JPH05182540A - Manufacture of ceramics superconductive conductor - Google Patents

Abstract

PURPOSE:To reduce dispersion and improving a superconductive characteristic in a magnetic field by using a thin wall pipe, which satisfies the thickness of a metallic pipe with a prescribed expression, for the metallic pipe making an inner layer excepting the outermost layer of a multilayer composite billet. CONSTITUTION:A thin wall pipe, where the thickness (t) of a metallic pipe satisfies the following formula: 0.05D<=t<=0.02D (D indicates an outer diameter of the metallic pipe), is used for the metallic pipe making an inner layer excepting the outermost layer of a multilayer composite billet. Then, at the time of performing drawing processing on a multilayer composite beam, this thin wall pipe is broken so as to fully and uniformly transmit compressive force of drawing processing to a raw material layer while dispersing broken pieces in a raw material layer in a corpuscular state in order to give a pinning effect of a magnetic flux for improving a superconductive characteristic under a magnetic field. Thereby, a substance, where Ag particles 3 and oxide particles 4 of a metal are dispersed in a ceramics superconductor layer 2, for instance, inside a metallic sheath 1, can be obtained so that dispersion can be reduced while improving a superconductive characteristic in a magnetic field.

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 which has excellent superconducting properties and is suitable as a conductor for magnets and cables.

[0002]

2. Description of the Related Art In recent years, Y- which exhibits superconductivity at liquid nitrogen temperature
Ba-Cu-O system, Bi- (Pb) -Sr-Ca-Cu
Ceramic superconductors such as -O type and Tl-Ba-Ca-Cu-O type have been found, and researches for practical use have been advanced in various fields. By the way, since these ceramic superconductors are fragile, it is necessary to process them into a wire or the like, which has a high workability.
A metal pipe such as g is filled with a raw material (hereinafter abbreviated as raw material) capable of forming a ceramics superconductor to form a composite billet, and the composite billet is drawn to form a wire material having a desired shape. A composite processing method is used in which the raw material is reacted with a superconductor by subjecting the wire material to a predetermined heat treatment. In this composite processing method, the wire material is processed into an arbitrary cross-sectional shape such as a circle, an ellipse, a quadrangle, or a tape. Then, for example, the tape-shaped wire material is laminated in a plurality of layers in parallel, concentrically or spirally, and then these laminated bodies are filled in a separately prepared pipe made of Ag to obtain a multilayer composite. A billet was not formed, and these multilayer composite billets were subjected to a stretching process and a heat treatment in the same manner as described above to manufacture a ceramics superconducting body.

[0003]

However, in the ceramic superconducting body manufactured as described above, since the raw material layer is drawn through the metal pipe, the compressive force at the time of drawing is the raw material. There is a problem that it is difficult to satisfactorily and uniformly apply to the material layer, and thus the obtained ceramic superconducting body tends to have a low superconducting property, has large variations, and the superconducting property under a magnetic field remarkably deteriorates.

[0004]

DISCLOSURE OF THE INVENTION The present invention has been made as a result of intensive studies in view of the above circumstances, and an object thereof is to provide a method for producing a ceramic superconducting body having excellent superconducting properties. It is in. That is, the present invention is
A metal bill is filled with a raw material that can be a ceramics superconductor to form a composite billet, and then this composite billet is drawn to form a composite material, and then the composite material is filled into a metal pipe to form a composite. With billet,
After repeatedly performing the step of stretching this composite billet to form a composite material as many times as desired, the obtained composite material is filled into a metal pipe to form a multi-layer composite billet, and the multi-layer composite billet is stretched. To form a multilayer composite wire rod, and then subject this multilayer composite wire to a predetermined heat treatment to produce a ceramic superconducting body.In the method of manufacturing a ceramic superconducting body, the metal pipe to be the inner layer excluding the outermost layer of the multilayer composite billet It is characterized by using a thin-walled pipe in which t satisfies the following equation: 0.05D ≧ t ≧ 0.02D (where D is the outer diameter of the metal pipe).

In the method of the present invention, a thin-walled metal pipe (hereinafter abbreviated as thin-walled pipe) within a specific range of thickness is used as the inner-layer metal pipe located inside the multi-layer composite billet filled with the multi-layer composite wire. Using the crushed thin-walled pipe during the drawing process of the multilayer composite billet to transmit the compressive force of the drawing process to the raw material layer sufficiently and uniformly, and the crushed pieces of the thin-walled pipe to the raw material. Dispersed in a layer in the form of particles, the resulting ceramic superconductor,
With the pinning effect of magnetic flux by the particulate matter,
It is intended to improve the superconducting property under a magnetic field. In the method of the present invention, the reason why the wall thickness t of the thin-walled pipe used for the inner layer is limited to the thickness satisfying the equation of 0.05D ≧ t ≧ 0.02D (where D is the outer diameter of the metal pipe). When the wall thickness t of the thin-walled pipe is more than 0.05D, the metal pipe is not sufficiently crushed during the stretching process, so that the compressive force of the stretching process is not evenly transmitted to the raw material layer and This is because the crushed pieces do not disperse into particles, and t is
This is because if the thickness is less than 0.02D, the metal billet of the outer layer is crushed too much during the stretching process and the composite billet cannot be stretched to a predetermined shape.

In the method of the present invention, an arbitrary metal material is used for the thin pipe used for the inner layer.
Al or an alloy thereof is preferable because it significantly enhances the crystal orientation of the obtained superconductor or the pinning effect of the magnetic flux. Further, it is preferable to use Ag or Ag alloy having excellent oxygen permeability as the material of the metal pipe which is the outermost layer, because the characteristics of the resulting ceramic superconductor are improved. Among the materials of the thin pipes exemplified above, Ag is dispersed as metal particles, and Mg and Al are dispersed as oxide particles in the ceramic superconducting layer, and each serves to pin the magnetic flux. It also serves to enhance the crystal orientation of the ceramic superconductor layer. In addition, Mg and Al
Since the oxide particles of No. 3 are brittle, they are easily miniaturized, and the pinning effect of magnetic flux is larger than that of Ag particles. Therefore, for thin pipes, A
In order to increase the crystal orientation of the ceramic superconducting layer with Ag particles and increase the magnetic flux with other oxide particles, a combination of g and Mg, or Ag and Al is used. It is good to make the effects synergistic, such as strong pinning. FIG. 1 shows a longitudinal sectional view showing an example of the embodiment of the ceramic superconductor manufactured by the method of the present invention. The Ag particles 3 and the oxide particles 4 are dispersed in the ceramic superconductor layer 2 in the metal sheath 1.

In the method of the present invention, the raw materials include the above-mentioned Y-based, Bi-based, Tl-based ceramics superconductors, and intermediates that react with the ceramics superconductor by heat treatment in an oxygen-containing atmosphere, For example, a mixture of constituent elements of a ceramics superconductor, or a coprecipitation mixture, or primary raw material powders of oxides or carbonates of the above constituent elements are mixed in predetermined amounts to form a mixed raw material, and the mixed raw material is calcinated. Oxygen-deficient complex oxides are used. Further, in order to fill the raw material into the thin-walled pipe of the innermost layer, in addition to the method of filling the raw material as it is by tapping or the like, the raw material may be previously compression-molded into a predetermined shape by the CIP method, or A method of filling after heating and sintering is used. When the raw material is previously processed into a molded body or a sintered body in this manner and then filled, the resulting ceramic superconducting body has a higher density and the characteristics such as Jc are further improved. When filling a metal pipe with a composite wire or a multi-layer composite wire, it is desirable to subject these wires to CIP treatment in advance.

In the method of the present invention, the stretching process applied to the above-mentioned multi-layer composite billet can be carried out by any process such as extrusion, drawing, swaging, rolling, forging and press compression. Is preferable since it can further increase the density of the superconductor layer. The final heat treatment applied to the multi-layer composite wire is to react the raw material with the ceramic superconductor, and the heating temperature is, for example, B
In the case of i-based ceramics superconductor, it is usually 820-885.
The temperature range is ° C. Further, it is preferable that the above-mentioned heat treatment is performed after the multilayer tape wire is molded into a magnet coil or the like because cracks and the like are less likely to occur in the internal ceramics superconductor layer.

[0009]

In the method of the present invention, since a thin metal pipe having a thickness within a specific range is used for the metal pipes other than the outermost layer, the multi-layer composite billet composed of the raw material and the thin pipe is drawn. Sometimes the thin-walled pipe crushes,
The compressive force of the stretching process is sufficiently and uniformly transmitted to the raw material layer, and the obtained ceramic superconducting body has uniform density and crystallographic orientation, which reduces variations in superconducting properties.
The crushed inner layer pipe is dispersed in the ceramic superconductor layer as metal particles or oxide particles to pin the magnetic flux and contribute to the improvement of the superconducting property under the magnetic field.
When Ag is used for the thin pipe, the Ag particles have a function of enhancing the crystal orientation of the superconductor layer, in addition to the pinning effect, so that the superconducting property is further improved.

