JPH0668729A - Manufacture of multilayer ceramic superconducting conductor - Google Patents

Abstract

PURPOSE:To provide the manufacture of a multilayer ceramic superconducting conductor with a high Jc value, in which a long multilayer ceramic superconducting conductor can be easily manufactured and improved in space factor. CONSTITUTION:After a ceramic superconductor 2 or a composite wire material of its precursor and composite metal 1 has the surface roughened and given heat treatment at a temperature of 200 deg.-800 deg., a plurality its of them are made into a complex material with the surfaces in mutual contact. Such an aggregate is rolled at a draft of 10%-80% and a resulting rolled product is given specific heat treatment. In this way, a long multilayer ceramic superconducting conductor with a high Jc value can be easily manufactured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a multilayer ceramic superconducting body applicable to a power transport conductor such as a magnet and a cable.

[0002]

2. Description of the Related Art In recent years, ceramic superconductors having a Tc value exceeding liquid nitrogen temperature such as Y series, Bi series, and Tl series have been found, and molded into various shapes for the purpose of application and utilization of these ceramic superconductors. It is being studied earnestly. For example, when making a wire, the metal sheath method is generally applied. This metal sheath method is to fill a metal pipe such as silver with a raw material of ceramics that can be a superconductor to form a composite billet, and subject the composite billet to cross-section reduction processing to obtain a desired cross-section shape, and It is a composite superconducting wire that is finished into a composite wire of dimensions and then heat treated.

As a method for reducing the cross section of the composite billet, conventional plastic working methods such as extrusion, rolling, drawing and swaging are applied as they are according to the shape of the target wire. As the material of the metal used for the sheath material, a material having excellent thermal conductivity and electrical conductivity, such as Ag, Ag alloy, Cu, Cu alloy is preferable, but Ag, Ag are preferable in view of oxygen permeability and oxidation resistance. There are many examples of using alloys.

Further, in general, when producing an Ag sheath tape wire of a ceramic superconductor of Bi type 2223 phase, for example, from the viewpoint that it is necessary to densify the ceramic superconductor inside, the raw material is also CIP molded. It is filled in a relatively high-density state by using means such as (cold isotropic pressure molding). Further, in the case of the Bi-based ceramics superconductor or its precursor, the Jc characteristics are improved by performing heat treatment a plurality of times in the processing process.

The shape of the wire obtained is a single core having a round shape, an elliptical shape, a quadrangle, a tape shape, or the like, or a multi-core wire made by bundling a plurality of these single-core wires, and further a metal wire. Inside the ceramic superconductor is a concentric cylinder,
Various prototypes of multilayer wire rods having a spirally arranged structure have also been studied. Fig. 1 is a cross-sectional view showing an example of a multi-layer wire rod. (A) is a concentric cylindrical laminated type with a round cross section, (b) is a spiral laminated type, (c) is a concentric laminated type with a rectangular cross section, ( d) is a spiral laminated type, (E) is a laminated type with a rectangular cross section, and (F) is a multi-core laminated type with a rectangular cross section.
Indicates a ceramics superconductor layer.

Conventionally, as a method for producing such a multilayer ceramic superconductor, for example, a composite tape-shaped wire is prepared in advance from a ceramic superconductor or its precursor and a composite metal, and a plurality of such tapes are prepared. Laminate and insert this laminate again into a metal pipe with a square cross section,
After forming the composite billet, the composite billet was subjected to cross-section reduction processing and heat treatment to finish the target wire rod. or,
As another method, a metal pipe having a circular or rectangular cross section provided with a plurality of rectangular through holes is prepared in advance, and the through holes are filled with a ceramics superconductor or a precursor thereof. After the composite billet is manufactured by the above, the composite billet is repeatedly subjected to the cross-section reduction processing and the heat treatment a desired number of times to form a multilayer ceramic superconducting wire.

