Seamless Titanium Tube Grade 7
Grade 7 seamless titanium tube (Ti-0.2Pd) with enhanced corrosion resistance to reducing acids; composition, mechanical properties, ASTM B861/B338 specifications and applications.
Description
1. Overview
Grade 7 titanium is the palladium-containing grade of commercially pure titanium, designated Ti-0.2Pd (UNS R52400). A small palladium addition of 0.12-0.25% markedly improves corrosion resistance to reducing acids such as hydrochloric and sulfuric acid, by lowering the cathodic overpotential and promoting stable passivation of the surface. Grade 7 seamless tubes combine the fabricability of the unalloyed grades with corrosion performance that exceeds any of the plain commercially pure grades.
2. Why Grade 7?
Compared with Grade 2 (the standard workhorse grade), Grade 7 provides substantially better corrosion resistance in acid, chloride and seawater environments. It is the preferred material where process media contain hydrochloric or sulfuric acid, or where crevice corrosion is a risk. For chemical heat exchangers and process piping, Grade 7 often replaces higher-alloyed materials at lower cost while offering a long, predictable service life.
3. Chemical Composition
| Element | Content (%, max unless stated) |
|---|---|
| Nitrogen (N) | 0.03 |
| Carbon (C) | 0.08 |
| Hydrogen (H) | 0.015 |
| Iron (Fe) | 0.30 |
| Oxygen (O) | 0.25 |
| Palladium (Pd) | 0.12 - 0.25 |
| Titanium (Ti) | Balance |
Composition limits per ASTM B265 / B338 / B861 for Grade 7.
4. Mechanical and Physical Properties (Annealed Condition)
| Property | Value |
|---|---|
| Tensile strength (UTS), min | 345 MPa (50 ksi) |
| 0.2% yield strength, min | 275 MPa (40 ksi) |
| Elongation, min | 20% (on 2 in or 50 mm) |
| Density | About 4.51 g/cm³ |
| Melting point | About 1668 °C |
5. Manufacturing and Specifications
Seamless Grade 7 tubes are produced from forged billet by rotary piercing and extrusion or by cold pilgering, followed by annealing and finishing. They are supplied to ASTM B861 (seamless titanium pipe) and ASTM B338 (seamless and welded titanium condenser and heat-exchanger tube). Typical supply ranges are 0.5-200 mm outside diameter with 0.1-10 mm wall thickness; lengths are customized to order (common 6 m and 12 m, or cut/bent sections). Surface treatment includes pickling, sandblasting or polishing.
6. Applications
- Chemical and petrochemical heat exchangers, reaction vessels and process piping
- Seawater desalination and offshore equipment
- Electroplating and metal-finishing lines
- Pulp and paper processing equipment
- Any service where hydrochloric or sulfuric acid attack is expected
7. Comparison Note
Grade 7 offers the same mechanical strength as Grade 2 (UTS ≥ 345 MPa, 0.2% yield ≥ 275 MPa) while adding the palladium corrosion advantage. Where the environment is mildly corrosive, Grade 2 is adequate; where reducing acids or crevice corrosion are present, Grade 7 is the correct specification.
about us
Founded in 2008, our company has steadily expanded over time and now stands as a top-tier manufacturer and supplier of metal products. We cater to diverse industries, constantly investing in R&D to enhance product quality and durability.
Customer satisfaction is our top priority. We're renowned for delivering high-quality items and outstanding customer service. Our efforts have paid off, enabling us to establish a global footprint. Presently, we serve customers across numerous countries worldwide, continuing to uphold our reputation for excellence.
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