A method for preparing a niobium tri-tin superconducting wire based on laser powder bed fusion

Abstract

The application belongs to the technical field of superconducting material processing, and discloses a preparation method of a niobium-tin superconducting wire based on laser powder bed melting. The application establishes a structural model of an integrated CuNbSn composite rod, and adopts laser powder bed melting technology to carry out partition powder laying according to the design structural model. The preparation method provided by the application realizes accurate arrangement of an Nb core and a Sn source and structural designability, significantly improves the core wire area of Sn reaction, optimizes the critical current density and magnetic hysteresis loss of the wire, simultaneously simplifies the preparation process, and can obtain the niobium-tin superconducting wire through one-time assembly and drawing, thereby improving the structural consistency and process stability of the wire. The critical current density of the niobium-tin superconducting wire prepared by the application is not less than 1164 A / mm 2 (12T), and the performance improvement effect is not less than 6% compared with that of a niobium-tin superconducting wire prepared by a traditional internal tin method.

Description

Technical Field

[0001] This invention belongs to the field of superconducting material processing technology, and relates to a method for preparing niobium-tin superconducting wire based on laser powder bed melting. Background Technology

[0002] Niobium-tritin (Nb3Sn) superconducting wires have been widely used in particle accelerators, high-field magnets, and nuclear fusion devices due to their excellent critical current density under high magnetic field conditions. Currently, the main methods for preparing Nb3Sn superconducting wires include the internal tin method, the bronze method, and the powder-coated tube method. Among these, the internal tin method, with its process compatibility and advantages in large-scale production, has become the preferred technology for the industrial-scale mass production of Nb3Sn superconducting wires. The existing process route for preparing Nb3Sn superconducting wires using the internal tin method is as follows: First, an Nb rod is inserted into a porous copper ingot prepared by drilling, and after extrusion, a CuNb composite rod is obtained. Then, a Sn core rod is inserted into a CuNb composite tube with a central hole, and sub-components are obtained through multiple drawing passes. Finally, the barrier layer and sub-components are assembled into an oxygen-free copper tube, and the finished superconducting wire is obtained through multiple drawing passes. Finally, heat treatment is used to react the components to generate the Nb3Sn superconducting phase.

[0003] However, the process of preparing Nb3Sn superconducting wires by the internal tin method requires multi-stage mechanical assembly and multi-pass drawing, which leads to the following defects in this technical route: (1) Structural constraints: The spatial arrangement of Nb core wires and Sn sources depends on the precision of mechanical processing, making it difficult to achieve complex irregular arrangement or gradient control of structural design; (2) Difficulty in controlling reaction uniformity: The diffusion path of Sn and the reaction process between Sn and Nb core wires cannot be precisely controlled, and the reaction uniformity of the two is difficult to guarantee, affecting the quality of subsequent Nb3Sn superconducting phase formation; (3) High processing difficulty and long cycle: The multi-stage assembly and drawing process is complex, the processing cycle is long, and the requirements for process stability are high; Traditional mechanical processing is difficult, and with the continuous increase in the demand for thinner wire cores, defects such as core wire breakage and overlap are prone to occur during processing. Therefore, it is of great significance to study a method for preparing niobium-tin superconducting wires with flexible wire structure design, controllable processing precision, and low processing difficulty. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for preparing niobium-tritin superconducting wires based on laser powder bed melting. This invention designs and establishes a structural model of an integrated CuNbSn composite rod. Using laser powder bed melting technology, powder is spread in sections according to the designed structural model, and CuNbSn composite rods are formed by layer-by-layer stacking using differentiated laser scanning parameters. Subsequently, hot isostatic pressing is performed for densification. Finally, niobium-tritin superconducting wires are obtained through a single assembly and drawing process. The preparation method provided by this invention achieves precise arrangement and structural designability of the Nb core and Sn source, significantly increases the core wire area for the Sn reaction, optimizes the critical current density and hysteresis loss of the wire, simplifies the preparation process, and improves the structural consistency and process stability of the wire. The critical current density of the niobium-tritin superconducting wire prepared by this invention is not less than 1164 A / mm². 2 (12T) The performance improvement of niobium-tin superconducting wire prepared by the traditional internal tin method is no less than 6%.

[0005] On one hand, the present invention provides a method for preparing niobium-tin superconducting wire based on laser powder bed melting, specifically including the following steps:

[0006] S1: The metal powder raw material is dried under vacuum at 100-120°C for 1-3 hours to remove adsorbed moisture. The metal powder raw material is Sn alloy powder, Cu metal powder, and Nb raw material powder, wherein the Nb raw material powder is Nb metal powder or NbTi metal powder.

