Which description best defines a sound TIG root pass on a square-edge butt joint?

Which description best defines a sound TIG root pass on a square-edge butt joint?

• A. A wide root bead with high porosity is ideal.
• B. A narrow, uniform root bead with proper penetration and tie-in, no excessive reinforcement, porosity, or undercut; consistent bead height along joint.
• C. Inconsistent bead height is acceptable if the fill passes.
• D. Porosity at root is acceptable if not visible.

Answer: (B)

In TIG welding, the root pass should establish a solid fusion at the joint root with a narrow, uniform bead that penetrates properly into both base metals and ties into them. A narrow, uniform root bead concentrates heat where it’s needed, creating true root penetration and a clean tie-in to both sides, so the weld is connected through the thickness rather than just on the surface. Avoiding excessive reinforcement keeps the joint flush and minimizes distortion, while avoiding porosity and undercut preserves root strength and integrity. A consistent bead height along the joint reflects controlled heat input and stable technique, which helps ensure uniform fusion from end to end. To achieve this, keep the surfaces clean, maintain proper shielding, use appropriate amperage and travel speed, and ensure proper fit-up of the square-edge joint.

In TIG welding, the root pass should establish a solid fusion at the joint root with a narrow, uniform bead that penetrates properly into both base metals and ties into them. A narrow, uniform root bead concentrates heat where it’s needed, creating true root penetration and a clean tie-in to both sides, so the weld is connected through the thickness rather than just on the surface. Avoiding excessive reinforcement keeps the joint flush and minimizes distortion, while avoiding porosity and undercut preserves root strength and integrity. A consistent bead height along the joint reflects controlled heat input and stable technique, which helps ensure uniform fusion from end to end. To achieve this, keep the surfaces clean, maintain proper shielding, use appropriate amperage and travel speed, and ensure proper fit-up of the square-edge joint.