Super Duplex S32750 Fasteners

Super Duplex S32750 Fasteners Supplier in Mumbai, India | ASTM A182 / A479

Nicorex Alloys is an ISO 9001 and ISO 14001 certified supplier, importer, and stockist of Super Duplex 2507 fasteners based in Mumbai, India. We offer UNS S32750 (Super Duplex) fasteners in accordance with ASTM A182 . This alloy is the primary choice for manufacturing heavy-duty bolts, stud bolts, nuts, washers, and threaded rods required for critical service environments.

Super Duplex S32750 (Werkstoff 1.4410, EN X2CrNiMoN25-7-4) is a duplex stainless steel with 24–26% Cr, 6–8% Ni, 3–5% Mo, and 0.24–0.32% N. The nominal PREN is approximately 42.7, well above the ≥40 threshold that defines the ‘super duplex’ classification. S32750 is the standard subsea and offshore bolting grade. With a tensile strength of 116 ksi (800 MPa) for bar diameters of 2 inches or less, F53 fasteners offer strong performance in environments with high levels of chloride and high temperatures. ASTM A182 F53 specifies size-dependent mechanical properties: fasteners from ≤2″ bar achieve 800 MPa tensile / 550 MPa yield, while those from >2″ bar achieve 730 MPa / 515 MPa. This distinction is critical for large-diameter flange stud bolt procurement.

Available sizes range from 1/4″ to 4″ (M6 to M100). All fasteners are solution annealed at ≥1050°C with water quench. S32750 fasteners comply with NACE MR0175/ISO 15156 and NORSOK MDS D54 (bar)/MDS D57 (forgings). Industries in which it is widely used include subsea Christmas tree bolting, offshore riser studs, seawater injection systems, desalination equipment, and chemical processing in aggressive chloride service above 35°C. Every shipment carries the EN 10204 3.1 certification and PMI verification.

Super Duplex ASTM A182 F53 Fastener Specifications

Super Duplex S32750 fastener specifications cover forging, bar, and bolting standards along with size ranges, heat treatment, and service temperature limits.

Standard	ASTM A182 F53 / ASME SA-182 F53; ASTM A479 / ASME SA-479
Forms	Bolts, Nuts, Screws, Washers, Studs, Threaded Rods, Hex Bolts, Socket Head Cap Screws, Hex Nuts, Lock Nuts, Stud Bolts
Size	M6 – M100 (Metric); 1/4″ – 4″ (Imperial)
Length	3 mm – 200 mm; Custom lengths available
Diameter	M6 – M100 (Metric); 1/4″ – 4″ (Imperial)
Thread Types	UNC, UNF, Metric Coarse, Metric Fine, BSW, BSF
Surface Finishes	Bright Finish, Pickled, Passivated, Hot-Dip Galvanized, Electropolished
Available Conditions	Solution Annealed
ASTM / ASME Standard	ASTM A182 F53 / ASME SA-182 F53; ASTM A479 / ASME SA-479

Chemical Composition of Super Duplex S32750 Fasteners

The chemical composition of Super Duplex S32750 per ASTM A182 F53 (UNS S32750) produces the high PREN that defines this grade’s corrosion performance.

Element	Carbon (C)	Manganese (Mn)	Phosphorus (P)	Sulphur (S)	Silicon (Si)	Chromium (Cr)	Nickel (Ni)	Molybdenum (Mo)	Nitrogen (N)	Copper (Cu)	Iron (Fe)
Specification Range (%)	0.030 max	1.20 max	0.035 max	0.020 max	0.80 max	24.0–26.0	6.0–8.0	3.0–5.0	0.24–0.32	0.50 max	Balance

PREN = %Cr + 3.3 × %Mo + 16 × %N. 25 + 3.3(4.0) + 16(0.28) = 42.7 nominally. Minimum specification-floor Cr, Mo, and N values surpass 40. S32750 has 2–3% more chromium, 1.5% more molybdenum, and roughly twice the nitrogen of Duplex 2205 (S32205/F60). This alloying raises PREN from ~35 (2205) to ~42 (2507), surpassing the crucial ≥40 super duplex barrier.

Mechanical Properties of Super Duplex Steel UNS S32750 (F53) Fasteners

ASTM A182 F53 specifies size-dependent mechanical minimums for Super Duplex S32750 fasteners in the solution-annealed condition. Properties vary based on the starting bar diameter.

Property	Tensile Strength, min	Yield Strength 0.2%, min	Elongation, min	Hardness, max	Charpy V-Notch, typical
Bar ≤2″ (50 mm)	800 MPa (116 ksi)	550 MPa (80 ksi)	15%	310 HBW	≥45 J at −46°C
Bar >2″ (50 mm)	730 MPa (106 ksi)	515 MPa (75 ksi)	15%	310 HBW	≥45 J at −46°C

Machined fasteners from ≤2″ (50 mm) bar achieve 800 MPa tensile / 550 MPa yield, while those from >2″ bar achieve 730 / 515 MPa. Slower cooling rates during solution annealing and water quenching result in a coarser microstructure for larger bar diameters. M36 stud bolts from >50 mm bar have poorer assured characteristics than M20 studs from ≤50 mm bar. EPC contractors must indicate the beginning bar diameter on large-diameter flange bolting procurement orders.

