Super duplex stainless steel casting grades primarily include S32760 (F55, 1.4501),
whose castings are widely used in the chemical, petroleum, and other fields.
Common Casting Grades
S32760 (F55, 1.4501): A super duplex stainless steel with high corrosion resistance and mechanical strength, suitable for highly corrosive environments.
Grade Characteristics
Composition: Contains 24%-26% chromium, 3%-4% molybdenum, and 0.2%-0.3% nitrogen. PREN value >40, with a tensile strength exceeding 750 MPa.
Applications: Suitable for chemical processing, petrochemicals, and marine engineering, especially for chloride corrosion and non-oxidizing acid corrosion.
Other grades, such as S32550 (Ferralium 255) and S32750 (SAF 2507), are mostly wrought-metal products and are less commonly used in castings.
How to choose the right duplex stainless steel casting grade for a specific application? Selecting the right duplex stainless steel casting grade for a specific application requires a comprehensive consideration of factors such as the corrosive environment, mechanical properties, temperature range, and cost. The following are key material selection guidelines:
1. Corrosive Environment Compatibility
For chloride-containing media (such as seawater and chemical fluids): Super duplex stainless steel (such as S32760/F55) is preferred. Its PREN value is >40, providing excellent resistance to pitting and crevice corrosion.
For reducing acids such as sulfuric acid: High-molybdenum (Mo ≥ 4%) duplex steel (such as S32750) or copper-containing austenitic-ferritic duplex steel is preferred.
For high-temperature oxidizing environments: Avoid prolonged use above 300°C to prevent the precipitation of brittle phases.
2. Mechanical Property Requirements
High Strength Requirements: Duplex steels can achieve a yield strength of 400-550 MPa (such as 2205), twice that of austenitic stainless steels. Welded Components: Choose a low-carbon grade (such as S31803) or add stabilizing elements (Ti/Nb) to resist intergranular corrosion.
3. Temperature Adaptability
Low Temperature (-50°C to 50°C): Standard duplex steel (such as 2205) is suitable, but ultra-low temperature brittleness must be avoided.
High Temperature (≤300°C): Super duplex steel (S32760) offers superior temperature resistance, but the dwell time must be controlled.
4. Casting Process and Standards
Casting Grade: Follow ASTM A890 (such as grades 1B and 3A) or GB/T 2100-2017, corresponding to forged grades (such as F55).
Heat Treatment: Solution treatment (rapid cooling from 1065-1100°C) is required to balance the duplex structure.
Typical Applications
Offshore Engineering: S32760 is used in seawater filters and platform structures. Chemical Equipment: 2205 (S31803) is suitable for reactors and pipelines.
Oil and Gas: High-strength duplex steel (such as 2507) is used for high-pressure pipelines.
Of course, super duplex stainless steel castings are typically used in harsh environments such as high strength, high humidity, and salinity, placing extremely high demands on the casting performance. Currently, only duplex stainless steel castings can meet these requirements.
If you need large-scale production of super duplex stainless steel castings, consider partnering with Mulan Metal. With 12 years of experience in stainless steel casting production, Mulan Metal has helped clients in over 30 countries complete large-scale commissioned super duplex stainless steel castings, earning consistent recognition. We look forward to hearing from you.
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