Tesco Steel & Engineering manufactures ASTM A182 F309 long weld neck flanges — the scaling ladder's middle rung: 309/309S, UNS S30900/S30908, W.Nr. 1.4833 — with ASME B16.5 flange ends in Classes 150–2500 and the barrel made to order. This page opens the heat-resisting wing: where the chloride ladder fights salt, this bench fights oxygen at furnace temperatures — 23% chromium keeps the oxide scale thin, adherent and self-healing to ~1000 °C, past 304's ~870 °C ceiling and one honest rung below 310's 1100 °C summit, while 13% nickel holds the austenite through the cycles. No molybdenum — the enemy is oxygen, not chlorides. The grade carries a second fame every fabricator knows: ER309L is the industry's dissimilar-weld buffer, the wire that joins stainless to carbon steel — and this page's closing-weld logic uses it. Supplied to the dual 309/309S convention (like our 310 pages), F309H named where code creep design requires it; the sigma-phase caveat handled openly below. One forging, one closing weld at the casing. 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.
309/309S · UNS S30900/S30908 · W.Nr. 1.4833The Furnace Stainless — 23Cr-13NiOxidation Service to ~1000 °CThe Scaling Ladder's Middle RungER309L — The Dissimilar-Weld Fame515 / 205 MPa Solution AnnealedB16.5 Flange Ends · Class 150–2500EN 10204 3.1 / 3.2 · ISO 9001:2015
ASTM A182 F309 Long Weld Neck Flanges — Specifications at a Glance
What is an ASTM A182 F309 Long Weld Neck Flange?
The furnace stainless, in the nozzle pattern. An F309 flange (309/309S, UNS S30900/S30908) whose neck continues as a long, heavy-walled straight barrel — the nozzle itself — bevelled for one closing butt weld at the furnace casing, duct or shell. 23% Cr holds the protective scale to ~1000 °C; 13% Ni holds the austenite through the cycles; no molybdenum — the enemy is oxygen. The scaling ladder: 304 (~870 °C) → 309 (~1000 °C) → 310 (~1100 °C). 515/205/30 solution annealed; F309H by name for code creep design. 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: F309 LWN flange, 309 long weld neck flange, 309S LWN flange, S30900 nozzle flange, furnace nozzle flange, heat-resisting LWN — all the same product. Related pages: the facings — LWNRF / LWNFF / LWNRTJ — the long weld neck hub, the ladder — F304 / F304H below, F310 above — the hubs — 310S grade hub / stainless hub — and the bench beyond — Incoloy 800H.
The rule of the ladder: buy the rung the metal temperature needs — 309 where 304 would flake, 310 only where 309 would; and remember the scaling figure describes the surface, not the strength — code allowables fade long before the scale fails.
What the 23Cr-13Ni Recipe Buys
A Scale That Heals Itself at 1000 °C
23% chromium keeps the oxide thin, adherent and self-repairing through thousands of thermal cycles — the flake-and-thin death of ordinary stainless simply starts a rung higher.
Structure That Survives the Cycling
13% nickel holds the austenite — toughness kept, thermal-expansion behaviour tame, no brittle transformation products from the heat itself.
The Economical Furnace Rung
Real furnace capability at a price well below the 310 summit — for the enormous middle of hot-plant duty, 309 is the honest buy and 310 the answer to a hotter question.
The Metallurgy Every Shop Knows
ER309L is the world's dissimilar-weld buffer — the wire in every welder's locker — so a 309 flange arrives as familiar metallurgy, and stainless-to-carbon closing joints reach for its logic naturally.
Specification Notes — Getting F309 Long Weld Necks Right
Three honest notes.Scaling limit is not strength limit: ~1000 °C says the surface survives — pressure duty is governed by code allowables that fade steeply first, and creep-governed design names F309H, ordered by name like every H grade on this site. The sigma band is real: long exposure between ~650 and 870 °C slowly embrittles high-chromium austenitics — state the operating profile and read the FAQ's honest account. And climb the ladder by arithmetic: under ~870 °C intermittent, the 304 family serves cheaper; past ~1000 °C continuous, 310 takes the summit; beyond stainless, the Incoloy bench continues the mission.
How Our F309 LWN Flanges Are Manufactured
1
Forging — each piece individually forged from certified heats with the barrel integral — no welded build-ups — in any section up to the heaviest HB patterns.
2
Solution annealing — the full-solution cycle and quench that sets the clean austenitic structure free of sigma and carbide history; records retained against the heat number.
3
Verification — chemistry and mechanicals per heat; dual 309/309S compliance documented; grain size where a specification invokes it.
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 — PMI-checked on every piece — the high-chromium, molybdenum-free signature separates the heat-resisting wing from the chloride ladder on the shelf; marked with grade, size, schedule and heat number.
6
Certification & packing — EN 10204 3.1 MTC with solution-anneal records (3.2 witnessed on request); WPS guidance covering matching and dissimilar-joint filler routes; faces and bevels protected, packed sea-worthy.
