Method for regulating the residual resistance ratio of a stabilized superconducting wire and superconducting wire

Abstract

This invention belongs to the field of superconducting wire technology, and relates to a method for controlling and stabilizing the residual resistivity (RRR) of superconducting wires, as well as the superconducting wires themselves. The method includes: presetting a target RRR value for the superconducting wire; obtaining NbTi / Cu superconducting bare wire by cold working deformation and aging heat treatment of an NbTi / Cu superconducting composite ingot; sequentially subjecting the NbTi / Cu superconducting bare wire to stretching, online annealing, and cooling to obtain a superconducting bare wire to be processed; subjecting the superconducting bare wire to be processed to single-pass small-volume deformation to achieve the target size specifications, and finally performing braided insulation treatment to obtain the finished superconducting wire. This invention, through annealing and single-pass small-volume deformation, allows the RRR value of the finished superconducting wire to be controlled according to annealing parameters, and also improves the dimensional uniformity and RRR value uniformity of the formed wire.

Description

Technical Field

[0001] This invention belongs to the field of superconducting wire technology, and relates to a method for controlling and stabilizing the residual resistivity of superconducting wires and superconducting wires. Background Technology

[0002] Due to its excellent superconducting properties, mechanical stability, and cost advantages, NbTi superconducting wires are widely used in high-tech fields such as magnetic resonance imaging (MRI), particle accelerators, and controlled nuclear fusion. The residual resistivity ratio (RRR) is a core indicator characterizing the purity and conductivity of the copper matrix in superconducting wires, directly affecting the wire's thermal stability, quench recovery capability, and overall operational reliability in the superconducting state. Different applications have significantly different requirements for the RRR value. However, current NbTi superconducting wire fabrication processes mainly rely on various techniques to maximize the RRR value. On the one hand, this results in large RRR value dispersion, making it difficult to precisely match target requirements; on the other hand, it cannot meet the market demand for superconducting wires with customized RRR values. Therefore, developing a fabrication method that can precisely control and stabilize the RRR value of NbTi superconducting wires while improving wire dimensional uniformity and simplifying the process has become a critical problem urgently needing to be solved in the field of superconducting wire technology. Summary of the Invention

[0003] To overcome the shortcomings of existing technologies, this invention provides a method for controlling and stabilizing the residual resistivity (RRR) of superconducting wires, as well as the superconducting wire itself. The method involves selecting the target RRR of the superconducting wire through online annealing, and fixing the target RRR through single-pass small-volume deformation after online annealing. The RRR of the finished superconducting wire produced by the technical solution provided by this invention can be controlled according to the annealing parameters, and the dimensional uniformity of the formed wire is also improved.

[0004] On one hand, the present invention relates to a method for controlling the residual resistivity ratio of a stable superconducting wire, comprising:

[0005] Preset the target RRR value for superconducting wires;

[0006] NbTi / Cu superconducting bare wires were prepared by cold working deformation and aging heat treatment of NbTi / Cu superconducting composite ingots;

[0007] The NbTi / Cu superconducting bare wire is sequentially stretched, annealed in the line and cooled to obtain a superconducting bare wire to be processed. The RRR value of the superconducting bare wire to be processed is 20~50 higher than the target RRR value.

[0008] The bare superconducting wire to be processed is deformed to the target size specification through a single pass of small processing. Finally, it is braided and insulated to obtain the finished superconducting wire. The absolute difference between the RRR value of the finished superconducting wire and the target RRR value does not exceed 15.

[0009] Those skilled in the art can select different annealing parameters based on the target RRR value of NbTi / Cu superconducting bare wire and finished superconducting wire to obtain superconducting bare wires with different RRR values. Finally, the RRR value of the finished superconducting wire is fixed by a single pass of small-volume processing, so as to achieve the purpose of obtaining the finished superconducting wire with the required RRR value as needed.

[0010] Furthermore, in the method for regulating the residual resistance ratio of a stable superconducting wire provided by the present invention, the processing rate of the single-pass small-scale deformation is 3~10%.

[0011] Furthermore, in the method for regulating and stabilizing the residual resistivity ratio of superconducting wires provided by the present invention, the online annealing temperature is 300~600℃ and the processing speed is 50~120m / min.

[0012] Furthermore, in the method for regulating the residual resistivity of a stable superconducting wire provided by the present invention, the length of the online annealing is 1~3m.

