High-performance multi-core Nb3Sn composite wire and its preparation method

Abstract

The application discloses high-performance multi-core Nb3Sn composite wire and a preparation method thereof. Specifically, Nb core rods and NbTaHf alloy rods are respectively loaded into oxygen-free copper pipes a, CuNb single-core rods and doped CuNb single-core rods are prepared; the CuNb single-core rods, the doped CuNb single-core rods, NbTaHf alloy pipes and hexagonal oxygen-free copper core rods are loaded into oxygen-free copper pipes b in a close-packed form to form a composite sheath; the composite sheath is treated to obtain a composite pipe; SnTi rods are loaded into the composite pipe to obtain round subunits; SnO2 powder and the round subunits are sequentially filled into oxygen-free copper pipes c to form hexagonal and fan-shaped subunits; finally, the hexagonal and fan-shaped subunits and Ta pipes are assembled into oxygen-free copper pipes d, and are treated to form Nb3Sn composite wire. The application solves the problem that the processing performance of Nb3Sn wire is sharply reduced due to the influence of doped atoms in the prior art.

Description

Technical Field

[0001] This invention belongs to the field of superconducting wire technology, specifically relating to high-performance multi-core Nb3Sn composite wire. This invention also relates to a method for preparing the above-mentioned high-performance multi-core Nb3Sn composite wire. Background Technology

[0002] The critical current density target value of the Nb3Sn superconducting material required for the magnet performance design of controlled nuclear fusion projects exceeds 2700 A / mm². 2 The temperature range of (4.2K, 12T) is approaching the current design limit for Nb3Sn wire performance. To achieve such high-performance Nb3Sn wire, the commonly used technique is to increase the grain boundary density of Nb3Sn through elemental doping, thereby further improving the wire's performance. Common doping methods involve doping Nb with Ta, Hf, Zr, and their corresponding oxides, followed by powder packaging technology to prepare the Nb3Sn superconducting wire. This technique of improving Nb3Sn superconducting wire performance through elemental doping has been widely proven. However, due to the drastic reduction in wire plasticity caused by doping atoms, this approach currently faces significant technical obstacles in the production of long and mass-produced wires. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing high-performance multi-core Nb3Sn composite wires, which solves the problem that the processing performance of Nb3Sn wires is drastically reduced due to the influence of doped atoms in the prior art.

[0004] Another objective of this invention is to provide a high-performance multi-core Nb3Sn composite wire.

[0005] The first technical solution adopted in this invention is a method for preparing high-performance multi-core Nb3Sn composite wire, which specifically includes the following steps: Step 1: Nb core rod and NbTaHf alloy rod are respectively loaded into oxygen-free copper tube a, and hot isostatic pressing, extrusion, straightening and cold stretching are performed in sequence to prepare CuNb single core rod and doped CuNb single core rod. Step 2: The CuNb single core rod, the doped CuNb single core rod, the NbTaHf alloy tube and the hexagonal oxygen-free copper core rod are packed into the oxygen-free copper tube b in a close-packed manner to form a composite cladding. Step 3: Process the composite sheath to obtain the composite tube; Step 4: The SnTi rod is inserted into the composite tube and subjected to several cold stretching and cleaning processes to obtain circular sub-components. Step 5: SnO2 powder and circular sub-components are sequentially filled into oxygen-free copper tube c to form hexagonal or fan-shaped sub-components. Step 6: Assemble the hexagonal sub-component, the fan-shaped sub-component, and the Ta tube into the oxygen-free copper tube d to form a composite wire. The composite wire is then subjected to several cold stretching and heat treatment processes to form an Nb3Sn composite wire.

[0006] The first technical solution of the present invention is further characterized in that, In step 1, the inner diameter of oxygen-free copper tube a is 100mm~310mm and the outer diameter is 115mm~335mm; Both the Nb core rod and the NbTaHf alloy rod have diameters ranging from 100 mm to 305 mm. In the NbTaHf alloy rod, the proportion of Ta atoms is 4%, and the proportion of Hf atoms is 0.5% to 4%. The diameters of CuNb monoliths and doped CuNb monoliths range from 2.2 mm to 11 mm, and the copper ratios are both 0.1 to 0.2. The hot isostatic pressing temperature is 650℃~720°C, the extrusion temperature is 450℃~550°C, the extrusion speed is 10mm / s~20mm / s, the straightening accuracy is 1mm per 3 meters, and the cold stretching processing rate between passes does not exceed 30%.

[0007] In step 2, the inner diameter of the oxygen-free copper tube b is 86mm~430mm, the outer diameter is 130mm~480mm, and the diameter of the hexagonal oxygen-free copper core rod is 2.2mm~11mm. Hexagonal oxygen-free copper core rods, CuNb single core rods or doped CuNb single core rods, and NbTaHf alloy tubes are densely packed inside oxygen-free copper tube b from the inside out. The outer diameter of the NbTaHf alloy tube is 86mm~430mm, and the thickness is 0.2mm~3mm. The ratio of the thickness of the NbTaHf alloy tube to the diameter of the Nb mandrel is 0.1~0.3.