[0007] Furthermore, the particle size of the Nb metal powder, Sn alloy powder, and NbTi metal powder is 15~50 μm, and the particle size of the Cu metal powder is 20~100 μm. The Ti content in the NbTi metal powder is 0.5~5 wt%, and the Sn content in the Sn alloy powder is 5~20 wt%.

[0008] S2: Construct a structural model of an integrated CuNbSn composite rod, which consists of a Cu matrix region, an Nb rod region, and a Sn source region.

[0009] Furthermore, in the structural model, the functional core wire region is composed of an Nb rod region and a Sn source region. The functional core wire region can be designed with conventional regular distribution, gradient distribution, axial spiral arrangement, and other arrangement methods.

[0010] Specifically, in the conventionally distributed functional core wire region, Nb rods or NbTi rods and Sn alloy rods are generally centrally symmetrically distributed. The functional core wire region is composed of Nb rods / NbTi rods and Sn alloy rods distributed in staggered layers from the outside to the inside, or composed of Nb rods / NbTi rods and Sn alloy rods distributed at intervals from the outside to the inside according to a certain regularity.

[0011] For example, both NbTi rods and Sn alloy rods are centrally symmetrically distributed. The second layer and the central layer of the functional core wire region from the outside to the inside are both composed of Sn alloy rods, while the remaining functional core wire layers are all composed of NbTi rods.

[0012] Specifically, the gradient-distributed functional core wire region consists of functional core wire layers with sequentially varying specifications from the outside to the inside. The functional core wire layers are composed of Nb rods / NbTi rods and Sn alloy rods, which are arranged alternately. The Nb rods and Sn source can be stacked in multiple layers with a continuous gradient change. The gradient change is either an increase or a decrease in gradient.

[0013] For example, both NbTi rods and Sn alloy rods are centrally symmetrically distributed. The functional core wire region consists of functional core wire layers with progressively larger specifications from the outside to the inside. When the functional core wire layers are composed of NbTi rods and Sn alloy rods, the NbTi rods and Sn alloy rods are arranged alternately. The largest functional core wire layer is composed of Sn alloy.

[0014] Specifically, the axially spirally arranged functional core wire region is composed of multiple stacked single-layer CuNbSn composite rods, and the functional core wire region is composed of Nb rods / NbTi rods and Sn alloy rods. The single-layer CuNbSn composite rods are stacked axially, and the positions of the Nb rods / NbTi rods and Sn alloy rods in the cross-sections of adjacent CuNbSn composite rods are rotated 1° to 10° axially to form an axially spiral structure.

[0015] For example, both Nb rods and Sn alloy rods are centrally symmetrically distributed. In the monolayer CuNbSn composite rod, the second and central layers of the functional core wire layers from the outside to the inside are composed of Sn alloy rods, while the remaining functional core wire layers are composed of Nb rods. The monolayer CuNbSn composite rods are stacked, and the positions of the Nb rods and Sn alloy rods in the cross-sections of adjacent CuNbSn composite rod layers are rotated 5° axially to form an axial helical structure.

[0016] S3: According to the design model, the powder is spread in sections by switching between multiple material bins, and then layered and formed by using differentiated laser scanning parameters. The Nb rod area is scanned by high laser energy density for complete melting, the Sn source area is scanned by low laser energy density micro-melting at a level below the threshold for continuous molten pool formation, and the Cu matrix area is scanned by medium energy density.

[0017] Furthermore, in the laser powder bed melting method, the thickness of the powder layer is 20~500μm, the protective atmosphere is high-purity argon gas with a flow rate of 10~50L / min, and the preheating temperature is 80~200℃.

[0018] Furthermore, the laser scanning parameters for the Nb rod region are: laser power 180~300W, scanning speed 600~1200mm / s, and scanning spacing 80~120μm; the laser scanning parameters for the Sn source region are: laser power 30~100W, scanning speed 800~2000mm / s, and scanning spacing 100~150μm; and the laser scanning parameters for the Cu matrix region are: laser power 120~250W, scanning speed 700~1500mm / s, and scanning spacing 80~130μm.

[0019] S4: The formed CuNbSn composite rod is subjected to hot isostatic pressing for densification. The hot isostatic pressing temperature is 300~600℃, the pressure is 100~400MPa, and the holding time is 1~5h.

