Nickel Alloy · UNS N08811 · W.Nr. 1.4959
Alloy 800HT Forgings
Seamless rolled rings, flanges, round bars, discs, shafts, sleeves, bushings and tube sheets, open-die forged to ASTM B564 / ASME SB-564.
Alloy 800HT (UNS N08811, W.Nr. 1.4959) is a nickel-iron-chromium alloy containing 30–35% nickel, 19–23% chromium and a minimum of 39.5% iron. It is used above 593 °C (1100 °F), where creep and stress-rupture strength govern the design rather than room-temperature strength. The base chemistry is the same as Alloy 800 and Alloy 800H. Carbon is held to 0.06–0.10%, combined aluminium plus titanium to 0.85–1.20%, and the material is solution annealed at 1149 °C (2100 °F) minimum to produce an ASTM No. 5 or coarser grain size. Those three controls account for the creep-rupture strength of the grade.
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory in Jiangyin, Jiangsu Province, China. It forges Alloy 800HT to customer drawings: rings, flanges, bars, discs, shafts, sleeves and tube sheets. Parts are supplied solution annealed, ultrasonically tested and certified to EN 10204 3.1 or 3.2. For a quotation, contact sales@steelforgepieces.com or +86 189 2135 9659.
Key temperatures for Alloy 800HT
Alloy 800HT at a glance
- Grade
- Alloy 800HT (also written Incoloy® 800HT, 800 HT)
- UNS number
- N08811
- Werkstoff / DIN
- 1.4959 / X8NiCrAlTi32-21
- Alloy family
- Nickel-iron-chromium, austenitic, non-hardenable
- Forging standard
- ASTM B564 / ASME SB-564
- Delivery condition
- Solution annealed, ≥1149 °C (2100 °F), rapid cooled
- Required grain size
- ASTM No. 5 or coarser
- Typical service range
- 593–982 °C (1100–1800 °F)
- Density
- 7.94 g/cm³ (0.287 lb/in³)
- Melting range
- 1357–1385 °C (2475–2525 °F)
- Certification
- EN 10204 3.1 or 3.2 (third-party witnessed)
- Forged by
- Jiangyin Jiangnan Metal Co., Ltd., Jiangyin, Jiangsu, China
What Alloy 800HT is, and when to specify it
Alloy 800HT is the high-temperature member of the Alloy 800 family. Alloy 800, 800H and 800HT carry the same nickel, chromium and iron content and behave almost identically in corrosion. They differ in carbon content, in combined aluminium plus titanium, and in annealing temperature. Those differences decide how the material holds up under sustained load at red heat.
Below about 593 °C (1100 °F), standard Alloy 800 (UNS N08800) is normally sufficient and cheaper. Above that temperature, short-term tensile strength stops being the governing property and creep-rupture strength takes over. Alloy 800HT is annealed high enough to coarsen the grain to ASTM No. 5 or larger, and its aluminium and titanium are held in the top half of the 800H range, which stabilises the structure and raises the allowable design stress.
For specification, use Alloy 800 for service up to 593 °C and 800H or 800HT above it. Choose 800HT where the design code calls for the higher allowable stresses, or where the part will carry load for tens of thousands of hours. Because 800HT chemistry always falls inside the 800H window, most of the material we forge is dual-certified to both N08810 and N08811, so one forging carries both grades on the certificate.
Chemical composition of Alloy 800HT (UNS N08811)
Composition limits below are per ASTM B564 / ASME SB-564 for UNS N08811, expressed in weight percent. The two highlighted rows are the composition controls that distinguish 800HT from 800 and 800H; the third control is the anneal temperature.
| Element | Minimum % | Maximum % | Role in the alloy |
|---|---|---|---|
| Nickel (Ni) | 30.00 | 35.00 | Stabilises the austenitic matrix; resists chloride stress-corrosion cracking |
| Chromium (Cr) | 19.00 | 23.00 | Forms the protective oxide against oxidation, sulfidation and carburisation |
| Iron (Fe) | 39.50 | balance | Base element. Keeps the alloy cheaper than nickel-base grades |
| Carbon (C) | 0.06 | 0.10 | Controlled high for creep strength. Tighter range than 800H (0.05–0.10) |
| Aluminium (Al) | 0.15 | 0.60 | Combines with Ti for high-temperature structural stability |
| Titanium (Ti) | 0.15 | 0.60 | Ties up carbon and nitrogen; contributes to rupture strength |
| Aluminium + Titanium | 0.85 | 1.20 | The defining restriction of 800HT. Alloy 800H allows 0.30–1.20 |
| Manganese (Mn) | — | 1.50 | Deoxidiser; combines with sulfur |
| Silicon (Si) | — | 1.00 | Deoxidiser; assists oxidation resistance |
| Copper (Cu) | — | 0.75 | Residual limit |
| Sulfur (S) | — | 0.015 | Kept low for hot workability and toughness |
Alloy 800HT chemistry always falls inside the Alloy 800H window; the reverse is not true. A specification written to 800H alone is still satisfied by a 800HT heat, which is why dual N08810 / N08811 certification is standard practice.
