JP3099460B2 - Nb-Ti alloy superconducting wire - Google Patents

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 for equipment operated in an alternating current mode.

[0002]

2. Description of the Related Art Most of current superconducting magnets are operated in a DC mode. This is because an ordinary copper (Cu) -stabilized Nb—Ti alloy superconducting wire has an extremely large AC loss during the AC mode operation.

[0003] The AC loss of a superconducting wire is composed of the sum of three components of "hysteresis loss", "coupling loss" and "eddy current loss". The coupling loss and the eddy current loss of the three losses are determined by the geometric structure of the conductor cross section and the stabilized copper by Cu-
Substantial reduction can be achieved by dividing with a high resistance layer of Ni alloy.

[0004] However, the hysteresis loss is caused by the pinning force of the superconductor, and the superconducting wire having a higher current density has a larger pinning force, so that the hysteresis loss of the superconductor increases. In other words, reducing the hysteresis loss while maintaining a high current density, which is a great advantage of superconductivity, is contradictory. Generally, the hysteresis loss is proportional to the product of the critical current density of the superconducting wire and the filament diameter.

Therefore, in order to produce a superconducting wire having a high current density and a low hysteresis loss, it is desirable to reduce the filament diameter. For this reason, the filament diameter of the DC superconducting wire is several μm to several tens μm, whereas that of the AC superconducting wire is submicron or 0.1 μm or less, which is tens of tenths thinner for DC.

FIG. 2 is a cross-sectional view showing the difference between the DC and AC filament sizes. That is, (A) has a conventional filament diameter of several μm to several tens μm, and has a large hysteresis loss. (B) is a filament diameter of 1μ for AC.
m or less. The space factor of the Nb-Ti alloy decreases, and the critical current density decreases. (C) shows the proximity effect caused by reducing the filament interval.

As described above, when the diameter of a filament is reduced while maintaining a high current density, the distance between filaments becomes very small. Adjacent filaments are electrically coupled to each other by superconducting electrons oozing out of the Nb-Ti filament, and superconducting current flows also to the base metal around the filament, and the filament diameter becomes substantially large. Becomes This is called a proximity effect. When the filaments are electrically coupled to each other due to the proximity effect, the hysteresis loss increases.

At present, in order to prevent electrical coupling between filaments due to the proximity effect, the resistance of the base metal is increased by replacing the conventionally used Cu-10 wt% Ni alloy with a Cu-30 wt% Ni alloy. , Cu-10% by weight Ni
By using a Cu-Mn alloy containing a magnetic element Mn instead of an alloy, a high critical current is maintained without increasing the filament interval.

[0009]

As described above, as described above, Cu
By using a -30% by weight Ni alloy or a Cu-Mn alloy, it is possible to prevent electrical coupling between filaments due to the proximity effect, reduce hysteresis loss, and produce a superconducting wire having a high critical current density. Becomes possible. However, the value has not yet reached the level of practical use, and further lowering of hysteresis loss and higher current density are desired.

At present, with the development of processing technology, it has become possible to produce a superconducting wire having an Nb-Ti alloy filament diameter of 0.05 μm or less. However, no matter how much the Cu-30 wt% Ni alloy or Cu-Mn alloy is used as the base metal, the effect of reducing the proximity effect is limited, and the reduction of the hysteresis loss by reducing the filament diameter is not sufficient. There is a limit.

Therefore, one Nb-Ti filament 1
It is necessary to increase the critical current density of the book without increasing the hysteresis loss. If the critical current density of the Nb-Ti alloy filament increases, the cross-sectional area of the superconducting wire can be reduced, and as a result, the volume of the superconducting wire decreases even if the hysteresis loss per unit volume cannot be reduced. Therefore, the loss of the entire device is also reduced.

An object of the present invention is to improve the structure around the Nb-Ti alloy filament of the conventional superconducting wire described above,
An object of the present invention is to provide a superconducting wire having a high critical current density while maintaining low hysteresis loss.

