A method for preparing a multi-core Nb3Sn composite wire and the composite wire

Abstract

The invention discloses a method for preparing a multi-core Nb3Sn composite wire and the composite wire. The method comprises: placing a Nb rod into an oxygen-free copper tube to obtain a CuNb single-core rod; arranging the CuNb single-core rod and a hexagonal copper core rod in a CuMn alloy tube in sequence and at intervals to obtain a multi-core CuNb composite sheath, and then processing the multi-core CuNb composite rod into a CuNb composite tube; placing a SnTi alloy rod into the CuNb composite tube to obtain a subcomponent; processing the subcomponent to obtain a hexagonal CuMn subcomponent; assembling the hexagonal CuMn subcomponent and the SnCu alloy rod into a Ta tube, and then assembling the whole into an oxygen-free copper tube to obtain a composite wire, and processing the Nb3Sn superconducting wire. The present invention solves the problem of processing cracking that is prone to occur during the subcomponent preparation stage due to the small amount of Cu on the outside of the subcomponent by adjusting the outermost layer of CuNb single core rods to be discontinuously densely packed. By using CuMn alloy on the outside of the subcomponent, the deformation consistency of the wire during the composite wire processing stage is further enhanced, and it is also ensured that the wire will not crack during stretching. By adding fan-shaped SnCu alloy rods, it is ensured that there is sufficient Sn when the wire Nb generates Nb3Sn.

Description

Technical Field

[0001] The present invention relates to the field of air purification, and in particular to a preparation method of a multi-core Nb3Sn composite wire and the 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. Summary of the Invention

[0003] The embodiments of the present invention provide a method for preparing a multi-core Nb3Sn composite wire and the composite wire, which are used to solve the problem in the prior art that the continuous reduction of the Cu content of the synergistic deformation effect causes the wire processing to be prone to wire cracking and uneven deformation.

[0004] In one aspect, an embodiment of the present invention provides a method for preparing a multi-core Nb3Sn composite wire, comprising:

[0005] The Nb rod is placed into the oxygen-free copper tube to obtain a CuNb single-core rod;

[0006] Arranging the outermost CuNb single core rod and the hexagonal copper core rod in the CuMn alloy tube in sequence in a close-packed hexagonal form to obtain a multi-core CuNb composite sheath;

[0007] Processing the CuNb composite sheath into a CuNb composite rod;

[0008] Drilling a hole in the center of the CuNb composite rod to obtain a CuNb composite tube;

[0009] Inserting a SnTi alloy rod into the CuNb composite tube to obtain a subcomponent;

[0010] Processing the subcomponent to obtain a hexagonal CuMn subcomponent;

[0011] Assembling the hexagonal CuMn subcomponent and the fan-shaped SnCu alloy rod into a Ta tube and then assembling the whole into an oxygen-free copper tube to obtain a composite wire;

[0012] The composite wire is processed to obtain a Nb3Sn superconducting wire.

[0013] In a possible implementation, before the Nb rod is loaded into the oxygen-free copper tube to obtain the CuNb single-core rod, the process further includes hot isostatic pressing, extruding, straightening, and cold stretching the Nb rod and the oxygen-free copper tube.

[0014] In a possible implementation, the CuNb composite sheath is processed into a CuNb composite rod by sequentially subjecting the CuNb composite sheath to hot isostatic pressing, extrusion, straightening, peeling, and multiple cold drawing steps to obtain the CuNb composite rod.

[0015] In a possible implementation, processing the subcomponent to obtain the hexagonal CuMn subcomponent is to subject the subcomponent to multiple cold stretching passes to obtain the hexagonal CuMn subcomponent.

[0016] In a possible implementation, before assembling the hexagonal CuMn subcomponents and the fan-shaped SnCu alloy rods into a Ta tube and then assembling the entire assembly into an oxygen-free copper tube to obtain a composite wire, the process further includes:

[0017] The hexagonal CuMn subcomponents and the fan-shaped SnCu alloy rods are closely packed and assembled in the Ta tube.

