Which polarity reduces tungsten erosion in GTAW?

Which polarity reduces tungsten erosion in GTAW?

• A. AC
• B. DCEN
• C. DCEP
• D. AC with high frequency

Answer: (B)

Heat distribution is what changes tungsten wear in GTAW. When the electrode is negative (DCEN), the electrode acts as the cathode and the arc heat is favored into the workpiece rather than the tungsten tip. The tungsten stays cooler, so it is less likely to melt, vaporize, or become contaminated, which reduces erosion of the tip. If the electrode is positive (DCEP), the tip ends up hotter and erodes faster, increasing wear. Alternating current switches polarity, so the tungsten experiences heating on the positive half-cycle and can wear more than with a steady negative polarity. High-frequency AC helps start and stabilize the arc but doesn’t inherently minimize tungsten erosion. So, using DCEN reduces tungsten erosion.

Heat distribution is what changes tungsten wear in GTAW. When the electrode is negative (DCEN), the electrode acts as the cathode and the arc heat is favored into the workpiece rather than the tungsten tip. The tungsten stays cooler, so it is less likely to melt, vaporize, or become contaminated, which reduces erosion of the tip. If the electrode is positive (DCEP), the tip ends up hotter and erodes faster, increasing wear. Alternating current switches polarity, so the tungsten experiences heating on the positive half-cycle and can wear more than with a steady negative polarity. High-frequency AC helps start and stabilize the arc but doesn’t inherently minimize tungsten erosion. So, using DCEN reduces tungsten erosion.