Influência do molibdênio em propriedades do metal de solda na soldagem molhada com eletrodos óxi-rutílicos

Abstract

the underwater wet welding with coated electrodes technique is undergoing an important use growth in underwater repairs of oil production floating unit's structural elements (up to 20 m depth). However, it presents problems such as increased risk of cold cracking and sharp porosity formation. This work aims to improve the weld metal's mechanical strength through the addition of molybdenum to experimental oxy-rutilic type electrodes. Both the microstructure and the mechanical properties of weld metals were studied while electrodes would receive additional Mo (up to 0.4%). The welds were done using a gravity welding system placed in an underwater welding simulator with an equivalent depth of 10 m. Analyses of micrographics shown that the increased level of Mo in weld metal (a) decreases significantly the average grain size of fine-grained reheated region while (b) increases tensile strength limit without loss of toughness and ductility up to 0,25% Mo approximately.