JPH07120581B2 - Manufacturing method of superconducting coil by explosive compression method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a superconducting coil 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 is referred to as an R-based oxide) is a liquid nitrogen. It is known to exhibit superconductivity at 77 ° K, where it can be cooled.

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 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. Wrap R type oxide powder filled Ag composite wire (Hereinafter referred to as “R-based oxide-filled coil”), the R-based oxide-filled coil was heat-treated at a temperature of 900 to 950 ° C. in the air or an oxygen atmosphere to produce an R-based oxide superconducting coil. .

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) are liquid nitrogen. Coolable 77 ° K
It was discovered that it exhibits superconductivity at the above temperatures.

First, the Bi-based oxides are Bi ₂ O ₃ powder and CaC as raw material powders.
O ₃ powder, SrCO ₃ powder and CuO powder are prepared, these raw material powders are mixed in a predetermined ratio and mixed, and the 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
The system oxides are Tl ₂ O ₃ powder, CaCO ₃ powder, Ba as raw material powder.
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.
Fill each of the Tl-based oxide powders into Ag tubes and
After sealing both ends of a Bi-based oxide powder-filled Ag tube or Tl-based oxide powder-filled Ag tube, these are wire-drawn to have a diameter of 5 mm or less and Bi-based oxide powder-filled Ag composite wire or Tl-based oxide. As a powder-filled Ag composite wire, these Ag composite wires are wound, and a Bi-based oxide powder-filled Ag composite wire coil (hereinafter referred to as Bi-based oxide-filled coil) or a Tl-based oxide-filled Ag composite wire coil (hereinafter, referred to as Tl-based oxide-filled coil) and the above Bi-based oxide-filled coil or
A Bi-based oxide superconducting coil or a Tl-based oxide superconducting coil was manufactured by heat-treating a Tl-based oxide-filled coil in the air or an oxygen atmosphere. The heat treatment temperature of the Bi-based oxide superconducting coil is 830 to 870 ° C, and the heat treatment temperature of the Tl-based oxide superconducting coil is 880 to 920 ° C.

[Problems to be Solved by the Invention]

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

With this level of critical current density, it cannot be put to practical use as a superconducting coil.
Attempts have also been made to increase the packing density of superconducting oxide powder by subjecting a Bi-based oxide-filled coil or a Tl-based oxide-filled coil to explosive compression, thereby improving the critical current density. When it is directly explosively compressed, the coil is deformed so that the coil does not have the shape of the coil, cutting occurs at various places, and there is a problem that it cannot be put to practical use as a coil to be incorporated into various industrial electric devices.

[Means for Solving the Problems]

Therefore, the inventors of the present invention have conducted research to obtain a superconducting coil having a higher critical current density that can be put to practical use, and as a result, the above R-based oxide-filled coil, Bi-based oxide-filled coil or Tl A superconducting oxide-filled coil, such as a system oxide-filled coil, is loaded with a pressure medium between the cylindrical outer mold and the pipe, between the pipe and between the pipe and the mandrel, and then between the pipes. By filling explosive and exploding the explosive, the superconducting oxide-filled coil can be explosively compressed and densified without deformation and cutting. It has been found that a superconducting coil obtained by heat treatment 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 coil by 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 superconducting oxide-filled coil is set in order to explosively compress the superconducting oxide-filled coil by the explosive compression method, and FIG. 2 is a superconducting oxide-filled coil. FIG. 2 is a plan view of the II-II cross section in FIG.

1 and 2, 1 is a cylindrical outer mold, 2 is a first tube, 3 is a second tube, 4 is a large-diameter superconducting oxide-filled coil,
4'is a small diameter superconducting oxide filled coil, 5 is a mandrel,
6 is a substrate, 7 is a pressure medium, 8 is a lid, 9 is explosive, and 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, ceramic pipes, cardboard pipes and the like 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 2. 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 size: 1 to 1,00
A powder that is hard to solidify by explosive compression of 0 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 these oxides, and Al.
N, TiN, 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, Z
Also used are silicide powders such as rSi, and solid solution powders such as carbonitride powders and carbon boride powders.