[0018] In a possible implementation, before processing the composite wire to obtain the Nb3Sn superconducting wire, the process further includes:

[0019] The composite wire is subjected to multiple cold drawing and heat treatment processes.

[0020] On the other hand, an embodiment of the present invention provides a multi-core Nb3Sn composite wire, which is prepared by any one of the methods described above.

[0021] The multi-core Nb3Sn composite wire preparation method and the composite wire of the present invention have the following advantages:

[0022] (1) By adjusting the outermost CuNb single core rod of the CuNb composite sheath to a non-continuous close-packed structure, the problem of processing cracking that is prone to occur during the subcomponent preparation stage due to the small amount of Cu on the outside is solved.

[0023] (2) By using CuMn alloy outside the subcomponent, the deformation consistency of the wire during the composite wire processing stage is further enhanced, and it is also ensured that the wire will not crack when stretched.

[0024] (3) By adding fan-shaped SnCu alloy rods, sufficient Sn is ensured when the wire Nb generates Nb3Sn. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 A flow chart of a method for preparing a multi-core Nb3Sn composite wire provided in an embodiment of the present invention;

[0027] Figure 2 A structural diagram of a multi-core Nb3Sn composite wire provided in an embodiment of the present invention;

[0028] Figure 3 A CuNb single-core rod of a multi-core Nb3Sn composite wire provided in an embodiment of the present invention;

[0029] Figure 4 A CuNb composite rod of a multi-core Nb3Sn composite wire provided in an embodiment of the present invention;

[0030] Figure 5 The CuMn-type subcomponent after assembly of a multi-core Nb3Sn composite wire provided by an embodiment of the present invention;

[0031] Figure 6 An embodiment of the present invention provides a SnCu alloy rod of a multi-core Nb3Sn composite wire. DETAILED DESCRIPTION

[0032] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making creative efforts are within the scope of protection of the present invention.

[0033] Figure 1 A flowchart of a method for preparing a multi-core Nb3Sn composite wire provided in an embodiment of the present invention. The present invention provides a method for preparing a multi-core Nb3Sn composite wire, comprising:

[0034] The Nb rod is placed into the oxygen-free copper tube to obtain a CuNb single-core rod;

[0035] Arranging the outermost CuNb single core rod and the hexagonal copper core rod in the CuMn alloy tube in sequence in a close-packed hexagonal form to obtain a multi-core CuNb composite sheath;

[0036] Processing the CuNb composite sheath into a CuNb composite rod;

[0037] Drilling a hole in the center of the CuNb composite rod to obtain a CuNb composite tube;

[0038] Inserting a SnTi alloy rod into the CuNb composite tube to obtain a subcomponent;

[0039] Processing the subcomponent to obtain a hexagonal CuMn subcomponent;

[0040] Assembling the hexagonal CuMn subcomponent and the fan-shaped SnCu alloy rod into a Ta tube and then assembling the whole into an oxygen-free copper tube to obtain a composite wire;

[0041] Processing the composite wire to obtain a Nb3Sn superconducting wire;

[0042] Before the Nb rod is loaded into the oxygen-free copper tube to obtain the CuNb single-core rod, the Nb rod and the oxygen-free copper tube are hot isostatically pressed, extruded, straightened and cold stretched;

[0043] Processing the CuNb composite sheath into a CuNb composite rod comprises sequentially subjecting the CuNb composite sheath to hot isostatic pressing, extrusion, straightening, peeling, and multiple cold drawing steps to obtain the CuNb composite rod;

[0044] Processing the subcomponent to obtain a hexagonal CuMn subcomponent comprises subjecting the subcomponent to multiple cold stretching passes to obtain the hexagonal CuMn subcomponent;

[0045] Before assembling the hexagonal CuMn subcomponents and the fan-shaped SnCu alloy rods into the Ta tube and then assembling the whole into the oxygen-free copper tube to obtain the composite wire, the process further includes:

[0046] Closely assembling the hexagonal CuMn subcomponent and the fan-shaped SnCu alloy rod in the Ta tube;

[0047] Before the composite wire is processed to obtain the Nb3Sn superconducting wire, the method further comprises:

[0048] The composite wire is subjected to multiple cold drawing and heat treatment processes.

