JPS63178419A - Superconducting wire and its manufacture - Google Patents

Abstract

PURPOSE:To heighten critical current density and to reduce manufacturing cost by a method wherein core parts of plural pieces of linear segments are made of an NbTi alloy, a thin film made of a superconducting element is formed thereon and a Cu or Cu alloy layer is formed further thereon. CONSTITUTION:In a superconducting wire where plural pieces of linear segments are arranged in a Cu or Cu alloy matrix, the core part of each linear segment is made of an NbTi alloy, a thin film made of a superconducting element is formed thereon and a Cu or Cu alloy layer is formed further thereon. Thereby, in a manufacturing process of the superconducting wire, no intermetallic compound of Cu and Ti is formed on the surface of an NbTi metal rod, as a result, breaking wire of an NbTi filament and lowering of critical current density caused by generation of the intermetallic compound of Cu and Ti can be prevented and manufacturing cost is reduced due to a rising yield.

Description

[Detailed Description of the Invention] This invention relates to a superconducting wire in which a plurality of linear segments are arranged in 7 trixes of copper (hereinafter referred to as Cu) or C (one alloy), and a method for manufacturing the same. be.

[Prior Art] A superconducting wire is a power transmission line using a superconducting material as a conductor, and is used as winding a of a superconducting magnet for generating a supermagnetic field used in magnetic levitation trains and NMR-CT.

First, a first conventional example of a method for manufacturing a super 1f conducting wire, in which the matrix is Cu or a Cu alloy and the core is an alloy made of niobium and butane (hereinafter referred to as NbTi alloy), will be described.

8! Made of CuJ or Cu alloy! Nb in the electric metal fi tube
Metal rod made of Ti alloy (hereinafter abbreviated as NbTi metal rod). ) to form an Nbl'i metal rod insertion conductive metal tube. Next, the conductive metal tube into which the NbTl metal rod is inserted is expanded and contracted. 1. The drawn conductive metal tube into which the NbTl metal rod is inserted is passed through a hexagonal die. The material passed through a hexagonal die is cut into pieces in the length direction to obtain hexagonal segments. A large number of hexagonal segments i· are inserted into a conductive metal tube made of CI+ or Cu alloy. Then, both ends of the conductive metal tube are covered with copper lids, and the conductive metal tube and the copper lid are welded together by electronic welding. As a result, a large number of hexagonal segments are vacuum sealed within the conductive metal tube. The S heavy metal tube in which the hexagonal segments 1 to 1 are vacuum-sealed is subjected to area reduction processing (processing to reduce the cross-sectional area of the conductive metal tube) by hot extrusion or hydrostatic extrusion. Then, by roughly wire drawing and heat treating the area-reduced conductive metal tube, a predetermined critical current can be achieved! A superconducting wire of a predetermined size with IQ is obtained.

[Problems to be Solved by the Invention] The method for manufacturing the superconducting wire described above is based on Nb7i fisimen 1.
There was no problem when the diameter was 50 μm or more. However, in order to improve the stability of superconducting magnet 1-,
Although there are cases where a filament diameter of less than m is required, problems arise when the above method is used as is in such cases. However, if the above method is applied as is, extrusion or aging heat smoke f'I! Due to the influence of heat during the process (processing required to ensure critical current density), Cu y 1-
Intermetallic compounds of CU and Ti, such as , are formed. This intermetallic compound with Cu and T1 is very hard and does not deform during wire drawing, which causes the NbI filament to break. If a disconnection occurs, the critical current density will decrease, causing a problem. Also, since the intermetallic compound layer of OLI and T1 is not a superconducting material, for example, 10 μm of NbT
Assuming that a compound layer of 1 μm is generated for the i filament diameter, the diameter of the Nb Ti filament through which the superelectric current flows is 8 μm, and U! iI+1. The iX flow density is 64% of that without the intermetallic compound layer.

Next, a second conventional example of a method for manufacturing a superconducting wire that has been developed to solve the problems of the first conventional example will be described.

A sheet made of Nb (hereinafter referred to as Nb sheet) is wrapped around the NbTi metal rod. Then, the NbTi metal rod wrapped with the Nb sheet is inserted into a conductive metal tube made of Cu or (1 alloy).Next, both ends of the conductive metal tube are covered with copper covers, and the parts between the conductive metal tube and the lid are are welded by electron beam welding.As a result, an Nb T+ :A metal rod insertion S electric metal bottom tube in which the Nb Ti metal rod is vacuum-sealed is formed.This Nb Ti metal rod insertion conductive metal tube is hot-pressed, Extrusion or isostatic extrusion is used to reduce the surface area.

