Tesco Steel & Engineering manufactures ASTM A182 F11 long weld neck flanges — the steam staircase's first rung: 1¼Cr-½Mo alloy steel, UNS K11572, Class 2 supply — with ASME B16.5 flange ends in Classes 150–2500 and the barrel made to order. The construction is the LWN's: the flange and the nozzle in one forging, one closing weld at the drum, header or shell. The chemistry serves steam, not sulphur: a guaranteed 0.10–0.20% carbon floor feeding the carbides creep strength depends on — the same guaranteed-carbon logic this site's H-grade thread runs on — with chromium for stability and molybdenum for decades at temperature. This is the power-plant classic: generations of boilers, drums and headers standardised on it, and its welding is the friendliest on the chrome-moly bench. The staircase climbs honestly: F22 for hotter steam and hydrogen, F91 for modern high-energy allowables; A105 waits below ~425 °C. Facings: RF / FF / RTJ. Every lot with EN 10204 3.1/3.2 MTC. ISO 9001:2015, made in Mumbai, India — exported to 50+ countries.
ASTM A182 F11 Cl.2 · UNS K11572 · 1.7335 eq.C 0.10–0.20% — The Creep Carbon FloorThe Power-Plant Classic485 / 275 MPa · 143–207 HBThe Friendliest Chrome-Moly WeldingB16.5 Flange Ends · Class 150–2500Barrel: Length & Bore to OrderEN 10204 3.1 / 3.2 · ISO 9001:2015
ASTM A182 F11 Long Weld Neck Flanges — Specifications at a Glance
What is an ASTM A182 F11 Long Weld Neck Flange?
The steam staircase's first rung, in the nozzle pattern. An ASTM A182 F11 Class 2 flange (1¼Cr-½Mo, UNS K11572) whose neck continues as a long, heavy-walled straight barrel — the nozzle itself — bevelled for one closing butt weld at the drum, header or shell. C 0.10–0.20% is a guaranteed floor — the creep carbon; Cr 1.00–1.50% holds the structure and the steam-side scale; Mo 0.44–0.65% carries decades at temperature. Boiler, header and steam-drum nozzles through the 500 °C class. Supplied normalized & tempered, 143–207 HB certified; welded under the bench's friendliest chrome-moly discipline. Flange ends per ASME B16.5, Classes 150–2500; barrel length and bore stated by you. EN 10204 3.1 on every lot.
Also searched as: F11 LWN flange, 1.25Cr-0.5Mo long weld neck flange, P11-matching nozzle flange, A182 F11 Cl.2 RFLWN, K11572 LWN — all the same product. Related pages: the facings — LWNRF / LWNFF / LWNRTJ — the long weld neck hub, the F11 socketweld on small bore, the ladder — A105 / F5 / F9 / F22 / F91 — and the alloy steel hub.
The rule of the two staircases:steam creep climbs F11 → F22 → F91; sulphur severity climbs F5 → F9. Our quotation asks the service before pricing the rung.
What the Carbon Floor and the 1¼ Chrome Buy
The Creep Carbon — Guaranteed
C 0.10–0.20% is a floor, not an allowance: the carbides that pin a hot microstructure need feeding — the same guaranteed-carbon logic as the site's H-grade thread, tuned for steam.
Stability at a Small Alloy Cost
1¼% chromium stabilises the structure and the steam-side scale through the 500 °C class — the economic sweet spot the steam age standardised on, with ½% molybdenum multiplying creep life.
The Fleet Everyone Knows
Generations of boilers, drums, headers and reheat systems run on 1¼Cr-½Mo and its pipe twin P11 — every power fabricator owns the WPS, and the closing weld is familiar territory.
The Friendliest Chrome-Moly Welding
Preheat ~120–200 °C, B2-class consumables, PWHT ~620–720 °C — the discipline's shape without the high-chrome severity: respected, scheduled, unremarkable.
Specification Notes — Getting F11 Long Weld Necks Right
Three honest notes.State the class: commerce assumes Class 2 (485/275) and so do B16.5 ratings — but Class 1 and Class 3 exist, and a silent data sheet gets our question rather than our assumption. Below ~425 °C, buy carbon steel:A105 serves clean cool duty at a fraction of the cost, with no PWHT overhead — F11 bought there is creep strength the design never uses. And climb when the steam does: through the 550 °C class the allowables hand to F22, and modern 600 °C-class plants jump to F91 outright — the staircase, not habit, picks the rung.
