JPH03108212A - Manufacture of superconductive alloy wire material - Google Patents

Abstract

PURPOSE:To prevent easily CuTi intermetallic compound from being formed by giving beforehand a metal film coating treatment to the surface of material before making a compound process of juxtaposing NbTi group alloy and Cu group alloy. CONSTITUTION:NbTi alloy rod 1, after metal film coating treatment like Ni plating, etc., is inserted into a Cu pipe 4 and given together a cold drawing process into a hexagonal wire. The Ni film on the alloy rod 1 surface thereby prevents CuTi metal compound from being formed. Even in manufacturing a wire material including NbTi filament of several mum or smaller diameter, the wire material does not break in the drawing process, the filament diameter does not disperse and a superconductive material excellent in current characteristics is obtainable at a low cost.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to a method for manufacturing a superconducting alloy wire for obtaining a superconducting alloy wire that can conduct current with zero electrical resistance at extremely low temperatures. .

[Conventional technology]

So-called ultra-fine multi-wire wires are made by embedding a large number of very thin filaments, such as NbTi alloy filaments with a diameter of 40 μm or less, in a normal conductive metal with low electrical resistance, such as an oxygen-free shell, and then twisting such composite wires. It is manufactured and used in the form of core twisted superconducting wire.

Figure 2 shows such an NbTi alloy ultrafine multi-core twisted superconducting wire, in which (1) is a NbTi alloy filament, (2) is a normal conductive metal such as oxygen-free copper,
A NbTi alloy i fine multicore superconducting wire (3), which is a composite wire, is formed by these. NbT i alloy f! The thin multicore superconducting wire (3) has a cross section like that shown in FIG. 2 over its entire length.

Conventionally, in order to manufacture the above superconducting wire (3), -
The following method is adopted for i. That is, a copper pipe is cleaned and one NbTi rod is inserted into it. When this is drawn, it becomes a NbTi wire coated with copper. A billet for extrusion is obtained by aligning and pushing a large number of copper-coated NbTi alloy single-core wires into a large-diameter copper pipe, and then welding copper plates together.

This billet is then extruded into a composite wire, which is then reduced in cross-section by swaging, wire drawing, rolling, etc., and heat treated during or after the cross-section reduction process to form a predetermined shape. Finish. Extrusion is an important process for manufacturing multi-core wires, especially for bonding copper to copper, and heat treatment during or after the cross-section reduction process is necessary to maintain high current characteristics. This is an essential process.

The NbTi alloy wire manufactured as described above is made into a composite wire of one or more wires and wound into a coil in order to correspond to a predetermined current capacity. When cooled to an extremely low temperature with liquid helium, it becomes a state of zero electrical resistance, allowing large currents to flow, and is used in electromagnets that generate strong magnetic fields such as nuclear fusion, accelerators, nuclear magnetic resonance medical diagnostic equipment, and superconducting magnetic levitation trains. used as.

[Problem to be solved by the invention]

In the conventional manufacturing method of superconducting alloy wire rods as described above, Ti in the NbTi alloy and the matrix are of Cu causes a diffusion reaction, converting the CuTi intermetallic compound to NbT.
Formed at the interface between i-filament and stabilized copper.

Once this compound is formed to a size close to the diameter of the filament, it causes breakage of the filament wire or the wire itself in the cross-section reduction step, which in turn causes a decrease in the critical current value. Particularly, in the case of a wire having a filament diameter of several μm or less, the presence or absence of the formation of a CuTi compound has a great effect on the drawability of the wire.

When manufacturing NbTi alloy superconducting wire, CuTi
As a well-known technique for suppressing the formation of compounds, NbT
There is a method of sandwiching a Nb pipe between an i-rod and a Cu pipe to form a three-layer structure, and then performing composite processing to produce a superconducting wire. However, the complicated methods required to manufacture Nb pipes make them very expensive. Moreover, when manufacturing Nb pipes, it is not possible to manufacture pipes with thin walls;
For the purpose of isolating the alloy and Cu, a lot of expensive N is used.
This results in unnecessary use of b. Furthermore, the heat transfer from the NbTi alloy to the Cu and the electrical conductivity deteriorate, resulting in a superconducting wire with poor stability.

This invention was made in order to solve this problem, and during the manufacturing process of NbTi alloy superconducting wire manufactured by the conventional manufacturing process, CuTi metal found at the interface between the NbTi filament and the stabilized copper. An object of the present invention is to obtain a method for manufacturing a superconducting alloy wire that can inexpensively and easily prevent the formation of intermediate compounds.

[Means to solve the problem]

The method for manufacturing a superconducting alloy wire according to the present invention includes
In the first step in the manufacturing process of alloy superconducting wire,
A metal film adhesion treatment is performed in advance on the NbTi alloy surface before composite processing.

