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Abstract
In this study, the effect of shielding gas (Ar, Ar/CO2, Ar/O2 and Ar/He/O2) and transfer mode (short circuit and pulsed current) in MIG/MAG welding with ER-NiCrMo-3 wire to produce bead-on-plate deposits and root passes in ‘V’ joints of ABNT 1020 steel were analysed. The most favourable results in root pass welding were obtained with pulsed current, employing a ‘V’ joint with a 90″ aperture and Ar+25% CO2 atmosphere. The use of shielding atmospheres with 20% helium and a low percentage of active gas did not produce the expected results, being effective only in bead-on-plate weld deposition. However, it was not very effective to produce satisfactory results in root pass welding. Poor results were obtained in welding with short-circuit transfer regardless of the shielding gas used and when an atmosphere of pure argon was used, regardless of the mode of transfer.