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Francis Briand - One of the best experts on this subject based on the ideXlab platform.

  • Study of the spray to Globular transition in gas metal arc welding: a spectroscopic investigation
    Journal of Physics D: Applied Physics, 2013
    Co-Authors: Flavien Valensi, Stéphane Pellerin, Quentin Castillon, Amar Boutaghane, Krzysztof Dzierzega, Sylwia Zielinska, Nadia Pellerin, Francis Briand
    Abstract:

    The gas metal arc welding (GMAW) process is strongly influenced by the composition of the shielding gas. In particular, addition of CO2 increases the threshold current for the transition from unstable Globular to more stable spray Transfer mode. We report on the diagnostics—using optical emission spectroscopy—of a GMAW plasma in pure argon and in mixtures of argon, CO2 and N2 while operated in spray and Globular Transfer modes. The spatially resolved plasma parameters are obtained by applying the Abel transformation to laterally integrated emission data. The Stark widths of some iron lines are used to determine both electron density and temperature, and line intensities yield relative contents of neutral and ionized iron to argon.Our experimental results indicate a temperature drop on the arc axis in the case of spray arc Transfer. This drop reduces with addition of N2 and disappears in Globular Transfer mode when CO2 is added. Despite the temperature increase, the electron density decreases with CO2 concentration. The highest concentration of iron is observed in the plasma column upper part (close to the anode) and for GMAW with CO2.Our results are compared with recently published works where the effect of non-homogeneous metal vapour concentration has been taken into account.

  • Study of the spray to Globular transition in Gas Metal Arc Welding : Spectroscopic investigation
    J.Phys.D, 2013
    Co-Authors: Flavien Valensi, Stéphane Pellerin, Quentin Castillon, Amar Boutaghane, Krzysztof Dzierzega, Sylwia Zielinska, Nadia Pellerin, Francis Briand
    Abstract:

    The shielding gas composition has a strong influence on the gas metal arc welding (GMAW) process. In particular, CO2 adjunction increases the current needed for the transition from unstable Globular to more stable spray Transfer. Plasma diagnostic using optical emission spectroscopy was performed using shielding gas composed of argon, argon-CO2 mixtures and argon-N2 mixtures for spray and Globular Transfer. Radial evolution of the studied parameters was determined thanks to Abel inversion: line broadening was used to get electron temperature and density, and intensity measurement yielded to ratio of neutral and ionized iron over argon. Results showed temperature drop on arc axis in the case of the spray arc Transfer. While maximal temperature increases this drop is reduced with nitrogen adjunction and disappears in Globular Transfer when CO2 rich shielding gas is used. On the contrary, the electron density decreases when CO2 is added to argon. The iron content highest values are observed on the upper part of the column, with overall quantity higher in the case of CO2 containing shielding gas. The obtained data were compared to other recent results dealing with the effect of non homogeneous metal vapour concentration.

  • Microstructural analysis of the anode in gas metal arc welding
    Journal of Materials Processing Technology, 2009
    Co-Authors: Sylwia Zielinska, Flavien Valensi, Stéphane Pellerin, Nadia Pellerin, Karol Musiol, Charles De Izarra, Francis Briand
    Abstract:

    The nature of the applied shielding gas has a strong influence on arc stability and Transfer metal mode of the welding process. In particular, increase of the percentage of carbon dioxide in argon induces the increase of the transition current value from the Globular to spray metal Transfer mode. This work shows that these effects are linked to the chemical and microstructural modifications of the anode tip during the gas metal arc welding process. The microstructure of the anode is investigated for various experimental conditions. Transition between the two Transfer modes is linked to the existence and disappearance of a rather insulating oxide "gangue" at the wire extremity whose nature depends of the shielding gas. Chemical reactions at high temperature such as oxidation-reduction reactions between shielding gas and melted metal govern the transition of the spray-arc to Globular Transfer mode.

  • Microstructural analysis of the anode in gas metal arc welding (GMAW)
    Journal of Materials Processing Technology, 2009
    Co-Authors: Sylwia Zielinska, Flavien Valensi, Stéphane Pellerin, Nadia Pellerin, Karol Musiol, Charles De Izarra, Francis Briand
    Abstract:

    Abstract The nature of the applied shielding gas has a strong influence on arc stability and Transfer metal mode of the welding process. In particular, increase of the percentage of carbon dioxide in argon induces the increase of the transition current value from the Globular to spray metal Transfer mode. This work shows that these effects are linked to the chemical and microstructural modifications of the anode tip during the gas metal arc welding process. The microstructure of the anode is investigated for various experimental conditions. Transition between the two Transfer modes is linked to the existence and disappearance of a rather insulating oxide “gangue” at the wire extremity whose nature depends of the shielding gas. Chemical reactions at high temperature such as oxidation–reduction reactions between shielding gas and melted metal govern the transition of the spray-arc to Globular Transfer mode.

