• 자원리싸이클링
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• 제29권1호
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• pp.70-80
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• 2020

본 연구에서는 유도로를 사용하여 알루미늄 캔 스크랩의 재활용 효율을 플럭스 종류와 혼합 비율의 영향에 대해 조사하였다. 알루미늄 캔 제조 공정에서 발생한 알루미늄 캔 스크랩의 표면 코팅층 약 500 ℃에서 30 분간 열처리를 통해 제거가 가능하였다. 용해 공정 온도는 알루미늄 합금 용해 온도보다 높은 온도로 설정하였고, 플럭스 종류와 혼합 비율에 따른 용탕처리를 진행하였다. 그 결과, 750 ℃에서 3 wt.%의 플럭스(Salt flux와 MgCl₂ 혼합비율 70:30)의 조건에서 알루미늄을 최적으로 회수 할 수 있었다. 회수된 Al합금은 인장강도 249 MPa과 연신율 14 %로써 Al5083 소재와 거의 동일한 기계적 특성을 나타냄을 알 수 있었다.

• 열처리공학회지
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• 제6권3호
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• pp.166-177
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• 1993

Bending fatigue strength tests were made for VC coated die steels which were coated by immersing in a molten borax bath and for hardened die steels which were quenched and tempered, in order to clarify the effect of VC coating at $1000^{\circ}C$ and $1025^{\circ}C$. The material used in this investigation was a representative cold and hot die steels STD11, STD61. The results obtained are as follows. 1) The endurance limit of VC coated die steels was a little lower than that of hardened die steels. It is considered to be mainly due to the decfl.lase of hardness in the substrates. Accordingly, the endurance limit reo covered almost to the level of hardened die steels by an additional diffusion treatment. 2) The initiation point of fatigue fracture of VC coated die steels in reversed bening was on the substrate just under the VC layer. Hence, the endurance limit is corrected to the hardness of this part. 3) But, there is a considerable scatter in this relationship and the endurance limit of VC coated die steels was a little lower than that of hardened die steels with equal hardness. These results suggest that the fatigue strength of VC coated die steels is determined not only by the hardness but also by other factors. For example. the residual stress in the substrate just under VC coating layer is one of the factors besides hardness which is mainly related to the retained austenite(${\gamma}_R$).

• 한국분말재료학회지
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• 제4권4호
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• pp.252-257
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• 1997

Cu-brazed layer between the sintered-cam(Fe-5Cr-lMo-0.5P-2.5C, wt%) and seamless steelpipe(0.25-0.35C, 0.3-1.0 Mn, bal Fe, wt%) in the camshaft shows a columnar structure of $\gamma$-phase growing from the steel pipe. Liquid phase sintered 60Fe-40Cu alloys are carburized to simulate the brazing process giving rise to the columnar growth. Liquid film migrations and columnar growth of $\gamma$-grains are observed in the carburized regions. The $\gamma$-grains grow in the same direction as the C-diffusion. Fe-solubility in the liquid of carburized region is higher than in the uncarburized by about 0.3 at%. The columnar growth is driven by the gradient of the supersaturated Fe-solute in the liquid between two adjacent $\gamma$-grains.

• Journal of Welding and Joining
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• 제16권5호
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• pp.86-92
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• 1998

High speed wire seam weldability of tin coated thin gage sheet steels was investigated. Thickness and coating weight ranges of the test materials were 0.21~0.35mm and 1.1/1.1~2.8/11.2g/$m^2$, respectively. Test results indicated that the surface roughness value, Rz decreased as increasing the coating weight. The Rz was thought to be one of the important factors to influence the optimum welding condition range, $\triangle$Q. The $\triangle$Q showed close relationship with welding conditions such as welding pressure and travel speed. Higher welding pressure widened the $\triangle$Q while higher travel speed reduced the $\triangle$Q value. Results also demonstrated that tin coating weight should be optimized based on the weldability or the serviceability after welding. At th HAZ of sheet materials with thinner coating layer, tin depleted zone was produced since molten film of the coating material on the base metal agglomerated by the surface tension, which could result in reducing the corrosion resistance of the HAZ in the service environment.

• 한국주조공학회지
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• 제27권3호
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• pp.135-139
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• 2007

To produce higher quality of titanium casting at a lower cost, the new titanium casting technology by using a permanent metal mold was developed and applied to fabricate hip joint for biomedical application. The present study was carried out to investigate the reactivity and fluidity of the Ti-6.0 wt%Al-4.0 wt%V alloy with metal mold by applying various ceramic powders coating on the mold surface. The molten titanium for manufacturing hip joint was poured into steel mold. No reaction layer was formed on the surface of specimens fabricated steel mold coated with $Y_2O_3$ powder.

