Seamless Titanium Gr7 Pipe
What is a Seamless Titanium Gr7 Pipe?
Seamless Titanium Gr7 Pipe (UNS R52400) is commercially pure titanium alloyed with 0.12–0.25 % palladium, produced from a solid billet without a welded seam. The small palladium addition transforms the corrosion behavior in reducing acids without measurably changing the mechanical properties of Grade 2.
Where plain titanium corrodes in dilute hydrochloric, sulfuric and phosphoric acids, Gr7 maintains its protective passive film even in de-aerated reducing media — making it the most corrosion-resistant standard titanium grade available.
Manufactured to ASTM B338/B861 equivalents, Gr7 seamless pipe protects chemical plants handling mixed oxidizing-reducing acid streams, hot brine and contaminated seawater where Grade 2's limits would be exceeded.
Titanium Grade 7 vs Grade 2 vs Grade 11 vs Grade 12: The Pd-Bearing Grades
Grade 7 is chemically identical to Grade 2 except for a small palladium addition — and that fraction of a percent redefines its corrosion envelope.
| Grade | Key Chemistry / Condition | Where It Fits |
|---|---|---|
| Grade 2 | CP titanium | Excellent in oxidizing media and seawater; crevice-corrosion risk in hot reducing acids |
| Grade 7 | Gr2 + 0.12-0.25 % Pd | Full Gr2 mechanics with dramatically extended crevice-corrosion immunity in hot HCl and H2SO4 |
| Grade 11 | Gr1 + Pd | The more formable, lower-strength Pd variant |
| Grade 12 | Ni-Mo addition | Better hot-salt and reducing-media behaviour at lower cost than Pd grades |
Product Specifications
Specification data for Seamless Titanium Gr7 Pipe is compiled from the governing ASTM/ASME/EN standards and our routine production records; typical values are shown where a standard leaves a limit open.
| Category | Standard / Designation |
|---|---|
| Seamless Pipe | ASTM B861 / ASME SB861 |
| Seamless & Welded Tube | ASTM B338 / ASME SB338 |
| UNS Designation | R52400 |
| Werkstoff Number | 3.7235 |
| Low-Pd Variant | Gr16 (0.04–0.08 % Pd) available on request |
Size and Weight Chart
| OD (mm) | Typical Wall (mm) | Weight (kg/m) |
|---|---|---|
| 6.35 | 0.9 | 0.07 |
| 9.53 | 0.9 | 0.11 |
| 12.7 | 1.0 | 0.17 |
| 19.05 | 1.2 | 0.3 |
| 25.4 | 1.65 | 0.56 |
| 38.1 | 2.0 | 1.02 |
| 50.8 | 2.5 | 1.71 |
| 76.2 | 3.0 | 3.11 |
| 101.6 | 4.0 | 5.53 |
The table lists typical production sizes with a common wall for each diameter; the full dimensional programme of the governing standard is available, and intermediate diameters, walls and lengths are cut to order.
Chemical Composition
| Element | Min (%) | Max (%) |
|---|---|---|
| Titanium (Ti) | Balance | — |
| Palladium (Pd) | 0.12 | 0.25 |
| Oxygen (O) | — | 0.25 |
| Iron (Fe) | — | 0.30 |
| Carbon (C) | — | 0.08 |
| Nitrogen (N) | — | 0.03 |
| Hydrogen (H) | — | 0.015 |
Mechanical Properties
| Property | Value |
|---|---|
| Tensile Strength, min | 345 MPa (50 ksi) |
| Yield Strength (0.2 % offset), min | 275 MPa (40 ksi) |
| Elongation in 2 in. / 50 mm, min | 20 % |
| Hardness (typical) | 145 – 200 HBW |
| Condition | Annealed per ASTM B338/B861 |
Physical Properties
| Property | Value |
|---|---|
| Density | 4.51 g/cm³ |
| Melting Point | ≈ 1665 °C |
| Elastic Modulus | 103 GPa |
| Coefficient of Thermal Expansion (20–100 °C) | 8.6 µm/m·°C |
| Thermal Conductivity (at 20 °C) | 17.0 W/m·K |
| Electrical Resistivity | 54 µΩ·cm |
| Specific Heat Capacity | 523 J/kg·K |
Equivalent Grades
| Standard System | Designation |
|---|---|
| UNS | R52400 |
| Werkstoff Nr. | 3.7235 |
| DIN | TiPd |
| ASTM | B338 / B861 |
Why Grade 7 Earns Its Premium in Reducing-Acid Service
In hot, dilute-to-mid concentrating hydrochloric and sulfuric acids — the environments that rapidly undermine commercially pure titanium — the 0.12-0.25 % palladium in Grade 7 shifts the alloy's corrosion potential into the passive range. Crevice corrosion under gaskets, deposits and tube supports, the classic failure mode of Grade 2 above about 80 °C in reducing media, is effectively eliminated. This makes Grade 7 the specified material for acetaldehyde, chlor-alkali and organic-acid heat exchangers where plant uptime carries a high price.
Mechanically the alloy delivers Grade 2 values — about 345 MPa tensile and 275 MPa yield — so designers substitute it one-for-one. Our seamless Grade 7 tube follows the same vacuum-melt, jacketed-extrusion, cold-pilger and vacuum-anneal route as all our titanium, certified to ASTM B338/B861 with palladium content verified on every heat.
