Effect of Nano TiO2 Flux on Depth of Penetration and Mechanical Properties of TIG-Welded SA516 Grade 70 Steel Joints—An Experimental Investigation

This research investigates the application of activated tungsten inert gas (A-TIG) welding on boiler grade SA516 Grade 70 carbon steel using nano titanium dioxide (TiO2) nano flux to enhance weld penetration depth, microstructure, and mechanical properties. A unique flux application technique was devised and experiments were carried out. Response Surface Methodology (RSM) was utilized to optimize weld parameters, namely arc length, welding current, and travel speed.The selection between A-TIG and TIG welding significantly influences penetration depth, as A-TIG benefits from arc constriction and elevated current density. The welding speed is crucial for controlling heat input, whereas current and arc length enhance penetration by influencing arc force and energy distribution. Optimizing all three parameters guarantees optimal penetration and weld quality. Microstructural research revealed enhanced mechanical properties in A-TIG weldments, distinguished by acicular ferrite in the fusion zone, which augmented toughness and tensile strength (520 MPa) compared to TIG weldments (470 MPa) and the base metal (480 MPa). Although A-TIG welds exhibited reduced impact toughness (68 J) relative to the base metal (128 J), A-TIG joints had superior ductility. The findings of this research clearly demonstrate the A-TIG welding process improved the depth of penetration and mechanical strength of the weld joints.