How Our F11 LWN Flanges Are Manufactured
1
Forging — each piece individually forged from the certified F11 heat with the barrel integral — no welded build-ups — in any section up to the heaviest HB patterns.
2
Normalizing & tempering — the full N&T cycle that sets the tough tempered structure the Class 2 certificate stands on; furnace records retained against the heat number.
3
Hardness verification — every lot confirmed inside the 143–207 HB window: the floor proves the transformation, the ceiling protects the welds.
4
Machining — flange end to ASME B16.5; barrel turned to pattern (standard / HB / equal) and bored to the ordered schedule or drawing; RF serrations, flat face or RTJ groove per B16.20; weld end bevelled 37.5°.
5
Testing & marking — chemistry and mechanicals per heat; PMI-checked; marked with grade, class, size, schedule and heat number.
6
Certification & packing — EN 10204 3.1 MTC with heat-treatment records (3.2 witnessed on request); chrome-moly WPS guidance included; faces and bevels protected, packed sea-worthy.
Where F11 LWN Flanges Are Used
The boiler island and its neighbours: steam-drum and header nozzles, main-steam and hot-reheat adjacent connections, economiser and superheater hardware, feedwater systems running hot, HRSG modules, refinery and petrochemical steam generation, and the level-bridle and instrument standpipes that ride on all of them. Production and supply below:
Seven elements — the design temperature confirms the staircase rung:
1
Size & standard — e.g. 6″ NB ASME B16.5.
2
Pressure class & facing — 150#–2500#; RF (the default), FF or RTJ with ring number.
3
Barrel length — overall, face to weld end: 150 / 230 / 300 mm stock or any stated length.
4
Barrel bore & pattern — pipe schedule to match or finished bore in mm; standard, heavy barrel or equal barrel; weld-end prep if non-standard.
5
Grade line & design temperature — ASTM A182 F11 Class 2 (Class 1/3 only if named); the design temperature stated — it confirms F11 against A105 below and F22/F91 above.
6
Certification — EN 10204 3.1 with heat-treatment records (our standard) / 3.2 witnessed; hardness documentation where applicable.
Example: “LWN Flange RF, 6″ NB, ASME B16.5 Class 900, barrel 300 mm, Sch 120 bore, heavy barrel, ASTM A182 F11 Cl.2, steam-drum nozzles at 510 °C, EN 10204 3.1 — 4 pcs.” Quotations normally within 24 hours with price, unit weight and delivery.
An ASTM A182 F11 long weld neck flange is a forged 1¼Cr-½Mo alloy steel flange — UNS K11572, the power-plant classic, supplied as Class 2 — whose neck continues as a long, heavy-walled straight barrel that is itself the nozzle, bevelled at its far end for one closing butt weld made out at the drum, header or vessel shell. Its chemistry serves the steam staircase: a guaranteed 0.10-0.20% carbon floor feeding the carbides creep strength depends on, chromium dosed for scale and stability rather than sulphur, molybdenum stiffening the lattice through decades at temperature. Flange ends follow ASME B16.5 in Classes 150 to 2500; the barrel is machined to the ordered length and bore. Boiler, header and steam-drum nozzles through the 500°C class are its home ground — supplied normalized and tempered with the 143-207 HB window certified.
How does a long weld neck differ from a standard weld neck flange?
Geometry and mission. A standard weld neck's hub tapers quickly down to the pipe's outside diameter and wall, ending in a weld bevel a few centimetres from the flange face — it is built to butt-weld to pipe and continue as a piping run. A long weld neck keeps a full-section straight barrel for its entire length: no taper to pipe dimensions, wall far heavier than the matching schedule, length made to order. The mission follows the shape — the LWN is not a fitting on a pipe run but a nozzle in its own right, projecting through insulation, vessel walls or exchanger channels, with the butt weld relocated to the shell side where the fabricator wants it. In one certified forging it replaces the weld neck flange, the pipe nipple and one whole circumferential weld.
Why does F11 guarantee a carbon floor — 0.10-0.20%?
For the same reason the creep world always does: carbides are the anchors that hold a hot microstructure still, and a floor guarantees the carbon to form them. This site's readers have met the logic before — the stainless bench turns the same dial from 304L up to 304H, and the Incoloy bench from 800 to 800H — and F11 belongs to that family of thinking: it is a creep grade first, so its carbon is a requirement, not merely an allowance. In the tempered structure, that carbon sits as chromium and molybdenum carbides pinning grain boundaries and dislocations against the slow deformation that defines steam service. The corrosion-staircase grades F5 and F9 cap carbon instead, because their mission is sulphur resistance with weldability; F11's mission is decades of stress at 500-and-something degrees, and the floor is where it starts.
