• Journal of Power System Engineering
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• v.5 no.3
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• pp.56-63
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• 2001

A slitter is a sort of machinery to cut sheet materials in rolls continuously in the longitudinal direction. Recently slitter line users have requiring higher quality and precision in products in addition to high productivity. A finite element analysis has been performed to investigate the effect of processing factors on shear planes in the slitting of Shrinkage Band(S,K.B.). For the analysis, Hot-dip 55% aluminum-zinc alloy-coated steel sheets and coils(SAZCC) is selected as a material. The results obtained are that deformation was concentrated along the very narrow zone and the maximum slitting load decreases by increasing the knife clearance. Also effective strain decreases according to the clearance increases.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.338-341
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• 2008

Galvannealed Sheet Steel, which is being widely used in the automotive industry, is made by reheat after dip zinc galvanizing process. By this, A Fe-Zn alloy is created which enhance anticorrosive property and weldability. This paper describes basic design for 2000kW induction heating inverter system for galvannealling process and test result of 250kW inverter module which is used in parallel to form 2000kW inverter system.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.362-365
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• 2000

Rapid Prototyping(RP) techniques have revolutionized traditional manufacturing methods. These techniques allow the user to fabricate a part directly from a conceptual model before investing in production tooling and help develop new models with significant short time. This paper suggests to new process to manufacture large size hollow shape parts for prototype-car using Rapid Prototyping technology and Vacuum Molding with the reduction of delivery time. In addition, This paper introduces the dividing and combining method to make large size RP master model in spite of the limit of the build chamber dimensions of commercialized RP system and post-processing method to achieve sufficient surface quality.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2009.05a
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• pp.132-132
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• 2009

마그네슘 합금은 비강도, 전동감쇠능 등 여러 장점으로 인하여 모바일 제품, 자동차 항공기 등 여러 영역에서 사용되고 있다. 하지만 내부식성 문제로 인하여 사용이 제한되고 있는 실정이다. 마그네슘 합금의 표면 처리는 기존에 전해 및 무전해 도금, 양극산화, 화성처리 등의 방법의 있으나 일반적으로 화성처리인 3가 크로데이트 후 도장 공정이 내식성 증가를 위해 적용되고 있다. 본 연구에서는 전기화학적인 방법으로 3가 크로메이트를 대체할 수 있는 친환경적이고 경제적인 아연 코팅을 마그네슘합금(AZ91) 소재에 생성시켰다. 표면특성 및 전기화학적인 분석은 SEM, EDX, XRD, potentiostat/galvanostat을 이용하였다.

• Journal of Power System Engineering
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• v.8 no.4
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• pp.38-43
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• 2004

Thermal spraying onto the metal substrate has been widely used as a technique of the surface treatment in the various industrial field. A wide range of thermal spray technologies exist and all rely on the fundamental process of fusing a metal feedstock, atomizing it and transporting it to the surface of a substrate. Specially, these methods have been taken into account as the protection method against the corrosion. In this study, the polarization characteristics were carried out on the thermal sprayed coating layer immersed in various pH of diluted aqueous solutions at $25^{\circ}C$. Aluminum, Zinc, Ni-base alloy, alumina and polyethylene powder were used with sprayed coating materials. From the polarization curves, the electrochemical corrosion potential($E_{corr}$) and the corrosion current density($I_{corr}$) were investigated.

• Korean Journal of Materials Research
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• v.12 no.4
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• pp.304-307
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• 2002

A zinc oxide (ZnO) single crystal was used as a substrate in the hydride vapor-phase epitaxy (HVPE) growth of GaN and the structural and optical properties of GaN layer were characterized by x- ray diffraction, transmission electron microscopy, secondary ion mass spectrometry, and photoluminescence (PL) analysis. Despite a good lattice match and an identical structure, ZnO is not an appropriate substrate for application of HVPE growth of GaN. Thick film could not be grown. The substrate reacted with process gases and Ga, being unstable at high temperatures. The crystallinity of ZnO substrate deteriorated seriously with growth time, and a thin alloy layer formed at the growth interface due to the reaction between ZnO and GaN. The PL from a GaN layer demonstrated the impurity contamination during growth possibly due to the out-diffusion from the substrate.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.11a
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• pp.121-122
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• 2012