[0007]

When a multilayer ceramic superconducting body is produced by the conventional method as described above, the former method is advantageous because the laminated body of the composite tape-shaped wire is inserted into the metal pipe. This is disadvantageous because the cross-sectional area of the superconductor occupies a small area of the cross-sectional area of the multi-layered wire. Further, in the case of a square wire having a rectangular cross section, a special square metal pipe is required on the outer side of the laminated body of the composite tape-shaped wire, which makes it difficult to produce a long wire. Further, in the latter method, a metal pipe provided with a plurality of through holes is produced and filled with a ceramics superconductor or its precursor, so the shape of the metal pipe provided with a plurality of through holes is complicated, and its production Not only is the work difficult, but it is also difficult to fabricate a long wire. The present invention provides a method for producing a multi-layered ceramic superconducting body which is easy to produce a long wire, has a high space factor of the ceramic superconductor, and has excellent characteristics.

[0008]

That is, according to the method of the present invention, the surface of a composite wire consisting of a ceramics superconductor or a precursor thereof and a composite metal is roughened, and
After heat treatment at a temperature of 00 ° C to 800 ° C,
It is characterized in that a plurality of them are formed into an aggregate in a surface contact state, this aggregate is rolled at a rolling reduction of 10% or more and 80% or less, and then the obtained rolled product is subjected to a predetermined heat treatment. It is a thing.

The present invention will be described in detail below. First, a composite wire rod made of a ceramics superconductor or its precursor and a composite metal such as silver or a silver alloy is prepared.
For example, a raw material powder of a ceramics superconductor is filled in a silver pipe to form a composite billet, and the composite billet is subjected to cross-section reduction processing to finish a composite wire rod having a desired shape and size. As the shape of the composite billet, a circular cross section or a square shape can be applied.
Conventional plastic working means such as rolling, swaging, and drawing can be applied as they are.

Next, the superposed surfaces of the composite wire thus obtained are roughened. As the method, continuous brushing or blasting can be applied. The composite wire having a roughened surface is heat-treated at a temperature of 200 ° C. or higher and 800 ° C. or lower to soften the composite metal. If the temperature at this time is less than 200 ° C., no improvement in the joint strength between the composite wire rods is observed, and if the temperature is higher than 800 ° C., the superconductor inside the composite wire rod is partially melted, resulting in A high Jc value cannot be obtained.

A desired number of the heat-treated composite wire rods are assembled in surface contact with each other, and the aggregates are joined by rolling or the like at a rolling reduction of 10% or more and 80% or less. At this time, if the rolling reduction is less than 10%, the surface-contacting composite wire rods are not sufficiently joined to each other. In addition, the rolling reduction is 80
If it is higher than 0.1%, the resulting multilayer wire rod may have cracks at the ends thereof, and it may be difficult to obtain a good wire rod.
The rolling process applied to the aggregate may be performed at room temperature, but it is preferable to perform the rolling process at a temperature of 200 ° C to 300 ° C because the bonding force between the composite wire rods is improved.

[0012] As described above, the aggregated body that has been rolled and integrated in the surface contact state is heat-treated under predetermined conditions to form a multilayer ceramic superconducting body. The Jc value can be improved by subjecting the multilayer ceramic superconducting body thus obtained to rolling and heat treatment repeatedly for about 2 to 3 times. There are no particular restrictions on the width and thickness of each individual composite wire, and the number of aggregates can be variously determined according to the target current capacity, but if there are too many, the joining force between composite wires will decrease toward the inside. , 5 to 6 or less are desirable. This method is particularly effective when a tape-shaped wire rod using a Bi-based 2223 phase superconductor is used.

[0013]

EXAMPLES The present invention will be described below with reference to examples. Example 1 Bi ₂ O ₃ , PbO, SrCO ₃ , CaCO ₃ , CuO
Bi: Pb: Ca: Cu in a molar ratio of primary raw material powders such as
= 1.6: 0.4: 2: 2: 3, and then mixed, then calcined in the air at 800 ° C for 100 hours and further pulverized to prepare a calcined powder. The calcined powder thus prepared was filled in an Ag pipe having an outer diameter of 25 mmφ and an inner diameter of 15 mmφ, and the cross-section was reduced to form a tape-shaped wire rod having a width of 9 mm and a thickness of 0.5 mm. After heat-treating the obtained tape-shaped wire at various temperatures, brushing the overlapping surfaces with 3 to 5 sheets,
They were laminated and rolled at various reduction ratios.