[0008] Step 3 involves processing the composite sheath, specifically by sequentially performing hot isostatic pressing, extrusion, straightening, cold stretching, and drilling. The outer diameter of the composite tube is 40mm to 100mm, and the diameter of the drilled hole is 12mm to 45mm. The hot isostatic pressing temperature is 650℃~720℃, the extrusion temperature is 450℃~550℃, the extrusion speed is 10mm / s~20mm / s, the straightening accuracy is 1mm per 3 meters, and the cold stretching processing rate between passes does not exceed 30%.

[0009] In step 4, the Ti atom content in the SnTi rod is 0.7%~2%, and the cold drawing rate in several passes does not exceed 30%. After cleaning, the outer Cu thickness of the circular subunit does not exceed 0.5 mm, and the diameter of the circular subunit is 1.8 mm to 5.7 mm.

[0010] In step 5, the oxygen-free copper tube c is hexagonal on the outside and circular on the inside, with a hexagonal width of 3mm to 7mm and an inner diameter of 2.8mm to 6.7mm. The circular sub-components are filled into the center of the oxygen-free copper tube c by extruding SnO2 powder. The oxygen atom content in the SnO2 powder is 1%~5%, and the thickness of the SnO2 powder is 0.5mm. The copper ratio of hexagonal or sector subunits is 0.1 to 0.27.

[0011] In step 6, the outer diameter of the oxygen-free copper tube d is 54mm~82mm, and the inner diameter is 48mm; The hexagonal and sector sub-components are closely packed together. The number of hexagonal sub-components is 31 to 163, and the number of sector sub-components is 6. The outer diameter of the Ta tube is 47 mm and the thickness is 1 mm. The gap between the outer hexagonal sub-component and the Ta tube forms an oxygen-free Cu insert filling region, which is filled with oxygen-free copper rods with a diameter of 1 mm. The copper superconductivity of the composite wire is 0.3~2, the cold drawing rate of the composite wire diameter is 15%~30%, and the heat treatment process is as follows: heating at 340℃ for 96 hours, then heating at 550℃ for 200~300 hours, and finally heating at 650℃ for 72~150 hours.

[0012] The second technical solution adopted in this invention is a high-performance multi-core Nb3Sn composite wire, which is prepared by the above-mentioned method for preparing high-performance multi-core Nb3Sn composite wire.

[0013] The beneficial effects of this invention are: The present invention discloses a method for preparing high-performance multi-core Nb3Sn composite wires. By employing NbTaHf alloy rods and NbTaHf alloy tubes, this method provides doping elements within the Nb3Sn wire to refine the Nb3Sn grains. Compared to the performance limits of undoped Nb3Sn wires, the performance of the Nb3Sn wires prepared by this invention is significantly improved through a specific heat treatment process. Furthermore, by using extremely thin NbTaHf alloy tubes, oxygen atoms are incorporated into the wire structure only at the composite wire stage. This greatly reduces the number of processing steps required after oxygen doping and provides a source of oxide doping for further performance enhancement. Compared to traditional tubular powder packaging designs, the processing difficulty of Nb3Sn wires is significantly reduced, and the produced wire length reaches the kilometer level. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the CuNb single core rod in the preparation method of the high-performance multi-core Nb3Sn composite wire of the present invention. Figure 2This is a schematic diagram of the structure of the doped CuNb single core rod in the preparation method of the high-performance multi-core Nb3Sn composite wire of the present invention. Figure 3 This is a schematic diagram of the composite sheath structure in step 2 of the preparation method of the high-performance multi-core Nb3Sn composite wire of the present invention; Figure 4 This is a graph showing the relationship between the diameter of the Nb mandrel and the thickness of the NbTaHf alloy tube in this invention; Figure 5 This is a schematic diagram of the structure of the hexagonal subunit in this invention; Figure 6 This is a schematic diagram of the structure of the sector-shaped sub-component in this invention; Figure 7 This is a schematic diagram of the composite wire structure in step 6 of the preparation method of the high-performance multi-core Nb3Sn composite wire of the present invention; Figure 8 This is the cross-section of the Nb3Sn superconducting wire obtained after the heat treatment in step 6 of this invention; Figure 9 This is a schematic diagram of the Nb3Sn grains obtained after the heat treatment in step 6 of this invention.