The setting of the superconducting oxide-filled coil 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. Inside the cylindrical outer mold 1 placed above, the first tube 2,
The second pipe 3 and the mandrel 5 are concentrically charged and installed.

A large diameter superconducting oxide-filled coil 4 having a diameter smaller than the inner diameter of the cylindrical outer mold 1 and larger than the outer diameter of the first pipe 2 is provided between the cylindrical outer mold 1 and the first pipe 2 in powder form. A small-diameter superconducting oxide-filled coil 4'having a diameter smaller than the inner diameter of the second tube and larger than the diameter of the mandrel is charged together with the pressure medium 7 and the second tube 3 and the mandrel 5 are provided.
During this period, the powdery pressure medium 7 is charged. It is preferable that the powdery pressure medium is filled more densely by applying vibration or the like.

In this way, the large-diameter superconducting oxide-filled coil 4, the small-diameter superconducting oxide-filled coil 4'and the powdery pressure medium 7 are charged, and then the lid 8 is closed. The lid 8 is provided to separate the powder 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 superconducting oxide-filled coils 4, 4'and the powdery pressure medium 7 and closing the lid 8, an 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. First tube 2
When the explosive charged between the second tube 3 and the second tube 3 explodes, the large-diameter superconducting oxide-filled coil 4 and the small-diameter superconducting oxide-filled coil 4 ′ embedded in the powdery pressure medium 7 are cut and deformed. Without this, the superconducting oxide powder with which the coil is filled is uniformly explosively compressed from the surroundings, and is compressed to a higher density. Particularly, in the apparatus used in the present invention, superconducting oxide-filled coils having different diameters can be explosively compressed by one explosion. Although two pipes, the first pipe 2 and the second pipe 3, are used in FIGS. 1 and 2 above, the number of pipes is not limited to this, and the third pipe and the fourth pipe are used. Tube, fifth tube and sixth tube (not shown), an even number of tubes are loaded into a cylindrical outer mold, and two or more superconducting oxide-filled coils with different diameters are blown by one explosion. Explosive compression can be used to increase the density.

〔Example〕

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

Example 1 As raw material powders, 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 (CuO) powder having an average particle size: 6 μm , And mix these powders in a molar ratio of Y ₂ O ₃ : BaCO ₃ : CuO = 1/2: 2: 3, and mix them. : Calcination at 900 ° C for 12 hours is carried out to produce a compound having a composition of YBa ₂ Cu ₃ O ₇ and having a perovskite structure (hereinafter referred to as Y-based oxide), and further crushing these compounds. Then, a Y-based oxide powder having an average particle diameter of 1.3 μm was produced.

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

The Y-based oxide-filled Ag composite wire was wound to produce a large-diameter Y-based oxide-filled coil having an inner diameter of 90 mm and a small-diameter Y-based oxide-filled coil having an inner diameter of 10 mm.

On the other hand, as the cylindrical outer mold 1, outer diameter: 180 mm × inner diameter: 100 mm ×
A steel cylinder mold having a height of 130 mm is prepared, and this steel cylinder mold is placed on the steel plate substrate 6 as shown in FIG.
Then, inside the steel cylinder mold, the first pipe 2 made of steel pipe with outer diameter: 80 mm x inner diameter: 75 mm x height: 110 mm, second pipe made of steel pipe with outer diameter: 30 mm x inner diameter: 26 mm x height: 110 mm Tube 3, mandrel 5 made of round steel rod with a diameter of 8 mm and a height of 110 mm is 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.

The large-diameter Y-based oxide-filled coil is provided between the steel cylindrical mold that is the cylindrical outer die 1 and the steel pipe first pipe 2, and between the steel pipe second pipe 3 and the mandrel 5, respectively. 4 and a small diameter Y-based oxide-filled coil 4 ', and
Filled with SiC powder having an average particle diameter of 2 μm, and further vibrated to insert the SiC powder so that it becomes sufficiently dense, and then the lid 8
Did. The lid 8 may be made of cardboard.

