JP2545939B2 - Manufacturing method of superconducting wire by explosive compression method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a superconducting wire having a high critical current density using an explosive compression method.

[Conventional technology]

In general, a compound having a perovskite structure composed of a rare earth element containing Y (hereinafter, this element is represented by R), an alkaline earth metal, Cu and an oxide (hereinafter, this compound is referred to as an R-based oxide) is liquid nitrogen. It is known to exhibit a superconducting phenomenon at 77 ° K, which can be cooled at.

More recently, Bi-Ca-Sr-Cu-O-based oxides (hereinafter, Bi
77) and Tl-Ca-Ba-Cu-O-based oxides (hereinafter referred to as Tl-based oxides) can be cooled with liquid nitrogen.
It was discovered that it exhibits superconductivity at temperatures above ° K.

In any of the methods for producing a superconducting wire using the R-based oxide, the Bi-based oxide, and the Tl-based oxide, the powder of these oxides is filled in an Ag tube, and both ends of the oxide-filled Ag tube are filled. After sealing, wire drawing such as swaging, groove roll processing, or die processing is performed to make an Ag composite wire with a diameter of 5 mm or less, and the Ag composite wire is heat treated in the air or in an oxygen atmosphere. It was manufactured.

The heat treatment temperature is 900 to 950 ° C for R-based oxide powder-filled Ag composite wire, 830 to 870 ° C for Bi-based oxide powder-filled Ag composite wire, and Tl-based oxide powder-filled Ag composite wire. Is 880-920 ° C.

[Problems to be Solved by the Invention]

However, the critical current density of the R-based oxide superconducting wire obtained by the above-mentioned conventional manufacturing method is 700 A / c
The critical current density of the Bi-based oxide superconducting wire produced by the conventional manufacturing method is about 100 A / cm ² at most, and the Tl-based oxide superconducting wire obtained by the conventional manufacturing method is about m ^2. The wire has a critical current density of up to about 180 A / cm ² .

At such a critical current density, it cannot be put to practical use as a superconducting wire, so an R-based oxide-filled wire, Bi
Attempts have also been made to increase the packing density of the superconducting oxide powder by subjecting the oxide-based oxide-filled wire or the Tl-based oxide-filled wire to explosive compression, thereby improving the critical current density. When the oxide-filled wire such as a material-filled wire and a big oxide-filled wire Tl-based oxide-filled wire is directly surrounded by explosives and explosively compressed, the oxide powder filled in the oxide-filled wire has pores or pores. Voids are generated, and a sufficient high density cannot be obtained, so that an excellent high critical current density cannot be obtained.

Furthermore, when the above oxide-filled wire is directly surrounded by explosives and explosively compressed, disconnection frequently occurs, and further, a chemical reaction occurs between the explosives and the Ag sheath, causing problems such as corrosion of the Ag sheath surface. However, it has not been possible to obtain a superconducting wire that can be put to practical use.

[Means for solving the problem]

Therefore, the inventors of the present invention have conducted research to obtain a superconducting wire having a higher critical current density that can be put to practical use, and as a result, the above R-based oxide-filled wire, Bi-based oxide-filled wire or
An oxide-filled wire such as a Tl-based oxide-filled wire is loaded together with a pressure medium into a ring-shaped gap formed by a pipe and a cylindrical support type so that the longitudinal direction of the wire is along the axis of the pipe,
When explosive compressed by the explosive charged in the pipe, the oxide-filled wire can densify the oxide powder in the wire without being cut, and obtain a superconducting wire having an extremely excellent high critical current density. I got the knowledge that I can do it.

The present invention has been made on the basis of such knowledge, and hereinafter, a method for manufacturing a superconducting wire according to the explosion compression method of the present invention will be specifically described with reference to the drawings.

1 is a sectional elevation view showing a state in which the oxide-filled wire is set in order to explosively compress the oxide-filled wire by an explosive compression method, and is a sectional view taken along the line I-I of FIG. 2. 2 is a II-II sectional plan view of FIG. 1 in a state in which the oxide-filled wire is set for explosive compression.

In FIGS. 1 and 2, 1 is a cylindrical support type,
2 is a pressure medium, 3 is an oxide-filled wire, 4 is a substrate, 5 is a pipe, 6 is a lid, 7 is explosive, and 8 is a detonator.

As the cylindrical support mold 1, it is preferable to use a thick cylindrical mold or a cylindrical reinforced concrete mold, but a bottomed cylindrical mold or concrete mold may be used. In the case of bottoming, it is not necessary to use the substrate 4. Further, the cylindrical support type may be one in which a hole is formed in the bedrock.

