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What Grade Should You Use? Start With These Three Questions

Titanium grade selection boils down to three sequential questions. Answer them in order, and the right grade becomes clear:

1. Is the part an implantable medical device that will be subject to cyclic loading (fatigue)?

Yes: Use Grade 23 (Ti-6Al-4V ELI, ASTM F136). No substitutions without regulatory review.
No: Continue to question 2.

2. Does the structural analysis require UTS greater than 50 ksi (345 MPa)?

Yes: Use Grade 5 (Ti-6Al-4V, AMS 4928) — 130 ksi UTS.
No: Continue to question 3.

3. Does the application require titanium's corrosion resistance (marine, chemical, medical)?

Yes: Use Grade 2 (CP titanium, ASTM B348) — lower cost, faster machining.
No: Reconsider whether titanium is the correct material at all. 304 stainless or 6061 aluminum may be more economical.

Key Takeaway

Most engineers default to Ti-6Al-4V Grade 5 for everything titanium. This is often an over-specification. If the structural FOS is well above 2.0 and the application is corrosion-dominated (not strength-dominated), Grade 2 reduces total part cost by 25–35% with no functional compromise.

Grade Summary

The Three Grades You Need to Know

Corrosion-first, cost-effective

CP Grade 2

ASTM B348 Grade 2

UTS50 ksi (345 MPa)
Machinability~30%
Material cost$10–18/lb ($22–40/kg)

Commercially pure titanium — the most machinable and most cost-effective titanium grade. Choose when corrosion resistance is required but the part is not load-bearing or high-stress.

The workhorse alloy

Grade 5 (Ti-6Al-4V)

AMS 4928

UTS130 ksi (896 MPa)
Machinability~22%
Material cost$15–30/lb ($33–66/kg)

The most widely used titanium alloy — over 50% of all titanium parts. Choose when both high strength and corrosion resistance are required: industrial, structural, and performance applications.

Medical implant grade

Grade 23 (ELI)

ASTM F136 / ISO 5832-3

UTS120 ksi (827 MPa)
Machinability~22%
Material cost$20–40/lb ($44–88/kg)

Extra Low Interstitials variant of Ti-6Al-4V with higher fracture toughness (KIc ~75 MPa√m). Required for load-bearing implantable medical devices. Not interchangeable with Grade 5 for regulated applications.

Grade Selection

Titanium Grade Decision Matrix

Decision matrix for selecting titanium grade for CNC machining
RequirementCP Grade 2Grade 5 (Ti-6Al-4V)Grade 23 (ELI)
UTS > 100 ksi (690 MPa)✗ (50 ksi max)✓ (130 ksi)✓ (120 ksi)
Corrosion resistance (seawater)✓ Excellent✓ Excellent✓ Excellent
Biocompatibility (ISO 10993)✓✓✓
Load-bearing implant (ASTM F136 / ISO 5832-3)✗✗✓ Required
Max service temp > 300°F (149°C)✗✓ (up to 600°F)✓ (up to 600°F)
Lowest material cost✓ $10–18/lb ($22–40/kg)Moderate $15–30/lb ($33–66/kg)✗ $20–40/lb ($44–88/kg)
Highest machinability✓ ~30%~22%~22%
Best formability (cold bending)✓ ExcellentModerateModerate
Weldability (GTAW)✓ ExcellentGoodGood
High-performance structural✗ (insufficient strength)✓✗ (overkill for structural — use AMS 4928 Grade 5)
Standard availability✓ Widely stocked✓ Widely stockedSpecialty — longer lead
By Industry

Grade Selection by Industry

Industrial & Structural

Grade 5 (AMS 4928)

130 ksi UTS + low density for high-performance brackets, machinery hardware, hydraulic fittings. STA condition (150+ ksi) for highest-strength applications.

Medical Implants

Grade 23 (ASTM F136)

Required for load-bearing implants per FDA guidance and ISO 5832-3 / ASTM F136. Grade 2 acceptable for non-load-bearing implanted components (check with regulatory counsel).

Marine & Offshore

CP Grade 2 (ASTM B348)

Corrosion immunity in seawater — chloride stress corrosion cracking does not occur in titanium. Grade 5 may be specified for structural components where strength matters.

Chemical Processing

CP Grade 2 (ASTM B348)

Superior resistance to reducing acids (HCl, H₂SO₄) where Grade 5 can suffer crevice corrosion. Reactor liners, piping, valves.

High-Performance Industrial

Grade 5 (AMS 4928)

Valves, compressor components, high-temp hardware. Grade 2 where corrosion is the sole concern.

Consumer / Sporting

Grade 5 (AMS 4928)

Bicycle components, eyeglass frames, watches, sports hardware. Grade 5 for structural; Grade 2 for jewelry/non-structural where machinability matters.