Mechanical properties of Alloy 800HT forgings
Specified minimums to ASTM B564 / ASME SB-564, annealed
These are the values a mill certificate must meet. They are minimums, not typical values.
| Property | Metric | Imperial |
|---|---|---|
| Tensile strength, min | 448 MPa | 65 ksi |
| Yield strength 0.2% offset, min | 172 MPa | 25 ksi |
| Elongation in 50 mm (2 in) or 4D, min | 30 % | 30 % |
| Average grain size | ASTM No. 5 or coarser | ASTM No. 5 or coarser |
Typical as-delivered values
Solution-annealed Alloy 800HT forgings normally test above the specified minimums. The values below are representative of our production and vary with section size and cooling rate.
| Property | Typical range (metric) | Typical range (imperial) |
|---|---|---|
| Tensile strength | 520–680 MPa | 75–99 ksi |
| Yield strength 0.2% | 210–310 MPa | 30–45 ksi |
| Elongation | 40–55 % | 40–55 % |
| Reduction of area | 50–70 % | 50–70 % |
| Hardness | 120–184 HB | 120–184 HB |
Typical values are for guidance in design screening only. The mill test certificate issued with each forging governs acceptance.
Physical properties of Alloy 800HT
| Property | Metric | Imperial |
|---|---|---|
| Density | 7.94 g/cm³ | 0.287 lb/in³ |
| Melting range | 1357–1385 °C | 2475–2525 °F |
| Modulus of elasticity | 196.5 GPa | 28.5 × 10⁶ psi |
| Specific heat | 460 J/kg·K | 0.11 Btu/lb·°F |
| Thermal conductivity, 20 °C | 11.5 W/m·K | 80 Btu·in/ft²·h·°F |
| Mean expansion, 20–100 °C | 14.4 µm/m·K | 8.0 × 10⁻⁶ in/in·°F |
| Electrical resistivity | 0.989 µΩ·m | 595 Ω·circ mil/ft |
| Magnetic permeability | 1.009 (at 200 Oe) | essentially non-magnetic |
Alloy 800 vs 800H vs 800HT: how to choose
These three grades are often confused on drawings and purchase orders. They differ in three things: carbon content, combined aluminium plus titanium, and anneal temperature. Nickel, chromium and iron content, and corrosion behaviour, are effectively the same.
| Criterion | Alloy 800 | Alloy 800H | Alloy 800HT |
|---|---|---|---|
| UNS number | N08800 | N08810 | N08811 |
| Werkstoff Nr. | 1.4876 | 1.4958 | 1.4959 |
| Carbon, % | 0.10 max | 0.05–0.10 | 0.06–0.10 |
| Al + Ti, % | not restricted | 0.30–1.20 | 0.85–1.20 |
| Grain size requirement | none specified | ASTM No. 5 or coarser | ASTM No. 5 or coarser |
| Anneal temperature | ~980 °C | ≥1121 °C (2050 °F) | ≥1149 °C (2100 °F) |
| Normal service ceiling | 593 °C / 1100 °F | above 593 °C | above 593 °C |
| Governing property | room-temp strength | creep & rupture | creep & rupture, highest allowables |
| Choose it when | Service stays below 593 °C and cost matters | Sustained high-temperature service, standard code allowables | Long-term load above 593 °C, or the code requires the higher allowable stress |
For service below 593 °C, specify Alloy 800. For sustained load above 593 °C, specify Alloy 800HT and ask for dual N08810 / N08811 certification.
Alloy 800HT equivalent designations
| System | Designation |
|---|---|
| UNS (USA) | N08811 |
| Werkstoff Nr. (Germany) | 1.4959 |
| DIN / EN name | X8NiCrAlTi32-21 |
| JIS (Japan) | NCF 800HT |
| AFNOR (France) | Z8NC32-21 (nearest) |
| BS (UK) | NA15 family (nearest) |
| Trade names | Incoloy® 800HT, Nicrofer® 3220 HT, Sandvik Sanicro® 31HT, Pyromet® 800HT |
Designations marked "nearest" are close but not identical matches. Where a code case or design registration is involved, order to the UNS number and confirm the equivalence against the mill certificate. Incoloy is a registered trademark of Special Metals Corporation; Jiangyin Jiangnan Metal Co., Ltd. is not affiliated with the trademark holder and the name is used here only to identify the alloy specification.
