JP2545938B2 - 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.

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. Oxide-filled wire rods such as material-filled wire rods, Bi-based oxide-filled wire rods, and Tl-based oxide-filled wire rods are directly surrounded by explosives and explosively compressed, resulting in pores in the oxide powder portion filled in the oxide-filled wire rods. Or, 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 charged into a void consisting of a large-diameter cylinder and a small-diameter cylinder together with a pressure medium, and an explosive is exploded simultaneously outside the large-diameter cylinder and inside the small-diameter cylinder. Therefore, it was found that the oxide-filled wire can be densified without cutting and a superconducting wire having an extremely high high critical current density can be obtained.

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 large-diameter cylinder, 2 is a small-diameter cylinder, 3 is an oxide-filled wire rod, 4 is a pressure medium, 5 is a cardboard container, 6 is explosive, 7 is a detonator, and 8 is a lid. is there.

The large-diameter cylinder 1 and the small-diameter cylinder 2 are preferably made of a metal such as steel or Al or an alloy thereof, but are not limited to the above metals and alloys, and plastic, tempered glass, ceramics, cardboard, etc. are used. It is also possible.

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, TiN, nitride powders such as Si ₃ N ₄ , and TiB ₂ , ZrB ₂ , MoB etc. boride powder, SiC, TiC, ZrC, WC etc. carbide powder, MoSi ₂ , TiSi, ZrSi etc. silicide powder, other carbonitride powder, carbon boride powder etc. solid solution powder Is used. Further, it may be a mixture of the above fluid and powder.

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

First, a cardboard container 5 is prepared, and a large-diameter cylinder 1 and a small-diameter cylinder 2 are vertically installed concentrically in the cardboard container 5,
A space is formed between the large diameter cylinder 1 and the small diameter cylinder 2. The pressure medium 4 and the oxide-filled wire 3 are charged into the void. After the pressure medium 4 is charged, it is preferable that the pressure medium 4 be vibrated and filled so as to have a sufficiently high density.

After the pressure medium 4 and the oxide-filled wire 3 are charged into the gap, the ring-shaped lid 8 is closed. The lid 8 is preferably fixed to the large diameter cylinder 1 and the small diameter cylinder 2 with an adhesive, an adhesive tape or the like.

After the lid 8 is closed, the cardboard container 5 is filled with the explosive 6 and exploded by the detonator 7 to explodely compress and densify the oxide-filled wire without cutting it, and then explode and compress to increase the density. The densified oxide-filled wire can be taken out and heat-treated in the air or an oxygen atmosphere to produce a superconducting wire having a particularly high critical current density.

In FIG. 1 and FIG. 2 described above, two cylinders (large diameter cylinder and small diameter cylinder) having different diameters are used for explosive compression, but the present invention is not limited to this, and in the present invention, different diameters are used. By using 2n (where n is a positive integer) cylinders, a plurality of types of oxide-filled wire rods can be explosively compressed at the same time.

〔Example〕

First, the present invention will be described more specifically based on examples.

Example 1 and Comparative Example 1 As raw material powders, yttrium oxide (Y ₂ O ₃ ) powder having an average particle size: 6 μm, barium oxide (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, prepare a cardboard container 5 made of cardboard with a thickness of 0.5 mm, and in the cardboard container 5 described above, an outer diameter: 75 mm × an inner diameter: 70 mm × a length: 1,100 mm of a steel pipe large-diameter cylinder 1, and A small-diameter steel pipe cylinder 3 having an outer diameter of 45 mm, an inner diameter of 40 mm, and a length of 1,100 mm was vertically installed in a concentric shape.

A Y-based oxide-filled Ag composite wire 3 and a SiC powder pressure medium 4 having an average particle diameter of 2 μm were charged into the void formed by the steel pipe large-diameter cylinder 1 and the steel pipe small-diameter cylinder 2 and further vibrated. After filling the SiC powder so as to be sufficiently dense, the lid 8 was put on. The lid 8 is an adhesive, and the large diameter cylinder 1 made of steel pipe is used.
And the small diameter cylinder 2 made of steel pipe.

Next, the cardboard container 5 is filled with the explosive 6 and the explosive 6 is arranged outside the steel pipe large-diameter cylinder 1 and inside the steel pipe small-diameter cylinder 2 to explode it by the detonator 7 to generate the Y system. The oxide-filled Ag composite wire 3 was blast-compressed and densified.

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.
And the oxide-filled wire 3 of FIG. 1 and FIG.
At the position of the above Y-based oxide-filled Ag composite wire cable
It was charged together with SiC powder and explosive-compressed and densified in the same manner as the Y-based oxide-filled Ag composite wire.

