Application of pulse plasma MIG welding process to Al/steel dissimilar joining

Abstract

Arc welding of aluminium and steel joins are commonly inundated by the formation of brittle intermetallic compounds (IMC) at the aluminium-steel interface. As the formation of IMC is closely related to the heat input into the base metals, it is hypothesised that the ability to regulate the heat input would enable the control of the thickness of IMC. This paper proposes the use of a pulse plasma MIGW system to regulate the heat input during the welding process. A shadowgraph method was used to compare the weld droplet stability of the pulse plasma MIGW with a pulse MIGW system. It was found that the plasma MIGW generated a regular heat input into the base metal due to the smoothness of the droplet detachment and resulted in the formation of IMC with uniform thickness. Al/steel joining was then conducted using both pulsed plasma MIGW and pulse MIGW systems, and the resulting IMC formations and thicknesses were evaluated. It was found that the formation and thickness of IMC in Al/steel dissimilar welding can be controlled by using pulse plasma MIGW. Its lower droplet temperature and decreased cooling rate during welding would suppress the formation of Fe2Al5 and FeAl3, and thus decreasing the overall thickness of IMC at the joining interface.