• Title/Summary/Keyword: Shield gas

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Investigation of Effects of Shield Gas on Counterflow Flame Structure (차폐가스가 대향류 화염구조에 미치는 영향의 조사)

  • Park, Woe-Chul
    • Journal of the Korean Society of Safety
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    • v.17 no.2
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    • pp.112-117
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    • 2002
  • The effects of shield gas on the structure of methane-air nonpremixed counterflow flames were numerically investigated. The near extinction flame of a low global strain rate 20 $s^{-1}$ of 19% methane diluted by 81% nitrogen by volume and undiluted air was computed. The flame shape, centerline temperature and axial velocity profiles were compared for different velocity of the shield gas and with and without the shield gas. The effects of the velocity of the shield gas were negligible for $V_{S}/V_{F}{\leq}2$ in normal gravity. Under normal gravity conditions, the flame shape and its position with the shield gas were different from those of the flame without the shield gas, whereas no discernible effects of the shield gas along the centerline were observed in zero gravity.

Characteristics of Plasma Emission Signals in Fiber Laser Welding of API Steel (III) -The Effect on Plasma Emission Signals by Shield Gas- (API강재의 파이버레이저 용접시 유기하는 플라즈마의 방사특성 (III) - 보호가스가 플라즈마 방사 신호에 미치는 영향 -)

  • Lee, Chang-Je;Kim, Jong-Do;Kim, Yu-Chan
    • Journal of Welding and Joining
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    • v.31 no.3
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    • pp.60-65
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    • 2013
  • Ar, $N_2$, and He are the conventional kind of shield gas that are used for laser welding. Many researches on the impact of laser welding shield gas have been done, and it is on going until now. However, there are few studies that analyze the changes and differences of the plasma emission signal. Therefore, in this study, we evaluated the change in the penetration characteristics according to the type of shield gas during fiber laser welding impacts to the plasma signal. As a result, if was checked that the difference in molecular weight of Ar, $N_2$, and He affects to the amount of spatter, and also found that the measured plasma radiation signal changes similar to the order of the molecular weight of the gases. Especially, clear change on the signal intensity per each shield gas was measured through RMS, and found that the shield gas was nothing to do with the FFT analyzed result.

A Study on the GMA Welding Characteristics of Al5083-O Aluminum Alloy According to the Shield Gas Mixing Ratio and Heat Input (Al5083-O 알루미늄합금의 보호가스 혼합비율 및 입열량에 따른 GMA용접 특성에 관한 연구)

  • 정재강;양훈승;이동길
    • Journal of Welding and Joining
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    • v.20 no.2
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    • pp.65-70
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    • 2002
  • This study was to evaluate GMA welding characteristics of the A15083-O aluminum alloy according to the shield gas mixing ratio and heat input change. The GMA welding of the base metal was carried out with flour different shield gas mixing ratios(Ar100%+He0%, Ar67%+He33%, Ar50%+He50%, and Ar33%+He67%). Regarding the if1uence on the bead shape of the shield gas mixing ratio and heat input, the bead width was greatest in Ar100%+He0% mixture. But the penetration depth and area were greatest in Ar33%+He67% mixture considering that the lower Ax gas ratio, the higher bead depth and area. Also, dilution was also best in the shield gas mixing ratio. The size and number of deflects were least in Ar33%+He67% mixture. Higher He gas ratio resulted in less deflects detected by the radiographic inspection.

Effect of shield gas on the characteristics of $CO_2$ laser welded 600MPa grade high strength steel (600MPa급 자동차용 고장렬강판의 $CO_2$ 레이저 용접부의 특성에 미치는 보호가스의 영향)

  • Han Tae-Kyo;Lee Bong-Keun;Kang Chung-Yun
    • Laser Solutions
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    • v.7 no.2
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    • pp.19-26
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    • 2004
  • The effect of shield gas on the weldability, mechanical properties and formability of CO2 laser weld joint in 600MPa grade high strength steel was investigated. Bead on plate welds were made under various welding speed and shield gas. Tensile test was carried out under the load of perpendicular and parallel direction to the weld line, Formability of the joint was evaluated by Erichsen test. As the welding speed increases, the porosity fraction decreases. The porosity fraction in the joint used Ar-$50\%He$ mixed gas as a shield gas was lower than that of the joint used Ar gas. Hardness at the weld metal of full penetrated joint was nearly equal to that of water quenched raw metal. In a tensile test under a perpendicular load to the weld axis, strength and elongation of joint produced by optimum condition were nearly equal to those of base metal. However, the strength of joint in a tensile test under a parallel load to weld axis was higher than that of raw metal, but the elongation of joint was lower than that of raw metal. Elongation and formability were further increased by the method of using Ar+He mixed gas as a shield gas as compared with Ar gas. Formabilities of joints were recorded ranging from $58\%\;to\;70\%$ of that of base metal with different shield gases.

