A method for mitigating the saddle effect of iron-based superconducting tapes
Patent Information
- Application Number
- CN202611252089.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-08-18
- Publication Date
- 2026-10-23
AI Technical Summary
然而，此时面临的问题为内外包套硬度差异增大，多芯圆线轧制成带材时超导芯变形不均匀，马鞍效应严重，容易出现断芯现象
[0022]（1）本发明不改变常规铁基超导带材的冷变形工艺参数，仅在轧制工艺中控制圆线进入轧辊的方向，使轧制下压方向与超导芯最密排方向不大于5度，即可达到缓解内外包套硬度差异较大时马鞍效应严重的问题，避免中部超导芯发生断裂。
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of superconducting materials technology, and particularly relates to a method for mitigating the saddle effect in iron-based superconducting tapes. Background Technology
[0002] 2008 iron-based superconductor LaFeAsO 1-x F x The discovery of this technology sparked a surge of research into iron-based superconductors (IBS). IBS possesses a high critical transition temperature (T0). c ), higher critical field (H c2 With advantages such as high temperature and low anisotropy (γ), it has significant application prospects in high-field applications. Currently, the most promising iron-based superconductor for practical application is the 122-series AEFe2As2. Taking (Ba,K)Fe2As2 as an example, its T... c 38K, H c2 It can exceed 100T, and more importantly, it has low anisotropy (1-2) and the weak grain boundary bonding effect is not obvious. Therefore, it can be prepared using the low-cost powder-in-tube method (PIT) to produce high J c Wire and strip materials.
[0003] In practical applications, silver cladding presents two problems. First, the manufacturing cost of the tape is very high when using pure silver as the outer cladding. Second, the mechanical properties of the sintered tape are very low, making it prone to damage in practical applications. Therefore, composite cladding is a better choice for 122-series iron-based superconducting tapes. The inner layer still uses a silver cladding that does not react with the superconducting core, while the outer layer can be selected from various low-cost and high-performance outer cladding options. Since the superconducting core of the superconducting tape also needs to consider both electrical and thermal conductivity, copper alloys are suitable materials for the outer cladding, such as cupronickel, chromium bronze, zirconium bronze, and beryllium bronze. When using copper alloys as the outer cladding, it can not only improve the density of the superconducting core to increase J... c This can also improve the mechanical properties of the strip. However, the problem at this time is that the hardness difference between the inner and outer sheaths increases, the superconducting core deformation is uneven when the multi-core round wire is rolled into strip, the saddle effect is severe, and core breakage is likely to occur. Summary of the Invention
[0004] To address the aforementioned technical problems, this invention provides a method for mitigating the saddle effect in iron-based superconducting tapes. This method can improve the deformation uniformity of the superconducting core, effectively alleviate the saddle effect, prevent superconducting core fracture, and ultimately increase the critical current density of the tape.
[0005] To achieve the above objectives, the present invention adopts the following technical solution:
[0006] A method to alleviate the saddle effect in iron-based superconducting strips is that the angle between the rolling direction and the direction of the densest packing of the superconducting core is no greater than 5 degrees.
[0007] The rolling process is performed in the same direction as the densest packing of the superconducting core.
[0008] Among them, the direction with the densest packing of superconducting cores is the direction with the largest number of superconducting cores.
[0009] The method includes the following steps:
[0010] S1: Load the iron-based superconducting powder into the primary tube and seal both ends;
[0011] S2: Pull out the primary tube after sealing, and then cut it into several single cores;
[0012] S3: Insert several single cores into the secondary tube and seal both ends;
[0013] S4: Pull-out samples are obtained by pulling out the sealed secondary pipe;
[0014] S5: Roll the drawn sample to obtain a rolled sample;
[0015] S6: The rolled sample is sintered and cooled to obtain an iron-based superconductor.
[0016] Specifically, step S5 involves first polishing the end (also called the head section) of the drawn sample until all single-core morphologies are exposed, then marking the densest packing direction of the superconducting core, and determining the rolling direction of the rolling process based on the densest packing direction of the superconducting core.
[0017] The rolling process involves multiple passes, and the angle between the downward pressing direction of each pass and the direction of the densest packing of the superconducting core is no greater than 5 degrees.
[0018] In each rolling process, the downward pressing direction is consistent.
[0019] The rolling process is flat roll rolling.
[0020] Among them, the iron-based superconductor is the 122 series iron-based superconductor.
[0021] The beneficial effects of this invention are as follows:
[0022] (1) This invention does not change the cold deformation process parameters of conventional iron-based superconducting strips. It only controls the direction of the round wire entering the roll in the rolling process, so that the rolling pressing direction is no more than 5 degrees from the direction of the densest superconducting core. This can alleviate the problem of severe saddle effect when the hardness difference between the inner and outer sheaths is large, and avoid the breakage of the middle superconducting core.
