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A Titanium Grades Chart for People Who Have to Buy Machined Parts

If you search for a titanium grades chart you get a table with thirty or more rows, most of which you will never buy. The useful chart is shorter. Nine grades cover nearly every machined part, and two of them cover most of the volume.

Here is the working list, with what each one is actually for. The full grade reference carries the UNS, Werkstoff and JIS cross-reference as a searchable table.

The commercially pure family: Grades 1, 2, 3 and 4

These are not alloys. They are titanium with controlled amounts of oxygen, iron, carbon, nitrogen and hydrogen. Oxygen is the lever. More of it raises strength and lowers ductility.

Grade	Typical min tensile	What it is for
Grade 1	around 240 MPa	The most formable. Deep drawn parts, explosive cladding, anode material
Grade 2	around 345 MPa	The workhorse. Chemical plant, marine, heat exchangers, general corrosion service
Grade 3	around 450 MPa	Pressure vessel work where Grade 2 is not quite strong enough
Grade 4	around 550 MPa	Strongest CP grade. Some surgical and hardware applications

Grade 2 is the one you will meet. Grades 1, 3 and 4 exist, but a machined part in Grade 3 is unusual enough that stock availability becomes the first question.

All four corrode the same way, which is to say almost not at all in sea water and oxidising acids. If corrosion is why you chose titanium, you are in this family unless the part also carries load.

Grade 5: Ti-6Al-4V

Roughly half of all titanium used anywhere, and more than half of everything machined. Nominally 6 percent aluminium and 4 percent vanadium.

• Minimum tensile strength around 895 MPa, close to three times Grade 2.
• Heat treatable, so a shop can receive it annealed and you can specify solution treated and aged where the part needs it.
• Useful to roughly 400 C, which is where it beats every aluminium alloy.
• Cuts at around half the surface speed of Grade 2 and wears tools noticeably faster.

If your drawing says “titanium” with no grade, Grade 5 is what the shop will assume and quote.

Grade 23: Ti-6Al-4V ELI

Same nominal composition as Grade 5, with tighter ceilings on oxygen, nitrogen, carbon and iron. ELI means extra low interstitial.

Slightly lower strength, considerably better fracture toughness and better behaviour at cryogenic temperature. It is the implant grade, specified by ASTM F136 for surgical use, and it turns up in offshore and cryogenic work too.

On the machine it behaves like Grade 5. The difference your shop feels is traceability and paperwork, not cutting data.

Grade 9: Ti-3Al-2.5V

Sometimes called half six four. Strength sits between Grade 2 and Grade 5, and it is cold formable in a way Grade 5 is not.

Most of the world’s Grade 9 is tube. Bicycle frames, aircraft hydraulic lines, sports equipment. If your part is a machined fitting that mates to Grade 9 tube, say so, because the stock form drives the quote.

Grades 7, 11 and 12: the corrosion specialists

When Grade 2 is not enough, it is almost always crevice corrosion in hot chloride that is the problem, not general corrosion.

Grade	Addition	Why
Grade 7	around 0.15 percent palladium	Best crevice corrosion resistance in hot reducing acids. Expensive
Grade 11	around 0.15 percent palladium, on a Grade 1 base	Same chemistry benefit, more formable
Grade 12	0.3 percent molybdenum, 0.8 percent nickel	Most of the benefit of Grade 7 at a lower price

All three machine much like Grade 2. The catch is stock. These are not shelf items in most sizes, so ask about lead time before you commit a drawing to Grade 7.

The quick chart

Grade	Family	Machinability	Typical use
1	CP	Easiest, very gummy	Formed parts, anodes
2	CP	Easy, gummy	Marine, chemical, heat exchangers
4	CP	Moderate	Higher strength CP hardware
5	Alpha beta	Hard	Structural, aerospace, consumer
7	CP plus Pd	Easy	Hot chloride service
9	Near alpha	Moderate	Tube, frames, hydraulic lines
12	CP plus Mo Ni	Easy	Chloride service, cheaper than Grade 7
23	Alpha beta ELI	Hard	Implants, cryogenic, offshore

Which standard your RFQ should name

The grade alone is not enough. The standard decides what the mill certificate says and what the mill had to test.

• ASTM B348 covers titanium bar and billet. This is the normal call for machined parts.
• ASTM B265 covers plate, sheet and strip.
• ASTM B338 and B861 cover tube and pipe.
• AMS 4928 is the aerospace specification for Grade 5 bar, with tighter requirements than B348.
• ASTM F136 covers Grade 23 for surgical implants, and ASTM F67 covers the CP grades for the same use.

If your customer requires AMS 4928 and your RFQ says only “Grade 5”, the shop will buy to B348 and your certificate will be wrong. Name the standard.

What to put on the RFQ

Grade, standard, stock form if you know it, and one line on the service conditions. If you are not sure of the grade, skip it and describe the service instead. Any shop that cuts titanium in production will tell you which grade it would quote, and it is often cheaper than the one you had in mind.

Frequently asked questions

Keep reading

• Grade 2 vs Grade 5 Titanium: Picking the Right Grade for a Machined Part
• Grade 23 ELI Titanium and the Paperwork That Comes With It