Functions of the metal tube of sheath over the wire for FCAW?

• A. Provide filler metal; conduct the welding current; contain the flux core
• B. Act as a shielding gas source
• C. Change the wire diameter
• D. Interrupt the current flow

Answer: (A)

In FCAW the electrode is a flux‑cored tubular wire. The metal tube around the wire does three things: it becomes part of the weld as filler metal when melted, it conducts the welding current to the arc, and it encloses the flux core inside. The flux within the tube provides shielding, deoxidizers, and alloying elements as it melts, and in many wires its decomposition helps generate shielding gas. The tube itself doesn’t change wire diameter or serve to interrupt current, and while shielding gas can come from the flux, the tube’s primary roles are to deposit metal, carry current, and contain the flux core.