JP3499687B2 - Method for producing Nb3Sn superconducting wire - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing an Nb ₃ Sn superconducting wire used in a superconducting magnet for generating a high magnetic field.

[0002]

2. Description of the Related Art Conventionally, in the production of Nb ₃ Sn superconducting wire, in order to produce an Nb ₃ Sn superconducting compound, Nb line and Sn line are contained in a Cu matrix or a bronze matrix composed of Cu and Sn. After the superconducting composite material obtained by inserting the Nb wire into the
The composite material is heat treated to thermally diffuse Sn. Also,
In general, around the Nb ₃ Sn superconducting wire, a stabilizing material made of Cu or the like having low electric resistance is provided in order to quickly dissipate the generated heat and to bypass the current when the normal conducting portion is generated. Providing is known.

However, when Sn is thermally diffused as described above, the diffused Sn contaminates the stabilizing material,
Therefore, there are disadvantages that the electric resistance of the stabilizing material is increased, the function as a bypass is reduced, the amount of heat is dissipated, and the function of the superconducting coil becomes unstable.

Therefore, as can be seen from the cross-sectional view of the conventional superconducting wire after the cross-section reduction processing shown in FIG. 3, in order to prevent contamination, a Ta or Ta-based alloy or a Ta-based alloy is used between the superconducting composite material and the stabilizing material. A diffusion preventing material made of Nb or an Nb-based alloy is provided.

However, in general, the diameter of the superconducting wire is not more than about 1.5 mm, and the thickness of the Ta layer which is the diffusion preventing material incorporated therein is not more than 1/100 of the diameter. The cross-section reduction processing is performed. At this time, since the diffusion preventing material is provided, between the superconducting composite material and the diffusion preventing material made of Ta or the like, for example, with respect to Vickers hardness, Cu is 80 to 120 and Ta is 150 to 150.
There is a big difference in the mechanical strength between No. 200 and No. 200, so as shown in Fig. 4, the shape of the Ta layer etc. changes in the radial direction of the obtained superconducting wire, causing waviness and rough skin, and in some cases diffusion. There is a problem that the preventive material and / or the superconducting wire itself is broken. As described above, when the diffusion preventing material is broken and the stabilizing material such as Cu is contaminated,
The stabilizing material exhibits a high electric resistance value, so that the superconducting magnet produced by using the obtained superconducting wire cannot withstand the thermal disturbance and becomes unstable.

[0006]

In view of the above problems, the object of the present invention is to provide at least three types of Nb or Nb-based alloys, Cu or Cu-based alloys, and Sn or Sn-based alloys existing in these. In the manufacturing process of Nb ₃ Sn superconducting wire consisting of superconducting composite material containing material, diffusion preventing material and stabilizing material, the diffusion preventing material inside the superconducting wire has almost constant thickness without breaking during cross section reduction processing. To obtain a Nb ₃ Sn superconducting wire.

[0007]

The present invention is based on at least N
b or Nb-based alloy, Cu or Cu-based alloy, and superconducting composite material containing three kinds of Sn or Sn-based alloy existing therein, diffusion preventive material surrounding it, and stabilizing material such as Cu around the same. In a method for producing an Nb ₃ Sn superconducting wire which is subjected to a composite reduction after arranging the superconducting layers, as shown in FIG. 1, a layer made of Cu or a Cu-based alloy is provided between the superconducting composite material and the diffusion preventive material. The present invention relates to a method for producing an Nb ₃ Sn superconducting wire, which is characterized in that it is arranged.

A plate made of Ta or a Ta-based alloy is used as a diffusion preventing material, and a clad plate formed by joining the plate and a plate made of Cu or a Cu-based alloy is a Cu or Cu-based alloy layer inside. Thus, it is preferable to form it into a tubular shape and use it in the composite assembly.

A plate made of Nb or an Nb-based alloy is used as a diffusion preventing material, and a clad plate formed by joining the plate and a plate made of Cu or a Cu-based alloy has a Cu or Cu-based alloy layer inside. It is also preferable to use such a tubular shape so as to be used in the composite assembly.

Further, it is preferable to arrange tubular Cu or a Cu-based alloy inside a tubular Ta or a Ta-based alloy as a diffusion preventing material for composite assembly.

