• Journal of Korea Foundry Society
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• v.11 no.1
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• pp.54-62
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• 1991

A computer program which consists of pre-processor, main solidification simulator and post-processor has been developed for three dimensional solidification analysis of steel castings. The pre-processor is used for mesh generation in a small personal computing system. The modified finite difference method is adopted for the main solidification simulation algorithm. The post -processor graphically presents the simulation results and shows the formation of shrinkage defects. Several experiments on large steel castings in sand mold were carried out. The temperature variations in casting and mold with time are measured experimentally, and the results are compared with calculation results. Several numerical examples for the prediction of shrinkage cavity in large steel casting of SC42 and SCNCrM2 alloys are compared with experimental results. The effect of sleeve and chills on solidification patterns are also studied. Formation of shrinkage defects for the three cases of experimental castings are relatively well predicted by present model.

• Journal of Korea Foundry Society
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• v.27 no.1
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• pp.42-47
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• 2007

Vacuum molding process(V-process) has several benefits such as a lower total production cost and a high quality casting comparing to the conventional sand molding. Influence of the gating design on the molten metal flow was investigated in this study. General criteria for the gating design of the castings and commercial codes for the flow and solidification analysis were used to attain the optimized gating design in V-process. Though mold cavity was filled smoothly under the low initial velocity of molten metal, molten metal dashed against the upper part of the mold before the completion of the mold filling with higher initial molten metal velocity and fell soon. This phenomenon may affect collapsing the mold shape, however it is thought that the possibility of burning out of the vinyl by the molten metal is not so high because vinyl is coated with refractory material.

• Journal of Korea Foundry Society
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• v.39 no.5
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• pp.87-93
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• 2019

The effects of mold materials on the microstructure and tensile properties were investigated to develop a mass production technique of aluminum alloy parts with excellent mechanical properties using a lost foam casting method. The microstructures of the plate-shaped cast alloy showed a tendency to be finer in proportion to the thickness of the plate, and a remarkably fine structure was obtained by applying a steel chill or a ball as a mold material compared to general sand. When a steel ball was used, it was observed that the larger the ball, the finer the cast structure and the better the tensile properties. The microstructure and tensile properties of the cast parts with complex shapes were greatly affected by the gating system, but the positive effects of the steel chill and the steel ball as a mold material were clear.

• Journal of the Korea Concrete Institute
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• v.14 no.3
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• pp.420-429
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• 2002

The amount of $CO_2$-silicate bonded waste foundry sand(WFS) occurred in Korea is over 800,000 ton per year. WFS, as a by-product, is generated through manufacturing process of foundry may affect our environmental contamination, The reason is that WFS has been buried itself not less than 90％ out of total WFS. So, it can give damage on the ground of contamination in soil and underwater. Therefore, it is necessary to establish the method recycling WFS because of being intensified waste management law. In this study, we performed the research with respect to harmful component analysis, the qualities of WFS mortar and concrete mixed with WFS. As the results the specific gravity of WFS is the same as that of natural aggregate while unit weight and percentage of solids of WFS are smaller than those of it. But it is found that WFS can be used by substituting WFS for natural aggregate after control of poor grade of WFS. The flowability of mortar and concrete with WFS is inferior to those of natural aggregate, and the setting time of concrete with WFS is faster than that with only natural aggregate, On the contrary, the bleeding of concrete with WFS is shown good result, and compressive and tensile strength of concrete substituted WFS for 30％ are higher than those with only natural aggregate regardless of elapsed time.

• Journal of Korea Foundry Society
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• v.10 no.1
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• pp.31-42
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• 1990

The full mould casting process in one of the newly developed techniques which has many advantages. Unbonded sand mould has been prepared for the major mould and $CO^2$ gas mould has been used occasionally for comparison. Patterns were built up with expanded polystyrene and coated with three different materials. Silica, graphite and zircon were used for the coating layer. The effects on fluidity and temperature loss of molten metals were investigated. The molten metals were Al-5% Si alloy, Cu-30% Zn alloy and gray iron of approximately 4.0% of carbon equivalent. Experimental variables were runner section area, superheat, sprue height, coating materials, coating thickness and apparent density of EPS pattern. The effects of coating materials on fluidity and temperature loss of the molten metals during transient pouring are summarized as follows : As runner section area, superheat and sprue height increased, fluidity increased. Temperature loss decreased as runner section area and sprue height increased. However, reversed effects were observed in the case of superheat increment. The coating materials decreased the fluidity of each alloy in the order of silica, graphite and zircon. Zircon brought to the highest temperature loss among the coating materials used. The fluidity increased in the order gray iron, Cu-30% Zn and Al-5% Si alloy while temperature loss in the reverse order. Especially in case of reduced pressure process, the fluidity was increased apparently. Al-5% Si alloy showed the lowest temperature loss among the alloys. The increment of the apparent density of EPS pattern resulted in the fluidity decrease and temperature loss increase. The relation between fluidity and temperature loss of each alloy can be expressed by the following equation within the coating thickness limit of 0.5-1.5㎜. F^*={\frac{a}{T^*-b}}-c$ where, $F^*$ : fluidity in the Full mould, $T^*$ : temperature loss in the mould. a : parameter for full mould. b, c : constants.

