What is the purpose of the root pass in a welded joint?

• A. The root pass establishes initial fusion and alignment.
• B. The root pass finishes the exterior appearance.
• C. The root pass is used to cool the joint rapidly.
• D. The root pass adds filler metal only.

Answer: (A)

The root pass is intended to establish initial fusion and alignment at the joint. It creates the first weld bead that penetrates to the root, fusing the base metals together and holding the joint halves in proper alignment as the weld is built up. This foundational step ensures there is sound penetration at the root and that the joint is properly seated before additional passes are added.

Once the root is sound, subsequent passes fill and cap the joint to achieve the final dimensions and surface finish. The other options describe outcomes that come later or reflect effects (like appearance or cooling) rather than the essential purpose of the root pass itself.