SS 304 FlangesASTM A182 F304 · Manufacturer, stockist & exporter, India
Also sold as AISI 304 · UNS S30400 · W.Nr 1.4301 · 18/8 stainless
SS 304 flanges are forged to ASTM A182 F304 and machined to ASME B16.5 (½"–24", Class 150–2500) or ASME B16.47 for larger sizes. It is a austenitic chromium-nickel stainless steel, chosen for general corrosion resistance, food, water and architectural work. Kanak Steel & Engineering Co. supplies it with EN 10204 3.1 mill certificates from Mumbai to buyers across India, the Gulf, South-East Asia, South America, Europe, the UK and the USA.
- Stock & mill supply
- EN 10204 3.1 / 3.2
- PMI on request
- Export packing
Reviewed by the Kanak Steel & Engineering Co. technical team · Updated October 2026
What is SS 304 Flanges?
SS 304 flanges is an austenitic chromium-nickel stainless steel supplied as flanges to ASTM A182 F304 (UNS S30400). Buyers specify it for general corrosion resistance, food, water and architectural work. It is also sold as AISI 304, UNS S30400, W.Nr 1.4301.
- What it is
- Austenitic chromium-nickel stainless steel
- Material
- ASTM A182 F304
- Dimensions
- ASME B16.5 · B16.47 · EN 1092-1
- Classes
- 150 · 300 · 600 · 900 · 1500 · 2500
- Facing
- RF · FF · RTJ
- Best at
- General corrosion resistance, food, water and architectural work
SS 304 Flanges Specification & Sizes
| Material standard | ASTM A182 F304 |
|---|---|
| Dimensional standards | ASME B16.5 (½"–24") · B16.47 Series A / B (26"–60") · B16.36 orifice · B16.48 line blanks · EN 1092-1 |
| Pressure classes | Class 150, 300, 400, 600, 900, 1500, 2500 · PN 6 – PN 100 |
| Facing | Raised face (RF) · flat face (FF) · ring type joint (RTJ) · tongue & groove |
| Bore | To match the pipe schedule — specify it on the order |
| Types | Weld neck flange · Slip-on flange · Blind flange · Socket weld flange · Threaded flange · Lap joint flange · Long weld neck flange · Orifice flange · Spectacle blind · Reducing flange · Ring type joint flange · Expander flange · Anchor flange · Swivel ring flange |
| Testing | PMI · dimensional · UT of forgings · IGC on request |
| Documents | EN 10204 3.1 · 3.2 with third-party inspection |
SS 304 Flange Pressure–Temperature Rating
The class is not a pressure: the allowable pressure for 304 flanges comes from the ASME B16.5 table for its material group, and falls as temperature rises (how ratings work). ASTM A182 F304 is in material group 2.1.
Take the actual pressures from the B16.5 rating table for group 2.1. A class is not a project pressure rating — your piping class sheet and design conditions govern.
Bolting & Gaskets for 304 Flanges
For SS 304 flanges the usual bolting is ASTM A193 B8 studs with A194 8 nuts — see SS 304 fasteners. Spiral-wound gaskets with a 304 or 316 winding suit most stainless raised-face joints. Facing and gasket options are compared in the flange guide.
SS 304 Flanges Chemical Composition
Under technical review for TDS.
| Element | Current requirement |
|---|---|
| Chromium | As specified |
| Nickel | As specified |
| Carbon | As specified |
| Manganese | As specified |
| Silicon | As specified |
| Nitrogen | As specified |
| Phosphorus | As specified |
| Sulphur | As specified |
| Iron | As specified |
Numerical specification requirements are published only after the applicable current standard edition has been verified. Governing specification to be verified: ASTM A240 for UNS S30400.
SS 304 Flanges Mechanical Properties
Under technical review for TDS.
| Property | Current requirement |
|---|---|
| Tensile strength | As specified |
| Yield strength 0.2% | As specified |
| Elongation | As specified |
| Hardness | As specified |
Numerical specification requirements are published only after the applicable current standard edition has been verified. Governing specification and condition to be verified: ASTM A240 for UNS S30400 — Annealed plate & sheet.
