Effect of welding current on morphology and microstructure ofAl alloy T-joint in double-pulsed MIG welding
(State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body,
Hunan University, Changsha 410082, China)
Hunan University, Changsha 410082, China)
Abstract: The effect of current on the morphology of Al alloy T-joint in double-pulsed metal inert gas (DP-MIG) welding process was investigated by simulation and experiment. A three-dimensional finite element model and the DP-MIG heat source of double-ellipsoidal volumetric model were developed to simulate the temperature and stress fields under different welding conditions. The macro-morphology and microstructure of welding joints at the corresponding currents were observed in the experiment. The results show that the best condition is at an average current of 90 A and current difference of 40 A, when the maximum temperature is 200 °C higher than the fusion points, with the temperature difference of about 100 °C and stress change of 10 MPa between thermal pulse and thermal base. Under these conditions, Al alloy T-joint with proper fusion condition has smooth fish-scale welding appearance and finer microstructure. Furthermore, the thermal curves and stress distribution in the experiment are consistent with those in the simulation, verifying the precision of the welding simulation.
Key words: double-pulsed MIG welding; Al alloy T-joint; welding current; stress