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The Eeffect of Arc Length and Shield Gas on Penetration Aspect Ratio in A-TIG Welding (A-TIG 용접에서 용입 형상비에 미치는 아크길이와 실드가스의 영향)

  • Park, In-Ki;Ham, Hyo-Sik;Cho, Sang-Myung
    • Journal of Welding and Joining
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    • v.26 no.6
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    • pp.42-47
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    • 2008
  • TIG welding enables to produce high quality weldment. However it has some problems such as shallow penetration and large distortion due to low penetration aspect ratio after welding. In order to overcome those problems, there are many ongoing studies on A-TIG welding, which use active flux. In this study, the effect of arc length and shield gas on penetration aspect ratio with melt-run welding on STS 304 6t, on which active flux was spreaded, was investigated. Arc length was changed from 1mm to 3mm, and aspect ratio became higher as arc length was decreased in this range. 100% Ar gas, Ar-$H_2$ mixed gas, Ar-He mixed gas, and 100% He gas were used as shield gas in this study. When Ar-$H_2$ mixed gas, Ar-He mixed gas, and 100% He gas were applied, penetration and melting efficiency were both increased as compared with 100% Ar gas. Aspect ratio was the highest with Ar-2.5% $H_2$ mixed gas.

A Study on Optimum Shape of Shield Gas Nozzle for Bead Shape Control in TIG Welding using Gas Force (Ⅰ) - Design and Performance Analysis of Venturi Nozzle - (TIG용접에서 가스력을 이용한 비드형상제어를 위한 실드가스 노즐의 최적 형상에 관한 연구 (I) - 벤투리노즐의 설계 및 성능분석 -)

  • Ham, Hyo-Sik;Seo, Ji-Seok;Choi, Yoon-Hwan;Lee, Yeon-Won;Cho, Sang-Myung
    • Journal of Welding and Joining
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    • v.29 no.3
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    • pp.51-57
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    • 2011
  • Bead shape control with gas force process has been developed to overcome the concave back bead in pipe orbital welding. However, It is impossible to make a convex back bead using the existing gas nozzle, because it has high gas-consuming and low gas force. The purpose of this paper, to develop optimum shape of nozzle which to reduce the consumption of gas, maximizing the shield gas force with low cost and high productivity coincide the Green welding. In this paper venturi-type nozzle was designed by using the Venturi meter and compared velocity, pressure, arc shape in the flat position with existing CP-nozzle. As a result, Venturi-type nozzle's maximum velocity and pressure was improved at the same flow rate. Also heat input was increased by the arc contraction in the flat position.

A Study on Optimum Shape of Shield Gas Nozzle for Bead Shape Control in TIG Welding using Gas Force (II) - Effect of Molten Metal Control by Venturi Nozzle in Overhead Position - (TIG용접에서 가스력을 이용한 비드형상제어를 위한 실드가스 노즐의 최적 형상에 관한 연구 (II) - 벤투리 노즐의 위보기 자세 용융금속제어 효과 -)

  • Ham, Hyo-Sik;Seo, Ji-Seok;Choi, Yoon-Hwan;Lee, Yeon-Won;Cho, Sang-Myung
    • Journal of Welding and Joining
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    • v.29 no.3
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    • pp.58-63
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    • 2011
  • Bead shape control with gas force process has been developed to overcome the concave back bead in pipe orbital welding. However, It is impossible to make a convex back bead using the existing gas nozzle, because it has high gas-consuming and low gas force. The purpose of this paper, to develop optimum shape of nozzle which to reduce the consumption of gas, maximizing the shield gas force with low cost and high productivity coincide the Green welding. In this paper venturi-type nozzle was compared with existing CP-type nozzle by TIG pulse welding in overhead position. As a result, CP-type occurs the wormholes in the overhead position, but the Venturi-type without the pore and formed a good bead appearance.

