Microstructure Behaviour Evolutions in the Heat-Affected Zone and Fusion Zones of the AISI 304 Stainless Steel Weldment in Double Pass Weld

The purpose of this study was to discuss the effect of the solidification rate on the microstructure of AISI 304 in various zones such as the fusion zone and heat-affected zone. In this experimental work Gas Metal Arc (GMA) Welding was used to bond AISI 304 stainless steel plates of 6-mm thick in a double pass with ER-308 filler wire. Welding was carried out by selecting the process parameters. The shielding gas used in this experimental work was pure Argon (Ar) to weld the AISI 304 steel. Microstructure and hardness of the various zones, i.e. Heat affected zone (HAZ), Fusion zone(FZ), and parent metal zone were investigated by using optical microscopy and the result revealed that the primary weld microstructures of weldments were austenite with δ-ferrite and contents of δ-ferrite in the weld zone increased by increasing the number of passes of weld hence, the hardness of weldment increased, as the number of passes of weld increases, and it was also observed that microstructure of fusion zone exhibited dendritic structure contained lathy and skeletal δ-ferrite.