# Alloy 800HT (UNS N08811) Forgings

**Supplier:** Jiangyin Jiangnan Metal Co., Ltd., open-die forging factory
**Address:** No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
**Telephone:** +86 189 2135 9659
**Email:** sales@steelforgepieces.com
**Page:** https://www.steelforgepieces.com/Nickel-Alloy/ALLOY-800HT.html
**Last updated:** 2026-08-14

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## Summary

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.

## Key temperatures

| Temperature | Significance |
|---|---|
| 593 °C (1100 °F) | Above this temperature specify 800H or 800HT rather than Alloy 800 |
| 816 °C (1500 °F) | Limit of the ASME BPVC Section VIII Div. 1 allowable stress table |
| 982 °C (1800 °F) | Permitted under ASME Code Case 1983 |
| 1149 °C (2100 °F) | Minimum solution anneal temperature for 800HT |

## At a glance

| Item | Value |
|---|---|
| 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 (ASTM B564 / ASME SB-564, weight %)

| Element | Minimum % | Maximum % |
|---|---|---|
| Nickel (Ni) | 30.00 | 35.00 |
| Chromium (Cr) | 19.00 | 23.00 |
| Iron (Fe) | 39.50 | balance |
| Carbon (C) | 0.06 | 0.10 |
| Aluminium (Al) | 0.15 | 0.60 |
| Titanium (Ti) | 0.15 | 0.60 |
| Aluminium + Titanium | 0.85 | 1.20 |
| Manganese (Mn) | — | 1.50 |
| Silicon (Si) | — | 1.00 |
| Copper (Cu) | — | 0.75 |
| Sulfur (S) | — | 0.015 |

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

### Specified minimums to ASTM B564 / ASME SB-564, annealed

| 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 forgings

| Property | Metric | 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 design screening only. The mill test certificate issued with each forging governs acceptance.

## Physical properties

| 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

| 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 |

For service below 593 °C, specify Alloy 800. For sustained load above 593 °C, specify Alloy 800HT and ask for dual N08810 / N08811 certification.

## 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. 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 only to identify the alloy specification.

## Applicable standards by product form

| Product form | ASTM | ASME |
|---|---|---|
| Forgings | 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 |

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 produced

Seamless rolled rings, forged flanges, round bars and billets, discs and blanks, shafts and spindles, sleeves and bushings, tube sheets, hollow bars and forged pipe, valve components, nozzles and manifolds. Every item is forged to the customer's drawing or dimensional sketch. There is no fixed catalogue and no tooling charge for open-die work.

| 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 the drawing states otherwise. Finish-machined parts to print are also supplied.

## Manufacturing route

1. **Melting.** EAF + AOD/VOD, with ESR remelting available where the specification or service requires improved cleanliness and reduced segregation.
2. **Ingot / billet inspection.** Heat chemistry verified by spectrometer against ASTM B564 limits, including the Al + Ti window that defines the grade.
3. **Open-die forging.** Hydraulic presses with a controlled reduction ratio to close porosity and develop a wrought grain flow following the part contour. Rings are ring-rolled seamless.
4. **Solution annealing.** Held 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.
5. **Rough or finish machining.** Turned, bored, drilled and faced to drawing.
6. **Non-destructive testing.** Ultrasonic examination to EN 10228-3, SEP 1921, ASTM A388 or nominated class. PT and dimensional inspection as required.
7. **Certification and despatch.** EN 10204 3.1 as standard; 3.2 with third-party witness on request.

## Applications

| 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 |
| 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 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

**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?**
Seamless rolled rings, discs, bars, shafts, sleeves, tube sheets and custom shapes are forged as open-die work to customer drawings, covering rings from 200 to 3,000 mm outside diameter and unit weights up to about 10,000 kg. 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 a drawing and a firm date is confirmed 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

Send a drawing, a sketch, or the dimensions and quantity. 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
- **Email:** sales@steelforgepieces.com
- **Website:** https://www.steelforgepieces.com/

## Related grades

Incoloy 800HT, Incoloy 800H, Incoloy 800, Incoloy 825, Inconel 617, Inconel 601, Inconel 600, Inconel 625, Inconel 718, Haynes 230, Hastelloy X, Nimonic 263.

Full grade index: https://www.steelforgepieces.com/Nickel-Alloy/

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Technical data on this page is compiled from ASTM B564 and published alloy literature and is offered for guidance only. The mill test certificate supplied with each forging governs acceptance.

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