Effect of preheating temperature of GTAW on weldability of the ferritic ductile cast iron

In this investigation effect of preheating temperature of the GTAW process on weldability of the ferritic ductile cast iron has been studied. The ductile cast iron plates were welded in butt joint design by GTAW with ERNiCu-B wire in different preheats (100-600) temperature. The XRF was used for determining of the chemical analysis of the weld metals. The OM and SEM were used for study of the microstructure characteristics of weld metal, fusion line and HAZ at different samples. In addition tensile, hardness and impact test were used for determining of mechanical properties of the weld metal and HAZ of different samples. The OM and chemical analysis of different samples weld metals result shows, that by increasing of the preheat temperature, the solidification time, percent of dilution, percent of the Fe, Si, Mn, C elements in the weld metals were increased while the tensile strength and hardness of the weld metals were increased. The hardness of UMZ and PMZ were reduced when the preheating temperature increased. The SEM and OM of the HAZ result shows, that the HAZ width increased and the graphite nodule size and volume fraction of the ferrite phase in the microstructure were changed when the preheating temperature increased, also the hardness of the HAZ decreased and impact energy increased. In a general summary, the 400 is the appropriate temperature for preheating of the welding of the ferritic cast iron by GTAW.