• Journal of the Korean institute of surface engineering
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• v.29 no.4
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• pp.253-260
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• 1996

Regular spangle hot dip galvanized steel sheets were made in the zinc bath containing a small amount of Al and with the addition of Pb, Sb, Sb-Mg, Sb-Cu and Bi respectively whose average glosses were measured. Zero-spangle hot dip galvanized steel sheets were also made by spraying a 2% $NH_4H_2PO_4$ solution on molten coating surfaces with exactly the same chemical compositions as above used for regular spangle and whose glosses and corrosion losses were also evaluated. For manufacturing zero- spangle hot dip galvanized steel sheets with high brightness, the zinc bath with 0.02%Sb and the spraying of a 2% $NH_4H_2PO_4$ solution were proposed and for better brightness and corrosion resistance, the zinc bath with 0.02% Sb-0.50%Mg and the spraying of a 2% $NH_4H_2PO_4$ solution were also proposed.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.2
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• pp.173-178
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• 2007

This paper is to establish an appropriate model for predicting the temperature decreases in the batch transferred from the refining process to the caster in steel-making companies. Mathematical modeling of the temperature decreases between the processes is difficult, since the reaction mechanism by which the temperature changes in a molten steel batch is dynamic, uncertain and complex. Three soft computing techniques are examined using the same data, namely the multiple regression, fuzzy regression, and neural net (NN) models. To compare the accuracy of these three models, a limited number of input variables are selected from those variables significantly affecting the temperature decrease. The results show that the difference in accuracy between the three models is not statistically significant. Nonetheless, the NN model is recommended because of its adaptive ability and robustness. The method presented in this paper allows the temperature decrease to be predicted without requiring any precise metallurgical knowledge.

• Journal of the Korean institute of surface engineering
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• v.31 no.6
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• pp.371-378
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• 1998

The zind bate contaminated in the hot dip galvannealed operation was successfully by appling the dross formation mechanism ; the Fe content was lowered from 0.028% to 0.011% and the dress size was decreased from 15~20$\mu\textrm{m}$ to under 3$\mu\textrm{m}$. The cooled metal from CGL zinc bath during operation of the galvannealed steel strip was remelted in graphite crucible at the lab and agitated after increasing Al content from 0.14% to 0.16% with decreasing the molten metal temperature from $470^{\circ}C$to $445^{\circ}C$. The agitating was done by agitator and nitrogen. The molten was analyed by SEM and EDS. It was considered that the Fe and the bottom dross($FeZN_7$) could react with aluminium to from the float dress($Fe_2Al_5$) according to the molten metal temperature down and the float dress rise to the surface of the zine bath. So the Fe and dross in the bath could be romoved out of the bath. It was confirmed that the proper purication conditions of GA zine bath is 0.02% of Al increasing, bath temperature down from $460^{\circ}C$ to $450^{\circ}C$and agitator and nitrogen.

• Tribology and Lubricants
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• v.33 no.6
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• pp.256-262
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• 2017

Molten zinc plating is a process in which zinc is thinly coated over a metallic or non-metallic surface. It is used in various industrial fields for corrosion resistance and decoration. During the process, a steel sheet is passed through a roll that rotates inside the molten zinc liquid in the temperature range of $460^{\circ}C$ to $680^{\circ}C$, and the plating liquid flows into the roll causing abrasion and erosion of the roll surface. This problem is known to accelerate the replacement cycle of the roll and cause considerable economic loss owing to production line stoppage. Here, we propose a mechanism that operates at high temperature and pressure with a labyrinth type seal design to resolve this problem. We theoretically investigate the flow of the plating solution inside the seal and compute the minimum rotation speed required to prevent the plating solution from entering the seal chamber. In addition, we calculate the thermal deformation of the seal during operation and display thermally deformed dimensions at high temperatures. To verify the theoretical results, we perform experiments using pilot test equipment working in the actual plating environment. The experimental results are in good agreement with theoretical results. We expect our results to contribute towards the extension of the roll's life span and thereby reduce the economic losses.

• Applied Chemistry for Engineering
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• v.10 no.8
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• pp.1119-1123
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• 1999

In this paper, electrorefining of uranium metal was studied to develop pyrometallurgical processing technology in molten salt system. The reaction between uranium metal and $CdCl_2$ was taken about 3 hours and the uranium metal deposits were obtained in the form of dendrite grown on the cathode surface in every electrotransport experiment. The shapes of dendrite were changed according to the applied voltages. Current efficiency was decreased with the increase of current density. Deposition rate was not changed after 6 hours and its maxium was obtained at $100{\sim}150mA/cm^2$ of current density and about 75 rpm of stirring speed, respectively. Also, the current efficiency was increased with decrease of the pitch of spiral groove curved on cathode.