[0013] Furthermore, in the method for regulating and stabilizing the residual resistivity ratio of superconducting wires provided by the present invention, the NbTi / Cu superconducting composite ingot is sequentially subjected to extrusion, drawing, aging heat treatment and twisting to obtain NbTi / Cu superconducting bare wire.

[0014] Furthermore, in the method for controlling the residual resistivity ratio of a stable superconducting wire provided by the present invention, the number of stretching passes is 10-30%.

[0015] Furthermore, in the method for regulating the residual resistivity of a stable superconducting wire provided by the present invention, the target size specification is a round wire with a diameter of Φ0.5mm to Φ3.0mm.

[0016] Furthermore, in the method for regulating the residual resistivity of a stable superconducting wire provided by the present invention, the target size is a flat wire with dimensions of 0.8mm×0.5mm~5.0mm×3.0mm.

[0017] Furthermore, in the method for regulating and stabilizing the residual resistivity ratio of superconducting wires provided by the present invention, the copper-to-superconducting ratio of the NbTi / Cu superconducting composite ingot is 0.6 to 20.0. Exemplarily, the copper-to-superconducting ratio of the NbTi / Cu superconducting composite ingot is 0.7 to 19.0, 0.7 to 11.0, or 11.0 to 19.0.

[0018] On the other hand, the present invention relates to an NbTi superconducting wire, which is prepared by the method described above for controlling and stabilizing the residual resistivity ratio of the superconducting wire.

[0019] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects or advantages:

[0020] (1) Achieve precise control and stable solidification of RRR value. By actively adjusting the online annealing process parameters, the RRR value can be preset according to the target requirements and fixed by subsequent single-pass small-volume deformation. This realizes the transformation from passively increasing the RRR value to actively designing and stably controlling the RRR value, and significantly reduces the dispersion of the RRR value, thereby improving the consistency and reliability of the product.

[0021] (2) Improve the overall quality and process controllability of wire. The optimized integrated process combining online annealing and single-pass small deformation not only effectively controls the RRR value performance, but also significantly improves the dimensional accuracy and uniformity of the wire, and enhances the stability and controllability of the overall process.

[0022] (3) Enhanced process applicability and support for customized production. This method is applicable to a wide range of copper-to-superconductor ratios, especially superconducting wires with copper-to-superconductor ratios as low as 0.6, and various finished product specifications (round wire Φ0.5~3.0mm or flat wire 0.8×0.5~5.0×3.0mm). It has strong process adaptability and scalability, and can meet the differentiated requirements of different application scenarios for RRR values. It provides a reliable and efficient solution for the production of high-performance, high-consistency, and customizable superconducting wires. Detailed Implementation

[0023] The technical solution of the present invention will be described below with reference to embodiments. However, the present invention is not limited to the following embodiments. Unless otherwise specified, the experimental and detection methods described in each embodiment are conventional methods; the reagents and materials described are commercially available unless otherwise specified. Unless otherwise specified, all percentages in the following embodiments refer to mass percentages. Unless otherwise specified, all proportions in the following embodiments refer to mass ratios.

[0024] Example 1

[0025] This embodiment provides a method for preparing NbTi superconducting wire with adjustable residual resistivity and insulation specification of Φ0.630mm, including the following steps:

[0026] Step 1: Set the RRR value of the finished wire to 120; prepare NbTi / Cu composite ingots, then extrude and cold draw them, with a processing rate of 30% for each processing pass, and perform 4 aging heat treatments at intervals during the process, followed by twisting. The wire to be stretched after twisting is an NbTi / Cu composite wire with a diameter of 0.56mm and a copper oversize ratio of 0.7.

[0027] Step 2: The superconducting NbTi / Cu composite bare wire is sequentially fed into the stretching module, the online annealing tube, and the pure water cooling module. A pass rate of 10-30% is used. The drawn wire has a diameter of Φ0.51mm. The annealing tube temperature is 320℃±5℃, and the wire passes through the annealing tube at a speed of 110m / min. After annealing, the wire enters the pure water cooling device, where the pure water temperature is controlled at 40℃±5℃.

