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Francis Briand - One of the best experts on this subject based on the ideXlab platform.
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Study of the Spray to globular transition in gas metal Arc welding: a spectroscopic investigation
Journal of Physics D: Applied Physics, 2013Co-Authors: Françoise Valensi, K. Dzierzega, Stéphane Pellerin, Quentin Castillon, Amar Boutaghane, Sylwia Zielinska, Nadia Pellerin, Francis BriandAbstract: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.
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Study of the Spray to globular transition in Gas Metal Arc Welding : Spectroscopic investigation
J.Phys.D, 2013Co-Authors: Françoise Valensi, K. Dzierzega, Stéphane Pellerin, Quentin Castillon, Amar Boutaghane, Sylwia Zielinska, Nadia Pellerin, Francis BriandAbstract: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.
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Microstructural analysis of the anode in gas metal Arc welding
Journal of Materials Processing Technology, 2009Co-Authors: Sylwia Zielinska, Stéphane Pellerin, Nadia Pellerin, Karol Musiol, Charles De Izarra, Francis BriandAbstract: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.
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Microstructural analysis of the anode in gas metal Arc welding (GMAW)
Journal of Materials Processing Technology, 2009Co-Authors: Sylwia Zielinska, Stéphane Pellerin, Nadia Pellerin, Karol Musiol, Charles De Izarra, Francis BriandAbstract: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.
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Investigations of GMAW plasma by optical emission spectroscopy
Plasma Sources Science and Technology, 2007Co-Authors: Sylwia Zielinska, K. Dzierzega, Françoise Valensi, Stéphane Pellerin, Karol Musiol, Charles De Izarra, Francis BriandAbstract:We report on investigations of gas metal Arc welding plasma operated in pure argon and in a mixture of argon and CO2 at a dc current of 326 A. The spatially resolved electron densities and temperatures were directly obtained by measuring the Stark widths of the Ar I 695.5 nm and Fe I 538.3 nm spectral lines. Our experimental results show a reduction of the plasma conductivity and transfer from Spray Arc to globular Arc operation with increasing CO2 concentration. Although the electron density ne increases while approaching the core of the plasma in the Spray-Arc mode, a drop in the electron temperature Te is observed. Moreover, the maximum Te that we measure is about 13 000 K. Our experimental results differ from the Haidar model where Te is always maximum on the Arc axis and its values exceed 20 000 K. These discrepancies can be explained as a result of underestimation of the amount of metal vapours in the plasma core and of the assumption of local thermal equilibrium plasma in the model.
Thomas Kannengiesser - One of the best experts on this subject based on the ideXlab platform.
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Hydrogen-assisted cracking in GMA welding of high-strength structural steels using the modified Spray Arc process
Welding in the World, 2020Co-Authors: Thomas Schaupp, Michael Rhode, Hamza Yahyaoui, Thomas KannengiesserAbstract:High-strength structural steels are used in machine, steel, and crane construction with yield strength up to 960 MPa. However, welding of these steels requires profound knowledge of three factors in terms of avoidance of hydrogen-assisted cracking (HAC): the interaction of microstructure, local stress/strain, and local hydrogen concentration. In addition to the three main factors, the used Arc process is also important for the performance of the welded joint. In the past, the conventional transitional Arc process (Conv. A) was mainly used for welding of high-strength steel grades. In the past decade, the so-called modified Spray Arc process (Mod. SA) has been increasingly used for welding production. This modified process enables reduced seam opening angles with increased deposition rates compared with the Conv. A. Economic benefits of using this Arc type are a reduction of necessary weld beads and required filler material. In the present study, the susceptibility to HAC in the heat-affected zone (HAZ) of the high-strength structural steel S960QL was investigated with the externally loaded implant test. For that purpose, both Conv. A and Mod. SA were used with same heat input at different deposition rates. Both conducted test series showed same embrittlement index “EI” of 0.21 at diffusible hydrogen concentrations of 1.3 to 1.6 ml/100 g of Arc weld metal. The fracture occurred in the HAZ or in the weld metal (WM). However, the test series with Mod. SA showed a significant extension of the time to failure of several hours compared with tests carried out with Conv. A.
