JPH0362905A - Manufacture of superconducting coil - Google Patents

Abstract

PURPOSE:To make it possible to wind superconductor wire material so that the superconductor wires are effectively insulated and to improve a generated magnetic field by filling the inside of a pipe coated with the metal of silver or silver alloy having a readily oxidizing metal layer on the outer surface with an oxide superconductor, winding the wire material in an intended shape, performing heat treatment, and oxidizing the readily oxidizing metal layer. CONSTITUTION:A readily oxidizing metal layer is formed on the outer surface of a superconductor wire material 2. The superconductor wire material 2 is wound around a suitable winding jig 3, and a wiring body having an intended shape is manufactured. The winding body is annealed in an atmosphere containing oxygen. Oxygen is introduced into an oxide superconductor by this heat treatment, and the superconductive characteristic is improved. The metal layer which is provided on the outer surface of the superconductor wire material is oxidized. An insulating oxide film is formed by itself, and the superconductor wire materials are insulated. Thus, a superconductive coil is obtained. Therefore, even if the superconductor wire material is wound tightly, the part between the wire materials can be securely insulated. Since the metal state is maintained in winding, the deformation in winding is not hindered, and the winding body having the intended shape can be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a method for manufacturing a tE conductive coil using an oxide superconductor.

(Prior art) Since it was announced in 1986 that Ba-La-Cu-0-based layered perovskite oxides have a high critical temperature of over 40, oxide-based superconductors have attracted attention. , research in the search for new materials is being actively conducted.

Among them, defective perovskite-type oxide superconductors represented by the Y-Ba-Cu-0 system, which have a high critical temperature higher than the liquid nitrogen temperature, and I3 i -8r-Ca-Cu
-0 series and Tl-Ra-Ca-Cu-0 series oxide superconductors can replace expensive liquid helium as a refrigerant.
Since inexpensive 1ff1 nitrogen can be used, it has important industrial value.

When considering the application of such oxide superconductors to the energy field, it is naturally necessary to form them into coils. Therefore,
Attempts have been made to fabricate superconducting coils by forming oxide superconductors into wires using various methods and forming the wires into coil shapes.

Methods for producing a superconducting wire using an oxide superconductor include (a) a method of enclosing an oxide superconductor in a metal tube and drawing it into a wire; (b) a method of forming an oxide superconductor powder into a wire; (C) A method of forming an oxide superconductor layer on a metal tape by thermal spraying or various insertion/removal forming methods and forming it into a wire. There is.

A superconducting coil is actually being prototyped using a superconducting wire to which the above methods (a) and (b) are applied.

For example, when using a superconducting wire to which the above-mentioned (a) orientation is applied,
For example, by winding the superconducting wire while forming a spiral shape and accommodating the superconducting wire inside the bay, the metal tubes can be wound with gaps left between them so that they do not touch each other, or the metal tubes can be wound with an insulator interposed between them. The superconducting coil is formed into a coil and then heat-treated in an oxygen atmosphere to obtain a superconducting coil.

(Problems to be Solved by the Invention) As described above, when winding the superconducting wires so that they do not contact each other, it is naturally impossible to wind the superconducting wires closely. Further, since a superconducting coil using an oxide superconductor requires heat treatment after winding as described above, ordinary organic insulators cannot be used as the insulating material.

As described above, there is currently no effective method for tightly winding superconducting wires while insulating them, and for this reason,
The superconducting coils that have been produced as prototypes generate a magnetic field of approximately several tens of Gauss. Therefore, it is strongly desired to improve the magnetic field generated by a superconducting coil by making it possible to insulate the superconducting wires while tightly winding them.

The present invention has been made to address these problems, and provides a method for manufacturing a superconducting coil that enables effective insulation between superconducting wires and winds them tightly, thereby improving the generated magnetic field. is intended to provide.

[Structure of the Invention] (Means for Solving the Problems) In other words, the method for manufacturing a superconducting coil of the present invention includes forming an oxide superconductor in a metal clad tube made of silver or a silver alloy having an easily oxidizable metal layer on the outer peripheral surface. a step of filling the body to form a superconducting wire, a step of winding the superconducting wire into a desired shape, and a heat treatment of the wound body obtained in this winding step to oxidize the easily oxidizable metal layer. and forming an insulating oxide film.

Many oxide superconductors are known, but in the present invention, rare earth element-containing perovskite oxide superconductors, B1-8r-Ca-Cu-0-based oxide superconductors, T An l-Ba-Ca-Cu-0 based oxide superconductor or the like is applied.

