An attempt has been made to evaluate the effect of welding parameters on the weld penetration, weld bead width and heat effective zone of Tungsten Inert Gas (TIG) welded 2 mm 304L stainless steel joints. The welding parameters including arc current, welding travel speed and gas flow rate were used to achieve the optimum joint. Taguchi technique has been implemented to optimize the welding parameters. Orthogonal array L9 (Three factors with three levels 3x3) was used to study the effect of arc current, welding travel speed and gas flow rate on the quality of 304 stainless steel welds. Signal to a noise ratio (SNR) and the analysis of variance (ANOVA) are also used to determine the main effects of different welding parameters on the weld bead width (WB), weld penetration (WP) and heat affected zone (HAZ). Results showed that welding current has significant effect, whereas gas flow rate showed no effect on the quality of 304Lwelded joints. Welding current of 185A, welding speed of 135mm/min and gas flow rate of 15lit/min have been selected as the best process parameter of weld bead width and weld penetration at level three of experiment seven. However, the optimum process parameter for heat affected zone are level one experimental three at165 A, 235 mm/min, 15 lit/min of welding arc current ,travel speed and gas feeding rate, respectively.

The effect of Traverse speed on the microstructures of friction stir welded 6 mm thick austenitic stainless steel (304) plate has been investigated. Quantitative optical, high resolution scanning electron microscopy and Vickers hardness have been used to qualify and examine the microstructure through the plate cross section. The tool material was used is Tungsten Rhenium. For this work, friction stir welding was performed at rotation speed of 350 revolution per minutes (rpm) and traversing speed from 150 to 250 millimeter per minutes (mm/min) with an interval of 50 mm/min. Fine austenite has been observed in the stir zone, indicating that dynamic recrystallisation with no phase transformation occurred during FSW. The hardness profile is relatively homogeneous with slightly higher values in the stir zone than that of the base metal, suggesting that deformation and the cooling rate are dominant in the FSW process.