• 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.

• 한국주조공학회지
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• 제24권6호
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• pp.314-322
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• 2004

The CaO crucible is expected to serve as a useful tool for melting Ti and its alloys due to its thermodynamic stability. However, tjere still remain problems that need to be resolved in the melting of Ti and its alloys to enable commerical use. The cause of the defects of Ti-6AI-4V alloy castings melted in the CaO crucible were examined and compared with induction skull melting. The key factors of the melting technique using the CaO crucible, affecting the quality of Ti-6AI-4V alloy castings, were investigated. Defects of the Ti-6AI-4V alloy castings are caused by the chemical reduction of CaO by Ti. Pressurizing with argon gas in a vacuum induction chamber is effective for reducing the defects. Preheating of the charged material in the crucible and quick pouring into a mold of lower temperature, just after melting down, are important for produsing sound Ti-6AI-4V castings.

• 한국자원리싸이클링학회:학술대회논문집
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• 한국자원리싸이클링학회 2006년도 춘계임시총회 및 제27회 학술발표대회
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• pp.56-60
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• 2006

In 2005, the imports of titanium metals was about 22.8 million US$(7,700 tons) in Korea. New scrap produced was estimated to be 359 tons and the exports were about 352 tons. Generally scrap is recylced into titanium ingot either with or without virgin metal using traditional vacuum-arc-melting and cold hearth melting. In Korea, there is no titanium ingot producers(recyclers). In this paper, the brief summary of major titanium melting technology, such as vacuum arc remelting(VAR), electron beam melting(EBM), plasma arc melting(PAM) is given and discussed. In view of titanium market situation of Korea, the technological development of ingot production from scrap is big problem to be solved in order to realize extensive cost reduction for titanium products.

• 한국입자에어로졸학회지
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• 제9권1호
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• pp.31-36
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• 2013

In this study, Mo metal powder was prepared by hydrogen reduction of Mo trioxides with different purity of 2N and 3N grades. We have obtained Mo metal powder with oxygen content of 1450 ppm by hydrogen reduction and subsequent heat treatment for degassing. Using the Mo metal powder, a low-oxygen Mo ingot was prepared by repetitive vacuum arc melting. The oxygen content of the obtained Mo ingot was less than 70 ppm after vacuum arc melting for 30 min. The purity of the Mo metal powder and the ingot was evaluated using glow discharge mass spectrometry. The purity of the respective Mo ingots was increased to 3N and 4N grades from the Mo powder of 2N and 3N grades after the repetitive vacuum arc melting. The low oxygen Mo ingot thus can be used as a raw material for sputtering targets.

• 한국진공학회:학술대회논문집
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• 한국진공학회 1997년도 제12회 학술발표회 논문개요집
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• pp.163-163
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• 1997

• 한국진공학회:학술대회논문집
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• 한국진공학회 2006년도 제31회 학술논문발표회 초록집
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• pp.184-184
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• 2006

• 한국진공학회지
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• 제12권1호
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• pp.1-6
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• 2003

50 kW급 출력의 전자빔을 발생시킬 수 있는 축선 방식 전자총 (axial electron beam gun)과 전원장치를 제작하였다. 전자총은 전자빔 발생장치와 전자빔 궤적제어장치로 이루어졌다. 전자빔 발생장치는 필라멘트와 음극(cathode), 양극(anode)으로 구성되었고 전자빔의 최대전류는 2A, 가속전압은 평균 25kV이다. 전자빔 궤적제어장치는 전자빔의 크기를 조절하는 초점 (focusing) 코일과 전자빔의 방향을 조절하는 편향(deflection) 코일 및 주사 (scanning) 코일로 구성되었다. 전자총과 별개로 진공용기 내부에 Helmholtz 코일을 설치하여 시료의 표면에 입사되는 전자빔의 입사각도를 최적화시켰다. 각 부분의 동작 특성을 측정한 결과와 제작된 전자총으로 고융점 원소인 지르코늄 (zirconium, Zr)과 가돌리늄(gadolinium, Gd) 금속을 증발시킨 결과를 정리하였다.

• Nuclear Engineering and Technology
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• 제51권6호
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• pp.1589-1595
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• 2019

In this paper, the CLAM steel strengthened by micro-scale Y-Zr-O was prepared by vacuum induction melting followed by electroslag remelting (VIM-ESR). Yttrium (Y) and zirconium (Zr) were easy to aggregates into massive yttrium-zirconium-rich inclusions in the steel melted by vacuum induction melting (VIM), which would interrupt the continuity of the matrix and reduce the mechanical properties of steel. Micron-sized Y-Zr-O inclusions would be produced with the removal of original blocky Y-Zr-rich inclusions and the submicron-sized inclusions smaller than $0.2{\mu}m$ could be retained in the steel. The small grain size and the better refinement and distribution uniformity of Y-Zr-O inclusions after remelting would be responsible for the better yield strength and toughness. For VIM-ESR alloy, the ultimate tensile strength is 749 MPa and the yield strength is 642 MPa at room temperature, meanwhile they are 391 MPa and 367 MPa at $600^{\circ}C$, respectively. Meanwhile, the ductile-brittle transition temperature (DBTT) reduced from $-43^{\circ}C$ (VIM) to $-76^{\circ}C$ (VIM-ESR).

• 한국주조공학회지
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• 제43권5호
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• pp.223-229
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• 2023

In this study, STS316L produced by a double-melting process involving vacuum induction melting (VIM) and vacuum arc remelting (VAR) was subjected to extrusion and drawing to form a tube and was subsequently electrolytic polished (EP). The grain size of the obtained STS316L without EP was approximately 55 ㎛, with no difference found after EP. The thickness of the EP layer was measured by AES and TEM, showing values of approximately 10 nm and 15 nm, respectively. After EP, the Cr/Fe and CrO/FeO ratios of the passive layer increased from 1.48 to 1.62 and from 2.15 to 2.26, respectively, while the surface roughness decreased significantly from 0.255 to 0.024 ㎛. Consequently, the corrosion rate decreased in both NaCl and HCl solutions after the EP process. Additionally, the amounts of eluted Cr and Fe ions were reduced from 1.2 to 0.8 ppb and 10.3 to 0.8 ppb, respectively. Furthermore, polarization tests revealed that STS316L treated with EP required a lower current density to reach a passive state, indicating that corrosion behavior was retarded.

• 한국세라믹학회지
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• 제15권2호
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• pp.72-78
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• 1978

The vapor pressure of the high melting point oxides, MgO, $Cr_2O_3$, and $MgCr_2O_4$ were measured over the temperature range 1300 to 175$0^{\circ}C$ under vacuum <$10^{-5}$ torr by the Langmuir and the Knudsen method. The Langmuir vapor pressure was increased with elevating temperature and with increasing porosity of the specimen. The difference between the vapor preseures measured by the Langmuir and the Knudsen method was decreased with elevating temperature and the Langmuir vapor pressure finally reached the Knudsen vapor pressure at the melting point when extrapolated. The vapor pressure of other important oxides with high melting points, i.e., $Al_2O_3$, $ThO_2$, $Yb_2O_3$ and $Y_2O_3$ were cited from the references. The Langmuir and the Knudsen vapor pressure of these oxides also showed the same results, i.e., they showed the same value at their melting points.