Manufacturing Process
Our seamless production route for Seamless Titanium Gr7 Pipe follows these documented stages:
- Sponge Consolidation & Double Melting: High-purity titanium sponge is compacted with alloying additions and double- or triple-melted in vacuum consumable-arc furnaces for homogeneity.
- Billet Forging: Ingots are forged to extrusion rounds with ultrasonic inspection for internal defects.
- Hot Extrusion / Rolling: Billets, jacketed to protect against oxygen pickup, are hot-extruded or hot-rolled into tube shells.
- Cold Pilgering: Cold pilgering produces the final precision wall with excellent surface finish.
- Vacuum Annealing: Final annealing under vacuum (typically 650-800 °C) preserves the low interstitial content and bright surface.
- Testing & Certification: Tensile, hardness, flare/flattening, eddy-current and ultrasonic testing confirm conformity to ASTM B338/B861.
Surface Finish Options
- Vacuum-Annealed Bright: Standard condition; oxygen-free reflective surface.
- Pickled: For weld-prep and chemical service.
- Precision Ground / Polished: For instrumentation and specialty equipment.
Dimensional Tolerances
Delivered dimensions are verified against the tolerances below; tighter tolerances can be negotiated for instrumentation and precision applications.
| Dimension | Tolerance |
|---|---|
| OD, tube ≤ 25.4 mm (cold worked) | ± 0.10 mm |
| OD, tube 25.4 – 38.1 mm | ± 0.15 mm |
| OD, tube 38.1 – 50.8 mm | ± 0.20 mm |
| OD, hot-finished pipe ≥ 50.8 mm | ± 1 % of OD |
| Wall thickness | - 12.5 % under-tolerance (min-wall basis) |
| Straightness | ≤ 1 mm per metre |
| Cut length | + 10 / - 0 mm (fixed lengths) |
Common Industrial Applications
Because of its characteristic property profile, Seamless Titanium Gr7 Pipe is specified in the following industries and services:
- Chemical & Fertilizer Plants: Piping for dilute reducing acids and mixed acid streams where Grade 2 is marginal.
- MSF Desalination Brine Heaters: Hot de-aerated brine at up to 120 °C — Gr7's signature desalination application.
- Acetic & Organic Acid Systems: Lines combining organic acids with chloride contamination.
- Offshore Sour Systems: Acidified seawater and process streams requiring premium titanium.
- Metals Refining: Pickling-line piping handling hot dilute sulfuric and hydrochloric acid.
- Flue-Gas Desulfurization: Scrubber service where chlorides, acid dew-point and abrasion combine.
Quality Assurance, Testing and Documentation
Every length of Seamless Titanium Gr7 Pipe passes through a documented quality-control chain before dispatch:
- Material Certification: EN 10204 3.1 mill test certificates are issued for every heat; 3.2 certification with third-party witness (TUV, SGS, BV) is available on request.
- Chemical & Mechanical Testing: Heat-level chemical analysis plus tensile, hardness and, where applicable, flattening, flaring and reverse-flattening tests per the governing standard.
- Non-Destructive Examination: 100 % eddy-current or ultrasonic testing and hydrostatic or pneumatic pressure testing in line with the standard's supplementary requirements.
- Dimensional & Visual Inspection: Full OD, wall thickness, ovality and length verification with visual surface inspection after pickling or finishing.
- Traceability & Marking: Heat numbers stenciled or banded on every length, maintaining complete melt-to-pipe traceability.
Export and Packaging
Pipes are bundled with steel strapping and fitted with plastic or steel end caps, then packed in seaworthy wooden cases or crates and secured in containers for long-distance ocean freight. Standard export documentation — commercial invoice, packing list, certificate of origin, mill test certificates and, where required, third-party inspection reports — accompanies every shipment. Container-load and bulk project orders receive priority production slots and consolidated shipping documentation.
Frequently Asked Questions
Q1. What exactly does the palladium in Gr7 do?
A: Palladium shifts the alloy's corrosion potential into the passive range even in de-aerated reducing acids, preventing the active corrosion that pure titanium suffers below roughly 0.5 % HCl or H2SO4 at moderate temperature.
Q2. Is Gr7 stronger than Gr2?
A: No — the mechanical properties are essentially identical. Gr7 is selected purely for its corrosion resistance in reducing environments.
Q3. What is the lower-palladium alternative to Gr7?
A: Grade 16 (0.04–0.08 % Pd) offers most of Gr7's benefit at lower alloy cost, and Grade 26 is its low-interstitial counterpart. Availability and duty determine the best choice.
Q4. Does Gr7 need special welding procedures versus Gr2?
A: No special procedures beyond standard titanium practice — clean joint preparation and rigorous inert-gas shielding preserve both ductility and the corrosion benefit.
Ready to Request a Quotation?
Send us your size range, wall thickness/schedule, standard and quantity for Seamless Titanium Gr7 Pipe, and our engineering team will respond with a detailed technical and commercial offer within 24 hours. Custom sizes, third-party inspection and full export documentation are part of our standard service.
