Enhanced multi-core Nb3Sn composite wire and preparation method thereof

Abstract

The invention discloses an enhanced multi-core Nb3Sn composite wire and a preparation method thereof. The preparation method specifically comprises the following steps: loading an Nb core rod into an oxygen-free copper pipe a for processing to obtain a CuNb single core rod; then the CuNb single core rod and the hexagonal copper core rod are assembled into the CuMn alloy pipe in a close-packed hexagonal mode, and a multi-core CuNb composite sheath is formed; processing the CuNb composite sheath, drilling to form a CuNb composite pipe, loading the SnTi alloy bar into the CuNb composite pipe to form a sub-component, and performing multi-pass cold stretching to form a hexagonal CuMn sub-component; and finally, the hexagonal CuMn subcomponents and the SnCu alloy bar are densely arranged and assembled into a Ta pipe, then the Ta pipe is assembled into an oxygen-free copper pipe b to form a composite wire, and the composite wire is treated to form the Nb3Sn composite wire. The method solves the problems of wire processing cracking and uneven deformation caused by reduction of the Cu content in the wire as the critical current-carrying density performance of the wire is improved in the prior art.

Description

Technical Field

[0001] The present invention belongs to the technical field of superconducting wires, and in particular relates to an enhanced multi-core Nb3Sn composite wire. The present invention also relates to a method for preparing the enhanced multi-core Nb3Sn composite wire. Background Art

[0002] Nb3Sn superconducting materials have been widely used in large-scale controlled thermonuclear fusion devices, electron colliders, and extremely high magnetic field magnet equipment. To meet future market demand for even higher magnetic field scenarios, the critical current density performance of Nb3Sn superconducting wires needs to be further improved. However, high-performance wire designs typically require a continuous reduction in the Cu content, which plays a synergistic deformation role. This can easily lead to problems such as wire cracking and uneven deformation during wire processing.

[0003] In order to obtain an extremely high critical current density while ensuring that the wire can be normally processed and prepared in a low-Cu environment, the present invention proposes a Nb3Sn superconducting wire and a preparation method thereof that meet this requirement. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing an enhanced multi-core Nb3Sn composite wire, which solves the problem in the prior art that as the critical current density performance of the wire increases, the Cu content in the wire decreases, resulting in cracking and uneven deformation during wire processing.

[0005] Another object of the present invention is to provide a reinforced multi-core Nb3Sn composite wire.

[0006] The first technical solution adopted by the present invention is a method for preparing a reinforced multi-core Nb3Sn composite wire, which specifically includes the following steps: Step 1: Place the Nb core rod into the oxygen-free copper tube a, and perform hot isostatic pressing, extrusion, straightening, and cold stretching in sequence to prepare a CuNb single core rod; Step 2: assembling the CuNb single core rod and the hexagonal copper core rod into a CuMn alloy tube in a close-packed hexagonal form to form a multi-core CuNb composite sheath; Step 3, hot isostatic pressing, extrusion, straightening, peeling, and multi-pass cold stretching are performed on the CuNb composite sheath in sequence to prepare a CuNb composite rod; Step 4: Drilling a hole in the center of the CuNb composite rod to form a CuNb composite tube, inserting the SnTi alloy rod into the CuNb composite tube to form a subcomponent, and subjecting the subcomponent to multiple cold drawing passes to form a hexagonal CuMn subcomponent; Step 5: The hexagonal CuMn subcomponents and SnCu alloy rods are densely packed into a Ta tube, and the Ta tube is assembled as a whole into an oxygen-free copper tube b to form a composite wire. The composite wire is subjected to multiple cold drawing and heat treatments to form a Nb3Sn composite wire.

[0007] The first technical solution of the present invention is also characterized in that: In step 1, the inner diameter of the oxygen-free copper tube a is 100 mm to 310 mm, the outer diameter is 115 mm to 335 mm, and the diameter of the Nb core rod is 100 mm to 305 mm; The hot isostatic pressing temperature is 650°C~720°C, the extrusion temperature is 450°C~550°C, the extrusion speed is 10mm / s~20mm / s, the straightening accuracy is 1mm per 3 meters, and the cold drawing processing rate between passes does not exceed 30%; The diameter of the CuNb single core rod is 2.2mm~11mm, and the copper ratio is 0.1~0.32.

[0008] In step 2, the diameter of the hexagonal oxygen-free copper core rod is 2.2 mm to 11 mm, the inner diameter of the CuMn alloy tube is 86 mm to 430 mm, and the outer diameter is 96 mm to 450 mm. The atomic ratio of the Mn element in the CuMn alloy tube is 0.5 to 6%.

