What is the primary cause of undercut in a weld?

The primary cause of undercut in a weld is associated with too high voltage and too high travel speed. When the voltage is excessively high, it can lead to a focused arc that penetrates deeply but does not allow sufficient time for the molten material to flow adequately. This results in the edges of the weld being heated too intensely, causing the base metal to melt away and create a groove or undercut along the edges of the weld.

Additionally, when the travel speed is high, there is less heat input into the welded joint. This combination can prevent the molten metal from adequately filling the joint, leaving a weakened area that is evident as an undercut. Understanding the welding parameters and their relationship to the welding process is crucial for achieving a sound joint and avoiding defects like undercut. Adjusting both voltage and travel speed, along with other variables, is essential for proper weld formation.