Preparation method of superconducting enameled wire and superconducting enameled wire

Abstract

This invention belongs to the field of wire processing and provides a method for preparing superconducting enameled wire. The method involves uniformly heating the core wire and then performing multiple alternating micro-powder coating and varnish coating processes. After acquiring thermal infrared images at each stage, the presence of localized accumulation is determined based on the pre-coating and post-coating thermal images. Increasing the micro-powder coating thickness while decreasing the varnish coating thickness in the next alternating coating stage allows for rapid identification of localized accumulation caused by thermocapillary convection. Reducing the varnish coating thickness in the next stage decreases the acetal varnish thickness, thereby reducing the varnish layer and the shrinkage stress during acetal varnish curing. This reduces the tendency of adjacent micro-powder particles to be pushed towards edges or defects, preventing the aggregation of adjacent micro-powder particles and mitigating the problem of localized aggregation exacerbated by the Maragoni effect. Simultaneously, it prevents the false detection of small amounts of sodium bismuth titanate nanopowder sputtering in the thermocapillary channels.

Description

Technical Field

[0001] This invention belongs to the field of wire processing technology, specifically relating to a method for preparing superconducting enameled wire and the superconducting enameled wire itself. Background Technology

[0002] As a key material in superconducting equipment, superconducting enameled wire has extremely stringent requirements for thermal conductivity and low-temperature resistance. The enamel coating of superconducting enameled wire includes acetal, polyurethane, polyester, polyesterimide, polyamideimide, and polyimide types, among others. The solid content (also known as non-volatile content, which refers to the percentage of remaining solids in emulsions, coatings, etc., after drying under specified conditions) of these coatings affects the quality of the superconducting enameled wire.

[0003] When the solid content is too high, the enamel film is denser and harder, but it is also more brittle (due to increased internal stress), which leads to deterioration of low-temperature resistance (embrittlement) and interface detachment (because the increased internal stress reduces the flexibility and adhesion of the enamel film). On the other hand, when the solid content is too low, the enamel film becomes loose and porous, which not only reduces insulation and makes it susceptible to moisture and short circuits, but also loses effective protection for the superconducting core wire (for example, it reduces insulation resistance and corrosion resistance). Both of these will seriously affect the reliability and service life of the superconducting enameled wire.

[0004] Existing technologies generally employ the addition of fillers (such as sodium bismuth titanate powder and titanium dioxide powder) to improve the performance of the coating film without altering its solid content. Although existing technologies, such as the invention patent with publication number CN118711897A, address the aforementioned technical problems by introducing sodium bismuth titanate nanopowder for alternating coating to produce superconducting enameled wires, which can reduce the surface tension of acetal paint during coating and improve the wettability of acetal paint, thereby ensuring that the sodium bismuth titanate nanopowder is uniformly distributed at the junctions of each layer of acetal paint, this method is more conducive to improving the thermal conductivity and low-temperature resistance of superconducting enameled wires. However, when alternating coatings with paints of different properties (such as acetal paint and sodium bismuth titanate nanopowder), the solvent of the later layer of acetal paint may penetrate and redissolve the previous layer of sodium bismuth titanate nanopowder, leading to local accumulation (lacquer nodules). Excessive differences between the two paints can lead to uneven flow. When a high-viscosity paint layer is applied to the surface of a low-viscosity paint layer, excess paint is easily retained (such as when acetal paint and sodium bismuth titanate micro powder are applied alternately). During curing, the difference in shrinkage rate between the sodium bismuth titanate filler particles and the acetal paint may induce micro-stress problems, causing the acetal paint to sag and form nodular protrusions. The bottoming and settling caused by the alternating application of filler particles in the paint liquid may lead to uneven local concentration, which can exacerbate the paint nodules. Furthermore, these mixed materials, as inorganic powders, have weak interfacial bonding with the paint film components, creating compatibility risks. This can lead to agglomeration of these fillers and paint film components, easily causing micropores or unevenness within the paint film, thereby reducing thermal conductivity, insulation performance, and mechanical strength. It can also easily lead to micropores or phase separation within the paint film, reducing density. In addition, the high dielectric constant of the rigid particles of these fillers may locally alter the electric field distribution, causing fluctuations in insulation performance. Unevenly dispersed particles may form conductive paths, causing a decrease in insulation resistance or local breakdown. If problems such as undercut, paint nodules, micropores, or unevenness occur in the filler layer and paint layer, interfacial stress accumulation will occur, accelerating paint film peeling. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing superconducting enameled wire and the superconducting enameled wire, so as to solve one or more technical problems existing in the prior art, and at least provide a beneficial option or create conditions.

