Tesco Steel & Engineering manufactures ASTM A182 F347 long weld neck flanges — the heavier lock: UNS S34700, W.Nr. 1.4550 / X6CrNiNb18-10 — with ASME B16.5 flange ends in Classes 150–2500 and the barrel made to order. Where 321's titanium serves the enormous middle, niobium at 10×C holds the edges: carbides stable at the hottest end of the 425–815 °C band, an element that crosses the arc intact, and the re-precipitation behaviour that fixed knife-line attack — at full standard strength, 515/205 MPa. Its franchise is the refinery's shutdown question: polythionic acids attack sensitised boundaries at turnaround, and 347's boundaries never sensitise — the FCC, reformer and hydroprocessing answer, cheaper than soda-ash washing forever. And the filler thread comes home: this is the grade whose ER347 wire welds the whole stabilised bench — here it simply welds itself. F347H (S34709) by name for code creep. One forging, one closing weld. Facings: RF / FF / RTJ; small bore on the F347 socketweld. Every lot with EN 10204 3.1/3.2 MTC. ISO 9001:2015, made in Mumbai, India — exported to 50+ countries.
ASTM A182 F347 · UNS S34700 · W.Nr. 1.4550The Heavier Lock — Nb 10×CPolythionic-SCC Answer — FCC & ReformerThe Knife-Line Fix515 / 205 MPa — Full Strength, Weld-SafeER347 — Its Own Famous FillerB16.5 Flange Ends · Class 150–2500EN 10204 3.1 / 3.2 · ISO 9001:2015
ASTM A182 F347 Long Weld Neck Flanges — Specifications at a Glance
What is an ASTM A182 F347 Long Weld Neck Flange?
The heavier lock, in the nozzle pattern. An ASTM A182 F347 flange (UNS S34700) whose neck continues as a long, heavy-walled straight barrel — the nozzle itself — bevelled for one closing butt weld at the reactor, duct or shell. Niobium at 10×C locks the carbon with carbides stable to the hottest end of 425–815 °C, survives the arc, and fixed knife-line attack — at full strength, 515/205/30, no molybdenum. The franchise: polythionic-SCC resistance for refinery shutdown cycles — FCC, reformer, hydroprocessing. Welded in its own famous ER347 wire. Supplied solution annealed with records; F347H (S34709) by name for code creep. Flange ends per ASME B16.5, Classes 150–2500; barrel length and bore stated by you. EN 10204 3.1 on every lot.
The rule of the locks, completed: titanium for the middle, niobium for the edges — and one wire welds them all: ER347, which on this page finally welds its own grade.
What the Niobium Lock Buys
Nothing for the Shutdown Acids to Find
Polythionic acids attack sensitised boundaries at turnaround — 347's boundaries never sensitise, which is why FCC and reformer specifications name it and why the grade is cheaper than protective washing, forever.
Carbides That Hold at the Hottest End
Niobium's grip outlasts titanium's where the band runs hottest — the property that gave 347 the high-cycle and nuclear franchises.
The Knife-Line Fix
Faster, more complete carbide re-precipitation at the fusion line — the weld-zone failure mode that haunted the titanium grades closes here, which matters most on fabrication-intensive and repair-welded systems.
Welded in Its Own Famous Wire
ER347 stabilises the whole bench's joints — here it welds its native grade: deposit and forging locked alike, no translation between chemistries, full strength kept at 515/205.
Specification Notes — Getting F347 Long Weld Necks Right
Three honest notes.Buy the heavier lock where the edges bite: for the enormous middle of cycling hot duty, 321 serves at the commodity price — 347 earns its premium on the hottest duty, severe weld-zone service and polythionic-risk circuits. The lock is not a creep certificate: code creep tables name F347H (S34709, niobium at 8×C on the deliberate carbon band) — order it by name. And name the sulphur's role: polythionic risk at shutdown is 347's franchise; active sulphidation wastage in hot service is a different question that belongs to the F5/F9 staircase.
How Our F347 LWN Flanges Are Manufactured
1
Forging — each piece individually forged from certified niobium-stabilised heats with the barrel integral — no welded build-ups — in any section up to the heaviest HB patterns.
2
Solution annealing — the cycle that sets the clean austenitic structure with the niobium already holding the carbon; records retained against the heat number.
3
Verification — chemistry per heat with the 10×C stabilisation arithmetic shown on the certificate; mechanicals per heat at the full 515/205 line; 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 reads the niobium line on every piece — F347 and the titanium grades 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); WPS guidance naming the grade's own ER347 filler; faces and bevels protected, packed sea-worthy.
