RapidBoltDuplex & Super Duplex
Dual-phase microstructure delivering twice the yield strength of austenitic stainless steel with superior resistance to pitting, crevice corrosion, and stress corrosion cracking.
Material Characteristics
Duplex stainless steels combine an approximately equal mixture of ferrite and austenite phases, delivering mechanical properties and corrosion resistance that significantly exceed those of standard austenitic stainless steels. The duplex microstructure provides roughly double the yield strength of 316L, allowing lighter, more efficient designs.
Super Duplex grades (2507, Zeron 100) push performance further with higher chromium, molybdenum, and nitrogen content, achieving Pitting Resistance Equivalent Numbers (PREN) above 40. This makes them the material of choice for aggressive offshore, subsea, and chemical processing environments where chloride-induced stress corrosion cracking is a primary failure mode.
EMG has extensive experience in supplying Duplex and Super Duplex fasteners for major offshore oil & gas projects. All materials are supplied with full EN 10204 3.1 certification, microstructure verification (ferrite/austenite phase balance), and NORSOK M-650 compliance where required.
Key Properties
Available Grades & Specifications
We stock and supply the following grades. All materials supplied with EN 10204 3.1 mill test reports and full chemical and mechanical certification.
| Designation | Description |
|---|---|
| UNS S31803 | Duplex 2205 (Standard) |
| UNS S32205 | Duplex 2205 (High Alloy) |
| ASTM A182 F51 | Duplex 2205 Forging |
| UNS S32750 | Super Duplex 2507 |
| UNS S32760 | Super Duplex Zeron 100 |
| ASTM A182 F53 | Super Duplex 2507 Forging |
| ASTM A182 F55 | Super Duplex Forging |
| UNS S32520 | Super Duplex UR52N+ |
Typical Applications
- Offshore oil & gas platform topside and subsea equipment
- FPSO mooring and riser bolting
- Seawater-cooled heat exchangers and condensers
- Chemical processing plants (chloride environments)
- Desalination plants and water treatment
- Subsea manifolds, trees, and flowlines
- Marine and shipbuilding structural fastening
- Pulp and paper bleaching equipment
- Phosphoric and sulphuric acid handling
Available Fastener Types
NORSOK M-650 Compliance
For North Sea and Norwegian Continental Shelf projects, we supply duplex and super duplex fasteners to NORSOK M-650 requirements including Qualification Test Reports (QTR) and Material Data Sheets (MDS).
Pitting Resistance (PREN)
PREN = %Cr + 3.3(%Mo) + 16(%N). Duplex 2205 achieves PREN > 34 and Super Duplex 2507 achieves PREN > 40, providing reliable chloride pitting resistance in seawater and process environments.
Phase Balance & Testing
All duplex/super duplex fasteners are supplied with verified ferrite/austenite phase balance (typically 40-60% ferrite). Testing per ASTM E562 or point counting ensures microstructural integrity.
Standards & Documentation
All duplex & super duplex fasteners are supplied with full documentation, EN 10204 3.1 mill test reports, and compliance with relevant industry standards.
EN 10204 3.1 Certification
Third-party verified material test reports with full chemical and mechanical data.
Heat Number Traceability
Complete material traceability from mill source through to final delivery.
PMI Testing
Positive Material Identification for critical alloy verification.
ISO 9001 Quality
Quality management ensuring consistent product quality and compliance.
Related Materials & Products
USA, Canada & International Projects
Duplex 2205 & Super Duplex 2507 Bolting in Inch Sizes (ASME / ASTM)
US and Canadian EPC, offshore and chemical-plant buyers usually specify duplex and super duplex bolting in inch sizes to ASME. EMG quotes UNS S31803/S32205, S32750 and S32760 studs, heavy hex bolts and nuts in UNC/8UN inch threads as well as metric, with phase-balance and PMI records.
| Item | Imperial (inch) | Metric | Dimensional reference |
|---|---|---|---|
| Flange stud bolts | 1/4" – 6" dia, 8UN above 1" | M5 – M150 | Lengths per ASME B16.5 / B16.47 flange class |
| Heavy hex bolts | 1/4" – 6" dia | M5 – M150 | ASME B18.2.1 to 1-1/2″, larger to project spec |
| Heavy hex nuts | 1/4" – 6" | M5 – M150 | ASME B18.2.2, oversize-tapped where required |
Inch and metric to your drawing
UNC, UNF and 8UN threads to ASME B1.1, or ISO metric. EMG supplies from 1/4″ up to 6″ diameter, or M5 to M150 metric; final size, grade and quantity are confirmed per RFQ.
ASTM / ASME documentation
- ASTM A182 F51 / F53 / F55 bar
- ASTM A276 / A479 duplex bar
- NORSOK M-650 qualified sources on request
- EN 10204 3.1 / 3.2 certification
Shipped to US & international sites
Air or sea freight arranged USA nationwide, to Canada and to other export destinations. Incoterms, packing and EN 10204 3.1/3.2 paperwork are agreed at quotation. Import duties are the buyer's responsibility.
Buying from North America? Send your RFQ with inch sizes, grade and certification level, or see our global supply and Canada supply pages.
Frequently Asked Questions
Common questions about duplex & super duplex fasteners, specifications, and applications.
What is the PREN and why does it matter?
PREN (Pitting Resistance Equivalent Number) = %Cr + 3.3(%Mo) + 16(%N). It predicts chloride pitting resistance. Duplex 2205 has PREN > 34, Super Duplex 2507 exceeds 40. Higher PREN means superior resistance to seawater pitting and crevice corrosion.
When should I use Super Duplex instead of Duplex?
Super Duplex 2507/Zeron 100 is specified when chloride concentration, temperature, or H₂S levels exceed the limits of Duplex 2205, particularly in subsea equipment, high-pressure seawater systems, and sour gas processing above 60°C.
What is the maximum service temperature for duplex fasteners?
Duplex and Super Duplex fasteners are limited to approximately 300°C. Above this temperature, prolonged exposure causes sigma phase embrittlement — a brittle intermetallic compound that severely reduces impact toughness.
How is phase balance verified in duplex fasteners?
Ferrite/austenite phase balance is verified by metallographic examination per ASTM E562 or point counting. Acceptable range is typically 40–60% ferrite. This is a mandatory requirement for NORSOK M-650 and most offshore specifications.
Need a Quote for Duplex & Super Duplex Bolting?
Tell us the grade, size and quantity you need in duplex & super duplex — we'll confirm availability, certification level and lead time to your site.
Phone
+61 (0)7 4055 6928Emergency Support
24/7 availability for critical projects