Titanium Grade 2 CNC Machining Guide
Not every titanium part needs to withstand 130 ksi (896 MPa). When the design requirement is corrosion resistance — not maximum strength — CP Grade 2 delivers titanium's immunity to seawater, chlorides, and acidic environments at lower cost and faster machining times than Ti-6Al-4V. This guide covers when to use it and how to machine it.
UTS: 50 ksi (345 MPa) · Machinability: ~30% (vs. 22% for Grade 5) · Material cost: $10–18/lb ($22–40/kg) · Cutting speed: 120–200 SFM (37–61 m/min)
Why Grade 2 Exists: Corrosion Without Compromise
The narrative around titanium usually focuses on its strength. Ti-6Al-4V is talked about because it is strong — 130 ksi (896 MPa) UTS at only 0.160 lb/in³. But that story misses a significant portion of real-world titanium applications where the requirement is not strength at all. It is corrosion resistance.
Titanium forms a passive TiO₂ (titanium dioxide) layer in air and aqueous environments. This oxide layer is stable and self-healing — scratch it, and it reforms. It resists seawater, chloride solutions, and many acids that would attack steel or even 316L stainless. CP Grade 2 delivers all of that at 50 ksi (345 MPa) UTS, excellent formability, and a machining speed that is 35% faster than Ti-6Al-4V.
When the structural load analysis shows 50 ksi (345 MPa) is sufficient, Grade 2 is the right choice. It machines faster, costs less per pound, and still gives you titanium's full corrosion resistance package. The tradeoff is structural capacity — Grade 2 has roughly 38% the tensile strength of Ti-6Al-4V.
Key Takeaway
Use Grade 2 when the part needs titanium's corrosion resistance but does not require high structural strength. Marine hardware, chemical plant valves, heat exchangers, and non-load-bearing medical devices are all strong candidates. Run a structural analysis first — if 50 ksi (345 MPa) UTS passes with adequate factor of safety, Grade 2 is the economical choice.
CP Grade 2 Titanium Properties
“Commercially pure” means no intentional alloying elements have been added. Unlike Ti-6Al-4V (Grade 5), which contains 6 wt.% aluminum and 4 wt.% vanadium to increase strength, Grade 2 is essentially just titanium with controlled trace amounts of oxygen, iron, nitrogen, and carbon. The grade number (1–4) reflects how much of these trace elements are allowed — Grade 2 sits in the middle, balancing strength, machinability, and availability.
The properties below reflect this pure-titanium character: high corrosion resistance from the passive TiO₂ layer, good formability, excellent weldability, and lower strength than alloy grades.
| Property | Value | Standard |
|---|---|---|
| UTS | 50 ksi (345 MPa) min | ASTM B348 |
| 0.2% Yield Strength | 40 ksi (275 MPa) min | ASTM B348 |
| Elongation | 20% min | ASTM B348 |
| Density | 0.163 lb/in³ (4.51 g/cm³) | ASTM B348 |
| Elastic Modulus | 15 Msi (105 GPa) | — |
| Thermal Conductivity | 16 W/m·K | ASM Handbook |
| Hardness | ~150–200 HB | — |
| Machinability Rating | ~30% vs. B1112 steel | Machining Data Handbook |
| O content max | 0.25 wt.% | ASTM B348 |
| Fe content max | 0.30 wt.% | ASTM B348 |
| Ti content (min) | ≥99.2 wt.% | ASTM B348 |
Grade 2 vs Ti-6Al-4V (Grade 5)
The comparison below answers one question: when is Grade 2 enough, and when do you need Grade 5? If the primary requirement is corrosion resistance and the structural analysis shows 50 ksi (345 MPa) UTS is sufficient with adequate safety factor, Grade 2 saves 25–35% on total part cost. If the part is structurally loaded and needs 130 ksi (896 MPa) — or the application requires heat resistance above 400°F (204°C) — Grade 5 is the only option.
| Property | CP Grade 2 | Ti-6Al-4V (Grade 5) |
|---|---|---|
| UTS | 50 ksi (345 MPa) | 130 ksi (896 MPa) |
| Strength-to-weight ratio | ~307 ksi/(lb/in³) | ~813 ksi/(lb/in³) |
| Density | 0.163 lb/in³ (4.51 g/cm³) | 0.160 lb/in³ (4.43 g/cm³) |
| Machinability | ~30% | ~22% |
| Relative cutting speed | +35% vs. Grade 5 | Baseline |
| Corrosion resistance | Excellent — superior in reducing acids | Excellent — similar in most environments |
| Weldability (GTAW) | Excellent — all positions | Good — shielding required |
| Material cost | $10–18/lb ($22–40/kg) | $15–30/lb ($33–66/kg) |
| Total part cost (similar geometry) | ~65–75% of Grade 5 cost | Baseline (1×) |
| Primary specification | ASTM B348 Grade 2 | AMS 4928 |
| Best for | Corrosion resistance, formability | High strength-to-weight, heat resistance |
CP Grade 2 Speeds and Feeds
CP Grade 2 machines 25–35% faster than Ti-6Al-4V due to lower strength and slightly higher thermal conductivity (16 vs. 6.7 W/m·K). The same tooling (PVD TiAlN carbide) and coolant strategy (high-pressure flood) apply.
| Operation | SFM (m/min) | Feed ipt/ipr (mm) | Notes |
|---|---|---|---|
| Rough Milling (4-flute TiAlN carbide) | 120–160 (37–49) | 0.003–0.006 ipt (0.08–0.15 mm/tooth) | 25–35% radial engagement; flood coolant 300+ psi (21+ bar) |
| Finish Milling | 150–200 (46–61) | 0.001–0.003 ipt (0.025–0.08 mm/tooth) | Fresh insert; Ra 32 µin. (0.8 µm) achievable |
| Rough Turning | 150–200 (46–61) | 0.010–0.015 ipr (0.25–0.38) | Positive rake insert; K-class carbide |
| Finish Turning | 180–250 (55–76) | 0.004–0.007 ipr (0.10–0.18) | Ra 16 µin. (0.4 µm) achievable with fresh insert |
| Drilling (TiAlN solid carbide) | 100–130 (30–40) | 0.003–0.005 ipr (0.08–0.13) | Peck every 1.5D; 130° drill point |
| Thread Milling | 80–100 (24–30) | — | Thread mill preferred; lower risk than Grade 5 tapping |
CP Grade 2 Applications
Propeller shafts, through-hulls, fasteners, heat exchangers — immune to seawater and chloride stress corrosion cracking
Reactor components, piping, valves, pumps — resistant to nitric acid, chlorinated organics, and oxidizing media
Reverse osmosis plant components, pressure vessels, heat exchanger tubes — high reliability in high-salinity brine
Trial implants, surgical instrument handles, fixation plate blanks, imaging components — biocompatible per ISO 10993
Cladding fasteners, structural connections in coastal environments — corrosion resistance with aesthetic finish via anodizing
Valve bodies, pump housings, heat exchanger baffles — where stainless steel fails from crevice corrosion in chlorinated water
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ASTM B348 Grade 2 is often the lower-cost titanium answer when corrosion resistance matters more than peak strength. Use quote review to confirm material fit, sourcing options, and tolerance risk before production starts.
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