High-temperature superconducting tape cladding alloy solder and preparation method and application thereof

Abstract

The application discloses alloy solder for high-temperature superconducting tape coating and a preparation method and application thereof. Four kinds of metal high-temperature fusion of tin, lead, bismuth and indium are mixed according to a proportion, and then are homogenized and cooled to obtain alloy solder Sn a Pb b Bi c In d , wherein a=0.60-0.662, b=0.20-0.26, c=0.021-0.078, and d=0-0.052, and further preferably d=0.035-0.052. According to the characteristics of the four kinds of metal of tin, lead, bismuth and indium, alloy solder is synthesized by melting and synthesizing solder components. The high-temperature superconducting tape is coated by the alloy solder and red copper tape. The high-temperature tape has strong flexibility, low surface roughness, wear resistance, scratch resistance and oxidation resistance, and has strong coating tape bonding force, so that the high-temperature superconducting tape after coating has excellent superconducting performance and mechanical performance in application.

Description

Technical Field

[0001] This invention relates to the field of high-temperature superconducting materials technology, specifically to an alloy solder for cladding high-temperature superconducting tapes, its preparation method, and its application in cladding high-temperature superconducting tapes. Background Technology

[0002] Second-generation high-temperature superconducting tapes, with their unique zero-resistance, high current-carrying-density characteristics and complete diamagnetism, enable crucial applications in new energy power industries, medical fields, scientific research, and military sectors that are irreplaceable by traditional conductors. In these applications, the high-temperature tapes require a 150μm thick copper strip to enhance their mechanical properties and protect the 5μm copper-plated stabilizing layer, allowing them to withstand fluctuating currents exceeding the critical current and preventing current interruption. The copper strip coating improves the tape's stability, making it more robust and flexible. A higher bonding strength between the copper strip and the copper layer is better, and this bonding strength is related to the solder characteristics and the optimal soldering temperature.

[0003] To ensure that a 150μm thick copper strip is firmly attached to the copper layer surface, the composition and performance of the solder used play a crucial role. Currently, manufacturers use tin-lead (6337) solder for coating, which results in a large surface roughness and sometimes spots on the coating layer, affecting the appearance quality and low bonding strength. When the high-temperature superconducting strip is cabled, microcracks will appear in the REBCO thin film ceramic layer due to external pressure, resulting in poor electrical performance (Ic) stability of the cable, which cannot meet customer needs.

[0004] The present invention is made to address the aforementioned problems existing in the prior art. Summary of the Invention

[0005] To address the aforementioned shortcomings of existing technologies, this invention provides an alloy solder for coating high-temperature superconducting tapes, its preparation method, and its application. This invention uses four metals—tin, lead, bismuth, and indium—that are characterized by low melting points, corrosion resistance, and good plasticity, which are then fused together at high temperatures, homogenized, and cooled to obtain an alloy solder. This alloy solder, along with copper strip, is used to coat high-temperature superconducting tapes. The resulting high-temperature tape exhibits high flexibility, low surface roughness, and resistance to wear, scratches, and oxidation. The coating also demonstrates strong adhesion, thus ensuring excellent superconducting and mechanical properties in applications.

[0006] The technical solution of this invention is as follows:

[0007] This invention relates to a method for preparing an alloy solder for coating high-temperature superconducting tapes. The method involves melting and homogenizing four metals—tin, lead, bismuth, and indium—at high temperature, followed by cooling to obtain the alloy solder. The molar ratio of tin:lead:bismuth:indium is tin:lead:bismuth:indium = (0.60-0.662):(0.20-0.26):(0.021-0.078):(0-0.052). This invention selects the solder composition based on the properties of these four metals to synthesize the alloy solder through melting. Metallic tin is inert, has a low melting point, and is highly malleable. Adding lead to tin can increase the oxidation resistance of solder joints, facilitate soldering, improve mechanical properties, and reduce interfacial tension. Due to the reduction in surface tension and viscosity, the diffusion rate (i.e., wettability) of the solder will be improved, thereby increasing fluidity and preventing whisker formation. The addition of bismuth effectively lowers the melting point of the solder, resulting in good wettability and bright, uniform, and full solder joints. Indium is the vitamin of the alloy; adding a small amount of indium to the solder increases the strength of the alloy, improves its ductility, and enhances its wear and corrosion resistance.

[0008] Preferably, the molar ratio of tin:lead:bismuth:indium is tin:lead:bismuth:indium = (0.60-0.662):(0.20-0.26):(0.021-0.078):(0.035-0.052).

[0009] Preferably, the molar ratio of tin, lead, bismuth, and indium is tin:lead:bismuth:indium = 0.61:0.26:0.078:0.052.

