Incoloy 800H · UNS N08810 · W. Nr. 1.4958 · Incoloy 800HT · UNS N08811 · W. Nr. 1.4959
Incoloy 800H / 800HT (N08810 / N08811): composition, properties, fittings and flanges
Incoloy 800H (UNS N08810, W. Nr. 1.4958) and Incoloy 800HT (UNS N08811, W. Nr. 1.4959) are controlled-chemistry versions of Incoloy 800 in which carbon, aluminium, titanium and grain size are restricted to maximise creep-rupture strength. Incoloy 800H requires 0.05-0.10 % carbon and ASTM grain size 5 or coarser; Incoloy 800HT…
- UNS
- N08810 / N08811
- W. Nr.
- 1.4958 / 1.4959
- Density
- 7.94 g/cm³ (0.287 lb/in³)
- Key strength
- 448 MPa / 65 ksi
Identification and standards
| Short form | Incoloy 800H · UNS N08810 · W. Nr. 1.4958 · Incoloy 800HT · UNS N08811 · W. Nr. 1.4959 |
|---|---|
| Classification | Controlled-carbon high-temperature iron-nickel-chromium alloys |
| UNS | N08810 / N08811 |
| Werkstoff number | 1.4958 / 1.4959 |
| Material family | Incoloy Alloys |
Chemical composition
| Element | Composition (wt %) | Why it is there |
|---|---|---|
| Nickel (Ni) | 30.0 - 35.0 | Austenite stability and carburisation resistance |
| Chromium (Cr) | 19.0 - 23.0 | Oxidation and hot corrosion resistance |
| Iron (Fe) | 39.5 min | Matrix |
| Carbon (C), Incoloy 800H | 0.05 - 0.10 | Controlled for creep strength |
| Carbon (C), Incoloy 800HT | 0.06 - 0.10 | Higher minimum than 800H |
| Aluminium + Titanium, Incoloy 800HT | 0.85 - 1.20 | Gamma prime contribution to creep strength |
| Aluminium (Al) | 0.15 - 0.60 | - |
| Titanium (Ti) | 0.15 - 0.60 | - |
| Manganese (Mn) | 1.50 max | - |
| Silicon (Si) | 1.00 max | - |
| Copper (Cu) | 0.75 max | - |
| Sulphur (S) | 0.015 max | - |
Note Single figures are maximum limits unless shown as a range. Always confirm against the heat-specific EN 10204 3.1 certificate supplied with your order.
Mechanical properties
| Tensile strength, min (annealed, ASTM B409) | 448 MPa / 65 ksi |
|---|---|
| 0.2 % yield strength, min | 172 MPa / 25 ksi |
| Elongation in 2 in, min | 30 % |
| Typical hardness, annealed | 135 - 185 HB |
| Required ASTM grain size, 800H / 800HT | No. 5 or coarser |
| ASME Section VIII Division 1 allowable up to | About 815 °C |
| Relative creep strength, 800HT vs 800H | Approximately 20 % higher |
Warning Values depend on product form, section thickness and heat treatment. Larger sections generally achieve lower strength than thin product; always design against the applicable code allowable stress rather than these figures.
Physical properties
| Density | 7.94 g/cm³ (0.287 lb/in³) |
|---|---|
| Melting range | 1357 - 1385 °C (2475 - 2525 °F) |
| Modulus of elasticity | 196 GPa (28.5 x 10⁶ psi) |
| Thermal conductivity at 20 °C | 11.5 W/m·K |
| Mean coefficient of thermal expansion, 20-100 °C | 14.4 µm/m·°C |
| Specific heat capacity | 460 J/kg·K |
Specifications by product form
| Plate / sheet / strip | ASTM B409 / ASME SB-409 |
|---|---|
| Bar / rod / shapes | ASTM B408 / ASME SB-408 |
| Seamless pipe & tube | ASTM B407 / B163 / ASME SB-407 |
| Forgings & flanges | ASTM B564 / ASME SB-564 (UNS N08810 / N08811) |
| Butt weld fittings | ASTM B366 / ASME SB-366 (WP800H / WP800HT) |
| Welding consumables | ERNiCr-3 or ENiCrFe-2; ERNiCrCoMo-1 for maximum creep strength |
| UNS / EN / China | UNS N08810 / N08811 · W. Nr. 1.4958 / 1.4959 · GB GH1180 |
Product forms available
Hangbo supplies this grade in the following forms. Sizes outside the listed range can often be produced to order.
- Seamless pipe and tube for reformer and cracker outlet systems
- Forged flanges and large-diameter rings
- Butt weld elbows, tees, reducers and pigtails to ASME B16.9
- Machined manifolds, headers and quench fittings
Typical applications
- Ethylene cracking furnace outlet manifolds, transfer lines and quench piping
- Steam methane reformer pigtails, outlet headers and collector systems
- Ammonia, methanol and hydrogen production plants
- Heat treatment furnace fixtures, radiant tubes and muffles
- Nuclear steam generator and high-temperature gas reactor components
- Coal gasification, waste incineration and mineral calcining equipment
Welding, forming and machining
- Welding
- Weld readily by GTAW, GMAW and SMAW using ENiCrFe-2 or ERNiCr-3 filler. For maximum creep strength above 700 °C, a higher alloy filler such as ERNiCrCoMo-1 is preferred. Control heat input and interpass temperature to avoid excessive grain growth.
- Heat treatment
- Solution anneal at 1120-1175 °C for high creep applications, or at 1035-1095 °C when a finer grain is wanted for lower temperature service.
- Hot forming
- Hot work between 1175 °C and 950 °C; the final hot working temperature should be high enough to develop the coarse grain size required by the specification.
- Machining
- Standard austenitic practice: sharp tooling, positive rake and enough feed to cut below the work-hardened layer.
Buy Incoloy 800H / 800HT from Hangbo
Material is supplied with full heat-number traceability, solution annealing or ageing performed under calibrated furnace control, and an EN 10204 3.1 certificate covering chemical analysis, mechanical properties, heat treatment records and the agreed NDT scope. Positive material identification and third party inspection and test reports from SGS are available for critical service.