Jicai Feng - One of the best experts on this subject based on the ideXlab platform.

  • Influence of calcium fluoride on underwater wet welding process stability
    Welding in the World, 2018
    Co-Authors: Ning Guo, Hao Chen, Jicai Feng
    Abstract:

    To explore the influence of calcium fluoride on underwater wet welding process stability, the relevance of calcium fluoride in the flux to metal Transfer mode and arc stability was discussed in the process of underwater wet welding using a set of wires with various calcium fluoride contents. The metal Transfer images were obtained using X-ray imaging system and the electric signal detection system was used to collect arc voltage and welding current signals synchronized with the film frames. Three metal Transfer modes, i.e., repelled Globular Transfer, surface tension Transfer, and spatter-like metal droplet Transfer, were observed during the underwater wet welding process. The spatter-like metal droplet Transfer mode was put forward firstly. Increasing the contents of calcium fluoride in the wire from 0 to 65%, the proportion of surface tension Transfer mode steadily climbed from approximately 15 to 40% while that of spatter-like metal droplet mode declined from 53 to 35%. The arc stability of the welding process firstly deteriorated and then ameliorated with the increasing calcium fluoride content.

  • effect of boric acid on metal Transfer mode of underwater flux cored wire wet welding
    Journal of Materials Processing Technology, 2015
    Co-Authors: Yongpeng Du, Yunlong Fu, Jicai Feng
    Abstract:

    Abstract For obtaining high quality of underwater welding repairing for nuclear power equipments, the influence of boric acid on metal Transfer process of underwater flux-cored wire wet welding in boric acid solution is explored by an X-ray transmission system. The research results show that the mixed repelled Globular Transfer and solid short circuit Transfer mode and the mixed repelled Globular Transfer and surface tension Transfer mode are two kinds of main metal Transfer modes during underwater welding in boric acid solution. The proportion of the mixed repelled Globular Transfer and surface tension Transfer mode is increasing with the increasing of concentration of boric acid solution, which is caused by the difference of force condition of the droplet.

R. Kovacevic - One of the best experts on this subject based on the ideXlab platform.

  • Hybrid laser-arc welding of advanced high-strength steel
    Journal of Materials Processing Technology, 2014
    Co-Authors: Wei Liu, Guang Yang, R. Kovacevic
    Abstract:

    Abstract This study investigated the synergetic effect between laser beam and electrical arc during hybrid welding by using a spectral diagnostic technique. The synergetic effect increased the energy density in the keyhole and deepened the weld penetration, resulting in a lower plasma electron temperature. The metal Transfer mode was a Globular one at a small offset distance while a spray mode was achieved with an increase in the offset distance. The decrease in the arc voltage and arc current due to the synergetic effect caused this transition from spray to Globular modes. Globular Transfer mode destabilized the molten pool and keyhole with the large droplet impingement, leading to the formation of porosity in the corresponding weld bead. The presence of porosity was on-line detected by identifying serious fluctuations in the Fe I electron temperature signals based on the fact that the instability of the molten pool and keyhole is strongly related to the signals coming from the plasma.

  • a unified model of transport phenomena in gas metal arc welding including electrode arc plasma and molten pool
    Journal of Physics D, 2004
    Co-Authors: R. Kovacevic
    Abstract:

    This paper presents a theoretical model for describing Globular Transfer in gas metal arc welding. The heat and mass Transfer in the electrode, arc plasma and molten pool are considered in one unified model. Using the volume of fluid method, the transport phenomena are dynamically studied in the following processes: droplet formation and detachment, droplet flight in arc plasma, impingement of droplets on the molten pool and solidification after the arc extinguishes. The simulation of heat and mass Transfer in the arc plasma considers the developing surface profile of the electrode and molten pool and also the effect of the flying droplet inside the arc plasma. Furthermore, the heat inputs to the electrode and the molten pool result from the simulation of the arc plasma. In addition, a He–Ne laser in conjunction with the shadow-graphing technique is used to observe the metal-Transfer process. The theoretical predictions and experimental results are shown to be in good agreement.

  • Droplet formation, detachment, and impingement on the molten pool in gas metal arc welding
    Metallurgical and Materials Transactions B, 1999
    Co-Authors: H. G. Fan, R. Kovacevic
    Abstract:

    A mathematical model is developed to describe the Globular Transfer in gas metal arc welding (GMAW). This work is both theoretical and experimental. Using the volume-of-fluid (VOF) method, the fluid-flow and heat-Transfer phenomena are dynamically studied during the following processes: droplet formation and detachment, impingement of a droplet on a solid substrate, impingement of multiple droplets on the molten pool, and solidification after the arc extinguishes. A He-Ne laser, in conjunction with the shadow graphing technique, is used to observe the metal Transfer processes. Theoretical predictions and experimental results are in close agreement, suggesting that the theoretical treatment of the model is good.