[0010] Preferably, the specific steps for high-temperature melting and homogenization of the four metals tin, lead, bismuth, and indium are as follows: accurately weigh the four metals according to the ratio, and then put them into the molten bath of the tin furnace titanium alloy. Heat the tin furnace to the melting and homogenization temperature. When the solid metal in the molten bath is completely melted into a liquid state, turn on the stirrer equipped with a corundum stirring rod to stir for 2-3 hours to make the four metals tin, lead, bismuth, and indium completely mixed and homogenized.

[0011] Preferably, the present invention uses a tin furnace with a 220mm × 150mm × 80mm titanium alloy melting tank to perform high-temperature synthesis based on the melting points of four metals (lead melting point 327.46℃, tin melting point 231.89℃, bismuth melting point 271.5℃, and indium melting point 156.51℃) and a melting homogenization temperature of 335℃.

[0012] Preferably, the cooling step after the four metals tin, lead, bismuth, and indium are fused together at high temperature and homogenized is as follows: the temperature is lowered to 185-210°C, stirring is stopped, the enriched impurity solids on the surface of the liquid are removed with a scraper, and the liquid is transferred to a mold in the molten state, cooled and removed to obtain the alloy solder.

[0013] Preferably, the temperature is lowered to 185-190℃.

[0014] This invention also relates to an alloy solder, prepared by the above-described method, wherein the chemical formula of the alloy solder is Sn. a Pb b Bi c In d Where a = 0.60-0.662, b = 0.20-0.26, c = 0.021-0.078, d = 0-0.052, further preferably d = 0.035-0.052, and even more preferably a = 0.61, b = 0.26, c = 0.078, d = 0.052.

[0015] This invention also relates to the application of alloy solder in the coating of high-temperature superconducting tape. Two reels of copper strips of equal length (10000mm×5mm×0.15mm) and one reel of high-temperature superconducting tape (10000mm×4mm×0.08mm) are installed on a coating device. The prepared alloy solder is placed into the tin bath of the coating device in the required quantity, and the temperature is raised to 210-260℃. After 60-70 minutes, the alloy solder is completely liquefied. The residual oxide on the surface of the liquid is scraped off with a scraper, and the high-temperature strip soldering equipment is turned on to coat the high-temperature superconducting tape with copper strips.

[0016] The beneficial effects of this invention are:

[0017] (1) In this invention, four metals, tin, lead, bismuth and indium, are melted and liquefied at 335°C. During the solution mixing process, impurities in the material will be enriched on the upper layer of the liquid surface and form a solid at low temperature. The solid impurities and oxides are removed, resulting in high purity solder. After coating, the surface roughness of the high temperature superconducting tape is low, the color is consistent, and the appearance is beautiful.

[0018] (2) The alloy solder of the present invention has a low melting point, especially Sn 0.60-0.662 Pb 0.2-0.26 Bi 0.021-0.078 In 0.035-0.052 This helps to eliminate the influence of coating temperature on the electrical properties of the functional layer of high-temperature strips;

[0019] (3) The alloy solder of the present invention has the characteristics of composite materials. The solder joints are uniform during use. The middle high-temperature superconducting strip and the two outer copper strips have strong bonding force and good flexibility. When the high-temperature superconducting strip is cabled, the REBCO thin film ceramic layer will not develop microcracks when subjected to external pressure, thus ensuring the electrical performance stability of the cable.

[0020] (4) After the alloy solder of the present invention is coated with copper strip, the surface of the high-temperature strip has wear resistance, scratch resistance and oxidation resistance.

[0021] (5) Sn 0.61 Pb 0.26 Bi 0.078 In 0.052Solder was used to coat high-temperature superconducting tapes, reducing the surface roughness from 3.2 μm to 0.8 μm. The bonding force of the coated tape was significantly enhanced, with the peel force increasing from 5.8 N to 18.6 N and the peel strength increasing from 11.673 (N / cm) to 37.179 (N / cm). This ensured that the coated high-temperature superconducting tapes had excellent superconducting and mechanical properties in applications. Attached Figure Description

[0022] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0023] Figure 1 This is a SEM image of the functional layer of a high-temperature superconducting finished product strip coated with tin-lead (6337) solder after peeling off;

[0024] Figure 2 Using Sn 0.61 Pb 0.26 Bi 0.078 In 0.052 SEM image of the functional layer after the solder-coated high-temperature superconducting tape has been peeled off.

[0025] (Note: The functional layer refers to the REBCO thin-film ceramic layer.) Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0027] The bonding strength testing equipment was model MXS-5KN (Suzhou Muxiang Testing Equipment Co., Ltd.), and the surface roughness testing device was a Bruker DektakXT model.