[0006] To achieve the above objectives, according to one aspect of the present invention, a method for preparing a superconducting enameled wire is provided, the method comprising the following steps: S100, wire feeding, rolling incoming round wire into core wire of a set specification; S200, cleans the core wires; S300, the core wire is annealed in an annealing furnace; S400 involves uniformly heating the core wire and then alternating between micro-powder coating and liquid coating multiple times. In this process, thermal infrared images are obtained before and after each alternating coating pass and are recorded as the pre-coating thermal image and the post-coating thermal image, respectively. After each thermal infrared image is obtained, the presence of local accumulation is determined based on the pre-coating thermal image and the post-coating thermal image. If so, the thickness of the micro powder coating is increased while the thickness of the liquid coating is decreased during the next alternating coating pass of this pass. S500 involves baking and sizing the core wire before testing; S600 winds the core wire into a finished spool.

[0007] Furthermore, in S100, the wire feeding process specifically includes: placing a 2.6mm round wire vertically below the ceramic ring of the wire feeding frame, and feeding it out using a wire feeding machine.

[0008] Furthermore, in S100, each wire-laying spool is wound with a round wire, and adjacent round wires are welded together to form a connection point.

[0009] Each of the steps S200 to S600 includes a wiring position identification step, in which the real-time process data of each core wire is recorded as a process node upon identification of the wiring position. The circular wire is an alloy superconducting material, and the alloy superconducting material is composed of niobium-based alloys (such as niobium-titanium alloys, niobium-zirconium alloys, etc.); preferably, the alloy superconducting material is a niobium-titanium alloy.

[0010] Furthermore, in S100, the specification is set to Φ1.500mm.

[0011] Furthermore, in S100, two adjacent superconducting wires are welded together with ferromagnetic material to form a connection point, and a connector identification mechanism is used to identify the connection point; the connector identification mechanism includes a pressure sensor and a strong magnet connected together, and the strong magnet is used to generate an attractive force on the connector to change the sensing data of the pressure sensor.

[0012] Furthermore, in S200, cleaning the core wire specifically includes: leading the drawn core wire to the cleaning water tank and cleaning the oil stains on the surface of the core wire with clean water.

[0013] Furthermore, in S300, annealing the core wire in an annealing furnace specifically includes: passing the cleaned core wire from the upper layer of the annealing furnace to the lower layer at a speed of 20~30m / min; the upper layer temperature of the annealing furnace is 280℃, the lower layer temperature is 320℃, and the annealing time is 80s~100s.

[0014] When alternating coats of paints with different properties (such as acetal paint and sodium bismuth titanate nanopowder), the solvent in the later layer of acetal paint may penetrate and redissolve the previous layer of sodium bismuth titanate nanopowder, leading to localized accumulation (lacquer nodules). Excessive differences between the two paints can cause uneven flow. When a high-viscosity paint layer is applied over a low-viscosity paint layer, excess paint may be retained (e.g., when acetal paint and sodium bismuth titanate nanopowder are applied alternately). During curing, the difference in shrinkage rates between the sodium bismuth titanate filler particles and the acetal paint may induce micro-stress problems, causing the acetal paint to sag and form nodular protrusions. The bottoming and settling caused by the alternating application of filler particles in the paint liquid may lead to uneven local concentration, exacerbating the nodules. Existing online detection methods, such as the invention patent with publication number CN118538481A, identify areas where the coating surface area is increased or the thickness is thinned by infrared thermal imaging, thus causing faster heat dissipation than other areas, and mark these suspected areas as abnormal enameling areas. This method of automatically controlling enameling production lines based on infrared thermal imaging identification has gradually become popular in the industry. However, these existing methods generally use the temperature difference effect to identify temperature differences in the same image. The presence of paint nodules, pinholes, or unevenness will reduce thermal conductivity, thus determining whether there are abnormal areas. However, in the application scenario of this invention, the interfacial bonding between the mixed materials such as sodium bismuth titanate nanopowder, as inorganic powder, and the paint film components is weak, and the interfacial compatibility is poor. The existing technology can only identify the differences between materials mixed in the same paint layer or multiple identical paint layers. However, in the alternating coating of inorganic powder of sodium bismuth titanate nanopowder and acetal paint, the inorganic powder isolates the temperature transfer between adjacent acetal paint layers, thus greatly reducing the temperature difference effect. This makes it impossible for the existing technology to identify anomalies through the thermal image differences of the same acetal paint layer, especially the subtle local accumulation changes caused by thermocapillary effect, because the small-scale local accumulation caused by thermocapillary effect is not significant. Therefore, this application solves this problem by means of the following method: Furthermore, in S400, the specific method for determining whether localized build-up exists based on pre-painting and post-painting thermal images is as follows: The thermal images before and after painting are image registered and converted to grayscale to form the before and after grayscale images, respectively. Contour and edge information are extracted from the front and back grayscale images using Canny edge detection. Edges in the front grayscale image whose average grayscale value is greater than the average grayscale value of the front grayscale image are designated as hot edges. Edges in the back grayscale image whose average grayscale value is less than the average grayscale value of the back grayscale image are designated as cold edges. The hot edges in the front grayscale image are projected onto the corresponding positions in the back grayscale image, and the corresponding closed regions after dilation are designated as the pre-projection region. The dilation results of the cold edges are designated as the post-projection region. Each front projection region is traversed sequentially, and its convection is matched with all the back projection regions one by one (i.e., each front projection region needs to be matched and compared with all the back projection regions). If a front projection region has a successful convection match, it is determined that there is local accumulation; otherwise, there is no local accumulation.