[0009] In step 2, the center of the CuMn alloy tube is densely packed with hexagonal copper core rods, and the outermost CuNb single core rods and the hexagonal copper core rods in the CuMn alloy tube are alternately arranged in sequence.

[0010] In step 3, 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, the peeling amount is between 2% and 5%, the peeling is done once, and the cold drawing processing rate between passes does not exceed 30%; The diameter of the CuNb composite rod is 25mm~100mm.

[0011] In step 4, the diameter of the drill hole is 10 mm to 45 mm, the proportion of Ti atoms in the SnTi alloy rod is 0.7 to 2%, and the subcomponent multi-pass cold drawing processing rate does not exceed 30%; The diameter of the hexagonal CuMn subcomponent is 3 mm to 6 mm, and the copper ratio is 0.1 to 0.27.

[0012] In step 5, the hexagonal CuMn subcomponents in the composite wire are close-packed, the number of hexagonal CuMn subcomponents is 61 to 169, the proportion of Cu atoms in the SnCu alloy rod is 1% to 3%, and the SuCn alloy rod is fan-shaped; The gap between the Ta tube, the hexagonal CuMn subcomponent, and the SnCu alloy rod forms a plug-filling area, which is filled with a CuMn alloy rod with a diameter of 2 mm. The outer diameter of the Ta tube is 47mm and the wall thickness is 1mm. The outer diameter of the oxygen-free copper tube b is 53mm~72mm and the inner diameter is 48mm. The copper ratio of the formed composite wire is 0.3~1.5.

[0013] In step 5, when the diameter of the composite wire is greater than 10 mm, the multi-pass cold drawing processing rate is 15-30%, and when the diameter of the composite wire is less than 10 mm, the multi-pass cold drawing processing rate is 8-15%; The heat treatment process is specifically heating at a temperature of 340°C for 96 hours, then heating at a temperature of 600°C for 72 hours, and finally heating at a temperature of 650°C for 96 hours.

[0014] The second technical solution adopted by the present invention is that the enhanced multi-core Nb3Sn composite wire is prepared by adopting the above-mentioned preparation method of the enhanced multi-core Nb3Sn composite wire.

[0015] The beneficial effects of the present invention are: The present invention's method for preparing a reinforced multi-core Nb3Sn composite wire addresses the problem of cracking during subcomponent preparation, often caused by the reduced amount of Cu on the outer surface of the subcomponents, by adjusting the CuNb single-core rods in the outermost layer of the CuNb composite sheath to a non-continuous, close-packed configuration. Furthermore, the use of a CuMn alloy on the outer surface of the subcomponents enhances the wire's deformation consistency during composite wire processing and prevents cracking during stretching. This results in a significantly longer average length of Nb3Sn wire produced in accordance with the present invention than existing wire products.

[0016] The present invention combines two methods to adjust the structural parameters of Nb3Sn wire within a wide range, meeting the design of Nb3Sn wires with different performance requirements. At the same time, the addition of fan-shaped SnCu alloy rods ensures that there is sufficient Sn when the Nb wire is converted into Nb3Sn. Finally, through a specific heat treatment process, the critical current density of the obtained Nb3Sn wire exceeds 2700A / mm 2 (4.2K, 12T), the performance indicators are higher than those of existing Nb3Sn products. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the structure of the enhanced multi-core Nb3Sn composite wire of the present invention; Figure 2 Schematic diagram of the structure of the CuNb single core rod in the method for preparing the enhanced multi-core Nb3Sn composite wire of the present invention; Figure 3 Schematic diagram of the structure of the CuNb composite rod in the method for preparing the enhanced multi-core Nb3Sn composite wire of the present invention; Figure 4 Schematic diagram of the structure of the CuMn subcomponent in the preparation method of the enhanced multi-core Nb3Sn composite wire of the present invention; Figure 5 It is a schematic structural diagram of the SnCu alloy rod in the method for preparing the enhanced multi-core Nb3Sn composite wire of the present invention.

