Microstructural analysis of the anode in gas metal arc welding (GMAW)

Zielińska, Sylwia; Valensi, Flavien; Pellerin, Nadia; Pellerin, Stéphane; Musioł, Karol; Izarra, Charles de; Briand, Francis

doi:10.1016/j.jmatprotec.2008.08.023

Cited by 19 publications

(10 citation statements)

References 14 publications

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“…The microstructural modifications of the anode tip during the MIG-MAG welding process as a function of the gas composition, must be also taken into account. These measurements are currently investigated using SEM (Scanning Electron Microscopy) analysis [24].…”

Section: Resultsmentioning

confidence: 99%

“…On the other hand, the vaporization of the electrode strongly changes the plasma composition by increasing its electric conductivity because of the presence of an important proportion of metallic vapors in the central part of the arc column; the tension of arc decreases then strongly. -The progressive increase in the CO 2 rate in the shielding gas produces the formation of an insulating layer on the drop surface of which thickness (and thus electric resistance R wire−arc ) increases with the CO 2 admixture for given arc current, but decreases when the arc current increases at given CO 2 rate [24]. This insulating layer thus leads to an increase in the arc voltage proportional to its thickness, without notable lengthening of the arc column.…”

Section: Influence Of Arc Currentmentioning

confidence: 99%

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Gas influence on the arc shape in MIG-MAG welding

Zielińska

Pellerin

Valensi

et al. 2008

Eur. Phys. J. Appl. Phys.

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Composition of the applied shielding gas has a strong influence on physical properties of the plasma and parameters of the welding process. In particular, increase of the percentage of carbon dioxide in argon results in an increase of the transition current value while changing from the globular to spray mode of metal transfer during the welding process. In order to explain this phenomenon, the MIG/MAG welding arc plasma was investigated for different mixtures of argon and carbon dioxide in the shielding gas. Applying a fast camera, recording distribution of spectral lines of the plasma components, we noticed some phenomena not described yet in the literature. Especially, there is a limit in the percentage of relative concentration CO2/Ar beyond which the arc shape is significantly modified.

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Section: Resultsmentioning

confidence: 99%

Section: Influence Of Arc Currentmentioning

confidence: 99%

Gas influence on the arc shape in MIG-MAG welding

Zielińska

Pellerin

Valensi

et al. 2008

Eur. Phys. J. Appl. Phys.

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“…In the same time, CO 2 presence in the shielding gas favors the formation of an of oxide gangue at the extremity of the wire, by chemical oxidation-reduction reaction [27]. This bad conductor layer hinders the current transfer and the arc needs a larger attachment zone all around the droplet.…”

Section: Thermophysical Properties Of the Plasma And Possible Effectsmentioning

confidence: 99%

Plasma diagnostics in gas metal arc welding by optical emission spectroscopy

Valensi¹,

Pellerin²,

Boutaghane³

et al. 2010

J. Phys. D: Appl. Phys.

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The plasma column in the metal inert gas welding process is investigated by optical emission spectroscopy and high-speed imaging. The concentration and repartition of iron vapours are measured and correlated to the plasma and electrode geometric configuration. Plasma temperatures and electron densities were also measured for each studied position in the plasma. The temperatures are calculated using two different methods, allowing validation of the local thermodynamic equilibrium state of the plasma. The results show a maximum temperature of 12500 K on the arc upper part, away from the arc axis. The iron concentration reaches a maximum of 0.3% close to the anode and strongly decreases along both the vertical and the radial directions. The plasma thermophysical properties, calculated from this plasma composition, are then discussed regarding the metal transfer mode.

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“…However, it is also suited for operating in spray and pulsed transfer modes (American Welding Society, 1991). It was reported by Zielinska et al (2009) that the addition of carbon dioxide to the argon shielding gas promotes a globular transfer mode, which can be seen in Figure 24, where the addition of 15% CO2 to the argon shielding gas changes the transfer mode from spray to globular. This was found not to be as stable as the spray arc transfer mode at the same currents without the addition of the carbon dioxide.…”

Section: Argon / Carbon Dioxidementioning

confidence: 88%

“…Showing effect on transfer mode of carbon dioxide addition to argon shielding gas(Zielinska, et al, 2009).…”

mentioning

confidence: 99%

Effects of cold metal transfer welding on properties of ferritic stainless steel

Magowan¹

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Stainless steels are a classification of materials that have been available for over 100 years and over that time manufacturers have created variations on chemical composition and manufacturing route, to create materials that meet specific criteria set by the consumer. One type of stainless steel, ferritic, is restricted in applications as a result of a reduction in properties, namely toughness, when it is welded as a result of grain coarsening in the heat affected zone. Welding equipment manufacturers are constantly incorporating new technologies and capabilities into welding equipment, to make welding easier and create better welds, which then gives that manufacturer a competitive advantage. Cold Metal Transfer (CMT) welding is one such innovation and is claimed by the manufacturer to be a lower heat input process. This research project examines the effects of this lower heat welding process, on the joining of ferritic stainless steels to determine if CMT can reduce the detrimental effects, seen in this material, through welding. The research examines the mechanical and metallurgical effects of using the Cold Metal Transfer (CMT) welding process to weld various grades of ferritic stainless steel including, EN1.4016, EN1.4509, EN1.4521 and EN1.4003 and compares them to welds created using a standard Gas Metal Arc Welding (GMAW) technique, with comparisons made using tensile testing, hardness testing, impact testing, fatigue testing and microstructural characterisation. Experimental results show that grades such as EN1.4016 and EN1.4003 are more sensitive to the welding process due to a phase change to martensite present within the heat affected zone. Work has been conducted to determine the temperature at which ferrite transforms to austenite, prior to transformation to martensite under non equilibrium cooling. Some of the findings from this work included; Fatigue testing and microstructural characterisation has shown a benefit in properties for using CMT over the conventional GMAW process for the EN1.4003 material. A relationship has also been proposed which examines the effect of the percentage of fusion zone defects on the fatigue life of the welded joints. Overall it was found that there was variation in the voltage and current by 1.9 Volts and 15 Amps respectively through a 400mm weld. The ALC settings from-30% to +30% affected the net heat input by 6J/mm NDT techniques utilised in the study were ineffective at detecting the lack of side wall fusion evident in some of the welds.

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Microstructural analysis of the anode in gas metal arc welding (GMAW)

Cited by 19 publications

References 14 publications

Gas influence on the arc shape in MIG-MAG welding

Gas influence on the arc shape in MIG-MAG welding

Plasma diagnostics in gas metal arc welding by optical emission spectroscopy

Effects of cold metal transfer welding on properties of ferritic stainless steel

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