Titanium Grade 2 Sheet Fabrication

Corrosion is the reason, springback is the price

Titanium Grade 2 sheet is chosen for what it does not do: it does not corrode in chlorides.

Every stainless steel depends on a chromium oxide film, and that film is attacked locally by chloride ions — which is how pitting, crevice corrosion and chloride stress-corrosion cracking begin. Titanium’s oxide film is more stable in the presence of chlorides and reforms essentially instantly if it is damaged, so the material is effectively immune to all three. That is why it appears in sea-water plant, desalination, chemical process equipment handling hypochlorite and wet chlorine, and anodizing racks that sit in acid baths all day.

Add a density roughly 43% below steel’s, and you have a material that solves a corrosion problem and a weight problem at once.

Property	Titanium Grade 2	The fabrication consequence
Modulus	~half of steel’s	Enormous springback
Density	~4.51 g/cm³	Light, and expensive per kilogram
Corrosion	Effectively immune in chlorides	The reason for choosing it
Tensile	~345 MPa	Comparable to a mild steel — not a high-strength material
Galling	Significant	Lubricants and clean tooling are part of the process
Formability	Moderate	Cold forming for gentle radii; tight radii need heat

The modulus row is the one that governs the forming operation, and it is where most titanium sheet projects first run into trouble.

Springback: the defining fabrication problem

Titanium’s modulus of elasticity is roughly half that of steel. Springback — the elastic recovery when the forming force is removed — depends on the ratio of yield strength to modulus, and titanium has a comparatively high yield relative to its modulus. So a large proportion of the deformation is elastic, and it springs back.

In practice, on a press brake, that means a bend that would come off a mild steel tool at the intended angle can come off a titanium tool ten or fifteen degrees off.

There is no trick that removes this. The answers are the standard ones, applied more aggressively than on any other common sheet metal:

• Overbend substantially. The tool angle is not the part angle, and the difference is large.
• Calculate the allowance into the flat pattern before the blank is cut, rather than correcting the angle at the machine.
• Bottom or coin where the angle matters. Air bending leaves the most springback; a bottoming or coining operation reduces it.
• Consider hot forming where the geometry would otherwise need an impractical overbend.
• Expect the radius to open up too. Springback affects the radius as well as the angle, so a bend that measures correctly on the tool may be a larger radius off it.

A part corrected after forming is a part being re-formed, and titanium — like any work-hardened material — tolerates that poorly. The allowance belongs in the flat pattern.

Cold forming or hot forming

Cold forming is practical for gentle radii — roughly 2 to 3 times the material thickness as a working range, widening with gauge. That is several times the radius mild steel handles.

Tighter radii need hot forming, and hot forming brings a constraint of its own: contamination. At elevated temperature titanium absorbs oxygen and nitrogen from the air, and that absorption creates a hard, brittle surface layer — commonly called alpha case — which has to be removed afterwards by pickling or machining.

So hot forming is done in an inert atmosphere or a protective furnace atmosphere, and the surface condition of the formed part is inspected and cleaned rather than assumed good. It is a controlled process with a follow-up step, not simply a matter of heating the sheet and bending it.

Deciding between cold and hot forming is a geometry question, and it determines both the tooling and the process route — so it is settled before the tool exists.

Galling, and the iron-contamination rule

Two surface issues are specific to titanium fabrication, and both are easy to overlook.

It galls against tooling. Titanium has a strong tendency to seize against steel tooling, which marks the part and can damage the tool. The controls are suitable high-pressure lubricants, protective film on the sheet, tooling surfaces that do not gall against titanium, and keeping the tooling clean. On a part with a cosmetic surface, galling marks are a defect — so the forming lubricant and the tool condition are part of the specification rather than shop-floor improvisation.

It must not be contaminated with iron. Titanium picks up iron from steel tooling, fixtures, brushes, and even from steel swarf in the work area. That iron then rusts on the surface of a part that is otherwise inert in the environment — so the part looks like it has failed when it has not. It is contamination, not corrosion of the titanium. The controls are to keep steel away from finished titanium parts, use dedicated or non-ferrous tooling where the surface matters, and passivate after any operation where contact occurred.

Welding: full shielding, not just the pool

Titanium welds well, but the shielding requirement is stricter than on steel or stainless.

