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ISO 9001:2015 · UNS S32750–S32760 · ASTM A182 F53/F55

Super Duplex Steel Fasteners Manufacturer, Supplier & Exporter of Advanced Fastening Solutions

Super Duplex steel fasteners offer the highest combination of strength and corrosion resistance available in stainless steel. We manufacture 2507, Zeron 100 and Ferralium 255 fasteners for offshore, subsea, and desalination applications.
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3

Grades

18

Products

-50°C

Min Temp

300°C

Max Temp

795 MPa

Min tensile strength · 2507 per ASTM A182 F53

Outstanding

PREN 40+ · seawater & sour gas resistance

7.80 g/cm³

Density (avg) · high-alloy dual-phase structure

The subsea-grade dual-phase alloy explained

What is Super Duplex Fasteners?

Super duplex stainless steel is an advanced two-phase alloy with higher alloy content than standard duplex, containing 24–26% chromium, 6–8% nickel, 3.5–5% molybdenum and 0.24–0.32% nitrogen, providing a PREN (Pitting Resistance Equivalent Number) of 40 or above. This high PREN makes super duplex immune to pitting in seawater at temperatures up to 60°C and resistant to sour gas (H₂S + CO₂ + chloride) environments per NACE MR0175 / ISO 15156. Super duplex fasteners are the standard for subsea wellhead equipment, FPSO structural connections, seawater injection systems and NORSOK M-630 qualified offshore bolting. Grade 2507 (UNS S32750) is the most widely specified super duplex fastener alloy, with 795 MPa tensile strength and 550 MPa yield — making it one of the strongest corrosion-resistant fastener materials available.
PropertySpecification
Microstructure50% Austenite + 50% Ferrite
Cr Content24–26%
Mo Content3.5–5%
PREN≥ 40
Density7.80–7.84 g/cm³
ASTM StandardsA182 F53, A182 F55

Super Duplex grades — which do you need?

Multiple fastener grades and material grades of Super Duplex Steel Fasteners serve distinct engineering applications, with each option balancing mechanical properties, corrosion resistance, temperature capability, and strength differently. Compare the available grades below to align material selection with specific industrial fasteners operating environments, industry standards, and detailed engineering requirements.

Grade UNS PREN Key Property Max Temp Best Application
Super Duplex 2507 (Most Popular) UNS S32750 41–43 Chloride resistant 300°C Offshore, desalination View grade
Zeron 100 UNS S32760 41–44 Superior seawater resistance 300°C Offshore, subsea View grade
Ferralium 255 UNS S32550 38–42 Acid resistant 300°C Chemical, marine View grade
Super Duplex 2507
Ferralium 255
Zeron 100

Super Duplex Steel Fasteners — International Standards & Material Certifications

Super Duplex Steel Fasteners from RealBolt Engineering Industries are manufactured to ASME SA-182 F53 (2507) and F55 (Zeron 100) material standards for subsea and offshore service. Every batch ships with EN 10204 MTC 3.2 third-party certification, Charpy impact at −46°C, hardness survey, PMI (XRF), and NACE MR0175/NORSOK M-630 documentation.
Standards
DIN 931 DIN 933 DIN 912 DIN 938 DIN 939 DIN 976-1 DIN 934 DIN 125A DIN 127 ISO 4014 ISO 4017 ISO 4762 ISO 4032 ASME B18.2.1 ASME B18.3 ASME B18.31.2 ASME B18.2.2 EN ISO 4014 EN ISO 4032 IS 1364 IS 1367 IS 12427
Certifications
ISO 9001:2015 NACE MR0175 NABL Lab NORSOK M-630 MTC 3.1 / 3.2

Super Duplex Steel Fasteners Applications — Industries & Use Cases

Super Duplex Steel Fasteners from RealBolt Engineering Industries are specified by engineers and procurement teams across demanding industries where PREN ≥ 40 seawater pitting immunity, 550 MPa yield strength, and NORSOK M-630 subsea qualification is critical to fastener performance and service life. Primary end-use sectors for Super Duplex Steel Fasteners include subsea oil and gas wellheads, FPSOs, NORSOK M-630 offshore bolting, desalination high-pressure systems, and naval marine — click each industry below to see specific application details and recommended grades.
Super Duplex 2507 (UNS S32750) fasteners are the standard for subsea wellhead connectors, flexible riser clamps and pipeline end manifolds (PLEMs) requiring PREN ≥ 40, NACE MR0175 and NORSOK M-630 qualification.
Hull structural bolting, seawater lift pump fasteners and topside process piping connections on FPSOs specify Super Duplex 2507 or Zeron 100 for the combination of yield strength (550 MPa), SCC immunity and seawater corrosion resistance.
High-pressure RO membrane vessel bolting and seawater pump shafting specify Super Duplex for its ability to resist chloride pitting at operating temperatures up to 60°C in concentrated brine.
Chemical tanker cargo pump columns, piping support bolting and inspection hatch fasteners use Super Duplex 2507 or F55 certified to DNV/LR class requirements.
Zeron 100 and 2507 fasteners are used in seawater cooling systems, fire main piping and desalination plant high-pressure brine loops on naval and commercial vessels.

