JPS60170112A - Copper coated nbti superconductive lead and method of producing same - 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 The present invention relates to a copper-clad NbTi superconducting wire and a manufacturing method thereof, and more particularly to a copper-clad NbTi superconducting ultrafine multifilamentary wire and a manufacturing method thereof.

Conventionally, a large number of NbTi alloy rods coated with copper are inserted into a copper billet, the diameter of the billet is reduced by hot extrusion, and then the wire is drawn through a die to form several thousand NbTi alloy filaments. It manufactured superconducting ultrafine multifilamentary wires.

However, this superconducting ultrafine multifilamentary wire has drawbacks such as a decrease in Ic and current attenuation when used in persistent current mode. This is because a layer of an intermetallic compound of Nl+Ti alloy and copper (e.g., Ti2Cu, (TiNb)2cu) is formed due to the temperature increase for hot extrusion and heat generation during extrusion, and this layer is formed by NbTi alloy filament. This is because it is harder and causes the NbTi alloy filament to sink into the NbTi alloy filament during wire drawing, resulting in numerous breakages of the N1) Ti alloy filament.

The present inventor discovered that when an oxide film is formed on the surface of a NbTi alloy rod in advance and the composite is formed into a billet by fitting it with a copper or copper alloy pipe, there is almost no disconnection of the NbTi alloy filament, and the present invention was completed based on this finding. I ended up doing it.

The gist of the present invention resides in a copper-coated NbTi superconducting wire, which is characterized in that an oxide film is formed on the surface of a NbTi alloy rod, and then a copper pipe or a copper alloy pipe is fitted to form a composite wire, and a method for manufacturing the same.

The manufacturing procedure of the superconducting ultrafine multifilamentary wire of the present invention will be described in detail below.

(1) NbTi with a thickness of 30 Å or more on the surface of the NbTi alloy rod
forms an oxide film. As a means for forming an oxide film, 5
Annealing at 0 to 900°C is preferred. This step is a feature of the present invention, and the subsequent steps are exactly the same as the conventional method.

(2) This alloy rod and copper pipe or copper alloy (e.g.
(Cu-Ni alloy) pipes are fitted, and a number of fittings are inserted into the copper billet.

(3) The diameter of the billet is reduced by hot extrusion, and then wire drawing is performed through a die.

The thickness of the oxide film can be adjusted by the annealing time and temperature, but the thickness of the NbTi alloy rod before fitting and the NbTi alloy rod at the final wire diameter
The oxide coating is applied to an appropriate thickness taking into account the dimensions of the bTi filament.

If the oxide film is thinner than 30, the oxide film is defective.

Due to the uniformity, there is a possibility that an intermetallic compound layer of NbTi alloy and copper may be formed, which may cause disconnection. If the oxide film is thick, it may affect the superconductivity or sink into the NbTi filament, so the thickness is preferably 3000 Å or less.

A feature of the superconducting wire of the present invention is that the NbTi alloy filament has almost no breakage and has excellent superconducting properties. The formation of an oxide film eliminates the metallic bond between the NbTi alloy and copper, and prevents the diffusion of the NbTi alloy and copper even at high temperatures during hot extrusion.
This is because there is no formation of intermetallic compounds between the alloy and copper.

Another feature of the superconducting wire of the present invention is that manufacturing costs can be reduced. This is because the diffusion of the NbTi alloy and copper is suppressed, so the hot extrusion temperature can be increased, and therefore the degree of workability of the hot extrusion can be increased (the area can be greatly reduced).

The superconducting wire of the present invention has a NbTi alloy filament diameter of 1
Superconducting wire with μI of 11 to 30 μm (for example, NMR
-Useful for CT superconducting wires).

EXAMPLES The present invention will be explained in more detail by showing Examples and Comparative Examples below.

Example An oxide film with a thickness of 1000 mm was formed on the surface of the NbTi alloy rod by annealing at 100°C for 1 hour, and a copper vibrator (outer diameter 1
5.5m+n, inner diameter 11. Smm), and 108 fittings were inserted into a copper billet with an outer diameter of 73 cm. The billet diameter was made to be 27 years old by hot extrusion at a temperature of 600° C. for 400 mm. Then, by a die, NbTi
The alloy filament was drawn until the diameter became 6 μm. At this time, the conductor diameter was approximately 0.15 mm. A conductive wire in the middle of being wire-drawn was sampled at a length of 10 On++n, the coated copper was dissolved in nitric acid, and the number of disconnections among 108 NbTi alloy filaments was counted.

Comparative example (conventional method) Example except that no treatment was performed on the surface of the NbTi alloy rod.
1) The filament was turned over and the number of filament breaks was measured.

It was found that the superconducting wire of the present invention has a significantly lower filament breakage rate than conventional superconducting wires, and the smaller the filament diameter, the more remarkable the difference becomes.

Patent applicant: Sumitomo Electric Industries, Ltd.

Claims (1)

[Claims] 1. A copper-coated NbTi superconducting wire, characterized in that an oxide film is formed on the surface of a NbTi alloy rod, and the wire is then fitted with a copper pipe or a copper alloy pipe to form a composite. 2. The copper-coated NbTiff1 conductive wire according to claim 1, wherein the oxide film has a thickness of 30 Å or more. 3. Copper-coated NbTi according to claim 1 or 2, in which an oxide film is formed by annealing a NbTi alloy rod at 50 to 900°C! ! conductive wire. 4. A method for producing a copper-coated NbTi superconducting wire, which comprises forming an oxide film on the surface of a NbTi alloy rod and then fitting it with a copper pipe or copper alloy pipe to form a composite. 5. The manufacturing method according to claim 4, wherein the oxide film has a thickness of 30 Å or more. 6. The manufacturing method according to claim 4 or 5, wherein the oxide film is formed by annealing the NbTi alloy rod at 50 to 900°C.