JPS602727B2 - Method for producing intermetallic superconductor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing intermetallic superconductors such as N-based Sn, V3Ga, N-based W, etc., which are extremely brittle and have no workability.

Metallic compound-based superconductors such as Nb-Ti and N
critical temperature compared to alloy superconductors such as b-Ti-Zn,
Development of manufacturing methods for use in unusually high-field superconducting magnets with high critical magnetic fields is underway.

However, because of this skill, there are many restrictions in manufacturing and usage. Taking N&Sn as an example, the conventional method used is a method based on Nb or Nb alloy.
One is after plating Sn on tape-shaped Nb.
One method is to perform heat treatment as described above to form a thin Nb layer with a thickness of approximately 11, and the other method is to embed a large number of Nb pongee wires in a Cu-Sn alloy and perform heat treatment at 600 to 800 degrees Celsius to form Nb wires. This is a method of generating NQSn of about 1 on the surface. All of these methods are based on the idea that by making the N/Sn layer thinner, efforts to improve the superconducting properties due to insulation treatment and bending during coil forming can be avoided.

However, since the compound layer is thin, a large current capacity cannot be obtained, and a certain degree of deterioration in characteristics due to bending must be expected. Moreover, when a Cu--Sn alloy matrix is used, there are many problems such as that it does not function as a current bypass when superconducting breakdown occurs. On the other hand, a method has been proposed in which heat treatment is performed after coil forming to generate a compound layer to avoid deterioration of properties due to bending.
Heating for several hours is required at 0qo, and the reality is that no insulating material that can withstand this has yet been developed.

The causes of the above-mentioned problems stem from the fact that intermetallic compounds such as N and Sn are essentially brittle materials. Needless to say, this problem can be solved if cold working can be applied and NQSn can be finally produced at a low temperature.

This invention was made based on the above knowledge.N
When manufacturing intermetallic compound-based superconducting materials such as Sn, V30e, and N-Q, they are made into non-crystalline materials, that is, so-called amorphous materials, and are made using cold workability, which is a major characteristic of amorphous alloys. The idea is to form an intermetallic compound with superconducting properties by processing it into a desired shape and finally heat-treating and crystallizing it. Ordinary metals and alloys have a crystalline structure with a certain regularity in atomic arrangement at room temperature. For example, NQSn has a crystal structure called 81W type,
It has a crystal structure in which Sn atoms are regularly substituted in the face-centered part of a cubic Nb crystal. This crystal structure makes it highly brittle and difficult to cold work, resulting in the manufacturing problems mentioned above. However, even metals and alloys that have crystallinity as described above are glass-like amorphous in a high-temperature molten state, and the atomic arrangement is random.

Amorphous alloys are "rapidly cooled in the amorphous atomic arrangement of this molten state and kept at room temperature without giving time for crystallization, and due to the randomness of the atomic arrangement, they become brittle when processed between sleeves." The amorphous alloy is made into an amorphous alloy.When the amorphous alloy is reheated at a low temperature, atomic movement occurs, and each atom changes according to thermodynamics. They begin to rearrange to the most stable position, and so-called crystallization occurs.
This crystallization temperature is 300-400oC, for example 7
An amorphous alloy with a composition of 0%Nb-30%Sn changes from an amorphous state to a crystalline state at this crystallization temperature, and is the most stable atomic group for this composition.
- A W-type intermetallic compound is generated, and N-rich Sn is generated, which exhibits superconducting properties. This crystallization temperature ranges from 600 to the formation temperature of NCSn due to diffusion formation as explained earlier.
This is much lower than 100,000. There are vacuum evaporation methods, electrodeposition methods, electroless finishing methods, and other methods for producing the above-mentioned amorphous alloys, but none of them are suitable for industrial production.

Industrially, the liquid lining method adopted by this invention is suitable.

The present invention will be specifically described below based on an example in the case of N wide Sn.

The component ratio that generates N-wide Sn is approximately 70% by weight.
It is Nb-30%Sn.

