A method for preparing artificially pinned NbTi multi-core superconducting wire

Abstract

The present invention belongs to the technical field of superconducting material processing, and discloses a method for preparing an artificially pinned NbTi multi-core superconducting wire. The method uses Nb‑Ti alloy powder to be filled into an oxygen-free copper sheath with an Fe barrier layer sleeve and a Ta tube to obtain an artificially pinned single core rod to prepare an artificially pinned Nb‑Ti superconductor. The barrier layer materials are Ta and Fe. The Fe barrier layer sleeve is used as an inner lining material to form a diffusion reaction with the Nb‑Ti alloy powder to generate an artificial pinning phase. The Ta tube is used as an outer lining material to prevent Fe from diffusing outward, and an oxygen-free copper tube is used as the matrix material. The critical current density at 2T can reach 8000A / mm 2 The Ta element is used to increase the upper critical magnetic field in Nb-Ti superconductors, because the addition of Ta as a spin-orbit scatterer reduces the paramagnetic limit. As a barrier layer, the Ta element can not only block the reaction of Fe and Cu, but also reduce the loss of superconducting wires.

Description

Technical Field

[0001] The invention relates to the technical field of superconducting material processing, in particular to a method for preparing an artificially pinned NbTi multi-core superconducting wire. Background Art

[0002] Traditional NbTi superconducting wire is a practical superconducting wire composed of multi-core NbTi superconducting wires in a high-purity oxygen-free copper sheath. Superconductors can be used more and more, mainly because of their super strong current carrying capacity. The important performance parameter that reflects the current carrying capacity of superconductors is the critical current density. In industrial mass production, the critical current density is mainly improved by controlling the precipitation amount and size of the second phase α-Ti precipitates through cold processing and aging heat treatment system. α-Ti in NbTi alloy is called the pinning center of superconducting material. The more pinning centers there are, the higher its critical current density. However, since the number of α-Ti precipitates in NbTi alloy is limited, the upper limit of α-Ti precipitation also limits the further improvement of the critical current density of conventional NbTi superconducting wires. Scientists have made various attempts to improve the critical current density of NbTi multi-core superconductors by artificially introducing artificial pinning centers.

[0003] Commonly used methods for preparing NbTi superconductors by artificial pinning include drilling, rolling, powder metallurgy, etc. In the rolling process, Nb, Ti, and artificial pinning materials are usually made into plates, and then the plates are stacked and rolled into cylinders. The combination of Nb, Ti, and artificial pinning materials is not very compact, resulting in uneven deformation of Nb, Ti, and artificial pinning materials during subsequent drawing or rolling processes, resulting in high wire loss during the preparation process and low critical current density of the final product under low field. Summary of the invention

[0004] The object of the present invention is to provide a method for preparing an artificially pinned NbTi multi-core superconducting wire to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for preparing an artificially pinned NbTi multi-core superconducting wire comprises the following steps:

[0007] S1, obtaining Nb-Ti alloy powder, Fe barrier layer casing, Ta cylinder, oxygen-free copper sheath and oxygen-free copper tube;

[0008] S2, loading the obtained Nb-Ti alloy powder into a Fe barrier layer sleeve, and drawing the Fe barrier layer sleeve loaded with the Nb-Ti alloy powder to obtain a Fe barrier layer Nb-Ti core rod;

[0009] S3, closely arranging the Fe barrier layer Nb-Ti core rods in the Ta tube;

[0010] S4, loading the Ta cylinder with the Fe barrier layer Nb-Ti core rod into the oxygen-free copper sheath to obtain the Fe / Ta double barrier layer Nb-Ti / Cu sheath, and vacuum-sealing the two ends of the Fe / Ta double barrier layer Nb-Ti / Cu sheath;

[0011] S5, placing the Nb-Ti / Cu package of the Fe / Ta double barrier layer after vacuum sealing into a vacuum heat treatment furnace for thermal diffusion treatment to obtain a Nb-Ti / Cu artificial pinning alloy ingot of the Fe / Ta double barrier layer;

[0012] S6, after keeping the Nb-Ti / Cu artificially pinned alloy ingot with Fe / Ta double barrier layer in a heating furnace, hot extrusion and drawing are performed through an extruder to obtain a Nb-Ti / Cu artificially pinned hexagonal rod with Fe / Ta double barrier layer;

[0013] S7, closely arranging the Nb-Ti / Cu artificially pinned hexagonal rods with Fe / Ta double barrier layers in an oxygen-free copper tube to obtain artificially pinned NbTi / Cu composite rods, and subjecting them to multiple aging heat treatments;

[0014] S8. The artificially pinned NbTi / Cu composite rods that have undergone multiple aging heat treatments are drawn multiple times to obtain artificially pinned NbTi multi-core superconducting wires.

