Tesco Steel & Engineering manufactures ASTM A182 F310/310S long weld neck flanges — the scaling ladder's summit: UNS S31000/S31008, W.Nr. 1.4841/1.4845 — with ASME B16.5 flange ends in Classes 150–2500 and the barrel made to order. The recipe reads almost as equal parts: 25% chromium holding the oxide scale thin, adherent and self-healing to ~1100 °C — the last stainless step above 309's 1000 °C rung — and a near-equal 20% nickel working three jobs: structure, thermal-cycle endurance and carburising resistance. No molybdenum — the enemy is oxygen. Supplied to the dual 310/310S convention this site's whole 310 family follows (this page serves both designations; F310H by name for code creep design). The summit's fine print stays honest below: sigma at its strongest, and the sulphur warning — high nickel is the wrong answer in reducing sulphidising gas. 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.
F310/310S · S31000/S31008 · 1.4841/1.4845The Stainless Summit — 25Cr-20NiOxidation Service to ~1100 °CNickel Working Three JobsDual 310/310S Supply — Both Served Here515 / 205 MPa Solution AnnealedB16.5 Flange Ends · Class 150–2500EN 10204 3.1 / 3.2 · ISO 9001:2015
ASTM A182 F310/310S Long Weld Neck Flanges — Specifications at a Glance
What is an ASTM A182 F310/310S Long Weld Neck Flange?
The stainless summit, in the nozzle pattern. An F310/310S flange (UNS S31000/S31008) 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. 25% Cr holds the scale to ~1100 °C — the ladder's last stainless step; 20% Ni works three jobs: structure, cycling, carburising resistance; no molybdenum — the enemy is oxygen. The ladder: 304 (~870 °C) → 309 (~1000 °C) → 310 (~1100 °C), then the Incoloy bench. 515/205/30 solution annealed; F310H 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: F310 LWN flange, 310S long weld neck flange, S31000 nozzle flange, S31008 LWN, 310 furnace flange, 25Cr-20Ni LWN — all the same product. Related pages: the facings — LWNRF / LWNFF / LWNRTJ — the long weld neck hub, the ladder — F304 / F309 below — the hubs — 310S grade hub / stainless hub — and the bench beyond — Incoloy 800H.
The rule of the ladder, completed: buy the rung the metal temperature needs — 310 only where 309 would flake — and on this bench the atmosphere chooses the alloy as much as the temperature: the sulphur warning below is the summit's own fine print.
What the Near-Equal-Parts Recipe Buys
The Last Stainless Step — ~1100 °C
25% chromium keeps the scale self-healing where every leaner grade has flaked and thinned — radiant sections, incinerator throats and the hottest kilns are this rung's native ground.
Nickel Working Three Jobs
Structure, thermal-cycle endurance, carburising resistance — 20% nickel holds the austenite against 25% chromium, tames the expansion mismatch that tears scale off cycling parts, and slows carbon ingress.
Both Designations, One Supply
F310 and F310S served on this page — modern heats melt to the S carbon limit and certify both, per the dual convention our whole 310 family follows; F310H stays its own named creep grade.
Fewest Joints Where Cycling Interrogates All of Them
A hot-casing nozzle wants its weld out at the shell and its joint count minimal — the one-forging LWN answers both, with the heavy barrel doing the opening's reinforcement work.
Specification Notes — Getting F310 Long Weld Necks Right
Three honest notes.State the atmosphere: in reducing, sulphur-bearing hot gas the 20% nickel becomes the vulnerability — nickel-sulphide attack inverts the ladder, and the answer walks down to 309 or across to the F5/F9 staircase. Sigma is at its strongest here: 25% chromium forms it fastest on the bench — state the real operating profile, especially part-load parking in the 650–870 °C band. And the summit is not a creep certificate: scaling figures describe the surface — code creep design names F310H, and pressure parts living hot for decades belong on the Incoloy bench.
How Our F310/310S 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 310/310S 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 25Cr-20Ni signature is unmistakable on the gun; 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 310 and dissimilar-joint filler routes; faces and bevels protected, packed sea-worthy.
Where F310/310S LWN Flanges Are Used
The hottest stainless duty in industry: furnace radiant sections and their instrument nozzles, the hottest kilns and calciners, incinerator and thermal-oxidiser throats, heat-treatment plant at the top of its range, combustion and hot-air systems beyond 309's rung, carburising-furnace adjacency where the nickel earns its third job, and the sight-port, burner and thermowell connections that hold summit metal temperatures for decades — extreme 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
F310/310S 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 — temperature and atmosphere together confirm the summit:
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 — F310/310S dual convention (F310H by name for code creep design); metal temperature, atmosphere (oxidising or reducing, sulphur stated) and cycling profile — they confirm the summit against 309 below and the Incoloy bench beyond.
