The Effect of Weld Gas Flow Rate on Al-Li Weldability

Adequate shield and plasma gas flow rate during plasma arc welding are crucial factors in achieving high quality welds. Too low a shield gas flow rate lets atmosphere enter into the arc and too high a rate wastes weld gas and may cause turbulence and entrain atmosphere. Sufficient plasma gas flow is required for keyhole welding and, as shown in this paper, can reduce hydrogen contamination in the weld. In-situ optical spectroscopy used to detect oxygen and hydrogen in the welding arc during variable polarity plasma arc (VPPA) welding of aluminum 2090 revealed that there is an easily detected critical shield gas flow rate needed to exclude atmosphere and that this critical rate can be used to automatically control gas flow rates during welding.