[0015] Further preferably, in S2, when the Fe barrier layer sleeve filled with Nb-Ti alloy powder is drawn to obtain a Fe barrier layer Nb-Ti core rod, the Fe barrier layer Nb-Ti core rod is processed into a Fe barrier layer Nb-Ti hexagonal rod with a side size of 3mm to 7mm by a drawing machine, and the Fe barrier layer Nb-Ti hexagonal rod is sawed to a fixed length.

[0016] Further preferably, in S4, when vacuum sealing the two ends of the Nb-Ti / Cu sheath of the Fe / Ta double barrier layer, firstly, copper covers are assembled at the two ends of the Nb-Ti / Cu sheath of the Fe / Ta double barrier layer, and then the Nb-Ti / Cu sheath and the copper cover of the Fe / Ta double barrier layer are vacuum sealed.

[0017] Further preferably, in said S5, when the Nb-Ti / Cu package of the Fe / Ta double barrier layer which has been vacuum sealed is placed in a vacuum heat treatment furnace for thermal diffusion treatment, the thermal diffusion treatment temperature is 900°C to 1000°C, and the holding time is 10h to 15h.

[0018] Further preferably, in said S6, after the Nb-Ti / Cu artificial pinning alloy ingot with Fe / Ta double barrier layer is kept warm in a heating furnace, when it is hot extruded through an extruder, the keeping temperature of the heating furnace is 500°C to 800°C, and the keeping time is 1h to 5h.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention uses Nb-Ti alloy powder to fill an oxygen-free copper sheath with an Fe barrier layer sleeve and a Ta tube to obtain an artificially pinned single core rod to prepare an artificially pinned Nb-Ti superconductor. The barrier layer materials are Ta and Fe. The Fe barrier layer sleeve is used as an inner lining material to form a diffusion reaction with the Nb-Ti alloy powder to generate an artificial pinning phase. The Ta tube is used as an outer lining material to prevent Fe from diffusing outward, and an oxygen-free copper tube is used as the matrix material. The critical current density at 2T can reach 8000A / mm 2 , the critical current density under low field has been greatly improved, opening up new space for the application of NbTi superconductors. The main role of Ta element in Nb-Ti superconductors is to increase the upper critical magnetic field, because the addition of Ta as a spin-orbit scatterer reduces the paramagnetic limitation. Ta element as a barrier layer can block the reaction of Fe and Cu on the one hand, and reduce the loss of superconducting wire on the other hand. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the cross-sectional structure of the Nb-Ti / Cu sheath of the Fe / Ta double barrier layer of the present invention. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] See also Figure 1 , the present invention provides a technical solution:

[0024] A method for preparing an artificially pinned NbTi multi-core superconducting wire comprises the following steps:

[0025] S1, obtaining Nb-Ti alloy powder, Fe barrier layer casing, Ta cylinder, oxygen-free copper sheath and oxygen-free copper tube;

[0026] S2, loading the obtained Nb-Ti alloy powder into the Fe barrier layer sleeve, and drawing the Fe barrier layer sleeve filled with the Nb-Ti alloy powder to obtain a Fe barrier layer Nb-Ti core rod;

[0027] S3, closely arranging the Fe barrier layer Nb-Ti core rods in the Ta tube;

[0028] S4, loading the Ta cylinder with the Fe barrier layer Nb-Ti core rod into the oxygen-free copper sheath to obtain the Fe / Ta double barrier layer Nb-Ti / Cu sheath, and vacuum-sealing the two ends of the Fe / Ta double barrier layer Nb-Ti / Cu sheath;

