What Is a Seamless Incoloy 800H Tube?
Seamless Incoloy 800H Tube — UNS N08810 — is the creep-resistant version of Alloy 800: the same nickel–iron–chromium base with carbon controlled to 0.05–0.10% and a minimum solution-annealing temperature of 1121 °C (2050 °F), produced to ASTM B407 from a solid billet with no weld seam.
The controlled carbon level and coarse grain size (ASTM No. 5 or coarser) give 800H substantially higher creep and stress-rupture strength than Alloy 800 above 593 °C (1100 °F). It is the specified material for furnace tubing, reformer headers and high-temperature heat-transfer service where thousands of hours at temperature are the design basis.
Size Range: OD 6–257 mm · WT 0.5–35 mm
Key Features and Advantages
Seamless UNS N08810 tube is engineered for long-term strength above 593 °C:
Superior Creep and Stress-Rupture Strength: carbon 0.05–0.10% plus a minimum 1121 °C solution anneal give the coarse grain structure rated for service above 1100 °F (593 °C).
Controlled Grain Size: ASTM No. 5 or coarser average grain size per ASTM B407 7.2 ensures consistent, predictable creep performance heat after heat.
Same Proven Corrosion Behavior as Alloy 800: identical Ni–Fe–Cr base delivers oxidation, carburization and chloride SCC resistance.
Excellent Metallurgical Stability: resists embrittlement and sigma-phase degradation during thousands of hours at temperature.
Established Code Acceptance: widely accepted in pressure-equipment codes for fired heaters, reformers and high-temperature exchangers.
Product Specifications and Data
To provide a comprehensive overview of this high-performance material, here are the detailed technical specifications and performance data for UNS N08810 seamless tube.
Equivalent Grade
| UNS | Common grade name | EN material number | EN steel name | JIS grade | GB/T grade |
|---|---|---|---|---|---|
| N08810 | Incoloy 800H | 1.4958 | X5NiCrAlTi31-20 | NCF800H | NS1102 / NS112 (legacy) |
Grade correspondence does not make ASTM, ASME, EN, JIS and GB delivery requirements interchangeable. Confirm chemistry, heat treatment, mechanical properties, dimensions, testing and certification against the purchase specification. Approximate or unconfirmed correspondences retain their qualification. See the grade designation index.
Chemical Composition
the nickel–iron–chromium balance of this family delivers the property mix.
| Grade | C | Mn | Si | P | S | Cu | Ni | Cr | Al | Ti | Fe | Others |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UNS N08800 | ≤0.10 | ≤1.50 | ≤1.00 | ≤0.045 | ≤0.015 | ≤0.75 | 30.0–35.0 | 19.0–23.0 | 0.15–0.60 | 0.15–0.60 | 39.5 min | – |
| UNS N08810 | 0.05–0.10 | ≤1.50 | ≤1.00 | ≤0.045 | ≤0.015 | ≤0.75 | 30.0–35.0 | 19.0–23.0 | 0.15–0.60 | 0.15–0.60 | 39.5 min | – |
| UNS N08811 | 0.06–0.10 | ≤1.50 | ≤1.00 | ≤0.045 | ≤0.015 | ≤0.75 | 30.0–35.0 | 19.0–23.0 | 0.25–0.60 | 0.25–0.60 | 39.5 min | Al+Ti 0.85–1.20 |
Chemical requirements per ASTM B407-22, Table 1 (composition limits, %). Single values are maximum content unless a range or minimum is indicated. Iron is determined arithmetically by difference (39.5% minimum). For Alloy 800HT (UNS N08811) the standard additionally requires Al + Ti = 0.85–1.20%. ASTM B407 supplies N08810 in the hot-finished annealed or cold-worked annealed condition.
