JP2637427B2 - Superconducting wire manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a superconducting wire formed by coating an oxide-based superconducting conductor with a metal stabilizing layer and used for a superconducting device such as a superconducting magnet. .

[Prior Art] In recent years, various oxide-based superconducting materials having a critical temperature (Tc) at which a transition from a normal conducting state to a superconducting state shows a high value equal to or higher than the temperature of liquid nitrogen are being discovered. Conventionally, among superconductors made of this type of superconducting material, Y-Ba-Cu-
A so-called AB-Cu-O system such as an O-system and a La-Sr-Cu-O system (where A represents a Group IIIa metal element of the periodic table III such as La, Y, Yb, Sc, etc., and B represents Sr Indicates alkaline earth metal elements such as Ba and Ba)
In order to produce a superconducting material, a mixed powder obtained by mixing the compound powder of the above-mentioned Group IIIa metal element, the compound powder of the above alkaline earth metal element and the copper oxide powder is molded into a predetermined shape, and further heat-treated. To obtain a superconducting material.

In addition, in order to apply the oxide-based superconductor such as the AB-Cu-O-based superconductor to a superconducting device such as a superconducting magnet, an attempt has been made to convert the oxide-based superconducting material into a wire.

`` Problems to be solved by the invention''As a method of manufacturing a superconducting wire using such an oxide-based superconducting material, for example, a raw material powder of an oxide-based superconductor is filled in a metal sheath such as copper, Thereafter, a method has been attempted in which wire drawing is performed, and further heat treatment is performed to cause a reaction between the respective component elements of the raw material powder to produce a superconducting conductor having superconductivity.

By the way, in oxide-based superconductors, the reaction between the raw material powder and oxygen has a significant effect on the superconducting properties during heat treatment, and the superconductivity generated in a state where oxygen is insufficient during heat treatment deteriorates the superconducting properties. Tend to. On the other hand, metal materials used for the stabilizing layer of the superconducting wire, such as copper and copper alloys (copper-nickel alloy, copper-tin alloy, etc.), stainless steel, and high melting point metals such as Nb, Mo, Ta, etc. , Which have an oxidizing property, particularly in a high temperature state. Therefore, at the time of heat treatment when manufacturing the above-described superconducting wire, the stabilizing layer made of these metal materials deprives the raw material powder of the oxide-based superconducting material of oxygen, resulting in oxygen deficiency in the superconducting conductor generated by the heat treatment, There is a problem that superconducting characteristics such as a critical temperature and a critical current of the superconducting wire are deteriorated.

Further, this defective portion is particularly likely to occur on the outer peripheral surface of the superconducting conductor, that is, on the contact portion with the stabilizing layer, so that there has been a problem that electrical connection between the superconducting conductor and the stabilizing layer cannot be made.

The present invention has been made in view of the above problems, and has as its object to provide a method for manufacturing a superconducting wire having excellent superconducting characteristics.

"Means for Solving the Problems" The present invention relates to a method for producing a superconducting wire in which an oxide-based superconducting conductor is covered with a metal stabilizing layer, and the raw material powder of the oxide-based superconducting material is compacted. After forming a non-oxidized layer made of a noble metal on the surface of the molded body obtained by molding, filling this into a metal sheath serving as a stabilizing layer, it is subjected to wire drawing to form a wire, and then to this wire Heat treatment was used as a means for solving the problem.

"Action" The metal sheath that serves as the stabilizing layer is filled with a molded body that has a non-oxidized layer made of a noble metal, and the wire is subjected to heat treatment after wire drawing. Oxygen deficiency of the oxide-based superconducting material that occurs can be prevented.

 Hereinafter, the method of the present invention will be described in detail with reference to the drawings.

Examples of the oxide-based superconducting material used in the method of the present invention include AB-Cu-O-based materials such as Y-Ba-Cu-O-based materials (where A is IIIa such as La, Y, Yb, Sc, etc.). (B represents an alkaline earth metal element such as Sr, Ba, Ca, etc.). AB-Cu
By way of example the typical ones -O-based superconducting _{material, YBa 2 Cu 3 O 9- x} (x = 0~7) (La 1- x Sr x) 2 CuO 4 (x = 0.025~0.5) , etc. is there. Examples of the stabilizing layer material used in the method of the present invention include simple metals such as copper, Nb, Mo, and Ta; copper alloys (such as copper-nickel alloys and copper-tin alloys); and stainless steels (JIS standard symbols). Alloys such as SUS304 and SUS316),
Although a metal material such as a composite material such as copper-stainless clad is used, copper, a copper alloy, stainless steel, and a copper-stainless clad are particularly preferably used. Further, as the noble metal used in the method of the present invention, Ag, Au, Pt,
Simple metals such as Ir, Os, Pd, Rh, and Ru, and alloys such as a silver alloy and a gold alloy.

 FIG. 1 shows an example of the method of the present invention.

In the manufacturing method of this example, first, a powder to be a raw material of an oxide-based superconducting material is mixed so that each component element has a predetermined mixing ratio, and then the powder is calcined and calcined. I do. Powder as a raw material for oxide superconductor material, for example, Y-Ba-CuO system in the case of creating a superconducting _{material, Y 2 O 3, BaCO 3} , CuO , etc. suitable oxide or carbonate of the elements Used for The conditions of the pre-baking are appropriately set depending on the type of the superconducting material to be used. For example, Y-Ba-Cu-
When using an O-based superconducting material, a temperature of about 700 ° C
Heat for about 10 hours, then at a temperature of about 850-950 ° C for 24-
It is preferable to heat for about 100 hours. This calcination is desirably performed under conditions including oxygen in the atmosphere gas, such as in an oxygen stream. In addition, when only the oxide of each component element is used as the raw material powder of the oxide-based superconducting material and it is not necessary to change the composition of the raw material powder such as decarboxylation during the preliminary firing, the preliminary firing is performed, particularly in the first firing. The heating operation may be omitted.

Next, the calcined raw material powder is compacted into a predetermined shape (a cylindrical shape in FIG. 1) to obtain a compact 1. For this compacting, a compression means such as a rubber press is suitably used. Next, a noble metal tape made of a noble metal such as silver is wound around the surface of the molded body 1 without gaps, and a non-oxidized layer 2 is formed on the surface of the molded body 1. The thickness of the non-oxidized layer 2 may be such that the contact between the molded body 1 and the metal sheath 3 is completely cut off.

Next, the molded body 1 is inserted into a metal sheath 3 which is made of a metal such as copper to be a stabilizing layer. (FIG. 1) Next, a wire in a state where the molded body 1 is inserted into the metal sheath 3 is subjected to wire drawing to obtain a wire having a predetermined diameter. Next, the wire is subjected to a heat treatment to cause a reaction between the raw material elements of the molded body, thereby producing a superconducting conductor having superconductivity. This heat treatment is appropriately set depending on the type of the oxide-based superconducting material to be used. For example, when a Y-Ba-Cu-O-based superconducting material is used, 800 to 1300 ° C. and about 1 to 30 hours are preferable. . By the above operation, as shown in FIG. 2, the non-oxidized layer 2 made of a noble metal is interposed between the superconducting conductor 4 made of an oxide-based superconducting material and the stabilizing layer 5 covering the superconducting conductor 4. The superconducting wire 6 is created.

By cooling the superconducting wire 6 below the critical temperature of the oxide-based superconducting material constituting the superconducting conductor 4, a current can flow through the superconducting conductor 4 without loss. Also,
Stabilizing layer 5 and non-oxidized layer 2 covering superconducting conductor 4
Acts as a stabilizer for the superconducting wire 6.

In the manufacturing method of this example, the heat treatment is performed after a noble metal tape is wound around the surface of the molded body 1 to form a non-oxidized layer. Therefore, it is necessary to prevent oxygen from being removed from the molded body 1 during the heat treatment of the wire. Can be. Therefore, a uniform and high-quality superconducting wire 6 can be obtained without generating a defective portion in which superconducting characteristics are deteriorated due to lack of oxygen in the generated superconducting conductor 4.

In this example, the non-oxidized layer 2 was formed by winding a noble metal tape around the surface of the molded body 1. However, the means for forming the non-oxidized layer 2 on the surface of the molded body 1 is not limited to this. The non-oxidized layer 2 may be formed by a thin film forming method such as a sputtering method and a CVD method.

In addition, it is naturally possible to form a multi-wire by bundling a number of superconducting wires obtained in this example.

