• 한국주조공학회지
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• 제26권5호
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• pp.211-216
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• 2006

The study for thixoextrusion process of 7075, 7003 Al wrought alloys and AZ31 Mg wrought alloy was carried out with respect to reheating rate, isothermal holding temperature and time with an emphasis to the effect of homogenization on thixotropic micro-structures during the partial remelting, especially in the low liquid fraction ($f_L<0.2$). The liquid fraction and average grain size with respect to reheating profile such as reheating rate, isothermal holding temperature and time were almost uniform. It is considered very useful for thixoextrusion in terms of process control such as billet temperature control and actual extrusion time. Micro-structural controls of 7075, 7003 Al wrought alloys and AZ31 Mg wrought alloy before and after homogenization were available and thixotropic microstructures were obtained in both specimens.

• 열처리공학회지
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• 제13권4호
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• pp.239-245
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• 2000

Effect of tin and iron content on the recrystallization behavior of temary Zr-0.8Sn-x%Nb alloys were studied. The specimens with 0.1, 0.2 and 0.4 wt.% of iron were prepared under various annealing temperatures from $400^{\circ}C$ to $800^{\circ}C$ and times from 30 to 5000 minutes after vacuum arc remelting. The recrystallization behavior was observed using a polarized optical microscope, TEM and micro-vickers hardness tester. The recrystallization temperature of the alloys slightly increased with iron content due to increase of activation energy. The grain growth of the alloys with 0.1 and 0.2 wt.% of iron occured rapidly, however, that of the alloys with 0.4 wt.% iron was gradually retarded due to precipitation. The hardness of the alloy with a high iron slightly increased by the precipitation of beta phase after annealing at $800^{\circ}C$.

• 한국주조공학회지
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• 제15권3호
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• pp.283-290
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• 1995

Molybdenum ingot of 50mm in diameter were obtained from sintered Mo bars by EB drip melting technique. Macroscopic observation of EB remelted ingot indicates that coarse and columnar grains grow in the direction parallel to ingot pulling direction. This can be explained by slow solidification (3mm/min), large temperature gradient and heat flow to this direction. The orientation of columnar structure was found to be <110>, <200> and <211> by the analysis of X-ray diffraction patterns. The contents of typical metallic impurities in Mo sintered bar are 1.2ppm Cr, 3ppm Fe, 44ppm Zr, 150ppm W. Most of metallic impurities were reduced below the order of ppm except zirconium and tungsten by the selective evaporation. In the removal of nonmetallic impurities, oxygen and carbon impurities were lowered from 120 to 6ppm and from 157 to 106ppm, respectively, after first melting. Although the purification effect was not significant with the number of remelting, Vickers hardness was reduced from 217 to 195 and 184 in sequence with increasing the number of remelting.

• 자원리싸이클링
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• 제30권1호
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• pp.26-34
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• 2021

타이타늄은 구조용 금속 중 알루미늄, 철, 마그네슘에 이어서 네 번째로 풍부한 금속이지만, 금속으로의 제련이 어려워 희소금속으로 분류되고 있다. 특히 타이타늄의 제련공정은 에너지 다소비형 공정이다. 타이타늄 스크랩으로 잉곳을 제조하면 에너지 소비량과 CO2 발생량을 약 95 %까지 절감할 수 있다. 그러나 스크랩 중의 철분과 산소 등의 불순물을 제거하기 어려워 리사이클링 되는 양은 한정되어 있다. 일반적으로 고품위 타이타늄 스크랩은 순타이타늄 스펀지의 재용해 공정에 투입하여 희석하고, 저품위 스크랩은 페로타이타늄 제조용 원료로 사용되고 있다. 본 논문에서는 이러한 타이타늄의 리사이클링 기술을 이해하기 위해 타아타늄의 제련기술과 리사이클링 기술에 대하여 고찰하였다.

