Amigo Impex is a duplex steel fasteners manufacturer, supplier and exporter operating from Mumbai, India, since 2013. Cutting, machining, threading, testing and packing are carried out in-house, allowing bolts, nuts, washers and other fastener components to be processed, inspected and packed according to the order requirements.
Duplex stainless steel fasteners are bolting components made of austenitic-ferritic stainless steel with a two-phase microstructure containing austenite and ferrite. This structure gives great strength along with good resistance to chloride pitting and stress corrosion cracking compared with many typical austenitic stainless steels. The chromium, molybdenum and nitrogen content contributes to corrosion resistance in chloride-containing environments such as seawater, brine and process media. The available range covers Duplex 2205, including UNS S31803 and S32205, and Lean Duplex S32304 (2304). Fasteners are supplied against the applicable product and dimensional standards, with bar stock to ASTM A276 / ASME SA-276 for both grades and ASTM A479 / ASME SA-479 for 2205 where pressure-vessel bar is specified.
Diameters range from M3 to M56 in metric sizes and from 3/16 in to 2 in in imperial sizes, with lengths up to 200 mm and non-standard dimensions available to drawing. The range includes ten fastener types, including duplex steel bolts, nuts, stud bolts, threaded rods, screws, washers, U-bolts, anchor bolts and eye bolts. Despatches cover pan-India from Mumbai, while export consignments are supplied to the USA, Gulf, Europe and Asia. Material test certificates accompany applicable consignments, while approximately 60 to 70 tonnes of ready stock support standard requirements.
A duplex steel fastener enquiry depends on the required grade, product specification, dimensions, thread system, fastener form and documentation. The following table summarises the available supply range.
A duplex stainless steel fastener order may involve separate standards covering the material, finished fastener, pressure-service bolting and dimensions. The applicable specification is selected according to the grade, product form and purchase-order requirements.
| Standard | Scope |
|---|---|
| ASTM A1082/ A1082M | High-strength precipitation-hardening and duplex stainless steel bolting for special-purpose applications such as pressure vessels |
| ASTM A276 / ASME SA-276 | Stainless steel bars and shapes used as machining stock |
| ASTM A479 / ASME SA-479 | Stainless steel bars for pressure-vessel and related service |
| ISO 3506 | Mechanical properties and designation of corrosion-resistant stainless steel fasteners |
| NACE MR0175 / ISO 15156 | Materials requirements for applicable sour-service environments |
| DIN 931 / 933 / 934 / 912 / 975 | Metric bolt, nut, socket screw and threaded rod dimensions |
| ASME B18.2.1 / ASME B1.1 | Inch-series dimensional requirements and unified thread forms |
| IS 1367 | Technical requirements for threaded steel fasteners |
The available duplex fastener range consists of Duplex 2205 and Lean Duplex 2304. Duplex 2205 is selected for applications requiring a combination of high strength and corrosion resistance, while Lean Duplex 2304 is suited to less demanding chloride environments where its lower alloy content is appropriate.
Duplex 2205 fasteners cover the UNS S31803 and S32205 designations. The grade combines high mechanical strength with resistance to chloride pitting, crevice corrosion and stress corrosion cracking. In ISO 3506 terms, 2205 is supplied as grade D6, the standard-duplex designation.
Lean Duplex S32304 fasteners contain lower levels of nickel and molybdenum than 2205. They provide a combination of strength and corrosion resistance for moderate chloride exposure, cooling-water systems and other applications where the service environment does not require the higher alloy content of 2205.
Metric and inch-series duplex fasteners are machined from certified bar stock. Sizes up to M39 follow ISO 3506-1 directly, while larger diameters are supplied against the same grade and property requirements, which are confirmed at the order stage.