• Korean Journal of Materials Research
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• v.18 no.5
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• pp.259-265
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• 2008

The corrosion and degradation factors of a current collector in a molten carbonate fuel cell (MCFC) were investigated to determine the optimized coating thickness of nickel on STS316L. The results show that the surface morphology and electrical properties depended on the nickel coating thickness. The surface morphology gradually changed from a flat to a porous structure along as the nickel coating thickness decreased, and the electrical resistance of the nickel-coated STS316L increased as the nickel coating thickness decreased. This can be attributed to the diffusion of elements of Fe and Cr from the substrate through the nickel grain boundaries. Additionally, carburization in the metal grains or grain boundaries in an anodic environment was found to influence the electrical properties due to matrix distortion. The resistance of Cr-oxide layers formed in an anodic environment causes a drop in the potential, resulting in a decrease in the system efficiency.

• Journal of the Korean Electrochemical Society
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• v.16 no.3
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• pp.138-144
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• 2013

Electrochemical reductions of $UO_2$ at various anode-to-cathode distances (1.3, 2.3, 3.2, 3.7 and 5.8 cm) were carried out to investigate the effect of the anode-to-cathode distance on the electrochemical reduction rate. The geometry of the electrolysis cell in this study, apart from the anode-to-cathode distance, was identical for all of the electrolysis runs. Porous $UO_2$ pellets were electrolyzed by controlling a constant cell voltage in molten $Li_2O-LiCl$ at $650^{\circ}C$. A steel basket containing the porous $UO_2$ pellets and a platinum plate were used as the cathode and anode, respectively. The metallic products were characterized by means of a thermogravimetric analyzer, an X-ray diffractometer and a scanning electron microscope. The electrolysis runs conducted during this study revealed that a short anode-to-cathode distance is advantageous to achieve a high current density and accelerate the electrochemical reduction process.

• Journal of Korea Foundry Society
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• v.23 no.2
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• pp.86-93
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• 2003

It has been a major concern in the foundry that steel castings manufactured by the evaporative pattern casting process encounter the carbon pick-up problem. A carbon rich layer at the evaporative pattern cast surface is a result of interactions between the gaseous products from foamed polystyrene and the molten metal. The carburized layer with a high hardness makes it difficult to machine the casting. In this study, the influence of the density of EPS pattern and coatings on carbon pick-up phenomena of S25C and S45C commercial carbon cast steel were investigated. As the density of EPS pattern is increased, the carbon concentration of decomposed pattern is increased and the thickness of carburized layer at the surface of steel castings is increased. Also as the density of coatings is increased, the permeability of coatings is decreased and the thickness of carburized layer at the surface of steel castings is increased. S25C steel which has lower original carbon content compared to S45C steel exhibited severe carburization.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.26 no.4
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• pp.357-364
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• 2017

Metal casting is a process in which molten metal or liquid metal is poured into a mold made of sand, metal, or ceramic. The mold contains a cavity of the desired shape to form geometrically complex parts. The casting process is used to create complex shapes that are difficult to make using conventional manufacturing practices. For the optimal casting process design of sleeve parts, various analyses were performed in this study using commercial finite element analysis software. The simulation was focused on the behaviors of molten metal during the mold filling and solidification stages for the precision and sand casting products. This study developed high-life sleeve parts for the sink roll of continuous hot-dip galvanizing equipment by applying a wear-resistant alloy casting process.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.1364-1367
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• 1996

Recently, direct rolling process, called as strip casting process, has been interested in to save production cost by reducing forming processes. In direct rolling process, since a steel strip of thickness 1-5(mm) can be produced directly from molten metal, it can eliminate secondary hot rolling process. On the other hand, since many process variables are existed in this process and relation of these variables is very complex, it is difficult to realize the process design and the quality control. In this paper, as first step to overcome above difficulties, the quantitative relationship of the process variables affected to quality of the strip has been carried out through the numerical analysis. Also, we determined the process variable to monitor the quality in the direct rolling process. As a result, we show that the solidification final point, called as Nip point, was related directly to quality of the strip.