Suck back is described as a root condition where the root becomes concave due to heat conduction issues.

• A. True
• B. False
• C. Sometimes
• D. Not applicable

Answer: (A)

Suck back at the root is a root-level defect caused by how heat flows through the joint during welding. It describes a situation where the molten metal at the root is drawn back or pulled away, so the root ends up concave rather than filled. This happens when heat conduction away from the weld pool is too effective or the energy input isn’t enough to keep the root filled, allowing the pool to solidify with a recessed, concave profile. Practically, you’d see a concave root when the heat is not staying with the root area long enough to maintain proper fill, which can stem from too-fast travel, insufficient current, or conditions that promote rapid heat loss. To prevent it, ensure stable heat input, appropriate travel speed, and proper heat distribution so the root can fill properly.