铋系超导线材拉拔过程中的粉体变形行为

Deformation Behavior of BSCCO Powder during the Drawing Process

摘要:

单芯和多芯拉拔工艺是铋系高温超导带材（Bi-2223/Ag）制备过程中必不可少的重要环节。为研究超导粉体在拉拔过程中的变形行为，对单芯超导线材的拉拔工艺进行理论分析，建立了工艺参数与粉体密度之间的关系，并通过试验验证其合理性。同时，采用大截面减缩率单芯拉拔工艺来实现铋系超导线材的节能高效成形。对1.86 mm61芯Bi-2223/Ag线材进行显微硬度测试，并结合数值模拟进行三道次拉拔加工，分析认为: 在加工过程中，各超导芯之间及芯内部均存在密度分布不均匀性，且各层粉体密度随拔制过程不断波动，将不利于后续轧制工艺。为此，提出渐进跑道形三道次拉拔工艺，并应用于铋系超导带材的后期拉拔加工，可提高最终带材的临界电流密度10.1 %

Abstract:

Monofilament and multi-filament drawing processes play important roles in the manufacture of Bi-based high-temperature superconductor (HTS) tapes. In order to investigate the deformation behavior of superconducting powder, the theoretical derivation was used to analyze the drawing process of the single filament superconductor wire, and a relationship between processing parameters and powder density was determined. The experiments were applied to verify the feasibility and effectiveness of the derivation. Also, the large cross-section reduction drawing technique was employed to optimize the process and to achieve advanced energy-saving forming. For 61-filament Bi-2223/Ag wire with a diameter of 1.86 mm, the Vickers hardness of the powder cores was measured, and the finite element model of the drawing of the multi-filament superconductor wire was established. It is found that the powder density of different filaments is of inhomogeneous distribution, especially the large fluctuation in the radial distribution for layers of filaments during process, which will directly affect the ultimate quality of tapes. Meanwhile, the Gradual Racetrack-type Tri-pass Drawing process was developed to fabricate Bi-2223/Ag tapes. The experimental results show that the Racetrack drawing can increase the critical current of HTS tape by 10.1%.