Stainless Steel 1.4557-AC (Spheroidize annealed)
Heat-treated state
EN 1.4557 · UNS J93254 · ASTM A351 CK3MCuN
Intermediate/rough-machining condition only — interdendritic Mo segregation and sigma/chi phase sharply reduce ductility and pitting resistance; never use in corrosive service.
Values for the AC condition
Other 1.4557 tempers and conditions
1.4557 is listed in 4 conditions; see the grade overview at 1.4557.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
SADefault Solution annealed ~1150–1200 °C, water quenched | Standard supply condition for all A351/EN 10283 CK3MCuN castings; required to dissolve Mo-rich segregation and sigma/chi phases before service. | 295 | 600 | 45 | 175 HB | — |
ACThis page Spheroidize annealed | Intermediate/rough-machining condition only — interdendritic Mo segregation and sigma/chi phase sharply reduce ductility and pitting resistance; never use in corrosive service. | 300 | 540 | 18 | 200 HB | 2 % IACS |
Hot isostatically pressed then solution annealed and quenched | Choose for pressure-retaining or high-cycle parts where shrinkage porosity must be closed — best ductility, toughness and NDT/radiographic quality. | 305 | 620 | 50 | 180 HB | 2 % IACS |
Centrifugally cast, solution annealed | Pick for seawater and FGD piping/sleeves — directional solidification gives a finer, denser wall than static castings. | 310 | 620 | 40 | 180 HB | 2 % IACS |
What is 1.4557-AC?
1.4557-AC is 1.4557 heat treated to AC — intermediate/rough-machining condition only — interdendritic Mo segregation and sigma/chi phase sharply reduce ductility and pitting resistance; never use in corrosive service. 1.4557-AC has a yield strength of 300 MPa (43.5 ksi) and a tensile strength of 540 MPa (78.3 ksi) — weaker than 68% of stainless steel grades. Elongation at break is 18% and the elastic modulus is 193 GPa (28 Msi). 1.4557-AC 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). SA is the default condition FabDigit quotes; AC is available on request or by drawing note.
Limitations
- Difficult to machine — 18/100, worse than 99% of stainless steel grades
- Limited formability — 12/100, worse than 93% of stainless steel grades
- High embodied carbon — 6.5 kg CO₂/kg, worse than 93% of stainless steel grades
- Limited service temperature — 300°C (572 °F), worse than 90% of stainless steel grades
- Poor heat conductor — 13 W/m·K (7.51 BTU/hr·ft·°F), worse than 85% of stainless steel grades
1.4557-AC properties
Typical room-temperature values for 1.4557-AC; 23 are specific to this condition. Other listed values are 1.4557 reference data and may not represent this condition. Bars are the position among stainless steel grades.
Physical3
1.4557-AC 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
1.4557-AC has a yield strength of 300 MPa (43.5 ksi) and a tensile strength of 540 MPa (78.3 ksi) — weaker than 68% of stainless steel grades. Elongation at break is 18% and the elastic modulus is 193 GPa (28 Msi).
Thermal6
1.4557-AC is rated for continuous service to 300°C (572 °F). It conducts heat at 13 W/m·K (7.51 BTU/hr·ft·°F), worse than 85% of stainless steel grades. Thermal expansion is 16.5 µm/m·K (9.17 µin/in·°F).
Electrical3
1.4557-AC conducts electricity at 2 % IACS, worse than 77% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is good (60/100), worse than 58% of stainless steel grades.
Sustainability4
Producing a kilogram of 1.4557-AC takes about 90 MJ of energy and emits 6.5 kg of CO₂ — more than 94% of stainless steel grades. Typical recycled content is 50%.
Manufacturability8
1.4557-AC's machinability is poor (18/100, worse than 99% of stainless steel grades); weldability fair (45/100); formability not recommended (12/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 1.4557-AC
Is 1.4557 easy to machine?
Tough, gummy and strongly work-hardening — use rigid setups, positive-rake coated carbide, heavy feed with low-to-moderate speed (~30–60 m/min), plenty of high-pressure coolant, and never dwell in the cut.
