During GTAW on 4 mm 6063 aluminum, using an AC inverter machine, the welder notices the tungsten electrode is melting back excessively and producing inconsistent arc starts. They are using a 2% Lanthanated tungsten, a 3.2 mm diameter electrode, and setting the amperage at 180 A. What is the most likely cause for the tungsten issues?

Question: During GTAW on 4 mm 6063 aluminum, using an AC inverter machine, the welder notices the tungsten electrode is melting back excessively and producing inconsistent arc starts. They are using a 2% Lanthanated tungsten, a 3.2 mm diameter electrode, and setting the amperage at 180 A. What is the most likely cause for the tungsten issues?

Answer options:

• The amperage is too low for the electrode size.
• The AC frequency is set too high. ✅ The tungsten electrode diamater is too small for the amperage.
• The AC balance is set too high towards electrode negative.

Correct answer: The tungsten electrode diamater is too small for the amperage.

Explanation: Excessive tungsten melt-back and inconsistent arc starts, especially at higher amperages, often indicate that the tungsten electrode diameter is too small for the current required. A 3.2 mm 2% Lanthanated tungsten can typically handle up to about 250 A with an inverter, but specific limits vary. If the electrode is melting back, it suggests it's being overloaded. Amperage being too low would not cause melt-back. High AC frequency usually improves arc stability. High AC balance (more EN) provides more cleaning but doesn't directly cause excessive melt-back unless the overall heat balance is off for the tungsten.