Applicable standards by product form
| Product form | ASTM | ASME |
|---|---|---|
| Forgings (our core product) | B564 | SB-564 |
| Rod and bar | B408 | SB-408 |
| Plate, sheet and strip | B409 | SB-409 |
| Seamless pipe and tube | B407, B163 | SB-407, SB-163 |
| Welded pipe | B514 | SB-514 |
| Welded tube | B515 | SB-515 |
For pressure-retaining design, Alloy 800H/800HT carry maximum allowable stresses in the ASME Boiler and Pressure Vessel Code, Section VIII Division 1 up to 816 °C (1500 °F), and are addressed to 982 °C (1800 °F) under Code Case 1983. Nuclear service is covered by Section III Code Cases N-201, N-253 and N-254.
Alloy 800HT forgings we produce
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory. Every item below is forged to the customer's drawing or dimensional sketch. There is no fixed catalogue and no tooling charge for open-die work.
Size and weight capability
| Product form | Dimensional range | Unit weight |
|---|---|---|
| Seamless rolled rings | OD 200–3,000 mm, height to 800 mm | 20–8,000 kg |
| Round bars | Ø80–800 mm, length to 6,000 mm | 20–6,000 kg |
| Discs, tube sheets | Ø200–2,500 mm, thickness to 600 mm | 30–10,000 kg |
| Shafts, sleeves, blocks | to 6,000 mm long | to 10,000 kg |
Machining allowance is normally 6–20 mm per surface depending on section size, unless your drawing states otherwise. We also supply finish-machined parts to print.
How we make Alloy 800HT forgings
- MeltingAlloy 800HT stock is melted by EAF + AOD/VOD, with ESR remelting available when the customer's specification or service requires improved cleanliness and reduced segregation.
- Ingot / billet inspectionHeat chemistry is verified by spectrometer against ASTM B564 limits, including the Al + Ti window that defines the grade, before any material is heated.
- Open-die forgingForged on hydraulic presses with a controlled reduction ratio to close porosity and develop a wrought grain flow that follows the part contour. Rings are ring-rolled seamless.
- Solution annealingHeld at 1149 °C (2100 °F) minimum, then rapidly cooled. This step produces the ASTM No. 5 or coarser grain size required for the creep strength of the grade. Alloy 800HT is not age-hardened.
- Rough or finish machiningTurned, bored, drilled and faced to your drawing, with agreed machining allowance or to final dimensions.
- Non-destructive testingUltrasonic examination to EN 10228-3, SEP 1921, ASTM A388 or your nominated class. PT and dimensional inspection as required.
- Certification and despatchEN 10204 3.1 mill certificate as standard; 3.2 with third-party witness (TÜV, BV, LR, SGS, DNV) on request. Marked, preserved and packed for sea or air freight.
Where Alloy 800HT forgings are used
| Industry | Components forged in Alloy 800HT |
|---|---|
| Petrochemical & refining | Ethylene cracking furnace headers and outlet fittings, hydrogen reformer pigtail connections, transfer line exchanger components, forged nozzles and flanges |
| Power generation | Superheater and reheater header forgings, steam-side flanges, tube sheets, valve bodies for high-temperature steam |
| Industrial furnaces & heat treatment | Radiant tube components, retort and muffle end rings, fixture and basket hardware, roller ends |
| Chemical processing | Nitric and sulfuric acid plant hardware, ammonia and urea plant exchanger forgings, catalyst grid supports |
| Pressure vessels & heat exchangers | Forged tube sheets, shell flanges, blind covers, girth rings for shell-and-tube exchangers |
| Nuclear | Steam generator tube sheet forgings and heat exchanger components under Section III Code Cases N-201, N-253, N-254 |
Alloy 800HT is chosen for these duties because it resists oxidation, carburisation and sulfidation at temperature and stays dimensionally stable. It does not form embrittling sigma phase in the way some higher-chromium stainless grades do. The iron base also makes it cheaper per kilogram than nickel-base alternatives such as Inconel 617 or Haynes 230.
Testing, inspection and certification
- Chemical analysis. Spectrometric heat analysis and, on request, product analysis on the finished forging.
- Mechanical testing. Room-temperature tensile and elongation per ASTM B564; elevated-temperature tensile, stress-rupture and impact testing to your specification.
- Grain size. Determined per ASTM E112; ASTM No. 5 or coarser is mandatory for N08811.
- Ultrasonic testing. EN 10228-3, SEP 1921 Class C/D/E, ASTM A388 or customer class.
- Surface NDT. Liquid penetrant examination per ASTM E165 / ASME V Article 6.
