JP2545937B2 - 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]

Generally, 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 oxygen (hereinafter, this compound will be referred to as R
It is known that a system oxide) exhibits a superconducting phenomenon at 77 ° K which can be cooled with liquid nitrogen.

As a method for producing a superconducting wire using the above R-based oxide powder, first of all, as raw material powder, R ₂ O ₃ powder having an average particle diameter of 10 μm or less, carbonate powder of alkaline earth metal, and CuO A powder is prepared, these raw material powders are mixed in a predetermined composition, mixed, and fired at a temperature of 850 to 950 ° C. in the air or an oxygen atmosphere to produce an R-based oxide having a perovskite structure. The R-type oxide powder is crushed to an average particle size of 10 μm or less to form an R-type oxide powder, the R-type oxide powder is charged into an Ag tube, and both ends of the R-type oxide powder-filled Ag tube are sealed. After that, wire drawing such as swaging, groove roll processing, or die processing is performed to obtain an R-based oxide powder-filled Ag composite wire having a diameter of 5 mm or less. A bundle of R-based oxide powder-filled Ag composite wires (Hereinafter, cables of R-based oxide powder-filled Ag composite wire and cables of R-based oxide powder-filled Ag composite wire, etc. are referred to as R-based oxide-filled wire), and the above R-based oxide-filled wire is in the atmosphere or oxygen. An R-based oxide superconducting wire was manufactured by heat treatment in an atmosphere at a temperature of 900 to 950 ° C.

Furthermore, in recent years, Bi-Ca-Sr-Cu-O-based oxides (hereinafter referred to as Bi-based oxides) and Tl-Ca-Ba-Cu-O-based oxides (hereinafter referred to as Tl-based oxides) have been cooled with liquid nitrogen. 77 ° K possible
It was discovered that it exhibits superconductivity at the above temperatures.

First, the Bi-based oxides are Bi ₂ O ₃ powder and C as raw material powders.
aCO ₃ powder, SrCO ₃ powder and CuO powder are prepared, these raw material powders are blended in a predetermined ratio and mixed, and this mixed powder is kept in the atmosphere at a temperature of 700 to 800 ° C. for 4 to 12 hours. It is created by firing under the conditions. Further above
Tl-based oxides include Tl ₂ O ₃ powder, CaCO ₃ powder, and Ba as raw material powders.
CO ₃ powder and CuO powder are prepared, these raw material powders are mixed in a predetermined ratio and mixed, and this mixed powder is heated at a temperature of 600 to 70.
It is prepared by carrying out a firing treatment in which the temperature is kept in the range of 0 ° C. for 4 to 12 hours in the atmosphere.

The Bi-based oxide or Tl-based oxide thus prepared is crushed to obtain a Bi-based oxide powder or Tl-based oxide powder having an average particle size of 5 μm or less. Each of the oxide powders was filled in an Ag tube, and both ends of these Bi-based oxide powder-filled Ag tubes or Tl-based oxide powder-filled Ag tubes were sealed, and then wire drawing was performed on them to obtain a Bi-based material having a diameter of 5 mm or less. Oxide powder-filled Ag composite wire or Tl-based oxide powder-filled Ag composite wire, bundled with the above Bi-based oxide powder-filled Ag composite wire and filled with Bi-based oxide powder
An Ag composite wire cable is manufactured (hereinafter, a Bi-based oxide powder-filled Ag composite wire, a Bi-based oxide powder-filled Ag composite wire cable, etc. is referred to as a Bi-based oxide-filled wire), and the above Tl-based oxide powder A bundle of Tl-based oxide powder-filled Ag composite wires is prepared by bundling the filled Ag-composite wires (hereinafter, Tl-based oxide powder-filled Ag composite wires, Tl-based oxide powder-filled Ag composite wire cables, etc. (Filled wire rod),
The Bi-based oxide superconducting wire or the Tl-based oxide superconducting wire is manufactured by heat-treating the Bi-based oxide-filled wire or the Tl-based oxide-filled wire in the air or the oxygen atmosphere, respectively.

