What is a cap bead and why is it important in multi-pass welds?

What is a cap bead and why is it important in multi-pass welds?

• A. The final bead on top of the weld; provides surface finish and ensures proper shape and reinforcement.
• B. The cap bead is the first bead laid down in welding.
• C. A decorative bead on top.
• D. A bead that seals the root.

Answer: (A)

In multi-pass welding, the final pass placed on top of the weld is called the cap bead. This last layer finishes the weld surface, builds the final profile, and adds reinforcement to the top of the joint. Its proper size and contour influence the weld’s surface appearance, crown height, and overall geometry, which are crucial for strength, fatigue resistance, and meeting dimensional requirements. If the cap isn't done well, you can get an uneven surface, undercut, or insufficient top reinforcement, which can compromise the weld's performance. The other descriptions refer to different passes or are decorative, not the functional top layer that completes and strengthens the weld.

In multi-pass welding, the final pass placed on top of the weld is called the cap bead. This last layer finishes the weld surface, builds the final profile, and adds reinforcement to the top of the joint. Its proper size and contour influence the weld’s surface appearance, crown height, and overall geometry, which are crucial for strength, fatigue resistance, and meeting dimensional requirements. If the cap isn't done well, you can get an uneven surface, undercut, or insufficient top reinforcement, which can compromise the weld's performance.

The other descriptions refer to different passes or are decorative, not the functional top layer that completes and strengthens the weld.