[0029] S5, placing the Nb-Ti / Cu package of the Fe / Ta double barrier layer after vacuum sealing into a vacuum heat treatment furnace for thermal diffusion treatment to obtain a Nb-Ti / Cu artificial pinning alloy ingot of the Fe / Ta double barrier layer;

[0030] S6, after keeping the Nb-Ti / Cu artificially pinned alloy ingot with Fe / Ta double barrier layer in a heating furnace, hot extrusion and drawing are performed through an extruder to obtain a Nb-Ti / Cu artificially pinned hexagonal rod with Fe / Ta double barrier layer;

[0031] S7, closely arranging the Nb-Ti / Cu artificially pinned hexagonal rods with Fe / Ta double barrier layers in an oxygen-free copper tube to obtain artificially pinned NbTi / Cu composite rods, and subjecting them to multiple aging heat treatments;

[0032] S8. The artificially pinned NbTi / Cu composite rods that have undergone multiple aging heat treatments are drawn multiple times to obtain artificially pinned NbTi multi-core superconducting wires.

[0033] In the present invention, in S2, when the Fe barrier layer sleeve filled with Nb-Ti alloy powder is drawn to obtain the Fe barrier layer Nb-Ti core rod, the Fe barrier layer Nb-Ti core rod is processed into a Fe barrier layer Nb-Ti hexagonal rod with a side size of 3mm to 7mm by a drawing machine, and the Fe barrier layer Nb-Ti hexagonal rod is sawed to a fixed length.

[0034] In the present invention, in S4, when vacuum sealing the two ends of the Nb-Ti / Cu sheath of the Fe / Ta double barrier layer, firstly, copper covers are assembled at the two ends of the Nb-Ti / Cu sheath of the Fe / Ta double barrier layer, and then the Nb-Ti / Cu sheath and the copper cover of the Fe / Ta double barrier layer are vacuum sealed.

[0035] In the present invention, in S5, when the Nb-Ti / Cu package of the Fe / Ta double barrier layer that has been vacuum sealed is placed in a vacuum heat treatment furnace for thermal diffusion treatment, the thermal diffusion treatment temperature is 900°C to 1000°C, and the insulation time is 10h to 15h.

[0036] In the present invention, in S6, after the Nb-Ti / Cu artificial pinning alloy ingot with Fe / Ta double barrier layer is kept warm in a heating furnace, when hot extrusion and drawing are performed through an extruder, the keeping temperature of the heating furnace is 500°C to 800°C, and the keeping time is 1h to 5h.

[0037] In the present invention, the sizes of the Nb-Ti alloy powder, Fe barrier layer sleeve, Ta cylinder, oxygen-free copper sheath and oxygen-free copper tube obtained in S1 are Alloy powder, outer diameter Fe barrier sleeve with thickness of 2mm to 5mm, The inner diameter of the Ta cylinder Oxygen-free copper sheath and oxygen-free copper tube with thickness of 5mm to 10mm.

[0038] Embodiment 1,

[0039] Prepare Nb-Ti alloy powder, outer diameter Fe barrier sleeve with a thickness of 2 mm, The inner diameter of the Ta cylinder 5mm thick oxygen-free copper sheath and oxygen-free copper tube.

[0040] Will obtain Nb-Ti alloy powder is loaded into the outer diameter A Fe barrier layer sleeve with a thickness of 2 mm, and the Fe barrier layer sleeve filled with Nb-Ti alloy powder is drawn into a Fe barrier layer Nb-Ti hexagonal rod with a side size of 3 mm by a drawing machine, and the Fe barrier layer Nb-Ti hexagonal rod is sawed to a fixed length;

[0041] The Fe barrier layer Nb-Ti hexagonal rods with a side size of 3 mm are closely arranged on In the Ta cylinder;

[0042] The Nb-Ti hexagonal rod with a 3 mm Fe barrier layer The Ta cylinder is filled to an inner diameter of A Nb-Ti / Cu sheath of a Fe / Ta double barrier layer is obtained in an oxygen-free copper sheath, copper covers are assembled at both ends of the Nb-Ti / Cu sheath of the Fe / Ta double barrier layer, and then the Nb-Ti / Cu sheath of the Fe / Ta double barrier layer and the copper cover are vacuum-sealed;