The heat treatment temperature of the Bi-based oxide-filled wire is 830 ℃ to 870 ℃.
The heat treatment temperature of the Tl-based oxide-filled wire is 880 ℃ ~ 920
° C.

The critical current density of the R-based oxide superconducting wire obtained by the above conventional manufacturing method is about 700 A / cm ² at the highest,
The Bi-based oxide superconducting wire manufactured by the conventional manufacturing method has a critical current density of at most 100 A / cm ² , and the Tl-based oxide superconducting wire manufactured by the conventional manufacturing method has a maximum of 180 A / cm ^2. It has a critical electrode density of about cm ² .

[Problems to be Solved by the Invention]

However, at this level of critical current density, it cannot be put to practical use as a superconducting wire, so an R-based oxide-filled wire, a Bi-based oxide-filled wire, or a Tl-based oxide-filled wire is directly surrounded by explosives for explosion compression It has been attempted to increase the packing density of the superconducting oxide powder and thereby improve the critical current density, but the above-mentioned R-based oxide-filled wire rod, B-based oxide-filled wire rod, and Tl-based oxide wire have been tried. When an oxide filled wire such as a filled wire is directly surrounded by explosives and explosively compressed, pores or voids are generated in the oxide powder part filled in the oxide filled wire, and sufficient high density cannot be obtained. However, because of this, 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 super-electric wire rod 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 used together with a pressure medium, between the cylindrical outer mold and the tube, between the pipe and the pipe, and between the pipe and the mandrel. By loading along the axial direction, then filling explosive between the pipes and exploding the explosive, the oxide-filled wire can be blast-compressed and densified without cutting. It has been found that a superconducting wire obtained by heat-treating the oxide-filled wire densified by explosive compression in the air or an oxygen atmosphere has an extremely excellent high critical current density.

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.

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

1 and 2, 1 is a cylindrical outer mold, 2 is a first tube, 3 is a second tube, 4 is an oxide-filled wire, 5 is a mandrel, 6 is a substrate, 7 is a pressure medium, and 8 is Lid, 9 is explosive, 10
Is a detonator.

As the cylindrical outer mold 1, a thick cylindrical mold or a cylindrical reinforced concrete mold is used, but a bottomed cylindrical mold or concrete mold may be used. In the case of bottoming, it is not necessary to use the substrate 6. Further, the cylindrical outer mold 1 may be one in which a rock is provided with holes.

The first pipe 2 and the second pipe 3 may be steel pipes.
However, it is not limited to the steel pipe, and other metals or alloys, plastic pipes, reinforced glass pipes, ceramics pipes, cardboard pipes, etc. can be used.

It is necessary that the outer diameter of the first pipe 2 is smaller than the inner diameter of the cylindrical outer mold 1, and the outer diameter of the second pipe 3 is smaller than the inner diameter of the first pipe. Furthermore, the mandrel 5
It is made of a metal or alloy round bar or a ceramic round bar, but its outer diameter needs to be smaller than the inner diameter of the second tube 3.

The pressure medium 7 may be a fluid, but the average particle diameter is 1 to 1,000 μm.
A powder that is hard to solidify by explosive compression of m 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 these oxides, AlN and Ti.
N, Si ₃ N ₄ etc.nitride powder, TiB ₂ , ZrB ₂ , MoB etc. boride powder, SiC, TiC, ZrC, WC etc. carbide powder, MoSi ₂ , TiSi, ZrSi
In addition, a solid solution powder such as a carbonitride powder or a carbon boride powder is also used. Further, it may be a mixture of fluid and powder.

Setting the oxide-filled wire as shown in FIGS. 1 and 2 is performed as follows.

