New Mexico Pipe Fitter Journeyman (JPF) Practice Exam

When using the GTAW welding process with AC current, the tungsten end will be?

1. Pointed

2. Balled

3. Flat

4. Rounded

The correct answer is: Balled

In the Gas Tungsten Arc Welding (GTAW) process, particularly when using alternating current (AC), the tungsten electrode undergoes a specific change in shape. When AC is used, a balled end typically forms on the tungsten due to the heating and cooling cycles that occur. This process is a result of the electrode's melting and the alternating current's direction, which allows the tungsten to stabilize in its balled form. The balled shape is advantageous in AC GTAW because it enhances the arc stability and helps create a more focused weld pool by providing a larger area for the arc to secure itself. This is particularly crucial when welding non-ferrous materials such as aluminum, which are commonly worked on with AC current due to their thermal conductivity and oxide layers. In contrast, a pointed, flat, or rounded end would not provide the optimal conditions for effective welding, as each of these shapes could lead to issues such as arc instability or inconsistent heat application, ultimately affecting the quality of the weld. Therefore, knowing that the tungsten takes on a balled end during AC GTAW is important for achieving the best welding results.