Density & Physical Properties
| Property | Value |
|---|---|
| Density | 8 g/cm³ |
| Melting range | 1400 – 1450 °C |
| Magnetic | Non-magnetic annealed; slightly magnetic after cold work |
| PREN (approx.) | ≈ 18 |
SS 304 Equivalent Grades
SS 304 flange dimensions — ASME B16.5 Class 150 & 300
Outside dimensions depend only on size and class, not on the alloy, so 304 flanges bolt to any B16.5 flange of the same size and class. Values in mm; thickness excludes the 1.6 mm raised face.
| NPS | Cl 150 OD | Cl 150 thickness | Cl 150 bolt circle | Cl 150 bolts | Cl 300 OD | Cl 300 thickness | Cl 300 bolt circle | Cl 300 bolts |
|---|---|---|---|---|---|---|---|---|
| ½" | 90 | 9.6 | 60.3 | 4 × ½" | 95 | 12.7 | 66.7 | 4 × ½" |
| 1" | 110 | 12.7 | 79.4 | 4 × ½" | 125 | 15.9 | 88.9 | 4 × ⅝" |
| 1½" | 125 | 15.9 | 98.4 | 4 × ½" | 155 | 19.1 | 114.3 | 4 × ¾" |
| 2" | 150 | 17.5 | 120.7 | 4 × ⅝" | 165 | 20.7 | 127.0 | 8 × ⅝" |
| 3" | 190 | 22.3 | 152.4 | 4 × ⅝" | 210 | 27.0 | 168.3 | 8 × ¾" |
| 4" | 230 | 22.3 | 190.5 | 8 × ⅝" | 255 | 30.2 | 200.0 | 8 × ¾" |
| 6" | 280 | 23.9 | 241.3 | 8 × ¾" | 320 | 35.0 | 269.9 | 12 × ¾" |
| 8" | 345 | 27.0 | 298.5 | 8 × ¾" | 380 | 39.7 | 330.2 | 12 × ⅞" |
| 10" | 405 | 28.6 | 362.0 | 12 × ⅞" | 445 | 46.1 | 387.4 | 16 × 1" |
| 12" | 485 | 30.2 | 431.8 | 12 × ⅞" | 520 | 49.3 | 450.8 | 16 × 1⅛" |
Full chart: ASME B16.5 flange dimensions.
Six-digit Harmonized System heading (iron and steel, chapter 72–73). Your country adds its own digits — confirm with your customs broker. All HS codes.
How to Verify SS 304 Flanges with PMI
Positive material identification with a handheld XRF gun confirms the alloy on the piece itself, in seconds, before it is cut or welded. SS 304 is most often mixed up with SS 316 / 316L — the table shows which elements tell them apart.
Handheld XRF does not measure carbon or nitrogen; those come from the mill certificate or optical emission (OES) testing. PMI can be arranged on request — state it on your enquiry.
Under technical review for TDS.
| Element | SS 304 | SS 316 / 316L |
|---|---|---|
| Nickel | As specified | As specified |
| Chromium | As specified | As specified |
| Molybdenum | — | As specified |
| Iron | As specified | As specified |
| Manganese | As specified | As specified |
SS 304 Flanges Price — What Decides It
Two quotes for "304 flanges" can differ by 20% and both be fair. We quote 304 flanges per kg for full sizes and per piece for cut sizes. These six things move the price per kg, so you can compare offers like for like.
SS 304 flanges by type
SS 304 Flanges Applications
SS 304 is specified when the cheaper grade will not survive the service but a higher alloy would be more than the job needs. These are the jobs our buyers use it for.