[0015] Furthermore, in S400, the specific method for performing convection matching is as follows: The point with the highest gray value in the current projection area is denoted as the origin of heat; the area of ​​the current projection area is denoted as the area of ​​the front area. All cooled regions with an area less than or equal to the area of ​​the front region are marked as candidate regions; the point with the largest gray value in the candidate region is recorded as a candidate point; the point with the smallest Euclidean distance from the heat origin among all candidate points is recorded as the near diffusion point; the point with the largest Euclidean distance from the heat origin among all candidate points is recorded as the far diffusion point; a straight line L is formed by connecting the near diffusion point and the far diffusion point; the distance between the heat origin and the near diffusion point is recorded as the diffusion distance threshold; the direction from the near diffusion point to the far diffusion point is recorded as the capillary heat flow direction. The perpendicular distance from each candidate point (excluding the near-diffusion point and the far-diffusion point) to line L is calculated and recorded as the diffusion deviation distance; the candidate region corresponding to the candidate point with the smallest diffusion deviation distance is recorded as the convection region. The straight line connecting the point with the highest gray value in the convection region and the origin of heat is taken as the high conduction line; The straight line connecting the point with the smallest gray value in the convection region and the point with the smallest gray value in the current projection area is the low conductivity line; then the high conductivity line and the low conductivity line form a thermocapillary channel; (due to the different cooling and drying rates of the acetal paint and the micro powder layer, there is a temperature gradient difference during the alternating coating process, which usually triggers the thermocapillary effect, which may cause thermocapillary convection (increasing the temperature will reduce the surface tension of the liquid, causing the liquid to flow from the hotter area to the colder area. In order to keep the liquid level, the colder liquid will fall to the low conductivity line, and the hotter part will rise to the high conductivity line, thus forming local accumulation. The thermocapillary convection region is the most likely thermocapillary region)). Along the direction of capillary heat flow, all candidate regions that geometrically intersect with the thermocapillary channel are sorted in ascending order according to the diffusion deviation distance of each candidate point, and traversed in this order. If all current candidate regions meet the capillary heat flow condition, the convection matching is successful; otherwise, the convection matching fails.

[0016] Specifically, the capillary heat flow condition is as follows: the average gray value of the previous candidate region is greater than the average gray value of the current candidate region, and the average gray value of the next candidate region is less than the average gray value of the current candidate region (heat transfer in the positive direction of capillary heat flow).

[0017] The average gray level of the candidate region refers to the average gray level of all pixels in the candidate region. (In the grayscale image of a thermal image, the hottest point usually has a larger gray level value, and the coldest point has a smaller gray level value. Therefore, the gray level is positively correlated with the temperature value.)

[0018] Preferably, the capillary heat flow conditions are as follows: the average gray value of the previous candidate region is less than the average gray value of the current candidate region, and the average gray value of the next candidate region is greater than the average gray value of the current candidate region. (In heat transfer in the reverse direction of capillary heat flow, both forward and reverse heat transfer involve thermocapillary convection, which can lead to local accumulation.)

[0019] Both of the above methods can indirectly detect localized accumulation caused by thermocapillary convection that cannot be directly identified by certain technologies. However, this method relies too much on the linear rules along the direction of capillary heat flow. If a large number of point-like temperature abrupt changes occur along the direction of capillary heat flow, such as a small amount of sodium bismuth titanate nanoparticles sputtered in the thermocapillary channel, it will also be judged as localized accumulation. Although this problem is not common, it is easy to cause false signals, thus leading to material waste.

