• Journal of Power System Engineering
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• v.11 no.2
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• pp.51-57
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• 2007

As a shot sleeve in die casting plays a critical role in delivering molten metal to a die cavity, any disruption to its function in the injection stage results in deterioration of the quality of final castings. To guarantee a smooth operation of a shot sleeve, its structural stability should be maintained. Despite the simple geometry, design of shot sleeve is based on individual engineer's experience and no agreement on the design is present. In this study, we newly propose a systematic methodology to determine a minimum wall thickness of a shot sleeve to prevent yielding or plastic deformation. Analytical calculations incorporating numerical analysis produce a rational design rule for minimum thickness of a shot sleeve subject to metal intensification pressure and geometric die constraint. To validate the proposed design guideline, authors present real data on a collection of actual shot sleeves. Upon checking their conformity to the new design rule, we discovered a strong correlation between the design of wall thickness and premature failures.

• The Journal of Korean Academy of Prosthodontics
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• v.44 no.6
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• pp.677-682
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• 2006

Statement of problem. Various double crown systems have been used with removable partial dentures in the clinical field. Although retentive force between inner and outer crown are affected by several factors, differences between the retentive forces of different double crown system types are expected. Purpose. The purpose of this study was to evaluate the initial retentive force of outer crowns fabricated by the conventional casting technique in conus and hybrid double crowns. Material and methods. Ten double crowns were fabricated. The groups were as follows. Group 1, double crowns of hybrid inner and outer crowns using the conventional casting method; Group 2, double crowns of conus inner and outer crowns using the conventional casting method. Tensile strengths of double crowns when the inner and outer crowns were separated on a universal testing machine were measured. These values of retentive force were then statistically analyzed using the Kruskal-Wallis test. Results. Retentive force in group 2 was significantly higher than that in group 1(p<.05). Conclusion. The initial retentive forces of double crowns were affected by the types of the double crown system.

• The Journal of Advanced Prosthodontics
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• v.9 no.1
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• pp.52-56
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• 2017

PURPOSE. Considering the importance of metal-ceramic bond, the present study aimed to compare the bond strength of ceramics to cobalt-chrome (Co-Cr) alloys made by casting and selective laser melting (SLM). MATERIALS AND METHODS. In this in-vitro experimental study, two sample groups were prepared, with one group comprising of 10 Co-Cr metal frameworks fabricated by SLM method and the other of 10 Co-Cr metal frameworks fabricated by lost wax cast method with the dimensions of $0.5{\times}3{\times}25\;mm$ (following ISO standard 9693). Porcelain with the thickness of 1.1 mm was applied on a $3{\times}8-mm$ central rectangular area of each sample. Afterwards, bond strengths of the samples were assessed with a Universal Testing Machine. Statistical analysis was performed with Kolmogorov-Smirnov test and T-test. RESULTS. Bond strength in the conventionally cast group equaled $74.94{\times}16.06\;MPa$, while in SLM group, it equaled $69.02{\times}5.77\;MPa$. The difference was not statistically significant ($P{\leq}.05$). CONCLUSION. The results indicated that the bond strengths between ceramic and Co-Cr alloys made by casting and SLM methods were not statistically different.

• Journal of Technologic Dentistry
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• v.27 no.1
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• pp.65-71
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• 2005

Experimental Ti-13%Zr and Ti-13%Zr-5%Cu alloys were made in an argon-arc melting furnace. The grade 2 CP Ti was used to control. The alloys were cast into phosphate bonded $SiO_2$ investment molds using an argon-arc casting machine, and The hardness and microstructures of the castings were investigated in order to reveal their possible use for new dental casting materials and to collect useful data for alloy design. The hardness of the Ti-13%Zr-5%Cu alloy(379Hv) became higher than that of Ti-13%Zr(317Hv) alloy, and the hardness of this alloys became higher than that of CP Ti(247Hv). Increasing in the hardness of the Ti-13%Zr-5%Cu alloy was considered to be solid solution hardening as the Ti-Zr system shows a completely solid solution for both high temperature $\beta$phase and low temperature $\alpha$ phase and also the inclusion of the eutectoid structure($\alpha Ti+Ti_{2}Cu$). No martensitic structures are observed in the specimen made of CP Ti, but Ti-13%Zr and Ti-13%Zr-5%Cu alloys show a kind of martensitic structure. Ti-13%Zr-5%Cu shows the finest microstructure. From these results, it was concluded that new alloys for dental casting materials should be designed as Ti-Zr-Cu based alloys.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.18 no.2
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• pp.130-136
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• 2009