Can 1.4557 be welded?
Weld with over-alloyed Ni-base fillers (ERNiCrMo-3/-4 or ENiCrMo-3), low heat input, interpass <150 °C, no preheat; autogenous or matching-filler welds lose pitting resistance and generally need re-solution treatment.
Can 1.4557 be formed, bent or molded?
Foundry grade: wide freezing range means generous feeding, chills and risers; solution anneal at 1150–1200 °C with rapid water quench is mandatory to dissolve sigma/chi and restore corrosion performance.
What surface finishes work on 1.4557?
Pickle (HNO₃-HF) and passivate per ASTM A967 or electropolish after all welding/grinding; avoid iron contamination from carbon-steel tooling and blasting media.
1.4557 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 |
|---|---|---|
| CEN 10283 allows ≤0.03 | ≤ 0.03 | 0.02 |
| Si | ≤ 1 | 0.6 |
| Mn | ≤ 1.2 | 0.8 |
| P | ≤ 0.05 | — |
| S | ≤ 0.01 | — |
| CrEN: 19.0–21.0 | 19.5 – 20.5 | 20 |
| Ni | 17.5 – 19.5 | 18.5 |
| Mo | 6 – 7 | 6.5 |
| Cu | 0.5 – 1 | 0.7 |
| NEN: 0.15–0.25 | 0.18 – 0.24 | 0.21 |
| Fe | balance | — |
1.4557-AC — frequently asked
What is 1.4557-AC used for?
1.4557-AC is typically used for seawater pump casings, desalination equipment and offshore valve bodies. In short: cast 254SMO equivalent; top chloride pitting resistance; hardest grade to machine.
What is the yield strength of 1.4557-AC?
1.4557-AC has a typical yield strength of 300 MPa (43.5 ksi) and a tensile strength of 540 MPa (78.3 ksi) — weaker than 68% of stainless steel grades. Strength varies by condition: see the 4 listed tempers.
Is 1.4557-AC easy to machine?
Not especially — machinability is rated poor (18/100, worse than 99% of stainless steel grades). Tough, gummy and strongly work-hardening — use rigid setups, positive-rake coated carbide, heavy feed with low-to-moderate speed (~30–60 m/min), plenty of high-pressure coolant, and never dwell in the cut.
Can 1.4557-AC be welded?
With care — weldability is rated fair (45/100). Weld with over-alloyed Ni-base fillers (ERNiCrMo-3/-4 or ENiCrMo-3), low heat input, interpass <150 °C, no preheat; autogenous or matching-filler welds lose pitting resistance and generally need re-solution treatment.
What surface finishes work on 1.4557-AC?
Pickle (HNO₃-HF) and passivate per ASTM A967 or electropolish after all welding/grinding; avoid iron contamination from carbon-steel tooling and blasting media.
Can 1.4557-AC be formed, bent or molded?
Foundry grade: wide freezing range means generous feeding, chills and risers; solution anneal at 1150–1200 °C with rapid water quench is mandatory to dissolve sigma/chi and restore corrosion performance.
What is the maximum service temperature of 1.4557-AC?
1.4557-AC 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 1.4557-SA and 1.4557 CENT-SA?
SA is the default condition — standard supply condition for all A351/EN 10283 CK3MCuN castings; required to dissolve Mo-rich segregation and sigma/chi phases before service. CENT-SA: pick for seawater and FGD piping/sleeves — directional solidification gives a finer, denser wall than static castings. Yield strength is 295 MPa in SA versus 310 MPa in CENT-SA.
Sources
- ASTM A351/A351M — Castings, Austenitic, for Pressure-Containing Parts (CK3MCuN) — ASTM International (2023)
- ASTM A743/A744 — Corrosion-Resistant Iron-Chromium-Nickel Castings — ASTM International (2021)
- EN 10283 — Corrosion resistant steel castings (GX2CrNiMoCuN20-18-6, 1.4557) — CEN (2019)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- 254 SMO / 6Mo austenitic stainless steel data sheet (physical & corrosion data for equivalent composition) — Outokumpu / Sandvik (2022)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.