Stainless Steel 654 SMO
UNS S32654 · ASTM A240/A312 · EN 1.4652, X1CrNiMoCuN24-22-8
Ultra-high-alloyed superaustenitic stainless with roughly 7.3% Mo and high nitrogen, delivering one of the highest pitting resistance equivalent numbers among wrought stainless steels for extreme chloride environments.
Reference datasheet — 654 SMO is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the SA condition
654 SMO tempers and conditions
654 SMO is supplied in 6 conditions, soft to hard. SA is the default FabDigit quotes; the values on this page are for it.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
hot finished (rolled/forged) and solution annealed bar & billet | Choose for heavy-section bar, flanges and valve bodies where cold drawing is impractical. | 460 | 790 | 45 | 210 HB | 2 % IACS |
Forged + SA | For forged fittings and pressure parts per ASTM A182 grade S32654 requirements. | 470 | 800 | 45 | 215 HB | 2 % IACS |
SADefault Solution annealed (≈1150–1200 °C, water quenched), plate/sheet/tube | Standard supply condition for plate, sheet, welded/seamless tube and fittings — maximum corrosion resistance and toughness. | 490 | 820 | 50 | 220 HB | — |
Cold drawn | Bright, close-tolerance bar with raised yield strength for shafts and fasteners; slightly reduced ductility. | 650 | 900 | 30 | 26 HRC | 2 % IACS |
Cold Worked 1/4 Hard | Use where higher yield strength is needed in thin strip, spring washers or cold-worked tubing. | 720 | 950 | 25 | 30 HRC | 2 % IACS |
Cold Worked 1/2 Hard | Highest-strength cold-worked condition; for wire, springs and high-load thin sections at the cost of ductility. | 900 | 1,100 | 15 | 35 HRC | 2 % IACS |
What is 654 SMO?
Ultra-high-alloyed superaustenitic stainless with roughly 7.3% Mo and high nitrogen, delivering one of the highest pitting resistance equivalent numbers among wrought stainless steels for extreme chloride environments. 654 SMO has a density of 8 g/cm³ (0.289 lb/in³), heavier than 92% of stainless steel grades. It melts at 1,320°C (2,408 °F). 654 SMO has a yield strength of 490 MPa (71.1 ksi) and a tensile strength of 820 MPa (119 ksi) — stronger than 76% of stainless steel grades. Elongation at break is 50% and the elastic modulus is 190 GPa (27.6 Msi).
What is 654 SMO used for?
- seawater desalination
- flue gas desulfurization scrubbers
- bleach plant equipment
- offshore and subsea components
Advantages
- Good corrosion resistance — 93/100, better than 100% of stainless steel grades
- Ductile — tolerates forming and impact — 50%, better than 90% of stainless steel grades
- Polishes to a fine finish — 80/100, better than 89% of stainless steel grades
- High strength — 490 MPa (71.1 ksi), better than 76% of stainless steel grades
Limitations
- Poor heat conductor — 8.6 W/m·K (4.97 BTU/hr·ft·°F), worse than 100% of stainless steel grades
- Difficult to machine — 18/100, worse than 99% of stainless steel grades
- High embodied carbon — 6.5 kg CO₂/kg, worse than 93% 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
654 SMO properties
Typical room-temperature values for 654 SMO-SA; bars are the position among stainless steel grades.
Physical3
654 SMO has a density of 8 g/cm³ (0.289 lb/in³), heavier than 92% of stainless steel grades. It melts at 1,320°C (2,408 °F).
Mechanical14
654 SMO has a yield strength of 490 MPa (71.1 ksi) and a tensile strength of 820 MPa (119 ksi) — stronger than 76% of stainless steel grades. Elongation at break is 50% and the elastic modulus is 190 GPa (27.6 Msi).
Thermal6
654 SMO is rated for continuous service to 400°C (752 °F). It conducts heat at 8.6 W/m·K (4.97 BTU/hr·ft·°F), worse than 100% of stainless steel grades. Thermal expansion is 15.5 µm/m·K (8.61 µin/in·°F).
Electrical3
654 SMO conducts electricity at 2 % IACS, worse than 77% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is excellent (93/100), better than 100% of stainless steel grades.
Sustainability4
Producing a kilogram of 654 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 40%.
Manufacturability7
654 SMO's machinability is poor (18/100, worse than 99% of stainless steel grades); weldability good (60/100); formability good (55/100).
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. 654 SMO is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 654 SMO
Is 654 SMO easy to machine?
