6. Variant-controlled pulse keyholing PAW
In normal keyhole PAW, the keyhole is maintained open and
stable to ensure weld quality. To this end, the welding process
parameters, especially the welding current, have to be within a
narrower range [16]. If the welding current is a little bit lower,
the keyhole may be closed, but if the welding current is a little bit
higher, the volume of keyhole expands too large and there is a tendency
of the molten metal being blown away from the weld pool,
causing burn-through or cutting instead of joining. To overcome the