6
Certification — EN 10204 3.1 with solution-anneal records (our standard) / 3.2 witnessed.
Example: “LWN Flange RF, 6″ NB, ASME B16.5 Class 150, barrel 300 mm, Sch 10S bore, equal barrel, F310/310S, incinerator secondary-chamber nozzles — 1050 °C metal temperature, oxidising, EN 10204 3.1 — 4 pcs.” Quotations normally within 24 hours with price, unit weight and delivery.
What is an ASTM A182 F310/310S long weld neck flange?
An ASTM A182 F310/310S long weld neck flange is a forged 25Cr-20Ni heat-resisting austenitic stainless steel flange — UNS S31000/S31008 in the dual convention, W.Nr. 1.4841/1.4845 — 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. F310 is the scaling ladder's summit: 25% chromium holds the protective oxide scale to roughly 1100°C — the highest figure on the stainless bench — while a near-equal 20% nickel buys the structure, thermal-cycle stability and carburising resistance the hottest plant demands. 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; F310H 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 310 the stainless summit?
Because 25% chromium is as much scale-building armour as a workable stainless steel carries. The scaling ladder this site follows climbs by chromium: 304's 18% holds its oxide to roughly 870°C intermittent, 309's 23% to about 1000°C, and 310's 25% takes the last stainless step — a scale that stays thin, adherent and self-healing to around 1100°C, within sight of the alloy's own melting arithmetic. Above it there is no hotter stainless rung: the mission passes to the nickel-iron-chromium bench, where the site's Incoloy 800H/800HT pages continue the story with creep strength added. The summit position shapes the buying rule: 310 is the answer when 309 would flake — radiant sections, the hottest kilns and incinerator throats — and an over-specification everywhere the middle rung honestly serves.
What does the high nickel buy — the 20% that isn't for corrosion?
Three things chromium alone cannot deliver. Structure: 25% chromium is a powerful ferrite former, and it takes nearly 20% nickel to hold the alloy safely austenitic — tough, weldable, dimensionally predictable. Thermal-cycle endurance: high nickel tempers the thermal-expansion mismatch that tears scale from cycling components, so the summit grade survives door-and-damper duty that punishes leaner recipes. And carburising resistance: nickel lowers carbon's solubility and diffusion in the alloy, which is why 310 outlasts lower-nickel grades around carburising furnaces, reformer adjacency and carbon-bearing atmospheres — the beginning of the property that the Incoloy bench above develops fully. The nickel is the summit's price and its second product: you pay for it once and it works three jobs.
What is the dual 310/310S convention?
The convention this site's whole 310 family follows, and this page serves both designations. Classic 310 allowed carbon to 0.25% — hot strength for cast-and-forged furnace hardware, at a weldability price; 310S caps carbon at 0.08%, the weldable standard of modern wrought supply. Today's heats are melted to the S limit as a matter of course, so material honestly certifying both — F310/F310S, S31000/S31008 — is the practical standard, and our designation strip and certificates carry the pair. The boundaries stay honest: this dual convention concerns oxidation-service supply, and where a project's code design runs on creep allowables, F310H with its deliberate carbon band is the grade the tables name, ordered by name exactly as the site's other H-grade pages explain.
What is the chemical composition of 310/310S?
Carbon ≤0.08% (the S limit of modern supply), manganese ≤2.00%, silicon ≤1.00%, phosphorus ≤0.045%, sulphur ≤0.030%, chromium 24.0-26.0%, nickel 19.0-22.0%. The recipe reads almost as equal parts — a quarter chromium for the scale, a fifth nickel for the structure — and carries the heat-resisting wing's signature absence: no molybdenum, because the enemy is oxygen and molybdenum's oxides are volatile at furnace temperatures. Beside 309 the step is visible in both columns: chromium up from 22-24, nickel up from 12-15 — the summit bought with both elements together, which is why the rung above 309 costs what it does. Chemistry is verified per heat, PMI-confirmed, and travels on the EN 10204 3.1 MTC.
