A WIC superconducting wire and a method of manufacturing the same

Abstract

This invention belongs to the field of superconducting wire technology and relates to a WIC superconducting wire and its preparation method. The invention provides a method for preparing a WIC superconducting wire, comprising: selecting a superconducting round wire and an aluminum groove wire matching the size of the superconducting round wire; threading the superconducting round wire into the groove of the aluminum groove wire; filling the groove between the aluminum groove wire and the superconducting round wire with a metal powder mixture; and finally obtaining the aluminum groove wire WIC superconducting wire through induction heating and hot-dip tin plating; wherein the metal powder mixture is composed of tin powder, aluminum powder, and titanium powder. This invention adds a metal powder mixture at the junction between the aluminum groove wire and the superconducting round wire, aiming to solve the technical problems of low RRR value and insufficient bonding strength in aluminum-based WIC superconducting wires.

Description

Technical Field

[0001] This invention belongs to the field of superconducting wire technology and relates to a WIC superconducting wire and its preparation method. Background Technology

[0002] Superconducting wires are the core carriers for the industrial application of superconducting technology, playing a crucial role in many high-end fields due to their excellent properties such as zero resistance and diamagnetism. Among them, aluminum channel wire (WIC) superconducting wire, as an important type of composite superconducting wire, is made by replacing traditional copper channel wire with aluminum channel wire. This type of wire not only fully utilizes the zero-resistance characteristics of superconducting materials to achieve efficient and lossless current transmission, but also, relying on its unique structural design and material composition, possesses advantages such as high strength, lightweight, and good stability. Therefore, it has irreplaceable application value in the field of magnetic levitation transportation, is a core material for the manufacture of superconducting magnets, and directly determines the efficient levitation and stable propulsion performance of maglev trains.

[0003] Currently, the conventional preparation method for aluminum channel wire WIC superconducting wires involves embedding a superconducting round wire into the groove of an aluminum channel wire, performing argon arc welding under argon protection, and then grinding and cleaning the weld joints after welding; or directly performing online soldering. Because aluminum typically has a much lower RRR value than copper, resulting in higher low-temperature resistance and poor shunting and protection effects, the uniformity of the interface between the copper-stabilized matrix of the core material and the aluminum channel wire is difficult to guarantee in traditional processes. These factors contribute to the low RRR value and insufficient bonding strength of the aluminum channel wire WIC superconducting wires. Therefore, developing a preparation technology for aluminum channel wire WIC superconducting wires with high stability, good product consistency, tight interface bonding, and excellent superconducting performance, optimizing the filling material system and key process parameters, and overcoming the inherent defects of conventional welding processes, is a key technical challenge for promoting the large-scale application of aluminum channel wire WIC superconducting wires in high-end fields such as maglev transportation. This invention addresses the shortcomings of the existing technology by proposing a novel preparation method for aluminum channel wire WIC superconducting wires, aiming to fundamentally improve the overall performance of the wire and meet the application needs of high-end fields. Summary of the Invention

[0004] The purpose of this invention is to solve the technical problems of low RRR value and insufficient bonding strength in aluminum-based WIC superconducting wires. To address this, this invention adds a metal powder mixture at the junction between the aluminum channel wire and the superconducting circular wire, providing a WIC superconducting wire and its preparation method to meet this need in the art.

[0005] On one hand, the present invention provides a method for preparing WIC superconducting wire, which includes: selecting a superconducting round wire and an aluminum groove wire with a size matching the superconducting round wire, and threading the superconducting round wire into the groove of the aluminum groove wire;

[0006] A metal powder mixture is filled into the groove between the aluminum channel wire and the superconducting round wire, wrapped with tin foil, and then subjected to induction heating and hot-dip tin plating to obtain the aluminum channel wire WIC superconducting wire.

[0007] The metal powder mixture is composed of tin powder, aluminum powder and titanium powder.

[0008] Furthermore, in the preparation method of WIC superconducting wire provided by the present invention, the volume ratio of tin powder, aluminum powder and titanium powder is 60:30~40:3~8.

[0009] Furthermore, in the preparation method of WIC superconducting wire provided by the present invention, the average particle size of copper powder, silicon powder or chromium powder is not higher than 500 nm.

[0010] Furthermore, in the preparation method of WIC superconducting wire provided by the present invention, the wire is immediately placed in water at -5~0℃ for water cooling after hot tin plating.

[0011] Furthermore, in the method for preparing WIC superconducting wire provided by the present invention, the superconducting round wire is an NbTi / Cu superconducting round wire.

[0012] Furthermore, in the method for preparing WIC superconducting wires provided by the present invention, the specifications of the superconducting round wire are Φ1.2mm~Φ1.8mm.

[0013] Furthermore, in the method for preparing WIC superconducting wire provided by the present invention, the induction heating temperature is 300~380℃.