Where F347 LWN Flanges Are Used
Refinery hot circuits first: FCC regenerator and reactor adjacency, catalytic reformer piping, hydroprocessing hot separators — the sulphur-bearing 425–815 °C world where polythionic shutdown risk makes stabilised metallurgy the default and 347 the named grade — plus high-cycle hot systems, nuclear-heritage plant, fabrication-intensive assemblies with repair welding in their future, and the thermowell standpipes and instrument nozzles riding on all of them. Hot joints are inspection items; refinery joints are turnaround items; the LWN deletes one from every nozzle. 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
F347 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 duty's edges confirm the heavier lock:
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 — ASTM A182 F347 (UNS S34700); F347H by name where code creep design requires it; temperature band, weld-zone duty and polythionic risk stated — they confirm the heavier lock against 321 across and the H benches beside.
6
Certification — EN 10204 3.1 with solution-anneal records (our standard) / 3.2 witnessed.
An ASTM A182 F347 long weld neck flange is a forged niobium-stabilised austenitic stainless steel flange — UNS S34700, W.Nr. 1.4550, the X6CrNiNb18-10 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 reactor, duct or vessel shell. F347 is the stabilised bench's heavier lock: niobium at ten times the carbon content claims the carbon with carbides stable to the hottest end of the 425-815°C band, survives weld thermal cycles that defeat titanium, and answers the refinery's polythionic-acid shutdown question — at full standard strength, 515/205 MPa, on the 18-10 frame with no molybdenum. 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; F347H (UNS S34709) is named 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 niobium the heavier lock?
Three properties titanium cannot match. Thermal stability: niobium carbides hold their grip at the hottest end of the service band, where titanium carbides begin to surrender their carbon — so 347's lock stays engaged in duties that stress 321's. Arc survival: niobium transfers across a welding arc essentially intact while titanium burns away in transfer — which is why 347's filler wire stabilises even 321's joints, and why 347 weld metal arrives locked the way the base metal is. And re-precipitation behaviour: after a weld's fusion-line excursion dissolves the protective carbides, niobium re-forms them faster and more completely on cooling — the property behind the knife-line-attack fix the next FAQ describes. The price of the heavier lock is modest — niobium costs more than titanium and the grade stocks thinner — which is why the practical rule keeps 321 for the enormous middle and names 347 where the edges genuinely bite.
What is polythionic acid SCC — the refinery shutdown question?
The failure mode that made stabilised grades mandatory in refinery hot circuits. In sulphur-bearing hot service — FCC regenerator circuits, reformers, hydroprocessing — the metal surface carries sulphide scale. At shutdown, that scale meets air and moisture and forms polythionic acids, which attack sensitised grain boundaries with alarming speed: a unit that ran for years without trouble cracks during the turnaround, when the metal is cold and the acids are active. The industry's answer is codified in NACE practice: either protective shutdown procedures (soda-ash washing, nitrogen blanketing) or — the engineering fix — stainless whose boundaries never sensitise at all. That is 347's franchise: the niobium lock keeps grain boundaries clean through years of hot service, so the shutdown chemistry finds nothing to attack. For flanges and nozzles in these circuits, specifying the stabilised grade is cheaper than specifying the washing, forever.
347 or 321 — choosing between the locks?
The same decision the 321 page frames, seen from the heavier side. Choose 347 when the edges bite: service at the hottest end of the stabilised band, where niobium's carbides hold and titanium's loosen; heavy or repeated weld-zone duty — repairs, multi-pass joints, fabrication-intensive assemblies — where niobium's arc survival and re-precipitation keep every zone locked; polythionic-risk refinery circuits where project specifications and NACE-informed practice commonly name 347 outright; and the nuclear and high-cycle traditions that standardised on it decades ago. Choose 321 for the enormous middle: cycling hot duty without those aggravations, at a commodity price and wider stocking. The two share everything else — frame, strength, the 425-815°C band — so the choice is genuinely about the edges, and stating the duty honestly on the enquiry settles it in one line.
What is the chemical composition of ASTM A182 F347?
Carbon ≤0.08%, manganese ≤2.00%, silicon ≤1.00%, phosphorus ≤0.045%, sulphur ≤0.030%, chromium 17.0-20.0%, nickel 9.0-13.0%, niobium at a minimum of ten times the carbon content, up to 1.10%. The frame is the stabilised bench's — no molybdenum, heat the enemy rather than chlorides — with 347's own slightly wider chromium and nickel bands giving the melt shop room around the niobium addition. The stabilisation formula reads differently from the titanium grades' 5×(C+N): niobium is a heavier atom doing the same job, so the multiple is higher and nitrogen is not counted against it. A certificate showing Nb at ten times carbon is showing the lock's arithmetic done and proven. Chemistry is verified per heat, PMI-confirmed with the niobium line read, and travels on the EN 10204 3.1 MTC.
