• 대한금속재료학회지
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• 제50권12호
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• pp.907-911
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• 2012

High purity silicon can be obtained from Al-Si alloys by a combination of solvent refining and centrifugation. Silicon purification by crystallization of silicon from an Al-Si alloy melt was carried out using 2N and 4N purity aluminum and 2N purity silicon as raw materials. The effect of the purity of raw materials on the final silicon ingot purity by centrifugation was investigated for an Al-50 wt% Si alloy. Alloys were melted using an electrical resistance furnace, and then poured into a centrifuging apparatus. A silicon lump like foam was obtained after centrifugation and was leached by an acid in order to get pure silicon flakes. Then silicon flakes were melted to make a silicon ingot using an induction furnace. The purities of the silicon flakes and silicon ingot were enhanced significantly compared to those of the raw materials of silicon and aluminum. The silicon ingot made of 4N aluminum and 2N silicon showed the lowest impurities.

• Journal of Welding and Joining
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• 제17권3호
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• pp.79-89
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• 1999

The study was carried out to examine in more detail metallurgical and mechanical properties of brazed joints of diamond cutting wheel. In this work, shank(mild steel) and sintered bronze-base tips were brazed with three different filler materials(W-40, BAgl and BAg3S). The machine used in this work was a high frequency induction brazing equipment. The joint thickness, porosities and microstructure of brazed joints with brazing variables(brazing temperature, holding time) were evaluated with OLM, SEM, EDS and XRD. Bending(torque) test was also performed to evaluate strength of brazed joints. Further wetting test was performed in a vacuum furnace in order to evaluate the wettability of filler metals on base metals9shank and tips). The brazing temperature had a strong influence on the joint strength and the optimum brazing temperature range was about $700~850^{\circ}C$ for the bronze/steel combinations. The strength of the brazed joint was found to be influenced by the three factors : degree of reaction region, porosity content, joint thickness. The reaction region was formed in the bronze-base tip adjacent to the joint. The reaction region resulted in a bad influence on the strength due to the formation of Cu5.6Sn, CuZn4, $\beta(CuZn)$ and CdAg, etc. Porosities increased as brazing variables(brazing temperature, holding time) increased, and the brazed joints with porosities of less than about 3-5% had an optimum strength for the bronze-base tip.

• 한국주조공학회지
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• 제41권4호
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• pp.342-348
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• 2021

거의 모든 철계 주조공장은 생압고철 (press scrap)을 주 장입재로 사용한다. 본 연구에서는 생압고철의 형상, 크기를 최적화하여 용해에너지를 절감하고자 하였다. 주조공장 두 곳의 3t/h 중주파 유도용해로를 활용하여 실험하였다. 개선 조건의 경우, 초기 장입 시에는 맞춤형 생압고철을 사용하였고, 추가 장입 시에는 소형 생압고철을 사용하였다. 개선 조건의 에너지 절감 효과를 높이기 위해, 회수철 표면의 청정화 공정을 강화하여 실시하였다. 개선 조건에 의한 용해에너지 원단위 (melting energy basic unit) 절감률은 두 주조공장에서 각각 23.3, 23.9%였고, 거의 유사하였다. 원단위 수준이 다른 두 곳의 주조공장 모두에서 개선 조건은 매우 효과적이었다. 개선 조건의 에너지 절감 원리 및 경제적 효과를 기술하였다.

• 한국주조공학회지
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• 제18권5호
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• pp.488-493
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• 1998

Commercially pure titanium(cp-Ti) and Ti-15wt%Zr-4wt%Nb-4wt%Ta alloy were melted in vacuum induction furnace. According to the chemical analysis, the content of carbon was above ASTM standard in the cast ingots because of using graphite crucible. The TEM micostructures of cp-Ti and Ti alloy shows that chemically stable TiC precipitates distribute in ${\alpha}-Ti$ matrix. In order to examine the properties of cp-Ti and Ti-Zr-Nb-Ta alloy for dental applications, mechanical properties and corrosion resistance were investigated. The anodic polarization properties of Ti-Zr-Nb-Zr alloy were almost same as that of cp-Ti in 1% lactic acid. However, as the results of the anodic polarization test in 5% HCl, it was known that Ti-Zr-Nb-Zr alloy showed a rapid decrease in current density at higher potential in comparison with cp-Ti. The yield stress and tensile strengh in Ti-Zr-Nb-Ta were ${\sigma}_{0.2}=623\;MPa$, ${\sigma}_{T.S.}=708\;MPa$ and these results showed 30% increase in yield stress in comparison with cp-Ti.

• Corrosion Science and Technology
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• 제17권2호
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• pp.74-80
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• 2018

The electronic industries require environmentally-friendly and highly functional materials to enhance the quality of human life. Home appliances require insect repellent steels that work to protect household microwave ovens from incurring damage by insects such as fire ants and cockroaches in tropical regions. Thus, POSCO has developed new types of functional steels, coated with an array of organic-inorganic hybrid composites on the steel surface, to cover panels in microwave ovens and refrigerators. The composite solution uses a fine dispersion of hybrid solution with polymeric resin, inorganic and a pyrethroid additive in aqueous media. The hybrid composite solution coats the steel surface, by using a roll coater and is cured using an induction curing furnace on both the continuous galvanizing line and the electro-galvanizing line. The new steels were evaluated for quality performances, salt spray test for corrosion resistance and biological performance for both insect repellent and antimicrobial activity. The new steels with organic-inorganic composite coating exhibit extraordinarily biological functionalities, for both insect repellent and antimicrobial activities for short and long term tests. The composite-coating solution and experimental results are discussed and suggest that the molecular level dispersion of insecticide on the coating layer is key to biological functional performances.