[0014] Furthermore, in the method for preparing WIC superconducting wire provided by the present invention, the number of layers of tin foil is 3 to 5, and the thickness of the tin foil is not higher than 0.5 mm.

[0015] Furthermore, in the method for preparing WIC superconducting wire provided by the present invention, the diameter of the groove in the aluminum groove wire is 0.01~0.05mm higher than the diameter of the superconducting circular wire.

[0016] On the other hand, the present invention relates to a WIC superconducting wire, which is specifically prepared using the aforementioned method for preparing WIC superconducting wire.

[0017] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects or advantages:

[0018] This invention effectively solves the problems of poor current shunting performance and insufficient bonding strength in traditional aluminum channel wire WIC superconducting wires caused by low RRR values ​​of the aluminum matrix and uneven interface bonding, by filling the groove between the aluminum channel wire and the superconducting circular wire with a specific composition of metal powder mixture (tin powder, aluminum powder, and titanium powder) and achieving interfacial metallurgical bonding during induction heating and hot-dip tin plating. Tin powder, as the main filler metal, melts and wets the interface during heating, promoting welding between the aluminum channel wire and the superconducting circular wire; the addition of aluminum powder helps to form good compatibility and bonding with the aluminum channel wire matrix, reducing interfacial thermal resistance; titanium powder may enhance the stability and mechanical strength of the interfacial structure through the formation of trace intermetallic compounds or solid solution strengthening effects. Furthermore, by controlling the powder particle size and ratio, the density and uniformity of the filler layer are further optimized, which is beneficial to improving thermal and electrical conductivity. The WIC superconducting wire prepared using the method of this invention exhibits a significantly improved RRR value (reaching 152-155) measured at 273K / 10K, which is more than 30% higher than the traditional single tin powder filling scheme (RRR value of 96-113). This indicates a significant reduction in low-temperature resistance and enhanced current shunting and protection effects. Furthermore, eddy current testing revealed no obvious interface defects, indicating a tight bond between the aluminum groove wire and the superconducting circular wire, free from incomplete soldering, and possessing excellent interfacial bonding and structural integrity. Detailed Implementation

[0019] 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 and detection methods described in each embodiment are conventional methods; the reagents and materials described are commercially available unless otherwise specified. Unless otherwise specified, all percentages in the following embodiments refer to mass percentages. Unless otherwise specified, all proportions in the following embodiments refer to mass ratios.

[0020] Example 1

[0021] This embodiment provides a process for preparing WIC superconducting wires.

[0022] A 36-core NbTi / Cu superconducting round wire with a diameter of 1.2mm was selected. A 4.0mm aluminum rod was selected, flattened by rolling, and then rectangularly shaped using a die. It was then rolled using a set of rectangular concave wheels and a semi-circular cam to form a 1.23mm groove. Finally, it passed through a forming die to ensure the aluminum groove wire had a smooth surface with a consistent inner and outer radius of 0.3mm. Tin powder, aluminum powder, and titanium powder were weighed in a volume ratio of 60:35:5, with an average particle size of 500nm for all three powders. The three powders were mixed in a high-speed mixer for 120 minutes to obtain a homogeneous metal powder mixture. The prepared NbTi / Cu superconducting round wire was threaded into the groove of the aluminum groove wire. The metal powder mixture was then evenly filled into the groove between the aluminum groove wire and the superconducting round wire, and excess powder was scraped off. A 0.4mm thick tin foil was used to wrap the assembled structure in four layers. The wrapped component was sequentially passed through a rectangular mold, an induction heating furnace, cooling water, a traction machine, and a take-up machine, with the rectangular mold exit and the induction heating furnace protected by argon gas. The induction heating temperature was set to 350℃, and the equipment operating speed was 150m / min to complete the induction heating and hot-dip tinning processes. After hot-dip tinning, the component was immediately placed in water at -2℃ for water cooling, ultimately producing an aluminum channel wire WIC superconducting wire with a specification of (3.0×2.1)mm. Eddy current testing was used to characterize deep defects in the solder joints between the channel wire and the round wire; no obvious defects were detected. The RRR value of this WIC superconducting wire, measured at 273K / 10K, was 152, compared to 113 when the metal powder mixture was replaced with tin powder. The bonding force between the 10 NbTi / Cu wires and the aluminum channel wires embedded after hot-dip tin plating was measured to be 89.91±6.08N; in contrast, when the metal powder mixture was replaced with tin powder, the bonding force was 62.86±6.11N.

[0023] Example 2

[0024] This embodiment provides a process for preparing WIC superconducting wires.

