Abstract

QUEIROZ, Alexandre; CAIRES PEREIRA, Ezequiel; PERDOMO, Lorenzo  and  QUINTANA, Rafael. The influence of the mineralogical composition of waterproof varnish layer of rutile electrodes on porosity in underwater wet welding. Rev.fac.ing.univ. Antioquia [online]. 2009, n.50, pp. 63-76. ISSN 0120-6230.

Waterproof varnish coated rutile electrodes are used frequently in the underwater wet welding because of their good technological behavior. An alternative to improve its behavior would be to incorporate chemical compounds to the waterproof varnish layer. In the present work the results obtained with the addition of an exothermic pyrometallurgical mixture in the first waterproof varnish layer of rutile electrode types 6013 and 7024 are presented. Depending on the temperature of coating, the proposed pyrometallurgical mixture provides oxygen by stages altering the partial pressure of hydrogen of surrounding means. The carrying chemical oxygen element in the pyrometallurgical mixture is reduced until its elementary state, interacting later with the metal in weld pool as deoxidizer. All this process offers a favorable energetic balance to the welding process. Welds were performed at 50 meters deep with electrodes having traditional varnish and varnish with additions. The technological behavior, amount of porous, metallographic structure and chemical composition were measured. For the E6013 electrodes the porosity was reduced to 16% while for the E7024 by 59%.

Keywords : Underwater wet welding; welding rutile electrodes; varnish layer.