JPH01130424A - Manufacture of superconductive wire - Google Patents

Abstract

PURPOSE:To prevent production of diffusion products by mutual diffusion of superconductive wires and stabilizer, breakage of a NbTi filament, and necking by forming a thin diffusion preventing layer on the surface of the stabilizer contacting the superconductive wire. CONSTITUTION:A thin layer 8 of diffusion preventing material of Nb, for example, is formed on the inner side of a tube 7 of stabilizer of high purity oxygen free copper, for example, by electroplating, flame coating, or deposition. Into the tube 7 of high purity oxygen free copper having the thin layer 8 of Nb formed inside is inserted a rod 5 of superconductive material of NbTi alloy, for example, and the diameter is reduced to a predetermined size by static water pressure extrusion or the like to form a single wire. A predetermined number of such single wires are embedded in oxygen free copper and the diameter is reduced to a predetermined size to form a superconductive wire. Production of a diffusion layer of both materials through the extrusion work and heat processes in the middle can thus be securely prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a superconducting wire consisting of a material exhibiting a superconducting wire and a material imparting stability in contact with the superconducting wire. The present invention relates to a method for manufacturing a superconducting wire that allows a thin diffusion prevention layer that prevents layer formation.

[Conventional technology]

As a conventional superconducting wire, there is one shown in Fig. 2.
It has a structure in which a large number of NbTi filaments 2 are dispersed and buried in a matrix 1, and Cu and NbTi are in contact with each other. Conventionally, the NbT i filament 2 is 30 to 5
Attempts have been made to reduce the current density to 0 μm or less, increase the critical current density, reduce magnetization loss, and reduce the AC power.

According to the configuration shown in FIG. 2, the Cu matrix 1 functions as a stabilizing material and creates a detour even if the superconductivity is locally broken for some reason when current is passed through the NbTi filament 2. Furthermore, the generated heat is dissipated in a direction perpendicular to the length of the wire rather than being conducted along the length of the wire. In this way a detour for current and heat is created,
Prevents quench from occurring.

Figure 3 shows NbTi, l! : It is a sectional view showing an enlarged view of the interface with Cu.

As shown in Figure 3, TizC is present at the interface between NbTi and Cu.
A diffusion product 3 such as u is generated.

This diffusion product is produced by heat during extrusion and heat treatment to impart superconducting properties, and is extremely brittle. Therefore, the NbTi filament is
When the thickness is about 0 μmφ, the wire drawability is hardly hindered, but when NbTi filaments are finely processed to several μmφ, the wire drawability is inhibited and processing becomes difficult. Therefore, in order to process NbTi filaments to a diameter of several μm, it is effective to prevent the formation of an alloy layer at the interface between NbTi and stabilizing oxygen-free copper.

Figure 4 shows a method conventionally used to prevent diffusion products, in which a pipe-shaped Nb pipe is used to prevent mutual diffusion at the interface between a stabilizing material 4 made of Cu and a superconducting material 5 made of NbTi. A prevention member 6 is inserted therein. The diffusion prevention material may be in the form of a plate, but there is a manufacturing limit to reducing its thickness. The diffusion prevention layer of Nb etc. is Nb
It needs to be made as thin as possible because it does not share current like T r and does not impart stability like Cu.

[Problem that the invention seeks to solve]

As described above, according to the conventional method for manufacturing superconducting wires, there is no established technology for producing a thin diffusion prevention layer, and there is a demand for its establishment.

[Means for solving problems]

The present invention has been made in view of the above, and in order to thinly interpose a substance that prevents or retards mutual diffusion at the interface between a material exhibiting superconductivity and a material imparting stability, it is possible to form a tube of a stable material. Provided is a method for manufacturing a superconducting wire in which the material is formed on the inner surface of the wire by plating, thermal spraying, vapor deposition, etc.

That is, the method for manufacturing a superconducting wire of the present invention includes the following steps.

(11 step-stabilizing material forming a thin layer of diffusion-inhibiting material;
For example, a diffusion-preventing material such as NbO thin layer (on the order of tens of microns) is formed on the inner surface of a high-purity oxygen-free copper tube by electroplating, thermal spraying, or vapor deposition. (2) Step of obtaining a composite wire. A superconducting material, for example, an alloy rod of NbTi, is inserted into a high-purity oxygen-free steel pipe formed in
A single wire whose diameter is reduced to a predetermined size by hydrostatic extrusion or the like.

