• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2013년도 춘계학술대회 논문집
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• pp.933-934
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• 2013

• 한국초전도ㆍ저온공학회논문지
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• 제8권3호
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• pp.23-26
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• 2006

For mechanical and electrical stability and environment protection. Cu and stainless steel stabilizers are laminated to a Ag layer to produce a composite neutral-axis(N-A) architecture in which the YBCO layer is centered between the oxide buffered metallic substrate and stabilizer strip lamination. This architecture allows the wire to meet operational requirements including stresses at cryogenic temperature. winding tensions as well as mechanical bending requirements including thermal and electrical stability under fault current conditions. We have experimentally studied mechanical properties of the laminated stainless steel and Cu stabilizers on YBCO coated conductors. We have laminated YBCO coated conductors by continuous dipping soldering process. We have investigated lamination interface between solder and stabilizer of the YBCO coated conductor. We evaluated bonding properties. tensile / shear bonding strength. and peeling strength laminated YBCO coated conductors.

• Journal of Welding and Joining
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• 제9권4호
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• pp.17-27
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• 1991

The direct brazing technology which could be used for the simplification of brazing process and the improvement of brazed joint quality was studied with $Al_2O_3$ and stainless steels. The brazing of $Al_2O_3$ to STS304 or STS430 was performed under different brazing conditions such as brazing filler metal, temperature, heating rate and brazing time. Microstructural observation and chemical analysis be SEM/EPAM were carried out to verify the quality of brazed joints. 4-point bending strength of brazed joints was also measured to find the optimal brazing conditions. The results showed that, in brazing of $Al_2O_3$, the mixed oxide layer resulted from the reaction between Ti in filler metal and oxide layer on the material surface to be brazed was found to be bery important for the joint quality. The width of oxide layer varied with the brazing conditions such as brazing time, heating rate and chemical composition of filler metals. The strength of brazed joints was more affected by the type of materials and their thermal properties than by brazing heat cycle.

• Journal of Welding and Joining
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• 제32권4호
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• pp.46-54
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• 2014

In this study, the effect of bonding temperature and bonding pressure on deformation and tensile properties of diffusion bonded joint of STS304 compact heat exchanger was investigated. The diffusion bonds were prepared at 700, 800 and $900^{\circ}C$ for 30, 60 and 90 min in pressure of 3, 5, and 7 MPa under high vacuum condition. The height deformation of joint decreased and the width deformation of joint increased with increasing bonding pressure at $900^{\circ}C$. The ratio of non-bonded layer and void observed in the joint decreased with increasing bonding temperature and bonding pressure. Three types of the fracture surface were observed after tensile test. The non-bonded layer was observed in diffusion bonded joint preformed at $700^{\circ}C$, the non-bonded layer and void were observed at $800^{\circ}C$. On the other hand, the ductile fracture occurred in diffusion bonded joint preformed at $900^{\circ}C$. Tensile load of joint bonded at $800^{\circ}C$ was proportional to length of bonded layer and tensile load of joint bonded at $900^{\circ}C$ was proportional to minimum width of pattern. The tensile strength of joint was same as base metal.

• 소성∙가공
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• 제20권3호
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• pp.257-264
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• 2011

Multilayer(clad) sheets, composed of two or more materials with different properties, are fabricated using the roll-bonding process. A good formability is an essential property for a multilayered sheet in order to manufacture parts by plastic deformation. In this study, the influences of temperature and strain rate on the plastic properties of stainless steel-aluminum-magnesium multilayered(STS-Al-Mg) sheets were investigated. Tensile tests were performed at various temperatures and strain rates on the multilayered sheet and on each separate layer. Fracture of the multilayered sheet was observed to be temperature-dependent. At the base temperature of $200^{\circ}C$, all materials fractured simultaneously. At lower temperatures, the Mg alloy sheet fractured earlier than the other materials. Conversely, the other materials fractured earlier than the Mg alloy sheet at higher temperatures. The uniform and total elongations of the multilayered sheet were observed to be higher than that of each material at a temperature of $250^{\circ}C$. Larger uniform elongations were obtained for higher strain rates at constant temperature. The same trend was observed for the Mg alloy sheet, which exhibited the lowest elongation among the three materials. The tensile strengths and elongations of the single layer sheets were compared to those of the multilayer material. The strength of the multilayered sheet was successfully calculated by the rule of mixture from the values of each single layer. However, no simple correlation between the elongation of each layer and that of the multilayer was obtained.

