JPS63213213A - Manufacture of internal diffusion type flat-type multicore superconductive wire - Google Patents

Abstract

PURPOSE:To prevent breakage of a thin diffusion barrier for preventing contamination of a stabilizing material to obtain a superconductive wire having a good characteristic by performing fixed heat treatment before molding a flat-type superconductive wire of internal diffusion type multicore structure by a rolling process. CONSTITUTION:A number of Nb or Nb alloy wires whose outsides are coated with Cu or a Cu alloy are arranged inside a Cu composite tube, in whose inside a diffusion barrier is arranged, centering round an Sn or Sn alloy rod coated with Cu or a Cu alloy. Then, a surface reducing process is applied thereon followed by heat treatment at 300-550 deg.C for 20-100 h, further being molded into a flat-type shape by a rolling process for being subjected to heat treatment to generate Nb3Sn. Breakage of the diffusion barrier can be prevented by diffusing Sn through heat treatment before the rolling process and making a matrix into the Cu-Sn alloy to uniformalize its hardness.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Field of Application) The present invention relates to a method for manufacturing a rectangular multicore superconducting wire by an internal diffusion method, and in particular a method for preventing rupture of a diffusion barrier during rectangular processing. Regarding.

(Prior art) The internal diffusion method, which is a type of manufacturing method for Nb3Sn superconducting wire, has advantages such as a simple manufacturing method and the ability to easily improve critical current density (Jc) by increasing Sni. The following method is known as a method for producing a multicore Nb3Sn superconducting wire using this internal diffusion method.

In other words, this method requires CLI to be installed on the outer periphery of the 3n rod.
A large number of B-wires are arranged, placed inside a Cu tube with a diffusion barrier inside, subjected to area reduction processing, and then heat-treated in the final cross-sectional shape.
Heat treatment for Qu-3n alloy formation by diffusion of n and Nb-3
The heat treatment for producing Nb3Sn through the reaction of n is carried out in two stages.

When the above-mentioned final cross-sectional shape is a rectangular shape, it is usually formed by rolling, but as the aspect ratio (the ratio of the width to the thickness of the rectangular cross section) increases, that is, the rolling reduction ratio increases. The problem is that the thin diffusion barrier breaks near the center, and the subsequent two-step heat treatment contaminates the stabilizing copper in the outermost layer with Sn, reducing the safety of the superconducting wire.

(Problems to be Solved by the Invention) The present invention has been made in order to solve the above-mentioned difficulties. The purpose is to provide a manufacturing method that can prevent breakage.

[Structure of the Invention] (Means for Solving the Problems) The method for manufacturing an internally diffused rectangular multicore superconducting wire of the present invention includes the following steps:
Inside a Cu composite tube with a diffusion barrier placed inside, there is a Sn or Sn alloy rod coated with Cu or Cu alloy as the center, and on the outside - a large number of Nb or Nb alloy wires coated with C1 or Cu alloy. After arranging the books and subjecting them to surface reduction processing,
It is characterized in that it is subjected to heat treatment for a period of time, then formed into a rectangular shape by rolling, and then subjected to heat treatment for NbzSn production.

In the method of the present invention, the heat treatment before rolling is limited as described above for the following reason. In other words, if the heat treatment temperature is less than 300°C, it will not be possible to perform rolling with an aspect ratio of 2 or more, while if it exceeds 550°C, N
This is because the characteristics deteriorate due to the formation of b3Sn, and furthermore, even if heat treatment is performed for more than 100 hours within the above temperature range, the aspect ratio cannot be improved.

More preferable conditions for the above heat treatment are 500 to 550'C.
x90 to 96 hours, and in this case, rolling can be performed with an aspect ratio of 3 or more. On the other hand, 300℃
The maximum possible aspect ratio for x24 hours is 2.

(Function) The reason why thin-walled Nb or Ta tubes used as diffusion barriers break during rolling is that the Sn (or 3n alloy) in the center is damaged by other constituent materials such as Cu, Nb, and T.
Since it is soft compared to a, it is thought that it escapes from the center of the rolling process to both sides during rolling, and breaks due to excessive tension acting on the diffusion barrier. This breakage of the diffusion barrier can be prevented by heat treatment before rolling to diffuse Sn and make the matrix a CU-sn alloy to make the hardness uniform.

(Example) 4218 CuwL-covered Nb wires with a hexagonal cross section are arranged on the outer periphery of a Cu-covered ISn rod with a hexagonal cross section, and further a Ta tube and a CU tube are arranged in order on the outer periphery.The outer diameter is 58111.
A wire rod with an outer diameter of 2.8 mmφ was produced by subjecting the composite body of mφ to hydrostatic extrusion and wire drawing.

The Sn' wire in this wire had an outer diameter of 1.26 mm, the Ti tube had an outer diameter of 2.3 mm, and a thickness of 0.1 mm. When this was rolled with an aspect ratio of 1.5, the Ta tube broke at the center of the rolling process. On the other hand, when this wire was heat treated at 300°C for 24 hours and then rolled at an aspect ratio of 2.0, no breakage of the Ta tube was observed, but when the wire rod was rolled at an aspect ratio of 2.5, no breakage of the Ta tube was observed. T for
A-tube rupture occurred.

Roughly the same wire rod as above (outer diameter 2.8mmφ) 550
After heat treatment at ℃ for 96 hours, the aspect ratio was 4.0.
When rolling was carried out, no breakage of the 7-a tube was observed and a good rectangular shape could be obtained.

At this time, it was confirmed that CD-32% Sn bronze was uniformly formed inside the Ta tube.

[Effects of the Invention] As described above, according to the method of the present invention, by subjecting a rectangular superconducting wire of an internal diffusion type multi-core structure to a predetermined heat treatment before forming it by rolling, a thin diffusion barrier can be formed. Since breakage can be prevented and thereby the stabilizing material can be prevented from being contaminated, a superconducting wire with good properties can be manufactured.

Applicant Showa Cable and Wire Co., Ltd. Representative Patent Attorney Sasa Su'yama - (1 idiot)

Claims (3)

[Claims] (1) Inside the Cu composite tube with a diffusion barrier placed inside,
Centering around a Sn or Sn alloy rod coated with Cu or Cu alloy, a large number of Nb or Nb alloy wires coated with Cu or Cu alloy are arranged on the outside thereof, and after performing area reduction processing on this, 20-10 at 300-550℃
1. A method for manufacturing an internally diffused rectangular multicore superconducting wire, which comprises performing a heat treatment for 0 hours, then forming the wire into a rectangular shape by rolling, and then performing a heat treatment to generate Nb_3Sn. (2) The method for manufacturing an internally diffused rectangular multicore superconducting wire according to claim 1, wherein the aspect ratio of the rectangular wire rod formed by rolling is 3 or more. (3) Heat treatment before rolling at 500-550°C and 90-90°C
The method for manufacturing an internally diffused rectangular multi-core superconducting wire according to claim 2, wherein the manufacturing time is 96 hours.