SS 304 Flanges vs 316L, 304L and 904L
| Grade | Flanges standard | PREN (approx.) | Pick it when |
|---|---|---|---|
| SS 304L | ASTM A182 F304L | ≈ 18 | Welded tanks, piping and vessels in general corrosive service |
| SS 304 | ASTM A182 F304 | ≈ 18 | General corrosion resistance, food, water and architectural work |
| SS 316 / 316L | ASTM A182 F316L | ≈ 24 | Chloride-bearing process fluids, marine air and pharmaceutical service |
| SS 904L | ASTM A182 F904L | ≈ 35 | Dilute sulphuric acid, phosphoric acid and chloride-bearing cooling water |
PREN = Cr + 3.3 Mo + 16 N, from mid-range chemistry. A screening guide, not a substitute for corrosion data on your medium.
SS 304 Corrosion Resistance — Element by Element
Each alloying addition has a job. Knowing which one protects against your medium is the quickest way to judge whether 304 fits.
About 18% chromium forms the passive film that makes the steel stainless.
Nickel keeps the structure austenitic — tough at low temperature and easy to form and weld.
Standard carbon level: fine for most work, but choose 304L where heavy sections are welded and service is corrosive.
Without molybdenum, 304 pits in chlorides — step up to 316L for coastal or salty service.
How your 304 flanges order runs
- 01Enquiry review — we confirm size, standard edition and documents against your MR or drawing.
- 02Heat selection & PMI — the mill certificate is checked against your order; PMI before processing is available on request.
- 03Processing — cutting, machining or bevelling to your specification, with heat numbers marked.
- 04Inspection — your third-party inspector witnesses, or we share photos and test reports.
- 05Packing & dispatch — seaworthy packing from Nhava Sheva (JNPT), Mumbai, FOB or CIF, documents sent before the vessel sails.
Standards on this page
Welding & Fabricating SS 304 Flanges
SS 304 welds by all common arc processes. A few points our buyers ask about:
| Matching filler | ER308 / ER308L (AWS A5.9) |
|---|---|
| Over-alloyed filler | ER309L for dissimilar joints to carbon steel |
| Preheat | Not required; keep interpass temperature low |
| Cutting | Thermal or abrasive cutting; grind off heat-tinted edges before welding |
Follow your approved WPS; this is general guidance. See also 304 fittings and 304 flanges for the matching pipe-system parts.
How to Order SS 304 Flanges: RFQ Checklist
Get an accurate quote the first time. Copy this list into your enquiry:
- Flange type and dimensional standard (B16.5 / B16.47 / EN 1092-1)
- Size, pressure class and facing
- Bore / schedule for weld neck and socket weld flanges
- Material standard and grade marking
- Certificate type and extra tests
- Delivery port, Incoterm and required date
SS 304 flanges for export
FOB / CIF · Nhava Sheva (JNPT), MumbaiSS 304 flanges — questions buyers ask
Is SS 304 the same as AISI 304?
AISI 304, UNS S30400, W.Nr 1.4301 are names used for SS 304 (W.Nr / EN numbers and older UNS variants are the closest designations; their limits can differ slightly, so specify the UNS number and ASTM grade on the order), and flanges is ordered to ASTM A182 F304 whichever name is on the enquiry.
Which standard covers SS 304 flanges?
ASTM A182 F304 is the material specification for the forging; dimensions follow ASME B16.5 for ½"–24" and ASME B16.47 for 26" and above. European projects use EN 1092-1.
What pressure can a SS 304 Class 300 flange take?
It depends on temperature. ASTM A182 F304 is in ASME B16.5 material group 2.1; read the Class 300 column of that group's table at your design temperature.
Which bolts should I use with SS 304 flanges?
Usually ASTM A193 B8 studs with A194 8 nuts. In corrosive or sour service the bolting material is set by the project specification.
Can a SS 304 flange be welded to a different pipe material?
Yes — ER309L (or E309L electrode) is the usual filler when joining it to carbon steel. Weld neck bores must match the mating pipe schedule.
SS 304 or SS 904L — which should I choose?
SS 304 is chosen for general corrosion resistance, food, water and architectural work. SS 904L is the step up when you need more pitting resistance or strength. See the comparison table on this page, or ask us with your process conditions.
Sources: the ASTM / ASME specifications named on this page and producer datasheets · Last updated October 2026