• Journal of Welding and Joining
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• 제20권6호
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• pp.830-837
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• 2002

This study investigated variations of micro-structures and mechanical properties of Ti / STS321L joint with various bonding temperature and time using brazing method. According to increasing bonding temperature and time, it was observed that the thickness of their reaction layer increased due So increasing diffusion rate and time. From the EPMA results, Ti diffused to the STS321L substrate according to increasing bending time to 30min. Hardness of bonded interface increased with increasing bonding temperature and time due to increasing their oxides and intermetallic compounds. XRD data indicated that Ag, Ag-Ti intermetallic compounds, TiAg and $Ti_3Ag$ and titanium oxide, $TiO_2$ were formed in interface. In tensile test, it was found that the tensile strength had a maximum value at the bonding temperature of $900^{\circ}C$ and time of 5min, and tensile strength decreased over bonding time of 5min. The critical thickness of intermetallic compounds was observed to about $30\mu\textrm{m}$, because of brittleness from their excessive intermetallic compounds and titanium oxide, and weakness from void.

• 한국정밀공학회지
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• 제2권3호
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• pp.41-46
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• 1985

The behavior of the burn-on in sand mold has been investigated by varying the pouring metal, bonding materials, additive materials and molding sand. The results obtained from thease experiments are as follows; 1) The burn-on layer of silica sand decreased in order of carbon steel, gray cast iron and stainless steel, and thease burn layer proceeded mostly by producing FeO. 2) The burning reaction of silica sand mold in carbon steel castings declined with increasingly bentonite content, but water-glass scarcely took part in the burn-on reaction. 3) The addition of feldspar and seacoal to silica sand promoted the inhibiting burn-on. 4) The burn-on layer of sand mold decreased of silica sand, chromite sand and olivine sand.

• 대한금속재료학회지
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• 제49권8호
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• pp.664-670
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• 2011

3-ply Mg/Al/STS clad-metal was fabricated by the roll bonding process. An interfacial reaction layer was formed at the Mg/Al interface at and above $300^{\circ}C$ whereas no interfacial reaction layer was observed up to $400^{\circ}C$. The effect of the interfacial reaction layer on the mechanical and fracture properties in clad metals after heat treatments were investigated The chemical compositions were analyzed at the Mg/Al interface by an Energy dispersive X-ray analysis (EDX). A tension test was performed to examine the interfacial cracking properties. The Mg layer fractured first, causing a sudden drop of the stress and Al/STS layer continued to deform until the final fracture. Periodic cracks and crack propagation was observed at the reaction layer between Mg and Al.

• 한국항공우주학회지
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• 제30권8호
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• pp.65-70
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• 2002

본 연구에서는 로켓엔진에 사용되고 있는 2상 스테인리스강의 브레이징 접합성에 관하여 접합 현상과 기계적 강도의 두가지 측면의 고찰을 통하여 검증하였다. UNS32550을 모재로, MBF-50을 인서트금속으로 사용하여 브레이징 접합온도를 1473K, 1498K로 변화시키고, 접합 시간은 0~1.8ks로 변화시키면서 각 조건에서의 접합현상을 고찰한 결과, 접합부에서는 모재와 인서트금속간의 반응으로 인해 다양한 상이 생성되었다. 접합 초기에는 접합계면 및 접합부 근방의 모재에서 BN가 생성되고, 접합계면에서는 Cr질화물이 생성되어 접합 시간이 증가함에 따라 BN과 Cr질화물의 양이 감소하였다. 전단시험 결과 500MPa의 우수한 전단강도를 얻었다.

• 마이크로전자및패키징학회지
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• 제11권4호
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• pp.1-5
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• 2004

다층 연성기판은 높은 전기 전도성과 낮은 절연상수로 잘 알려진 구리와 폴리이미드로 구성되어 있다. 본 연구에서는 이러한 다층연성기판을 패턴된 스테인리스 스틸 위에 구리선을 전기도금하고 폴리이미드를 코팅함에 의해서 균일한 형태의 $5{\mu}m$-pitch의 전도선을 제조하는데 성공하였다. 또한, 다층기판 형성시 비아흘은 UV 레이저로 형성시켰으며 구리와 주석을 전기 도금함으로 이를 채웠다. 그런다음 비아와 전도선이 붙은 채로 스테인리스 스틸에서 벗겨냈다. 이렇게 형성된 각각의 층을 한번에 적층하여 다층연성기판을 완성하였다. 적층시 주석과 구리사이에 고체상태 반응(Solid state reaction)이 발생하여 $Cu_6Sn_5$ and $Cu_3Sn$을 형성하였으며 비아패드에 비아가 수직으로 위치한 완전한 형태의 층간 연결을 형성하였다. 이러한 비아 형성 공정은 V형태의 비아나 페이스트 비아와 비교할 때 좋은 전기적 특성, 저가공정등의 여러 장점을 가지고 있다.