What is arc blow and how can it be prevented?

• A. Arc deflection caused by magnetic fields in the work circuit; prevent by proper grounding, adjusting lead placement, polarity reversal, and proper joint/welding sequence
• B. Arc blow is a defect caused by only cold joints
• C. Arc blow occurs when the shielding gas is not flowing
• D. Arc blow is caused by voltage fluctuations in the power supply

Answer: (A)

Arc blow happens when the welding arc wanders because magnetic fields in the welding circuit interact with the current flowing through the workpiece and clamps. Those magnetic fields create forces that push or deflect the arc away from the joint, especially when you have long ground leads, fixtures that form magnetic loops, or high current. To keep the arc centered and stable, focus on reducing those magnetic effects: place the grounding clamp as close to the weld as possible with a clean, solid connection, and keep leads short and routed to avoid creating circulating magnetic loops. Adjusting how the leads are arranged—so they don’t reinforce a magnetic field around the joint—can help, and in DC welding, changing the polarity can alter how the magnetic field interacts with the arc. Also plan the welding sequence so current paths don’t concentrate in one area, which minimizes field buildup.

This isn’t caused by cold joints, shielding gas flow, or voltage fluctuations in the power supply, so those factors don’t produce arc blow.