The Titanium Grade System
Titanium is classified into commercially pure grades designated Grade 1 through Grade 4 and alloy grades such as Grade 5 and Grade 9. The pure grades differ mainly in oxygen and iron content, which control strength and formability. Alloy grades add elements such as aluminum, vanadium, molybdenum and palladium to achieve higher strength or improved corrosion resistance. Each grade is identified by a UNS number such as R50400 for Grade 2.
Commercially Pure Grades 1 to 4
Grade 1 is the softest grade with a minimum tensile strength of 240 MPa and the best formability, used for chemical equipment and heat exchanger tubing. Grade 2 offers 345 MPa minimum tensile strength and is the general-purpose grade for industrial piping and marine service. Grade 3 provides 450 MPa and Grade 4 reaches 550 MPa, with Grade 4 used for surgical instruments, fasteners and higher-strength components.
Grade 5: Ti-6Al-4V
Grade 5 is the most widely used titanium alloy, containing 5.5 to 6.75 percent aluminum and 3.5 to 4.5 percent vanadium. Annealed material provides a minimum tensile strength of 895 MPa, and the alloy is used in aerospace structures, engine components, marine hardware and high-performance industrial equipment. Grade 23 is the low-interstitial version with reduced oxygen, specified for medical implants.
Grade 7, 11 and 12 for Corrosion Service
Grade 7 adds 0.12 to 0.25 percent palladium to the Grade 2 base for superior resistance to reducing acids and crevice corrosion. Grade 11 is the palladium version of Grade 1 with the same corrosion benefits and lower strength. Grade 12 uses molybdenum and nickel to reach 483 MPa minimum tensile strength while resisting crevice corrosion, and it is a popular choice for chemical and marine applications.
Grade 9 and Other Specialty Alloys
Grade 9, or Ti-3Al-2.5V, offers a minimum tensile strength of 620 MPa with good formability, making it a standard for aerospace hydraulic tubing and bicycle frames. Other specialty grades include Grade 6 with aluminum and tin additions, Grade 19 through 21 beta alloys for high-strength fasteners, and heat-resistant alloys such as Ti-6Al-2Sn-4Zr-2Mo for jet engine service at elevated temperature.
How to Choose a Grade
Selection starts with the service environment: temperature, media, pressure and load. Corrosion-driven applications usually start with Grade 2 and move to Grade 7, 11 or 12 when crevice corrosion is a risk. Strength-driven applications move from Grade 4 to Grade 5 or 9. Cost, availability and fabrication method then narrow the choice, and the final grade is verified against the governing product standard.
Frequently Asked Questions
Q: What is the strongest commercially pure titanium grade?
A: Grade 4 is the strongest pure grade with a minimum tensile strength of 550 MPa and a minimum yield strength of 480 MPa.
Q: What is the most commonly used titanium alloy?
A: Grade 5, or Ti-6Al-4V, is the most widely used titanium alloy across aerospace, marine and industrial applications.
Q: What grade of titanium is used for medical implants?
A: Grade 23, the low-interstitial version of Ti-6Al-4V, and the commercially pure grades are commonly used for implants and surgical hardware.
Q: How is titanium grade identified?
A: Grades follow the ASTM designation system with UNS numbers, for example R50400 for Grade 2 and R56400 for Grade 5.
Q: Which titanium grade resists crevice corrosion best?
A: Palladium-bearing grades such as Grade 7 and Grade 11, and the molybdenum-nickel Grade 12, provide the best resistance to crevice corrosion.
