Avaliação da aplicabilidade da máquina para soldagem ER para avaliar a influência da polaridade da corrente na taxa de fusão dos eletrodos revestidos

Abstract

Welding with coated electrodes is an important manufacturing process and a better understanding of this area is fundamental. In the literature, many studies comparing the polarity influence of the welding current on the melting rate of coated electrodes are found. The tests are done using one electrode at a time in the positive electrode polarity (CCEP) and then in negative electrode polarity (CCEN) or vice versa. Results show that the electrode in the negative polarity has a higher fusion rate. This work aimed to evaluate the use of an ER welding machine for this purpose when the two electrodes are used at the same time, one against each other and each with its polarity. For this, the machine was adapted so that in a test 2 equal electrodes were used. The parameters of current, tension, time, initial and final length of the electrodes were computed and the melting rate was calculated for each of the electrodes (positive and negative polarity). The results showed values contrary to expected because the electrode fusion rate was higher with the electrode in positive polarity than in the negative polarity. Further tests were made to evaluate the influence of other parameters, such as position and arc length. New results suggested a very small influence of these parameters. The fact that the electrode fusion rate with the positive polarity is higher may be related to the interaction of plasma jets, and the negative electrode is predominant (known fact of the literature) and thus pass on an add heat to the tip of the electrode positive causing a faster fusion of it. It was concluded that the proposed test cannot be used because the dynamics of the process change when an electrode is positioned against the other. Also, it was also concluded that a longer arc length generates greater heat loss and therefore lower fusion rates.