[0020] Preferably, the capillary heat flow condition is as follows: the heat flow accumulation gray value of the previous candidate region is greater than that of the current candidate region, and the heat flow accumulation gray value of the subsequent candidate region is less than that of the current candidate region.

[0021] Preferably, the capillary heat flow condition is as follows: the heat flow accumulation gray value of the previous candidate region is less than that of the current candidate region, and the heat flow accumulation gray value of the next candidate region is greater than that of the current candidate region.

[0022] The specific method for obtaining the heat flow deposition grayscale is as follows: Let the average of the average gray values ​​of the first candidate region to the current candidate region (note, if it is the previous candidate region, then the previous candidate region is the current candidate region, and so on) along the direction of capillary heat flow be the first accumulated gray value; let the average of the average gray values ​​of the current candidate region to the last candidate region to the last candidate region along the direction of capillary heat flow be the second accumulated gray value; let the difference between the first accumulated gray value and the second accumulated gray value be the accumulated gray value difference; then the heat flow accumulated gray value is the sum of the average gray value of the candidate region and the accumulated gray value difference.

[0023] Furthermore, in S400, the specific method for increasing the thickness of the micro-powder coating while reducing the thickness of the liquid coating is as follows: during the next alternating coating pass, increase the single-pass thickness of the micro-powder coating by 10-20% and reduce the single-pass thickness of the liquid coating by 10-20%. (In the coating process of superconducting wires, reducing the thickness of the acetal coating layer and increasing the thickness of the sodium bismuth titanate micro-powder coating layer is more conducive to reducing local accumulation problems. This is because reducing the thickness of the acetal coating layer reduces the coating layer, reduces the shrinkage stress during the curing of the acetal coating layer, and reduces the pushing of adjacent micro-powders to the edges or defects, thus avoiding the compression and aggregation of adjacent micro-powders and reducing the problem of local aggregation aggravated by the Maragoni effect. On the other hand, increasing the coating thickness of the micro-powder is to balance the total coating thickness and prevent uneven thickness.)

[0024] Furthermore, in S400, the method of alternating micro-powder coating and liquid coating is as follows: the core wire is subjected to alternating micro-powder coating and liquid coating, with the number of passes for micro-powder coating and liquid coating being the same and 6 to 15 passes respectively. Among them, micro powder coating is achieved by coating with sodium bismuth titanate nanoparticles.

[0025] Among them, paint coating refers to coating with paint liquid; where the paint liquid is acetal paint.

[0026] Furthermore, in the S400, the heating temperature is 50-70°C.

[0027] Furthermore, in S400, the completion of each alternating coating pass means that both the micro-powder coating and the liquid coating of that pass have been completed.

[0028] Furthermore, in S400, after alternating between powder coating and liquid coating, 5 to 10 coats of liquid coating are applied.

[0029] Furthermore, the solid content of the acetal paint is 20%, the single-coat thickness of the micro powder coating is 1~5μm, and the single-coat thickness of the liquid paint is 10~15μm.

[0030] Furthermore, in S400, both powder coating and liquid coating are applied using high-pressure annular nozzles.

[0031] Furthermore, in S400, the outlet temperature of the high-pressure annular nozzle is 40~45℃; Furthermore, in S400, the temperature of the core wire before spraying is at least 5°C higher than the outlet temperature.

[0032] Furthermore, in S400, the particle size of sodium bismuth titanate nanoparticles is 5~10 nm.

[0033] Furthermore, in the S500, the baking temperature is 280℃~300℃, and the time is 90~120s.

[0034] Furthermore, in the S500, sizing is performed using a diamond die with a roughness of 0.1~0.15μm, and the overall dimensional accuracy of the wire after coating is controlled within ±0.003mm.

[0035] Furthermore, in the S500, the detection method is: 1500V pinhole test, that is, the core wire is passed through a 1500V electrode at a speed of 3m / min, and visible electric sparks will be generated at the pinhole due to insufficient insulation.

[0036] Preferably, in S500, the detection method is to test the core wire using an enameled wire pinhole tester.

[0037] Furthermore, in the S600, the core wires are cut according to the wiring position so that each core wire (superconductor) is wound onto a finished spool.