[0023] (2) The method of the present invention can also improve the lateral width of the superconducting core, improve the texture of the superconducting core, and further improve the critical current density of the tape. Attached Figure Description
[0024] Figure 1 This is a schematic diagram showing that the rolling pressing direction of Embodiments 1, 3 and 5 of the present invention forms an angle of 5 degrees with the direction of the densest packing of the superconducting core.
[0025] Figure 2 This is a schematic diagram showing that the rolling pressing direction of Embodiments 2, 4 and 6 of the present invention is consistent with the direction of the densest packing of the superconducting core.
[0026] Figure 3 This is a schematic diagram showing that the rolling pressing direction of Comparative Examples 1, 3, and 5 of the present invention forms an angle of 30 degrees with the direction of the densest packing of the superconducting core.
[0027] Figure 4 This is a schematic diagram showing that the rolling pressing direction of Comparative Examples 2, 4, and 6 of the present invention forms an angle of 15 degrees with the direction of the densest packing of the superconducting core.
[0028] Figure 5 This is the cross-sectional morphology of the strip obtained in Embodiment 1 of the present invention.
[0029] Figure 6 The image shows the strip cross-sectional morphology obtained in Embodiment 2 of the present invention.
[0030] Figure 7 The image shows the cross-sectional morphology of the strip obtained in Comparative Example 1 of the present invention.
[0031] Figure 8 The image shows the strip cross-sectional morphology obtained in Comparative Example 2 of this invention. Detailed Implementation
[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.
[0033] The inventors discovered that the main reason for the saddle effect in the PIT method for preparing superconducting multicore tapes is that the round wire undergoes cold deformation such as forging and drawing before rolling, transforming the superconducting core powder from a loose powder into a dense powder, significantly increasing its hardness to exceed that of the silver cladding. At this point, existing rolling processes exhibit a mismatch between the deformation of the inner and outer claddings, resulting in a severe saddle effect, which easily leads to superconducting core breakage and significantly reduces the critical current density of the tape.
[0034] To address this, the inventors discovered that by controlling the angle between the downward direction of the rolling process and the direction of the densest packing of the superconducting core to be no greater than 5 degrees, and by relying on the high-hardness superconducting core to resist the downward deformation caused by the high-hardness outer sheath, the saddle effect can be effectively alleviated and the risk of core breakage can be reduced.
[0035] The specific operation involves using existing processes for multi-core strip composite processing and drawing, with improvements made only to the rolling process. Before rolling, the head section of the round wire to be rolled (i.e., the drawn sample) is ground and polished until the superconducting core is clearly visible to the naked eye, and then the direction of the densest packing of the superconducting core is marked. During rolling, the direction in which the round wire enters the rolls is strictly controlled, ensuring that the angle between the rolling pressing direction and the direction of the densest packing of the superconducting core is no greater than 5 degrees. Subsequent rolling follows the same rolling direction requirements until the target thickness is achieved.
[0036] Example 1:
[0037] This embodiment describes the fabrication of a chromium-zirconium-copper / silver composite-clad iron-based superconducting 7-core tape. See also... Figure 1 During the rolling process, the angle between the rolling direction and the direction of the closest packing of the superconducting core is 5 degrees. The specific operation is as follows:
[0038] S1: Load 122 series iron-based superconducting powder into a silver tube (primary tube) with an outer diameter of 10 mm and an inner diameter of 8 mm, and seal both ends.
[0039] S2: Use a carbide mold to pull the sealed silver tube to a diameter of 5.33mm, and then cut it into 7 single cores of the same length.
[0040] S3: Insert 7 single cores into a chromium-zirconium copper tube (secondary tube) with an outer diameter of 20mm and an inner diameter of 16mm, and seal both ends.
[0041] S4: The secondary tube after sealing was drawn using a carbide mold to obtain a drawn sample. The surface reduction rate of a single drawing was 12%, the drawing speed was 3m / min, and the final diameter after several drawings was 1.7mm.
[0042] S5: As Figure 1 The head section of the drawn sample was polished using a polishing machine until the 7-core morphology was clearly visible to the naked eye. The direction of the densest packing of the superconducting core was marked. Then, the 7-core round wire with a diameter of 1.7 mm was rolled by flat roll at a deviation of 5 degrees, with a single rolling reduction of 31%. After 4 rolling passes, the final thickness of the rolled sample was 0.4 mm.
[0043] S6: The rolled sample with a thickness of 0.4 mm was sintered at 700℃ for 5 hours, and then cooled in the furnace after sintering.
