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Nickel alloy · Fe-Ni-Cr creep grade · UNS N08810

Incoloy 800H for reformers, crackers and hot headers

In short: Incoloy 800H is alloy 800 with carbon held at 0.05–0.10% and a coarse grain (ASTM 5 or coarser). Those controls give it the creep and rupture strength needed above about 600 °C, which is why it is a standard material for reformer pigtails and headers, ethylene furnace parts and hot gas piping.

Quote Incoloy 800H →What to verify
Where alloy 800H sits in a steam reformerIn a steam-methane reformer, cast catalyst tubes hang in the radiant box. Hot reformed gas leaves each tube through a small-bore pigtail into an outlet header. Pigtails and outlet manifolds operating in the creep range are a classic use of alloy 800H and 800HT. Radiant box (burners) Pigtails + outlet headerAlloy 800H / 800HT Catalyst tubes(usually cast alloys) SCHEMATIC · LAYOUTS VARY BY LICENSOR
Schematic of a steam reformer outlet system.

Overview

Incoloy 800H in brief

  • Carbon 0.05–0.10% for creep strength
  • Grain size ASTM No. 5 or coarser
  • ASME code design stresses into the creep range
  • Used in reformers, crackers and furnaces

800H restricts carbon to 0.05–0.10% and requires a solution-anneal that gives an average grain size of ASTM No. 5 or coarser. Those two controls raise creep-rupture strength far above standard 800, which is why 800H is a staple of petrochemical and industrial heating equipment.

Typical applications are ethylene and steam-methane reformer pigtails and outlet manifolds, hydrodealkylation units, superheater and reheater components, and industrial furnace hardware.

Available as

Incoloy 800H product forms

Select a form for its specification, sizes and weights.

Where it's used

Industries that specify Incoloy 800H

Chemistry

Carbon and grain, controlled together

Special Metals introduced the controlled-carbon, coarse-grain variant after finding that higher-carbon material had better creep and rupture properties.[1]

UNS
N08810
EN / W.Nr.
1.4958 · X5NiCrAlTi31-20
Density
7.94 g/cm³
Incoloy 800H chemical composition, % (ASTM B409)
ElementLimit, %Why it matters
Ni30.0 – 35.0
Cr19.0 – 23.0
Fe39.5 min
C0.05 – 0.100.05–0.10%: creep strength
Al0.15 – 0.60With Ti, forms strengthening phases
Ti0.15 – 0.60With Al, forms strengthening phases
Mn1.50 max
Si1.00 max
Cu0.75 max

Limits per ASTM B409; other product forms and specifications differ slightly. Your order's specification and edition govern.

0%5%10%15%20%25%30%35%40% Ni Cr Mn Si
Main alloying elements of Incoloy 800H: bars show the permitted range (ASTM B409).
  1. Chemistry

    Carbon 0.05–0.10%; aluminium and titanium within limits.

  2. Solution anneal

    Temperature recorded on the certificate.

  3. Grain size

    ASTM 5 or coarser, measured and reported.[1]

  4. PMI on receipt

    800H, 800 and SS 304H look alike; verify every piece.

Verification

Four things to see before installation

Creep alloys fail early when the wrong variant slips through. These checks catch it at receiving inspection. See PMI testing.

Mechanical properties

Solution-annealed room-temperature values

Lower room-temperature strength than plain 800 is normal: the coarse grain trades it for creep strength.

450 MPa (65 ksi)Tensile strength (min. unless max)
170 MPa (25 ksi)Yield strength (0.2%) (min. unless max)
30%Elongation (min. unless max)

ASTM B409 (solution-annealed): room-temperature specification values for the annealed condition.

Supply

Incoloy 800H by product form

Product formSpecification and designation
Incoloy 800H pipesASTM B407 / B514
Incoloy 800H tubesASTM B407 / B515
Incoloy 800H platesASTM B409
Incoloy 800H sheetsASTM B409
Incoloy 800H coilsASTM B409
Incoloy 800H barsASTM B408
Incoloy 800H fittingsASTM B366 WPNIC10
Incoloy 800H flangesASTM B564 N08810
  1. Grade 800H or dual 800H/800HT
  2. Grain size ASTM 5 or coarser reported
  3. Carbon 0.05–0.10% confirmed
  4. Solution-anneal temperature stated
  5. PMI at receipt

Ordering

What to put on an order for Incoloy 800H

Getting these on the enquiry avoids the usual back-and-forth and makes sure the certificate matches your specification.

Incoloy 800H questions

Answers about Incoloy 800H

What is the difference between 800 and 800H?

800H is restricted to 0.05–0.10% carbon and must have a grain size of ASTM 5 or coarser, which raises creep and rupture strength.[1] Plain 800 has no carbon minimum or grain-size requirement and is used below the creep range.

800H or 800HT?

800HT sits within 800H's limits but tightens carbon to 0.06–0.10% and Al + Ti to 0.85–1.20%, with a 1149 °C minimum anneal, to keep the highest allowable stresses.[1] Much material is supplied dual-certified 800H/800HT. Compare 800H vs 800HT.

Where is 800H used?

Steam-methane reformer pigtails and outlet manifolds, ethylene furnace components, superheaters and reheaters, industrial furnace hardware and hot process-gas heat exchangers.

What should the certificate show?

Carbon, aluminium and titanium, solution-anneal temperature and the measured grain size, plus the usual tensile results and dimensions.

Which specifications cover 800H?

Pipe: ASTM B407 / B514. Tube: ASTM B407 / B515. Plate: ASTM B409. Fittings: ASTM B366 WPNIC10.

Sources

References

Incoloy® is a trademark of Special Metals Corporation. Composition per the cited specifications and bulletins.

  1. Special Metals: INCOLOY alloys 800H and 800HT technical bulletin
  2. ASTM B407: nickel-iron-chromium alloy seamless pipe and tube

Updated 2026-10-17Technical review: Bright Tubes, Director

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