[0038] The beneficial effects of this invention are as follows: This invention provides a method for preparing superconducting enameled wires, which can quickly mark the local accumulation caused by thermal capillary convection. By reducing the thickness of the enamel coating in the next pass, the thickness of the acetal enamel can be reduced, thus reducing the enamel layer thickness. This reduces the shrinkage stress during the curing of the acetal enamel layer, reduces the pushing of adjacent microparticles to the edges or defects, and avoids the problem of local agglomeration caused by the Maragoni effect being exacerbated by the squeezing and agglomeration of adjacent microparticles. At the same time, it can prevent the problem of false detection of a small amount of sodium bismuth titanate nanoparticles sputtering in the thermal capillary channel. Attached Figure Description

[0039] The above and other features of the present invention will become more apparent from the detailed description of the embodiments shown in conjunction with the accompanying drawings. In the accompanying drawings, the same reference numerals denote the same or similar elements. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort. In the drawings: Figure 1 The diagram shows a flowchart of a method for preparing a superconducting enameled wire. Detailed Implementation

[0040] The following will provide a clear and complete description of the concept, specific structure, and technical effects of the present invention in conjunction with the embodiments and accompanying drawings, so as to fully understand the purpose, solution, and effects of the present invention. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0041] like Figure 1 The diagram shows a flowchart of a method for preparing a superconducting enameled wire. The following section will discuss this method in conjunction with... Figure 1 This invention describes a method for preparing a superconducting enameled wire according to an embodiment of the present invention, the method comprising the following steps: Example 1 S100, wire feeding, rolling incoming round wire into core wire of a set specification; S200, cleans the core wires; S300, the core wire is annealed in an annealing furnace; S400 involves uniformly heating the core wire and then alternating between micro-powder coating and liquid coating. The number of passes for micro-powder coating and liquid coating is the same, and each pass consists of 15 passes. In this process, thermal infrared images are obtained before and after each alternating coating pass and are recorded as the pre-coating thermal image and the post-coating thermal image, respectively. After each thermal infrared image is obtained, the presence of local accumulation is determined based on the pre-coating thermal image and the post-coating thermal image. If so, the thickness of the micro powder coating is increased while the thickness of the liquid coating is decreased during the next alternating coating pass of this pass. S500 involves baking and sizing the core wire before testing; S600 winds the core wire into a finished spool.

[0042] Furthermore, in S100, the wire feeding process specifically includes: placing a 2.6mm round wire vertically below the ceramic ring of the wire feeding frame, and feeding it out using a wire feeding machine.

[0043] Furthermore, in S100, each wire-laying spool is wound with a round wire, and adjacent round wires are welded together to form a connection point.

[0044] Each step in steps S200 to S600 includes a wiring position identification step, in which the real-time process data of each core wire is recorded as a process node upon identification of the wiring position. Among them, the circular line is an alloy superconducting material, and the alloy superconducting material is a niobium-titanium alloy.

[0045] Furthermore, in S100, the specification is set to Φ1.500mm.

[0046] Furthermore, in S100, two adjacent superconducting wires are welded together with ferromagnetic material to form a connection point, and a connector identification mechanism is used to identify the connection point; the connector identification mechanism includes a pressure sensor and a strong magnet connected together, and the strong magnet is used to generate an attractive force on the connector to change the sensing data of the pressure sensor.

[0047] Furthermore, in S200, cleaning the core wire specifically includes: leading the drawn core wire to the cleaning water tank and cleaning the oil stains on the surface of the core wire with clean water.

[0048] Furthermore, in S300, the annealing of the core wire in the annealing furnace specifically includes: annealing the cleaned core wire from the upper layer to the lower layer of the annealing furnace at a speed of 20 m / min; the upper layer temperature of the annealing furnace is 280°C, the lower layer temperature is 320°C, and the annealing time is 80 s.

[0049] Furthermore, in S400, the specific method for determining whether there is local accumulation based on the pre-painting thermal image and the post-painting thermal image is as follows: the pre-painting thermal image and the post-painting thermal image are image registered and grayscaled to form a pre-grayscale image and a post-grayscale image, respectively. Contour and edge information are extracted from the front and back grayscale images using Canny edge detection. Edges in the front grayscale image whose average grayscale value is greater than the average grayscale value of the front grayscale image are designated as hot edges. Edges in the back grayscale image whose average grayscale value is less than the average grayscale value of the back grayscale image are designated as cold edges. The hot edges in the front grayscale image are projected onto the corresponding positions in the back grayscale image, and the corresponding closed regions after dilation are designated as the pre-projection region. The dilation results of the cold edges are designated as the post-projection region. Each projection region is traversed sequentially, and its convection is matched with all the cooled regions one by one. If a convection match is successful in a projection region, it is determined that there is local accumulation; otherwise, there is no local accumulation.

