JPH07120580B2 - 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.
m ² and about, the critical current density of the Bi-based oxide resistive coils produced by conventional manufacturing methods, at most 100A / cm ² only shown additionally, Tl-based oxide superconductor obtained by the conventional production methods 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 charged into a ring-shaped gap composed of a pipe and a cylindrical support type together with a pressure medium, and the coil explosively compressed by the explosive filled in the pipe is deformed and The inventors have found that the superconducting oxide powder in the coil can be densified without being cut, and a superconducting coil having an extremely 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 coil by the explosion compression method of the present invention will be specifically described with reference to the drawings.

FIG. 1 is a sectional elevational view showing a state in which the superconducting oxide-filled coil is set in order to explode-compress the superconducting oxide-filled coil by the explosive compression method.
FIG.

FIG. 2 is a plan view of II-II cross section in FIG. 1 in a state in which the superconducting oxide-filled coil is set for explosive compression.

1 and 2, 1 is a cylindrical support type, 2
Is a pressure medium, 3 is a superconducting oxide-filled coil, 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 1,00
A powder that is hard to solidify by explosive compression of 0 μm is preferable.
Examples of these powders include Al ₂ O ₃ , SiO ₂ , MgO, and ZrO _2.
Oxide powders such as and complex oxide powders of those oxides,
Nitride powder such as AlN, TiN, Si ₃ N ₄ , boride powder such as TiB ₂ , ZrB ₂ , MoB, carbide powder such as SiC, TiC, ZrC, WC, MoS
Silicide powders such as i ₂ , TiSi and ZrSi, and solid solution powders such as carbonitride powders are used.

The pipe 5 is preferably a steel pipe, but is not limited to a steel pipe, and other metals or alloys, plastics,
It is also possible to make it with tempered glass, ceramics, cardboard, or the like.

As shown in FIGS. 1 and 2, the superconducting oxide-filled coil is set in the following steps.

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 superconducting oxide-filled coil 3 and the pressure medium 2 are placed in the gap between the cylindrical support mold 1 and the pipe 5. The outer diameter of the superconducting oxide-filled coil 3 must be smaller than the inner diameter of the cylindrical support mold 1 and larger than the outer diameter of the pipe 5. After the charging of the superconducting oxide-filled coil 3 and the pressure medium 2 is completed, it is preferable to apply vibration or the like to more densely fill the pressure medium 2. After charging the superconducting oxide-filled coil 3 and the pressure medium 2, the lid 6
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 in the pipe 5 is detonated, the superconducting oxide-filled coil 3 embedded in the pressure medium 2 is uniformly exploded and compressed without cutting and deformation, and the superconducting oxide filling the coil is filled. The powder is compressed more densely.

〔Example〕

Next, the present invention will be described more specifically 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-type oxide-filled Ag composite wire was wound to produce two Y-type oxide-filled coils having an inner diameter of 90 mm, and one of them was subjected to explosive compression as follows.

First, as the cylindrical support type 1, outer diameter: 180 mm × inner diameter: 100 mm ×
A steel cylinder mold having a height of 130 mm and a steel plate base plate 4 are prepared, and the steel cylinder mold is erected on the steel plate base plate 4 as shown in FIG. Inside the cylindrical mold, a steel pipe 5 having an outer diameter of 69 mm, an inner diameter of 65 mm, and a height of 110 mm and having a height slightly lower than the height of the steel cylindrical mold was placed upright. The steel cylindrical mold and the steel pipe 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.

Average particle size between the steel cylinder mold and the steel pipe: 2
After the SiC powder having a thickness of μm and the above Y-based oxide-filled coil were charged and further vibrated so that the SiC powder became sufficiently dense, the lid 6 was put on. The lid is made of SiC
This is done for the purpose of preventing the powder and the explosive to be filled later from mixing, and can be carried out without a lid depending on the conditions.

After charging the above-mentioned SiC powder and closing the lid 6, explosives (explosion speed: 2,30
(0 m / sec) 7 is filled in the steel pipe 5 and further so as to rise on the upper end of the steel cylindrical mold, and is exploded by the detonator 8 to explosively compress the Y-based oxide-filled coil 3. did.

The explosive-compressed Y-based oxide-filled coil 3 is taken out and heat-treated together with the other non-explosive-compressed Y-based oxide-filled coil in an oxygen atmosphere at a temperature of 920 ° C. for 24 hours to perform explosive compression. A Y-based oxide superconducting coil (Example 1) and a Y-based oxide superconducting coil not subjected to explosive compression (Comparative Example 1) were prepared, and the superconducting characteristics of these two types of superconducting coils were measured. The results are 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.