[0028] Comparative Example 1

[0029] Two rolls of copper strip of equal length (10000mm×5mm×0.15mm) and one roll of high-temperature superconducting strip (10000mm×4mm×0.08mm) were installed on the coating equipment. Tin-lead (6337) solder purchased from the market was placed into the tin bath of the coating equipment and heated to 265℃. After 70 minutes, when all the solid solder in the tin bath had liquefied, the residual oxide on the surface of the liquid was scraped off with a scraper. The high-temperature strip soldering equipment was turned on and the conveying speed was set to 5m / min. The high-temperature superconducting strip was then coated with copper strip.

[0030] Samples of the coated superconducting tape were taken and tested using a surface roughness profilometer and a bonding strength tester, respectively. The results are shown in Table 1 below:

[0031] Table 1

[0032] Maximum peel force (N) Minimum peeling force (N) Average peel force (N) Peel strength (N / cm) Roughness (μm) 6.6 5.3 5.8 11.673 3.2

[0033] Comparative Example 2

[0034] According to alloy solder Sn 0.688 Pb 0.312 The molar percentages of each element were determined. Using a carbide cutter and an electronic scale, 8.167 kg of tin and 6.465 kg of lead metal were accurately weighed and placed into a titanium alloy (220 mm × 150 mm × 80 mm) molten bath in a tin furnace. The furnace was heated to 335°C. When the solid metal in the bath was completely melted into a liquid state, a stirrer equipped with a corundum stirring rod was turned on and stirred for 2 hours to ensure complete and homogeneous mixing of tin and lead. The temperature was then lowered to 220°C, stirring was stopped, and the accumulated impurities on the surface were scraped off. The molten material was transferred to a 320 × 25 × 22 mm 99 corundum ceramic mold, cooled, and removed, thus producing Sn. 0.688 Pb 0.312 Alloy solder.

[0035] Two reels of equal-length copper strips (10000mm×5mm×0.15mm) and one reel of high-temperature superconducting strip (10000mm×4mm×0.08mm) are mounted on the coating equipment, and Sn is then applied. 0.688 Pb 0.0.312 The solder is placed in the tin bath of the coating equipment and heated to 265°C. After 70 minutes, the solid solder in the tin bath is completely liquefied. The residual oxide on the surface of the liquid is scraped off with a scraper. The high-temperature strip soldering equipment is turned on and the conveyor speed is set to 5m / min. The high-temperature superconducting strip is then coated with copper strip.

[0036] Samples of the coated superconducting tape were taken and tested using a surface roughness profilometer and a bonding strength tester, respectively. The results are shown in Table 2 below:

[0037] Table 2

[0038] Maximum peel force (N) Minimum peeling force (N) Average peel force (N) Peel strength (N / cm) Roughness (μm) 5.5 4.9 5.1 10.167 3.5

[0039] Example 1

[0040] According to alloy solder Sn 0.662 Pb 0.26 Bi 0.078The molar percentages of each element were determined. Using a carbide cutter and an electronic balance, 7.859 kg of tin, 5.387 kg of lead, and 1.63 kg of bismuth metal were accurately weighed and placed into a titanium alloy (220 mm × 150 mm × 80 mm) molten bath in a tin furnace. The furnace was heated to 335°C. When the solid metal in the bath was completely melted into a liquid state, a stirrer equipped with a corundum stirring rod was turned on and stirred for 2 hours to ensure complete and homogeneous mixing of tin and lead. The temperature was then lowered to 210°C, stirring was stopped, and the accumulated impurities on the surface were scraped off. The molten metal was transferred to a 320 × 25 × 22 mm 99 corundum ceramic mold, cooled, and removed, thus producing Sn. 0.662 Pb 0.26 Bi 0.078 Alloy solder.

[0041] Two reels of equal-length copper strips (10000mm×5mm×0.15mm) and one reel of high-temperature superconducting strip (10000mm×4mm×0.08mm) are mounted on the coating equipment, and Sn is then applied. 0.662 Pb 0.26 Bi 0.078 The solder is placed in the tin bath of the coating equipment and heated to 260°C. After 70 minutes, the solid solder in the tin bath is completely liquefied. The residual oxide on the surface of the liquid is scraped off with a scraper. The high-temperature strip soldering equipment is turned on and the conveyor speed is set to 5m / min. The high-temperature superconducting strip is then coated with copper strip.

[0042] Samples of the coated superconducting tape were taken and tested using a surface roughness profilometer and a bonding strength tester, respectively. The results are shown in Table 3 below:

[0043] Table 3

[0044] Maximum peel force (N) Minimum peeling force (N) Average peel force (N) Peel strength (N / cm) Roughness (μm) 14.2 12.9 13.4 26.854 0.82

[0045] Example 2

[0046] According to alloy solder Sn 0.61 Pb 0.26 Bi 0.078 In 0.052 The molar percentages of each element were determined. Using a carbide cutter and an electronic balance, 7.24 kg of tin, 5.39 kg of lead, 1.63 kg of bismuth, and 0.597 kg of bismuth metal were accurately weighed and placed into a titanium alloy (220 mm × 150 mm × 80 mm) molten tin furnace. The furnace was heated to 335°C. When the solid metal in the molten tin was completely melted into a liquid state, a stirrer equipped with a corundum stirring rod was turned on and stirred for 2 hours to ensure complete and homogeneous mixing of tin and lead. The temperature was then lowered to 190°C, stirring was stopped, and the accumulated impurities on the surface were scraped off. The molten tin was transferred to a 320 × 25 × 22 mm 99 corundum ceramic mold, cooled, and removed, thus producing Sn. 0.61Pb 0.26 Bi 0.078 In 0.052 Alloy solder.

