JPS5837644B2 - 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 made of a compound superconductor such as n v V 3 Ga.

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, the case where a gSn layer is formed will be described here as an example.

(1) After melting an alloy in which Cu has been added with Nb and Sn, it is cooled and shaped into a cylindrical ingot, for example, and this ingot is subjected to a neck reduction process to become a thin wire, and then heat treated, This results in intermittent fibrous Nb3 in the conductor.
Method of forming a Sn layer.

(2) An alloy made of Cu with Nb added is melted, and the molten metal liquid is poured into a cooling block with column-shaped holes to rapidly cool it, resulting in a rod-shaped ingot in which the cutting particles are uniformly precipitated in the Cu. This ingot is processed to reduce its area and made into fine wires, so that Nb 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 to form an 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 method (1), considering the flexibility when processing the Cu-Nb-Sn alloy to reduce the amount of metal, the amount added for sleeves is limited to 10 atomic %, and that of Sn is limited to 5 atoms. .

For this reason, the critical current value (IC,) of the obtained superconducting wire (overall) is very small, which has the drawback that it cannot be manufactured into a practical product.

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 (■
e) 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, unless it is rapidly cooled uniformly and at a high cooling rate, the sleeve particles that are precipitated in the Cu are combined to form large dendrites, resulting in segregation of Nb.

If Nb segregation occurs in this way, a decrease in the critical current value and variations in characteristics along the longitudinal direction of the wire will occur.

In order to uniformly cool the ingot at a high cooling rate to prevent segregation, it is necessary to reduce the diameter of the ingot, and as a result, mass production is difficult with this method.

Further, in the method (3), there is a problem that the blending ratio tends to become non-uniform along the longitudinal direction during powder filling, making it 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 4.

First, as shown in FIG.
b... are prepared, and the first element among the elements constituting the compound superconductor is added to the normal conducting metal in the cylindrical spaces 2a, 2b... of these containers 1a, t1b..., respectively. Contains Alloy 3.

Next, the containers 1a, 1b, . . . are heated simultaneously or sequentially to melt the alloy 3 contained in each cylindrical space 2a, 2b, .

Next, the containers 1a, 1b, etc. containing the composite liquid are put into water, oil, or molten low-melting point metal and rapidly cooled. , and a plurality of cylindrical bodies 4a, 4b, . . . in which the first element is uniformly precipitated are formed.

Next, as shown in FIG. 3, the cylindrical bodies 4a, 4b,... A core material 6 made of a conductive metal rod is inserted to form a composite conductor.

Next, the composite conductor L is subjected to an area reduction process to make the wire thinner, thereby distributing the particles of the first element in an intermittent fibrous shape.

Next, a second element of the elements constituting the compound superconductor is deposited on the surface of the thin wire as described above, and then heat treatment is performed.

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 4 shows the compound superconducting wire X1 manufactured 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, CutAltNi or an alloy thereof can be used as the normal conductive metal, and Nb3 or Nb3 can be used as the first and second elements.
Sn, Nb3Al, Nb3(Al, Ge), V Ga,
Compounds 33 such as NbGa, Nb3Ge, and NbCN that can constitute a superconductor can be used.

Of course, some of the elements constituting the above compound superconductor are I n t Ga t Hf t Z r t Mg
, Alt Ta, etc., to improve the superconducting properties.

Furthermore, the above-described manufacturing method can be modified as follows.

That is, as shown in FIG. 5, a core material or a second element formed by covering a pure metal made of the second element of the elements constituting the compound superconductor with a normal conductive metal layer is placed in the center of the multiple cylinder 5. A composite superconducting substrate 11 is prepared by inserting a core material 10 formed by covering an alloy 8 containing the above with a normal conducting metal layer 9.

Next, a compound superconducting wire similar to that shown in FIG. 4 can be manufactured by subjecting this base body 11 to a thinning process and heat-treating the thin wire.

In this case, the normal conductive metal layer 9 prevents deterioration in workability that is likely to occur when the first element and the second element come into contact during area reduction processing.

In addition, in adopting the method explained in FIG. 5, the composite superconducting substrate L1 is covered with a diffusion prevention cylinder that prevents the diffusion of the second element in the substrate 1, and this is formed of a stabilizing material. After the compound superconducting wire is installed in a pipe, the wire is made thinner by area reduction processing, and then heat treatment is performed in the same manner as described above, thereby making it possible to obtain a compound superconducting wire with excellent stability.

Figure 6 shows the compound superconducting wire X produced in this way.
2, in which R represents a stabilizing metal, S represents a diffusion prevention metal, Y represents a normal conducting metal, and Z represents an intermittent fibrous compound superconductor.