[0043] The vacuum-sealed Fe / Ta double barrier layer Nb-Ti / Cu package is placed in a vacuum heat treatment furnace for thermal diffusion treatment. Through the thermal diffusion process, the Fe in the Fe / Ta double barrier layer Nb-Ti / Cu package diffuses into the Nb-Ti alloy to form an artificial pinning phase. The thermal diffusion treatment temperature is 900°C, and the holding time is 10h to obtain the Fe / Ta double barrier layer Nb-Ti / Cu artificial pinning alloy ingot;

[0044] After the Nb-Ti / Cu artificial pinning alloy ingot with Fe / Ta double barrier layer is kept warm in a heating furnace, it is hot extruded and drawn by an extruder to obtain a Nb-Ti / Cu artificial pinning hexagonal rod with Fe / Ta double barrier layer. The heating furnace is kept warm at 500℃ for 1h. The size of the single mandrel rod with Fe / Ta double barrier layer after extrusion is Will The Fe / Ta double barrier layer Nb-Ti / Cu artificial pinned single core rod is drawn into a Fe / Ta double barrier layer Nb-Ti / Cu artificial pinned hexagonal rod with a side size of 4.2 mm in a drawing machine.

[0045] The artificially pinned Nb-Ti / Cu hexagonal rods with Fe / Ta double barrier layers are closely arranged in an oxygen-free copper tube to obtain artificially pinned NbTi / Cu composite rods, which are then subjected to multiple aging heat treatments.

[0046] The artificially pinned NbTi / Cu composite rods that have undergone multiple aging heat treatments are obtained by multiple drawing passes. Artificially pinned NbTi multi-core superconducting wire.

[0047] Embodiment 2,

[0048] Prepare Nb-Ti alloy powder, outer diameter Fe barrier sleeve with a thickness of 3mm, The inner diameter of the Ta cylinder 8mm thick oxygen-free copper sheath and oxygen-free copper tube.

[0049] Will obtain Nb-Ti alloy powder is loaded into the outer diameter A Fe barrier layer sleeve with a thickness of 3 mm, and the Fe barrier layer sleeve filled with Nb-Ti alloy powder is drawn into a Fe barrier layer Nb-Ti hexagonal rod with a side size of 6 mm by a drawing machine, and the Fe barrier layer Nb-Ti hexagonal rod is sawed to a fixed length;

[0050] The Fe barrier layer Nb-Ti hexagonal rods with a side size of 6 mm are closely arranged on In the Ta cylinder;

[0051] The Nb-Ti hexagonal rod with a 6 mm Fe barrier layer The Ta cylinder is filled to an inner diameter of A Nb-Ti / Cu sheath of a Fe / Ta double barrier layer is obtained in an oxygen-free copper sheath, copper covers are assembled at both ends of the Nb-Ti / Cu sheath of the Fe / Ta double barrier layer, and then the Nb-Ti / Cu sheath of the Fe / Ta double barrier layer and the copper cover are vacuum-sealed;

[0052] The vacuum-sealed Fe / Ta double barrier layer Nb-Ti / Cu package is placed in a vacuum heat treatment furnace for thermal diffusion treatment. Through the thermal diffusion process, the Fe in the Fe / Ta double barrier layer Nb-Ti / Cu package diffuses into the Nb-Ti alloy to form an artificial pinning phase. The thermal diffusion treatment temperature is 950°C, and the holding time is 13h to obtain the Fe / Ta double barrier layer Nb-Ti / Cu artificial pinning alloy ingot;

[0053] After the Nb-Ti / Cu artificial pinning alloy ingot with Fe / Ta double barrier layer is kept warm in a heating furnace, it is hot extruded and drawn by an extruder to obtain a Nb-Ti / Cu artificial pinning hexagonal rod with Fe / Ta double barrier layer. The heating furnace is kept warm at 650℃ for 3h. The size of the single mandrel rod with Fe / Ta double barrier layer after extrusion is Will The single core rod of Nb-Ti / Cu artificial pinning with Fe / Ta double barrier layer is drawn into hexagonal rod of Nb-Ti / Cu artificial pinning with Fe / Ta double barrier layer with side size of 6.5mm in a drawing machine.

