What Is Grade 12 Titanium
Grade 12 titanium is an alloyed titanium grade with the nominal composition of 0.3 percent molybdenum and 0.8 percent nickel added to commercially pure titanium. The molybdenum stabilizes the beta phase and improves the elevated-temperature strength, and the nickel improves the corrosion resistance in reducing and crevice conditions. The alloy is often designated Ti-0.3Mo-0.8Ni, and it is available in all standard wrought forms including tube, pipe, plate, sheet, bar and wire. It is highly weldable and exhibits improved strength at elevated temperatures compared with the pure grades.
Key Properties
Grade 12 combines the corrosion resistance of titanium with higher mechanical strength. Its tensile strength is approximately 485 to 550 MPa depending on the product form, significantly higher than the pure grades, and it retains improved strength at elevated temperature. It offers superior crevice corrosion resistance compared with the pure grades, and excellent resistance under oxidizing to mildly reducing conditions, especially in chloride environments. The alloy is weldable using standard titanium practices, and it maintains good ductility and toughness.
Why the Molybdenum and Nickel Additions
The molybdenum addition stabilizes the beta phase, which improves the strength and hardenability of the alloy, and it contributes to the corrosion resistance in reducing media. The nickel addition is the key to the crevice corrosion performance: nickel shifts the corrosion potential in crevices and reduces the susceptibility to the localized attack that limits the pure grades in hot chloride service. The combination extends the useful envelope of titanium into conditions where the pure grades would suffer crevice corrosion, which is the main reason Grade 12 is specified for elevated-temperature chloride service.
Applications
Grade 12 titanium is used in chemical processing equipment, heat exchangers, pressure vessels and piping handling hot chlorides and mildly reducing media. It serves the pulp and paper industry in chlorine dioxide bleaching service, the chemical industry in brine and chloride processes, and the marine industry in seawater service at elevated temperature. Its combination of strength, weldability and corrosion resistance makes it the preferred titanium grade for equipment that must operate at temperature in chloride service.
Selection Considerations
Select Grade 12 where the service combines chlorides, elevated temperature and the need for higher strength than the pure grades. Where the temperature is moderate and the medium oxidizing, the pure grades or Grade 7 may suffice; where the medium is reducing or crevice-prone at temperature, Grade 12 is the appropriate choice. Confirm the applicable specification, such as ASTM B265 for plate or B338 for tubes, and require the material certificate with composition and mechanical properties.
Frequently Asked Questions
What is Grade 12 titanium? Titanium with 0.3 percent molybdenum and 0.8 percent nickel, designated Ti-0.3Mo-0.8Ni.
Why is Grade 12 stronger than pure titanium? The molybdenum stabilizes the beta phase and improves the elevated-temperature strength.
What does the nickel addition do? It improves the crevice corrosion resistance in hot chloride and reducing conditions.
Where is Grade 12 used? Chemical processing, heat exchangers, pulp and paper bleaching service and elevated-temperature marine applications.
Is Grade 12 weldable? Yes, it is highly weldable using standard titanium practices.
