Tesco Steel & Engineering manufactures ASTM A182 F317L long weld neck flanges — the chloride ladder's half-rung: UNS S31703, W.Nr. 1.4438 / X2CrNiMo18-15-4 — with ASME B16.5 flange ends in Classes 150–2500 and the barrel made to order. The recipe is 316L's logic continued: a full molybdenum step to 3.00–4.00% lifting PREN to ~30, chromium back up to 18–20%, nickel to 11–15% — for the scrubber, FGD and bleach-plant duties where 316L pits on a five-year horizon. And the certificate carries the family's rare distinction: full standard strength, 515/205 MPa — no L-grade tax, no dual-certification arithmetic. The ceilings stay honest: still a lean austenitic — chloride SCC above ~60 °C belongs to duplex F51, the seawater line to the super duplex twins, acids to 904L. One forging, one closing weld with 317L filler — and nothing for that weld to spoil. A262 testing on request. Facings: RF / FF / RTJ; small bore on the F317L socketweld. Every lot with EN 10204 3.1/3.2 MTC. ISO 9001:2015, made in Mumbai, India — exported to 50+ countries.
ASTM A182 F317L · UNS S31703 · W.Nr. 1.4438The Half-Rung — Full Moly Step to 3–4%PREN ~30 — Beyond 316L515 / 205 MPa — The L Without the TaxScrubbers · FGD · Bleach PlantsNothing for the Weld to SpoilB16.5 Flange Ends · Class 150–2500EN 10204 3.1 / 3.2 · ISO 9001:2015
ASTM A182 F317L Long Weld Neck Flanges — Specifications at a Glance
What is an ASTM A182 F317L Long Weld Neck Flange?
The half-rung between 316L and duplex, in the nozzle pattern. An ASTM A182 F317L flange (UNS S31703) whose neck continues as a long, heavy-walled straight barrel — the nozzle itself — bevelled for one closing butt weld at the absorber, column or shell. Mo 3.00–4.00% — the full step — PREN ~30, with Cr back up to 18–20% and Ni 11–15%; carbon starved, so the weld can spoil nothing. The rare distinction: full standard strength, 515/205 MPa, on an L chemistry. Honest ceilings: SCC above ~60 °C belongs to duplex; seawater to the twins. Habitat: FGD, bleach plants, aggressive wet process. Supplied solution annealed with records; A262 on request. 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: F317L LWN flange, 317L long weld neck flange, S31703 nozzle flange, 1.4438 LWN flange, high-moly stainless LWN, FGD nozzle flange — all the same product. Related pages: the facings — LWNRF / LWNFF / LWNRTJ — the long weld neck hub, the F317L socketweld on small bore, the ladder — F316L below / F51 / F53 above — the acid bench — 904L / 254 SMO — and the 317 grade hub / stainless hub.
The rule of the half-rung: it buys pitting margin in the wet-chemistry band between 316L's retirement and duplex's mandate — and no molybdenum moves the SCC wall: cracking questions go to the ferrite half, always.
What the Full Moly Step Buys
PREN ~30 — The Scrubber Number
A full percent of molybdenum over 316 — the margin between chloride-bearing process duty and the recirculating-slurry, bleach-stage habitats where 316L pits on a five-year horizon.
The L Without the Tax
515/205 MPa on a starved-carbon chemistry — the family's rare full-strength L grade: weld-zone immunity with no dual-certification arithmetic and nothing given up on the yield line.
Austenitic Fabricability Kept
No phase balance, no ferrite checks, no interpass ceilings — where duplex answers with discipline, 317L answers with ordinary stainless welding, plus cryogenic capability duplex cannot offer.
Fewer Crevices Where Slurry Interrogates All of Them
FGD slurry and bleach filtrate probe every joint — the one-forging LWN deletes a circumferential weld and a nipple from every absorber nozzle and spray-header connection.
Specification Notes — Getting F317L Long Weld Necks Right
Three honest notes.Pitting margin is not cracking immunity: 317L is still a lean austenitic — above ~60 °C in warm stressed chlorides the answer is duplex, not more molybdenum. Match the filler to the step:317L consumables, not 316L — a leaner weld plants a lower-PREN band exactly where the slurry concentrates. And check the rung both ways: where 316L honestly serves, the half-rung is margin never used; where immersion chemistry wants more film on the austenitic route, 254 SMO continues it, and reducing acids belong to 904L's bench.
How Our F317L LWN Flanges Are Manufactured
1
Forging — each piece individually forged from certified low-carbon high-molybdenum 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; records retained against the heat number.
3
Verification — chemistry per heat with the ≤0.030% carbon and the 3.00–4.00% molybdenum certified; mechanicals per heat at the full 515/205 line; A262 testing arranged where invoked.
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 with the molybdenum line read on every piece — 317L and 316L can never mix 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); stainless WPS guidance naming 317L fillers; faces and bevels protected, packed sea-worthy.