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Influence of heat control on hydrogen distribution in high-strength multi-layer welds with narrow groove
Welding in the World, 2019Co-Authors: Thomas Schaupp, Michael Rhode, Hamza Yahyaoui, Thomas KannengiesserAbstract:High-strength low-alloyed (HSLA) steels with yield strength ≥ 690 MPa are gaining popularity in civil engineering and construction of heavy vehicles. With increasing yield strength, the susceptibility for degradation of the mechanical properties in the presence of diffusible hydrogen, i.e., hydrogen-assisted cracking (HAC), generally increases. HAC is a result of the critical interaction between local microstructure, mechanical load, and hydrogen concentration. In existing standards for welding of HSLA-steels, recommendations including working temperatures and dehydrogenation heat treatment (DHT) are given to limit the amount of introduced hydrogen during welding. These recommendations are based on investigations into conventional Arc welding processes. In the past decade, modern weld technologies were developed to enable welding of narrower weld seams with V-grooves of 30°, e.g., the modified Spray Arc process. In that connection, a reduced number of weld runs and weld volume are important technical and, economic benefits. In the present study, the hydrogen distribution in S960QL multi-layer welds with thickness of 20 mm was analyzed. The influence of different weld seam opening angles, heat input, working temperature and DHT were investigated. The results show that weldments with narrow grooves contained an increased amount of diffusible hydrogen. Hydrogen concentration has been reduced by decreasing both the heat input and working temperature. Hydrogen-free weldments were only achieved via subsequent DHT after welding. Furthermore, hydrogen distribution was experimentally determined across the weld seam thickness in HSLA gas metal Arc welded multi-layer welds for the first time.
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Influence of welding parameters on diffusible hydrogen content in high-strength steel welds using modified Spray Arc process
Welding in the World, 2018Co-Authors: Thomas Schaupp, Michael Rhode, Thomas KannengiesserAbstract:In order to satisfy the growing requirements towards lightweight design and resource efficiency in modern steel constructions, e.g., mobile cranes and bridges, high-strength steels with typical yield strength ≥ 690 MPa are coming into use to an increasing extent. However, these steels require special treatment in welding. The susceptibility for degradation of the mechanical properties in the presence of hydrogen increases significantly with increasing yield strength. In case of missing knowledge about how and the amount of hydrogen that is uptaken during welding, hydrogen-assisted cracking (HAC) can be a negative consequence. Moreover, modern weld technology like the modified Spray Arc process enables welding of narrower weld seams. In this context, a reduced number of weld beads, volume, and total heat input are technical and economical benefits. This work presents the influence of welding parameters on the diffusible hydrogen content in both (1) single-pass and (2) multi-layer welds. Different hydrogen concentrations were detected by varied contact tube distance, wire feed speed, Arc length, and varied Arc type (transitional Arc and modified Spray Arc). The results show that all welding parameters have significant influence on the diffusible hydrogen concentration in the single-pass welds. By increasing the number of weld beads in case of multi-layer welding, the hydrogen concentration has been reduced. Whereby, differences in hydrogen concentrations between both Arc types are present.
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Optimization of welding loads with narrow groove and application of modified Spray Arc process
Welding in the World, 2017Co-Authors: Dirk Schroepfer, Arne Kromm, Thomas KannengiesserAbstract:Current efforts for lightweight design result in a growing application of high-strength fine-grained structural steel in modern constructions, e.g. mobile cranes, with yield strength from 960 MPa. The design of welded structures and welding processes becomes more challenging with increasing material strength and elastic ratios. High residual stresses are able to diminish lifetime, load capacity and component safety and should be avoided. Recent analyses have shown strong influences of heat control and restraint of the weld due to arising reaction stresses, superimposing with local residual welding stresses. Modern inverter technologies allowed the development of numerous modified Spray Arc processes driven by power source manufacturers, which provide virtually similar features and several benefits, enabling welding of narrower seams with reduced weld volumes and total heat inputs. This reseArch focuses on welding loads due to modified weld seams. The global reaction forces and moments and their superposition with local residual stresses in welded components due to external shrinkage restraints were investigated using a special testing facility and XRD. The restraint intensity, weld seam geometry and welding process were varied for statistical evaluations of resulting welding loads. When welding under restraint, a reduction of the weld seam volume causes significantly lower reaction stress levels.
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Suitability of high-alloyed flux-cored wire electrodes for laser-GMA hybrid welding
2012Co-Authors: S. Lorenz, Thomas Kannengiesser, G. PoschAbstract:The object of this reseArch project related to investigations into the qualification of flux-cored wire electrodes for the laser-GMA hybrid welding of high-alloyed steels. Because of its annular metal shell and the powdery filling, this type of wire electrode permits stable, low-spatter metal transfer comparable with that in the Spray Arc, particularly in the upper range of the attainable deposition rates. In contrast with this, controlled metal transfer during the deposition of solid wire electrodes is achieved using pulsed Arc technology. When these filler materials are welded, the properties specific to the material and to the process have a significant influence on the weld metallurgy as well as on the process stability. Tests were carried out on the AISI 403L (X2CrNi1911) high-alloyed base material in order to investigate the transferability of the attainable material properties from GMA welding to laser-GMA hybrid welding. Four wire electrodes were used according to DIN EN 12072 and DIN EN ISO 17633: a T 19 9 L P M 1 rutile fluxcored wire designed specifically for welding in position, a T 19 9 L R M (C) 3 rutile flux-cored wire suitable for welding in the flat position, a T 19 9 L M M 1 metal-powder flux-cored wire as well as a G 19 9 L Si solid wire.
