JPS5837643B2 - Method for manufacturing compound superconducting wire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a compound superconducting wire, and particularly relates to an improvement in the method for producing a compound superconducting wire in which a compound superconductor is distributed in the form of intermittent fibers in a normal conducting metal.

Compound superconducting wires usually contain Nb 3 S in a normal conducting metal.
It is a compound superconductor such as n, VsGa, etc.

These compound superconducting wires can be roughly divided into those in which a continuous compound superconductor layer is provided in a normal conducting metal along the longitudinal direction of this metal, and those in which a fibrous layer is disposed in a normal conducting metal. There are some types in which compound superconductors are distributed.

The latter is designed to exhibit superconducting function through the proximity effect, microresistance, fine superconducting precipitates, etc., and because the compound superconductor is distributed in the form of intermittent fibers, the critical current value due to strain is smaller than the former. It is characterized by low deterioration.

By the way, as a method for manufacturing a compound superconducting wire in which a compound superconductor is distributed in a normal conducting metal in the form of intermittent fibers as described above, the following method has been conventionally employed.

That is, here, the case where the Nb3Sn layer is used as an example will be explained.

(1) After melting an alloy in which Cu has been added with Nb and Sn, it is cooled to form, for example, a cylindrical ingot, and this ingot is thinned by thinning, and then
A method of applying heat treatment to form an interrupted fibrous Nb3Sn layer in the conductor.

(2) An alloy made of Cu with Nb added is melted, and the resulting alloy liquid is poured into a cooling block with columnar holes and rapidly cooled, resulting in a rod-shaped ingot in which grains are uniformly precipitated in the Cu. This ingot is processed to reduce its area and made into fine wires, so that cold is distributed inside in the form of intermittent fibers.

Next, after attaching Sn to the surface of this thinned conductor,
A method of applying heat treatment to diffuse Sn and forming a Nb3Sn layer around the intermittent fibrous Nb existing inside.

(3) A method in which Nb, Cu-Sn alloy powder is filled into a Cu pipe, etc., the area is reduced to make the wire thinner, and then heat treatment is performed to form an intermittent fibrous Nb3Sn layer in the conductor. .

However, in such conventional manufacturing methods,
It had the following drawbacks.

That is, in consideration of flexibility when surface-reducing the Cu--Nb--Sn alloy in method (1), the limit for the amount of Nb added is 10 atoms, and the limit for Sn is 5 atoms.

For this reason, the critical current value (Ic) of the obtained superconducting wire (overall) is very small, which has the disadvantage that it is impossible to manufacture a practical product after all.

Furthermore, in the method (2), since the Cu--Nb alloy is processed to reduce its surface area and made into thin wires, flexibility during processing is good.

Therefore, the amount of Nb added can be tolerated up to 40 atoms,
The critical current value (I
c) can be significantly improved.

However, when the amount of Nb added increases, when the Cu-Nb alloy liquid is cooled to form a rod-shaped ingot, if it is not uniformly and rapidly cooled at a high cooling rate, Nb particles will precipitate in the Cu. are combined to form large dendrites, and Nb segregation occurs.

When Nb segregation occurs in this way, the critical current value decreases,
This results in variations in properties along the length of the wire.

In order to rapidly cool the ingot uniformly and at a high cooling rate, it is necessary to reduce the diameter of the ingot.

In order to reduce the diameter of the ingot in this way, it is necessary to reduce the diameter of the hole into which the alloy liquid is poured, and it is not possible to obtain a satisfactory rod-shaped ingot due to soot, air bubbles, etc. in the alloy liquid during pouring.

In addition, when Sn is attached and heat treated, this S
There is also the problem that n easily melts or falls off, and as a result, it is difficult to obtain a uniform critical current value along the longitudinal direction of the wire.

In addition, it took a long time to generate the Nb3Sn layer, making it difficult to mass-produce with this method.

In addition, in the method (3), the blending ratio tends to be non-uniform along the longitudinal direction when the powder is filled, so there is a problem that it is difficult to obtain uniform properties along the longitudinal direction.

The present invention was made in view of the above circumstances, and its purpose is to produce a compound superconducting wire in which a compound superconductor is distributed intermittently and in the form of fibers in a normal conducting metal in a small number of steps. It is an object of the present invention to provide a manufacturing method that can produce a large number of wire rods with uniform critical current values along the longitudinal force direction of the wire rod.

Hereinafter, details of the present invention will be explained with reference to FIGS. 1 to 5.

First, as shown in FIG. 1, a container 1 having a cylindrical inner space is prepared, and in the cylindrical space 2 of the container 1, one of the elements constituting a compound superconductor is added to a normal conducting metal. The alloy 3 to which the first element is added is housed.

Next, the container 1 is heated to melt the alloy 3 contained in the cylindrical space 2.

Next, the container 1 containing the alloy liquid was put into water, oil, or a molten low-melting metal to be rapidly cooled, whereby the first element was uniformly precipitated as shown in FIG. A cylindrical alloy ingot 4 is formed.

