JPH0594722A - Nb-ti alloy superconductive wire rod - Google Patents

Abstract

PURPOSE:To realize high critical current density and a low alternating current loss by substituting a Cu-Ni-Mn alloy for a Cu-Ni alloy included in an Nb-Ti superconductive wire rod. CONSTITUTION:An Nb-Ti filament 1 made of an Nb-Ti alloy including 46.5% by weight of Nb is composed with a coating material 2 made of a Cu-Ni-Mn alloy incorporating 10% by weight of Cu, 1% by weight of Ni, thus obtaining an extruding material having a diameter of 12mm, followed by wire drawing, thereby providing a single wire of a hexagonal cross section, where a distance between opposed sides is 1.39mm. 256 pieces of these single wires are inserted into a tube 3 made of a Cu-Ni alloy including 10% by weight of Cu, to be formed in a diameter of 12mm by hydrostatic extruding, followed by wire drawing, thereby providing a submultiple wire of a hexagonal cross section, where a distance between opposed sides is 1.39mm. 198 pieces of these submultiple wires and 55 of dummy wires made of a Cu-Ni alloy coated copper wire incorporating 10% by weight of Cu are inserted into a tube 4 made of a Cu-Ni alloy including 10% by weight of Cu, thus obtaining extruding billets, followed by machining into an extruding diameter of 12mm. The extruding materials which are extruded at 300-375 deg.C for 50 hours by an aged heat treatment and the extruding materials which are extruded not by a heat treatment are twisted together.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting wire used in equipment operated in an AC mode.

[0002]

2. Description of the Related Art Most of current superconducting magnets are designed to be operated in a direct current mode. This is because the loss of the ordinary copper (Cu) -stabilized Nb-Ti alloy superconducting wire during AC mode operation is very large.

The AC loss of the superconducting wire is composed of the sum of three components: hysteresis loss, coupling loss and eddy current loss. In order to reduce the loss of these three components, the following measures have been taken.

(1) The Nb-Ti alloy filament is ultrafine-thinned to the submicron order.

(2) As shown in the sectional view of FIG. 3, Nb-
C between the Ti alloy filament 1 and the Cu-Ni alloy 4
A high resistance layer made of the u-Mn alloy material 6 is interposed.

(3) The wire diameter is reduced and the twist pitch is reduced.

(4) The stabilized copper is divided by a high resistance layer of Cu-Ni alloy.

[0008] Coupling losses and eddy current losses have been significantly reduced by making these geometrical improvements,
It is still insufficient to reduce the hysteresis loss.

The hysteresis loss is a loss due to the magnetization of the superconducting wire, and in order to reduce it, it is desirable to reduce the filament diameter. Theoretically Nb-
For a Ti superconducting wire, a filament diameter of 0.1 μm is said to be optimal. However, as the filament diameter was reduced, the spacing between the filaments became very narrow, the superconducting conductor exuded into the Cu-Ni alloy, and the filaments were electrically coupled to each other, and the filament was substantially thickened. It will behave like this. This is called the proximity effect. Since this proximity effect means an increase in the filament diameter in fact, it causes an increase in hysteresis loss. As measures against this, the following three methods have been tried until now.

(1) Widen the filament spacing.

(2) By increasing the Ni concentration of the Cu-Ni alloy from 10% by weight to 30% by weight, the resistance is increased and the exudation of the superconducting conductor is prevented.

(3) A Cu-Mn alloy containing a Mn element having a strong magnetic moment is arranged around the Nb-Ti alloy filament to prevent the superconducting conductor from seeping out.

The hysteresis loss can be further reduced by any of the above three methods.

[0014]

The three methods considered as the countermeasures for the reduction due to the proximity effect described above are as follows: "(1) Increase the filament interval. (2) Cu-"
The Ni concentration of the Ni alloy is increased from 10% by weight to 30% by weight. (3) The Cu-Mn alloy is arranged in the inner layer of Cu-Ni alloy (around the Nb-Ti alloy filament). "
However, in the case of (1) above, the space factor of the Nb-Ti alloy with respect to the entire wire is reduced, so that the current density is reduced. In the case of (2) above, Cu-3
When 0 wt% Ni is used, there is a large difference in hardness between Nb-Ti alloys, and there is a problem in workability. Furthermore, in the case of (3) above,
There is no problem in terms of workability, and the filament spacing can be reduced, but Nb-Ti alloy / Cu-Mn alloy /
Due to the three-layer structure of Cu-Ni alloy, conventional Nb-T
Compared to the i-alloy / Cu-Ni alloy two-layer structure, the number of processing steps increases.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art and to produce a superconducting wire capable of achieving high critical current density and low AC loss.

[0016]

In order to achieve the above-mentioned object, the gist of the present invention is to provide a Cu-Ni-Mn alloy having a two-layer structure composed of a Cu-Mn alloy / Cu-Ni alloy around an Nb-Ti alloy filament. By using an alloy, the structure is simplified without impairing the effect of reducing the proximity effect, and Nb-Ti with high critical current density and low AC loss is obtained without increasing the number of processing steps.
An alloy superconducting wire is produced.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing the structure of an Nb-Ti alloy superconducting wire according to an embodiment. In this figure, the respective material portions are also drawn out and enlarged. That is, Nb-Ti
Nb-46.5 wt% T as alloy filament material 1
An i alloy material is prepared, and this Nb-Ti alloy bar is Cu-1
An extruded material having a diameter of 12 mmφ was prepared by compounding with the coating material 2 made of 0 wt% Ni-1 wt% Mn alloy. This was drawn and drawn to obtain a single wire having a hexagonal cross section with an opposite side distance of 1.39 mm.