Typical Mechanical Properties
Values below are specification minimums for the delivery condition; they define the acceptance basis for UNS N08810 seamless tube.
| Alloy & Condition | Yield Strength, min, ksi (MPa) | Tensile Strength, min, ksi (MPa) | Elongation in 2 in. or 50 mm, min, % |
|---|---|---|---|
| UNS N08800, cold-worked annealed | 30 (205) | 75 (520) | 30 |
| UNS N08800, hot-finished annealed | 25 (170) | 65 (450) | 30 |
| UNS N08810 / N08811, hot-finished annealed or cold-worked annealed | 25 (170) | 65 (450) | 30 |
Mechanical properties per ASTM B407-22, Table 2. Annealed UNS N08810 and N08811 shall conform to an average grain size of ASTM No. 5 or coarser (7.2). The final anneal for N08810 shall be at 2050 °F (1121 °C) minimum (5.1), producing the coarse, stable grain structure behind its creep and stress-rupture strength.
Typical Physical Properties
These physical properties highlight the material’s ability to perform reliably across a range of environments.
| Density | Melting Range | Thermal Expansion | Thermal Conductivity | Modulus of Elasticity | Electrical Resistivity |
|---|---|---|---|---|---|
| 7.94 g/cm3 | 1350 – 1400 °C | 14.4 μm/m·°C (20–100°C) | 11.5 W/m·K | 196 GPa | 0.99 μΩ·m (20°C) |
Size Tolerance Chart (mm)
Permissible variations for seamless nickel alloy tube in accordance with ASTM B407-22, Table 3:
| Nominal Outside Diameter, mm | Permissible Variation in OD, mm | Average Wall, % | Minimum Wall |
|---|---|---|---|
| 12.7 to 15.8, excl | ±0.127 | ±15 | +28.5% / −0 |
| 15.8 to 38.1, incl | ±0.190 | ±10 | +28.5% / −0 |
| 38.1 to 88.9, incl | ±0.254 | ±10 | +28.5% / −0 |
| 88.9 to 114.3, incl | ±0.381 | ±10 | +28.5% / −0 |
| 114.3 to 152.4, incl | ±0.508 | ±12.5 | +28.5% / −0 |
| 152.4 to 168.3, incl | ±0.635 | ±12.5 | +28.5% / −0 |
| Hot-finished: 63.5 to 139.7, excl | ±0.787 | ±12.5 | +28.5% / −0 |
| Hot-finished: 139.7 to 234.9, incl | ±1.19 | ±12.5 | +28.5% / −0 |
Notes (ASTM B407-22, Table 3): tolerances apply to individual measurements and include ovality. For cold-finished tube, wall variation in any cross section (eccentricity) shall not exceed ±10% of the actual average wall. If minimum wall is ordered, the tolerance is +28.5% / −0. When tube is specified by OD and average wall, ordering to minimum wall is subject to agreement between manufacturer and purchaser.
Length Tolerance
- Cut lengths shall not be less than the specified length; a variation of +3.2 mm (cold-worked) or +4.8 mm (hot-finished) is permitted (ASTM B407-22, 8.2).
- For lengths over 9.1 m (30 ft), a variation of +6.4 mm is permitted.
- Tube is normally supplied in mill lengths or specific cut lengths as agreed in the order.
Disclaimer: Dimensional data above are summarized from ASTM B407-22, Table 3. The full and most current specification document must always be consulted for official design and procurement purposes.
Common Industrial Applications
The combination of corrosion resistance, mechanical strength and manufacturing quality makes UNS N08810 seamless tube a preferred choice for:
Ethylene and Steam Reformer Furnaces
Furnace tubes, pigtails, manifolds and transfer lines in cracking and reforming service.
Hydrogen Production Plants
Reformer convection-section and process tubing in hydrogen and syngas service.
High-Temperature Heat Exchangers
Exchanger tubing operating continuously above 593 °C.
Power and Industrial Heating
Superheater, reheater and furnace components where creep life sets the design margin.
Frequently Asked Questions
What sizes are available for Incoloy 800H seamless tube?
Which specification governs Incoloy 800H seamless tube?
What inspection documents are provided?
Technical review: page data reviewed by the Xinzhe technical desk on 2026-09-27. Property values are typical reference data compiled from Special Metals Corporation alloy data sheets and the governing ASTM specifications; they are not acceptance guarantees unless stated in the purchase order. “Incoloy” is a trademark of Special Metals Corporation, used here to identify the alloy family only.
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Send the NPS and schedule (or actual OD and wall), quantity, length, end finish and the inspection items you need as acceptance criteria — you will get a written quotation stating the specification and edition, delivery condition, documents included and lead time.