[0020] S5: The hot isostatically pressed CuNbSn composite rod is sequentially loaded into the barrier layer and the stabilizing matrix. After assembly, it is subjected to multi-pass stretching to obtain niobium-tin wire.

[0021] Furthermore, the barrier layer is made of Ta, the stabilizing substrate is made of oxygen-free copper or CuTi alloy, the outer diameter of the stabilizing substrate tube is Φ20~Φ80mm, the inner diameter is Φ10~Φ60mm, the outer diameter of the barrier layer is 1mm smaller than the inner diameter of the stabilizing substrate tube, and the thickness is 1~5mm. The stretching speed of the multi-pass stretching is 5~50m / min, and the processing rate per pass is 5%~30%.

[0022] On the other hand, the present invention claims protection for a niobium-tin superconducting wire, which is prepared by the above-described method for preparing niobium-tin superconducting wire based on laser powder bed melting.

[0023] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects or advantages:

[0024] (1) This invention provides a method for preparing niobium-Ti-Sn superconducting wires based on laser powder bed melting. The method directly constructs an integrated Cu-Nb / NbTi-Sn composite rod using laser powder bed melting, achieving spatially controllable arrangement and precise forming of the Nb rod region and Sn source region. It has the following advantages: First, it offers high freedom in structural design, breaking through the limitations of traditional assembly processes in structural design and arrangement accuracy. It allows for the design of various complex wire structures according to magnetic field distribution requirements, optimizing the critical current density and hysteresis loss of the wire. The preparation method provided by this invention significantly increases the core wire area for the Sn reaction, and the critical current density of the prepared niobium-Ti-Sn superconducting wire is not less than 1164 A / mm². 2(12T) Compared with the traditional internal tin method, the performance improvement of niobium tritin superconducting wire is no less than 6%; secondly, through the integrated molding of Cu-Nb / NbTi-Sn composite rods and hot isostatic pressing densification treatment, internal defects are effectively reduced, the uniformity of the structure is improved, the consistency of wire structure and process stability are improved, and the preparation process is simplified. Only one assembly and drawing process is required to obtain the finished niobium tritin superconducting wire, which significantly shortens the processing cycle; thirdly, through digital precise control of the contact area and interface morphology of Nb core and Sn source, it is conducive to the uniform diffusion of Sn in subsequent heat treatment, ensuring the uniform and sufficient generation of Nb3Sn superconducting phase.

[0025] (2) This invention uses differentiated scanning parameters to control the energy input of the Cu matrix region, Nb rod region, and Sn source region, ensuring the stable formation of each region and constructing a controllable Nb-Sn spatial structure. This prevents problems such as uncontrollable Sn melting and Cu overmelting caused by using parameters from traditional laser powder bed melting technology or using the same parameters for the three materials, which can lead to problems due to the different melting behaviors of Nb / NbTi, Cu, and Sn. This invention performs hot isostatic pressing densification on the formed CuNbSn composite rod to improve density and interfacial bonding strength, providing a deformation basis for subsequent large deformation extrusion and drawing processes. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a flowchart of a method for preparing niobium-tin superconducting wires based on laser powder bed melting.

[0028] Figure 2 The figure shows a cross-sectional view of a niobium-tin triplex superconducting wire with a regular distribution between the Nb rod region and the Sn source region. The reference numerals are as follows: 1. Stabilizing matrix; 2. Barrier layer; 3. Cu matrix region; 4-1. NbTi rod; 5. Sn alloy rod.

[0029] Figure 3 This is a cross-sectional view of a niobium-tin superconducting wire with a gradient distribution between the Nb rod region and the Sn source region.

[0030] Figure 4 This is a cross-sectional view of a single-layer CuNbSn composite rod in which the Nb rod region and the Sn source region are spirally arranged. The reference numerals are as follows: 1. Stabilizing matrix; 2. Barrier layer; 3. Cu matrix region; 4-2. Nb rod; 5. Sn alloy rod. Detailed Implementation

[0031] The technical solution of the present invention will be described below with reference to embodiments. However, the present invention is not limited to the following embodiments. Unless otherwise specified, the experimental methods and detection methods described in each embodiment are conventional methods; unless otherwise specified, the reagents and materials can be purchased commercially. Unless otherwise specified, the percentages in the following embodiments refer to mass percentages.

[0032] The purity of both Nb metal powder and Cu metal powder is ≥99.9%.

