What is the purpose of a hot pass in GTAW pipe welding?

• A. To correct problems caused by a poor root pass.
• B. To produce a larger weld bead.
• C. To remove oxide.
• D. To accelerate cooling.

Answer: (A)

In GTAW pipe welding, a hot pass is used after the root pass to refine and salvage the root area by re-melting and fusing the root metal to fill gaps and correct imperfections. The heat from this pass helps ensure full fusion along the weld root, smoothing out irregularities such as undercuts, shallow penetration, or porosity left by the initial root pass, and it helps establish a solid foundation for the subsequent filler passes. This approach improves the integrity of the joint by making the root weld more uniform and less prone to defects that could compromise strength or leak tightness. It’s not primarily about removing oxide—cleanliness and shielding are handled during preparation and welding, rather than by the hot pass itself. It also isn’t aimed at simply creating a larger bead or accelerating cooling; its main purpose is to address issues introduced by the root pass and improve root fusion.