Parametric Optimization of Pulsed Current Gas Arc Welding of Dissimilar Welding Between UNS32750 and AISI 321 Based on Taguchi Method

Abstract

In this research, Taguchi method (DOE technique) was used to optimize welding parameters in a dissimilar joint between the duplex stainless steel UNS32750 and the austenite stainless steel AISI 321 for the corrosion resistance. For joining, pulsed current gas arc welding with the ER2594 electrode was used. Pulse current, background current, % on time and current frequency were considered in three levels. Welding conditions were based on the L9 Taguchi’s orthogonal array design of experiment. Signal-to-noise ratio was used to estimate the optimal conditions. The parameters and levels were considered as the optimal conditions in which the higher pitting potential could be obtained. Analysis of variance was carried out to determine the influential effect of each parameter. The pitting potential was evaluated by the potentiodynamic polarization test in the 3.5% NaCl solution at room temperature. Microstructural characterization and mechanical properties of the optimal joint were determined by optical microscopy and Vickers microhardness, respectively. According to the results of Taguchi method, the pulse current of 130 A, the Background current of 60 A, the % on time of 90% and the current frequency of 3 Hz were obtained as the optimal conditions. Pitting potential under optimal conditions (1.03 V) was close to Taguchi prediction (0.99 V). Analysis of Variance also indicated that the most effective parameter on the pitting corrosion was Background current. The percentage contributions of pulse current, background current, current frequency and % on time were 38.01, 32.48, 22.85 and 6.6%, respectively. The results showed that adjusting heat input led to the equal austenite-ferrite proportion.