- Intergranular corrosion. ASTM A262 practice as agreed.
- Certification. EN 10204 3.1 as standard; EN 10204 3.2 witnessed by TÜV, BV, LR, SGS or DNV on request. Full heat traceability and hard stamping.
Frequently asked questions about Alloy 800HT
What is the difference between Alloy 800H and Alloy 800HT?
Both are high-temperature versions of Alloy 800. Alloy 800H (UNS N08810) allows 0.05–0.10% carbon and 0.30–1.20% aluminium plus titanium. Alloy 800HT (UNS N08811) tightens those to 0.06–0.10% carbon and 0.85–1.20% Al + Ti, and requires a solution anneal of at least 1149 °C (2100 °F) instead of 1121 °C. This gives higher creep-rupture strength and a higher allowable design stress. The 800HT window sits inside the 800H window, so a 800HT heat also meets 800H, and most material is certified to both.
What is the maximum service temperature of Alloy 800HT?
For pressure-retaining parts, ASME Boiler and Pressure Vessel Code Section VIII Division 1 assigns maximum allowable stresses up to 816 °C (1500 °F), and Code Case 1983 extends this to 982 °C (1800 °F). For non-pressure parts such as furnace fixtures, the practical limit is set by oxidation and by the applied load, and continuous service around 1000 °C is common. Alloy 800HT is not intended for service below 593 °C (1100 °F), where standard Alloy 800 is the more economical choice.
Is Alloy 800HT the same as Incoloy 800HT?
Yes. Both names refer to the same material, UNS N08811. Incoloy® is a registered trademark of Special Metals Corporation. "Alloy 800HT" is the generic name used when the material is supplied by a producer other than the trademark holder. When ordering, specify UNS N08811 and ASTM B564 so the requirement is unambiguous.
Which heat treatment is correct for Alloy 800HT forgings?
Solution annealing at 1149 °C (2100 °F) minimum, followed by rapid cooling. Alloy 800HT is a solid-solution alloy and is not precipitation hardened, so no ageing treatment is applied. The high anneal temperature coarsens the grain to ASTM No. 5 or larger, which is what delivers the creep-rupture strength. Annealing too low produces a fine grain, and the material then fails the grain size requirement of ASTM B564.
Can Alloy 800HT be welded?
Yes. Alloy 800HT is readily welded by GTAW, GMAW and SMAW. For high-temperature service, filler metals based on Inconel 617 or Inconel 82 are commonly specified, because a matching 800HT filler does not develop the same rupture strength across the weld. Post-weld heat treatment is not normally required for the alloy itself, though the design code may call for it.
What sizes of Alloy 800HT forgings can you supply?
We forge seamless rolled rings, discs, bars, shafts, sleeves, tube sheets and custom shapes as open-die work to your drawing. See the capability table above for our current outside diameter, length and unit weight ranges. Open-die forging needs no dies, so one-off and prototype quantities are economic. There is no tooling charge and no minimum order quantity by piece.
Do you supply a material certificate?
Every Alloy 800HT forging ships with an EN 10204 3.1 mill test certificate as standard, showing heat number, chemical analysis, mechanical results, grain size, heat treatment record and NDT results. EN 10204 3.2 certification witnessed by a third party such as TÜV, BV, LR, SGS or DNV is available on request at the time of order.
How long does an Alloy 800HT forging take to produce?
Lead time depends on whether the grade is in raw stock and on the size of the forging. Simple rings and discs from stock material typically run 25–40 days. Parts needing a new melt, ESR remelting, heavy machining or third-party witnessed inspection take longer. Send your drawing and we will confirm a firm date with the quotation.
Who supplies open-die forged Alloy 800HT parts in China?
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory located at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. It forges Alloy 800HT and other nickel alloys, stainless steels, tool steels, alloy steels and carbon steels into rings, flanges, bars, discs, shafts, sleeves and tube sheets, and exports worldwide. Enquiries: sales@steelforgepieces.com, +86 189 2135 9659.
Request a quotation for Alloy 800HT forgings
Send a drawing, a sketch, or just the dimensions and quantity. We quote open-die forgings in Alloy 800HT with no tooling charge and no piece minimum.
Useful details if you have them: grade and standard (Alloy 800HT / UNS N08811 / ASTM B564), product form, dimensions with machining allowance, quantity, delivery condition, NDT class, certificate type (EN 10204 3.1 or 3.2) and required delivery date.
- Company
- Jiangyin Jiangnan Metal Co., Ltd.
- Business
- Open-die forging factory
- Address
- No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
- Telephone / WhatsApp
- +86 189 2135 9659
- sales@steelforgepieces.com
- Website
- www.steelforgepieces.com