[0049] For example, Figure 2 、 3 As shown in , 4, 5, and 6, the inner diameter of the oxygen-free copper tube in the CuNb single-core rod obtained by inserting the Nb rod into the oxygen-free copper tube is 100-310 mm, the outer diameter is 115-335 mm, and the size of the Nb rod is 100-305 mm; the hexagonal forming size of the CuNb single-core rod is 2.2-11 mm, and the copper ratio is 0.1-0.32; the hot isostatic pressing temperature during processing is 650-720°C, the extrusion temperature is 450-550°C, the extrusion speed is 10-20 mm / s, the straightening accuracy is 1 mm per 3 meters, and the cold drawing processing rate between passes does not exceed 30%.

[0050] The size of the hexagonal copper core rod is 2.2-11 mm, the inner diameter of the CuMn alloy tube is 86-430 mm, the outer diameter is 96-450 mm, and the atomic proportion of the Mn element in the CuMn alloy is 0.5-6%;

[0051] The center of the CuMn tube is densely packed with hexagonal copper core rods, the outermost layer of CuNb single core rods and the hexagonal copper core rods are densely packed in sequence, and the outermost layer of CuNb single core rods are discontinuously arranged.

[0052] The size of the CuNb composite rod is Φ25~Φ100mm; the hot isostatic pressing temperature of the CuNb composite sheath processed into the CuNb composite rod is between 650~720°C, the extrusion temperature is between 450~550°C, the extrusion speed is 10~20mm / s, the straightening accuracy is 1mm per 3 meters, the stripping amount is between 2~5%, the stripping is one time, and the multi-pass cold drawing processing rate does not exceed 30%.

[0053] When drilling a hole in the center of the CuNb composite rod to obtain a CuNb composite tube, the hole size is between 10 and 45 mm, and the Ti atom content in the SnTi alloy rod is 0.7 to 2%.

[0054] The multi-pass cold drawing processing rate of the subcomponent does not exceed 30%, the forming size of the hexagonal CuMn subcomponent is 3-6 mm, and the copper ratio is between 0.1-0.27.

[0055] The CuMn subcomponents in the composite wire are close-packed, and the number of subcomponents is 61 to 169;

[0056] The Cu atoms in the SnCu alloy account for 1-3%. The SuCn alloy rods are fan-shaped and are used to fill the gaps between the close-packed CuMn subcomponents near the Ta tube. There are 6 of them. The remaining gaps inside the composite wire are filled with CuMn alloy rods with a diameter of Φ2 mm, where the Mn content is the same as that in the subcomponents.

[0057] The Ta tube has a size of Φ47 mm and a thickness of 1 mm. The oxygen-free copper tube has an outer diameter of Φ53 to Φ72 mm and an inner diameter of Φ48 mm. The copper ratio of the composite wire is 0.3 to 1.5.

[0058] When the diameter of the composite wire is greater than Φ10mm, the multi-pass cold drawing processing rate is 15-30%, and when the diameter of the composite wire is less than Φ10mm, the multi-pass cold drawing processing rate is 8-15%;

[0059] The heat treatment process is: 340°C / 96h + 600°C / 72h + 650°C / 96h.

[0060] In a possible embodiment, according to the above method, the embodiments are listed as follows:

[0061] Example 1

[0062] 1) A 100mm diameter Nb rod was assembled into an oxygen-free copper tube with an outer diameter of 115mm and an inner diameter of 100mm. The tube was 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 was 650°C, the extrusion temperature was 450°C, the extrusion speed was 20mm / s, the straightening accuracy was 1mm per 3 meters, and the cold drawing ratio between passes was no more than 30%.

[0063] 2) The CuNb single core rods and 2.2 mm hexagonal copper core rods from step 1) were assembled into a CuMn alloy tube in a close-packed hexagonal pattern. The center of the CuMn tube was filled with the hexagonal copper core rods to form a multi-core CuNb composite sheath. The outermost CuNb single core rods were non-continuously close-packed, with the hexagonal copper core rods spaced sequentially. The inner and outer diameters of the CuMn alloy tube were Φ86 and Φ96 mm, respectively, and the Mn atomic ratio was 0.5%.

