JPH0443514A - Manufacture of ceramics superconductor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a ceramic superconductor suitable as a conductor for cables, magnets, current leads, and the like.

[Conventional technology]

In recent years, Y-Ba-Cu-0, which exhibits superconductivity at liquid nitrogen temperature, has been developed.
system, B1-3r-Ca-Cu-0 system, T1-Ba-Ca
-Exceeds ceramics such as Cu-0 series.

However, since these ceramic superconductors are brittle, the metal sheath method is generally applied to process them into wire rods and the like. This metal sheath method, for example, uses A
A composite material is produced by filling a metal container such as G or Cu with a raw material that can be made into a ceramic superconductor, or by heating and melting the calcined powder of the raw material and casting it into a hollow metal billet. Next, these composite materials are made into wire rods of desired shapes such as circular, polygonal, tape-like, etc. by ordinary ram extrusion, rolling, swager-1 drawing, etc. A method is used in which the raw material is reacted with a superconductor through heat treatment.

(Problems to be Solved by the Invention) However, in the ceramic superconductor produced as described above, the density of the internal ceramic superconductor layer is low, so the critical current density (Jc) is at most 30,000 A/
The limit was about CD.

[Means to solve problems]

The present invention was made as a result of intensive research in view of the above situation, and its purpose is to provide a method for manufacturing a ceramic superconductor having superconducting properties superior to those of the prior art.

That is, in the present invention, a metal container is filled with a raw material that can be made into a ceramic superconductor to form a composite material, and then this composite material is stretched to form a wire rod in a desired shape, and then the resulting wire rod is A method for producing a ceramic superconductor in which a predetermined heat treatment is performed is characterized in that hot isostatic extrusion is included in the stretching process.

In the present invention, when stretching a composite material in which a metal container is filled with a raw material that can be made into a ceramic superconductor,
The density of the internal ceramic superconductor layer is increased by applying a hot isostatic extrusion method that enables uniform and strong processing.

In the method of the present invention, the stretching step may be performed only by hot isostatic extrusion, but hot isostatic extrusion may be combined with processing methods such as rolling, swaging, and drawing. When used in combination, it is preferable to first perform a hot isostatic extrusion process, since the internal ceramic superconductor layer can be processed to have a uniform thickness throughout.

The hot isostatic extrusion method used in the method of the present invention will be specifically explained below with reference to the drawings.

FIG. 1 is an explanatory longitudinal cross-sectional view showing an embodiment of the hot isostatic extrusion method. In the figure, l is a hydraulic medium and 2 is a container.

First, a composite material of metal and raw material is created.

As raw materials, primary raw material powders such as oxides and carbonates containing the constituent elements of the ceramic superconductor are blended and mixed to a desired composition, and the mixture is pre-fired to produce a pre-sintered powder.
This calcined powder may be used as it is, or may be CIP-molded, sintered, or melted to form an intermediate before the ceramic superconductor is synthesized into a conductor, such as a mixture or coprecipitation mixture of ceramic superconductor constituent elements, or Oxygen-deficient composite oxides or alloys of the above constituent elements can be used, and these are filled or cast into a metal container to form a composite material.The shape of this composite material is not particularly limited, and the cross-section In addition to being circular, it may also be square, polygonal, etc.

Next, the composite material produced in this manner is set in a container 2 with the tip of the composite material 3 passing through the die 4, and then the container 2 is filled with hydraulic medium l. The entire container 2 is heated to a predetermined temperature by the heater 5, and then the planter 6 is lowered to supply the hydraulic medium l.
The pressure is increased to continuously extrude the composite material 3 from the die 4.

In the above, it is also possible to extrude by heating the composite material separately without using a heater, setting it in a container, and immediately extruding it, which can improve productivity.

In the hot isostatic extrusion method used in the method of the present invention, pressure is applied isotropically to the composite material to be extruded by a hydraulic medium, so the extrusion pressure acts uniformly, resulting in a processing rate (
The extrusion ratio) can be high, and the raw material layer inside the extruded wire has a high density. In addition, according to the hot isostatic extrusion process, a thin film of hydraulic medium is formed on the surface of the composite material during extrusion, which acts as a lubricant.
Seizure with the die is eliminated, and as a result, the surface quality and cross-sectional shape of the composite material are improved, and the life of the die is extended. Furthermore, since the processing rate can be increased, it is possible to shorten the process and improve workability.

In the method of the present invention, the extrusion temperature in hot isostatic extrusion is 100°C or higher, preferably 200°C, since the ceramic superconductor layer cannot be sufficiently densified if the temperature of the composite material is lower than 100°C. The above, and sound extrusion,
Furthermore, from the viewpoint of making it difficult to use tools such as containers, dies, planters, etc., the temperature should be lower than the melting point of the metal used for the metal container (preferably 800°C or lower), and the extrusion ratio should be lower than the ceramic superconductor. In order to make the body layer sufficiently dense, it is preferable that the number is 5 or more.