In this case, if each component is shaped into a rectangular tube shape, a compound superconducting wire X3 having the structure shown in FIG. 7 can be obtained. By using this, a compound superconducting wire X4 having the structure shown in FIG. 8 can be obtained.

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

That is, the first compound forming a compound superconductor in a normal conducting metal
, instead of reducing the area of the alloy formed by adding the second element, the process reduces the area of the alloy in a state where the first element and the second element are mechanically separated to make the wire thinner. Therefore, even if the amounts of the first and second elements added are increased, there is no risk that the workability will be impaired.

In addition, as a means of obtaining an alloy block made by adding the first element to a normal conducting metal, a plurality of cylindrical bodies 4a, 4b... having the above composition and different inner and outer diameters are polymerized concentrically. Since the alloy block is formed into a multi-tubular alloy block, even if the thickness is sufficiently thin, an alloy block with an arbitrary cross-sectional area can be formed by selecting the number of these stacks.

In this way, since the wall thickness of each cylindrical body can be made sufficiently thin, when forming each cylindrical body, it is possible to cool the alloy liquid uniformly and at a high cooling rate. Even when the amount of the added element is large, segregation of the first element can be prevented, and a cylindrical body in which the particles of the first element are uniformly dispersed can be formed. The amount can be increased.

After inserting a core material 6 made of a normal conductive metal rod into the center of the multi-tube 5 formed in this way, the core material 6 is thinned into a second wire.
After attaching the element or inserting the core material 10 containing the second element into the center of the multi-layer tube 5, the wire is thinned, so the so-called addition amount of the second element is also increased. be able to.

Therefore, a compound superconducting wire with a large critical current value, that is, with high characteristics, can be easily produced.

In addition, by increasing the cross-sectional area of the multiple tube 5, or by increasing the inner diameter and outer diameter of the center of the multiple tube 5, the amount of wire that can be obtained at one time can be increased, which ultimately improves productivity. It is possible to aim for

Incidentally, if the method explained using FIG. 5 is adopted, that is, the method of thinning the core material 10 containing the second element is attached to the center of the multiple tube 5, then the step of attaching the second element can be performed. can be omitted, and a compound superconducting wire can be obtained that exhibits even more uniform characteristics in the longitudinal direction of the wire.

Next, examples of the present invention will be described.

Example 1 First, an alloy made by adding 30 atomic proportions of Nb, which is the first element constituting the compound superconductor Nb3Sn, to Cu, which is a normal conducting metal, was heated in argon gas using the container shown in Figure 1. The composite liquid was melted and rapidly cooled in a container to form a cylindrical body with different inner and outer diameters in which particles of Nb, the first element, were uniformly precipitated in Cu, a normal conducting metal, as shown in Figure 2. Formed.

The formed alloy cylinders each had a length of about 100 mm,
The inner diameter is about 20ynttt and the outer diameter is about 30mm, the inner diameter is about 30mm and the outer diameter is about 40mm, the inner diameter is about 40mm.
There are four in total: one with a TIL outer diameter of about 50 m, and one with an inner diameter of about 50 m and an outer diameter of about 60 m.

Next, as shown in Fig. 3, these cylindrical bodies are concentrically superimposed to form a multiple cylinder, and a rod of normal conductive metal Cu with an outer diameter of 20 mm is inserted as a core material in the center of the multiple cylinder. The composite conductor was then processed to reduce its surface area, and a 350 m long wire with a wire diameter of 1 mm, consisting of Nb distributed in the form of intermittent fibers in Cu, was produced.

Next, Sn, which is the second element constituting the compound superconductor, is attached to this wire, and then the wire is heat-treated at 700°C for 100 hours in argon gas to diffuse Sn. As shown in the figure, the normal conducting metal Cu-S
A compound superconducting wire in which Nb3Sn is distributed in an intermittent fibrous form in an n-alloy was manufactured.

When the critical current value of the superconducting wire thus obtained was measured, the critical current value was ■ in an external magnetic field of 4 Tesla.

=120OA, critical current density J. =1. 5 X]
0 3 A/mrN and I at an external magnetic field of 7 Tesla.

=470AXJo=0.6X103A/1, which was an excellent value.

Furthermore, when similar measurements were made by randomly sampling in the longitudinal force direction of the wire, almost equal values were obtained.

