• Title/Summary/Keyword: Directional Casting

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Micro-macroscopic analysis on the directional casting of a metal alloy (합금의 방향성 주조에 대한 미시적-거시적 해석)

  • Yu, Ho-Seon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.21 no.10
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    • pp.1303-1313
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    • 1997
  • A micro-macroscopic analysis on the conduction-controlled directional casting of Al-Cu alloys is performed, in which emphases are placed on the microstructural features. In order to facilitate the solution procedure, an iterative micro-macroscopic coupling algorithm is developed. The predicted results show that the effect of finite back diffusion on the transient solidification process in comparison with the lever rule depends essentially on the initial concentration of an alloy. In the final casting, the eutectic fraction is distributed in an increasing-decreasing-increasing pattern, each mode of which is named the chill, interior and end zones. This nonuniformity per se suffices to justify the necessity of this work because it originates from the combined effects of finite back diffusion and cooling path-dependent nature of the eutectic formation. As the cooling rate is enhanced, not only the influence depths of boundaries narrow, but also the eutectic fractions in the chill and interior zones increase. In addition, it is revealed for the first time that the micro segregation band is formed in response to a sudden change in cooling rate during the directional casting. An increasing change creates an overshooting band in the eutectic fraction distribution, and vice versa.

A Similarity Solution for the Directional Casting of Peritectic Alloys in the Presence of Shrinkage-Induced Flow (체적수축유동이 있는 포정합금의 방향성주조에 대한 상사해)

  • Yu, Ho-Seon;Jeong, Jae-Dong;Lee, Jun-Sik
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.25 no.4
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    • pp.485-495
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    • 2001
  • This paper presents a similarity solution for the directional casting of binary peritectic alloys in the presence of shrinkage-induced flow. The present model retains essential ingredients of alloy solidification, such as temperature-solute coupling, macrosegregation, solid-liquid property differences, and finite back diffusion in the primary phase. An algorithm for simultaneously determining the peritectic and liquidus positions is newly developed, which proves to be more efficient and stable than the existing scheme. Sample calculations are performed for both hypo- and hyper-peritectic compositions. The results show that the present analysis is capable of properly resolving the solidification characteristics of peritectic alloys so that it can be used for validating numerical models as a test solution.

The Study on the Dimensional Computer Simulation of Solidification behavior by FDM in Al-Bronze Casting (Al-bronze에 있어서 직접차분법에 의한 2차원 응고해석에 관한 연구)

  • Choe, Jeong-Gil;Jeong, Un-Jae;Kim, Dong-Ok
    • 한국기계연구소 소보
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    • s.17
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    • pp.111-123
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    • 1987
  • Two dimensional computer simulation of solidification behavior using FDM as simulation tool was applied to AI-bronze casting. By the comparison of computer simulation with the experimental results, it was showed that the final shrinkage position and solidification time are good accordance with results of computer simulation. It is expected that this software will be widely applied to casting design or rise ring for directional solidification.

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Directional texture information for connecting road segments in high spatial resolution satellite images

  • Lee, Jong-Yeol
    • Proceedings of the KSRS Conference
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    • 2005.10a
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    • pp.245-245
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    • 2005
  • This paper addresses the use of directional textural information for connecting road segments. In urban scene, some roads are occluded by buildings, casting shadow of buildings, trees, and cars on streets. Automatic extraction of road network from remotely sensed high resolution imagery is generally hindered by them. The results of automatic road network extraction will be incomplete. To overcome this problem, several perceptual grouping algorithms are often used based on similarity, proximity, continuation, and symmetry. Roads have directions and are connected to adjacent roads with certain angles. The directional information is used to guide road fragments connection based on roads directional inertia or characteristics of road junctions. In the primitive stage, roads are extracted with textural and direction information automatically with certain length of linearity. The primitive road fragments are connected based on the directional information to improve the road network. Experimental results show some contribution of this approach for completing road network, specifically in urban area.

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Development of Casting Furnace for Directional Solidification Ingot (잉곳의 방향성 응고를 위한 주조 로 개발)

  • Ju, Jin-Young;Lee, Seung-Jun;Baek, Ha-Ni;Oh, Hun;Cho, Hyun-Seob;Lee, Choong-Hun
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.13 no.2
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    • pp.808-816
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    • 2012
  • This paper is the study for the directional solidification of the ingot through the thermal analysis simulation and structural change of casting furnace. With the results of thermal analysis simulation, the silicon as a whole has reached the melting temperature as the retention time 80 min. The best cooling conditions showed at the upper cooling temperature $1,400^{\circ}C$ and cooling time 60min. The fabricated wafers showed the superior etching result at the grain boundary than that of existing commercial wafers. The FTIR measurements of oxygen and carbon impurities were not in the critical value for solar conversion efficiency. The NAA analysis of metal impurities were also detected the total number of 18 different metals, but the concentration distribution showed no significant positional deviations in the same position from the top to the bottom.