"Example" A superconducting wire using a Y-Ba-Cu-O-based superconducting material was produced by the method of the present invention. First, it becomes a raw material for superconducting materials
Each raw material powder of Y ₂ O ₃ , BaCO ₃ , and CuO was mixed so as to have a composition of YBa ₂ Cu ₃ O ₇ . Next, this mixed powder was heated at 700 ° C. for 3 hours, and further heated at 900 ° C. for 12 hours to obtain a calcined powder. Next, the calcined powder was pulverized and homogenized, and then subjected to compacting by a rubber press to obtain a cylindrical compact having a diameter of 10 mm. Next, the molded body was heated at 900 ° C. for 12 hours.
After heating in an oxygen stream, continuous vapor deposition was performed for 3 hours using Ag as the vapor deposition source to form a 2 μm Ag thin film on the surface of the molded body. Next, insert this into a stainless steel tube (made of JIS standard code SUS304) with an outer diameter of 12 mm and a wall thickness of 0.75 mm, and further arrange a copper tube with an outer diameter of 20 mm and a wall thickness of 3.5 mm on the outside, and wire drawing the whole Processing was performed to obtain a wire having a final outer diameter of 2 mm. Next, apply this wire to 9
Heat treatment was performed at 00 ° C. for 3 hours to obtain a superconducting wire.

As a result of measuring the critical temperature and critical current of the superconducting wire obtained by the above operation, the critical temperature was 91 K at zero resistance.
showed that. The critical current (Jc) measured by the four-terminal method showed Jc = 500 A / cm ² at the temperature of liquid nitrogen.

In addition, using a Y-Ba-Cu-O-based superconducting material having the same composition as in this example, a superconducting wire was formed without forming an Ag thin film on the surface of the molded body, and the critical temperature and critical current of the superconducting wire were determined. As a result of the measurement, the critical temperature was 89 k, and the critical current was 60 A / cm ² .

[Effects of the Invention] As described above, in the method for manufacturing a superconducting wire according to the present invention, a non-oxidized layer made of a noble metal is formed on the surface of a compact obtained by compacting a raw material powder of an oxide-based superconducting material. After forming and filling this into the metal sheath that will be the stabilizing layer,
This is subjected to wire drawing to form a wire, and then heat treatment is performed on the wire, so that it is possible to prevent oxygen from being removed from the molded body in the metal sheath during the heat treatment. Accordingly, a uniform and high-quality superconducting wire can be obtained without generating a defective portion in which superconductivity is deteriorated due to lack of oxygen in the generated superconductor.

[Brief description of the drawings]

FIG. 1 is a view for explaining an example of a method for manufacturing a superconducting wire according to the present invention, and is a perspective view showing a state when a molded body is inserted into a metal sheath, and FIG. 2 is a manufacturing method shown in FIG. It is a figure which shows the example of the superconducting wire manufactured by one example, Comprising: It is a cross-sectional view of a superconducting wire. 1 ... molded body, 2 ... non-oxidized layer, 3 ... metal sheath, 4
... superconducting conductor, 5 ... stabilizing layer, 6 ... superconducting wire.

Continued on the front page (72) Inventor: Yu Sugimoto, 1-5-1 Kiba, Koto-ku, Tokyo Inside Fujikura Electric Wire Co., Ltd. (72) Inventor Mikio Nakagawa 1-5-1, Kiba, Koto-ku, Tokyo Inside Fujikura Electric Wire Co., Ltd. (56) References JP-A-1-163910 (JP, A) JP-A-63-225409 (JP, A) JP-A-63-274023 (JP, A) JP-A-63-279523 (JP, A)

Claims (4)

(57) [Claims] 1. A method for producing a superconducting wire, comprising coating an oxide-based superconducting conductor with a metal stabilizing layer, comprising: forming a compact obtained by compacting raw material powder of an oxide-based superconducting material; Superconducting characterized by forming a non-oxidized layer made of a noble metal on the surface, filling this into a metal sheath to be a stabilizing layer, drawing it into a wire, and then subjecting this wire to heat treatment. Wire manufacturing method. 2. A method for manufacturing a superconducting wire according to claim 1, wherein a non-oxidized layer made of a noble metal is provided on an inner surface of said metal sheath. 3. The method for manufacturing a superconducting wire according to claim 1, wherein a non-oxidized layer is formed by winding a noble metal tape around the surface of the molded body. 4. A method for manufacturing a superconducting wire according to claim 2, wherein a non-oxidized layer is formed by plating a noble metal on the inner surface of said metal sheath.