JPH01175128A - Manufacture of oxide superconducting linear body - Google Patents

Abstract

PURPOSE:To realize the high critical current density by heating and melting an oxide to become a superconductor and quickly solidifying it via a roll made of the preset material on the surface layer. CONSTITUTION:A mixture of oxides to become a superconductor, e.g., powder of Y2O3, BaCO3 and CuO or the like, with the preset quantity ratio is heated and melted by the high-frequency induction heat or the like and stored in a crucible 1 as an oxide molten body 2 and fed on a rotating roll 3 or between a pair of rotating rolls 3A and 3B and quickly cooled and solidified. The material forming the surface layer of the roll is made of one or two kinds of metal oxide, nitride, carbide and boride. In this case the metal is selected depending on the shape of a linear body after molding, e.g., flake shape or thin plate shape. An oxide superconducting linear body with large critical current density is obtained according to this manufacture.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing an oxide-based superconducting wire, and particularly a thin plate having a high density and a high value of critical current density (J,). The present invention relates to a method for manufacturing an oxide-based superconducting wire body.

[Conventional technology and its problems]

Oxide-based superconductors made of alkaline earth metals, rare earth elements, copper, and oxygen have high critical temperatures (T c ), and are expected to be used for this purpose. However, oxide-based superconductors are generally processed into linear shapes. However, in order to form a wire, oxide powder material that will become a superconductor is filled into a metal tube made of silver, silver alloy, copper alloy, etc., and then wire drawn, swaged, grooved rolls, or flat rolls are used. The wires or thin plates were cold-worked into wires or thin plates to obtain wires of desired dimensions, and then heat-treated to produce oxide-based superconducting wires.

Other methods have also been attempted, such as kneading the oxide powder and binder and then forming it into a wire rod through extrusion processing, or coating it on the outer periphery of the core material and then performing heat treatment including removal of the binder. It is being

[Problem that the invention seeks to solve]

However, in these methods, since oxide powder is used as the material that becomes the superconductor, even if processing is performed with a high area reduction rate, the density of the superconducting wire after heat treatment is not the same as its true density. There was a problem that a value close to the density could not be obtained, and therefore the critical current density (Jc) was low.

[Means for solving problems]

The present invention was made as a result of intensive studies in view of the above points, and its purpose is to provide a method for manufacturing an oxide-based superconducting wire having high density and a high value of critical current density (Je). It is to provide.

That is, the present invention provides an oxide-based superconducting wire characterized by heating and melting an oxide to become a superconductor, and then supplying it onto the surface of a rotating roll or between a pair of rolls and rapidly solidifying it. It is a method of manufacturing the body.

In the present invention, as the base material of the oxide that becomes the superconductor, for example, in the case of Y-Ba-Cu-0 system, Y2O3, B
a Raw material powders such as COx and CuO are adjusted to the desired composition (Y B
a zc u 5ot-x, etc., however, 0〈x〈0.5)
After mixing, it is preferable to pre-sinter at about 900°C.The oxide powder material (fiber, bulk, etc.) obtained in this way is heated. As for the melting method, for example, an oxide to be a superconductor may be filled in a crucible, and the crucible may be melted by high-frequency induction heating, an electric furnace, infrared heating, or the like.

At this time, the material of the crucible for melting the oxide base material is 9
, for example, pure metals such as W and Mo, or Al.

01. Products made of oxides such as MgO or other ceramics may react with the molten oxide that becomes the superconductor and change the properties of the oxide, or the reaction with the molten oxide may be significant. However, crucibles made of platinum, iridium, or their alloys (for example, Pt--Rd, etc.) are particularly preferred because they do not have this tendency.

In addition, if the holding temperature of the oxide melt is less than 1200°C, the solution becomes extremely viscous and has poor moldability;
If it exceeds C, the reaction with the crucible material will be significant and the life of the crucible will be shortened, so the temperature of the melt should be 1200-1
It is desirable to keep the temperature within the range of 500°C.

In the method of the present invention, various materials can be used for the roll for rapidly solidifying the oxide melt obtained in this way depending on the purpose. For example, metals such as iron and copper can be used. When used, the cooling rate of the oxide melt increases because the roll has a high thermal conductivity, and as a result, the rapidly solidified oxide melt breaks off and becomes flaky thin pieces. That is, in order to obtain the aforementioned flake-like thin pieces, such a metal roll may be used.On the other hand, in order to obtain a relatively long continuous thin plate, metal oxides (AI!, etc.) with low thermal conductivity may be used. , O, ZrzOs, etc.), nitrides (Af
It is desirable to use a roll made of ceramics such as fiN, BN, etc.), carbides (SiC, Tic, etc.), borides (ZrB, TiBx, etc.); in this case, only the surface layer of the roll is made of the ceramics. Even if it is, the same effect can be obtained.

Next, embodiments of the present invention will be specifically described using the drawings. FIG. 1 is an explanatory diagram showing an example of the method of the present invention,
2 is a crucible, 2 is an oxide melt that becomes a superconductor, 3 is a roll, 4 is a thin plate, and 5 is a heater. In this method, one plate 4 is obtained by dropping a melt 2 of an oxide, which becomes a superconductor, melted in a crucible 1 onto a rotating roll 3 and rapidly solidifying it.

