• Progress in Superconductivity
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• v.8 no.1
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• pp.98-103
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• 2006

[$Bi_2Sr_2Ca_1Cu_2O_x$](BSCCO 2212) tubes were fabricated by centrifugal melting process(CMP). BSCCO 2212 powder was melted in a Pt crucible and solidified in a rotating steel mold. The BSCCO 2212 tube samples separated from steel mold were heat-treated at $800^{\circ}C\;and\;810^{\circ}C$ in oxygen flow. The critical current($I_c$) of the samples was measured by transport measurement at 77K, and the microstructure was investigated by scanning electron microscope. The $J_c$ at 77K of the tubes heated treated at $800^{\circ}C\;and\;810^{\circ}C$ were 197 and 240 $A/cm^2$, respectively. It was observed that the plate like grains in BSCCO 2212 tube was more developed in the sample heat treated at $810^{\circ}C\;and\;800^{\circ}C$ heated tube. It is found that the critical current($I_c$) of the BSCCO 2212 sample was dependent on the heating schedule regarding the growth of the BSCCO 2212 grains.

• Progress in Superconductivity
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• v.7 no.2
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• pp.174-178
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• 2006

For the practical application on SCFCL, Bi2212 tubes were fabricated by Centrifugal Forming Process (CFP) in terms of many different processing parameters. Typical sizes of tubes were 60, 150 mm in length and 2.5, 3.5, 4.8 mm in thickness. Initially powder was melted by induction heating. The optimum range of melting temperatures and preheating temperature were $1100^{\circ}C$ and $500^{\circ}C$ for 30min respectively. The nominal mold rotating speed was around 1000 RPM. A tube was annealed at $840^{\circ}C$ for 80 hours in oxygen atmosphere. The tube of 50mm x 70mm x 2.5mm, rotated with 1000 RPM showed $I_c=890\;A\;and\;T_c=80$. It was found that the tube processed with faster rate of mold rotation speed, thinner tube thickness and shorter tube length shows better electric characteristics as compared with the tube normally processed. In order to study the uniformity heat and fluid flow analysis tool was adopted along tube.

• Journal of the Korean Society for Heat Treatment
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• v.32 no.5
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• pp.195-200
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• 2019

For expanding the applications and workability of TiAl alloy, elongation is very important property. Fine microstructure is needed for elongation and physical properties of TiAl alloys. In this study, The effects of cyclic heat treatment process for fine microstructure of Ti-46Al-Nb-W-Cr-Si-C alloy, which was made by VAR (vacuum arc remelting) and VIM(vacuum induction melting) centrifugal casting process, was investigated. Cycle heat treatment process was very effective for recrystallization of this TiAl system, which has microstructure size of $50{\sim}100{\mu}m$ through pre-heat treatment, cyclic heat treatment in ${\alpha}+{\gamma}$ phase region and solution heat treatment respectively. Refined grain size was finally confirmed by photos of optical microscope and scanning electron microscope.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.4
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• pp.2364-2369
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• 2015

In this paper, the optimum RPM was suggested comparing rotor filling rate of RPM through the analysis of rotor's filling rate as studying and developing centrifugal-casting machine's method for high precision rotor in order to increase the related types of business's productivity. The result was similar to other result in industrial site, showing 99.47% of filling rate when rotational speeds are 600 rpm, so it is considered that if this result is conducted with additional research, it will be possible to plan a better process design. Besides, the optimum temperature of compact ladle was examined to produce high quality casting product through the analysis of compact ladle's conductivity. In the case of the heating device's absence using nicrome wire, Al solution solidifies falling drastically into $427^{\circ}C$. However, it is feasible to work over $427^{\circ}C$ which is the melting temperature of aluminium solution when the heating device of nicrome wire is included. It reveals that there is little temperature change.

• 한국초전도학회:학술대회논문집
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• v.16
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• pp.85-85
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• 2006

• Nuclear Engineering and Technology
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• v.49 no.8
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• pp.1727-1732
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• 2017

Pyroprocessing is an alternative method of reprocessing spent fuel, usually involving the dissolving spent fuel in a molten salt media. The National Nuclear Laboratory designed, built, and commissioned a molten salt dynamics rig to investigate the transfer characteristics of molten lithium chloride-potassium chloride eutectic salt. The efficacy and flow characteristics of a high-temperature centrifugal pump and argon gas lift were obtained for pumping the molten salt at temperatures up to $500^{\circ}C$. The rig design proved suitable on an industrial scale and transfer methods appropriate for use in future molten salt systems. Corrosion within the rig was managed, and melting techniques were optimized to reduce stresses on the rig. The results obtained improve the understanding of molten salt transport dynamics, materials, and engineering design issues and support the industrialization of molten salts pyroprocessing.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.267-267
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• 2006