Super Duplex vs Duplex 2205 vs Inconel 625

This comparison table provides subsea engineers, offshore procurement specialists, and NORSOK M-630 specification writers with a structured evaluation of Super Duplex Steel Fasteners versus Duplex 2205 and Inconel 625 — covering PREN pitting resistance, yield strength, maximum service temperature, NACE MR0175 and NORSOK M-630 compliance, and relative cost for subsea, FPSO, and seawater service bolting. Use this data to make an informed alloy selection for your specific operating environment, design code, and budget — or contact RealBolt’s technical team for a project-specific recommendation.
Property Super Duplex 2507 Duplex 2205 Inconel 625
PREN (pitting resistance) >=40 >=35 ~51
Max service temp 300°C 300°C 980°C
Yield strength (min) 550 MPa 450 MPa 414 MPa
Tensile strength (min) 795 MPa 620 MPa 758 MPa
Relative cost High Medium-High Very High
NACE MR0175 compliant Yes Yes Yes

Verdict: Super Duplex 2507 is the best choice for NORSOK M-630 subsea bolting at PREN >=40. Inconel 625 is required above 300°C or in extreme acid conditions. Duplex 2205 is adequate for standard offshore topside service.

Need Super Duplex fasteners? Get a competitive price today.

Partner with RealBolt Engineering Industries for certified Super Duplex Steel Fasteners backed by full EN 10204 material test reports, competitive pricing, and reliable global delivery from our Mumbai facility. Our subsea and offshore technical team supplies NORSOK M-630 qualified Super Duplex Steel Fasteners in 2507, Zeron 100, and F55 with EN 10204 3.2 MTRs, impact test at −46°C, hardness survey, PMI testing, and DNV/Lloyd’s Register third-party inspection in sizes M12–M100. Request a quote today and receive a competitive price within 24 hours.
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Super Duplex Steel Fasteners — Common Questions Answered by Our Technical Team

Browse the expert answers below to the most frequently asked questions about Super Duplex Steel Fasteners — covering 2507 vs Zeron 100 selection, PREN calculation and seawater immunity, NORSOK M-630 qualification requirements, NACE MR0175 sour gas compliance, impact testing at −46°C, sigma-phase temperature limits, and EN 10204 3.2 third-party certification. If your question is not answered here, contact the RealBolt technical team directly for grade-specific guidance, project support, and competitive pricing on Super Duplex Steel Fasteners.
Super Duplex has higher alloy content (Cr 24–26%, Mo 3.5–5%, N 0.24–0.32%) giving PREN ≥ 40 vs Duplex 2205’s PREN ≥ 35. This translates to immunity to seawater pitting at temperatures up to 60°C, higher yield strength (550 MPa vs 450 MPa), and compliance with stricter NORSOK M-630 qualification for subsea service.
NORSOK M-630 is the Norwegian offshore standard for material qualification of subsea bolting. It requires impact toughness testing at -46°C, seawater corrosion testing, and hardness limits (≤ 28 HRC). Real-Bolt supplies NORSOK M-630 qualified Super Duplex 2507 fasteners with full documentation.
Super Duplex requires careful weld procedure qualification to maintain the 50/50 austenite/ferrite balance. On-site welding of Super Duplex fasteners is not recommended. For field applications requiring welded connections, specify flange or mechanical coupling systems. Pre-welded assemblies can be supplied from our facility.
Both are PREN ≥ 40 super duplex alloys. Zeron 100 (UNS S32760) adds tungsten (W 0.5–1%) and copper (Cu 0.5–1%) for improved resistance to reducing acids and crevice corrosion. 2507 (UNS S32750) has higher nitrogen for strength. Choose Zeron 100 for demanding crevice and reducing acid environments; 2507 for maximum strength in seawater.

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