Titanium must be protected from the atmosphere while it is hot — not only in the weld pool, but on the surrounding metal until it has cooled below the temperature at which it would absorb oxygen and nitrogen. That means full inert-gas shielding, typically with a trailing shield, and often a backing purge as well.

Coloured heat tint beside a titanium weld is the visible sign that the shielding was inadequate, and it is a defect rather than an appearance issue — the tinted metal is contaminated and embrittled. So a titanium weld is inspected for colour, and the acceptable result is a clean silver or very light straw, not the blues and purples that would be unremarkable on stainless.

Formed-feature rules

The geometric rules around a bend matter more on titanium than on any other sheet metal, because the material gives less.

Holes and slots must clear the bend generously. A hole inside the bend zone distorts as the material stretches, and titanium stretches less than most metals. The working rule is to keep a hole at least a distance of roughly three times the material thickness plus the bend radius away from the bend line — measured from the edge of the hole, not its centre.

Flanges have a minimum length, and on titanium the practical minimum is worth confirming rather than assumed, because the forming operation is less forgiving.

Bend relief is not optional. Where a bend runs into a corner or up to an edge, a relief notch at the end of the bend line stops the material tearing. Titanium has limited stretch available and does not tear gracefully.

Grain direction affects the achievable radius. A bend made with the rolling grain has less ductility to spend than one made across it, so where a part has a tight radius the orientation of the flat pattern is worth agreeing.

Design for the overbend, not against it. Where the geometry allows, a design that tolerates a slightly open angle is far cheaper than one that demands a precise 90° on a thick titanium section.

Where titanium Grade 2 sheet is the right choice

• Chemical process equipment and liners handling chlorides, hypochlorite or wet chlorine
• Heat-exchanger plates and tube sheets
• Desalination and water-treatment components
• Marine structures and fittings that must not corrode and must not be heavy — see marine parts
• Anodizing racks, jigs and fixtures in acid service
• Medical and surgical equipment where inertness matters
• Offshore and architectural components expected to survive salt for decades without a coating
• Any chloride duty beyond what 316L can hold, where a coating is not acceptable

Where titanium Grade 2 sheet is the wrong choice

The duty is within what 316L handles. In flowing sea water at moderate temperature, 316L performs adequately and costs a fraction as much. Titanium earns its cost where the duty is genuinely beyond 316L, or where the weight saving matters.

The part has tight bends and hot forming is not practical. Cold forming will not achieve radii that mild steel, aluminium or brass handle easily. A different material, or a redesign, is the answer.

The environment is a reducing acid, hydrofluoric acid or dry chlorine gas. Titanium is attacked in all three. Name the chemical and the temperature before a material is fixed.

The part has to be cheap. Titanium is an expensive material that is also slower to form — the two penalties compound.

The application requires high strength. Grade 2 is around 345 MPa annealed, comparable to a mild steel. Where strength-to-weight is the reason for using titanium, Grade 5 is the alloy.

A shop cannot keep steel tooling away from the finished surfaces. Iron contamination will show as rust on an inert part. The control has to be in place rather than assumed.

What to put on the drawing

Instead of	Write
Titanium sheet	Titanium Grade 2, where chloride resistance is the driver
Titanium, bend angle	State the angle and tolerance — springback is far larger than on steel or aluminium
Titanium, bend radius	State it — cold forming needs roughly 2–3× thickness as a minimum
Titanium, tight radius	Say so — tight radii need hot forming and a post-form cleaning step
Titanium, hot formed	Flag it — inert atmosphere and alpha-case removal are part of the route
Titanium, cosmetic surface	Say so — galling and iron contamination both show
Titanium, welded	Say so — full shielding with a trailing shield; heat tint is a defect
Titanium, reducing acid or HF	Wrong material — titanium is attacked

The three lines that decide most titanium Grade 2 sheet parts are the chemical and the temperature, the bend radii and the springback allowance, and the surface protection through forming and welding. The first settles whether titanium is needed at all. The second sets the tooling and whether hot forming is in the route. The third is what keeps the part as inert as the material promised.

Send the drawing through the request a quote form and the reply comes back within 24 hours with DFM feedback — including a note on the forming route, the springback allowance, the shielding and the surface protection where any of them need settling.