AAZ stands for arc attachment zone. It is the exact region on the base metal where the plasma column of the arc transfers current and heat into the workpiece. The size and stability of this zone dictate the penetration profile and the width of the resulting weld pool.
Heard on the job
If you lose shielding gas, the AAZ wanders all over the joint and you get terrible spatter.
Related terms
Arc blow
A DC arc pushed sideways off the joint by unbalanced magnetic fields in the work, making the bead wander.
Puddle
Shop word for the weld pool, the molten metal under the arc that the welder watches and steers.
Penetration
How deep the weld fuses into the base metal or the joint beyond the original surface.