3-D porosity in T-welded connections repaired by grinding and wet welding

This work presents a methodology to create 3-D porosity into finite element models of T-welded connections repaired by rectangular grinding and filled with wet welding. In a wet welding process, the porosity increases with water depth, as a result, the developed wet welding can present low mechanical properties. T-welded connections are employed to fabricate fixed platform, which are used to exploit hydrocarbons located in shallow waters and because they are subjected to dynamic loads, so cracking can occur in such connections. Therefore, a combination of grinding and wet welding repair techniques can be used to repair damage in such offshore structures. To define the level of porosity, it was performed a metallographic analysis at the weld toe of T-welded connections which were grinded with a width of 4 mm and two grinding depths of 6 and 10 mm using conventional grinding equipment. Then, those grinded regions were filled by wet welding employing the shielded metal arc welding (SMAW) and a hyperbaric chamber simulating the different water depths: 50, 70, and 100 m. To apply the wet weld beads, there were employed E6013 coated electrodes with vinyl varnish. So, for the porosity analysis, samples were extracted from T-welded connections, which were analyzed employing an optical microscopy (OM) and scanning electronic microscopy (SEM). Results showed that the porosity can appear in spherical and elliptical shape in low part of every weld beads, and the pores are aligned at the bottom of the lower weld beads, while in the upper weld bead there was no porosity. The experimentally analyzed levels of porosity were created in the 3-D finite element models of the T-welded connections in the wet weld beads.