If shielding gas flow is too low, which defect is likely?

• A. Cracking
• B. Porosity
• C. Warping
• D. No defects

Answer: (B)

Shielding gas protects the weld pool from the surrounding air. When the gas flow is too low, air—containing oxygen, nitrogen, and moisture—can reach the molten metal and become trapped as the weld solidifies. These trapped gas pockets form porosity, tiny voids that weaken the weld and can act as crack initiation sites under stress.

Other defects aren’t driven by low shielding gas flow in the same direct way: cracking is more tied to hydrogen or high residual stresses and brittle structures, and warping comes from excessive heat input and restraint rather than shielding gas levels. No defects would not describe what typically happens when shielding gas flow is insufficient. To fix it, increase the shielding gas flow to the recommended level and ensure the gas coverage is continuous and free of leaks.