Tesco Steel & Engineering manufactures ASTM A182 F304L long weld neck flanges — the 18-8 carbon dial turned down: UNS S30403, W.Nr. 1.4307 — with ASME B16.5 flange ends in Classes 150–2500 and the barrel made to order. The chemistry is one deliberate subtraction: carbon starved below 0.030%, so the weld heat-affected zone has nothing to precipitate — no carbides, no sensitisation, no weld decay — making this the as-welded grade of chemical process, nitric acid and water-treatment plant, and (with the family's no-brittle-transition toughness plus the cleanest grain boundaries on the dial) the cryogenic default to −196 °C. The trade is stated honestly: 485/170 MPa against 304's 515/205 — with nickel widened to 8.0–13.0% to hold the austenite alone. The construction argument is at its purest here: one forging, one closing weld with 308L filler — and nothing for that weld to spoil. Dial and ladder stay honest: 304/dual-certified for the 205 MPa line, 304H for creep, 316L when chlorides join the welds. ASTM A262 intergranular testing on request. 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 F304L · UNS S30403 · W.Nr. 1.4307C ≤0.030% — Nothing to PrecipitateAs-Welded Corrosion Duty485 / 170 MPa — The Honest TradeCryogenic Default to −196 °CA262 Testing on RequestB16.5 Flange Ends · Class 150–2500EN 10204 3.1 / 3.2 · ISO 9001:2015
ASTM A182 F304L Long Weld Neck Flanges — Specifications at a Glance
What is an ASTM A182 F304L Long Weld Neck Flange?
The as-welded setting of the 18-8 dial, in the nozzle pattern. An ASTM A182 F304L flange (UNS S30403) whose neck continues as a long, heavy-walled straight barrel — the nozzle itself — bevelled for one closing butt weld at the vessel or column shell. Carbon ≤0.030% — the weld zone has nothing to precipitate: no sensitisation, no weld decay, corrosion resistance kept exactly as welded. The trade is honest — 485/170 MPa against 304's 515/205 — and nickel widens to 8.0–13.0% to hold the austenite alone. The family's cryogenic default to −196 °C. Supplied solution annealed with records; A262 intergranular testing 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.
The rule of the dial: L for cold and corrosive, straight for everyday, H for hot — and the L rung is where the site's as-welded honesty lives: the weld keeps the film because the carbon never arrives.
What the Missing Carbon Buys
Weld Zones That Cannot Sensitise
Below 0.030% there is not enough carbon to build a damaging carbide network — the joint keeps its passive film exactly as welded, with no post-weld anneal, which is the entire reason the grade exists.
The Family's Best Cryogenic Toughness
No brittle transition plus the cleanest grain boundaries on the dial — the grade cryo specifications reach for by name, to −196 °C and below.
A Weld the Grade Was Born For
The LWN leaves one closing weld per nozzle — and on 304L that weld can spoil nothing: the construction that deletes joints, in the grade that forgives the one that remains.
Paperwork for the Corrosion Engineer
L-only or dual 304/304L documentation as the specification directs, A262 intergranular testing where invoked — the certificate proves the metallurgy, not the luck of the lot.
Specification Notes — Getting F304L Long Weld Necks Right
Three honest notes.The yield line is real: L-only supply certifies 170 MPa, and designs that lean on 205 MPa at moderate temperature belong on dual-certified or straight-grade stock — say which regime your specification follows. L answers welds, not chlorides: there is still no molybdenum — salty as-welded duty belongs to 316L, cracking duty to the duplex rungs. And keep L away from creep: above ~525 °C the dial swings fully over to 304H — starved carbon is the wrong chemistry for hot strength by definition.
How Our F304L LWN Flanges Are Manufactured
1
Forging — each piece individually forged from certified low-carbon 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 dissolves any carbides and sets the clean austenitic structure; records retained against the heat number.
3
Verification — chemistry per heat with the ≤0.030% carbon certified; mechanicals per heat; A262 intergranular testing arranged where the specification invokes it; impacts at MDT for cryogenic work.
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; marked with grade, size, schedule and heat number; L-only or dual documentation per the order line.
6
Certification & packing — EN 10204 3.1 MTC with solution-anneal records (3.2 witnessed on request); stainless WPS guidance naming 308L fillers; faces and bevels protected, packed sea-worthy.