This step is not included in the first conventional example, and is a step for improving the adhesion between the Nb sheet and the NbTi metal rod. Then, the NbTim metal rod-inserted conductive metal tube whose area has been reduced is wire-drawn. After wire drawing, the conductive metal tube into which the Nb Ti metal rod is inserted is passed through a hexagonal die. The material passed through the hexagonal die is divided lengthwise to obtain hexagonal segments. Since the hexagonal segment obtained here has a Nb film at the interface between the CLI and the NbTi metal rod, the formation of a layer of intermetallic compound between Cu and l-i due to heat can be avoided in subsequent steps. This hexagonal segment () is then inserted into a conductive metal tube made of CLI or Cu alloy.

Then, both ends of the conductive metal tube are covered with copper lids, and the conductive metal tube and the lid are welded together by electron beam welding. By this welding, a large number of hexagonal segments are vacuum-sealed within the conductive gold tube. The conductive metal tube in which the hexagonal segments are vacuum-sealed is subjected to area reduction processing by hot extrusion or hydrostatic extrusion. Then, this area-reduced conductive metal tube is further subjected to wire drawing and heat treatment to produce a superconducting wire of a predetermined size and a predetermined critical current density.

As mentioned above, in this second conventional example, the CLImarc has an Nb sheet interposed between the conductive metal tube made of a Cu alloy and the Nbl':metal rod.
A layer of intermetallic compound of CLI and Ti is not formed on the surface of the metal rod. Therefore, N b due to surface reduction processing
Even when the filament diameter of i' i is made smaller, the increase in the filament breakage rate is almost 4. Also, since Nb is a superconducting element, Nb Ti7
45378 Even if a thin film made of Nb is formed on the first
There is no significant decrease in critical current density as seen in the conventional example.

However, although the second conventional example has the advantage of producing a superconducting wire in which the decrease in critical current density is suppressed compared to the first conventional example,
In order to improve the adhesion with the bTi metal rod, it must necessarily go through an extrusion process such as thermal extrusion or hydrostatic extrusion. In the manufacturing method according to the first conventional example, hexagonal segments are produced only by wire drawing, so hexagonal 1 = NbTi in the segment! l! Nh added and suspended
The ratio of Ti to Toyo (hereinafter referred to as NbTi yield) was 0.90, but since the second conventional manufacturing method includes the extrusion step, the NbT'i yield was 0.90. It decreases to 65. NbTi metal rods are expensive, and if the C1 yield decreases, it will significantly increase the manufacturing cost of superconducting wires, which is a problem.

As mentioned above, the manufacturing method according to the first conventional example has the problem that the critical current density of the obtained superconducting wire decreases, and the manufacturing method according to the second conventional example has the problem that Nb
There was a problem in that the manufacturing cost of superconducting wires increased significantly as a result of the decrease in the yield of Ti.

This invention was made to solve the above problems, and critical current! The purpose of the present invention is to provide a superconducting wire with high 5 degrees and low manufacturing cost, and a method for manufacturing the same.

[Means for solving the problem] The supermolar conducting wire of the first invention of this application is made of Cu or Ct+
This is a superconducting wire made up of eleven or more linear segments arranged in an alloy matrix.

The core of each of the linear segments is Nb]゛1
It is characterized by forming a thin film made of a superconducting element thereon, and further forming a layer of Cu or a Cu alloy thereon.

The second invention of this application is based on the invention of the first method for manufacturing a superconducting wire, and a method for manufacturing a superconducting wire by inserting an Nbl"i metal rod into a conductive metal tube made of Cu or a Cu alloy.
IfL curved rod-inserted conductive metal tube is formed, and the Nb Ti metal rod-inserted conductive metal tube is stretched, the stretched Nb Ti metal rod-inserted conductive metal tube is divided in the length direction to form the Nb Ti metal rod. A segment of the inserted conductive metal tube is formed, and a plurality of segments of the Nb Ti metal rod inserted conductive metal tube are bundled and inserted into a conductive metal tube made of CIJ or Cu alloy to form legmen 1 to inserted conductive gold IiI tube. Then, the present invention relates to a method of manufacturing a superconducting wire by stretching the segment-inserted conductive metal tube.

A thin film made of a superconducting element is formed on the surface of the NbTi metal rod before the NbTi metal rod is inserted into the electric metal tube.

[Function] The superelectric SSS according to the present invention has linear segments of Nb Ti arranged in a matrix of CLI or Cu alloy.
Since a thin film made of a superconducting element is interposed at the interface with the conductive metal tube made of J alloy, C
No intermetallic compound between LI and T1 is formed.