[0018] In the figure, 1. oxygen-free copper tube a, 2. Nb core rod, 3. hexagonal copper core rod, 4. CuMn alloy tube, 5. CuMn alloy area, 6. CuNb core rod area, 7. SnCu alloy rod, 8. oxygen-free copper tube b, 9. Ta tube, 10. plug filling area. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0020] Example 1 The method for preparing the enhanced multi-core Nb3Sn composite wire of the present invention specifically comprises the following steps: Step 1: Place the Nb core rod 2 into the oxygen-free copper tube a1, and perform hot isostatic pressing, extrusion, straightening, and cold stretching in sequence to prepare a CuNb single core rod; Step 2: assemble the CuNb single core rod and the hexagonal copper core rod 3 into the CuMn alloy tube 4 in a close-packed hexagonal form to form a multi-core CuNb composite sheath; Step 3, hot isostatic pressing, extrusion, straightening, peeling, and multi-pass cold stretching are performed on the CuNb composite sheath in sequence to prepare a CuNb composite rod; Step 4: Drill a hole in the center of the CuNb composite rod to form a CuNb composite tube, insert the SnTi alloy rod into the CuNb composite tube to form a subcomponent, and the subcomponent is subjected to multiple cold stretching steps to form a hexagonal CuMn subcomponent, such as Figure 4 As shown, the outer side of the hexagonal CuMn subcomponent is a CuMn alloy region 5, and the inner side is a CuNb core rod region 6; Step 5, such as Figure 1 As shown, the hexagonal CuMn subcomponents and SnCu alloy rods 7 are closely packed and assembled into the Ta tube 9, and then the Ta tube 9 is assembled as a whole into the oxygen-free copper tube b8 to form a composite wire. The composite wire is subjected to multiple cold drawing and heat treatments to form a Nb3Sn composite wire.

[0021] Example 2 This embodiment is based on the above-mentioned embodiment 1, and is a method for preparing a reinforced multi-core Nb3Sn composite wire of the present invention. In step 1, the inner diameter of the oxygen-free copper tube a1 is 100 mm to 310 mm, the outer diameter is 115 mm to 335 mm, and the diameter of the Nb core rod 2 is 100 mm to 305 mm. The temperature of hot isostatic pressing 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 drawing processing rate between passes does not exceed 30%; Figure 2 As shown in FIG, a CuNb single core rod is finally formed. The diameter of the CuNb single core rod is 2.2 mm to 11 mm, and the copper ratio is 0.1 to 0.32.

[0022] In step 2, the diameter of the hexagonal oxygen-free copper core rod 3 is 2.2 mm to 11 mm, the inner diameter of the CuMn alloy tube 4 is 86 mm to 430 mm, and the outer diameter is 96 mm to 450 mm. The atomic ratio of the Mn element in the CuMn alloy tube 4 is 0.5% to 6%.

[0023] The center of the CuMn alloy tube 4 is densely packed with hexagonal copper core rods 3, and the outermost CuNb single core rods in the CuMn alloy tube 4 and the hexagonal copper core rods 3 are arranged in sequence.

[0024] In step 3, 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, the peeling amount is between 2% and 5%, the peeling is done once, and the cold stretching processing rate between passes does not exceed 30%; Figure 3 As shown, a CuNb composite rod is finally formed. The diameter of the CuNb composite rod is 25 mm to 100 mm.

[0025] In step 4, the diameter of the drill hole is 10 mm to 45 mm, the proportion of Ti atoms in the SnTi alloy rod is 0.7 to 2%, and the multi-pass cold drawing processing rate of the subcomponent does not exceed 30%; the diameter of the hexagonal CuMn subcomponent is 3 mm to 6 mm, and the copper ratio is 0.1 to 0.27.

[0026] In step 5, the hexagonal CuMn subcomponents in the composite wire are close-packed, the number of hexagonal CuMn subcomponents is 61 to 169, and the Cu atoms in the SnCu alloy rod 7 account for 1% to 3%. Figure 5 As shown, the SuCn alloy rods 7 are fan-shaped and are used to fill the gaps between the close-packed CuMn subcomponents near the Ta tubes. There are six of them.

[0027] The gap between the Ta tube 9 and the hexagonal CuMn subcomponent and SnCu alloy rod 7 forms a rod filling area 10, which is filled with a CuMn alloy rod with a diameter of 2 mm, wherein the Mn content is the same as the corresponding content in the subcomponent.

[0028] The outer diameter of the Ta tube 9 is 47 mm, the wall thickness is 1 mm, the outer diameter of the oxygen-free copper tube b8 is 53 mm to 72 mm, and the inner diameter is 48 mm; the copper ratio of the formed composite wire is 0.3 to 1.5.