The pressure medium 2 may be a fluid, but the average particle size: 1 to 10
A powder that is hard to solidify by explosive compression of 00 μm is preferable.
Examples of these powders include oxide powders such as Al ₂ O ₃ , SiO ₂ , MgO, and ZrO ₂ and complex oxide powders of those oxides, AlN, TiN, nitride powders such as Si ₃ N ₄ , and TiB. A boride powder such as ₂ , ZrB ₂ or MoB, a carbide powder such as SiC, TiC, ZrC or WC, a silicide powder such as MoSi ₂ , TiSi or ZrSi, or a solid solution powder such as carbonitride powder is used.

Further, the pressure medium may be a mixture of the fluid and the powder.

The pipe 5 is preferably a steel pipe, but is not limited to the steel pipe, and may be made of other metal or alloy, plastic, tempered glass, ceramics, cardboard or the like.

In order to set the oxide-filled wire as shown in FIGS. 1 and 2, the following steps are performed.

First, the substrate 4 is placed, the cylindrical support mold 1 made of a cylindrical mold is placed on the substrate 4, and the pipe 5 is erected inside the cylindrical support mold 1. The oxide-filled wire 3 and the pressure medium 2 are charged in the gap between the cylindrical support mold 1 and the pipe. After charging the oxide-filled wire 3 and the pressure medium 2,
It is preferable to apply vibration to fill the pressure medium 2 more closely. After charging the oxide-filled wire 3 and the pressure medium 2,
The lid 6 is closed, and then the explosive 7 is filled inside the pipe 5. The explosive 7 may be partially filled so as to rise above the cylindrical support die 1. The charged explosive 7 is detonated by the detonator 8. When the explosive 7 of the pipe 5 is detonated, the oxide-filled wire 3 embedded in the pressure medium 2 is uniformly exploded and compressed without cutting,
The oxide powder filled in the wire is compressed to a higher density without generating pores or voids.

〔Example〕

Next, the present invention will be described more specifically based on embodiments.

Example 1 and Conventional Example 1 As raw material powder, yttrium oxide (Y ₂ O ₃ ) powder having an average particle size: 6 μm, barium carbonate (BaCO ₃ ) powder having an average particle size: 6 μm, and copper oxide having an average particle size: 6 μm (CuO) powder is prepared, and these powders are mixed and mixed in a molar ratio of Y ₂ O ₃ : BaCO ₃ : CuO = 1/2: 2: 3, and the mixed powder is mixed in the air. At that temperature, a temperature of 900 ° C. is maintained for 12 hours for calcination to prepare a compound having a composition of YBa ₂ Cu ₃ O ₇ and a perovskite structure (hereinafter referred to as Y-based oxide). These compounds were pulverized to prepare a Y-based oxide powder having an average particle size of 1.3 μm.

The above Y-based oxide powder is filled in an Ag tube having an inner diameter of 20 mm, a wall thickness of 1.5 mm, and a length of 200 mm, and the filled Ag tube is swaged and then groove-rolled to a diameter of 2 mm.
A Y-based oxide-filled Ag composite wire was manufactured.

Explosive compression was performed as follows using the above Y-based oxide-filled Ag composite wire.

First, as the cylindrical support type 1, outer diameter: 180 mm × inner diameter: 100 mm
B. A length of 1300 mm of an iron cylinder die and a steel plate base plate 4 are prepared, and the steel cylinder die is erected on the steel plate base plate 4 as shown in FIG. Since the cylindrical support mold 1 is long, it may be fixed to the steel plate substrate 4 with an adhesive or the like so as not to fall. Then, inside the steel cylindrical mold, the outer diameter having a height slightly lower than the height of the steel cylindrical mold: 69 mm × inner diameter: 65
mm × height: A 1100 mm steel pipe 5 was erected. The steel cylindrical mold and the steel pie do not have to be placed exactly concentrically, and the steel pipe may be placed substantially in the center of the inside of the steel cylindrical die.

Between the steel cylindrical mold 1 and the steel pipe 5, the SiC powder 2 having an average particle diameter of 2 μm and the Y-based oxide-filled Ag composite wire 3 are arranged such that the wire is parallel to the axis of the steel pipe. Then, the SiC powder was charged so that the SiC powder became sufficiently dense, and then the lid 6 was closed. The lid is provided for the purpose of preventing the charged SiC powder from mixing with the explosive to be filled later, and can be carried out without the lid depending on the conditions.

After charging the above SiC powder and closing the lid 6, explosives (explosion speed: 2,
300 m / sec) 7 is filled inside the steel pipe 5 and further so as to rise on the upper end of the steel cylindrical mold, and is exploded by a detonator 8 to produce the Y-based oxide-filled Ag composite wire 3 Explosion compressed.