[0015] In the figure, 1. Oxygen-free copper tube a, 2. Nb core rod, 3. NbTaHf alloy rod, 4. Oxygen-free copper tube b, 5. NbTaHf alloy tube, 6. CuNb single core rod, 7. Doped CuNb single core rod, 8. Hexagonal oxygen-free copper core rod, 9. Oxygen-free copper tube c, 10. SnO2 powder, 11. Circular subcomponent, 12a. Hexagonal subcomponent, 12b. Fan-shaped subcomponent, 13. Oxygen-free copper tube d, 14. Ta tube, 15. Oxygen-free Cu insert rod filling area. Detailed Implementation

[0016] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0017] Example 1 The method for preparing high-performance multi-core Nb3Sn composite wire of the present invention specifically includes the following steps: Step 1: Nb mandrel 2 and NbTaHf alloy rod 3 are respectively inserted into oxygen-free copper tube a1, and then subjected to hot isostatic pressing, extrusion, straightening, and cold drawing processes in sequence, as follows: Figure 1 and Figure 2 As shown, CuNb single-core rod 6 and doped CuNb single-core rod 7 were prepared. Step 2: The CuNb single-core rod 6, the doped CuNb single-core rod 7, the NbTaHf alloy tube 5, and the hexagonal oxygen-free copper core rod 8 are packed closely into the oxygen-free copper tube b4, as shown below. Figure 3 As shown, a composite sheath is formed; Step 3: Process the composite sheath to obtain the composite tube; Step 4: The SnTi rod is inserted into the composite tube and subjected to several cold stretching and cleaning processes to obtain the circular sub-component 11. Step 5, as follows Figure 5 and Figure 6 As shown, SnO2 powder 10 and circular sub-component 11 are sequentially filled into oxygen-free copper tube c9 to form hexagonal sub-component 12a or fan-shaped sub-component 12b. Step 6, as follows Figure 7 As shown, hexagonal subunit 12a, sector subunit 12b, and Ta tube 14 are assembled into oxygen-free copper tube d13 to form a composite wire. The composite wire undergoes several cold drawing and heat treatment processes to form an Nb3Sn composite wire. Figure 8 The image shows the final cross-section of the wire. The wire exhibits good overall deformation, indicating a complete heat treatment reaction.

[0018] Example 2 Based on the above embodiments, in step 1 of this invention, the inner diameter of the oxygen-free copper tube a1 is 100mm~310mm and the outer diameter is 115mm~335mm; the diameters of the Nb core rod 2 and the NbTaHf alloy rod 3 are both 100mm~305mm, and the Ta atom ratio in the NbTaHf alloy rod 3 is 4%, and the Hf atom ratio is 0.5%~4%; the diameters of the CuNb single core rod 6 and the doped CuNb single core rod 7 are 2.2mm~11mm, and the copper ratio is 0.1~0.2. The hot isostatic pressing temperature is 650℃~720°C, the extrusion temperature is 450℃~550°C, the extrusion speed is 10mm / s~20mm / s, the straightening accuracy is 1mm per 3 meters, and the cold stretching processing rate between passes does not exceed 30%.

[0019] In step 2 of this invention, the inner diameter of the oxygen-free copper tube b4 is 86mm~430mm, and the outer diameter is 130mm~480mm. The diameter of the hexagonal oxygen-free copper core rod 8 is 2.2mm~11mm. The hexagonal oxygen-free copper core rod 8, CuNb single core rod 6 or doped CuNb single core rod 7, and NbTaHf alloy tube 5 are arranged in a dense packing from the inside to the outside inside the oxygen-free copper tube b4. The outer diameter of the NbTaHf alloy tube 5 is 86mm~430mm, and the thickness is 0.2mm~3mm. Figure 4As shown, the thickness of the NbTaHf alloy tube 5 is 0.1 to 0.3 times the diameter of the Nb core rod 2. The change in the thickness of the alloy tube 5 with the Nb core wire ensures a suitable alloy doping ratio, which is beneficial to the improvement of wire performance.

[0020] Step 3 of this invention specifically involves processing the composite sheath by sequentially performing hot isostatic pressing, extrusion, straightening, cold stretching, and drilling. The outer diameter of the composite tube is 40mm~100mm, and the diameter of the drilled hole is 12mm~45mm. The hot isostatic pressing temperature is 650℃~720℃, the extrusion temperature is 450℃~550℃, the extrusion speed is 10mm / s~20mm / s, the straightening accuracy is 1mm per 3 meters, and the cold stretching processing rate between passes does not exceed 30%.

[0021] In step 4 of this invention, the proportion of Ti atoms in the SnTi rod is 0.7%~2%, and the cold drawing rate in several passes does not exceed 30%; after cleaning, the outer Cu thickness of the circular sub-component 11 does not exceed 0.5mm, and the diameter of the circular sub-component 11 is 1.8mm~5.7mm.

[0022] In step 5 of this invention, the oxygen-free copper tube c9 is hexagonal on the outside and circular on the inside, with a hexagonal width of 3mm to 7mm and an inner diameter of 2.8mm to 6.7mm. The circular sub-component 11 is filled into the center of the oxygen-free copper tube c9 by extruding SnO2 powder 10. The oxygen atom ratio in the SnO2 powder 10 is 1% to 5%, and the thickness of the SnO2 powder 10 is 0.5mm. The copper ratio of the hexagonal sub-component 12a or the fan-shaped sub-component 12b is 0.1 to 0.27.

