Study on insufficient fusion of NG-GMAW for 5083 Al alloy

The lack of fusion at sidewall is one of the most frequently occurred problems in narrow-gap gas metal arc welding for joining thick plates of aluminum alloys. For better understanding the sidewall fusion mechanism and eventually solving such a problem, a series of welding experiments were carried out to investigate the sidewall penetration characteristics for 5083 Al alloys under various technological conditions. A Taguchi method was adopted to study the effect of welding current, arc voltage, and welding speed on the sidewall penetration and surface concavity, which is related to the quality of welding joint. The result shows that higher welding current or lower welding speed will contribute to a better fusion between weld bead and sidewalls; thus, optimized welding parameters can be obtained. The analysis of formation mechanism for lack of fusion defect shows that the molten pool surface tension, which is greatly influenced by temperature and oxide, is a main reason. Therefore, increasing the heat input to sidewalls by arc-swing, improving the gas protection of molten pool against oxidization, or reducing the heat dispersion of molten pool by preheating, are all effective measures for eliminating the lack of sidewall fusion defect.