Where F304L LWN Flanges Are Used
Welded, corrosive, cold: chemical process vessels and columns, nitric acid and urea-adjacent systems, water and wastewater treatment, food, beverage and pharmaceutical plant welded and left as-welded, cryogenic cold boxes, liquid-gas storage standpipes and vacuum-jacketed connections — and the instrument bridles and level nozzles that ride on all of them. 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
F304L LWN Flange Dimensions
Flange-end dimensions are class-governed per ASME B16.5 (ratings per the low-carbon austenitic group); barrel length and bore per order. Full class-by-class charts:
Seven elements — the documentation regime completes the grade line:
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 F304L (L-only) or dual 304/304L, as the specification directs; medium, temperature and as-welded status stated — they confirm L against the straight grade, 316L and 304H; A262 practice and condition named where invoked; impacts at MDT for cryo.
6
Certification — EN 10204 3.1 with solution-anneal records (our standard) / 3.2 witnessed.
Example: “LWN Flange RF, 4″ NB, ASME B16.5 Class 150, barrel 230 mm, Sch 10S bore, standard pattern, ASTM A182 F304L (L-only), nitric acid column nozzles — as-welded, A262 Practice E on the heat, EN 10204 3.1 — 10 pcs.” Quotations normally within 24 hours with price, unit weight and delivery.
An ASTM A182 F304L long weld neck flange is a forged low-carbon austenitic stainless steel flange — UNS S30403, W.Nr. 1.4307 — 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 vessel, column or exchanger shell. F304L is the 18-8 carbon dial turned down: carbon is starved below 0.030% so the weld heat-affected zone has nothing to precipitate — no chromium carbides, no sensitisation, no locally stripped film — making this the grade specified wherever stainless must be welded and then left as-welded in corrosive service. 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 intergranular 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.
Why does 304L exist — what is sensitisation?
Sensitisation is the classic austenitic weld-zone failure: hold 18-8 stainless between roughly 450 and 850°C — exactly what every weld's heat-affected zone experiences — and carbon finds chromium, precipitating chromium carbides along the grain boundaries. Each carbide locks up many times its weight in chromium, so a narrow band beside every grain boundary drops below the ~11% chromium the passive film needs, and in aggressive service that band corrodes as a network of grain-boundary trenches: intergranular attack, weld decay. 304L removes the raw material: with carbon capped at 0.030% there is simply not enough of it to build a damaging carbide network, so the welded joint keeps its film — as-welded, with no post-weld anneal — which is the entire reason the grade exists and the reason chemical plant is written around it.
What does the L certificate trade away — and when does it matter?
Strength, honestly stated: carbon is an interstitial strengthener, so starving it costs the certificate — 485 MPa tensile and 170 MPa yield against the straight grade's 515/205. When does it matter? Less often than the numbers suggest. B16.5 flange geometry is class-governed, and the low-carbon grades carry their own slightly lower pressure-temperature ratings — real, but modest at the warm end and irrelevant at the cold end where the grade actually lives. It matters most in code calculations that lean on yield at moderate temperatures, which is exactly the territory dual-certified stock answers: heats melted low in carbon that still meet straight-grade strength, certifying both numbers at once. The rule of thumb: where a design genuinely needs 205 MPa on paper, dual-certified supply provides it; where the specification demands L-grade documentation for as-welded corrosion duty, this page is the grade — and the 170 MPa line is the honest price of the weld-zone immunity.
When is L-only supply demanded rather than dual-certified stock?
When the paperwork must prove the corrosion behaviour, not the strength. Dual-certified 304/304L covers most of the world's needs — but some specifications write 304L alone deliberately: nitric acid and urea-adjacent systems qualified with ASTM A262 intergranular testing, as-welded chemical duty where the corrosion engineer wants the L allowables used so no one ever leans on strength the low-carbon heat might not owe, and projects that simply forbid dual marking for traceability reasons. In those cases the order line reads F304L, UNS S30403, the certificate documents the L grade on its own terms, and A262 practice testing travels with the lot where invoked. State which regime your specification follows and the certificate is built to match — both are routine at our works.
What is the chemical composition of ASTM A182 F304L?
Carbon ≤0.030% — the identity, three decimal places of it — manganese ≤2.00%, silicon ≤1.00%, phosphorus ≤0.045%, sulphur ≤0.030%, chromium 18.0-20.0%, nickel 8.0-13.0%. Two details reward attention. The nickel range is wider than plain 304's 8.0-11.0: carbon is a powerful austenite stabiliser, and with it starved out, the specification gives nickel room to do that work alone. And there is still no molybdenum — 304L answers the weld zone, not the chloride ladder; the grade that answers both at once is 316L, one bench over. Chemistry is verified per heat, PMI-confirmed, and travels on the EN 10204 3.1 MTC.
