JPH10154422A - Nb-ti superconducting wire rod - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the critical current density at 1T or higher while devising to decrease hysteresis loss in an Nb-Ti superconducting wire rod. SOLUTION: In the central portion 199, stabilized copper hexagonal wires 17 which are formed by coating the stabilized copper 7 with a Cu-Ni layer, are concentrating arranged, and 648 single stacks 18 are arranged so as to surround the same. A single stack 18 is a hexagonal wire which has a structure such that mutual gaps among 847 Nb-Ti filaments 2a are filled by Cu-Ni-Mn layers 1a, and the peripheries thereof are filled by a Cu-Ni layer 5a. In such a Nb-Ti superconducting wire rod, the Mn concentration of the Cu-Ni-Mn layers 1a is set to be 1 percentage by weight to 3 percentage by weight. Thereby, the critical current density per Nb-Ti filament is enhanced, while decreasing the hysteresis loss.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an Nb-T used for a superconducting winding of a power device operated at a commercial frequency or a superconducting magnet for generating an AC magnetic field.
It relates to an i superconducting wire.

[0002]

2. Description of the Related Art Nb-Ti superconducting wires used in an AC magnetic field at a commercial frequency level are required to reduce AC loss and improve critical current density (Jc). The AC loss of the superconducting wire is composed of the sum of three of hysteresis loss (magnetization history loss), coupling loss and eddy current loss. Among these losses, the hysteresis loss is a loss associated with the magnetization of the superconducting filament, and decreases in proportion to the diameter of the superconducting filament. The ratio of this hysteresis loss to the total loss is large.

The spacing between filaments (= filament spacing) decreases in proportion to the filament diameter. However, when the distance is less than a certain distance, the superconducting filaments are electromagnetically coupled to each other, so that a large number of filament groups behave as one filament. As a result, even if the filament diameter is geometrically small, the filament diameter becomes electromagnetically large, and the hysteresis loss increases. This is called a proximity effect, and the value of the filament interval at which the hysteresis loss increases due to the proximity effect is determined by the type of matrix (base material) arranged around the filament. Further, the coupling between the filaments due to the proximity effect becomes more remarkable as the filament interval becomes smaller. On the other hand, from the viewpoint of improving the critical current density, it is advantageous that the space factor of the superconducting filament is higher. Therefore, it is desirable to reduce the filament interval and improve the filling rate of the superconducting filament.

[0004] The matrix is required to have a function of suppressing the proximity effect, and specific examples thereof include a method of increasing the electric resistance of the matrix and a method of adding a magnetic element to the matrix. In the case of an Nb-Ti superconducting wire, to suppress the proximity effect, use a Cu-Ni alloy in the matrix around the filament to increase the electric resistance, or add a magnetic element such as Mn as a third element to the Cu-Ni alloy. By doing so, the proximity effect can be suppressed.

Further, the diameter of the superconducting filament is set to 0.1 μm.
It is known that when the thickness is reduced to about m, the interval between the quantized magnetic flux in the superconducting wire and the superconducting filament size are matched, and the critical current density is improved.

[0006]

However, according to the conventional superconducting wire described above, the diameter df of the superconducting filament is set to 0.1 to reduce the hysteresis loss of the superconducting wire.
If ds ÷ df (ds is the distance between superconducting filaments) is about 1, the hysteresis loss is greatly reduced due to the large ds, but the critical current density is slightly increased. The critical current density tended to decrease extremely in the above magnetic field.

On the other hand, ds ÷ df is about 0.5, or
Below that, the critical current density is greatly improved,
The electromagnetic coupling of the filament due to the proximity effect becomes stronger, and the hysteresis loss increases. Therefore, in consideration of the balance between both the reduction of the hysteresis loss and the increase of the critical current density, conventionally, ds ÷ df is 0.5 to
It was set to 0.7. From an application point of view, the empirical magnetic field of the power device is almost 0.5 T or less, but the armature (stator) winding of the generator is 1 to 1.5 T. For this reason, a superconducting wire used in a relatively high magnetic field such as an armature winding is required to have a high current density of 1 T or more, but as described above, the critical current density of an AC superconducting wire is required. Is high in a low magnetic field of 1T or less, but sharply decreases in 1T or more. For this reason, a high critical current density at 1 T or more is required.

Accordingly, an object of the present invention is to provide an Nb-Ti superconducting wire capable of increasing the critical current density at 1 T or more while reducing the hysteresis loss.

[0009]

In order to achieve the above-mentioned object, the present invention provides an Nb-N-Mn alloy having a structure in which a Cu-Ni-Mn alloy layer is arranged between a predetermined number of Nb-Ti filaments.
In the Ti superconducting wire, the Cu—Ni—Mn alloy layer has a Mn concentration of 1 wt% to 3 wt%.

