Titanium and stainless steel can look similar on a bench and behave nothing alike under heat. Titanium reacts with oxygen and nitrogen at welding temperatures, and the result of that reaction is a hard, brittle surface that will not survive service. Stainless tolerates a certain amount of exposure, and titanium does not.
The consequence is that a fabricator cannot simply change filler wire and carry on. Every step, from cleaning and cutting through fixturing, shielding and inspection, has to be rethought for the material rather than adapted from what already worked.
Contamination begins before the arc. Dust, grease, machining residue and the wrong abrasive all leave something on the surface that will be drawn into the weld. Titanium is usually cut and cleaned with dedicated tools, and a grinding wheel that has touched steel should never come near it.
Handling matters too. Skin oils and marking pens are enough to cause problems, so parts are handled clean and stored so they cannot pick up material from a shared bench that has been used for other metals.
Titanium conducts heat less readily than stainless, which concentrates heat at the joint instead of spreading it. That makes the weld pool behave differently and raises the risk of distortion in thin sections. A fabricator used to stainless will typically run too hot and travel too fast at first.
The answer is a tighter technique: less current, better fit-up so the joint needs less filler, and a sequence that balances shrinkage from one side of the part to the other. Tacking in a planned order rather than wherever is convenient makes a visible difference by the end.
Titanium work-hardens at the cut and springs back more than steel during forming. Dies and rolls have to allow for that springback, and cutting tools have to stay sharp because a dull edge generates heat and hardens the surface further. Bending a tube that has already been worked once is noticeably harder than bending it in one pass.
Pressed, formed and machined items all behave this way, which is one reason titanium fab components take longer to make than their steel equivalents even when the finished geometry is identical.
The weld pool, the cooling bead and the back face all have to be protected until the metal is cool enough to stop reacting. That means trailing shields, a gas lens, and purge gas inside any closed section. For tube work the purge has to reach the whole joint, which is a matter of sealing the ends and allowing enough flow time before the arc starts.
Where the geometry is open, as it is on many TIG titanium welding parts, the shielding is arranged around the joint rather than inside it, but the requirement is exactly the same. There is no acceptable shortcut.
A sound weld is clean, evenly spaced, and has a controlled colour that stops before the metal goes grey or flaky. The back side should look similar to the front. Distortion should be small enough that the part still fits its fixture after cooling, not only while it is clamped in place.
The final test is the one every owner can apply. Does the part still measure the same when it is cold? If it does, the heat input and the welding sequence were right. If it has pulled, no amount of polishing will correct it.
