• Structural Engineering and Mechanics
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• v.68 no.6
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• pp.691-700
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• 2018

Ground granulated blast furnace slag (GGBS) is a by product obtained from iron and steel industries, useful in the design and development of high quality cement paste/mortar and concrete. This paper investigates the applicability of relevance vector machine (RVM) based regression model to predict the compressive strength of various GGBS based concrete mixes. Compressive strength data for various GGBS based concrete mixes has been obtained by considering the effect of water binder ratio and steel fibres. RVM is a machine learning technique which employs Bayesian inference to obtain parsimonious solutions for regression and classification. The RVM is an extension of support vector machine which couples probabilistic classification and regression. RVM is established based on a Bayesian formulation of a linear model with an appropriate prior that results in a sparse representation. Compressive strength model has been developed by using MATLAB software for training and prediction. About 70% of the data has been used for development of RVM model and 30% of the data is used for validation. The predicted compressive strength for GGBS based concrete mixes is found to be in very good agreement with those of the corresponding experimental observations.

• Journal of Korea Foundry Society
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• v.42 no.6
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• pp.347-357
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• 2022

In this study, 3D visualization of the packing behavior of the charge material in a foundry was attempted. It was simulated based on the practical conditions of the charge material and the melting furnace. It was confirmed whether the 3D visual simulation realistically implements the packing behavior of the manufacturing site. The realistic packing state by the 3D visual simulation was compared with the ideal packing state. It was analyzed in which case the difference between the two packing states occurred. The advantages of applying the 3D visual simulation to the manufacturing process were investigated, and various application plans in the casting industry were proposed.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.12 no.2
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• pp.68-72
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• 2002

The $\beta$-$FeSi_2$ and $\alpha$-$FeSi_2$ single crystals were synthesized by chemical vapour transport (CVT) using iodine as a transporting agent from the commercially available $FeSi_2$ powder. The $FeSi_2$ powder together with iodine were sealed in an evacuated quartz ampoule and the ampoule then being placed in two-zone electrical furnace for growing crystal. The CVT of $FeSi_2$ with iodine yielded $\beta$-$FeSi_2$ and $\alpha$-FeSi$_2$ single crystals at deposition temperature of 750 and $950^{\circ}C$ respectively. The source temperature was $1050^{\circ}C$ in both cases. The crystals of the $\alpha$-FeSi$_2$ phase were typically plate shaped with dimensions of about $10\times 10 \textrm{mm}^2$, whereas the crystals of orthorhombic $\beta$-$FeSi_2$ phase grew predominantly in the fonts of thin needle of about 10 mm in length. The composition of$\alpha$-FeSicrystal determined by electron probe microanalysis (EPMA) resulted in Si-rich $FeSi_{2.58}$ . 57. Furthermore, the CVT $\beta$-$FeSi_2$ crystal was found to be transformed to the high temperature $\alpha$-$FeSi_2$phase above $930^{\circ}C$.

• Journal of Conservation Science
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• v.38 no.4
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• pp.289-300
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• 2022

In the 6^th and 7^th centuries, 5 iron artifacts excavated form the Baekje Stone Tomb in Guryong-ri site, Ungcheon, Boryeong, were studied. The sample were metal microscopic observation, SEM-EDS analysis and Raman micro-spectroscopy analysis were conducted to understand the metallurgical characteristics. The microstructure observation showed the presence of ferrite and pearlite throughout, and differences in carbon content existed depending on the direction. Non-metallic inclusions were in the form of long lines, and most of them were wüstite, fayalite. It is indicated that the artifacts were forge welded using hypoeutectoid steel, with signs of carburizing and decarburizing processes. Some crystals with high P₂O₅, TiO₂, CaO content were identified as sarcopside, ulvöspinel, and perovskite, respectively, through Raman spectroscopy. A comparison of the results with previous studies on the sites of Bujang-ri site in Seosan and Bongseon-ri site in Seocheon, which are adjacent sites in the coastal area, revealed that, while heat treatment technology was available, the artifacts were not heat-treated considering the purpose for use for these artifacts. The chemical composition of the non-metallic inclusions P₂O₅, TiO₂, CaO were plotted in proportions to SiO₂ and compared with adjacent sites. Considering that the P₂O₅/SiO₂ ratio was widely distributed, the refining technology was not uniform. In addition, the TiO₂/SiO₂ ratio was found to be higher than that of other sites, meaning that a titanium-containing ore was used to manufacture the artifacts, unlike in surrounding sites, but it is not detected in all artifacts, so it may have been affected by various factors such as furnace walls in addition to raw materials. Although slag formers were used, considering the CaO/SiO₂ ratio and the (Al₂O₃/SiO₂)/(CaO/SiO₂) ratio, which appear to be similar to the surrounding sites, but it is possible that CaO containing raw ore was used because it is also affected by the components of raw ore. As a result of the study, it is highly likely that ore different from that of the surrounding sites was used for production, but a more comprehensive comparative study with the surrounding sites is needed in the future.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.3
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• pp.329-336
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• 2006