If the Mn concentration is less than 1 wt%, the filament spacing must be increased in order to suppress the proximity effect.
If the content is more than t%, Mn, which is a magnetic element, precipitates without dissolving in the Cu-Ni-Mn matrix, and the Cu-Ni-Mn alloy itself generates a large hysteresis loss. Therefore, it is desirable that the Mn concentration be 1 wt% to 3 wt%. Thereby, it becomes possible to improve the critical current density per Nb-Ti filament while reducing the hysteresis loss.

The Nb-Ti filament has a diameter of 0.1 mm.
It is preferable that the ratio ds / df of the distance ds between adjacent Nb-Ti filaments and the diameter df of the Nb-Ti filaments is 0.3 to 0.4. The critical temperature of the Nb-Ti ultrafine multicore superconducting wire depends on the Nb-Ti filament, and tends to decrease as the filament diameter decreases. In particular, from 0.1 μm
The decrease of the critical temperature is remarkable from around 0.07 μm,
It has a significant effect on the stability of superconducting wires. On the other hand, Nb-T
When the i-filament diameter exceeds 0.15 μm, the critical value is close to the limit value of the hysteresis loss in practical use, and the critical current density is reduced. Therefore, the filament diameter is set to 0.07 μm
It is desirable that the thickness be about 0.15 μm.

When ds / df is smaller than 0.3, the influence of the proximity effect appears remarkably, and the hysteresis loss is greatly increased. Further, when ds / df is larger than 0.4, the hysteresis loss can be reduced, but a significant improvement in the critical current density cannot be expected. Therefore, ds / df is 0.3
It is desirable to set it to 0.4.

[0013]

DETAILED DESCRIPTION OF THE INVENTION The present inventors have found that by increasing the Mn concentration of a Cu-Ni-Mn alloy matrix around a Nb-Ti superconducting filament, the hysteresis loss is reduced and the critical current per Nb-Ti filament is reduced. It has been found that the density can be improved. Furthermore, by making the filament interval smaller than the conventional wire rod,
It has also been found that the average critical current density in a magnetic field of 1 T or more can be greatly improved.

Hereinafter, the effectiveness of the present invention will be described based on examples.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing a completed state of an Nb-Ti superconducting wire according to the present invention. FIG. 2 shows N
It is a perspective view which shows the typical state in the manufacturing process of a b-Ti superconducting wire, and FIG. 3 is explanatory drawing which shows the manufacturing process of the Nb-Ti superconducting wire by this invention.

The manufacturing steps shown here are roughly divided into a single billet incorporating step 100, a single wire incorporating (single stack) step 200, a Cu / Cu-Ni billet step 300, and a final billet incorporating step 40.
0. First, the single billet incorporating step 100 will be described. FIG. 2A shows the appearance of the single billet manufactured by the process 100. 170mm length, 30mm outer diameter, 2 inner diameter
In a Cu-Ni-Mn tube 1 having a composition of 1 mm Cu-30 wt% Ni-1.34 wt% Mn, a length of 150 m
A Nb-Ti rod 2 having a composition of Nb-46.5 wt% Ti having a diameter of 20.8 mm and a diameter of 20.8 mm was inserted (step 100).
Then, the front and rear ends were sealed with a sealing material 3, and “Sample-
1 "was produced.

Further, Cu-30 wt% Ni-0.9 wt% Mn having a length of 170 mm, an outer diameter of 30 mm and an inner diameter of 18 mm.
150 mm length, 18.2 mm diameter, N
b-46.5 wt% Ti rod was inserted, and the front and rear ends were sealed and “Sample-2” having the same structure as “Sample-1”
Was prepared. The “Sample-1” and “Sample-2” manufactured as described above are subjected to hydrostatic extrusion (step 101) and wire drawing (step 102), and then formed into a hexagonal wire having an opposite side distance of 0.85 mm. After straightening, it was cut into a length of 150 mm (step 103).

As shown in FIG. 2B, 847 hexagonal wires 4 having a length of 150 mm and having a length of 17 mm were prepared.
Cu-10 of 0 mm, outer shape 28 mm, inner diameter 24.5 mm
It was inserted into a Cu-Ni tube 5 having a composition of wt% Ni. Thereafter, the front and rear ends were sealed with a sealing material 6 to produce a sub-multi billet (Step 200). This sub-multi billet is subjected to hydrostatic extrusion (step 201) and wire drawing (step 202) in that order, and then the opposite side distance is 0.85 m.
m was processed as a hexagonal line. Then, length 150m
m to produce a sub-multi-hexagonal wire (Step 2
03).

Further, the length is 150 mm and the diameter is 22.8 mm.
A stabilized copper rod 7 is produced from high-purity copper of the above, and the stabilized copper rod 7 is 170 mm long, 27 mm outside diameter, and 23 mm inside diameter.
Was inserted into a Cu-Ni tube 8 having a composition of Cu-10 wt% Ni. Next, the front and rear ends were sealed with a sealing material 9 to produce a stabilized copper billet 10 as shown in FIG. 2C (step 300).