[0029] In step 5, when the diameter of the composite wire is greater than 10 mm, the multi-pass cold drawing processing rate is 15-30%, and when the diameter of the composite wire is less than 10 mm, the multi-pass cold drawing processing rate is 8-15%; The heat treatment process is specifically heating at a temperature of 340°C for 96 hours, then heating at a temperature of 600°C for 72 hours, and finally heating at a temperature of 650°C for 96 hours.

[0030] Example 3 The enhanced multi-core Nb3Sn composite wire of the present invention is prepared by the preparation method of the enhanced multi-core Nb3Sn composite wire as described in Example 1 and Example 2.

[0031] Example 4 This embodiment further details the preparation method of the reinforced multi-core Nb3Sn composite wire of the present invention, which specifically includes the following steps: In step 1, a 100mm diameter CuNb core rod (2) is assembled into an oxygen-free copper tube (a1) with an outer diameter of 115mm and an inner diameter of 100mm. The tube is then subjected to hot isostatic pressing (HIP), extrusion, straightening, and cold drawing to produce a hexagonal CuNb single core rod with a diameter of 2.2mm and a copper ratio of 0.2. The HIP 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 inter-pass cold drawing ratio is no more than 30%.

[0032] In step 2, the CuNb single core rods and a 2.2 mm diameter hexagonal copper core rod 3 from step 1 are assembled into a CuMn alloy tube 4 in a close-packed hexagonal configuration. The center of the CuMn alloy tube 4 is closely packed with the hexagonal copper core rod 3 to form a multi-core CuNb composite sheath. The outermost layer of CuNb single core rods is non-continuously close-packed, with the hexagonal copper core rod 3 spaced sequentially. The inner and outer diameters of the CuMn alloy tube 4 are Φ86 and Φ96 mm, respectively, and the Mn atomic ratio is 0.5%.

[0033] In step 3, the CuNb composite sheath undergoes hot isostatic pressing, extrusion, straightening, peeling, and multi-pass cold drawing to produce a CuNb composite rod with an outer diameter of 25 mm. The hot isostatic pressing temperature is 650°C, the extrusion temperature is 450°C, the extrusion speed is 15 mm / s, the straightening accuracy is less than 1 mm per 3 meters, the peeling amount is 2.1%, and the multi-pass cold drawing processing rate is within 15-30%.

[0034] In step 4, a 10 mm diameter hole was drilled in the center of the CuNb composite rod to form a CuNb composite tube. A SnTi alloy rod was then inserted into the hole to form the assembled subcomponent. This was then subjected to multiple cold-drawing passes to form the hexagonal CuMn subcomponent. The Ti atomic content in the SnTi alloy rod was 1.5%, and the processing rate during the multiple cold-drawing passes of the subcomponent was within 15-30%. The hexagonal CuMn subcomponent had a molded size of 3.0 mm and a copper ratio of 0.22. Compared to conventional multi-core subcomponents, the subcomponent preparation process in this embodiment exhibited no cracking during processing.

[0035] In step 5, the hexagonal CuMn subcomponents and SnCu alloy rods 7 are closely packed and assembled into the Ta tube 9, and then the Ta tube 9 is assembled as a whole into the oxygen-free copper tube b8 to form an assembled composite wire. The composite wire is then subjected to multiple cold drawing, heat treatment and other processes to form the final Nb3Sn superconducting wire.

[0036] The hexagonal CuMn subcomponents in the composite wire are close-packed, with 163 hexagonal CuMn subcomponents. The number of SuCn alloy rods 7 is 6, and the SnCu alloy rods 7 are fan-shaped, with Cu atoms accounting for 2%. The remaining voids within the composite wire are filled with Φ2mm diameter CuMn alloy rods, with the same Mn content as the corresponding subcomponents. The Ta tube measures Φ47mm and is 1mm thick. The inner and outer diameters of the oxygen-free copper tube b8 are Φ48 / Φ72mm, respectively, resulting in a copper excess ratio of 1.5 in the composite wire. For composite wire diameters greater than Φ10mm, the multi-pass cold drawing processing ratio is 15-30%, while for composite wire diameters less than Φ10mm, the multi-pass cold drawing processing ratio is 8-15%.

[0037] When the 3-meter-long assembled composite wire of this embodiment was stretched to Φ0.8mm, the composite wire broke five times, and the average output length was 4,300 meters, far exceeding the average output length of existing Nb3Sn composite wires. The heat treatment process was: 340°C / 96h + 600°C / 72h + 650°C / 96h. After the heat treatment, the critical current density was 2703A / mm 2 (4.2K, 12T), which is about 2500A / mm higher than the existing mass-produced Nb3Sn products 2 (4.2K, 12T) average performance level.

