STUDY THE INFLUENCE OF WELDING PARAMETERS BY TAGUCHI’S DESIGN ON THE MECHANICAL PROPERTIES OF WELDED MILD STEEL (S235JR)

Gas metal arc welding is a leading process in fusion welding with increased productivity and good quality. The welding parameters are crucial in determining welding quality, cost, and productivity. In this study, mild steel with a 10-mm-thick sheet was welded by gas metal arc welding under predetermined parameters of welding voltage, wire feed speed, and groove shape. The analysis made by Taguchi’s design to investigate the effect of these parameters on tensile strength and Vickers micro-hardness of welding. The microstructure of the fusion zone and heat-affected zone is analyzed to monitor their change concerning the mechanical properties. The results showed that tensile strength decreased with decreased hardness. Also, the tensile strength and hardness were higher (a maximum of 305 MPa and 2170 HVN) at welding made at a lower voltage (20 volts), lower wire feed speed (5.9 m/min), and V-shaped base metal groove. The increased precipitation of perlite structure was shown during welding, which has lower tensile strength and hardness. Widmanstatten ferrite and coarser α-ferrite were presented for welding with a lower cooling time. Taguchi’s design showed that voltage at 20 volts has the highest effect on tensile strength, followed by wire feed speed at 5.9 m/min and V-shaped welding.