Where F317L LWN Flanges Are Used
Where wet chemistry concentrates: flue-gas desulphurisation absorbers and their spray-bank, recirculation and mist-eliminator connections — where evaporating slurry drives chlorides far past what the gas suggests — pulp and paper bleach plants cycling chlorine dioxide, acid-dew-point and condensing ducting, textile and dye works, and the aggressive end of chemical process where 316L retires early. Large diameters, modest pressures, corrosion 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
F317L 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 chloride numbers and the stress state confirm the half-rung:
1
Size & standard — e.g. 8″ 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 — ASTM A182 F317L (UNS S31703); medium, chloride content, temperature and stress state stated — they confirm the half-rung against 316L below and duplex above; A262 practice named where invoked.
6
Certification — EN 10204 3.1 with solution-anneal records (our standard) / 3.2 witnessed.
An ASTM A182 F317L long weld neck flange is a forged high-molybdenum low-carbon austenitic stainless steel flange — UNS S31703, W.Nr. 1.4438, the X2CrNiMo18-15-4 of European practice — 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 absorber, column or vessel shell. F317L is the chloride ladder's half-rung between 316L and duplex: a full molybdenum step to 3.00-4.00% lifts PREN to around 30 for the scrubber, FGD and bleach-plant duties that find 316L, while the starved carbon keeps every weld sensitisation-proof — and unusually for an L grade, the certificate carries full standard strength, 515/205 MPa. 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, ASTM A262 testing on request.
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.
What does the full molybdenum step buy — the half-rung at PREN 30?
The gap between 316L's honest limit and duplex's price. Molybdenum defends the passive film where chlorides breach it, and 317L's 3.00-4.00% — a full percent over 316's addition — lifts PREN from the mid-twenties to around 30. In service terms that is the difference between chloride-bearing process duty and the genuinely punishing wet-chemistry habitats: flue-gas desulphurisation absorbers where chlorides concentrate in recirculating slurry, pulp-mill bleach washers cycling chlorine dioxide, condensing acid-dew-point ducting, and the aggressive ends of chemical process where 316L pits on a five-year horizon. Chromium steps back up to 18-20% and nickel to 11-15% to keep the balance, so the grade reads as 316L's logic continued rather than changed. What the half-rung does not buy is cracking immunity — the honest ceilings FAQ holds that line.
Why is 317L the rare L grade at full strength?
Because A182 certifies it at 515/205 MPa — the straight-grade numbers — where 304L and 316L accept 485/170. The metallurgy behind the paperwork: 317L's heavier substitutional alloying (the full molybdenum step, the higher nickel) and modern nitrogen-balanced melting practice recover the solid-solution strength that starving the carbon gives away, so the specification never needed to discount the certificate. For specifiers the consequence is pleasantly simple: the weld-zone immunity of an L grade with none of the dual-certification arithmetic the 304/316 benches manage — designs that lean on the 205 MPa line take F317L as-is, one grade, one certificate, no companion designation. It is a small distinction that saves real paperwork on projects where both corrosion behaviour and yield strength are specified hard.
What is the chemical composition of ASTM A182 F317L?
Carbon ≤0.030%, manganese ≤2.00%, silicon ≤1.00%, phosphorus ≤0.045%, sulphur ≤0.030%, chromium 18.0-20.0%, nickel 11.0-15.0%, molybdenum 3.00-4.00%. Three moves beside 316L tell the story: molybdenum takes its full step from 2.00-3.00 to 3.00-4.00 — the entire commercial point; chromium climbs back to the 18-20 band that 316 traded away, stacking film-former on film-former; and nickel rises to 11-15 to hold the austenite against both. The starved carbon keeps the L franchise — nothing for a weld to precipitate — and PMI separates 317L from 316L in seconds on the molybdenum line. Chemistry is verified per heat and travels on the EN 10204 3.1 MTC.
What are the mechanical properties of F317L long weld neck flanges?
Solution annealed: tensile strength 515 MPa (75 ksi) minimum, yield strength 205 MPa (30 ksi) minimum, elongation 30% minimum — full standard-316 strength on an L-grade chemistry, the rare combination the previous FAQ explains. In nozzle practice the numbers serve exactly as the bench's: class-governed flange geometry, the austenitic group's B16.5 ratings, generous elongation for forging and field welding. The austenitic gifts carry over — no ductile-brittle transition, cryogenic toughness with impacts documented where required, hardness comfortably low with nothing to manage in supply. Where a project's calculation leans on yield at moderate temperature, F317L carries it without a companion grade — one of the few corrosion upgrades on the ladder that costs nothing on the strength line.
Where do F317L LWN flanges serve — the scrubber habitat?