First, the substrate 6 is placed, and the cylindrical outer mold 1 is placed thereon. The first tube 2, the second tube 3, and the mandrel 5 are concentrically charged and installed inside the cylindrical outer mold 1 placed above.

Then, the oxide-filled wire 4 is vertically inserted together with the pressure medium 7 between the cylindrical outer mold 1 and the first tube 2 and between the mandrel 5 and the second tube 3. When the pressure medium 7 is a powder, it is preferable that the pressure medium 7 is vibrated to be packed more densely.

After the oxide-filled wire 4 and the pressure medium 7 are thus charged, the lid 8 is closed. The lid 8 is provided to separate the pressure medium 7 and the explosive 9 to be filled next, and may be implemented without the lid 8 depending on conditions.

After filling the oxide-filled wire 4 and the pressure medium 7 and closing the lid 8, the explosive 9 is filled between the first tube 2 and the second tube 3. The explosive 9 is preferably filled to the extent that it rises above the cylindrical outer mold. The explosive 9 thus filled is detonated by the detonator 10. When the explosive charged between the first tube 2 and the second tube 3 explodes, the oxide-filled wire 4 embedded in the pressure medium 7 is uniformly exploded and compressed from the surroundings without cutting, The oxide powder filled in the oxide-filled wire 4 is compressed to a higher density. Although two pipes, the first pipe 2 and the second pipe 3, are used in FIGS. 1 and 2, the number of pipes is not limited to this, and an even number of pipes may be used as a cylindrical outer pipe. Insert into a mold, install a mandrel in the center, and use a single explosion to create multiple types of oxide-filled wire rods, such as R-based oxide-filled wire rods, Bi-based oxide-filled wire rods, and Tl-based oxide filler wires. Multiple wires can be explosively compressed at the same time to increase the density, and multiple oxide-filled wires arranged in the same ring shape can be densified almost uniformly to obtain a uniform superconducting wire. be able to.

〔Example〕

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

Example 1 As raw material powders, yttrium oxide (Y ₂ O ₃ ) powder having an average particle size of 6 μm, barium carbonate (BaCO3) powder having an average particle size of 6 μm, and copper oxide (CuO) powder having an average particle size of 6 μm were used. These powders were prepared and mixed so that the molar ratio was Y ₂ O ₃ : BaCO ₃ : CuO = 1/2: 2: 3, and the mixed powders were heated in the air at a temperature of: Calcined at 900 ° C for 12 hours, and then YBa ₂
A compound having a composition of Cu ₃ O ₇ and having a perovskite structure (hereinafter referred to as a Y-based oxide) was prepared, and these compounds were crushed to obtain a Y-based oxide powder having an average particle diameter of 1.3 μm. It was made.

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.

Further, seven Y-based oxide-filled Ag composite wires were bundled to produce a Y-based oxide-filled Ag composite wire cable.

On the other hand, as the cylindrical outer mold 1, outer diameter: 180 mm × inner diameter: 100 mm
× Length: 1,300 mm steel cylinder mold is prepared, this steel cylinder mold is installed on the steel plate substrate 6 as shown in FIG. 1, and then the inside of the steel cylinder mold Outer diameter: 80 mm × inner diameter: 75 mm × length: 1,100 mm steel pipe first pipe 2, outer diameter: 30 mm × inner diameter: 26 mm × length: 1,100 mm steel pipe second pipe 3, diameter: 8 mm × A mandrel 5 made of a round steel rod having a length of 1,100 mm was concentrically charged and installed.

The steel cylindrical mold, the first tube 2, the second tube 3 and the mandrel 5 are preferably installed in exactly concentric circles, but it is sufficient to install them in substantially concentric circles.

As shown in FIG. 1 and FIG. 2, between the steel cylindrical mold which is the cylindrical outer die 1 and the steel pipe first pipe 2 and between the mandrel 5 and the steel second pipe 3 as shown in FIGS. System oxide filled Ag
The composite wire was filled with SiC powder having an average particle diameter of 2 μm, and further vibrated to make the SiC powder sufficiently dense, and the lid 8 was closed. It is sufficient to fix the lid 8 with an adhesive or an adhesive tape.

