Special features of double pulsed gas metal arc welding

Since the pulsation of heat input provides a flexible and effective way to control temporal variation of weld pool geometry, cooling rate and solidification parameters, double pulsed (DP) gas metal arc welding (GMAW) serves as an unique tool for controlling the structure and properties of welds. A comprehensive model of DP-GMAW, when adequately tested with experimental data, provides a powerful tool for achieving predictable, high-quality welds. Here we develop a three-dimensional, transient, numerical model of DP-GMAW and test it against carefully planned experiments. The variation of current amplitude enables tailoring of weld attributes such as geometry, cooling rates, solidification parameters and microstructure and its role in the welding of an aluminum alloy is examined both experimentally and theoretically. Since the grain size in the fusion zone is significantly affected by its cooling rate, experimental measurements of grain size for various current amplitudes are correlated with the corresponding computed cooling rates at a constant heat input. Results indicate that cooling rates can be increased and grain size can be refined at a constant heat input while using DP-GMAW. The current amplitude of DP-GMAW can be used to adjust the average cooling rate without changing the heat input. The effects of current amplitude on the fusion zone geometry, cooling rates, solidification parameters, and grain size are investigated for improved understanding of DP-GMAW.