• 한국주조공학회지
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• 제31권6호
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• pp.366-370
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• 2011

The influence of aging treatment on the microstructure, mechanical and electrical properties of Cu-Be alloy for connector material applications was investigated. The properties of mechanical strength and electrical conductivity were found to increase with increasing aging temperature. By the way, SEM/EDS and TEM analysis exhibited that beryllides precipitation (CoBe and NiBe) with a size of 50 nm were distributed in grains. It was, therefore concluded that these beryllide precipitates improved the mechanical strength and also it was favor in increasing of electrical conductivity.

• 한국주조공학회지
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• 제14권5호
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• pp.412-418
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• 1994

Efficient algorithm for the solidification simulation by FDM is described from the practical point of views. If a proper time step ${\Delta}t$ is selected, the calculation is accelerated by implicit algorithm with the temperature recovery method of latent heat method. The implicit routine in the calculation is processed by SOR method(relaxation factor＝1.5, truncation error＝$10^{-4}$). The calculation is more accelerated by linear-interpolated explicite algorithm with a time step larger than the minimum value of the time step. This explicit method, which is applicable to the practical casting simulation problems, produces almost same results with about 40% faster calculation speed compared with the conventional explicit method.

• 한국주조공학회지
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• 제30권6호
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• pp.205-209
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• 2010

This study evaluates the influence of strontium addition and holding time on mechanical properties for Al-10.5wt%Si-2wt%Cu secondary die-casting alloy and the measured electrical conductivity of modified alloys. A general improvement in the mechanical properties of the alloy was observed after adding the strontium. Ultimate tensile strength, elongation and electrical conductivity of modified alloys were improved by increasing strontium content and holding time. From these results, the optimal strontium content and holding time were identified on the mechanical properties of Al-10.5wt%Si-2wt%Cu secondary die-casting alloys.

• 한국주조공학회지
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• 제17권6호
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• pp.569-576
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• 1997

Coating materials for Evaporative Pattern Casting (EPC) process have been developed to investigate the effect of refractories on coating material properties. Three types of developed and one foreign coating materials were used. The former designated as A, B, C and the latter named S.K. The refractory of coating material A is spherical shape of zirconia, and the ones of B, C and S.K. is flake shape of mica. Strength, permeability at room and elevated temperature, anti-sand attachability and carbon residuary were evaluated at each coating materials. Permeability measurement device for elevated temperature was also designed. The zirconia type of coating material had excellent permeability, on the other hand the mica type had good strength and anti-sand attachability. It was found that the refractories were not broken during casting, so permeability indicated same trend at both room and elevated temperature. Based on results, coating material contained small size of mica which is designated as B has the best combination for cast iron.

• 한국주조공학회지
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• 제38권3호
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• pp.60-65
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• 2018

In the present study, the characteristics of Mg inverter cases for hybrid cars are investigated. Concerns over the use of lightweight materials to reduce energy use and to mitigate emission problems are inevitable in the twenty-first century. Magnesium is a promising material for the manufacturing of lightweight parts. Several cases for thermal cooling channels have been designed and simulated, and the effects of materials and coatings on the thermal cooling efficiency have been discussed. The effects of the coating thickness on heat extraction in an Mg inverter housing case using the PEO (plasma electrolyte oxidation) coating method were also discussed. In order to produce an inverter case by the diecasting process, the filling sequence and cooling behavior during the diecasting process were simulated. The optimized process conditions from the simulation result were then used in a trial diecasting experiment.

• 한국주조공학회지
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• 제31권3호
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• pp.130-136
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• 2011

Effects of GBF (gas bubbling filtration) treatment conditions and scrap ratio on the electric conductivity of a commercial pure aluminum for diecasting were investigated using by specific gravity and electrical conductivity measurement system, hydrogen gas analyzer, XRD, and EDS. Electrical conductivities of specimen mixed Al scrap ratio until 60% from 0% were decreased with increasing the precipitates amount and size of AlFeSi ternary intermetallic compound on the grain boundary as well as amount of porosity in the grain. On the other hand, electrical conductivities was reincreased gradually in spite of scrap ratio increase from 80% to 100%. Size of AlFeSi compound formed on the grain boundary were coarsened with the increament of scrap ratios untill 80% and GBF treatment time simultaneously.

