Correlação entre a regularidade da transferência metálica no modo curto-circuito com o desempenho do processo para a soldagem MIG/MAG posicional

Abstract

The growing need for application of MIG/MAG welding positional has motivated studies that crave a better understanding of the parameters that directly demonstrate the good performance under certain conditions. An index relevant in comparing the performance between multiple processes is the determination of the heat input. Such measurement is routinely carried out welding with the use of calorimetry, which technique using liquid nitrogen has been one of the best reliability. Other fronts study addresses the analysis of electrical signals monitored during the course of the weld, which also enable the verification of the performance of the process in a more direct and simplified way. While this is fact, so far few studies have led to the application of such techniques in other welding positions, beyond ordinary flat position. Therefore, the present work has as main objective to establish a correlation between the metal transfer short-circuit mode stability, measured by Laprosolda Criterion for Regularity, with the deposition efficiency, heat input and thermal contribution of the MIG / MAG (operating in constant voltage) the most common welding positions. Weldments were performed at 60 ° chamfer preparation with V groove in carbon mild steel using electrode of 1.2 mm diameter ER70S-6, two shielding gases (Ar +25% CO2 and pure CO2) three current ranges (arising from wire feed speed) and three different welding positions (flat, vertical downhill and overhead), enabled through a device for fixing the test plate adapted to a robotic unit. Enjoying the parameters measured and the results obtained for setting practical operating envelope, observed that the position, shielding gas, welding current and inductive effect influenced specifically measured responses (IVCC, short-circuit rate, deposition efficiency, heat input and thermal efficiency). In addition, from obtained results, burn-off rate models were developed (simplified and expanded model), derived from the original equation of consumption in order to have practical results and used for industrial purposes, being the expanded model the one with better experimental fitness and statistical significance.