The above-mentioned SiC powder is a powder that is hard to solidify even if explosive compressed,
Moreover, since it is a powder that is easily available, it is one of the most preferable powders as a pressure medium.

After filling the above SiC powder and closing the lid 8, explosives (explosion speed: 2,30
(0 m / sec) 9 is filled between the first pipe 2 made of steel pipe and the second pipe 3 made of steel pipe, and an explosive device 10 is used to explode the large diameter Y.
The system oxide-filled coil 4 and the small diameter Y-system oxide-filled coil 4'were explosively compressed at the same time.

The explosively compressed large-diameter Y-based oxide-filled coil 4 and small-diameter Y-based oxide-filled coil 4 ′ were taken out and heat-treated in a furnace in an oxygen atmosphere at a temperature of 920 ° C. for 24 hours to obtain a large diameter. A Y-based oxide superconducting coil and a small-diameter Y-based oxide superconducting coil were produced, and the superconducting properties of these superconducting coils were measured and shown in Table 1.

Example 2 As a raw material powder, Bi ₂ O _{3 having an} average particle size of 10 μm or less was used.
Prepare powder, CaCO ₃ powder, SrCO ₃ powder and CuO powder,
These powders are Bi ₂ O ₃ powder: 53.4%, CaCO ₃ powder: 11.5%,
SrCO ₃ powder: 16.9% and CuO powder: 18.2% (above weight%)
To obtain a Bi-based oxide, which is then subjected to a firing treatment in the atmosphere at a temperature of 800 ° C. for 12 hours to prepare a Bi-based oxide, which is then obtained by the firing treatment. The obtained Bi-based oxide was pulverized to produce a Bi-based oxide powder having an average particle diameter of 5 μm.

The above Bi-based oxide powder, inner diameter: 20 mm × wall thickness: 1.5 mm × length:
Fill a 200 mm Ag tube, swage this Ag tube, and then groove roll it.
A Bi-based oxide-filled Ag composite wire was prepared.

The above Bi-based oxide-filled Ag composite wire was wound to produce a large-diameter Bi-based oxide-filled coil with an inner diameter of 90 mm and a small-diameter Bi-based oxide-filled coil with an inner diameter of 10 mm.

The large-diameter Bi-based oxide-filled coil and the small-diameter Bi-based oxide-filled coil were charged as shown in FIG. 1, subjected to explosive compression under exactly the same conditions as in Example 1, and then taken out, in an oxygen atmosphere, Heat treatment was carried out at a temperature of 850 ° C. for 15 hours to prepare a large-diameter Bi-based oxide superconducting coil and a small-diameter Bi-based oxide superconducting coil.

Then, the superconducting characteristics of these superconducting coils were measured, and the results are shown in Table 1.

Example 3 As a raw material powder, Tl ₂ O _{3 having an} average particle size of 10 μm or less was used.
Prepare 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, inner diameter: 20 mm × wall thickness: 1.5 mm × length:
Fill a 200 mm Ag tube, swage this Ag tube, and then groove roll it.
A Tl-based oxide-filled Ag composite wire was prepared.

The above Tl-based oxide-filled Ag composite wire was wound to produce a large-diameter Tl-based oxide-filled coil with an inner diameter of 90 mm and a small-diameter Tl-based oxide-filled coil with an inner diameter of 10 mm.

The large-diameter Tl-based oxide-filled coil and the small-diameter Tl-based oxide-filled coil were charged as shown in FIG. 1, subjected to explosive compression under exactly the same conditions as in Example 1, and then taken out, in an oxygen atmosphere, Heat treatment was carried out under the conditions of a temperature of 900 ° C. and a holding time of 3 hours to produce a large diameter Tl-based oxide superconducting coil and a small diameter Tl-based oxide superconducting coil.

Then, the superconducting characteristics of these superconducting coils were measured, and the results are shown in Table 1.