In the method for manufacturing a superconducting wire of the present invention, before inserting the NbTi metal rod into the LM conductive metal tube, the N1) T
Since a thin film of a superconducting element is formed on the surface of the i-metal rod, an intermetallic compound between CIJ and Ti is not formed on the surface of the NbTi metal rod during the manufacturing process of the superconducting wire. Furthermore, since a thin film made of a superconducting element is avoided on the surface of the Nl)TI metal strip, an extrusion process for improving adhesion, as in the case of using a Nb sheet, is not necessary.

[Example 1] Hereinafter, an example of the method for manufacturing a superconducting wire according to the present invention will be explained using an example, but the present invention is not limited thereto.

X-concentration example 1 Rod-shaped Nb-T with a diameter of 16 mmφ and a length of 3000 nu
-1 Kinku rod is placed in the plasma CVD reactor.

Separately, put Nt)CQs into the gasifier and
Heat to ℃. In this gasifier, H2 gas is supplied to the main 1/
Rear gas is sent at a rate of 0.3Q/win.

Then, the gas coming out of the gasifier is turned into the plasma 0.
D. Introduce into reactor.

Next, a 13.56 MHz radio wave was applied while heating the inside of this plasma CVDHiffi to 400°C.
Hold time. Then, 80μ was applied to the surface of the NbTi metal rod.
A thin film of Nb with a thickness of m is formed. Nb to 4
≧ A Nb”ri metal rod with an i9 film formed on it has an outer diameter of 20 m.
Nb--Ti metal rod is inserted into a Qu tube, which is a conductive metal tube with an inner diameter of 17 mm and a length of 3000 am, to create a conductive metal tube. The obtained conductive metal tube into which the Nb Ti metal rod is inserted is stretched by wire drawing.

Next, this drawn NbTi metal rod-inserted conductive metal tube is passed through a hexagonal die to be processed into a hexagonal rod having a distance across opposite sides of 5IRI11. After that, the hexagonal bar is 500n1 in the length direction.
Divide and cut every m, and make 1 to 1 hexagonal legmen! :l.

In this case, the yield of Nb Ti was 0.93. Since extrusion processing was not performed, a high yield was obtained.

Next, bundle 1200 hexagonal segments,
It is inserted into a Cu tube which is a conductive metal tube with an outer diameter of 2601 mm, an inner diameter of 210 mm, and a length of 500 ml. Then, both ends of the Cu tube are fixed with a copper tool, and the CLI tube and the lid are welded together using an electron beam. This vacuum-seals 1200 wood hexagonal segments into the Cu tube.

The CLItf in which the hexagonal segments are vacuum-sealed, that is, the conductive metal tube into which the segments are inserted, is placed in a furnace at 550° C., and extruded with an extruder to a diameter of 6 Q mmφ. Then, this extruded segment-inserted conductive metal tube was wire-drawn to a diameter of 31φ.
Cu tube, subjected to aging heat treatment at 380°C for 50 hours,
The wire is further drawn to 2 mmφ. Suddenly, a superconducting wire with a critical current of 2,500 amperes was blown in a 5 Tesla magnetic field.

[19 Theory 1 The manufacturing method according to the conventional example of L 412 is used as Comparative Example 1.
Do 1.

Cylindrical N b with a diameter of 60 mmφ and a length of 500 mm
T t 0.0 on the metal rod. 21111 Thickness Nll Seatler Tighten to 374°. Next, this Nb sheet was wrapped around a Nb Ti metal strip with an outer diameter of 70 mm and an inner diameter of 62 mm.

Insert into a Cu tube with an IQ of 520 mm. And Cu
After covering both sides of the tube with copper plates, the Qu tube and the copper lid are welded together using an electron beam. As a result, a NbTi metal rod insertion CLI tube in which the NbTl metal rod is vacuum-sealed is formed. This NbT'i metal rod insertion Cu tube is placed in a 550° C. furnace, heated, and extruded to a diameter of extruder F25IIfflφ. Through this extrusion, the Nb sheet is transformed into a NbT river gold rod with W5
wear it. The obtained Nb Ti metal rod-inserted Cu tube is wire-drawn using a wire-drawing machine. Insertion of Nb Ti metal rod after wire drawing C
Pass the U-tube through a hexagonal die and process it into a hexagonal bar with a distance across opposite sides of 5+nm. Thereafter, it is cut into sections every 500 mm in the length direction to obtain hexagonal segments.

In this case, the yield of NbTi was 0.65g. Low values were obtained because extrusion processing was performed.

