Stainless Steel 255
AISI/SAE 255 · UNS S32550 · EN 1.4507, X2CrNiMoCuN25-6-3 · also Ferralium 255
255 (Ferralium 255, S32550, 1.4507) is a copper-bearing super duplex stainless — a 25Cr-6Ni-3Mo ferritic-austenitic grade with nitrogen and copper additions.
Values for the Solution Annealed condition
255 tempers and conditions
255 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 |
|---|---|---|---|---|---|---|
Cast + Solution Annealed | Cast counterpart of 255 for seawater pump casings and impellers; lower strength and ductility than wrought product but same alloy chemistry family. | 550 | 760 | 20 | 23 HRC | 2.2 % IACS |
Forged + Solution Annealed | Condition for valve bodies, flanges and heavy forged components; heavy sections give slightly lower typical strength and toughness than thin plate. | 580 | 800 | 25 | 26 HRC | 2.2 % IACS |
Solution AnnealedDefault 1040–1120 °C, water quenched | Standard stocked condition for plate, hot-finished bar, forgings, pipe and fittings; balanced 50/50 ferrite–austenite with best corrosion resistance and toughness. | 610 | 830 | 28 | 27 HRC | — |
Ferralium 255-SD50 | Proprietary high-nitrogen variant used when 80 ksi (550 MPa) minimum yield must be guaranteed in heavy sections and forgings, with PREN at the top of the S32550 range. | 660 | 880 | 25 | 29 HRC | 2.2 % IACS |
Solution Annealed + Cold Worked | Pick for small-diameter bar, shafting and fasteners needing higher strength and tighter tolerance; ductility and toughness are reduced. | 760 | 950 | 20 | 32 HRC | — |
What is 255?
255 (Ferralium 255, S32550, 1.4507) is a copper-bearing super duplex stainless — a 25Cr-6Ni-3Mo ferritic-austenitic grade with nitrogen and copper additions. Engineers select it for 610 MPa yield, 830 MPa tensile and 28 % elongation combined with pitting and crevice resistance in chloride and seawater service; it is supplied as plate, bar, forgings and castings in solution-annealed, cold-worked (SA+CW, SD50), forged and cast conditions. Service is capped near 300 °C to avoid sigma-phase and 475 °C embrittlement, machinability is low (score 25) and cold forming needs high press loads. Zeron 100 (S32760) is the closest alternative. 255 has a density of 7.81 g/cm³ (0.282 lb/in³), heavier than 57% of stainless steel grades. It melts at 1,400°C (2,552 °F). 255 has a yield strength of 610 MPa (88.5 ksi) and a tensile strength of 830 MPa (120 ksi) — stronger than 87% of stainless steel grades. Elongation at break is 28% and the elastic modulus is 205 GPa (29.7 Msi).
What is 255 used for?
- Subsea oil and gas manifolds
- FPSO seawater pipework
- Valve bodies and stems
- Pump casings and impellers
- Marine propeller and pump shafts
- Offshore flanges and fasteners
- Desalination plant components
Advantages
- Good corrosion resistance — 85/100, better than 92% of stainless steel grades
- High strength — 610 MPa (88.5 ksi), better than 87% of stainless steel grades
Limitations
- Limited service temperature — 300°C (572 °F), worse than 90% of stainless steel grades
- Difficult to machine — 25/100, worse than 88% of stainless steel grades
- High embodied carbon — 5.6 kg CO₂/kg, worse than 83% of stainless steel grades
255 properties
Typical room-temperature values for 255-Solution Annealed; bars are the position among stainless steel grades.
Physical3
255 has a density of 7.81 g/cm³ (0.282 lb/in³), heavier than 57% of stainless steel grades. It melts at 1,400°C (2,552 °F).
Mechanical16
255 has a yield strength of 610 MPa (88.5 ksi) and a tensile strength of 830 MPa (120 ksi) — stronger than 87% of stainless steel grades. Elongation at break is 28% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal5
255 is rated for continuous service to 300°C (572 °F). It conducts heat at 13.5 W/m·K (7.8 BTU/hr·ft·°F), worse than 83% of stainless steel grades. Thermal expansion is 13 µm/m·K (7.22 µin/in·°F).
Electrical3
255 conducts electricity at 2.2 % IACS, worse than 61% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is excellent (85/100), better than 92% of stainless steel grades.
Sustainability4
Producing a kilogram of 255 takes about 85 MJ of energy and emits 5.6 kg of CO₂ — more than 92% of stainless steel grades. Typical recycled content is 50%.
Manufacturability8
255's machinability is poor (25/100, worse than 88% of stainless steel grades); weldability very good (70/100); formability fair (40/100).
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. 255 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 255
Is 255 easy to machine?
Machine like a super duplex: rigid setup, 30–50 % of 316 cutting speed, heavy positive feed to cut under the work-hardened layer, sharp coated carbide and flood coolant.
Can 255 be welded?