Example 2 In order to omit the Sn adhesion step in Example 1, a Sn-5 covered with a Cu pipe with a thickness of 2 tnx was placed in the center of a concentrically polymerized Cu-Nb multiple cylinder instead of a Cu rod. %
A composite superconducting substrate was constructed by inserting a Cu alloy rod, and this substrate was subjected to surface reduction processing to form a 350 m wire diameter 1xx (D wire rod) in which Nb was uniformly precipitated in the form of intermittent fibers in Cu.

Next, this wire was heated at 700°C and 100°C in argon gas.
A heat treatment was performed for a period of time to diffuse Sn, thereby producing a compound superconducting wire in which Nb3Sn was distributed in the form of interrupted fibers in a Cu--Sn alloy, which was a normal conducting metal, as shown in FIG.

When the critical current value of the superconducting wire obtained in this way was measured, it was found that Io = 1 450 in an external magnetic field of 4 Tesla.
Shows AXJo=1.8XI O3A/ii, I at an external magnetic field of 7 Tesla.

=570AXJo=0. 7 2 x 1 03A/m
T? t, which was better than that obtained in Example 1, and the uniformity along the longitudinal direction of the wire was also good.

Example 3 Composite superconducting substrate in Example 2 (Sn-5% Cu rod covered with Cu was inserted into the center of a Cu-Nb multilayer tube).

) to reduce the wire diameter to a thinner wire with an inner diameter of approximately 20 mm, which functions as a diffusion prevention material to prevent the diffusion of Sn from reaching the stabilizing material during heat treatment.
It is inserted into a Ta pipe with an outer diameter of about 24mm, and this is then used as a stabilizing material with an inner diameter of about 24mm and an outer diameter of about 3mm.
It was inserted into a 0M1n Cu pipe.

Next, this was subjected to surface reduction processing to make the wire thinner, and the wire diameter was 1.5 mm.
A wire rod was formed.

Next, this wire was heat-treated at 700°C for 100 hours in argon gas to diffuse Sn, and as shown in Figure 6, fibers with Nb3Sn intermittent in the Cu-Sn alloy covered with the stabilizing material We manufactured a compound superconducting wire with a pattern of distribution.

When the critical current of the superconducting wire thus obtained was measured, it was found to be ■ in an external magnetic field of 4 Tesla.

=1 5 00AXJo=0.8 5X1 03k/m
i with an external magnetic field of 7 Tesla.

=58OA,J. =0.33X103A/m4,
Although the critical current density was smaller than that obtained in Example 2, stable characteristics were obtained in which the voltage in the current-voltage characteristics was gradual and stable when the critical current value was exceeded.

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 4 are diagrams for explaining an embodiment of the manufacturing method according to the present invention in the order of steps, and FIG. 5 is a diagram for explaining a case where the above embodiment is partially modified. 6 to 8 are diagrams showing end faces of compound superconducting wires of different configurations manufactured by the manufacturing method according to the present invention, respectively. 4a, 4b...Cylindrical body, Dan...Multiple tube, 6, 10...Core material, R...Safety metal, S... ...Diffusion prevention metal, Y...Normal conductive metal, Z...Compound superconductor, X1, X2
,X3...Compound superconducting wire.

Claims (1)

[Scope of Claims] 1. A step of forming a plurality of cylindrical bodies having different inner and outer diameters from an alloy made by adding a first element of the elements constituting a compound superconductor to a normal conducting metal; a step of concentrically polymerizing a plurality of cylindrical bodies with different values to form a multiple tube, and inserting a core material made of a normal conductive metal material into the center of the multiple tube to form a composite conductor; A step of thinning the composite conductor by thinning the composite conductor, and adhering a second element constituting the compound superconductor to the wire thinned by this step, followed by heat treatment to make the wire thinner. 1. A method for manufacturing a compound superconducting wire, comprising the step of diffusing an element to form an intermittent fibrous compound superconductor in a normal conducting metal. 2 What constitutes a compound superconductor in a normal conducting metal? a step of forming a plurality of cylindrical bodies with different inner and outer diameters from an alloy formed by adding the first element of the above, and forming a multiple cylinder by concentrically polymerizing the plurality of cylindrical bodies with different inner and outer diameters. At the same time, a core material formed by covering a second elemental metal of the elements constituting the compound superconductor with a normal conducting metal or an alloy containing the above second element is placed in the center of the multi-tube with a normal conducting metal. A step of forming a composite superconducting substrate by inserting a covering core material, a step of reducing the area of the composite superconducting substrate to make it thin, and heat-treating the wire made thin by this step. A method for manufacturing a compound superconducting wire, comprising the step of diffusing the second element to form an intermittent fibrous compound superconductor in a normal conducting metal.