Tesco Steel & Engineering forges Incoloy 800HT weld neck flanges — UNS N08811, Werkstoff Nr. 1.4959, the top rung of the Fe-Ni-Cr alloy 800 ladder — to ASTM B564, from 1/2″ NB to 56″ NB in ASME B16.5 Class 150–2500 and European PN patterns. To 800H's controlled carbon and coarse grain, 800HT adds one further guarantee: combined Al+Ti held at 0.85–1.20% — buying the family's highest stress-rupture strength for the hottest rupture-limited plant: steam-methane reformer pigtails, headers and manifolds, ethylene furnaces and fired heaters at 800–985 °C metal temperatures. Mating B407 pipe, welded with ERNiCrCoMo-1. Supplied with grain size reporting, PMI and EN 10204 3.1/3.2. ISO 9001:2015, made in Mumbai, India — exported worldwide.
Incoloy 800HT · UNS N08811 · 1.4959C 0.06–0.10% · Al+Ti 0.85–1.20%ASTM B564 / ASME SB-564Peak Rupture Life · Coarse GrainReformers · Ethylene Furnaces1/2″ – 56″ NB · Class 150–2500ISO 9001:2015 · Exported Worldwide
Incoloy 800HT (UNS N08811 / 1.4959) is the alloy 800 family at maximum creep tune: carbon at 0.06–0.10%, a solution-annealed coarse grain, and — the grade's signature — combined aluminium + titanium guaranteed at 0.85–1.20%, strengthening the matrix at temperature for the highest stress-rupture life in the family. An Incoloy 800HT weld neck flange pairs that metallurgy with a long tapered hub butt-welded to the pipe, forged to ASTM B564.
The ladder in one line: 800 (N08800) for general hot duty to ~593 °C; 800H (N08810) where code creep design begins; 800HT where the metal runs hottest and rupture life rules. Chemistry windows overlap, so mill product meeting both is routinely dual-certified 800H/800HT.
In the plant that means one thing: when a steam-methane reformer or ethylene furnace runs 800–985 °C metal temperatures for years between turnarounds, 800HT's rupture curves — sitting above 800H's at the top of the range — are what the design life is drawn from.
Also searched as: Alloy 800HT flange, UNS N08811 flange, 1.4959 flange, X8NiCrAlTi32-21 flange, reformer flange, ethylene furnace flange — all refer to the product on this page.
Chemical Composition of Incoloy 800HT
C
Mn
Si
S
Cu
Fe
Ni
Cr
Al
Ti
0.06-0.10
1.50 max
1.00 max
0.015 max
0.75 max
39.50 min
30.00-35.00
19.00-23.00
0.15-0.60
0.15-0.60
Values in weight %. On top of the individual ranges, 800HT carries the defining extra requirement: combined Al+Ti at 0.85–1.20% — the guaranteed matrix strengthening that separates it from 800H and buys the family's best rupture curves.
Mechanical Properties of Incoloy 800HT
Tensile Strength, MPa
Yield Strength, Min, MPa
Elongation % min.
450
170
30
Minimums per ASTM B564 for N08811 in the solution-annealed (coarse grain) condition — the same ambient minimums as 800H, deliberately below standard 800's 520/205. The 800HT advantage lives in the high-temperature stress-rupture curves, not the room-temperature test.
Equivalent Grades of Incoloy 800HT
Standard
Werkstoff Nr.
UNS
JIS
BS
GOST
EN
OR
Incoloy 800HT
1.4959 / 1.4876
N08811
NCF 800HT
NA 15(HT)
ЭИ670
X8NiCrAlTi32-21
ХН32Т
The family members are 800 / N08800 / 1.4876 and 800H / N08810 / 1.4958. System partners: ASTM B407 seamless pipe, B366 butt-weld fittings, B409 plate and B564 forgings.
Incoloy 800HT Weld Neck Flange Specifications
Incoloy 800HT Weld Neck Flanges are available in the following specifications:
Size
1/2"NB to 56"NB
Class
150#, 300#, 400#, 600#, 900#, 1500#, 2500#
Sch (Schedule)
XS, XXS, STD & Schedule 20, 40, 80, 160
Pressure Ratings
PN 2.5 - PN 400
Standards
ASTM B564 / ASME SB-564; ASME B16.5, ASME B16.47, EN 1092-1, DIN 2631–2635, BS 4504
0.85–1.20% combined aluminium + titanium — matrix strengthening that is optional luck in other heats, certified chemistry here.
Best Rupture Curves in the Family
At the hottest metal temperatures, 800HT's stress-rupture allowables sit above 800H's — the margin reformer designers draw their life calculations from.
Coarse Grain, Controlled Carbon
Everything 800H does — carbon window, coarse-grain anneal, code creep listing — 800HT does too, then adds the Al+Ti floor.
Oxidation & Carburization Duty
The 20% chromium scale and stable Fe-Ni-Cr austenite handle reformer flue paths and ethylene coils' carburizing side without embrittling.