Sylwia Zielinska - One of the best experts on this subject based on the ideXlab platform.
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Study of the Spray to globular transition in gas metal Arc welding: a spectroscopic investigation
Journal of Physics D: Applied Physics, 2013Co-Authors: Françoise Valensi, K. Dzierzega, Stéphane Pellerin, Quentin Castillon, Amar Boutaghane, Sylwia Zielinska, Nadia Pellerin, Francis BriandAbstract: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.
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Study of the Spray to globular transition in Gas Metal Arc Welding : Spectroscopic investigation
J.Phys.D, 2013Co-Authors: Françoise Valensi, K. Dzierzega, Stéphane Pellerin, Quentin Castillon, Amar Boutaghane, Sylwia Zielinska, Nadia Pellerin, Francis BriandAbstract: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.
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Microstructural analysis of the anode in gas metal Arc welding
Journal of Materials Processing Technology, 2009Co-Authors: Sylwia Zielinska, Stéphane Pellerin, Nadia Pellerin, Karol Musiol, Charles De Izarra, Francis BriandAbstract: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.
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Microstructural analysis of the anode in gas metal Arc welding (GMAW)
Journal of Materials Processing Technology, 2009Co-Authors: Sylwia Zielinska, Stéphane Pellerin, Nadia Pellerin, Karol Musiol, Charles De Izarra, Francis BriandAbstract: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.
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Investigations of GMAW plasma by optical emission spectroscopy
Plasma Sources Science and Technology, 2007Co-Authors: Sylwia Zielinska, K. Dzierzega, Françoise Valensi, Stéphane Pellerin, Karol Musiol, Charles De Izarra, Francis BriandAbstract:We report on investigations of gas metal Arc welding plasma operated in pure argon and in a mixture of argon and CO2 at a dc current of 326 A. The spatially resolved electron densities and temperatures were directly obtained by measuring the Stark widths of the Ar I 695.5 nm and Fe I 538.3 nm spectral lines. Our experimental results show a reduction of the plasma conductivity and transfer from Spray Arc to globular Arc operation with increasing CO2 concentration. Although the electron density ne increases while approaching the core of the plasma in the Spray-Arc mode, a drop in the electron temperature Te is observed. Moreover, the maximum Te that we measure is about 13 000 K. Our experimental results differ from the Haidar model where Te is always maximum on the Arc axis and its values exceed 20 000 K. These discrepancies can be explained as a result of underestimation of the amount of metal vapours in the plasma core and of the assumption of local thermal equilibrium plasma in the model.
Stéphane Pellerin - One of the best experts on this subject based on the ideXlab platform.
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Study of the Spray to globular transition in gas metal Arc welding: a spectroscopic investigation
Journal of Physics D: Applied Physics, 2013Co-Authors: Françoise Valensi, K. Dzierzega, Stéphane Pellerin, Quentin Castillon, Amar Boutaghane, Sylwia Zielinska, Nadia Pellerin, Francis BriandAbstract: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.
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Study of the Spray to globular transition in Gas Metal Arc Welding : Spectroscopic investigation
J.Phys.D, 2013Co-Authors: Françoise Valensi, K. Dzierzega, Stéphane Pellerin, Quentin Castillon, Amar Boutaghane, Sylwia Zielinska, Nadia Pellerin, Francis BriandAbstract: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.
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Microstructural analysis of the anode in gas metal Arc welding
Journal of Materials Processing Technology, 2009Co-Authors: Sylwia Zielinska, Stéphane Pellerin, Nadia Pellerin, Karol Musiol, Charles De Izarra, Francis BriandAbstract: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.
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Microstructural analysis of the anode in gas metal Arc welding (GMAW)
Journal of Materials Processing Technology, 2009Co-Authors: Sylwia Zielinska, Stéphane Pellerin, Nadia Pellerin, Karol Musiol, Charles De Izarra, Francis BriandAbstract: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.
