Seamless Zirconium 702 Pipe
What is a Seamless Zirconium 702 Pipe?
Seamless Zirconium 702 Pipe (UNS R60702, zirconium with up to 4.5 % hafnium) is produced from a solid billet without any welded seam. Zirconium is the ultimate answer to the most aggressive reducing-acid environments — boiling sulfuric, hydrochloric, nitric and organic acids that destroy every stainless steel and most nickel alloys.
Zirconium's superb corrosion resistance comes from an exceptionally stable zirconium oxide film that re-forms instantly when damaged. The metal is also transparent to thermal neutrons and nearly free of long-lived activation, which made it indispensable to the nuclear industry and gives it unique process advantages.
Manufactured to ASTM B658 (pipe) and B523 (tube), Zr 702 seamless pipe protects acetic acid plants, urea units and nuclear fuel processing facilities where nothing else survives.
Zirconium 702 vs Zirconium 704 vs 705 vs Titanium: Reactor-Grade Corrosion Metals
Zirconium's family is defined by small alloying changes with outsized effects. The table locates R60702 against its siblings and its closest alternative metal.
| Grade | Key Chemistry / Condition | Where It Fits |
|---|---|---|
| Zr 702 (R60702) | unalloyed, Hf ≤ 4.5 % | Highest corrosion resistance of the group; the chemical-industry standard |
| Zr 704 (R60704) | Zr + 1.5 Sn | Nuclear fuel-cladding variant with controlled sn for in-reactor service |
| Zr 705 (R60705) | Zr + 2.5 Nb | Roughly double the strength for pressure-part design; slightly lower corrosion margin |
| Titanium Gr.2 | CP titanium | Broader oxidizing-media performance but far weaker in hot reducing acids and caustic |
Product Specifications
Specification data for Seamless Zirconium 702 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 B658 / ASME SB658 |
| Seamless & Welded Tube | ASTM B523 / ASME SB523 |
| Bars & Billet | ASTM B550 / B351 |
| UNS Designation | R60702 |
| Nuclear Grade Variant | Low-hafnium (Zr 704/705 Nb-alloyed) grades for reactor internals |
Size and Weight Chart
| OD (mm) | Typical Wall (mm) | Weight (kg/m) |
|---|---|---|
| 15.9 | 1.5 | 0.44 |
| 19.05 | 1.5 | 0.54 |
| 25.4 | 2.0 | 0.96 |
| 31.8 | 2.0 | 1.22 |
| 38.1 | 2.5 | 1.82 |
| 50.8 | 3.0 | 2.93 |
| 76.2 | 4.0 | 5.91 |
| 101.6 | 5.0 | 9.88 |
| 152.4 | 6.0 | 17.96 |
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 (%) |
|---|---|---|
| Zirconium + Hafnium (Zr+Hf) | 99.20 | — (min) |
| Hafnium (Hf) | — | 4.50 |
| Iron + Chromium (Fe+Cr) | — | 0.20 |
| Carbon (C) | — | 0.05 |
| Nitrogen (N) | — | 0.025 |
| Oxygen (O) | — | 0.16 |
| Hydrogen (H) | — | 0.005 |
| Niobium (Nb) | — | 0.05 (residual) |
Mechanical Properties
| Property | Value |
|---|---|
| Tensile Strength, min | 379 MPa (55 ksi) |
| Yield Strength (0.2 % offset), min | 240 MPa (35 ksi) |
| Elongation in 2 in. / 50 mm, min | 16 % |
| Hardness (typical) | ≤ 230 HV |
| Condition | Annealed per ASTM B523/B658 |
Physical Properties
| Property | Value |
|---|---|
| Density | 6.51 g/cm³ |
| Melting Point | ≈ 1852 °C |
| Elastic Modulus | 99 GPa |
| Coefficient of Thermal Expansion (20–100 °C) | 5.8 µm/m·°C |
| Thermal Conductivity (at 20 °C) | 22.0 W/m·K |
| Specific Heat Capacity | 285 J/kg·K |
Equivalent Grades
| Standard System | Designation |
|---|---|
| UNS | R60702 |
| Werkstoff Nr. | — (per ASTM B658) |
| ASTM | B658 / ASME SB658 |
| Applications Spec. | NACE MR0175 (sour service) applicable |
Why Zirconium 702 Survives Where Everything Else Dissolves
Zirconium 702 is the metal of last resort for the harshest organic and inorganic chemical duties: boiling sulfuric acid up to about 70 %, hydrochloric acid across all concentrations, acetic, formic and lactic acids, urea plant media and hot caustic. Its passive zirconia film is among the most corrosion-resistant known, and — uniquely — the metal is virtually transparent to thermal neutrons, which keeps 702 and its siblings central to nuclear fuel assemblies and reactor internals.
