Mechanical Properties of Gas Metal Arc Weldments of AISI 304 Stainless Steel Using Different Shielding Gas Compositions

In this work, gas metal arc welding of AISI 304 stainless steel at varying compositions of argon-CO2 shielding environment was performed using an established optimum parametric combination. Thereafter, investigations on the microstructure of the welded joints and mechanical properties of the weldments were carried out. Weldments of excellent surface quality that are void of spatters and pores were obtained when the shielding gas composition (wt.%) range is between 100% argon and 75% argon - 25% CO2. Increasing percentage composition of CO2 beyond 25% resulted in irregular bead formation characterized with spatters and pores. The hardness of the welded joint became significantly high as the CO2 composition in the shielding gas increased. The highest value of 310 HV was obtained when the shielding gas composition was 5% argon- 95% CO2. The least (220 HV) was obtained when the shielding gas was 100% argon. High ultimate tensile strength (596 - 378 MPa) was achieved when the shielding gas composition range is between 100% argon and 75% argon-25% CO2. The UTS dropped significantly as the CO2 composition in the shielding gas increased beyond 25%. It decreased from 336 MPa at 70% argon-30% CO2 shielding gas composition to 133 MPa when 100% CO2 was utilized as the shielding gas. At the end, the effects of the CO2 addition and suitable composition of CO2 addition to argon shielding environment during GMAW of AISI 304 stainless steel have been established.