JPH0227622A - Manufacture of superconductive filament - Google Patents

Abstract

PURPOSE:To enable a fragile ceramic series superconductor to be processed into a long filament with a desired shape by filling the superconductor or raw material mixture thereof in a metal container and subjecting it to pressing process in one direction at a temperature within 300 deg.C range below the melting point thereof, then to drawing process, and thereafter to heating process. CONSTITUTION:A ceramic superconductor or raw material mixture 2 is filled in a metal container 1 and the container 1 is sealed at the opening thereof if necessary, and heated at a high temperature within 300 deg.C range below the melting point thereof, and made thinner by pressing vertically. Then, it is subjected to drawing process in the direction to reduce the thickness or diameter thereof. When the metal container is work hardened during the drawing process and the process becomes difficult to be carried out, low temperature annealing and subsequent redrawing process are repeated as required to obtain a desired size. Then, a sintering reaction is caused to proceed by a high temperature heating treatment to connect the ceramics superconductor particles. Thus, a fragile ceramics series superconductor can be efficiently processed into a long filament with a desired shape.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for manufacturing a ceramic superconducting wire, and in particular to a method for manufacturing a ceramic superconducting wire plate (hereinafter referred to as a wire This article relates to a method for manufacturing a strip (abbreviated as a strip).

(Prior art) Recently, alloys such as NbTi, NbZr, Nb, Pb and N
It exhibits a higher critical temperature than intermetallic compounds such as b5Sn, Nb5AI2°Nb, and (AI2Ge). Ceramic superconductors such as oxides are attracting industrial attention. Representative examples of these include:

■ (LaBa)zcuoa.

(LaSr)xcuOa etc. La, CuO, system.

■ LnBa*Cu5Oy (in the formula, Ln is Ce.

rare earths (excluding Tb, etc.).

■ B 1-5r-Ca-Cu-0 system, e.g. Ba5r
CaCuaOx, Bi zsracaxcufu0x (x=8)BizS
rzCaxCusOx (x=IO) ■ T El −
B a -Ca -Cu-0 system, e.g. Tl2iBai
CaCutOa Tnz Bax Ca x Cu 30+.

Among the above-mentioned (1) to (2), (2) has a critical current temperature Tc of 30 to 50, but (2), (2), and (3) can have a higher Tc, especially higher than the liquid nitrogen temperature. These are type 2 superconductors and lO~
Since it has a large upper critical magnetic field of 200T, it is expected to be used as a high-field magnet.

(Problems to be Solved by the Invention) However, ceramic superconductors such as the above-mentioned oxides have poor processability, and cannot be formed into plate shapes or linear bodies necessary for electric wires, cables, magnetic coil conductors, permanent magnets, shield plates, etc. Some attempts have been made to deposit these substances onto a linear substrate using PVD methods such as vapor deposition or sputtering, but even this method has poor productivity and there is still no effective method. It has not been discovered.

(Purpose of the invention) The purpose of the present invention is as follows.

■ Inherent characteristics of ceramic superconductors Tc, Hc+
An object of the present invention is to realize a method for manufacturing a striatum that can usefully realize Hcx and the like.

■ To realize a method of processing a brittle ceramic body into a long filament of a desired shape.

■ To realize a method for manufacturing a striatum that allows superconducting current to flow up to the highest possible critical current density (Jc).

■ To realize a method for manufacturing a striatum in which the above-mentioned superconducting current is practically stabilized without causing the "quench" phenomenon.

■ To realize a method for manufacturing a striatum that has practical strength and resistance to deformation strain.

■ Manufacture of a striatum that guarantees a long lifespan, as the superconducting material does not react with moisture, gas, chemicals, etc. in the external environment and undergo deterioration during manufacturing, storage, and during the period of use when it is incorporated into equipment. To realize the method.

■ The above aspects can be realized industrially and economically.

(Means for Solving the Problems) In order to achieve the above-mentioned various objects, the present invention has the following configuration.

