A method for preparing a sealed bi-based superconducting tape

Abstract

This invention discloses a method for preparing a Bi-based superconducting tape seal. The method includes: 1. Drawing a Bi-based round bar prepared by the PIT method to obtain a Bi-based round wire; 2. Rolling the Bi-based round wire with a pre-reserved head and tail to obtain a primary rolled tape; 3. Rolling the primary rolled tape with a pre-reserved head and tail to obtain a secondary rolled tape; 4. Repeating the rolling process on the secondary rolled tape to obtain a Bi-based rolled tape; 5. Winding and melting the two ends of the Bi-based rolled tape with Ag wire to seal; 6. Sintering under high pressure to obtain the Bi-based superconducting tape. This invention, by reserving the head and tail lengths in each rolling process, obtains a wire-plus-tape Bi-based tape structure with round wires at both ends and a flat tape in the middle. Utilizing the non-anisotropic nature of the round wires at both ends, the uniformity of the sealing molten pool is ensured, improving the sealing success rate of the Bi-based tape and thus increasing the yield of the Bi-based superconducting tape.

Description

Technical Field

[0001] This invention belongs to the technical field of Bi-based high-temperature superconducting materials, specifically relating to a method for preparing a Bi-based superconducting tape seal. Background Technology

[0002] Bi-based high-temperature superconducting materials have broad application prospects in superconducting motors, superconducting magnets, and superconducting cables. Currently, Bi-based high-temperature superconducting tapes are typically prepared using the powder-in-tube method, which involves loading precursor powder into a silver tube, using bundled plastic deformation and rolling processes to prepare the superconducting green tape, and then using high-pressure heat treatment technology to form high-density superconducting core wires and high current-carrying capacity Bi-based tapes. To achieve high-pressure heat treatment, a sufficient pressure difference must be maintained between the inside and outside of the tape, creating an external pressure that is much higher than the gas pressure generated inside the wire during heat treatment. This suppresses the increase in tape thickness and increases the core wire density. Therefore, the development of high-temperature and high-pressure heat treatment technology has significantly improved the critical current density performance of Bi-based tapes.

[0003] Because the superconducting core wire does not form the final superconducting phase before heat treatment, it is composed of powdered oxide powder. During high-pressure heat treatment, the ambient gas pressure is much higher than the internal gas pressure of the superconducting core wire. The ambient gas enters the superconducting core wire through the two ends of the tape opening and then gradually diffuses into the tape interior through the gaps in the powdered oxide. During the high-temperature and high-pressure sintering of Bi-based tapes, the ambient gas diffuses rapidly within the superconducting tape core wire, with a diffusion distance reaching tens of meters, resulting in a decrease in the density and current-carrying capacity of this part of the tape.

[0004] Some scholars have attempted to wrap the ends of the strip with rectangular silver alloy sheets, then heat them to melt the silver alloy sheets and form a cap. However, because the width-to-thickness ratio of Bi-based strips is usually greater than 10, there is a significant difference in heat dissipation between the edges and the center of the strip. This results in temperature differences at different locations of the silver alloy sheet wrapping the strip, making it impossible for it to melt simultaneously and instantaneously. This easily leads to incomplete melting in some areas or excessively high temperatures causing the molten pool to move and detach from both ends of the strip, resulting in a strip sealing welding success rate of less than 20%.

[0005] The aforementioned problems not only lead to significant waste in the production of superconducting tapes, but also severely restrict the progress of heat treatment condition testing for Bi-based tapes due to the uncertainty of sealing. Therefore, providing a Bi-based tape preparation technology with low testing costs and high sealing success rate is extremely important for the development of this material. Summary of the Invention