What are the mechanical properties of F304L long weld neck flanges?
Solution annealed: tensile strength 485 MPa (70 ksi) minimum, yield strength 170 MPa (25 ksi) minimum, elongation 30% minimum — the deliberately lower certificate that pays for the weld-zone immunity, as the trade-off FAQ explains. In nozzle practice the numbers serve comfortably: the class-governed flange end carries the low-carbon group's B16.5 ratings, the heavy barrel's area-replacement work is a geometry calculation the generous wall answers, and the 30% elongation keeps forging, machining and field welding easy. Toughness is the quiet strength — austenite has no brittle transition, and the L grade's cleanliness makes it the family's cryogenic default. Hardness sits low with nothing to manage in supply.
Why is 304L the cryogenic default of the family?
Two reasons stack. Like all the austenitics, it has no ductile-to-brittle transition — usable toughness continues to -196°C and below, which is why liquid nitrogen, oxygen and LNG-adjacent plant is austenitic as a matter of course. And within the family, lower carbon means lower interstitial hardening and cleaner grain boundaries, so the L grade posts the best cryogenic toughness of the dial — the reason cryo specifications reach for it by name. For LWN work the fit is direct: cold-box nozzles, cryogenic storage-tank standpipes, vacuum-jacketed connections and cold-service instrument bridles are classic long weld neck territory, and the one-forging construction removes a weld from systems where every joint is a potential cold leak. Impact testing at the minimum design temperature is documented on the certificate where projects require it — and the duplex family's -50°C floor never enters the conversation.
What is ASTM A262 intergranular testing?
The laboratory proof that a stainless heat resists the grain-boundary attack 304L exists to prevent. ASTM A262 is a family of practices — screening etches and boiling-acid immersion tests, with Practice E's copper-copper sulphate-sulphuric acid boil the workhorse for L grades — in which sensitised-condition samples are exposed and then examined or bent to reveal intergranular penetration. Specifications for nitric acid, urea and fine-chemical duty commonly invoke it, sometimes on samples deliberately heat treated to simulate a weld cycle, so the test certifies the metallurgy rather than the luck of the lot. Where your specification names A262, the practice letter and condition go on the order line, the testing is arranged against the heat, and the report travels with the EN 10204 certificate.
How is the closing weld on an F304L LWN made?
With the friendliest procedure on the site, and — uniquely — with nothing for the weld to spoil. No preheat beyond dryness, no PWHT, ordinary austenitic technique with matching 308L fillers: the heat-affected zone that would sensitise a high-carbon stainless simply has no carbon to work with, so the joint keeps its corrosion resistance exactly as welded, which is the grade's whole promise. Finishing discipline still applies on corrosion-critical and hygienic work — heat tint removed by pickling or passivation to restore the surface film — and the closing weld at the shell inherits the vessel's own qualified stainless 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 F304L hand off — along the dial or up the ladder?
Along the dial by temperature: where strength at moderate heat governs, dual-certified stock or the straight grade carries the 205 MPa line; where sustained metal temperature climbs past roughly 525°C, the dial swings fully over to 304H, whose deliberately retained carbon becomes the strength mechanism — L in creep service is the wrong end of the dial entirely. Up the chloride ladder by chemistry: when the as-welded duty is also salty, 316L is the natural sibling — the same low-carbon logic with molybdenum added — and beyond it the duplex rungs take the cracking question away altogether. Off the bench: hot reducing acids point to the nickel-bearing acid ladder. The L page's own franchise is clear and large: welded, corrosive, cold — chemical process, nitric acid, cryogenics — and inside it the grade has no rival on price.
What sizes and pressure classes do F304L 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 F304L order book mirrors its habitats: chemical process and water treatment concentrate in Classes 150-300, cryogenic and gas systems reach for 300-600, and the L-grade group's pressure-temperature ratings govern per B16.5. 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 F304L 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 F304L (L-only) or dual 304/304L, as your specification directs — with the service stated (medium, temperature, as-welded or not) so the dial setting is confirmed, A262 practice and condition named where invoked, and impacts at minimum design temperature for cryogenic work; (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 F304L long weld neck flanges in India?
Tesco Steel & Engineering is an ISO 9001:2015 certified flange manufacturer based in Mumbai, India, producing ASTM A182 F304L 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 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, L-only or dual 304/304L documentation as the specification directs, ASTM A262 intergranular testing and cryogenic impact testing where invoked, and stainless WPS guidance naming 308L fillers — alongside the straight and H rungs of the dial, the 316L sibling, and the complete long weld neck range. Exported to more than 50 countries.
