Análise da influência dos parâmetros do processo de soldagem com eletrodos revestidos na estabilidade do arco e características geométricas do cordão

Abstract

This work has the aim to analyze the influence of parameters welding current, polarity and arc length in the arc stability and geometrical weld bead characteristics of a Shielded Metal Arc Welding SMAW process. In order to complain with the objectives a prototype of an automatic welding equipment was developed. Based on this equipment a set of tests were design by the use of statistical tools based on the Design of Experiments techniques through a Minitab software. The electrical arc signals, in particular, voltage, were recorded by a data acquisition system and after processed by the use of a fast Fourier Transform (FFT) technique with a low-pass filter with a cut-off frequency of 4 kHz. The arc stability analysis were based on the variation coefficient by the voltage arc signal filtered. The geometrical characteristics and productivity of the welding bead specimens were evaluated by direct recorded dimensions after cross-sectioning, polishing and measuring of the penetration, dilution and bead convexity index, deposition and fusion rate, and deposition efficiency by the use of three different kind of covered electrodes, i.e., rutile, basic and celulosic. It was found that the automatic welding increased the arc stability compared with the manual welding procedure for all covered electrodes. Also the polarity had an important effect in the arc welding stability. The celulosic electrode had a higher arc stability in straight and reverse polarity, despite of its non recommended use in straight polarity, followed by rutile and basic electrodes, but this electrodes not showed conduct variations with the polarity.