Arc Blow Welding Defect in DC Current

Arc blow is an undesirable phenomenon in arc welding where the welding arc deviates from its intended path between the electrode and the workpiece.

Causes of Arc Blow

This deviation is primarily caused by magnetic forces acting on the arc. In Arc welding using DC current, a unidirectional current creates a relatively stable magnetic field around the welding circuit. This magnetic field, especially when unevenly distributed or strong, can exert a force on the ionized gases of the arc, deflecting it.

• DC Welding: The steady magnetic field in DC welding can significantly deflect the arc, leading to inconsistent welds, spatter, and incomplete fusion. This effect is more pronounced with direct current electrode negative (DCEN) and direct current electrode positive (DCEP).
• AC Welding: While AC welding also generates magnetic fields, the rapidly alternating polarity of the current tends to neutralize the deflecting forces, making arc blow less common and severe compared to DC welding.
• Other Processes: Gas welding and Thermit welding do not rely on an electric arc in the same manner as arc welding, and therefore, arc blow is not typically encountered in these processes.

Therefore, arc blow is a characteristic defect associated with arc welding processes utilizing direct current.

Conclusion

Arc blow is specifically a defect found in arc welding when using DC current due to magnetic field disturbances.