Iron manufacturing process involves production of various by-product including slag, sludge, sintering and EAF(Electric Arc furnace dust). Some of the by-products such as EAF and sintering dust are disposed of as waste due to their high heavy metal contents. It has been notice for many years that the EAF dust also contain about 65% of Fe(0) and Fe(II) and then the possible utilization of the iron. One possibility is to apply the EAF as a lining material in conjunction with clay or HDPE liners, in waste landfill. The probable reaction between the leachate containing toxic elements such as TCE, PCE dioxine and $Cr^{6+}$ is reduction of the toxic materials in corresponding to the oxidation of the reduced iron and therefore diminishing the toxicity of the leachate. It is, however, prerequisite to evaluate the leaching characteristics of the EAF dust before application. Amelioration of the leachate would be archived only when the level of toxic elements in the treated leachate is less than that of in the untreated leachate. Several leaching techniques were selected to cover different conditions and variable environments including time, pH and contact method. The testing methods include availability test, pH-stat test and continuous column test. Cr and Zn are potentially leachable elements among the trace metals. The pH of the EAF dust is highly alkaline, recording around 12 and Zn is unlikely to be leached under the condition. On the contrary Cr is more leachable under alkaline environment. However, the released Cr should be reduced to $Cr^{3+}$ and then removed as $Cr(OH)_3$. Removal of the Cr is observed in the column test and further study on the specific reaction of Cr and EAF dust is underway.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.3
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• pp.115-122
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• 2019

Electric arc furnace dust (EAFD), which is a dust waste generated in the steel manufacturing process, contains heavy metals. Recently, researches of recycling a large amount of valuable metals such as zinc and iron in EAFD are being actively carried out. In this study, EAFD is used as a substitute for cobalt in blue ceramic pigments without any pretreatment. Then, the synthesized blue ceramic pigment using EAFD was micronized and formulated as a ceramic ink for inkjet printer. The particle size distribution, crystal structure and color characteristics during the micronization process were investigated for the development of ceramic ink. $Co_{0.75}Zn(EAFD)_{0.25}Al_2O_4$ ceramic pigments showed excellent blue coloric properties and monomodal distribution through micronization process. The average particle size of $Co_{0.75}Zn(EAFD)_{0.25}Al_2O_4$ ceramic pigments after 3 hours of milling was $0.271{\mu}m$, which is smaller than $0.303{\mu}m$, which is the average particle size of $CoAl_2O_4$ ceramic pigments without EAFD after 5 hours of milling. Especially, it was confirmed that $Co_{0.75}Zn(EAFD)_{0.25}Al_2O_4$ ceramic pigments showed a color difference (${\Delta}E{^*}_{ab}$) value of 5.67, which smaller than ${\Delta}E{^*}_{ab}$ value of $CoAl_2O_4$ during micronization. These results show that EAFD can be used as a raw material for a blue ceramic pigment by replacing expensive cobalt without any pretreatment.

• Clean Technology
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• v.6 no.1
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• pp.61-69
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• 2000

In this study, generation process and properties of inorganic industrial waste which can be used in cement industry were investigated. The scheme of recycling to use the selected waste as raw materials, mineralizer and flux, admixture and raw materials for special cement was decided and then various experiments were carried out. The experimental results were as follows ; In the use of industrial waste as raw materials, ferrous materials could be substituted by Cu-slag, Zn-slag, electric arc furnace or convertor furnace slag etc., and a siliceous material could be substituted by sand from cast-iron industry. By-products from sugar or fertilizer industry, which has $CaF_2$ as the main component, and jarosite from Zn refinery enabled clinker phases to be formed at lower temperature by $100{\sim}150^{\circ}C$. Adding Cu slag and STS sludge in proper proportion to cement improved properties of cement. Fly ash and limestone powder as admixture had the same effect on cement. As a raw material for special cement, aluminium waste sludge could be used in making ultra early strength cement, which had the compressive strength of $300kg/cm^2$ within 2hours. And two different ashes from municipal incinerator could be raw materials of the cement which was mainly composed of $C_3S$ and $C_{11}A_7{\cdot}CaCl_2$ as clinker phases.