The 253 single wires were inserted into the Cu-10 wt% Ni alloy tube 3 and assembled to form an extruded billet.
Each of these extrusion billets was subjected to hydrostatic extrusion to obtain an outer shape 12
mm, and then drawn and drawn to form a submulti-wire having a hexagonal cross section with a distance between opposite sides of 1.39 mm.

Next, 55 dummy wires made of Cu-10 wt% Ni alloy-coated copper wire of the same size as the 198 sub-multi-wires are inserted and assembled into the tube 4 made of Cu-10 wt% Ni alloy. And billets for extrusion, respectively. Each of the extrusion billets was hydrostatically extruded to form an outer shape of 12 mm.

Thereafter, those extruded materials were subjected to aging heat treatment in the temperature range of 300 ° C. to 375 ° C. for 50 hours and then drawn and drawn, and those drawn and drawn without this heat treatment ( Twist processing was performed on each of the materials (only cold working) to obtain a wire material having an outer diameter of 0.1 mm, a filament diameter of 0.2 μm, a filament interval of 0.08 μm, a twist pitch of 0.8 mm, and a wire diameter of 0.1 mm. The cross-sectional composition ratio of this wire is Cu: Cu-Ni-Mn alloy: Nb-Ti alloy = 0.6: 3.09: 1.

Table 1 shows the critical current density Jc of the five kinds of wire rods manufactured as described above in the externally applied magnetic field of 0.5 (T) and ± 0.5 measured by the SQUID type magnetometer.
The hysteresis loss per (T / cycle) is shown.

[0022]

[Table 1]

From this table, the hysteresis loss is 0.4 to
A value of 0.8 kJ / m ³ was taken, and it was reduced to about 2/3 of the hysteresis loss of the line produced under all the same conditions except that the Cu—Ni—Mn alloy part was changed to a Cu—Ni alloy excluding Mn. ..

Incidentally, this time, the N of the Cu--Ni--Mn alloy layer is
The i concentration was set to 10% by weight and the Mn concentration was set to 1% by weight. The distance can be made smaller, and further higher current density can be expected.

Next, as another embodiment, Cu-Ni-Mn
A wire having an Nb layer with a weight ratio of 10% or less with respect to the Nb-Ti alloy between the alloy and the Nb-Ti alloy was processed in the same manner as in the above example. The wire rod on which the Nb layer is arranged has Tn and Cu-N in the Nb-Ti alloy generated during the aging heat treatment.
It has the effect of suppressing the formation of the compound Cu-Ti with Cu in the i-Mn alloy.

As mentioned above, Cu--Mn alloy and C
The u-Ni-Mn alloy has the effect of reducing the proximity effect,
Since Mn has a strong magnetic moment, Cu-Ni-M
The n alloy itself has hysteresis loss. Therefore, the Mn concentration has a limit, and the upper limit is 2% by weight. In addition, the Ni concentration is 3 by weight in terms of workability.
0% is the upper limit.

Further, the superconducting wire according to the present invention does not have to be a single wire having a multi-core structure, and may be a twisted wire in which a plurality of wires having a multi-core structure are used to increase the capacity of the wire. It doesn't matter.

As described above, according to the present invention, the Nb-
According to the Ti alloy superconducting wire, in the Nb-Ti alloy superconducting wire having a filament diameter of 1 μm or less for the purpose of alternating current application, Cu-around the Nb-Ti alloy filament.
By arranging the Ni-Mn alloy layer, the proximity effect is reduced, the structure is simpler than the conventional Cu-Mn alloy / Cu-Ni alloy structure, and the Nb-Ti superconducting wire with low AC loss can be easily manufactured. There is an effect that can be.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a Nb-Ti alloy superconducting wire according to the present invention,

FIG. 2 is a structural diagram around an Nb-Ti alloy filament of the present invention,

FIG. 3 is a structural diagram around a conventional Nb-Ti alloy filament.

[Explanation of sign]

 1 Nb-Ti alloy filament material 2 Cu-Ni-Mn alloy 3 Cu-Ni alloy 4 Cu-Ni alloy 5 Nb-Ni alloy Superconducting wire rod 6 Cu-Mn alloy

Claims (2)

[Claims] 1. Cu-surrounding Nb-Ti filaments
A Nb-Ti superconducting wire rod, wherein the Cu-Ni alloy is replaced by a Cu-Ni-Mn alloy in an Nb-Ti superconducting wire rod having a Ni alloy layer. 2. Cu-surrounding Nb-Ti filaments
In an Nb-Ti superconducting wire having a Ni alloy layer, the Cu-Ni alloy is replaced with a Cu-Ni-Mn alloy, and the Nb layer is arranged inside the Nb-Ti alloy superconducting wire. ..