[0033] The process flow diagram for preparing niobium-tin superconducting wires based on laser powder bed melting is as follows: Figure 1 As shown, the specific steps include the following:

[0034] S1: The metal powder raw material is dried under vacuum at 100-120°C for 1-3 hours to remove adsorbed moisture. The metal powder raw material is Sn alloy powder, Cu metal powder, and Nb raw material powder, wherein the Nb raw material powder is Nb metal powder or NbTi metal powder.

[0035] Furthermore, the particle size of the Nb metal powder, Sn alloy powder, and NbTi metal powder is 15~50 μm, and the particle size of the Cu metal powder is 20~100 μm. The Ti content in the NbTi metal powder is 0.5~5 wt%, and the Sn content in the Sn alloy powder is 5~20 wt%.

[0036] S2: Design a structural model of an integrated CuNbSn composite rod, which consists of a Cu matrix region, an Nb rod region, and a Sn source region.

[0037] Furthermore, the Nb rod region and Sn source region in the structural model can be designed with conventional regular distribution, gradient distribution, axial spiral arrangement, or other arrangement methods.

[0038] Specifically, in the conventionally distributed CuNbSn composite rod, the Nb rods or NbTi rods and Sn alloy rods are generally centrally symmetrically distributed, and the functional core wire region in the CuNbSn composite rod is composed of Nb rods / NbTi rods and Sn alloy rods that are staggered from the outside to the inside or distributed at regular intervals.

[0039] Specifically, the gradient-distributed CuNbSn composite rod consists of functional core wire layers with progressively varying specifications from the outside to the inside. The functional core wire region is composed of Nb rods / NbTi rods and Sn alloy rods. The Nb rods and Sn source can be stacked in multiple layers with continuous gradient changes.

[0040] Specifically, the axially spirally arranged CuNbSn composite rods are composed of multiple stacked single-layer CuNbSn composite rods, and the functional core wire region is composed of Nb rods / NbTi rods and Sn alloy rods. The single-layer CuNbSn composite rods are stacked axially, and the positions of the Nb rods / NbTi rods and Sn alloy rods in the cross-sections of adjacent CuNbSn composite rods are rotated 1° to 10° axially to form an axially spiral structure.

[0041] S3: According to the design model, the powder is spread in sections by switching between multiple material bins, and then layered and formed by using differentiated laser scanning parameters. The Nb rod area is scanned by high laser energy density for complete melting, the Sn source area is scanned by low laser energy density micro-melting at a level below the threshold for continuous molten pool formation, and the Cu matrix area is scanned by medium energy density.

[0042] Furthermore, in the laser powder bed melting method, the thickness of the powder layer is 20~500μm, the protective atmosphere is high-purity argon gas with a flow rate of 10~50L / min, and the preheating temperature is 80~200℃.

[0043] Furthermore, the laser scanning parameters for the Nb rod region are: laser power 180~300W, scanning speed 600~1200mm / s, and scanning spacing 80~120μm; the laser scanning parameters for the Sn source region are: laser power 30~100W, scanning speed 800~2000mm / s, and scanning spacing 100~150μm; and the laser scanning parameters for the Cu matrix region are: laser power 120~250W, scanning speed 700~1500mm / s, and scanning spacing 80~130μm.

[0044] S4: The formed CuNbSn composite rod is subjected to hot isostatic pressing for densification. The hot isostatic pressing temperature is 300~600℃, the pressure is 100~400MPa, and the holding time is 1~5h.

[0045] S5: The hot isostatically pressed CuNbSn composite rod is sequentially loaded into the barrier layer and the stabilizing matrix. After assembly, it is subjected to multi-pass stretching to obtain niobium-tin wire.

[0046] Furthermore, the barrier layer is made of Ta, the stabilizing substrate is made of oxygen-free copper or CuTi alloy, the outer diameter of the stabilizing substrate tube is Φ20~Φ80mm, the inner diameter is Φ10~Φ60mm, the outer diameter of the barrier layer is 1mm smaller than the inner diameter of the stabilizing substrate tube, and the thickness is 1~5mm. The stretching speed of the multi-pass stretching is 5~50m / min, and the processing rate per pass is 5%~30%.

[0047] Example 1

[0048] This embodiment provides a method for preparing niobium-tin superconducting wires based on laser powder bed melting, specifically including the following steps:

[0049] S1: NbTi metal powder with a Ti content of 0.5wt% and a particle size of 50μm, Sn10Cu alloy powder with a particle size of 50μm, and Cu metal powder with a particle size of 100μm are dried under vacuum at 100℃ for 1h to remove adsorbed moisture.