Treat like a nickel alloy: rigid setup, sharp coated carbide, low speed (~15–25 m/min) with heavy positive feed, flood coolant and no dwelling — the high-N austenite work hardens extremely fast.
Can 654 SMO be welded?
GTAW/GMAW/SMAW with over-alloyed Ni-base filler (ERNiCrMo-3/-13 or Alloy 59) to avoid Mo segregation; low heat input, interpass < 100 °C, no preheat, no post-weld heat treatment except full re-solution when possible.
Can 654 SMO be formed, bent or molded?
Cold forms well but needs ~2× the press force of 316L and generous springback allowance; hot work 1150–1200 °C and finish above 1000 °C, then always solution anneal and quench.
654 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 weldability | ≤ 0.02 | 0.01 |
| Si | ≤ 0.5 | 0.3 |
| Mnaids N solubility | 2 – 4 | 3 |
| P | ≤ 0.03 | 0.02 |
| S | ≤ 0.01 | 0 |
| Cr | 24 – 25 | 24.5 |
| Ni | 21 – 23 | 22 |
| Mokey to PREN ≈ 54–56 | 7 – 8 | 7.3 |
| Cu | 0.3 – 0.6 | 0.45 |
| Nstrengthening + pitting resistance | 0.45 – 0.55 | 0.5 |
| Fe | balance |
What surface finishes work on 654 SMO?
Pickle in HNO3–HF or bead blast + passivate after welding to restore the chromium/molybdenum oxide film; electropolishing gives the best crevice/pitting performance in seawater service.
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).
Passivation
Organic Coating
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Stainless Steel 654 SMO in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- S32654
- ASTM
- A240/A312
- EN / DIN / Werkstoff-Nr.
- 1.4652X1CrNiMoCuN24-22-8
How much does 654 SMO cost?
654 SMO is a high-cost stainless steel ($$$$), pricier than about 78% 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.
654 SMO — frequently asked
What is 654 SMO used for?
654 SMO is typically used for seawater desalination, flue gas desulfurization scrubbers, bleach plant equipment and offshore and subsea components. In short: highest-PREN wrought stainless; nickel-alloy chloride resistance; costlier than 254 SMO.
What is the yield strength of 654 SMO?
654 SMO has a typical yield strength of 490 MPa (71.1 ksi) and a tensile strength of 820 MPa (119 ksi) — stronger than 76% of stainless steel grades. Strength varies by condition: see the 6 listed tempers.
Is 654 SMO easy to machine?
Not especially — machinability is rated poor (18/100, worse than 99% of stainless steel grades). Treat like a nickel alloy: rigid setup, sharp coated carbide, low speed (~15–25 m/min) with heavy positive feed, flood coolant and no dwelling — the high-N austenite work hardens extremely fast.
Can 654 SMO be welded?
Yes — weldability is rated good (60/100). GTAW/GMAW/SMAW with over-alloyed Ni-base filler (ERNiCrMo-3/-13 or Alloy 59) to avoid Mo segregation; low heat input, interpass < 100 °C, no preheat, no post-weld heat treatment except full re-solution when possible.
What surface finishes work on 654 SMO?
Pickle in HNO3–HF or bead blast + passivate after welding to restore the chromium/molybdenum oxide film; electropolishing gives the best crevice/pitting performance in seawater service.
Can 654 SMO be formed, bent or molded?
Cold forms well but needs ~2× the press force of 316L and generous springback allowance; hot work 1150–1200 °C and finish above 1000 °C, then always solution anneal and quench.
What is the maximum service temperature of 654 SMO?
654 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 654 SMO-SA and 654 SMO-CD?
SA is the default condition — standard supply condition for plate, sheet, welded/seamless tube and fittings — maximum corrosion resistance and toughness. CD: bright, close-tolerance bar with raised yield strength for shafts and fasteners; slightly reduced ductility. Yield strength is 490 MPa in SA versus 650 MPa in CD.
How much does 654 SMO cost?
654 SMO is a high-cost stainless steel ($$$$), pricier than about 78% 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.
Sources
- ASTM A240/A240M — Chromium and Chromium-Nickel Stainless Steel Plate, Sheet and Strip (UNS S32654) — ASTM International (2023)
- ASTM A312/A312M — Seamless and Welded Austenitic Stainless Steel Pipes — ASTM International (2022)
- EN 10088-2 — Stainless steels, grade 1.4652 (X1CrNiMoCuN24-22-8) — CEN (2014)
- 654 SMO (EN 1.4652) data sheet — Outokumpu (2022)
- 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.