Wrap the above Bi-based oxide-filled Ag composite wire and have an inner diameter of 90 mm B
Two i-based oxide-filled coils were produced, one of which was placed in the apparatus shown in FIG. 1, subjected to explosive compression under exactly the same conditions as in Example 1, and then taken out, and the above explosive compression was not applied.
With Bi-based oxide-filled coil, temperature: 8 in oxygen atmosphere
Heat-treated under conditions of holding at 50 ℃ for 15 hours and subjected to explosive compression
Bi-based oxide superconducting coils (Example 2) and Bi-based oxide superconducting coils not subjected to explosive compression (Comparative Example 2) were prepared, and the superconducting characteristics of these superconducting coils were measured. The results are shown in Table 1. Indicated.

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, The filled Ag tube was swaged and then groove-rolled to produce a Tl-based oxide-filled Ag composite wire having a diameter of 2 mm.

Wrap the above Tl-based oxide-filled Ag composite wire and the inner diameter: 90 mm of T
Two l-type oxide-filled coils were prepared, one of which was placed in the apparatus shown in FIG. 1, subjected to explosive compression under the exact same conditions as in Example 1, and then taken out, and the above explosive compression was not applied.
Temperature: 9 in oxygen atmosphere with Tl-based oxide-filled coil
Heat-treated under conditions of holding at 00 ℃ for 3 hours and subjected to explosive compression
A Tl-based oxide superconducting coil (Example 3) and a Tl-based oxide superconducting coil not subjected to explosive compression (Comparative Example 3) were produced, and the superconducting characteristics of these superconducting coils were measured. The results are shown in Table 1. Indicated.

〔The invention's effect〕

When a superconducting oxide-filled coil is charged with a pressure medium between a pipe and a cylindrical support type, and the explosive charged inside the pipe is exploded, the coil is exploded, compressed and densified without deformation and cutting. By further increasing the inner diameter of the cylindrical support type, a large-diameter coil can be explosively compressed, and a book obtained by heat-treating the explosively-compressed large-diameter coil in the air or an oxygen atmosphere The superconducting coils of Examples 1 to 3 of the invention have remarkably excellent critical current densities as compared with the superconducting coils of Comparative Examples 1 to 3 which are not subjected to explosive compression, and have high critical current densities for practical use. The superconducting coil obtained by the manufacturing method of the present invention 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 supporting mold for explosive compression, and Fig. 2 is a II-II sectional view of Fig. 1, 1: cylindrical supporting type , 2: Pressure medium 3: Superconducting oxide filled coil 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 House (201) (72) Kazuki Takashima 1000-10 Yasukubomoto-cho, Kumamoto-shi, Kumamoto 401 (56) References JP-A 1-1112709 (JP, A) JP-A 63-287010 (JP, A) JP-A 64-9861 (JP, A) JP-A 63-222063 (JP, A)

Claims (8)

[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. And a coil (hereinafter referred to as a coil) and a pressure medium obtained by winding a superconducting oxide powder-filled Ag composite wire in the ring-shaped gap in the pressure medium. It is charged so that it is buried in the pipe, the inside of the pipe is filled with explosive, and the explosive is exploded to explode and compress the coil to increase the density, and then the explosive compression to increase the density. A method for manufacturing a superconducting coil by the explosive compression method, which comprises heat-treating the formed coil in the air or an oxygen atmosphere. 2. The method for producing a superconducting coil by the explosion compression method according to claim 1, wherein the cylindrical support die is a cylindrical die. 3. The method for producing a superconducting coil according to claim 1, wherein the cylindrical support type is a cylindrical reinforced concrete type. 4. The pressure medium has an average particle size of 1 to 1,000 μm.
2. The method for producing a superconducting coil by the explosion compression method according to claim 1, wherein the powder is a powder which is hard to be solidified by the explosion compression. 5. The explosive compression method according to claim 1, wherein 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. Superconducting coil manufacturing method. 6. The superconducting oxide powder is Bi-Ca-Sr-Cu.
The superconducting coil manufacturing method according to claim 1, wherein the superconducting coil is an -O-based oxide powder. 7. The superconducting oxide powder is Tl-Ca-Ba-Cu.
The superconducting coil manufacturing method according to claim 1, wherein the superconducting coil is an -O-based oxide powder. 8. The method for producing a superconducting coil according to claim 1, wherein the pressure medium is a fluid.