Next, as shown in FIG. 3, a core material made of a pure metal material made of a second element constituting the compound superconductor covered with a normal conductive metal layer or the second material is placed in the cavity 5 of the alloy ingot 4. A core material formed by covering an alloy material 6 with added elements with a normal conductive metal layer 7 is installed, and a plurality of these are bundled and installed in a normal conductive metal cylinder 9 as shown in FIG. A superconducting base 10 is formed.

Next, this composite superconducting substrate 10 is subjected to a thinning process to make the wire thinner, thereby uniformly distributing the particles of the first element in the form of intermittent fibers.

Next, the thin wires as described above are subjected to heat treatment.

When the heat treatment is performed in this way, the second element is diffused,
A compound superconductor is formed on the surface of the first element in the form of interrupted fibers, and a compound superconductor wire can be obtained here.

Figure 5 shows the compound superconducting wire X produced in this way.
In the figure, Y indicates a normal conducting metal, and Z indicates a compound superconductor distributed in the form of interrupted fibers.

In addition, when adopting such a manufacturing method, Cu, Al, Ni, or an alloy thereof can be used as the normal conductive metal, and Nb3, etc. can be used as the first and second elements.
Sn, Nb3A#, Nb3(Al,Ge)tV 3 G
a , Nb 3 Ga t Nb 3 Ge , N
b A material capable of forming a compound superconductor such as CN can be used.

Of course, it is also possible to improve the superconducting properties by replacing some of the elements constituting the compound superconductor with In, GatHftZrtMgyAltTa, or the like.

Further, the normal conductive metal layer 7 forming the outermost layer of the core material is intended to prevent workability during area reduction processing from being impaired when the first element and the second element come into contact with each other. be.

In addition, in carrying out such a manufacturing method, in order to stabilize the obtained superconducting wire, the cylinder 9 is formed of a stabilizing metal material, and the inside of the cylinder 9 is If the composite superconductor 10 is formed with a diffusion prevention cylinder made of a metal material capable of preventing the second element from diffusing into the composite superconductor 10 and then manufactured by the process described above, stability can be achieved. A compound superconducting wire can be obtained.

Figure 6 shows the compound superconducting wire X produced in this way.
' In the figure, R represents a stabilizing metal, S represents a diffusion prevention metal, Y represents a normal conducting metal, and 2 represents a compound superconductor distributed in the form of intermittent fibers. .

In addition, multiple perforated blocks are formed with stabilizing metal material,
A diffusion prevention cylinder is installed in each hole of this block, and a plurality of the above-mentioned alloy ingots with core materials are installed in these prevention cylinders to constitute the composite superconducting substrate 10, and then the above-mentioned steps are carried out. A compound superconducting wire may be manufactured through the above steps.

Figure 7 shows the compound superconducting wire X' produced in this way.
The end face is shown.

If such a manufacturing method according to the present invention is adopted, there are the following advantages.

That is, instead of processing an alloy formed by adding the first and second elements constituting a compound superconductor into a normal conducting metal, the alloy is formed by adding the first element to a normal conducting metal. A composite superconductor 10 is formed by simply mechanically bonding the alloy and a pure metal consisting of the second element or an alloy containing the same through a normal conducting metal, and this base body 10 is subjected to surface reduction processing. The first and second
Even when the amount of elements is large, there is no risk of deterioration of workability.

In addition to this, inside the container 1 whose internal space is formed into a cylindrical shape,
After storing the alloy 3 made by adding the first element in a normal conductive metal and melting the alloy 3, the container 1 is rapidly cooled to form a cylindrical alloy ingot 4. , by rapidly cooling the entire container 1 and by setting the internal space of the container 1 in a cylindrical shape, it is possible to uniformly and rapidly cool each part of the combined liquid. For example, when a large amount of the first element is Even when it is added, it is possible to form a relatively large-diameter alloy ingot 4 in which particles of the first element are uniformly dispersed.

Since the above-mentioned cooling method is adopted, it is also possible to form the alloy ingot 4 according to the target without being affected by soot, bubbles, etc.

In addition, since the core material containing the second element constituting the compound superconductor is loaded into the cavity 5 of the alloy ingot 4, a large amount of the second element can be added to the wire in a simple process. Uniform distribution can be set along the longitudinal force direction.

Therefore, a compound superconducting wire having a uniform critical current value along the longitudinal direction of the wire and a high critical current density can be easily manufactured.

In addition, a composite superconducting base 10 is formed by assembling a plurality of alloy ingots 4 with a core material attached to the cavity 5, and this is thinned by thinning processing, so that a sufficiently long compound superconducting wire is made at a time. can be manufactured, and productivity can be improved, and as a result, productivity can be improved and the properties of the compound superconducting wire can be improved at the same time.

Next, examples of the present invention will be described.

Example 1 First, an alloy formed by adding 30 atoms of Nb, the first element constituting a compound superconductor, to Cu, which is a normal conducting metal, was heated to a thickness of 2mm and an inner diameter of 10n1 in an argon gas atmosphere.
The mixture was heated and melted in an open carbon container with a depth of 200+ m and a bottle with a diameter of 4 mm set up in the center of the bottom plate.

Next, put the entire container into oil, cool it quickly, and place about 4 m in the center.
It has a cavity of yn, an outer diameter of about 10 mw, and a length of about 150 mm.
A solid Cu-Nb alloy ingot was formed.

Next, a second element, S, is added to the cavity of the alloy ingot.
A core material made by covering the outer periphery of Sn-5at/ocu alloy containing n with Cu, which is a normal conductive metal, with a thickness of about 0.5 mm is attached, and 19 pieces of this are bundled to form a material with an inner diameter of about 50 u and an outer diameter of about 65 tons.
A composite superconducting substrate was formed by installing it in a Cu pipe, which is a normal conducting metal.

Next, this base is subjected to surface reduction processing to make the wire thinner, and the wire diameter is
A wire rod of 400 m was formed.

Next, this wire was heat-treated in Alcon gas at 700°C for 50 hours to diffuse the second element Sn, and as shown in Figure 5, the wire was made into intermittent fibers in the Cu-Sn alloy, which is a normal conducting metal. A compound superconducting wire in which a Nb3Sn superconductor exists was manufactured.

When the critical current value of the compound superconducting wire obtained in this way was measured, the critical current value Ie = 68 OA and the critical current density Jc = 8.6 5 X at an external magnetic field of 4 Tesla.
102A/mm, external magnetic field 7 Tesla, Ic=2
It exhibited excellent superconducting properties of 7OA, Jc=3.44X102A/m4, and was almost uniform in the longitudinal direction of the wire.

Example 2 This example is an example implemented in a device equipped with a stabilizing function.

First, a cavity of an alloy ingot formed in the same manner as in Example 1 is filled with a normal conductive metal having a thickness of 0. After bundling 19 pieces with a core material of Sn-5at/oCu, which is an alloy containing a second element and covered with 5 mm of Cu, this was bundled with an inner diameter of about 50 mm made of Ta, which is a metal for preventing diffusion. , outer diameter approximately 551
It was installed in a diffusion prevention cylinder of nN, and then installed in a pipe made of Cu as a stabilizing material and having an inner diameter of about 55 mm and an outer diameter of about 65 mm to form a composite superconducting substrate.

Next, the above composite superconducting substrate was subjected to surface reduction processing to obtain a wire with a wire diameter of 1 m.
l! 400 m of wire was formed.

Next, this wire was heat-treated in argon gas at 700°C for 50 hours to diffuse the second element, Sn, into the Cu-Sn alloy, which is a normal conducting metal, as shown in Figure 6. A compound superconducting wire containing a fibrous Nb3Sn superconductor and covered with Cu as a stabilizing material was manufactured.

When the critical current value of the compound superconducting wire obtained in this way was measured, the critical current value Ic = 69OA and the critical current density Jc - 8.7 x 1 at an external magnetic field of 4 Tesla.
02k/mtl, external magnetic field 7 tesla, Ic=2 7
0 AX Jc = 3.4 4X 1 02 A/mA, the same result as in Example 1, was obtained, and in this case, when the critical current value was exceeded, the voltage in the current-voltage characteristic was gradual and stable. The following characteristics were obtained.

Thus, it was confirmed that by employing the manufacturing method according to the present invention, compound superconducting wires with high characteristics can be easily produced in large quantities.

[Brief explanation of drawings]

1 to 5 are diagrams for explaining embodiments of the manufacturing method according to the present invention in the order of steps, and FIGS. 6 and 7 are diagrams showing different compound superconducting wires manufactured by the manufacturing method according to the present invention. FIG. 1... Container, 4... Alloy ingot,
10... Core material, 10... Composite superconducting substrate.

Claims (1)

[Claims] 1. An alloy formed by adding a first element of the elements constituting a compound superconductor to a normal conducting metal is melted in a container with a cylindrical interior space, and then the container is rapidly cooled to form the first forming a cylindrical alloy ingot in which elemental particles are uniformly dispersed and precipitated, and adding a pure metal consisting of a second element of the elements constituting the compound superconductor into the cavity of the alloy ingot. A core material formed by coating with a conductive metal or a core material formed by coating an alloy containing the above-mentioned second element with a normal conducting metal is attached, and a plurality of these are attached to a plurality of normal conducting metals to form a composite superconducting substrate. A step of forming a composite superconducting substrate, a step of reducing the area of the composite superconducting substrate to make it thin, and heat-treating the thin wire obtained by this step to form an intermittent fibrous compound superconductor in a normal conducting metal. A method for manufacturing a compound superconducting wire, comprising the steps of: