A method for efficiently preparing niobium-tin superconducting flat wire
By cold processing of soft copper groove wires and tin-plated superconducting circle wires, a nested structure Nb3Sn flat wire is formed, which solves the long-term, high cost and process difficulty problems in the existing Nb3Sn superconducting flat wire production process, and realizes efficient and low-cost Nb3Sn superconducting flat wire preparation, ensuring the stable performance and high current carrying capacity of the wire.
Patent Information
- Application Number
- CN202411957533.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-30
- Publication Date
- 2025-04-08
AI Technical Summary
The existing production process of Nb3Sn superconducting flat wire has the risk of long production cycle, high cost, high process difficulty and reduced current carrying capacity. The superconducting phase is prone to breakage, affecting the quality of the wire.
The soft copper groove wire and the tin-plated superconducting circle wire are used for cold processing. The surface tin layer of the tin plated superconducting circle wire is used as the diffusion agent to achieve mutual diffusion and stable bonding of the copper matrix, forming a nested structure Nb3Sn flat line, and maintaining the integrity of the superconducting phase during the heat treatment process.
The goal of Nb3Sn superconducting flat wire is achieved with high mechanical strength, strong current carrying capacity and low production cost, avoiding defects in traditional processes, shortening the production cycle, reducing raw material costs, and ensuring the stable performance of the wire.
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Figure CN119786147A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of superconducting wires and relates to a method for efficiently preparing niobium-tin superconducting flat wires. Background Art
[0002] Since the upper critical field of niobium tin (Nb3Sn) superconducting wire at low temperature is as high as 22.5T, which is much higher than other low-temperature superconducting materials, and it has a high critical current density, it performs well in the manufacture of high-field magnets. Compared with other superconducting materials, Nb3Sn superconducting wire also has machining performance and cost advantages, and occupies a dominant position in commercial superconducting materials. It is currently widely used in nuclear magnetic resonance (NMR), high energy physics (HEP) and the International Thermonuclear Experimental Reactor (ITER).
[0003] Since the Nb3Sn superconducting phase is a brittle intermetallic compound, it is easy to lose its superconducting properties under strain and has poor mechanical strength. Therefore, the Nb3Sn superconducting wire must be wound into a magnet first and then subjected to reactive heat treatment to avoid the specific quenching of the magnet and the wire breakage during the winding process. In order to solve these problems, the nested structure of the Wire inchannel NbTi superconducting wire (WIC wire for short) used in the magnetic resonance imaging device (MRI) is used to increase the copper ratio of the Nb3Sn wire, and the mechanical strength of the Nb3Sn wire is improved by the external copper slot wire. At the same time, under the condition that the superconducting flat wire is not turned over and does not pass through a small diameter guide wheel, the brittle Nb3Sn superconducting phase will not be broken during the winding process, and then the Nb3Sn superconducting wire can be subjected to eddy current flaw detection, insulation braiding and other links after the reactive heat treatment of the wire, ensuring the reliable quality of the wire wound into the magnet.
[0004] However, the traditional Nb3Sn superconducting flat wire is produced by the inlay welding method, which mainly includes: round wire chrome plating (to protect the Nb3Sn composite wire from corrosion), inlay welding (to obtain WIC structure flat wire), flat wire tin stripping (to avoid wire adhesion during reaction heat treatment), reaction heat treatment (to generate superconducting phase) and other steps. This production process has the following disadvantages: 1) The round wire chrome plating and flat wire tin stripping process are too slow, the production cycle is long, and it is not conducive to mass production; 2) The cost of round wire chrome plating is high; 3) The WIC flat wire obtained by inlay welding of round wire and slot wire has many defects and the process is difficult; 4) During the inlay welding process, because the temperature is higher than the melting point of solder, the distribution of tin source in Nb3Sn composite round wire changes, resulting in a greater risk of a decrease in the current carrying capacity of the final Nb3Sn superconducting wire, and the more concentrated the tin source, the greater the impact.
[0005] Therefore, it is necessary to improve the technical defects of the process and prepare a Nb3Sn superconducting flat wire that can ensure that the Nb3Sn superconducting phase is not broken and has strong current carrying capacity and low production cost. Summary of the invention
[0006] In order to produce a Nb3Sn superconducting flat wire with high mechanical strength, strong current carrying capacity and low production cost, the present invention uses a soft copper slot wire and a tinned superconducting round wire for cold working combination. During the reaction heat treatment process, the copper matrix in the soft copper slot wire and the tinned superconducting round wire diffuses mutually, and the surface tin layer of the tinned superconducting round wire is used as a diffusion agent to achieve a stable combination of the two. Based on this technical route, the present invention provides the following technical solutions: The present invention provides a method for efficiently preparing Nb3Sn superconducting flat wire, the method comprising: S1. Select copper slot wire and Nb3Sn composite round wire processing parts; S2. The copper groove wire is rewound onto a steel wheel for annealing to obtain a soft copper groove wire; S3. The Nb3Sn composite round wire is soldered, and then passed through a round die to tin the surface of the Nb3Sn composite round wire to obtain a tinned superconducting round wire; S4. The soft copper slot wire and the tinned superconducting round wire are simultaneously passed through a rectangular die and cold worked to obtain a nested structure Nb3Sn flat wire; S5. The nested structure Nb3Sn flat wire is wound on a steel wheel, placed in a heat treatment furnace, and the furnace body is evacuated for heat treatment to obtain a finished Nb3Sn superconducting flat wire.
[0007] Furthermore, in S2 of the above method, the annealing temperature is 100-200° C., and the annealing time is 1-2 hours.
[0008] Furthermore, in S3 of the above method, the solder used for soldering includes: SnIn solder and SnBi solder.
[0009] Furthermore, in S3 of the above method, the soldering temperature is 150-200° C., and the soldering speed is 80-200 m / min.
[0010] Furthermore, before the cold working and combining in S4, the method further includes: ultrasonically cleaning and pickling the soft copper slot wire obtained in S2 and the tinned superconducting round wire obtained in S3 to ensure that there is no copper oxide on the contact surface between the soft copper slot wire and the tinned superconducting round wire.
[0011] Furthermore, in S4 of the above method, the processing rate of cold working is 20-30%, and the speed is 70-120 m / min.
[0012] Furthermore, in S5 of the above method, the vacuum degree of the evacuation is less than 5×10 -3 Pa; Heat treatment conditions: heat treatment at 600~700℃ for 70~300h.
[0013] Furthermore, in S5 of the above method, the nested structure Nb3Sn flat wire must not turn over when it is wound on the steel wheel.
[0014] Furthermore, in S5 of the above method, the diameter of the steel wheel is greater than or equal to 200 mm.
[0015] The present invention also claims protection for the Nb3Sn superconducting flat wire prepared by the above method.
[0016] Compared with the prior art, the present invention "a method for efficiently preparing niobium-tin superconducting flat wire" has at least the following beneficial effects: The method for efficiently preparing Nb3Sn superconducting flat wire provided by the present invention combines the soft copper slot wire and the tin-plated superconducting round wire by cold working. The process is simpler and more controllable, and the defects of tin nodules, tin ash inclusions and the like existing in the inlay welding of the traditional method are avoided. There is no gap between the soft copper slot wire and the tin-plated superconducting round wire, and the combination is stable.
[0017] The present invention provides a method for efficiently preparing Nb3Sn superconducting flat wire. The Nb3Sn composite round wire is only subjected to low-temperature dip soldering tin plating, and the temperature is lower than the melting point of the tin source in the round wire, 232°C. After tin plating, the distribution of the tin source in the Nb3Sn composite round wire remains unchanged, and the performance is stable. At the same time, no tin stripping process is required, the cost is lower, and it is more environmentally friendly.
[0018] The method for efficiently preparing Nb3Sn superconducting flat wire provided by the present invention has a fast soldering tinning speed and low price in S3, which is 500 times the chromium plating speed of the round wire surface in the traditional method. In addition, the use of soldering tinning instead of electroplating chromium reduces the cost of raw materials (the unit price of electroplating chromium is about 10,000 yuan / 10,000 meters, and the unit price of soldering is about 2,500 yuan / 10,000 meters, which is only 25% of the cost).
[0019] The Nb3Sn superconducting flat wire prepared by the method of the present invention can still maintain a stable LC value after repeated winding, and the wire has stable current-carrying performance and high mechanical strength.
[0020] Compared with the traditional preparation method, the present invention reduces the working hours required for production by about 95%, thus greatly shortening the production cycle. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 A cross-sectional view of a copper slot line.
[0022] Figure 2 This is the appearance of tinned superconducting round wire.
[0023] Figure 3 This is a cross-sectional diagram of a nested structure Nb3Sn flat wire.
[0024] Figure 4 This is a cross-sectional view of the finished Nb3Sn superconducting flat wire. DETAILED DESCRIPTION
[0025] The technical solution of the present invention is clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0026] The embodiment of the present invention provides a method for efficiently preparing Nb3Sn superconducting flat wire, the method comprising: S1. Select copper slot wire and Nb3Sn composite round wire workpiece; the cross section of the copper slot wire is as follows Figure 1 shown.
[0027] S2. Rewind the copper slot wire selected in S1 onto a steel wheel for annealing to obtain a soft copper slot wire.
[0028] S3. Solder the Nb3Sn composite round wire selected in S1, and then pass it through a round die to tin the surface of the Nb3Sn composite round wire to obtain a tinned superconducting round wire; the tinned superconducting round wire is as follows Figure 2 shown.
[0029] S4. The soft copper slot wire obtained in S2 and the tinned superconducting round wire obtained in S3 are simultaneously passed through a rectangular die and cold worked to obtain a nested structure Nb3Sn flat wire; the cross section of the nested structure Nb3Sn flat wire is as follows. Figure 3 shown.
[0030] S5. The nested structure Nb3Sn flat wire obtained in S4 is wound on a steel wheel and placed in a heat treatment furnace. The furnace is evacuated for heat treatment to obtain a finished Nb3Sn superconducting flat wire; the finished Nb3Sn superconducting flat wire has a cross section such as Figure 4 shown.
[0031] Illustratively, in S2 of the above method, the annealing temperature is 100-200° C., and the annealing time is 1-2 hours.
[0032] Illustratively, in S3 of the above method, the solder used for soldering includes: SnIn solder and SnBi solder.
[0033] Illustratively, in S3 of the above method, the soldering temperature is 150-200° C., and the soldering speed is 80-200 m / min.
[0034] Exemplarily, before the cold working and bonding in S4, the method further includes: ultrasonically cleaning and pickling the soft copper slot wire obtained in S2 and the tinned superconducting round wire obtained in S3 to ensure that there is no copper oxide on the contact surface between the soft copper slot wire and the tinned superconducting round wire.
[0035] Illustratively, in S4 of the above method, the processing rate of cold working is 20-30%, and the speed is 70-120 m / min.
[0036] For example, in S5 of the above method, the vacuum degree of the evacuation is less than 5×10 -3 Pa; Heat treatment conditions: heat treatment at 600~700℃ for 70~300h.
[0037] For example, in S5 of the above method, the nested structure Nb3Sn flat wire must not flip over when it is wound on the steel wheel.
[0038] Exemplarily, in S5 of the above method, the diameter of the steel wheel is greater than or equal to 200 mm.
[0039] Example 1 This embodiment provides a method for efficiently preparing Nb3Sn superconducting flat wire.
[0040] S1. Select copper slot wire and Nb3Sn composite round wire workpieces. In this embodiment, the copper slot wire has a width of 2.6 mm, a height of 1.8 mm, and a slot width of 1.35 mm; the Nb3Sn composite round wire has a diameter of 1.30 mm.
[0041] S2. The copper slot wire selected in S1 is rewound onto a steel wheel for annealing at a temperature of 200°C for 1 hour to obtain a soft copper slot wire.
[0042] S3. The Nb3Sn composite round wire selected in S1 is first passed through a flux and then immersed in a SnIn tin bath for soldering at a soldering temperature of 200°C and a soldering speed of 200 m / min. The wire is then passed through a round die with a diameter of 1.30 mm to tin the surface of the Nb3Sn composite round wire to obtain a tinned superconducting round wire.
[0043] S4. The soft copper slot wire obtained in S2 and the tinned superconducting round wire obtained in S3 are simultaneously cold-processed and combined through a rectangular die with a size of 2.40×1.60 mm. The processing rate of the cold processing combination is 22.9% and the speed is 70 m / min to obtain a nested structure Nb3Sn flat wire.
[0044] S5. The nested Nb3Sn flat wire obtained in S4 is wound on a steel wheel with a diameter of 300 mm, and the nested Nb3Sn flat wire does not turn over during the winding process; then the wire is placed in a heat treatment furnace, and the furnace body is evacuated for heat treatment, and the vacuum degree of the evacuation is less than 5×10 -3 Pa; Heat treatment conditions: 700℃ heat treatment for 300h to obtain the finished Nb3Sn superconducting flat wire.
[0045] In the above method, before the cold working and bonding of S4, the soft copper slot wire obtained in S2 and the tinned superconducting round wire obtained in S3 are ultrasonically cleaned and pickled. The ultrasonic cleaning conditions are: the ultrasonic cleaning temperature is 70°C, the ultrasonic cleaning length is 40m; the pickling conditions are: H + The concentration of nitric acid is 1.5 mol / L, and the pickling length is 2 m to ensure that there is no copper oxide on the contact surface between the soft copper slot wire and the tinned superconducting round wire.
[0046] Example 2 This embodiment provides a method for efficiently preparing Nb3Sn superconducting flat wire.
[0047] S1. Select copper slot wire and Nb3Sn composite round wire workpieces. In this embodiment, the copper slot wire has a width of 1.6 mm, a height of 1.2 mm, and a slot width of 0.75 mm; the Nb3Sn composite round wire has a diameter of 0.70 mm.
[0048] S2. The copper slot wire selected in S1 is rewound onto a steel wheel for annealing at a temperature of 100°C for 2 hours to obtain a soft copper slot wire.
[0049] S3. The Nb3Sn composite round wire selected in S1 is first passed through a flux and then immersed in a SnIn tin bath for soldering at a soldering temperature of 150°C and a soldering speed of 80m / min. The wire is then passed through a round die with a diameter of 0.70mm to tin the surface of the Nb3Sn composite round wire to obtain a tinned superconducting round wire.
[0050] S4. The soft copper slot wire obtained in S2 and the tinned superconducting round wire obtained in S3 are simultaneously cold-processed and combined through a rectangular die with a size of 1.45×1.05 mm. The processing rate of the cold processing combination is 27.5%, and the speed is 120 m / min to obtain a nested structure Nb3Sn flat wire.
[0051] S5. The nested Nb3Sn flat wire obtained in S4 is wound on a steel wheel with a diameter of 200 mm, and the nested Nb3Sn flat wire does not turn over during the winding process; then the wire is placed in a heat treatment furnace, and the furnace body is evacuated for heat treatment, and the vacuum degree of the evacuation is less than 5×10 -3 Pa; Heat treatment conditions: 600℃ heat treatment for 70h to obtain the finished Nb3Sn superconducting flat wire.
[0052] In the above method, before the cold working and bonding of S4, the soft copper slot wire obtained in S2 and the tinned superconducting round wire obtained in S3 are ultrasonically cleaned and pickled. The ultrasonic cleaning conditions are: the ultrasonic cleaning temperature is 70°C, the ultrasonic cleaning length is 40m; the pickling conditions are: H + The concentration of nitric acid is 1.5 mol / L, and the pickling length is 2 m to ensure that there is no copper oxide on the contact surface between the soft copper slot wire and the tinned superconducting round wire.
[0053] Example 3 This embodiment provides a method for efficiently preparing Nb3Sn superconducting flat wire.
[0054] S1. Select copper slot wire and Nb3Sn composite round wire workpieces. In this embodiment, the copper slot wire has a width of 2.03 mm, a height of 1.37 mm, and a slot width of 0.97 mm; the Nb3Sn composite round wire has a diameter of 0.92 mm.
[0055] S2. The copper slot wire selected in S1 is rewound onto a steel wheel for annealing at a temperature of 100°C for 2 hours to obtain a soft copper slot wire.
[0056] S3. The Nb3Sn composite round wire selected in S1 is first passed through a flux and then immersed in a SnIn tin bath for soldering at a soldering temperature of 170°C and a soldering speed of 120 m / min. The wire is then passed through a round die with a diameter of 0.92 mm to tin the surface of the Nb3Sn composite round wire to obtain a tinned superconducting round wire.
[0057] S4. The soft copper slot wire obtained in S2 and the tinned superconducting round wire obtained in S3 are simultaneously cold-processed and combined through a rectangular die with a size of 1.85×1.23 mm. The processing rate of the cold processing combination is 23.7% and the speed is 100 m / min to obtain a nested structure Nb3Sn flat wire.
[0058] S5. The nested Nb3Sn flat wire obtained in S4 is wound on a steel wheel with a diameter of 200 mm, and the nested Nb3Sn flat wire does not turn over during the winding process; then the wire is placed in a heat treatment furnace, and the furnace body is evacuated for heat treatment, and the vacuum degree of the evacuation is less than 5×10 -3 Pa; Heat treatment conditions: heat treatment at 630°C for 130h to obtain the finished Nb3Sn superconducting flat wire.
[0059] In the above method, before the cold working and bonding of S4, the soft copper slot wire obtained in S2 and the tinned superconducting round wire obtained in S3 are ultrasonically cleaned and pickled. The ultrasonic cleaning conditions are: the ultrasonic cleaning temperature is 70°C, the ultrasonic cleaning length is 40m; the pickling conditions are: H + The concentration of nitric acid is 1.5 mol / L, and the pickling length is 2 m to ensure that there is no copper oxide on the contact surface between the soft copper slot wire and the tinned superconducting round wire.
[0060] Example 4 This embodiment describes the performance test of the Nb3Sn superconducting flat wires prepared in Embodiments 1 to 3, including critical current (Ic value), cross-sectional observation, and preparation cost comparison.
[0061] 1.Ic value The Ic value of the Nb3Sn superconducting flat wires prepared in Examples 1 to 3 was tested as follows: 1) Take the Nb3Sn superconducting flat wire product obtained in S5 and name it "superconducting wire-1"; 2) Take the finished Nb3Sn superconducting flat wire obtained from S5 and repeat winding it twice on a steel wheel and then take a sample. The diameter of the winding steel wheel is the same as S5 and is named "superconducting wire-2"; 3) Repeat winding the "superconducting wire-2" sample twice and then take a sample. The diameter of the winding steel wheel is the same as S5 and it is named "superconducting wire-3".
[0062] 4) The Ic values (4.2K, 12T) of the “superconducting wire-1”, “superconducting wire-2” and “superconducting wire-3” samples were measured respectively. The results are shown in Table 1.
[0063] Table 1. Ic values of Nb3Sn superconducting flat wires prepared in Examples 1 to 3 (4.2K, 12T)
[0064] It can be seen from Table 1 that in Examples 1 to 3, the Ic values of the samples "superconducting wire-1", "superconducting wire-2" and "superconducting wire-3" are basically the same, indicating that the current carrying capacity of the Nb3Sn superconducting flat wire is stable, and it can still maintain good wire performance after repeated winding and has high mechanical strength.
[0065] 2. Cross-sectional observation In addition, the cross sections of the samples of each embodiment were cut to observe whether there was a gap between the copper slot wire and the round wire. By observing the cross sections of the finished Nb3Sn superconducting flat wires in Examples 1 to 3, it was confirmed that there was no gap between the soft copper slot wire and the tinned superconducting round wire, and the combination was stable.
[0066] 3. Comparison of preparation costs Table 2 compares the total time required to prepare 100,000 meters of superconducting wire by the traditional method and the method provided in this application.