[0054] The artificially pinned Nb-Ti / Cu hexagonal rods with Fe / Ta double barrier layers are closely arranged in an oxygen-free copper tube to obtain artificially pinned NbTi / Cu composite rods, which are then subjected to multiple aging heat treatments.

[0055] The artificially pinned NbTi / Cu composite rods that have undergone multiple aging heat treatments are obtained by multiple drawing passes. Artificially pinned NbTi multi-core superconducting wire.

[0056] Embodiment 3,

[0057] Prepare Nb-Ti alloy powder, outer diameter Fe barrier sleeve with a thickness of 5 mm, The inner diameter of the Ta cylinder 5mm thick oxygen-free copper sheath and oxygen-free copper tube.

[0058] Will obtain Nb-Ti alloy powder is loaded into the outer diameter A Fe barrier layer sleeve with a thickness of 5 mm, and the Fe barrier layer sleeve filled with Nb-Ti alloy powder is drawn into a Fe barrier layer Nb-Ti hexagonal rod with a side size of 9 mm by a drawing machine, and the Fe barrier layer Nb-Ti hexagonal rod is sawed to a fixed length;

[0059] The Fe barrier layer Nb-Ti hexagonal rods with a side size of 9 mm are closely arranged on In the Ta cylinder;

[0060] The Nb-Ti hexagonal rod with a 9 mm Fe barrier layer The Ta cylinder is filled to an inner diameter of A Nb-Ti / Cu sheath of a Fe / Ta double barrier layer is obtained in an oxygen-free copper sheath, copper covers are assembled at both ends of the Nb-Ti / Cu sheath of the Fe / Ta double barrier layer, and then the Nb-Ti / Cu sheath of the Fe / Ta double barrier layer and the copper cover are vacuum-sealed;

[0061] The vacuum-sealed Fe / Ta double barrier layer Nb-Ti / Cu package is placed in a vacuum heat treatment furnace for thermal diffusion treatment. Through the thermal diffusion process, the Fe in the Fe / Ta double barrier layer Nb-Ti / Cu package diffuses into the Nb-Ti alloy to form an artificial pinning phase. The thermal diffusion treatment temperature is 1000°C, and the holding time is 15h to obtain the Fe / Ta double barrier layer Nb-Ti / Cu artificial pinning alloy ingot;

[0062] After the Nb-Ti / Cu artificial pinning alloy ingot with Fe / Ta double barrier layer is kept warm in a heating furnace, it is hot extruded and drawn by an extruder to obtain a Nb-Ti / Cu artificial pinning hexagonal rod with Fe / Ta double barrier layer. The heating furnace is kept warm at 800℃ for 5h. The size of the single mandrel rod with Fe / Ta double barrier layer after extrusion is Will The Fe / Ta double barrier layer Nb-Ti / Cu artificial pinned single core rod is drawn into a Fe / Ta double barrier layer Nb-Ti / Cu artificial pinned hexagonal rod with a side size of 8.8 mm in a drawing machine.

[0063] The artificially pinned Nb-Ti / Cu hexagonal rods with Fe / Ta double barrier layers are closely arranged in an oxygen-free copper tube to obtain artificially pinned NbTi / Cu composite rods, which are then subjected to multiple aging heat treatments.

[0064] The artificially pinned NbTi / Cu composite rods that have undergone multiple aging heat treatments are obtained by multiple drawing passes. Artificially pinned NbTi multi-core superconducting wire.

[0065] The maximum critical current density of traditional NbTi superconductors at 2T is about 5500A / mm 2 In the artificially pinned NbTi multi-core superconducting wire prepared in the above-mentioned Examples 1-3, the barrier layer materials are Ta and Fe. The Fe barrier layer sleeve is used as the inner lining material to form a diffusion reaction with the Nb-Ti alloy powder to generate an artificial pinning phase. The Ta tube is used as the outer lining material to prevent Fe from diffusing outwards. The matrix material is an oxygen-free copper tube. The critical current density at 2T can reach 8000A / mm 2 , the critical current density under low field has been greatly improved, opening up new space for the application of NbTi superconductors. The main role of Ta element in Nb-Ti superconductors is to increase the upper critical magnetic field, because the addition of Ta as a spin-orbit scatterer reduces the paramagnetic limitation. Ta element as a barrier layer can block the reaction of Fe and Cu on the one hand, and reduce the loss of superconducting wire on the other hand.