Where F309 LWN Flanges Are Used
Where plant meets flame: furnace and kiln casings and their instrument nozzles, heat-treatment and annealing plant, flue-gas and hot-air ducting connections, combustion-air preheaters, incinerator and thermal-oxidiser penetrations, sight-port and burner mounts, and the thermowell standpipes that hold metal temperatures ordinary stainless should not face for decades — high temperature, modest pressure, cycling as the real load. Production and supply below:
Stainless Long Weld Necks — Machined at Our WorksLong Weld Neck — Heavy Barrel, Bevelled Weld EndDN600 RF Long Weld Neck — Large Diameter, B16.5 Drilling
F309 LWN Flange Dimensions
Flange-end dimensions are class-governed per ASME B16.5 (ratings per the austenitic material group); barrel length and bore per order. Full class-by-class charts:
Seven elements — the metal temperature and atmosphere confirm the rung:
1
Size & standard — e.g. 6″ NB ASME B16.5.
2
Pressure class & facing — 150#–2500#; RF, 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 & service — 309/309S dual convention (F309H by name for code creep design); metal temperature, atmosphere and cycling profile stated — they confirm the rung against the 304 family below and 310 above.
6
Certification — EN 10204 3.1 with solution-anneal records (our standard) / 3.2 witnessed.
An ASTM A182 F309 long weld neck flange is a forged 23Cr-13Ni heat-resisting austenitic stainless steel flange — UNS S30900/S30908 in the dual 309/309S convention, W.Nr. 1.4833 — 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 furnace casing, duct or vessel shell. F309 is the scaling ladder's middle rung: 23% chromium builds the protective oxide scale that holds to roughly 1000°C — past 304's ceiling, short of 310's summit — while 13% nickel keeps the structure austenitic and thermally stable through the cycles. Flange ends follow ASME B16.5 in Classes 150 to 2500; the barrel is machined to the ordered length and bore. Supplied solution annealed with records; F309H is named separately where code creep design requires it.
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 is 309 the furnace stainless — what do the 23Cr and 13Ni buy?
Scale and structure, the two things extreme heat demands. Above roughly 850°C, ordinary stainless steels lose the fight at their own surface: the chromium-oxide layer that protects them grows, cracks and flakes with each thermal cycle, and every flake carries chromium away until the metal beneath scales like plain steel. The answer is more chromium — 309's 23% keeps the scale thin, adherent and self-healing to around 1000°C — and more nickel, because chromium alone would push the structure toward brittle phases: 13% nickel holds the austenite, keeps thermal-expansion behaviour tame and preserves toughness through years of cycling. What 309 pointedly lacks is molybdenum — the enemy here is oxygen, not chlorides, and molybdenum's oxides are actually volatile at furnace temperatures. Different war, different armour: this is the chloride ladder's logic inverted, and the reason the heat-resisting wing is its own bench.
What is the scaling ladder — and where does 309 sit?
The heat-resisting wing's version of the site's ladders, climbed by scaling temperature. 304 holds its scale to roughly 870°C in intermittent service — the everyday grade's honest ceiling. 309 takes the middle rung: continuous oxidation duty to about 1000°C on 23% chromium, at a price well below the summit's. 310, with 25% chromium and 20% nickel, holds to roughly 1100°C — the stainless summit, with its own pages on this site. Beyond stainless, the Incoloy 800-series bench carries the same mission into nickel-iron-chromium territory where scaling and creep both demand more. The rule of the ladder: buy the rung the metal temperature needs — 309 bought for 850°C duty is money well spent where 304 would flake, and money wasted where 310's extra nickel answers a question nobody asked.
What is the dual 309/309S convention?
The same modern-supply logic the site's 310 pages follow. Classic 309 allowed carbon to 0.20% — useful for hot strength, hard on weldability; 309S caps it at 0.08%, the weldable standard of modern supply. Today's heats are melted to the S limit as a matter of course, so material honestly certifying both designations is the practical standard — our designation strip reads 309/309S and the certificate shows the arithmetic. Two boundaries stay honest: this dual convention concerns oxidation-service supply, and where a project's code design runs on creep allowables, F309H — with its deliberate 0.04-0.10% carbon band — is the grade the tables name, ordered by name exactly as the site's other H-grade pages explain. State the duty and the right variant follows.
What is the chemical composition of 309/309S?
Carbon ≤0.08% (the S limit of modern supply), manganese ≤2.00%, silicon ≤1.00%, phosphorus ≤0.045%, sulphur ≤0.030%, chromium 22.0-24.0%, nickel 12.0-15.0%. Seven columns and a deliberate absence: no molybdenum line, because the grade's enemy is oxygen — the chromium does the scale work, the nickel holds the structure, and the missing column is what separates the heat-resisting wing from the chloride ladder at a glance. Beside its neighbours the proportions tell the ladder's story: chromium up from 304's 18-20 toward 310's 24-26, nickel up from 8-11 toward 19-22 — each rung buying its temperature with both elements together. Chemistry is verified per heat, PMI-confirmed, and travels on the EN 10204 3.1 MTC.
What are the mechanical properties of F309 long weld neck flanges?