[0050] Furthermore, in S400, the specific method for performing convection matching is as follows: The point with the highest gray value in the current projection area is denoted as the origin of heat; the area of ​​the current projection area is denoted as the area of ​​the front area. All cooled regions with an area less than or equal to the area of ​​the front region are marked as candidate regions; the point with the largest gray value in the candidate region is recorded as a candidate point; the point with the smallest Euclidean distance from the heat origin among all candidate points is recorded as the near diffusion point; the point with the largest Euclidean distance from the heat origin among all candidate points is recorded as the far diffusion point; a straight line L is formed by connecting the near diffusion point and the far diffusion point; the distance between the heat origin and the near diffusion point is recorded as the diffusion distance threshold; the direction from the near diffusion point to the far diffusion point is recorded as the capillary heat flow direction. The perpendicular distance from each candidate point (excluding the near and far diffusion points) to line L is calculated and recorded as the diffusion deviation distance. The candidate region corresponding to the candidate point with the smallest diffusion deviation distance is recorded as the convection region. The straight line connecting the point with the largest gray value in the convection region and the heat origin is the high conduction line. The straight line connecting the point with the smallest gray value in the convection region and the point with the smallest gray value in the current projection area is the low conduction line. The high conduction line and the low conduction line form a thermal capillary channel. Along the direction of capillary heat flow, all candidate regions that geometrically intersect with the thermocapillary channel are sorted in ascending order according to the diffusion deviation distance of each candidate point, and traversed in this order. If all current candidate regions meet the capillary heat flow condition, the convection matching is successful; otherwise, the convection matching fails.

[0051] Specifically, the capillary heat flow condition is as follows: the average gray value of the previous candidate region is greater than the average gray value of the current candidate region, and the average gray value of the next candidate region is less than the average gray value of the current candidate region.

[0052] The average gray level of the candidate region refers to the average gray level of all pixels in the candidate region.

[0053] Furthermore, in S400, the specific method for increasing the thickness of the micro powder coating while decreasing the thickness of the liquid paint coating is as follows: when applying the next alternating coat, increase the single-coat thickness of the micro powder coating by 10% and decrease the single-coat thickness of the liquid paint coating by 10%.

[0054] The method for obtaining thermal infrared images is to acquire thermal images using an infrared imager.

[0055] Among them, micro powder coating is achieved by coating with sodium bismuth titanate nanoparticles.

[0056] Among them, paint coating refers to coating with paint liquid; where the paint liquid is acetal paint.

[0057] Furthermore, in the S400, the heating temperature is 55°C.

[0058] Furthermore, in S400, the completion of each alternating coating pass means that both the micro-powder coating and the liquid coating of that pass have been completed.

[0059] Furthermore, in S400, after alternating between powder coating and liquid coating, five coats of liquid coating are applied.

[0060] Furthermore, the solid content of the acetal paint is 20%, the single-coat thickness of the micro powder coating is 5μm, and the single-coat thickness of the liquid paint is 15μm.

[0061] Furthermore, in S400, both powder coating and liquid coating are applied using high-pressure annular nozzles.

[0062] The outlet temperature of both the first high-pressure annular nozzle and the second high-pressure annular nozzle is 40℃.

[0063] The first high-pressure annular nozzle is used for coating sodium bismuth titanate nanopowder, and the second high-pressure annular nozzle is used for coating acetal paint.

[0064] Furthermore, in the S400, the outlet temperature of the high-pressure annular nozzle is 40°C. Furthermore, in S400, the particle size of sodium bismuth titanate nanoparticles is 5 nm.

[0065] Furthermore, in the S500, the baking temperature is 280°C and the baking time is 90 seconds.

[0066] Furthermore, in the S500, sizing is performed using a diamond die with a roughness of 0.1μm, and the overall dimensional accuracy of the wire after coating is controlled within ±0.003mm.

[0067] Furthermore, in the S500, the detection method is: 1500V pinhole test, that is, the core wire is passed through a 1500V electrode at a speed of 3m / min, and visible electric sparks will be generated at the pinhole due to insufficient insulation.

[0068] Furthermore, in the S600, the core wires are cut according to the wiring position so that each core wire (superconductor) is wound onto a finished spool.

[0069] Example 2 Replace the capillary heat flow conditions in Example 1 with: Preferably, the capillary heat flow condition is as follows: the heat flow accumulation gray value of the previous candidate region is greater than that of the current candidate region, and the heat flow accumulation gray value of the subsequent candidate region is less than that of the current candidate region.

[0070] The specific method for obtaining the heat flow deposition grayscale is as follows: Let the average of the average gray values ​​of the first candidate region to the current candidate region, which is one of the candidate regions geometrically intersecting with the thermocapillary channel along the direction of capillary heat flow, be the first accumulated gray value; let the average of the average gray values ​​of the current candidate region to the last candidate region, which is one of the candidate regions geometrically intersecting with the thermocapillary channel along the direction of capillary heat flow, be the second accumulated gray value; let the difference between the first accumulated gray value and the second accumulated gray value be the accumulated gray value difference; then the heat flow accumulated gray value is the sum of the average gray value of the candidate region and the accumulated gray value difference.

