What is arc blow?

• A. A deflection of the welding arc due to magnetic fields, causing irregular weld beads.
• B. A nozzle obstruction during welding.
• C. A sudden stop in welding current.
• D. A visual distortion in the weld bead.

Answer: (A)

Arc blow happens when magnetic fields around the welding arc push the arc off its straight path, causing the arc to wander and the weld bead to become irregular. The current flowing through the electrode and workpiece generates these magnetic fields, and nearby ferromagnetic materials or other current paths can distort them, bending the arc as you weld. This leads to an uneven bead with inconsistent width and penetration.

The other scenarios describe problems that aren’t caused by arc deflection: a nozzle obstruction would disrupt shielding gas flow, a sudden stop in current would shut the arc off rather than deflect it, and a visual distortion in the bead can result from optics or heat effects rather than magnetic arc deflection.