(3) Step of obtaining a superconducting wire A predetermined number of the single wires are buried in oxygen-free copper and reduced in diameter to a predetermined size to obtain a superconducting wire.

[Effect]

By manufacturing a superconducting wire through the above steps, it becomes possible to interpose a thin layer of material between the superconducting material and the stabilizing material to prevent diffusion of both materials. Therefore, it is possible to reliably prevent the formation of a diffusion layer of both materials during extrusion processing and intermediate heat treatment. Moreover,
It does not reduce the quality of the product obtained.

〔Example〕

Examples of the present invention will be described in detail below.

As shown in FIG. 1, the inner surface of the tube 7 made of stabilizing material contains Nb,
The present invention is characterized in that the metal 8 such as Ta, V, Ni, etc. is previously formed thinly by a method such as plating or thermal spraying to prevent the generation of diffusion products such as Ti2Cu. The metal 8 acts to prevent or delay mutual diffusion of the superconducting material and the stabilizing material.

The process when NbTi is used as the metal 8 will be described in detail below. High purity oxygen-free copper (outer diameter 122n+φ, wall thickness 1
Nb is plated to a thickness of approximately 50 μm on the inner surface of the 0.0 liter by electroplating. A NbTi alloy rod (diameter 100 Illφ) was inserted into this copper tube and processed into an extruded billet, and then hydrostatically extruded once to form a single wire. After that, it was processed in the same process as the normal superconducting wire manufacturing process, and the final superconducting wire was made into a superconducting wire with an outer diameter of 0.511φ (5 μmφ x 3.300 NbTi filaments).

The Cu of a superconducting wire with an outer diameter of 0.5×φ was dissolved and removed using nitric acid, and the surface of the NbTi filament was observed using a scanning electron microscope. As a result, necking and disconnection of the NbTi filament were observed compared to a wire without a diffusion prevention layer. No defects were observed, and it was confirmed that an extremely good filament was produced.

〔Effect of the invention〕

As explained above, according to the present invention, since the diffusion prevention layer is formed thinly on the surface of the stabilizing material in contact with the superconducting wire, diffusion products are generated due to the mutual expansion of the superconducting wire and the stabilizing material. This prevents disconnection and necking of the NbTi filament, and also prevents the accompanying decrease in current capacity.

[Brief explanation of the drawing]

Figure 1 (, 11, (b) is a cross-sectional view showing an embodiment of the superconducting wire of the present invention, Figure 2 is a cross-sectional view showing a conventional superconducting wire, and Figure 3 is a heat treatment in the conventional superconducting wire manufacturing process. A cross-sectional view of the later NbTi filament, and FIG. 4 is a partially enlarged view of a conventional superconducting wire with a diffusion prevention layer. −−−−～
---Superconducting filament 3----------Diffusion layer 5------1--Superconducting material 6---
~---Diffusion prevention pipe 7------------~---Stabilizing material 8---1 Diffusion prevention thin layer

Claims (3)

[Claims] (1) A method for manufacturing a superconducting wire comprising a first material exhibiting superconductivity and a second material surrounding it to impart stability, wherein the first material and forming a thin layer of diffusion-preventing material that prevents the formation of a diffusion layer of a second material; and inserting a rod of the first material into the tube formed with the thin layer to a predetermined size. and a step of embedding a predetermined number of the composite wires in the second material and then reducing the diameter to a predetermined size to obtain a superconducting wire. A method for manufacturing superconducting wire. (2) The superconductor according to claim 1, wherein the step of forming the thin layer forms the thin layer of the diffusion preventing material on the inner surface of the tube by one method selected from plating, thermal spraying, and vapor deposition. Method of manufacturing wire. (3) using NbTi-based metal as the first material;
2. The method of manufacturing a superconducting wire according to claim 1, wherein copper or a copper alloy is used as the second material, and one selected from Nb, Ta, V, and Ni is used as the diffusion prevention material.