| Parameter | Range | Applicable Standard |
|---|---|---|
| Bolt and Screw Diameter (metric) | M3 to M39 | ISO 3506-1, property class 70 (2205 and 2304) and class 80 (2205) |
| Bolt and Screw Diameter (metric, oversize) | Above M39 to M56 | ISO 3506-1 chemistry and property requirements, confirmed on order |
| Bolt and Screw Diameter (inch) | 3/16 in to 2 in | ASTM A1082 / A1082M with ASTM A962 / A962M |
| Nut Size | M5 to M39; M3 to M4 and above M39 to M56 confirmed on order | ISO 3506-2, property class matched to the bolt |
| Stud Bolt and Threaded Rod Diameter | M6 to M39; above M39 to M56 confirmed on order | ISO 3506-1; ASTM A1082 for inch-series studs |
| Length | 3 mm to 200 mm; longer lengths to order | Per drawing and purchase order |
| Metric Thread Standards | Coarse M3 to M39; fine M8x1 to M39x3 | ISO 68-1, ISO 261, ISO 262, ISO 965-1 / 965-2 |
| Inch Thread Standards | UNC and UNF | ASME B1.1 |
| Dimensional Standards | Hex, socket and threaded rod forms | ISO 4014, ISO 4017, ISO 4032, ISO 4762, DIN 975; ASME B18.2.1 and B18.2.2 |
| Custom Dimensions | Non-standard diameters, lengths and head configurations to drawing | Purchase-order specific |
Head style is selected according to the assembly method, while thread form follows the application drawing and mating component. Available configurations include:
Duplex screws, including socket head cap screws, for recessed or counterbored applications
The duplex fastener range includes ten forms, supplied according to the applicable grade, dimensions and production requirements:
Stud bolt assemblies can be supplied for flange connections, while other fastener forms are produced according to the application and purchase-order requirements.
Duplex steel fastener lots are packed according to quantity, size and transport requirements. Small quantities can be supplied in poly-lined cartons, while bulk consignments can be packed in wooden cases. Export orders receive suitable protective and seaworthy packaging for international transport.
Each package is identified with the applicable grade, size, heat number and specification. Despatch from Mumbai covers pan-India, while export consignments are supplied to the USA, Gulf, Europe and Asia. Ready-stock items can generally be dispatched within 1 to 2 days, while made-to-order requirements typically require around 30 days, subject to grade, dimensions and quantity.
Each duplex steel fastener lot undergoes applicable dimensional inspection, thread gauging and positive material identification before dispatch. Material test certificates provide traceability to the supplied material, while third-party inspection can be arranged when specified in the purchase order. Amigo Impex operates under AS 9120B, PED, ISO 9001:2015 and ISO 45001:2018 certifications.
Contact Amigo Impex for a current duplex steel fasteners quotation based on the required grade, fastener type, size and quantity.
Request a Quote60–70 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
Duplex bolting is manufactured from austenitic-ferritic stainless steel, which contains both austenite and ferrite phases. The available range includes Duplex 2205, covering UNS S31803 and S32205, and Lean Duplex S32304 (2304), with applicable material standards selected according to the order.
Duplex steel fasteners are supplied in Duplex 2205, covering UNS S31803 and S32205, and Lean Duplex S32304. Super duplex grades are not included in this range.
Yes, duplex steel fasteners generally offer higher mechanical strength than typical 316 stainless steel fasteners and provide superior resistance to chloride-induced stress corrosion cracking. However, the proper grade depends on the application, operating temperature, corrosive environment and design limits. 316 stainless steel may still be preferred where specific corrosion resistance characteristics, manufacturing features or non-magnetic properties are required.
Duplex steel fasteners are available from M3 to M56 in metric sizes and from 3/16" to 2" in imperial sizes. Lengths range up to 200 mm, with longer and non-standard dimensions machined to drawing, subject to production requirements.
Duplex 2205 has a dual-phase microstructure of austenite and ferrite, whereas 304 stainless steel is fully austenitic. That two-phase structure, together with its nitrogen content, gives 2205 roughly double the minimum yield strength of 304. Its higher chromium, molybdenum and nitrogen levels also give significantly better resistance to pitting and chloride stress corrosion cracking compared with 304 stainless steel.
Ready-stock duplex steel fasteners can generally be dispatched within 1 to 2 days. Made-to-order fasteners typically require around 30 days, subject to the required grade, dimensions, quantity and production requirements.
Duplex steel fasteners are commonly selected for load-bearing applications involving chloride-containing or corrosive environments. Major application sectors include:
