Ti-45Nb, Grade 36, 55Ti-45Nb, UNS R58450: A Technical Guide
Introduction
Initially developed for application as an aerospace alloy because of its relative ease of formability, high strength, and ductility at temperatures up to 427°C (801°F), Ti-45Nb, Grade 36, 55Ti-45Nb, UNS R58450 is an ideal candidate for rivets that secure aluminum aircraft panels, particularly in areas exposed to high engine exhaust temperatures.
Low Elastic Modulus
This alloy has been used as welded flange components that secure high-energy physics RF linear accelerator cavities (made from high-purity niobium), and has been drawn into superconductivity wire. It is used as a medical device material for cochlear hearing implants, and its low elastic modulus makes it a consideration for various medical and dental devices.
Machinability
Ti-45Nb, Grade 36, 55Ti-45Nb, UNS R58450 is easily fabricated into structures and components. Although it is considered a refractory metal, processing techniques are the same as those for other titanium alloys. Parts are typically welded using the GTAW process but require the addition of trailing and backing shields. Due to its simple metallurgical structure, there is no requirement for post-weld heat treatment. Machining requires the use of solid fixture setups and high torque at low RPM ridge machine tools with sharp high rake cutters.
High Formability
With a minimal bend radius capability (down to a bend radius of 1t where t=sheet thickness) and low modulus of elasticity, Ti-45Nb Alloy is highly formable yet retains excellent tensile and elongation properties. It can also be cast into shapes with the same processes used to cast CP titanium.
Surface Oxidation Treatment
Ti-45Nb, Grade 36, 55Ti-45Nb, UNS R58450 readily accepts surface oxidation treatment to enhance its hardness and wear resistance. “Nobelizing” is a common commercially available process to apply this type of surface treatment.
Corrosion Resistance Higher Ignition Resistance
Ti-45Nb, Grade 36, 55Ti-45Nb, UNS R58450 provides improved corrosion resistance along with higher strength compared to that of Ti-7, 12, 16, and 26 in many chemical environments. Ti-45Nb Alloy has also proven to be a great success in the autoclave processing of gold ore. For many years gas vents, oxygen lances, steam spargers, valves and other pressure oxidation reactor components have been produced, put into service, and survived hot, concentrated sulfuric or hydrochloric acid. In addition, the metal has been shown to have higher ignition resistance when compared to CP Ti, thereby allowing further process optimization.
Another chemical processing application for Ti-45Nb, Grade 36, 55Ti-45Nb, UNS R58450 is the oxygen-based, low-pressure, wet oxidation process for the treatment of wastewater and sludge. Because of its corrosion and higher ignition resistance, this material is an ideal candidate for the 200°C (392°F), 20 bar pressure with oxygen environment. The superior corrosion resistance of Ti-45Nb, Grade 36, 55Ti-45Nb, UNS R58450 makes it well suited for service in various environments, including most organic and mineral acids below 150°C (302°F). Because of its stable oxide film, Ti-45Nb, Grade 36, 55Ti-45Nb, UNS R58450 has excellent resistance to oxidizing acids, including mixtures of HNO3 and HCL; however, it is susceptible to attack from HF and other fluoride ions.
Acids and corrosive solutions that Ti-45Nb, Grade 36, 55Ti-45Nb, UNS R58450 has shown good chemical resistance to include:
Hydrochloric (HCL)
Sulfuric (H2SO4)
Hydrobromic (HBr)
Hydroiodic (HI)
Saltwater / Brine / Salt Solutions
Potential Applications
Aerospace rivet material
High pressure oxygenated gas vents
Oxygen lances for pressure oxidation reactors
Valves for corrosive oxygenated processes
Chemical corrosion resistance
Medical implant devices
High energy physics and superconducting wire
Figure 1. Ferrallum 255 super duplex stainless (top coupon) showed extensive corrosion (50% of wall thickness) after eight months in a mining autoclave. Ti-45Nb, Grade 36, 55Ti-45Nb, UNS R58450 (bottom coupon) showed no measurable corrosion after four months and has tested well for nearly two years.