The oxide superconductor containing a rare earth element and having a perovskite structure may be one that can realize a superconducting state, for example, REMCuO-based 237-δ (RE is Y, I, aSScSNds 311% El
l, Gds 07% 110%Er, Tα, Yl)
At least one element selected from rare earth elements such as SLu, H is at least an IFffl element selected from Ba5Sr and Ca, δ represents an oxygen defect, usually a number less than 1, and a part of Cu is TI%. V s Crs Mn1
Can be replaced with Fe, Co, Nl, Zn, etc. ) are exemplified. Note that rare earth elements are broadly defined and include 5csY and La-based elements.

In addition, the former -3r-Ca-Cu-0-based oxide superconductor has the chemical formula: B105r2Ca2Cu30x -
-(I):B12(Sr,Ca)3Cu20x-
(II) (In the formula, a part of B1 can be replaced with pb etc.)
It is expressed as Tl-Ba-Ca-Cu-
The chemical formula of the 0-based oxide superconductor is: Tl2 Ba2 Ca2 Cu30x
・-(III): Tl2(Ba, Ca)3Cu20x
---(IV) etc.

The superconducting wire used in the present invention is a metal clad tube filled with an oxide superconductor.

Note that the oxide superconductor to be filled is not limited to one that has been crystallized in advance by calcining, and it is also possible to use a mixture of starting materials for the oxide superconductor.

The metal clad tube of the superconducting wire used is one in which a metal layer that can easily form an insulating oxide by heat treatment described below is formed on the outer peripheral surface of a tubular base made of silver or a silver alloy.

The metal forming the insulating oxide is Mg.

Al5St, Ca, TI, Cr, Nis 5rXY
s Zr, Nb580%In%Sn, Ba5Ta
% W or alloys thereof. , the method for forming these metal layers on the outer peripheral surface of the chain tube is as follows:
Various methods can be employed, such as thin film forming methods such as plating method, vapor deposition method, and liquid coating method, and machining method in which a metal layer is formed by inserting a chain pipe into the metal pipe material and drawing it. is possible.

Also, if the thickness of the metal coating layer is too thin, sufficient insulation effect will not be obtained, and if it is too thick, heat treatment ■! j due to insufficient oxygen supply to the oxide superconductor, several μ
It is preferable to set it as (about several 1 to several 100 rods 2 micrometers - too micrometers).

This metal layer becomes an insulating oxide film through heat treatment performed after winding into a coil shape, and insulates between the superconducting wires.

The superconducting coil of the present invention is produced, for example, as follows.

First, a superconducting wire having an easily oxidizable metal layer formed on its outer peripheral surface as described above is wound around a suitable winding jig to produce a wound body having a desired shape. Next, this wound body is subjected to heat treatment, that is, annealing in an oxygen-containing atmosphere.

Although this heat treatment differs depending on the oxide superconductor used, it can be carried out under various conditions, such as at a temperature of approximately 400° C. to 900° C. or under pressurized oxygen.

Through this heat treatment, oxygen is introduced into the oxide superconductor to improve the superconducting properties, and the metal layer provided on the outer peripheral surface of the superconducting wire is oxidized to self-form an insulating oxide film. A desired superconducting coil can be obtained by insulating the superconducting wires.

Note that the metal layer provided on the outer peripheral surface of the superconducting wire is easily oxidized to become an oxide, and is made thin enough to provide an insulating effect, so the oxide inside the metal cladding tube is not formed during heat treatment. Oxygen can be supplied to superconductors.

(Function) In the present invention, after forming an easily oxidizable metal layer on the outer peripheral surface of the superconducting wire in advance and producing a wound body in this state,
By applying heat treatment, an insulating oxide film is self-formed to provide insulation between the superconducting wires. therefore,
Even when the superconducting wires are tightly wound, it is possible to reliably insulate the electromotive conductive wires. In addition, since it is in a metal state at the end of the fourth roll, it does not prevent deformation due to winding.
It is possible to manufacture a wound body having a desired shape. Furthermore, since the formation of the insulating oxide film can be performed simultaneously with the heat treatment of the oxide superconductor, there is no need to perform a separate insulating step compared to conventional manufacturing processes.

(Example) Next, examples of the present invention will be described.

Example 1 FIG. 1 is a sectional view schematically showing the structure of a superconducting coil according to an example of the present invention.

This superconducting coil 1 is constructed by winding a superconducting wire 2 around a winding jig 3 made of an insulating cylindrical base material.

As shown in FIG. 2(a), the superconducting wire 2 has a silver metal cladding tube 4 filled with an oxide superconductor 5, and an insulating oxide coating on the outer peripheral surface of the fully curved cladding tube 4. JJ! 6
is formed, and this insulating oxide film 6 is
As shown in FIG. 2(b), the easily oxidizable metal layer 7 formed in advance on the surface of the silver metal sheath 4 is oxidized by heat treatment after winding, thereby self-forming. be.

