What causes tungsten contamination in TIG welding?

• A. Excessive heat
• B. Improper shielding gas
• C. Touching tungsten to weld pool or filler rod
• D. Using old tungsten

Answer: (C)

Tungsten contamination happens when the electrode touches the weld pool or the filler rod. The tungsten electrode is non-consumable, but if it makes contact with molten metal, tungsten can be drawn into the weld. Those tungsten particles form hard, brittle inclusions in the weld metal, which can cause cracking, reduced toughness, and porosity or poor fusion around the inclusion. This is why keeping the electrode at the proper distance and angle and avoiding dipping it into the pool is essential for a clean, sound weld. Other issues like excessive heat, incorrect shielding gas, or using old tungsten can cause different problems (arc stability, porosity, or electrode wear), but they don’t introduce tungsten contamination in the weld in the same direct way.