JPH05174647A - Manufacture of compound superconductive wire - Google Patents

Abstract

PURPOSE:To manufacture a compound superconductive wire having a reduced AC loss by setting a diameter of a superconductive filament in submicrons without connection between the superconductive filaments due to a superconductive current. CONSTITUTION:In a bronzing method for manufacturing an A15 type compound superconductive wire, a plurality of core members 1 each made of Nb or an Nb alloy are filled in a matrix 2 made of a Cu alloy not including elements composing an A15 type compound and having high resistance and a Cu alloy including magnetic elements. Furthermore, bronze 3 is disposed around the matrix, followed by wire drawing.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a compound superconducting wire.

[0002]

2. Description of the Related Art Nb ₃ Sn, a compound superconducting wire,
A15 type compound superconducting wires such as Nb ₃ Al and Nb ₃ Ga are known.

Conventionally, the A15 type compound superconducting wire is manufactured by the bronze method described below. First, the core material made of one or a plurality of Nb or Nb alloy is A1
It is embedded in a matrix made of bronze containing Sn, Al, Ga, etc., which are one of the constituent elements of the 5-type compound. Subsequently, these are drawn to form a composite material, and a plurality of the composite materials are arranged in a tube made of bronze and drawn again to form a wire material, so that the diameter of the core material is usually about several microns. Reduce the diameter to. At this time, since the bronze is easily work-hardened, hot working such as hot extrusion is performed, and then wire drawing is performed while performing intermediate heat treatment. Then, heat treatment is applied to the obtained wire material so that A of Nb ₃ Sn, Nb ₃ Al, Nb ₃ Ga or the like is formed at the interface between the core material and the bronze.
By producing a 15-type compound layer, an A15-type compound superconducting wire having the core material as a superconducting filament is manufactured.

By the way, in the pulse or AC application type A15 type compound superconducting wire, it is an important subject to make the diameter of the superconducting filament submicron in order to reduce the AC loss.

However, in the conventional method for producing an A15 type compound superconducting wire by the bronze method, the NbSn compound, the NbAl compound and the NbGa compound are present at the interface between the core material and the bronze during the hot working and the annealing during the wire drawing. A compound that is difficult to process is produced. Such a difficult-to-work compound significantly deteriorates wire drawing workability. Therefore, when the wire drawing is performed until the diameter of the core material becomes 1 μm or less, the core material may be broken or the wire itself may be broken. For these reasons, it was difficult to reduce the diameter of the superconducting filament to about submicron.

In order to make the diameter of the superconducting filament submicron, the Sn concentration in the bronze is reduced to lower the reactivity at the interface between the core material and the bronze, thereby making it difficult to process the compound during annealing. Although attempts have been made to suppress the formation reaction of the, the sufficient effect has not been obtained.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the conventional problems, and an object thereof is to provide a method for producing a compound superconducting wire capable of reducing the diameter of a superconducting filament to a submicron size. Is.

[0008]

The present invention provides a method for producing an A15 type compound superconducting wire by the bronze method,
A plurality of core materials made of Nb or Nb alloy were embedded in a matrix made of a Cu alloy having a high resistance containing no constituent element of the A15 type compound or a Cu alloy containing a magnetic element, and bronze was arranged around the matrix. After that, the method for producing a compound superconducting wire is characterized by comprising a step of drawing these.

As the high resistance Cu alloy, for example, C
u-Si alloy, Cu-Ag alloy, Cu-Ni alloy, Cu
-Pd alloy, Cu-Zn alloy, etc. can be mentioned,
It is necessary that the resistance is higher than that of the remaining bronze after the A15 formation reaction. Examples of the magnetic element include Fe and Mn.

As the bronze, a Cu--Sn alloy,
Cu-Al alloy and Cu-Ga alloy are mentioned.

