High Quality UNS S32750
Super Duplex Fasteners
Mumbai · India
Why Phase Balance Is Everything with High Quality UNS S32750 Super Duplex Fasteners
UNS S32750’s dual microstructure is exactly where its advantages come from — roughly equal parts austenite and ferrite, each phase contributing something the other doesn’t. Ferrite provides high strength and resistance to chloride stress corrosion cracking; austenite provides ductility and toughness. Get that balance close to 50/50, and the result is an alloy with roughly double the yield strength of standard austenitic stainless, alongside chloride resistance that austenitic grades simply can’t match.
Get the balance wrong, and the alloy stops behaving like duplex stainless at all. Improper solution annealing temperature or cooling rate can push the phase ratio too far toward ferrite, and worse, can allow sigma phase — a brittle intermetallic compound — to precipitate during slow cooling or improper heat treatment. Sigma phase formation is the single most common cause of duplex stainless fastener failure in the field, and it happens silently: the material can look correct and even pass a cursory visual inspection while being genuinely embrittled underneath.
Akbar Fasteners Pvt. Ltd. exports to over 50 countries, and our UNS S32750 fastener range is manufactured with controlled solution annealing and rapid quenching specifically to avoid sigma phase formation, verified by hardness testing and, where specified, ferrite content measurement under our ISO 9001:2015 quality system.
Where S32750 Genuinely Earns Its Place
Roughly Double the Strength of 316
550 MPa minimum yield strength allows smaller bolt sizes for the same load, or higher safety margin at the same size.
Exceptional Chloride SCC Resistance
Duplex microstructure resists chloride stress corrosion cracking far better than standard austenitic stainless grades.
High PREN for Pitting Resistance
PREN of 38-41 gives pitting resistance that meaningfully exceeds standard duplex 2205 and most austenitic grades.
Verified Phase Balance Every Batch
Ferrite content and hardness testing confirms correct heat treatment rather than assuming the marking alone is enough.
Our Quality Control Checklist for S32750
Specific checks that verify the phase balance is genuinely correct, not just assumed.
Controlled Solution Annealing Temperature
Precise temperature control during annealing to establish the correct starting phase balance.
Rapid Quenching to Prevent Sigma Phase
Fast cooling from annealing temperature avoids the slow-cool window where sigma phase forms.
Hardness Verification Every Batch
Hardness testing flags abnormal embrittlement that visual inspection alone would miss.
Ferrite Content Measurement on Request
Magnetic ferrite scope testing available to confirm phase ratio for critical applications.
Mechanical Testing Against Full Spec
Tensile, yield, and elongation testing confirms the alloy actually delivers duplex-level properties.
Full Chemical Composition Verification
Cr, Ni, Mo, and N content confirmed against UNS S32750 specification for every heat.
UNS S32750 Detailed Properties
UNS S32750 Alloying Elements
- Chromium 24.0 – 26.0%
- Nickel 6.0 – 8.0%
- Molybdenum 3.0 – 5.0%
- Nitrogen 0.24 – 0.32%
- PREN (Cr+3.3Mo+16N) 38 – 41
Solution-Annealed Condition
- Tensile Strength 800 MPa min
- Yield Strength 550 MPa min
- Elongation 15% min
- Hardness ~ 28–32 HRC max
- Testing MTC / NABL on request
Available Dimensions
- Metric Diameter M6 – M48
- Imperial Diameter 1/4″ – 2″
- Length Custom to drawing
- Thread Type UNC / UNF / Metric
- Finish As-machined / Passivated
UNS S32750 vs 316 vs Standard Duplex 2205
S32750 sits above standard duplex 2205 in both strength and corrosion resistance, at a proportionate cost. The comparison below is the one we walk through with buyers before quoting, so the extra cost over 2205 is a deliberate decision.
| Property | UNS S32750 (Super Duplex) | UNS S32205 (Duplex 2205) | Type 316 Stainless |
|---|---|---|---|
| PREN | 38 – 41 | ~35 | ~24 |
| Yield Strength | 550 MPa min | 450 MPa min | 205–240 MPa min |
| Chloride SCC Resistance | Excellent | Very Good | Limited |
| Best Suited For | Severe offshore, high chloride | General offshore/marine | Moderate corrosion resistance |
| Relative Cost | Highest | Moderate-High | Lower |
Application Areas
Wherever high strength and severe chloride resistance are both non-negotiable.
Offshore Oil & Gas Platforms
fastening in high-chloride service
Desalination Plants
equipment fastening
Subsea Umbilicals & Risers
subsea connection fastening
Chemical Tanker & Marine
marine structural fastening
Pulp & Paper Processing
plant fastening
Seawater Handling Systems
fastening for seawater service
Heat Exchanger Bolting
heat exchanger flange fastening
General Severe Marine Engineering
the most demanding chloride service
Standard Export Documentation
Prepared as standard practice for every UNS S32750 fastener shipment.
Mill Test Certificate (MTC)
Heat number, chemical composition, and mechanical property verification for every lot.
Ferrite Content Report (On Request)
Magnetic ferrite scope measurement confirming correct phase balance for critical orders.
Certificate of Conformance
Confirms the shipment matches the purchase order specification and grade in full.
Certificate of Origin (COO)
Confirms India as country of manufacture for destination customs purposes.
NABL Accredited Test Reports
Independent mechanical and chemical testing available on request for critical applications.
Bill of Lading
Ocean or air freight shipping document confirming carrier, mode, and consignee details.
Internationally Recognised Standards Coverage
Related Fastener Grades & Materials
Super Duplex Fasteners Manufacturer in India
Our broader super duplex manufacturing capability across both major grades.
View Super Duplex Range →Stainless Steel 316 Fasteners
The economical baseline worth comparing against before specifying super duplex.
View SS 316 →ASTM B150 Aluminum Bronze Fasteners
Another marine corrosion-resistant option, solving galling and non-sparking needs instead.
View Aluminum Bronze →Fastener Applications By Industry
A broader guide to matching fastener material grades to the right industry and environment.
View Applications Guide →Need Verified Phase Balance,
Not Just a Grade Marking?
Ask us for ferrite content verification alongside your MTC — for critical applications, that’s the difference between genuine super duplex and a compromised one. Akbar Fasteners Pvt. Ltd. responds within 24 hours.
Sales: +91 724 0000 733 · Support: +91 800 9315 333 · sales@akbarfasteners.in