1. Executive summary
CE3MN is the cast counterpart to wrought super-duplex alloys (e.g., UNS S32750): it combines very high chromium (≈24–26 %), significant molybdenum (≈3–4 %), elevated nickel (≈6–8 %), controlled copper and nitrogen
to produce a two-phase microstructure with high yield strength, excellent resistance to pitting/crevice corrosion and substantially improved resistance to chloride-induced stress-corrosion cracking relative to conventional austenitics.
Its cast form allows complex geometry components for harsh environments (valve bodies, pump casings, manifolds), but requires strict process control (melting, solidification, solution anneal) to deliver the expected performance and to avoid embrittling intermetallic phases.
2. What is CE3MN Cast Duplex Stainless Steel?
CE3MN cast duplex stainless steel is a high-performance, two-phase (ferritic-austenitic) stainless alloy engineered specifically for demanding corrosive and mechanically stressed environments where conventional austenitic or ferritic stainless steels do not provide adequate durability.
It belongs to the super-duplex stainless steel family, distinguished by elevated chromium (Cr), molybdenum (Mo), nitrogen (N) and nickel (Ni) contents that deliver an exceptional combination of strength, localized corrosion resistance and crack resistance.
In standardized nomenclature, CE3MN is commonly referenced in casting specifications such as ASTM A995 / ASME SA351 & SA995 grades (for example CD3MWCuN, also marketed as “6A”). Its UNS designation is J93404.
It is widely accepted as the cast equivalent to wrought super-duplex stainless steels like UNS S32750 / ASTM A F55, and is used when lightweight, complex geometries or single-piece components of high corrosion resistance are required.
The conceptual goal behind CE3MN is to bridge the gap between conventional duplex stainless steels (e.g., 2205) and nickel-base alloys
by maximizing corrosion resistance (particularly pitting and crevice corrosion in chloride environments) while maintaining good mechanical performance, weldability and cost efficiency for large or intricate cast parts.
It is frequently selected for valve bodies, pump casings, manifolds and subsea components in the oil & gas, petrochemical, marine, desalination and power industries.
3. Chemical Composition of CE3MN Cast Duplex Stainless Steel
| Element | Typical range (wt%) | Role / comment |
| Cr (Chromium) | 24.0 – 26.0 | Primary element for passivity and general corrosion resistance; major contributor to PREN. |
| Ni (Nickel) | 6.0 – 8.0 | Austenite stabiliser; improves toughness and helps achieve duplex phase balance. |
| Mo (Molybdenum) | 3.0 – 4.0 | Strongly increases pitting and crevice corrosion resistance; key PREN contributor. |
| N (Nitrogen) | 0.14 – 0.30 | Potent pitting-resistance and strength enhancer (multiplies in PREN formula); critical for duplex performance. |
| Cu (Copper) | 0.3 – 1.5 | Present in some cast grades to improve resistance in certain reducing environments and to modify solidification behaviour. |
C (Carbon) |
≤ 0.03 | Kept low to limit carbide precipitation and intergranular embrittlement. |
| Mn (Manganese) | ≤ 2.0 | Deoxidiser / partial austenite former; controlled to avoid excessive inclusion formation or segregation. |
| Si (Silicon) | ≤ 1.0 | Deoxidiser; limited to control oxidation and inclusion formation. |
| P (Phosphorus) | ≤ 0.03 | Impurity control — kept low to preserve toughness. |
| S (Sulfur) | ≤ 0.01 | Impurity — minimised to avoid hot cracking and loss of ductility. |
| Fe (Iron) | Balance (≈ 40–50%) | Remainder of alloy — ferrite + austenite matrix. |
4. Microstructure and phase balance
- Dual-phase structure: CE3MN is intentionally duplex — ferrite (δ) + austenite (γ).
The mechanical and corrosion properties are a direct function of the phase fraction, chemistry partitioning and microstructural homogeneity. - Target phase balance: Typically aim for ~40–60% ferrite; too much ferrite lowers toughness and weldability; too little ferrite reduces strength and resistance to chloride stress-corrosion cracking.