The material of the metal container filled with the above raw materials includes Ag.
, Au, Cu, Ir, Pd, PL, or their alloys, among others, Ag or Ag alloys have good oxygen permeability, so oxygen can be sufficiently supplied to the ceramic superconductor in the heat treatment process. Therefore, a superconductor having a high Jc can be obtained, and since the thermal conductivity is also high, the obtained superconductor has excellent quench resistance and is suitable because it can further increase the amount of current passed.

[Effect]

In the method of the present invention, hot isostatic extrusion processing that can be uniformly and strongly worked during the drawing process is included in drawing a composite material in which a metal container is filled with a raw material that can be made into a ceramic superconductor. The resulting ceramic superconductor has a high-density ceramic superconductor layer inside, and therefore has a high Jc value.

〔Example] The present invention will be explained in detail below using examples.

Example 1 As starting material, B L 03. S r COi, Ca
Using CO3, CuO, this was converted into B::Sr:Ca:
The CU was blended and mixed in an atomic ratio of 2:2:1:2, and then this mixture was heated to 800"c x
Calcined for 20 hours, pulverized and classified to obtain calcined powder, and then crushed the calcined powder into a powder with an outer diameter of 25 mm and an internal diameter of 20 am.
Fill a pipe-shaped container made of Ag with a length of 100 mm with a tap,
Both ends were vacuum sealed to create a composite material. Thereafter, this composite material was processed into a wire rod under various conditions using the hot isostatic extrusion method illustrated in FIG. This tape material was then subjected to heat treatment at 850° C. for 50 hours in the atmosphere to produce a tape-shaped ceramic superconductor.

Example 2 The same method as in Example 1 was used, except that the calcined powder obtained in Example 1 was CIP-molded into a 20 mmφ bar material by applying a pressure of 4000 atmospheres in advance, and this molded body was filled into an Ag container. A tape-shaped ceramic superconductor was manufactured using the following method.

Example 3 The calcined powder obtained in Example 1 had an outer diameter of 6 holes.

Inner diameter 4III11. It was filled into a 50 mm long Ag container, and then processed by hot isostatic extrusion to an outer diameter of 11 mm. A linear ceramic superconductor was produced in the same manner as in Example 1, except that a wire rod of No. ll11 was used and the wire rod was heat-treated as it was without being rolled.

Comparative Example 1 The composite material produced in Example 1 was subjected to a normal hot extrusion method at extrusion temperatures and extrusion ratios of 80"C and 5.0"C, respectively.
Comparative Example 1-14), 80°C, 9,8 (Comparative Example 1-15)
), 500°C, and 2.7 (Comparative Example 1-16), and processed into wire rods of various diameters, and the wire rods were rolled and heat-treated in the same manner as in Example 1 to produce tape-shaped ceramic superconductors. was manufactured.

For each of the ceramic superconductors manufactured in Examples 1 to 3 and Comparative Example 1 in this way, liquid nitrogen (7
7K), Jc was measured under zero magnetic field. The results are shown in Table 1 together with hot isostatic extrusion conditions, extrusion diameter, etc.

*Comparison method product Table 1 As is clear from Table 1, the invention method product (Ni11~
No. 13) all had high Jc values. This is because the ceramic superconductor layer inside the composite material is processed to a high density by hot isostatic extrusion.

Regarding hot isostatic extrusion conditions, the higher the extrusion ratio, the
Furthermore, it was observed that the extrusion temperature tended to increase with the peak at so o'c. If the extrusion temperature exceeds 800℃, Jc
The reason for this decrease is that the outer layer of the Ag container of the composite material was partially melted when passing through the die, resulting in a decrease in pressure, making it impossible to sufficiently improve the density of the internal ceramic superconductor layer. In addition, it was found that the Jc of raw materials that were preformed and filled using CIP was generally improved compared to those that were filled as a powder.Those that were subjected to six-prong drawing processing using only hot isostatic extrusion (Nα13 ) is also combined with rolling process (N[]1
~7) showed a similar high Jc.

On the other hand, the comparison method products (No. 14 to 16) were Jc
had a low value. This is because the density of the internal ceramic superconductor layer did not improve because the drawing process was performed by conventional hot extrusion and rolling.

〔effect〕

As described above, according to the method of the present invention, a ceramic superconductor having excellent superconducting properties such as Jc can be easily manufactured, and it has a remarkable industrial effect.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of the hot isostatic extrusion method used in the present invention.

Claims (1)

[Claims] A metal container is filled with a raw material that can be used as a ceramic superconductor to form a composite material, and this composite material is then stretched to form a wire rod of a desired shape, and the resulting wire rod is subjected to a prescribed heat treatment. A method for manufacturing a ceramic superconductor, characterized in that the stretching step includes hot isostatic extrusion.