• 한국주조공학회지
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• 제38권1호
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• pp.1-8
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• 2018

In this study, we focused on the correlation between the solidification structure, heat treatment and mechanical properties of the A356 alloy according to the conditions of Sr modification. The microstructural evolution of the eutectic Si and ${\alpha}-Al$ phase in the A356 alloy castings depending on the amount of Sr were investigated during solid solution heat treatment using an optical microscope, a scanning electron microscope and an image analyzer. In addition, tensile tests on the heat treated materials examined the relationship between the microstructure and the fracture surface. The as-cast A356 alloys under 40 ppm Sr showed an undermodified microstructure, but that of the added 60-80 ppm Sr had well modified structure of fine fibrous silicon. After solid solution treatment, the microstructure of the undermodified A356 alloy exhibited a partially spheroidized morphology, but the remainder showed the fragmentation of fibrous shaped silicon. The spheroidization of the eutectic silicon in the modified A356 alloys was completed during heat treatment, which was very effective in increasing the elongation. This is supported by the fracture surface in the tensile test.

• Korean Membrane Journal
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• 제10권1호
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• pp.1-7
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• 2008

Polystyrene-co-divinylbenzene (PS-co-DVB) asymmetric membranes were prepared. In order to control their structure and mechanical properties the degree of cross-linking and the composition of casting solution were varied. The rubber added PS-DVB membranes was also prepared to overcome the mechanical limitation of cross-linked membrane, and their mechanical properties were investigated. It was revealed that the concentration of polymer in the casting solution affected the determination of skin formation. When the PS-co-DVB membrane consists of styrene-butadiene (SB) rubber or liquid polybutadiene (PBD), the structures formed showed that the PS content in the PS/DVB system played an important role in determining the porous sublayer structure.

• 한국주조공학회지
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• 제12권5호
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• pp.397-402
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• 1992

The effect of the solution & aging treatment on the tensile strength, yield strength, elongation, reduction of area, hardness was studied in the 17-4 PH stainless steel. SEM pictures were also taken in order to examine the fracture surfaces and precipitated particles. X-ray diffraction patterns for the heat treated samples were also observed. Mechanical properties of the heat treated samples were superior to those of as cast samples. Tensile strength, yield strength, hardeness decreased with the increase of aging temperature. On the other hand, elongation and reduction of area increased as the aging temperature increased.

• 한국산업보건학회지
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• 제16권1호
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• pp.27-35
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• 2006

The aim of this study was to identify the sources of benzene detected in airborne of casting workplace where benzene was not used as raw material. We have identified benzene by GC/FID and GC/MSD. In this pilot test, small size iron chamber(diameter 30 cm, height 20 cm) was used. As the raw materials, new sand, recovered sand, and mixed casting sand(new sand + solidifying agent + organic resin + coating material) was tested, respectively. In the new sand benzene was not detected, but in the recovered sand and the mixed casting sand was detected. Xylenesulfonic acid(solidifying agent), one of the mixed casting sand ingredients was thought to product benzene by thermal decomposition above $400^{\circ}$..., but the other raw materials(organic resin and coating material) were thought not to product benzene. In this experiment, the most of benzene by thermal decomposition was produced within 1 hour after pouring the iron solution($1560^{\circ}$...) in small size iron chamber. When the mixed casting sand with coating material was used, the concentration of the produced benzene was average 2.91 ppm(range 1.98~3.72 ppm), and without coating material, benzene concentration was average 0.11 ppm(range 0.08~0.14 ppm).

• 한국주조공학회지
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• 제42권4호
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• pp.218-225
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• 2022

본 연구에서는 고압 다이캐스팅 (High pressure die-casting, HPDC)을 통해 알루미늄 합금 (상업코드: ALDC12종)으로 수소 자동차용 부품 (Air pressure control valve housing, APCVH)을 제조하였으며 주조품의 기밀성을 향상시키기 위해 유기 함침액을 개발하였다. 개발된 2종류의 유기 함침액 (INNO-series, 한국)과 상용 합침액 (P601, 일본)을 사용하여 함침공정 조건 및 후 처리에 따른 미세결함과 기밀성을 비교 평가하였다. 컴퓨터 단층촬영 및 3차원 X-선 현미경 분석을 통해 함침된 알루미늄 주조품의 결함제어 및 성능 개선을 확인하였다. 또한, 함침 공정 후 기밀성 시험에서 INNO-01이 함침된 시료의 경우 성능 개선율이 70%인 것으로 확인하였다. 따라서, 개발된 유기 함침액은 상용 가능하며 다이캐스팅 제품의 기밀성 향상에 도움이 될 것으로 판단된다.

