JP2536080B2 - 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 contained in 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 coil using the above R-based oxide powder, first, 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-based oxide is crushed to have an average particle size of 10 μm or less to form R-based oxide powder, and the R-based oxide powder is filled in an Ag tube, and both ends of the R-based oxide powder-filled Ag tube are sealed. After that, wire drawing processing such as swaging, groove roll processing, or die processing is performed to form an R-based oxide-filled Ag composite wire with a diameter of 5 mm or less, and the R-based oxide-filled Ag composite wires are bundled together. R-type oxide-filled Ag composite wire cable (below , R-type oxide-filled cable) and heat-treat the R-type oxide-filled Ag composite wire and the R-type oxide-filled cable at a temperature of 900 to 950 ° C. in the air or oxygen atmosphere. Manufactured wires and R-based oxide superconducting cables.

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.

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
BaCO 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
It is prepared by carrying out a firing treatment in the atmosphere at a temperature within the range of 700 ° C. for 4 to 12 hours.

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 filled Ag composite wire or
A Tl-based oxide-filled Ag composite wire, and these Ag composite wires are bundled to form a Bi-based oxide-filled Ag composite wire cable (hereinafter referred to as Bi-based oxide-filled cable) or a Tl-based oxide-filled Ag composite wire cable ( (Hereinafter referred to as Tl-based oxide-filled cable), and the above Bi-based oxide-filled Ag composite wire, Bi-based oxide-filled cable, Tl-based oxide-filled Ag composite wire, and Tl-based oxide-filled cable in the atmosphere or oxygen atmosphere. By heat-treating in it, Bi-based oxide superconducting wire, Bi-based oxide superconducting cable, Tl-based oxide superconducting wire and Tl-based oxide superconducting cable were manufactured.
The heat treatment temperature of the Bi-based oxide superconducting wire or cable is 830 to 870 ° C, and the heat treatment temperature of the Tl-based oxide superconducting wire or cable is 880 to 920 ° C.

[Problems to be Solved by the Invention]

However, the critical current density of the R-based oxide superconducting wire or cable obtained by the above conventional manufacturing method is
It is as high as about 700 A / cm ² , and the critical current density of Bi-based oxide superconducting wire or cable manufactured by the conventional manufacturing method shows only 100 A / cm ² at most, and further, it can be obtained by the conventional manufacturing method. The obtained Tl-based oxide superconducting wire or cable has a critical current density of up to about 180 A / cm ² .

Since it cannot be put to practical use as a superconducting wire with such a critical current density, R-based oxide-filled Ag composite wire, R-based oxide-filled cable, Bi-based oxide-filled Ag composite wire, and Bi-based oxide-filled cable. , Tl-based oxide-filled Ag composite wires, Tl-based oxide-filled cables, etc. have been subjected to explosive compression to increase the packing density of superconducting oxide powders, thereby attempting to improve the critical current density. In the above-mentioned attempt, the superconducting oxide-filled Ag composite wire or the superconducting oxide-filled cable is surrounded by a direct explosive and explosively compressed, and the superconducting oxide-filled Ag composite wire or the superconducting oxide-filled cable is directly explosive. When surrounded and explosively compressed, the R-type, Bi-type, or Tl-type superconducting oxide powder filled in the above-mentioned superconducting oxide-filled Ag composite wire or superconducting oxide cable. Moiety pores or voids are generated in a sufficient density can not be obtained a high critical current density superior to not be obtained, further breaking occurred frequently, and explosives
Since a chemical reaction occurs with the Ag sheath and the surface of the Ag sheath is corroded, a superconducting wire that can be put to practical use cannot be obtained.

[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 R-based oxide-filled Ag composite wire and the Bi-based oxide-filled Ag
Explosion compression by loading composite wire, Tl-based oxide-filled Ag composite wire, R-based oxide-filled cable, Bi-based oxide-filled cable, Tl-based oxide-filled cable, etc. into a long groove together with a pressure medium. Since it was found that it is possible to obtain a superconducting wire having an excellent high critical current density without severing the pores or voids in the filled superconducting oxide, and without cutting. is there.

The present invention has been made based on such knowledge, and a superconducting oxide-filled Ag composite wire or a superconducting oxide-filled cable is inserted into a long groove together with a pressure medium to cover the whole long groove. After placing a lid on the lid, place an explosive on the lid and explode the explosive to explode and compress the superconducting oxide-filled Ag composite wire or superconducting oxide-filled cable to densify it. It is characterized by a method for producing a superconducting wire by an explosive compression method, in which a superconducting oxide-filled Ag composite wire or a superconducting oxide-filled cable that has been densified by explosion compression is heat-treated in the air or an oxygen atmosphere.

A method for manufacturing a superconducting wire by the explosion compression method of the present invention will be specifically described with reference to the drawings.

FIG. 1 is a perspective view of a long bottomed mold used in the present invention, and FIG. 2 is a long groove of a long bottomed mold in which a superconducting oxide-filled Ag composite wire is loaded together with a pressure medium. Then, the lid is closed, and a cross-sectional view of the state in which the explosive is placed on the lid, FIG. 3 is a view showing that a superconducting oxide-filled cable is loaded into a long groove of a long bottomed mold together with a pressure medium, FIG. 3 is a cross-sectional view of a state in which a lid is put on and an explosive is placed on the lid.