[0064] 3) The CuNb composite sheath was subjected to a series of hot isostatic pressing (HIP) processes, followed by extrusion, straightening, peeling, and multi-pass cold drawing, to produce a Φ25mm outer diameter CuNb composite rod. The HIP temperature was 650°C, the extrusion temperature was 450°C, the extrusion speed was 15mm / s, the straightening accuracy was less than 1mm per 3 meters, the peeling rate was 2.1%, and the multi-pass cold drawing process yield was between 15% and 30%.

[0065] 4) A 10 mm diameter hole was drilled through 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 of the SnTi was 1.5%, and the processing rate during the multiple cold-drawing passes was within 15-30%. The hexagonal CuMn subcomponent had a final size of 3.0 mm and a copper ratio of 0.22. Compared to conventional multi-core subcomponents, the subcomponent preparation process in this invention exhibited no cracking during processing.

[0066] 5) CuMn subcomponents and SnCu alloy rods are closely packed into a Ta tube, which is then assembled into an oxygen-free copper tube to form a composite wire. The composite wire then undergoes multiple cold-drawing and heat treatment processes to form the final Nb3Sn superconducting wire. The CuMn subcomponents in the composite wire are closely packed, with 163 subcomponents. The SuCn alloy rods are six, and the SnCu alloy rods are fan-shaped, with Cu atoms comprising 2%. The remaining voids within the composite wire are filled with 2mm diameter CuMn alloy rods, with the same Mn content as the corresponding subcomponents. The Ta tube measures 47mm in diameter and is 1mm thick. The inner and outer diameters of the oxygen-free copper tube are 48 / 72mm, respectively, resulting in a Cu / superconducting ratio of 1.5. For composite wire diameters greater than 10mm, the multi-pass cold-drawing processing ratio is 15-30%. For composite wire diameters less than 10mm, the multi-pass cold-drawing processing ratio is 8-15%.

[0067] When a 3-meter-long assembled composite wire was stretched to 0.8 mm in diameter, the wire broke five times, resulting in an average length of 4,300 meters, significantly exceeding the average length of existing Nb3Sn composite wires. The heat treatment process consisted of 340°C for 96 hours, 600°C for 72 hours, and 650°C for 96 hours. After heat treatment, the critical current density reached 2,703 A / mm² (4.2 K, 12 T), exceeding the average performance level of approximately 2,500 A / mm² (4.2 K, 12 T) for currently mass-produced Nb3Sn products.

[0068] Example 2

[0069] 1) A 150mm diameter Nb rod was assembled into an oxygen-free copper tube with an outer diameter of 170mm and an inner diameter of 150mm. The tube was 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 was 650°C, the extrusion temperature was 550°C, the extrusion speed was 15mm / s, the straightening accuracy was 1mm per 3 meters, and the cold drawing ratio between passes did not exceed 30%.

[0070] 2) The CuNb single core rods and 5.75 mm hexagonal copper core rods from step 1) were assembled into a CuMn alloy tube in a close-packed hexagonal pattern. The center of the CuMn tube was filled with a 5.75 mm hexagonal copper core rod to form a multi-core CuNb composite sheath. The outermost CuNb single core rods were closely packed in a non-continuous pattern, alternately spaced with the hexagonal copper core rods. The inner and outer diameters of the CuMn alloy tube were Φ195 / Φ220 mm, respectively. The Mn atomic ratio was 1.0%.

[0071] 3) The CuNb composite sheath was subjected to a series of hot isostatic pressing (HIP) processes, followed by extrusion, straightening, peeling, and multi-pass cold drawing, to produce a Φ70mm outer diameter CuNb composite rod. The HIP temperature was 650°C, the extrusion temperature was 550°C, the extrusion speed was 20mm / s, the straightening accuracy was less than 1mm per 3 meters, the peeling rate was 2.4%, and the multi-pass cold drawing process yield was between 15% and 30%.

