• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2005.05a
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• pp.174-179
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• 2005

In the super slow speed die casting process, the casting defects due to melt flow should be controlled in order to obtain sound casting products. The casting defects that are caused by molten metal were cold shut formation, entrapment of air, gas, and inclusion. But the control of casting defects has been based on the experience of the foundry engineers. The calculation of simulation can produce very useful and important results. The calculation data of die casting process condition from the computer simulation by the Z-CAST is made to insure that the liquid metal is injected at the right velocity range and that the filling time is small enough to prevent premature solidification. The parameters of runner shape that affected on the optimized conditions that was calculated with simple equation were investigated. These die casting process control techniques of automobile valve body mid-plate have achieved good agreement with the experimental data of tensile strength, hardness test, and material structure photographies satisfactory results.

• Journal of Technologic Dentistry
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• v.8 no.1
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• pp.37-43
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• 1986

The purpose of this study is to evalute the effects of melting and casting procedures on the castability of some N-Cr and Ag-Pd alloys. One Ag-Pd alloy and two Ni-Cr alloys were chosen for study, and the first casting group of these alloys were used as the control, and with which the castability of the first recase group and the mixture group of the first recast and as much amount of the first casting alloy was compared. The results of this study were as follows: 1. The castability of the first recast alloys veried significantly depending upon the presence or abscence of the first casting alloy and the kind of alloys. 2. When the first recast alloy was mixed with as much amount of the first casting alloy, there was no significant difference in castabilityh between the first recast group and the first casting group. 3. When the first recast alloy was used alone, the castability veried significantly depending upon the kind of alloys, i.e., the castability of Rexillium III and Palliag M was decreased significantly when compared with that of the first casting groups, while that of C & B Alloy was not.

• Journal of Technologic Dentistry
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• v.7 no.1
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• pp.5-12
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• 1985

This experimental study is perform to study the effect of the direction for the centrifugal force in operating centrifugal casting machine. In order to investigate the effect of direction for centrifugal force action on the casting ability 20 pieces of specimen are produced including one vertical direction and four horizontal directions. Casting shows us that the 15 pieces of specimen among them are included within $\pm$16. The results obtained through the comparison with 5 groups of the casting ability are as follows: 1. In the experiment of the casting, statistically significant difference are found between the vertical direction and the group of horizontal direction, namely, the direction of 3, 6, 9 and 12 o'clock, and also statistically there are significant differences between the direction of 9 o'clock and of 6 o'clock, and between the direction of 9 o'clock and of 12 o'clock which lie between the groups of horizontal directions. 2. The degree of casting ability is showing us on an average, 23.80 in the vertical direction. And also in the group of horizontal direction it prove in turn 15.60 in the direction of 9 o'clock, 14.47 of 3 o'clock, 13.30 of 12 o'clock, and 12.80 of 6 o'clock.

• Journal of Conservation Science
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• v.37 no.4
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• pp.340-356
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• 2021

We have tried the experimental research of lost-wax casting to reconstruct Gilt-Bronze Pensive Bodhisattva; preliminary and reconstruction experiment based on ancient texts. Main object to reconstruct is Korean National Treasure No.83, Gilt-Bronze Pensive Bodhisattva (Maitreya), then we measure alloy ratio and casting method based on the scientific analysis. Other impurities were removed from the base metal components(copper : tin : lead) and their ratio was set to 95.5 : 6.5 : 3 where the ratios for tin and lead were increased by 2.5% each. The piece-mold casting method was used, and piece-mold casting experiments were carried out twice in this study but supplementary research on piece-mold casting was necessary. The microstructure was confirmed to be typical cast microstructure and the component analysis result was similar to that of the prior study. Analysis of the chemical composition is confirmed to copper, tin, lead, and zinc, and the chemical composition of the matrix was 87.8%Cu-7.5%Sn-2.7%Pb-2.1%Zn, and similar to previous experimental research. Also resulted in the detection of small impurity in Zn. Analysis of the mould revealed that the mould was fabricated by adding quartz and organic matter for structural stability, fire resistance, and air permeability. We expect that our research will contribute to provide base data for advanced researches in future.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.5
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• pp.239-244
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• 2019

Traditional casting methods require long production lead time and high cost while not accommodating design changes easily. One of the technological alternatives to improve casting method to meet diversifying needs is Additive Manufacturing (AM). Among the 7 AM techniques, Powder Bed Fusion (PBF) is deemed most appropriate for casting applications. Currently, most AM machines are imported; therefore limiting the scope of available services and applications. This paper explores the domestic development of AM machines as well as the applications in casting. Each chapter describes development phases of PBF machines, applicable materials and parameter settings, while the last chapter illustrates a successful case of additive manufacturing industrial casting cores.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.5
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• pp.889-898
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• 2022

