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Exothermic Additions in a Tubular Covered Electrode and Oxidizing Reactions Influence on Underwater Wet Welding

[+] Author Affiliations
Ezequiel C. P. Pessoa, Alexandre Q. Bracarense

Federal University of Minas Gerais, Belo Horizonte, MG, Brazil

Stephen Liu

Colorado School of Mines, Golden, CO

Paper No. OMAE2007-29734, pp. 259-268; 10 pages
doi:10.1115/OMAE2007-29734
From:
  • ASME 2007 26th International Conference on Offshore Mechanics and Arctic Engineering
  • Volume 4: Materials Technology; Ocean Engineering
  • San Diego, California, USA, June 10–15, 2007
  • Conference Sponsors: Ocean, Offshore and Arctic Engineering Division
  • ISBN: 0-7918-4270-3 | eISBN: 0-7918-3799-8
  • Copyright © 2007 by ASME

abstract

During Underwater Wet Welding (UWW), the water that surrounds the arc decomposes liberating large amount of hydrogen and oxygen. As a consequence of the presence of these gases in the arc atmosphere and weld pool, porosity in the weld metal occurs. In the past years, many research programs had been carried out with the objective to reduce or eliminate porosity in wet welds. A simple way to accomplish this goal is using chemical elements or ingredients to promote or avoid certain chemical reactions in the weld pool. In conventional stick (shielded metal arc - SMA) electrodes, it is possible to add alloying elements or other ingredients through the external covering. A tubular covered electrode (TCE) (a hybrid process between SMA and flux cored arc - FCA welding) allows the addition of reactive elements in the hollow rod, separate from the other ingredients used in the flux covering. This way, it is possible to use exothermic elements, placed inside the tube, to control the oxidation reactions, but limiting these reactions to the arc plasma and in the weld pool. Exothermic additions in welding consumables can promote desirable oxidation reactions, change the metal transfer mode, reduce the cooling rate, and decrease the electrical dependence of the welding process. Theoretically, the application of flux cored shielded metal arc (FC-SMA) welding with exothermic additions will permit better control the weld metal composition and reduce the porosity in wet welds. This paper describes underwater wet welding with tubular covered electrodes that contain exothermic additions such as (CaC2 ) and aluminum (A1), and the influence of these ingredients on weld metal composition and porosity.

Copyright © 2007 by ASME
Topics: Welding , Electrodes

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