[0011]

According to the present invention, a plurality of core materials made of Nb or Nb alloy are embedded in a matrix made of a Cu alloy having a high resistance or a Cu alloy containing a magnetic element, and bronze is arranged around the matrix. .. This allows
Since the direct contact between the core material and the bronze is avoided, the formation reaction of the hardly workable compound is suppressed during hot working and during annealing during wire drawing. As a result, it is possible to reduce the diameter of the core material with a sound surface property until the diameter of the core material becomes about submicron without causing the disconnection due to the difficult-to-process compound. Further, by using a Cu alloy having a high resistance or a Cu alloy containing a magnetic element as the matrix material, it is possible to suppress the proximity effect in the obtained compound superconducting wire, and thus it is possible to prevent the superconducting filaments from being coupled by a superconducting current.

By heat-treating the wire thus reduced in diameter until the diameter of the core becomes about submicron, Sn or the like in the bronze diffuses through the matrix and Nb ₃ Sn or the like at the interface of the core. A15 type compound is produced. Therefore, the diameter of the superconducting filament can be made submicron, and the superconducting filaments can be prevented from being coupled with each other by the superconducting current, so that the A15 type compound superconducting wire with reduced AC loss can be manufactured.

Although the arrangement of the matrix lowers the bronze ratio, the core material has a diameter of the submicron level, so that the A15 type compound can be sufficiently produced by the heat treatment similar to the conventional method.

[0014]

Embodiments of the present invention will now be described in detail with reference to the drawings.

Example 1 First, as shown in FIG. 1A, Nb- having a diameter of 2.5 mm was used.
A Cu-2.5 wt% Si alloy rod (matrix) 2 having a diameter of 37.5 mm, in which 55 core materials 1 made of 0.7 wt% Ti alloy are embedded, has an outer diameter of 45.3 mmφ and an inner diameter of 38.
It is inserted into a tube 3 made of a Cu-14.3 wt% Sn alloy of mmφ. Subsequently, after hot extruding these at 700 ° C., wire drawing is performed. Thereby, as shown in FIG. 1B, a hexagonal composite material 4 having an opposite side distance of 2 mm was formed.

Next, as shown in FIG. 2 (a), 260 composite materials 4 are put together into an outer diameter of 45.3 mmφ and an inner diameter of 36.
It is inserted into a tube 5 made of a Cu-14.3 wt% Sn alloy of mmφ. Subsequently, these are hot extruded at 600 ° C. and then subjected to wire drawing. Thereby, the wire rod 6 as shown in FIG. 2B was formed. At this time, four kinds of wire rods 6 having different wire diameters were formed by changing the drawing ratio. Table 1 below shows the wire diameters of these four kinds of wire rods 6 and the core wire diameters calculated from the wire diameters. The material composition ratio of these wire rods 6 (Cu-Sn alloy: Cu-Si alloy: Nb-Ti alloy)
Is 5.3: 3.2: 1.

Comparative Example 1 A Cu-14.3% by weight Sn alloy (bronze) rod having a diameter of 37.5 mm, in which a core material having the same material and arrangement as in Example 1 was embedded, was used. 38 mm
It is inserted into a tube made of φ Cu-14.3 wt% Sn alloy. Then, hot extrusion and wire drawing were performed in the same manner as in Example 1 to form two types of wire rods having wire diameters of 0.6 mm and 0.4 mm. The core material diameters of these two types of wire materials are shown in Table 1 below together with the wire diameters. The material composition ratio (Cu-Sn alloy: Nb-Ti alloy) of these wires is 8.5: 1. In the wire drawing, wire breakage frequently occurred when the wire diameter was 0.4 mm, and subsequent wire drawing became impossible.

With respect to each of the obtained wire rods of Example 1 and Comparative Example 1, the Cu alloy portion was etched with nitric acid to expose the core material, and the surface texture of the core material was examined by a scanning electron microscope (SE).
Observed by M). The results are also shown in Table 1 below.