[0028] Step 3: The surface of the superconducting NbTi / Cu composite bare wire with an RRR value of 140 is polished, and then it enters the stretching module. After a single pass of small-volume deformation, the wire's dimensions after stretching are Φ0.50mm. After stretching, the wire enters the ultrasonic cleaning tank and is ultrasonically cleaned with warm water at 50℃±10℃ for at least 1 minute. After cleaning, the wire is dried in an air dryer to remove surface water.

[0029] Step 4: Use an 8-spindle braiding machine to braid the superconducting wire with polyester filaments. The polyester filament specification is 110 dtex, the braiding pitch is 3.3 mm, and the braiding speed is 20 m / h. Finally, 21,000 m of finished wire with a finished size of Φ0.630 mm is obtained.

[0030] The RRR value of the superconducting wire was tested. Nine intervals, each 10cm long, were evenly selected from the beginning to the end. The tested RRR value was controlled within the range of 120±15. The dimensional accuracy of the entire wire was checked and controlled within ±0.015mm of the center value.

[0031] Comparative Example 1

[0032] This comparative example is used to compare with Example 1, and the specific steps are as follows:

[0033] Step 1: Prepare NbTi / Cu composite ingots, followed by extrusion and cold drawing. The processing rate of each processing pass is 30%. Four aging heat treatments are performed at intervals during the process. Then, the ingots are twisted. The wire to be stretched after twisting is an NbTi / Cu composite wire with a diameter of 0.56mm and a copper-to-weight ratio of 0.7.

[0034] Step 2: The superconducting NbTi / Cu composite bare wire is sequentially fed into the stretching module, the online annealing tube, and the pure water cooling module. A pass rate of 10-30% is used. The drawn wire has a diameter of Φ0.50mm. The annealing tube temperature is 320℃±5℃, and the wire passes through the annealing tube at a speed of 110m / min. After annealing, the wire enters the pure water cooling device, where the pure water temperature is controlled at 40℃±5℃.

[0035] Step 3: Perform surface polishing and ultrasonic cleaning on the superconducting NbTi / Cu composite bare wire in sequence. Use warm water at 50℃±10℃ to ultrasonically clean the wire. The ultrasonic cleaning time should be no less than 1 minute. After cleaning, put the wire into a dryer to dry the water stains on the wire surface.

[0036] Step 4: Use an 8-spindle braiding machine to braid the superconducting wire with polyester filaments. The polyester filament specification is 110 dtex, the braiding pitch is 3.3 mm, and the braiding speed is 20 m / h. Finally, 21,000 m of finished wire with a finished size of Φ0.630 mm is obtained.

[0037] The RRR value of the superconducting wire was tested. Nine intervals, each 10cm long, were evenly selected from the beginning to the end. The tested RRR value was 180±50. The dimensional accuracy of the entire wire was checked and found to be ±0.020mm at the center.

[0038] Example 2

[0039] This embodiment provides a method for preparing NbTi superconducting wire with an adjustable residual resistivity and insulation specification of (1.100 × 0.820) mm, including the following steps:

[0040] Step 1: Set the RRR value of the finished wire to 150; prepare NbTi / Cu composite ingots, then extrude and cold draw them, with a processing rate of 30% for each processing pass, and perform 4 aging heat treatments at intervals during the process, followed by twisting. The wire to be stretched after twisting is an NbTi / Cu composite wire with a specification of Φ0.800mm and a copper super-ratio of 0.7.

[0041] Step 2: The superconducting NbTi / Cu composite bare wire is sequentially fed into the stretching module, the online annealing tube, and the pure water cooling module. A pass rate of 10-30% is used. The drawn wire dimensions are (0.820 × 0.520) mm. The annealing tube temperature is 400℃ ± 5℃, and the wire speed through the annealing tube is 110 m / min. After annealing, the wire enters the pure water cooling device, where the pure water temperature is controlled at 40℃ ± 5℃.

[0042] Step 3: The surface of the superconducting NbTi / Cu composite bare wire with an RRR value of 180 is polished, and then it enters the stretching module. After a single pass of small-volume deformation, the dimensions of the stretched wire are (0.800 × 0.500) mm. After stretching, the wire enters the ultrasonic cleaning tank and is ultrasonically cleaned with warm water at 50℃±10℃ for at least 1 minute. After cleaning, the wire is dried in an air dryer to remove surface water.