The wound superconducting wires 2 are insulated by the insulating oxide film 6.

A superconducting coil having the above configuration was manufactured according to the manufacturing method shown below.

First, a predetermined amount of each powder of Y2 0 3 , BaCO3, and CuO was weighed and mixed thoroughly, and then the mixed powder was fired in air at 700°C for 48 hours, and the fired product was milled in a ball mill. Pulverization and mixing were repeated to produce a Y-based oxide superconducting 237-δ body powder having a composition of YBaCuO.

Next, this Y-based oxide superconductor powder is filled into a silver tube,
This was subjected to area reduction processing to produce a wire rod with an outer diameter of 1IIffl. Next, the outer surface of this wire is coated using the plating method.
A 3 μm thick N1 layer was formed as an oxidizable metal layer.

The wire thus obtained was wound eight times around a cylindrical alumina winding jig to form a coil.

Thereafter, this rolled body was heated to 800°C in an oxygen atmosphere of 1 atm.
Heat treatment was performed by holding at a temperature of ~900°C for 8 hours to obtain the desired superconducting coil.

When we investigated the surface condition of the superconducting wire after heat treatment, we found that Ni
It was confirmed that the plating layer was oxidized and NiO was formed. Furthermore, when the insulation between the superconducting wires was measured using a tester, it was IMΩ or more, confirming that the superconducting wires were well insulated. Incidentally, when the critical temperature and critical current density of the obtained superconducting coil were measured, good results of 86 and 14,500 A/c7 were obtained. From this, it was confirmed that even if the insulating oxide film was present, it did not adversely affect the heat treatment of the oxide superconductor.

Example 2 Y23 with YBa Cu O composition prepared in Example 1
First, a silver tube was filled with 7-δ-based oxide superconductor powder, and the chain tube was compressed into an aluminum tube, followed by wire drawing to obtain a wire rod with an outer diameter of 11. At this time, the thickness of the aluminum layer on the surface of the chain tube was 10 μm.

Next, this superconducting wire was wound around an alumina winding jig under the same conditions as in Example 1 to form a coil.

Thereafter, this wound body was first held at a temperature of 400° C. to 500° C. for 8 hours in an oxygen atmosphere of 10 atm, and then held at a temperature of 800° C. to 900° C. for 8 hours to perform heat treatment. The reason why the heat treatment temperature was divided into two stages is that heat treatment at a high temperature causes aluminum to form a solid solution in silver, lowering its melting point and making it difficult to form an oxide wave film. When using such metals, the insulation between the superconducting wires can be ensured by first converting aluminum into alumina at a temperature that allows oxidation, and then performing heat treatment to improve the characteristics of the oxide ffl conductor. It becomes possible to do so.

When we examined the surface condition of the superconducting wire after heat treatment, we confirmed that the aluminum layer was oxidized and alumina was formed. Furthermore, when the insulation between the superconducting wires was measured using a tester, it was IMΩ or more, confirming that the superconducting wires were well insulated.

Comparative Example 1 A superconducting coil was produced under the same conditions as in Example 1 above, except that the Nl plating layer was not formed on the surface of the superconducting wire. After the heat treatment, the insulation between the superconducting wires was similarly measured using a tester and found to be 10 wΩ or less, and it was confirmed from the appearance that the silver was fused together and conductive.

[Effects of the Invention] As described above, according to the present invention, it is possible to wind the superconducting wires closely and to reliably insulate each superconducting wire. Moreover, since an insulating coating can be formed in the same manner during the heat treatment O,'j for improving the superconducting properties of the oxide superconductor, the manufacturing efficiency is high and the method is industrially effective.

[Brief explanation of drawings]

FIG. 1 shows a superconducting coil 17+' according to an embodiment of the present invention. FIG. 2(a) is an enlarged cross-sectional view of the superconducting wire, and FIG. 2(b) is an enlarged cross-sectional view of the superconducting wire before heat treatment. 1... Superconducting coil, 2... Superconducting wire, 3... Winding jig, 4... Silver metal sheath tube, 5...・・Oxide superconductor, 6・・・・
...Insulating oxide film, 7...Easily oxidizable metal interlayer.

Claims (1)

[Claims] (1) Forming a superconducting wire by filling an oxide superconductor into a metal-clad tube made of silver or silver alloy having an easily oxidizable metal layer on the outer peripheral surface, and winding the superconducting wire into a desired shape. and a step of heat-treating the wound body obtained in this winding step to oxidize the easily oxidizable metal layer to form an insulating oxide film. Production method.