The method for producing a superconducting wire body according to claim 1 includes filling a metal container with a superconductor or a raw material mixture thereof, and then heating the superconductor or a raw material mixture thereof to
A unidirectional pressure treatment is performed at a temperature of 00° C. or less, followed by stretching processing, and then a heat treatment is performed.

A method for producing a superconducting wire body according to claim 2 is such that the molded product that has been subjected to pressure treatment and stretching processing according to claim 1 is slit and cut into thin strips prior to heat treatment. .

A method for manufacturing a superconducting wire body according to claim 3 is such that the wire body stretched by the method according to claim 1 is further filled into a metal tube body and stretched again, which is repeated one or more times. It is something.

The superconductor in the present invention may be a ceramic superconducting compound such as the Cu composite oxide, or a mixture of oxides of elements of these compounds. However, these materials may be in powder form or may be compression molded and sintered in advance.

The metal container l in the present invention is Ag, Pt, Au, Cu,
It is a container made of metals such as Ni, Fe, Mo, Ta, etc., or alloys thereof, such as SUS, Fe-Ni, Cu-Ni, etc., such as a metal tube as shown in Figure 1a, or as shown in Figure 2. a
- one or more holes 4 in a metal block 3 such as d
It is opened.

The metal container l shown in FIG. 2 has an oblong cross-sectional shape, and a plurality of holes 4 having a square cross section are drilled in the direction of the yam.

The metal container l shown in FIG. 2 is a nearly square metal block 3 in which a plurality of holes 4 having a square cross section are bored in the elongated direction. In this case, it is also useful to perform the pressurization process multiple times in the vertical and horizontal directions.

The metal container l shown in FIG.
The metal container 1 shown in FIG. d is made by punching a plurality of holes 4 having a hexagonal cross-section in a circular metal block 3, and repeating this process as necessary to obtain a desired size.

The metal container l shown in FIG. 1a is a metal tube with a rectangular cross section. In the case of this metal container l, the above ceramic superconductor or its raw material mixture 2 is placed inside, and the opening is sealed as necessary. After that, it is heated to a high temperature and pressurized in the vertical direction to make it thinner as shown in the figure. This treatment is usually performed by pressing such as hot forging. The processing rate is 5% or more and usually about 10 to 70%.

Pressure processing can also be repeated multiple times. In particular, it is effective to repeatedly apply pressure in the vertical and horizontal directions one or more times.

In the present invention, after the pressure treatment as described above, for example, the first
As shown in Figure C, they are stretched in a direction to further reduce their thickness or diameter. As the stretching process, methods such as rolling, extrusion, drawing, wire drawing, and swaging are possible.

If machining strain accumulates in the metal part during stretching and machining becomes difficult, low-temperature annealing is performed midway through the process and then the stretching is proceeded again.

Next, a sintering reaction is advanced by high-temperature heat treatment to connect the ceramic and superconductor particles. In this case, it can be sintered to a high temperature close to the melting point in a short time, and it is also possible for partial melting to occur.

Prior to the above-mentioned sintering process, it is often useful to slit vertically with a width W and cut into thin pieces as shown in Fig. 1d. It will look like Figure e.

FIG. 3 shows a ceramic superconductor or its raw material mixture 2 put into the hole of the metal block 3 shown in FIG. 2, and then pressure-treated to form a thin comb.

4a and 4b are cross sections of the thin wire 5 obtained by slitting the metal block 3 of FIG. 3 into thin pieces, and in both cases, a part of the superconductor 2 is exposed on the surface.

In addition to ordinary rotating blades, lasers and the like can also be used for slitting.

After sintering, any treatment can be added as necessary.For example, many of the oxide superconductors mentioned above have a transformation point at a temperature lower than the sintering temperature, so low-temperature heat treatment in the presence of 02 is effective. There are many cases.

After sintering, coating with a conductor such as metal or an insulator such as plastic is also performed.

(Function) In the process of high-temperature pressure treatment in the present invention, the material is deformed along the arm opening plane or the shear plane, and the crystal orientation is oriented. This treatment is effective within a high temperature range of 300° C. below the melting point. At lower temperatures, the alignment effect is reduced.