The Influence of Shield Gas Ratio on the Toughness of A15083-0 GMAW Weld Zone (A15083-O GMAW 용접시 불활성가스 혼합비가 용접부의 인성에 미치는 영향에 관한 연구)

  • 이동길;김건호
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • pp.113-199
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    • 2002
  • In this study, the toughness was evaluated by using the instrumented Charpy impact testing procedures for A15083-O aluminum alloy used in the LNG carrying and storing tank. The specimens were GMAW welded with four different mixing shield gas ratios (Ar100%+He0%, Ar67%+He33%, Ar50%+He50%, and Ar33%+He67%), and tested at four different temperatures(+25, -30, -85, and -196$^{\circ}C$ ) in order to investigate the influence of the mixing shield gas ratio and the low temperature. The specimens were divided into base metal, weld metal, fusion line, and HAZ specimen according to the worked notch position. From experiment, the maximum load increased a little up to -85$^{\circ}C$, and the maximum load and maximum displacement were shown the highest and the lowest at -196$^{\circ}C$ than the other test temperatures. The absorption energy of weld metal notched specimens was not nearly depends on test temperature and mixing shield gas ratio because the casting structure was formed in weld metal zone. In the other hand, the others specimens was shown that the lower temperature, the higher absorption energy slightly up to -85$^{\circ}C$ but the energy was decreased so mush at -196$^{\circ}C$

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The Strength Evaluation of Al5083-O GMA Welding Zone According to the Heat Input and Mixing Shield Gas Ratio (Al5083-O GMA 용접부의 입열량과 보호가스 혼합비율에 따른 강도 평가)

  • 이동길;양훈승;정재강
    • Transactions of the Korean Society of Automotive Engineers
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    • v.10 no.6
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    • pp.158-165
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    • 2002
  • This study was to evaluate mechanical properties and toughness of the Al5083-O aluminum alloy welding zone according to the mixing shield gas ratio and heat input change. The GMA(Gas Metal Arc) welding of the base metal was carried out with four different mixing shield gas ratios(Ar100%+He0%, Ar67%+He33%, Ar50%+He50%, and Ar33%+He67%) and three different heat inputs(low, medium, and high). To investigate the Charpy absorbed energy of the weld zone, the specimens were divided base metal, weld metal, fusion line, and HAZ notched specimen according to the worked notch position. The different gas ratio and heat input had little effect upon the tensile strength. But Ar33%+He67% mixture had the greatest mechanical properties considering that the more He gas ratio concentrations, the higher yield strength and elongation. The maximum load and displacement of the weld metal notche specimen was so much low more than that of the base metal, but fusion line and HAZ notched specimens showed almost same regardless of the mixing shield gas ratio and heat input. The Charpy absorbed energy was lowest in weld metal notched specimen, and increased in the fusion line, and HAZ notche specimen in order. Ar33%+He67% mixture had the greatest toughness considering that the more He gas ratio, the higher absorption energy.

The Low Temperature Toughness of A15083-O Welding Zone According to the Mixing Shield Gas Ratio (보호가스 혼합비율에 따른 Al5083-O 용접부의 저온 인성에 관한 연구)

  • 정재강;양훈승;이동길
    • Journal of Welding and Joining
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    • v.20 no.6
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    • pp.762-768
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    • 2002
  • In this study, the low temperature toughness was evaluated by using the instrumented Charpy impact testing procedures for A15083-O aluminum alloy used in the LNG carrying and storage tank. The specimens were GMA(Gas Metal Arc) welded with four different mixing shield gas ratios (Ar100%+He0%, Ar67%+He33%, Ar50%, and Ar33%+He67%), and tested at four different temperatures(+25, -30, -85, and $-196^{\circ}C$) in order to investigate the influence of the mixing shielding gas ratio and the low temperature. The specimens were divided into base metal, weld metal, fusion line, and HAZ specimen according to the notch position. From experiment the maximum load and displacement were shown the highest and He lowest at $-196^{\circ}C$ than the other test temperatures. The absorption energy of weld metal notched specimens was not nearly depends on test temperature and mixing shield gas ratio because the casting structure was formed in weld metal zone by melting welding wire. On the other hand, the others specimens was shown that the lower temperature, the higher absorption energy slightly up to $-85^{\circ}C$ but the energy was decreased so mush at $-196^{\circ}C$.