Stainless and duplex flanges are specified for what the steel resists rather than for what it carries. The austenitic A182 grades cover general corrosion service; duplex and super duplex add chloride stress-corrosion resistance, which is why offshore, desalination and chemical work calls for them.
Grades supplied are ASTM A182 F304 and F304L, F316 and F316L, F321 and F347, duplex F51, and super duplex grades confirmed by project review. The flange type and dimensions still come from ASME, EN, DIN, GOST or your drawing - the grade decision changes the certificate route, not the table.
For F304/F316 RFQs, define the PMI scope when the purchase specification requires it. For duplex or super duplex, request a grade-specific MTC plus PMI; add ferrite, corrosion, UT, MT, PT or third-party inspection only when the project specification names them. State passivation or any special surface finish rather than assuming it is included.
Product family: Flanges
Stainless and duplex flange RFQs are reviewed by material grade, corrosion service, standard, pressure rating, heat treatment, PMI, inspection and document needs.
The nearest designation of each grade in the US, European, Japanese, Korean, Chinese and Russian systems, for reading a line list written in any of them. These are nearest designations, not equivalences: the purchase specification governs, and substituting one for another needs the purchaser's written approval.
| Common name | US: ASTM A182 (UNS) | EU: EN 10222-5 (no.) | JIS G 3214 | KS D 4115 | China: NB/T 47010 (GB/T 20878) | GOST 5632 (nearest) | Differences to state |
|---|---|---|---|---|---|---|---|
| 304 | F304 (S30400) | X5CrNi18-10 1.4301 | SUSF304 | STS F304 | S30408 (06Cr19Ni10) | 08Х18Н10 | 08Х18Н10 allows Cr 17-19 % against 18-20 % for F304 |
| 304L | F304L (S30403) | X2CrNi18-9 1.4307 | SUSF304L | S30403 (022Cr19Ni10) | 03Х18Н11 | Dual 304/304L certification is common but must be asked for, not assumed | |
| 316 | F316 (S31600) | X5CrNiMo17-12-2 1.4401 | SUSF316 | STS F316 | S31608 (06Cr17Ni12Mo2) | Compare the molybdenum windows of the two specifications before accepting one against the other | |
| 316L | F316L (S31603) | X2CrNiMo17-12-2 1.4404 | SUSF316L | S31603 (022Cr17Ni12Mo2) | 03Х17Н14М3 | The GOST mark reads about 14 % Ni and 3 % Mo - richer than 316L; not interchangeable without review | |
| 316Ti | F316Ti (S31635) | — | — | 10Х17Н13М2Т | Titanium-stabilised 316: order it by name, it is not 316L | ||
| 321 | F321 (S32100) | X6CrNiTi18-10 1.4541 | SUSF321 | S32168 (06Cr18Ni11Ti) | 08Х18Н10Т (nearest) 12Х18Н10Т | 12Х18Н10Т allows C up to 0.12 % against 0.08 % max for F321 (GOST 5632), so it is not automatically F321 | |
| 347 / 347H | F347 (S34700) F347H (S34709) | SUSF347 SUSF347H | S34778 (06Cr18Ni11Nb) | 08Х18Н12Б | 347H has a carbon minimum for creep strength; our Annex I lists F347, not F347H |
A dash means no designation was found in that system; a blank cell means we have not yet checked that system's current edition, so we list nothing rather than guess. Every row and every designation has its own anchor, e.g. #s30408, #1-4404 or #12x18n10t.