• 한국재료학회지
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• 제11권4호
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• pp.266-271
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• 2001

Al-Cu-Mn 주조합금의 응력부식균열 저항성에 미치는 Cd첨가의 영향을 C-ring test와 전기전도도 시험을 통하여 조사하였다. Cd첨가량이 증가함에 따라 전기전도도가 증가하였고 SCC 저항성도 증가하였다. SCC 시험결과 균열이 입계를 따라 전파되는 입계파괴가 일어났으며, 파면은 취성파괴양상을 나타내었고, 입계를 따라 조대 석출물과 무석출대가 나타난 것으로 보아서 이 합금의 SCC 기구는 anodic dissolution model이라고 판단된다. Cd을 첨가하지 않은 경우 최대경도값은 127Hv였으나, Cd을 첨가한 경우 최대경도값은 138∼146Hv로 증가하였다.

• 한국주조공학회지
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• 제28권4호
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• pp.184-189
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• 2008

Ag-Cd alloy has been widely used as an electrical contact material, since Ag-Cd alloy has a good wear resistance and stable contact resistance. But nowadays Ag-Cd alloy is not considered as electrical contact material any more due to detrimental effect on environments. Currently, active researches are being performed on ($Ag-SnO_2$ and $Ag-SnO_{2}-In_{2}O_{3}$) as an alternative solution which can fix the remaining environmental problems. However, $In_{2}O_{3}$ is relatively expensive and Ag-Sn alloy has low wear resistance. Our recent research results show that Ag-X%Zn-Y%Sn has similar physical and chemical properties. In the present study, so we tried to change and to optimize the Zn oxide content to over 6 wt% and Sn oxide content with 0.5, 1.0, 1.5 wt%. Results obtained from the experiments on the Ag-X%ZnO-Y%$SnO_2$ are discussed.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2015년도 추계학술대회 논문집
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• pp.256-257
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• 2015

마그네슘 합금은 낮은 비중, 높은 비강도, 주조성 및 절삭가공성, 치수안정성, 내흠집성이 우수한 특성을 지니고 있는 경량금속으로써 우수한 주조성과 상온강도, 연신율을 나타낸다. 최근에는 마그네슘 합금을 사용한 IT 기기의 케이스 및 자동차 내, 외장 부품 등의 제품이 다양하게 출시되어지며 금속 질감의 감성 기능까지 적용시킨 전자 기기 제품에 대한 수요가 급증하고 있는 추세이다. 하지만 마그네슘 합금의 낮은 부식 저항성은 마그네슘 합금을 적용시킨 제품에 큰 단점으로 작용되고 있으며 이를 해결하기 위한 연구가 활발히 진행 중이다. 본 연구에서는 플라즈마 전해산화법과 실리카 졸-겔 코팅법을 이용하여 마그네슘 합금의 내부식성을 향상시킴과 동시에 금속질감의 감성 기능을 구현하고자 하였다. 플라즈마 전해산화 공정으로 형성된 산화피막층과 $SiO_2$ 코팅으로 형성된 코팅층의 표면과 단면에 대해서는 FE-SEM(Field emission Scanning Electron Microscope)과 FE-TEM(Field emission Transmission Electron Microscope)으로써 확인하였고 전기화학적 특성 분석을 통한 동전위(Potentiodynamic polarization)와 EIS(Eletrochemical Impedance Spectroscopy) 그리고 Salt spray등을 분석하였다.

• 한국주조공학회지
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• 제17권3호
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• pp.286-291
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• 1997

Influence of Si contents on the mechanical properties and microstructure of austempered ductile iron was investigated. Four different Si contents between 2.0 and 2.9% were used. Austenitizing was performed at $890^{\circ}C$ for 2 hrs and austempering temperatures were both 340 and $380^{\circ}C$ for 0.5, 1, and 2 hrs. Nodule content was more than $300/mm^2$ and nodularity was more than 90%. Microstructure was revealed using nital and retained austenite was measured by x-ray diffractometer. Tensile test, no-notch Charpy impact test and wear test were performed. Tensile strength was improved as Si content increased and both elongation and impact toughness had peak at 2.6%Si. The specimen austempered at $380^{\circ}C$ showed lower tensile strength than that of $340^{\circ}C$, but showed higher elongation. However, austempering temperature of $380^{\circ}C$ was desirable because that of $340^{\circ}C$ was close to lower bainite transformation. As austempering time increased, tensile strength and elongation were improved and optimum condition was obtained for 2 hrs heat treatment.