[0072] 4) A 35 mm diameter hole was drilled through 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 of the SnTi was 1.5%, and the processing rate during the multiple cold-drawing passes was within 15-30%. The hexagonal CuMn subcomponent had a final size of 3.5 mm and a copper ratio of 0.27. Compared to conventional multi-core subcomponents, the subcomponent preparation process in this invention exhibited no cracking during processing.

[0073] 5) CuMn subcomponents and SnCu alloy rods are closely packed and assembled into a Ta tube. The Ta tube is then assembled into an oxygen-free copper tube to form an assembled composite wire. The composite wire then undergoes multiple cold-drawing and heat treatment processes to form the final Nb3Sn superconducting wire. The CuMn subcomponents in the composite wire are closely packed, with 121 subcomponents. The SuCn alloy rods are six, and the SnCu alloy rods are fan-shaped, with Cu atoms comprising 3%. The remaining voids within the composite wire are filled with 2mm diameter CuMn alloy rods, with the same Mn content as the corresponding subcomponents. The Ta tube measures 47mm in diameter and is 1mm thick. The inner and outer diameters of the oxygen-free copper tube are 48 / 53mm, respectively, resulting in a Cu / superconducting ratio of 0.3. For composite wire diameters greater than 10mm, the multi-pass cold-drawing processing ratio is 15-30%. For composite wire diameters less than 10mm, the multi-pass cold-drawing processing ratio is 8-15%.

[0074] When a 3-meter-long assembled composite wire was stretched to 0.8 mm in diameter, the wire broke three times, resulting in an average length of 4,100 meters, also exceeding the average length of existing Nb3Sn composite wires. The heat treatment process consisted of: 340°C for 96 hours, 600°C for 72 hours, and 650°C for 96 hours. After heat treatment, the critical current density reached 2,787 A / mm² (4.2 K, 12 T), exceeding the average performance level of approximately 2,500 A / mm² (4.2 K, 12 T) for currently mass-produced Nb3Sn products.

[0075] Example 3

[0076] 1) 305mm diameter Nb rods were assembled into oxygen-free copper tubes with an outer diameter of 335mm and an inner diameter of 310mm. The tubes were then subjected to hot isostatic pressing (HIP), extrusion, straightening, and cold drawing to produce hexagonal CuNb single-core rods with a diameter of 11mm and a copper ratio of 0.1. The HIP temperature was 720°C, the extrusion temperature was 550°C, the extrusion speed was 10mm / s, the straightening accuracy was 1mm per 3 meters, and the inter-pass cold drawing ratio did not exceed 30%.

[0077] 2) The CuNb single core rods and 11 mm hexagonal copper core rods from step 1) were assembled into a CuMn alloy tube in a close-packed hexagonal pattern. The center of the CuMn tube was filled with the 11 mm hexagonal copper core rods to form a multi-core CuNb composite sheath. The outermost CuNb single core rods were closely packed in a non-continuous pattern, alternately spaced with the hexagonal copper core rods. The inner and outer diameters of the CuMn alloy tube were Φ430 / Φ450 mm, respectively, and the Mn atomic ratio was 6.0%.

[0078] 3) The CuNb composite sheath was subjected to a series of hot isostatic pressing (HIP) processes, followed by extrusion, straightening, peeling, and multi-pass cold drawing to produce a Φ100mm outer diameter CuNb composite rod. The HIP 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 rate was 5.0%, and the multi-pass cold drawing process yield was between 15% and 30%.

[0079] 4) A 45 mm diameter hole was drilled through 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 of the SnTi was 2%, and the processing rate during the multiple cold-drawing passes was within 15-30%. The hexagonal CuMn subcomponent had a final dimension of 5.1 mm and a copper ratio of 0.1. Compared to conventional multi-core subcomponents, the subcomponent preparation process in this invention exhibited no cracking during processing.