The stabilized copper billet 10 is subjected to hydrostatic extrusion (step 301) and wire drawing (step 302).
And then straightened as a hexagonal wire having a distance of 0.85 mm on the opposite side, and then cut into a length of 150 mm to produce a stabilized copper hexagonal wire (Step 303). Next, as shown in FIG. 2D, 199 stabilized copper hexagonal wires 11 obtained in step 303 were prepared, and these were Cu-10 wt% Ni having a length of 170 mm, an outer shape of 28 mm, and an inner diameter of 24.3 mm. Was inserted into the Cu-Ni tube 12 having the composition shown in FIG. Further, 648 sub-multi-hexagonal wires 13 produced in step 203 are prepared, and these are Cu-Ni
Insert the tube into the tube 12 and insert the Cu-N
Most of the space inside the i-tube 12 was filled. Then
The front and rear ends of the Cu-Ni tube 12 were sealed with the sealing material 14 to produce the multi billet 15 (step 400).

The multi billet 15 was subjected to hydrostatic extrusion (step 401), wire drawing (step 402), and twist processing (step 403).
As described above, the total number of Nb-Ti filaments is 548,
856 [847 (hexagonal wire 4) x 648 (submulti-hexagonal wire 13)] ultrafine multicore Nb-Ti superconducting wires for AC were completed.

The thus obtained extra-fine multicore Nb-T for AC
FIG. 1 is a sectional view of the i superconducting wire 16. In the figure, 1a is Cu- after processing the Cu-Ni-Mn tube 1.
The Ni—Mn layer, 2a is the Nb—Ti rod 2 after processing
b-Ti filaments 2a and 5a are Cu-Ni layers 5a and 8a after processing the Cu-Ni tube 5, Cu is a Cu-Ni layer after processing the Cu-Ni tube 8, 17 is a stabilized hexagonal copper wire, 1
8 is a single stack.

In the wire using the single billet of "Sample-1", the matrix around the Nb-Ti filament is Cu-30wt% Ni-1.34wt% Mn, and the filaments adjacent to the Nb-Ti filament diameter df are adjacent to each other. Interval (filament interval) ds ratio, ds /
df = 0.4. On the other hand, in the wire rod using the single billet of "Sample-2", the matrix around the Nb-Ti filament was Cu-30wt% Ni-0.9wt.
% Mn, and the Mn concentration (1.
34% by weight). In this case, ds / df is 0.65, which is smaller than that of “sample-1”.
f is increasing.

The present inventors have prototyped "Sample-3". Similarly to “Sample-1,” the matrix around the Nb—Ti filament was changed to Cu-30 wt% Ni—
The content was 1.34 wt% Mn. Then, ds / df is set to 0.
25, and the filament interval was made smaller than that of “Sample-1”. Table 1 shows the filament diameter d of each of "Sample-1,""Sample-2," and "Sample-3."
f shows the critical current density λJc and the hysteresis losses Qh and Qh / λJc of the wire rod having a diameter of 0.1 μm. here,
The hysteresis loss is measured using a SQUID (superconducting quantum flux interference device) type high-resolution magnetometer and is ± 0.5T.
The area in the magnetization curve in the magnetic field amplitude was divided by the volume of the wire. The critical current Ic was measured by a DC four-terminal method in an externally applied magnetic field. The critical current Ic was defined as a current value when a voltage corresponding to resistivity ρ = 10 ⁻¹⁴ Ω · m appeared between the voltage terminals. The value obtained by dividing Ic by the cross-sectional area of the wire was defined as the average critical current density λJc.

[0025]

[Table 1]

In Table 1, “Sample-2” indicates the magnetic field B
At = 1T or less, the hysteresis loss Qh shows a considerably lower value than that of “Sample-1”, but the difference from “Sample-1” becomes smaller as the magnetic field B becomes higher than the magnetic field B = 1T. On the other hand, as for the average critical current density λJc, “Sample-1” exceeds “Sample-2”. Qh / λ
Comparing with Jc, in a magnetic field of 1T or more, "sample-
"1" is smaller than "sample-2". Therefore, as a superconducting wire used in a magnetic field of 1T or more, such as an armature winding of a generator, “sample-1” is “sample-
It can be seen that performance is superior to "2".

Although "Sample-3" has a higher Jc than other wire rods, the electromagnetic coupling between the filaments due to the proximity effect is strong and Qh is greatly increased. is there. Here, Nb-
The optimum value of each condition of the Ti superconducting wire will be described. (A) Cu-N disposed around Nb-Ti filament
The Ni concentration of the i-Mn alloy is set to 20 wt% to 30 wt%.

