JPH11250746A - High-temperature oxide superconductive wire rod and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-temperature oxide superconductive wire rod with a metal sheath having high critical current density, by filling an aggregate of one or more kinds of powder in a metal tube. SOLUTION: In this manufacture, a core metal is put in a metal tube 3 of silver or silver alloy, etc., and second powder 2 is filled into space formed between the metal tube 3 and the core metal with a ratio (a loading ratio) of bulk density to theoretical density of the powder after the filling adjusted to lie in the range of 1/3-1. Then a first powder is filled into space formed by drawing the core metal out, to make up a compound material by repeating the filling and compression of the powder, with the loading ratio adjusted in the same way. The compound material is extruded, then it is drawn, and the diameter of it is reduced by methods of wiredrawing and rolling, etc., thereafter it is heat-treated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a high-temperature oxide superconducting wire having a high critical current density provided with a metal sheath and a method for producing the same.

[0002]

2. Description of the Related Art Since high-temperature oxide superconducting wires exhibit a superconducting state at liquid nitrogen temperature, they are expected to be applied to wires for superconducting magnets, superconducting cables, and the like, and their development is being promoted. In particular, high-temperature oxide superconducting wires provided with a metal sheath using a bismuth-based high-temperature oxide superconductor have been researched and developed with the aim of improving superconducting characteristics such as increasing the critical current density.

[0003] Many high-temperature oxide superconducting wires with a metal sheath are prepared by packing a high-temperature oxide superconducting calcined powder in a metal tube such as silver or silver alloy, reducing the diameter of the powder, stretching it, and cutting it to a fixed size. The bundle is manufactured by a powder-in-tube method of filling, reducing, and stretching a metal pipe such as silver or a silver alloy, and then processed into a wire having a round cross section or a tape depending on the application.

[0004]

However, in the conventional method, only a single type of powder is filled in a metal tube.
Filling two or more kinds of powders with different properties according to the layout as designed is because the high-temperature oxide superconducting calcined powder is a ceramic fine powder with a particle size of several microns to several tens of microns, and exhibits the behavior as a powder fluid. For this reason, there is a problem that two or more kinds of powders are mixed with each other even if the metal tube is filled.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to use one or more types of high-temperature oxide superconducting calcined powder, and to form a first powder around a core material formed by elongating the first powder. An object of the present invention is to provide a high-temperature oxide superconducting wire in which an aggregate of a second powder having a different material or composition from the powder is arranged, and a metal tube is arranged around the second powder.

According to the present invention, as shown in FIG. 1, a second powder aggregate 2 having a material or composition different from that of the first powder is provided around a first powder core material 1 formed in a long shape. And place
Further, a high-temperature oxide superconducting wire having a metal tube 3 disposed therearound is produced by the following procedure. First, a metal core 4 is placed in a metal tube 3 made of silver or a silver alloy, and a space formed between the metal tube 3 and the metal core 4 is filled with a second powder. The powder is pushed in the axial direction, and then the pipe-shaped pushing jig 6 is pulled out. Further, the work of adding and compressing the powder whose volume has been reduced and adjusting the bulk density is performed. Next, the space formed by extracting the cored bar 4 is filled with the first powder, and the powder is pushed in with a rod-shaped jig, and the powder is poured while the bulk density is adjusted in the same manner, and compression is repeated.
The composite 9 is extruded, reduced in diameter and stretched by a method such as wire drawing or rolling to form a wire rod, and heat-treated to form a metal sheath in which two or more kinds of powders are arranged in a metal tube in a cross section according to a predetermined design. , A high-temperature oxide superconducting wire can be obtained.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, an aggregate of a second powder having a different material or composition is arranged around a core material of a first elongate aggregated powder. Or a high-temperature oxide superconducting wire in which a metal tube made of a silver alloy is arranged and a method for producing the same, wherein the first powder or the second powder has improved crystal orientation and improved crystal bonding by mechanical processing. High temperature oxide superconducting material is desirable,
A high-temperature oxide superconducting material such as a Bi-based or Tl-based material can be used.

[0008] In order to increase the critical current density of the high-temperature superconducting wire, the first powder core material formed into a long length and the second powder assembly provided around the first powder core material are composed of a superconducting wire when energized. Can be placed in consideration of the current distribution inside the
When a plurality of high-temperature oxide superconducting wires are symmetrically arranged on a cable or a coil, the first powder formed into a long length and the second powder arranged around the first powder are considered in consideration of current distribution and magnetic field distribution. Is preferably arranged coaxially. Furthermore, in consideration of the current distribution inside the superconducting wire at the time of energization, the third powder aggregate and the like can be arranged in multiple layers around the second powder aggregate.