[0038] Example 5 This embodiment further details the preparation method of the reinforced multi-core Nb3Sn composite wire of the present invention, which specifically includes the following steps: In step 1, a 150mm diameter Nb core rod (2) is assembled into an oxygen-free copper tube (a1) with an outer diameter of 170mm and an inner diameter of 150mm. The tube is then subjected to hot isostatic pressing (HIP), extrusion, straightening, and cold drawing to produce a hexagonal CuNb single core rod with a diameter of 5.75mm and a copper ratio of 0.32. The HIP temperature is 650°C, the extrusion temperature is 550°C, the extrusion speed is 15mm / s, the straightening accuracy is 1mm per 3 meters, and the inter-pass cold drawing ratio does not exceed 30%.

[0039] In step 2, the CuNb single core rods and 5.75 mm hexagonal copper core rods 3 from step 1 are assembled into a CuMn alloy tube 4 in a close-packed hexagonal configuration. The center of the CuMn alloy tube 4 is closely packed with the 5.75 mm hexagonal copper core rods 3 to form a multi-core CuNb composite sheath. The outermost layer of CuNb single core rods is non-continuously close-packed, with the hexagonal copper core rods 3 spaced apart from each other. The inner and outer diameters of the CuMn alloy tube 4 are Φ195 and Φ220 mm, respectively, and the Mn atomic ratio is 1.0%.

[0040] In step 3, the CuNb composite sheath was subjected to hot isostatic pressing, extrusion, straightening, peeling, and multi-pass cold drawing to produce a CuNb composite rod with an outer diameter of 70 mm. The hot isostatic pressing temperature was 650°C, the extrusion temperature was 550°C, the extrusion speed was 20 mm / s, the straightening accuracy was less than 1 mm per 3 meters, the peeling amount was 2.4%, and the multi-pass cold drawing processing rate was within 15-30%.

[0041] In step 4, a 35 mm diameter hole was drilled in the center of the CuNb composite rod to form a CuNb composite tube. A SnTi alloy rod was then inserted into the hole to form an assembled subcomponent. This was then subjected to multiple cold-drawing passes to form a hexagonal CuMn subcomponent. The Ti atomic content in the SnTi was 1.5%, and the processing rate during the multiple cold-drawing passes of the subcomponent was within 15-30%. The hexagonal CuMn subcomponent had a molded size of 3.5 mm and a copper ratio of 0.27. Compared to conventional multi-core subcomponents, the subcomponent preparation process in this embodiment exhibited no cracking during processing.

[0042] In step 5, the hexagonal CuMn subcomponents and SnCu alloy rods 7 are closely packed and assembled into the Ta tube 9, and then the Ta tube 9 is assembled as a whole into the oxygen-free copper tube b8 to form an assembled composite wire. The composite wire is then subjected to multiple cold drawing, heat treatment and other processes to form the final Nb3Sn superconducting wire.

[0043] The hexagonal CuMn subcomponents in the composite wire are closely packed, numbering 121. The SuCn alloy rods 7 contain six, and the SnCu alloy rods 7 are fan-shaped, with Cu atoms comprising 3%. The remaining voids within the composite wire are filled with Φ2mm diameter CuMn alloy rods, with the same Mn content as the corresponding subcomponents. The Ta tube 9 measures Φ47mm and is 1mm thick. The inner and outer diameters of the oxygen-free copper tube b8 are Φ48 / Φ53mm, respectively, resulting in a copper excess ratio of 0.3 in the composite wire. For composite wire diameters greater than Φ10mm, the multi-pass cold drawing processing ratio is 15-30%, while for composite wire diameters less than Φ10mm, the multi-pass cold drawing processing ratio is 8-15%.

[0044] When the 3-meter-long assembled composite wire of this embodiment was stretched to Φ0.8mm, the composite wire broke three times, and the average output length was 4100 meters, which is also longer than the average output length of existing Nb3Sn composite wires. The heat treatment process was: 340°C / 96h + 600°C / 72h + 650°C / 96h. After the heat treatment, the critical current density was 2787A / mm 2 (4.2K, 12T), which is about 2500A / mm higher than the existing mass-produced Nb3Sn products 2 (4.2K, 12T) average performance level.