Next, bundle 1200 of the obtained hexagonal hairmen 1 to C.
1 outer diameter 2601+1L inner diameter 210mm, [% 500m
Insert into the Cu tube of m. Then, both ends of the Cu tube are covered with copper plates, and the Cu tube and the copper lid are welded together using an electron beam. As a result, 1200 hexagonal segments are vacuum-sealed into the CIJ tube. The vacuum-sealed Qu tube of the hexagonal segment was placed in a 550°C furnace and extruded into 6Qnunφ.
extrude to a diameter of Then, this extruded Cu tube was wire-drawn to make a 3IIIllφ Cu tube, and was heated at 380°C to
It is subjected to aging heat treatment for 0 hours and further stretched to 2+11+Ilφ. Then, in the magnetic field of 5j sura, the critical current is 2500
Obtain ampere superconducting wire.

(Example 1, Comparative Example 1, First Conventional Example (Comparative Example 2))
Cut 60CI11 of the superconducting wire obtained, and cut both ends with 5c.
m to be excised. Then, 1q of superconducting wire of 50 cm is immersed in nitric acid to dissolve the CIJ. Next, the number of unbroken NbTi filaments is counted. Then, calculate the number of broken wires by calculating backwards. The results are summarized in Table 1. At the same time, the yield of Nb Ti is also shown.

As is clear from Table 1, Example 1 according to the present invention
The number of wire breaks is almost the same as in Comparative Example 1 using the Nb sheet. On the other hand, the yield of Nb Ti in Example 1 is significantly higher than that in Comparative Example 1.

In addition, although the said Example showed the case where Cu tube was used as a conductive metal tube, this invention is not limited to this, Even if a C11 alloy tube is used, the same effect as an Example can be obtained.

In addition, in the above embodiment, a thin film made of UNtl was exemplified as a preferable example of the thin film formed on the NbTi metal support surface, but the present invention (not limited to Makort, but made of other superconducting elements such as TaW) Even with a thin film, the same effects as in the embodiment can be achieved.

Further, in the above embodiment, a case is shown in which thin film formation is carried out by the 1-scrap CVD method, but the present invention is not limited to this, and thin film forming methods such as ion blating method, sputtering method, and ion evaporation method may be employed. , achieves the same effect as the embodiment.

[Effects of the Invention] As described below, in the superconducting wire mounting method according to the present invention, prior to inserting the NbTi metal rod into the S electric metal, superconductivity is applied to the metal surface of the NbTi metal rod. Since a thin film made of a chemical element is formed, an intermetallic compound of Cu and T1 is not formed on the surface of the NbTi metal rod during the manufacturing process of the superconducting wire. As a result, CLI and Ti
NbT'i due to the 71-formation of intermetallic compounds with
The filament breakage problem J'3 and the problem of reduced critical current density are solved.

In addition, since the formation of an A'l film made of superconducting elements on the surface of the Nh i' i metal rod is avoided, an extrusion process to avoid tightness, such as when using a Nb sheet, is not required1. , the price of Nb Ti is 61% upper gastrointestinal, and the production cost per 1st is cheaper.

Further, the superconducting wire according to the present invention obtained by the method described in (e) above, for example, has a thin film of a superconducting element interposed between the NbTi filament and the Cu tube. therefore,
Even if heat is applied to this material, the Cu-ri intermetallic compound
h Not formed on Ti filament I. therefore,
This results in a superconducting wire with a high critical current density and fewer disconnections.

Claims (5)

[Claims] (1) A superconducting wire comprising a plurality of linear segments arranged in a matrix of Cu or Cu alloy, each linear segment having a core made of an NbTi alloy, on which a thin film made of a superconducting element is coated. A superconducting wire characterized in that a layer of Cu or a Cu alloy is further formed on the superconducting wire. (2) The superconducting wire according to claim 1, wherein the superconducting element is Nb. (3) N in a conductive metal tube made of Cu or Cu alloy
After inserting a bTi metal rod to form a NbTi metal rod insertion conductive metal tube and stretching the NbTi metal rod insertion conductive metal tube,
The stretched NbTi metal rod-inserted conductive metal tube is divided in the length direction to form segments of the NbTi metal rod-inserted conductive metal tube, and a plurality of segments of the NbTi metal rod-inserted conductive metal tube are bundled to form Cu or In a method for manufacturing a superconducting wire by inserting the NbTi metal rod into a conductive metal tube made of a Cu alloy to form a segment-inserted conductive metal tube, and then stretching the segment-inserted conductive metal tube, the NbTi metal rod is inserted into the conductive metal tube. A method for producing a superconducting wire, which comprises forming a thin film made of a superconducting element on the surface of the NbTi metal rod before inserting it into the wire. (4) The method for manufacturing a superconducting wire according to claim 3, wherein the superconducting element is Nb. (5) The method for manufacturing a superconducting wire according to claim 3 or 4, wherein the thin film made of the superconducting element is formed by a CVD method.