254 SMO (F44) Flanges
Teshi Group manufactures 254 SMO (F44) flanges (ASTM A182 F44, UNS S31254, 6Mo super austenitic) 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.
254 SMO (F44) flanges at a glance
| Material | 254 SMO (F44) |
|---|---|
| Specification | ASTM A182 F44 |
| UNS / W.Nr. | S31254 / 1.4547 |
| 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 |
254 SMO (F44) chemistry and mechanical properties
Chemical composition of 254 SMO (F44) (weight %, maximum unless a range)
| Grade | C | Mn | Si | Cr | Ni | Mo | Cu | N |
|---|---|---|---|---|---|---|---|---|
| 254 SMO (6Mo) | 0.020 | 1.00 | 0.80 | 19.5–20.5 | 17.5–18.5 | 6.0–6.5 | 0.50–1.00 | 0.18–0.25 |
Mechanical properties of 254 SMO (F44) (minimum, room temperature)
| Grade | Tensile strength | Yield strength (0.2 %) | Elongation | Note |
|---|---|---|---|---|
| 254 SMO (6Mo) | 650 MPa (94 ksi) | 300 MPa (44 ksi) | 35 % | PREN ≥ 42 |
Matching specifications by product form
| Grade | Forged flanges & fittings | Butt weld fittings | Plate | Pipe |
|---|---|---|---|---|
| 254 SMO (6Mo)UNS S31254 · W.Nr. 1.4547 | ASTM A182 F44 | ASTM A403 WPS31254 | ASTM A240 S31254 | ASTM A312 S31254 |
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 254 SMO (F44) 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
254 SMO (F44) flanges: common questions
What specification covers 254 SMO (F44) flanges?
254 SMO (F44) flanges are forged to ASTM A182 F44 and dimensioned to ASME B16.5, ASME B16.47 or EN 1092-1.
What is the chemical composition of 254 SMO (6Mo)?
254 SMO (6Mo) (UNS S31254): C 0.020, Mn 1.00, Si 0.80, Cr 19.5–20.5, Ni 17.5–18.5, Mo 6.0–6.5, Cu 0.50–1.00, N 0.18–0.25 (weight %; single values are maximums).
What are the minimum mechanical properties of 254 SMO (6Mo)?
Tensile strength 650 MPa (94 ksi), yield strength 300 MPa (44 ksi), elongation 35 %.
Is Teshi Group a manufacturer of 254 SMO (F44) 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 254 SMO (F44) 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.
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