[0010]

EXAMPLES The present invention will be described in detail below with reference to examples. Example 1 Bi ₂ O ₃ , PbO, SrCO ₃ , CaCO ₃ , CuO
Primary raw material powders such as Bi: Pb: Sr: Ca:
Cu was mixed so that the atomic ratio was 1.6: 0.4: 2: 2: 3, and the mixed powder was calcined in the air at 800 ° C for 50 hours, and then this calcined body was crushed to obtain calcined powder. Done Then, the calcined powder is CIP-molded into rods having various outer diameters, which are inserted into a thin pipe made of high-purity Mg having an outer diameter of 10 mmφ and various thicknesses to form a composite billet. did. This composite billet is then swaged and rolled to
The tape wire rod has a thickness of 4.8 mm and a thickness of 0.1 mm. Next, forty-five pieces of this tape wire material were laminated and the inner diameter was changed with various wall thicknesses.
A 5.0 mm square thin-walled pipe made of Ag was filled into a multilayer composite billet. Next, this multi-layer composite billet was sequentially rolled by a 4-way roll and a flat roll to obtain a width of 4.8 mm and a thickness of 0.1 mm.
mm multi-layer tape wire. Then, the step of filling the multilayer tape wire into a thin pipe to form a multilayer composite billet and rolling the billet
Alternating between g and Ag, repeating 9 times, finally filling the multilayer tape wire rod into a square Ag pipe with an outer diameter of 5.5 mm and an inner diameter of 5.0 mm to form a multi-layer composite billet. Is sequentially rolled with a four-way roll and a flat roll to finish a multilayer tape wire with a width of 5 mm and a thickness of 2 mm.
This wire was heat-treated in the atmosphere at 840 ° C for 100 hours to produce a ceramic superconductor.

Example 2 Bars made of Bi, Pb, Sr, Ca, and Cu having various outer diameters were inserted into thin pipes made of high-purity Mg having various outer diameters of 10 mmφ to form a composite billet. This composite billet is swaged and rolled to a width of 4.8m.
m tape wire. The thickness of the tape wire is Bi
Or a composite of Sr or Ca rods is 0.1 mm,
A composite of Pb or Cu bars is 0.03 or respectively
It was set to 0.12 mm. Next, these five kinds of tape wire materials are Bi, P
B, Sr, Ca, Cu, 9 sheets each, 45 sheets in total, were laminated.
Filling a thin-walled pipe made of g to form a multi-layer composite billet,
Width of 4.8
mm multi-layer tape wire with a thickness of 0.1 mm. Then, the multi-layer tape wire is filled in a thin metal pipe to form a multi-layer composite billet, and the process of rolling this is repeated 19 times by alternately changing the material of the thin pipe to Mg and Ag,
Finally, the multilayer tape wire obtained has an outer diameter of 5.5 mm and an inner diameter of
A 5.0 mm square Ag pipe was filled to form a multilayer composite billet. This multi-layer composite billet is sequentially rolled by a 4-way roll and a flat roll to make a multi-layer tape wire rod with a width of 5 mm and a thickness of 2 mm, and this wire rod is heat-treated at 840 ° C for 100 hours in the atmosphere to obtain ceramic superconductivity. Manufactured body.

Example 3 A ceramic superconducting body was manufactured by the same method as in Example 1 except that Mg thin-walled pipes were used for all the metal thin-walled pipes forming the inner layer. Example 4 Primary raw material powders of Bi ₂ O ₃ , SrCO ₃ , CaCO ₃ , CuO, etc. were respectively mixed with Bi: Sr: Ca: Cu in an atomic ratio.
2: 2: 1: 2 so that the mixed powder is mixed in the air 8
After calcining at 50 ° C. for 50 hours, the calcined body was crushed to form calcined powder, and then the calcined powder was CIP molded into bars having various outer diameters. Next, this rod was filled into a thin pipe made of high-purity Mg with an outer diameter of 10 mmφ with various wall thicknesses to form a composite billet, and then this composite billet was swaged and rolled to a width of 4.8 mm, thickness. 0.1 mm
It was made into a tape wire rod. Next, 45 tape wire rods were laminated and filled in Ag pipes with 5.0 mm square inner diameter with various wall thicknesses to form a multi-layer composite billet. The multi-layer composite billet was formed by a 4-way roll and a flat roll. Sequential rolling was performed to obtain a multilayer tape wire having a width of 4.8 mm and a thickness of 0.1 mm.
Then, the multi-layer tape wire was filled in a metal pipe to form a multi-layer composite billet, and the process of rolling this was repeated 9 times by alternately changing the material of the metal pipe to Mg and Ag, and finally obtained. Multi-layer tape wire material, outer diameter 5.5mm,
A square Ag pipe with an inner diameter of 5.0 mm was filled to form a multi-layer composite billet, and this multi-layer composite billet was sequentially rolled by a 4-way roll and a flat roll to finish into a multi-layer tape wire rod with a width of 5 mm and a thickness of 2 mm. The wire was passed through a semi-molten state in the air and then heat-treated at 850 ° C for 50 hours to produce a ceramic superconductor.

