What is a primary cause of arc blow in shielded metal arc welding?

Arc blow is primarily caused by distortion in the electromagnetic field around the welding arc. This phenomenon occurs when there are imbalances in the magnetic field, which can be affected by nearby magnetic materials, incorrect workpieces, or even the configuration of the welding leads. When the arc blow takes place, it can cause the arc to stray from the intended welding path, making it difficult to maintain a stable arc and leading to inconsistent weld quality.

The presence of nearby magnetic fields can create a situation where the arc is deflected away from the weld pool, making it challenging for the welder to maintain control. Understanding the factors that influence the electromagnetic field is crucial for welders to mitigate this issue effectively, ensuring that the arc remains stable and the welding process produces strong, clean welds.

In contrast, factors like insufficient electrode length, high humidity levels, and excessive welding speed are not intrinsic to the electromagnetic characteristics that lead to arc blow. While those factors can affect the welding process in various ways, they do not primarily cause the distortion in the electromagnetic field that is at the root of arc blow.