JPH0362416A - Oxide superconducting wire - Google Patents

Abstract

PURPOSE:To easily obtaining a fine wire and particularly a round wire of very small diameter by constituting a metal pipe with an outer silver pipe and an inner silver pipe or rod inserted in the aforesaid silver pipe, and filling a superconducting material in a gap between the outer silver pipe and the inner silver pipe or rod. CONSTITUTION:Two silver materials comprising an inner silver pipe or rod arranged in an outer silver pipe are used, instead of an ordinary single silver pipe. In a superconducting wire applied with the aforesaid double silver construction, an oxide superconducting powder is filled in a gap between both silver materials and, therefore, a shearing force always acts on a power part due to a speed difference in the plastic flow of the inner and outer silver materials during a fine wire processing. No cavity, therefore, is formed in the powder part and in particular and it becomes possible to obtain in particular a fine round wire. The method for reducing the diameter of the wire is not limited specifically, but a die wire drawing process is adopted specifically for obtaining a round wire.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a novel oxide superconducting wire made by filling a metal pipe with an oxide superconducting material to form a wire.

[Conventional technology]

At present, various oxide-based superconducting materials are known, and research into the practical use of these materials in forming superconducting materials into elongated objects such as wires and tapes is flourishing worldwide.

Generally, a powder method is known as a manufacturing process for forming oxide superconductors into wires. In the powder method, ■ a metal pipe (usually a silver pipe) is filled with raw material powder of oxide superconductor,
Encapsulating raw material powder inside a metal pipe by welding both ends of the pipe, ■ Swaging, die wire drawing (drawing with a die), or rolling processing the metal pipe to convert thick wire into thin wire or thin wall. (2) Sintering a thin diameter wire or thin tape to produce a product as a superconducting wire.

[Problem to be solved by the invention]

Currently, among die wire drawing and rolling processing, rolling processing is exclusively performed to produce superconductor wires, and die wire drawing processing is hardly employed. The reason why die wire drawing is not carried out is that 0.1
(1) There is a limit to the degree, and if the diameter is made smaller than this, breakage will occur frequently.

Regarding this, in the die wire drawing process for ordinary metal wire, when the wire 10 has a large diameter, the inside of the silver pipe is The raw material powder moves in the axial direction due to the tensile force caused by wire drawing, and the apparent deformation progresses, but the wire rod 1
As the diameter of 0 becomes smaller, the powder particles become finer, making it difficult for the particles to slide in the axial direction, and as a result, cranks are more likely to occur in the center of the raw material powder. Moreover, as can be seen from Figure 4,
Since a larger tensile force acts on the center portion of the wire 10 than on the outer layer portion, the amount of deformation at the center portion is greater than that on the outer layer portion.

Therefore, the occurrence of a crank and a large amount of deformation at the center cause wire breakage.

On the other hand, in rolling processing, the deformation progresses due to compressive force rather than tensile force, that is, the amount of deformation due to tensile force is small, so cracks are less likely to occur inside the wire. However, as seen in metallic superconducting wires, most superconducting wires have a round wire shape, except for those with rectangular shapes.

Furthermore, regarding the use of superconducting wires as products, there are many specifications that use pulsed current or alternating current. For example, when using an oxide superconducting wire for AC specifications, a round superconducting filament with a diameter of several μm is required, according to rough estimates. In particular, when applied to various types of equipment in AC power transmission systems, it is essential to use filamentary superconducting wires in the form of twisted wires.

Therefore, when putting oxide superconducting wires into practical use, rolled tape-shaped superconducting wires are almost limited to use in DC equipment, but thinner round-shaped superconducting wires are needed for a wide range of applications such as AC specifications. Superconducting wire is required.

Therefore, in view of the above points, an object of the present invention is to provide an oxide superconducting wire that can be easily reduced in diameter, particularly in a round shape, without any inconvenience such as wire breakage. .

[Means for Solving the Problem] The object is to provide a metal pipe consisting of an outer silver pipe and an inner silver pipe or silver rod inserted into the silver pipe, and the outer silver pipe and the inner silver pipe or silver rod. This is achieved by using a superconducting wire formed by filling the gap between the superconducting material and the superconducting material.

That is, the oxide superconducting wire of the present invention uses two silver materials in which an inner silver pipe or silver rod is arranged inside an outer silver pipe instead of the usual single silver pipe (see Fig. 1). reference).

In a superconducting wire that adopts such a double silver material structure, oxide superconducting powder is filled in the gap between the two silver materials, so when thinning the wire, the powder part is constantly subjected to shearing force due to the difference in plastic flow speed between the inner and outer silver materials. This prevents the formation of cavities within the powder portion, making it possible to form thin, round wires in particular.

In the present invention, the method for thinning the wire is not particularly limited, but when the wire is to be made into a round wire, it is particularly preferable to employ die wire drawing (that is, drawing with a die).