Cost Comparison

Grade Cost Comparison

Cost comparison for titanium grade selection
Cost FactorCP Grade 2Grade 5Grade 23
Bar stock $/lb ($/kg)$10–18 ($22–40)$15–30 ($33–66)$20–40 ($44–88)
Relative machining time0.8×1.0× (baseline)1.0×
Material availabilityWidely stockedWidely stockedSpecialty (2–6 wk lead)
Relative total part cost~0.65–0.75×1.0× (baseline)~1.2–1.5×
When cost premium is justifiedNever over Grade 2 for corrosion-only appsWhen strength requiredMedical implant regulatory compliance

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Common Questions

Frequently Asked Questions

What does "titanium grade" mean, and how is it different from a single material?
A titanium grade is a formal material specification that defines the chemical composition limits, mechanical property minimums, and acceptable product forms (bar, sheet, plate, etc.). Different grades have different amounts of alloying elements or different purity levels, which produce significantly different strength, machinability, and cost characteristics. When you specify "Grade 2 titanium per ASTM B348," you are communicating a complete material requirement — not just a metal type. Without the grade designation, "titanium" on a drawing is an incomplete specification. A supplier could legally ship any titanium material if no grade is called out.
Does using a stronger grade always mean better performance?
No — over-specifying is a common and costly mistake. Using Ti-6Al-4V (Grade 5) where Grade 2 would meet the structural requirement adds 50–70% to material cost and 15–25% to cycle time, without any functional benefit. Stronger materials also machine more aggressively — higher cutting forces, faster tool wear — which increases scrap risk. The correct approach is to run a structural analysis first: if Grade 2 passes with an adequate factor of safety (typically FOS ≥ 2.0 on UTS for static loads), it is the better specification. Only upgrade to Grade 5 when the analysis shows Grade 2 is insufficient.
What is the most commonly used titanium grade for CNC machining?
Ti-6Al-4V (Grade 5, AMS 4928) is the most commonly used titanium alloy for CNC machined parts, accounting for over 50% of all titanium machined components. It provides the best balance of strength (130 ksi / 896 MPa UTS), weight (4.43 g/cm³), and availability. CP Grade 2 (ASTM B348) is the second most common grade, used primarily for applications where corrosion resistance is the primary requirement and high strength is not — marine hardware, chemical processing, and non-load-bearing medical devices. Grade 23 ELI (ASTM F136) is used exclusively for implantable medical devices.
When should I use CP Grade 2 instead of Ti-6Al-4V?
Use CP Grade 2 titanium when: (1) Corrosion resistance is the primary requirement and the part is not load-bearing or highly stressed. (2) Higher formability or weldability is needed — Grade 2 bends and forms more easily than Ti-6Al-4V without cracking. (3) Cost reduction is important — Grade 2 material costs $10–18/lb ($22–40/kg) vs. $15–30/lb ($33–66/kg) for Ti-6Al-4V, and machines 15–25% faster. (4) You are producing parts for chemical processing, marine environments, or desalination equipment where CP purity ensures superior resistance to reducing acid environments. If the structural analysis shows Ti-6Al-4V provides FOS > 3:1 on yield, Grade 2 is likely acceptable and will reduce total part cost by 25–35%.
Is Grade 5 titanium strong enough for most engineering applications?
Yes — Ti-6Al-4V Grade 5 at 130 ksi (896 MPa) UTS covers the vast majority of structural applications requiring titanium. For context: 6061-T6 aluminum is 45 ksi (310 MPa), 304 stainless is 84 ksi (579 MPa), 4140 steel heat-treated is 125–150 ksi (862–1,034 MPa). Grade 5 titanium provides steel-level strength at 57% of steel's density. The cases where Grade 5 is insufficient: ultra-high-cycle fatigue applications requiring Grade 23 ELI (medical implants), or applications requiring 150+ ksi that specify Grade 5 STA condition (solution treat and age to 150–165 ksi). Beta titanium alloys (Grade 19, 21) can reach 180+ ksi but are rarely specified for CNC machined parts.
Can I switch titanium grades after a design is released?
Switching titanium grades on a released engineering drawing requires an Engineering Change Order (ECO) and potentially additional qualification data. For non-regulated applications (industrial, commercial), switching Grade 5 to Grade 2 or vice versa is a material substitution that requires re-analysis (stress analysis, corrosion analysis) and drawing revision. For regulated applications (medical devices, etc.), a grade change typically requires: updated material specification on drawing, re-validation per the applicable standard (ISO 13485 or equivalent quality system), and potentially customer or regulatory notification. Never substitute grades on a drawing without formal approval — material substitution is a common nonconformance finding in quality audits.

Related Resources

Titanium Grades Explained (1–5)
Full properties table for all titanium grades
Grade 23 vs Grade 5
ELI vs standard: composition, toughness, regulatory
Titanium CNC Machining Guide
Complete guide: grades, speeds/feeds, DFM, cost

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