SS 904L Pipe FittingsASTM A403 WP904L · Manufacturer, stockist & exporter, India
Also sold as Alloy 904L · UNS N08904 · W.Nr 1.4539 · 2RK65
SS 904L pipe fittings are made to ASTM A403 WP904L for buttweld fittings and ASTM A182 F904L for forged socket-weld and threaded fittings, with dimensions to ASME B16.9 and B16.11. It is a super-austenitic stainless steel with high nickel, molybdenum and copper, chosen for dilute sulphuric acid, phosphoric acid and chloride-bearing cooling water. 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 904L Pipe Fittings?
SS 904L pipe fittings is a super-austenitic stainless steel with high nickel, molybdenum and copper supplied as pipe fittings to ASTM A403 WP904L (UNS N08904). Buyers specify it for dilute sulphuric acid, phosphoric acid and chloride-bearing cooling water. It is also sold as Alloy 904L, UNS N08904, W.Nr 1.4539.
- What it is
- Super-austenitic stainless steel with high nickel, molybdenum and copper
- Buttweld
- ASTM A403 WP904L
- Forged
- ASTM A182 F904L
- Dimensions
- ASME B16.9 · B16.11 · MSS SP-43
- Sizes
- Buttweld ½" – 48" · forged ⅛" – 4"
- Best at
- Dilute sulphuric acid, phosphoric acid and chloride-bearing cooling water
SS 904L Pipe Fittings Specification & Sizes
| Buttweld fittings | ASTM A403 WP904L — dimensions to ASME B16.9, MSS SP-43 |
|---|---|
| Forged fittings | ASTM A182 F904L — dimensions to ASME B16.11 |
| MSS SP-43 light-wall fittings | ASTM A403 CR904L — the A403 CR grade for MSS SP-43 dimensions (no class suffix) |
| Short-radius elbows | ASME B16.9 (formerly B16.28) |
| Buttweld sizes | NPS ½" to 48", schedule to match the pipe |
| Forged classes | Socket weld 3000 / 6000 / 9000 · threaded 2000 / 3000 / 6000 |
| Types | Elbow · Tee · Reducer · Cap · Stub end · Cross · Bend · Lateral · Coupling · Union · Nipple · Plug |
| Testing | PMI · dimensional · radiography of welded fittings · IGC on request |
| Documents | EN 10204 3.1 · 3.2 with third-party inspection |
Choosing SS 904L Fittings: Elbow Radius, Schedule & Class
ASTM A403 fittings come in classes: S seamless, W welded (welds radiographed or ultrasonically examined), WX all welds radiographed, WU all welds ultrasonically tested. Write the class after the grade, e.g. WP904L-S.
Radius (LR, SR, 3D), the schedule-to-class map and the 1.5 mm socket-weld gap are explained in the fittings guide. For 904L, buttweld fittings are ASTM A403 WP904L and forged fittings ASTM A182 F904L.
SS 904L Pipe Fittings Chemical Composition
Under technical review for TDS.
| Element | Current requirement |
|---|---|
| Nickel | As specified |
| Chromium | As specified |
| Molybdenum | As specified |
| Copper | 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 N08904.
SS 904L Pipe Fittings 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 N08904 — Annealed plate & sheet.
Density & Physical Properties
| Property | Value |
|---|---|
| Density | 7.95 g/cm³ |
| Melting range | 1300 – 1390 °C |
| Magnetic | Non-magnetic (annealed) |
| PREN (approx.) | ≈ 35 |
SS 904L Equivalent Grades
SS 904L buttweld fitting dimensions — ASME B16.9
Centre-to-end and end-to-end dimensions are the same for every alloy; the wall thickness follows the pipe schedule. Values in mm.
