Process Variables:

In GTAW , the primary variables are arc voltage (arc length), travel speed, welding current,  and shielding gas. The amount of energy generated by the arc is proportional to the voltage and current. The amount transferred per unit length of weld is inversely proportional to the travel speed. In helium the arc is more penetrating than that in argon. However, because of all these variables interact powerfully, it is impossible to treat them as truly independent variables while establishing welding procedures for fabricating specific joints.