[0023] In step 6 of this invention, the outer diameter of the oxygen-free copper tube d13 is 54mm~82mm and the inner diameter is 48mm; the hexagonal sub-component 12a and the fan-shaped sub-component 12b are closely arranged, the number of hexagonal sub-component 12a is 31~163, the number of fan-shaped sub-component 12b is 6, and the outer diameter of the Ta tube 14 is 47mm and the thickness is 1mm. The gap between the outer hexagonal subunit 12a and the Ta tube 14 forms an oxygen-free Cu insert filling region 15, which is filled with an oxygen-free copper rod with a diameter of 1 mm. The copper superconductivity of the composite wire is 0.3~2, the cold drawing rate of the composite wire diameter is 15%~30%, and the heat treatment process is as follows: heating at 340℃ for 96 hours, then heating at 550℃ for 200~300 hours, and finally heating at 650℃ for 72~150 hours.

[0024] Example 3 The high-performance multi-core Nb3Sn composite wire of the present invention is prepared by the preparation method of the high-performance multi-core Nb3Sn composite wire in Examples 1 and 2 above.

[0025] Example 4 This embodiment further details the preparation method of the high-performance multi-core Nb3Sn composite wire of the present invention, specifically including the following steps: Step 1: Circular Nb core rods 2 (110mm diameter) and NbTaHf alloy rods 3 are densely packed into oxygen-free copper tubes a1 with inner and outer diameters of 110mm and 115mm, respectively. The entire assembly undergoes hot isostatic pressing, extrusion, straightening, and cold drawing processes to produce CuNb single-core rods 6 and doped CuNb single-core rods 7, respectively. The NbTaHf alloy rod 3 contains 4% Ta atoms and 0.5% Hf atoms. Both CuNb single-core rods 6 and 7 have a hexagonal forming dimension of 2.2mm and a copper ratio of 0.2. The hot isostatic pressing temperature is 650°C, the extrusion temperature is 450°C, the extrusion speed is 10~20mm / s, the straightening accuracy is 1mm per 3 meters, and the cold drawing rate between passes does not exceed 30%.

[0026] Step 2: The hexagonal oxygen-free copper core rod 8, CuNb single core rod 6, doped CuNb single core rod 7, and NbTaHf alloy tube 5 are sequentially and closely packed into the oxygen-free copper tube b4 to form a composite cladding. The oxygen-free copper tube b4 has an inner diameter of 86 mm and an outer diameter of 130 mm. The hexagonal oxygen-free copper core rod 8 has a diameter of 2.2 mm. The NbTaHf alloy tube 5 has the same composition as the NbTaHf alloy rod 3, an outer diameter of Φ86 mm, and a thickness of 0.2 mm. The thickness ratio to the diameter of the Nb core rod 2 is 0.1.

[0027] Step 3: The composite sheath is processed sequentially through hot isostatic pressing, extrusion, straightening, cold drawing, and drilling to produce a composite tube with an outer diameter of Φ40mm and a bore diameter of Φ12mm. The hot isostatic pressing temperature is 650°C, the extrusion temperature is 450°C, the extrusion speed is 20mm / s, the straightening accuracy is 1mm per 3 meters, and the cold drawing rate between passes is 15~30%.

[0028] Step 4: A SnTi rod with a Ti atomic percentage of 0.7% is inserted into a composite tube, and a circular sub-component 11 is obtained through multiple cold drawing and cleaning processes. After cleaning, the Cu thickness on the outside of the sub-component is 0.2 mm, the cold drawing rate between passes is 15~30%, and the outer diameter of the circular sub-component 11 is Φ1.8 mm.

[0029] Step 5: SnO2 powder 10 and circular sub-component 11 are sequentially filled into oxygen-free copper tube c9 to form hexagonal and sector-shaped sub-components. The oxygen-free copper tube c9 is hexagonal on the outside and circular on the inside, with a hexagonal width of 3 mm and an inner diameter of 2.8 mm. The circular sub-component 11 is filled into the center of the oxygen-free copper tube c9 by extruding SnO2 powder 10. The oxygen atom ratio of SnO2 powder 10 is 1%, the powder thickness is 0.5 mm, and the copper ratio of the hexagonal and sector-shaped sub-components is 0.1.

[0030] Step 6: Assemble the hexagonal subunit 12a, the sector subunit 12b, and the Ta tube 14 into the oxygen-free copper tube d13 to form a composite wire. Then, subject the composite wire to multiple cold drawing and heat treatment processes to form the final Nb3Sn superconducting wire. The oxygen-free copper tube d13 has an outer diameter of Φ67mm and an inner diameter of Φ48mm, with a copper-to-superconductivity ratio of 1.0. The hexagonal and sector subunits are densely packed, with 163 and 6 units respectively. The Ta tube 14 has a diameter of Φ47mm and a thickness of 1mm. The gap between the outermost hexagonal subunit 12a and the Ta tube 14 is filled with a 1mm diameter oxygen-free copper rod. The cold drawing pass ratio is 8-15%. The heat treatment process is: 340°C / 96h + 550°C / 200h + 650°C / 72h.

