Titanium Grades Explained (Grade 1–5)
When a drawing says “titanium,” that is not a complete material specification. There are more than 30 ASTM-recognized titanium grades — each with different strength, machinability, corrosion resistance, and cost. Choosing the wrong one either over-specifies (costing more than needed) or under-specifies (failing in service). This guide explains the grades that matter for CNC machined parts.
6 grades cover 95% of CNC applications · Grade 2 (CP) best machinability + strength balance · Grade 5 (Ti-6Al-4V) most common · Grade 23 required for implants
What Are Titanium Grades and Why Do They Matter?
A grade is a standardized material specification — a defined combination of composition, mechanical properties, and processing conditions that any qualified supplier must meet. When you put “Ti-6Al-4V per AMS 4928, Condition Annealed” on an engineering drawing, you are telling every supplier, inspector, and manufacturer exactly what material you expect. If you write “titanium,” you have said almost nothing.
Titanium grades fall into two families: commercially pure (CP) grades (1–4), which are essentially pure titanium with controlled trace elements, and alloy grades (Grade 5 and beyond), which have intentional additions of aluminum, vanadium, or other elements to achieve specific properties. The distinction matters because CP grades prioritize formability and corrosion resistance, while alloy grades prioritize strength.
For most CNC machined parts, you only need to know three grades well: Grade 2 (CP, best machinability), Grade 5 (Ti-6Al-4V, most common alloy), and Grade 23 (Ti-6Al-4V ELI, required for implantable medical devices). The sections below give you the full picture for each.
Titanium Grade Classification System
ASTM International classifies titanium alloys by grade number under ASTM B265, B348, and related standards. Grades 1–4 are commercially pure (CP) titanium — primarily titanium with controlled interstitial element content (oxygen, nitrogen, hydrogen, iron). Grade 5 and above are alloys with intentional alloying additions.
Classification Structure
Commercially Pure (CP)
Grades 1–4
≥99% Ti; strength varies with O and Fe content
Alpha + Beta Alloys
Grade 5 (Ti-6Al-4V), Grade 23 (ELI)
Most common engineering grades; heat-treatable
Beta Alloys
Grade 19, 21, etc.
High strength; complex machining; rarely specified for CNC parts
Commercially Pure Titanium: Grades 1–4
CP grades differ only in interstitial element content — primarily oxygen and iron. Interstitial elements are atoms small enough to fit between titanium atoms in the crystal lattice. They distort the lattice and resist dislocation movement — which is the mechanism behind plastic deformation. More oxygen means more lattice distortion: higher yield strength, but also lower ductility and harder machining.
The grade number roughly tracks interstitial content: Grade 1 has the lowest (softest, most formable), Grade 4 has the highest (strongest, least ductile). Grade 2 is by far the most widely used CP grade for CNC machined parts because it balances strength, machinability, and availability.
Highest formability. Chemical processing equipment, heat exchangers, marine hardware where maximum corrosion resistance and cold-forming are needed.
Most common CP grade. Marine, chemical, desalination, medical devices, architecture. Best balance of strength, ductility, and machinability.
Intermediate strength with good corrosion resistance. Less common than Grade 2 or 4; used when Grade 2 is too weak and Grade 4 is too stiff to form.
Highest strength CP grade. Surgical fasteners, chemical plant tubing, marine fittings requiring CP purity with near-alloy strength.
Grade 5: Ti-6Al-4V — The Workhorse Alloy
Ti-6Al-4V accounts for over 50% of all titanium mill product shipments globally. Its defining feature is an alpha+beta microstructure. Titanium exists in two crystal structures: alpha phase (hexagonal close-packed, stable at room temperature) and beta phase (body-centered cubic, stable at high temperature). Adding 6 wt.% aluminum stabilizes the alpha phase; 4 wt.% vanadium stabilizes the beta phase — so both phases coexist at room temperature.
This matters because the alpha phase provides creep resistance and weldability, while the beta phase enables heat treatment to a wide range of strength levels. The combination is why Ti-6Al-4V can be used across such a broad range of applications — from annealed bar stock for general machining to solution-treated-and-aged forgings for high-load structural parts.
| Condition | UTS | 0.2% Yield | Elongation | Hardness | Primary Standard |
|---|---|---|---|---|---|
| Annealed (mill anneal) | 130 ksi (896 MPa) | 120 ksi (827 MPa) | 10% | 302–340 HB | AMS 4928 |
| STA (solution treat + age) | 150–165 ksi (1,034–1,138 MPa) | 140–155 ksi (965–1,069 MPa) | 8–10% | 36–40 HRC | AMS 4967 (forgings) |
| Recrystallize Anneal | 130 ksi (896 MPa) | 120 ksi (827 MPa) | 10% | 296 HB | AMS 4911 (sheet) |
Key Takeaway
Ti-6Al-4V in the Annealed condition (AMS 4928) is the correct default specification for most structural CNC machined parts. STA condition (solution treat + age) delivers higher strength but is harder to source and costs more. Only specify STA when the structural analysis shows annealed strength is insufficient.