[0043] Step 4: Use a 16-spindle braiding machine to braid the superconducting wire with polyester filaments. The polyester filaments are 230 dtex, the braiding pitch is 4.5 mm, and the braiding speed is 30 m / h. Finally, 18,000 m of finished wire with a finished size of (1.100 × 0.820) mm is obtained.

[0044] The RRR value of the superconducting wire was tested. Nine intervals, each 10cm long, were evenly selected from the beginning to the end. The tested RRR value was controlled within the range of 150±15. The dimensional accuracy of the entire wire was checked and controlled within ±0.015mm of the center value.

[0045] Comparative Example 2

[0046] This comparative example is used to compare with Example 2, and the specific steps are as follows:

[0047] Step 1: Prepare NbTi / Cu composite ingots, followed by extrusion and cold drawing. The processing rate of each processing pass is 30%. Four aging heat treatments are performed at intervals during the process. Then, the ingots are twisted. The wire to be stretched after twisting is an NbTi / Cu composite wire with a diameter of 0.800mm and a copper super-ratio of 0.7.

[0048] Step 2: The superconducting NbTi / Cu composite bare wire is sequentially fed into the stretching module, the online annealing tube, and the pure water cooling module. A pass rate of 10-30% is used. The drawn wire dimensions are (0.800 × 0.500) mm. The annealing tube temperature is 400℃ ± 5℃, and the wire speed through the annealing tube is 110 m / min. After annealing, the wire enters the pure water cooling device, where the pure water temperature is controlled at 40℃ ± 5℃.

[0049] Step 3: Perform surface polishing and ultrasonic cleaning on the superconducting NbTi / Cu composite bare wire in sequence. Use warm water at 50℃±10℃ to ultrasonically clean the wire. The ultrasonic cleaning time should be no less than 1 minute. After cleaning, put the wire into a dryer to dry the water stains on the wire surface.

[0050] Step 4: Use a 16-spindle braiding machine to braid the superconducting wire with polyester filaments. The polyester filaments are 230 dtex, the braiding pitch is 4.5 mm, and the braiding speed is 30 m / h. Finally, 18,000 m of finished wire with a finished size of (1.100 × 0.820) mm is obtained.

[0051] The RRR value of the superconducting wire was tested. Nine intervals, each 10cm long, were evenly selected from the beginning to the end. The tested RRR value was 220±50. The dimensional accuracy of the entire wire was checked and found to be ±0.020mm at the center.

[0052] Example 3

[0053] This embodiment provides a method for preparing NbTi superconducting wire with adjustable residual resistivity and insulation specification of Φ2.750mm, including the following steps:

[0054] Step 1: Set the RRR value of the finished wire to 180; prepare NbTi / Cu composite ingots, then extrude and cold draw them, with a processing rate of 30% for each processing pass, and perform 4 aging heat treatments at intervals during the process, followed by twisting. The wire to be stretched after twisting is an NbTi / Cu composite wire with a specification of Φ3.000mm and a copper-to-weight ratio of 11.0.

[0055] Step 2: The superconducting NbTi / Cu composite bare wire is sequentially fed into the stretching module, the online annealing tube, and the pure water cooling module. A pass rate of 10-30% is used. The drawn wire has a diameter of Φ2.600mm. The annealing tube temperature is 500℃±5℃, and the wire passes through the annealing tube at a speed of 80m / min. After annealing, the wire enters the pure water cooling device, where the pure water temperature is controlled at 40℃±5℃.

[0056] Step 3: The surface of the superconducting NbTi / Cu composite bare wire with an RRR value of 225 is polished, and then it enters the stretching module. After a single pass of small-volume deformation, the wire's dimensions after stretching are Φ2.500mm. After stretching, the wire enters the ultrasonic cleaning tank and is ultrasonically cleaned with warm water at 50℃±10℃ for at least 1 minute. After cleaning, the wire is dried in an air dryer to remove surface water.

[0057] Step 4: Use a 16-spindle braiding machine to braid the superconducting wire with polyester filaments. The polyester filaments are 500 dtex, the braiding pitch is 10.2 mm, and the braiding speed is 60 m / h. Finally, 8700 m of finished wire with a finished size of Φ2.750 mm is obtained.

[0058] The RRR value of the superconducting wire was tested. Nine intervals, each 10cm long, were evenly selected from the beginning to the end. The tested RRR value was controlled within the range of 180±15. The dimensional accuracy of the entire wire was checked and controlled within ±0.015mm of the center value.

