Duplex Stainless Steel Fasteners
RAYCHIN SPECIALTY METALS FASTENERS: BOLTS, NUTS, SCREWS, WASHERS, STUDS, THREADED RODS, U-BOLT, J-BOLTS
STANDARD AND CUSTOMIZED, SMALL BATCH AND LARGE BATCH, IMPERIAL AND METRIC
Key properties:
• High strength and fatigue resistance
• Good toughness & ductility
• Temperature usage limit: 570°F
• Low thermal expansion
Corrosion Resistance
• Saltwater: salt air, brackish water and marine environments.
• Localized chloride corrosion: pitting and crevice corrosion as well as stress corrosion cracking.
• Sulfide stress corrosion resistance
• Oxidation
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RAYCHIN LIMITED
Specialist in Duplex Stainless Steel Fasteners · Bolts · Nuts · Screws · Washers · Stud Bolts · Threaded Rods · CustomDuplex Stainless Steel Fasteners: High-Strength Corrosion-Resistant Bolts, Nuts, Screws, Washers, Stud Bolts & Threaded Rods for Extreme Environments
RAYCHIN LIMITED is a recognized expert in duplex stainless steel fasteners — from duplex bolts, duplex nuts, duplex screws, duplex washers, duplex stud bolts, duplex threaded rods to super duplex and custom non-standard configurations. Duplex stainless steels are a family of steels characterized by a dual-phase microstructure of approximately 50% ferrite and 50% austenite, offering a unique combination of high mechanical strength and exceptional corrosion resistance. These alloys provide approximately twice the yield strength of austenitic stainless steels like 316L, while exhibiting excellent resistance to chloride stress corrosion cracking, pitting, and crevice corrosion. Our portfolio includes standard duplex grades (UNS S31803 / S32205 / 1.4462) and super duplex grades (UNS S32750 / S32760 / 1.4410) manufactured to NAS, AN, MS, ANSI, ASTM, ASME, SAE, API, NACE, ISO, DIN and KS standards. Engineered for extreme environments where high strength and corrosion resistance are critical. Duplex stainless steel fasteners are supplied in solution annealed condition with full traceability and third-party certifications.
Complete Range of Duplex Stainless Steel Fasteners – Types & Configurations
Duplex & Super Duplex Bolts
Duplex stainless steel bolts manufactured to DIN 931, DIN 933, ISO 4014, ISO 4017, ASME B18.2.1, and aerospace standards. Available in hex head, heavy hex, flange head, and socket head configurations. Ideal for offshore platforms, chemical processing, and marine applications requiring high strength and corrosion resistance. Available in grades UNS S31803 (F51), UNS S32205, and super duplex UNS S32750 (F53), UNS S32760 (F55). Sizes from M6 to M100 (metric) and 1/4" to 4" (inch).
Duplex & Super Duplex Nuts
Duplex stainless steel nuts manufactured to DIN 934, ISO 4032, ISO 4033, ISO 4034, and ASME B18.2.2 standards. Available in hex nuts, heavy hex nuts, jam nuts, and lock nuts. Precision tapped to Class 2B and 3B tolerances for reliable engagement. Ideal for pressure vessel closures, valve assemblies, and flange connections in corrosive environments. Available in all duplex and super duplex grades. Sizes from M3 to M100 (metric) and #4 to 4" (inch).
Duplex & Super Duplex Screws
Duplex stainless steel screws including hex head screws, socket head cap screws (DIN 912, ISO 4762, ASME B18.3), flat head screws, button head screws, pan head screws, and set screws. Available with various drive types including hex socket, Torx, Phillips, and slotted. Ideal for instrument connections, valve components, and equipment in chloride-laden environments. Sizes from M3 to M36 and #2 to 1-1/2".