[0025] 48-core NbTi / Cu superconducting round wire with a diameter of 1.5mm was selected. A 4.5mm aluminum rod was selected, flattened by rolling, and then rectangularly shaped. A 1.55mm groove was formed by rolling using a rectangular concave wheel and a semi-circular cam. The groove was then processed with a forming die to ensure a smooth inner surface and a 0.3mm radius on both sides. Tin powder, aluminum powder, and titanium powder were weighed in a volume ratio of 60:30:8, with an average particle size of 500nm. After mixing for 150 minutes, a uniform metal powder mixture was obtained. The NbTi / Cu superconducting round wire was embedded into the groove of the aluminum groove. After filling with the metal powder mixture, excess powder was scraped off, and the wire was then wrapped in three layers of 0.5mm thick tin foil. The component was placed in an argon-protected process, with the induction heating temperature set to 380℃ and the equipment operating speed at 120m / min to complete the induction heating and hot-dip tin plating. After hot-dip tin plating, the wires were immediately immersed in 0°C water for cooling, resulting in (3.2×2.3) mm aluminum channel wire WIC superconducting wire. Eddy current testing was used to characterize deep-seated defects in the solder joints between the channel wire and the round wire; no obvious defects were detected. The RRR value of this WIC superconducting wire was 143 under 273K / 10K conditions, compared to 96 when the metal powder mixture was replaced with tin powder. The bonding strength between the 10 NbTi / Cu wires embedded after hot-dip tin plating and the aluminum channel wire was measured to be 91.64±6.21N; compared to 69.81±5.74N when the metal powder mixture was replaced with tin powder.

[0026] Example 3

[0027] This embodiment provides a process for preparing WIC superconducting wires.

[0028] A 60-core NbTi / Cu superconducting round wire with a diameter of 1.8mm was selected. A 5.0mm aluminum rod was selected, rolled and shaped, and then cam-rolled to form a 1.81mm groove. This groove was then processed using a forming die to ensure a smooth inner surface and a 0.3mm radius. Tin powder, aluminum powder, and titanium powder were weighed in a volume ratio of 60:40:3, with an average particle size of 500nm. After mixing for 100 minutes, a uniform metal powder mixture was obtained. The superconducting round wire was inserted into the groove of the aluminum groove, and after filling with the metal powder mixture, excess powder was scraped off. The wire was then wrapped in five layers of 0.3mm thick tin foil. Under argon protection, the induction heating temperature was set to 300℃, and the equipment operating speed was 180m / min to complete the induction heating and hot-dip tin plating. After hot-dip tin plating, the wire was immediately placed in water at -5℃ for cooling, ultimately producing a (3.5×2.5)mm aluminum groove WIC superconducting wire. Eddy current testing was used to characterize deep defects in the solder joints between the slotted and round wires; no obvious defects were detected. The RRR value of the WIC superconducting wire, measured at 273K / 10K, was 155, compared to 104 when the metal powder mixture was replaced with tin powder. The bonding strength between the 10 NbTi / Cu wires embedded after hot-dip tin plating and the aluminum slotted wires was measured to be 87.61±4.86N; compared to 61.05±6.16N when the metal powder mixture was replaced with tin powder.

[0029] The embodiments described above are only some, not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate preferred embodiments. All other embodiments obtained by those skilled in the art through related deductions and substitutions based on the inventive concept, without inventive effort, are within the scope of protection of the present invention.

Claims

1. A method for preparing WIC superconducting wire, characterized in that, include: Select a superconducting round wire and an aluminum groove wire that matches the size of the superconducting round wire, and thread the superconducting round wire through the groove of the aluminum groove wire; A metal powder mixture is filled into the groove between the aluminum channel wire and the superconducting round wire, wrapped with tin foil, and then subjected to induction heating and hot-dip tin plating to obtain the aluminum channel wire WIC superconducting wire. The metal powder mixture is composed of tin powder, aluminum powder and titanium powder, with a volume ratio of tin powder, aluminum powder and titanium powder of 60:30~40:3~8, and the average particle size of copper powder, silicon powder or chromium powder is not higher than 500nm. The superconducting round wire is an NbTi / Cu superconducting round wire, and the induction heating temperature is 300~380℃.

2. The method for preparing WIC superconducting wire according to claim 1, characterized in that, Immediately after the hot-dip tin plating is completed, the sample is placed in water at -5~0℃ for water cooling.

3. The method for preparing WIC superconducting wire according to claim 1, characterized in that, The specifications of the superconducting circular wire are Φ1.2mm~Φ1.8mm.

4. The method for preparing WIC superconducting wire according to claim 1, characterized in that, The number of layers of tin foil is 3 to 5, and the thickness of the tin foil is not higher than 0.5 mm.

5. The method for preparing WIC superconducting wire according to claim 1, characterized in that, The diameter of the groove in the aluminum channel is 0.01~0.05mm higher than the diameter of the superconducting circular wire.

6. A WIC superconducting wire, characterized in that, The WIC superconducting wire was prepared using the method described in any one of claims 1 to 5.