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São Paulo, Brazil

Do Nascimento V.C.,Air Products Brazil LTDA | Scotti A.,Federal University of Uberlandia
Welding International | Year: 2012

To minimize the detrimental effects of zinc during resistance spot welding of galvanized plates, a technique known as Burn-Zinc is usually employed. However, there is not much information and studies available in the current literature about when and how to use this technique. The objective of this paper is to assess and understand this technique. To do so, a methodology to determine the ideal burn-zinc parameters as a function of the plates was proposed. This methodology was evaluated by a series of welds by systematically varying current and pressure at compatible levels for zinc burning. High-speed filming, synchronized with electrical signals, was employed to visualize and to analyse results. Once the burn-zinc parameters were defined, new welds were performed with and without the burn-zinc application. The proposed experimental procedure was shown to be efficient for checking and parametrizing the burn-zinc technique. However, there was evidence that the application of burn-zinc does not always lead to a reduction in operating time. © 2012 Taylor and Francis Group, LLC. Source


For minimizing the detrimental effects of zinc during resistance spot welding of galvanized sheets, a technique denominated Burn-Zinc is usually employed. However, there is no much information and studies available in the current literature about when and how to use this technique. The present work had the objective of assessing and understanding better this technique. For that, a methodology for determination of ideal burn-zing parameters as a function of the sheets was proposed. The evaluation of this methodology was carried out by a series of weldments, by systematically varying current and pressure at compatible levels for zinc burning. High speed filming, synchronized with the electrical signals, was employing for visualizing and results analyses. Once the burn-zinc parameters were defined, new weldments were done with and without the burn-zing application. The proposed experimental procedure showed to be efficient for checking and parameterization of the burn-zing technique. However, there were evidences that not always the application of the burn-zing will lead to reduction of the operational time. Source


Souza D.,Federal University of Uberlandia | Rossi M.L.,Federal University of Uberlandia | Keocheguerians F.,Air Products Brazil LTDA | do Nascimento V.C.,Air Products Brazil LTDA | And 2 more authors.
Soldagem e Inspecao | Year: 2011

Due to the wide applicability of short-circuiting GMA welding, a fully understanding of the parameter settings on the metal transfer stability turn into an important issue. Bead-on-plate welds were carried out for assessing the influence of voltage, CTWD and up and down current rates over the metal transfer regularity, using 3 commercial shielding gas blends. As comparative criterion, the transfer regularity was quantified through an index taken from voltage and current traces. The results shown that, working with shortcircuits, the setting voltage has strong influence on the metal transfer stability; there is an optimum range. This range is remarkably influenced by the shielding gas type, current value, CTWD and inductance factor settings. The lower the CO2 content in the blend, the more regular the transfer. The inductance factor effect is dependant of the CO2 content in the blend. Source


Souza D.,Federal University of Uberlandia | Rossi M.L.,Federal University of Uberlandia | Keocheguerians F.,Air Products Brazil LTDA | do Nascimento V.C.,Air Products Brazil LTDA | And 2 more authors.
Soldagem e Inspecao | Year: 2011

The MIG/MAG process operating as short-circuiting is widely used when low heat input is a demand. However, in this operating mode, excessive spattering may occur. To mitigate this problem, it is necessary to act on parameter settings. It is known that inductance governs the current increasing/decreasing rate, reflecting on the short-circuiting transfer regularity. However, little is known about the effect of arc voltage and the gas composition on this rate. Thus, in this work it was pursued the influence of the welding voltage and shielding gas composition in the correlation between inductance and metal transfer regularity in short-circuiting MIG/MAG carbon-steel welding. Weldments were carried out scanning the voltage settings at three different inductance settings and with two differed shielding gases, using the same current level. A quantitative criterion was employed to assess the metal transfer regularity. Metal transfer conditions were visualized by means of synchronized high-speed filming shadowgraphy. The results showed that voltage and shielding gas do not interfere in the up and down current rate for a same inductance setting, but the regularity of the process is dependent of the shielding gas composition and arc voltage. Source

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