Duplex & Super Duplex Washers
Duplex stainless steel washers manufactured to DIN 125, DIN 9021, ISO 7089, ISO 7093, and ASME B18.22.1 standards. Available in flat washers, heavy washers, and spring washers. Precision stamped or machined from solution annealed duplex stainless steel, these washers provide uniform load distribution under bolt heads and nuts. Ideal for flange connections, heat exchanger tube sheets, and vessel assemblies. Sizes from M3 to M100 and #2 to 4".
Duplex & Super Duplex Stud Bolts
Duplex stainless steel stud bolts manufactured to DIN 938, DIN 939, DIN 976, ASME B16.5, and ASME B18.31.2 standards. Available in double-end studs, fully threaded studs, and tap-end studs. Designed for flange connections, pressure vessel closures, and heat exchanger applications in aggressive environments. Essential for ASME B16.5 flange bolting in offshore platforms, chemical plants, and desalination facilities. Sizes from 1/4" to 4" (M6 to M100).
Duplex & Super Duplex Threaded Rods
Duplex stainless steel threaded rods manufactured to DIN 975, DIN 976, ASME B18.31.1M, and ASME B18.31.2 standards. Continuous threads along the entire length allow for cutting to any required length for custom applications. Ideal for pipe supports, flange connections, and structural assemblies in corrosive environments. Available in diameters from 1/4" to 4" (M6 to M100) in standard lengths up to 6 meters. Precision rolled threads for superior strength and consistency.
Key Benefits of Duplex Stainless Steel Fasteners
Exceptional Strength
Duplex stainless steels offer yield strength approximately twice that of austenitic grades like 316L. Typical yield strength: 450-550 MPa for duplex, ≥550 MPa for super duplex. This allows for weight reduction and thinner sections in structural applications.
Superior Chloride SCC Resistance
The duplex microstructure provides excellent resistance to chloride stress corrosion cracking, making these fasteners ideal for marine, offshore, and desalination environments where austenitic stainless steels would fail.
High Pitting & Crevice Corrosion Resistance
With PREN (Pitting Resistance Equivalent Number) values typically >35 for duplex and >40 for super duplex grades, these fasteners offer outstanding resistance to localized corrosion in chloride-containing media.
Good Toughness & Ductility
Despite high strength, duplex stainless steels maintain good impact toughness and ductility, with elongation typically >25% at room temperature and excellent toughness down to -50°C.
Sour Service Approved
NACE MR0175 / ISO 15156 qualified for H₂S environments. Suitable for wellhead equipment, valve assemblies, and subsea connections in oil and gas applications.
Fatigue & Wear Resistance
High strength and good fatigue properties make duplex fasteners ideal for dynamic loading applications such as rotating equipment, vibration-prone assemblies, and cyclic pressure vessels.
Duplex Stainless Steel Grade Selection Guide
Standard Duplex Grades
UNS S31803 / S32205 / 1.4462 (F51): The most widely used duplex grade, offering an excellent combination of high strength and corrosion resistance. PREN >35. Yield strength ≥450 MPa. Ideal for chemical processing, oil & gas, and marine applications.
Super Duplex Grades
UNS S32750 (F53) / 1.4410: Enhanced corrosion resistance with PREN >40. Higher alloy content (25% Cr, 7% Ni, 4% Mo, 0.27% N) provides superior pitting resistance. Yield strength ≥550 MPa. Ideal for severe environments, offshore, and high-chloride applications.
Super Duplex with Copper/Tungsten
UNS S32760 (F55) / 1.4501: Similar to S32750 with additions of copper and tungsten for enhanced corrosion resistance in specific media. Yield strength ≥550 MPa. Suitable for seawater, FGD systems, and aggressive chemical environments.
Manufacturing Standards for Duplex Stainless Steel Fasteners
RAYCHIN LIMITED manufactures duplex stainless steel fasteners to the following national and international standards, ensuring full compliance for projects worldwide. Both standard and non-standard custom configurations are available.
International Standards & Global Designations for Duplex Stainless Steel Fasteners
To serve clients worldwide, RAYCHIN LIMITED manufactures duplex stainless steel fasteners from material conforming to the following national and international specifications.