[0067] Table 2. Summary of total working hours for preparing 100,000 m Nb3Sn superconducting flat wire by conventional method and the present invention
[0068] As shown in Table 2, the total working time for preparing 100,000 meters of Nb3Sn superconducting flat wire by the traditional method is about 5940 hours, while the method provided by the present invention takes about 300 hours, and the total working time is shortened by about 95%.
[0069] In summary, the method for efficiently preparing Nb3Sn superconducting flat wire provided by the present invention combines the cold processing of soft copper slot wire and tin-plated Nb3Sn round wire, and the process is simpler and more controllable, avoiding the defects of tin nodules and tin ash inclusions in the inlay welding of the traditional method, and there is no gap between the soft copper slot wire and the tin-plated superconducting round wire, and the combination is stable. The prepared Nb3Sn superconducting flat wire can still maintain a stable lc value after repeated winding, and the wire current carrying performance is stable and the mechanical strength is high. Compared with the traditional preparation method, the production time required for the present invention is shortened by about 95%, and the surface coating of the round wire adopts the method of dip soldering tin plating instead of electroplating chromium, which shortens the preparation time and reduces the cost of raw materials, and has important contribution significance.
[0070] The embodiments described above are only some embodiments of the present invention, not all embodiments. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but only represents selected embodiments of the present invention. All other embodiments obtained without creative work and related deductions and substitutions made by ordinary technicians in the field under the conditions of the concept of the present invention belong to the scope of protection of the present invention.
Claims
1. A method for efficiently preparing Nb3Sn superconducting flat wire, characterized in that: The method comprises: S1. Select copper slot wire and Nb3Sn composite round wire processing parts; S2. The copper groove wire is rewound onto a steel wheel for annealing to obtain a soft copper groove wire; S3. The Nb3Sn composite round wire is soldered, and then passed through a round die to tin the surface of the Nb3Sn composite round wire to obtain a tinned superconducting round wire; S4. The soft copper slot wire and the tinned superconducting round wire are simultaneously passed through a rectangular die and cold worked to obtain a nested structure Nb3Sn flat wire; S5. The nested structure Nb3Sn flat wire is wound on a steel wheel, placed in a heat treatment furnace, and the furnace body is evacuated for heat treatment to obtain a finished Nb3Sn superconducting flat wire.
2. The method for efficiently preparing Nb3Sn superconducting flat wire according to claim 1, characterized in that: In S2, the annealing temperature is 100-200°C, and the annealing time is 1-2 hours.
3. The method for efficiently preparing Nb3Sn superconducting flat wire according to claim 1, characterized in that: In S3, the solder used for soldering includes: SnIn solder and SnBi solder.
4. The method for efficiently preparing Nb3Sn superconducting flat wire according to claim 1, characterized in that: In S3, the soldering temperature is 150~200℃ and the speed is 80~200m / min.
5. The method for efficiently preparing Nb3Sn superconducting flat wire according to claim 1, characterized in that: Before the cold working of S4, the process also includes: ultrasonically cleaning and pickling the soft copper slot wire obtained in S2 and the tinned superconducting round wire obtained in S3 to ensure that there is no copper oxide on the contact surface between the soft copper slot wire and the tinned superconducting round wire.
6. The method for efficiently preparing Nb3Sn superconducting flat wire according to claim 1, characterized in that: In S4, the processing rate of cold working is 20~30% and the speed is 70~120m / min.
7. The method for efficiently preparing Nb3Sn superconducting flat wire according to claim 1, characterized in that: In S5, the vacuum degree of the evacuation is less than 5×10 -3 Pa; Heat treatment conditions: heat treatment at 600~700℃ for 70~300h.
8. The method for efficiently preparing Nb3Sn superconducting flat wire according to claim 1, characterized in that: In S5, the nested structure Nb3Sn flat wire shall not turn over when it is wound on the steel wheel.
9. The method for efficiently preparing Nb3Sn superconducting flat wire according to claim 1, characterized in that: In S5, the diameter of the steel wheel is greater than or equal to 200 mm.
10. Nb3Sn superconducting flat wire prepared by the method of claim 1.