TIG welding uses argon gas to shield the arc and weld pool from air. Its sensitivity to wind, contaminants (rust, oil, moisture), and strict process requirements makes it prone to porosity. Below are key causes and solutions:
I. Argon Gas Issues
Low Purity: Ensure purity ≥99.7% (carbon steel), ≥99.9% (aluminum), ≥99.99% (titanium).
Incorrect Flow Rate:
Too high: Causes turbulence, draws in air.
Too low: Reduces wind resistance.
Solution: Use stable, optimal flow.
Gas Leaks: Check hoses/connections; leaks reduce flow and draw in air.
Wind (>2m/s): Use windshields; seal pipe ends to prevent drafts.
Excessive Torch Angle: Draws air into pool, reduces shielding. Maintain proper angle.
Unstable Flow Meter: Replace faulty meters causing flow fluctuations.
Small Nozzle Diameter: Use larger nozzles (especially outdoors/for large pipes) for adequate coverage.
Large Nozzle-Work Distance: Minimize distance to improve wind resistance.
Faulty Torch Parts: Ensure compatible/clean collets and clear gas passages for even shielding.
II. Welding Consumables
Wrong Wire: Never use SAW wire for TIG; causes porosity.
Dirty Wire: Clean wire thoroughly (remove rust, oil, moisture).
III. Base Metal
Plate/Pipe Defects: Laminations/impurities promote porosity.
Steel Type: Avoid rimmed steel (high oxygen/impurities) for TIG.
IV. Tungsten Electrode
Blunt Tip: Causes arc wander, poor shielding. Maintain sharp tip.
Arc Crawling (HF start): Clean oxides off tungsten surface to prevent initial long arc/poor shielding.
V. Welding Technique
Poor Groove Cleaning: Clean groove + 10mm each side to prevent rust contamination.
Excessive Speed: Slower speed prevents gas deflection.
Incorrect Current:
Too low: Unstable arc.
Too high: Gas turbulence.
Abrupt Arc Stop: Use current decay, add filler, or move arc to groove side to protect crater.
Excessive Tungsten Stick-out: Minimize protrusion for better shielding.
Conclusion: Understanding TIG characteristics and systematically addressing these factors prevents porosity and improves weld quality.