[0050] S2: Design and establish a structural model of an integrated CuNbSn composite rod with a conventional and regular distribution of the Nb rod region and the Sn source region. In this structural model, both the NbTi rod and the Sn10Cu rod are centrally symmetrically distributed. The functional core wire layers in the CuNbSn composite rod, from the outside to the inside, are: NbTi rod, Sn10Cu rod, NbTi rod, NbTi rod, NbTi rod, and the central Sn10Cu rod. The diameter of the CuNbSn composite rod is Φ30mm, the diameter of the NbTi rod is Φ2mm, the diameter of the central Sn10Cu rod is Φ4.5mm, and the diameter of the Sn10Cu rod is Φ0.82mm.

[0051] S3: Following the design model, powder is spread in zones using multi-bin switching, and then layered using differentiated laser scanning parameters. The powder layer thickness is 150μm. The protective atmosphere is high-purity argon gas with a flow rate of 50L / min and a preheating temperature of 80℃. The laser scanning parameters for the Nb rod region are: laser power 250W, scanning speed 800mm / s, and scanning spacing 80μm; the laser scanning parameters for the Sn source region are: laser power 100W, scanning speed 800mm / s, and scanning spacing 100μm; the laser scanning parameters for the Cu matrix region are: laser power 200W, scanning speed 700mm / s, and scanning spacing 100μm.

[0052] S4: The formed CuNbSn composite rod is subjected to hot isostatic pressing for densification. The hot isostatic pressing temperature is 350℃, the pressure is 400MPa, and the holding time is 5h.

[0053] S5: The hot isostatically pressed CuNbSn composite rod is sequentially loaded into the Ta barrier layer and the stabilizing matrix. Figure 1 The stabilizing substrate is a CuTi alloy tube with an outer diameter of Φ42mm and an inner diameter of Φ31.5mm (Ti element mass percentage is 1.5wt%). The barrier layer has an outer diameter 1mm smaller than the inner diameter of the stabilizing substrate tube and a thickness of 1mm. After assembly, it undergoes multi-pass stretching forming at a stretching speed of 50m / min and a processing rate of 20% per pass to obtain a niobium-tin superconducting wire with a diameter of Φ0.74mm.

[0054] The obtained niobium-tin superconducting wire was subjected to heat treatment and performance testing. The heat treatment regime was 575℃ / 100h + 650℃ / 100h. After stretching and heat treatment, the core wire showed good uniformity, and the measured critical current density was 1164 A / mm². 2 (12T) shows an improvement of approximately 6% in performance compared to niobium-tin superconducting wires prepared by the traditional internal tin method.

[0055] Example 2

[0056] This embodiment provides a method for preparing niobium-tin superconducting wires based on laser powder bed melting, specifically including the following steps:

[0057] S1: NbTi metal powder with a Ti content of 1.5wt% and a particle size of 20μm, Sn5Cu alloy powder with a particle size of 20μm, and Cu metal powder with a particle size of 40μm were dried under vacuum at 120℃ for 2h to remove adsorbed moisture.

[0058] S2: Design and establish a structural model of an integrated CuNbSn composite rod in which the Nb rod region and the Sn source region are distributed in a gradient manner. In this structural model, both the NbTi rod and the Sn5Cu rod are centrally symmetrically distributed. The functional core wire layers in the CuNbSn composite rod, from the outside to the inside, are: small-size functional core wire layer, medium-size functional core wire layer, large-size functional core wire layer, and central Sn5Cu rod. The small-size functional core wire layer is composed of small-size NbTi rod and small-size Sn5Cu rod arranged alternately. The medium-size functional core wire layer is composed of medium-size NbTi rod and medium-size Sn5Cu rod arranged alternately. The large-size functional core wire layer is composed of large-size NbTi rod. The diameter of the CuNbSn composite rod is Φ40mm, the diameter of the small-sized NbTi rod is Φ3mm, the diameter of the medium-sized NbTi rod is Φ4mm, the diameter of the large-sized NbTi rod is Φ5mm, the diameter of the small-sized Sn5Cu rod is Φ1.2mm, the diameter of the medium-sized Sn5Cu rod is Φ1.6mm, and the diameter of the central Sn5Cu rod is Φ6.5mm.