[0045] Example 6 This embodiment further details the preparation method of the reinforced multi-core Nb3Sn composite wire of the present invention, which specifically includes the following steps: In step 1, a 305mm diameter Nb core rod (2) is assembled into an oxygen-free copper tube (a1) with an outer diameter of 335mm and an inner diameter of 310mm. The tube is then subjected to hot isostatic pressing (HIP), extrusion, straightening, and cold drawing to produce a hexagonal CuNb single core rod with a diameter of 11mm and a copper ratio of 0.1. The HIP 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 inter-pass cold drawing ratio does not exceed 30%.

[0046] In step 2, the CuNb single core rods and 11 mm hexagonal copper core rods 3 from step 1 were assembled into a CuMn alloy tube 4 in a close-packed hexagonal configuration. The center of the CuMn alloy tube 4 was closely packed with the 11 mm hexagonal copper core rods 3 to form a multi-core CuNb composite sheath. The outermost layer of CuNb single core rods was non-continuously close-packed, with the hexagonal copper core rods 3 spaced apart in sequence. The inner and outer diameters of the CuMn alloy tube 4 were Φ430 and Φ450 mm, respectively, and the Mn atomic ratio was 6.0%.

[0047] In step 3, the CuNb composite sheath was subjected to hot isostatic pressing, extrusion, straightening, peeling, and multi-pass cold drawing to produce a CuNb composite rod with an outer diameter of 100 mm. The hot isostatic pressing temperature was 720°C, the extrusion temperature was 550°C, the extrusion speed was 10 mm / s, the straightening accuracy was less than 1 mm per 3 meters, the peeling amount was 5.0%, and the multi-pass cold drawing processing rate was within 15-30%.

[0048] In step 4, a Φ45mm hole was drilled in the center of the CuNb composite rod to form a CuNb composite tube. A SnTi alloy rod was then inserted into the hole to form an assembled subcomponent. This was then subjected to multiple cold-drawing passes to form a hexagonal CuMn subcomponent. The Ti atomic content in SnTi was 2%, and the processing rate during the multiple cold-drawing passes of the subcomponent was within 15-30%. The hexagonal CuMn subcomponent had a molded size of 5.1mm and a copper ratio of 0.1. Compared to conventional multi-core subcomponents, the subcomponent preparation process in this embodiment exhibited no cracking during processing.

[0049] In step 5, the hexagonal CuMn subcomponents and SnCu alloy rods 7 are closely packed and assembled into the Ta tube 9, and then the Ta tube 9 is assembled as a whole into the oxygen-free copper tube b8 to form an assembled composite wire. The composite wire is then subjected to multiple cold drawing, heat treatment and other processes to form the final Nb3Sn superconducting wire.

[0050] The hexagonal CuMn subcomponents in the composite wire are close-packed, with 55 of them. The number of SuCn alloy rods 7 is 6, and the SnCu alloy rods 7 are fan-shaped, with Cu atoms accounting for 3%. The remaining voids within the composite wire are filled with Φ2mm diameter CuMn alloy rods, with the Mn content being the same as that in the corresponding subcomponents. The Ta tube 9 measures Φ47mm and is 1mm thick. The inner and outer diameters of the oxygen-free copper tube b8 are Φ48 / Φ60mm, respectively, resulting in a copper excess ratio of 0.65 in the composite wire. For composite wire diameters greater than Φ10mm, the multi-pass cold drawing processing ratio is 15-30%, while for composite wire diameters less than Φ10mm, the multi-pass cold drawing processing ratio is 8-15%.

[0051] When the 3-meter-long assembled composite wire of this embodiment was stretched to Φ0.8mm, the composite wire broke eight times, and the average output length was 2000 meters, which is comparable to the average output length of existing Nb3Sn composite wires. The heat treatment process was: 340°C / 96h + 600°C / 72h + 650°C / 96h. After the heat treatment, the critical current density was 2734A / mm 2 (4.2K, 12T), which is about 2500A / mm higher than the existing mass-produced Nb3Sn products 2 (4.2K, 12T) average performance level.

[0052] Example 7 This embodiment further details the preparation method of the reinforced multi-core Nb3Sn composite wire of the present invention, which specifically includes the following steps: In step 1, a 205mm diameter Nb core rod (2) is assembled into an oxygen-free copper tube (a1) with an outer diameter of 225mm and an inner diameter of 210mm. The tube is then subjected to hot isostatic pressing (HIP), extrusion, straightening, and cold drawing to produce a hexagonal CuNb single core rod with a diameter of 5.5mm and a copper ratio of 0.1. The HIP temperature is 670°C, the extrusion temperature is 550°C, the extrusion speed is 15mm / s, the straightening accuracy is 1mm per 3 meters, and the inter-pass cold drawing ratio does not exceed 30%.

