Estudo exploratório dos efeitos das variáveis de soldagem por arco submerso sobre depósitos de revestimento duro utilizando fluxo ligado

Abstract

The wear resistant coatings industry operates in the areas of manufacturing and repair of parts and equipment for applications that require good performance under abrasive conditions. The challenge of the coating industry is the increase of the production combined with the gains of quality. SAW adds high rates of welding speed and deposition with a good surface finish of the weld bead, so this technique fits as a tool with great potential for applications of these coatings, mainly with the use of alloy flux. However, the lack of studies associated to the use of the submerged arc and alloy flux in hardfacing, slows the technological advance. Motivated to this, this work aims to contribute to the study of the exploration of the effects of the variables of submerged arc welding applied to hard coatings using alloy flux on aspects of the weld bead. Using alternating current, the voltage and the parameters of intensity and time of the current in a certain polarity (offset and balance), composed the control factors to be studied. Afterwards, the geometric profile, visual aspects, microhardness, analysis of chemical composition by EDS (Energy Dispersive System) and microstructural characterization were evaluated. Was used the AWS SFA-5.17 EL12 electrode with 3.2 mm diameter, base metal ASTM A36 and alloy flux DIN 8555/UP-1-GW-350. The results showed that offset was the factor that most influenced the surface porosity and the balance caused a greater variation in the weld deposition. The welding energy was affected only by the voltage. The 50% increase in voltage proved that it is possible to add higher Mn, Cr and Si contents in the melt zone and, consequently, increase the hardness by 87.5%. The welded samples with higher energy were characterized by a dendritic structure in the molten zone accompanied by microssegregation of alloying elements, with microstructure composed of bainite, martensite and Widmanstatten ferrite. And for welded samples with lower energy, in the molten zone, the microstructure was martensite, acicular ferrite, allotriomorphic ferrite and Widmanstatten ferrite.