• Journal of the Mineralogical Society of Korea
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• v.5 no.2
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• pp.72-78
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• 1992

The Earth outer core accomodates moderately considerable amount of lighter elements than pure iron itself. Hydrogen is one of the possible candidates of minor constituents in the outer core. It would be worth while to extend for the pressure effect on the solubility of hydrogen in the metal-hydrides including iron hydride. In view of hydrogen being one of the potential substitutes for petroleum, searching a more efficient way for storing hydrogen in the form of hydrides is of considerable value. For two purposes, $TiH_2$was selected among lot of hydrides for its characteristics under pressure and temperature. There have been two kinds of experiment carried out on $TiH_2$ under different experimental conditions. As one of these attempts, polycrystalline $TiH_2$ was loaded up to 15 GPa stepwise at the constant temperature 500${\circ}$ using a piston-cylinder diamond anvil cell equipped with a miniature furnace of an electric power supply. The X-ra diffraction technique was employed on the quenched samples after the simultaneous high pressure and temperature treatments. During these high pressure-temperature runs, and irreversible phase of $TiH_2$ has been observed at the pressures higher than 11.3 GPa, which would be assigned to the orthorhombic crystal system as one of the new phase(s) of $TiH_2$. Molar volume change on this phase transition is ∼10%.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2001.11a
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• pp.7-7
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• 2001

The increasing interest in light weight materials coupled to the need for cost -effective processing have combined to create a significant opportunity for aluminum P/M. particularly in the automotive industry in order to reduce fuel emissions and improve fuel economy at affordable prices. Additional potential markets for Al PIM parts include hand tools. Where moving parts against gravity represents a challenge; and office machinery, where reciprocating forces are important. Aluminum PIM adds light weight, high compressibility. low sintering temperatures. easy machinability and good corrosion resistance to all advantages of conventional iron bm;ed P/rv1. Current commercial alloys are pre-mixed of either the AI-Si-Mg or AL-Cu-Mg-Si type and contain 1.5% ethylene bis-stearamide as an internal lubricant. The powder is compacted in closed dies at pressure of 200-500Mpa and sintered in nitrogen at temperatures between $580~630^{\circ}C$ in continuous muffle furnace. For some applications no further processing is required. although most applications require one or more secondary operations such as sizing and finishing. These sccondary operations improve the dimension. properties or appearance of the finished part. Aluminum is often considered difficult to sinter because of the presence of a stable surface oxide film. Removal of the oxide in iron and copper based is usually achieved through the use of reducing atmospheres. such as hydrogen or dissociated ammonia. In aluminum. this occurs in the solid st,lte through the partial reduction of the aluminum by magncsium to form spinel. This exposcs the underlying metal and facilitates sintering. It has recently been shown that < 0.2% Mg is all that is required. It is noteworthy that most aluminum pre-mixes contain at least 0.5% Mg. The sintering of aluminum alloys can be further enhanced by selective microalloying. Just 100ppm pf tin chnnges the liquid phase sintering kinetics of the 2xxx alloys to produce a tensile strength of 375Mpa. an increilse of nearly 20% over the unmodified alloy. The ductility is unnffected. A similar but different effect occurs by the addition of 100 ppm of Pb to 7xxx alloys. The lend changes the wetting characteristics of the sintering liquid which serves to increase the tensile strength to 440 Mpa. a 40% increase over unmodified aIloys. Current research is predominantly aimed at the development of metal matrix composites. which have a high specific modulus. good wear resistance and a tailorable coefficient of thermal expnnsion. By controlling particle clustering and by engineering the ceramic/matrix interface in order to enhance sintering. very attractive properties can be achicved in the ns-sintered state. I\t an ils-sintered density ilpproaching 99%. these new experimental alloys hnve a modulus of 130 Gpa and an ultimate tensile strength of 212 Mpa in the T4 temper. In contest. unreinforcecl aluminum has a modulus of just 70 Gpa.

• Journal of the Korean Institute of Gas
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• v.2 no.4
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• pp.60-66
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• 1998

The hot stove system is a process that is continuously and constantly generating the hot combustion air required for the blast furnace. The hot stove process is considered as a main energy consumption process because it consumes about $20\%$ of the total energy in steel making works. So, many researchers have interested in the improvement of the heat efficiency of the hot stove to reduce the energy consumption. But they have difficulties in improving the heat efficiency of the hot stove because there is no precise information on heat transformation occurring during the heating period. In order to model the relationship between the operating conditions and heat efficiencies, we propose a neural network using feature extraction as one of experimental modeling methods. In order to show the performance of the model, we compare it with Partial Least Square (PLS) method. Both methods have similarities in using the dimension reduction technique. And then we present the simulation results on the prediction of the heat efficiency of the hot stove.