Further, the inner silver material inserted into the outer silver pipe may be either a silver pipe or a silver rod, but it is preferable to use a silver pipe from the viewpoint of workability as described below.

That is, when an inner silver pipe is used, it is preferable to fill the hollow part of the inner silver pipe with a fluid (particularly a volatile fluid) during the die wire drawing process. The reason for this is that, as mentioned earlier based on Figure 4, the center of the wire is the part that undergoes the highest degree of processing during wire drawing and is most susceptible to cracks. This is because by filling the gap with oxide powder and filling the hollow part of the inner silver pipe corresponding to the center with fluid, it is possible to effectively prevent the occurrence of cracks during wire drawing.

Therefore, the fluid is preferably volatile enough to be easily removed from the hollow part of the inner silver pipe by evacuation or the like after the final wire drawing. In addition, unlike gas, liquid is incompressible, so even if external pressure is applied to the inner pipe due to wire drawing, a uniform internal pressure can be applied to the inner pipe, preventing buckling during wire drawing. From this point of view, it is preferable to use a liquid rather than a gas. Such volatile liquids include:
Examples include ethyl alcohol, methyl alcohol, isopropyl alcohol, acetone, and dolchloroethane. There is no limit to the oxide superconducting material that can be filled into the gap between the inner and outer silver materials. When shown,
YBalC+gO,, ErBatCus○a, HoBa
zCu, O,, BielPbo, 5SrCaCu+,
5Oys Bio, 5Pbo, zSrCaCu+, s○
.

etc. are listed.

〔Example〕

The oxide superconducting wire of the present invention will be described in detail below using Examples, but the present invention is not limited to the following Examples.

FIG. 1 shows one embodiment, and the superconducting wire is an outer silver pipe 1.
An oxide superconducting material 3 is filled in the gap between the pipe 1 and a silver pipe 2 coaxially arranged. Volatile fluid is removed from the central portion 4 of the superconducting wire, ie, inside the silver pipe 2, by evacuation or the like after final wire drawing.

Example 1 Next, a specific example will be described.

In this example, a silver pipe having a structure as shown in FIG. 2 was used. This silver pipe is made by integrally forming the inner and outer silver pipes 2.1, and its cross section has a shape as shown in FIG. The dimensions are that the outer diameter of the outer silver pipe 1 is 20 mm and the wall thickness is 1.5 m.
m, the outer diameter of the inner pipe 2 is 8 mm, and the wall thickness is 1ffi [I,
The length of the raw material powder filling part is 10 cm.

Oxide raw material powder (in this example, Y
BazCusOy) and the center 4 was filled with ethyl alcohol as a volatile liquid.

Thereafter, a cap 7 made of silver or copper was joined to the other end of the silver pipe by welding, and the raw material powder and ethyl alcohol were sealed inside the pipe. At this time, as shown in the figure, a water cooling block 8 was placed near the welding location to cool the volatile liquid ethyl alcohol so that it would not ignite due to welding heat.

The base material thus obtained was swaged into fine wires until the outer diameter became approximately 711I111, and then passed through a die 20 as shown in Fig. 3 until the outer diameter became 0.07 rm.
A thin wire with a diameter of about 8000 m was obtained. A wire having a length of 5c11 was sampled from the obtained thin wire, the ethyl alcohol in the center portion 4 was removed by vacuuming, and both ends of the sampling wire were sealed by crimping. This sampling line was first heated at 920'C for 12 hours in an O2 atmosphere.
A superconducting wire was produced by sintering at 450° C. for 5 hours in the same atmosphere.

As a result of investigating the superconducting properties of this superconducting wire with a length of 5 cI11, the superconducting transition temperature (zero resistance temperature) is 92 K, the temperature at which resistance begins to decrease is 88 K, and the critical current density at 77 is 460 A/c-J. there were.

〔Effect of the invention〕

As explained above, the oxide superconducting wire of the present invention uses a double-structured silver material consisting of an outer silver pipe and an inner silver pipe or silver rod, so that it can be made into a round thin wire. can be easily obtained.

In particular, even if die wire drawing is used to thin the wire, no cranks will occur inside the wire, so there will be no breakage, and high-quality superconducting wire with almost no defects can be easily produced.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the oxide superconducting wire of the present invention, FIG. 2 is a sectional view of the base material of the superconducting wire before thinning processing, and FIG. 3 is the base material shown in FIG. 2. FIG. 4 is a sectional view showing the deformation process of a normal metal wire by die drawing. 1 : Outer silver pipe 2 : Inner silver pipe 3 : Oxide superconducting material 4 : Center part Fig. 1 8 Fig. 3

Claims (1)

[Claims] A superconducting wire made by filling a metal pipe with an oxide superconducting material, where the metal pipe consists of an outer silver pipe and an inner silver pipe or silver rod inserted into the silver pipe. An oxide superconducting wire characterized in that the gap between a silver pipe or a silver rod is filled with a superconducting material.