Titanium Grade 2
Designation and equivalent standards
Section titled “Designation and equivalent standards”Titanium Grade 2 (UNS R50400, ASTM B265) is commercially pure titanium with a minimum purity of 99.2%. It is governed by international standards such as ASTM B265, ASME SB-265, AMS 4902 and DIN 3.7035. It is the most widely used grade of commercially pure titanium thanks to its excellent balance of strength, ductility and corrosion resistance.
Chemical composition
Section titled “Chemical composition”Chemical composition in % by mass according to ASTM B265:
| Element | Titanium (Ti) | Iron (Fe) max. | Oxygen (O) max. | Carbon (C) max. | Nitrogen (N) max. | Hydrogen (H) max. |
|---|---|---|---|---|---|---|
| % | Balance | 0.30 | 0.25 | 0.08 | 0.03 | 0.015 |
Mechanical properties in annealed condition
Section titled “Mechanical properties in annealed condition”Values correspond to annealed sheet/plate per ASTM B265 at room temperature. Minimum yield strength is 275 MPa (40 ksi).
| Property | Min. value (SI) | Typical value (SI) | Unit (SI) | Min. value (Imp.) | Unit (Imp.) |
|---|---|---|---|---|---|
| Tensile strength | 345 | 415 | MPa | 50 | ksi |
| Yield strength (0.2%) | 275 | 310 | MPa | 40 | ksi |
| Elongation (50 mm) | 20 | 25 | % | 20 | % |
| Brinell hardness | – | 150 | HB | – | HB |
| Elastic modulus | 100 | 105 | GPa | 14.5 | Msi |
Mechanical properties in strain-hardened condition
Section titled “Mechanical properties in strain-hardened condition”Strength can be increased by cold working. After a 25–30% reduction in section, typical values are:
| Property | Typical value (SI) | Unit (SI) | Typical value (Imp.) | Unit (Imp.) |
|---|---|---|---|---|
| Tensile strength | 550 | MPa | 80 | ksi |
| Yield strength (0.2%) | 480 | MPa | 70 | ksi |
| Elongation (50 mm) | 15 | % | 15 | % |
Physical properties
Section titled “Physical properties”Density of Titanium Grade 2 is 4.51 Mg/m³ (281 lb/ft³), approximately 57% of steel.
| Property | Value (SI) | Unit (SI) | Value (Imp.) | Unit (Imp.) |
|---|---|---|---|---|
| Density | 4.51 | Mg/m³ | 281 | lb/ft³ |
| Atomic volume | 0.0106 | m³/kmol | 646 | in³/kmol |
| Elastic modulus | 100–105 | GPa | 14.5–15.2 | Msi |
| Shear modulus | 36–39 | GPa | 5.2–5.7 | Msi |
| Poisson’s coefficient | 0.35–0.37 | – | 0.35–0.37 | – |
Thermal properties
Section titled “Thermal properties”Melting point is around 1668 °C (3034 °F).
| Property | Value (SI) | Unit (SI) | Value (Imp.) | Unit (Imp.) |
|---|---|---|---|---|
| Melting point | 1665–1671 | °C | 3030–3040 | °F |
| Thermal conductivity | 16.3–18 | W/m·K | 113–125 | BTU·in/(h·ft²·°F) |
| Specific heat | 539–541 | J/kg·K | 0.129–0.129 | BTU/lb·°F |
| Coefficient of thermal expansion (20–100 °C) | 8.5–9.3 | 10⁻⁶/K | 4.7–5.2 | 10⁻⁶/°F |
Electrical properties
Section titled “Electrical properties”Electrical resistivity of Titanium Grade 2 at 20 °C is approximately 0.56 μΩ·m.
| Property | Value (SI) | Unit (SI) | Value (Imp.) | Unit (Imp.) |
|---|---|---|---|---|
| Electrical resistivity | 0.55–0.575 | 10⁻⁶ Ω·m | 0.55–0.575 | μΩ·cm |
Corrosion resistance
Section titled “Corrosion resistance”Titanium Grade 2 exhibits exceptional resistance in aggressive environments. The surface oxide layer is self-repairing and protects it even in seawater, chlorides and oxidizing media.
| Medium | Resistance (1 = poor, 5 = excellent) | Observations |
|---|---|---|
| Fresh water | 5 | Completely immune |
| Seawater | 5 | Excellent, no corrosion up to 120 °C |
| Weak acids | 5 | High resistance in moderate concentrations |
| Strong acids (reducing) | 3 | Acceptable with inhibitors; concentrated HCl may attack it |
| Weak/strong alkalis | 4 | Good, with slight loss in hot concentrated NaOH |
| Organic solvents | 5 | Inert in almost all cases |
| Oxidation at 500 °C | 4 | Surface oxide formation without catastrophic degradation |
| Wear | 3 | Moderate wear resistance; improves with nitriding |
| UV / radiation | 5 | No appreciable changes |
Applications by industry
Section titled “Applications by industry”Thanks to its combination of moderate strength, light weight and high corrosion resistance, Titanium Grade 2 is the most widely used in:
- Chemical and process industry: heat exchangers, distillation towers, reactors, piping for corrosive media.
