• Journal of the Korean Society for Heat Treatment
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• v.21 no.4
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• pp.183-188
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• 2008

Hot press forming allows geometrically complicated parts to be formed from sheet and the rapid cooling hardens them to extremely high strength. The main purpose of this research is to characterize Al coated layer in Al coated boron steel during hot press forming. For the hot press hardening experiment, test specimens were heated up to $810{\sim}930^{\circ}C$ and held for 3, 6 and 9 minutes, respectively. And then, some specimens were press hardened and others were air-cooled without any pressing for the comparison purpose. Al coated layer shows four distinct micro-structural regions of interest; diffusion zone, Al-Fe zone(I) low-Al zone(LAZ) and Al-Fe zone(II). Band-like LAZ is clearly shown at temperature ranges of $810{\sim}870^{\circ}C$ and sparsely dispersed at temperature higher than 900oC. The micro-cracking behavior in the Al coated layer during forming were also analyzed by bending and deep drawing tests. The strain concentration in softer LAZ is found to be closely related with micro-cracking and exfoliation in coated layer during forming.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.05a
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• pp.128-129
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• 2015

Al-rich coatings were prepared on hot rolled low carbon steel by hot dipping method in molten Al-bath to investigate the corrosion resistance with the possible outcomes and defects of aluminized coatings in air and $Ar-0.2%SO_2$ mixed gases. Coating microstructure was composed of an inner Al-Fe intermetallic layer and outer Al-rich layer. Aluminum oxidized preferentially to the thin, outer, protective ${\alpha}-Al_2O_3$ layer, without forming the nonprotective iron/sulfur-oxide layer after heating at $800^{\circ}C$ for 20 h, in both the gases and provided the resistance against corrosion.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.05a
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• pp.122-122
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• 2015

Al-rich coatings were prepared on hot rolled low carbon steel by hot dipping method in molten Al-bath to investigate the corrosion resistance with the possible outcomes and defects of aluminized coatings in air and $Ar-0.2%SO_2$ mixed gases. Coating microstructure was composed of an inner Al-Fe intermetallic layer and outer Al-rich layer. Aluminum oxidized preferentially to the thin, outer, protective ${\alpha}-Al_2O_3$ layer, without forming the nonprotective iron/sulfur-oxide layer after heating at $800^{\circ}C$ for 20h, in both the gases and provided the resistance against corrosion.

• Journal of Korean Society for Atmospheric Environment
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• v.17 no.1
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• pp.75-84
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• 2001

Hot gas filtration method via using ceramic filters is an evolving technology applicable to numerous industrial and air pollution control processes. Alumino silicate, organic and inorganic binders were the major raw materials in manufacturing ceramic filters. In this work, disc type ceramic filters(50$\phi$$\times$10t) were manufactured by vacuum forming processes using ceramic raw materials. The porosity and bulk density of disc type ceramic filers ranged from 86 to 89% and from 0.27 to 0.36 g/㎤, respectively. In this work disc type ceramic medium were tested utilizing coupon experimental apparatus. Disc type filters showed high collection efficiencies over 99.96% with Darchs law coefficients of 4.1$\times$10(sup)10~9.63$\times$10(sup)10/$m^2$ depending on mean pore sizes. In addition, filtration and detachment of ceramic filters turned out to be performed effectively using 10 cm/sec face velocity, 5 minutes filtration cycle, 100msec pulse jet valve opening time and 3 bar pulsing pressure.

• Journal of the Korean Society of Food Science and Nutrition
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• v.30 no.1
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• pp.48-55
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• 2001

This study investigated the quality characteristics of sponge cakes with addition of yam (Dioscorea) powders prepared by different drying methods, hot air (HDYP : hot air dried yam powder) and freeze drying (FDYP: freeze dried yam powder), using several physical and sensory examinations. For the foam forming ability and foam stability, the specific gravities of egg foams containing 5% yam powders were measured by drainage using funnels for 78 hrs. The results showed that HDYP and FDYP did not affect the foam forming ability but FDYP increased foam stability due to increased viscosity. When the strength of 8% gels composed of wheat starch and HDYP/FDYP was measured to predict the setting of cake structure, the strengths of starch gels containing yam powders were higher than those of control without yam powders. The volume of sponge cake containing 5% HDYP increased whereas those containing FDYP decreased at the levels of 5, 7%. From the texture profile analysis data, hardness, gumminess and chewiness of cakes containing yam powders increased. The color of cake crust and crumb became darker as the amount of yam powders increased. The results of sensory evaluation by QDA (quantitative descriptive analysis) to compare two different drying methods showed that appearance and texture of cakes containing 5% HDYP were closer to those of control than cakes containing 5% FDYP but overall acceptability of sponge cakes containing yams were comparable to the control cakes regardless of drying methods. The addition of yam powders to sponge cakes increased yam flavor and decreased egg smell. Therefore, it can be suggested that HDYP and FDYP can be added to the sponge cake formula up to 7% and 5%, respectively.