[0031] When a 3-meter-long assembly composite wire is stretched to Φ0.8mm, two 1000-meter-long wires of 1142 meters and 3380 meters respectively are produced, with the length of a single wire exceeding 3000 meters, meeting the length requirements of Nb3Sn wires for existing controlled nuclear fusion projects. After heat treatment, the critical current density is 3120 A / mm². 2 (4.2K, 12T), far exceeding the approximately 2500A / mm of existing undoped Nb3Sn wires. 2 The average performance level of (4.2K, 12T) is higher than the highest known performance of undoped Nb3Sn wire.

[0032] like Figure 9 As shown, the Nb3Sn grain size of the superconducting wire of the present invention is in the range of 40~120 nm, which is significantly lower than the Nb3Sn grain size (120~200 nm) in conventional Nb3Sn superconducting wires. As is common knowledge in the field, the reduction in grain size leads to the improvement of wire performance and is also the source of the high-performance current carrying capacity of the wire of the present invention.

[0033] Example 5 This embodiment further details the preparation method of the high-performance multi-core Nb3Sn composite wire of the present invention, specifically including the following steps: Step 1: Circular Nb core rods 2 (150mm diameter) and NbTaHf alloy rods 3 are densely packed into oxygen-free copper tubes a1 with inner and outer diameters of 150mm and 170mm, respectively. The entire assembly undergoes hot isostatic pressing, extrusion, straightening, and cold drawing processes to produce CuNb single-core rods 6 and doped CuNb single-core rods 7, respectively. The NbTaHf alloy rod 3 contains 4% Ta atoms and 4% Hf atoms. Both CuNb single-core rods 6 and 7 have a hexagonal forming dimension of 5.5mm and a copper ratio of 0.2. The hot isostatic pressing temperature is 720°C, the extrusion temperature is 550°C, the extrusion speed is 10~20mm / s, the straightening accuracy is 1mm per 3 meters, and the cold drawing rate between passes does not exceed 30%.

[0034] Step 2: The hexagonal oxygen-free copper core rod 8, CuNb single core rod 6, doped CuNb single core rod 7, and NbTaHf alloy tube 5 are sequentially and closely packed into the oxygen-free copper tube b4 to form a composite cladding. The oxygen-free copper tube b4 has an inner diameter of 195 mm and an outer diameter of 240 mm. The hexagonal oxygen-free copper core rod 8 has a diameter of 5.5 mm. The NbTaHf alloy tube 5 has the same composition as the NbTaHf alloy rod 3, an outer diameter of Φ195 mm, and a thickness of 0.9 mm. The thickness ratio to the diameter of the Nb core rod 2 is 0.18.

[0035] Step 3: The composite sheath is processed sequentially through hot isostatic pressing, extrusion, straightening, cold drawing, and drilling to produce a composite tube with an outer diameter of Φ70mm and a bore diameter of Φ25mm. The hot isostatic pressing temperature is 700°C, the extrusion temperature is 500°C, the extrusion speed is 15mm / s, the straightening accuracy is 1mm per 3 meters, and the cold drawing rate between passes is 15~30%.

[0036] Step 4: A SnTi rod with a Ti atom content of 1% is loaded into a composite tube, and a circular sub-component 11 is obtained through multiple cold drawing and cleaning processes. After cleaning, the Cu thickness on the outside of the sub-component is 0.3 mm, the cold drawing rate between passes is 15~30%, and the outer diameter of the circular sub-component 11 is Φ3.5 mm.

[0037] Step 5: SnO2 powder 10 and circular sub-component 11 are sequentially filled into oxygen-free copper tube c9 to form hexagonal and sector-shaped sub-components. The oxygen-free copper tube c9 is hexagonal on the outside and circular on the inside, with a hexagonal width of 5.1 mm and an inner diameter of 4.5 mm. The circular sub-component 11 is filled into the center of the oxygen-free copper tube c9 by extruding SnO2 powder 10. The oxygen atom ratio of SnO2 powder 10 is 2%, the powder thickness is 0.5 mm, and the copper ratio of the hexagonal and sector-shaped sub-components is 0.27.

[0038] Step 6: Assemble the hexagonal subunit 12a, the sector subunit 12b, and the Ta tube 14 into the oxygen-free copper tube d13 to form a composite wire. Then, subject the composite wire to multiple cold drawing and heat treatment processes to form the final Nb3Sn superconducting wire. The oxygen-free copper tube d13 has an outer diameter of Φ72mm and an inner diameter of Φ48mm, with a copper-to-superconductivity ratio of 1.5. The hexagonal and sector subunits are densely packed, with 55 and 6 units respectively. The Ta tube 14 has a diameter of Φ47mm and a thickness of 1mm. The gap between the outermost hexagonal subunit 12a and the Ta tube 14 is filled with a 1mm diameter oxygen-free copper rod. The cold drawing pass ratio is 8-15%. The heat treatment process is: 340°C / 96h + 550°C / 300h + 650°C / 96h.

