Alloy Overview
Titanium Grade 12 (UNS R53400) is a highly corrosion-resistant titanium alloy, containing small additions of nickel (Ni) and molybdenum (Mo). These elements enhance corrosion resistance and increase strength, providing better mechanical properties than commercially pure titanium grades. It performs well in mildly reducing or fluctuating conditions, especially excelling in crevice corrosion resistance in hot brines. Its extra strength allows for lighter structural designs, making it a cost-effective alternative to palladium-bearing grades (e.g., Grades 7 and 11).
Key Properties
1. Chemical Composition (Nominal, wt%)
| Element | Content Range |
| Ti | Balance |
| O | ≤0.18 |
| C | ≤0.08 |
| H | ≤0.015 |
| N | ≤0.03 |
| Fe | ≤0.30 |
| Mo | 0.2–0.4 |
| Ni | 0.6–0.9 |
2. Tensile Requirements
| Property | Minimum Value |
| Tensile Strength | 70 ksi (438 MPa) |
| Yield Strength | 50 ksi (345 MPa) |
| Elongation | 18% |
3. Microstructure & Phase Transformation
- Microstructure: Equiaxed alpha with acicular alpha (primarily in welds or heat-affected zones) and small amounts of beta phase.
- Beta Transus Temperature: 890°C ± 15°C (transforms to beta phase above this temperature).
Design Features & Advantages
- Corrosion Resistance: Excellent in both oxidizing and mildly reducing environments (especially chlorides), with superior crevice corrosion resistance compared to pure titanium grades.
- Mechanical Traits: Higher strength than unalloyed grades (1–4) while remaining formable; good heat and wear resistance.
- Fabrication: Highly weldable (avoiding oxy-acetylene methods); suitable for forging, cold working, and standard machining.
- Cost Efficiency: Additions of Mo and Ni offer enhanced corrosion resistance at a lower cost than palladium-bearing grades (Grades 7, 11).
Applications
Widely used in industries requiring corrosion resistance and strength at elevated temperatures:
- Chemical processing (elevated-temperature manufacturing, shell and heat exchangers).
- Power generation, desalination, and hydrometallurgical applications.
- Marine, hydrocarbon processing, and mining equipment.
- Aerospace and marine components.
Specifications & Standards
| Product Form | ASTM Specification |
| Bar | ASTM B348 Gr12 |
| Sheet/Plate | ASTM B265 Gr12 |
| Nuts | ASTM F467 Gr12 |
| Bolts | ASTM F468 Gr12 |
| Castings | ASTM B367 Gr12 |
| Heat Exchange Tubes* | ASTM B338 Gr12 |
| Forgings | ASTM B381 Gr12 |
Fabrication Guidelines
- Weldability: Good; compatible with common fusion and resistance welding (inert gas shielding recommended).
- Annealing: 732–816°C (1350–1500°F).
- Stress Relief Annealing: 538–649°C (1000–1200°F) for 1 hour, followed by air cooling (AC).
- Pressure Vessels: Qualified under AS1210 and ASME Boiler & Pressure Vessel Code for use up to 300°C.
Availability
Supplied in forms including plate, sheet, strip, rod, bar, seamless/welded pipe, weld fittings, seamless/welded tube, forging billet, and forgings.