  • Dynamic analysis of Globular metal Transfer in gas metal arc welding—a comparison of numerical and experimental results
    Journal of Physics D: Applied Physics, 1998
    Co-Authors: H. G. Fan, R. Kovacevic
    Abstract:

    A mathematical model to describe the Globular Transfer in gas metal arc welding is developed. This work is both theoretical and experimental. Using the volume-of-fluid (VOF) method, the fluid-flow and heat-Transfer phenomena during the impingement of a droplet on a solid substrate, arc striking, the impingement of multiple droplets on the molten pool and finally the solidification after the arc extinguishes are dynamically studied. A He-Ne laser in conjunction with the shadow-graphing technique is used to observe the metal-Transfer processes. Theoretical predictions and experimental results are shown to be in good agreement, suggesting that the theoretical treatment of the model is sound.

  • dynamic analysis of Globular metal Transfer in gas metal arc welding a comparison of numerical and experimental results
    Journal of Physics D, 1998
    Co-Authors: H. G. Fan, R. Kovacevic
    Abstract:

    A mathematical model to describe the Globular Transfer in gas metal arc welding is developed. This work is both theoretical and experimental. Using the volume-of-fluid (VOF) method, the fluid-flow and heat-Transfer phenomena during the impingement of a droplet on a solid substrate, arc striking, the impingement of multiple droplets on the molten pool and finally the solidification after the arc extinguishes are dynamically studied. A He-Ne laser in conjunction with the shadow-graphing technique is used to observe the metal-Transfer processes. Theoretical predictions and experimental results are shown to be in good agreement, suggesting that the theoretical treatment of the model is sound.

Mauri´cio J. Monteiro - One of the best experts on this subject based on the ideXlab platform.

  • Arc Stability Indexes Evaluation on Underwater Wet Welding
    29th International Conference on Ocean Offshore and Arctic Engineering: Volume 6, 2010
    Co-Authors: Ezequiel Caires Pereira Pessoa, Alexandre Queiroz Bracarense, Leandro F. Ribeiro, Weslley C. Dias, Luciano G. D. Andrade, Stephen Liu, Valter Rocha Dos Santos, Mauri´cio J. Monteiro
    Abstract:

    Underwater wet welding (UWW) with shielded metal arc welding (SMAW) is employed basically in repairs of offshore structures, including platforms, ships and others. The main problems of this type of welds are related, of course, with water presence in the electric arc that causes higher cooling rates, Oxygen and Hydrogen availability in the arc atmosphere and arc instability. Many of research and test welding programs in laboratory are undertaken in shallow water performed by automatic devices using hyperbaric chambers to simulate depths. Also, welding arc signals are acquired using data acquisition systems and the arc stability is estimated through indexes calculated from values acquired and analyzed. It is very well known the reduced stability of the wet welding process at shallow depths — less than approximately five meters. So this effect would be considerable significant since it can be used to make correlations between the arc stability indexes and the welds quality results. The main objective of this work was to evaluate the efficiency of the most used arc stability indexes reported in the literature in detect the arc instability effect of shallow water wet welding. Bead-on-plate welds had been made using a gravity feeding system device inside a hyperbaric chamber, applying straight polarity (DCEN) in ASTM A36 steel plates, using the same weld parameters in two different depths, 0.5 and 20.0 meters. Rutile, basic and oxidizing commercial electrodes types prepared for UWW with 3.25mm rod diameter were used. Visual analysis, bead morphology and arc stability were the criteria used to evaluate the weld quality. The voltage and current arc signals were acquired at 10 KHz rate. The arc stability indexes measured were average voltage and current and its standard deviation, S (Imax/Imin) parameter, voltage and current square mean, arc “re-ignition” voltage and current, metal Transfer time and its deviation, metal Transfer frequency and its deviation, short circuit time and its deviation and the voltage versus current graph area. The results shown that none of the stability indexes tested has been shown to indicate, alone, a good relationship to the surface appearance obtained for the three electrodes studied. The rutile type electrode was the only one that clearly produced better weld appearance at 20 meters than in shallow water depth. The rutile and oxidizing electrodes showed better surface appearance with the increased number of short circuits. For the rutile electrode, the Globular Transfer mode with high voltage were directly related with poor weld bead surface appearance.Copyright © 2010 by ASME

Flavien Valensi - One of the best experts on this subject based on the ideXlab platform.