Where wet chemistry concentrates chlorides and acids together: flue-gas desulphurisation — absorber towers, recirculation piping, mist-eliminator and spray-bank connections, where evaporating slurry drives chloride levels far past what the flue gas alone suggests; pulp and paper bleach plants — washers, filtrate systems and D-stage adjacency cycling chlorine dioxide; acid-dew-point ducting and condensing service; textile, dye and fine-chemical process at the aggressive end of 316L's world. The duty profile suits the LWN doubly: slurry and condensate interrogate every crevice, so the deleted weld and nipple remove initiation sites, and absorber-wall nozzles, spray-header connections and instrument standpipes are exactly the one-forging pattern's territory. Classes 150 and 300 dominate — the corrosion is the load, not the pressure.
What does 317L NOT fix — the honest ceilings?
The same walls as its parents, one rung higher. Chloride stress corrosion cracking: 317L is still a lean austenitic — under tensile stress in warm chlorides above about 60°C it cracks like its siblings, and no amount of molybdenum moves that wall; the cure remains the duplex family's ferrite half. The seawater line: PREN around 30 outruns 316L's pitting but stays well short of the 40 threshold — continuous warm seawater belongs to the super duplex twins and the 6Mo austenitic above. And heat: the starved carbon disqualifies creep service exactly as on the other L pages. The rule of the half-rung: it buys pitting margin in the wet-chemistry band between 316L's retirement and duplex's mandate — inside that band it is the honest economical answer, and at either edge the ladder's neighbours take over.
F317L or duplex F51 — the real decision at this altitude?
The two grades bracket the same duties from different sides, and the decision usually turns on two questions. Cracking: if chloride SCC is credible — warm, wet, stressed, above the ~60°C line — duplex wins outright, because its ferrite half removes the mechanism 317L merely endures; no pitting arithmetic overrides that. Fabricability: where SCC is not in play, 317L's fully austenitic nature is the quiet advantage — ordinary stainless welding with no phase-balance discipline, no ferrite measurement, no interpass ceilings, plus cryogenic capability duplex cannot offer and immunity from the 475°C embrittlement clock. Price and PREN run close between them (about 30 versus 35), so the tiebreakers are real: FGD and bleach-plant practice often stays austenitic for the welding economics, while offshore and hot-brine practice went duplex a generation ago. State temperature, stress state and chloride level — the answer follows in one line.
How is the closing weld on an F317L LWN made?
Under the friendly austenitic rules, with the L franchise's as-welded promise intact. No preheat beyond dryness, no PWHT, ordinary technique and interpass control, with matching 317L fillers so the joint keeps the full molybdenum step — stepping down to 316L consumables would plant a lower-PREN band exactly where slurry and condensate concentrate. The heat-affected zone has no carbon to precipitate, so the joint stays intergranular-safe exactly as welded, and A262 testing is available where bleach-plant or fine-chemical specifications invoke it. Heat tint is removed by pickling or passivation on corrosion-critical work — the tinted band is where the molybdenum-bought margin is spent first — and the closing weld at the absorber or shell inherits the vessel's own qualified stainless procedure. WPS guidance travels with every supply, filler class stated.
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 F317L hand off — along the ladder?
Down by economics: where 316L's mid-twenties PREN honestly serves — most chemical process, coastal utility, pharmaceutical work — the half-rung is margin paid for and never used; the 316L page makes that case. Up by cracking: the moment chloride SCC becomes credible, duplex F51 takes the question away entirely, and the super duplex twins hold the seawater line at PREN 40. Up by pitting alone: where immersion chemistry demands more film without duplex's welding discipline, the 6Mo austenitic 254 SMO continues the austenitic route. Sideways by acid: when reducing acids dominate the chlorides, 904L and the nickel-bearing acid bench answer a different chemistry. The half-rung's own franchise — FGD, bleach plant, aggressive wet process below the cracking line — is narrow on paper and enormous in practice: the world keeps building scrubbers.
What sizes and pressure classes do F317L 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 habitat: FGD, bleach-plant and scrubber work concentrates in Classes 150 and 300 — large diameters, modest pressures, corrosion as the real load — with the higher classes serving aggressive process systems that carry pressure too. 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 F317L LWN flange quotation?
Seven elements plus commercial terms: (1) size and dimensional standard — e.g. 8" 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 F317L, UNS S31703 — with the service stated (medium, chloride content, temperature, stress state) so the half-rung is confirmed against 316L below and duplex above, and A262 practice named where invoked; (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 F317L long weld neck flanges in India?
Tesco Steel & Engineering is an ISO 9001:2015 certified flange manufacturer based in Mumbai, India, producing ASTM A182 F317L 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 low-carbon high-molybdenum heats, solution annealed with records retained, machined with the barrel bored to the ordered schedule or drawing, bevelled for the closing weld, PMI-checked with the molybdenum line read on every piece, and marked with grade, size, schedule and heat number. Supplied with EN 10204 3.1/3.2 certification, ASTM A262 intergranular testing where invoked, and stainless WPS guidance naming 317L fillers — alongside the 316L rung below, the duplex ladder above, the 904L acid bench beside, and the complete long weld neck range. Exported to more than 50 countries.