[0006] The technical problem to be solved by this invention is to provide a method for preparing Bi-based superconducting tape seals, addressing the shortcomings of the prior art. This method employs a powder-packing method to prepare Bi-based round wires and then rolls them. By reserving head and tail extension lengths during each rolling process, a wire-plus-tape Bi-based tape structure is obtained, consisting of round wires at both ends and a flat strip in the middle. Utilizing the anisotropic nature of the round wires at both ends, the uniformity of the sealed molten pool is ensured, significantly improving the sealing success rate of the Bi-based tape. This solves the problem of uneven molten pools, difficulty in sealing, and high cost caused by excessive dimensional anisotropy of Bi-based tapes.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for preparing a Bi-based superconducting tape seal, characterized in that the method includes the following steps:

[0008] Step 1: The Bi-based round bar prepared by the PIT method is drawn to obtain a Bi-based round wire with a diameter of R0 and a length of L0.

[0009] Step 2: Lift the rolls of the rolling mill, pass the Bi-series round wire obtained in Step 1 through the rolls, and leave the head of the Bi-series round wire extended by a length L1 without rolling. Then press down the rolls to perform the first rolling, leaving a length L2 at the tail of the Bi-series round wire without rolling, and L0 > L1 + L2. Lift the rolls and take out the rolled strip.

[0010] Step 3: Lift the rolls of the rolling mill, pass the first-rolled strip obtained in Step 2 through the rolls, and leave the head of the first-rolled strip with a length L3 not rolled, and L3≥L1. Then press down the rolls to perform a second rolling, leaving the tail of the first-rolled strip with a length L4 not rolled, and L4≥L2. Lift the rolls and take out the second-rolled strip.

[0011] Step 4: Repeat the rolling process in Step 3 1 to 5 times on the secondary rolled strip obtained in Step 3 to obtain a Bi-based rolled strip with round ends, a flat middle section and a thickness of R in the middle flat section.

[0012] Step 5: Seal the two ends of the Bi-based rolled strip obtained in Step 4 by winding Ag wire and melting it.

[0013] Step Six: Place the sealed Bi-based rolled strip from Step Five into a high-pressure heat treatment furnace for high-pressure heat treatment and sintering to obtain a thickness of R. H Bi-based superconducting tapes.

[0014] The above-mentioned method for preparing a Bi-based superconducting tape seal is characterized in that the diameter R0 of the Bi-based circular wire in step one is 0.8 mm to 2.0 mm, and the length L0 is greater than 100 mm. This method can effectively seal Bi-based circular wires with diameters of 0.8 mm to 2.0 mm. If the diameter is too small, the operation is difficult; if the diameter is too large, the sealing effect is poor. Therefore, the sealing success rate decreases for wires exceeding this diameter range. Simultaneously, since the melting and sintering temperatures at both ends of the wire are high during sealing, controlling the length L0 of the Bi-based circular wire to be greater than 100 mm avoids the influence of the high temperature during melting and sintering at both ends, thus meeting the requirements of subsequent experiments.

[0015] The method for preparing a Bi-based superconducting tape seal described above is characterized in that the head extension length and tail allowance length in steps two, three, and four are all not less than 30 mm. This allowance length effectively avoids the adverse effects on the performance of the wire caused by the melting and sintering of the ends of the wire for sealing.

[0016] The above-described method for preparing a Bi-based superconducting strip seal is characterized in that, during the rolling processes in steps three and four, the head extension length and tail allowance are both no less than the head extension length and tail allowance in the previous rolling process. This invention employs a step-by-step rolling process to prepare the strip. The aforementioned limitations ensure that subsequent rolling is performed based on the previous rolling pass, avoiding excessive processing rates that could cause surface defects in the strip and guaranteeing the quality of the Bi-based rolled strip.

[0017] The above-mentioned method for preparing a Bi-based superconducting strip seal is characterized in that the thickness R of the intermediate flat strip of the Bi-based rolled strip in step four is 0.20 mm to 0.40 mm.

[0018] The above-mentioned method for preparing a Bi-based superconducting tape seal is characterized in that the Ag wire in step five has a purity of 99.99%. By limiting the purity of the Ag wire, impurities are avoided, and the impact of the sealing process on the tape performance is reduced.

