The Formation and Control of Porosity During GMA Welding of Galvanized Steel

GMA lap welding of 1.4 mm thick galvanized steel DP780 was conducted in this investigation. Effects of different welding modes, heating inputs, and assembly conditions on the porosity in weld bead were examined by X-ray nondestructive detection. The experimental results reveal that the number of pores in the weld bead formed with double pulse (DP) mode is the minimum, compared to those formed under direct current (DC), pulse (P), cold metal transfer (CMT) and cold metal transfer and pulse (CMT+P) welding modes. The porosities ratios of the weld bead obtained using high heating input are improved compared to those obtained employing low heating input in DC, P, DP and CMT welding modes, respectively. The escape of zinc vapors through the reserved gap of 1 mm between steel plates effectively lessens the weld porosity, while the number of pores in the weld evidently increases as a copper liner board placed below galvanized steel plates for lap welding.