UNS S31803 UNS S32205 1.4462 F51 UNS S32750 UNS S32760 1.4410 F53 F55 NACE MR0175
Chemical Composition (Weight %) – Duplex & Super Duplex Stainless Steels
Our duplex stainless steel fasteners are produced from melts that strictly conform to the limits below per ASTM A182 / A276. The balanced duplex microstructure provides the unique combination of high strength and corrosion resistance.
Standard Duplex (UNS S31803 / S32205 / 1.4462 / F51)
Super Duplex (UNS S32750 / 1.4410 / F53)
Super Duplex with Copper/Tungsten (UNS S32760 / 1.4501 / F55)
Expert note: The duplex microstructure (approximately 50% ferrite / 50% austenite) provides the exceptional combination of high strength and corrosion resistance. PREN (Pitting Resistance Equivalent Number) is calculated as PREN = %Cr + 3.3 × %Mo + 16 × %N. Standard duplex grades achieve PREN >35, while super duplex grades achieve PREN >40, offering superior resistance to pitting and crevice corrosion in chloride environments.
Complete Mechanical Properties of Duplex Stainless Steel Fasteners
Duplex stainless steel fasteners are supplied in the solution annealed condition (1040-1120°C followed by rapid water quenching). The data below represent minimum requirements per ASTM A182 / A479 unless otherwise noted.
Mechanical Properties by Grade
Physical Properties
Elevated Temperature Properties & Limitations
Duplex stainless steel fasteners are not recommended for sustained service above 300°C (572°F). Exposure to temperatures in the range of 350-1000°C can lead to precipitation of harmful secondary phases (sigma, chi, chromium nitrides) that severely reduce toughness and corrosion resistance. Maximum recommended service temperature is 300°C.
Exceptional Corrosion Resistance of Duplex Stainless Steel Fasteners
Duplex stainless steels offer outstanding resistance to a wide range of corrosive environments, combining the benefits of both ferritic and austenitic grades.
Chloride Stress Corrosion Cracking (SCC) Resistance
Duplex stainless steel fasteners have excellent resistance to chloride SCC, significantly better than austenitic grades like 304L and 316L. The duplex microstructure and high nickel content provide immunity to SCC in most chloride-containing environments up to elevated temperatures.
Pitting and Crevice Corrosion Resistance
High chromium, molybdenum, and nitrogen contents provide exceptional resistance to localized corrosion. PREN values >35 for standard duplex and >40 for super duplex ensure reliable performance in seawater, brines, and other chloride-laden media.
Resistance to Specific Environments
Heat Treatment & Microstructural Stability
Duplex stainless steel fasteners are supplied in the solution annealed condition for optimum corrosion resistance and mechanical properties. Solution annealing should be performed at 1040-1120°C followed by rapid water quenching to maintain the balanced ferrite-austenite microstructure.
Exposure to temperatures between 350-1000°C must be avoided as it can cause precipitation of harmful secondary phases:
- Sigma Phase (σ): Forms rapidly at 700-950°C, severely reducing toughness and corrosion resistance.
- Chi Phase (χ): Forms at 600-800°C, also detrimental to properties.
- Alpha Prime (α′): Forms at 350-550°C (475°C embrittlement), causing hardening and loss of toughness.
- Chromium Nitrides (Cr₂N): Can precipitate at high temperatures, reducing pitting resistance.
All fasteners are fully solution annealed and rapidly quenched to ensure optimal performance. Hot forging temperatures must be carefully controlled to avoid deleterious phase formation.
Special focus: Duplex Stainless Steel Fasteners for Critical Applications
For critical applications requiring exceptional strength and corrosion resistance, RAYCHIN offers duplex stainless steel fasteners manufactured to ASTM, ASME, NACE, and customer-specific specifications. Our capabilities include:
- Offshore Oil & Gas: NACE MR0175 compliant fasteners for wellhead equipment, subsea connectors, riser clamp bolts, valve assemblies, Christmas tree hardware, and platform structural connections.