[0066] It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be regarded as exemplary and non-limiting from any point of view, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention, and any reference numerals in the claims should not be regarded as limiting the claims involved.

[0067] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing an artificially pinned NbTi multi-core superconducting wire, characterized in that: The following steps are involved: S1, obtaining Nb-Ti alloy powder, Fe barrier layer casing, Ta cylinder, oxygen-free copper sheath and oxygen-free copper tube; S2, loading the obtained Nb-Ti alloy powder into a Fe barrier layer sleeve, and drawing the Fe barrier layer sleeve loaded with the Nb-Ti alloy powder to obtain a Fe barrier layer Nb-Ti core rod; S3, closely arranging the Fe barrier layer Nb-Ti core rods in the Ta tube; S4, loading the Ta cylinder with the Fe barrier layer Nb-Ti core rod into the oxygen-free copper sheath to obtain the Fe / Ta double barrier layer Nb-Ti / Cu sheath, and vacuum-sealing the two ends of the Fe / Ta double barrier layer Nb-Ti / Cu sheath; S5, placing the Nb-Ti / Cu package of the Fe / Ta double barrier layer after vacuum sealing into a vacuum heat treatment furnace for thermal diffusion treatment to obtain a Nb-Ti / Cu artificial pinning alloy ingot of the Fe / Ta double barrier layer; S6, after keeping the Nb-Ti / Cu artificially pinned alloy ingot with Fe / Ta double barrier layer in a heating furnace, hot extrusion and drawing are performed by an extruder to obtain a Nb-Ti / Cu artificially pinned hexagonal rod with Fe / Ta double barrier layer; S7, closely arranging the Nb-Ti / Cu artificially pinned hexagonal rods with Fe / Ta double barrier layers in an oxygen-free copper tube to obtain artificially pinned NbTi / Cu composite rods, and subjecting them to multiple aging heat treatments; S8. The artificially pinned NbTi / Cu composite rods that have undergone multiple aging heat treatments are drawn multiple times to obtain artificially pinned NbTi multi-core superconducting wires.

2. The method for preparing an artificially pinned NbTi multi-core superconducting wire according to claim 1, characterized in that: In S2, when the Fe barrier layer sleeve filled with Nb-Ti alloy powder is drawn to obtain the Fe barrier layer Nb-Ti core rod, the Fe barrier layer Nb-Ti core rod is drawn by a drawing machine to be processed into a Fe barrier layer Nb-Ti hexagonal rod with a side size of 3mm to 7mm, and the Fe barrier layer Nb-Ti hexagonal rod is sawed to a fixed length.

3. The method for preparing an artificially pinned NbTi multi-core superconducting wire according to claim 1, characterized in that: In S4, when vacuum-sealing the two ends of the Nb-Ti / Cu sheath of the Fe / Ta double barrier layer, firstly, copper covers are installed at the two ends of the Nb-Ti / Cu sheath of the Fe / Ta double barrier layer, and then the Nb-Ti / Cu sheath and the copper cover of the Fe / Ta double barrier layer are vacuum-sealed.

4. The method for preparing an artificially pinned NbTi multi-core superconducting wire according to claim 1, characterized in that: In S5, when the Nb-Ti / Cu package of the Fe / Ta double barrier layer that has been vacuum sealed is placed in a vacuum heat treatment furnace for thermal diffusion treatment, the thermal diffusion treatment temperature is 900° C. to 1000° C., and the insulation time is 10 h to 15 h.

5. The method for preparing an artificially pinned NbTi multi-core superconducting wire according to claim 1, characterized in that: In the above S6, after the Nb-Ti / Cu artificial pinning alloy ingot with Fe / Ta double barrier layer is kept warm in a heating furnace, when it is hot extruded through an extruder, the keeping temperature of the heating furnace is 500°C to 800°C, and the keeping time is 1h to 5h.

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