[0059] S3: Following the design model, powder is spread in zones using multi-bin switching, and then layered using differentiated laser scanning parameters. The powder layer thickness is 90μm. The protective atmosphere is high-purity argon gas with a flow rate of 20L / min and a preheating temperature of 150℃. The laser scanning parameters for the Nb rod region are: laser power 230W, scanning speed 1000mm / s, and scanning spacing 100μm; the laser scanning parameters for the Sn source region are: laser power 30W, scanning speed 1800mm / s, and scanning spacing 130μm; the laser scanning parameters for the Cu matrix region are: laser power 120W, scanning speed 1500mm / s, and scanning spacing 130μm.

[0060] S4: The formed CuNbSn composite rod is subjected to hot isostatic pressing for densification. The hot isostatic pressing temperature is 400℃, the pressure is 100MPa, and the holding time is 3h.

[0061] S5: The hot isostatically pressed CuNbSn composite rod is sequentially loaded into the Ta barrier layer and the stabilizing matrix. Figure 3 The stabilizing substrate is a CuTi alloy tube with an outer diameter of Φ51mm and an inner diameter of Φ41mm (Ti element accounts for 1.5wt% by mass). The barrier layer has an outer diameter 1mm smaller than the inner diameter of the stabilizing substrate tube and a thickness of 3mm. After assembly, it undergoes multi-pass stretching forming at a stretching speed of 35m / min and a processing rate of 15% per pass to obtain a niobium-tin wire with a diameter of Φ0.91mm.

[0062] The obtained niobium-tin-niobium wire was subjected to heat treatment and performance testing. The heat treatment regime was 575℃ / 100h + 650℃ / 100h. The results showed that the core wire area reacting with Sn in the superconducting wire increased by about 6%, and the measured critical current density was 1178 A / mm². 2 (12T) Compared with the traditional niobium-tin superconducting wire prepared by the internal tin method, the performance is improved by about 8%. In this embodiment, the Nb rod region and the Sn source region are distributed in a gradient. The gradient structure compensates for the difference in diffusion path during the reaction of the inner and outer rings, making the reaction more complete and uniform. On the other hand, it improves the internal stress distribution of the wire, significantly improving the processing stability and consistency of the wire.

[0063] Example 3

[0064] This embodiment provides a method for preparing niobium-tin superconducting wires based on laser powder bed melting, specifically including the following steps:

[0065] S1: Nb metal powder with a purity ≥99.9% and a particle size of 15μm, Sn20Cu alloy powder with a particle size of 15μm, and Cu metal powder with a particle size of 50μm are dried under vacuum at 100℃ for 3h to remove adsorbed moisture.

[0066] S2: Design and establish a structural model of an integrated CuNbSn composite rod in which the Nb rod region and the Sn source region are arranged in an axial spiral. In this structural model, both the Nb rod and the Sn20Cu rod are centrally symmetrically distributed. The functional core wire layers in the CuNbSn composite rod, from the outside to the inside, are: Nb rod, Sn20Cu rod, Nb rod, Nb rod, and central Sn20Cu rod. The diameter of the CuNbSn composite rod is Φ46mm, the diameter of the Nb rod is Φ4mm, the diameter of the central Sn20Cu rod is Φ8mm, and the diameter of the Sn20Cu rod is Φ1.5mm.

[0067] S3: Following the design model, powder is spread in zones using multi-bucket switching, and then layered using differentiated laser scanning parameters. The powder layer thickness is 500μm, protected by high-purity argon gas at a flow rate of 10L / min, and preheated at 200℃. The cross-sectional structure of the first powder layer is as follows. Figure 4 As shown, the cross-sectional structure of the second powder layer is the same as that of the first layer. The Nb rods and Sn10Cu rods in each layer are rotated 5° axially, accumulating to form an axial helical structure. The laser scanning parameters for the Nb rod region are: laser power 180W, scanning speed 600mm / s, and scanning spacing 120μm; the laser scanning parameters for the Sn source region are: laser power 60W, scanning speed 2000mm / s, and scanning spacing 150μm; and the laser scanning parameters for the Cu matrix region are: laser power 250W, scanning speed 1000mm / s, and scanning spacing 80μm.

[0068] S4: The formed CuNbSn composite rod is subjected to hot isostatic pressing for densification. The hot isostatic pressing temperature is 600℃, the pressure is 250MPa, and the holding time is 1h.

[0069] S5: The hot isostatically pressed CuNbSn composite rod is sequentially loaded into a Ta barrier layer and a stabilizing matrix. The stabilizing matrix is ​​a CuTi alloy tube with an outer diameter of Φ60mm and an inner diameter of Φ47mm (Ti element mass percentage is 1.5wt%). The outer diameter of the barrier layer is 1mm smaller than the inner diameter of the stabilizing matrix tube, and the thickness is 5mm. After assembly, multiple stretching is performed at a stretching speed of 5m / min, with a processing rate of 5% per pass, to obtain a niobium-tritin superconducting wire with a diameter of Φ1.2mm.

