• Design & Manufacturing
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• v.7 no.1
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• pp.45-49
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• 2013

Since the shell-molds are used to make casting the metal parts for the automobile industry, the quality may well be inconsistent with the lower productivity, increasing the cost of the end products. The primary elbow design shell molded steel castings being produced through extrusion process has $180^{\varnothing}$ O.D., $150^{\varnothing}$ I.D., 14mm thickness and 400mm length, while being processed onto the left side of the tubing. The primary cause for the poor processing is the uneven manual shell molding. If the manual shell molds should be produced to have even quality, they would not be processed for tube linking. The purpose of this study was to develop the flask-molds for manufacturing of the shell molds to ensure mass-production, consistent quality, ommission of processing and comfortable working environment. For this purpose, four flask-molds were produced and thereby, four shell molds were assembled. In particular, the shell molds for processing were formed of the fine coated sand to be blown. As a result, productivity increased about three times, while a consistent quality was ensured. Furthermore, the tubes could be linked with each other without being processed, while pallets could be stacked, stored, transported and managed more easily. In a nut-shell, the molding theory could be applied more effectively. However, it is conceived that this study should be followed up by future studies which will research into reliability and endurability of the end products.

• Journal of the Korean Applied Science and Technology
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• v.29 no.1
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• pp.13-18
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• 2012

A die casting mold releasing agent was prepared from aqueous mixture of powdery carbon black and water soluble natural polymeric materials such as xanthan gum(X-gum) and carboxymethyl cellulose(CMC), which were used as thickening agent as well as curing agent with aldehydes. The suitable concentration of natural polymers for stable dispersion of carbon black in water was 0.25 wt% of X-gum or 1.0 wt% of CMC. When CMC was used less than 1 wt%, the final carbon black disperion showed a rapid phase separation. The adhesion of carbon black releasing agent on glass plate was improved with the amount of crosslinking agent, glutaraldehyde and chain extender, oligosaccharide. However, the affinity of carbon black releasing agent prepared with X-gum was stronger than that with CMC on glass plate. The final carbon black mold releasing agents prepared under our mixing conditions can be applied to the production of castings of high quality with good workability and without worthening evironmental situations.

• Journal of Korea Foundry Society
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• v.21 no.1
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• pp.41-47
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• 2001

Computer simulation of the solidification grain structure was applied to the casting process by using CA-DFDM. The Direct Finite Difference Method (DFDM) for temperature field calculation and latent heat treatment was coupled with Cellular Automaton (CA) method for the grain growth. 2-dimensional simulation of the solidification grain structures and calculation of the concentration fields were carried out and the calculated concentration distributions were compared with exact solution. Castings having complex geometries such as turbine blades were applied for 3-dimensional CA-DFDM. Effects of grain selector and mold extraction speed on the solidification grain structures in the turbine blade were examined.

• Journal of Korea Foundry Society
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• v.24 no.2
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• pp.94-100
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• 2004

Gas porosity which is a common defect in aluminum alloy casting, is also thought to be severer in aluminum alloy castings produced by lost foam process due to the pyrolysis of the polystyrene foam pattern during pouring. Fundamental experiments were carried out to evaluate the effect of process variables such as the melt treatment, the cooling rate and pouring temperature on the density and mechanical properties in A356.2 castings with simple bar shape. The density of grain refined specimen was slightly lower than that of degassed one, but was higher than that of no treated one and that of shot ball packed specimen was higher than the other specimens. The tensile strength and elongation were in the ranges of $200{\sim}230MPa$ and $0.5{\sim}1.5%$ respectively. The density and hardness of lost foam cast specimens decreased with increase in pouring temperature.

• 한국금형공학회:학술대회논문집
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• 2008.06a
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• pp.203-208
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• 2008

Recently, the modern society in development and industrial growth is investing a lot of time and much effort to improvement and environment of life quality. Thus, the casting tape which uses environmentally friendly and human body friendly water hardening process Polymer is rapidly substituted for the gypsum cast product which has been plentifully used in medical treatment. Until currently, prior researches have a tendency to focusing the analysis about chemical creation expense and reaction quality rather than the issue about optimization of the process for this polymerization. In the polymerization process which has been accomplished with actual same chemical creation expense, there has been a problem which is the possibility of getting a different result. This is because the optimization of respectively control factors is not accomplished which affect at polymerization process. Therefore, this research sees the chemical qualities of casting tape Polymer, consequently selects the polymerization process which is suitable. And, by using a experimental design, this research will evaluate the affects which the respective factors have on remaining NCO and viscosity. futhermore, this research will carry out the process optimization which can get the above results.