합금도금강판의 일시 방청과 기능성 부여 후처리는 크로메이트, 인산염처리 등과 같은 방법을 시행하는 것이 일반적이다. 최근에는 아연합금도금 강판의 사용 및 보관 환경이 가혹해짐에 따라 보다 우수한 일시 방청성과 내식성이 요구되고 있다. 본 연구는 솔젤법을 이용하여 zirconium n-propoxide와 3-glycidoxypropyltrimethoxysilane(GPTS)으로부터 중합된 코팅막과 이에 zirconia nanoparticle입자를 첨가한 코팅막의 공극율(prosity)과 방식효율(protective efficiency)을 분극데이터를 이용하여 비교 평가하였으며, 염수분무시험을 통해 내식성 평가를 진행하였다.

• Journal of Electrochemical Science and Technology
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• v.14 no.4
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• pp.349-360
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• 2023

This study investigated the tri-metallic galvanic coupling of different metals in the tubes, fillers, and fins of a heat exchanger. The goal was to prevent corrosion of the tubes using the fin as a sacrificial anode while ensuring that the filler metal has a more noble potential than the fin, to avoid detachment. The metals were arranged in descending order of corrosion potential, with the noblest potential assigned to the tube, followed by the filler metal and the fin. To address a reduction in protection current of the fin, the filler metal was modified by adding Zn to decrease its corrosion potential. However, increasing the Zn content of filler metal also increases its corrosion current. The study examined three different filler metals, considering their corrosion potential, and kinetics. The results suggest that a filler metal with 1.5 wt.% Zn addition is optimal for providing cathodic protection to the tube while reducing the reaction rate of the sacrificial anode.

• Journal of Korean Society of Steel Construction
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• v.28 no.5
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• pp.373-382
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• 2016

Painting or thermally sprayed metal coating is often used in corrosion protection of steel structures. In recently, duplex coating system which combines thermally sprayed metals with paint is selected as a new generic type of coatings on steel structures under the highly corrosive environments. In this study, the structural steel specimens were surface treated, thermally sprayed with zinc, zinc-15%aluminum alloy, aluminum and aluminum-5%magnesium alloy, and finally sealing or painted with acrylic urethane. And as a reference specimens, steel specimens were painted with acrylic urethane after surface treatment. Circular defects with 1.0, 3.0 and 5.0 mm in diameters and line defect with 2.0 mm width, which reach the steel substrate were created on all specimens. The specimens were exposed into an environmental testing chamber controlled by the ISO 20340, which is a laboratory cyclic accelerated exposure test condition of spraying/UV/low temperature, for up to 175 days. Based on the corrosion tests, corrosion deterioration from the initial defects were evaluated and weathering performance of the specimens are compared.

• Corrosion Science and Technology
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• v.9 no.2
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• pp.92-97
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• 2010

Many kinds of alternative fuels such as biodiesel, ethanol, methanol, and natural gas have been developed in order to overcome the limited deposits in fossil fuels. In some cases, the alternative fuels have been reported to cause degrade materials. The corrosion rates of metals were measured by immersion test, a kind of time consuming test because low conductivity of these fuels was not allowed to employ electrochemical tests. With twin two-electrode cell newly designed for the study, however, electrochemical impedance spectroscopy (EIS) test was successfully applied to evaluation of the corrosion resistance ($R_p$) of zinc, iron, aluminum, and its alloys in an oxidized biodiesel and gasoline/ethanol solutions and the corrosion resistance from EIS was compared with the corrosion rate from immersion test. In biodiesel, $R_p$ increased in the order of zinc, iron, and aluminum, which agreed with the corrosion resistance measured from immersion test. In addition, on aluminum showing the best corrosion resistance ($R_p$), the effect of magnesium as an alloying element was evaluated in gasoline/ethanol solutions as well as the oxidized biodiesel. $R_p$ increased with addition of magnesium in gasoline/ethanol solutions containing chloride and the oxidized biodiesel. In the mean while, in gasoline/ethanol solutions containing formic acid, Al-Mg alloy added 1% magnesium had the highest $R_p$ and the further addition of magnesium decreased $R_p$. It can be explained with the fact that the addition of more than 1% magnesium increases the passive current density of Al-Mg alloys.