Descriptions of Titanium Gr7 Seamless Tube (ASTM B861)
Titanium Grade 7 seamless tube (ASTM B861) is a corrosion-resistant titanium–palladium alloy known for its exceptional performance in highly oxidising or mildly reducing environments. Grade 7 is essentially commercially pure titanium (similar to Gr2) with 0.12–0.25% palladium added, which significantly enhances resistance to crevice corrosion, pitting, and stress corrosion cracking.
Titanium Gr7 seamless tubes provide an excellent combination of corrosion resistance, strength, fabricability, and weldability, making them suitable for demanding chemical, marine, and industrial applications.
Key Features
Excellent resistance to oxidising and reducing acids
Outstanding performance in chloride-containing environments
High resistance to crevice and pitting corrosion
Fully weldable and easy to fabricate
Suitable for high-purity chemical and pharmaceutical equipment
Corrosion Resistance of Titanium Gr7 Seamless Tube
Titanium Grade 7 exhibits exceptional corrosion resistance in a wide range of environments:
1. Neutral & Oxidising Media
Excellent resistance in neutral solutions, oxidising acids, and oxidising salts.
Highly resistant to wet chlorine gas, chlorite, hypochlorite, and chloride solutions.
2. Reducing Acids
Titanium Gr7 can be used in some dilute reducing acids, including:
Nitric acid with various concentrations
Mild sulfuric acid conditions
3. Alkaline Solutions
Highly resistant to saturated solutions of Ba(OH)₂, Ca(OH)₂, and Mg(OH)₂ at room temperature.
Not recommended for boiling sodium hydroxide due to potential corrosion.
4. Seawater & Marine Atmosphere
Completely resistant to corrosion in seawater.
Performs well in marine splash zones and subsea environments.
5. Organic Acids
Excellent resistance to most organic acids
Exception: Not suitable for formic acid or oxalic acid.
Mechanical Properties (ASTM B861 – Titanium Grade 7)
Tensile Strength (min): 348 MPa
Yield Strength (min): 275 MPa (max: 450 MPa)
Elongation (min): 20%
These properties provide a balanced combination of ductility and strength, similar to commercially pure titanium Grade 2 but with superior corrosion performance.
Chemical Composition of Titanium Grade 7 (ASTM B861)
(Typical Specification)
| Element |
Content (wt%) |
| Palladium (Pd) |
0.12–0.25 |
| Nitrogen (N), max |
0.03 |
| Carbon (C), max |
0.08 |
| Hydrogen (H), max |
0.015 |
| Iron (Fe), max |
0.30 |
| Oxygen (O), max |
0.25 |
| Titanium (Ti) |
Balance |
Applications of Titanium Gr7 Seamless Tube
Titanium Grade 7 tubes are widely used in environments requiring high corrosion resistance combined with moderate strength.
1. Aerospace Components
Compression members
Tubular struts
Fasteners and structural tubing
2. Marine Engineering
Propeller shafts
Heat exchanger tubes
Seawater cooling systems
Subsea structural components
3. Chemical Processing
Pumps
Valves
Heat exchangers
Reactors
Chlorine-handling equipment
4. Medical & Dental
Orthopaedic pins and screws
Dental implants
Surgical instruments
(Note: Grade 7 is less common than Grades 1, 2, or 23 but is still used in speciality applications)
5. Automotive
High-performance exhaust systems
Suspension components
Brake system hardware