Semi-solid casting(SSC) of magnesium alloys is increasingly being used to produce high quality components. This process is similar to the injection molding of plastics and is called thixomolding. Using this process, higher strength, thinner wall sections and tighter tolerances without porosity are obtained. The high strength and low weight characteristics of magnesium alloys render the high-precision fabrication of thin-walled components with large surface areas. They are widely used for the IT, auto and consumer electronics industries. However, warpage of the thin-walled sections degrade quality of the parts produced in the SCC process. To produce thin-walled magnesium alloy parts, the geometry of gating system on the quality of the finished products should be clearly studied. In this paper, to minimize warpage of the thin-walled sections, Taguchi method is applied to the optimal design of the gate geometry in the thixomolding process. Width, height, length and angle of the gating system are selected for the robust design parameters. Effectiveness of the robust design is verified through the CAE software.

• 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 Korea Foundry Society
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• v.28 no.5
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• pp.237-241
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• 2008

This study has been carried out to investigate the wear and heat resistant properties of durable moldwash agent for Al gravity casting according to mold washing process conditions. The wear properties of coated specimen were performed by sliding wear testing machine and heat resistance were evaluated by measuring the loss of coated moldwash agent during emerging of coated specimen in Al melts. During testing, experimental variables were mold surface temperature, moldwash agent/distilled wear, and additive concentrations. The lower additive concentration and mold temperature caused the smooth surface roughness of coated specimen, It was found that the specimen coated with moldwash/water ratio 1:3, additive concentration 9wt% and mold temperature higher than $200^{\circ}C$ showed superior wear and heat treatment. Also, these results were supported by fluidity test.

• Journal of Korea Foundry Society
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• v.26 no.4
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• pp.174-179
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• 2006

This study aims to investigate the microstructures and mechanical properties of DCI manufactured by sand and metal mold casting. To prohibit the formation of the chill, carbon, silicon and rare earth($0{\sim}0.2\;wt%$) were controlled and temperature of metal mold was constantly kept at $160^{\circ}C$. The sizes, counts and nodularity ratios of nodules were analyzed by image analysis device. Wear test using pin-on-disc wear tester was carried out under the conditions of load 47.2N, velocity 0.4 m/s and distance 2000 m. Tensile test using Instron type testing machine was performed with velocity of 0.1 mm/min according to the KS B 0802. The formation of the chill was not observed when percentage of the carbon and silicon were 3.8 and 2.5. Mechanical properties of GCD manufactured by metal mold were better than sand casting.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.371-374
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• 2009

Die casting process has been used widely for complex automotive products such as the knuckle, arm and etc. Generally, a part fabricated by casting has limited strength due to manufacturing defects by origin such as the dendrite structure and segregation. As an attempt to offer a solution to these problems, forging has been used as an alternative process. However, the forging process provides limited formability for complex shape products. Rheo-forging of metal offers not only superior mechanical strength but also requires significantly lower machine loads than solid forming processes. This paper presents the results of an A356 aluminum alloy sample, which were obtained by experiment and by simulation using DEFORM 3D. Samples of metal parts were subsequently fabricated by using hydraulic press machinery.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.1
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• pp.120-126
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• 2010

It was known that the excellent wear resistance of hyper eutectic aluminum alloy is based on the primary Si particles which are distributed in the base metal. When the primary Si volume fraction increases, the smaller size have excellent wear resistance characteristics. However, this trend always does not match. There is no investigation result based on the materials and methods for real using parts. In this study, using the automotive parts manufacturer currently in use hyper eutectic Al alloy tensile test specimen type sample was fabricated by 350Ton high pressure die-casting machine. Then, fluidity, tensile, impact and wear resistance properties were evaluated. If the casting quality, primary Si size, fraction and distribution are similar, mechanical properties and wear resistance are equivalent.