[0071] Comparative example: A method for preparing a superconducting enameled wire, characterized by comprising the following steps: Step 1: After the core wire is uniformly heated to 45°C, it passes through a high-pressure annular nozzle. The high-pressure annular nozzle is used for coating the mixture of sodium bismuth titanate nanopowder and acetal varnish (solid content of 20%) with a mass ratio of 1:5. Step 2: The core wire is coated with paint in 10 alternating passes. The outlet temperature of the first high-pressure annular nozzle and the second high-pressure annular nozzle is 40℃.

[0072] Step 3: Immediately after painting, perform baking and sizing; The first high-pressure annular nozzle is used for coating sodium bismuth titanate nanopowder, and the second high-pressure annular nozzle is used for coating acetal paint (solid content of 20%).

[0073] In the comparative example, all conditions such as cleaning, annealing, baking, and sizing were the same as those in Examples 1 and 2.

[0074] Test results: To demonstrate the difference, during the fabrication of superconducting enameled wires in Examples 1 and 2 and the comparative example, artificial induction of thermocapillary convection was performed using the following method: A heater (slightly larger in diameter than the wire) was installed 5-10 mm above a second high-pressure annular nozzle, with adjustable power (200W), and an air-cooled spray nozzle was positioned below it. The heater generated heat (65°C) to create an annular high-temperature zone on the wire surface, while the air-cooled spray nozzle provided cooling (10°C) below, forming an axial temperature gradient. Under natural conditions without artificial induction, the probability of significant spontaneous thermocapillary convection is approximately 5%. After the above artificial induction, the probability of significant spontaneous thermocapillary convection increased to 90%.

[0075] Superconducting enameled wires were prepared in Examples 1 and 2 and the comparative example after artificial induction. The performance of 30 batches of samples after being placed in liquid nitrogen for 7 days and then restored to room temperature is compared as follows: Example 1: No alarm was triggered under 1500V pinhole detection, and no wrinkles or powdering were observed.

[0076] Example 2: No alarm was triggered under 1500V pinhole detection, and no wrinkles or powdering were observed.

[0077] Comparative example: An alarm was triggered under 1500V pinhole detection, and wrinkles or powdering appeared.

[0078] Therefore, it can be seen that Examples 1 and 2 have significant advantages over the Comparative Example when spontaneous thermocapillary convection occurs, and can improve the product qualification rate.

[0079] Although the invention has been described in considerable detail and particularly with regard to several of the described embodiments, it is not intended to limit itself to any of these details or embodiments or any particular embodiment, thereby effectively covering the intended scope of the invention. Furthermore, the invention has been described above with respect to embodiments foreseeable by the inventors in order to provide a useful description, and non-substantial modifications to the invention that have not yet been foreseen may still represent equivalent modifications.

[0080] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A method for producing a superconducting enameled wire, characterized by, The method includes the following steps: S100, wire feeding, rolling incoming round wire into core wire of a set specification; S200, cleans the core wires; S300, the core wire is annealed in an annealing furnace; S400 involves uniformly heating the core wire and then alternating between micro-powder coating and liquid coating multiple times. In this process, thermal infrared images are obtained before and after each alternating coating pass and are recorded as the pre-coating thermal image and the post-coating thermal image, respectively. After each thermal infrared image is obtained, the presence of local accumulation is determined based on the pre-coating thermal image and the post-coating thermal image. If so, the thickness of the micro powder coating is increased while the thickness of the liquid coating is decreased during the next alternating coating pass of this pass. S500 involves baking and sizing the core wire before testing; S600 winds the core wire into a finished spool.

2. The method for preparing a superconducting enameled wire according to claim 1, characterized in that, In S400, the specific method for determining the existence of local accumulation based on the pre-painting and post-painting thermal images is as follows: The pre-painting and post-painting thermal images are image registered and converted to grayscale to form a pre-grayscale image and a post-grayscale image, respectively. Contour and edge information is extracted from the pre-grayscale and post-grayscale images through edge detection. Edge lines in the pre-grayscale image where the average grayscale value of all pixels is greater than the average grayscale value of the pre-grayscale image are recorded as hot edges. Edge lines in the post-grayscale image where the average grayscale value of all pixels is less than the average grayscale value of the post-grayscale image are recorded as cold edges. The corresponding closed region after dilation of the hot edges in the pre-grayscale image onto the corresponding position in the post-grayscale image is recorded as the pre-projection region. The dilation of the cold edges is recorded as the post-cold region. Each pre-projection region is sequentially traversed, and convection matching is performed between it and all post-cold regions. If a convection match between a pre-projection region and a post-projection region is successful, local accumulation is determined to exist; otherwise, local accumulation does not exist.

