Thin-wall tube bows and flanges pull because heat expands restrained metal. Tack sequence, back-stepping, fixtures and cooling all decide whether a part still fits after welding.
Titanium filler has to match the parent metal, not add strength for its own sake. Matching pure and alloyed tube, sizing wire to wall thickness and keeping a build consistent.
On stainless, a hot root exposed to air turns to brittle black oxide. When purging is genuinely required, how to arrange it, and how to judge the inside of a finished joint.
Aluminium welds without a colour warning, carries an oxide skin and moves heat fast. How those three traits change the way intercoolers and tanks are welded and checked.
Mirror welding is an appearance standard rather than a separate process. Where a show-quality stainless bead earns its cost, where it is the wrong call, and how heat input decides the result.
Heat tint on titanium is a thin oxide film, and its colour records both temperature and shielding. What silver, straw, purple, blue and grey actually mean on a finished weld.
Titanium absorbs oxygen on the back side of a weld, so the inside of a joint needs its own shielding gas. How an argon back-purge is set up, held and read on tube work.
Titanium reacts with air at welding temperature and work-hardens differently from stainless. This explains what has to change in cleaning, heat input, tooling and shielding.