Weldable by GTAW/GMAW/SMAW with 25.10.4.L or Ferralium 255 matching filler; keep interpass below ~150 °C, heat input roughly 0.5–1.5 kJ/mm, Ar+2 %N₂ backing, and no post-weld stress relief below 1040 °C.
Can 255 be formed, bent or molded?
Cold forming needs ~2× the press force of 304 with generous bend radii and springback allowance; hot working at 1000–1150 °C followed by full solution anneal and quench.
Manufacturability
The process limits FabDigit applies to 255. Every 255 part is priced by an engineer; design inside these and the quote comes back without a redesign loop.
CNC machining
| Machinability | Fair25 / 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 | Fair40 / 100 |
|---|---|
| Weldability | Better70 / 100 |
| Bendable | Yes |
255 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 |
|---|---|---|
| C | ≤ 0.04 | 0.03 |
| Si | ≤ 1 | 0.5 |
| Mn | ≤ 1.5 | 0.8 |
| P | ≤ 0.04 | |
| S | ≤ 0.03 | |
| Cr | 24 – 27 | 25.5 |
| Ni | 4.5 – 6.5 | 5.7 |
| Mo | 2.9 – 3.9 | 3.4 |
| Cuimproves resistance in reducing acids | 1.5 – 2.5 | 2 |
| Nupper end for SD50 high-strength variant | 0.1 – 0.25 | 0.2 |
| Fe | balance |
What surface finishes work on 255?
Pickle and passivate or electropolish after welding to restore the passive film; not anodizable, and grinding must avoid embedding carbon-steel contamination.
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 255 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- S32550
- EN / DIN / Werkstoff-Nr.
- 1.4507X2CrNiMoCuN25-6-3
- Trade names
- Ferralium 255
- Also called
- Ferralium255
How much does 255 cost?
255 is a premium-cost stainless steel ($$$), cheaper than about 51% 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.
255 — frequently asked
What is 255 used for?
255 is typically used for subsea oil and gas manifolds, FPSO seawater pipework, valve bodies and stems, pump casings and impellers, marine propeller and pump shafts and offshore flanges and fasteners. In short: premium duplex stainless plate.
What is the yield strength of 255?
255 has a typical yield strength of 610 MPa (88.5 ksi) and a tensile strength of 830 MPa (120 ksi) — stronger than 87% of stainless steel grades. Strength varies by condition: see the 5 listed tempers.
Is 255 easy to machine?
Not especially — machinability is rated poor (25/100, worse than 88% of stainless steel grades). Machine like a super duplex: rigid setup, 30–50 % of 316 cutting speed, heavy positive feed to cut under the work-hardened layer, sharp coated carbide and flood coolant.
Can 255 be welded?
Yes — weldability is rated very good (70/100). Weldable by GTAW/GMAW/SMAW with 25.10.4.L or Ferralium 255 matching filler; keep interpass below ~150 °C, heat input roughly 0.5–1.5 kJ/mm, Ar+2 %N₂ backing, and no post-weld stress relief below 1040 °C.
What surface finishes work on 255?
Pickle and passivate or electropolish after welding to restore the passive film; not anodizable, and grinding must avoid embedding carbon-steel contamination.
Can 255 be formed, bent or molded?
Cold forming needs ~2× the press force of 304 with generous bend radii and springback allowance; hot working at 1000–1150 °C followed by full solution anneal and quench.
What is the maximum service temperature of 255?
255 is rated for continuous use to about 300°C (572 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 255 Solution Annealed and 255-SD50?
Solution Annealed is the default condition — standard stocked condition for plate, hot-finished bar, forgings, pipe and fittings; balanced 50/50 ferrite–austenite with best corrosion resistance and toughness. SD50: proprietary high-nitrogen variant used when 80 ksi (550 MPa) minimum yield must be guaranteed in heavy sections and forgings, with PREN at the top of the S32550 range. Yield strength is 610 MPa in Solution Annealed versus 660 MPa in SD50.
How much does 255 cost?
255 is a premium-cost stainless steel ($$$), cheaper than about 51% 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 255?
Yes — 255 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 (S32550) — ASTM International (2023)
- ASTM A479/A479M — Stainless Steel Bars and Shapes for Boilers and Pressure Vessels — ASTM International (2021)
- ASTM A182/A182M — Forged or Rolled Alloy and Stainless Steel Pipe Flanges and Fittings (F61) — ASTM International (2022)
- ASTM A890/A995 — Castings, Iron-Chromium-Nickel-Molybdenum (Grade 1B, CD4MCuN) — ASTM International (2020)
- EN 10088-2/-3 — Stainless steels, grade 1.4507 (X2CrNiMoCuN25-6-3) — CEN (2014)
- Ferralium alloy 255 / 255-SD50 technical datasheet — Langley Alloys / Meighs (2022)
- ASM Handbook Vol.13B — Corrosion: Materials (duplex stainless steels) — ASM International (2005)
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.