• 한국산업융합학회 논문집
• /
• 제23권4_1호
• /
• pp.541-547
• /
• 2020

This paper relates a rheo die casting using electromagnetic force, which is one of the representative semi-solid methods for aluminum. The most important factors in electromagnetic stirring would be the melt temperature, sleeve temperature, electromagnetic force, and input time. The effect of the temperature of molten alloy on the direct rheo-casting is assessed in this study. The temperature of the molten alloy is set to 590 ℃ with a solidification of 40%, 600 ℃ with 30%, and 610℃ with less than 20%. Under the condition of 590 ℃ with a solidification of 40%, the whole molten alloy is solidified, causing non-forming during forming process. Meanwhile, under the condition of 600 ℃, where the solidification was 30%, appropriate amount of molten alloy is solidified, filled well into the mold, resulting in good forming, while at 610 ℃ with the solidification of 20%, the molten alloy is not sufficiently solidified and scattered away. The investigation of the defects inside the product with the help of the X-ray equipment shows that the electromagnetic stirring at 590 ℃ with a solidification of 30% produces many air-pores inside the product.

• 한국주조공학회지
• /
• 제25권3호
• /
• pp.115-122
• /
• 2005

In the present study, an EMC (Electromagnetic Casting) process, using a segmented Cu cold crucible under a high frequency alternating magnetic field of 20 kHz, was practiced for the fabrication of poly-crystalline Si ingot of 50 mm diameter. The effects of Joule heating and electromagnetic pressure in molten Si were systematically investigated with various processing parameters such as electric current and crucible configuration. A preliminary experimental work was initiated with the pure Al system for the establishment of a stabilized non-contact working condition, and further adapted to the semiconductor-off-grade Si system. A commercialized software such as Opera-3D was utilized in order to simulate electromagnetic pressure and Joule heating. In order to evaluate the meniscus shape of the molten melts, shape parameter was used throughout the research. A segmented graphite crucible, which was attached at the upper part of the cold crucible, was introduced to enhance significantly the heating efficiency of Si melt keeping non-contact condition during continuous melting and casting processes.

• 한국주조공학회지
• /
• 제33권2호
• /
• pp.69-74
• /
• 2013

Silicon (Si) wafer was grown by using direct growth from Si melt and contaminations of wafer during the process were investigated. In our process, BN was coated inside of all graphite parts including crucible in system to prevent carbon contamination. In addition, coated BN layer enhance the wettability, which ensures the favorable shape of grown wafer by proper flow of Si melt in casting mold. As a result, polycrystalline silicon wafer with dimension of $156{\times}156$ mm and thickness of $300{\pm}20$ um was successively obtained. There were, however, severe contaminations such as BN and SiC on surface of the as-grown wafer. While BN powders were easily removed by brushing surface, SiC could not be eliminated. As a result of BN analysis, C source for SiC was from binder contained in BN slurry. Therefore, to eliminate those C sources, additional flushing process was carried out before Si was melted. By adding 3-times flushing processes, SiC was not detected on the surface of as-grown Si wafer. Polycrystalline Si wafer directly grown from Si melt in this study can be applied for the cost-effective Si solar cells.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2007년도 추계학술대회 논문집
• /
• pp.150-153
• /
• 2007

Apply electromagnetic stirring system to making rheology slurry of Al7075. This experiment has important element which is the relation between solid fraction percent and melt temperature of Al7075. The rheology slurry of Al7075 eliminated liquid phase to include alloying element of copper and zinc by squeeze casting process. In result the most structure was composed entirely of globular primary $\alpha$. Used this material for this study. This study made a comparison of mechanical property according to heat treatment T6 at each melt temperature ($619^{\circ}C$ and $615^{\circ}C$). The microstructure and component are observed how heat treatment T6 weight with the mechanical property by SEM-EDS.

• 한국주조공학회지
• /
• 제19권6호
• /
• pp.493-500
• /
• 1999

Squeeze casting was used for fabricating a light metal base composite having high strength and wearresistance. Reactive sintering was used to prepare the preform of Squeeze casting. To utilize Fe-Al intermetallic compounds and SiC particle as a reinforcement, there needs to prepare Fe-Al mixed powder at 50, 60, 70at.%Al, and add SiC powder to the above mixture at 4, 7, 16, 24wt.%. The prepared mixture with SiC was reactive sintered in a tube furnace at $660^{\circ}C$ to get a porous hybrid preform of intermetallic compound and SiC. The preform prepared above was placed in a metal mold, preheated at $660^{\circ}C$ AC4C matrix was injected into the mold with the temperature of the melt at $610^{\circ}C$ After these processes, 66MPa was applied to the mold for 5 minute to finish the whole procedure. The maximum reaction temperature was increased with the increased Al amount, but decreased with the increased SiC amount. The density of the preform was decreased with SiC amount increase in the compacts due to swelling of the preform. An optical microscope was applied to observe the micro structure and the dispersion of the reinforcements. To analyze phases, We utilized XRD, EDS. Hardness test were chosen to get the information of mechanical properties. There were no significant changes in micro structure between the composite and preform. However, it was shown that uniform dispersion of the reinforcers and complete infiltration of the melt into the preform were achieved through the procedure of the squeeze casting. It was observed that the hardness of the composite is decreased with increased SiC amount, resulting from the volumetric expansion of the preform.