The name 2205 covers two UNS windows, and super duplex splits into two grades that are not interchangeable. Reading the exact designation on your line list tells you which certificate and tests apply.
| Common name | US: ASTM A182 (UNS) | EU (no.) | JIS | KS | China: NB/T 47010 (GB/T 20878) | GOST | Differences to state |
|---|---|---|---|---|---|---|---|
| 2205, wider window | F51 (S31803) | X2CrNiMoN22-5-3 1.4462 | SUS329J3L - bar and plate only; JIS G 3214 has no duplex forging grade | S22253 (022Cr22Ni5Mo3N) | S31803 window: Cr 21.0-23.0, Mo 2.5-3.5, N 0.08-0.20 % | ||
| 2205, tighter window | F60 (S32205) | 1.4462 | as above | S22053 (022Cr23Ni5Mo3N) | — | S32205 window: Cr 22.0-23.0, Mo 3.0-3.5, N 0.14-0.20 % - the windows printed on our S22053 type-test report | |
| 2507 super duplex | F53 (S32750) | S25073 (022Cr25Ni7Mo4N) | — | Cr 24-26, Mo 3-5, N 0.24-0.32 % | |||
| Super duplex with Cu and W | F55 (S32760) | X2CrNiMoCuWN25-7-4 1.4501 | — | — | S27603 (022Cr25Ni7Mo4WCuN) | — | Adds Cu 0.50-1.00 and W 0.50-1.00 %; not interchangeable with F53 without approval |
Same conventions as the table above. JIS G 3214 has no duplex forging grade (SUS329J3L is a bar and plate designation), so a duplex forging bought against a JIS line list is ordered by an ASTM, EN or project grade.
Our duplex type test was run on S22053, the Chinese designation (022Cr23Ni5Mo3N) in NB/T 47010. The report prints the windows the sample was held to: chromium 22.00-23.00 %, nickel 4.50-6.50 %, molybdenum 3.00-3.50 % and nitrogen 0.14-0.20 %. Those are the S32205 windows of A182 F60, so S22053 is nearest to F60, not merely to 2205 in general.
A heat inside the S32205 window also sits inside the wider S31803 window of F51, which is why F51/F60 dual certification is common. The chemistry overlap does not make the certificates interchangeable: the mechanical and test requirements are still checked against each grade the certificate names.
Nitrogen on our sample came in at 0.14 %, the lowest value the window allows. If your line class relies on nitrogen for pitting resistance, put a minimum or a PREN requirement on the RFQ so it is checked per heat.
Each of these can turn a stainless line item into a re-quote. The standard does not settle them - the RFQ has to.
Each approval prints its own duplex line and limits; the table keeps every figure on its own document. An approval covers our manufacturing process - each classed order is still certified by that society's surveyor where its rules require.
| Society | Document | Duplex as printed | Limit printed for duplex | Forging method printed |
|---|---|---|---|---|
| ABS | FOR-0055952 | Duplex stainless (work-order attachment) | 500 kg | Free forge; die forge |
| Bureau Veritas | SMS.W.II./152398/A.0 | Duplex stainless steel forging | 500 kg | Not printed |
| DNV | AMMM0000388 | 22 Cr duplex; 25 Cr duplex | 600 kg, 150 mm, solution heat treated | Closed and open die |
| Lloyd's Register | LR25409452WA | Duplex stainless steel | 500 kg | Open die (free) |
| Korean Register | DLN51990-SF001 | 22Cr duplex; 25Cr duplex stainless steel | 3,000 kg - one limit for the whole approval | Open die |
| ClassNK | ST628CF (TA2677E) | Duplex Stainless Steels (ASTM A182/A182M) | None printed | Forging / heat treatment, method not printed |
The six documents in full, with every material family and limit, are compared on the marine and shipbuilding page.
F51, F53, F55 and F60 are also listed in Annex I of our materials certification to ASME Section II Part A by TÜV NORD. That is a certified material scope, not a record of shipments: super duplex F53 and F55 are quoted after review of the exact grade, sizes and tests.
