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초전도 선재의 전 열처리에 따른 기계적 및 초전도 특성에 미치는 효과
양주생,하동우,이동훈,최정규,황선역,하홍수,오상수,권영길,김명호 한국초전도학회 2004 Progress in superconductivity Vol.5 No.2
Many of research efforts have been focused on the improvement of critical current density (Jc) of silver-sheathed Bi-2223 tapes far practical applications. In this study, the transformation of Bi-2212 phase was investigated, which was transformed to orthorhombic from tetragonal through pre-annealing during powder packing and drawing process. The relationship between hardness of Bi-2212 orthorhombic phase and workability of Bi-2223/Ag tape was investigated. Bi-2223 superconducting wires with 55 filaments were fabricated by stacking and drawing process with different heat-treatment histories. Before rolling process, round wires were pre-annealing at 76$0^{\circ}C$ and in a low oxygen partial pressure. We confirmed that pre-annealing step was to transform to Bi-2212 orthorhombic structure from Bi-2212 tetragonal structure and to reduce the formation of second phases. However the breakages were created at Ag-alloy clad during rolling for pre-annealed Bi-22231Ag tapes. Several pre-annealing scenarios were introduced to reduce the breakages during rolling process. Microstructure and critical current density of pre-annealed Bi-2223 superconducting tapes were investigated. We could achieve proper pre-annealing conditions for Ag-alloy clad Bi-2223 superconducting tapes.
초저온용 밸브의 초저온성능 시험평가방법 국제표준에 대한 연구
김윤철(Yoon-Chul Kim),허중식(Joong-Sik Heo),황선역(Sun-Yeok Hwang) 표준인증안전학회 2013 표준인증안전학회지 Vol.3 No.2
There have not been international standards about the test evaluation for cryogenic valves so far. It just follows local or organization standards at the moment. To develop the international standard of cryogenic test method and procedure, we have studied domestic and international techniques and trends about the test method. We also have attended international conference meetings and seminars for technical agreement of the standard procedure and test method. The standard procedure has been revised by analysing a lot of test results using the standard test method. Finally we try to register the test method for cryogenic valves as an international standard through activities in the international working group or international conference meetings. In this paper, the results of the ISO international conference meeting(ISO/TC 153) at Canada are briefly presented.