• 한국주조공학회지
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• 제26권2호
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• pp.98-103
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• 2006

Metal-mold reactions between investment mold and TiAl alloys were investigated for the economic net-shape forming of TiAl alloys. The effect of mold preheating temperatures on the metal-mold reaction were investigated using a vacuum induction-melting furnace. In the case of TiAl alloys, there were no ${\alpha}$-case formation reactions. There were neither interstitial nor substitutional ${\alpha}$-case formations as TiAl alloys have both negligible solubility of oxygen and low activity in molten states. The fluidity of TiAl alloys increases with mold preheating temperature since they have a peritectic reaction that appears in the form of envelope, surrounding each particles of the primary constituent. The results of the investment casting of TiAl alloys confirm that the casting route in our study can be an effective approach for the economic net-shape forming of TiAl alloys.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.163-166
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• 1997

Aluminium foam material is a highly porous material having complicated cellular structure defined by randomly distributed air pores in metallic matrix. this structure gives the aluminium a set of properties which cannot be achieved by any of conventional treatments. The properties of aluminium foam material significantly depend on its porosity, so that a desired profile of properties can be tailored by changing the foam density. Melting method is the one of foaming processes, which the production has long been considered difficult to realize becaues of such problems as the low foamability of molten metal, the varying size of. cellular structures, solidification shrinkage and so on. These problems, however, have gradually been solved by researchers and some manufacturers are now producing foamed aluminum by their own methods. Most of all, the parameters of solving problem in electric furnace were stirring temperature, stirring velocity, foaming temper:iture, and so on. But it has not considered about those in induction heating, foaming velocity and foaming temperature in semi-solid state yet. Therefore, this paper presents the effects on these parameter to control cell size, quantity and distribution.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 The 6th International Symposium of East Asian Resources Recycling Technology
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• pp.542-546
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• 2001

Converter slag has some compositional similarities to portland cement. But it has no hydration properties due to it's quite high concentrations of FeO(20-35%), MnO(4-6.5%). So it is needed to reduce the concentrations of iron and manganese of converter slag to use as cement additives by enhancing it's hydration properties. In this study, converter slag was modified it's composition by mixing of silica, alumina and quenched BF slag and reduced in induction furnace and quenched in running water. The hydraulic properties and structures of modified and quenched converter slag are significantly changed depend on the amount and kinds of additives. The addition of alumina up to 10% and BFQ slag up to 20% by weight on converter slag was effective to enhance the hydraulic properties of modified and quenched slag. The addition of reduced and quenched converter slag up to 20% by weight in replacement of portland cement in mixing of concrete mortar were shown higher compressive strength than 100% cement concrete mortar.

• 한국세라믹학회지
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• 제30권1호
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• pp.46-54
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• 1993

$\beta$-SiC was chemically vapor deposited by pyrolysis of MTS＋H2 gas mixture. The experiments were conducted in the temperature range of 1100~150$0^{\circ}C$ with a r.f. induction furnace under atmospheric pressure. The IR, XRD, EDS and AES analysis revealed that the free Si was always codeposited with SiC below 140$0^{\circ}C$, regardless of the total flow rate and MTS concentration, whereas $\beta$-SiC single phase was deposited at 150$0^{\circ}C$. C3H8 or CH2Cl2 as an excess C sources, was supplied with MTS in order to obtain stoichiometric SiC at low temperature. With the addition of C3H8 or CH2Cl2, the deposition rate was increased and $\beta$-SiC single phase could be deposited even at temperature as low as 110$0^{\circ}C$. In the absence of C3H8 or CH2Cl2, the microhardness of the layer was quite low (

• 한국주조공학회지
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• 제25권1호
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• pp.30-35
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• 2005

The structures and mechanical property of the unidirectionally solidified Al-Co eutectic alloy were investigated. Al-Co eutectic alloy was unidirectionally solidified with growth rates(R) between I cm/hr and 10 cm/hr in the induction furnace maintaining the thermal gradient (G) at solid-liquid interface, $32^{\circ}C$/cm. The eutectic microstructure was varied with the growth condition(G/R ratio). When the G/R ratio was larger than $8.5{\times}10^{3}^{\circ}C/cm^{2}/sec$, a lamellar structure was formed, But the G/R ratio was smaller than $8.5{\times}10^{3}^{\circ}C/cm^{2}/sec$, a colony structure was formed. It was found that the interlamellar spacing(${\lambda}$) was dependent on the growth rate(R) with the relationship, ${\lambda}^{2}{\cdot}R=constant$. The microhardness of this eutectic alloy increased with increase in the growth rate.