What happens if the post-flow duration is too short?

• A. Tungsten oxidation and crater contamination
• B. Bead looks shiny and uniform
• C. Arc stability improves
• D. Gas consumption decreases

Answer: (A)

Post-flow duration keeps shielding gas flowing after the arc stops to protect the hot weld area and the tungsten tip from exposure to air. If that gas flow is too short, air reaches the hot crater and tungsten, causing oxidation of the tungsten and contamination of the crater. This oxidation can degrade the weld quality and lead to defects, especially in the next pass or when restarting the arc. A shiny, uniform bead usually indicates good shielding, so cutting post-flow short wouldn’t improve appearance. Arc stability relies on proper gas coverage, which is compromised if post-flow is too brief. While shorter post-flow might save gas, it doesn’t prevent contamination and instead increases the risk of oxidation and crater contamination.