Titanium Grade 3, also known as commercially pure titanium (CP Ti) Grade 3, is a unalloyed titanium grade classified under the ASTM B265 (for plate, sheet, and strip) and ASTM B338 (for seamless pipe and tube) standards, among others. It is part of the commercially pure titanium family, which differs from alloyed titanium grades (e.g., Ti-6Al-4V) by containing minimal alloying elements-its composition is primarily titanium (over 99%) with trace impurities.
Compared to lower-grade commercially pure titanium (e.g., Grade 1 and Grade 2), Grade 3 offers a balance of higher strength and moderate ductility. It is not as soft as Grade 1/2 (which prioritize formability) nor as strong as alloyed grades (which prioritize high strength-to-weight ratios). Its key defining trait is its excellent corrosion resistance in aggressive environments, including oxidizing acids (e.g., nitric acid), saltwater, and many industrial chemicals-properties inherent to pure titanium's stable oxide layer (TiO₂) that forms on its surface.
Common applications of Grade 3 titanium include components for chemical processing equipment (e.g., valves, pumps, heat exchangers), marine hardware (e.g., fasteners, hull components), medical devices (e.g., surgical instruments, dental implants where moderate strength is needed), and aerospace parts (e.g., low-stress structural components in aircraft).
Titanium Grade 3 exhibits moderate-to-high strength relative to other commercially pure titanium grades, though it is less strong than titanium alloys like Ti-6Al-4V. Its mechanical properties are standardized under ASTM specifications, with typical values (for annealed condition, the most common heat treatment) as follows:
Tensile Strength: Typically ranges from 480 MPa to 620 MPa (70,000 psi to 90,000 psi). This is significantly higher than Grade 2 titanium (345–550 MPa / 50,000–80,000 psi) and Grade 1 titanium (240–370 MPa / 35,000–54,000 psi).
Yield Strength: Generally between 370 MPa and 485 MPa (54,000 psi to 70,000 psi), again exceeding lower CP Ti grades.
Elongation: Typically 15–25% (in 50 mm gauge length), indicating good ductility-enough to allow forming processes like bending, rolling, or drawing, though less formable than Grade 1/2.
A critical context for its strength is its strength-to-weight ratio: titanium has a density of ~4.51 g/cm³ (about 56% the density of steel). Even with lower absolute strength than high-strength steel or Ti-6Al-4V, Grade 3 delivers exceptional strength relative to its weight, making it ideal for weight-sensitive applications where corrosion resistance is also critical.
Titanium Grade 3 is a commercially pure titanium grade, meaning its composition is dominated by titanium (≥99.0%) with strict limits on trace impurities (no intentional alloying elements). The chemical composition is standardized by organizations like ASTM International (e.g., ASTM B265) and ISO (e.g., ISO 5832-3), with the following typical ranges (by weight percentage, wt%):