[0019] The above-mentioned method for preparing a Bi-based superconducting strip seal is characterized in that, in step five, the melting process involves sintering the Ag wire with a cartridge torch for 5 to 10 seconds. When sealing both ends of the strip with Ag wire, the melting time of Ag and the strip itself differs due to the different diameters of the round wires at both ends of the Bi-based rolled strip. By controlling the melting and sintering method and time, the fusion and effective sealing between the round wires and Ag at both ends of the Bi-based rolled strip are ensured.

[0020] The above-mentioned method for preparing a Bi-based superconducting tape seal is characterized in that the atmosphere used in the high-pressure heat treatment sintering in step six is ​​an Ar-O2 mixed gas, the gas pressure inside the furnace is 20 atm to 100 atm, the oxygen partial pressure is 1 atm or 0.075 atm, the heat treatment temperature is 800℃ to 830℃, and the holding time is 2h to 20h.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1. This invention first uses the powder-in-tube (PIT) method to prepare Bi-based round wires, and then performs a rolling process of lifting rolls and pressing rolls. By reserving the head extension length and tail length during each rolling process, a wire-plus-strip Bi-based rolled strip structure with round wires at both ends and a flat strip in the middle is obtained. Then, after melting and sealing by wrapping Ag wire around the round wires at both ends of the structure, high-pressure heat treatment is performed to obtain Bi-based superconducting strip. By utilizing the non-anisotropic characteristic of the round wires at both ends of the wire-plus-strip Bi-based rolled strip structure, the uniformity of the sealed molten pool is ensured, which greatly improves the sealing success rate of Bi-based strip.

[0023] 2. This invention uses a design where both ends of the Bi-based rolled strip are rounded and wrapped with Ag wire instead of the conventional foil wrapping. This avoids the problem of uneven molten pool caused by overlapping or gaps between the inner and outer ends of the foil, thereby further improving the uniformity of the molten pool and increasing the sealing success rate of Bi-based strip to 100%.

[0024] 3. The high sealing rate of Bi-based tape prepared by the present invention effectively avoids the huge waste caused by poor sealing effect at both ends of the tape in the production of Bi-based tape, and greatly improves the qualification rate of Bi-based superconducting tape.

[0025] 4. The high sealing rate of Bi-seam tape prepared by the present invention avoids the test failure problem caused by the failure of sealing at both ends during the heat treatment test of Bi-seam tape, reduces the test cost, and greatly promotes the new research and development process of Bi-seam tape.

[0026] 5. The preparation method of the present invention designs the structure of Bi-based tape without requiring any modification to existing processing equipment, and is easy to implement.

[0027] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0028] Figure 1 The images show the Bi-based rolled strip prepared in Example 1 of this invention before and after sealing.

[0029] Figure 2 The thickness change diagram of the Bi-based rolled strip prepared in Example 1 of the present invention before and after high-pressure heat treatment and sintering is shown.

[0030] Figure 3a This is a diagram showing the placement of the Bi-tethered tape during the sealing process of the Bi-tethered tape using a conventional rectangular silver alloy sheet, as shown in Comparative Example 1 of the present invention.

[0031] Figure 3b This is a diagram showing the silver alloy sheet completely wrapping the end of the Bi tape during the sealing process of the Bi tape using a conventional rectangular silver alloy sheet, as shown in Comparative Example 1 of the present invention.

[0032] Figure 3c This is a diagram of the end cap of Comparative Example 1 of the present invention, after sealing the Bi-series tape with a conventional rectangular silver alloy sheet.

