JPH01102811A - Superconductive electric wire - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electric wire using a superconducting material, and particularly to a superconducting wire suitable for power transmission.

[Conventional technology]

Conventional superconducting wires mainly use niobium-based metal superconducting materials, but in recent years research has begun to explore the use of ceramic materials such as oxide superconducting materials. Unlike metal superconducting materials, ceramic superconducting materials often form granular materials with poor stretchability, and it is not easy to make them into wires or tapes, but some experimental examples have already been reported. for example,
Applied Fixtures Letter Volume 51, No. 3 (1
July 20, 987 issue), pages 203 to 204 (
Appl, Phys, Lett, 51 (3)
, 20 July 1987, pp. 203-204)
B a @ Y Cu @ in the chain tube as described in
O? Yb-Ba-Cu composite oxide melt as described in Bulletin of the Japan Institute of Metals, Vol. 26, No. 8 (1987), pages 818 to 819. is rapidly cooled down into a rotating cooling cylinder to yield Yb, B
There are known methods for producing amorphous tapes such as a, Cu5O,,8. In addition, as a literature that considers the influence of pressure, Electronic Ceramics 1987
January issue, pages 19 to 25 and the same magazine, 1985, 1
There are pages 30 to 34 of the January issue, and the former describes the inference that the crystal orientation with a large effective coefficient of thermal expansion is oriented in the pressure direction, and the crystal orientation with a small coefficient is oriented in the direction perpendicular to the pressure. ing. The latter describes the macroscopic anisotropy relationship between shape anisotropy and Kakuda forming.

[Problem that the invention seeks to solve]

Among the conventional techniques mentioned above, the technique of filling a silver tube with oxide superconducting material is not suitable for manufacturing long electric wires, and the technique of making amorphous tape requires a combination of the type of oxide superconducting material and manufacturing conditions. Besides being difficult to determine, concerns about mechanical strength and electromagnetic instability remain.

The objects of the present invention are: (1) to form a superconducting material with poor stretchability into a dense edge material to improve its characteristics; (2) to bring a stabilizing shunt material into close contact with the superconducting material; The purpose is to strengthen the tensile strength.

[Means for solving problems]

The above objectives are to make the cross-sectional structure of the electric wire a three-layered structure consisting of the core wire, superconducting material, and outer sheath, (1) to appropriately select the thermal expansion coefficients of the core wire and the outer sheath, and (2) to heat-treat the core wire or the outer sheath. Forming one or both of them with a stabilizing shunt material, +31
This can be achieved by forming one or both of the 7j wire and the jacket from a material with high tensile strength.

[Effect]

The effects of the present invention will be described in three points: (1) densification of the superconducting material, (2) formation of a stabilizing shunt material, and (3) strengthening of tensile strength.

(1) Now, Hl is the thermal expansion coefficient of the core wire, R1 is the radius at the reference temperature, R7 is the thermal expansion coefficient of the outer jacket, R8 is the inner radius at the reference temperature, and T is the reference temperature. , the envelope forming temperature T
1. Assuming that the heat treatment temperature is T, the gap length G formed between the core wire and the jacket at an arbitrary temperature T is calculated by the following formula (%) when the gap is a cavity. Therefore, R1 praise, , H, >> H,
If so, the effective coefficient of thermal expansion of the gap becomes very large, and if the envelope is formed at a high temperature, a strong pressure will be generated due to gap contraction at a low temperature. Of course, if the relationship between the coefficients of thermal expansion of the core wire and the jacket is reversed, forming the jacket at a low temperature will produce a gap shrinkage force during high-temperature heat treatment. Due to this contraction pressure, the superconducting material filled in the gap becomes a dense structure.

(2) The stabilizing shunt material must be made of a good electrical and thermal conductor, such as aluminum, copper, or silver, in close contact with the superconductor. The structure of an electric wire is generally formed at a higher temperature than the superconducting state, so when using the core wire as a shunt material, the above-mentioned gap shrinkage force at low temperatures must be sufficiently strong, or the thermal expansion coefficient must be higher than that of the superconducting material. It is necessary to use a small core wire.

In addition, when used as an outer sheathing shunt material, it is necessary to increase the gap contraction force at low temperatures or use an outer covering material with a higher coefficient of thermal expansion than the superconducting material, and these conditions and the conditions necessary for cooling If it satisfies the following, it can be stabilized.

(3) Regarding tensile strength, first of all, it is preferable to provide the core wire or the outer sheath with enough strength to prevent breakage, but it is especially important to prevent cracks from forming in the superconducting material. To achieve this, the overall coefficient of thermal expansion of the wire is basically set to be larger than the coefficient of thermal expansion of the superconductor, and in use conditions, that is, at room temperature and low temperature, the superconductor is shortened by compressive force in the longitudinal direction. This is desirable. Naturally, it is also desired that the core wire, superconductor, and outer sheath are in close contact with one another.

