Stainless Steel 254 SMO
UNS S31254 · ASTM A240/A312 · EN 1.4547, X1CrNiMoCuN20-18-7 · GB 022Cr20Ni18Mo6CuN, 015Cr20Ni18Mo6CuN
254 SMO (S31254, 1.4547) is a 6 % molybdenum superaustenitic stainless with nitrogen and copper additions, covered by A240/A312.
Values for the Solution Annealed condition
254 SMO tempers and conditions
254 SMO is supplied in 5 conditions, soft to hard. Solution Annealed is the default FabDigit quotes; the values on this page are for it.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Hot Finished + Solution Annealed | Heavy plate, forged flanges and thick bar; slightly lower strength than thin annealed product but same corrosion performance. | 330 | 680 | 45 | 180 HB | 2 % IACS |
Solution AnnealedDefault 1150–1200 °C, rapid quench (plate, sheet, bar, tube) | Standard supply condition for all product forms; maximum corrosion resistance and toughness. | 350 | 700 | 45 | 190 HB | — |
joint made with over-alloyed Ni-base filler (ERNiCrMo-3 / -4), no PWHT | Condition of fabricated vessels and piping; expect weld-metal properties governed by the Ni-base filler. | 400 | 700 | 35 | 205 HB | 2 % IACS |
Cold Rolled 1/4 Hard | Use for springy strip, gaskets and thin-gauge parts needing extra yield strength with some remaining ductility. | 600 | 860 | 25 | 26 HRC | 2 % IACS |
Cold drawn | Pick for higher-strength fasteners, shafts and pump parts where tight tolerance and bright finish are needed. | 620 | 850 | 25 | 25 HRC | 2 % IACS |
What is 254 SMO?
254 SMO (S31254, 1.4547) is a 6 % molybdenum superaustenitic stainless with nitrogen and copper additions, covered by A240/A312. It is used where 316L and 317L fail by chloride pitting or crevice corrosion, providing 350 MPa yield, 700 MPa tensile and 45 % elongation as solution-annealed plate and pipe, cold-drawn bar, quarter-hard cold-rolled sheet and hot-finished product. Cost and lead time are higher than 300-series austenitics, machining is slow, and service is limited to about 400 °C. AL-6XN (N08367) is the closest alternative. 254 SMO has a density of 8 g/cm³ (0.289 lb/in³), heavier than 92% of stainless steel grades. It melts at 1,325°C (2,417 °F). 254 SMO has a yield strength of 350 MPa (50.8 ksi) and a tensile strength of 700 MPa (102 ksi) — weaker than 52% of stainless steel grades. Elongation at break is 45% and the elastic modulus is 195 GPa (28.3 Msi).
What is 254 SMO used for?
- Seawater pipework and manifolds
- Offshore platform piping and tubing
- Flue-gas desulfurization scrubbers
- Heat exchanger plates and tubesheets
- Desalination evaporator components
- Chemical tanker cargo tanks
- Pulp bleaching equipment
Advantages
- Tough — resists crack growth — 220 MPa·√m (200.2 ksi·√in), better than 97% of stainless steel grades
- Good corrosion resistance — 86/100, better than 94% of stainless steel grades
- Polishes to a fine finish — 80/100, better than 89% of stainless steel grades
- Ductile — tolerates forming and impact — 45%, better than 76% of stainless steel grades
Limitations
- High embodied carbon — 6.5 kg CO₂/kg, worse than 93% of stainless steel grades
- Difficult to machine — 25/100, worse than 88% of stainless steel grades
- Limited service temperature — 400°C (752 °F), worse than 78% of stainless steel grades
- Low electrical conductivity — 2 % IACS, worse than 77% of stainless steel grades
254 SMO properties
Typical room-temperature values for 254 SMO-Solution Annealed; bars are the position among stainless steel grades.
Physical3
254 SMO has a density of 8 g/cm³ (0.289 lb/in³), heavier than 92% of stainless steel grades. It melts at 1,325°C (2,417 °F).
Mechanical16
254 SMO has a yield strength of 350 MPa (50.8 ksi) and a tensile strength of 700 MPa (102 ksi) — weaker than 52% of stainless steel grades. Elongation at break is 45% and the elastic modulus is 195 GPa (28.3 Msi).
Thermal6
254 SMO is rated for continuous service to 400°C (752 °F). It conducts heat at 14 W/m·K (8.09 BTU/hr·ft·°F), worse than 80% of stainless steel grades. Thermal expansion is 16.5 µm/m·K (9.17 µin/in·°F).
Electrical3
254 SMO conducts electricity at 2 % IACS, worse than 77% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is excellent (86/100), better than 94% of stainless steel grades.
Sustainability4
Producing a kilogram of 254 SMO takes about 85 MJ of energy and emits 6.5 kg of CO₂ — more than 92% of stainless steel grades. Typical recycled content is 45%.
Manufacturability8
254 SMO's machinability is poor (25/100, worse than 88% of stainless steel grades); weldability very good (75/100); formability good (60/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the stainless steel family
Yield strength against density for every stainless steel grade FabDigit runs. 254 SMO is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 254 SMO
Is 254 SMO easy to machine?
