What are two reasons for using high frequency in GTAW?

• A. Decreases arc stability and focus.
• B. Increases welding speed but worsens control.
• C. Non-contact arc starting, improve arc stability and focus.
• D. Eliminates the need for shielding gas.

Answer: (C)

High frequency in GTAW is used to start the arc without touching the electrode and to keep the arc stable and focused once welding begins. The non-contact arc start comes from ionizing the shielding gas with a high-frequency current, which creates a conductive plasma path that lets you strike the arc cleanly without electrode-to-workpiece contact. After the arc is established, the HF helps maintain a stable arc and concentrates the heat at the electrode tip, giving better control and a tighter, more focused weld bead. These two effects—easy, non-contact arc initiation and improved arc stability and focus—are why high frequency is used. Shielding gas is still required; HF doesn’t replace it.