• 한국추진공학회지
• /
• 제4권1호
• /
• pp.65-73
• /
• 2000

금속기지 복합재료의 주조는 폭넓은 재료의 선택과 공정조건들을 제공하는 좋은 공정이다. 용탕교반기술은 압착주조 또는 분말야금과 비교하면 매우 간단하고 값이 싸기 때문에 주조방법중에서 산업응용에 가장 널리 쓰이는 좋은 방법이다. 최근에는 $\alpha$ -$Al_2O_{3(p)}$/Lo-Ex alloy 복합재료의 입자크기, 입자의 부피 분율, 기계적 성질에 있어서 Mg첨가 그리고 열팽창계수 등이 연구되어 왔다. $\alpha$ -$Al_2O_3$는 입자계면과 기지에 형성되어 기계적 성질에 중요한 역할을 하였다 대부분 복합재료의 인장강도는 증가하지 않지만 16$\mu\textrm{m}$ $\alpha$ -$Al_2O_3$ 입자를 5vol%로 첨가한 경우, 3wt.% Mg를 첨가한 복합재료의 인장강도는 증가한다. 강화재의 부피분율과 mg은 복합재료의 열팽창계수를 감소시켰다.

• 대한기계학회논문집B
• /
• 제21권4호
• /
• pp.525-540
• /
• 1997

The effect of mold rotation on the transport process and resultant macrosegregation pattern during solidification of an Al-Cu alloy contained in a vertical axisymmetric annular mold cooled from the inner wall is numerically investigated. The mold initially at rest starts to rotate at a prescribed angular velocity simultaneously with the beginning of cooling. Computed results for a representative case show that the mold rotation essentially suppresses the development of both thermal and solutal convections in the melt, creating distinct characteristics such as the liquidus front, flow pattern and temperature distribution from those for the stationary mold. Thermal convection which develops at the early stages of cooling is soon extinguished by the rotating flow induced during spin-up, and thus does not effectively remove the initial superheat from the melt. On the other hand, solutal convection, though it weakens considerably and is confined within the mushy zone, still predominates over the solute redistribution process. With increasing the angular velocity, the solute transport in the axial direction is enhanced, whereas that in the radial direction is reduced. The final macrosegregation formed in the mold rotating at moderate angular velocities appears to be favorable in comparison with the stationary casting, in that not only relatively homogenized composition is achieved, but also a severely positive-segregated channel is restrained.

• 한국주조공학회지
• /
• 제12권3호
• /
• pp.203-209
• /
• 1992

Directional solidification of Al-Ti peritetic alloys was carried out using Upward Continuous Casting Process. The morphology of a solid-liquid interface and solidification microstructures were investigated under various crystal growing conditions. The experimental results were compared with those attained by the Bridgman method. The cell spacing of the Al-Ti peritetic alloys and the primary dendrite arm spacing of the Al-Ti peritetic alloys decreased with an increase in pulling speed. The primary ${\beta}$ phase of the Al-Cr and Al-Ti peritectic alloys did not appear in solidification microstructures because of the depleted solute contents in the melt ahead of the solid-liquid interface.

• 한국표면공학회지
• /
• 제29권1호
• /
• pp.36-44
• /
• 1996

Fe-Cr-Al and Fe-Cr-Al-Hf alloys prepared either by arc melting or by single roll casting(melt spinning) were exposed to air isothermally at 900~$1100^{\circ}C$. Whisker-like alumina was observed on the surface of the specimens when oxidized at $900^{\circ}C$, but convoluted alumina above $1000^{\circ}C$. All the Hf-free specimens and Hf-added specimens produced by single roll casting formed only external scale mainly composed of $Al_2O_3$ after oxidation at 900~$1100^{\circ}C$ for 100 hours, but Hf-added specimen produced by arc melting formed Hf-rich internal oxides below the thin external $Al_2O_3$ scale except at $900^{\circ}C$. Most of the rapidly solidified Fe-Cr-Al alloys showed smaller weight gains than conventionally casted ones besides Hf-added one oxidized at $1100^{\circ}C$.

• 한국주조공학회지
• /
• 제21권3호
• /
• pp.163-178
• /
• 2001

The squeeze infiltration process is potentially of considerable industrial importance. The performance enhancements resulting from incorporation of short alumina fiber into aluminum are well documented. These are particularly significant for certain automobile components. Aluminum matrix composite automotive parts, such as diesel engine pistons or engine blocks are produced using squeeze casting apparatus or pressure die-casting apparatus. But the solidification process gets complicated with manufacturing parameters and the factors for porosity formation have not fully understood yet. In this study the formation of porosity during squeeze infiltration has been studied experimentally to achieve an improved understanding of the squeeze infiltration process for manufacture of short-fiber-reinforced components, particularly the mechanism of porosity formation. Al-based MMCs produced under a range of conditions were examined metallographically and the porosity characterised;a kind of matrix, an initial temperature of melt, and a volume fraction of reinforcement. The densimetry and the microscopic image analysis were done to measure the amount of porosity. A correlation between manufacturing parameters and defects was investigated through these.