In FCAW, what is the purpose of slag and how is it removed after welding?

• A. Slag strengthens the weld; it does not need removal
• B. Slag protects the weld as it cools; it is removed by grinding away while hot
• C. Slag protects the weld as it cools; it is removed by chipping and brushing after the weld cools
• D. Slag has no functional purpose and is discarded after welding

Answer: (C)

Slag in FCAW forms a protective layer over the weld as the molten metal solidifies, shielding it from air and helping control the cooling and contamination of the weld. It does not add strength to the joint, so it must be removed to inspect and finish the weld surface. The usual removal method is to chip the slag off with a chipping hammer and then brush the weld once it has cooled. Grinding while the slag is hot isn’t standard practice because it can cause burns, distortion, or damage; slag is typically cleaned after cooling to reveal a clean bead for inspection and any final finishing.