[0070] The obtained niobium-tin superconducting wire was subjected to heat treatment and performance testing. The heat treatment regime was 575℃ / 100h + 650℃ / 100h, and the measured hysteresis loss was 235mJ / cm. 3 (4.2K, 3T), the hysteresis loss of Nb3Sn superconducting wires prepared by the internal tin method using existing technology is typically 400~600 mJ / cm. 3 The niobium-tin superconducting wire prepared by the method of this invention has significantly lower losses compared to existing technologies. Furthermore, the area of ​​the core wire reacting with Sn in the superconducting wire prepared by this invention is increased by approximately 8%, and the measured critical current density is 1201 A / mm². 2 (12T) Compared with the traditional niobium-tin superconducting wire prepared by the internal tin method, the performance is improved by about 10%. The spatial helical structure in this embodiment improves the effective reaction of Sn, reduces losses, and greatly improves the stability of long-line processing through rearrangement in axial and radial space.

[0071] Comparative Example 1

[0072] The preparation method of the niobium-tin superconducting wire in this comparative example is the same as that in Example 1, except that: the laser scanning parameters for the Nb rod region are: laser power 350W, scanning speed 500mm / s; the laser scanning parameters for the Sn source region are: laser power 150W, scanning speed 500mm / s; and the laser scanning parameters for the Cu matrix region are: laser power 300W, scanning speed 500mm / s. Since the melting point of Sn is much lower than that of Nb and Cu, a low laser energy density below the continuous melt pool formation threshold is required for micro-melting scanning. In this comparative example, a higher power and slower scanning speed are used, causing Sn to overheat and melt, resulting in uncontrolled and violent flow, volatilization, and splashing, making it difficult to form the desired precision structure. The scanning parameters used in the Cu matrix region cause overmelting, leading to coarsening of the microstructure, introduction of defects such as porosity, and reduced density of the Cu matrix. This affects key parameters of the superconducting wire, such as the residual resistivity and critical current density, and is also detrimental to subsequent multi-pass processing. Similarly, excessive energy input in the Nb rod region leads to overmelting and defects such as porosity, making it prone to forming crack initiation points during subsequent molding. The niobium-tin superconducting wire prepared using the above parameters frequently breaks in the Φ3.12mm specification, making it difficult to produce long wires. Furthermore, the actual arrangement structure deviates significantly from the intended wire structure, resulting in a substantial decrease in wire performance.

[0073] Comparative Example 2

[0074] The preparation method of the niobium-tin superconducting wire in this comparative example is the same as that in Example 1, except that the hot isostatic pressing method of S5 is replaced with a hot pressing process. The formed CuNbSn composite rod is subjected to vacuum hot pressing, with pressure applied along the uniaxial direction at 300 MPa and a temperature of 350°C. After holding at this temperature and pressure for 3 hours, it is cooled in the furnace. All other processes are exactly the same as in Example 1. The radial density of the composite rod after hot pressing is insufficient. Due to the anisotropy of the densification process caused by the unidirectional axial pressure, radial porosity is difficult to effectively eliminate, resulting in an overall density far lower than that of the hot isostatic pressing process. This easily leads to cracks in subsequent processing, affecting wire performance and long-line processing. Furthermore, under unidirectional high pressure and high temperature, the Sn region undergoes severe unidirectional deformation, resulting in extrusion, flow, and other behaviors that seriously affect the wire structure, causing problems such as uneven core wire distribution, overlap, and uneven core wire deformation, which affect the formation and reaction uniformity of the subsequent niobium-tin phase.

[0075] The resulting niobium-tin superconducting wire was difficult to process into long wires, and the number of wire breaks increased from 3 in Example 1 to 16. The measured critical current density was 673 A / mm². 2 (12T).

[0076] As described above, the basic principles, main features, and advantages of the present invention have been well described. The above embodiments and specifications are merely descriptions of preferred embodiments of the present invention, and the present invention is not limited to the above embodiments. Various changes and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit and scope of the present invention should fall within the protection scope defined by the present invention.