From the results shown in Table 1, the superconducting coil manufactured by the explosive compression method of the present invention has an extremely excellent critical current as compared with the conventional superconducting coil shown in the above [Problems to be solved by the invention]. It can be seen that it has a density.

In addition, in these Examples 1-3, 2 of a 1st pipe and a 2nd pipe is used.
Although the case where the individual steel pipes are charged into the cylindrical outer mold is shown, the number of the above pipes is not limited to the above-mentioned embodiment, and is generally 2n (where n is a positive integer). With this tube, 2n-1 superconducting oxide-filled coils can be explosively compressed at the same time.

〔The invention's effect〕

According to the present invention, it is possible to simultaneously manufacture a plurality of superconducting coils having different diameters and having an extremely excellent high critical current density that can be put to practical use, which greatly contributes to industrial development.

[Brief description of drawings]

FIG. 1 is a sectional elevation view showing a state in which a superconducting oxide-filled coil is set in a cylindrical outer die for explosive compression, and FIG. 2 is a II-II sectional view of FIG. 1, 1: Cylindrical outer type, 2: First tube 3: Second tube 4: Large diameter superconducting oxide filled coil 4 ': Small diameter superconducting oxide filled coil 5: Mandrel, 6: Substrate 7: Pressure medium, 8: Lid 9: Explosives, 10: Detonator

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location H01B 13/00 565 D (72) Inventor Hideki Tonda 4-2, Higashimachi, Kumamoto-shi, Kumamoto Prefecture 6 ― 201 (72) Inventor Kazuki Takashima 1000-10 Yasukubohonmachi, Kumamoto City, Kumamoto Prefecture Hirai Heights 401 (56) Reference JP-A-1-112709 (JP, A) JP-A-63-287010 (JP, A) Special Kai 64-9861 (JP, A) JP-A-63-222063 (JP, A)

Claims (9)

[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 smallest inner diameter 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. In between, superconducting oxide powder filled Ag
A coil obtained by winding the composite wire (hereinafter referred to as a coil) and a pressure medium are charged so that the coil is embedded in the pressure medium, and further, an explosive is filled between the tubes, The superconductivity by the explosive compression method, characterized in that the coil is explosively compressed and densified by detonating the explosive, and then the explosively compressed and densified coil is heat-treated in air or oxygen atmosphere. Coil 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 the cylindrical outer mold and the first pipe. In between, and between the second tube and the mandrel, the coil and the pressure medium, respectively, is charged so that the coil is embedded in the pressure medium,
The explosive compression method according to claim 1, further comprising filling an explosive between the first tube and the second tube, and exploding the explosive to explodely compress and densify the coil. Superconducting coil manufacturing method. 3. The method for producing a superconducting coil by the explosion compression method according to claim 1, wherein the outer cylindrical mold is a cylindrical mold. 4. The method for producing a superconducting coil by the explosive compression method according to claim 1, wherein the cylindrical outer mold is a cylindrical reinforced concrete mold. 5. The pressure medium has an average particle size of 1 to 1,000 μm.
3. The method for producing a superconducting coil by the explosive compression method according to claim 1 or 2, wherein the powder is a powder which is hard to be solidified by the explosive compression. 6. The superconducting oxide powder is a compound powder having a perovskite structure composed of a rare earth element containing Y, an alkaline earth metal, Cu and oxygen. Alternatively, a method for manufacturing a superconducting coil by the explosive compression method described in 5 above. 7. The superconducting oxide powder is Bi-Ca-Sr-Cu.
-O-based oxide powder, Claims 1, 2, 3,
A method for manufacturing a superconducting coil by the explosion compression method described in 4 or 5. 8. The superconducting oxide powder is Tl-Ca-Ba-Cu.
-O-based oxide powder, Claims 1, 2, 3,
A method for manufacturing a superconducting coil by the explosion compression method described in 4 or 5. 9. The method for producing a superconducting coil according to claim 1 or 2, wherein the pressure medium is a fluid.