JIS SUS329J3L Stainless Steel: Duplex Stainless Steel for High Corrosion Resistance & Strength Applications
JIS SUS329J3L is a low-carbon duplex stainless steel (DSS) grade combining austenitic and ferritic microstructures in a balanced 50:50 ratio. This alloy, standardized under JIS G4304/G4305, delivers superior corrosion resistance, high tensile strength (twice that of 304/316), and excellent stress corrosion cracking (SCC) resistance. Its optimized composition—21-24% chromium, 4.5-6.5% nickel, and 2-3% molybdenum—makes it ideal for chemical processing, marine environments, and high-pressure systems where 300-series stainless steels fall short. This article explores its chemical properties, mechanical performance, fabrication guidelines, and industry-specific applications.
1. Chemical Composition (JIS G4304/G4305 Standard)
| Element | Content Range | Function |
|---|---|---|
| Carbon (C) | ≤ 0.030% | Minimized to prevent intergranular corrosion and maintain weldability |
| Chromium (Cr) | 21.00 – 24.00% | Forms passive Cr₂O₃ film; enhances pitting/crevice corrosion resistance |
| Nickel (Ni) | 4.50 – 6.50% | Balances austenite-ferrite phase ratio; improves toughness and low-temperature performance |
| Molybdenum (Mo) | 2.00 – 3.00% | Boosts resistance to chloride-induced pitting (PREN ≥ 32) |
| Manganese (Mn) | ≤ 1.20% | Stabilizes austenite phase; aids in sulfur control during smelting |
| Silicon (Si) | ≤ 0.80% | Enhances oxidation resistance; improves scale removal during hot rolling |
| Nitrogen (N) | 0.10 – 0.30% | Strengthens austenite phase; compensates for low nickel content |
| Phosphorus (P) | ≤ 0.035% | Controlled impurity; excessive levels reduce corrosion resistance |
| Sulfur (S) | ≤ 0.020% | Minimized to prevent hot cracking and reduce inclusions |
2. Mechanical Properties (Room Temperature)
- Tensile Strength (σb): ≥ 620 MPa (minimum; typically 650-850 MPa in solution-annealed condition)
- Yield Strength (σ0.2): ≥ 450 MPa (duplex structure provides ~2× yield strength vs. 316L)
- Elongation (δ): ≥ 25% (lower than austenitic grades but sufficient for forming)
- Hardness (HB): ≤ 290 (Brinell; higher than 304/316 due to ferrite phase)
- Impact Toughness (CVN): ≥ 100 J at 0°C (retains ductility in sub-zero temperatures)
- Pitting Resistance Equivalent (PREN): 32-36 (calculated as %Cr + 3.3×%Mo + 16×%N)
3. Manufacturing & Fabrication Guidelines
- Hot Forming: Perform at 1000-1150°C; avoid temperatures below 950°C to prevent sigma phase precipitation. Rapid air cooling recommended.
- Cold Forming: Requires ~20-30% higher force than 304 due to higher yield strength. Use over-sized tooling to account for springback.
- Machining: Use carbide tools with slow speeds (60-80 m/min) and heavy feeds. Ferrite phase increases tool wear; coolant recommended.
- Welding: Prefer GTAW (TIG) or GMAW (MIG) with ER2209 filler metal. Maintain interpass temperature ≤ 150°C; post-weld annealing not typically required.
- Heat Treatment: Solution anneal at 1020-1100°C followed by water quenching to restore phase balance and corrosion resistance.
- Surface Finishing: Pickling with nitric-hydrofluoric acid blend (20-30% HNO₃ + 2-5% HF) to remove oxide scale and passivate the surface.
4. Key Application Fields
Chemical & Petrochemical Processing
Heat exchangers, reaction vessels, and piping systems handling organic acids (acetic, formic), chlorides, and sulfuric acid (≤ 10% concentration). Resists stress corrosion cracking in H₂S environments.
Marine & Offshore Engineering
Seawater desalination plants, offshore platform components, and ballast water systems. Superior resistance to chloride pitting vs. 316L (PREN ≥ 32).
Oil & Gas Industry
Subsea pipelines, wellhead equipment, and sour gas (H₂S + CO₂) handling systems. Meets NACE MR0175/ISO 15156 requirements for sulfide stress cracking resistance.
Pulp & Paper Mills
Bleach plant equipment, digesters, and white liquor tanks. Resists corrosion from chlorides and hypochlorites at elevated temperatures (up to 80°C).
Structural & Pressure Vessels
High-pressure tanks, bridges, and architectural components requiring high strength-to-weight ratios. Approved under ASME BPVC Section VIII Div. 1 for pressure vessel construction.
Wastewater Treatment
Scrubbers, flue gas desulfurization (FGD) systems, and sludge handling equipment. Withstands abrasive and corrosive slurries with pH 3-12.
5. Comparison with Similar Duplex Grades
| Grade | Key Alloying Elements | PREN | Strength | Typical Applications |
|---|---|---|---|---|
| SUS329J3L | 22Cr-5Ni-3Mo-0.15N | 32-36 | High | Chemical processing, marine environments, moderate chloride exposure |
| SUS329J4L | 23Cr-4Ni-0.1N | 28-30 | Moderate | Less aggressive environments; lower Mo content reduces cost |
| S32205 (2205) | 22Cr-5Ni-3Mo-0.17N | 34-38 | Very High | Offshore platforms, high-pressure systems, severe chloride conditions |
| S32750 (2507) | 25Cr-7Ni-4Mo-0.27N | 40-44 | Extreme | Subsea equipment, FGD systems, highly corrosive media |
6. Selection & Handling Precautions
- Temperature Limits: Avoid prolonged exposure above 300°C to prevent embrittlement from sigma phase formation. Maximum service temperature: 250°C for pressure applications.
- Welding Procedures: Use low heat input (≤ 1.5 kJ/mm) to maintain phase balance. Post-weld cleaning is critical to remove slag and restore passivation.
- Galvanic Corrosion: Avoid direct contact with carbon steel in moist environments; use insulating gaskets or coatings if necessary.
- Surface Contamination: Remove iron particles (e.g., from grinding) with nitric acid passivation to prevent localized corrosion.
- Material Certification: Verify compliance with JIS G4304/G4305 via mill test reports (MTR), including ferrite-austenite phase balance (40-60% ferrite).
- Alternative Grades: For higher corrosion resistance, consider S32205 (2205) or S32750 (2507); for cost-sensitive applications, SUS329J4L may suffice.
7. Request a Quote for JIS SUS329J3L Stainless Steel
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