Tubular Nb or Nb as diffusion preventing material
It is also preferable to place tubular Cu or a Cu-based alloy inside the base alloy for composite assembly.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Nb obtained by the method of the present invention
_As shown in FIG. 2, the ₃ Sn superconducting wire is a conventional superconducting composite material, a diffusion preventive material, and a stabilizing material in a superconducting wire before cross-section reduction processing, in which Cu or the diffusion preventing material is used between the superconducting composite material and the diffusion preventing material. It can be obtained by subjecting one having a layer of a Cu-based alloy to cross-section reduction processing and heat treatment.

The superconducting composite material may be made of at least Nb or Nb-based alloy, Cu or Cu-based alloy, and Sn or Sn-based alloy existing in these materials, and is shown in FIG. 5, for example. Like Cu
There is a matrix in which Sn lines and Nb lines are inserted. The cross-sectional shape of the superconducting composite material at the time of composite assembly may be circular, rectangular, hexagonal, or the like. Further, in order to improve the critical current value of the obtained superconducting wire, the surface of the superconducting composite material may be Sn-plated by a conventional method.

As for the dimensions of the superconducting composite material in FIG. 2 when assembled, in the case of assembling seven pieces, the diameter is 2 to 30 mm,
From the industrial viewpoint, it is preferably 2 to 19 mm from the viewpoint of facilitating the processing of the superconducting wire, and particularly preferably 2 to 11 m from the viewpoint of stably maintaining the processing elongation margin of Ta.
It should be m.

As the diffusion preventing material, any conventional material may be used, and examples thereof include those made of Ta, Ta-based alloys, Nb, and Nb-based alloys, which may be appropriately selected depending on the type of superconducting composite material used.

For example, when the AC loss of the superconducting wire is limited, Ta is used because it does not generate a superconducting layer.
Alternatively, it is preferable to use a diffusion preventive material made of a Ta-based alloy and an inexpensive diffusion preventive material made of Nb or an Nb-based alloy when the AC loss is not limited.

Further, the stabilizing material may be a conventional one having a low electric resistance and a function of imparting electrical stability and mechanical strength to the obtained superconducting wire, and it has high electric conductivity and thermal conductivity. From Cu, for example, is used.

The stabilizing material has an inner diameter of 6-9.
0 mm, an outer diameter of 9 to 250 mm, and an inner diameter of 6 to 60 from the viewpoint of facilitating the processing of a superconducting wire from an industrial viewpoint.
mm, the outer diameter is preferably 9 to 70 mm, and further T
The inner diameter is 6 from the viewpoint of stably maintaining the processing elongation margin of a.
It is particularly preferable that the outer diameter is 33 mm and the outer diameter is 9-40 mm.

The composite assembly in the present invention means, for example, as shown in FIG. 2, a Ta tube as a diffusion preventing material is inserted into a Cu tube which is a stabilizing material, and a Cu tube is further provided inside thereof.
Alternatively, it means that after inserting a tube made of a Cu-based alloy, finally inserting a superconducting composite material. In this case, the filling number of the superconducting composite material varies depending on the required performance specifications, and is 7, 19, or 121, for example.

As for the method of reducing the cross section of the superconducting wire after the composite assembling, conventionally used methods such as drawing, swaging or rolling may be used, but it is preferable from the viewpoints of homogeneous processing and processing speed. It is preferable to use a method called drawing.

In the present invention, cross-section reduction processing is performed,
The superconducting wire that has not yet been heat treated is called the base material.

The superconducting wire after the cross-section reduction processing, that is, the base material, generally has a diameter of 0.3 to 10 from the viewpoint of difficulty in coil winding.
The stabilizer in the matrix has a dimension of 3.0 mm and usually has a thickness of 0.1 to 1.0 mm. In addition, the diffusion preventive material in the base material is usually 0.2 m in order to make it thin.
It has a thickness of m or less.

In the present invention, the Cu or Cu-based alloy disposed between the superconducting composite material and the diffusion preventive material is processed between the superconducting composite material and the diffusion preventive material having greatly different mechanical properties such as Vickers hardness. In the superconducting wire of the present invention, which plays a role of mediating stress transmission, when the cross-section is reduced, the diffusion preventive material made of particularly hard Ta or Ta-based alloy or Nb or Nb-based alloy has no irregular shape in the radial direction. Prevent homogenization.