In this method, the shape of the opening (nozzle) at the bottom of the crucible 1,
By controlling the rotational speed (or circumferential speed) of the roll 3, the gap between the nozzle and the roll 3, etc., it is possible to obtain thin plates 4 of various dimensions (width and thickness).

FIG. 2 is an explanatory diagram showing another example of the method of the present invention,
A and 3B are a pair of rotating rolls.

In this method, an oxide melt 2 which becomes a superconductor is melted in a crucible 1 between a pair of rotating rolls 3A and 3B.
In this method, the thin plate 4 is obtained by supplying and rapidly solidifying the thin plate 4.

In this method, the nozzle opening shape, roll 3A.

The dimensions of the thin plate 4 can be changed by changing the gap between the sheets 3B, the number of rotations of the rolls, etc. For example, in order to reduce the thickness of the plate, it is generally sufficient to reduce the outer diameter of the roll or increase the number of rotations of the roll.

The thin plate-like filament obtained by the first recovery method or the method shown in FIG. A superconducting wire is manufactured.

[Effect]

In the method of the present invention, after melting the oxide powder material that becomes the superconductor, it is supplied onto the surface of a rotating roll or between a pair of rolls, and then cooled and solidified. Since the filament is formed into a filament, the density of the filament obtained is improved, and an oxide-based superconducting filament having a large critical current density (Jc) can be obtained.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples. By the method shown in FIGS. 1 and 2, an oxide base material that becomes a superconductor is heated and melted, and this is rotated on the surface of one roll 3 or on a pair of rolls 3A.

The thin plate 4 was obtained by rapid solidification at a temperature of 3B. The base material of the oxide that will become the superconductor used is Y-Ba-Cu -0 system, and the raw materials are Y, 01, BaCO5, CuO powder and Y:Ba:Cu is 1 = 2:3 (mole ratio). The mixture was weighed and mixed, and then this mixture was pre-calcined in an oxygen atmosphere for 900@C x 1 Ohr, and then ground in a ball mill and used. Further, the heating method was radial frequency induction heating, and the material of the crucible was PT.

Regarding the above method, as shown in Table 1, thin plates 4 were produced by changing various conditions such as the melting temperature of the oxide, the material of the roll, and the circumferential speed, and each of the obtained thin plates was placed in an oxygen atmosphere. 9
A heat treatment was performed at 00°C for 10 hours to obtain an oxide superconducting thin plate. For each thin plate thus obtained, superconductivity such as dimensions (width and thickness), density (ratio to true density, %), critical temperature (Tc), critical current density (Jc) at liquid nitrogen temperature (77K), etc. Characteristics were measured. The results obtained are summarized in Table 2.

For comparison, the above Y20. , B a COs, and CuO powder were weighed and mixed so that Y:Ba:Cu-1 = 2:3 (mole ratio), and this was heated at 900°C x 1 in an oxygen atmosphere.
After Ohr pre-sintering, the oxide powder obtained by crushing in a ball mill was filled into an Ag pipe with an outer diameter of 8 mm (inner diameter 6 mm), and then cold wire drawing was performed to form a 0.8 mm composite wire. did. Subsequently, the composite wire was heated at 900° in an oxygen atmosphere.
An oxide-based superconducting wire was manufactured by performing CX heat treatment for 10 hours. The properties of the oxide superconducting wire thus obtained were measured. The obtained results are also listed in Table 2 as Comparative Example 11.

As is clear from Table 2, oxide-based superconducting thin plates with high density and high p = field current density (Jl:) were obtained in the products 1 to 7 according to the present invention manufactured by the method of the present invention. There is. On the other hand, in the method shown in Fig. 2, the comparative product 9 in which the temperature of the oxide melt was too low could not be continuously supplied with the melt from the crucible, and the comparative product in which the temperature of the melt was too high. Regarding product 10, the melt reacted with the crucible and the crucible was damaged, and a thin plate could not be obtained. In Comparative Product 8, which used iron rolls, the thin plate was broken and became flaky, and it was not possible to obtain a continuous long thin plate.

In addition, for comparative product 11, whose wire rod was manufactured using the conventional method, the wire rod was 85
Although the sample exhibited superconductivity, the critical current density (J) value was significantly lower than that of Inventive Products 1 to 7 due to the low density of the superconductor.

〔Effect of the invention〕

According to the method of the present invention, it is possible to obtain an oxide-based superconducting wire having a large critical current density (JC), which brings about significant industrial effects.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are explanatory diagrams showing an example of the method for manufacturing an oxide-based superconducting wire according to the present invention. 1. - Crucible, 2-... Oxide melt, 3.3A, 3B
=・-Roll, 4-・Thin plate, 5- Heater. Patent Applicant Agent Patent Attorney - Figure 1 Figure 2

Claims (2)

[Claims] (1) An oxide-based superconducting filament characterized by heating and melting an oxide to become a superconductor and then supplying it onto the surface of a rotating roll or between a pair of rolls and rapidly solidifying it. Production method. (2) A patent claim characterized in that at least the surface layer of the rotating roll is composed of one or more of metal oxides, nitrides, carbides, and borides. A method for producing an oxide-based superconducting wire according to Item 1.