Operational behavior assesment of coated tubular electrodes for SMAW hardfacing

Coated electrodes for SMAW have presented their advantages for longer than one century. Means of boosting their performance, in especial for hardfacing, would be an increase in the alloying transfer efficiency and a lowering in dilution with the substrate, without losing the production capacity. In this work is described an evaluation study about the operational behavior of experimental coated tubular electrodes for hardfacing, comparatively to a conventional commercial coated electrode. Bead-on-plate welds were carried out, covering a wide range of setting current. Through processing of the instantaneous voltage and current signals, the metal transfer behavior of the electrodes was determined at each current. Fusion and deposition rates, and respective deposition efficiency, were measured by weighing electrode and test plates before and after weldings. The geometric parameters were taken from cross sections from the weldments and the dilution was calculated. The outputs were analyzed under conditions of either the same current or the same bead volume. Justifications for the behavior differences were proposed and discussed. It was concluded that, from the operational point of view, the coated tubular electrodes present a favorable performance in comparison to the conventional coated electrode, making possible to reach lower dilutions yet keeping the same deposition rates. These results encourage further researches aiming the exploitation of this fabrication conception of SMAW electrodes.