Investigation of mig welding on dissimilar thickness of metal sheets (steel and stainless steel)

Based on different welding parameters, a welding process between mild steel and stainless steel were performed in this experiment using metal inert gas (MIG) machine. The objective of this experiment was to investigate the effect of welding voltages (15V, 20V and 25V) wire feed rates (80 ipm and 100ipm) and filler metals (ER70S-6 and ER308L) to the microstructure and mechanical properties of the welded mild steel to stainless steel specimens. The microstructure changes and the mechanical properties result from tensile and hardness test were analyzed and compared between the welded zones, heat affected zone (HAZ) and base metal. From the results obtained the grain size of weld zone and HAZ increases when the welding voltage and wire feed rate increases. The strength of the welded joint was directly proportional to the increasing in voltage and wire feed rate but their hardness value was irreversibly proportional towards the increasing parameter value. Filler metal of ER70S-6 shows better result in hardness test while filler metal of ER308L shows better strength in the joint. In conclusion, increasing voltage and wire feed rate will increases the strength but lowered the hardness of the joint. Filler ER308L was suitable to be used to increase strength of the joint while filler ER70S-6 was more suitable in increasing the hardness of the joint