The raw material having this composition is melted by high frequency flotation melting method. Although the figure is shown as an omitted view because it merely shows the state of filament production, the container 2 has a pipe shape and is elongated upward. Such containers are made of quartz glass and have approximately 0.0
．． There is a nozzle 3 made of quartz glass with the same diameter on two sides, and the upper part is a gateway through which raw materials are introduced and inert gas is blown. A high-frequency coil is wound around the pipe-shaped container, and a high-frequency current is applied. Then, the raw material in the container is held in space by electromagnetic force and floats between the coils, and is melted while floating in the container by being subjected to conductive heating by the high-frequency current. When melting is complete, turn off the high frequency current. Then, the electromagnetic force disappears, and the molten metal 4 falls to the bottom of the container. Since an inert gas is blown into the container, an internal pressure is generated by this inert gas, and the molten metal 4 that has fallen to the bottom is immediately blown out from the nozzle 3 due to this internal pressure, and the inner surface of the rotating copper cylinder turtle. It solidifies at the moment it is injected quickly and smoothly.The cooling rate at this time is 1 pi°C'sec, and the solidified raw material has no time for atoms to diffuse, forming an amorphous alloy that remains in the molten state. In addition, the inner diameter of the copper rotating cylinder in the above is 300 mm, and the rotation speed is 300 mm.
The desk is min. Although the rotating spinal cord 1 may be subjected to cooling treatment, there is no problem in practical use if it remains at room temperature. The raw material injected onto the inner surface of the rotary tube 1 in this way solidifies into a filament 5 with a thickness of about 20 mm in the front and back of the four legs, and at the same time as it solidifies, it peels off by itself from the inner surface of the rotary tube 1, forming an amorphous alloy. It is formed as a thin coiled filament 5.

Such a filament 5 has the properties of an amorphous alloy as described above, and can be easily subjected to cold working.

Such a filament 5 is processed into a required wire material by cold working together with high-purity steel or aluminum as a stabilizing material, coated with insulation, and formed into a coil.

As it is, the Nb-Sn alloy is still an amorphous alloy, and therefore does not have predetermined superconducting properties.

After this, a superconducting magnet made of Nb3Sn can be obtained by heat-treating the coil molded body to crystallize the filament contained therein and giving the filament super-conducting properties.
This heat treatment is heating to the so-called crystallization temperature, and as explained above, it can be used at a much lower temperature than the conventional diffusion reaction method, so it does not deteriorate the applied heat-resistant insulation material and can be used as a safety metal. There is no reduction in the purity of the knots. Of course, most of the Nb/Sn filaments present in the copper become superconducting compounds (N-Sn) through this heat treatment, so the current capacity can be increased, and the current capacity can be easily adjusted depending on the amount buried. You can also do it. This is not limited to the case where the superconductor is N-rich Sn, but also applies to other compound-based superconductors such as V3G and Nb3Q.

As is clear from the above description, the present invention improves workability by using an amorphous superconducting filament embedded in a stabilizing metal, making it possible to use conventional insulating materials and achieving high purity. This makes it possible to provide a compound superconducting coil stabilized with metal, and it also makes it possible to adjust the current capacity by adjusting the amount of filament, and its industrial value is extremely high, such as reducing the cost of the product and stabilizing its characteristics. It's expensive.

[Brief explanation of the drawing]

The figure is an explanatory view showing an example of a filament manufacturing method applied to the method according to the present invention. 1: rotating cylinder, 2: container, 3: nozzle, 4: molten metal, 5: filament.

Claims (1)

[Claims] 1 A thin mixed molten stream of metals constituting a superconducting intermetallic compound is rapidly cooled to obtain a continuous thin amorphous filament, which is then combined with a stabilizing metal and an insulating material to form a predetermined shape. 1. A method for manufacturing an intermetallic superconductor, which comprises molding the filament into a crystalline superconductor, and then heat-treating the molded body to form a crystalline superconductor in the filament.