What are the mechanical properties of F310/310S 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. The two honest distinctions from the 309 page apply with more force at the summit. Oxidation limit versus strength limit: ~1100°C says the surface survives — the code's allowable-stress tables fade steeply long before, and pressure-retaining duty is governed by them. Oxidation supply versus creep design: where a design formally runs on creep-range allowables, F310H is the named grade. For the radiant-section nozzles, sight ports and hot-duct connections that are the summit's daily work — extreme surface temperature, modest pressure — the standard supply serves exactly as intended.
How strong is the sigma-phase caveat at 25% chromium?
The strongest on the stainless bench — the summit's fine print. Sigma phase precipitates from high-chromium austenite held between roughly 650 and 870°C, and the more chromium, the faster the clock: 310 forms it more readily than any grade below it on the ladder. The saving grace is geography — the summit's natural duty often lives above the band, where sigma is unstable, and components that run truly hot stay cleaner than mid-band ones. The exposure to watch is cycling and part-load service that parks metal in the danger zone for months at a time; the symptom is toughness lost at shutdown, when the metal is cold and maintenance handles it. Good practice states the real operating profile on the enquiry, accepts sigma as furnace metallurgy's known companion, and uses a full solution anneal as the reset when refurbishment justifies it — the same honest account the 309 page gives, underlined twice at the summit.
When is high nickel the wrong answer — the sulphur warning?
When the hot gas is reducing and carries sulphur. Nickel and sulphur form a low-melting eutectic, and in reducing sulphidising atmospheres — refinery heater flue sides burning sour fuel, gasifiers, some kiln atmospheres — a high-nickel alloy can be attacked catastrophically along its grain boundaries while a leaner grade survives. That inverts the ladder: 310's 20% nickel, its pride everywhere else, becomes its vulnerability, and the honest answers are lower-nickel 309, the chrome-moly refinery staircase's F5/F9 rungs where sulphidation is the whole question, or atmosphere control. The rule for specifiers is one line: state the atmosphere — oxidising or reducing, and what it carries — because on the heat-resisting bench the atmosphere chooses the alloy as much as the temperature does. It is the wing's version of the chloride ladder's SCC honesty: no single number tells the whole story.
How is the closing weld on an F310/310S LWN made?
Under the ordinary austenitic rules, with the summit grade's own consumables and the furnace-service disciplines. No preheat beyond dryness, no PWHT; matching 310-class fillers for like-to-like joints, with the 309 family available in its famous buffer role where the shell side is carbon or low-alloy steel. Weld cleanliness carries the same weight as on the 309 page — cyclic oxidation interrogates every crevice and poor toe, so full fusion and clean profiles are the real quality metric — and one summit-specific note: fully austenitic 310 weld metal runs a known hot-cracking sensitivity, so procedures favour low heat input, controlled bead shapes and clean consumables; qualified furnace-fabrication shops know the drill. The closing weld at the casing inherits the fabricator's own procedure, and 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 F310 hand off — down the ladder or off the bench?
Down by economics: everywhere 309's ~1000°C rung honestly serves, the summit is capability paid for and never used — and below that the 304 family and the H benches carry their own territory; the ladder is climbed by metal temperature, not by prestige. Off the bench by mission: when creep strength must accompany the scaling resistance — pressure parts living hot for decades — the Incoloy 800H/800HT pages continue the story in nickel-iron-chromium, with the carbon-band logic this site's H-grade pages share; and when the atmosphere turns reducing and sulphur-bearing, the sulphur warning applies and the answer walks down the nickel, toward 309 or the chrome-moly F5/F9 staircase. State metal temperature, atmosphere and duty profile — on this bench those three choose the alloy together.
What sizes and pressure classes do F310/310S 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 order book mirrors the summit's duty: furnace, radiant-section and incinerator work concentrates overwhelmingly in Classes 150 and 300 — extreme temperature, modest pressure — with higher classes appearing on hot process systems that carry real pressure alongside the heat. 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 F310/310S 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 — F310/310S dual convention as standard, F310H by name where code creep design requires it — with the service stated (metal temperature, atmosphere oxidising or reducing, cycling profile) so the summit is confirmed against 309 below and the Incoloy bench beyond; (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 F310/310S long weld neck flanges in India?
Tesco Steel & Engineering is an ISO 9001:2015 certified flange manufacturer based in Mumbai, India, producing 310/310S 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 WPS guidance covering matching 310 and dissimilar-joint filler routes — alongside the 309 rung below, the 304 family, the Incoloy 800H/800HT bench beyond, and the complete long weld neck range. Exported to more than 50 countries.
