Duplex Stainless Steel Fasteners Supplier
MT.BOLTS manufactures Duplex and Super Duplex stainless steel fasteners using high-strength, corrosion-resistant materials such as F51 (UNS S31803/S32205), F53 (UNS S32750), F55 (UNS S32760), F60 (UNS S32550), and F61 (UNS S32520). These fasteners are designed for demanding environments that require excellent resistance to chloride-induced stress corrosion cracking, pitting, and crevice corrosion while providing superior mechanical strength. They are widely used in offshore platforms, desalination plants, chemical processing, and power generation.
Our Duplex & Super Duplex Stainless Steel Fasteners 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 / F53 / F55 / F60 / F61, ASTM A479, ASTM A276
- Types: Bolts, Screws, Nuts, Washers, Studs
Duplex stainless steel refers to a category of stainless steels with a two-phase microstructure consisting of 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 the following grades: F51 (UNS S31803/S32205) and F53 (UNS S32750). Their chemical compositions and physical properties are provided below for your procurement reference.
| ASTM Grade | UNS Number | Key Characteristics |
| F51 | S31803 / S32205 | Twice the strength of austenitic stainless steel, excellent resistance to pitting, crevice, and stress corrosion |
| F53 | S32750 | Higher chloride corrosion resistance and mechanical strength, PREN ≥ 40, ideal for seawater |
| F55 | S32760 | Contains tungsten and copper, excellent acid resistance and outstanding corrosion fatigue and cracking resistance |
| F60 | S32550 | Copper and molybdenum enhance resistance to sulfuric acid and other corrosive media, good weldability and workability |
| F61 | S32520 | Excellent resistance to phosphoric, sulfuric, and strong oxidizing environments; ideal for high-strength, aggressive media |
Duplex Stainless Steel Chemical Composition
| Element | 17-4 PH (UNS S17400) | 15-5 PH (UNS S15500) |
| Chromium (Cr) | 15.0 – 17.5 | 14.0 – 15.5 |
| Nickel (Ni) | 3.0 – 5.0 | 3.5 – 5.5 |
| Copper (Cu) | 3.0 – 5.0 | 2.5 – 4.5 |
| Manganese (Mn) | ≤ 1.0 | ≤ 1.0 |
| Silicon (Si) | ≤ 1.0 | ≤ 1.0 |
| Columbium + Tantalum (Nb + Ta) | 0.15 – 0.45 | — |
| Molybdenum (Mo) | — | ≤ 0.5 |
| Phosphorus (P) | ≤ 0.04 | ≤ 0.03 |
| Sulfur (S) | ≤ 0.03 | ≤ 0.03 |
| Carbon (C) | ≤ 0.07 | ≤ 0.07 |
| Iron (Fe) | Balance | Balance |
Duplex Stainless Steel Mechanical Properties
| Grade | F51 | F53 | F55 | F60 | F61 |
| UNS No. | S31803 / S32205 | S32750 | S32760 | S32550 | S32520 |
| Tensile Strength (MPa) | ≥ 620 | ≥ 795 | ≥ 770 | ≥ 760 | ≥ 760 |
| Yield Strength 0.2% (MPa) | ≥ 450 | ≥ 550 | ≥ 550 | ≥ 550 | ≥ 550 |
| Elongation (%) | ≥ 25 | ≥ 25 | ≥ 25 | ≥ 25 | ≥ 25 |
| Hardness (HRB / HB) | ≤ 100 HRB / ~290 HB | ≤ 100 HRB / ~310 HB | ≤ 100 HRB / ~310 HB | ≤ 100 HRB / ~310 HB | ≤ 100 HRB / ~310 HB |
Duplex Stainless Steel Fastener Types
MT.BOLTS offers a comprehensive range of Duplex Stainless Steel Fasteners for your selection to meet various application requirements:
Duplex Stainless Steel Hex Head Screw Bolts
Duplex Stainless Steel Square Head Bolts
Duplex Stainless Steel Flange Bolts
Duplex Stainless Steel Serrated Flange Bolts
Duplex Stainless Steel Eye bolts
Duplex Stainless Steel Carriage Bolts
Duplex Stainless Steel Elevator Bolts
Duplex Stainless Steel U-Bolts
Duplex Stainless Steel Anchor Bolts
Duplex Stainless Steel Expansion Bolt
Duplex Stainless Steel Lag Bolts
Duplex Stainless Steel U-Bolts
Duplex Stainless Steel Hex Head Lag Screws
Duplex Stainless Steel Shoulder Screws
Duplex Stainless Steel Socket Cap Screws
Duplex Stainless Steel Self-Tapping Screws
Duplex Stainless Steel Hex Nuts
Duplex Stainless Steel Serrated Flange Nuts