[0053] In step 2, the CuNb single core rods and 5.5 mm hexagonal copper core rods 3 from step 1 are assembled into a CuMn alloy tube 4 in a close-packed hexagonal configuration. The center of the CuMn alloy tube 4 is closely packed with the 5.5 mm hexagonal copper core rods 3 to form a multi-core CuNb composite sheath. The outermost layer of CuNb single core rods is non-continuously close-packed, with the hexagonal copper core rods 3 spaced apart from each other. The inner and outer diameters of the CuMn alloy tube 4 are 240 mm and 270 mm, respectively, and the Mn atomic ratio is 2.2%.

[0054] In step 3, the CuNb composite sheath was subjected to hot isostatic pressing, extrusion, straightening, peeling, and multi-pass cold drawing to produce a CuNb composite rod with an outer diameter of 70 mm. The hot isostatic pressing temperature was 670°C, the extrusion temperature was 550°C, the extrusion speed was 20 mm / s, the straightening accuracy was less than 1 mm per 3 meters, the peeling amount was 2.4%, and the multi-pass cold drawing processing rate was within 15-30%.

[0055] In step 4, a Φ35mm hole is drilled in the center of the CuNb composite rod to form a CuNb composite tube. A SnTi alloy rod is then inserted into the hole in the composite tube to form an assembled subcomponent. This is then subjected to multiple cold drawing passes to form a hexagonal CuMn subcomponent. The Ti atomic content in SnTi is 0.7%, and the processing rate during the multiple cold drawing passes of the subcomponent is within 15-30%. The hexagonal CuMn subcomponent has a molded size of 4.2mm and a copper ratio of 0.25. Compared to conventional multi-core subcomponents, the subcomponent preparation process in the present invention is free of processing cracking.

[0056] In step 5, the hexagonal CuMn subcomponents and SnCu alloy rods 7 are closely packed and assembled into the Ta tube 9, and then the Ta tube 9 is assembled as a whole into the oxygen-free copper tube b8 to form an assembled composite wire. The composite wire is then subjected to multiple cold drawing, heat treatment and other processes to form the final Nb3Sn superconducting wire.

[0057] The hexagonal CuMn subcomponents in the composite wire are close-packed, with 85 of them. The number of SuCn alloy rods 7 is 6, and the SnCu alloy rods 7 are fan-shaped, with Cu atoms accounting for 1%. The remaining voids within the composite wire are filled with CuMn alloy rods with a diameter of 2 mm, where the Mn content is the same as that of the corresponding subcomponents. The Ta tube 9 measures 47 mm in diameter and is 1 mm thick. The inner and outer diameters of the oxygen-free copper tube b8 are 48 mm in diameter and 60 mm in diameter, respectively, resulting in a copper excess ratio of 0.65 in the composite wire. For composite wire diameters greater than 10 mm, the multi-pass cold drawing process rate is 15-30%, while for composite wire diameters less than 10 mm, the multi-pass cold drawing process rate is 8-15%.

[0058] When the 3-meter-long assembled composite wire of this embodiment was stretched to Φ0.8mm, the composite wire broke five times, and the average output length was 3300 meters, which is higher than the average output length of existing Nb3Sn composite wires. The heat treatment process was: 340°C / 96h + 600°C / 72h + 650°C / 96h. After the heat treatment, the critical current density was 2784A / mm 2 (4.2K, 12T), which is about 2500A / mm higher than the existing mass-produced Nb3Sn products 2 (4.2K, 12T) average performance level.

[0059] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0060] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present application. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a reinforced multi-core Nb3Sn composite wire, characterized in that: The specific steps include: Step 1, placing the Nb core rod (2) into the oxygen-free copper tube a (1), and sequentially performing hot isostatic pressing, extrusion, straightening, and cold stretching to prepare a CuNb single core rod; Step 2, assembling the CuNb single core rod and the hexagonal copper core rod (3) into the CuMn alloy tube (4) in a close-packed hexagonal form to form a multi-core CuNb composite sheath; Step 3, hot isostatic pressing, extrusion, straightening, peeling, and multi-pass cold stretching are performed on the CuNb composite sheath in sequence to prepare a CuNb composite rod; Step 4: Drilling a hole in the center of the CuNb composite rod to form a CuNb composite tube, inserting the SnTi alloy rod into the CuNb composite tube to form a subcomponent, and subjecting the subcomponent to multiple cold stretching passes to form a hexagonal CuMn subcomponent; Step 5: densely assemble the hexagonal CuMn subcomponents and the SnCu alloy rod (7) into the Ta tube (9), and then assemble the Ta tube (9) as a whole into the oxygen-free copper tube b (8) to form a composite wire, and perform multiple cold drawing and heat treatment on the composite wire to form a Nb3Sn composite wire.