[0033] Figure 3d This is a top view of the seal after using a conventional rectangular silver alloy sheet to seal the Bi-tie tape in Comparative Example 1 of the present invention. Detailed Implementation

[0034] Example 1

[0035] This embodiment includes the following steps:

[0036] Step 1: The Bi-based round bar prepared by the PIT method is drawn to obtain a Bi-based round wire with a diameter of R0 = 1.50 mm and a length of L0 = 370 mm;

[0037] Step 2: Lift the rolls of the rolling mill, pass the Bi-series round wire obtained in Step 1 through the rolls, and leave the head of the Bi-series round wire 45mm out without rolling. Then press down the rolls to perform the first rolling, leaving the tail of the Bi-series round wire 60mm out without rolling. Lift the rolls and take out the rolled strip to obtain the first rolled strip.

[0038] Step 3: Lift the rolls of the rolling mill, pass the first rolled strip obtained in Step 2 through the rolls, and leave the head of the first rolled strip 50mm out without rolling. Then press down the rolls to perform a second rolling, leaving the tail of the first rolled strip 65mm out without rolling. Lift the rolls and take out the second rolled strip.

[0039] Step 4: Repeat the rolling process in Step 3 once on the secondary rolled strip obtained in Step 3 to obtain a Bi-based rolled strip with round ends, a flat middle section and a thickness of R = 0.325 mm in the middle flat section.

[0040] Step 5: Wrap both ends of the Bi-based rolled strip obtained in Step 4 with Ag wire of 99.99% purity and seal the Ag wire by sintering it with a cassette torch for 8 seconds.

[0041] Step Six: Place the sealed Bi-based rolled strip from Step Five into a high-pressure heat treatment furnace for high-pressure heat treatment sintering. The atmosphere used is an Ar-O2 mixture, the furnace gas pressure is 50 atm, the oxygen partial pressure is 0.075 atm, the heat treatment temperature is 825℃, and the holding time is 15 hours, resulting in a thickness R. H Bi-based superconducting tape with a diameter of 0.308 mm.

[0042] Figure 1 These are physical images of the Bi-based rolled strip prepared in this embodiment before and after sealing. Figure 1 It can be seen that the Bi-based rolled strip has a wire-plus-strip structure, that is, the two ends retain the round wire before rolling, and the middle part is the flat strip after rolling. The length of the round wire is 40mm to 100mm, and the length of the flat strip is 280mm to 330mm. The lengths can meet the sealing and testing requirements.

[0043] Figure 2 This is a graph showing the thickness change of the Bi-based rolled strip prepared in this embodiment before and after high-pressure heat treatment and sintering. Figure 2 It can be seen that the thickness of the Bi-based rolled strip before high-pressure heat treatment and sintering is 0.325 mm, while the thickness of the Bi-based rolled strip before high-pressure heat treatment and sintering, i.e. the Bi-based superconducting strip, is 0.308 mm, which is 5.2% less. This indicates that the preparation method of the present invention has successfully implemented effective sealing of the strip, realized high-pressure heat treatment of Bi-based strip, and significantly reduced the test cost.

[0044] Comparative Example 1

[0045] This comparative example includes the following steps:

[0046] Step 1, such as Figure 3a As shown, one end of a Bi-tethered tape with a width of 4.3 mm and a thickness of 0.325 mm is placed at half the length of a silver alloy sheet with a length of 30 mm, a width of 20 mm, and a thickness of 0.2 mm. The silver alloy sheet is then rolled up along the wide side, folded back and forth three times, and pressed tightly so that the silver alloy sheet completely covers the end of the Bi-tethered tape. Figure 3b As shown;

[0047] Step 2: Heat the half silver alloy sheet that is not wrapped with Bi series strip with a high temperature gun of more than 1000℃, so that the sheet melts and forms a head for sealing.

[0048] Testing revealed that existing traditional Bi-based tape end caps sealed with silver-based alloy sheets exhibit significant tilting, such as... Figure 3c As shown, an open leak can be observed at the top of the seal, such as... Figure 3d As shown, therefore, melting Ag-based alloy sheets failed to achieve a complete seal at both ends of the strip.

[0049] Example 2

[0050] This embodiment includes the following steps:

[0051] Step 1: The Bi-based round bar prepared by the PIT method is drawn to obtain a Bi-based round wire with a diameter of R0 = 1.50 mm and a length of L0 = 310 mm;

[0052] Step 2: Lift the rolls of the rolling mill, pass the Bi-series round wire obtained in Step 1 through the rolls, and leave the head of the Bi-series round wire 60mm out without rolling. Then press down the rolls to perform the first rolling, leaving the tail of the Bi-series round wire 60mm out without rolling. Lift the rolls and take out the rolled strip to obtain the first rolled strip.

[0053] Step 3: Lift the rolls of the rolling mill, pass the primary rolled strip obtained in Step 2 through the rolls, and leave the head of the primary rolled strip 65mm out without rolling. Then press down the rolls to perform a second rolling, leaving the tail of the primary rolled strip 80mm out without rolling. Lift the rolls and remove the strip to obtain the secondary rolled strip.

[0054] Step 4: Repeat the rolling process in Step 3 four times on the secondary rolled strip obtained in Step 3 to produce a Bi-based rolled strip with round ends, a flat middle section, and a thickness of R = 0.27 mm in the middle flat section.

[0055] Step 5: Wrap both ends of the Bi-based rolled strip obtained in Step 4 with Ag wire of 99.99% purity and seal the Ag wire by sintering it with a cassette torch for 8 seconds.

[0056] Step Six: Place the sealed Bi-based rolled strip from Step Five into a high-pressure heat treatment furnace for high-pressure heat treatment sintering. The atmosphere used is an Ar-O2 mixture, the furnace gas pressure is 50 atm, the oxygen partial pressure is 0.075 atm, the heat treatment temperature is 825℃, and the holding time is 15 hours, resulting in a thickness R. H Bi-based superconducting tape with a diameter of 0.257 mm.

[0057] Testing revealed that the thickness of the Bi-based rolled strip after high-pressure heat treatment and sintering, i.e. the Bi-based superconducting strip, was reduced by 4.8% compared to before high-pressure heat treatment and sintering, indicating that the preparation method of the present invention successfully achieved effective sealing of the strip.

[0058] Example 3

[0059] This embodiment includes the following steps:

[0060] Step 1: The Bi-based round bar prepared by the PIT method is drawn to obtain a Bi-based round wire with a diameter of R0 = 0.8 mm and a length of L0 = 400 mm;

[0061] Step 2: Lift the rolls of the rolling mill, pass the Bi-series round wire obtained in Step 1 through the rolls, and leave the head of the Bi-series round wire 50mm out without rolling. Then press down the rolls to perform the first rolling, leaving the tail of the Bi-series round wire 55mm out without rolling. Lift the rolls and take out the rolled strip to obtain the first rolled strip.

[0062] Step 3: Lift the rolls of the rolling mill, pass the first rolled strip obtained in Step 2 through the rolls, and leave the head of the first rolled strip 55mm out without rolling. Then press down the rolls to perform a second rolling, leaving the tail of the first rolled strip 60mm out without rolling. Lift the rolls and take out the second rolled strip.

[0063] Step 4: Repeat the rolling process in Step 3 5 times on the secondary rolled strip obtained in Step 3 to obtain a Bi-based rolled strip with round ends, a flat middle section and a thickness of R = 0.26 mm in the middle flat section.

[0064] Step 5: Wrap both ends of the Bi-based rolled strip obtained in Step 4 with Ag wire of 99.99% purity and seal the Ag wire by sintering it with a cassette torch for 5 seconds.

[0065] Step Six: Place the sealed Bi-based rolled strip from Step Five into a high-pressure heat treatment furnace for high-pressure heat treatment sintering. The atmosphere used is an Ar-O2 mixture, the furnace gas pressure is 50 atm, the oxygen partial pressure is 1 atm, the heat treatment temperature is 810℃, and the holding time is 5 hours, resulting in a thickness R. H Bi-based superconducting tape with a diameter of 0.25 mm.