[0013]

The gist of the present invention is that Nb
-An Nb layer is arranged around a Ti alloy filament, and a Cu-Mn alloy or a Cu-Ni-Mn alloy is arranged around the Nb layer . As a result, first, Nb-
The superconducting conductor oozing out of the Ti alloy filament pins the magnetic flux at the surface of the filament to increase the critical current density in the magnetic field, and the Cu-Mn alloy layer or the Cu-Ni layer disposed around the Nb layer. -The Mn alloy layer prevents electrical coupling of the filament due to the proximity effect, and suppresses an increase in hysteresis loss.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing a cross-sectional structure of a wire rod, in which a part of a wire is drawn out and enlarged. That is, Nb-Ti
An Nb-45 wt% Ti material was used as an alloy material 1, and a rod of this Nb-Ti alloy was combined with a coating material 2 as shown in Table 1 and each extruded billet having an outer diameter of about 29 mm in a warm state. And Each of the extruded billets was subjected to hydrostatic extrusion to an outer diameter of 12 mm in a warm state, and then drawn and drawn to form single wires having a hexagonal cross section with a distance of opposite sides of 1.39 mm. 253 pieces of this single wire cut into a predetermined length are each Cu-10 having an outer diameter of about 28 mm.
The extruded billets were inserted and assembled into tubes 4 made of Ni by weight. Each of the extruded billets was hydrostatically extruded to an outer diameter of about 12 mm, and then drawn and drawn to form a sub-multi wire having a hexagonal cross section having a distance of opposite sides of 1.39 mm.

[0015]

[Table 1]

Next, 198 pieces of the sub-multi wires cut to a predetermined length and 55 dummy wires made of a Cu-10% by weight Ni alloy-coated copper wire having the same size as the sub-multi wires were used as Cu-10 wires. The assembly was inserted into a tube 4 made of a weight% Ni alloy, and each was formed into an extruded billet. Each of the extruded billets was subjected to hydrostatic extrusion to be processed into an outer diameter of about 12 mm.

Each of the obtained wires is drawn and drawn several times, then twisted, and each has an outer diameter of 0.1.
mm, a wire having an Nb-Ti alloy filament diameter of 0.2 mm and a twist pitch of 0.8 mm was used as a sample.

Table 2 shows the sectional composition ratio, critical current density and SQ of the four types of wire rod samples prepared as described above.
The hysteresis loss per ± 0.5 T1 cycle measured by the UID type magnetometer is shown.

[0019]

[Table 2]

[0020] The critical current density was as follows: Sample No. 4-Sample No. 3-
Sample No. 2 increased in the order of Sample No. 1, and the critical current density at 0.5 T of Sample No. 1 reached about twice that of Sample No. 4. On the other hand, the hysteresis loss was as follows:
Sample No. 2 increased in the order of Sample No. 1, and the hysteresis loss of Sample No. 1 was about 1.5 times that of Sample No. 4.

From the above results, it was found that Sample No. 1 has a high current density, but the hysteresis loss of Sample No. 2 and Sample No. 3 is an intermediate value between the two (Sample No. 1 and Sample No. 4). Was.

[0022]

As a modified example of the present invention, one in which the Nb layer corresponding to Sample No. 2 in the above embodiment was replaced with copper was manufactured. In the embodiment, the Nb layer is formed of a metal having a critical temperature of 4.2 K or more, for example, vanadium (V), lead (P).
b) or the like. In these cases, almost the same results as in the example were obtained. In addition to the above, substantially the same results were obtained in the case where the superconducting element was easily oozed and the case where the Nb layer was replaced with a low-resistance metal.

[0024]

As described above, according to the present invention, the Nb-
According to the Ti alloy superconducting wire, when disposed around the Nb-Ti alloy filament, Cu-N
Rather than placing an i-alloy layer or a Cu-Ni-Mn alloy layer,
High critical current density was obtained. In addition, since the rate of increase of the critical current density exceeds the rate of increase of the hysteresis loss per unit volume, when the superconducting wires having the same length and the same critical current density were produced in sample numbers 1 and 2, The superconducting wire having the structure (1) can reduce the cross-sectional area of the wire, and can also reduce the hysteresis loss of the entire wire. Further, the small cross-sectional area means that the amount of superconducting wire used is small, and the cooling capacity of the wire is improved. In addition, since the coupling loss and the eddy current loss are proportional to the diameter of the wire, the coupling loss and the eddy current loss can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of an embodiment of an Nb—Ti alloy superconducting wire according to the present invention;

FIGS. 2A, 2B, and 2C are cross-sectional views for explaining a difference between DC and AC filament sizes;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Nb-Ti alloy raw material 2 Coating material 3 Single wire 4 Cu-10 wt% Ni tube

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01B 12/10

Claims (1)

(57) [Claims] 1. Cu / Cu-Ni alloy / Cu-Mn alloy or Cu / Cu-Ni alloy / Cu-Ni-Mn alloy / N
In a superconducting wire composed of a b-Ti alloy, Nb
-An Nb-Ti alloy superconducting wire characterized in that an Nb layer is arranged inside a Cu-Mn alloy layer or a Cu-Ni-Mn alloy layer arranged around a Ti alloy filament.