• Korean Journal of Metals and Materials
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• v.49 no.11
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• pp.831-838
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• 2011

Effects of spangle size and crystallographic characteristics on the surface appearance, galling properties, and adhesive strength of hot-dip galvanized steel sheets have been investigated. Both spangle size and crystallographic orientation measured by optical microscopy, scanning electron microscopy, and X-ray diffraction were identified as critical factors influencing the galvanized coating performance. By decreasing the spangle size, surface appearance and galling properties related to the friction coefficient were significantly improved. However, low temperature adhesive-strength with small spangle galvanized steel sheets showed lower values compared to commercially used galvanized coating. The variation of adhesive strength in terms of spangle size has been clarified.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2003.10a
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• pp.86-87
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• 2003

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.2
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• pp.109-115
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• 2022

The demand for metal 3D printing technology is increasing in various industries. The materials commonly used for metal 3D printing include aluminum alloys, titanium alloys, and stainless steel. In particular, for applications in the aviation and defense industry, aluminum alloy 3D printing parts are being produced. To improve the corrosion resistance in the 3D printed aluminum alloy outputs, a post-treatment process, such as chromate coating, should be applied. However, powdered materials, such as AlSi7Mg and AlSi10Mg, used for 3D printing, have a high silicon content; therefore, a suitable pretreatment is required for chromate coating. In the desmut step of the pretreatment process, the chromate coating can be formed only when a smut composed of silicon compounds or oxides is effectively removed. In this study, suitable desmut solutions for 3D printed AlSi7Mg and AlSi10Mg materials with high silicon contents were presented, and the chromate coating properties were studied accordingly. The smut removal effect was confirmed using an aqueous desmut solution composed of sulfuric, nitric, and hydrofluoric acids. Thus, a chromate coating was successfully formed. The surfaces of the aluminum alloys after desmut and chromate coating were analyzed using SEM and EDS.

• Journal of Power System Engineering
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• v.16 no.2
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• pp.49-53
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• 2012

Thermal spray coatings developed by deposition of splats, it formed by impacting molten droplets on substrates during thermal spray process. In this study, the Ni-based coatings were fabricated by thermal spray process with two different process parameters, oxygen gas flow and acetylene gas flow, with three different levels of each parameters. The morphology of splats and microstructure were observed by optical microscope. Hardness test were performed on the Ni-based coatings. It was confirmed that process parameters of thermal spray process have effect in morphology of splats. These effects also have important implications on the deposit microstructure and properties of Ni-based coatings.

• International Journal of Automotive Technology
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• v.1 no.2
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• pp.89-94
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• 2000

As a promising catalyst reducing cold start emissions of automobiles, a photocatalyst systems has been studied. Since the photocatalyst is only activated by UV wavelength light, it needs no heat energy like a conventional TWC, therefore no light-off time. However, as a cold temperature catalyst to treat cold start emissions of a vehicle, previous studies on characteristic of photocatalyst have room for improvement in terms of performance and durability investigated from the viewpoints of performance and durability improvement. Eleven different coating samples were prepared with the combination of six kinds of additives and two kinds of photocatalyst materials. Then these samples were aged with a hydrothermal aging process. The performance of these samples was measured on a model gas apparatus with simulated exhaust gases. The durability was also analyzed with X-ray diffraction meter.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.6
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• pp.81-86
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• 2004

Generally, automotive cylinder head is manufactured by FCD45 material that is hard to cutting materials, and it needs the accurate machining tool fir higher output of engine. This paper is concerned with a study on TiN coated 6 edges reamer for improving machining accuracy of cylinder head guide pin. The reamer shape is changed from 4 edges to 6 edges for the improvement of machining accuracy. Also, TiN coating is applied to the improvement of surface roughness of cylinder head guide pin and tool life of 6 edges reamer. It is noted that 6 edges reamer are effective in controlling the dimensional accuracy and surface roughness as well as increasing tool life.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.2
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• pp.40-47
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• 2002

Because UV wavelength lights can activate photocatalysts, plasma is used as a light source of a photocatalytic reactor. Even though plasma has good intensity for photo reaction, substrate of catalyst coating was limited by the geometry of plasma generator. Usually bead type substrate was used for a pack bed type reactor. Honeycomb monolith type substrate was used with UV lamps instead plasma, due to the light penetration the honeycomb monolith length was too short to show good activity In this study a photocatalytic reactor, which is using a honeycomb monolith substrate, was investigated with plasma as an activation light source. As a parametric study the effects of 1311owing factors on plasma generation and power consumption are examined; supply voltage, substrate length, environment condition, catalyst loading and ratio. Using the test results, the practicability test was done with simulated synthetic gases representing bad smells and automotive exhaust gases.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.6
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• pp.141-147
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• 2008

Hot-dip galvannealed sheet (GA) with high strength of 590MPa grade in tensile strength, has developed for automotive applications. However, for a successful application, the microstructure and galvannealing behavior of galvannealed TRIP steel sheets must be strictly controlled. High silicon contents steel has problems with weld-ability, zinc coating and reduction of retained austenite volume fraction after galvannealing process. The main purpose of this study is to solve the problem as indicated above.

• Journal of the Korean institute of surface engineering
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• v.37 no.5
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• pp.263-272
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• 2004

High strength steels such as transformation induced plastic steel, dual phase and solid solution Hardening have been developed and continuously improved due to the intensified needs in the automotive industry. But silicon and manganese in transformation induced plastic steels were known to exhibit harmful effects on galvannealing reaction by oxide film formed during heat treatment. Therefore, in this work, the applicability of Zn-Ni electrodeposition instead of hot dip galvannealed coating to transformation induced plastic steels was evaluated and optimum electroplating condition was investigated. Based on these investigations optimized electroplating conditions were proposed and Zn-Ni electrogalvanized steel sheet was produced by EGL (electrogalvanized line). Its perfomance properties for automotive steel was evaluated.

• Journal of the Korean institute of surface engineering
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• v.34 no.4
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• pp.297-302
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• 2001

As GA (Hot dip galvannealed steel sheet) has good corrosion resistance, weldability and paintability as well as excellent formability, it's demand is rapidly increasing for automotive panels. The GA coated layers are composed of several kinds of brittle Fe-Zn Metallic compounds which are susceptible to powdering during the press forming, however, very careful controls of manufacturing conditions such as galvannealing heat-treatment or bath composition are essential to meet with the required quality of automotive use. In this study the required characteristics of automotive panel are practically surveyed in detail and the appropriate manufacturing conditions of galvannealing or bath composition have experimentally investigated by using the various analyzing and simulating equipments. The result in this study indicated that the corrosion resistance at the cut edges was improved by increasing of coating weight and decreasing of thickness of sheet steels.