- Intermetallics risk: Slow cooling, improper heat cycles (or local re-heating) promote σ (sigma), χ, and other chromium-rich intermetallics which are brittle, Cr/Mo-rich and Ni-poor; these dramatically reduce toughness and corrosion resistance.
5. Typical physical & mechanical properties — CE3MN (cast super-duplex stainless steel)
Scope & caveats: values below are typical engineering ranges for cast CE3MN/J93404 in a properly solution-annealed condition.
Castings (especially large/thick sections) show greater scatter than wrought products and are sensitive to section size, heat treatment, and actual phase balance (δ/γ).
For design and safety-critical work always use supplier-certified test data for the specific heat/lot and validate with part-level tests.
Physical properties (typical)
| Property | Typical value (cast CE3MN, solution-annealed) | Comment |
| Density | ≈ 7.8 – 8.0 g·cm⁻³ | Similar to other stainless alloys; use 7.85 g/cm³ for mass calculations. |
| Melting / solidification range | ≈ 1,375 – 1,425 °C | Broad solidification range due to high alloying; affects feeding and shrinkage. |
| Thermal conductivity (20 °C) | ≈ 12 – 18 W·m⁻¹·K⁻¹ | Lower than carbon steels; impacts thermal gradients during casting and welding. |
| Specific heat (20 °C) | ≈ 420 – 500 J·kg⁻¹·K⁻¹ | Use ~460 J·kg⁻¹·K⁻¹ for thermal calculations. |
Coefficient of thermal expansion (20–300 °C) |
≈ 12.5 – 14.5 ×10⁻⁶ K⁻¹ | Lower than many austenitic grades; important when joining to other metals. |
| Young’s modulus (room temp) | ≈ 190 – 210 GPa | For elastic design use 200 GPa conservatively. |
| Electrical resistivity (20 °C) | ≈ 0.6 – 0.9 μΩ·m | Typical stainless range; varies with exact composition. |
| Magnetism | Slightly ferritic; may show weak magnetic response | Fully austenitic regions non-magnetic; duplex shows mild magnetism due to ferrite. |
Mechanical properties (typical, solution-annealed cast form)
| Property | Typical range | Notes |
| Yield strength (Rp0.2) | ≈ 400 – 550 MPa | Much higher than 300-series stainless steels; depends on section, heat-treatment and ferrite fraction. |
| Tensile strength (Rm) | ≈ 750 – 900 MPa | Use certified lot data for allowable stresses. |
| Elongation (A, % in 50 mm) | ≈ 10 – 25 % | Cast parts trend toward the lower end; thicker sections and residual σ/χ reduce ductility. |
Hardness (HB) |
≈ 220 – 360 HB | Cast super-duplex values vary with microstructure and any intermetallics; hardness correlates with strength and embrittlement. |
| Charpy V-notch impact | ≈ 30 – 120 J (room temp) | Wide range: cast, section size and precipitates lead to scatter—measure for critical parts. |
Fracture toughness (K_IC, approximate) |
≈ 50 – 120 MPa·√m | Highly dependent on microstructure, notch size and testing method; use part-specific fracture mechanics where necessary. |
| Fatigue (rotating bending / endurance) | Indicative endurance ≈ 250 – 400 MPa | Surface finish, residual stress and porosity dominate fatigue life—quantify experimentally. |
| Creep resistance | Moderate (not high-temperature creep alloy) | Suitable for intermittent elevated-temperature exposure; not recommended for sustained high-stress creep service above ~350–400 °C without qualification. |
Elevated-temperature behaviour & service guidance
- Practical continuous service temperature: typically ≤ ~300 °C for corrosion-sensitive applications; mechanical strength will drop progressively with temperature.
- Short-term exposure: material retains reasonable strength to ~400–500 °C but long-term exposure risks precipitation of intermetallics (σ, χ) that embrittle the alloy.
- Creep & stress rupture: CE3MN offers better high-temperature strength than many austenitics but is not a substitute for nickel-base alloys where long-term creep is required.
For sustained load at elevated temperature select appropriate creep-rated material and perform creep testing.
