Avaliação de fluxos visando a aplicação em cobrejunta moldável não permanente em soldagem de passe de raiz por mig/mag

Abstract

In this work, it was proposed to evaluate different flux compositions that could be used in non-permanent moldable backing, for welding root passes deposited by the MIG/MAG welding process with high current (high production). In this context, the objective of the work was to gather knowledge of the effects of the physical-chemical characteristics of flux on the performance of this raw material in the manufacture of moldable backing. A method was developed for using flux as a backing, simulating the conditions of a moldable backing in a welding joint, thus avoiding masking the results by the binders of a non-permanent moldable backing. Criteria for the non-acceptability of root passes, based on bead geometry and production capacity, were proposed and applied in performance analyses. Five different types of non-commercial fluxes were evaluated (different basicities, particle sizes, and melting points), under a single welding current condition (spray transfer) and a root gap range. Root passes were made with each flux at different welding speeds, to determine the maximum welding speed capacity with each flux. A statistical analysis to differentiate means and uncertainty reduction was applied as an analysis tool. The effects of each flux on the root geometry (convexity index, regularity, and reinforcement depth). Optical microscopy was used to evaluate the effect of the slag-metal reaction on the microstructure. In conclusion, it was found that the 3 characteristics of the fluxes act concurrently on the performance of the copper joint. Coarser particle size fluxes have a moderate effect in terms of increasing production capacity. On the other hand, coarse grain size provides root reinforcement with greater depth, which is also achieved by more acidic fluxes. Finally, for fluxes with similar basicity index and grain size, fluxes with lower melting temperatures attributed more regular and fewer convex beads.