Which action helps prevent undercutting in a horizontal fillet weld?

Which action helps prevent undercutting in a horizontal fillet weld?

• A. Increasing the welding speed
• B. Stopping momentarily at the upper end of each electrode movement
• C. Using a longer arc length
• D. Increasing welding current slightly

Answer: (B)

Undercutting happens when the weld metal doesn’t properly wet and fill the toe of the joint, leaving a groove in the base metal. In a horizontal fillet, the molten pool can advance faster than it can wet the toe, especially as gravity pulls metal away from the toe along the edge. Stopping momentarily at the upper end of each electrode movement gives the puddle time to stabilize and flow into the joint, allowing the molten metal to wet the toe and fill the edge more effectively. This helps shape a smooth bead and prevents the formation of a groove along the weld toe. In contrast, increasing speed, using a longer arc length, or increasing current tends to spread or intensify heat without giving the toe time to wet properly, which can promote undercut.

Undercutting happens when the weld metal doesn’t properly wet and fill the toe of the joint, leaving a groove in the base metal. In a horizontal fillet, the molten pool can advance faster than it can wet the toe, especially as gravity pulls metal away from the toe along the edge. Stopping momentarily at the upper end of each electrode movement gives the puddle time to stabilize and flow into the joint, allowing the molten metal to wet the toe and fill the edge more effectively. This helps shape a smooth bead and prevents the formation of a groove along the weld toe. In contrast, increasing speed, using a longer arc length, or increasing current tends to spread or intensify heat without giving the toe time to wet properly, which can promote undercut.