  • Study of the spray to Globular transition in gas metal arc welding: a spectroscopic investigation
    Journal of Physics D: Applied Physics, 2013
    Co-Authors: Flavien Valensi, Stéphane Pellerin, Quentin Castillon, Amar Boutaghane, Krzysztof Dzierzega, Sylwia Zielinska, Nadia Pellerin, Francis Briand
    Abstract:

    The gas metal arc welding (GMAW) process is strongly influenced by the composition of the shielding gas. In particular, addition of CO2 increases the threshold current for the transition from unstable Globular to more stable spray Transfer mode. We report on the diagnostics—using optical emission spectroscopy—of a GMAW plasma in pure argon and in mixtures of argon, CO2 and N2 while operated in spray and Globular Transfer modes. The spatially resolved plasma parameters are obtained by applying the Abel transformation to laterally integrated emission data. The Stark widths of some iron lines are used to determine both electron density and temperature, and line intensities yield relative contents of neutral and ionized iron to argon.Our experimental results indicate a temperature drop on the arc axis in the case of spray arc Transfer. This drop reduces with addition of N2 and disappears in Globular Transfer mode when CO2 is added. Despite the temperature increase, the electron density decreases with CO2 concentration. The highest concentration of iron is observed in the plasma column upper part (close to the anode) and for GMAW with CO2.Our results are compared with recently published works where the effect of non-homogeneous metal vapour concentration has been taken into account.

  • Study of the spray to Globular transition in Gas Metal Arc Welding : Spectroscopic investigation
    J.Phys.D, 2013
    Co-Authors: Flavien Valensi, Stéphane Pellerin, Quentin Castillon, Amar Boutaghane, Krzysztof Dzierzega, Sylwia Zielinska, Nadia Pellerin, Francis Briand
    Abstract:

    The shielding gas composition has a strong influence on the gas metal arc welding (GMAW) process. In particular, CO2 adjunction increases the current needed for the transition from unstable Globular to more stable spray Transfer. Plasma diagnostic using optical emission spectroscopy was performed using shielding gas composed of argon, argon-CO2 mixtures and argon-N2 mixtures for spray and Globular Transfer. Radial evolution of the studied parameters was determined thanks to Abel inversion: line broadening was used to get electron temperature and density, and intensity measurement yielded to ratio of neutral and ionized iron over argon. Results showed temperature drop on arc axis in the case of the spray arc Transfer. While maximal temperature increases this drop is reduced with nitrogen adjunction and disappears in Globular Transfer when CO2 rich shielding gas is used. On the contrary, the electron density decreases when CO2 is added to argon. The iron content highest values are observed on the upper part of the column, with overall quantity higher in the case of CO2 containing shielding gas. The obtained data were compared to other recent results dealing with the effect of non homogeneous metal vapour concentration.

  • Microstructural analysis of the anode in gas metal arc welding
    Journal of Materials Processing Technology, 2009
    Co-Authors: Sylwia Zielinska, Flavien Valensi, Stéphane Pellerin, Nadia Pellerin, Karol Musiol, Charles De Izarra, Francis Briand
    Abstract:

    The nature of the applied shielding gas has a strong influence on arc stability and Transfer metal mode of the welding process. In particular, increase of the percentage of carbon dioxide in argon induces the increase of the transition current value from the Globular to spray metal Transfer mode. This work shows that these effects are linked to the chemical and microstructural modifications of the anode tip during the gas metal arc welding process. The microstructure of the anode is investigated for various experimental conditions. Transition between the two Transfer modes is linked to the existence and disappearance of a rather insulating oxide "gangue" at the wire extremity whose nature depends of the shielding gas. Chemical reactions at high temperature such as oxidation-reduction reactions between shielding gas and melted metal govern the transition of the spray-arc to Globular Transfer mode.

  • Microstructural analysis of the anode in gas metal arc welding (GMAW)
    Journal of Materials Processing Technology, 2009
    Co-Authors: Sylwia Zielinska, Flavien Valensi, Stéphane Pellerin, Nadia Pellerin, Karol Musiol, Charles De Izarra, Francis Briand
    Abstract:

    Abstract The nature of the applied shielding gas has a strong influence on arc stability and Transfer metal mode of the welding process. In particular, increase of the percentage of carbon dioxide in argon induces the increase of the transition current value from the Globular to spray metal Transfer mode. This work shows that these effects are linked to the chemical and microstructural modifications of the anode tip during the gas metal arc welding process. The microstructure of the anode is investigated for various experimental conditions. Transition between the two Transfer modes is linked to the existence and disappearance of a rather insulating oxide “gangue” at the wire extremity whose nature depends of the shielding gas. Chemical reactions at high temperature such as oxidation–reduction reactions between shielding gas and melted metal govern the transition of the spray-arc to Globular Transfer mode.