SS 904L Flanges
Teshi Group manufactures SS 904L flanges (ASTM A182 F904L, UNS N08904, 1.4539) as an OEM in India — forged, machined, marked and certified in-house to ASME B16.5, ASME B16.47, EN 1092-1 and customer drawings.
Super austenitic stainless steels combine high nickel, molybdenum and copper (904L) or 6 % molybdenum with nitrogen (254 SMO) to resist sulphuric and phosphoric acid, chloride pitting and stress corrosion cracking.
SS 904L flanges at a glance
| Material | SS 904L |
|---|---|
| Specification | ASTM A182 F904L |
| UNS / W.Nr. | N08904 / 1.4539 |
| Sizes | NPS ½"–24" (ASME B16.5), 26"–60" (ASME B16.47 A / B), DN 10–600 (EN 1092-1) |
| Pressure class | Class 150, 300, 600, 900, 1500, 2500 · PN 6–40 |
| Facing / ends | RF, FF, RTJ, tongue & groove, male-female; serrated or smooth finish |
| Certification | EN 10204 3.1 standard · 3.2 with third-party inspection · IBR on request |
| Testing | PMI, hardness, dimensional; UT, IGC, impact and ferrite as specified |
SS 904L chemistry and mechanical properties
Chemical composition of SS 904L (weight %, maximum unless a range)
| Grade | C | Mn | Si | Cr | Ni | Mo | Cu | N |
|---|---|---|---|---|---|---|---|---|
| 904L | 0.020 | 2.00 | 1.00 | 19.0–23.0 | 23.0–28.0 | 4.0–5.0 | 1.00–2.00 | 0.10 |
Mechanical properties of SS 904L (minimum, room temperature)
| Grade | Tensile strength | Yield strength (0.2 %) | Elongation | Note |
|---|---|---|---|---|
| 904L | 490 MPa (71 ksi) | 215 MPa (31 ksi) | 35 % | PREN ≈ 34 |
Matching specifications by product form
| Grade | Forged flanges & fittings | Butt weld fittings | Plate | Pipe |
|---|---|---|---|---|
| 904LUNS N08904 · W.Nr. 1.4539 | ASTM A182 F904L | ASTM A403 WP904L | ASTM A240 / B625 | ASTM A312 / B677 |
Limits and minimums from the governing ASTM / ASME specifications, summarised for convenience; the current edition takes precedence.
Pressure rating
Pressure–temperature ratings follow the ASME B16.5 / B16.47 material group for the grade. The applicable rating table is issued with every quotation, and flanges are marked with class, material and heat number.
Types we manufacture
Dimension charts
Where SS 904L is used
- Sulphuric acid dilution, cooling and storage
- Zinc and copper smelter roaster gas cleaning and leaching circuits
- Phosphoric acid evaporators
- Flue-gas desulphurisation scrubbers
- Seawater and brackish cooling water
Testing & certification
- Solution annealed and water quenched
- PMI on every piece for Ni, Mo and Cu
- Intergranular corrosion test to ASTM A262 when specified
- EN 10204 3.1 certificate; 3.2 with third-party inspection on request
FAQ
SS 904L flanges: common questions
What specification covers SS 904L flanges?
SS 904L flanges are forged to ASTM A182 F904L and dimensioned to ASME B16.5, ASME B16.47 or EN 1092-1.
What is the chemical composition of 904L?
904L (UNS N08904): C 0.020, Mn 2.00, Si 1.00, Cr 19.0–23.0, Ni 23.0–28.0, Mo 4.0–5.0, Cu 1.00–2.00, N 0.10 (weight %; single values are maximums).
What are the minimum mechanical properties of 904L?
Tensile strength 490 MPa (71 ksi), yield strength 215 MPa (31 ksi), elongation 35 %.
Is Teshi Group a manufacturer of SS 904L flanges in India?
Yes. Teshi Group has manufactured flanges and fittings in India since 1971 and is ISO 9001:2015 certified and IBR approved. Every SS 904L piece is hard-stamped with its heat number and supplied with an EN 10204 3.1 certificate; 3.2 with third-party inspection on request.
Why is SS 904L used in sulphuric acid plants?
904L (UNS N08904) has 23–28 % nickel, 4–5 % molybdenum and 1–2 % copper, which give good resistance to dilute and moderately concentrated sulphuric acid at temperatures where 316L corrodes quickly.
What is the difference between 904L and 254 SMO?
904L relies on nickel and copper for acid resistance. 254 SMO (UNS S31254, ASTM A182 F44) has 6 % molybdenum and 0.18–0.25 % nitrogen, giving a PREN above 42 and much better resistance to chloride pitting and crevice corrosion.
Ready to build to spec?
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