[0044] Example 2:
[0045] See Figure 2 In the rolling process, the downward pressing direction of the rolling process is consistent with the direction of the densest packing of the superconducting core, that is, the angle between the downward pressing direction of the rolling process and the direction of the densest packing of the superconducting core is 0 degrees. The remaining operation steps are the same as in Example 1.
[0046] Comparative Example 1:
[0047] See Figure 3 In Comparative Example 1, the angle between the rolling direction and the direction of the densest packing of the superconducting core during the rolling process is 30 degrees. The remaining operating steps are the same as in Example 1.
[0048] Comparative Example 2:
[0049] See Figure 4 In Comparative Example 2, the angle between the rolling direction and the direction of the densest packing of the superconducting core in the rolling process is 15 degrees. The remaining operating steps are the same as in Example 1.
[0050] Example 3:
[0051] This embodiment describes the fabrication of a copper / silver composite-clad iron-based superconducting 7-core tape. See also... Figure 1 During the rolling process, the angle between the rolling direction and the direction of the closest packing of the superconducting core is 5 degrees. The specific operation is as follows:
[0052] S1: Load 122 series iron-based superconducting powder into a silver tube (primary tube) with an outer diameter of 10 mm and an inner diameter of 8 mm, and seal both ends.
[0053] S2: Use a carbide mold to pull the sealed silver tube to a diameter of 5.33mm, and then cut it into 7 single cores of the same length.
[0054] S3: Insert 7 single cores into a white copper tube (secondary tube) with an outer diameter of 20mm and an inner diameter of 16mm, and seal both ends.
[0055] S4: The secondary tube after sealing was drawn using a carbide mold to obtain a drawn sample. The single drawing surface reduction rate was 9%, the drawing speed was 2.25m / min, and the final diameter after several drawings was 1.7mm.
[0056] S5: As Figure 1 The head section of the drawn sample was polished using a polishing machine until the 7-core morphology was clearly visible to the naked eye. The direction of the densest packing of the superconducting core was marked. Then, the 7-core round wire with a diameter of 1.7 mm was rolled by flat rolls at a deviation of 5 degrees, with a single rolling pressure of 15.5%. After 4 rolling passes, the final thickness of the rolled sample was 0.4 mm.
[0057] S6: The rolled sample with a thickness of 0.4 mm was sintered at 700℃ for 5 hours, and then cooled in the furnace after sintering.
[0058] Example 4:
[0059] See Figure 2 In the rolling process, the downward pressing direction of the rolling process is consistent with the direction of the densest packing of the superconducting core, that is, the angle between the downward pressing direction of the rolling process and the direction of the densest packing of the superconducting core is 0 degrees. The remaining operation steps are the same as in Example 3.
[0060] Comparative Example 3:
[0061] See Figure 3 In Comparative Example 3, the angle between the rolling direction and the direction of the densest packing of the superconducting core in the rolling process is 30 degrees. The remaining operating steps are the same as in Example 3.
[0062] Comparative Example 4:
[0063] See Figure 4 In Comparative Example 4, the angle between the rolling direction and the direction of the densest packing of the superconducting core during the rolling process is 15 degrees. The remaining operating steps are the same as in Example 3.
[0064] Example 5:
[0065] This embodiment describes the fabrication of a beryllium bronze / silver composite-clad iron-based superconducting 7-core tape. See also... Figure 1 During the rolling process, the angle between the rolling direction and the direction of the closest packing of the superconducting core is 5 degrees. The specific operation is as follows:
[0066] S1: Load 122 series iron-based superconducting powder into a silver tube (primary tube) with an outer diameter of 10 mm and an inner diameter of 8 mm, and seal both ends.
[0067] S2: Use a carbide mold to pull the sealed silver tube to a diameter of 5.33mm, and then cut it into 7 single cores of the same length.
[0068] S3: Insert 7 single cores into a beryllium bronze tube (secondary tube) with an outer diameter of 19.6mm and an inner diameter of 16mm, and seal both ends.
[0069] S4: The secondary tube after sealing was drawn using a carbide mold to obtain a drawn sample. The surface reduction rate of a single drawing was 9%, the drawing speed was 2.7 m / min, and the final diameter after several drawings was 1.7 mm.
[0070] S5: The head section of the drawn sample is polished using a polishing machine until the 7-core morphology is clearly visible to the naked eye. The direction of the densest packing of the superconducting core is marked. Then, the 7-core round wire with a diameter of 1.7 mm is rolled by flat roll at a deviation of 5 degrees, with a single rolling reduction of 24.8%. The final thickness of the rolled sample after 4 rolling passes is 0.4 mm.
[0071] S6: The rolled sample with a thickness of 0.4 mm was sintered at 700℃ for 5 hours, and then cooled in the furnace after sintering.