Full Incoloy Range In-House
800, 800H, 800HT, 825 and 925 flanges from one forge — dual-certification where chemistry allows, certificates matched across the piping bill.
Welding Incoloy 800HT — Match the Rupture Life
For creep-range joints the standard call is ERNiCrCoMo-1 (alloy 117-type) consumables, whose stress-rupture life matches the base metal; ERNiCr-3 (Inconel 82) serves joints designed below the creep range. Nickel-alloy discipline throughout: sulphur-free cleanliness, moderate heat input, no preheat, no PWHT in normal practice — and procedures for code creep service qualified at the design temperature.
Grade-selection note: 800HT earns its premium only where rupture life at the hottest temperatures governs. Most creep duty is covered by 800H, and below ~593 °C standard 800 is the economical pick. State the design temperature in the enquiry and the grade follows.
Where Incoloy 800HT Weld Neck Flanges Are Used
Steam-methane reformers lead — pigtails, headers, manifolds and their flanged connections at 800–985 °C — then ethylene and pyrolysis furnaces, petrochemical fired heaters, hydrogen and syngas plants, superheaters and hot-gas ducting. Our nickel-alloy production below:
Incoloy 800HT weld neck flanges share their dimensions with every other material in the same class — OD, thickness, hub, bore, bolt circle and bolting per the standard tables. Full ASME B16.5 charts:
800HT pricing tracks nickel plus the testing scope, so we quote live with a stated validity rather than publish a static list. To get a firm quotation, usually within 24 hours:
1
List your requirement — size (NB), class or PN, standard (ASME B16.5 / B16.47 / EN / DIN / BS), grade (800HT — or dual-certified 800H/800HT), pipe schedule or bore, and quantity.
2
State the service & testing scope — design temperature, grain size requirement, plus 3.2 witness, PMI or project specifications.
3
Send it across — via the inquiry form, WhatsApp, or email to sales@tescosteel.com — and we reply with price, delivery and stock position.
It is a weld neck flange forged from Incoloy 800HT — the peak stress-rupture member of the alloy 800 family, UNS N08811 / 1.4959, with carbon at 0.06-0.10% and the combined aluminium-plus-titanium content tightened to 0.85-1.20%, solution annealed to a coarse grain — to ASTM B564. The long tapered hub is butt-welded to the pipe with the bore matched to the schedule, giving a radiographable joint in the grade specified for the hottest rupture-limited plant: reformers, ethylene furnaces and fired heaters.
What is the difference between Incoloy 800HT and 800H?
One extra control. Both grades hold carbon in a window (800H at 0.05-0.10%, 800HT at 0.06-0.10%) and both are solution annealed to a coarse grain — but 800HT additionally requires the combined aluminium-plus-titanium content to sit at 0.85-1.20%. Those elements strengthen the matrix at temperature, so 800HT delivers the highest stress-rupture strength in the family. Mill product whose chemistry meets both windows is often dual-certified 800H/800HT.
What is the difference between Incoloy 800HT and standard Incoloy 800?
Standard 800 (UNS N08800) caps carbon at 0.10% with no floor, makes no Al+Ti demand beyond 0.15-0.60% each, and is the general-purpose grade to about 593 °C design. 800HT floors carbon at 0.06%, tightens combined Al+Ti to 0.85-1.20% and is coarse-grain annealed — buying code-listed creep and the family's best rupture life for continuous service at 800-985 °C metal temperatures. Below the creep range the standard grade is the economical pick.
Why does the Al+Ti window matter in Incoloy 800HT?
Aluminium and titanium strengthen the austenitic matrix at temperature — partly in solution, partly as fine gamma-prime-type phases — and they tie up carbon and nitrogen. Below about 0.85% combined, that strengthening is inconsistent heat to heat; the 800HT window of 0.85-1.20% guarantees it, which is why the grade's stress-rupture curves sit above 800H's at the hottest temperatures. It is chemistry control converted directly into certified design allowables.
What temperature is Incoloy 800HT used at?
Its home is the top of the family's range: continuous metal temperatures of 800-985 °C on reformer and ethylene-furnace components, with ASME code coverage for time-dependent design to 899 °C in pressure service and oxidation resistance holding to about 1093 °C. Below roughly 593 °C its creep advantage is irrelevant and standard 800 serves; between the two, 800H usually suffices — 800HT is bought for the hottest rupture-limited components.
What are the equivalent designations for Incoloy 800HT?
UNS N08811; Werkstoff Nr. 1.4959 (dual-certifiable with 1.4876); EN X8NiCrAlTi32-21; JIS NCF 800HT; BS NA 15(HT); GOST ЭИ670 (ХН32Т); and the trade names Incoloy 800HT or Alloy 800HT. System partners: ASTM B407 seamless pipe, B366 butt-weld fittings, B409 plate and B564 forgings. An enquiry in any of these designations is quoted as the same material.