Since many ceramic superconductors have a layered structure, the direction of pressure tends to coincide with the C axis perpendicular to the layers - YB
Taking atCuzOy as an example, if y>6.5, it is orthorhombic, y
= s ~ 6.5, it is a square product, and the former, especially y46, is used for superconductivity.
．． 8 to 7.0 is useful. Cu-0 parallel to a and b planes
A superconducting current flows through the surface. According to actual temperatures, superconducting current is about 10 to 100 times easier to flow in the direction parallel to the a and b planes than in the perpendicular direction, that is, in the C-axis direction.

After being densified and oriented by the above pressure treatment,
This tendency is further advanced in the distraction process. Since the superconductor is pulverized into a dense aggregate around the arm opening plane, a rapid sintering reaction progresses in the first sintering process, and the a and b planes are oriented in the longitudinal direction of the filament, forming a structure. is obtained.

The sintering temperature is typically 750°C to 980°C.

Since YBatCuzOy transforms into a tetragonal product at a high temperature of around 600° C. or higher, oxygen is depleted by sintering. During low-temperature treatment (or during cooling during the sintering process, 1M element is absorbed and transformation occurs.) In the present invention, the slit process exposes the surface of the superconductor at its edges, so that oxygen can be absorbed quickly.

By slitting, not only can thin wires be produced in large quantities efficiently, but also many essential effects can be brought to the ceramic superconductor. Therefore, the maximum amount of oxygen, which is essential to the oxide superconductor, can be added. Y
In the example of B az C11s Oy, Tc -90° C. is possible when y≧6.8, and matching of thermal expansion between the superconductor 2 and the metal portion 6 of the metal block 3 is possible.

If the entire surface is coated with metal without slit processing, it is necessary to use an 02-permeable metal such as Ag as the metal block 3 in advance. Ag is not only expensive, but also has defects in mechanical strength and melting point, and has the disadvantage that it cannot match the thermal expansion between the superconductor 2 and the metal portion 6 of the metal block 3.

In the conventional method, it is essential to use Ag with 0□ permeability, and in addition, Ag is not only expensive as it is a precious metal, but also disadvantageous in that it has poor mechanical strength and a low melting point. However, in the present invention, stronger base metals such as Cu alloys such as Cu-Ni, Fe alloys such as SO5, and Ni such as Fe-Ni are used.
Alloy, Ta.

Since Mo or the like can be used, there is no such problem.

According to the example of Y-based oxide superconductors, Ag has a coefficient of thermal expansion that is approximately twice as high, and generates large strains during cooling after sintering and heating, which tends to cause cracking in the fragile Y-based oxide superconductors. There is also the problem.

If oxidation reaction is a problem in the present invention, Ag, Pt
, Pd, Au or alloys thereof can also be used as a barrier layer on the inner surface of the hole 4.

In the present invention, by using the metal container 1, not only can processing techniques developed for metal parts be applied (the container 1 also serves as mechanical reinforcement and is also effective in shielding the external environment.

(Example 1) DyBazCusOy coating 2 (y~ 6.9, particle size 12u average) was filled at a filling rate of 60%, then degassed and sealed. When pressurized to 117 cm at 830°C and held for 3 hours, the pipe thickness was 2.9 cm.
It became mm.

A portion of the crystal was taken out and subjected to X-ray diffraction.

Σ(OOR)/Σ(n, m, ε)=62%.

Σ(00g)/Σ(n, m) of the above-mentioned Song-Song filling body.

R)=19%, the C-axis orientation progressed.

Next, one piece is rolled and finished to a thickness of 0.3mm.
Next, heat treatment was performed at 860°C for 6 hours in a 02 air flow, and cooling was performed at 3°C/min.

(Example 2) In the above Example 1, after rolling, a 2 mm slit was performed to take out the strip 5, which was treated in the same manner.

(Comparative Example 1) In the above Example 1, the treatments including rolling were performed without performing the pressure treatment.