Simulation by heat transfer of ADS process for large sized polycrystalline silicon ingot growth (대형 다결정 실리콘 잉곳 성장을 위한 ADS 법의 열유동에 관한 공정모사)

  • Shur, J.W.;Hwang, J.H.;Kim, Y.J.;Moon, S.J.;So, W.W.;Yoon, D.H.
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.18 no.1
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    • pp.45-49
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    • 2008
  • The development of manufacturing process of silicon (Si) ingots is one of the important issues to the growth of the photovoltaic industry. Polycrystalline Si wafers shares more than 60% of the photovoltaic market due to its cost advantage compared to mono crystalline silicon wafers. Several solidification processes have been developed by industry including casting, heat exchange method (HEM) and electromagnetic casting. In this paper, the advanced directional solidification (ADS) method is used to growth of large sized polycrystalline Si ingot. This method has the advantages of the small heat loss, short cycle time and efficient directional solidification. The numerical simulation of the process is applied using a fluid dynamics model to simulate the temperature distribution. The results of simulations are confirmed efficient directional solidification to the growth of large sized polycrystalline Si ingot above 240 kg.

Uniform Crystal Growth during Directional Solidification of Hypermonotectic Alloys (과편정 합금의 일방향 응고시 균일한 결정 성장)

    • Korean Journal of Materials Research
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    • v.10 no.1
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    • pp.3-6
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    • 2000
  • Liquid-liquid phase separation due to the very different density and composition occurs when the hypermonotectic alloys are solidified on the ground. Besides this, other factors such as preferential wetting and coalescence make it difficult to get uniform microstructures during the directional solidification of hypermonotectic alloys. Therefore a few novel solidification methods to get rid of such a nonuniformity have been reviewed and the recent experimental work using ultrasonic energy in conjunction with directional solidification has been presented. The uniformly solidified structures have been obtained when the ultrasonic of 20kHz applied to transparent organic system, Succinonitrile-Glycerol, varying ultrasonic amplitude and composition etc.

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Real-time Observation and Analysis of Solidification Sequence of Fe-Rich Al-Si-Cu Casting Alloy by Synchrotron X-ray Radiography (가속 방사광을 활용한 Fe함유 Al-Si-Cu 주조용 합금의 응고과정 실시간 관찰 및 분석)

  • Kim, Bong-Hwan;Lee, Sang-Hwan;Yasuda, Hideyuki;Lee, Sang-Mok
    • Journal of Korea Foundry Society
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    • v.30 no.3
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    • pp.100-110
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    • 2010
  • The solidification sequence and formation of intermetallic phase of Fe-rich Al-Si-Cu alloy were investigated by using real-time imaging of synchrotron X-ray radiation. Effects of cooling rate during uni-directional solidification on the resultant solidification behavior was also studied in a specially constructed vacuum chamber in the SPring-8 facility. The series of radiographic images were complementarily analyzed with conventional analysis of OM and SEM/EDX for phase identification. Detailed solidification sequence and formation mechanisms of various phases were discussed based on real-time image analysis. The growth rates of $\alpha$-AlFeMnSi and ${\beta}-Al_5FeSi$ were measured in order to understand the growth behavior of each phase. It is suggested that real-time imaging technique can be a powerful tool for the precise understanding of solidification behavior of various industrial materials.

Squeeze Casting of SiC Whisker Reinforced Magnesium Composites (용탕단조를 이용한 SiC 휘스카 강화 마그네슘복합재료의 제조)

  • Chang, Si-Young;Shin, Dong-Hyuk;Hong, Sung-Kil;Choi, Jung-Chul
    • Journal of Korea Foundry Society
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    • v.20 no.3
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    • pp.167-172
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    • 2000
  • Squeeze casting was performed to fabricate the SiC whisker reinforced magnesium matrix composites, and the suitability of the squeeze casting for the production of the sound composites was determined by micro/macro-structures observations and tensile test. The two-directional infiltration of the melt and the removal of air during infiltration using the devised mold were necessary to produce the composites. The pressure of 100 MPa was effective for the production of composites with the SiC whisker volume fraction of 30%, but the pressure should be lower than 50 MPa in case of below 20% in the volume fraction. The SiC whiskers in the squeeze cast composites were randomly and densely aligned, and the SiC whiskers/magnesium interfaces were continuously well-bonded. The elastic modulus, 0.2% proof stress and tensile strength in the composite were about 2.5times, l0times and 4times as large as those of magnesium, respectively, indicating that the squeeze casting sufficiently provides the high strength magnesium composites reinforced with SiC whiskers.

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