In AC GTAW, the majority of welding heat is delivered to which part?

• A. The tungsten
• B. The workpiece
• C. The filler rod
• D. The shielding gas

Answer: (B)

Heat in AC GTAW is concentrated in the metal being welded—the workpiece—because the arc’s energy is delivered to melt and raise the temperature of the base metal to form the weld pool. The tungsten electrode is non-consumable and serves to create the arc; it remains relatively cool compared with the molten workpiece. The filler rod, when used, must melt and fuse with the pool, but it generally uses less total heat than melting the base metal itself. The shielding gas protects the molten metal but does not carry significant heat. In AC, the current reverses to clean the surface, but the majority of heat input still goes into the workpiece.