Product Description
1. Grades in ASTM A790 Standard
| Grade |
Chemical Composition (wt%) |
Mechanical Properties |
Typical Applications |
| S31803 |
Cr: 21.0-23.0, Ni: 4.5-6.5, Mo: 2.5-3.5, N: 0.08-0.20, Fe balance |
Yield Strength: ≥450 MPa
Tensile Strength: 620-820 MPa
Elongation: ≥25% |
General corrosion resistance in oil/gas pipelines, chemical processing, and water treatment. |
| S32205 |
Cr: 22.0-23.0, Ni: 4.5-6.5, Mo: 3.0-3.5, N: 0.14-0.20, Fe balance |
Yield Strength: ≥450 MPa
Tensile Strength: 650-850 MPa
Elongation: ≥25% |
Offshore platforms, high-pressure chemical reactors, and chloride-rich environments. |
| S32750 |
Cr: 24.0-26.0, Ni: 6.0-8.0, Mo: 3.0-5.0, N: 0.24-0.32, Fe balance, minor Cu |
Yield Strength: ≥550 MPa
Tensile Strength: 750-950 MPa
Elongation: ≥25% |
Extreme conditions like deep-sea oil exploration, highly corrosive acids, and high-pressure systems. |
| S32760 |
Cr: 24.0-26.0, Ni: 6.0-8.0, Mo: 3.0-4.0, N: 0.20-0.30, Fe balance, Cu: 0.5-1.0, W: 0.5-1.0 |
Yield Strength: ≥550 MPa
Tensile Strength: 750-950 MPa
Elongation: ≥25% |
Seawater desalination, marine engineering, and applications requiring resistance to crevice corrosion. |
2. Explanation of Grades and Standard
ASTM A790 Standard Overview
The ASTM A790 standard specifies requirements for welded and seamless ferritic-austenitic (duplex) stainless steel pipes designed for general corrosive service. It emphasizes resistance to stress corrosion cracking (SCC) and sets strict guidelines for manufacturing processes, chemical composition, and mechanical testing. Key tests include tension, flattening, hydrostatic, and non-destructive examinations to ensure dimensional accuracy and material integrity.
Grade-Specific Analysis
S31803 (2205 Duplex)
- Composition & Properties: This grade balances chromium (Cr) for passive film formation, nickel (Ni) for austenite stability, and molybdenum (Mo) with nitrogen (N) to enhance pitting resistance. Its moderate alloy content provides a cost-effective solution for moderate corrosion environments.
- Applications: Widely used in onshore oil/gas pipelines, chemical plants handling mild acids, and water treatment facilities where a balance of strength and corrosion resistance is needed.
S32205 (Upgraded 2205 Duplex)
- Composition & Properties: Slightly higher Cr and N content than S31803 improve resistance to localized corrosion (pitting/crevice) in chloride-rich media. Tighter composition control ensures superior phase balance and mechanical consistency.
- Applications: Offshore risers, flowlines, and high-pressure chemical reactors where exposure to seawater or aggressive process fluids demands enhanced durability.
S32750 (2507 Super Duplex)
- Composition & Properties: High Cr, Ni, Mo, and N levels create a robust microstructure with exceptional strength and corrosion resistance. The elevated alloy content makes it highly resistant to SCC and pitting in extreme chloride environments.
- Applications: Deep-sea oil/gas extraction, chemical plants processing concentrated sulfuric/hydrochloric acids, and high-temperature/high-pressure systems where failure risks are critical.
S32760 (Zeron 100 Super Duplex)
- Composition & Properties: Incorporates copper (Cu) and tungsten (W) to further boost resistance to sulfide stress cracking and erosion-corrosion. These additions enhance performance in complex environments with high salinity and abrasive media.
- Applications: Seawater intake systems in desalination plants, offshore platforms with high-mud content, and marine structures exposed to harsh tidal zones.
Key Advantages of Duplex Grades
- High Strength: Yield strength 2-3 times higher than conventional austenitic stainless steels (e.g., 304/316), reducing wall thickness and weight for cost-efficient designs.
- Corrosion Resistance: Superior to single-phase steels in resisting pitting, crevice corrosion, and SCC, especially in chloride, sulfur, and acidic environments.
- Thermal Stability: Operates effectively from cryogenic temperatures (≥-50°C) up to 300-350°C, with controlled heat treatment to prevent intermetallic phase precipitation.
3. Application Considerations
- Environment Severity: Select grades based on chloride concentration, temperature, and mechanical loads. For example, S31803 for mild conditions, S32750 for extreme severity.
- Manufacturing Processes: Welding requires careful control to maintain phase balance; post-weld heat treatment (PWHT) may be necessary for critical applications to avoid sensitization.
- Standards Compliance: Ensure compliance with ASTM A790 testing protocols, including chemical analysis, impact testing, and non-destructive evaluation, to meet industry requirements (e.g., API, ASME).
Processing of Production
Audited Supplier 
){kind=link}