As a method for disposing the Cu or Cu-based alloy between the superconducting composite material and the diffusion preventive material, the Cu or Cu-based alloy may be contacted with the inside of the Ta tube which is the diffusion preventive material during the composite assembly. A tube made of an alloy may be inserted, or a plate made of Ta or a Ta-based alloy and a plate made of Cu or a Cu-based alloy may be brazed in advance and joined by simultaneous deformation processing or hydrostatic pressing to produce Ta / C.
u clad plate (see Figure 6), then Cu or Cu
There is also a method of using a Ta / Cu clad tube (see FIG. 7) obtained by forming a tube made of a base alloy into a tubular shape in the composite assembly, but from the viewpoint of processing the superconducting wire, the clad that is joined is used. It is preferable to use the method called a plate.

The superconducting wire can be obtained by heat-treating the base material. The heat treatment is to thermally diffuse Sn in the superconducting composite material of the base material to make the superconducting composite material superconducting. Is normally 600 ° C using heat treatment equipment
It is carried out by a method of holding at a temperature of ˜750 ° C. for 50 hours or more.

[0026]

EXAMPLES The present invention will be described below with reference to examples.
It is not limited to these.

The diameter 4.2mm subjected to Sn plating thickness 5μm in Comparative Example 1 the surface
Of the superconducting composite material having the structure shown in FIG. 5, a Cu pipe having an outer diameter of 25 mm and an inner diameter of 15 mm which is a stabilizing material (hereinafter,
"Cu tube A"), outer diameter of 14.5 which is diffusion prevention material
mm, a Ta tube having an inner diameter of 14.1 mm, and a Cu tube having an outer diameter of 13.5 mm and an inner diameter of 13.1 mm (hereinafter referred to as "Cu tube B"), which is the Cu or Cu-based alloy layer of the present invention.
After composite assembling, the base material 1 of the superconducting wire having an outer diameter of 0.7 mm was obtained by drawing with a draw bench and a drum type wire drawing machine. The thickness of the stabilizing material in the obtained base material was 0.14 mm, and the thickness of the diffusion preventing material was 0.005 mm.

The cross section of the obtained base material 1 was polished with a buff, and the roughened condition of the Ta layer as a diffusion preventing material was observed.
The observation results are 1 when the Ta layer is broken, 2 when the Ta layer is not broken but has large waviness, 3 when the Ta layer is lightly wavy, and 4 when the Ta layer is not wavy. Evaluated as. The results are shown in Table 1.

Comparative Example 2 As a diffusion preventing material, a thickness of 0.2 m was used instead of the Ta tube.
A base material 2 was obtained in the same manner as in Comparative Example 1 except that a tubular Ta obtained by bending a Ta plate of m by a press was used, and the same evaluation as in Comparative Example 1 was performed. The results are shown in Table 1.

Example 1 A Ta plate having a thickness of 2 mm and a Cu plate having a thickness of 2 mm were overlapped with each other, and at the same time, subjected to strong rolling to bond them to form Ta / 0.4 mm in thickness.
Obtain a Cu clad plate, then bend it with a press to C
Outer diameter 14.5 mm, inner diameter 13.
A 7 mm Ta / Cu clad tube was obtained. A base material 3 was obtained in the same manner as in Comparative Example 1 except that the Ta / Cu clad tube was used instead of the diffusion preventive material and the Cu tube B, and the same evaluation as in Comparative Example 1 was performed. The results are shown in Table 1.

Comparative Example 3 A base material 4 was obtained in the same manner as in Comparative Example 1 except that the surface of the superconducting composite material was not plated with Sn, and the same evaluation as in Comparative Example 1 was performed. The results are shown in Table 1.

Comparative Example 4 A comparative base material 5 was obtained in the same manner as in Comparative Example 1 except that the Cu tube B was not used, and the same evaluation as in Comparative Example 1 was performed. The results are shown in Table 1.

Comparative Example 5 A comparative base material 6 was obtained in the same manner as in Comparative Example 2 except that the Cu tube B was not used, and the same evaluation as in Comparative Example 1 was performed. The results are shown in Table 1.

Comparative Example 6 A comparative base material 7 was obtained in the same manner as in Comparative Example 3 except that the Cu tube B was not used, and the same evaluation as in Comparative Example 1 was performed. The results are shown in Table 1.

