The filler pass in GTAW pipe welding comes after which pass, and what is its purpose?

• A. After the hot pass; used to quickly fill the groove; should be complete fusion but little penetration.
• B. Before the root pass; to shape the groove.
• C. During the root pass; to ensure root penetration.
• D. As the final pass; to smooth the surface.

Answer: (A)

In GTAW pipe welding, welding is done in a sequence: root, hot, then filler, with a final cap to finish. The filler pass comes after the hot pass. Its job is to deposit filler metal to fill the groove quickly so the weld can reach its full width and strength, while keeping penetration mainly at the root and avoiding deepening the groove further. This creates the bulk of the weld with good fusion between the base metal and the filler without adding extra penetration that could distort the weld geometry. The final cap pass then smooths and shapes the surface.