Example 5 A ceramic superconducting body was manufactured by the same method as in Example 4, except that the thin-walled pipe made of Al was used in place of the thin-walled pipe made of Mg as the inner layer. did. Example 6 In Example 2, Bi, Sr, Ca, Cu having various outer diameters were used.
The bar material was filled into high purity Mg pipes having various wall thicknesses and having an outer diameter of 10 mmφ to form a composite billet, and the composite billet was rolled and processed into a tape wire material having a width of 4.8 mm. The thickness of the tape wire rod was 0.12 mm for the composite bar material made of Bi, Sr, and Ca, and 0.14 mm for the composite bar material made of Cu. Next, these 5 types of tape are B
i, Sr, Ca, Cu were laminated in the order of 9 pieces, 36 pieces in total, and the thickness of this laminated body was changed to various thicknesses of 5 mm square inner diameter A
It was filled in a thin-walled pipe made of g to obtain a multilayer composite billet. The multi-layer composite billet was sequentially rolled by a 4-way roll and a flat roll to obtain a multi-layer tape wire having a width of 4.8 mm and a thickness of 0.1 mm. Then, the step of inserting the multi-layer tape wire into the metal pipe and rolling it into a multi-layer composite billet is repeated 19 times by alternately changing the material of the metal pipe to Mg and Ag, and finally obtained the multi-layer tape. The wire rod was filled into a square Ag pipe with an outer diameter of 5.5 mm and an inner diameter of 5.0 mm to form a multi-layer composite billet.
5mm wide and 2mm thick by rolling one side and one side
mm multi-layer tape wire. Next, this multilayer tape wire was heat-treated in the atmosphere at 840 ° C for 100 hours to manufacture a ceramic superconductor. The critical current density (Jc) of each multilayer ceramic superconductor thus obtained was measured in liquid nitrogen (77K). The magnetic field strength at the time of measurement was changed to 0 and 1 Tesler. The measurement results are shown in Tables 1 and 2.

[0014]

[Table 1]

[0015]

[Table 2]

As is clear from Tables 1 and 2, the method products of the present invention (Nos. 1 to 18) had a high Jc value not only in the absence of a magnetic field but also in a magnetic field of 1 Tesler, and the variation was small. As a result of observing the structure, particles of Ag, MgO or Al ₂ O ₃ were finely dispersed in the ceramic superconductor layer, and the crystal orientation was also good. On the other hand, the comparative examples (Nos. 19 to 30) had a low Jc, which was extremely lowered particularly in the state where a magnetic field was applied, and the variation was increased. The decrease in Jc was due to the absence of particles effective for pinning in the ceramic superconductor layer, and the reason for the large variation was that the compressive force of the stretching process was separated by many layers of metal pipe and the raw material layer It was because it was not transmitted uniformly.

[0017]

As described above, according to the method of the present invention, it is possible to easily manufacture a ceramics superconducting body having a small variation and excellent superconducting properties under a magnetic field, and to exert a remarkable industrial effect. ..

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional explanatory view showing an embodiment of a ceramic superconductor manufactured by the method of the present invention.

[Explanation of symbols]

 1 Metal sheath 2 Ceramics superconductor layer 3 Ag particles 4 Metal oxide particles

Claims (1)

[Claims] 1. A metal pipe is filled with a raw material capable of forming a ceramics superconductor to form a composite billet, and then this composite billet is drawn to form a composite material.
Next, the composite material is filled into a metal pipe to form a composite billet, and the step of stretching the composite billet to form a composite material is repeatedly performed a desired number of times, and then the obtained composite material is placed in a metal pipe. Filling into a multilayer composite billet, forming a multilayer composite wire by subjecting this multilayer composite billet to stretching, and then subjecting this multilayer composite wire to a predetermined heat treatment. For a metal pipe that is an inner layer excluding the outermost layer, the thickness t of the metal pipe is calculated by the following equation: 0.05D ≧ t ≧ 0.02
A method for producing a ceramics superconducting body, characterized in that a thin pipe satisfying D (where D is the outer diameter of a metal pipe) is used.