Stainless Steel CD6MN-AC (Spheroidize annealed)
Heat-treated state
ASTM CD6MN · UNS J93371
Only for non-critical wear or structural parts; sigma/nitride precipitation leaves low toughness and degraded pitting resistance.
Values for the AC condition
Other CD6MN tempers and conditions
CD6MN is listed in 5 conditions; see the grade overview at CD6MN.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ACThis page Spheroidize annealed | Only for non-critical wear or structural parts; sigma/nitride precipitation leaves low toughness and degraded pitting resistance. | 500 | 690 | 12 | 24 HRC | 2.2 % IACS |
Weld repaired, then re-solution annealed and quenched | Standard route for foundry-repaired castings; full re-anneal after major repairs restores phase balance in the weld and HAZ. | 515 | 710 | 28 | 21 HRC | 2.2 % IACS |
SADefault Solution annealed ≥1120 °C and water quenched | The only condition permitted for pressure-retaining service; restores 40–55 % ferrite balance and dissolves sigma/nitrides. | 520 | 720 | 32 | 21 HRC | — |
Hot isostatically pressed, then solution annealed and quenched | Choose for thick-section pump/valve castings needing closed microporosity, higher ductility and better NDE/radiographic acceptance. | 540 | 750 | 36 | 22 HRC | 2.2 % IACS |
Centrifugally cast (ASTM A872 class), solution annealed and quenched | For seamless duplex tubulars and rings; directional solidification gives cleaner, finer structure and slightly higher strength than static castings. | 550 | 760 | 30 | 23 HRC | 2.2 % IACS |
What is CD6MN-AC?
CD6MN-AC is CD6MN heat treated to AC — only for non-critical wear or structural parts; sigma/nitride precipitation leaves low toughness and degraded pitting resistance. CD6MN-AC has a yield strength of 500 MPa (72.5 ksi) and a tensile strength of 690 MPa (100 ksi) — stronger than 77% of stainless steel grades. Elongation at break is 12% and the elastic modulus is 195 GPa (28.3 Msi). CD6MN-AC has a density of 7.8 g/cm³ (0.282 lb/in³), heavier than 50% of stainless steel grades. It melts at 1,400°C (2,552 °F). SA is the default condition FabDigit quotes; AC is available on request or by drawing note.
Advantages
- High strength — 500 MPa (72.5 ksi), better than 77% of stainless steel grades
Limitations
- Limited service temperature — 250°C (482 °F), worse than 99% of stainless steel grades
- Limited ductility — 12%, worse than 95% of stainless steel grades
- Difficult to machine — 24/100, worse than 93% of stainless steel grades
- Limited formability — 12/100, worse than 93% of stainless steel grades
- Low fracture toughness — 60 MPa·√m (54.6 ksi·√in), worse than 88% of stainless steel grades
CD6MN-AC properties
Typical room-temperature values for CD6MN-AC; 23 are specific to this condition. Other listed values are CD6MN reference data and may not represent this condition. Bars are the position among stainless steel grades.
Physical3
CD6MN-AC has a density of 7.8 g/cm³ (0.282 lb/in³), heavier than 50% of stainless steel grades. It melts at 1,400°C (2,552 °F).
Mechanical17
CD6MN-AC has a yield strength of 500 MPa (72.5 ksi) and a tensile strength of 690 MPa (100 ksi) — stronger than 77% of stainless steel grades. Elongation at break is 12% and the elastic modulus is 195 GPa (28.3 Msi).
Thermal6
CD6MN-AC is rated for continuous service to 250°C (482 °F). It conducts heat at 16 W/m·K (9.24 BTU/hr·ft·°F), better than 58% of stainless steel grades. Thermal expansion is 12.8 µm/m·K (7.11 µin/in·°F).
Electrical3
CD6MN-AC conducts electricity at 2.2 % IACS, worse than 61% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is good (58/100), worse than 62% of stainless steel grades.
Sustainability4
Producing a kilogram of CD6MN-AC takes about 53 MJ of energy and emits 4.5 kg of CO₂ — less than 67% of stainless steel grades. Typical recycled content is 80%.
Manufacturability8
CD6MN-AC's machinability is poor (24/100, worse than 93% of stainless steel grades); weldability fair (50/100); formability not recommended (12/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with CD6MN-AC
Is CD6MN easy to machine?