- Marine engineering: propeller shafts, pumps, valves and fittings for seawater.
- Power generation: condensers in power plants and desalination plants.
- Medicine and dentistry: surgical implants, bone screws and prosthetic structures due to its biocompatibility and osseointegration.
- Aerospace: components of compressed air systems, bleed ducts and fairings that do not require very high strength.
- Sports equipment: bicycle frames, rackets and components subjected to medium fatigue.
- Architecture and consumer goods: exterior cladding, frames for glasses and high-end watches.
Comparison with similar materials
Section titled “Comparison with similar materials”The following table compares Titanium Grade 2 with other grades of pure titanium and the reference alloy Ti-6Al-4V.
| Material | Yield strength (MPa) | Tensile strength (MPa) | Elongation (%) | Density (g/cm³) | Main advantage |
|---|---|---|---|---|---|
| Titanium Grade 1 | 170–310 | 240–370 | 24 | 4.51 | Maximum ductility and formability |
| Titanium Grade 2 | 275–345 | 345–480 | 20 | 4.51 | Best strength/ductility balance |
| Titanium Grade 3 | 380–450 | 480–550 | 18 | 4.51 | Higher strength than Grade 2 |
| Titanium Grade 4 | 483–550 | 550–680 | 15 | 4.51 | Maximum strength among CP Ti |
| Ti-6Al-4V (Grade 5) | 828–1100 | 895–1170 | 10 | 4.43 | Very high strength and heat treatable |
Frequently Asked Questions (FAQ)
Section titled “Frequently Asked Questions (FAQ)”What is the minimum tensile strength of Titanium Grade 2 in annealed condition?
Section titled “What is the minimum tensile strength of Titanium Grade 2 in annealed condition?”The minimum tensile strength of annealed Titanium Grade 2 is 345 MPa (50 ksi), with a typical value of 415 MPa. This value is obtained in sheet per ASTM B265 with a minimum elongation of 20%.
What is the yield strength of Titanium Grade 2 and how does it vary with cold working?
Section titled “What is the yield strength of Titanium Grade 2 and how does it vary with cold working?”The minimum yield strength in annealed condition is 275 MPa (40 ksi), but after a 25–30% cold reduction it can exceed 480 MPa (70 ksi). The gain in strength is accompanied by a reduction in elongation to approximately 15%.
At what temperature does Titanium Grade 2 melt?
Section titled “At what temperature does Titanium Grade 2 melt?”The melting point of Titanium Grade 2 is 1668 °C (3034 °F). This temperature enables its use in applications requiring dimensional stability at high temperatures, although above 400 °C its mechanical strength drops significantly.
What is the density of Titanium Grade 2 and how does it compare to steel?
Section titled “What is the density of Titanium Grade 2 and how does it compare to steel?”The density of Titanium Grade 2 is 4.51 g/cm³ (281 lb/ft³), approximately 43% lower than carbon steel (7.85 g/cm³). This low density, together with a strength similar to some stainless steels, provides an excellent strength-to-weight ratio.
What is the thermal conductivity of Titanium Grade 2?
Section titled “What is the thermal conductivity of Titanium Grade 2?”The thermal conductivity of Titanium Grade 2 is 16.3–18 W/m·K (113–125 BTU·in/(h·ft²·°F)). This value is low compared to aluminum or copper, limiting its use in high-efficiency heat exchangers, but it is suitable for chemical applications where stability against corrosive media is required.
What type of weldability does Titanium Grade 2 have?
Section titled “What type of weldability does Titanium Grade 2 have?”Titanium Grade 2 is easily weldable by TIG, MIG and resistance welding, provided the molten zone and back face are protected with inert gas (high-purity argon) to avoid oxygen and nitrogen absorption. With a proper procedure, joints reach 100% of the base metal strength.
References
Section titled “References”- azom.com: https://www.azom.com/properties.aspx?ArticleID=712
- engineeringtoolbox.com: https://www.engineeringtoolbox.com/material-properties-t_24.html
- steelnumber.com: https://www.steelnumber.com/en/search_form_eu.php