(Example 3) Figure 2: Metal block 3 (68x68mm.

Made of Cu-3ONi, hole 4: lO10X10, metal part 6
: 3mm, 20μ Ag plating on the inner surface of the hole 4) Yo, s Ho, s Ba x Cu 3 Dy
(y~6.8) boundary body (Σ(OOI2)/Σ(n.

m, Q) = 18%, density 81%) were inserted, deaerated and sealed, and treated at 810°C with a pressure of 37/cm" once each in the vertical and horizontal directions for 3 hours. 48X48mm (Σ(OOR)/Σ(n, m, O2) = 71%)
0 This product was rolled and heat treated at 590°C for 15 minutes three times during the rolling process.

One side finished to 0.6mm thickness is 6mm.

Cut a slit in the center to a width of 9 mm to obtain the strip 5, which was treated at 910°C for 6 hours in an 02 air flow, and then heated at 550°C.
It was treated for 3 hours.

(Comparative Example 2) In Example 3, heat treatment was performed as it was without performing pressure processing and without slitting.

(Comparative Example 3) In the above Example 3, pressure processing was performed at 600°C. The melting point of the superconductor is 950°C, which is 350°C lower. Stays at 51X51mm, Σ(OOI2)/Σ(n
, m, O2) = 33%. However, the slit processing is 6mm on both sides and 9.7m in the center.
It was set as m.

For the above linear body, Tc and J at 77° are determined by the usual method.
c was measured and the results are shown in Table 1.

Table-1 Tc (K) Jc (A/am”) Example
1 92 11000 Comparative example 1 91
12002 <4.2 0 As is clear from Table 1, all of the example products of the present invention exhibit high characteristics.

Compared to Example 1, Comparative Example 1, which was not subjected to pressure treatment, was approximately 1
/I stayed in Jc of IO.

The reason why Example 2 showed higher Jc and Tc than Example 1 was because absorption of 02 occurred more fully.

Compared to Example 3, Comparative Example 2 showed no superconductivity at all.

Further, for comparison, even when the wide material of Example 3 without slit processing was heat-treated as it was, Tc was less than 4.2, and it did not exhibit superconductivity. The reason is that the Cu-3ONi used is 0
This is due to lack of oxygen due to impermeability to □.

Also, when the pressure treatment temperature in Comparative Example 3 was insufficient, the orientation was insufficient and the Jc was inferior.

(Effects of the Invention) According to the method for producing a superconducting wire body of the present invention, even a ceramic-based superconductor with poor workability can be efficiently linearized, and the obtained wire body has superconductivity. It is excellent and can be used in a wide range of applications such as electric wire cables and magnetic coil conductors.

The manufacturing method of the present invention is particularly useful for linearizing ceramic superconductors, which has recently attracted attention, and has great industrial value.

[Brief explanation of the drawing]

Fig. 1 a''-e is a sectional view showing an example of the manufacturing process of the present invention;
Figures 2 a - d are cross-sectional views of different metal blocks according to the present invention, Figure 3 is a cross-sectional view of the metal block of Figure 2 which has been stretched, and Figures 4 a - b are sectional views of the metal block of Figure 3 that has been stretched. FIG. 2 is a cross-sectional view of a linear body obtained by processing. 1 is a metal container 2 is a superconductor or its raw material mixture 3 is a metal block 4 is a hole 5 is a strip 6 is a metal part

Claims (3)

[Claims] (1) A metal container is filled with a superconductor or its raw material mixture, and then subjected to unidirectional pressure treatment at a temperature below the melting point of 300°C, followed by stretching processing, and then heat treatment. A method for manufacturing a superconducting wire. (2) The method for manufacturing a superconducting wire body according to claim 1, characterized in that the molded product, which has been subjected to pressure treatment and stretching processing prior to heat treatment, is slit and cut into narrow pieces. (3) A method for manufacturing a superconducting wire according to claim 1 or claim 2, characterized in that filling a metal tube with the stretched wire and subjecting it to stretching again is repeated one or more times.