• Journal of Advanced Marine Engineering and Technology
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• v.36 no.2
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• pp.294-301
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• 2012

Shipbuilding industry has used a lot of $CO_2$ gas as a shielding gas for arc welding and thus, development of welding equipment which can reduce the amount of $CO_2$ gas is requested widely. Therefore, this study is focused on the examination of optimum welding torch distance of Tandem welding system as a fundamental study for the optimum shape design of torch nozzle. $CO_2$ shielding gas distribution and welding bead shape formation by the torch distance are examined. Results show that according to the torch distance variation, most effective shielding gas layer can be formed and quantitative determination of the optimum torch distance can result in the reduction of $CO_2$ shielding gas consumption.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.2
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• pp.535-541
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• 2013

The present study was carried out to investigate the effects of welding parameters such as current, voltage and shielding gases on the bead shape, microstructures and hardness. It was confirmed that bead height was lowered and bead depth was increased with increasing voltages while height, depth and width of beads increased with welding currents. The hardness of weld metals with Ar+10% $O_2$ and Ar+20% $CO_2$ was low due to the formation of grain boundary and polygonal ferrites while that of weld metals with Ar+2% $O_2$ was high due to the presence of acicular, bainitic and sideplate ferrites.

• Journal of Welding and Joining
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• v.12 no.1
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• pp.51-58
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• 1994

Amount of spatter, welding conditions and welding costs were investigated for MAG welding. $CO_2$, Ar+18%;$CO_2$ and Ar+8%$O_2$ were used for shielding gases. As results, arc characteristics and appropriate range for welding were obtained. Amount of spatter in Ar+18%$CO_2$ gas welding was 20% of that of $CO_2$ welding, and Ar+8%$O_2$ was 10% of that of $CO_2$ welding. Therefore by using Ar+18%$CO_2$and Ar+8%$O_2$ gases, welding costs could be reduced compared with $CO_2$ welding due to avoiding spatter.

• Proceedings of the KWS Conference
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• v.43
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• pp.52-54
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• 2004

• Journal of Welding and Joining
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• v.13 no.1
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• pp.127-137
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• 1995

The possibility of new GMAW process using economic shielding gases including CO$_{2}$ gas was investigated on the effect of shielding gas on weldabilty. In the optimum welding condition using 600A power source, FCAW process showed low depositions rate, 114 g/min at 300A, but new GMAW using other mixed shielding gases exhibited high deposition rate, 208-224 g/min at 450A. TIME gas, Ar+CO$_{2}$ gas and Ar+CO$_{2}$+O$_{2}$ gas as a shielding gas were able to be used to the very high welding current(450A), moreover TIME gas and Ar+CO$_{2}$ gas showed the highest arc stability among shielding gases studied in this experiments. The weld penetration was performed by axial spray transfer mode of weld droplet. On the basis of workability, weldability and economic point of view, Ar mixture (80%Ar+20%CO$_{2}$) gas was recommended as a shielding gas for the development and application of new GMAW process. This shielding gas showed the low spatter, good weld quality, stable arc and low cost at the region of high welding current.

• Korean Journal of Materials Research
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• v.10 no.11
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• pp.778-783
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• 2000

Effects of the $Al_2$O$_3$surface protective layer, deposited on the SnO$_2$sensing layer by aerosol flame deposition (AFD) method, on the sensing properties of SnO$_2$thin film ags sensors were investigated.Effects of Pt doping to the $Al_2$O$_3$surface protective layer on the selectivity of CH$_4$ gas were also investigated. 0.3$\mu\textrm{m}$ thick SnO$_2$thin sensing layers on Pt electrodes were prepared by R.F. magnetron sputtering with R.F. power of 50 W, at working pressure of 4mTorr, and at 20$0^{\circ}C$ for 30 min. $Al_2$O$_3$surface protective layers on SnO$_2$layers were prepared by AFD using a diluted aluminum nitrade (Al(NO$_3$).9$H_2O$) solution. The sensitivity of CO gas in the SnO$_2$gas sensor with an $Al_2$O$_3$surface protective layer was significantly decreased. But that of CH$_4$gas remained almost same with pure SnO$_2$gas sensor. This result shows that the selectivity of CH$_4$gas is increased because of the $Al_2$O$_3$surface protective layer. In the case of SnO$_2$gas sensors with Pt-doped $Al_2$O$_3$surface protective layers, low sensing property to CO gas and high sensing property to CH$_4$were observed. This results in the increasing of selectivity of CH$_4$gas selectivity are discussed.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.73.2-73.2
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• 2011