[0039] When a 3-meter-long assembly composite wire is stretched to Φ0.8mm, three kilometer-long wires of 1760 meters, 1232 meters, and 2270 meters in length are produced, meeting the length requirements of Nb3Sn wires for existing controlled nuclear fusion projects. The critical current density after heat treatment is 3274 A / mm². 2 (4.2K, 12T), far exceeding the approximately 2500A / mm of existing undoped Nb3Sn wires. 2 The average performance level of (4.2K, 12T) is higher than the highest known performance of undoped Nb3Sn wire.

[0040] Example 6 This embodiment further details the preparation method of the high-performance multi-core Nb3Sn composite wire of the present invention, specifically including the following steps: Step 1: Circular Nb core rods 2 (305mm diameter) and NbTaHf alloy rods 3 are densely packed into oxygen-free copper tubes a1 with inner and outer diameters of 310mm and 335mm, respectively. The entire assembly is then subjected to hot isostatic pressing, extrusion, straightening, and cold drawing processes to produce CuNb single core rods 6 and doped CuNb single core rods 7, respectively. The NbTaHf alloy rod 3 contains 4% Ta atoms and 2% Hf atoms. The hexagonal forming dimensions of CuNb single core rod 6 and doped CuNb single core rod 7 are 11mm, and the copper ratio is 0.1. The hot isostatic pressing temperature is 720°C, the extrusion temperature is 550°C, the extrusion speed is 10~20mm / s, the straightening accuracy is 1mm per 3 meters, and the cold drawing rate between passes does not exceed 30%.

[0041] Step 2: The hexagonal oxygen-free copper core rod 8, CuNb single core rod 6, doped CuNb single core rod 7, and NbTaHf alloy tube 5 are sequentially and closely packed into the oxygen-free copper tube b4 to form a composite cladding. The oxygen-free copper tube b4 has an inner diameter of 430 mm and an outer diameter of 480 mm. The hexagonal oxygen-free copper core rod 8 has a diameter of 11 mm. The NbTaHf alloy tube 5 has the same composition as the NbTaHf alloy rod 3, an outer diameter of Φ430 mm, and a thickness of 3 mm. The thickness ratio to the diameter of the Nb core rod 2 is 0.3.

[0042] Step 3: The composite sheath is processed sequentially through hot isostatic pressing, extrusion, straightening, cold drawing, and drilling to produce a composite tube with an outer diameter of Φ100mm and a bore diameter of Φ40mm. The hot isostatic pressing temperature is 720°C, the extrusion temperature is 550°C, the extrusion speed is 10mm / s, the straightening accuracy is 1mm per 3 meters, and the cold drawing rate between passes is 15~30%.

[0043] Step 4: A SnTi rod with a Ti atom content of 2% is inserted into a composite tube, and a circular sub-component 11 is obtained through multiple cold drawing and cleaning processes. After cleaning, the Cu thickness on the outside of the sub-component is 0.5 mm, the cold drawing rate between passes is 15~30%, and the outer diameter of the circular sub-component 11 is Φ3.6 mm.

[0044] Step 5: SnO2 powder 10 and circular sub-component 11 are sequentially filled into oxygen-free copper tube c9 to form hexagonal and sector-shaped sub-components. The oxygen-free copper tube c9 is hexagonal on the outside and circular on the inside, with a hexagonal width of 5.1 mm and an inner diameter of 4.6 mm. The circular sub-component 11 is filled into the center of the oxygen-free copper tube c9 by extruding SnO2 powder 10. The oxygen atom ratio of SnO2 powder 10 is 5%, the powder thickness is 0.5 mm, and the copper ratio of the hexagonal and sector-shaped sub-components is 0.24.

[0045] Step 6: Assemble the hexagonal subunit 12a, the sector subunit 12b, and the Ta tube 14 into the oxygen-free copper tube d13 to form a composite wire. Then, subject the composite wire to multiple cold drawing and heat treatment processes to form the final Nb3Sn superconducting wire. The oxygen-free copper tube d13 has an outer diameter of Φ54mm and an inner diameter of Φ48mm, with a copper-to-superconductivity ratio of 0.3. The hexagonal and sector subunits are densely packed, with 55 and 6 units respectively. The Ta tube 14 has a diameter of Φ47mm and a thickness of 1mm. The gap between the outermost hexagonal subunit 12a and the Ta tube 14 is filled with a 1mm diameter oxygen-free copper rod. The cold drawing pass ratio is 8-15%. The heat treatment process is: 340°C / 96h + 550°C / 300h + 650°C / 96h.

[0046] Stretching a 3-meter-long composite assembly line to Φ0.8mm produces a 1492-meter-long wire, meeting the length requirements of existing controlled nuclear fusion projects for Nb3Sn wire. After heat treatment, the critical current density is 3235 A / mm². 2 (4.2K, 12T), far exceeding the approximately 2500A / mm of existing undoped Nb3Sn wires. 2 The average performance level of (4.2K, 12T) is higher than the highest known performance of undoped Nb3Sn wire.