• 산업경영시스템학회지
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• 제31권3호
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• pp.17-23
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• 2008

In this research article, scheduling a casting sequence in a job-shop type foundry involving a variety of casts made of an identical alloy but with different shapes and II weights, has been investigated. The objective is to produce the assigned mixed orders satisfying due dates and obtaining the highest ingot efficiency simultaneously. Implementing simple integer programming instead of complicated genetic algorithms accompanying rigorous calculations proves that it can provide a feasible solution with a high accuracy for a complex, multi-variable and multi-constraint optimization problem. Enhancing the ingot efficiency under the constraint of discrete ingot sizes is accomplished by using a simple and intelligible algorithm in a standard integer programming. Employing this simple methodology, a job-shop type foundry is able to maximize the furnace utilization and minimize ingot waste.

• 한국주조공학회지
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• 제11권6호
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• pp.482-490
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• 1991

This study presents the wear characteristics of Ti alloys (Pure Ti, Ti-6Al-4V, Ti-5Al-2.5Sn) fabricated by centrifugal precision casting in an Ohara dental titanium casting machine. It was found that the hardness of the surface region is higher than that of the interior region. It is considered that the oxygen adsorption in the surface region during casting, leads to the interstitial solid solution hardening. Wear resistance incerases in the order of pure Ti, Ti-6Al-4V, Ti-5Al-2.5Sn alloys. The interior hardness value increases in the same order. The specific wear rate increases with applied load and increases monotonously with sliding speed. The Fe transfer from the counterpart material was observed on the worn surface of the Ti-5Al-2.5Sn alloy. Oxidative wear occurs at low sliding speeds and mechanical fracture wear occurs at high sliding speeds.

• 대한금속재료학회지
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• 제47권2호
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• pp.129-137
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• 2009

Corrosion behaviors of TiN coated dental casting alloys have been researched by using various electrochemical methods. Three casting alloys (Alloy 1: 63Co-27Cr-5.5Mo, Alloy 2: 63Ni-16Cr-5Mo, Alloy 3: 63Co-30Cr-5Mo) were prepared for fabricating partial denture frameworks with various casting methods; centrifugal casting(CF), high frequency induction casting(HFI) and vacuum pressure casting(VP). The specimens were coated with TiN film by RF-magnetron sputtering method. The corrosion behaviors were investigated using potentiostat (EG&G Co, 263A. USA) in 0.9% NaCl solution at $36.5{\pm}1^{\circ}C$. The corrosion morphologies were analyzed using FE-SEM and EDX. Alloy 1 and Alloy 2 showed the ${\alpha}-Co$ and ${\varepsilon}-Co$ phase on the matrix, and it was disappeared in case of TiN coated Alloy 1 and 2. In the Alloy 3, $Ni_2Cr$ second phases were appeared at matrix. Corrosion potentials of TiN coated alloy were higher than that of non-coated alloy, but current density at passive region of TiN coated alloy was lower than that of non-coated alloy. Pitting corrosion resistances were increased in the order of centrifugal casting, high frequency induction casting and vacuum pressure casting method from cyclic potentiodynamic polarization test.

• 한국재료학회지
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• 제24권10호
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• pp.509-514
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• 2014

We demonstrate a simple and effective method to accurately position silicon nanowires (Si NWs) at desirable locations using drop-casting of Si NW inks; this process is suitable for applications in nanoelectronics or nanophotonics. Si NWs were assembled into a lithographically patterned sacrificial photoresist (PR) template by means of capillary interactions at the solution interface. In this process, we varied the type of solvent of the SiNW-containing solution to investigate different assembly behaviors of Si NWs in different solvents. It was found that the assembly of Si NWs was strongly dependent on the surface energy of the solvents, which leads to different evaporation modes of the Si NW solution. After Si NW assembly, the PR template was cleanly removed by thermal decomposition or chemical dissolution and the Si NWs were transferred onto the underlying substrate, preserving its position without any damage. This method enables the precise control necessary to produce highly integrated NW assemblies on all length scales since assembly template is easily fabricated with top-down lithography and removed in a simple process after bottom-up drop-casting of NWs.

• 대한치과기공학회지
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• 제34권2호
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• pp.145-153
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• 2012

Purpose: The purpose of this study was to investigate to effect of the electro-polishing condition according to electrolyte temperature and current and polishing time on surface morphology and composition by scanning electron microscopy(SEM) and energy dispersive X-ray spectrometer(EDS) in dental casting Co-Cr-Mo alloys. Methods: 16 specimens were divided into 4 groups which have each 4 specimens. The size of specimens were 10mm wide and 5mm height. the electro-polishing of specimens are by polishing solution temperature and times in Co-Cr-Mo alloy by SEM and EDS analysis. Results: The results shows that most smooth surface is obtained when electro-polishing is performed at $49^{\circ}C$ for 30-40sec with electro gap of 10mm and 8 voltage. Conclusion: The morphologies of specimens after electro-polishing were scratch absent and significant between at $40^{\circ}C$ for 45sec and at $49^{\circ}C$ for 45sec.