• Journal of Welding and Joining
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• v.15 no.4
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• pp.109-115
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• 1997

Laser cladding is a technique for modification of metal surface. In this laser cladding experiment a metal powder feeding system was developed for more efficient laser cladding. This system can reduce processing time and be used simpler than the conventional method. The feeding of metal powder has given a rise to the process for sequential buildup of bulk rapidly solidified materials in the form of fine powder stream to the laser cladding process. The parameters of laser cladding have been investigated using this experimental equipment. Bronze on aluminum alloy and copper on aluminum alloy were experimented by using defocused beam, powder feeding system, and gas shielding. Good cladding was achieved in the range of beam travel speed of 2.25m/min. In the case of copper/aluminum and bronze/aluminum substrate, the absorption of laser beam was too high to produce low diluted clad. In the case of copper/1050 aluminum, the optimal laser cladding condition was of laser power of 2.8kW, powder feed rate of 0.31g/s and beam travel speed of 2.25m/min. In the case of bronze/aluminum the optimal condition is of laser power of 2.5kW, powder feed rate of 0.31g/s, and beam travel speed of 2.36m/min.

• 한국전기화학회:학술대회논문집
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• 2005.07a
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• pp.383-390
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• 2005

Effect of applying a DC voltage on the interfacial reaction at the metal to zirconia interface was investigated utilizing an oxygen ionic conductivity of partially stabilized zirconia. The joining of copper rod and zirconia tube was carried out in Ar gas atmosphere at $1000^{\circ}C$. There are two type of the joining. The one is the reaction bond consisting of copper and zirconia was dominated by surface reaction with a undetectable very thin layer. It was found that copper elements were diffused to zirconia side, but that Zr ions were not diffused to copper side. These results mean application of a DC voltage to migrate oxygen to the copper-zirconia interface can oxidize metal at the copper-zirconia interface and the bonding reaction between zirconia and copper oxide may occur. The other is the reaction bonding was dominated by interdiffusion with a very thick interface layer. This result mean application of a DC voltage can reduce zirconia at the interface. The bonding reaction is to be an alloying between Zr and Cu.

• Journal of Welding and Joining
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• v.23 no.1
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• pp.41-47
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• 2005

Arc pressure is one of important factors in understanding physical arc phenomena. Especially it affects on the penetration, size and shape of TIG welding. Some researches were reported on the effect of arc pressure in low and middle current region. But there are not any research in high current region. The purpose of this study is to investigate the arc pressure distribution with mixing ratio of shield gas such as Ar and He gases. A Cu block with water cooling was specifically designed and used as an anode electrode in order to measure the arc pressure in high current region. Then, the arc pressure distribution was measured with change in welding current and mixing ratio of shield gases. The arc force was obtained by numerically integrating the measured results. As the results, it was shown that the arc pressure was concentrated at the central part of the arc in middle and high current regions when a pure Ar gas was used. In case of Ar + He mixing gas, the arc pressure was much lower than that of pure Ar gas. In addition, it was widely distributed to radial direction.

• Journal of Welding and Joining
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• v.22 no.5
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• pp.65-72
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• 2004

The tendency and degree of hot cracking of high strength 5083, 6N01 and 7N01 Al alloy welds by using DCSP-GTAW through modified Varestraint test and autogenous butt welding were investigated. In hot cracking test, 6N01 alloy showed the highest susceptibility to hot cracking in the weld metal and HAZ. Cracking susceptibilities generally increased with increase of solidification temperature range of the base metal and bead penetration-to-width ratio of the weld metal. The cracks in welds of the alloys vertically formed to solid-liquid interface and propagated along with columnar grain boundaries. The fracture facets of cracks showed the typical morphology of solidification crack observed as dendritic structures. Especially, in 6N01 alloy, liquation cracks which were due to elements of Si, Fe and Mg also observed in HAZ near fusion boundary. In butt welding of different Al alloys, the bead crack was mainly occurred in the welds of 6N01, 7N01 and other Al alloys together with 6N01 or 7N01. In the butt welds of 7N01, it was found that the component of Cu had an effect on the higher susceptibility to the hot cracking.

• Journal of Welding and Joining
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• v.33 no.4
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• pp.7-16
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• 2015

New lasers such as high power, high brightness and short wavelength laser are using diverse industry. Also new technologies are developing actively to solve various issues such as spattering, process monitoring, deep penetration and key-hole stability. ICALEO is the international congress where recent technology for laser material processing and laser system are present. At 2014, it was held at San Diego in USA and more than 260 papers were presented from 28 country. The effect of the laser beam shape such as Gaussian like and top-hat was investigated on acoustic emission signal and pore formation in welding. Inline penetration depth was measured with ICI(Inline Coherent Imaging) technique and the data was verified with real time X-ray image on laser welding. The laser welding performance at low pressure environment was evaluated for the thick plate alloy steel. UV laser was used to weld various metals such as Cu, Aluminum, steel and stainless steel. The effect of the wavelength of the laser on the formation of the wave at the wall of the key-hole front and the absorptivity was investigated.

