What is the recommended sequence for a typical GMAW weld on a plate: root, fill, cap?

• A. Cap pass first, then root pass, then fill passes.
• B. Root pass for penetration, then fill passes to reach final thickness, finish with cap pass for shape.
• C. Fill passes only.
• D. Root and cap only.

Answer: (B)

When welding a plate with GMAW, you build the weld from the inside out: establish a solid root to ensure penetration, then add material with fill passes to reach the final thickness, and finish with a cap pass to shape and seal the weld. The root pass is crucial because it creates fusion right at the joint’s root, giving the weld its strength and preventing lack of penetration. If you skip the root or try to cap first, you won’t have a solid base for proper fusion at the bottom of the joint, and the top finish won’t fix that deficiency. Filling up the joint with additional passes adds material gradually and controls heat input to avoid burn-through or excessive distortion. The final cap pass provides the surface contour, a clean finish, and protection of the weld crown, ensuring the weld is complete and ready for service.