Table 1 shows the materials used as the base material and the evaluation results.

[0036]

[Table 1]

As shown in Table 1, from Comparative Example 1 and Comparative Example 4 or Comparative Example 2 and Comparative Example 4 , when the superconducting composite material was Sn-plated, the Cu tube B was placed inside the diffusion preventing material. Doing so causes less reduction in rough skin of the obtained base material Ta. From Example 1 , the reduction in the roughness of the Ta layer when using the Ta / Cu clad tube is the smallest. Also,
From Comparative Example 3 and Comparative Example 6 , even if the superconducting composite material is not plated with Sn, placing the Cu tube B reduces the roughness of the Ta layer.

The diffusion preventing material is Ta-based alloy, Nb or Nb.
Even in the case of the base alloy, since these have the same hardness as Ta or higher, it is needless to say that the same effect can be obtained by disposing the layer made of Cu or the Cu base alloy.

[0039]

According to the present invention, a superconducting composite material containing at least three kinds of materials of Nb or Nb-based alloy, Cu or Cu-based alloy and Sn or Sn-based alloy existing in these, a diffusion preventive material and a stabilizing material. Nb made of chemical material
_{In the} process of producing a ₃ Sn superconducting wire, it is possible to obtain an Nb ₃ Sn superconducting wire which does not break during the cross-section reduction process and has a substantially constant thickness of the diffusion preventing material inside the obtained superconducting wire.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a superconducting wire obtained by the present invention after cross-section reduction processing.

FIG. 2 is a cross-sectional view of the superconducting wire obtained according to the present invention during assembly.

FIG. 3 is a cross-sectional view of a conventional superconducting wire.

FIG. 4 is a cross-sectional view of a conventional superconducting wire with a roughened diffusion preventing material.

FIG. 5 is an example of a superconducting composite material.

FIG. 6 is a perspective view of a Ta / Cu clad plate.

FIG. 7 is a perspective view of a Ta / Cu clad tube.

[Explanation of symbols]

1 Superconducting composite material after cross-section reduction processing, 2 Diffusion prevention material after cross-section reduction processing, 3 Cu or Cu after cross-section reduction processing
Base alloy layer, 4 Stabilizer after cross-section reduction, 5
Superconducting composite material, 6 Diffusion prevention material, 7 Cu or Cu
Base alloy layer, 8 stabilizer, 9 roughened diffusion preventive material, 10 Nb or Nb base alloy, 11 C
u or Cu based alloy, 12 Sn or Sn based alloy, 1
3 Ta layer, 14 Cu layer.

Continuation of front page (56) Reference JP 62-271306 (JP, A) JP 3-238717 (JP, A) JP 5-123875 (JP, A) JP 8-339728 (JP , A) JP-A-2-66814 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01B 12/00-13/00

Claims (2)

(57) [Claims] 1. At least Nb or an Nb-based alloy, Cu
Alternatively, a Cu-based alloy and a superconducting composite material containing three kinds of materials, Sn or Sn-based alloy, existing inside these, a diffusion preventive material surrounding the superconducting composite material, and a stabilizing material such as Cu disposed around the composite material are assembled. Nb _{3 which is} later processed to reduce the cross section
In a method of manufacturing a Sn superconducting wire, T is used as a diffusion preventing material.
A plate made of a or Ta-based alloy is used.
Is a clad plate formed by joining a plate made of a Cu-based alloy
Tubular with the Cu or Cu-based alloy layer on the inside
A method for producing an Nb ₃ Sn superconducting wire which is molded into a composite and used in the composite assembly . 2. At least Nb or Nb-based alloy, Cu
Alternatively, Cu-based alloys and Sn existing in these
Or a superconducting composite material containing three types of Sn-based alloys,
Diffusion prevention material surrounding it, and stabilizing material such as Cu around it
Nb _{3 for} reducing cross-section after arranging
In the manufacturing method of Sn superconducting wire, N is used as a diffusion preventing material.
A plate made of b or Nb-based alloy is used.
Is a clad plate formed by joining a plate made of a Cu-based alloy
Tubular with the Cu or Cu-based alloy layer on the inside
A method for producing an Nb ₃ Sn superconducting wire which is molded into a composite and used in the composite assembly .