One of the first powder and the second powder is B
i-based high-temperature oxide superconducting calcined powder, and on the other hand, MgO, SrTi
Ceramic powder of a different material such as O ₃ can be used. By using a Bi-based high-temperature oxide superconducting calcined powder as the first powder and a ceramic powder of a different material such as MgO or SrTiO ₃ that does not react with the high-temperature oxide superconducting calcined powder as the second powder, The ceramic powder serves as a barrier layer, and it is possible to obtain effects such as a reduction in coupling loss between the high-temperature oxide superconductors during AC current application and a prevention of contamination of the high-temperature oxide superconductor from the metal tube to the high-temperature oxide superconductor during heat treatment. .

In addition, both the first powder and the second powder have B
A calcined powder of i- or Tl-based high-temperature oxide superconducting material, powders having different compositions can be used. By controlling the current distribution between the high-temperature oxide superconductors, AC loss reduction or critical current Superconducting characteristics such as an increase in density can be improved.

As shown in FIG. 1, the high-temperature oxide superconducting wire of the present invention has a material or composition different from that of the first powder around the core 1 of the first powder formed in a long shape. This is a high-temperature oxide superconducting wire in which a second powder aggregate 2 is arranged, and a metal tube 3 made of silver or a silver alloy is arranged around the second powder aggregate 2.
It is produced by the procedure shown in FIG. First, a metal core 4 is fixed to a metal tube 2 made of silver or a silver alloy with a terminal jig 5.
The space formed between them is filled with the second powder, and this powder is pushed in the axial direction by the pipe-shaped pushing jig 6, and then the pipe-shaped pushing jig is pulled out. The operation of adding and compressing the second powder whose volume has been reduced by the compression and repeating the compression can adjust the bulk density of the second powder.

Next, the space created by pulling out the metal core 4 is filled with the first powder using a powder guide jig 7, and the first powder is pushed in with a pushing jig 8 to reduce the volume of the first powder. The composite 9 can be produced by adding and adding the powder 1 and repeating the compression to adjust the bulk density of the first powder in the same manner as the filling rate of the second powder.

As a method of manufacturing the composite 9 of a high-temperature oxide superconducting wire according to the present invention, when the bulk density of the first powder and the second powder is small, the space formed by the second powder layer prepared in advance is used. There is a problem that the second powder layer collapses when the first powder is filled and compressed, and in order to increase the strength of the powder layer,
By setting the bulk density after filling of the first powder and the second powder to be 1/3 to 1 of the theoretical density, the interface between the aggregates of the first powder and the second powder is uniform. 9 can be produced.

The composite 9 is extruded, reduced in diameter and stretched by a method such as wire drawing or rolling to produce a high-temperature oxide superconducting wire. In addition, this wire rod is cut into fixed lengths, bundled into many pieces, and filled in a metal pipe such as silver or silver alloy,
The high-temperature oxide superconducting wire of a multifilamentary filament can also be produced by reducing and stretching the diameter. These high-temperature oxide superconducting wires may be round cross-section wires or may be roll-rolled into tape-like wires.

[0015]

EXAMPLES As the first powder, Bi ₂ O ₃ , PbO, Sr
The heat treatment and the pulverization for the preliminary sintering were repeated three times for the mixture of the powders of CO ₃ , CaCO ₃ and CuO, and the precursor of the oxide superconductor (Bi, Pb) ₂ Sr ₂ Ca ₂ C
We were prepared u ₃ O _y superconductor calcined powder.

Outer diameter 50 mmφ, inner diameter 42 mmφ, length 5
Using a silver metal tube 3 of 00 mm, a stainless steel core 4 having a diameter of 38 mmφ longer than the length of the silver metal tube 3 was fixed through a terminal jig 5. A space formed between the silver metal tube 3 and the stainless steel core 4 is filled with a second powder of the type shown in Table 1 and has an outer diameter of 42 mm and an inner diameter of 38 m.
The work of pushing in the axial direction with a pipe-shaped jig 6 of mφ, pulling out, adding the powder whose volume has been reduced, and further compressing the powder is performed by the following method. The process was repeated until the density became a times (filling rate).

Next, a powder guide jig 7 having an inner diameter of 38 mmφ is attached to the end of the silver metal tube 3, and a stainless steel core 4 is attached.
Was pulled out from the opposite side to which the powder guide jig 7 was attached, and the space formed was filled with the first superconducting calcined powder without interruption. Further, in this state, the diameter is 38 mmφ.
The compression is repeated while adjusting the stroke of pushing the tip of the stainless steel pushing jig 8 so as not to enter the silver metal tube 3, and the bulk density of the superconducting calcined powder of the first powder is the same as that of the second powder. Filling and compression were performed until the density became a times the theoretical density (filling ratio). Table 1 shows the results of producing the composite 9 with respect to the type of the filled powder and the filling rate a times.

[0018]

[Table 1]

Filling rate a times (ratio of bulk density of filled powder to theoretical density of filled powder) for all powders used
Is in the range of 1/3 to 1, the second powder layer is not collapsed when the first powder is compressed, and the interface between the first powder and the second powder is uniform and the composite 9 having a good cross-sectional arrangement is provided. was gotten.