For a duplex or super duplex order that runs across several heats and heat-treatment batches, consistency comes from records kept per heat and per batch, and from tests whose frequency the order fixes before production starts. Our forging output across all grades is about 3,000 tonnes a month.
| Item | What we do | What the order should state |
|---|---|---|
| MTC 3.1 | Issued per heat number. | The certificate type and any project-specific fields. |
| Solution annealing record | Kept for every heat-treatment furnace load or batch: the heat or batch link, temperature, soaking time, cooling method and the temperature chart. | Whether the heat-treatment report or chart should travel with the certificates; we supply it on request. |
| PMI | Scope set per order: every piece, or sampling. | Every piece, or a sampling plan with the sampling ratio, lot definition and acceptance rule. Testing every piece gives stronger traceability and protection against mixed material, at a higher cost. |
| Ferrite content | A focus for duplex and super duplex. Test frequency, sampling and acceptance range follow the material standard and the project specification. | The frequency you need, for example per heat or per heat-treatment batch; we then test at that frequency. |
| Corrosion test (e.g. ASTM G48) | Done when the purchase order or project specification asks for it. A standard MTC 3.1 does not come with a G48 report. | Test method, temperature, duration, sampling frequency and acceptance criteria. |
China Quality Mark Certification Group (CQM) verified the cradle-to-gate carbon footprint of our stainless steel forgings to ISO 14067:2018, using 2024 data. Statement CQM25CFPX700075R0 was first issued on 10 November 2025 and is valid to 9 November 2027.
| Stage | kg CO2e per tonne | Share |
|---|---|---|
| Raw material acquisition and pre-processing | 9,365.99 | 94.6 % |
| Raw material transport | 183.22 | 1.85 % |
| Manufacturing | 351.2 | 3.55 % |
| Total, cradle to gate | 9,900.41 | 100 % |
| Scope and rating | |
|---|---|
| Grade scope | ASTM A182 F304/F304L, F316/F316L, F316Ti, F321, F347, duplex F51/F60; super duplex F53/F55 are in our certified material scope and quoted after project review. |
| Standards and materials | |
| Standards / drawings |
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| Material grades |
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| Geometry, tolerance and inspection | |
| Shape scope | ASME/EN/DIN/GOST or drawing controls the flange type; stainless/duplex controls PMI, corrosion-service notes and certificate route. |
| Critical dimensions | Facing, bore, bolt pattern, wall schedule, surface condition and passivation or special finish when specified. |
| Document focus | MTC 3.1, PMI, heat number traceability, ferrite or NACE notes when specified, and dimensional report. |
| Inspection depth | PMI is normally central; UT/MT/PT, surface condition and third-party inspection are added by project requirement. |
| Reviewed before quotation |
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| Buying logic | |
| Best-fit RFQ | Best for ASTM A182 stainless, duplex and project-specified corrosion-resistant forged flange RFQs. |
| Buyer application | Chemical, offshore, desalination, food-adjacent utilities, petrochemical and corrosive service systems. |
Your standard, drawing revision and project specification govern.
On one type-test sample set in S22053, report YSY202450081 records 55 % ferrite on both specimens against a 40-60 % window, chemistry inside the S32205-matching windows printed on the report, and tensile clear of the minima. The ferrite value belongs to S22053 only.
Evidence
Applies when
The sample was a DN80 (NPS 3) Class 150 raised-face weld neck flange in S22053 from our own production, tested as part of a special-equipment type test; two pieces were tested.
Limits
One sample set of one grade: the ferrite, chemistry and tensile values are not typical or guaranteed values, and they say nothing about F51, F53, F55 or any austenitic grade. The report holds no impact value and no corrosion test. Your order's ferrite, PREN or corrosion-test requirement is tested on your heat and reported on its own certificate.
Sources
Every value above was checked against the linked documents on 2026-09-26.
Two pages of one 3.1 inspection certificate we issued on 24 November 2025 for ASTM A182 weld neck flanges: page 1 for 304L (heat NY250804AS03), page 2 for 316L (heat 250809CE01). Each page lists the solution treatment, the heat's chemistry against the grade limits, tensile and hardness results, and the visual, dimensional and surface-crack inspection. Customer, contract and customer item codes are covered.
