clear from the above, according to the present invention, by cladding the reinforcing metal material, there is an advantage that the JC value and bending properties can be dramatically improved. It is extremely effective in practice as a conductor.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the cross-sectional structure of an oxide superconducting wire according to an embodiment of the present invention, and FIG. 2 is a graph showing the bending strain dependence of the critical flow density of a silver-coated oxide superconducting wire according to a conventional method. It is. 1. Silver coating, 2. Dioxide superconductor, 3. Ni reinforcement layer. Lol Figure 1 Figure 2 Bending strain amount (E)

Claims (1)

[Claims] (1) An oxide superconducting wire characterized by comprising a tape-shaped reinforcing metal material clad on one side of a metal-coated oxide superconducting tape-shaped wire.