After investigating the bonding condition of the thus-prepared multilayer laminate, the multilayer laminate was placed in the atmosphere at 840 ° C. for 50 hours.
Was applied to obtain a multilayer ceramic superconductor. The Jc value in an O magnetic field in liquid nitrogen was measured for the obtained multilayer ceramic superconductor. The results obtained are shown in Table 1.

[0015]

[Table 1]

As is apparent from Table 1, the method product sample of the present invention
No. In Nos. 1 to 8, the joining of the composite wire rods was good, the heat treatment temperature was high, and the rolling reduction was also high.
The value was obtained. Further, the sample No. manufactured by setting the heat treatment temperature or the rolling reduction outside the range specified in the present invention.
9, No. In No. 11, the composite wire rods were not joined to each other and did not become an integrated wire rod. The sample No. whose heat treatment temperature was too high.
In No. 10, the joining of the composite wires was good, but the Jc value was remarkably low because partial melting occurred in the superconductor inside the composite wires.

Example 2 Sample No. obtained in Example 1 The multilayer ceramic superconducting body of No. 3 was again rolled at a rolling reduction of 30%, and then 840
A heat treatment was carried out at 50 ° C. for 50 hours. The Jc value of the multilayer ceramic superconducting body thus produced was measured and found to be 1
The characteristics were improved to 3100 A / cm ² .

Example 3 The calcined powder of the primary raw material for the Bi-based ceramics superconductor produced in Example 1 was filled in a square pipe made of Ag to produce a composite billet, which was then rolled to a width of 100 mm. Thickness 3
mm tape-shaped composite wire was produced. Next, the tape-shaped composite wire thus obtained was heat-treated at various temperatures shown in Table 2, and then both surfaces were brushed to roughen the surface, while being spirally formed on an Ag round bar having an outer diameter of 10 mmφ. Then, 15 layers were wound around and were inserted into an Ag pipe having an inner diameter of 20 mmφ and an outer diameter of 24 mmφ to obtain a multilayer composite billet having a length of about 100 mm.

The multilayer composite billet thus produced was swaged to form a round wire having an outer diameter of 5 mmφ, which was then heated to 500 ° C. and passed through a four-direction roll twice at a reduction rate of 20%. As a result, a multilayer wire having a square cross section of 3 × 2 mm was produced. For comparison, the tape-shaped composite wire produced in the same manner as in the example was subjected to no heat treatment and was used to form a multilayer composite billet without roughening both surfaces. The outer diameter is 5
A round wire having a diameter of mmφ was formed, heated to 800 ° C., and passed through a four-direction roll twice at a reduction rate of 20% to produce a multilayer wire having a square cross section of 3 × 2 mm.

The state of joining between the layers of the spiral type multilayer wire of Example 3 and the spiral type multilayer wire of Comparative Example thus produced was examined. In addition, this spiral multi-layer wire rod was heated to 840 ° C in the atmosphere.
By performing heat treatment for 5 hours, a spiral multilayer ceramic superconductor having a rectangular cross section was obtained. The Jc value of the obtained multilayer ceramic superconductor in an O magnetic field was measured in liquid nitrogen. The results obtained above are also shown in Table 2.

[0021]

[Table 2]

[0022]

[Effects] According to the method for manufacturing a multilayer ceramic superconducting body of the present invention described above, since a composite wire can be joined and integrated without using a metal pipe, it is easy to manufacture a long multi-layer ceramic superconducting body. In addition, the space factor of the ceramic superconductor can be increased. Moreover, according to the manufacturing method of the present invention, a multilayer superconducting body having high Jc characteristics can be manufactured.

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view showing an example of the form of a multilayer ceramic superconductor.

[Explanation of symbols]

 1 Composite metal 2 Ceramics superconductor

Claims (1)

[Claims] 1. A surface of a composite wire made of a ceramics superconductor or a precursor thereof and a composite metal is roughened, subjected to heat treatment at a temperature of 200 ° C. or higher and 800 ° C. or lower, and then a plurality of them are surface-treated. No contact state aggregate,
A method for producing a multilayer ceramic superconducting body, which comprises rolling this assembly at a rolling reduction of 10% or more and 80% or less, and then subjecting the obtained rolled product to predetermined heat treatment.