After filling the above-mentioned SiC powder and closing the lid 8, explosive (explosion speed: 2,
(300 m / sec) 9 was filled between the first pipe 2 made of steel pipe and the second pipe 3 made of steel pipe, and was detonated by the detonator 10 to explosively compress the Y-based oxide-filled Ag composite wire.

Y produced by bundling the above Y-based oxide-filled Ag composite wire
A cable (not shown) of Ag-based oxide composite wire filled with
Like the above Y-based oxide-filled Ag composite wire, it was embedded together with SiC powder and subjected to explosive compression.

The explosion-compressed Y-based oxide-filled Ag composite wire and the Y-based oxide-filled Ag composite wire cable are heat-treated in an oxygen atmosphere at a temperature of 920 ° C. for 24 hours to perform heat treatment on the Y-based oxide superconducting wire and the Y-based oxide superconducting wire. A cable of a system oxide superconducting wire was used, and the superconducting properties thereof were measured. The results are shown in Table 1.

Example 2 As a raw material powder, Bi _{2 having an} average particle size of 10 μm or less was used.
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 wt%), and mixed, and this mixed powder was kept 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, seven Bi-based oxide-filled Ag composite wires were bundled to produce a Bi-based oxide-filled Ag composite wire cable.

The Bi-based oxide-filled Ag composite wire 4 was charged together with the SiC powder 7 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 together with the SiC powder at the position of the oxide-filled wire 4 in FIGS. 1 and 2 and subjected to explosive compression.

The above-mentioned explosively compressed Bi-based oxide-filled Ag composite wire and
A Bi-based oxide-filled Ag composite wire cable was heat-treated in an oxygen atmosphere at a temperature of 800 ° C. for 15 hours to prepare a Bi-based oxide superconducting wire and a Bi-based oxide superconducting wire cable.

The superconducting properties of these Bi-based oxide superconducting wires and the cables of the Bi-based oxide superconducting wires were measured, and the results are shown in Table 1.

Example 3 As a raw material powder, Tl _{2 having an} average particle size of 10 μm or less was used.
O ₃ powder, CaCO ₃ powder, BaCO ₃ powder and CuO powder were prepared, and these powders were 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 1.55 mm, and a length of 200 mm, and then 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 of the above Tl-based oxide-filled Ag composite wires were bundled to produce a Bi-based oxide-filled Ag composite wire cable.

The Tl-based oxide-filled Ag composite wire 4 was charged together with the SiC powder 7 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 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
The Tl-based oxide-filled Ag composite wire cable was heat-treated in an oxygen atmosphere at a temperature of 900 ° C for 3 hours to prepare a Tl-based oxide superconducting wire and a Tl-based oxide superconducting wire cable.

The superconducting properties of these Tl-based oxide superconducting wires and cables of the Tl-based oxide superconducting wires were measured, and the results are shown in Table 1.

In the above-mentioned Examples 1 to 3, the cylindrical outer mold was erected vertically and explosively compressed, but the cylindrical outer mold was placed horizontally. It is also possible to perform explosive compression as a state. Further, the number of tubes to be loaded in the cylindrical outer mold is not limited to the two tubes shown in the first to third embodiments, and generally an even number of tubes can be used.

The critical current density of the superconducting wire manufactured by the explosive compression method of the present invention shown in Table 1 is as follows.
Comparing the critical current densities of the conventional superconducting wire rods shown in the above section, it can be seen that the values are remarkably excellent.

〔The invention's effect〕

According to the present invention, a plurality of superconducting wire rods having an extremely high high critical current density that can be put to practical use can be simultaneously produced, which greatly contributes to industrial development.

