UNS S31803 / S32205 Fasteners Supplier
MT.BOLTS manufactures Duplex stainless steel fasteners using high-strength, corrosion-resistant material UNS S31803 / S32205 (commonly referred to as F51). These fasteners are engineered for demanding environments that require outstanding resistance to chloride-induced stress corrosion cracking, pitting, and crevice corrosion, while offering superior mechanical strength. They are widely used in offshore platforms, desalination plants, chemical processing, and power generation.
Our Duplex Stainless Steel Fasteners (UNS S31803 / S32205) Have the Following Specifications:
- Diameter: M3 to M64 | #4 to 2.5″
- Length: 6mm to 500mm | 0.25″ to 20″
- Thread Pitch: Metric (Coarse/Fine) | UNC/UNF
- Standards: ASME B18.2.1, ASME B18.3, ASME B18.2.2, DIN/ISO/EN (e.g., DIN 933, DIN 934)
- Material Specifications: ASTM A182 F51 (UNS S31803 / S32205), ASTM A479, ASTM A276
- Types: Bolts, Screws, Nuts, Washers, Studs
Duplex stainless steel refers to a category of stainless steels characterized by a two-phase microstructure comprising austenite and ferrite. It offers an excellent combination of high strength and superior corrosion resistance, especially against chloride-induced stress corrosion cracking, pitting, and crevice corrosion.
We regularly supply duplex stainless steel fasteners and bolts in UNS S31803 / S32205 (commonly designated as F51). Their chemical compositions and physical properties are provided below for your reference during procurement.
UNS S31803 / S32205 Fasteners Chemical Composition
| Element | Content Range (%) |
| Chromium (Cr) | 21.0 – 23.0 |
| Nickel (Ni) | 4.5 – 6.5 |
| Molybdenum (Mo) | 2.5 – 3.5 |
| Manganese (Mn) | ≤ 2.00 |
| Silicon (Si) | ≤ 1.00 |
| Nitrogen (N) | 0.08 – 0.20 |
| Carbon (C) | ≤ 0.030 |
| Phosphorus (P) | ≤ 0.030 |
| Sulfur (S) | ≤ 0.020 |
| Iron (Fe) | Balance |
Note: S32205 generally lies at the upper end of Cr, Mo, and N ranges, offering enhanced corrosion resistance compared to S31803.
UNS S31803 / S32205 Fasteners Mechanical Properties
| Property | Value | Unit |
| Tensile Strength | ≥ 620 | MPa |
| Yield Strength (0.2% offset) | ≥ 450 | MPa |
| Elongation (in 50mm) | ≥ 25 | % |
| Brinell Hardness (HBW) | ≤ 290 | — |
| Impact Toughness @ -46°C | ≥ 74 (typical, not always specified) | J (Charpy V-notch) |
Duplex Stainless Steel UNS S31803 / S32205 Fasteners Types
MT.BOLTS offers a comprehensive range of duplex stainless steel f51 fasteners for your selection to meet various application requirements:
UNS S31803 / S32205 Hex Head Screw Bolts
UNS S31803 / S32205 Square Head Bolts
UNS S31803 / S32205 Flange Bolts
UNS S31803 / S32205 Serrated Flange Bolts
UNS S31803 / S32205 Eye bolts
UNS S31803 / S32205 Carriage Bolts
UNS S31803 / S32205 Elevator Bolts
UNS S31803 / S32205 U-Bolts
UNS S31803 / S32205 Anchor Bolts
UNS S31803 / S32205 Expansion Bolt
UNS S31803 / S32205 Lag Bolts
UNS S31803 / S32205 U-Bolts
UNS S31803 / S32205 Hex Head Lag Screws
UNS S31803 / S32205 Shoulder Screws
UNS S31803 / S32205 Socket Cap Screws
UNS S31803 / S32205 Self-Tapping Screws
UNS S31803 / S32205 Hex Nuts
UNS S31803 / S32205 Serrated Flange Nuts
UNS S31803 / S32205 Lock Nuts
UNS S31803 / S32205 Wing Nuts
UNS S31803 / S32205 Coupling Nut
UNS S31803 / S32205 Square Nuts
UNS S31803 / S32205 Acorn Nuts
UNS S31803 / S32205 Wing Nuts
UNS S31803 / S32205 Fully Threaded Rods & Studs
UNS S31803 / S32205 Equal Thread Length Rods & Studs
UNS S31803 / S32205 Unequal Thread Length Rods & Studs
UNS S31803 / S32205 Single End Threaded Studs
UNS S31803 / S32205 Weld Studs
UNS S31803 / S32205 Press-In Captive Studs
UNS S31803 / S32205 Flat Washers
UNS S31803 / S32205 Lock Washers
UNS S31803 / S32205 Curved Washers
UNS S31803 / S32205 Wave Washers
UNS S31803 / S32205 Square Washers
UNS S31803 / S32205 Belleville Washers
Why Choose MT.BOLTS
- Material Diversity
- Standardized Production
- Ample Inventory
- Competitive Pricing
- Low-MOQ Customization
Reasons to Choose UNS S31803 / S32205 Fasteners
- Excellent Corrosion Resistance
Resistant to pitting, crevice corrosion, and chloride-induced stress corrosion cracking—ideal for harsh environments like offshore or chemical processing. - High Mechanical Strength
About twice the yield strength of standard austenitic stainless steels (e.g., 304, 316), allowing for weight reduction and stronger joints. - Good Weldability and Fabrication
Suitable for various fabrication methods, including welding, machining, and forming, with proper procedures. - Cost-Effective Alternative
Offers performance comparable to higher-alloyed stainless steels or super duplex, but at a more economical cost. - Balanced Microstructure
The duplex (austenitic–ferritic) structure provides a unique combination of toughness, fatigue resistance, and stress corrosion resistance.
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Application of UNS S31803 / S32205 Fasteners
- Offshore Oil & Gas Platforms
– Structural bolting, flanged connections, risers - Desalination Plants
– Saltwater corrosion-resistant assemblies - Chemical and Petrochemical Processing
– Pumps, valves, and pressure vessel components - Pulp and Paper Industry
– Digesters, bleach plants, storage tanks - Power Generation
– Heat exchangers, turbines, pressure systems - Marine & Shipbuilding
– Hull structures, decks, and fastened joints exposed to seawater
FAQ About UNS S31803 / S32205 Fasteners and Bolts
Yes, in most cases. S32205 is an improved version of S31803, featuring tighter nitrogen control and slightly enhanced corrosion resistance—more information here (S31803 vs S32205: Key Differences Between Duplex Stainless Steels).
Absolutely. Their high PREN values (≥ 32) make them suitable for chloride-rich environments like seawater.
Duplex fasteners have nearly twice the yield strength and significantly better resistance to chloride-induced corrosion than 316.
Yes. While weldable, duplex stainless steels require controlled heat input and interpass temperatures to maintain phase balance and avoid sensitization.
Yes. Materials typically conform to ASTM A182, A479, or A276, and dimensions follow ASME, DIN, ISO, and EN standards.
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