[0066] Testing revealed that the thickness of the Bi-based rolled strip after high-pressure heat treatment and sintering, i.e. the Bi-based superconducting strip, was reduced by 4.8% compared to before high-pressure heat treatment and sintering, indicating that the preparation method of the present invention successfully achieved effective sealing of the strip.

[0067] Example 4

[0068] This embodiment includes the following steps:

[0069] Step 1: The Bi-based round bar prepared by the PIT method is drawn to obtain a Bi-based round wire with a diameter of R0 = 0.8 mm and a length of L0 = 320 mm;

[0070] Step 2: Lift the rolls of the rolling mill, pass the Bi-series round wire obtained in Step 1 through the rolls, and leave the head of the Bi-series round wire 55mm out without rolling. Then press down the rolls to perform the first rolling, leaving the tail of the Bi-series round wire 55mm out without rolling. Lift the rolls and take out the rolled strip to obtain the first rolled strip.

[0071] Step 3: Lift the rolls of the rolling mill, pass the first rolled strip obtained in Step 2 through the rolls, and leave the head of the first rolled strip 60mm out without rolling. Then press down the rolls to perform a second rolling, leaving the tail of the first rolled strip 60mm out without rolling. Lift the rolls and take out the second rolled strip.

[0072] Step 4: Repeat the rolling process in Step 3 four times on the secondary rolled strip obtained in Step 3 to obtain a Bi-based rolled strip with round ends, a flat middle section and a thickness of R = 0.20 mm in the middle flat section.

[0073] Step 5: Wrap both ends of the Bi-based rolled strip obtained in Step 4 with Ag wire of 99.99% purity and seal the Ag wire by sintering it with a cassette torch for 5 seconds.

[0074] Step Six: Place the sealed Bi-based rolled strip from Step Five into a high-pressure heat treatment furnace for high-pressure heat treatment sintering. The atmosphere used is an Ar-O2 mixture, the furnace gas pressure is 20 atm, the oxygen partial pressure is 1 atm, the heat treatment temperature is 800℃, and the holding time is 2 hours, resulting in a thickness of R. H Bi-based superconducting tape with a diameter of 0.192 mm.

[0075] Testing revealed that the thickness of the Bi-based rolled strip after high-pressure heat treatment and sintering, i.e., the Bi-based superconducting strip, was reduced by 4% compared to before high-pressure heat treatment and sintering, indicating that the preparation method of the present invention successfully achieved effective sealing of the strip.

[0076] Example 5

[0077] This embodiment includes the following steps:

[0078] Step 1: The Bi-based round bar prepared by the PIT method is drawn to obtain a Bi-based round wire with a diameter of R0 = 2.0 mm and a length of L0 = 250 mm;

[0079] Step 2: Lift the rolls of the rolling mill, pass the Bi-series round wire obtained in Step 1 through the rolls, and leave the head of the Bi-series round wire 30mm out without rolling. Then press down the rolls to perform the first rolling, leaving the tail of the Bi-series round wire 30mm out without rolling. Lift the rolls and take out the rolled strip to obtain the first rolled strip.

[0080] Step 3: Lift the rolls of the rolling mill, pass the first rolled strip obtained in Step 2 through the rolls, and leave the head of the first rolled strip 35mm out without rolling. Then press down the rolls to perform a second rolling, leaving the tail of the first rolled strip 35mm out without rolling. Lift the rolls and take out the second rolled strip.

[0081] Step 4: Repeat the rolling process in Step 3 5 times on the secondary rolled strip obtained in Step 3 to obtain a Bi-based rolled strip with round ends, a flat middle section and a thickness of R = 0.40 mm in the middle flat section.

[0082] Step 5: Wrap both ends of the Bi-based rolled strip obtained in Step 4 with Ag wire of 99.99% purity and seal the Ag wire by sintering it with a cassette torch for 10 seconds.