Why is F11 the power-plant classic?
Because it hit the economic sweet spot of the steam age and never left it. 1¼% chromium is enough to stabilise the microstructure and resist steam-side oxidation through the 500°C class; ½% molybdenum multiplies creep life at a small alloy cost; and the steel remains forgiving — weldable with moderate preheat, tough, cheap enough to build entire boiler islands from. Generations of utility boilers, steam drums, headers, main-steam and hot-reheat systems standardised on 1¼Cr-½Mo and its pipe twin P11, so the world's power fleet is full of it and every fabricator knows it. F11 LWN nozzles carry that metallurgy into drums, headers and vessels — penetrations matching the shell, with the closing weld in familiar territory. Where steam conditions climbed further, F22 and later F91 took over — but the classic rung still carries an enormous share of the world's steam.
What is the difference between F11 Class 1, Class 2 and Class 3?
Strength classes of the same chemistry, set by heat treatment and certified separately. Class 1 is the softest — a lower tensile floor with a slightly leaner carbon-silicon recipe, occasionally wanted for its maximum ductility. Class 2 — 485 MPa tensile, 275 MPa yield minimum — is the standard flange and fitting supply, the class B16.5 ratings and the trade assume, and what this page describes; write F11 with no class and Class 2 is what commerce delivers, though a specification should say so. Class 3 raises the floors again (515/310) for designs that call the extra strength. All three share the 1¼Cr-½Mo identity and the welding practice. Our certificates state the class explicitly — and if your data sheet names Class 1 or 3, the forging and paperwork follow exactly.
What is the chemical composition of ASTM A182 F11?
Carbon 0.10-0.20% — a floor and a ceiling, the creep carbon — manganese 0.30-0.80%, silicon 0.50-1.00%, phosphorus ≤0.040%, sulphur ≤0.040%, chromium 1.00-1.50% and molybdenum 0.44-0.65%. Seven specified elements, no nickel line. Two comparative readings: against the refinery rungs, the P/S caps relax a shade (0.040 against F5/F9's 0.030) — the steam staircase's enemies are creep and oxidation, not hot sulphur; and the silicon range carries the same deoxidation-plus-scale logic as F9's, at the service temperatures where steam-side oxidation matters. Chemistry is verified per heat, PMI-confirmed — the low-Cr Mo signature reads clearly — and travels on the EN 10204 3.1 MTC.
What are the mechanical properties of F11 long weld neck flanges?
Class 2, normalized and tempered: tensile strength 485 MPa (70 ksi) minimum, yield strength 275 MPa (40 ksi) minimum, elongation 20% minimum, hardness 143-207 HB. The room-temperature certificate matches F5's numbers — but the certificate is not the mission: what F11 sells is the creep and stress-rupture strength behind B16.5's alloy-group ratings, which carry its flanges through the 500°C class where carbon steel's tables have long since ended. The hardness window's logic is familiar from the whole chrome-moly bench: the floor certifies the transformation, the ceiling protects welds. And the two-ceilings honesty applies as everywhere — on a hot steam joint the gasket system and B7/B16 bolting retire before the flange metal does.
How demanding is the welding on F11 — compared with F5, F9 and F91?
The friendliest on the chrome-moly bench, which is part of why the grade conquered the steam world. The discipline's shape is the same — this is still an air-hardening low-alloy steel — but every dial sits lower: preheat typically 120-200°C rather than the high-chrome rungs' 200-300°C, matching B2-class 1¼Cr consumables, and PWHT commonly around 620-720°C, with thin non-pressure attachments sometimes exempted by code where thicker joints are not. Compare upward: F5 and F9 demand hotter preheat and stricter hydrogen control as chromium climbs, and F91 lives under a famously exacting regime where tempering precision decides the creep rating. For an F11 LWN, the closing weld at the drum or header is ordinary boiler-shop practice — respected, scheduled, and unremarkable to any power-plant fabricator. WPS guidance travels with every supply.
How are the barrel length and bore of a LWN specified?