What is the chemical composition of Incoloy 800HT?
Per ASTM B564: carbon 0.06 to 0.10%, nickel 30.00 to 35.00%, chromium 19.00 to 23.00%, iron 39.50% minimum, aluminium 0.15 to 0.60%, titanium 0.15 to 0.60% — with the defining extra requirement that combined aluminium plus titanium sit at 0.85 to 1.20% — and manganese capped at 1.50%, silicon 1.00%, copper 0.75%, sulphur 0.015%. The Al+Ti window plus coarse-grain anneal is what separates 800HT from 800H.
What are the mechanical properties of Incoloy 800HT flanges?
Per ASTM B564 in the solution-annealed condition: tensile strength 450 MPa (65 ksi) minimum, yield strength 170 MPa (25 ksi) minimum and elongation 30% minimum — the same room-temperature minimums as 800H, and deliberately below standard 800's 520/205, because the coarse-grain anneal trades ambient strength for the stress-rupture life the grade is bought for. 800HT's advantage over 800H appears in the high-temperature rupture curves, not the ambient test.
Which pipe and fittings do Incoloy 800HT weld neck flanges mate with?
ASTM B407 seamless alloy 800HT pipe is the standard partner, with B366 butt-weld fittings and B409 plate completing the system. The weld neck bore is machined to the pipe schedule you state, so the bore runs flush through the joint and the bevel arrives ready for a matched creep-grade butt weld.
How are Incoloy 800HT flanges welded to pipe?
For creep-range joints the standard call is ERNiCrCoMo-1 (alloy 117-type) consumables, whose stress-rupture life matches the base metal; ERNiCr-3 (Inconel 82) serves joints designed below the creep range. Nickel-alloy discipline applies throughout: sulphur-free cleanliness, moderate heat input, no preheat and no PWHT in normal practice, with procedures for code creep service qualified at the design temperature.
Why is Incoloy 800HT the reformer and ethylene-furnace grade?
Steam-methane reformers and ethylene furnaces run continuous metal temperatures of 800-985 °C for years between turnarounds, and design life there is set entirely by stress-rupture data. 800HT's guaranteed Al+Ti window delivers the family's best rupture curves while the Fe-Ni-Cr base resists oxidation and carburization, so pigtails, headers, manifolds and their flanged connections default to it. We forge 800HT alongside 800 and 800H, with dual-certification where chemistry allows.
Is Incoloy 800HT resistant to chloride stress corrosion cracking?
Yes — the 30-35% nickel base lifts it above the chloride-SCC threshold that limits 300-series stainless, the same as the rest of the family. But 800HT is bought for creep, not wet corrosion: for chloride-rich immersion the molybdenum-bearing Incoloy 825 is the family's answer, and paying the 800HT premium for sub-creep service buys nothing standard 800 does not already give.
What testing and certification do you supply with Incoloy 800HT flanges?
Every lot ships with EN 10204 3.1 mill test certificates covering chemical analysis — demonstrating the 0.06-0.10% carbon and 0.85-1.20% combined Al+Ti windows — mechanical properties, the solution-anneal record and grain size measurement, with 3.2 certification witnessed by Lloyd's, DNV, BV or TÜV on request. We also offer PMI verification, hydrostatic testing and dye-penetrant examination, with full heat-number traceability.
Where are Incoloy 800HT weld neck flanges used?
Steam-methane reformer pigtails, headers and manifolds; ethylene and pyrolysis furnaces; petrochemical fired heaters; hydrogen and syngas plants; superheaters, hot-gas ducting and furnace hardware — the hottest rupture-limited positions in the plant, where the design temperature has already climbed past what 800 and often 800H are rated for.
What sizes and standards do you manufacture Incoloy 800HT weld neck flanges in?
From 1/2 inch NB to 56 inch NB: ASME B16.5 Class 150 to 2500 up to 24 inch, ASME B16.47 above, and European PN 2.5 to PN 400 patterns to EN 1092-1, DIN and BS 4504. Raised face is standard, ring joint on request, and every bore is machined to the mating pipe schedule from Sch 10 through XXS.
Do you keep Incoloy 800HT weld neck flanges in stock? What is the lead time?
800HT moves almost entirely in project quantities against reformer and furnace specifications, so most orders are forged to order — typically 4 to 6 weeks depending on size, class and testing scope — with dual-certified 800H/800HT stock sometimes available sooner. Prices track nickel, so quotations carry a validity period.
Do you export Incoloy 800HT flanges outside India?
Yes. Tesco Steel & Engineering is an ISO 9001:2015 certified manufacturer based in Mumbai, and Incoloy 800HT flanges ship to reformer, petrochemical and power projects across the Middle East, Europe, Africa, Southeast Asia and the Americas. Flanges travel face-protected and seaworthy-packed, with full heat-number and test traceability.
