Effect of welding current and sheet thickness on microstructural and mechanical properties of MIG welded mild steel plates

Abstract

In this study, the effects of the process parameter of the Metal Inert Gas welding on the microstructural evolution, grain size variation of different zones, impact energy, microhardness and depth of penetration in IS 2062 Grade B mild steel have been inspected. The welding was carried out manually using different welding current and different sheet thickness values. Increase in the current value resulted in increase of the grain size and maximum value of 15.93 μm was observed in the metal coarsening zone. lowest grain size was found to be 7.82 μm in the grain refinement zone and all were by the help of ImageJ software, by using the intercept method. Microscopic of the weld cross-sections, were also conducted to observe and distinguish the microstructure of fusion zone and heat affected zones. Maximum and minimum hardness values were found as 327.4 Hv and 237.5 Hv, in the grain refinement and fusion zone, respectively. Impact energy was calculated and showed a variation from 178.4J/cm2 to 66.81J/cm2 , as the highest and lowest value, for different samples. Depth of penetration for each of the weld cross-section was measured and co-related with welding current and sheet thickness.