What are the mechanical properties of F347 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 strength on a weld-safe chemistry, the stabilised route's signature. Through the band the grade holds useful hot strength — marginally better than 321's at the top end, which the high-cycle traditions valued — while formal creep-range allowables belong to F347H, whose deliberate 0.04-0.10% carbon band inside the niobium lock (stabilised at eight times carbon for the H variant) carries the ASME tables; it is ordered by name like every H grade on this site. The austenitic gifts carry over: no ductile-brittle transition, cryogenic toughness where duty cycles demand it, hardness comfortably low with nothing to manage in supply.
What is knife-line attack — and how did niobium fix it?
The stabilised bench's own historical failure mode, and the reason the heavier lock earned its reputation. Immediately beside a weld's fusion line, temperatures spike high enough to dissolve even stabilising carbides. On cooling, titanium re-precipitates its carbides poorly in that narrow zone — so a knife-thin band is left with its carbon unlocked, and a subsequent sensitising excursion (a stress relief, a second pass, hot service itself) lets chromium carbides form there: a line of sensitised metal one or two grains wide, invisible until aggressive service etches a knife-cut along the weld. Niobium's faster, more complete re-precipitation closes that window — the dissolved carbides re-form before chromium can be robbed — which is why 347 historically out-served 321 in fabrication-intensive and weld-repaired hot systems, and why the heavier lock became the nuclear industry's stabilised grade of record. Modern low-carbon practice has narrowed the gap; the physics still favours niobium at the weld line.
How is the closing weld on an F347 LWN made?
Under the friendly austenitic rules — and this is the page where the filler story comes home. The consumable is ER347, matching the base metal natively: the same wire the whole stabilised bench borrows (even 321 is classically welded with it, because titanium won't cross an arc) here simply welds its own grade — deposit and forging locked alike, no translation between chemistries. No preheat beyond dryness, no PWHT, ordinary technique and interpass control; the fusion-line physics of the knife-line FAQ is exactly where niobium's re-precipitation earns its keep, and on polythionic-risk circuits the as-welded joint arrives with nothing for the shutdown acids to find. Weld cleanliness carries its usual hot-service weight, and the closing weld at the reactor or shell 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.
Where do F347 LWN flanges serve?
Refinery hot circuits first: FCC regenerator and reactor adjacency, catalytic reformer piping, hydroprocessing hot separators and their connections — the sulphur-bearing 425-815°C world where polythionic shutdown risk makes stabilised metallurgy the specification default and 347 the named grade. Beyond the refinery: high-cycle hot systems whose weld-zone duty earned the heavier lock, nuclear-heritage plant and its maintenance supply chains, fabrication-intensive hot assemblies with repair welding in their future, and the thermowell standpipes and instrument nozzles riding on all of them. The construction argument doubles here: hot joints are inspection items, refinery joints are turnaround items — the one-forging LWN deletes one from every nozzle, and what remains is welded in the grade's own famous wire.
When does F347 hand off — across the locks or up the benches?
Down by economics: the enormous middle of cycling hot duty belongs to 321 — the lighter lock at the commodity price — and below roughly 425°C the 304 family serves without any lock at all. Across by enemy: chlorides with the heat go to 316Ti on the molybdenum frame. Up by mission: creep-governed code design names F347H or the H benches; surface scaling beyond roughly 815°C passes to the 309/310 scaling ladder and the Incoloy 800H/HT bench beyond; and when the hot sulphur is the corrosion mechanism itself rather than a shutdown risk — sulphidation wastage — the chrome-moly F5/F9 staircase answers a different question entirely. State temperature band, weld-zone duty, and whether polythionic risk is in the operating history — those three place the lock.
What sizes and pressure classes do F347 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 F347 order book mirrors its refinery habitat: FCC, reformer and hydroprocessing hot circuits carry Classes 150-900, with process systems that combine real pressure and the hot band reaching higher. 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 F347 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 F347, UNS S34700, with F347H named where code creep design requires it — and the service stated (temperature band, weld-zone duty, polythionic risk in the operating history) so the heavier lock is confirmed against 321 across and the H benches beside; (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 F347 long weld neck flanges in India?
Tesco Steel & Engineering is an ISO 9001:2015 certified flange manufacturer based in Mumbai, India, producing ASTM A182 F347 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 niobium-stabilised 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 niobium line read on every piece, and marked with grade, size, schedule and heat number. Supplied with EN 10204 3.1/3.2 certification and stainless WPS guidance naming the grade's own ER347 filler — alongside the 321 sibling, the 316Ti cousin on the chloride side, the H benches and the scaling ladder above, and the complete long weld neck range. Exported to more than 50 countries.