The Y-based oxide-filled Ag composite wire 3 that has been explosively compressed is taken out, and the other Y-based oxide-filled Ag that is not explosively compressed is used.
A Y-based oxide superconducting wire rod (Example 1) that was heat-treated under an oxygen atmosphere with a composite wire under the conditions of a temperature of 920 ° C. and kept for 24 hours, and was subjected to explosive compression (Example 1) and a Y-based oxide superconducting wire rod that was not subjected to explosive compression ( Conventional example 1) was produced.

Furthermore, a cable of Y-based oxide-filled Ag composite wire (not shown) is formed by bundling seven Y-based oxide-filled Ag composite wires.
We also made a cable for this cable and filled it with the above Y-based oxide.
The same heat treatment as that of the Ag composite wire was performed to produce a Y-based oxide superconducting cable that was subjected to explosive compression (Example 1) and a Y-based oxide superconducting cable that was not subjected to explosive compression (Conventional Example 1).

Of the Y-based oxide superconducting wire and the Y-based oxide superconducting cable (Example 1) that have been subjected to the above-described explosive compression, and the Y-based oxide superconducting wire and the Y-based oxide superconducting cable that have not undergone the explosive compression (Conventional example 1). The superconducting properties of each were measured, and the results are shown in Table 1.

Example 2 and Conventional Example 2 As raw material powder, Bi _{2 having an} average particle size of 10 μm or less
O ₃ powder, CaCO ₃ powder, SrCO ₃ powder and CuO powder were prepared, and these powders were Bi ₂ O ₃ powder: 38.8%, CaCO ₃ powder: 16.7%.
%, SrCO ₃ powder: 24.6% and CuO powder: 19.9% (above weight%), mix and mix, and this mixed powder is held in the air at a temperature of 800 ° C for 12 hours. A Bi-based oxide was prepared by firing, and the Bi-based oxide obtained by this firing was then pulverized to produce a Bi-based oxide powder having an average particle diameter of 5 μm.

The above Bi-based oxide powder, the inner diameter: 20mm × wall thickness: 1.5mm × length: 200mm Ag tube was filled, after swaging the filling Ag tube, then groove roll processing, diameter: 2mm
A Bi-based oxide-filled Ag composite wire was prepared. Further, 7 cables of the above Bi-based oxide-filled Ag composite wire were bundled to produce a Bi-based oxide-filled Ag composite wire cable.

The Bi-based oxide-filled Ag composite wire 3 was charged together with the SiC powder 2 as shown in FIGS. 1 and 2, explosive compression was performed under the same conditions as in Example 1, and the Bi-based oxide filling was performed. A cable (not shown) in which Ag composite wires were bundled was also charged with the SiC powder at the position of the oxide-filled wire 3 in FIGS. 1 and 2 and subjected to explosive compression.

The above-mentioned explosively compressed Bi-based oxide-filled Ag composite wire and
Cables of Bi-based oxide-filled Ag composite wire and non-explosive-compressed Bi-based oxide-filled Ag composite wire and Bi-based oxide-filled Ag composite wire cable in oxygen atmosphere at temperature: 8
Heat-treated under conditions of holding at 50 ℃ for 15 hours and subjected to explosive compression
A Bi-based oxide superconducting wire and a Bi-based oxide superconducting cable (Example 2), and a Bi-based oxide superconducting wire and a Bi-based oxide superconducting cable (conventional example 2) that are not subjected to explosive compression were produced and their superconductivity was determined. The properties were measured and the results are shown in Table 1.

Example 3 and Conventional Example 3 As the raw material powder, both of the average particle size: 10 μm or less of Tl ₂
O ₃ powder, CaCO ₃ powder, BaCO ₃ powder and CuC powder are prepared, and these powders are used as Tl ₂ O ₃ powder: 35.4%, CaCO ₃ powder: 15.5
%, BaCO ₃ powder: 30.6% and CuO powder: 18.5% (above weight%), mix and mix, and this mixed powder is kept in an oxygen atmosphere at a temperature of 800 ° C for 10 hours To make a Tl-based oxide powder, and crush the Tl-based oxide obtained by this baking to give a Tl-based oxide with an average particle size of 5 μm.
A system oxide powder was produced.

The above Tl-based oxide powder was filled into an Ag tube having an inner diameter of 20 mm, a wall thickness of 1.5 mm, and a length of 200 mm, and the filled Ag tube was swaged and then groove-rolled to a diameter of 2 mm.
A Tl-based oxide-filled Ag composite wire was prepared. Further, seven Tl-based oxide-filled Ag composite wires were bundled to produce a Tl-based oxide-filled Ag composite wire cable.