Grade 23: Ti-6Al-4V ELI — Medical Grade
Grade 23 is Ti-6Al-4V with Extra Low Interstitials (ELI) — tighter limits on oxygen, iron, nitrogen, and carbon vs. standard Grade 5. The lower interstitials improve fracture toughness and fatigue crack growth resistance, making it the required grade for load-bearing implantable medical devices.
| Property | Grade 5 (Ti-6Al-4V) | Grade 23 (ELI) |
|---|---|---|
| UTS (annealed) | 130 ksi (896 MPa) | 120 ksi (827 MPa) |
| Oxygen max | 0.20 wt.% | 0.13 wt.% (ELI limit) |
| Iron max | 0.30 wt.% | 0.25 wt.% |
| Primary standard | AMS 4928, ASTM B348 Gr.5 | ASTM F136, ISO 5832-3 |
| Key application | Structural, industrial, high-performance hardware | Load-bearing implants (hip, knee, spine, dental) |
| Machining parameters | SFM 80–150, flood coolant | Identical to Grade 5 |
| Cost premium over Grade 5 | Baseline | 20–50% |
When Grade 23 is Required
ASTM F136 Grade 23 ELI is required for implantable load-bearing devices (hip stems, tibial trays, spinal rods, trauma plates) per FDA guidance for Class III implants. For non-load-bearing medical devices (surgical instruments, trial implants) or non-implantable applications, standard Grade 5 per AMS 4928 is acceptable. Never substitute Grade 5 for Grade 23 in implant drawings that call out ASTM F136.
Key Takeaway
Grade 23 and Grade 5 are machined identically — same speeds, feeds, tooling, and coolant. The difference is raw material specification and cost (20–50% premium for Grade 23). If your drawing calls out ASTM F136, you must use Grade 23. If it calls out AMS 4928, standard Grade 5 is correct. Never substitute without explicit engineering approval.
Full Properties Comparison Table
| Property | Grade 1 | Grade 2 | Grade 3 | Grade 4 | Grade 5 | Grade 23 |
|---|---|---|---|---|---|---|
| Designation | CP Ti Gr.1 | CP Ti Gr.2 | CP Ti Gr.3 | CP Ti Gr.4 | Ti-6Al-4V | Ti-6Al-4V ELI |
| UTS (annealed) | 35 ksi (241 MPa) | 50 ksi (345 MPa) | 65 ksi (448 MPa) | 80 ksi (552 MPa) | 130 ksi (896 MPa) | 120 ksi (827 MPa) |
| 0.2% Yield | 25 ksi (172 MPa) | 40 ksi (275 MPa) | 55 ksi (380 MPa) | 70 ksi (483 MPa) | 120 ksi (827 MPa) | 110 ksi (758 MPa) |
| Elongation | 24% | 20% | 18% | 15% | 10% | 10% |
| Density (lb/in³) | 0.163 | 0.163 | 0.163 | 0.163 | 0.160 | 0.160 |
| Elastic Modulus | 15 Msi (105 GPa) | 15 Msi (105 GPa) | 15 Msi (105 GPa) | 15 Msi (105 GPa) | 16 Msi (110 GPa) | 16 Msi (110 GPa) |
| Machinability | ~40% | ~30% | ~28% | ~25% | ~22% | ~22% |
| Weldability | Excellent | Excellent | Excellent | Excellent | Good (GTAW) | Good (GTAW) |
| Primary Std. | ASTM B348 Gr.1 | ASTM B348 Gr.2 | ASTM B348 Gr.3 | ASTM B348 Gr.4 | AMS 4928 | ASTM F136 |
Which Titanium Grade Should You Specify?
If you need: Need corrosion resistance, moderate strength, low cost
CP Grade 2 per ASTM B348
Best machinability (~30%) among titanium grades; widely available; $10–18/lb ($22–40/kg). Use for marine hardware, chemical processing, non-load-bearing medical devices.
If you need: Need high strength-to-weight ratio; structural or high-load
Ti-6Al-4V Grade 5 per AMS 4928
130 ksi (896 MPa) UTS, 4.43 g/cm³ density. Standard for high-load structural parts, performance automotive, industrial fittings. Most widely stocked alloy.
If you need: Need implantable medical device (load-bearing)
Ti-6Al-4V ELI Grade 23 per ASTM F136
Required by FDA and ISO 5832-3 for load-bearing implants. Higher fracture toughness than Grade 5. Specify explicitly — cannot substitute with standard Ti-6Al-4V.
If you need: Not sure titanium is the right material at all
Start with 6061-T6 aluminum or 304 stainless steel
Titanium is justified only when you need the strength-to-weight ratio, biocompatibility, or chloride corrosion resistance that aluminum and steel cannot provide. If none of those apply, titanium will cost 5–10× more without functional benefit.
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MakerStage can quote CNC machined titanium parts in CP Grade 2, Ti-6Al-4V (Grade 5), and Grade 23 ELI. Upload your drawing to scope grade selection plus certification and traceability requirements during quote review.
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CP Grade 2, Ti-6Al-4V (Grade 5), and Grade 23 ELI can be reviewed during quoting so the material, cert, and traceability requirements match the part before production starts.
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