[0072] Example 6:
[0073] See Figure 2 In the rolling process, the downward pressing direction of the rolling process is consistent with the direction of the densest packing of the superconducting core, that is, the angle between the downward pressing direction of the rolling process and the direction of the densest packing of the superconducting core is 0 degrees. The remaining operation steps are the same as in Example 5.
[0074] Comparative Example 5:
[0075] See Figure 3 In Comparative Example 5, the angle between the rolling direction and the direction of the densest packing of the superconducting core in the rolling process is 30 degrees. The remaining operating steps are the same as in Example 5.
[0076] Comparative Example 6:
[0077] See Figure 4 In Comparative Example 6, the angle between the rolling direction and the direction of the densest packing of the superconducting core during the rolling process is 15 degrees. The remaining operating steps are the same as in Example 5.
[0078] The iron-based superconductors obtained in Examples 1 to 6 and Comparative Examples 1 to 6 were tested, and the results are shown in Table 1.
[0079] Table 1
[0080]
[0081] Figure 5 This is the cross-sectional morphology of the strip obtained in Embodiment 1 of the present invention. Figure 6 The image shows the strip cross-sectional morphology obtained in Embodiment 2 of the present invention. Figure 7 The image shows the cross-sectional morphology of the strip obtained in Comparative Example 1 of the present invention. Figure 8 This is the cross-sectional morphology of the strip obtained in Comparative Example 2 of the present invention. From... Figures 5 to 8 The comparison shows that when the angle between the rolling process and the direction of the densest superconducting core is 30 degrees (Comparative Example 1) and 15 degrees (Comparative Example 2), the superconducting core in the middle breaks. However, the superconducting core of the strip obtained by rolling process in Examples 1 and 2 with an angle between the rolling process and the direction of the densest superconducting core is no greater than 5 degrees is intact and basically does not break.
[0082] As can be seen from Table 1, controlling the angle between the rolling direction and the densest packing direction of the superconducting core to be no greater than 5 degrees, especially controlling the rolling direction to be consistent with the densest packing direction of the superconducting core, can effectively alleviate the saddle effect, prevent the middle superconducting core from breaking, and at the same time increase the critical current density of iron-based superconductors.
[0083] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention. The above embodiments are provided only for the purpose of describing the present invention and are not intended to limit the present invention. Parts not described in detail in this specification are well-known in the art and are not intended to limit the scope of the present invention. The scope of the present invention is defined by the appended claims. All equivalent substitutions and modifications made without departing from the spirit and principle of the present invention should be covered within the scope of the present invention.
Claims
1. A method for mitigating the saddle effect in iron-based superconducting tapes, characterized in that, The angle between the rolling direction and the direction of the densest packing of the superconducting core is no greater than 5 degrees.
2. The method for mitigating the saddle effect in iron-based superconducting tapes according to claim 1, characterized in that, The rolling process is performed in the same direction as the densest packing of the superconducting core.
3. The method for mitigating the saddle effect in iron-based superconducting tapes according to claim 1, characterized in that, The direction of the densest packing of superconducting cores is the direction with the largest number of superconducting cores.
4. The method for mitigating the saddle effect in iron-based superconducting tapes according to any one of claims 1 to 3, characterized in that, The method includes the following steps: S1: Load the iron-based superconducting powder into the primary tube and seal both ends; S2: Pull out the primary tube after sealing, and then cut it into several single cores; S3: Insert several single cores into the secondary tube and seal both ends; S4: Pull-out samples are obtained by pulling out the sealed secondary pipe; S5: Roll the drawn sample to obtain a rolled sample; S6: The rolled sample is sintered and cooled to obtain an iron-based superconductor.
5. The method for mitigating the saddle effect in iron-based superconducting tapes according to claim 4, characterized in that, Step S5 specifically involves first polishing the ends of the drawn sample until all single-core morphologies are exposed, then marking the direction of the densest superconducting core, and determining the rolling direction of the rolling process based on the direction of the densest superconducting core.
6. The method for mitigating the saddle effect in iron-based superconducting tapes according to claim 5, characterized in that, The rolling process is a multi-pass rolling process, and the angle between the downward pressing direction of each pass and the direction of the densest packing of the superconducting core is no greater than 5 degrees.
7. The method for mitigating the saddle effect in iron-based superconducting tapes according to claim 6, characterized in that, The downward pressing direction is consistent in each rolling process.
8. The method for mitigating the saddle effect in iron-based superconducting tapes according to claim 4, characterized in that, The rolling process is flat roll rolling.
9. The method for mitigating the saddle effect in iron-based superconducting tapes according to claim 1, characterized in that, The iron-based superconductor is a 122-series iron-based superconductor.