[0083] Step Six: Place the sealed Bi-based rolled strip from Step Five into a high-pressure heat treatment furnace for high-pressure heat treatment sintering. The atmosphere used is an Ar-O2 mixture, the furnace gas pressure is 100 atm, the oxygen partial pressure is 0.075 atm, the heat treatment temperature is 830℃, and the holding time is 20 hours, resulting in a thickness of R. H Bi-based superconducting tape with a diameter of 0.379 mm.

[0084] Testing revealed that the thickness of the Bi-based rolled strip after high-pressure heat treatment and sintering, i.e., the Bi-based superconducting strip, was reduced by 5.3% compared to before high-pressure heat treatment and sintering, indicating that the preparation method of the present invention successfully achieved effective sealing of the strip.

[0085] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing a Bi-based superconducting tape seal, characterized in that, The method includes the following steps: Step 1: The Bi-based round bar prepared by the PIT method is drawn to obtain a Bi-based round wire with a diameter of R0 and a length of L0. Step 2: Lift the rolls of the rolling mill, pass the Bi-series round wire obtained in Step 1 through the rolls, and leave the head of the Bi-series round wire extended by a length L1 without rolling. Then press down the rolls to perform the first rolling, leaving a length L2 at the tail of the Bi-series round wire without rolling, and L0 > L1 + L2. Lift the rolls and take out the rolled strip. Step 3: Lift the rolls of the rolling mill, pass the first-rolled strip obtained in Step 2 through the rolls, and leave the head of the first-rolled strip with a length L3 not rolled, and L3≥L1. Then press down the rolls to perform a second rolling, leaving the tail of the first-rolled strip with a length L4 not rolled, and L4≥L2. Lift the rolls and take out the second-rolled strip. Step 4: Repeat the rolling process in Step 3 1 to 5 times on the secondary rolled strip obtained in Step 3 to obtain a Bi-based rolled strip with round ends, a flat middle section and a thickness of R in the middle flat section. Step 5: Seal the two ends of the Bi-based rolled strip obtained in Step 4 by winding Ag wire and melting it. Step six, the Bi-based rolled strip sealed in step five is placed in a high-pressure heat treatment furnace for high-pressure heat treatment sintering to obtain a Bi-based superconducting tape with a thickness of R H .

2. The method for preparing a Bi-based superconducting tape seal according to claim 1, characterized in that, The diameter R0 of the Bi-series circular wire mentioned in step one is 0.8mm to 2.0mm, and the length L0 is greater than 100mm.

3. The method for preparing a Bi-based superconducting tape seal according to claim 1, characterized in that, In steps two, three, and four, the length of the head extending out and the length of the tail remaining are all not less than 30mm.

4. The method for preparing a Bi-based superconducting tape seal according to claim 1, characterized in that, In steps three and four, the length of the head extending out and the length of the tail leaving out during the rolling process shall not be less than the length of the head extending out and the length of the tail leaving out during the previous rolling process.

5. The method for preparing a Bi-based superconducting tape seal according to claim 1, characterized in that, The thickness R of the intermediate flat strip of the Bi-based rolled strip mentioned in step four is 0.20 mm to 0.40 mm.

6. The method for preparing a Bi-based superconducting tape seal according to claim 1, characterized in that, The Ag line mentioned in step five has a purity of 99.99%.

7. The method for preparing a Bi-based superconducting tape seal according to claim 1, characterized in that, The melting process described in step five involves sintering the Ag wire using a cartridge torch for 5 to 10 seconds.

8. The method for preparing a Bi-based superconducting tape seal according to claim 1, characterized in that, The atmosphere used in the high-pressure heat treatment sintering in step six is ​​an Ar-O2 mixed gas, the gas pressure inside the furnace is 20 atm to 100 atm, the oxygen partial pressure is 1 atm or 0.075 atm, the heat treatment temperature is 800℃ to 830℃, and the holding time is 2h to 20h.

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