Our R60702 seamless pipe is produced from double electron-beam/vacuum-arc melted ingots, beta-extruded, cold-pilgered and vacuum annealed per ASTM B658/ASME SB658, with oxygen and hafnium strictly controlled. For plants running aggressive organic-acid service — acetic acid evaporators, urea strippers, hydrogen-peroxide systems — Zr 702 routinely outlasts competing alloys by an order of magnitude, which is why its lifecycle cost, despite the premium metal price, is often the lowest on the sheet.
Manufacturing Process
Our seamless production route for Seamless Zirconium 702 Pipe follows these documented stages:
- Sponge & Double Electron-Beam / Arc Melting: Zirconium sponge from the Kroll process is consolidated and double-melted (electron-beam and/or vacuum arc) to achieve nuclear-grade purity.
- Forging & Beta Extrusion: Ingots are forged and hot-extruded, commonly above the allotropic transition, into seamless shells.
- Cold Pilgering: Cold pilger reduction delivers the precise wall and smooth internal surface required for heat-exchanger duty.
- Vacuum Annealing: Vacuum annealing (about 650-750 °C) restores ductility without surface contamination.
- Pickling: An HF-HNO3 pickling bath removes any oxygen-rich surface layer.
- Testing: Hydrostatic, ultrasonic and eddy-current testing plus full chemical verification are completed before dispatch.
Surface Finish Options
- Pickled (HF-HNO3): Standard condition removing oxygen-enriched layer.
- Vacuum Annealed: Bright surface for heat-exchanger and nuclear components.
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 Zirconium 702 Pipe is specified in the following industries and services:
- Acetic Acid Plants: Reactor and distillation piping in PVA/PTA plants — Zr 702 is the reference metal for hot acetic acid with formic acid contamination.
- Urea & Ammonia Plants: Carbamate service and high-pressure urea lines where stainless passivation fails.
- Hydrochloric Acid Systems: Piping for boiling HCl up to 37 % concentration, including contaminated streams.
- Sulfuric Acid Plants: Handling 55–70 % H2SO4 in the temperature band where glass-lined steel is impractical.
- Nuclear Fuel Reprocessing: Dissolver and process piping exploiting zirconium's corrosion resistance and neutron transparency.
- Organic Chemical Production: Formic, lactic and other organic acid service at boiling temperatures.
Quality Assurance, Testing and Documentation
Every length of Seamless Zirconium 702 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. How does Zr 702 compare with Hastelloy B-3 in hydrochloric acid?
A: In pure boiling HCl up to about 37 %, zirconium generally shows lower corrosion rates than Hastelloy B-3 and weighs 30 % less. In oxidizing acid contamination (e.g., Fe3+ or chlorine), Hastelloy C-family alloys tolerate conditions that destroy zirconium — the impurity profile decides.
Q2. Why is zirconium vulnerable in oxidizing media?
A: Zirconium's passive film dissolves in strong oxidizing acids containing ferric or cupric ions, and reacts with wet chlorine. Media containing more than roughly 100 ppm Fe3+/Cu2+ need careful review or a different alloy.
Q3. Is Zr 702 pipe available without hafnium?
A: Yes — for nuclear applications, low-hafnium (< 100 ppm) zirconium is produced by the same supply chain; hafnium-free melts are quoted on request.
Q4. What welding precautions apply to zirconium pipe?
A: Standard reactive-metal practice: TIG welding with excellent inert shielding of the weld puddle, root and backing, plus cleanliness controls to avoid oxygen/nitrogen pickup that embrittles the weld.
Ready to Request a Quotation?
Send us your size range, wall thickness/schedule, standard and quantity for Seamless Zirconium 702 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.
