What Is a Seamless Incoloy 800HT Tube?
Seamless Incoloy 800HT Tube — UNS N08811 — takes the 800 family one step further: combined Al + Ti = 0.85–1.20% with carbon 0.06–0.10% and a minimum solution anneal of 1149 °C (2100 °F), produced to ASTM B407 from a solid billet with no weld seam.
The higher aluminum plus titanium level boosts high-temperature strength through a controlled precipitation response, giving 800HT the best creep and stress-rupture properties in the family, particularly above 700 °C. It is selected for the most demanding furnace and superheater positions — the same corrosion behavior as Alloy 800 and 800H, with more strength margin at temperature.
Size Range: OD 6–257 mm · WT 0.5–35 mm
Key Features and Advantages
Seamless UNS N08811 tube maximizes creep strength in the 800 family through elevated Al + Ti:
Highest Creep-Rupture Strength in the Family: Al + Ti 0.85–1.20% and a 1149 °C minimum anneal deliver superior strength above 700 °C.
Elevated-Temperature Stability: coarse-grain solution-annealed structure resists degradation through long service exposure.
Controlled Chemistry Windows: carbon 0.06–0.10% with tightly banded Al and Ti keeps heat-to-heat properties consistent.
Same Corrosion Behavior as the 800 Family: oxidation, carburization and chloride SCC resistance equal to Alloy 800/800H.
Drop-In Design Confidence: same fabrication and welding practice as 800/800H, letting designers upgrade strength margin without changing procedures.
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 N08811 seamless tube.
Equivalent Grade
| UNS | Common grade name | EN material number | EN steel name | JIS grade | GB/T grade |
|---|---|---|---|---|---|
| N08811 | Incoloy 800HT | 1.4959 | X8NiCrAlTi32-21 (approx.) | Not listed in grade index | NS1104 |
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 N08811 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 N08811 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 N08811 shall be at 2100 °F (1149 °C) minimum (5.1).
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 N08811 seamless tube a preferred choice for:
Superheater and Reheater Tubing
The highest-temperature positions in fired equipment and waste-heat boilers.
Furnace Components and Manifolds
Manifolds, headers and collection systems running continuously hot.
Reformer and Cracker Hardware
Pigtails, transfer lines and support components in ethylene and hydrogen plants.
Industrial Thermal Processing
Radiant tubes and fixtures in high-temperature heat-treat equipment.
Frequently Asked Questions
What sizes are available for Incoloy 800HT seamless tube?
Continuous supply covers OD 6–257 mm and WT 0.5–35 mm. Requirements outside this range are reviewed against mill capability on request.
Which specification governs Incoloy 800HT seamless tube?
ASTM B407 / ASME SB407 is the governing seamless specification for Incoloy 800HT tube (Grade HT, aluminium + titanium 0.85–1.20%); the edition in force at order time is stated on the quotation and purchase order.
What inspection documents are provided?
Each order is documented with a mill test certificate stating heat chemistry and mechanical test results. EN 10204 3.1 certification, hydrostatic testing, eddy-current or ultrasonic inspection and PMI are performed when specified in the purchase order.
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.
Ready to Request a Quotation?
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.
