What adjustment is likely to correct the problem of undercutting while arc welding?

Reducing the current can indeed help correct the problem of undercutting in arc welding. Undercutting occurs when the welding arc is too intense or the heat input is too high, causing the base metal on either side of the weld bead to melt away unintentionally. By lowering the current, you decrease the heat input, which helps to minimize the chances of excessive melting at the edges of the weld. This adjustment allows for a more controlled weld bead formation and better fusion between the base metal and the weld metal, ultimately leading to a cleaner and stronger weld without undercut.

In contrast, increasing the voltage would typically increase the heat input, which could exacerbate the issue of undercutting instead of solving it. Changing the electrode type may have a minimal impact on undercutting as specific electrode characteristics could help, but it's not as direct a solution as adjusting the current. Lastly, increasing the travel speed tends to reduce the heat input but can also lead to inadequate fusion if done excessively, which can create other issues. Thus, reducing the current is the most effective approach to address undercutting in this context.