[For production]

In this invention, NbTi at the initial stage of the manufacturing process
The existence of a metal film attached to the alloy surface indicates that Cu and NbTi
Prevents direct contact of the alloy and therefore reduces T in the heating process
NbTi prevents the interfacial diffusion reaction between i and Cu, which is harmful.
Suppresses the formation of CuTi intermetallic compounds on the filament.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. 1, which shows a cross section at an early stage of manufacturing. A Cu pipe (4) having an outer diameter of 7.3 mm and an inner diameter of 5.3 mm was immersed in a nitric acid and sulfuric acid solution to clean the surface and then dried. On the other hand, diameter 5.01
- Immerse the NbTi alloy rod (1) in the old electroplating solution,
We proceeded with the Metsuki work. The thickness of N1J11 (5) is 3.
When the thickness of the NbTi alloy rod (1) reached 5 μm, it was taken out, washed with water, and dried. After that, the above Cu pipe (4
) was inserted into the Ni-plated NbTi rod (1), and then cold-drawn as one piece to form a hexagonal wire with a distance across flats of 6 mm, and this hexagonal wire was straightened to give it straightness. , cut to a certain length. A large number of them were aligned and inserted into a copper container having an outer diameter of 1401, and copper members were applied to the front and rear ends. After that, the two unreliable joints were irradiated with an electron beam and hermetically welded to produce a composite billet for extrusion.

Next, the above composite billet was heated to about 580° C. and hot extruded into a composite rod having a diameter of 40 mm, which was then subjected to drawing. 2 at 390℃ during this drawing process.
Nb with a wire diameter of 0.1 mm was heat treated twice for 0 hours.
A Ti alloy superconducting wire was used. This wire did not break during the drawing process, and could be processed easily. In addition, the body portion of this wire was dissolved and removed using an acid such as nitric acid, and the surface of the filament was observed using a scanning electronic closed microscope.

No foreign matter such as a CuTi intermetallic compound was observed on the surface of the NbTi filament, and no abnormally thick or thin portions were observed.

When the critical current density of the NbTi alloy wire manufactured by the above process was measured, it was found to be 2850 A/mm under a 5 T magnetic field and 1750 A/mm under a 2.7 T magnetic field at 4.2 k.
A very high current characteristic of /mm2 was obtained.

In addition, in the above embodiment, the case of NbTi alloy was described as the superconducting alloy, but NbTi alloy such as NbTiTa alloy
It can also be widely applied to the production of alloy superconducting wires.

In addition, although we have described the case where a Ni film is attached to the surface of a NbTi alloy, it is also possible to attach a Ni film to the surface of a NbTi alloy. Can be isolated, CuTi
Effective in preventing the formation of intermetallic compounds.

Furthermore, in the above example, a case was described in which a coating was applied by a plating method which is generally used to attach an old coating to the surface of an NbTi alloy rod, but these are CvD,
Sputtering, vapor deposition, etc. may also be used, and any of them are effective. The same applies to the case where a film of Nb, Ta, Cr, etc. is formed.

The above explanation has been given for the case of superconducting wire made of Cu and NbTi alloy, but for example, 3NIN containing CuNi alloy, such as NbTi alloy superconducting wire for pulse use,
Even in the case of bTi alloy wire, Cu or CuNi alloy and N
Since the bTi alloy is in direct contact, the present invention is also effective in this case.

〔Effect of the invention〕

As described above, according to the present invention, in the initial stage of the manufacturing process of NbTi-based alloy superconducting wire, N
By attaching a coating such as Ni to the surface of the bTi alloy rod, the formation of CuTi intermetallic compounds in the later process is prevented, and it is also possible to manufacture wire rods containing NbTi filaments with a diameter of several μM or less during drawing processing. without the wire breaking,
Further, in the produced wire rod, there is no disconnection of the NbTi filament, and there is no variation in the diameter of the NbTi filament. Therefore, a superconducting wire with excellent current characteristics can be easily obtained at low cost.

[Brief explanation of drawings]

FIG. 1 shows NbT for explaining one embodiment of the present invention.
FIG. 2 is a cross-sectional view of an i-alloy superconducting wire at an early stage of production, and FIG. 2 is a cross-sectional view of a conventional ultrafine multicore superconducting wire. (1) --NbTi alloy rod, (4) --Cu vibe, (5) old N (adhered metal coating). In each figure, the same reference numerals indicate the same or corresponding parts. Figure 1 Figure 2

Claims (1)

[Claims] A NbTi-based alloy as a superconducting alloy and a Cu-based metal as a stabilizing metal are placed side by side, this composite is extruded, a cross-sectional reduction process by drawing, etc., and a heat treatment process during or after this cross-section reduction process. A method for producing a superconducting alloy wire comprising the step of subjecting the surface of the NbTi alloy before composite processing to a metal coating deposition treatment.