6. Casting behavior and solidification challenges
CE3MN’s design as a cast alloy enables one-piece components with complex internal passages, integrated features and fewer joints — advantages in manufacturing efficiency, leak minimization and part integrity compared with fabrications from multiple forgings or weldments.
Casting CE3MN introduces process-specific risks:
- Non-equilibrium solidification and segregation: interdendritic residual liquid becomes enriched in Cr, Mo and Ni (or conversely depleted depending on element partition coefficients),
producing local chemistry variations that can foster intermetallic formation (σ/χ) in the as-cast condition. - Wide freezing range: high alloy content broadens solidification interval, increasing shrinkage risk and feeding difficulty—requiring careful riser design, chills and feeding strategy.
- Hot tearing and hot cracking: duplex cast alloys can be susceptible to hot tearing if restraint and thermal gradients are not managed; grain refinement and gating optimization help.
- Surface and internal defects: porosity (gas and shrinkage), oxide entrainment and inclusions are common if melt control and filtration are insufficient.
Mitigation: precise melt chemistry control, ceramic-foam filtration, degassing, optimized gating and feeder layout guided by solidification simulation, and post-casting solution annealing are essential.
7. Heat treatment, welding, and fabrication controls
Solution anneal & quench
- Purpose: dissolve as-cast intermetallics and homogenize chemistry to achieve the desired duplex balance.
- Typical practice: solution anneal in the range 1,050–1,100 °C (exact range depends on part section) followed by rapid quench to avoid intermetallic reprecipitation.
- Caveats: large/ thick castings require hold times and quench strategies tailored to section size; insufficient solutionizing leaves residual σ/χ and segregation.
Welding & thermal cutting
- Weld metallurgy: consumables should be selected to match or slightly overmatch alloy chemistry and to promote balanced phase ratio in HAZ/weld metal.
- Heat input control: excessive or improperly sequenced heat input shifts phase balance and can locally precipitate σ/χ.
- Post-weld treatment: for critical assemblies, post-weld solution anneal or local heat treatment may be required to restore microstructure.
- Thermal cutting caution: as observed in practice, preheating + local hot cutting (e.g., oxy-fuel) followed by slow cooling can produce σ/χ precipitation and embrittlement at the cut edge;
best practice is to solution-treat before any thermal cutting or to use cold-cutting (sawing) followed by solution anneal.
8. Common defects and failure modes (practical focus)
- σ / χ intermetallic precipitation: forms in interdendritic and α/γ interfaces on slow cooling or during post-casting thermal exposure; causes embrittlement and corrosion susceptibility.
- Segregation (Ni/Cr/Mo partitioning): leads to local PREN depression and preferential attack.
- Gas and shrinkage porosity: reduce load-bearing section and fatigue life.
- Hot tearing: from constrained solidification in thick sections.
- Thermal-cut induced embrittlement: cutting risers on as-cast components without prior solution anneal can precipitate σ/χ at the cut root and initiate cracking (practical remedy: solution anneal before thermal cutting or cold saw then solutionize).
9. Typical Applications of CE3MN Cast Duplex Stainless Steel
CE3MN cast duplex stainless steel is selected for applications where high mechanical strength, excellent resistance to localized corrosion, and structural reliability under severe service conditions are simultaneously required.
As a cast super-duplex grade, it is particularly well suited to complex, thick-walled, pressure-containing components that are difficult or uneconomical to manufacture from wrought products.