Solution annealed: tensile strength 515 MPa (75 ksi) minimum, yield strength 205 MPa (30 ksi) minimum, elongation 30% minimum — the familiar austenitic certificate, and as everywhere on the hot benches, not the point. Two honest distinctions govern the grade's use. Oxidation limit versus strength limit: the ~1000°C scaling figure says the surface survives — it does not say the metal is strong there, and pressure-retaining duty at high temperature is governed by the code's allowable-stress tables, which fade steeply long before the scale fails. And oxidation supply versus creep design: where a design formally runs on creep-range allowables, the deliberately carbon-floored F309H is the named grade. For the furnace-adjacent nozzles, sight ports and duct connections that are 309's daily work — hot surface, modest pressure — the standard supply serves exactly as intended.
What is the sigma-phase caveat on high-chromium austenitics?
The heat-resisting wing's version of the fine print. Hold any high-chromium austenitic long enough between roughly 650 and 870°C and sigma phase — a hard, brittle chromium-rich intermetallic — precipitates slowly through the structure, trading room-temperature toughness away year by year; the more chromium, the readier the reaction, so the very alloying that buys the scale resistance carries the caveat. The engineering answer is context: components living above the band stay largely clear of it, components cycling through it accumulate exposure, and embrittlement shows at shutdown — the metal serves hot but grows notch-sensitive cold. Good practice names the operating profile honestly on the enquiry, accepts sigma as a known companion of long furnace service, and treats a full solution anneal as the reset where refurbishment justifies it. Awareness, not alarm — the grade's service record across a century of furnace engineering speaks for itself.
Why does every fabricator already know 309 — the dissimilar-weld fame?
Because 309's filler wire is the industry's standard bridge between stainless and carbon steel. When an austenitic stainless part must weld to a carbon or low-alloy component, matching fillers from either side make brittle or crack-prone joints — the answer is an over-alloyed filler whose deposit, after dilution from the carbon-steel side, still lands in safe austenitic territory, and ER309L's 23Cr-13Ni chemistry is precisely that buffer. Every transition joint, every stainless overlay on a carbon vessel, every buttered nozzle seat has spread the grade's name through the world's fabrication shops. For this page the fame is more than trivia: plants that keep 309L consumables in every welder's locker find a 309 flange a comfortable, familiar metallurgy — and where a stainless LWN must close onto a carbon-steel or low-alloy shell, the 309-family filler logic is exactly what the joint design reaches for.
How is the closing weld on an F309 LWN made?
Under the ordinary austenitic rules, with the grade's own consumables and one furnace-service nuance. No preheat beyond dryness, no PWHT; matching 309/309L-class fillers for stainless-to-stainless joints, and the same family doing its famous buffer work where the shell side is carbon or low-alloy steel — the dissimilar-joint case this grade's filler was made for. The nuance: welds destined for cyclic high-temperature service deserve clean profiles and full fusion, because oxidation interrogates every crevice and re-entrant a weld leaves behind, and scale wedging in a poor toe becomes a crack-starter over thousands of cycles. Heat tint matters less here than on the chloride ladder — the first hours of furnace service rewrite the surface anyway — and the closing weld at the casing inherits the fabricator's own qualified procedure. 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.
When does F309 hand off — up the ladder or off the bench?
Down by economics: where metal temperatures stay under roughly 870°C intermittent, 304-family grades serve at everyday prices — 309 there is scale resistance paid for and never used; and where the duty is creep-governed rather than scale-governed, the H benches (304H, 316H, F309H by name) carry the code allowables. Up by temperature: past about 1000°C continuous, 310's 25Cr-20Ni takes the stainless summit — its own pages on this site. Off the bench entirely: when scaling and creep both demand more, or carburising and nitriding atmospheres join the heat, the Incoloy 800H/800HT bench continues the mission in nickel-iron-chromium; and when the hot gas carries sulphur, the chrome-moly refinery staircase and its F5/F9 rungs answer a different chemistry. State metal temperature, atmosphere and cycling profile — the three numbers place the rung.
What sizes and pressure classes do F309 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 F309 order book mirrors its duty profile: furnace, kiln and ducting work concentrates overwhelmingly in Classes 150 and 300, where the pressure is modest and the temperature is the story, with higher classes appearing on hot-gas process systems that carry real pressure. 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 F309 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 — 309/309S dual convention as standard, F309H by name where code creep design requires it — with the service stated (metal temperature, atmosphere, cycling profile) so the scaling rung is confirmed against 304 below and 310 above; (7) certification — EN 10204 3.1 with solution-anneal records (our standard) or 3.2 witnessed. Add quantity and destination; quotations normally within 24 hours.
Who manufactures ASTM A182 F309 long weld neck flanges in India?
Tesco Steel & Engineering is an ISO 9001:2015 certified flange manufacturer based in Mumbai, India, producing 309/309S 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, solution annealed with records retained, machined with the barrel bored to the ordered schedule or drawing, bevelled for the closing weld, PMI-checked, and marked with grade, size, schedule and heat number. Supplied with EN 10204 3.1/3.2 certification and stainless WPS guidance covering matching and dissimilar-joint filler routes — alongside the 310 rungs above, the 304 family below, the Incoloy 800H/800HT bench beyond, and the complete long weld neck range. Exported to more than 50 countries.