[0047] Two reels of equal-length copper strips (10000mm×5mm×0.15mm) and one reel of high-temperature superconducting strip (10000mm×4mm×0.08mm) are mounted on the coating equipment, and Sn is then applied. 0.61 Pb 0.26 Bi 0.078 In 0.052 The solder is placed in the tin bath of the coating equipment and heated to 210°C. After 60 minutes, the solid solder in the tin bath is completely liquefied. The residual oxide on the surface of the liquid is scraped off with a scraper. The high-temperature strip soldering equipment is turned on and the conveyor speed is set to 5m / min. The high-temperature superconducting strip is then coated with copper strip.

[0048] Samples of the coated superconducting tape were taken and tested using a surface roughness profilometer and a bonding strength tester, respectively. The results are shown in Table 4 below:

[0049] Table 4

[0050] Maximum peel force (N) Minimum peeling force (N) Average peel force (N) Peel strength (N / cm) Roughness (μm) 19.6 17.9 18.6 37.179 0.80

[0051] This invention, based on the practical application of superconducting tapes, employs a high-temperature interfusion of four metals—tin, lead, bismuth, and indium—which are characterized by low melting points, corrosion resistance, and good plasticity, followed by homogenization and then cooling of the alloy solder. Example 2 shows the Sn alloy prepared... 0.61 Pb 0.26 Bi 0.078 In 0.052 The solder used for coating high-temperature superconducting tapes reduced the surface roughness from 3.2 μm to 0.8 μm compared to Comparative Example 1. The bonding force of the coated tape was significantly enhanced, the peel force increased from 5.8 N to 18.6 N, and the peel strength increased from 11.673 (N / cm) to 37.179 (N / cm). This ensured that the coated high-temperature superconducting tapes had excellent superconducting and mechanical properties in applications.

[0052] like Figure 1 As shown, when a high-temperature superconducting tape coated with tin-lead (6337) solder is cabled, microcracks appear in the REBCO thin-film ceramic layer due to external pressure. Figure 2 As shown, Sn 0.61 Pb 0.26 Bi 0.078 In 0.052The alloy solder coats the superconducting strip, resulting in uniform solder joints during use. The middle high-temperature superconducting strip has a strong bond with the two outer copper strips, exhibiting good flexibility. When the high-temperature superconducting strip is cabled, the REBCO thin-film ceramic layer will not develop microcracks under external pressure, ensuring the electrical performance stability of the cable.

[0053] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A method for preparing an alloy solder for coating high-temperature superconducting tapes, characterized in that, According to the formula, tin, lead, bismuth, and indium are fused together at high temperature and homogenized, then cooled to obtain an alloy solder. The molar ratio of tin:lead:bismuth:indium is tin:lead:bismuth:indium = (0.60-0.662):(0.20-0.26):(0.021-0.078):(0.035-0.052). The specific steps of homogenization are as follows: according to the ratio, accurately weigh the four metals tin, lead, bismuth and indium, and then put them into the molten pool of tin furnace titanium alloy. Heat the tin furnace to the melting homogenization temperature. When the solid metal in the molten pool is completely melted into liquid, turn on the stirrer equipped with a corundum stirring rod to stir so that the four metals tin, lead, bismuth and indium are completely mixed and homogenized. The cooling step is as follows: cool down to 185-210℃, stop stirring, use a scraper to remove the enriched impurity solids on the surface of the liquid, transfer it to a mold in the molten state, cool and remove it to obtain the alloy solder.

2. The method for preparing the alloy solder for high-temperature superconducting tape coating according to claim 1, characterized in that, The molar ratio of tin, lead, bismuth, and indium is tin:lead:bismuth:indium = 0.61:0.26:0.078:0.

052.

3. The method for preparing the alloy solder for high-temperature superconducting tape coating according to claim 1, characterized in that, The melting uniformity temperature is 335℃.

4. The method for preparing the alloy solder for high-temperature superconducting tape cladding according to claim 1, characterized in that, The temperature will drop to 185-190℃.

5. An alloy solder, characterized in that, It is prepared by the preparation method according to any one of claims 1-4.

6. The application of the alloy solder according to claim 5 in high-temperature superconducting tape coating.

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