• Journal of Welding and Joining
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• v.33 no.2
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• pp.23-31
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• 2015

Stainless steel is used in automobile muffler and exhaust systems. However, in comparison with other steels it has a high thermal expansion rate and low thermal conductivity, and undergoes excessive thermal deformation after welding. To address this problem, we evaluated the use of arc brazing in place of welding for the processing of an exhaust system, and investigated the parameters that affect the joint characteristics. Muffler parts STS439 and hot-dipped Al coated steel were used as test specimens, and CuAl brazing wire was used as the filler metal for the cold metal transfer (CMT) welding machine, which is a low heat input arc welder. In addition, a Box-Behnken design of experiment was used, which is a response surface methodology. The main process parameters (current, speed, and torch angle) were used to determine the appropriate welding quality and the mechanical properties of the brazing part was evaluated at the optimal welding condition. The optimal processing condition for arc brazing was 135A current, 51cm/min speed and $74^{\circ}$ torch angle. The process was applied to an actual exhaust system muffler and the prototype was validated by thermal fatigue, thermal shock, and endurance limit tests.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.168-168
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• 2013

도전성 섬유(Conductive textile)는 섬유자체의 고유 특성을 유지하면서 전기적인 도전 특성을 갖는 섬유로서, Cu, Ag, Ni 등의 전기전도성이 높은 금속 박막을 증착하여 제작하고 있다. 그러나, 이러한 금속은 공기 중의 산소와 결합하여 쉽게 산화되는 특성을 지니고 있기 때문에 사용 중에 산화되어 도전 특성이 감소하는 단점이 있다. TiN은 금속 못지않은 높은 전기전도성을 지니고 있을 뿐만 아니라, 금속에 비하여 높은 경도에 따른 우수한 내마모 특성, 내부식성 및 낮은 마찰계수를 지니고 있다. 그러나, TiN은 경도가 높기 때문에 섬유의 고유 특성인 유연성이 저하되는 문제가 있다. 본 연구에서는 면(Cotton), PE (Polyester), PP (Polypropylene) 등의 섬유 위에 TiN 박막을 증착하여, 섬유의 유연성을 유지하며 전기전도성과 내마모 특성이 우수한 도전성 섬유를 제작하고자 하였다. TiN 박막 증착을 위하여 ICP-assisted pulsed-DC reactive magnetron sputtering 장비를 사용하였으며, Ar:N2 유량비(Flow rate), Ti 타겟 power, ICP RF power 등을 변화시켜 Ti와 N의 조성비를 조절하였고, 이를 통하여 섬유의 휨이나 접힘에도 도전 특성이 변하지 않고 내마모 특성이 우수한 TiN 박막을 증착하였다. TiN 박막이 증착된 섬유의 전기전도도는 일정한 압력 하에 전기전도도를 측정할 수 있는 장치를 제작하여 측정하였으며, 표면 조성 분포 및 접합력 측정을 위하여 XPS (X-ray Photoelectron Spectroscopy)와 Peel-tester를 이용하였다.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.91-94
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• 1999

A new type of high-T$_c$ superconducting Josephson junctions has been prepared by Ar ion beam etching and electron beam lithography. YBa$_2Cu_3O_{7-x}$ (YBCO) films deposited on (001) SrTiO$_3$ single crystal substrate by pulsed laser deposition were patterned by Ar ion milling with photolithography. The narrow slit with a electroresist mask, about 1000 ${\AA}$ wide, was constructed over a 3 ${\sim}$ 5 ${\mu}$m bridge of a 1200-${\AA}$-thick YBCO film by electron beam lithography. The slit was then etched by the Ar ion beam to form a damaged 600-${\AA}$-thick YBCO. Thus prepared structure forms an S-N-S (YBCO - damaged YBCO - YBCO) type Josephson junctions. Those junctions exhibit RSI-like I-V characteristics at 77 K. The properties of the Josephson junctions such as I$_c$ R$_N$, and J$_c$ were characterized.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.147-151
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• 1999

YBCO step-edge Josephson junction were fabricated on sapphire substrates. The steps were formed on R-plane sapphire substrates by using Ar ion milling with PR masks. The step angle was controlled in the wide range from 25$^{\circ}$ to 50$^{\circ}$ by adjusting both the Ar ion incident angle and the photoresist mask rotation angle relative to the incident Ar ion beam. CeO$_2$ buffer layer and in-situ YBa$_2Cu_3O_{7-{\delta}}$ (YBCO) thin films was deposited on the stepped R-plane sapphire substrates by pulsed laser deposition method. The YBCO film thickness was varied to obtain the ratio of film thickness to step height in the range from 0.5 to 1. The step edge junction exhibited RSJ-like behaviors with I$_cR_n$ product of 100 ${\sim}$ 300 ${\mu}$V, critical current density of 10$^3$ ${\sim}$ 10$^5$ A/ cm$^2$ at 77 K.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.63-66
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• 1999

We fabricated ramp-edge Josephson junctions with barriers formed by interface treatments instead of epitaxially grown barrier layers. Low-dielectric Sr$_2AITaO_6$(SAT) layer was used as an ion-milling mask as well as an insulating layer for the ramp-edge junctions. An ion-milled YBa$_2Cu_3O_{7-x}$ (YBCO)-edge surface was not exposed to solvent through all fabrication procedures. The barriers were produced by structural modification at the bottom YBCO edge using plasma treatment prior to deposition of the top YBCO electrode. We investigated the effects of pre-annealing and post-annealing on the characteristics of the interface-treated Josephson junctions. The junction parameters were improved by using in-situ RF plasma cleaning treatment.