1 to 3, 1 is a long bottomed mold, 2 is a long groove, 3 is a pressure medium, 4 is a superconducting oxide-filled Ag composite wire, 5 is a superconducting oxide-filled cable, 6 is a lid, 7 is an explosive, and 8 is a detonator.

The long bottomed mold 1 is preferably made of cast steel,
It may be made of reinforced concrete. The long groove 2 provided in the long bottomed mold 1 may be a U-shaped groove in cross section or a V-shaped groove in cross section, and the long groove 2 may be, for example, one excavated in rock. Good. The pressure medium 3 may be a fluid, but a powder having an average particle diameter of 1 to 1000 μm which is hard to be solidified by explosive compression, for example, oxide powder such as Al ₂ O ₃ , SiO ₂ , MgO, ZrO _{2 and the} like. Complex oxide powder, AlN, TiN, Si ₃ N ₄ etc. nitride powder, TiB ₂ , ZrB ₂ , MoB etc. boride powder, MoSi ₂ , TiSi, ZrSi etc. silicide powder, other carbonitride powder Solid solution powder such as is used.
Further, it may be a mixture of the fluid and the powder.

The lid 6 can be made of a metal plate such as a steel plate, a plastic plate, a glass plate, a ceramics plate, and a cardboard.

 The explosive compression of the present invention is carried out as follows.

First, after inserting the superconducting oxide-filled Ag composite wire 4 or the superconducting oxide-filled cable 5 together with the pressure medium 2 into the long groove 2 of the long bottomed mold 1 shown in FIG. As shown in FIG. 2 or FIG. 3, when the explosive 7 is placed on the lid 6 and the explosive 7 is detonated by the detonator 8, the plane shock wave generated is passed through the pressure medium 3 and superconducting oxide-filled Ag composite. It propagates to the wire 4 or the superconducting oxide-filled cable 5 to increase the density. The pressure medium 2 is preferably packed as closely as possible. Therefore, it is preferable to apply vibration or the like after filling the long groove 2 with the pressure medium.

When a metal plate is used for the lid 6, a solid powder used as a pressure medium is used so that the metal plate lid 6 does not come into pressure contact with the upper end of the long bottomed die 1 due to the explosion of the explosive 7. It is preferable to interpose it on the upper end of the bottomed mold 1.

The superconducting oxide-filled Ag composite wire or the superconducting oxide-filled cable that has been explosively compressed and densified as described above is
It is taken out of the long bottomed die 1 and heat-treated in the air or in an oxygen atmosphere to obtain a superconducting wire having an excellent critical current density.

〔Example〕

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

Example 1 and Conventional Example 1 As raw material powders, yttrium oxide (Y ₂ O ₃ ) powder having an average particle size of 6 μm, barium carbonate (BaCO ₃ ) powder having an average particle size of 6 μm, and copper oxide ( CuO) powder was prepared, and these powders were mixed and mixed so that the molar ratio was Y ₂ O ₃ : BaCO ₃ : CuO = 1/2: 2: 3. Calcined under the conditions of temperature: 900 ℃, 12 hours hold, YBa ₂ Cu
A compound having a composition of ₃ O ₇ and having a perovskite structure (hereinafter referred to as a Y-based oxide) was prepared, and these compounds were pulverized to prepare a Y-based oxide powder having an average particle diameter of 1.3 μm. did.

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. 24 Y-based oxide-filled Ag composite wires were bundled to produce a Y-based oxide-filled cable.

Next, the above Y-based oxide-filled Ag composite wire and Y-based oxide-filled cable were placed in the long grooves of a cast steel long bottomed mold,
As shown in FIG. 2 and FIG. 3, respectively, with the SiC powder pressure medium having an average particle diameter of 2 μm, the length direction of the Y-based oxide-filled Ag composite wire and the Y-based oxide-filled cable is the above-mentioned long length. It was charged so as to be parallel to the longitudinal direction of the groove, and was further vibrated to sufficiently fill the SiC powder, and then the lid 6 was placed.

Explosive 7 (explosion speed: 2300 m / sec) was placed on the lid, and exploded by the detonator 8 to perform explosive compression.

The Y-oxide-filled Ag composite wire and the Y-oxide-filled cable that were blast-compressed and densified, and the Y-oxide-filled Ag composite wire and the Y-oxide-filled cable that were not explosion-compressed were both placed in an oxygen atmosphere. Medium, temperature: 920 ℃,
Y-type oxide superconducting wire and Y-type oxide superconducting cable heat-treated under the condition of holding for 24 hours and Y-type oxide superconducting cable (Example 1), and Y-type oxide superconducting wire and Y-type oxide not subjected to explosive compression A superconducting cable (conventional example 1) was produced, and the superconducting characteristics of these 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 CrO powder: 19.9% (above weight%), 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.

