Welding titanium — why it's different
Titanium welds beautifully — if you keep air away from them. The rules, the filler metals, and how to read a weld by its color.
The one rule: no air above 400 °C
Above roughly 400 °C, molten and hot titanium dissolves oxygen, nitrogen and hydrogen straight from the atmosphere. The result is brittle, contaminated welds that pass visual inspection and fail in service. Every credible titanium weld therefore needs three shields: the torch shielding gas, a trailing shield behind the torch, and back-purging of the inside of the joint.
- 100% argon (or Ar/He mixes for penetration) — never CO₂, never mixed gas from steel work.
- Trailing shield or argon saver covering the cooling bead — the weld is still vulnerable behind the arc.
- Back purge of tubes and boxes — the underside of the weld is a weld too.
- Gloves, fresh abrasives, acetone wipe-down: fingerprints and shop dust contaminate welds just like air does.
- Titanium-only grinding discs and brushes — a stainless brush dragged across titanium embeds iron and ruins corrosion resistance.
Filler metal selection (AWS A5.16)
| Filler | Matches | Notes |
|---|---|---|
| ERTi-1 | Grades 1–4 (ductility max) | Purest, most ductile deposit |
| ERTi-2 | Grades 1–4 (general) | The default CP filler |
| ERTi-5 | Grade 5 | Matches Ti-6Al-4V base |
| ERTi-9 | Grade 9 | 3Al-2.5V, the tubing filler |
| ERTi-23 | Grade 23 / F136 | ELI filler for medical & cryo |
Rule of thumbYou may weld “down” — ERTi-2 filler on Grade 5 base is accepted where ductility matters more than matching strength. Never weld “up” (ERTi-5 on CP base).
Reading a weld by color
The oxide film that forms during welding tells you exactly how much shielding the bead saw. Inspectors grade welds by color, silver being perfect.
SilverPerfect — full shield
Straw / Gold~15 V oxide — acceptable edge
BlueInsufficient shield — evaluate
PurpleContaminated — reject zone
White / greySevere — scrap
Buying tipAsk any supplier for photos of finished welds. A silver bead with clean delineation is the cheapest quality inspection you will ever run.
Updated 2026-09
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