• Journal of Korea Foundry Society
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• v.17 no.5
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• pp.494-501
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• 1997

In order to manufacture large rod preforms of 2014 Al alloy with a good mechanical property by spray forming method, it was spray-formed at a droplet temperature of $715^{\circ}C$, a droplet flight distance of 400mm, and a spraying angle of $35^{\circ}$. The rod preforms were extruded at $397^{\circ}C$ with the die temperature of $420^{\circ}C$ under the hot extrusion ratio 21:1 and T6 heat treatment was performed. The 2014 Al alloys cast by hot top process were also extruded and heat-treated at the same condition as a reference material. Microstructural observation and tensile test were carried out to investigate the effects of extrusion on microstructure and mechanical property of spray-formed Al alloy. Spray-formed Al alloys had many porosities due to inappropriate process conditions such as long droplet flight distance and low droplet temperature but have fine equiaxed grain. These porosities were reduced with decreasing in grain size by hot extrusion. Ultimate tensile strength and yield strength of spray formed-extruded 2014 Al alloy were inferior to those of the normal cast-extruded 2014 Al alloy, but elongations were superior. The control of porosity was important to get spray formed preform with a good mechanical property.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.08a
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• pp.111-118
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• 1999

This article describes the basic engineering concepts to be considered in the application of an induction heating furnace in the hot-dip galvanizing line. Experience in the Dongkuk project in Pohang, has shown that this arrangement has many advantages over the conventional method of using a combustion-gas heated furnace. Investment and operating costs are lower, the line length is much shorter, line operation is more convenient, air pollution is reduced, and the coated strip at of top-quality. As these benefits become well known, it is anticipated that the concept of induction heating will be more widely used in both new and revamped process lines. Induction heating is suitable for the production of Commercial Quality hot galvanized coils. More research is required to extend the present concept to the production of higher forming grades such as Drawing, Deep Drawing and Extra Deep Drawing Quality steels. A combination of induction heating and combustion-gas heating may lead to the way to the processing of these qualities of strip.

• Journal of the Korean Society of Propulsion Engineers
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• v.4 no.2
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• pp.46-53
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• 2000

Hot forging of aluminum alloy has the bad machinability due to continuous chip formation caused from the ductility The bad machinability requires a labor and a high cost to produce final products after hot forging. In industrial field, T4 heat treatment is performed to improve the machinability, and the annealing and the cold sizing are followed. In this study, a series of heat treatments are introduced during hot forging operation without T4 heat treatment after forming so that it improves the machinability with reduction of the number of operations and machining cost. Instead of T4 heat treatment, water cooling and air cooling are tried and compared to find out an optimum cooling condition

• Journal of the Korean institute of surface engineering
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• v.50 no.1
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• pp.42-45
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• 2017

The magnesium-base AZ61 alloy was cast while adding 1% CaO powder into the melt. It was hot extruded, and oxidized at $550-650^{\circ}C$ in air in order to study its microstructure and oxidation behavior. Initially added CaO powder reacted with Al in the melt to $Al_2Ca$ particles that aligned along the extrusion direction. The formed $Al_2Ca$ particles increased the oxidation resistance through forming the superficial CaO scale at the upper part of the thin MgO oxide scale.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.05a
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• pp.217-218
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• 2016

Sheet based waterproofing methods are factory produced and have a advantage or forming uniform waterproofing layer in construction sites, allowing them to become a commonly used material domestically. Particularly in the case of EVA waterproofing sheets, they can be manufacturing using recycled materials and are thus increasing in application due to their eco-friendly factors. However, heating adhesion method has to be used in case of overlapping areas of waterproofing sheets, but not enough studies have been made on the adhesion stability based on different heat adhesion speed. In this paper, EVA sheets have been studied with their overlap area properties following a heat adhesion method in wintertime ambient conditions and have been observed for the changes in the tensile strength based on different head adhesion speed and rates. According to the results, 6~7m/min adhesion speed was shown to have produce the best tensile strength.