[0047] Example 7 This embodiment further details the preparation method of the high-performance multi-core Nb3Sn composite wire of the present invention, specifically including the following steps: Step 1: Circular Nb core rods 2 (210mm in diameter) and NbTaHf alloy rods 3 are densely packed into oxygen-free copper tubes a1 with inner and outer diameters of 210mm and 225mm, respectively. The entire assembly undergoes hot isostatic pressing, extrusion, straightening, and cold drawing processes to produce CuNb single-core rods 6 and doped CuNb single-core rods 7, respectively. The NbTaHf alloy rod 3 contains 4% Ta atoms and 2% Hf atoms. Both CuNb single-core rods 6 and 7 have a hexagonal forming dimension of 5.4mm and a copper ratio of 0.2. The hot isostatic pressing temperature is 700°C, the extrusion temperature is 500°C, the extrusion speed is 10~20mm / s, the straightening accuracy is 1mm per 3 meters, and the cold drawing rate between passes does not exceed 30%.

[0048] Step 2: The hexagonal oxygen-free copper core rod 8, CuNb single core rod 6, doped CuNb single core rod 7, and NbTaHf alloy tube 5 are sequentially and closely packed into the oxygen-free copper tube b4 to form a composite cladding. The oxygen-free copper tube b4 has an inner diameter of 240 mm and an outer diameter of 270 mm. The hexagonal oxygen-free copper core rod 8 has a diameter of 5.4 mm. The NbTaHf alloy tube 5 has the same composition as the NbTaHf alloy rod 3, an outer diameter of Φ240 mm, and a thickness of 0.9 mm. The thickness ratio to the diameter of the Nb core rod 2 is 0.18.

[0049] Step 3: The composite sheath is processed sequentially through hot isostatic pressing, extrusion, straightening, cold drawing, and drilling to produce a composite tube with an outer diameter of Φ70mm and a bore diameter of Φ25mm. The hot isostatic pressing temperature is 700°C, the extrusion temperature is 500°C, the extrusion speed is 15mm / s, the straightening accuracy is 1mm per 3 meters, and the cold drawing rate between passes is 15~30%.

[0050] Step 4: A SnTi rod with a Ti atom content of 1% is loaded into a composite tube, and a circular sub-component 11 is obtained through multiple cold drawing and cleaning processes. After cleaning, the Cu thickness on the outside of the sub-component is 0.3 mm, the cold drawing rate between passes is 15~30%, and the outer diameter of the circular sub-component 11 is Φ5.5 mm.

[0051] Step 5: SnO2 powder 10 and circular sub-component 11 are sequentially filled into oxygen-free copper tube c9 to form hexagonal and sector-shaped sub-components. The oxygen-free copper tube c9 is hexagonal on the outside and circular on the inside, with a hexagonal width of 7.0 mm and an inner diameter of 6.5 mm. The circular sub-component 11 is filled into the center of the oxygen-free copper tube c9 by extruding SnO2 powder 10. The oxygen atom ratio of SnO2 powder 10 is 1%, the powder thickness is 0.5 mm, and the copper ratio of the hexagonal and sector-shaped sub-components is 0.15.

[0052] Step 6: Assemble the hexagonal subunit 12a, the sector subunit 12b, and the Ta tube 14 into the oxygen-free copper tube d13 to form a composite wire. Then, subject the composite wire to multiple cold drawing and heat treatment processes to form the final Nb3Sn superconducting wire. The oxygen-free copper tube d13 has an outer diameter of Φ82mm and an inner diameter of Φ48mm, with a copper-to-superconducting ratio of 2. The hexagonal and sector subunits are densely packed, with 31 and 6 units respectively. The Ta tube 14 has a diameter of Φ47mm and a thickness of 1mm. The gap between the outermost hexagonal subunit 12a and the Ta tube 14 is filled with a 1mm diameter oxygen-free copper rod. The cold drawing pass ratio is 8-15%. The heat treatment process is: 340°C / 96h + 550°C / 300h + 650°C / 150h.

[0053] Stretching a 3-meter-long composite assembly wire to Φ0.8mm produces two kilometer-long wires of 1524 meters and 3504 meters, meeting the length requirements of Nb3Sn wires for existing controlled nuclear fusion projects. The critical current density after heat treatment is 3274 A / mm². 2 (4.2K, 12T), far exceeding the approximately 2500A / mm of existing undoped Nb3Sn wires. 2 The average performance level of (4.2K, 12T) is higher than the highest known performance of undoped Nb3Sn wire.