The Tl-based oxide-filled Ag composite wire 3 was charged together with the SiC powder 2 as shown in FIGS. 1 and 2, explosive-compressed under the same conditions as in Example 1, and further the Tl-based oxide-filled. A cable (not shown) in which Ag composite wires were bundled was also charged together with the SiC powder at the position of the oxide-filled wire 4 in FIGS. 1 and 2 and subjected to explosive compression.

Explosion-compressed Tl-based oxide-filled Ag composite wire and
Cables of Tl-based oxide-filled Ag composite wire and Tl-based oxide-filled Ag composite wire and explosion-compressed Tl-based oxide-filled Ag composite wire in oxygen atmosphere, temperature: 900
Tl heat-treated under conditions of holding at ℃ for 3 hours and subjected to explosive compression
-Based oxide superconducting wire and Tl-based oxide superconducting cable (Example 3), and Tl-based oxide superconducting wire and Tl-based oxide superconducting cable (conventional example 3) that were not subjected to explosive compression were manufactured, and their superconducting characteristics Was measured and the results are shown in Table 1.

In the above-mentioned Examples 1 to 3, the cylindrical support mold was vertically installed and exploded and compressed, but it is also possible to place the cylindrical support mold in a horizontal state and perform explosive compression.

〔The invention's effect〕

The superconducting wire rods of Examples 1 to 3 of the present invention obtained by subjecting the results of Table 1 to explosive compression and then performing heat treatment in the atmosphere or oxygen atmosphere are Comparative Examples 1 to 3 in which explosive compression is not applied.
Compared with the superconducting wire of No. 3, it was found that the critical current density was particularly excellent, and a superconducting wire that could be put to practical use could be obtained, which greatly contributes to the development of industry.

[Brief description of drawings]

FIG. 1 is a sectional elevation view showing a state in which an oxide-filled wire is set in a cylindrical support mold for explosive compression, and FIG. 2 is a II-II sectional view of FIG. 1: Cylindrical support type, 2: Pressure medium 3: Oxide filled wire, 4: Substrate 5: Pipe, 6: Lid 7: Explosive, 8: Detonator

Front page continuation (72) Inventor Hideki Tonda 4-2 Higashimachi, Kumamoto-shi, Kumamoto 6-201 Higashimachi Minami Housing (201) Inventor Kazuki Takashima 1000-10 Yasukubomoto-cho, Kumamoto-shi, Kumamoto 401 (56) Reference Documents JP-A 1-212204 (JP, A) JP-A 64-28265 (JP, A) JP-A 63-297262 (JP, A) JP-A 63-222063 (JP, A)

Claims (10)

(57) [Claims] 1. A pipe and a cylindrical support die having an inner diameter larger than the outer diameter of the pipe are prepared, and the pipe is concentrically loaded into the cylindrical support die to form the pipe and the cylindrical support die. A ring-shaped gap is formed, and an oxide powder-filled Ag wire (hereinafter referred to as Ag wire) and a pressure medium are charged into the ring-shaped gap so that the Ag wire is embedded in the pressure medium. , The inside of the pipe is filled with explosive, and the explosive is exploded to explodely compress and densify the Ag wire, and then the explosive-compressed and densified Ag wire is exposed to the atmosphere or oxygen atmosphere. A method of manufacturing a superconducting wire by an explosive compression method, characterized by heat treatment in a vacuum. 2. The method for manufacturing a superconducting wire according to claim 1, wherein the cylindrical support die is a cylindrical die. 3. The method for producing an isoelectric wire according to claim 1, wherein the cylindrical support mold is a cylindrical reinforced concrete mold. 4. The pressure medium has an average particle size of 1 to 1,000 μm.
2. The method for producing a superconducting wire by the explosive compression method according to claim 1, which is a powder that is hard to solidify by explosive compression. 5. The method for producing a superconducting wire according to claim 1, wherein the pressure medium is a fluid. 6. The method for producing a superconducting wire according to claim 1, wherein the pressure medium is a mixture of powder and fluid. 7. The oxide powder is a rare earth element containing Y,
A method for producing a superconducting wire, which is a compound powder having a perovskite structure composed of an alkaline earth metal, Cu and oxygen. 8. The method for producing a superconducting wire according to claim 1, wherein the oxide is a Bi-Ca-Sr-Cu-O-based oxide powder. 9. The method for producing a superconducting wire according to claim 1, wherein the oxide is a Tl-Ca-Ba-Cu-O-based oxide powder. 10. The Ag wire is an Ag composite wire obtained by filling an Ag sheath with the oxide powder according to claim 7, 8, or 9.
2. The method for producing a superconducting wire by the explosion compression method according to claim 1, wherein the cable is an Ag composite wire cable obtained by bundling the Ag composite wires.