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쌍롤식 박판 연속주조공정에 있어서 용탕과 냉각롤의 접촉 열저항을 고려한 전열해석
김영도,강충길,Kim, Y.D,Kim, C.G 대한기계학회 1996 大韓機械學會論文集A Vol.20 No.1
The twin-roll type strip continuous casting process(or direct rolling process) of steel materials is characterized by two rotating water cooled rolls receiving a steady supply of molten metal which solidifies onto the rolls. A solidification analysis of molten metal considering phase transformation and thermofluid is performed using finite diffefence method with curvilinear coordinate to reduce computing time and molten region analysis with arbitrary shape. An enthalpy-specific heat method is used to determine the temperatures inthe roll and the steel. The temperature distribution of cooling roll is calculated using two dimensional finite element method, because of complex roll shape due to cooling hole in rolls and improvemnt accuracy of calculation result. The energy equaiton of cooling roll is solved simultanuously with the conservation equaiton of molten metal in order to consider heat transfer through the cooling roll. The calculated roll temperature is compared to experimental results and the heat transfer coefficient between cooling roll surface and rolling material(steel) is also determined from comparison of measured roll temperature and calculated temperature.
최주,김유형,김수철,백종현,김종원,김영도 한국전통과학기술학회 1994 한국전통과학기술학회지 Vol.1 No.1
In this investigation, furnace was constructed on the basis of old Korean reference published in early 19C by Kyukyung Lee entitled $quot;Oju Yunmun Jangjeon Sango$quot; and irons were obtained by smelting process. It is believed that the restoration of the ancient iron making process will help to understand the principle of the ancient iron making process. The furnace was constructed with clay and nine tuyers were installed in one side of the furnace. Ore lumps were obtained by the use of iron ore and oak tree charcoal. Temperature and atmosphere of the furnacc were controlled during smelting process. For refining, ore lumps from this furnace were melted by charcoal refining furnace or by induction furnace. Forging was performed for refined blooms. Smelting process was studied through the microstructures and chemical analyses of the produced slags and iron pieces. Since ores from Dalcheon mine close to Koungju were used, the results from this experiment will give great contribution to appraise abundant iron remains of Shilla dynasty excavated in Kyongju area and to identify whether excavated furnace is smelting or melting furnaces.
WC-0.8SiC-10Ni 초경합금의 제조 및 기계적 성질의 연구
박원구,이억섭,황선근,김영도 대한금속재료학회(대한금속학회) 1996 대한금속·재료학회지 Vol.34 No.8
Effects of the amounts of SiC coating on the properties of WC-SiC-Ni cemented carbide were investigated. A highly condensed sintered material with a theoretical density higher than 98% was obtained for SiC with 0.8w/o when W powders coated with SiO2 were carburized at 1450℃ and SiC coated WC was sintered with Ni. The particle size of W C powders in this sintered material was about 0.9 ㎛ and very uniform. The Vickers hardness was measured to be as high as 1760 ㎏/㎟. Transeverse Rupture Strength (TRS) to be 338 ㎏/㎟. These good properties of the cemented carbide were able to be obtained by forming a condensed SiC layer for SiC of 0.8w/o which enhanced the interface reaction of the carbide with Ni and thus by inhibiting WC particle growth, making the particle size uniform, and making the sintered material condensed.