In GTAW, filler metal is often not used with which joints?

• A. Thin sections or autogenous welds
• B. Thick sections
• C. For all joints
• D. When using DCEN

Answer: (A)

In GTAW, filler metal is often not used when welding thin sections or performing an autogenous weld. The TIG process gives you very precise heat control and a small, focussed molten pool, which lets the edge surfaces fuse together cleanly without adding material. In very thin sections, introducing filler can easily cause burn-through or undesirable excess weld bead, so welding without filler keeps the joint as a true fusion of the base metals. An autogenous weld, where the base metals themselves fuse without filler, relies on that same level of control to achieve a sound joint and preserve the original alloy characteristics.

Thick sections, on the other hand, usually need filler to provide enough material and throat, help fill the joint, and manage penetration and support the weld geometry. The polarity setting (DCEN) isn’t what determines whether filler is used; filler presence is determined by the joint design and thickness.