[0059] Comparative Example 3

[0060] This comparative example is used to compare with Example 3, and the specific steps are as follows:

[0061] Step 1: Prepare NbTi / Cu composite ingots, followed by extrusion and cold drawing. The processing rate of each processing pass is 30%. Four aging heat treatments are performed at intervals during the process. Then, the ingots are twisted. The wire to be stretched after twisting is an NbTi / Cu composite wire with a diameter of Φ3.000mm and a copper-to-weight ratio of 11.0.

[0062] Step 2: The superconducting NbTi / Cu composite bare wire is sequentially fed into the stretching module, the online annealing tube, and the pure water cooling module. A pass rate of 10-30% is used. The drawn wire has a diameter of Φ2.500mm. The annealing tube temperature is 500℃±5℃, and the wire passes through the annealing tube at a speed of 80m / min. After annealing, the wire enters the pure water cooling device, where the pure water temperature is controlled at 40℃±5℃.

[0063] Step 3: Polish the surface of the superconducting NbTi / Cu composite bare wire and perform ultrasonic cleaning. Use warm water at 50℃±10℃ to perform ultrasonic cleaning on the wire. The ultrasonic cleaning time should be no less than 1 minute. After cleaning, put the wire into a dryer to dry the water stains on the surface of the wire.

[0064] Step 4: Use a 16-spindle braiding machine to braid the superconducting wire with polyester filaments. The polyester filaments are 500 dtex, the braiding pitch is 10.2 mm, and the braiding speed is 60 m / h. Finally, 8700 m of finished wire with a finished size of Φ2.750 mm is obtained.

[0065] The RRR value of the superconducting wire was tested. Nine intervals, each 10cm long, were evenly selected from the beginning to the end. The tested RRR value was 260±50. The dimensional accuracy of the entire wire was checked and found to be ±0.020mm at the center.

[0066] Example 4

[0067] This embodiment provides a method for preparing NbTi superconducting wire with adjustable residual resistivity and insulation specification of (4.670 × 2.670) mm, including the following steps:

[0068] Step 1: The preset RRR value of the finished wire is 210; NbTi / Cu composite ingots are prepared, followed by extrusion and cold drawing, with a processing rate of 30% for each processing pass. Four aging heat treatments are performed at intervals during the process, followed by twisting. The wire to be stretched after twisting is an NbTi / Cu composite wire with a specification of Φ4.30mm and a copper super-ratio of 19.

[0069] Step 2: The superconducting NbTi / Cu composite bare wire is sequentially fed into the stretching module, the online annealing tube, and the pure water cooling module. A pass rate of 10-30% is used. The final wire dimensions after stretching are (4.650 × 2.650) mm. The annealing tube temperature is 580℃ ± 5℃, and the wire speed through the annealing tube is 60 m / min. After annealing, the wire enters the pure water cooling device, where the pure water temperature is controlled at 40℃ ± 5℃.

[0070] Step 3: The surface of the superconducting NbTi / Cu composite bare wire with an RRR value of 260 is polished, and then it enters the stretching module. After a single pass of small-volume deformation, the dimensions of the stretched wire are (4.500 × 2.500) mm. After stretching, the wire enters the ultrasonic cleaning tank and is ultrasonically cleaned with warm water at 50℃±10℃ for at least 1 minute. After cleaning, the wire is dried in an air dryer to remove surface water.

[0071] Step 4: Use a 32-spindle braiding machine to braid the superconducting wire with polyester filaments. The polyester filaments are 48 tex, the braiding pitch is 13.5 mm, and the braiding speed is 35 m / h. Finally, a finished wire with a size of 4300 m (4.670 × 2.670) mm is obtained.

[0072] The RRR value of the superconducting wire was tested. Nine intervals, each 10cm long, were evenly selected from the beginning to the end. The tested RRR value was controlled within the range of 210±15. The dimensional accuracy of the entire wire was checked and controlled within ±0.015mm of the center value.

[0073] Comparative Example 4

[0074] This comparative example is used to compare with Example 4, and the specific steps are as follows:

[0075] Step 1: Prepare NbTi / Cu composite ingots, followed by extrusion and cold drawing. The processing rate of each processing pass is 30%. Four aging heat treatments are performed at intervals during the process. Then, the ingots are twisted. The wire to be stretched after twisting is an NbTi / Cu composite wire with a diameter of Φ4.30mm and a copper super-ratio of 19.