- Chemical Processing: Reactor bolts, heat exchanger fasteners, distillation column studs, pump and valve hardware, piping flanges.
- Desalination Plants: Reverse osmosis (RO) plant fasteners, evaporator studs, piping flanges, pump bolts, high-pressure piping connections.
- Marine Engineering: Seawater piping fasteners, propeller bolts, valve studs, offshore platform hardware, shipbuilding components.
- Pulp & Paper: Bleaching plant fasteners, digester bolts, paper machine hardware, chemical handling systems.
- Flue Gas Desulfurization (FGD): Scrubber fasteners, absorber tower bolts, ductwork studs, mist eliminator hardware.
- Pressure Vessels: ASME B16.5 flange studs, manway cover bolts, reactor closure fasteners, autoclave hardware.
- Heat Exchangers: Tube sheet studs, channel cover bolts, floating head fasteners, tie rods.
- Standards: DIN 931, DIN 933, DIN 934, DIN 912, DIN 938, DIN 939, DIN 975, DIN 976 (metric); ASME B18.2.1, ASME B18.2.2, ASME B18.3, ASME B16.5 (inch); ASTM A182, A276, A479.
- Thread Classes: 2A, 3A, UNJF-3A, 6g, 6H.
- Sizes: M3 through M100, #2 through 4".
- Certifications: EN 10204 3.1/3.2 material certifications, NACE MR0175, API 20F, PED 2014/68/EU.
All duplex stainless steel fasteners are supplied with full traceability and third-party NDT upon request. Material certifications included. Note: These fasteners are not recommended for sustained service above 300°C due to risk of embrittlement from secondary phase precipitation.
Why RAYCHIN LIMITED – The Duplex Stainless Steel Fastener Authority
Metallurgical competence
Engineers on staff with deep expertise in duplex and super duplex metallurgy. We ensure proper solution annealing (1040-1120°C) and rapid quenching for optimal phase balance and corrosion resistance across all duplex stainless steel fasteners. Every heat is verified by in-house PMI testing to confirm chemistry. With precise control over ferrite-austenite ratios, our fasteners provide the exact balance of strength and corrosion resistance required for your application.
Global approvals & traceability
Our quality system is ISO 9001:2015 and AS9100D certified; we also comply with NAS, AN, MS, ANSI, ASTM, ASME, SAE, API, NACE, ISO, DIN and KS. Full material traceability from melt to final packaging (EN 10204 3.1/3.2). Third-party inspections (ABS, DNV, Lloyds) available. All duplex fasteners meet applicable ASTM, ASME, NACE MR0175, and API standards.
Precision forming & thread rolling
In-house cold heading, hot forging, and precision thread rolling capabilities ensure consistent head dimensions and thread geometry. Precision rolled threads provide superior fatigue life and dimensional accuracy. 100% thread and dimensional inspection available. Controlled underhead fillet for improved fatigue resistance. Hot forging parameters carefully controlled to avoid deleterious phase precipitation.
Custom solutions
Need a special head style, unusual thread configuration, or custom material certification for your extreme environment application? Our engineering team works with you to produce custom duplex stainless steel fasteners to your drawing. We provide specialized surface treatments, passivation, and NACE MR0175 compliant processing per customer requirements.
Contact the duplex stainless steel fastener experts today
Request a quote for duplex stainless steel bolts, nuts, screws, washers, stud bolts, threaded rods & custom configurations – any global standard (NAS, AN, MS, ANSI, ASTM, ASME, SAE, API, NACE, ISO, DIN, KS), any quantity. Inquire about standard duplex (F51/2205) or super duplex (F53/2507, F55) fasteners for offshore, chemical, or desalination applications.
sales@ray-chin.com | +86 534 2166 566Our team speaks English, German, Mandarin, and Japanese – ready for your global procurement.
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