| NPS | OD | 90° LR elbow A | 45° elbow B | Tee C | Reducer H | Cap E |
|---|---|---|---|---|---|---|
| ½" | 21.3 | 38 | 16 | 25 | — | 25 |
| 1" | 33.4 | 38 | 22 | 38 | 51 | 38 |
| 1½" | 48.3 | 57 | 29 | 57 | 64 | 38 |
| 2" | 60.3 | 76 | 35 | 64 | 76 | 38 |
| 3" | 88.9 | 114 | 51 | 86 | 89 | 51 |
| 4" | 114.3 | 152 | 64 | 105 | 102 | 64 |
| 6" | 168.3 | 229 | 95 | 143 | 140 | 89 |
| 8" | 219.1 | 305 | 127 | 178 | 152 | 102 |
| 10" | 273.1 | 381 | 159 | 216 | 178 | 127 |
| 12" | 323.9 | 457 | 190 | 254 | 203 | 152 |
Full chart to 24": ASME B16.9 fitting 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 904L Pipe Fittings 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 904L is most often mixed up with Inconel 825 — 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 904L | Inconel 825 |
|---|---|---|
| Nickel | As specified | As specified |
| Chromium | As specified | As specified |
| Molybdenum | As specified | As specified |
| Copper | As specified | As specified |
| Titanium | — | As specified |
| Iron | As specified | As specified |
| Manganese | As specified | As specified |
SS 904L Pipe Fittings Price — What Decides It
Two quotes for "904L pipe fittings" can differ by 20% and both be fair. We quote 904L pipe fittings 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 904L pipe fittings by type
SS 904L Pipe Fittings Applications
SS 904L 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 904L Pipe Fittings vs 316L, 2205 and 825
| Grade | Pipe Fittings standard | PREN (approx.) | Pick it when |
|---|---|---|---|
| SS 316 / 316L | ASTM A403 WP316L | ≈ 24 | Chloride-bearing process fluids, marine air and pharmaceutical service |
| Inconel 825 | ASTM B366 WPNICMC | ≈ 31 | Sulphuric and phosphoric acid service, chloride stress-corrosion cracking and sour gas |
| Duplex 2205 | ASTM A815 WPS31803 / WPS32205 | ≈ 35 | Strength with chloride resistance at a stainless-steel budget |
| SS 904L | ASTM A403 WP904L | ≈ 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 904L 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 904L fits.
Elevated nickel gives far better resistance to chloride cracking than 316L.
Molybdenum lifts pitting resistance well above ordinary austenitic grades (screening PREN on the grade page).
Copper is what makes 904L the stainless steel of choice for dilute sulphuric acid.
Very low carbon limits carbide precipitation, so welds keep their corrosion resistance.
How your 904L pipe fittings 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 904L Pipe Fittings
SS 904L welds by all common arc processes. A few points our buyers ask about:
| Matching filler | ER385 (AWS A5.9) |
|---|---|
| Over-alloyed filler | ERNiCrMo-3 for severe chloride service |
| 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 904L fittings and 904L flanges for the matching pipe-system parts.
How to Order SS 904L Pipe Fittings: RFQ Checklist
Get an accurate quote the first time. Copy this list into your enquiry:
- Fitting type, size and schedule / class
- Buttweld, socket weld or threaded
- Seamless or welded (buttweld fittings)
- Material standard and grade marking
- Certificate type and extra tests
- Delivery port, Incoterm and required date
SS 904L pipe fittings for export
FOB / CIF · Nhava Sheva (JNPT), MumbaiSS 904L pipe fittings — questions buyers ask
Is SS 904L the same as Alloy 904L?
Alloy 904L, UNS N08904, W.Nr 1.4539 are names used for SS 904L (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 pipe fittings is ordered to ASTM A403 WP904L whichever name is on the enquiry.
Which standard covers SS 904L buttweld fittings?
ASTM A403 WP904L is the material specification; dimensions follow ASME B16.9 (light-wall MSS SP-43 fittings are ordered as CR904L). Forged socket-weld and threaded fittings are made from ASTM A182 F904L material to ASME B16.11.
What is the difference between SS 904L WP-S and WP-W fittings?
S is seamless; W is welded from plate or welded pipe, with the welds examined by radiography or ultrasonics. WX means all welds radiographed and WU all welds ultrasonically tested. Seamless costs more and is preferred for critical service.
Can SS 904L fittings be welded to carbon steel?
Yes — ER309L (or E309L electrode) is the usual filler when joining it to carbon steel.
SS 904L or Inconel 825 — which should I choose?
SS 904L is chosen for dilute sulphuric acid, phosphoric acid and chloride-bearing cooling water. Inconel 825 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