SMO 254 Plates | UNS S31254 Super Austenitic for Marine, Chemical & Power Applications
Table of Contents:
A Middle Eastern desalination plant feeding coastal power generation had already upgraded seawater intake screens and tube sheets from 316L to duplex stainless, but within 18 months the inspection divers reported the familiar sight of pitting clusters around welds and gasket faces where biofouling and stagnant chloride pockets had concentrated. When the engineering team redesigned the most critical condenser plates, strainer baskets and pipe spools in SMO 254 Plates (UNS S31254, EN 1.4547), they switched to a super austenitic alloy with 19.5–20.5% chromium, 17.5–18.5% nickel, 6–6.5% molybdenum and PREN values typically above 40, delivering yield strength around 310 MPa, tensile strength around 650 MPa and elongation above 35%; subsequent inspections showed clean, pit-free surfaces where previous materials had failed, extending maintenance intervals from 18 months to over 4 years.
SMO 254 (also known as 254 SMO, 6Mo, or 20Mo) is a high-performance super austenitic stainless steel containing approximately 20% chromium, 18% nickel and 6% molybdenum, with controlled nitrogen additions for enhanced pitting resistance. Designated UNS S31254 and EN 1.4547, plate and sheet products are typically supplied under ASTM B625 / ASME SB-625 specifications, with mechanical properties including minimum tensile strength of 650 MPa, minimum yield strength of 310 MPa and minimum elongation of 35% in the solution-annealed condition. The alloy achieves a pitting resistance equivalent number (PREN) typically ranging from 40–43, positioning it between conventional austenitic grades and nickel-base alloys in chloride resistance.
For procurement heads, corrosion engineers, fabricators, OEMs and hardware supply stores serving chemical, oil & gas, marine, pharma and power-generation sectors, SMO 254 plates fill the critical gap where 316L/317L suffer rapid pitting and crevice corrosion, but fully nickel-base alloys prove cost-prohibitive. Industry corrosion data demonstrate that SMO 254 maintains corrosion rates below 0.1 mm/year in seawater at temperatures up to 40°C, resists chloride stress-corrosion cracking up to 80°C where 316L fails above 60°C, and provides superior resistance to dilute sulfuric and phosphoric acids compared to standard austenitics.
Aurico Alloys LLP supports these applications as an affordable, authentic SMO 254 Plates supplier, manufacturer and stockist in India with exports abroad, providing plate to UNS S31254 / EN 1.4547 specifications with ASTM B625 mechanical compliance and EN 10204 certification for global EPC, OEM and MRO requirements.
High-quality SMO 254 Plates ready for industrial use.
Specification Overview
| Supplier & Role | Aurico Alloys LLP – SMO 254 Plates supplier, stockist, exporter in India to abroad |
|---|---|
| Alloy Description | Super austenitic stainless steel with 20Cr-18Ni-6Mo and controlled nitrogen for extreme chloride resistance |
| UNS / Werkstoff / EN | UNS S31254, EN 1.4547, WNR 1.4547 |
| Main Plate Standards | ASTM B625 / ASME SB-625 Grade S31254 for plate, sheet and strip |
| Pitting Resistance (PREN) | Typically 40–43 (= Cr + 3.3×Mo + 16×N) |
| Price | INR 1,000 – 1,750 per kg. Indicative USD 12 – 21 per kg; quoted against grade, form, size and quantity. |
UNS & Equivalent Grades
| Property | Value |
|---|---|
| UNS number | S31254 |
| Werkstoff / EN number | 1.4547 |
| EN designation | X1CrNiMoCuN20-18-7 |
| Density | 8.00 g/cm3 |
| Modulus of elasticity | 195 GPa |
| Coefficient of expansion | 16.5 µm/m·°C |
| Thermal conductivity | 14 W/m·°C |
| Specific heat | 500 J/kg·°C |
| Electrical resistivity | 0.85 µΩ·m |
| Magnetic | no |
| Plate, sheet and strip specification | ASTM A240 |
Identifiers and physical constants for 254 SMO. A dash means no such designation is published for this grade.
Stock & Product Availability
As an SMO 254 Plates stockist, Aurico Alloys LLP supplies thicknesses ideal for seawater condensers, desalination tube sheets, chemical reactor linings, offshore pipe spools and structural plates serving chemical, oil & gas, marine, pharma and power applications within ASTM B625 dimensional ranges. Plates ship in solution-annealed condition (typically 1150°C water quenched) for maximum pitting resistance, with cut-to-size, plasma profiling and edge beveling services minimising fabrication costs while maintaining full PMI and heat traceability.
Chemical Composition
| Element | Min (%) | Max (%) |
|---|---|---|
| Carbon (C) | — | 0.020 |
| Silicon (Si) | — | 0.80 |
| Manganese (Mn) | — | 1.00 |
| Phosphorus (P) | — | 0.030 |
| Sulfur (S) | — | 0.010 |
| Chromium (Cr) | 19.5 | 20.5 |
| Molybdenum (Mo) | 6.0 | 6.5 |
| Nickel (Ni) | 17.5 | 18.5 |
| Copper (Cu) | 0.50 | 1.00 |
| Nitrogen (N) | 0.18 | 0.25 |
| Iron (Fe) | — | Balance |
Composition limits for 254 SMO. These are specification limits for the grade, not measured values for a lot; the mill test certificate supplied with your order states the actual analysis.
Mechanical & Physical Properties
| Property (Annealed Plate) | Typical Value – SMO 254 |
|---|---|
| Tensile Strength | ≥650 MPa min |
| Yield Strength (0.2%) | ≥310 MPa min |
| Elongation | ≥35% min |
| Hardness | ≤217 HB max |
| PREN | 40–43 typical |
| Seawater CCT | >80°C (vs 316L ~60°C) |
Applications & Benefits
- Chemical & Oil & Gas: SMO 254 plates excel in dilute sulfuric/phosphoric acid tanks, flue gas desulfurization, offshore manifolds where 6% Mo + N deliver 10× better pitting resistance than 316L in chloride-contaminated acids.
- Marine & Desalination: Seawater condensers, intake screens, desalination plant components where UNS S31254 maintains <0.1 mm/y corrosion in 35°C seawater vs 316L's 0.5–1 mm/y.
- Power Generation: FGD systems, wet stack gas scrubbers, coastal cooling water boxes where PREN 40+ prevents pitting failures common in 317L.
FAQ & Search Trends
Global Export Destinations
We ship worldwide from Mumbai. See every destination we export to on our export markets page.
Domestic Supply Network
We deliver across India from our Mumbai stockyard. See every city we supply on our supply locations page.
Conclusion
SMO 254 Plates from Aurico Alloys LLP, supplied to UNS S31254 / EN 1.4547 chemistry and ASTM B625 Grade requirements, give chemical, oil & gas, marine, pharma and power users a super austenitic solution with PREN 40+ pitting resistance and SCC immunity up to 80°C are your seawater condensers, FGD systems and coastal assets still risking 316L failures instead of proven SMO 254 protection?