In a multi-pass weld, which statement correctly describes the root pass and fill passes?

• A. Root pass builds up weld metal to height; fill passes establish root fusion.
• B. Root pass establishes root fusion and penetration; fill passes build up weld metal to the correct height; cap pass finishes.
• C. Root pass is optional; fill passes are for cosmetic finish.
• D. Root pass uses flux; fill pass uses shielding gas.

Answer: (B)

In multi-pass welding, you start by the root pass, which must establish a solid root fusion and penetration so the joint is truly welded through to the opposite side. Then the fill passes deposit additional weld metal to raise the weld to the correct height and fill the groove, building up the bead and ensuring proper width and fusion. Finally, the cap pass sits on top to finish the weld, provide surface finish, and complete the reinforcement and final dimensions. This sequence—root fusion and penetration first, followed by height-building fill passes, then a finishing cap—is why this option is the best. The other descriptions misstate the roles or the order, such as treating the root as merely for height, claiming it’s optional, or focusing on process specifics rather than the intended weld sequence.