Evidence
Applies when
The two pages are a certificate we issued for ASTM A182/A182M-25 weld neck flanges, one page per heat: 304L heat NY250804AS03 and 316L heat 250809CE01.
Limits
Two heats of two grades: the values are those of these heats, not typical or guaranteed values, and say nothing about other heats, grades or orders. The pages hold no impact, ferrite or corrosion-test value. PMI, ferrite and corrosion testing are fixed by your order.
Sources
Every value above was checked against the linked documents on 2026-10-24.
Use the matrix to separate the buyer's requirement from the evidence that must be agreed for the exact grade, heat and project. Availability, production volume and delivery timing are confirmed only after the complete RFQ is reviewed.
| Project requirement | Evidence to request | RFQ fields to send | Capability boundary |
|---|---|---|---|
| F304/F304L or F316/F316L flange | Heat-linked MTC 3.1 and PMI scope when required | Exact grade, standard, size, rating, facing, quantity and certificate wording | The required grade and inspection scope are confirmed against the purchase specification before quotation |
| Duplex or super duplex flange | Grade-specific MTC plus PMI; ferrite or other project tests only when stated in the specification | Exact ASTM or project grade, service condition, dimensions, quantity and acceptance criteria | Evidence for one duplex grade or heat does not establish another grade, heat or service suitability |
| Mill certificate required | Certificate type, heat-number traceability and the separate inspection reports named by the project | 3.1 or 3.2 wording, standard revision, tests, language and third-party hold points | An MTC does not automatically include PMI, dimensional, ferrite or NDT reports |
| High-volume request | Written feasibility review for the exact grade, size mix, quantity, inspection scope and requested date | Line-item quantities, target delivery date, destination, drawing or standard and document package | No production capacity or lead-time commitment is made until the complete line list is reviewed |
| Sour-service or NACE wording | The buyer's named standard, edition and project acceptance criteria | Service conditions, exact grade, hardness or test limits and required document wording | Material family alone does not establish NACE compliance or fitness for sour service |
Also known as
We confirm each step against your drawing or standard before we quote.
Material grade, heat number, certificate basis and substitution limits are checked against the Stainless Steel Forged Flanges drawing or standard before procurement is released.
The forging route is selected around flange type, section thickness, bore allowance, hub or neck geometry and pressure-service requirements.
Heat treatment is planned with the required record package, mechanical testing basis and impact-test condition where low-temperature or alloy service applies.
Rough machining opens reference faces, bore, hub, neck or sealing-face stock needed to control allowance before final flange machining.
Final machining controls facing, bore, bolt pattern, groove, sealing surface and flange-table or drawing tolerances before dimensional inspection is issued.
Inspection covers dimensional report, MTC 3.1, PMI and required UT, MT or PT records before the release documents are matched to the purchase order.
Marking, packing and export documents are prepared by PO line item so the Stainless Steel Forged Flanges shipment can clear customs and be identified at site receiving.
List document requirements in the first RFQ; they affect price and schedule.
Not automatically. Both are titanium-stabilised 18-10 steels, but GOST 5632 allows up to 0.12 % carbon in 12Х18Н10Т against 0.08 % maximum for F321. 08Х18Н10Т is the closer mark; state which one your specification requires.
S22053 is the Chinese designation whose printed windows match UNS S32205, the tighter 2205 window (A182 F60). A heat inside that window also sits inside S31803 (F51), which is why F51/F60 dual certification exists - but the tests and certificate wording are still checked per grade.
F53 and F55 are listed in the Annex I material scope of our certification to ASME Section II Part A by TÜV NORD. That is a certified scope, not a shipment record: send the exact grade, sizes and tests, and they are confirmed by review before quotation.
No. JIS G 3214 lists austenitic and other stainless forging grades but no duplex grade; SUS329J3L is a bar and plate designation. A JIS-based order for duplex flanges therefore names an ASTM, EN or project grade.
Email quote@bldforgedirect.com with standard, drawing, material, quantity and inspection requirements.