Since the resistivity of the Cu—Ni alloy increases in proportion to the Ni concentration, a practically required Ni concentration of 20 wt% or more is required to reduce AC loss such as hysteresis loss and coupling loss. That's why. If the Ni concentration is higher than 30% by weight, the workability of the superconducting wire is remarkably reduced, the wire is frequently broken, and it becomes difficult to produce a long wire. Therefore, the Ni concentration of the Cu—Ni—Mn alloy is 20 wt.
% To 30 wt% is the optimum value. (B) Cu-N arranged around Nb-Ti filament
The Mn concentration of the i-Mn alloy is 1 wt% to 3 wt%.

If the Mn concentration is less than 1 wt%, the filament spacing must be increased in order to suppress the proximity effect, which hinders an improvement in the critical current density. On the other hand, as the Mn concentration is increased, Cu—Ni—Mn
The hysteresis loss of the alloy itself increases. In particular, M
When the n concentration is 3 wt% or more, the magnetic element Mn becomes C
The Cu—Ni—Mn alloy itself generates a large hysteresis loss because it precipitates without being dissolved in the u—Ni—Mn matrix, and its value far exceeds the hysteresis loss Qh of the Nb—Ti filament. The concentration is 3w
t% or less. (C) The diameter of the Nb-Ti filament is 0.07 μm
And the ratio ds / df of the distance ds between the Nb-Ti filaments to the filament diameter df is set to 0.3 to 0.4.

The critical temperature of the Nb-Ti ultrafine multicore superconducting wire depends on the Nb-Ti filament, and tends to decrease as the filament diameter decreases. In particular, from 0.1 μm
From around 0.07 μm, the critical temperature decreases significantly,
While the critical temperature of bulk Nb—Ti is about 9.3K, the critical temperature at a filament diameter of 0.05 μm drops to 6.5K to 7K. Since a decrease in the critical temperature greatly affects the stability of the superconducting wire, the diameter of the Nb-Ti filament needs to be 0.07 [mu] m or more. On the other hand, when the diameter of the Nb—Ti filament is 0.15 μm or more, considering the application to an AC magnetic field of the commercial frequency order, it is close to the limit value of the hysteresis loss from a practical viewpoint, and in addition to the ultrafine filament. The improvement in the critical current density becomes remarkable at a filament diameter smaller than 0.15 μm. Therefore, the Nb-Ti filament diameter is 0.1
Make it 5 μm or less. In the case where a Cu-Ni-Mn alloy is used around the Nb-Ti filament, if ds / df is smaller than 0.3, the influence of the proximity effect appears remarkably, and the hysteresis loss greatly increases. Also, ds /
When df is larger than 0.4, the hysteresis loss can be reduced, but a significant improvement in the critical current density cannot be expected.

As apparent from the above description, when a superconducting wire used in a magnetic field of 1 T or more is used, Cu
Good superconductivity is obtained when the Mn concentration of the -Ni-Mn alloy is 1 wt% to 3 wt%. Furthermore, the diameter of the filament is set to 0.07 to 0.15 μm or less, and the ratio ds / df of the distance ds between adjacent Nb-Ti filaments to the filament diameter df is set to 0.3 to 0.4. , And even better superconductivity can be obtained.

[0032]

As is clear from the above, according to the present invention, the Mn concentration of the Cu—Ni—Mn alloy layer is 1 wt% to 3 wt%.
wt%, while reducing hysteresis loss,
The critical current density per Nb-Ti filament can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a completed state of an Nb—Ti superconducting wire according to the present invention.

FIG. 2 is a perspective view showing a typical state in a process of manufacturing an Nb—Ti superconducting wire according to the present invention.

FIG. 3 is an explanatory view showing a manufacturing process of an Nb—Ti superconducting wire according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cu-Ni-Mn tube 2 Nb-Ti rod 2a Nb-Ti filament 5,8,12 Cu-Ni tube 5a, 8a Cu-Ni layer 7 Stabilized copper rod 10 Stabilized copper billet 11 Stabilized copper hexagonal wire 13 Sub multi hexagonal wire 15 Multi billet 16 Ultra-fine multi-core Nb-Ti superconducting wire for AC 17 Stabilized copper hexagonal wire 18 Single stack

Claims (2)

[Claims] An Nb-T having a structure in which a Cu-Ni-Mn alloy layer is arranged between a predetermined number of Nb-Ti filaments.
In the i superconducting wire, the Mn concentration of the Cu—Ni—Mn alloy layer is 1 wt% or more.
A Nb-Ti superconducting wire characterized by being 3 wt%. 2. The method according to claim 1, wherein the Nb-Ti filament has a diameter of 0.07 μm to 0.15 μm,
The ratio ds / df of the distance ds between the Ti filaments to the diameter df of the Nb-Ti filament is 0.3 to 0.4.
The Nb-Ti superconducting wire according to claim 1, wherein