[0076] Step 2: The superconducting NbTi / Cu composite bare wire is sequentially fed into the stretching module, the online annealing tube, and the pure water cooling module. A pass rate of 10-30% is used. The final wire dimensions after stretching are (4.500 × 2.500) mm. The annealing tube temperature is 580℃±5℃, and the wire speed through the annealing tube is 60 m / min. After annealing, the wire enters the pure water cooling device, where the pure water temperature is controlled at 40℃±5℃.

[0077] Step 3: Polish the surface of the superconducting NbTi / Cu composite bare wire and perform ultrasonic cleaning. Use warm water at 50℃±10℃ to perform ultrasonic cleaning on the wire. The ultrasonic cleaning time should be no less than 1 minute. After cleaning, put the wire into a dryer to dry the water stains on the surface of the wire.

[0078] Step 4: Use a 32-spindle braiding machine to braid the superconducting wire with polyester filaments. The polyester filaments are 48 tex, the braiding pitch is 13.5 mm, and the braiding speed is 35 m / h. Finally, a finished wire with a size of 4300 m (4.670 × 2.670) mm is obtained.

[0079] The RRR value of the superconducting wire was tested. Nine intervals, each 10cm long, were evenly selected from the beginning to the end. The tested RRR value was 300±50. The dimensional accuracy of the entire wire was checked and found to be ±0.020mm at the center.

[0080] As can be seen from Examples 1-4 and Comparative Examples 1-4, the superconducting wires produced without the single-pass small-volume deformation and fixation step have a large range of RRR values ​​and low wire dimensional accuracy.

[0081] The embodiments described above are only some, not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate preferred embodiments. All other embodiments obtained by those skilled in the art through related deductions and substitutions based on the inventive concept, without inventive effort, are within the scope of protection of the present invention.

Claims

1. A method for controlling the residual resistivity ratio of a stable superconducting wire, characterized in that, include: Preset the target RRR value for superconducting wires; NbTi / Cu superconducting bare wires were prepared by cold working deformation and aging heat treatment of NbTi / Cu superconducting composite ingots; The NbTi / Cu superconducting bare wire is sequentially stretched, annealed in the line and cooled to obtain a superconducting bare wire to be processed. The RRR value of the superconducting bare wire to be processed is 20~50 higher than the target RRR value. The bare superconducting wire to be processed is deformed to the target size specification through a single pass of small processing. Finally, it is braided and insulated to obtain the finished superconducting wire. The absolute difference between the RRR value of the finished superconducting wire and the target RRR value does not exceed 15.

2. The method for regulating the residual resistivity ratio of a stable superconducting wire according to claim 1, characterized in that, The processing rate for single-pass small-volume deformation is 3~10%.

3. The method for regulating the residual resistivity ratio of a stable superconducting wire according to claim 1, characterized in that, The online annealing temperature is 300~600℃, and the processing speed is 50~120m / min.

4. The method for regulating the residual resistivity ratio of a stable superconducting wire according to claim 1, characterized in that, The length of the online annealing process is 1~3m.

5. The method for regulating the residual resistivity ratio of a stable superconducting wire according to claim 1, characterized in that, The NbTi / Cu superconducting composite ingot is sequentially processed by extrusion, drawing, aging heat treatment and twisting to obtain NbTi / Cu superconducting bare wire.

6. The method for regulating the residual resistivity ratio of a stable superconducting wire according to claim 1, characterized in that, The processing rate for the stretching passes is 10-30%.

7. The method for regulating the residual resistivity ratio of a stable superconducting wire according to claim 1, characterized in that, The target size is a round line with a diameter of Φ0.5mm to Φ3.0mm.

8. The method for regulating the residual resistivity ratio of a stable superconducting wire according to claim 1, characterized in that, The target size is a flat wire with dimensions of 0.8mm×0.5mm to 5.0mm×3.0mm.

9. The method for regulating the residual resistivity ratio of a stable superconducting wire according to claim 1, characterized in that, The copper-to-superconducting ratio of the NbTi / Cu superconducting composite ingot is 0.6 to 20.

0.

10. An NbTi superconducting wire, characterized in that, It is prepared by the method of adjusting the residual resistivity of a stable superconducting wire as described in any one of claims 1 to 9.