[0019]

[Table 1] As is clear from Table 1, in the production method of Example 1, even if the core material diameter was reduced to 0.37 μm, a difficult-to-process compound such as Nb ₃ Sn was not formed, and a good surface property was obtained. It can be seen that the wire can be drawn. This is because the Cu-Si alloy is arranged between the core material and the bronze (Cu-Sn alloy), direct contact between the core material and the bronze is avoided, and the annealing treatment temperature in the wire drawing process, This is because Sn in the bronze hardly diffuses into the Cu-Si alloy in time.

On the other hand, in the manufacturing method of Comparative Example 1, since the core material and the bronze are in direct contact with each other, Nb ₃ Sn is generated during hot extrusion and annealing during wire drawing, and as a result, It can be seen that when the diameter of the core material is 1 μm or less, the wire drawing workability is significantly deteriorated and the core material is broken.

Further, each of the wire rods of Example 1 and Comparative Example 1 was heat-treated at a temperature of 650 ° C. for 24 hours, whereby Sn in the Cu-14.3 wt% Sn alloy was used as the core material. A compound superconducting wire in which a Nb ₃ Sn layer was formed by diffusion reaction was manufactured. The obtained compound superconducting wire was subjected to Jc measurement and magnetization measurement, and the effective filament diameter was calculated from these measured values using the following formula (1). The results are also shown in FIG.

Ph = (8 / 3π) · λ · Jc · def · Bm (1) (where, Ph in the formula (1) is hysteresis loss of AC loss, and λ / Jc is per wire cross-sectional area. (Critical current density, deff is the effective filament diameter, and Bm is the amplitude of external magnetization.) As is clear from FIG.
It can be seen that in the compound superconducting wire, the effective filament diameter is reduced in proportion to the core material diameter before the heat treatment. this is,
As a matrix material in which the core material is embedded, bronze (Cu-14.3 wt% Sn alloy resistivity: 1.1 ×
^10-7 Ωm: 4.2K) and Cu-2.
5 wt% Si alloy (specific resistance: 1.7 × 10 ⁻⁷ Ωm: 4.
2K), the reason is that even when the diameter of the superconducting filament is made submicron, the coupling due to the superconducting current between the superconducting filaments is prevented.

On the other hand, in the compound superconducting wire of Comparative Example 1, when the superconducting filament diameter was made to be 0.98 μm submicron, the Sn concentration in the bronze matrix decreased after Nb ₃ Sn formation, resulting in low resistance, It can be seen that the effective filament diameter is significantly larger than the core material diameter before the heat treatment because the superconducting filaments are connected by the superconducting current.

In the above embodiment, as the matrix material in which the core material is embedded, C having a higher resistance than bronze is used.
Although the case of using the u alloy has been described, Cu containing a magnetic element such as Cu—Mn alloy is used as the matrix material.
Similar results were obtained with alloys.

[0025]

As described in detail above, according to the present invention, the diameter of the superconducting filament can be made submicron without inducing coupling between the superconducting filaments due to the superconducting current, and thus AC loss is reduced. A method may be provided by which the wire may be manufactured.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a manufacturing process of a compound superconducting wire of Example 1.

2 is an explanatory view showing a manufacturing process of the compound superconducting wire of Example 1. FIG.

FIG. 3 is a characteristic diagram showing a change in effective filament diameter with respect to a core material diameter before heat treatment in the compound superconducting wires of Example 1 and Comparative Example 1.

[Explanation of symbols]

1 ... Core material, 2 ... Cu-Si alloy rod (matrix), 3
... Cu-Sn alloy tube, 4 ... Composite material, 5 ... Cu-Sn alloy tube.

Claims (1)

[Claims] 1. A method for producing an A15 type compound superconducting wire by a bronze method, which comprises a high resistance Cu alloy containing no constituent elements of the A15 type compound or C containing a magnetic element.
A compound superconducting wire, comprising a step of embedding a plurality of core materials made of Nb or Nb alloy in a matrix made of u alloy, further arranging bronze around the matrix, and then wire-drawing these. Manufacturing method.