As a first powder having a good cross section, the composite 9 was drawn to a diameter of 4.6 mmφ, and the cross section was observed. In each sample, the first powder and the second powder were mixed. The cross-sectional area ratio is approximately the same as the design value of the cross-sectional area ratio of the first powder and the second powder in the composite 9, and
A good cross-sectional structure was obtained without mixing of powders and non-uniformity in the longitudinal direction.

Further, as the first powder (Bi, P
b) Using ₂ Sr ₂ Ca ₂ Cu ₃ O _y superconducting calcined powder 1, a composite material 9 having a diameter of 4.6 mm using MgO as the second powder is cut to a fixed size, and has an outer diameter of 50 mmφ, an inner diameter of 42 mmφ, and a length. 1.25mm diameter after filling into a 500mm silver metal tube
It is drawn to φ, and further rolled to a thickness of 0.25 mm.
After a heat treatment at 5 ° C. for 50 hours, the critical current density Jc was measured at 77 K by a four-terminal method, and 1.3 ×
A high-temperature oxide superconducting wire exhibiting 10 ⁴ A / cm ² was obtained.

Similarly, as the first powder, (Bi, Pb) ₂
4.6 mmφ in diameter using Sr ₂ Ca ₂ Cu ₃ O _y superconducting calcined powder 1 and SrTi ₃ powder 2 as the second powder
Was processed into a wire, heat-treated, and the critical current density was measured. As a result, a high-temperature oxide superconducting wire showing 1.4 × 10 ⁴ A / cm ² was obtained.

Similarly, as the first powder (Bi,
Pb) using _{2 Sr 2 Ca 2 Cu 3 O} y superconductor calcined powder 1,
Processing the _{Bi 2 Sr 2 Ca 2 Cu 3} O y superconductor calcined powder 2 composite 9 of diameter 4.6mmφ using as the second powder in the wire was heat-treated, was measured critical current density, 1.
A high-temperature oxide superconducting wire exhibiting 5 × 10 ⁴ A / cm ² was obtained.

[0024]

As described above, according to the present invention, a metal core is placed in a metal tube such as silver or a silver alloy, and a space formed between the metal tube and the metal core is filled with a second powder, and a pipe is formed. Pressing this powder in the axial direction with a pressing jig, then pulling out the pipe, adding the powder whose volume has been reduced, and compressing it, the work of filling the powder with the ratio of the bulk density to the theoretical density (filling Rate) in the range of 1/3 to 1. Next, the space formed by pulling out the core is filled with the second powder, and the powder is pushed in with a rod-shaped jig, and while the filling rate is similarly adjusted, the powder is added and compressed, and a composite is produced. . The composite is extruded, reduced in diameter and stretched by a method such as wire drawing or rolling to form a wire, and then heat-treated to form a first powder around the core 1 of the first powder formed into a long piece. A high-temperature oxide superconductor having a high critical current density provided with a metal sheath, in which an aggregate 2 of a second powder having a different material or composition from the powder of the above is arranged, and a metal tube 3 is arranged therearound as a predetermined design. A wire can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a high-temperature oxide superconducting wire of the present invention.

FIG. 2 is a cross-sectional view of the jig before the second powder of the present invention is filled.

FIG. 3 is a sectional view of a jig in a state where the second powder of the present invention is being compressed.

FIG. 4 is a cross-sectional view of the jig in a state where the first powder of the present invention is being filled.

FIG. 5 is a sectional view of the jig in a state where the first powder of the present invention is being compressed.

FIG. 6 is a longitudinal sectional view of the composite of the present invention.

[Explanation of Signs] Aggregate of first powder Aggregate of second powder Metal tube Core metal Terminal jig Pipe-shaped pushing jig Powder guide jig Push jig Composite

Claims (4)

[Claims] 1. A method according to claim 1, wherein at least one kind of high-temperature oxide superconducting calcined powder is used, and a second powder having a material or composition different from that of the first powder is surrounded by a core formed by elongating the first powder. A high-temperature oxide superconducting wire characterized by arranging an aggregate of powder and further arranging a metal tube around the aggregate. 2. The method according to claim 1, wherein the first powder is a Bi-based high-temperature oxide superconducting calcined powder, and the second powder is a ceramic powder that does not react with the high-temperature oxide superconducting calcined powder. High temperature oxide superconducting wire described in 3. The first powder is a Bi-based high-temperature oxide superconducting calcined powder, and the second powder has a composition different from that of the first powder.
The high-temperature oxide superconducting wire according to claim 1, wherein the high-temperature oxide superconducting wire is an i-based high-temperature oxide superconducting calcined powder. 4. A method comprising: using at least one kind of high-temperature oxide superconducting calcined powder; preliminarily disposing a metal core in a space for forming a core material formed by elongating a first powder in a metal tube; Is filled in the gap between the metal tube and the core metal and compressed to 1/3 to 1 of the theoretical density, and then the first powder is filled into a space formed while pulling the core metal. 2. A method for producing a high-temperature oxide superconducting wire, comprising compressing under the same conditions as powder 2.