The above Y-oxide-filled Ag composite wire and its cable, which have been densified by explosion compression, and the Y-oxide-filled Ag composite wire and its cable, which are not explosion-compressed, are both kept in an oxygen atmosphere at a temperature of 920 ° C for 24 hours. Of the Y-based oxide superconducting wire and cable (Example 1) that were heat-treated under the conditions of No. 1 and Explosive compression, and the Y-based oxide superconducting wire and cable (Conventional example 1) that were not subjected to explosive compression, were prepared. The superconducting properties 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 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, 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 4 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
Bi-based oxide-filled Ag composite wire cables and non-explosive-compressed Bi-based oxide-filled Ag composite wires and Bi-based oxide-filled Ag composite wire cables in oxygen atmosphere at temperature: 850
Bi that has been heat-treated under the conditions of 15 ℃ for 15 hours and explosive compressed
-Based oxide superconducting wire and Bi-based oxide superconducting cable (Example 2), and Bi-based oxide superconducting wire and Bi-based oxide superconducting cable (conventional example 2) that were not subjected to explosive compression were manufactured, and their superconducting characteristics Was measured and the results are shown in Table 1.

Example 3 and Conventional Example 3 As raw material powder, Tl _{2 having an} average particle size of 10 μm or less was used.
Prepare O ₃ powder, CaCO ₃ powder, BaCO ₃ powder and CuO powder,
These powders, Tl ₂ O ₃ powder: 35.4%, CaCO ₃ powder: 15.5%,
BaCO ₃ powder: 30.6% and CuO powder: 18.5% (above wt%)
The mixed powder is mixed and mixed, and the mixed powder is fired in an oxygen atmosphere at a temperature of 800 ° C. for 10 hours to prepare a Tl-based oxide powder, which is then fired. The resulting Tl-based oxide was pulverized to produce a Tl-based oxide powder having an average particle size of 5 μm.

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 4 as shown in FIGS. 1 and 2, explosive compression was performed under the same conditions as in Example 1, and the Tl-based oxide-filled Ag was further added. A cable (not shown) in which the composite wires were bundled was also charged together with the SiC powder at the position of the oxide-filled wire 3 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
Explosion-compressed Tl-based oxide superconducting wire and Tl-based oxide superconducting cable (Example 3), which were heat-treated under conditions of holding at ℃ for 3 hours, and Tl-based oxide superconducting wire and Tl-based wire without explosive compression An oxide superconducting cable (conventional example 3) was produced, and the superconducting properties of the cables were measured, and the results are shown in Table 1.

In the above-mentioned Examples 1 to 3, the cylinder was erected vertically and explosively compressed, but the cylinder was placed horizontally and exploded. It is also possible to compress.

〔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 oxide filled wires are set between cylinders having different diameters for explosive compression, and FIG. 2 is a sectional view taken along line II-II of FIG. 1: Large diameter cylinder, 2: Small diameter cylinder 3: Oxide filled wire, 4: Pressure medium 5: Cardboard container, 6: Explosion 7: Detonator, 8: Lid

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 (8)

(57) [Claims] 1. An even number of cylinders having different diameters are prepared, and by arranging the even number of cylinders vertically in a concentric shape, the concentric voids formed by the inner surface and the outer surface of the even number of cylinders. To form explosives and oxides in the concentrically arranged voids.
Ag wire and pressure medium are alternately filled from the center outward, and an explosive is arranged inside the cylinder having the smallest diameter and outside the cylinder having the largest diameter among the even numbered cylinders, The oxide-filled Ag wire rod is explosively compressed and densified by detonating the explosive, and the oxide-filled Ag wire rod explosively-compressed and densified is heat-treated in the air or an oxygen atmosphere. Method for manufacturing superconducting wire by explosive compression method. 2. A large-diameter cylinder and a small-diameter cylinder having an outer diameter smaller than the inner diameter of the large-diameter cylinder are prepared, the large-diameter cylinder is erected vertically, and the small-diameter cylinder is provided at the center of the large-diameter cylinder. Vertically, while filling the oxide filled Ag wire and pressure medium into the void formed by the inner surface of the large-diameter cylinder and the outer surface of the small-diameter cylinder, and the explosive charge on the outside of the large-diameter cylinder and the inside of the small-diameter cylinder. The oxide-filled Ag wire rod is explosively compressed and densified by detonating an explosive from the outside of the large-diameter cylinder and the inside of the small-diameter cylinder. The method for producing a superconducting wire according to claim 1, wherein the wire is heat-treated in the air or an oxygen atmosphere. 3. The pressure medium has an average particle diameter 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. 4. The method for producing a superconducting wire according to claim 1 or 2, wherein the pressure medium is a fluid. 5. The method for producing a superconducting wire according to claim 1 or 2, wherein the pressure medium is a mixture of a fluid and a powder. 6. The oxide-filled Ag wire rod is obtained by filling a compound powder having a perovskite structure composed of a rare earth element containing Y, an alkaline earth metal, Cu and oxygen, or a bundle of the Ag composite wires. 3. The method for producing a superconducting wire according to claim 1, wherein the superconducting wire is a cable. 7. The oxide-filled Ag wire rod is made of Bi-Ca-Sr-Cu.
The method for producing a superconducting wire according to claim 1 or 2, which is an Ag composite wire filled with -O-based oxide powder or a cable obtained by bundling the Ag composite wire. 8. The oxide-filled Ag wire rod is made of Tl-Ca-Ba-Cu.
The method for producing a superconducting wire according to claim 1 or 2, which is an Ag composite wire filled with -O-based oxide powder or a cable obtained by bundling the Ag composite wire.