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Investigations of GMAW plasma by optical emission spectroscopy
Plasma Sources Science and Technology, 2007Co-Authors: Sylwia Zielinska, K. Dzierzega, Françoise Valensi, Stéphane Pellerin, Karol Musiol, Charles De Izarra, Francis BriandAbstract:We report on investigations of gas metal Arc welding plasma operated in pure argon and in a mixture of argon and CO2 at a dc current of 326 A. The spatially resolved electron densities and temperatures were directly obtained by measuring the Stark widths of the Ar I 695.5 nm and Fe I 538.3 nm spectral lines. Our experimental results show a reduction of the plasma conductivity and transfer from Spray Arc to globular Arc operation with increasing CO2 concentration. Although the electron density ne increases while approaching the core of the plasma in the Spray-Arc mode, a drop in the electron temperature Te is observed. Moreover, the maximum Te that we measure is about 13 000 K. Our experimental results differ from the Haidar model where Te is always maximum on the Arc axis and its values exceed 20 000 K. These discrepancies can be explained as a result of underestimation of the amount of metal vapours in the plasma core and of the assumption of local thermal equilibrium plasma in the model.
Françoise Valensi - One of the best experts on this subject based on the ideXlab platform.
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Influence of Wire Initial Composition on Anode Microstructure and on Metal Transfer Mode in GMAW: Noteworthy Role of Alkali Elements
Plasma Chemistry and Plasma Processing, 2018Co-Authors: Françoise Valensi, Q. Castillon, K. Dzierzega, François-xavier Briand, Nicolas Pellerin, Sylvain Pellerin, J.-p. PlanckaertAbstract:Metal Active Gas (MAG) welding in presence of Argon and CO2 mixture as shielding gas is a largely developed process allowing the transfer of the liquid metal from the consumable wire anode to the workpiece according to various modes (short-Arc, globular, Spray-Arc). The CO2 presence in the shielding gas leads to the formation of an oxide layer, or gangue, wrapping the droplet, limiting the access to the Spray-mode transfer, taking into account the low conductivity and the high viscosity of this layer. Several electrodes of various compositions have been tested thanks to Flux Cored Arc Welding, to limit the gangue formation or its negative contribution, based on Ti, La, Zr and alkali metals addition or reduction in silicon content. The results are interpreted considering the metal transfer mode for a given current intensity (330 and 410 A), with various CO2 concentrations in the shielding gas. Finally, the role of the gangue, compared to the other factors governing the droplet detachment, is discussed. A decrease in silicon content limits significantly the gangue formation and gives access to Spray Arc transfer up to 30 vol.% of CO2 at 330 A. Titanium addition leads to the same results. The tests in presence of zirconium proved the conductivity improvement of the gangue. The addition of alkali allows to stabilize the Spray Arc up to the noteworthy value of 60 vol.% of CO2 at 330 A, supporting the hypothesis of a strong influence of viscosity on droplets detachment in the process.
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Study of the Spray to globular transition in gas metal Arc welding: a spectroscopic investigation
Journal of Physics D: Applied Physics, 2013Co-Authors: Françoise Valensi, K. Dzierzega, Stéphane Pellerin, Quentin Castillon, Amar Boutaghane, Sylwia Zielinska, Nadia Pellerin, Francis BriandAbstract: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.
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Study of the Spray to globular transition in Gas Metal Arc Welding : Spectroscopic investigation
J.Phys.D, 2013Co-Authors: Françoise Valensi, K. Dzierzega, Stéphane Pellerin, Quentin Castillon, Amar Boutaghane, Sylwia Zielinska, Nadia Pellerin, Francis BriandAbstract: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.
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Investigations of GMAW plasma by optical emission spectroscopy
Plasma Sources Science and Technology, 2007Co-Authors: Sylwia Zielinska, K. Dzierzega, Françoise Valensi, Stéphane Pellerin, Karol Musiol, Charles De Izarra, Francis BriandAbstract:We report on investigations of gas metal Arc welding plasma operated in pure argon and in a mixture of argon and CO2 at a dc current of 326 A. The spatially resolved electron densities and temperatures were directly obtained by measuring the Stark widths of the Ar I 695.5 nm and Fe I 538.3 nm spectral lines. Our experimental results show a reduction of the plasma conductivity and transfer from Spray Arc to globular Arc operation with increasing CO2 concentration. Although the electron density ne increases while approaching the core of the plasma in the Spray-Arc mode, a drop in the electron temperature Te is observed. Moreover, the maximum Te that we measure is about 13 000 K. Our experimental results differ from the Haidar model where Te is always maximum on the Arc axis and its values exceed 20 000 K. These discrepancies can be explained as a result of underestimation of the amount of metal vapours in the plasma core and of the assumption of local thermal equilibrium plasma in the model.