• Nuclear Engineering and Technology
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• 제55권3호
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• pp.1097-1104
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• 2023

A preliminary criticality analysis for novel pyrochemical apparatuses for the reprocessing of mixed uranium-plutonium nitride spent nuclear fuel from the BREST-OD-300 reactor was performed. High-temperature processing apparatuses, "metallization" electrolyzer, refinery remelting apparatus, refining electrolyzer, and "soft" chlorination apparatus are considered in this work. Computational models of apparatuses for two neutron radiation transport codes (MCU-FR and MCNP) were developed and calculations for criticality were completed using the Monte Carlo method. The criticality analysis was performed for different loads of fissile material into the apparatuses including overloading conditions. Various emergency situations were considered, in particular, those associated with water ingress into the chamber of the refinery remelting apparatus. It was revealed that for all the considered computational models nuclear safety rules are satisfied.

• Corrosion Science and Technology
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• 제2권6호
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• pp.272-276
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• 2003

High nitrogen-bearing stainless steel (HNS) containing more than Imass% N was successfully created by means of pressurized electro-slag remelting (P-ESR) without the addition of manganese. Excellent localized corrosion resistant properties of the HNS were confirmed in terms of pitting and crevice corrosion in artificial seawater. The repassivation kinetics proved higher repassivation rate for HNS.

• 자원리싸이클링
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• 제21권5호
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• pp.58-64
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• 2012

본 연구는 타이타늄 선삭 스크랩을 진공 아크 용해에 의해 건전한 버튼형 잉곳으로 제조하여 아크 발생용 소모성 전극으로의 재활용을 위해 타이타늄 내 불순물의 거동 및 특성을 평가하였다. 먼저 가스불순물인 산소는 진공 아크 용해에 의해 초기 표면의 산화층에 의해 제거되지만 이후 타이타늄에 고용된 산소는 제거되지 않는 것으로 확인되었다. 타이타늄 스크랩의 대표 금속불순물인 철의 경우 타이타늄과의 증기압 차이로 인해 진공 아크 용해에 의해 최종 20분간 용해시 약 43%의 제거율을 보이며, 최종 제조된 타이타늄 버튼형 잉곳은 ASTM 규격의 순 타이타늄 등급 3에 해당하는 순도를 보여 VAR(Vacuum Arc Remelting)용 소모성 전극의 제조에 가능한 것으로 확인하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 추계학술대회 논문집
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• pp.276-276
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• 2009

Solar cells has been studied mainly the high efficiency and lower prices. Using recycling wafer as a way to realize their money in it, there is a way to manufacture a solar cell substrate. How to play the recycling wafer, CMP(Chemical Mechanical Polishing) and remelting process is the complex and the expensive equipment. However, using the Micro-Blaster, the process easier, and cheaper prices. Micro-Blaster confirmed that the remaining amount of material left after the process recycling wafer surface.

• 마이크로전자및패키징학회지
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• 제27권1호
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• pp.1-7
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• 2020

The backside metallization process is typically used to attach a chip to a lead frame for semiconductor packaging because it has excellent bond-line and good electrical and thermal conduction. In particular, the backside metal with the Ag/Sn/Ag sandwich structure has a low-temperature bonding process and high remelting temperature because the interfacial structure composed of intermetallic compounds with higher melting temperatures than pure metal layers after die attach process. Here, we introduce a die attach process with the Ag/Sn/Ag sandwich structure to apply commercial semiconductor packages. After the die attachment, we investigated the evolution of the interfacial structures and evaluated the shear strength of the Ag/Sn/Ag sandwich structure and compared to those of a commercial backside metal (Au-12Ge).

• Journal of Advanced Marine Engineering and Technology
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• 제21권5호
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• pp.527-534
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• 1997

Freezing of an aqueous sodium cWoride solution (Nacl- H20) saturating a packed bed with ini¬tial salt concentrations of 5, 10, 15(k by weight is investigated experimentally in a rectangular cav¬ity. The system was cooled from the top, bottom and a vertical side wall. For the freezing experi¬ments from below, there was little effect of the initial salt concentration throughout the freezing process, and the global freezing rate was not affected by the initial salt concentration. For the freezing from above, the size of the mush region decreased and the mushlliquid interface became flatter as the initial liquid concentration is decreased. For the freezing from vertical side wall, reheating of the mixture was intensified with an increase in the initial salt concentration. For Ci= 5%, supercooling was observed only at the early times of freezing process, but for Ci= 15% small supercooling was observed throughout the freezing process.