• 한국결정성장학회지
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• 제11권4호
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• pp.133-137
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• 2001

고출력 이산화탄소 레이저빔에 의한 TiC/Al 표면합금의 특성을 연구하였다. 이 과정을 분석하기 위해 기본금속[Al]과 TiC 분말입자 사이의 물리적 특성을 측정하였다. 표면층의 크기와 모양, 광학적 흡수율 그리고 분말효율을 TiC/Al 행력에서 레이저출력의 함수로 측정하였다. TiC 분말을 사용한 경우와 사용하지 않은 경우의 기본금속내의 흡수율은 레이저 출력이 증하가면 감소하였다. 레이저출력이 2kW에서 4.5kW 범위로 증가되면 분말효율은 4%에서 12%까지 증가하였다. 그러나 TiC 분말입자는 용융된 알루미늄에는 용해되지 않는다. 이 결과 분말입자가 증가되면 쉽게 표면층을 투과하여 금속행렬속에 2개의 위상상태로 생성된다.

• 한국재료학회지
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• 제16권11호
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• pp.698-704
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• 2006

In this study, the effect of chill layers occurred in shot sleeve on the molten metal filling was analyzed through computer simulation. The behavior of chill layers with temperature variation of shot sleeve set from 200 to $280^{\circ}C$ was also investigated. The simulation results showed the chill layers set in the in-gates during the injection process change the main filling direction and cause turbulent flow pattern, resulting in porosities inside the castings. The amount of chill layers with the increasing temperature of shot sleeve was considerably reduced. Particularly, at the setting temperature of $280^{\circ}C$ by heat control unit, the biggest reduction in chill layers, excellent trimmed surface and the highest density were achieved, suggesting that as the optimal sleeve condition in aluminum high pressure diecasting, especially for highly complex parts like valve body.

• 한국표면공학회지
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• 제54권5호
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• pp.285-293
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• 2021

High-entropy TiAlCrSiN nano-composite coating was designed to improve mold life for high temperature liquid molding. Alloy design, powder fabrication and single alloying target fabrication for the high-entropy nano-composite coating were carried out. Using the single alloying target, an arc ion plating method was applied to prepare a TiAlCrSiN nano-composite coating had a 30 nm TiAlCrSiN layers are deposited layer by layer, and form about 4 ㎛-thickness of multi-layered coating. TiAlCrSiN nano-composite coating had a high hardness of about 39.9 GPa and a low coefficient of friction of less than about 0.47 in a dry environment. In addition, there was no change in the structure of the coating after the dissolution loss test in the molten metal at a temperature of about 1100 degrees.

• Nuclear Engineering and Technology
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• 제54권4호
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• pp.1206-1212
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• 2022

Cold-crucible induction melting (CCIM) technology has been intensively studied as an advanced vitrification process for the immobilization of highly radioactive waste. This technology uses high-frequency induction to melt a glass matrix and waste, while the outer surface of the crucible is water-cooled, resulting in the formation of a frozen glass layer (skull). In this study, for the fabrication of borosilicate glass waste form, CCIM operation test with 60 kg of glass per batch was conducted using surrogate wastes composed of Cs, Sr, and Nd as a representative of highly radioactive nuclides generated during spent nuclear fuel management. A 60 kg-scale glass waste form was successfully fabricated through melting and draining processes using a CCIM system, and its physicochemical properties were analyzed. In particular, to enhance the controllability and reliability of the draining process, an air-cooling drain control method that can control draining through air-cooling near drain holes was developed, and its validity for draining control was verified. The method can offer controllability on various draining processes, such as molten salt or molten metal draining processes, and can be applied to a process requiring high throughput draining.

• 헤리티지:역사와 과학
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• 제56권1호
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• pp.100-116
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• 2023

당진 신암사는 고려 후기에 창건된 사찰이며, 경내의 극락전에는 금동여래좌상이 봉안되어 있다. 이 불상의 개금층은 박락과 광택이 저하되는 등 여러 손상이 발생하였다. 이 연구에서는 재료학적 분석과 비파괴 진단을 통해 불상의 내부와 외부에 대한 보존상태를 정밀 검토하였으며, 이를 근거로 제작기법을 해석하였다. 이 결과, 개금층은 순금을 사용한 것으로 판단되며 안료에서 흑색은 먹, 녹색은 석록과 염화동 및 동록 등으로, 적색은 연단 또는 진사가 사용된 것으로 추정된다. 손상도 평가 결과, 개금층의 벗겨짐, 균열, 탈락 및 박리 등이 확인되나 보존상태는 비교적 건전하다. 그러나 개금층의 광택은 유지부에 비해 저하부가 더 넓게 산출된다. 이 불상에 대한 초음파 속도측정 결과 1,230~3,987(평균 2,608)m/s로 비교적 넓은 범위를 보였으며, 적외선 열화상으로 박리는 확인되지 않았고 특별한 접합흔도 발견되지 않는다. 내시경 검사에서는 내부 소지금속의 부식과 생물학적 피해가 다소 관찰되었으며, 봉안된 복장물이 확인되었다. 이를 종합하여 제작기법을 검토한 결과, 이 금동여래좌상은 통주조로 제작하였으며 주형을 거꾸로 뒤집어 용탕을 주입한 것으로 판단된다.