[0080] 5) CuMn subcomponents and SnCu alloy rods are closely packed and assembled into a Ta tube. The Ta tube is then assembled into an oxygen-free copper tube to form an assembled composite wire. The composite wire then undergoes multiple cold drawing and heat treatment processes to form the final Nb3Sn superconducting wire. The CuMn subcomponents in the composite wire are closely packed, with 55 subcomponents, the SuCn alloy rods are six, and the SnCu alloy rods are fan-shaped, with a Cu atomic ratio of 3%. The remaining voids within the composite wire are filled with 2mm diameter CuMn alloy rods, with the same Mn content as the corresponding subcomponents. The Ta tube measures 47mm in diameter and 1mm in thickness. The inner and outer diameters of the oxygen-free copper tube are 48 / 60mm, respectively, resulting in a Cu / superconducting ratio of 0.65. For composite wire diameters greater than 10mm, the multi-pass cold drawing processing ratio is 15-30%. For composite wire diameters less than 10mm, the multi-pass cold drawing processing ratio is 8-15%.

[0081] When a 3-meter-long assembled composite wire was stretched to 0.8 mm in diameter, the wire broke eight times, with an average output length of 2000 meters, comparable to the average output length of existing Nb3Sn composite wires. The heat treatment process consisted of: 340°C for 96 hours, 600°C for 72 hours, and 650°C for 96 hours. After heat treatment, the critical current density reached 2734 A / mm2 (4.2 K, 12 T), exceeding the average performance level of approximately 2500 A / mm2 (4.2 K, 12 T) for currently mass-produced Nb3Sn products.

[0082] Example 4

[0083] 1) A 205mm diameter Nb rod was assembled into an oxygen-free copper tube with an outer diameter of 225mm and an inner diameter of 210mm. The tube was 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 was 670°C, the extrusion temperature was 550°C, the extrusion speed was 15mm / s, the straightening accuracy was 1mm per 3 meters, and the cold drawing ratio between passes did not exceed 30%.

[0084] A 5 mm diameter Nb rod was assembled into an oxygen-free copper tube with an outer hexagonal size of 5.5 mm and an inner circular diameter of 5.05 mm to form a CuNb single-core rod with a copper ratio of 0.1.

[0085] 2) The CuNb single core rods and 5.5 mm hexagonal copper core rods from step 1) were assembled into a CuMn alloy tube in a close-packed hexagonal pattern. The center of the CuMn tube was filled with a 5.5 mm hexagonal copper core rod to form a multi-core CuNb composite sheath. The outermost CuNb single core rods were closely packed in a non-continuous pattern, alternately spaced with the hexagonal copper core rods. The inner and outer diameters of the CuMn alloy tube were 240 mm and 270 mm, respectively. The Mn atomic ratio was 2.2%.

[0086] 3) The CuNb composite sheath was subjected to a series of hot isostatic pressing (HIP) processes, followed by extrusion, straightening, peeling, and multi-pass cold drawing, to produce a Φ70mm outer diameter CuNb composite rod. The HIP temperature was 670°C, the extrusion temperature was 550°C, the extrusion speed was 20mm / s, the straightening accuracy was less than 1mm per 3 meters, the peeling capacity was 2.4%, and the multi-pass cold drawing processing rate was between 15% and 30%.

[0087] 4) A 35 mm diameter hole was drilled through 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 of the SnTi was 0.7%, and the processing rate during the multiple cold-drawing passes was within 15-30%. The hexagonal CuMn subcomponent had a final dimension of 4.2 mm and a copper ratio of 0.25. Compared to conventional multi-core subcomponents, the subcomponent preparation process in this invention exhibited no cracking during processing.

[0088] 5) CuMn subcomponents and SnCu alloy rods are closely packed into a Ta tube, which is then assembled into an oxygen-free copper tube to form an assembled composite wire. The composite wire then undergoes multiple cold-drawing and heat treatment processes to form the final Nb3Sn superconducting wire. The CuMn subcomponents in the composite wire are closely packed, with 85 subcomponents, six SuCn alloy rods, and fan-shaped SnCu alloy rods, with a Cu atomic ratio of 1%. The remaining voids within the composite wire are filled with 2mm diameter CuMn alloy rods, with the same Mn content as the corresponding subcomponents. The Ta tube measures 47mm in diameter and 1mm in thickness. The inner and outer diameters of the oxygen-free copper tube are 48 / 60mm, respectively, resulting in a Cu / superconducting ratio of 0.65. For composite wire diameters greater than 10mm, the multi-pass cold-drawing processing ratio is 15-30%, while for composite wire diameters less than 10mm, the multi-pass cold-drawing processing ratio is 8-15%.