[Brief description of drawings]

FIG. 1 is a sectional elevation view showing a state of being set in a cylindrical outer die for explosively compressing an oxide-filled wire, and FIG. 2 is a II-II sectional view of FIG. 1: Cylindrical outer mold, 2: First tube 3: Second tube, 4: Oxide filled wire 5: Mandrel, 6: Substrate 7: Pressure medium, 8: Lid 9: Explosive, 10: Detonator

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideki Tonda 4-2, Higashimachi, Kumamoto-shi, Kumamoto 6-201, Higashimachi Minami Housing (201) Inventor Kazuki Takashima 1000-10, Yasukubo, Kumamoto-shi, Kumamoto 401 Hirai Heights 401 ( 56) References 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 (11)

(57) [Claims] 1. A cylindrical outer die, an even number of tubes having an outer diameter smaller than the inner diameter of the cylindrical outer die, and a mandrel having a diameter smaller than the inner diameter of the smallest of the even number of tubes. Prepare the even number of tubes and the mandrel, concentrically charged into the cylindrical outer mold, between the mandrel and the tube, between the tubes, and between the tube and the cylindrical outer mold. An oxide powder-filled wire rod (hereinafter referred to as a wire rod) and a pressure medium are embedded in the pressure medium so that the wire rod is along the axis of the mandrel or the tube, and between the tube and the tube. It is characterized by filling explosives and exploding the explosives to explodely compress and densify the wire, and then heat-treat the explosively compressed and densified wire in air or oxygen atmosphere. Of superconducting wire by explosive compression method Manufacturing method. 2. A cylindrical outer mold, a first pipe having an outer diameter smaller than the inner diameter of the cylindrical outer mold, a second pipe having an outer diameter smaller than the inner diameter of the first pipe, and the first pipe. A mandrel having a diameter smaller than the inner diameter of the two pipes is prepared, and the first pipe, the second pipe, and the mandrel are concentrically charged in the cylindrical outer mold, and Between one pipe, and between the second pipe and the mandrel, the wire rod and the pressure medium, respectively, the wire rod is embedded in the pressure medium so as to be along the axial direction of the mandrel, the first pipe and the second pipe, The explosive compression method according to claim 1, further comprising filling an explosive between the first pipe and the second pipe, and exploding the explosive to explode-compress and densify the wire rod. Superconducting wire manufacturing method. 3. The method for producing a superconducting wire according to claim 1 or 2, wherein the cylindrical outer die is a cylindrical die. 4. The method for producing a superconducting wire according to claim 1 or 2, wherein the cylindrical outer die is a cylindrical reinforced concrete die. 5. The pressure medium has an average particle size of 1 to 1,000 μm.
3. The method for producing a superconducting wire by the explosive compression method according to claim 1 or 2, which is a powder that is hard to solidify by explosive compression. 6. The method for producing a superconducting wire according to claim 1 or 2, wherein the pressure medium is a fluid. 7. The method for producing a superconducting wire according to claim 1 or 2, wherein the pressure medium is a mixture of a powder and a fluid which are hard to be solidified by the explosive compression. 8. The oxide powder is a rare earth element containing Y,
The method for producing a superconducting wire according to claim 1, 2, 3, 4 or 5, which is a compound powder having a perovskite structure composed of an alkaline earth metal, Cu and oxygen. 9. The superconducting wire according to claim 1, 2, 3, 4 or 5, wherein the oxide powder is a Bi-Ca-Sr-Cu-O-based oxide powder. Manufacturing method. 10. The oxide powder is Tl-Ca-Ba-Cu-O.
The method for producing a superconducting wire according to claim 1, 2, 3, 4 or 5, wherein the superconducting wire is a system oxide powder. 11. The wire is an Ag composite wire obtained by filling an Ag sheath with the oxide powder according to claim 8, 9 or 10, or an Ag composite wire cable obtained by bundling the Ag composite wires. The method for producing a superconducting wire by the explosion compression method according to claim 1.