2. The method for preparing the reinforced multi-core Nb3Sn composite wire according to claim 1, characterized in that: In step 1, the inner diameter of the oxygen-free copper tube a (1) is 100 mm to 310 mm, the outer diameter is 115 mm to 335 mm, and the diameter of the Nb core rod (2) is 100 mm to 305 mm; The hot isostatic pressing temperature is 650°C to 720°C, the extrusion temperature is 450°C to 550°C, the extrusion speed is 10mm / s to 20mm / s, the straightening accuracy is 1mm per 3 meters, and the cold drawing processing rate between passes does not exceed 30%; The diameter of the CuNb single core rod is 2.2 mm to 11 mm, and the copper ratio is 0.1 to 0.

32.

3. The method for preparing the reinforced multi-core Nb3Sn composite wire according to claim 1, characterized in that: In step 2, the diameter of the hexagonal oxygen-free copper core rod (3) is 2.2 mm to 11 mm, the inner diameter of the CuMn alloy tube (4) is 86 mm to 430 mm, and the outer diameter is 96 mm to 450 mm. The atomic proportion of the Mn element in the CuMn alloy tube (4) is 0.5 to 6%.

4. The method for preparing the reinforced multi-core Nb3Sn composite wire according to claim 1, characterized in that: In step 2, the center of the CuMn alloy tube (4) is densely packed with hexagonal copper core rods (3), and the outermost CuNb single core rods and the hexagonal copper core rods (3) in the CuMn alloy tube (4) are arranged in sequence.

5. The method for preparing the reinforced multi-core Nb3Sn composite wire according to claim 1, characterized in that: In step 3, the hot isostatic pressing temperature is 650°C to 720°C, the extrusion temperature is 450°C to 550°C, the extrusion speed is 10mm / s to 20mm / s, the straightening accuracy is 1mm per 3 meters, the peeling amount is between 2% and 5%, the peeling is performed once, and the cold drawing processing rate between passes does not exceed 30%; The diameter of the CuNb composite rod is 25 mm to 100 mm.

6. The method for preparing the reinforced multi-core Nb3Sn composite wire according to claim 1, characterized in that: In step 4, the diameter of the drill hole is 10 mm to 45 mm, the proportion of Ti atoms in the SnTi alloy rod is 0.7 to 2%, and the subcomponent multi-pass cold drawing processing rate does not exceed 30%; The diameter of the hexagonal CuMn subcomponent is 3 mm to 6 mm, and the copper ratio is 0.1 to 0.

27.

7. The method for preparing the reinforced multi-core Nb3Sn composite wire according to claim 1, characterized in that: The hexagonal CuMn subcomponents in the composite wire of step 5 are close-packed, the number of hexagonal CuMn subcomponents is 61 to 169, the proportion of Cu atoms in the SnCu alloy rod (7) is 1% to 3%, and the SuCn alloy rod (7) is fan-shaped; The gap between the Ta tube (9) and the hexagonal CuMn subcomponent and SnCu alloy rod (7) forms a rod inserting area (10), and the rod inserting area is filled with a CuMn alloy rod with a diameter of 2 mm; The outer diameter of the Ta tube (9) is 47 mm, and the wall thickness is 1 mm. The outer diameter of the oxygen-free copper tube b (8) is 53 mm to 72 mm, and the inner diameter is 48 mm. The resulting composite wire has a copper excess ratio of 0.3 to 1.

5.

8. The method for preparing the reinforced multi-core Nb3Sn composite wire according to claim 1, characterized in that: In step 5, when the diameter of the composite wire is greater than 10 mm, the multi-pass cold drawing processing rate is 15-30%, and when the diameter of the composite wire is less than 10 mm, the multi-pass cold drawing processing rate is 8-15%; The heat treatment process is specifically heating at a temperature of 340°C for 96 hours, then heating at a temperature of 600°C for 72 hours, and finally heating at a temperature of 650°C for 96 hours.

9. Enhanced multi-core Nb3Sn composite wire, characterized in that: The reinforced multi-core Nb3Sn composite wire is prepared by the preparation method of any one of claims 1 to 8.

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