Which statement correctly describes the heat distribution in AC GTAW?

Which statement correctly describes the heat distribution in AC GTAW?

• A. Most heat goes to the tungsten
• B. Most heat goes to the work
• C. Heat is split evenly
• D. No heat goes to the work

Answer: (B)

In GTAW, the arc’s energy is directed mainly into the workpiece to create and sustain the weld pool. The tungsten electrode is non-consumable and is kept relatively cool by its geometry and cooling; although some heat does rise in the electrode during the cycle, the majority of the arc energy ends up heating and melting the workpiece. In alternating current, the polarity reverses, so each half-cycle shifts heat toward the work or toward the electrode, but the overall average heat input still favors the work. That’s why the statement that most heat goes to the work is the best description of heat distribution in AC GTAW. The other ideas conflict with the practical goal of forming the weld—the electrode would overheat if most heat went there, heat wouldn’t split evenly in real practice, and saying no heat reaches the work would make welding impossible.

In GTAW, the arc’s energy is directed mainly into the workpiece to create and sustain the weld pool. The tungsten electrode is non-consumable and is kept relatively cool by its geometry and cooling; although some heat does rise in the electrode during the cycle, the majority of the arc energy ends up heating and melting the workpiece. In alternating current, the polarity reverses, so each half-cycle shifts heat toward the work or toward the electrode, but the overall average heat input still favors the work. That’s why the statement that most heat goes to the work is the best description of heat distribution in AC GTAW. The other ideas conflict with the practical goal of forming the weld—the electrode would overheat if most heat went there, heat wouldn’t split evenly in real practice, and saying no heat reaches the work would make welding impossible.