Machine like a nickel alloy: rigid setup, sharp positive-rake carbide, low speed with heavy positive feed, flood coolant, and never dwell — the surface work-hardens instantly.
Can 254 SMO be welded?
Weld with over-alloyed Ni-base filler (ERNiCrMo-3/625 or ERNiCrMo-4/C-276), low heat input, interpass < 100 °C, argon backing; no preheat or PWHT, and pickle/passivate the heat tint.
Can 254 SMO be formed, bent or molded?
Cold forms well but needs ~50 % more press force than 316L and generous springback allowance; hot work 1150–1200 °C followed by mandatory solution anneal and quench.
Manufacturability
The process limits FabDigit applies to 254 SMO. Every 254 SMO part is priced by an engineer; design inside these and the quote comes back without a redesign loop.
CNC machining
| Machinability | Poor25 / 100 |
|---|---|
| ISO material group | M.1 |
| Cutting speed (rough / finish) | 150 / 180 m/min |
| Minimum wall | 0.8 mm |
| Minimum internal radius | 1.5 mm |
| Drill depth limit | 4× diameter |
| Best surface (machined / polished) | Ra 1.6 / — |
| Hardenable after machining | No |
Sheet metal
| Formability | Better60 / 100 |
|---|---|
| Weldability | Better75 / 100 |
| Bendable | Yes |
254 SMO chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Clow carbon for intergranular resistance | ≤ 0.02 | 0.01 |
| Si | ≤ 0.8 | 0.4 |
| Mn | ≤ 1 | 0.6 |
| P | ≤ 0.03 | 0.02 |
| S | ≤ 0.01 | 0 |
| Cr | 19.5 – 20.5 | 20 |
| Ni | 17.5 – 18.5 | 18 |
| Mo | 6 – 6.5 | 6.2 |
| Cu | 0.5 – 1 | 0.7 |
| N | 0.18 – 0.22 | 0.2 |
| Febalance, ~54 % | balance |
What surface finishes work on 254 SMO?
Pickle in HNO₃–HF or electropolish to restore the passive film; mechanical polish to Ra < 0.5 µm gives best crevice performance — do not use carbon-steel-contaminated abrasives.
Surface treatments FabDigit runs on stainless steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Plating
Organic Coating
CVD Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Stainless Steel 254 SMO in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
How much does 254 SMO cost?
254 SMO is a premium-cost stainless steel ($$$), cheaper than about 58% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
254 SMO — frequently asked
What is 254 SMO used for?
254 SMO is typically used for seawater pipework and manifolds, offshore platform piping and tubing, flue-gas desulfurization scrubbers, heat exchanger plates and tubesheets, desalination evaporator components and chemical tanker cargo tanks. In short: pitting-resistant super-austenitic.
What is the yield strength of 254 SMO?
254 SMO has a typical yield strength of 350 MPa (50.8 ksi) and a tensile strength of 700 MPa (102 ksi) — weaker than 52% of stainless steel grades. Strength varies by condition: see the 5 listed tempers.
Is 254 SMO easy to machine?
Not especially — machinability is rated poor (25/100, worse than 88% of stainless steel grades). Machine like a nickel alloy: rigid setup, sharp positive-rake carbide, low speed with heavy positive feed, flood coolant, and never dwell — the surface work-hardens instantly.
Can 254 SMO be welded?
Yes — weldability is rated very good (75/100). Weld with over-alloyed Ni-base filler (ERNiCrMo-3/625 or ERNiCrMo-4/C-276), low heat input, interpass < 100 °C, argon backing; no preheat or PWHT, and pickle/passivate the heat tint.
What surface finishes work on 254 SMO?
Pickle in HNO₃–HF or electropolish to restore the passive film; mechanical polish to Ra < 0.5 µm gives best crevice performance — do not use carbon-steel-contaminated abrasives.
Can 254 SMO be formed, bent or molded?
Cold forms well but needs ~50 % more press force than 316L and generous springback allowance; hot work 1150–1200 °C followed by mandatory solution anneal and quench.
What is the maximum service temperature of 254 SMO?
254 SMO is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 254 SMO Solution Annealed and 254 SMO-CD?
Solution Annealed is the default condition — standard supply condition for all product forms; maximum corrosion resistance and toughness. CD: pick for higher-strength fasteners, shafts and pump parts where tight tolerance and bright finish are needed. Yield strength is 350 MPa in Solution Annealed versus 620 MPa in CD.
How much does 254 SMO cost?
254 SMO is a premium-cost stainless steel ($$$), cheaper than about 58% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Can FabDigit make parts in 254 SMO?
Yes — 254 SMO is available for CNC machining and sheet metal; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- ASTM A240/A240M — Chromium and Chromium-Nickel Stainless Steel Plate, Sheet and Strip (S31254) — ASTM International (2023)
- ASTM A182/A182M — Forged Fittings and Flanges (Grade F44) — ASTM International (2022)
- EN 10088-2 — Stainless steels, sheet/plate (1.4547) — CEN (2014)
- 254 SMO / Outokumpu Ultra 254 SMO alloy datasheet — Outokumpu (2022)
- Sandvik SANICRO 28 / 254 SMO-class 6Mo austenitic tube data — Alleima (Sandvik Materials Technology) (2021)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.