• Journal of Korea Foundry Society
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• v.37 no.3
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• pp.71-77
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• 2017

Casting defects produced during the casting process seriously affect the mechanical properties of the resulting products, reduce the performance capabilities of the product, and also result in economic losses. Therefore, this paper mainly investigates the causes of defects and methods by which to reduce these defects stemming from molten metal flows in a runner system of the type widely used in the sand mold casting process. The flow characteristics of a molten alloy are difficult to observe during the actual casting process. For this reason, a water model was used to observe the flow in the casting process, and the flow in each case was recorded using high-speed cameras as part of the experimental process of this study. Several repetitive experiments were performed to improve the accuracy of the experimental results. The traditional casting system was modified according to the design rules proposed by Campbell, and the system was termed flow-adaptive gating system with a water model. Comparing the flow characteristics of traditional and adaptive gating systems with a water model shows that the bubbles in the water in the latter case are reduced more significantly than in the former case. A ceramic filter system was adapted to the flow-adaptive gating system to minimize the instability of the flow during filling, which occurs as the fluid velocity in the runner increases. In additional, the flow behavior with and without the filter system were compared. The water model system in this work was shown to be able to verify that the adaptation of the filter system brings improvements by stabilizing the flow and reducing the amount of bubbles in the runner system. Moreover, using the flow-adaptive runner system with the filter system leads to considerably stable flows in the runner system.

• Journal of Korea Foundry Society
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• v.4 no.4
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• pp.20-29
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• 1984

It is very important to obtain gray and ductile cast irons with completely pearlitic structure by addition more economical alloying elements. In this study, 9 melts of gray iron and 5 melts of Mg-treated ductile cast iron were made according to Sb content (0-0.08% Sb). Each melt were casted to ${\phi}20mm$ test bars in sand mold under the same condition and inspected microstructure, mechanical and thermal properties. The results obtained from this study are as follows: 1. It is confirmed that Sb should be an economical, simple and useful additive for avoiding ferrite in gray and even in ductile cast irons. 2. For gray cast iron, the recommended ladle addition of metallic Sb amounts to 0.05%. At these levels, Sb has no detrimental influence on the mechanical properties of gray cast irons, which are normally modified according to their pearlite content without increasing the chilling tendency. 3. Despite its adverse influence on graphite shape in ductile iron, Sb can be used as a pearlite stabilizing alloying element even in the case of Mg - treated iron. The quantity to be added does not exceed 0.04% in the case of thinwalled castings. 4. The nodule count is increased very much and the shape of graphite particles become remarkably spheroidal. The matrix may be fully pearlitized, except for thin - walled castings, because the high nodule count results inevitably in some ferrite. 5. The $Ac_1$ and pearlite decomposition temperature are rised in accordance with increasing of additive Sb amount.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.10a
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• pp.5-21
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• 2005

Urbanization rates of population range from about 1% in the developed countries to about 4% in developing countries. For a global population that may reach 10 billion within the next 40 years, pressure has arisen for an increase in the large-scale use of wastes and byproducts in construction. Ironically, most of the wastes that need to be recycled are generated in large cities where the need for constructed facilities to serve large population is high. Waste and recycled materials (WRM) that are used in construction are required to satisfy material strength, durability and contaminant teachability requirements. These materials exhibit a wide variety of characteristics owing to the diversity of industrial processes through which they are produced. Several laboratory-based investigations have been conducted to assess the pollution potential and load bearing capacity of materials such as petroleum-contaminated soils, coal combustion ash, flue-gas desulphurization gypsum and foundry sand. For full-scale systems, although environmental pollution potential and structural integrity of constructed facilities that incorporate WRM are interrelated, comprehensive schemes have not been developed for integrated assessment of the relevant field-scale performance factors. In this presentation, a framework for such an assessment is proposed and presented in the form of a flowchart. The proposed scheme enables economic, environmental, worker safety and engineering factors to be addressed in a number of sequential steps. Quantitative methods and test protocols that have been developed can be incorporated into the proposed scheme for assessing the feasibility of using WRM as partial or full substitutes for earthen highway materials in the field.

• Journal of Conservation Science
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• v.26 no.3
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• pp.341-348
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• 2010

After excavation work of relics, historical site which has historically meaningful, are preserved using the various methods. There are three method in the relocation methods that are original relocation method, the remaining structure-peel method, and soil peel method. The original relocation method is restored after relocating in historical site such as residential site, iron foundry site, kiln site, old mound. The remaining structure-peel method are restored only the feature of exposed remaining structure using polymeric resin, when it is difficult to relocate the entire remaining structure. And soil-peel method is exhibited after peeling in case when soil layers such as grave of old mound, foundation of building site, sedimentary deposit layer, shell heap, and etc. Soil-peel method becomes important historical data of changes according to environment at that time, that is, flooding by storm, traces of fire and living features of that time such as heaps of shells discarded after eating shellfish and living wastes. In particular, in case of soil layer for preparing foundation sites of building by compacting in turn soils with different components such as clay soil, rough sand soil and etc, it becomes important data which can judge foundation technology of that time. It can be said to be an important data preservation method for utilizing these historical data as historical data as well as for the purpose of education, exhibitions and public relations which can be shared not only by experts but also by general public. In this paper, we present the reliable definition of soil-peel method in various preservation methods and explain the using polymer in this method. So, we will come up with the accurate index about this method that is used the eminent analysis method for soil layer.