Claims

1. A method for preparing niobium-tin superconducting wire based on laser powder bed melting, characterized in that, include: Construct a structural model of an integrated CuNbSn composite rod; Based on the structural model, the powder is spread in sections, and differentiated laser scanning is performed using the laser powder bed melting method to obtain the formed CuNbSn composite rod. The formed CuNbSn composite rod is hot isostatically pressed and then inserted into a barrier layer and a stabilizing matrix, and then stretched in multiple passes to obtain the niobium-tin superconducting wire. The CuNbSn composite rod consists of an Nb rod region, a Sn source region, and a Cu matrix region. In the differentiated laser scanning forming process, the Nb rod region is fully melted by high laser energy density scanning, the Sn source region is micro-melted by low laser energy density scanning, and the Cu matrix region is scanned by medium energy density. The laser power of the high laser energy density complete melting scan is 180~300W, the scanning speed is 600~1200mm / s, and the scanning spacing is 80~120μm; The laser power of the low laser energy density micro-fusion scanning is 30~100W, the scanning speed is 800~2000mm / s, and the scanning spacing is 100~150μm; The laser power for the medium energy density scanning is 120~250W, the scanning speed is 700~1500mm / s, and the scanning spacing is 80~130μm; Before the partitioned powder spreading, the metal powder raw material is dried in vacuum at 100~120℃ for 1~3 hours; The metal powder raw material is composed of Sn alloy powder, Cu metal powder and Nb raw material powder; The Nb raw material powder is Nb metal powder or NbTi metal powder; In the structural model of the CuNbSn composite rod, the functional core wire region is composed of the Nb rod region and the Sn source region, and the functional core wire region is designed to be distributed in a conventional and regular manner. The conventionally distributed functional core wire region is composed of Nb rods / NbTi rods and Sn alloy rods distributed in staggered layers from the outside to the inside, or composed of Nb rods / NbTi rods and Sn alloy rods distributed at regular intervals from the outside to the inside.

2. The method for preparing niobium-tin superconducting wire based on laser powder bed melting according to claim 1, characterized in that, Alternatively, the functional core wire region may be designed with a gradient distribution; The gradient-distributed functional core wire region is composed of functional core wire layers with sequentially varying specifications from the outside to the inside. When the functional core wire layers are composed of Nb rods / NbTi rods and Sn alloy rods, the Nb rods / NbTi rods and Sn alloy rods are arranged alternately. The gradient change is either an increase in gradient or a decrease in gradient.

3. The method for preparing niobium-tin superconducting wire based on laser powder bed melting according to claim 1, characterized in that, Alternatively, the functional core wire region may be designed with an axial spiral arrangement; The CuNbSn composite rod is composed of multiple single-layer CuNbSn composite rods stacked together. The positions of the Nb rod / NbTi rod and Sn alloy rod in the cross section of two adjacent CuNbSn composite rods are rotated 1°~10° along the axial direction, accumulating to form an axial spiral structure.

4. The method for preparing niobium-tin superconducting wire based on laser powder bed melting according to claim 1, characterized in that, The thickness of the powder layer in the partitioned powder spreading is 20~500μm; The partitioned powder spreading is carried out under argon protection, with an argon flow rate of 10~50L / min and a preheating temperature of 80~200℃.

5. The method for preparing niobium-tin superconducting wire based on laser powder bed melting according to claim 1, characterized in that, The particle size of the Nb metal powder, NbTi metal powder and Sn alloy powder is 15~50μm, and the particle size of the Cu metal powder is 20~100μm. The NbTi metal powder contains 0.5-5 wt% Ti, and the Sn alloy powder contains 5-20 wt% Sn.

6. The method for preparing niobium-tin superconducting wire based on laser powder bed melting according to claim 1, characterized in that, The hot isostatic pressing process is performed at a temperature of 300~600℃, a pressure of 100~400MPa, and a holding time of 1~5h.

7. The method for preparing niobium-tin superconducting wire based on laser powder bed melting according to claim 1, characterized in that, The barrier layer is made of Ta, and the stabilizing substrate is made of oxygen-free copper or CuTi alloy. The outer diameter of the stable substrate is Φ20~Φ80mm, and the inner diameter is Φ10~Φ60mm.

8. The method for preparing niobium-tin superconducting wire based on laser powder bed melting according to claim 1, characterized in that, The stretching speed of the multi-pass stretching is 5~50m / min, and the processing rate of each pass is 5%~30%.

9. A niobium-tin superconducting wire, characterized in that, It is prepared by the method for preparing niobium-tin superconducting wire based on laser powder bed melting as described in any one of claims 1 to 8.

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