• 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.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.6
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• pp.482-489
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• 2020

This study conducted a prototype development and evaluation by performing die-casting mold design, mold manufacturing, and injection condition optimization based on flow and solidification analysis to meet the needs of the coupling parts produced by die casting. Through flow analysis, the injection conditions suitable for 100% filling in the cavity were found to be a molten metal temperature of 670 ℃, injection speed of 1.164 m/s, and filling pressure of 6.324~18.77 MPa. In addition, solidification close to 100 % occurred in all four cavities when the solidification rate was 69.47 %. A defect inspection on the surface and inside the product revealed defects, such as poor molding and pores. In addition, the dimensions of the injected product were within the target tolerance and showed good results. Through the feedback of the results of flow and solidification analysis, it was possible to optimize the mold design, and the injection optimization conditions were confirmed to be a total cycle time of approximately 6.5 seconds. Good quality carrier parts with an average surface hardness of approximately 45 mm from the gate measured at 97.48(Hv) could be produced.

• Journal of Korea Foundry Society
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• v.40 no.3
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• pp.66-75
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• 2020

The aim of this study was to optimize a solid solution treatment for a high pressure die casting Al-10Si-0.3Mg-0.6Mn alloy to avoid blistering and to improve the strength of the alloy. To achieve this goal, the number density of the blisters and the strength of the alloy under various solid solution treatment (SST) conditions were evaluated. The SST was performed at 470, 490, 510 and 530℃ for 20, 60, 120, 240 and 480 min on the alloy. The number density of the blisters increased with the increasing temperature and time of the SST and the defect area fraction. The yield strength of the alloy after the T6 heat treatment increased with the increasing SST temperature and time. Based on the results, it is suggested that SST should be performed at 510℃ within 60 min. or at 470 and 490℃ within 240 min. to avoid blistering and to improve the strength.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.1
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• pp.57-64
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• 2010

Metal Injection Molding (MIM) is attractive because it produces consistent, complex-geometry components for high-volume, high-strength, and high-performance applications. Also MIM using in optical communication field, display field, and semi-conductor field is a cost-effective alternative to metal machining or investment casting parts. It offers tremendous single-step parts consolidation potential and design flexibility. The objective of this paper is to study the suitability of design, flow analysis, debinding and sinterin processes, and capability analysis. The suitable injection conditions were 0.5~1.5 second filling time, 11.0~12.5 MPa injection pressure derived from flow analysis. The gravity of the product is measured after debinding an sintering. The maximum and minimum gravity levels are 7.5939 and 7.5097. the average and standard deviation are 7.5579 and 0.0122; when converted into density, the figure stands at 98.154%. According to an analysis of overall capacity, PPM total, which refers to defect per million opportunities(DPMO), stands at 166,066.3 Z.Bench-the sum of defect rates exceeding the actual lowest and highest limits-is 0.97, which translates into the good quality rate of around 88.4% and the sigma level of 2.47.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.8
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• pp.79-87
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• 2012

Currently, The method to produce a brewing body for dentistry supplementation water produces a brewing body by fabrication, burying and it is heat wish in city gas and oxygen. It uses an original judgment found airplane the brewing body uses a spring of the back wait that melting temperature dissolved various alloys in by a blow pipe, and to generate centrifugal force and produces it. In addition, because it uses preheating to dissolve an alloy in general, it is hard to regulate the appropriate melting temperature of the alloy and brewing time and generates a brewing defect hereby same as gas industry and pinhole and shows the defect of the supplementation thing due to the super-heating. In this paper, We developed the high induction heating system which it could set brewing time,temperature and had durability and security,by the kind of the alloy to produce a high quality prosthetic thing brewing body.

• Journal of Korea Foundry Society
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• v.31 no.4
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• pp.198-204
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• 2011

The present study was aimed to investigate the dependence of fatigue property on microporosity variation of low-pressure die-cast (LPDC) A356 alloy. The fatigue property of A356 alloy was evaluated through high cycle fatigue test, and the microporosity-terms used were the fractographic porosity measured from SEM observation on fractured surface and the volumetric porosity obtained through the density measurement using Archimedes's principle. The number of cycles to failure of A356 alloys depends obviously upon the variation of fractographic porosity, and can describe in terms of the defect susceptibility which depends on the microporosity variation at a given value of stress amplitude. The modified Basquin's equation was suggested through the combination of microporosity variation and static maximum tensile stress to fatigue strength coefficient. Using modified Basquin's equation, it could suggest that the maximum values of fatigue strength coefficient and exponent achievable in defect-free condition of A356 alloy are 265 MPa, -0.07, respectively.

• Proceedings of the KWS Conference
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• 2006.10a
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• pp.225-227
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• 2006

As rail steel at a crossing area must undergo much higher loading than those at regular railway, Mn-alloyed steel is normally used for its high load-carrying capability and reduced wear rate. However, as these Mn-alloyed steel is tend to have casting defects, manufacturing cost to produce defect-free Mn-alloyed steel becomes quite expensive. Therefore, in order to replace Mn-alloyed steel, we performed build-up welding using CH-90 and investigated regarding to wear characteristics of build-up weld metal.

• Journal of Korea Foundry Society
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• v.22 no.6
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• pp.293-298
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• 2002

The effects of alloying elements added on the microstructure and high temperature oxidation behavior of the electro-slag remelted Fe-22Cr-5Al alloy were investigated. The amount of casting defect was makedly reduced by the electro-slag remelting. The electro-slag remelted ingot had a directionally solidified structure and cleaner surface than that of air-melted one. The high temperature oxidation reststance was greatly improved by the addition of Be and Zr.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.10a
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• pp.268-271
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• 2001

The die design of the liquid and semi-solid forming process is performed by CAE technology, The die design by the computer simulation has some advantages compared with the conventional method which has been performed by the designer's experiences in trials and emu. The defect zones such as porosity and shrinkage has been predicted by simulation results. The result of the numerical analysis for the proposed casting condition shows the characteristics of thixotropic flow, and was used to determine the geometry of the gating system and die cavity. The optimized production conditions were also proposed by result of computer aided engineering.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.102-106
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• 2009

Thermal energy control is a important factor in a large size casting and forging. Good control of thermal energy makes characteristics and defect of large cast-forged part, such as large sized forged shell. We have studied about not only large size ring forging process and after heat treatment by FEM simulation. Also, changes of temperature and microstructure for forged shell were predicted. Therefore, we can choose the proper heat treatment condition by FEA. The sectional properties confirmed by practical experiment and evaluation have presented possibilities of process design by computational analysis.