Amigo Impex has been a super duplex steel fasteners manufacturer, stockist, supplier and exporter in Mumbai, India, for over a decade. Cutting, machining, threading, testing and packing stay in-house. One certified heat covers every bolt, nut and washer that leaves for a single joint.
Super duplex stainless steel fasteners are 25% chromium dual-phase bolting components. High nitrogen and molybdenum contents push the pitting resistance equivalent number past 40 to qualify the material as super duplex. This specific alloy chemistry protects super duplex fasteners against thread corrosion in seawater, brine, and hot chloride process streams. Two grades cover the range we machine: Super Duplex S32750, the higher-nitrogen F53 chemistry, and Super Duplex S32760, the F55 grade carrying deliberate copper and tungsten additions. ASTM A1082 governs the finished bolting in both grades. Metric bolts, screws, studs and nuts are classed to the duplex grades of ISO 3506-1 and ISO 3506-2, where S32750 and S32760 both fall under grade D8 in property classes 70, 80 and 100. Both parts tabulate up to M39, so larger diameters are supplied to the same grade and class by agreement, with every chemical and mechanical requirement met in full. Bar stock arrives to ASTM A276 or ASTM A479.
Diameters span M3 to M56 and 3/16 in to 2 in. Bolt and stud lengths reach 200 mm off the shelf, threaded rod runs to 1 m and 3 m stock lengths, and non-standard pieces are cut against the drawing. Orders draw on 60 to 70 tonnes of ready stock held in Mumbai, despatching pan-India and exporting to the USA, the Gulf, Europe and Asia. Offshore platforms, desalination trains, chemical plants and pump and valve OEMs account for most demand. AS 9120B, ISO 9001:2015 and ISO 45001:2018 certifications are held by our company.
A super duplex fastener order is written against four separate documents: the bolting specification, the raw-material standard, the dimensional code, and the service-limit standard where sour or subsea duty applies. The table below sets out the ones Amigo Impex works to.
The bolting specification, the raw-material standard, the dimensional code and the sour-service limits each govern part of a super duplex fastener order. The table assigns every document its scope so a purchase order cites the right one.
| Standard | Scope |
|---|---|
| ASTM A1082 | High-strength duplex and super duplex stainless bolting |
| ISO 3506-1 / ISO 3506-2 | Mechanical property classes for duplex (austenitic-ferritic) stainless bolts, screws, studs and nuts |
| ASTM A276 / ASME SA-276 | Bar and shapes in S32750 and S32760 |
| ASTM A479 / ASME SA-479 | Bar stock for pressure-retaining service |
| ASTM A564 / ASME SA-564 | Age-hardening stainless bars, the third bar specification ASTM A1082 permits |
| ASTM A962 / A962M | Common requirements for bolting, mandatory alongside ASTM A1082 |
| NACE MR0175 / ISO 15156 | Material limits for sour service |
| DIN 912 / 931 / 933 / 934 / 975 | Metric socket screw, bolt, nut and threaded rod geometry |
| ASME B18.2.1 / ASME B1.1 | Inch-series head dimensions; unified thread form |
| IS 1367 | Supply conditions for threaded fasteners on Indian drawings |
Amigo Impex supplies two super duplex fastener grades, both 25Cr alloys separated by chemistry rather than strength class.
Super Duplex S32750 fasteners answer orders written to ASTM A1082 for UNS S32750, machined from ASTM A276 or ASTM A479 bar. Higher nitrogen makes S32750 the default 25Cr bolting grade.
Copper and tungsten set the F55 chemistry apart. S32760 fasteners are named where a project data sheet demands those additions for severe seawater or sour duty.
Certified Super Duplex S32750 bars and rods and matching S32760 stock feed the thread-cutting line. Anything outside the band is machined to the drawing.
| Parameter | Range |
|---|---|
| Bolt and Screw Diameter | M3 to M56; 3/16 in to 2 in |
| Nut Size | M3 to M56 (ISO 3506-2 tabulates property classes from M5 to M39; sizes outside that band are supplied to the same grade and class by agreement) |
| Stud Bolt and Threaded Rod Diameter | M6 to M56 |
| Bolt, Screw and Stud Length | 10 mm to 200 mm; longer to drawing |
| Threaded Rod Length | 1 m and 3 m standard; cut lengths to order |
| Thread Standards | ISO metric coarse and fine; UNC, UNF |
A super duplex bolt's head suits the tooling that seats it, while its thread matches the drawing series. We cut both in-house, so either choice pairs freely with the other.
Amigo Impex machines the following super duplex types in both S32750 and S32760, all cut from certified bar or forged stock.
Super duplex fastener prices move with nickel and molybdenum rates. Share your grade, size and quantity today for a current per-kg figure in INR or USD.
As a leading super duplex fasteners manufacturer in India, Poly-lined cartons carry small super duplex fastener lots, while wooden cases and seaworthy crating take bulk consignments and long export legs. Every pack is stencilled with heat number, grade, size and specification. Despatch from Mumbai serves pan-India, and export shipments move to the USA, the Gulf, Europe and Asia. Ready sizes leave in 1 to 2 days, while machined-to-order lots need about 30 days.
Positive material identification comes first on super duplex steel fasteners because S32750 and S32760 look identical to the naked eye. Dimensional checks and thread gauging complete lot verification. As a super duplex steel fastener supplier, we provide mill test certificates linking original mill heat chemistry directly to our internal test data. We hold AS 9120B, ISO 9001:2015, and ISO 45001:2018 certifications.
60–70 tonnes held in Mumbai, with urgent requirements dispatched within one to two days.
AS 9120B, PED, ISO 9001:2015 and ISO 45001:2018, with an MTC on every order.
Cutting, machining, threading, fabrication and testing all handled at our own Mumbai facility.
Original mill certificates plus our own test reports, so every batch can be traced back.
Non-standard sizes and specifications made to order.
Dispatched from Mumbai to every major Indian city, and exported to USA, Gulf, Europe, Asia
Super duplex steel fasteners are supplied in UNS S32750 and UNS S32760.
Alloying level: duplex fasteners carry about 22% chromium, while super duplex fasteners hold around 25% with more molybdenum and nitrogen, lifting the PREN above 40.
Specify S32760 fasteners when the project specification names the F55 chemistry; its copper and tungsten additions target severe seawater and sour environments.
ASTM A1082 covers super duplex bolting, with ISO 3506-1 and ISO 3506-2 giving the metric property classes for duplex bolts and nuts, and NACE MR0175 / ISO 15156 setting sour service limits.
Super duplex fasteners serve submerged and splash-zone joints, and a PREN above 40 holds off the pitting and crevice corrosion that seawater chlorides drive. Where the joint sits inside a cathodic protection system the governing risk changes to hydrogen-induced stress cracking. DNV-RP-F112 does not recommend duplex stainless steel for subsea fasteners exposed to cathodic protection and excludes their design from its scope, so a bolted joint of this kind needs the project's own materials engineer to rule on it before any super duplex fastener is specified.
Yes, A mill test certificate accompanies every super duplex fastener consignment, combining mill chemistry with our own laboratory results for traceability.
Super duplex steel fasteners deliver critical high-strength, corrosion-resistant bolting solutions across eight demanding industrial applications subject to harsh chloride environments.
