• 한국주조공학회지
• /
• 제42권5호
• /
• pp.273-281
• /
• 2022

Al-Cu-Si 3원계 공정합금의 응고거동과 미세조직 변화를 이해하기 위해서, 금형 예열온도를 달리하여 Al-Cu-Si 3원계 공정합금의 미세조직 변화를 관찰하였다. 금형 예열온도가 500℃일 때, 초정 Si과 덴드라이트 형상의 Al2Cu상이 관찰되며, 이후 (α-Al+Al2Cu)의 2원계 공정상이 관찰된다. 금형 예열온도가 300℃일 때 미제조직은 금형 예열온도가 500℃일 때와 유사하나 (α-Al+Al2Cu+Si)의 3원계 공정상이 관찰되는 영역과 관찰되지 않는 영역이 나타난다. 금형 예열온도가 150℃인 경우에는 미세조직이 (α-Al+Al2Cu)의 2원계 공정상과 (α-Al+Al2Cu+Si)의 3원계 공정상이 관찰되는 Bimodal 구조를 나타낸다. 금형 예열온도를 달리 하였을 때 가장 큰 변화를 나타내는 상은 Si상이며, 임계냉각속도를 지나면 (α-Al+Al2Cu+Si)의 3원계 공정상이 형성되는 순간에 빠른 냉각에 의한 Si의 성장이 억제되면 Cooperative 성장을 하기 때문에 Al, Cu의 성장도 함께 억제된다. 서로 다른 합금설계 전산모사 프로그램을 통해 Al-27wt%Cu-5wt%Si의 3원계 공정 합금을 분석한 결과, 합금설계 전산모사 프로그램에 따라 결과의 차이가 발생하며, 전산모사의 신뢰성을 높이기 위해서는 실제 주조를 통한 미세조직 분석이 수반되어야 한다.

• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 1993년도 특별강연 및 춘계학술발표 개요집
• /
• pp.79-81
• /
• 1993

• Journal of Welding and Joining
• /
• 제16권6호
• /
• pp.32-34
• /
• 1998

• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 2002년도 춘계학술발표대회 개요집
• /
• pp.81-82
• /
• 2002

• 한국연소학회:학술대회논문집
• /
• 한국연소학회 제26회 KOSCO SYMPOSIUM 논문집
• /
• pp.153-158
• /
• 2003

Catalytic Combustion used to be applied to specific conditions because of the characteristics different from flame combustion. However, many researches are focused on widening the applicant range of catalytic combustion with the competences of catalytic combustion. The development of many catalytic combustion appliances is one of the trials to overcome the restrictions of reaction and maximize the merits. In this research, past developments of appliances are depicted and new conceptual system will be introduced - sequential system. Sequential catalytic combustion system is composed of units - existing catalytic heat exchangers. This system is performed with parallel in composition and serially in operation. First, the burden of the preheating can be dramatically reduced. Second, stable operation control is expected. Lastly, Capacity expansion is flexible.

• 산업기술연구
• /
• 제17권
• /
• pp.233-239
• /
• 1997

The effects of preheating the gas stream on deposition characteristics of ultrafine $SiO_2$ particles were investigated theoretically. The model equations such as mass and energy balance equations and aerosol dynamic equations were solved to predict the particle growth and deposition. The gas temperatures, $SiCl_4$ concentrations, $SiO_2$ particle volumes, $SiO_2$ particle sizes and deposition efficiencies of $SiO_2$ particles were calculated for various preheating temperatures. As the preheater setting temperature increases, the $SiO_2$ particle size distribution becomes more uniform, because the effect of $SiCl_4$ diffusion decreases.

• 설비공학논문집
• /
• 제9권2호
• /
• pp.112-121
• /
• 1997

This study is focused on the development and selection of optimal cool tube system to maximize its thermal performance. Cool tube is devised to reduce the heating and cooling load of building by preheating or refreshing of intake air. Finite volume method was adopted to solve the conduction problem between the cool tube and earth. We examine the cool tube system for two operating periods, a short term(12 hours) and a long term(3 months). The results of short term operations reveal that condensation significantly influences and raises the exit air temperature. For long term operations, optimum conditions of cool tube system are obtained with variations of flow-rate, depth, length and diameter of cool tube.

• Journal of Mechanical Science and Technology
• /
• 제14권8호
• /
• pp.851-860
• /
• 2000

Temperature field and cooling rate are important parameters to influence the properties of clad layer and the heat affected zone. In this paper the temperature field and cooling rate of laser cladding are studied by a two-dimensional time-dependent finite element model. Experiment has been carried out by Nd:YAG laser cladding with wire feeding. Research results indicate that at the beginning of cladding, the width and depth of melt pool increase with cladding time. The cooling rate is related to position, cladding time, cladding speed, and preheating temperature. The temperature near melt pool changes rapidly while the temperature far from melt pool changes slowly. With the increase of cladding time, cooling rate decreases. The further the distance from the melt pool, the lower the temperature and the slower the cooling rate. The faster the cladding speed, the faster the cooling rate. The higher the preheating temperature, the slower the cooling rate. The FEM results coincide well with the experiment results.

• 한국해양공학회지
• /
• 제17권2호
• /
• pp.14-20
• /
• 2003

In this paper, a practical design criteria for judgement of crack occurrence in weldments is presented as a function of typical welding parameters, such as diffusible hydrogen, restraint intensity, and preheating temperature. The elastic analyses using the finite element techniques are employed in order to quantify the restraint intensities, numerically. Systematic experiments are also conducted in order to investigate the propensity of crack to typical welding parameters. The results of numerical estimation using the proposed method for the experimental specimens show the usefulness as a practical tool in welding induced crack problems with extensive uncertainties. Systematic experiments are also conducted in order to investigate the propensity of crack to typical welding parameters. The results of numerical estimation using the proposed method for the experimental specimens show the usefulness as a practical tool in welding induced crack problems with extensive uncertainties.

• 한국세라믹학회지
• /
• 제35권3호
• /
• pp.251-258
• /
• 1998

박슬라브 연주용 침지노즐 슬래그 라인부위의 ZrO2-C의 사용중 거동을 조사한 결과 지르코니아 골재의 탈안정화에 의한 조직열화는 예열단계에서 거의 완료되고 사용된 원료의 순도 및 첨가제인 금속 Si의 함량에 의해 크게 좌우되었다. 주조중에는 예열단계에서 발생된 입계로 몰드 파우더로부터 환원된 성분이 축적되어 입계가 더욱 넓어지면서 조직열화가 심화되었으나 환원성분에 의한 추가적인 지르코니아의 탈안정화 현상은 거의 발생되지 않았다.