• 한국분말재료학회지
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• 제25권4호
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• pp.336-339
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• 2018

A unique porous material with controlled pore characteristics can be fabricated by the freeze-drying process, which uses the slurry of organic material as the sublimable vehicle mixed with powders. The essential feature in this process is that during the solidification of the slurry, the dendrites of the organic material should repel the dispersed particles into the interdendritic region. In the present work, a model experiment is attempted using some transparent organic materials mixed with glass powders, which enable in-situ observation. The organic materials used are camphor-naphthalene mixture (hypo- and hypereutectic composition), salol, camphene, and pivalic acid. Among these materials, the constituent phases in camphor-naphthalene system, i.e. naphthalene plate, camphor dendrite, and camphor-naphthalene eutectic exclusively repel the glass powders. This result suggests that the control of organic material composition in the binary system is useful for producing a porous body with the required pore structure.

• 한국재료학회지
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• 제14권2호
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• pp.101-109
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• 2004

The influences of solidification rates and carbon contents on the formation of the $\delta$-ferrite were studied by directional solidification in modified 12%Cr-l %Mo steels. Directional solidification experimental results showed that solidification microstructure depended on solidification rate and carbon content and chromium equivalent. The length of the mushy zone increased and the dendrite arm spacings decreased as the solidification rate increased. The volume fraction of the 8-ferrite decreased with increasing the solidification rate and carbon content. The volume fraction of the ferrite showed much higher at low solidification rates with planar and cellular interfaces than that at high solidification rates with dendritic interface. It is expected that macro-segregation of C causes lower C content at the lower solidification fraction in the directionally solidified sample, where lower C results in higher volume fraction of the ferrite. In order to estimate solidification microstructure in modified 12Cr-l%Mo steels, various solidification conditions, such as solidification rate, cooling rate, segregation, alloy composition, should be considered.

• 한국주조공학회지
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• 제41권3호
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• pp.235-240
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• 2021

진공 가스분사법으로 제조된 Fe₇₅B₁₃P₅Nb₂Hf₁C₄ 합금의 응고중 액상의 크기와 이에 따른 냉각속도의 변화가 정출상의 형성에 미치는 영향에 대한 고찰을 하였다. 고온 액상에서 동일한 조건으로 응고된 서로 다른 크기의 액상이 구형의 분말형태로 응고될 때 크기에 따른 임계냉각속도의 차이를 계산하였으며, 액상의 평균 반지름이 3배정도 크기 차이가 날 경우 고상으로 변태할 때 임계냉각속도가 13.5배까지 차이가 나는 것을 알 수 있었다. 이러한 임계냉각 속도의 차이에 따른 정출상의 형성과 정출상의 형태와 크기에 따른 탄화물의 형성 거동을 조사하여 열역학 계산으로 예측된 결과와 비교 분석하였으며, 분말입자의 크기가 20~45 마이크론일 경우 Hf과 Nb이 포함된 MC타입의 탄화물이 초정으로 형성 되는 것을 알 수 있었으며 이때 Hf과 Nb의 비율은 합금의 조성 및 냉각속도에 따라 변화됨을 관찰 할 수 있었다.

• 수산해양기술연구
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• 제17권2호
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• pp.85-91
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• 1981

평판 강괴를 연속적으로 주조할 경우에 초기주조 상태에서 Mold 내부의 Support bar 및 용강자중, 주조속도, 용강두께, 이를 지지하는 제어 Roller, 유압기구, 구동 Motor, 그리고 주조조직의 응고 등이 용강의 인발력을 유도하는 Pinch Roller와의 사이에서 동력학적 부평형을 일으켜 Slip 현상을 초래하므로 본 논문에서는 이상의 제요인들을 근거로 Slip 현상을 규명하는 식을 유도하고 강괴의 주조속도, 비중량, 두께의 변화에 대한 Slip Force 거동을 규명하였다. 그 결과 1. 본 논문의 해석식에 의하여 평판강괴 연속주조용 Pinch Roller의 적정압을 설계할 수 있다. 2. 비중량은 순수히 자중만 증가시키는 요인이며 Slip Force는 주조속도변화에 대해서 포물선적으로 증가한다. 3. 주조두께 및 비중량의 변화에 대한 Slip Force는 이에 비례하여 증가하나 특히 두께의 값이 소폭보다 대폭에서 그 변화 값이 크게 나타났다.