Specifications & Certificates
Plate, sheet, tube, pipe, bar, billet, extrusions, wire, castings.
Product Forms
ASTM
B265 – Titanium and Titanium Alloy Strip, Sheet and Plate
B338 – Seamless and Welded Titanium and Titanium Alloy Tubes
B348 – Titanium and Titanium Alloy Bars and Billets
B381 – Titanium and Titanium Alloy Forgings
B363 – Seamless and Welded Unalloyed Titanium and Titanium Alloy Welding Fittings
B861 – Titanium and Titanium Alloy Seamless pipe
B862 – Titanium and Titanium Alloy Welded Pipe
B863 – Titanium and Titanium Alloy Wire
AWS
AWS A5.16/A5.16M:2007 – Specification for Titanium and Titanium-Alloy Welding Electrodes and Rods. Ti Grade 36 weld wire is designated in AWS A5.16/A5.16M as ERTi-36.
AWS G2.4/G2.4M:2007 – Guide for the Fusion Welding of Titanium and Titanium Alloys
Chemical Composition
Nominal 55 wt% Titanium, 45 wt% Niobium
| Ingot Chemistry | Nb | O | C | N | H | Fe | Ti |
| Typical | +/- 1.5% | 850 | 175 | 75 | 5 | 250 | +/- 1.5% |
| Specification | 42.0-47.0 | < 1600 | < 400 | < 200 | < 35 | < 300 | Balance |
Note: Interstitials are in units of ppm. To obtain units of wt%, divide by 10,000.
Physical Properties
| Property | Value |
| Density | 5.7 g/cm³ (0.206 lb/cu.in) |
| Melting Point | 1900°C (3452°F) |
| Phase Transition or Beta Transus | No beta transus. Alloy is beta phase to room temperature. |
| Coefficient of Thermal Expansion (CTE) | 9.03 x 10^-6/°C (5.02 x 10^-6/°F) |
| Thermal Conductivity | 10 W/m·K (5.78 BTU/hr·ft·°F) |
| Specific Heat | 0.427 J/g·°C (0.102 BTU/lb·°F) |
| Thermal Diffusivity | 4.3 x 10^-6 m²/s (46.3 ft²/sec) |
Mechanical Properties
| Property | Value |
| Ultimate Tensile Strength (at RT) | 450 MPa (65,000 psi) |
| Yield Strength (at RT) | Minimum 410 MPa (60,000 psi), Maximum 655 MPa (95,000 psi) |
| Elongation (at RT) | 10% (in 2 inches) |
| High Temperature Strength Graphs | See Figure 2 and Table 4 |
| Bend Radius | Under 0.070 inch (1.8 mm) thickness = 4.5T<br>0.070 to 0.187 inch (1.8-4.75 mm) thickness = 5T |
| Modulus of Elasticity | 62.05 GPa (9 x10^6 psi) |
Table 4. Mechanical Properties for Titanium Grade 2 and Niobium vs. Ti-45 Niobium
| Material | Elastic Modulus (psi) | Yield Strength (psi) | Ultimate Strength (psi) | Integrated Thermal Contraction 293K to 1.88K (in/in) |
| Niobium | 1.52E+07 | 55000 | 46000 | 0.0014 |
| Ti-45 Niobium | 9.00E+06 | 69000 | 79000 | 0.0019 |
| Titanium Grade 2 | 1.55E+07 | 40000 | 50000 | 0.0015 |
Other Properties and Pertinent Information
Ti-45Nb, Grade 36, 55Ti-45Nb, UNS R58450, provides a unique solution for demanding applications requiring both high performance and biocompatibility. Its advantages are clear, from medical implants to high-stress aerospace parts. By understanding its properties and choosing it wisely for the right applications, you can harness the potential of Ti-45Nb to improve outcomes, extend product life, and contribute to advancements in multiple industries.