[0089] When a 3-meter-long assembled composite wire was stretched to 0.8 mm in diameter, the wire broke five times, resulting in an average length of 3,300 meters, exceeding the average length of existing Nb3Sn composite wires. The heat treatment process consisted of: 340°C for 96 hours, 600°C for 72 hours, and 650°C for 96 hours. After heat treatment, the critical current density reached 2,784 A / mm² (4.2 K, 12 T), exceeding the average performance level of approximately 2,500 A / mm² (4.2 K, 12 T) for currently mass-produced Nb3Sn products.

[0090] Figure 2 A structural diagram of a multi-core Nb3Sn composite wire provided in an embodiment of the present invention; an embodiment of the present invention provides a multi-core Nb3Sn composite wire, which is prepared by any of the methods described above.

[0091] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including all changes and modifications that fall within the scope of the present invention and the preferred embodiments.

[0092] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for preparing a multi-core Nb3Sn composite wire, characterized in that: include: The Nb rod is placed into the oxygen-free copper tube to obtain a CuNb single-core rod; Arranging the outermost CuNb single core rod and the hexagonal copper core rod in the CuMn alloy tube in sequence in a close-packed hexagonal form to obtain a multi-core CuNb composite sheath; The center of the CuMn alloy tube is densely packed with the hexagonal copper core rods, and the outermost CuNb single core rods and the hexagonal copper core rods are densely packed in sequence; Processing the CuNb composite sheath into a CuNb composite rod; Drilling a hole in the center of the CuNb composite rod to obtain a CuNb composite tube; Inserting a SnTi alloy rod into the CuNb composite tube to obtain a subcomponent; Processing the subcomponent to obtain a hexagonal CuMn subcomponent; Assembling the hexagonal CuMn subcomponent and the fan-shaped SnCu alloy rod into a Ta tube and then assembling the whole into an oxygen-free copper tube to obtain a composite wire; Before assembling the hexagonal CuMn subcomponents and the fan-shaped SnCu alloy rods into the Ta tube and then assembling the whole into the oxygen-free copper tube to obtain the composite wire, the process further includes: Closely assembling the hexagonal CuMn subcomponent and the fan-shaped SnCu alloy rod in the Ta tube; The SnCu alloy rod is fan-shaped and is used to fill the gaps between the closely packed hexagonal CuMn subcomponents near the Ta tube; The composite wire is processed to obtain a Nb3Sn superconducting wire.

2. The method for preparing a multi-core Nb3Sn composite wire according to claim 1, characterized in that: Before the Nb rod is loaded into the oxygen-free copper tube to obtain the CuNb single-core rod, the method further includes hot isostatic pressing, extruding, straightening and cold stretching the Nb rod and the oxygen-free copper tube.

3. The method for preparing a multi-core Nb3Sn composite wire according to claim 1, characterized in that: The CuNb composite sheath is processed into a CuNb composite rod by sequentially subjecting the CuNb composite sheath to hot isostatic pressing, extrusion, straightening, peeling and multiple cold stretching steps to obtain the CuNb composite rod.

4. The method for preparing a multi-core Nb3Sn composite wire according to claim 1, wherein: Processing the subcomponent to obtain the hexagonal CuMn subcomponent involves subjecting the subcomponent to multiple cold stretching passes to obtain the hexagonal CuMn subcomponent.

5. The method for preparing a multi-core Nb3Sn composite wire according to claim 1, wherein: Before the composite wire is processed to obtain the Nb3Sn superconducting wire, the method further comprises: The composite wire is subjected to multiple cold drawing and heat treatment processes.

6. A multi-core Nb3Sn composite wire, characterized in that: The multi-core Nb3Sn composite wire is prepared by the method according to any one of claims 1 to 5.

Images