3. The method for preparing a superconducting enameled wire according to claim 2, characterized in that, In S400, the specific method for performing convection matching is as follows: The point with the highest gray value in the current projection area is denoted as the origin of heat; the area of ​​the current projection area is denoted as the area of ​​the front area. All cooled regions with an area less than or equal to the area of ​​the front region are marked as candidate regions; the point with the largest gray value in the candidate region is recorded as a candidate point; the point with the smallest distance from the heat origin among all candidate points is recorded as the near diffusion point; the point with the largest distance from the heat origin among all candidate points is recorded as the far diffusion point; Connect the near-diffusion point and the far-diffusion point to form a straight line L; denote the distance between the thermal origin and the near-diffusion point as the diffusion distance threshold. The direction between the near diffusion point and the far diffusion point is taken as the direction of capillary heat flow. The perpendicular distance from each candidate point (excluding the near-diffusion point and the far-diffusion point) to line L is calculated and recorded as the diffusion deviation distance; the candidate region corresponding to the candidate point with the smallest diffusion deviation distance is recorded as the convection region. The straight line connecting the point with the highest gray value in the convection region and the origin of heat is the high conduction line; the straight line connecting the point with the lowest gray value in the convection region and the point with the lowest gray value in the current projection area is the low conduction line; then the high conduction line and the low conduction line form a thermal capillary channel. Along the direction of capillary heat flow, all candidate regions that geometrically intersect with the thermocapillary channel are sorted in ascending order according to the diffusion deviation distance of each candidate point, and traversed in this order. If all current candidate regions meet the capillary heat flow condition, the convection matching is successful; otherwise, the convection matching fails.

4. The method for preparing a superconducting enameled wire according to claim 3, characterized in that, The capillary heat flow conditions are as follows: the average gray value of the previous candidate region is greater than the average gray value of the current candidate region, and the average gray value of the next candidate region is less than the average gray value of the current candidate region.

5. The method of claim 3, wherein the step of applying the superconducting layer is performed by a method selected from the group consisting of sputtering, vacuum deposition, and thermal decomposition. The capillary heat flow conditions are as follows: the average gray value of the previous candidate region is less than the average gray value of the current candidate region, and the average gray value of the next candidate region is greater than the average gray value of the current candidate region.

6. The method for preparing a superconducting enameled wire according to claim 3, characterized in that, The capillary heat flow conditions are as follows: the heat flow accumulation gray value of the previous candidate region is greater than that of the current candidate region, and the heat flow accumulation gray value of the next candidate region is less than that of the current candidate region.

7. The method for preparing a superconducting enameled wire according to claim 3, characterized in that, The capillary heat flow conditions are as follows: the heat flow accumulation gray value of the previous candidate region is less than that of the current candidate region, and the heat flow accumulation gray value of the next candidate region is greater than that of the current candidate region.

8. The method of claim 6, wherein the step of applying the superconducting layer is performed by a sputtering method. The specific method for obtaining the heat flow accumulation gray value is as follows: the average of the average gray values ​​of the first candidate region to the current candidate region of all candidate regions that geometrically intersect with the heat capillary channel along the direction of capillary heat flow is recorded as the first accumulation gray value. The average of the average gray values ​​of the last candidate region, from the current candidate region to all candidate regions that geometrically intersect with the thermocapillary channel along the direction of capillary heat flow, is taken as the second stacked gray value. The difference between the first and second accumulation gray values ​​is taken as the accumulation gray value difference; then the heat flow accumulation gray value is the sum of the average gray value of the candidate region and the accumulation gray value difference.

9. The method for preparing a superconducting enameled wire according to claim 1, characterized in that, In S400, the specific method for increasing the thickness of the micro powder coating while reducing the thickness of the liquid paint coating is as follows: when applying the next alternating coat, increase the thickness of the single coat of the micro powder coating by 10-20% and reduce the thickness of the single coat of the liquid paint coating by 10-20%.

10. The method for preparing a superconducting enameled wire according to claim 1, characterized in that, In S400, the method of alternating micro-powder coating and liquid coating is as follows: the core wire is subjected to alternating micro-powder coating and liquid coating, with the number of passes for micro-powder coating and liquid coating being the same and ranging from 6 to 15 passes respectively.

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