Welding Titanium

Titanium reacts with oxygen, nitrogen, and hydrogen above 500F. Any weld surface exposed to air while still hot absorbs these elements and becomes brittle. A contaminated titanium weld can look fine and still crack under the first load cycle. Inert gas coverage on both sides of the joint, from the moment the arc starts until the metal cools below 500F, is not optional.

TIG (GTAW) on DCEN is the standard process. Use 100% argon shielding at 20-35 CFH through a gas lens cup for laminar flow. A trailing shield extends argon coverage 4-6 inches behind the torch to protect the cooling weld bead. Without the trailing shield, even a good puddle turns blue or gray within seconds of the torch passing.

Back purging protects the root side. On pipe, seal the ends and fill with argon at 10-15 CFH, monitoring oxygen content with an inline analyzer. For sheet and plate, a backing fixture with argon flowing underneath prevents root contamination. Full purge chambers (glove boxes) provide the best coverage for critical aerospace parts but aren’t always necessary for general fabrication.

Filler selection matches the base alloy. ERTi-2 (commercially pure Grade 2) welds Grade 1 and 2 CP titanium. ERTi-5 (6Al-4V) welds the most common structural titanium alloy, Ti-6-4. Always use a filler grade equal to or slightly lower than the base metal’s strength level.

Weld color tells you everything. Bright silver means clean coverage. Light straw is acceptable. Blue is marginal. Purple, dark blue, gray, or white means the weld is contaminated and must be completely removed. There’s no repairing it with another pass. Grind it out and start over with better gas coverage.

Joint prep uses carbide tools or stainless-only abrasives. No carbon steel contact, no chlorinated solvents, no fingerprints in the weld zone. Clean with acetone and lint-free wipes immediately before welding.