• Journal of the Korean Society for Heat Treatment
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• v.16 no.2
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• pp.90-96
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• 2003

The effect of betatizing temperature on microstructure and transformation characteristics in a Cu-AI-Ni based pseudoelastic alloy fabricated by heated mold continuous casting by using metallography, XRD and calorimetry. The microstructure of cast rod betatized at $600^{\circ}C$ revealed a ${\beta}_1$ parent phase and a ${\gamma}_2$ phase precipitated along the casting direction. When the cast rod was betatized at the elevated temperature above $600^{\circ}C$, the ${\gamma}_2$ phase is completely dissolved into the matrix so that the volume fraction of the ${\gamma}_2$ phase was decreased. The parent phase was stabilized by betatizing at $600^{\circ}C$. However, the ${\beta}_1$ parent phase was transformed to both ${{\beta}_1}^{\prime}$ and ${{\gamma}_1}^{\prime}$ martensites with increasing betatizing temperatures above $600^{\circ}C$, while $M_s$ and $A_s$ temperatures were decreased. The stress-strain curves for compression test were not same with betatizing temperature; the stress-strain curves of the specimen betatized at $600^{\circ}C$ and $700^{\circ}C$ were linear but those of the specimen betatized at $800^{\circ}C$ and $900^{\circ}C$ were not linear.

• Journal of Korea Foundry Society
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• v.19 no.1
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• pp.54-65
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• 1999

The present work is an attempt to evaluate the relationship between dendrite arm spacing and average cooling rate in gasatomized $Al_{87.3}misch$ $metal_{8.3}Ni_{4.4}$ powder by means of the following methods. One is calculation of heat transfer coefficient and average cooling rate, which are derived from estimated particle velocity during gas-atomization. The other is measurement of secondary dendrite arm spacing, which are observed on the particle surface. Then, we make experimental equation for this relationship in case of permanent mold casting and compare it with similar equation in case of rapidly solidified powder. Both average cooling rates and solidification rates are considered to represent the variance of dendrite arm spacings in two types soidification route. Even though there is a considerable difference in each average cooling rate, the dendrite arm spacing values are similar in two cases; particle diameter, $100\;{\mu}m$, and casting width, 2.05 mm. It is because that each solidification route has similar solidification rate.

• Journal of Korea Foundry Society
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• v.24 no.6
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• pp.314-322
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• 2004

The CaO crucible is expected to serve as a useful tool for melting Ti and its alloys due to its thermodynamic stability. However, tjere still remain problems that need to be resolved in the melting of Ti and its alloys to enable commerical use. The cause of the defects of Ti-6AI-4V alloy castings melted in the CaO crucible were examined and compared with induction skull melting. The key factors of the melting technique using the CaO crucible, affecting the quality of Ti-6AI-4V alloy castings, were investigated. Defects of the Ti-6AI-4V alloy castings are caused by the chemical reduction of CaO by Ti. Pressurizing with argon gas in a vacuum induction chamber is effective for reducing the defects. Preheating of the charged material in the crucible and quick pouring into a mold of lower temperature, just after melting down, are important for produsing sound Ti-6AI-4V castings.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.5
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• pp.140-146
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• 2003

Metal matrix composites had generated a lot of interest in recent time because of their high specific strength and stiffness in specific properties. It was also highlighted as the material of frontier industry because strength, heat-resistance, corrosion-resistance and wear-resistance were superiored. In this study, the strength properties of $Al_{18}B_{4}O_{33}$/AC4CH composites were represented mixing the binder of $SiO_2$. It was also fabricated by squeeze casting. $Al_{18}B_{4}O_{33}$/AC4CH was fabricated at the melt temperature of $760^{\circ}C$, the perform temperature of $700^{\circ}C$ and mold temperature of $200^{\circ}C$ under the pressure of 83.4MPa. Consequently, fatigue life was observed roughly in the order of AC4CH> nobiner> $SiO_2$, independently on crack propagation direction and stress ratio.

• Korean Journal of Metals and Materials
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• v.50 no.9
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• pp.669-675
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• 2012

Hot tearing was the most significant casting defect when the castability evaluation of the Al-Zn-Mg-Cu alloy system was conducted. It was related to the solidification range of the alloy. Therefore, the hot tear susceptibility of the AA7075 alloy, whose solidification range is the widest, was evaluated. The hot tear susceptibility was evaluated by using a mold for a hot tearing test designed to create the condition for the occurrence of hot tear in 8 steps. According to the tearing location and shape, a hot tear susceptibility index (HTS) score was measured. The solidification range of each alloy and hot tear susceptibility was compared and thereafter the microstructure of a near tear defect was observed. As a result, the HTS of the AA7075 alloy was found to be 67. Also, the HTS in relation to a change in Zn, Mg, Cu composition showed a difference of about 6-11% compared to the AA7075 alloy.