7 Bi-based oxide-filled Ag composite wires were bundled to form a Bi-based oxide-filled cable, and the Bi-based oxide-filled Ag composite wire and Bi-based oxide-filled cable were exploded under exactly the same conditions as in Example 1. Take out after compressing, along with the Bi-based oxide-filled Ag composite wire and Bi-based oxide-filled cable that are not subjected to the above-mentioned explosive compression, in an oxygen atmosphere, temperature: 850 ° C, 15
A Bi-based oxide superconducting wire and a cable (Example 2) that were heat-treated under the conditions of holding time and subjected to explosive compression, and a Bi-based oxide superconducting wire and a cable that did not undergo explosive compression (Conventional Example 2) were produced, These superconducting properties were 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.
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 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 was swaged. After that, groove rolling was performed to produce a Tl-based oxide-filled Ag composite wire having a diameter of 2 mm.

Seven Tl-based oxide-filled Ag composite wires were bundled to form a Tl-based oxide-filled cable, and the Tl-based oxide-filled Ag composite wire and Tl-based oxide-filled cable exploded under exactly the same conditions as in Example 1. After compressing, take out, and together with the Tl-based oxide-filled Ag composite wire and Tl-based oxide-filled cable that have not been subjected to the above-mentioned explosive compression, in an oxygen atmosphere, temperature: 900 ° C, 3
It heat-processed on the condition of time holding.

The superconducting properties of the thus obtained explosive-compressed Tl-based oxide superconducting wire and cable (Example 3) and the non-explosive-compressing Tl-based oxide superconducting wire and cable (Conventional example 3) were measured. The results are shown in Table 1.

From the results shown in Table 1 above, it is understood that the explosive-compressed superconducting wire of the present invention has a remarkably excellent critical current density as compared with the conventional example.

[Advantages of the Invention] When the superconducting oxide-filled wire and cable are embedded in a long groove together with a pressure medium and explosively compressed, the wire and cable can be densified without being cut, and the critical current density is remarkably high. It is possible to obtain excellent superconducting wire and to put it to practical use, which greatly contributes to the development of industry.

[Brief description of drawings]

FIG. 1 is a perspective view of a long bottomed mold used in the present invention, and FIG. 2 is a cross-sectional view of the long bottomed mold in which a superconducting oxide-filled Ag composite wire is charged together with a pressure medium. FIG. 3 is a sectional view showing a state in which a superconducting oxide-filled cable is charged together with a pressure medium. 1: Long bottomed mold, 2: Long groove 3: Pressure medium 4: Superconducting oxide filled Ag composite wire 5: Superconducting oxide filled cable 6: Lid, 7: Explosive 8: 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 superconducting oxide-filled Ag composite wire (hereinafter referred to as a wire) is loaded into a long groove together with a pressure medium, a lid covering the whole long groove is provided, and then an explosive is placed on the lid. Is placed and the explosive is exploded to explodely compress the wire to densify it, and then the explosively compressed and densified wire is heat-treated in air or oxygen atmosphere. Manufacturing method of superconducting wire by explosive compression method. 2. A superconducting oxide-filled cable (hereinafter referred to as a cable) in which the wires are bundled is loaded into a long groove together with a pressure medium, and a lid covering the whole long groove is provided, and then the lid is covered. By placing an explosive on top of it and exploding the explosive, the cable is explosively compressed and densified, and then the explosively compressed and densified cable is heat treated in air or oxygen atmosphere. Characteristic method of manufacturing superconducting wire by explosive compression method. 3. The method for producing a superconducting wire according to claim 1 or 2, wherein the pressure medium is a powder having an average particle diameter of 1 to 1000 μm which is hard to be solidified by explosive compression. 4. The pressure medium is a fluid or a mixture of a fluid and the powder, according to claim 1 or 2.
A method for producing a superconducting wire by the described explosion compression method. 5. The superconducting oxide with which the wire or cable is filled is a compound powder having a perovskite structure composed of a rare earth element containing Y, an alkaline earth metal, Cu and oxygen. A method for manufacturing a superconducting wire by the explosive compression method described in 1, 2, 3 or 4. 6. The superconducting oxide with which the wire or cable is filled is a Bi—Ca—Sr—Cu—O-based oxide powder, according to claim 1, 2, 3 or 4. Manufacturing method of superconducting wire by explosive compression method. 7. The superconducting oxide with which the wire or cable is filled is a Tl—Ca—Ba—Cu—O-based oxide powder, according to claim 1, 2, 3, or 4. Manufacturing method of superconducting wire by explosive compression method. 8. The explosion compression method according to claim 1, wherein the elongated groove has a U-shaped or V-shaped cross section and is provided in an elongated bottomed mold. Manufacturing method of superconducting wire. 9. The explosive compression method according to claim 1, wherein the long groove has a U-shaped or V-shaped cross section and is provided in a long bottomed reinforced concrete mold. Manufacturing method of superconducting wire. 10. The long groove is a long hole having a U-shaped or V-shaped cross section, which is dug in a rock.
A method for producing a superconducting wire by the explosive compression method described in 2, 3, or 4. 11. The method for producing a superconducting wire by the explosive compression method according to claim 1, 2, 3 or 4, wherein the wire or cable is charged together with a pressure medium along the longitudinal direction of the elongated groove. Law.