[0054] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0055] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing high-performance multi-core Nb3Sn composite wire, characterized in that, Specifically, the following steps are included: Step 1: Nb core rod (2) and NbTaHf alloy rod (3) are respectively loaded into oxygen-free copper tube a (1), and hot isostatic pressing, extrusion, straightening and cold stretching are performed in sequence to prepare CuNb single core rod (6) and doped CuNb single core rod (7). Step 2: The CuNb single core rod (6), the doped CuNb single core rod (7), the NbTaHf alloy tube (5) and the hexagonal oxygen-free copper core rod (8) are packed into the oxygen-free copper tube b (4) in a close-packed manner to form a composite cladding; Step 3: Process the composite sheath to obtain the composite tube; Step 4: The SnTi rod is inserted into the composite tube and subjected to several cold stretching and cleaning processes to obtain the circular sub-component (11). Step 5: SnO2 powder (10) and circular sub-component (11) are sequentially filled into oxygen-free copper tube c (9) to form hexagonal sub-component (12a) or fan-shaped sub-component (12b). Step 6: Assemble the hexagonal sub-component (12a), the fan-shaped sub-component (12b), and the Ta tube (14) into the oxygen-free copper tube d (13) to form a composite wire. The composite wire is subjected to several cold stretching and heat treatment processes to form Nb3Sn composite wire. In step 1, the inner diameter of the oxygen-free copper tube a (1) is 100mm~310mm and the outer diameter is 115mm~335mm. The diameters of the Nb core rod (2) and the NbTaHf alloy rod (3) are both 100mm~305mm. The NbTaHf alloy rod (3) contains 4% Ta atoms and 0.5%~4% Hf atoms. The diameters of the CuNb single core rod (6) and the doped CuNb single core rod (7) are 2.2 mm to 11 mm, and the copper ratios are both 0.1 to 0.

2. The hot isostatic pressing temperature is 650℃~720°C, the extrusion temperature is 450℃~550°C, the extrusion speed is 10mm / s~20mm / s, the straightening accuracy is 1mm per 3 meters, and the cold stretching processing rate between passes does not exceed 30%.

2. The method for preparing high-performance multi-core Nb3Sn composite wire according to claim 1, characterized in that, In step 2, the inner diameter of the oxygen-free copper tube b (4) is 86mm~430mm, the outer diameter is 130mm~480mm, and the diameter of the hexagonal oxygen-free copper core rod (8) is 2.2mm~11mm. Hexagonal oxygen-free copper core rod (8), CuNb single core rod (6) or doped CuNb single core rod (7), NbTaHf alloy tube (5) are densely packed inside oxygen-free copper tube b (4) from the inside out; The outer diameter of the NbTaHf alloy tube (5) is 86mm~430mm and the thickness is 0.2mm~3mm. The ratio of the thickness of the NbTaHf alloy tube (5) to the diameter of the Nb mandrel (2) is 0.1~0.

3.

3. The method for preparing high-performance multi-core Nb3Sn composite wire according to claim 1, characterized in that, The processing of the composite sheath in step 3 specifically includes hot isostatic pressing, extrusion, straightening, cold stretching and drilling of the composite sheath in sequence. The outer diameter of the composite tube is 40mm~100mm and the diameter of the drilled hole is 12mm~45mm. The hot isostatic pressing temperature is 650℃~720℃, the extrusion temperature is 450℃~550℃, the extrusion speed is 10mm / s~20mm / s, the straightening accuracy is 1mm per 3 meters, and the cold stretching processing rate between passes does not exceed 30%.

4. The method for preparing high-performance multi-core Nb3Sn composite wire according to claim 1, characterized in that, In step 4, the proportion of Ti atoms in the SnTi rod is 0.7% to 2%, and the cold drawing rate of the several passes does not exceed 30%. After cleaning, the outer Cu thickness of the circular subunit (11) does not exceed 0.5 mm, and the diameter of the circular subunit (11) is 1.8 mm to 5.7 mm.

5. The method for preparing high-performance multi-core Nb3Sn composite wire according to claim 1, characterized in that, In step 5, the oxygen-free copper tube c (9) is hexagonal on the outside and circular on the inside, with a hexagonal width of 3mm to 7mm and an inner diameter of 2.8mm to 6.7mm. The circular sub-component (11) is filled into the center of the oxygen-free copper tube c (9) by extruding SnO2 powder (10), and the thickness of SnO2 powder (10) is 0.5 mm. The copper ratio of the hexagonal subunit (12a) or the sector subunit (12b) is 0.1 to 0.

27.

6. The method for preparing high-performance multi-core Nb3Sn composite wire according to claim 1, characterized in that, In step 6, the outer diameter of the oxygen-free copper tube d (13) is 54mm~82mm and the inner diameter is 48mm. The hexagonal subunit (12a) and the fan-shaped subunit (12b) are arranged in close packing. The number of hexagonal subunits (12a) is 31 to 163, and the number of fan-shaped subunits (12b) is 6. The outer diameter of the Ta tube (14) is 47 mm and the thickness is 1 mm. The gap between the outer hexagonal subunit (12a) and the Ta tube (14) forms an oxygen-free Cu insert filling region (15), which is filled with an oxygen-free copper rod with a diameter of 1 mm. The copper superconductivity of the composite wire is 0.3~2, the cold drawing rate of the composite wire diameter is 15%~30%, and the heat treatment process is as follows: heating at 340℃ for 96 hours, then heating at 550℃ for 200~300 hours, and finally heating at 650℃ for 72~150 hours.

7. A high-performance multi-core Nb3Sn composite wire, characterized in that, It is prepared by the method described in any one of claims 1 to 6 for the preparation of high-performance multi-core Nb3Sn composite wire.

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