Work-hardens rapidly and is abrasive — use rigid setups, sharp coated carbide, low speed (~60–90 m/min) with heavy positive feed and flood coolant; avoid dwelling.
Can CD6MN be welded?
GTAW/GMAW/SMAW with 25-9-4 (E2595/ER2594) or matching over-alloyed filler, interpass ≤150 °C, moderate heat input 0.5–2.0 kJ/mm, no preheat, no post-weld temper — re-solution anneal after major repairs.
Can CD6MN be formed, bent or molded?
Sand or centrifugal cast with generous risering; solidification range and 2.0–2.2 % shrinkage require good feeding, then mandatory ≥1120 °C solution anneal with rapid water quench.
What surface finishes work on CD6MN?
Grit blast, pickle in HNO₃-HF and passivate per ASTM A967; polish to Ra ≤0.8 µm for maximum pitting resistance — no anodizing, and keep free of embedded carbon-steel iron.
CD6MN 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 to limit carbide precipitation | ≤ 0.06 | 0.03 |
| Mn | ≤ 1 | 0.7 |
| Si | ≤ 1 | 0.8 |
| P | ≤ 0.04 | — |
| S | ≤ 0.04 | — |
| Cr | 24 – 27 | 25.5 |
| Ni | 4 – 6 | 5 |
| Mo | 1.75 – 2.5 | 2.1 |
| Naustenite stabiliser, raises PREN and strength | 0.15 – 0.25 | 0.2 |
| Cunot specified — copper-free variant of CD4MCu | — | — |
| Fe | balance | — |
CD6MN-AC — frequently asked
What is CD6MN-AC used for?
CD6MN-AC is typically used for feedwater heater components, pump casings, valve trim and paper mill equipment. In short: copper-free 25Cr cast duplex; strong feedwater service grade; abrasive, work-hardening to machine.
What is the yield strength of CD6MN-AC?
CD6MN-AC has a typical yield strength of 500 MPa (72.5 ksi) and a tensile strength of 690 MPa (100 ksi) — stronger than 77% of stainless steel grades. Strength varies by condition: see the 5 listed tempers.
Is CD6MN-AC easy to machine?
Not especially — machinability is rated poor (24/100, worse than 93% of stainless steel grades). Work-hardens rapidly and is abrasive — use rigid setups, sharp coated carbide, low speed (~60–90 m/min) with heavy positive feed and flood coolant; avoid dwelling.
Can CD6MN-AC be welded?
With care — weldability is rated fair (50/100). GTAW/GMAW/SMAW with 25-9-4 (E2595/ER2594) or matching over-alloyed filler, interpass ≤150 °C, moderate heat input 0.5–2.0 kJ/mm, no preheat, no post-weld temper — re-solution anneal after major repairs.
What surface finishes work on CD6MN-AC?
Grit blast, pickle in HNO₃-HF and passivate per ASTM A967; polish to Ra ≤0.8 µm for maximum pitting resistance — no anodizing, and keep free of embedded carbon-steel iron.
Can CD6MN-AC be formed, bent or molded?
Sand or centrifugal cast with generous risering; solidification range and 2.0–2.2 % shrinkage require good feeding, then mandatory ≥1120 °C solution anneal with rapid water quench.
What is the maximum service temperature of CD6MN-AC?
CD6MN-AC is rated for continuous use to about 250°C (482 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between CD6MN-SA and CD6MN CENT-SA?
SA is the default condition — the only condition permitted for pressure-retaining service; restores 40–55 % ferrite balance and dissolves sigma/nitrides. CENT-SA: for seamless duplex tubulars and rings; directional solidification gives cleaner, finer structure and slightly higher strength than static castings. Yield strength is 520 MPa in SA versus 550 MPa in CENT-SA.
Sources
- ASTM A995/A995M — Castings, Austenitic-Ferritic (Duplex) Stainless Steel, for Pressure-Containing Parts — ASTM International (2020)
- ASTM A890/A890M — Castings, Iron-Chromium-Nickel-Molybdenum Corrosion-Resistant, Duplex — ASTM International (2023)
- EN 10283 — Corrosion resistant steel castings (GX2CrNiMoN25-6-3, 1.4468) — CEN (2010)
- Steel Castings Handbook, Supplement 8 — High Alloy Data Sheets, Corrosion Series — Steel Founders' Society of America (2004)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- Practical Guidelines for the Fabrication of Duplex Stainless Steels — IMOA (2014)
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.