석탄 합성가스 중에는 $H_2S$, HCl, $NH_3$와 같은 불순물이 포함되어 있다. 이러한 가스들은 오염가스 배출과 관련한 환경기준 준수와 터빈과 같은 설비의 보호를 위해 제거되어야 한다. 석탄 합성가스 중 HCl 농도는 탄종에 따라 다르기는 하지만 많게는 1000 ppmv 수준까지 존재한다. 합성가스를 이용하여 발전을 하는 경우 가스터빈 보호를 위해 HCl은 <3 ppmv 이하로 정제되어야 하고, 합성가스를 연료전지에 사용하고자 하는 경우에는 HCl을 <0.5 ppmv 수준까지, 화학원료로 사용하고자 하는 경우에는 <10 ppbv 수준까지 정제하여야 한다. 또한 HCl은 고온 탈황공정에 사용되는 흡수제의 활성에도 장기적으로 부정적인 영향을 주기 때문에 고온에서 HCl을 정제할 수 있는 흡수제가 필요하다. 본 연구에서는 알칼리금속을 활성물질로 사용하여 분무건조법으로 제조한 HCl 흡수제에 대해 물성 및 HCl과의 반응성을 살펴보았다. $300-500^{\circ}C$ 영역에서 K-계 및 Na-계 흡수제에 대해 고정층반응기에서 HCl 가스를 함유한 모사 합성가스를 이용하여 상압 조건에서 Cl 흡수능을 측정한 결과 15wt% 이상의 흡수능을 나타내었으며 반응온도가 높을수록 흡수능이 증가함을 알 수 있었다. XRD 분석을 통하여 Cl은 K 및 Na와 반응하여 KCl과 NaCl을 형성하면서 흡수됨을 알 수 있었다. 20 bar 조건에서 실험한 결과에서도 동일한 경향의 반응성을 나타내었으며 반응온도가 낮을수록 흡수능은 감소하지만 Cl을 더 낮은 농도로 정제할 수 있었다. 본 실험에 사용된 Na 및 K계 흡수제는 모두 연소 후 배가스 중 $CO_2$를 제거하기 위한 흡수제로 사용되는 고체 흡수제이다. 석탄화력발전소 배가스에 연계되어 $CO_2$ 회수실험에 사용되었던 사용 후 $CO_2$ 흡수제에 대해 HCl 흡수 실험을 수행한 결과에서도 우수한 HCl 제거 성능을 보여 주었다. 이로부터, 폐 $CO_2$ 흡수제의 HCl 흡수제로서의 활용가능성을 확인 하였다.

• Proceedings of the KWS Conference
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• 2002.05a
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• pp.224-227
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• 2002

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.4
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• pp.399-406
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• 2005

Alloy 625 is used widely in industrial applications such as aeronautical aerospace, chemical, petrochemical and marine applications. Because of a good combination of yield strength. tensile strength, creep strength, excellent fabricability, weldability and good resistance to high temperature corrosion on prolonged exposure to aggressive environments. High qualify weldments for this material are readily produced by commonly used processes. But all of processes are not applicable to this material by reason of unavailability of matching, position or suitable welding filler metals and fluxes may limit the choice of welding processes. Recently, the flux cored wire is developed and applied for the better productivity in several welding position including the vortical position. In this study. the weldability and weldment characteristics of Alloy 625 are evaluated in FCAW weld associated with the several shielding gases($80\%Ar+20\%\;CO_2,\;50\%Ar+50\%\;CO_2.\;100\%\;CO_2$) in viewpoint of welding productivity. The results of the experimental study on corrosive characteristics of Alloy 625 are as follows; There is no remarkable difference among shielding gases. however they has a striking difference among corrosive solutions by results of distinguished density and time of corrosive solution. Generally, the shielding gases($80\%Ar+20\%\;CO_2$) was superior to the other gases on high temperature tensile and a low temperature impact. but all of the shield gases were making satisfactory results on corrosion test.

• Proceedings of the KWS Conference
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• 2004.05a
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• pp.57-59
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• 2004

$CO_2$ 용접은 다른 용접에 비하여 와이어와 보호가스의 가격이 저렴하기 때문에 재료비 측면에서 매우 경제적이라는 장점이 있다. 그러나 $CO_2$ 용접은 타 용접에 비해 스패터 발생량이 많다는 문제점이 있었으나, 최근 파형제어 기법의 개발로 스패터 발생량을 SCR용접기에 비하여 80%이상 향상된 인버터 용접기가 개발되었다. (중략)