전력에 큰 손실을 초래하는 고장전류를 차단하기 위한 한류기(FCL) 소재로서 고온 초전도체인 BSCCO 2212가 사용된다. 고온에서 용융된 BSCCO 2212 분말은 원심성형법에 의해 한류기용 튜브로 제조되었다. BSCCO 튜브의 기계적 특성을 높이고 용융온도를 낮추기 위해 $SrSO_4$(10wt-%)를 첨가하였다. 용탕은 $1200^{\circ}C$에서 완전히 용융되어 금속 몰드로 주입되었고 원심성형에 사용되는 금속 몰드는 $550^{\circ}C$ 온도로 2시간 예열 후 1020 ~ 2520 RPM으로 회전시켰다. 원심력에 의해 성형된 BSCCO 튜브는 약 48시간 동안 로에서 서냉 후 금속 몰드로부터 분리하였다. 튜브의 용이한 분리를 위해 이형제로서 BSCCO 2212 powder를 사용하였고 임계전류측정을 고려하여 Ag tape 단자를 튜브 끝단에 부착하였다. BSCCO 제조 공정에 있어서 몰드의 예열온도, 용융온도, 몰드 회전속도 등의 변수를 조절하여 최적의 조건을 확립하였다. 제조한 BSCCO 튜브의 임계전류($I_c$)와 임계전류밀도($J_c$)는 77K에서 536A와 $205A/cm^2$ 이었다. 본 연구에서는 BSCCO 2212 튜브를 제조하는 공정조건 변화와 각 조건에서 제조된 BSCCO 2212 튜브의 전기적 특성 및 그에 따른 분석에 대해 기술하였다.

• Journal of Technologic Dentistry
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• v.31 no.1
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• pp.55-61
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• 2009

Passive fitting of meso-structure and super-structures is a predominant requirement for the longevity and clinical success of osseointegrated dental implants. However, precision and passive fitting has been unpredictable with conventional methods of casting as well as for corrective techniques. Alternative to conventional techniques, electro discharge machining(EDM) is an advanced method introduced to dental technology to improve the passive fitting of implant prosthesis. In this technique material is removed by melting and vaporization in electric sparks. Regarding the efficacy of EDM, the application of this technique induces severe surface morphological and elemental alterations due to the high temperatures developed during machining, which vary between $10,000{\sim}20,000^{\circ}C$. The aim of this study was to investigate the morphological and elemental alterations induced by EDM process of casting dental gold alloy and non-precious alloy used for the production of implant-supported prosthesis. A conventional clinical dental casting alloys were used for experimental specimens patterns, which were divided in three groups, high fineness gold alloy(Au 75%, HG group), low fineness gold alloy(Au 55%, LG group) and nonprecious metal alloy(Ni-Cr, NP group). The UCLA type plastic abutment patterns were invested with conventional investment material and were cast in a centrifugal casting machine. Castings were sandblasted with $50{\mu}m\;Al_2O_3$. One casting specimen of each group was polished by conventional finishing(HGCON, LGCON, NPCON) and one specimen of each group was subjected to EDM in a system using Cu electrodes, kerosene as dielectric fluid in 10 min for gold alloy and 20 min for Ni-Cr alloy(HGEDM. LGEDM, NOEDM). The surface morphology of all specimens was studied under an energy dispersive X-ray spectrometer (EDS). The quantitative results from EDS analysis are presented on the HGEDM and LGEDM specimens a significant increase in C and Cu concentrations was found after EDM finishing. The different result was documented for C on the NPEDM with a significant uptake of O after EDM finishing, whereas Al, Si showed a significant decrease in their concentrations. EDS analysis showed a serious uptake of C and Cu after the EDM procedure in the alloys studied. The C uptake after the EDM process is a common finding and it is attributed to the decomposition of the dielectric fluid in the plasma column, probably due to the development of extremely high temperatures. The Cu uptake is readily explained from the decomposition of Cu electrodes, something which is also a common finding after the EDM procedure. However, all the aforementioned mechanisms require further research. The clinical implication of these findings is related with the biological and corrosion resistance of surfaces prepared by the EDM process.