• 대한기계학회논문집B
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• 제26권11호
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• pp.1578-1584
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• 2002

Combustion stability is one of the most important factors that must be considered in burning of heavy fuel oil, especially low-grade oil. This paper describes the combustion characteristics of petrochemical process by- product in the combustion furnace of heavy fuel oil. Main experimental parameters were combustion load, excess 02, fuel preheating temperature and air/fuel ratio. The capacity of CRF(combustion research facility) used in this study was 1.0 ton/hr and the burner is steam jet type suitable far heavy oil combustion and manufactured by UNIGAS in Italy. The fuel used in this experiment were 0.5 B-C, petrochemical process by-product and 3 kinds of 0.5 B-C/process by-product mixtures. The combustion stability was monitored and exhaust gases such as CO, NOx, SOx and particulates were measured with the excess $O_2$ and combustion load. The main purpose of this study is to clarify whether process by-product can be used as a boiler fuel or not in consideration of flame stability and emission properties.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 제5회 압연심포지엄 신 시장 개척을 위한 압연기술
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• pp.55-62
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• 2004

In this study, the effects of Ca content and processing variables on hot rolling properties of gravity cast AZ31-xCa alloys were evaluated systematically. The number and length of side crack were decreased with increasing preheating temperature and decreasing reduction ratio per pass and Ca content. The UTS and YS were not strongly dependent on the Ca content but the elongation decreased with increasing Ca content. The decrease of elongation in Ca containing alloys was least when the sheets were fabricated under preheating temperature of $400^{\circ}C$ and reduction ratio per pass of $15\%$. The sheets had the sound external features with little side cracks by homogenization of gravity cast AZ31-xCa alloys before hot rolling. In the cases of AZ31-xCa alloys containing under $1wt.\%$ Ca, the annealed sheets after homogenization and hot rolling had the similar tensile properties to those of AZ31 sheet.

• 한국해양공학회지
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• 제11권1호
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• pp.10-15
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• 1997

Copper and its alloy had been used widely because of its pronouncing characteristics on their high thermal and electrical conductivity. Various fusion welding methods, such as SMAW, SAW, GTAW, GMAW, Electroslag welding amd so on are applied to weld copper and its alloy. But fusion welding of copper has so many welding problems. THe most serious problems were poor penetration amd high thermal contration stress due to its high thermal conductivity and porosity could be formed by rapid cooling rate of fusion welding. In order to avoid such fusion welding problems, preheating, peering and heat treatment must be applied to obtain sound weld joint of copper. But preheating induce another welding problem such as grain coarsening of weld heat affected zone. This grain coarsening reduces ductility and strength of weld joint. In this view of point, friction welding of copper is triedm to obtain sound weld joint of copper by reducing metallurgical problems. This study introduced new concept of heat input for evaluating the friction weldability of copper. As a result, weldability of copper could be evaluated by this new concept of heat input.

• 한국주조공학회지
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• 제14권5호
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• pp.419-428
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• 1994

The microvickers hardness and microstructure of Fe/Al composite fabricated by squeeze casting method were investigated. Pure Al and A356 Alloy were chosen for the matrix composition and Fe preform was fabricated with sintered Fe powder at $1000^{\circ}C$ for 30min. under hydrogen atmosphere. Experimental variables were included preheating temperature, melt temperature and applied pressure. Analysing the experimental result concerning microstructure of fabricated composites, Fe/A356 composite showed improved microstructure at $600^{\circ}C$ melt temperature and $350^{\circ}C$ preform preheating temperature in Fe distribution and Infiltrated distance. The results of EDX and XRD showed that the interfacial zones of Fe/Al composite were composed of non-equilibrium intermetallic layers[$(Al_5Fe_2)_x$, $Al_{13}Fe_4m\;Fe_3Al$, FeAl]. The microvickers hardness of Fe/Al composite showed higher value than Fe/A356 composite in interface.

• Progress in Superconductivity
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• 제12권1호
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• pp.68-73
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• 2010

Y123 films have been deposited on $LaAlO_3$ (100) single-crystal and IBAD substrates by spray pyrolysis method using nitrate precursors. Ultrasonic atomization was adopted to decrease the droplet size, spraying angle and its moving velocity toward substrate for introducing the preheating tube furnace in appropriate location. A small preheating tube furnace was installed between spraying nozzle and substrate for fast drying and enhanced decomposition of precursors. C-axis oriented films were obtained on both LAO and IBAD substrates at deposition temperature of around $710{\sim}750^{\circ}C$ and working pressures of 10~15 torr. Thick c-axis epitaxial film with the thickness of $0.3{\sim}0.6\;{\mu}m$ was obtained on LAO single-crystal by 10 min deposition. But the XRD results of the film deposited on IBAD template at same deposition condition showed that the buffer layers of the IBAD metal substrate was affected by long residence of metal substrate at high temperature for YBCO deposition.