Two numbers that belong on every enquiry. Length: measured overall from the flange face to the weld end — 150 mm (6"), 230 mm (9") and 300 mm (12") are the common stock lengths, and any length machines to order; state it explicitly, because 'long' is not a dimension. Bore: the barrel is drilled and bored to order — most commonly to match the inside diameter of the connecting pipe schedule, sometimes cylindrical special bores for level bridles, instrument standpipes or restriction work; state the schedule or the finished bore in millimetres. Add the weld-end preparation (standard 37.5° bevel unless told otherwise) and the nozzle is fully defined.
What are standard, heavy-barrel and equal-barrel LWN flanges?
Three barrel weights for three duties. The standard LWN carries a barrel a little heavier than the matching pipe — the general-purpose vessel nozzle. The heavy-barrel (HB) pattern thickens the wall substantially — often approaching the hub section for its full length — for high-pressure nozzles, heavy nozzle loads and reinforcement-limited openings, where the extra metal does the area-replacement work the code asks of a vessel opening; steam drums and high-pressure headers use it constantly. The equal-barrel pattern keeps the barrel outside diameter equal to the hub for a clean cylindrical profile — favoured on manway and instrument connections. All three share B16.5 flange ends; the design calculation or the equipment drawing decides which is wanted.
When does F11 hand off — to F22 above, or A105 below?
Both boundaries are honest and well-trodden. Downward: clean service below roughly 425°C is carbon steel country — A105 nozzles serve at a fraction of the cost with no PWHT overhead, and F11 bought there is money spent on creep strength the design never uses. Upward: as steam conditions climb through the 550°C class, F11's allowable stresses taper and F22's 2¼Cr-1Mo chemistry takes over — the second rung of the same staircase, also serving hot hydrogen duty per the Nelson curves — while modern high-energy plants at 600°C-class conditions jump to F91's enhanced allowables outright. The refinery corrosion staircase (F5, F9) answers a different question — sulphur, not steam. State the design temperature and duty on the enquiry; the staircase and our quotation pick the rung together.
What sizes and pressure classes do F11 LWN flanges come in?
Flange ends follow ASME B16.5 from ½" to 24" NB in Classes 150, 300, 400, 600, 900, 1500 and 2500 — with the full class-by-class LWN dimension charts on this site — and larger diameters forge to order against B16.47 or drawing dimensions, with EN 1092-1 drilling machined on the same barrels. The F11 order book reads like a boiler island: Classes 300-600 on feedwater and auxiliary steam, Classes 900-2500 with heavy-barrel patterns on drums, headers and main-steam duty where pressures climb with the temperature. State size, class, barrel length and bore together — the four numbers define the forging — and our quotation returns price, unit weight and delivery per class.
What details are needed to get an accurate F11 LWN flange quotation?
Seven elements plus commercial terms: (1) size and dimensional standard — e.g. 6" NB ASME B16.5; (2) pressure class — 150 to 2500; (3) facing — RF (the default), FF or RTJ with ring number; (4) barrel length overall, face to weld end — 150/230/300 mm stock or any stated length; (5) barrel bore — pipe schedule to be matched or finished bore in millimetres, with pattern (standard, heavy barrel, equal barrel) and weld-end prep if non-standard; (6) the grade line — ASTM A182 F11 Class 2 (Class 1 or 3 only if your specification names them) — with the design temperature stated so the staircase rung is confirmed against A105 below and F22/F91 above; (7) certification — EN 10204 3.1 with heat-treatment records (our standard) or 3.2 witnessed, hardness documentation where applicable. Add quantity and destination; quotations normally within 24 hours.
Who manufactures ASTM A182 F11 long weld neck flanges in India?
Tesco Steel & Engineering is an ISO 9001:2015 certified flange manufacturer based in Mumbai, India, producing ASTM A182 F11 Class 2 long weld neck flanges with B16.5 flange ends from ½" to 24" NB (larger to order) in Classes 150-2500, in standard, heavy-barrel and equal-barrel patterns — each forged individually from certified heats, normalized and tempered with furnace records, hardness verified inside the 143-207 HB window, machined with the barrel bored to the ordered schedule or drawing, bevelled for the closing weld, PMI-checked, and marked with grade, size, class, schedule and heat number. Supplied with EN 10204 3.1/3.2 certification and chrome-moly WPS guidance — alongside the F22 and F91 steam rungs above, the F5/F9 refinery staircase, the A105/LF2 carbon pair and the complete LWN range. Exported to more than 50 countries.
