Grade 2 Titanium
Also: CP titanium, commercially pure titanium, Ti Grade 2, Ti CP-2, UNS R50400, ASTM B265 Grade 2, Ti 3.7035, unalloyed titanium, CP Ti Gr 2
Grade 2 is commercially pure titanium: top corrosion resistance and formability, weldable, 57% of steel's density, near 6061 strength. Values annealed.
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At a glance
| Density | 4.51 g/cm³ (0.163 lb/in³) |
|---|---|
| Tensile strength | 345 MPa (50 ksi) min; typically 400-480 MPa (58-70 ksi) |
| Yield strength | 275-450 MPa (40-65 ksi) per spec; typically 340-400 MPa (49-58 ksi) |
| Hardness | About 80 HRB (145-200 HB) |
| Elongation | 20% min; typically 25-30% |
| Modulus of elasticity | 105 GPa (15.2 Msi) |
| Thermal | Melts at about 1665 °C (3030 °F); thermal conductivity ~16 W/m·K; beta transus about 913 °C (1675 °F); long-term service to about 300 °C (570 °F) |
| Composition | Ti, up to 0.30% Fe, up to 0.25% O, up to 0.08% C, up to 0.03% N, up to 0.015% H |
Typical values, Annealed (mill annealed sheet, plate and bar per ASTM B265 / B348). Confirm against the mill certificate and the purchase spec.
- MachinabilityFair
- Easier than Ti-6Al-4V but still slow: low conductivity heats the tool, the low modulus lets thin parts spring away from the cutter, and it galls. Rigid setups, sharp carbide, heavy flood coolant, low speed and steady feed; never let the tool dwell.
- WeldabilityExcellent
- The most weldable titanium: TIG with ERTi-2 filler and complete argon shielding of the weld pool, the trailing hot metal and the root. A silver or light straw weld is good; blue or grey means air contamination and a brittle weld.
- FormabilityGood
- The best-forming titanium grade: cold bends at about 2-2.5x thickness inside radius with heavy springback, and it draws and spins. Warm forming at 200-300 °C (400-570 °F) tightens radii; keep it under the alpha-case range unless the surface will be removed.
- Corrosion resistanceExcellent
- Immune to seawater, chlorides, wet chlorine, hypochlorite and nitric acid, and unaffected by crevice attack below about 70 °C (160 °F). Attacked by hydrofluoric acid and hot reducing acids (concentrated sulfuric, hydrochloric); Grade 7 or 12 covers those.
Grade 2 is unalloyed titanium with controlled oxygen and iron, the most widely used of the four commercially pure (CP) grades. It is chosen for corrosion resistance rather than strength: a stable oxide film makes it essentially immune to seawater, wet chlorine, chlorides, hypochlorite and oxidizing acids, and it is biocompatible. It is the titanium of chemical process equipment, heat exchangers, desalination plants, marine hardware, medical implants and architectural cladding.
Its strength is modest, about 345 MPa (50 ksi) minimum tensile, in the range of 6061-T6 aluminum or annealed 304 stainless, at 4.51 g/cm3, which is 57% of the density of steel. What it adds over the alloyed grades is ductility and weldability: Grade 2 bends cold, deep draws and spins, and welds cleanly by TIG when it is shielded from air. Grades 1, 3 and 4 trade formability for strength along the same chemistry; Grade 7 and Grade 12 add palladium or molybdenum-nickel for reducing acids.
Working it costs more than the material alone. Titanium has a low modulus (half of steel), so parts spring back in forming and deflect under cutting loads; it gall against tools and against itself; it conducts heat poorly, so machining is slow and coolant matters; and any hot work in air above about 600 °C (1100 °F) forms a brittle oxygen-rich surface layer (alpha case) that must be removed. None of this is exotic for a shop that runs titanium, but it is a different shop from the one that runs aluminum.
Heat treatment
Not hardenable by heat treatment; the only treatments are annealing and stress relief. Anneal at about 650-760 °C (1200-1400 °F) and air cool; stress relieve after welding or heavy forming at about 480-595 °C (900-1100 °F) for 30-60 minutes. Do both in vacuum or protective atmosphere, or budget to remove the alpha case by machining or pickling afterward; oxygen pickup above about 600 °C (1100 °F) in air embrittles the surface.
Tempers and conditions
- Annealed (the standard condition)
- Stress-relieved
- Cold worked (strip and wire)
Stock forms
- Sheet and strip
- Plate
- Round bar and billet
- Welded and seamless tube
- Pipe
- Forgings
- Wire
- Fasteners
Relative cost
Tier 4 of 5. Roughly 5-8x the price of 304 stainless per pound, and machining and welding cost more per hour. Cheaper than Ti-6Al-4V and much easier to fabricate, so it is the economical titanium for corrosion service.
Typical applications
- Chemical process vessels, columns and piping
- Heat exchanger tubing and tube sheets
- Desalination and seawater cooling systems
- Marine hardware, shafts and fasteners
- Medical implants and surgical instruments (with Grade 4)
- Architectural roofing and cladding
- Aircraft ducting, firewalls and non-structural sheet parts
- Pollution control and chlor-alkali equipment
Process compatibility
How Grade 2 titanium takes each process, and what to specify. Each process links to its own guide and to the shops that do it.
| Process | Rating | Notes |
|---|---|---|
| CNC Machining | FairFair | Machinable in any shop that runs titanium: slow speeds, steady feeds, sharp carbide and flood coolant. Plan 3-4x the cycle time of 6061. |
| TIG Welding | ExcellentExcellent | The standard joining process; ERTi-2 filler with full argon shielding, trailing shield and back purge. Inspect weld colour. |
| Welding | ExcellentExcellent | TIG, plasma, EB and laser all work with inert shielding; no preheat, no post-weld heat treatment beyond an optional stress relief. |
| Sheet Metal Fabrication | GoodGood | Cuts, bends, draws and welds; allow for springback and use urethane or radiused tooling to avoid galling the sheet. |
| Press Brake Forming | GoodGood | Cold bend at 2-2.5x thickness inside radius with 15-25 degrees of overbend for springback; warm forming tightens the radius. |
| Deep Drawing | FairFair | Draws in the annealed condition with lubricated, polished tooling and intermediate anneals; galling is the usual failure. |
| Laser Cutting | GoodGood | Fiber lasers cut sheet and plate cleanly; use argon or nitrogen assist and expect an oxidized, slightly hardened edge that critical parts have removed. |
| Waterjet Cutting | ExcellentExcellent | No heat, no alpha case, no oxide edge; the preferred way to blank titanium plate for machined and welded parts. |
| Forging | GoodGood | Forged for flanges, fittings and pump parts; hot work in air forms alpha case that is machined off afterward. |
| Metal 3D Printing | GoodGood | CP titanium prints well by laser powder bed fusion and EB melting, mostly for implants and lattices; Ti-6Al-4V is more common where strength matters. |
| Anodizing | GoodGood | Titanium anodizing (AMS 2488) for colour coding, appearance or an anti-galling surface; a different process from aluminum sulfuric anodize, and the film is thin. |
| Shot Peening | GoodGood | Improves fatigue life on fasteners and shafts; use clean media reserved for titanium to avoid iron contamination. |
| Heat Treating | PoorPoor | Cannot be hardened; only anneal and stress relief exist. Buy Ti-6Al-4V if the part needs higher strength. |
| Die Casting | Not recommendedNot recommended | Titanium cannot be die cast; its melt attacks every die material. Investment casting in vacuum foundries is the only casting route, and it is rare for CP grades. |
Design and sourcing tips
- Specify "Titanium Grade 2 per ASTM B265" (sheet and plate) or "ASTM B348" (bar), annealed; add AMS 4902 for aerospace sheet and plate.
- Design to the low modulus: a Grade 2 part deflects about twice as much as the same steel part, so stiffness, not strength, often sizes it.
- Call out full inert shielding and weld colour acceptance (silver to light straw) on welded parts; contaminated titanium welds look fine and break.
- Avoid galling: do not run titanium against titanium in sliding contact without a coating, a dissimilar mating material or anodize.
- Keep it out of hydrofluoric acid and hot reducing acids; for those, specify Grade 7 (palladium) or Grade 12.
- Ask for alpha case removal, or an inert-atmosphere anneal, on any part that was hot formed, forged or annealed in air.
Frequently asked questions
- What is the difference between Grade 2 and Grade 5 titanium?
- Grade 2 is unalloyed titanium: about 345 MPa (50 ksi) minimum tensile, very ductile, easy to weld and form, and the most corrosion-resistant. Grade 5 is Ti-6Al-4V, an alloy with 895 MPa (130 ksi) minimum tensile, harder to form and machine, used for structural and load-bearing parts. Choose Grade 2 for corrosion service and fabrication, Grade 5 for strength.
- Is Grade 2 titanium magnetic?
- No. Titanium is paramagnetic, so Grade 2 does not attract a magnet and does not interfere with MRI or magnetic instruments. That, plus its biocompatibility, is one reason CP titanium is used for implants and medical hardware.
- Can Grade 2 titanium be welded?
- Yes, and it is the most weldable titanium grade. TIG with ERTi-2 filler is standard, with argon shielding on the torch, a trailing shield behind it and a purge on the back side. Titanium absorbs oxygen and nitrogen above about 425 °C (800 °F), so the weld colour is inspected: silver or light straw passes, blue or grey is rejected.
- How strong is Grade 2 titanium?
- About 345 MPa (50 ksi) minimum tensile and typically 400-480 MPa, with a yield of 275-450 MPa (40-65 ksi). That is comparable to 6061-T6 aluminum or annealed 304 stainless. Per unit weight it is stronger than either, but if strength is the goal, Ti-6Al-4V is more than twice as strong.
- Does Grade 2 titanium rust or corrode in salt water?
- No. It forms a stable oxide film that is essentially immune to seawater and chlorides at ambient temperature, which is why it is used for desalination, offshore piping and marine hardware. It is attacked by hydrofluoric acid and hot concentrated reducing acids, and it can suffer crevice corrosion in hot chloride brines above about 70 °C (160 °F).
Processes that commonly use it
Related materials
Where to verify these values
- ASTM B265 and ASTM B348 (mechanical property minimums by grade)
- AMS 4902 (CP titanium sheet, strip and plate)
- ASM Handbook, Volume 2 (Properties and Selection: Nonferrous Alloys)
- TIMET and other producer data sheets for CP titanium