• 한국정밀공학회지
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• 제32권2호
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• pp.167-172
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• 2015

In order to prevent crack in thick weld zones, the preheating process such as induction and gas torch heating needs to be applied. Among them induction heating is the most effective heat source because it has rare thermal effect and very rapid heating characteristics. In this paper, when the induction heating method is used to improve arc welding, the temperature distribution and magnetic field density of the welding zones are analyzed by simultaneously solving heat transfer and electromagnetic field equation. In particular, cone and flat type coils are designed and induction heating effects of each type are compared to identify heating characteristics on a V-groove weld joint. As a result, a cone shape coil is more efficient in the preheating process. When induction heating and arc welding system is designed for thick plate with V-groove weld joint, the results in this paper could be applied.

• 한국에너지공학회:학술대회논문집
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• 한국에너지공학회 2001년도 춘계 학술발표회 논문집
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• pp.45-52
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• 2001

촉매연소의 응용기기 개발을 위한 연구의 일환으로, 촉매연소가 도입된 열교환기에 대한 연소특성을 분석하였다. 정상상태에서 촉매연소를 이용한 혼합가스의 예열과 가열매체에 대한 열 공급이 동시에 이루어지도록 장치를 구성하고, 특성실험을 수행하였다. 혼합가스의 예열온도, 유속, 당량비 등에 대한 연소특성을 분석하고, 촉매 층의 온도분포에 따른 연소특성도 살펴보았다. 제한된 온도범위 내에서 연소반응이 정상상태에 도달되는 것은 촉매연소 기기 개발에 매우 중용한 요소이며, 이를 위해서 혼합가스의 예열온도, 유속 당량비 등이 일정한 범위에서 제어되어야 하고, 촉매 층의 열평형이 이루어져야 됨을 알았다.

• 공업화학
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• 제8권6호
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• pp.901-906
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• 1997

유기금속화합물인 Tetraethylorthosilicate(TEOS)를 출발원료로 기상열분해법을 이용하여 초미립 실리카분말을 제조하였다. 반응온도, 가스유량, 반응물질의 농도, 및 반응물질의 예비가열온도가 초미립 실리카분말의 입자크기 특성에 미치는 영향을 조사하였다. 반응온도가 증가할수록 또한 체류시간이 감소할수록 생성분말의 입자크기가 작아지는 것을 알 수 있었다. 반응물농도가 증가할수록 입자크기가 증가하였고, 또한 반응물질의 예비가열온도가 증가하여도 입자크기는 큰 변화가 없음을 알 수 있었다. 본 연구조건에서 제조된 초미립 실리카분말의 평균 입자크기는 30~58 nm이었다.

• 한국주조공학회지
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• 제24권6호
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• pp.331-339
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• 2004

Melt-extrusion process, a metallic melt poured and solidified up to semisolid state in the container can be directly extruded through the die exit to form a product of bar shape without other intermediate processes. In this study, the fabrication characteristics of the process were evaluated with various process parameters, such as preheating temperature of extrusion dies, extrusion temperature and extrusion ratio. AI-Cu alloys were successfully extruded after squeezing out of liquid during melt-extrusion with smaller force compared to the solid extrusion. Soundly AI-Cu alloy bar was fabricated at the preheating temperature of $500{\sim}520^{\circ}C$. The range of extrusion temperature for soundly melt-extruded AI-Cu alloy bar was increased with increasing extrusion ratio. Mechanical properties of melt-extruded AI-Cu alloy bars were found change with Cu content of the melt-extruded bars due to the occurrence of segregation. The various extrusion temperature yielded equiaxed structure with a grains size about 200 ${\mu}m$.

• 한국세라믹학회지
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• 제55권1호
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• pp.36-43
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• 2018

The physical and chemical analyses of mineral waste such as moisture content, water absorption, freezing-thawing resisting sexual, chemical composition and crystal structure were investigated. In the technological process of crushing, screening, molding, drying, preheating, sintering and cooling, many parameters were changed to eliminate the influence of freeze thaw stability and the ball billets were processed into slate ceramsites eventually. Adopting orthogonal experiment and range analysis, the optimal technology parameters were confirmed as preheating temperature of $300^{\circ}C$ for 25 minutes and sintering temperature of $1230^{\circ}C$ for 20 minutes. Slate wastes in Shangri-la could foam and expand without any additive. The ultra-light ceramsite could be directly used as building aggregate, since the analysis results of its leaching toxicity were eligible. Besides, effects of sintering temperature on physical property and crystal phase were also explored in this study.