• 한국주조공학회지
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• 제15권2호
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• pp.194-200
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• 1995

Rapidly Solidified (RS) Al-Zr base splats with various alloy contents were prepared by atomization-splat quenching method to understand the continuous and discontinuous precipitation in the aged alloys. And the RS alloys were consolidated by hot extrusion and swaging to analyze the effect of plastic deformation on the precipitation behavior. Discontinuous precipitation dominated at relatively low temperature in the Al-Zr alloy, whereas both V additions to Al-Zr alloys and hot metal working appeared to suppress the discontinuous precipitation. As continuous precipitation is favored in the grain interiors, the driving force for discontinuous precipitation become to disappear with a further process.

• 한국주조공학회지
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• 제17권6호
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• pp.545-551
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• 1997

14 cm length Al-15Cu-1Mg alloys have been directionally solidified in 3 mm diameter alumina tubes in a furnace moved with a constant velocity V=12 cm/hr under various furnace temperatures of 660, 710 and $760^{\circ}C$. By analysing the evolution of the temperature profiles along the alloy length during the solidification, the growth characteristics such as the position of the solid/liquid interface, the local growth velocity (R) and the temperature gradient at the solid/liquid interface (G) have been determined. The effects of the furnace temperature on the growth behavior have been investigated by the comparison of R and G values for each temperature. Under the furnace temperature of $760^{\circ}C$, steady state growth region was observed for the latter half of the growth period.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.769-773
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• 2002

The die easting process was used to manufacture a motor housing for automobile. Specially automobile parts were required light and high strength. Therefore simulations have been carried out die casting process of motor housing. In this paper, we investigated about characteristics of the die casted motor housing with HPDC(High Pressure Die Casting) process. Also the MAGMAsoft was used as computer simulation code and used material was ADC12(Aluminum Die Casting Alloy). We present the results of filling behavior and solidification process of a motor housing cast. The analysis results obtained about filling behavior and solidification of cast showed good agreement with test results.

• 한국주조공학회지
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• 제21권6호
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• pp.343-349
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• 2001

The effect of cooling rate on the solidification microstructure and segregation behavior of 7075 and 7050 aluminum alloy was investigated. Samples were solidified with cooling rates from 0.3 to $17^{\circ}K/sec$. Using the cooling curves of each sample, liquidus, eutectic and intermetallic reaction temperatures were estimated. The microstructures were characterized in terms of dendrite arm spacing and eutectic volume fraction. The segregation behavior of each alloying element of these alloys in various cooling rates was discussed.

• Journal of Welding and Joining
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• 제19권3호
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• pp.325-333
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• 2001

The effect of base metal grain size on isothermal solidification behavior of Ni-base superalloy, CMSX-2 during transient liquid phase (TLP) bonding was investigated employing MBF-80 insert metal. TLP-bonding of single crystal. coarse-grained and fine-grained CMSX-2 was carried out at 1373∼1548k for various holding time in vacuum. The eutectic width diminished linearly with the square root of holding time during isothermal solidification process for single crystal, coarse-grained and fine-grained base metals. The completion time for isothermal solidification decreased in the order ; single crystal, coarse-grained and fine-grained base metals. The difference of isothermal solidification rates produced when bonding the different base metals could be explained quantitatively by the effect of base metal grain boundaries on the apparent average diffusion coefficient of boron in CMSX-2.

• 한국막학회:학술대회논문집
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• 한국막학회 1994년도 추계 총회 및 학술발표회
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• pp.72-73
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• 1994

Whey는 일명 lactoserum 이라고도 하며 치즈제조시 우유를 응고시키는 과정에서 Casein과 지방으로부터 분리되어 나오는 액상의 부산물로 본래 우유 부피의 약 90%를 차지하며, 용해성 단백질, 유당, 비타민과 무기질 등을 함유하고 있다. 유청에 함유되어 있는 단백질은 건조고형분의 약 13%가 되는데, 주요 단백질은 $\beta$-lactoglobulin(50%), $\alpha$-lactalbumin(22%), Serum albumin(5%), Immunoglobulin(12%), Proteose-peptone(10%) 등이 있다. 유청단백질중 가장 많이 함유되어 있는 $\beta$-lactoglobulin은 구형의 단백질로 단량체의 분자량은 약 18,400이며, pH 3.5~7 범위내에서는 해리되지 않는 이량체(dimer)를 형성한다. pH 3.5 이하에서 이량체는 해리되고 다량체의 형성으로 재평성한다. pH 7.0 이상의 알칼리 영역에서는 Conformational Change가 일어나는 것으로 알려져 있으며, 등전점(isoelectric point)은 pH 5.2이다. $\alpha$-lactalbumin은 14,200의 분자량을 가지는 구형의 단백질로 등전점은 pH 4.8이다.