Oil & gas and petrochemical industry
- Valve bodies and valve components (ball valves, gate valves, check valves) for sour service and high-chloride environments
- Pump casings and impellers handling seawater, produced water, or aggressive hydrocarbon mixtures
- Manifolds and flow control components exposed to high pressure, erosion, and corrosive fluids
Offshore and marine engineering
- Seawater handling systems (pump housings, strainers, valve blocks)
- Offshore platform structural castings subject to continuous seawater exposure
- Desalination plant components including brine pumps and valve bodies
Chemical and process industries
- Reactor internals and casings exposed to mixed acids, chlorides, and elevated temperatures
- Heat exchanger components such as channel heads and water boxes
- Agitator housings and pump components in aggressive chemical service
Power generation and energy systems
- Cooling water systems in thermal and nuclear power plants
- Flue gas desulfurization (FGD) system components
- High-pressure water handling castings in renewable energy facilities
Pulp, paper, and environmental engineering
- Digester and bleaching system components
- Pumps, mixers, and valve bodies exposed to chloride-rich and alkaline media
- Wastewater and effluent treatment equipment
Mining, mineral processing, and slurry handling
- Slurry pump casings and impellers
- Wear- and corrosion-resistant housings for mineral transport systems
High-integrity pressure-containing components
- Pressure vessel components
- Thick-walled cast housings and covers
- Custom-engineered cast parts with complex internal passages
10. Comparison with Other Alternative Materials
CE3MN cast duplex stainless steel is often selected over other stainless steels, super-austenitic alloys, and nickel-based alloys because of its unique combination of corrosion resistance, mechanical strength, and cost-effectiveness in cast form.
The following comparison highlights its relative performance and application suitability.
| Property / Criterion | CE3MN (Cast Duplex, 25Cr-7Ni-Mo-N) | 316L / 1.4404 (Austenitic SS) | 904L / 1.4539 (Super-Austenitic SS) | Nickel-Based Alloys (e.g., Hastelloy C-22) |
| Corrosion Resistance | Excellent resistance to pitting, crevice corrosion, and stress corrosion in chloride environments; PREN ≈ 40 | Moderate; prone to pitting/crevice in high-chloride media | Very high; comparable PREN (≈ 40–42), strong acid resistance | Outstanding in oxidizing and reducing acids |
| Mechanical Strength | High strength (Rp0.2 ≈ 450–550 MPa, Rm ≈ 750–900 MPa); good toughness | Moderate (Rp0.2 ≈ 200–250 MPa, Rm ≈ 500–600 MPa) | Moderate to high; lower than duplex in yield | High, but often expensive to fabricate |
Phase / Microstructure |
Duplex (ferrite + austenite) for optimized strength-corrosion balance | Fully austenitic | Fully austenitic | Fully austenitic or complex |
| Castability | Excellent for complex, thick-walled parts; lower shrinkage than high-alloy austenitics | Good, but lower strength in thick sections | Poor; expensive for large castings | Difficult; high cost, complex melt control |
Elevated-Temperature Performance |
Moderate; suitable ≤ 300–350 °C; limited creep | Moderate; austenite softens at high T | Moderate; slightly better than 316L | Excellent; can handle 400–600 °C in aggressive media |
| Cost & Availability | Moderate; more economical than 904L and nickel alloys | Low; widely available | High; limited casting suppliers | Very high; specialty alloy |
| Typical Applications | Valves, pumps, pressure housings in chloride-rich, high-pressure, chemical service | General chemical equipment, food, water handling | Acid-resistant tanks, heat exchangers | Highly aggressive chemical processes, extreme temperature or corrosion |
Key Takeaways:
- CE3MN vs 316L: CE3MN offers far superior corrosion resistance in chloride and aggressive chemical environments, with higher strength, making it ideal for high-pressure or thick-walled components.
- CE3MN vs 904L: CE3MN provides higher mechanical strength and castability, often at lower cost, while 904L is preferable for thin-walled, highly acid-resistant components.
- CE3MN vs Nickel-Based Alloys: Nickel alloys outperform in extreme corrosive and high-temperature conditions,
but CE3MN provides an economical balance of strength, corrosion resistance, and manufacturability for most industrial applications.
11. Conclusion
CE3MN cast duplex stainless steel is a purpose-built alloy for demanding corrosive and mechanically loaded environments where complex cast geometries are required.
Its super-duplex chemistry delivers an attractive combination of high strength and excellent localized-corrosion resistance — but these advantages only materialize when melting, casting, solution annealing and fabrication are executed with discipline to avoid segregation and brittle intermetallic precipitation.
For critical industrial or subsea components, procuring CE3MN from proven suppliers with rigorous qualification and testing will yield durable, high-performance castings that justify the material and processing premium.