Duplex Stainless Steel Lock Nuts
Duplex Stainless Steel Wing Nuts
Duplex Stainless Steel Coupling Nut
Duplex Stainless Steel Square Nuts
Duplex Stainless Steel Acorn Nuts
Duplex Stainless Steel Wing Nuts
Duplex Stainless Steel Fully Threaded Rods & Studs
Duplex Stainless Steel Equal Thread Length Rods & Studs
Duplex Stainless Steel Unequal Thread Length Rods & Studs
Duplex Stainless Steel Single End Threaded Studs
Duplex Stainless Steel Weld Studs
Duplex Stainless Steel Press-In Captive Studs
Duplex Stainless Steel Flat Washers
Duplex Stainless Steel Lock Washers
Duplex Stainless Steel Curved Washers
Duplex Stainless Steel Wave Washers
Duplex Stainless Steel Square Washers
Duplex Stainless Steel Belleville Washers
Why Choose MT.BOLTS
- Material Diversity
- Standardized Production
- Ample Inventory
- Competitive Pricing
- Low-MOQ Customization
Reasons to Choose Duplex Stainless Steel Fasteners
Duplex stainless steel fasteners offer a unique combination of high mechanical strength and excellent corrosion resistance, making them ideal for harsh environments. With twice the yield strength of austenitic stainless steels (e.g., 304/316) and outstanding resistance to chloride-induced stress corrosion cracking, pitting, and crevice corrosion, they are a preferred choice for applications in marine, offshore, and chemical industries. Their dual-phase (austenite + ferrite) microstructure ensures better stress resistance, durability, and longer service life in aggressive environments. They also offer cost-efficiency by reducing the need for thicker materials or frequent replacements.
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Application of Duplex Stainless Steel Fasteners
Duplex and super duplex stainless steel fasteners are widely used in applications where high strength, corrosion resistance, and reliability are critical. Key industries and uses include:
- Oil & Gas: offshore platforms, subsea piping, pressure vessels
- Marine & Shipbuilding: propeller systems, seawater pumps, hull fittings
- Chemical Processing: heat exchangers, reactors, storage tanks
- Desalination Plants: high-pressure piping, structural joints, brine handling systems
- Pulp & Paper: bleaching equipment, digesters, clarifiers
- Structural Engineering: bridges, tunnels, and buildings in corrosive environments
FAQ About Duplex Stainless Steel Fasteners and Bolts
Duplex stainless steel is a type of stainless steel with a dual-phase microstructure of austenite and ferrite. This gives it a superior combination of high strength, excellent corrosion resistance, and better stress corrosion cracking resistance compared to standard austenitic stainless steels.
The most widely used grades include F51 (UNS S31803/S32205), F53 (UNS S32750), F55 (UNS S32760), F60 (UNS S32550), and F61 (UNS S32520).
Duplex fasteners offer approximately twice the yield strength of 316 stainless steel and significantly better resistance to chloride-induced corrosion, pitting, and crevice corrosion, especially in marine and chemical environments.
Yes. Especially super duplex grades like F53 and F55 are excellent for seawater applications due to their high PREN values (Pitting Resistance Equivalent Number) and resistance to localized corrosion.
Yes, but special procedures must be followed to preserve the correct phase balance and prevent the formation of intermetallic phases. Post-weld heat treatment may be required depending on the grade and application.
Relevant standards include ASTM A182, ASTM A479, ASTM A276, and ASME B18.2.1 / B18.3 for dimensions. For pressure equipment, NACE MR0175 / ISO 15156 compliance is often required.
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