In this study, sand casting process was applied to manufacture a large aluminum turbo-type fan used for tank powerpack. To apply the sand casting method, the turbo fan was reverse engineered, and after designing three gating systems, the optimal gating system design was selected by performing casting simulation. In the case of the bottom up-gating system, there is a significant temperature loss of the molten alloy during blade filling. When the molten alloy is completely filled into the sand mold, the blade upper tip and front shroud are below the liquidus temperature. In the case of the top down-gating system, molten alloy scattering occurs, but the temperature loss while the blade is filled is smaller than that of the bottom up type. And after the inflow of molten alloy into the mold is completed, the blade upper tip and front shroud are higher than the liquidus temperature. A sand mold was manufactured with the top down-gating system and the casting process was performed. The fan was made perfectly in appearance without any unfilled parts.

• Journal of Conservation Science
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• v.28 no.4
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• pp.417-425
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• 2012

Bronze Mirror with fine linear designs in the bronze age shows the greatest alloy and casting skills of the day and presents the highest level of handcrafting and molding techniques. Lately, Lost-wax casting and sand-mould casting were used for the restoration of the national treasures of No. 141 and No. 143 Bronze Mirror with fine linear designs. Also the Principle Component Analysis, Microstructure Analysis, X-ray and SEM-EDS analysis were carried out on the restored Bronze Mirror with fine linear designs. Bronze Mirror that is made of sand-mould casting, hardly has a eutectoid and it is observed as a ${\alpha}$ dendrite. In contrast, Bronze Mirror that is made of lost-wax casting, the eutectoid has found through the ${\alpha}$ dendrite. As we compare lost-wax casting to the sand-mould casting through an analysis of restored Bronze Mirror, mostly, sand-mould casting has better castability and it seems that it brings a clear and equal Bronze Mirror as it has a low cooling rate. In this way, we are able to confirm that there is a big difference between the method by lost-wax casting and by sand-mould casting through an analysis of microstructure and restored Bronze Mirror. If such research will be continued, it will be an opportunity that investigates diverse methods of production techniques.

• Journal of Korea Foundry Society
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• v.41 no.3
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• pp.241-251
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• 2021

7000-series aluminum alloys are noted for their superior strength compared with other Al alloys, and their billets are generally fabricated by direct-chill (DC) casting. Surface defects in a DC-cast aluminum billet are mainly related to exudation and the meniscus freezing phenomenon, which are influenced by alloy compositions, casting speed, and casting temperature. 7000-series aluminum alloys have a wide freezing range during solidification, which makes it easy for casting defects to occur. In this study, we investigated surface defect evolution in casting billets of Al-8Zn-2Mg-2Cu alloy fabricated by a DC casting process. The billets showed "wavy" or "dotted" surfaces. The wavy surface was formed by meniscus freezing at a lower casting speed (200 mm/min) and temperature (655 ℃). In the wavy surface, refined dendritic cells were observed in a concave region due to the constitutional supercooling caused by meniscus freezing. Meanwhile, at a higher casting temperature (675 ℃), the dotted surface was formed by pore formation. In the dotted surfaces in the billet formed at a high casting speed (230 mm/min), an exudation layer was formed by the high metallostatic head pressure. The dotted region and the smooth region had a refined dendritic morphology and a columnar morphology at the exudation layer, respectively. This is attributed to the formation of gas pores in the dotted region.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.1035-1040
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• 2001

Recently, Sea-sand containing high levels of chloride is being applied to on reinforced concrete structures due to the exhaustion of river-sand and environmental problems, which affects directly corrosion of rebar in the RC structures. In this paper, characteristics of corroded rebar before and after casting were studied. Test results showed that bond strength of rebar corroded after casting was decreased with increase of corrosion level more rapidly than that of rebar corroded before casting.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.4
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• pp.50-55
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• 1998

Mould level control system for continuous casting process involves stick-slip friction in the sliding gate , time-delay, non-linearity, and certain uncertainties such as friction force variations between molten steel and the inner wall of mould. In this paper, sliding mode control technique was used to solve these complex control problem. The controller is then designed and implemented onto the continuous casting process. Testing result shows that sliding mode controller can decrease the fluctuating magnitude of the mould level and is superior to the existing PID controller.