However, cracks in the superconducting material can be compensated for by the stabilizing shunt material and do not necessarily have to occur.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. FIG. 1 is a sectional view of a superconducting wire according to the present invention, in which a superconductor 2 is formed around a core wire 3 having a cavity 4, and its periphery is covered with a jacket 1. FIG. 2 is a side view showing the details of the sheath 1 of a superconducting wire according to an embodiment of the present invention. Welded parts 12 are formed by metal applied to the gaps between the tapes at the side edges, completing a gap-free coating. Figure 3 shows an outline of the equipment for manufacturing the superconducting wire shown in Figure 2.
The core wire 3 is supplied from zero to the processing equipment 50, and the completed wire is wound around a wire coil 31. At this time, the core wire coil 30, the core wire 3, and the electric wire coil/L'31 rotate around the core wire 3 while feeding out the core wire 3 and winding up the electric wire.

Inside the processing equipment 50, a material 20 for forming an oxide superconductor is attached to the core @ 3 which rotates and advances in the direction of the electric wire coil 31, and a furnace 40 having a high temperature dry oxygen atmosphere is fed thereto. After the time required for the sintering process has elapsed, a metal tape 11 supplied from a tape coil 10 is wound around the wire to coat it with molten metal 13, and the wire is wound into a wire coil 31 through the outlet of the furnace. Examples of the material 20 include powder of YBaCusOs-4 mixed with a binder such as glycerin to form a clay-like material, or raw materials such as yttrium oxide (Y*Os), barium carbonate (BaCO5), and oxidized steel. (Cub) mixed with a binder as a powder, or a mixture of yttrium octoate, barium carbonate, and copper naphthenate with alcohol, etc. are used.

In such an implementation situation, desirable combinations of qualities for each member include, for example, the core wire 3 is a titanium alloy tube plated with silver and the silver surface is oxidized, and the superconductor 2 is YBa at an operating temperature of 77.

(A combination is obtained in which a copper tape is plated with silver and the silver surface is oxidized as the JOy+ metal tape 11 for the outer covering, and silver is used as the molten metal 13.The coefficient of thermal expansion of each material is that of a titanium alloy for the core wire (Ti5AA' 2 .5Sn) is approximately 9
．． 5×10'/'C, oxide superconductor is approximately 10×10'
/'C, copper is about 17X10'/'C, and if the coating is formed at 600°C to 700°C, a slight gap shrinkage force can be obtained even at the crystal structure transition temperature (about 570°C), Sufficient contractile force can be obtained at low temperatures in the superconducting state. Furthermore, if the winding temperature of the metal tape 11 is selected to be around 500°C, the base material of the metal tape 11 can be an aluminum alloy (the thermal expansion coefficient is 5056H38 material of about 24X10-' instead of copper).
/"C), it becomes possible to use a steel pipe instead of a titanium alloy pipe as the base material for the core wire 3. Furthermore, the silver oxide formed on the surface of the core wire 3 and sheath 1 has high electrical conductivity. However, since it can be formed thinly as a so-called passive film, it cannot prevent the stabilizing shunt effect.

〔Effect of the invention〕

According to the present invention, by skillfully combining the thermal expansion characteristics of the various materials that make up the superconducting wire, it is possible to form a dense superconductor using superconducting materials with poor stretchability, which is electromagnetically stable and mechanically stable. This has the effect of forming durable superconducting wires.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a superconducting wire that is an embodiment of the present invention, Figure 2 is a side view of a superconducting wire that is an embodiment of the present invention, and Figure 3 is a method for manufacturing the superconducting wire shown in Figure 2. FIG. DESCRIPTION OF SYMBOLS 1... Outer cover, 2... Superconductor, 3... Core wire, 4...
. . . Hollow portion inside the core wire, 11 . . . Metal tape that becomes the main part of the outer covering, 12 . . . Welded part that fills the gap between the tapes of the outer covering.

Claims (1)

[Scope of Claims] 1. An electric wire consisting of a core wire, a superconductor surrounding the core wire, and a sheath surrounding the superconductor, wherein the coefficient of thermal expansion of the core wire and the coefficient of thermal expansion of the sheath are different, A superconducting wire characterized in that the outer surface of the core wire and the inner surface of the jacket are made of a small amount of material, and both are normal conductors. 2. A superconducting wire according to claim 1, wherein the outer sheath is formed of a diagonally wound metal tape. 3. In the superconducting wire according to claim 2, the tape-side end of the sheath formed of tape is melt-sealed, or a metal or metal oxide is applied near it, thereby forming the sheath. A superconducting wire characterized by improved sealing performance. 4. A superconducting wire according to claim 1, characterized in that a hollow tubular structure is used as the core wire.