At 550 MPa yield (≤2″), F53 delivers 2.7× the yield strength of 316L and 1.22× that of Duplex 2205. Charpy impact typically exceeds 45 J at −46°C per NORSOK requirements. For sour service, Hardness must be verified at ≤28 HRC when NACE compliance is required.

Super Duplex Steel S32750 Fasteners Equivalent Grades

The Super Duplex S32750 is recognised internationally with several designations. The primary equivalents are listed below.

Standard System	UNS	Werkstoff Number	DIN/EN	JIS	GOST	AFNOR	ISO
Equivalent Grade	S32750	1.4410	X2CrNiMoN25-7-4	SUS329J4L	Not Specified	Z3CND25-06Az	Not Specified

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Types of Super Duplex S32750 Fasteners

Super Duplex S32750 fasteners are available in 10 standard product forms to cover every bolted connection in subsea, offshore, and chemical process service:

UNS S32750 Hex Bolts

Duplex 2507 Stud Bolts

Super Duplex S32750 Socket Head Cap Screws

UNS S32750 Hex Nuts

Duplex 2507 Lock Nuts

Super Duplex S32750 Flat Washers

Duplex 2507 U-Bolts

C2000 U-Bolts

Super Duplex S32750 Set Screws

UNS S32750 Eye Bolts

Surface Finish & Coating Options

Super Duplex S32750 fasteners come in mill finish, ASTM A967 passivation, PTFE-coated threads for anti-galling, and manganese phosphate. Anti-seize chemical is required during installation. Due to its hardness (310 HBW), super duplex galls more than regular duplex. PTFE coating or thread lubrication avoids thread seizing during installation and disassembly.

Industries and Applications for Super Duplex S32750 Fasteners

Following are some of the industries where Super Duplex S32750 Fasteners is widely used

Subsea Oil & Gas, such as stud bolts for Christmas trees, manifold flange bolting, riser connections, subsea production equipment, umbilical termination hardware, and wellhead bolting per API 17D. S32750 is the default subsea bolting grade where PREN ≥ 40 is mandated.
Offshore Platforms. Seawater lift pump bolting, topside process piping in high-chloride environments, firewater system connections, caisson equipment, and FPSO mooring connections.
RO high-pressure pump bolting, thermal desalination evaporator flanges, and brine heater equipment studs where hot seawater exceeds 40°C.
We offer UNS S32750 (Super Duplex) for high-strength fasteners, such as heavy-duty bolts, stud bolts, nuts, washers, and threaded rods, for use in harsh chemical environments.
We supply heavy-duty bolting for mining and mineral equipment, handling high mechanical loads and corrosive acidic slurries reliably.

How to Order Super Duplex S32750 / F53 Fasteners

To order Super Duplex S32750 fasteners from Nicorex Alloys, provide the following 11 details:

Grade - S32750 / A182 F53
Specification - A182 F53, A479 S32750, or A1082
Bar Diameter - Critical for F53: mechanical properties are size-dependent, ≤2" vs >2"
NORSOK MDS - D54/D57 if offshore
NACE Compliance - NACE MR0103: ≤28 HRC
ASTM G48 CPT Requirement - Specify minimum CPT value
ASTM A923 - Detrimental intermetallic phases
Ferrite Content - 35–65%
Impact Testing - Temperature and Minimum Energy (e.g., ≥45 J at −46°C)
Size / Thread / Length / Quantity / Finish - Size / Thread / Length / Quantity / Finish
Certification - EN 10204 3.1/3.2 + PMI mandatory

Frequently Asked Questions

What is the Difference Between S32750 and S32205?

S32750 is super duplex (PREN ≥40), and S32205 is normal duplex (PREN ~34-36). S32750 has 2–3% more Cr, ~1.5% more Ni, up to 1.5% more Mo, and nearly twice the nitrogen. F53 exhibits a 65°C pitting temperature and 80 ksi yield strength, vastly outperforming F60’s 35°C and 65 ksi, while maintaining a superior 116 ksi tensile threshold. Select S32750 for PREN ≥40, hot seawater over 40°C, or subsea service.

What is the Price of Super Duplex S32750 Fasteners per Kg in India?

Super Duplex S32750 fastener prices in India range approximately from ₹1,200 to ₹3,000/kg depending on size, testing scope, and NORSOK/NACE requirements. S32750 costs approximately 25–40% more than Duplex 2205 due to higher Cr, Mo, Ni, and N content. Large-diameter studs (>2″ bar) may cost more due to limited availability.

Why does ASTM A182 F53 have Size-Dependent Mechanical Properties?

Slower cooling rates during solution annealing and water quenching cause a coarser microstructure and inferior mechanical properties in larger bar diameters. ASTM A182 defines two tiers: ≤2″ (50 mm) bar at 116 ksi tensile / 80 ksi yield, and >2″ bar at 106 ksi / 75 ksi. When buying large-diameter stud bolts, choose the starting bar diameter.

Is Super Duplex S32750 Susceptible to Hydrogen Embrittlement?

Yes. Precipitation-hardened nickel alloys are more vulnerable than S32750. Austenite sinks hydrogen near ferrite cracks. Extreme cathodic protection or high H₂S partial pressures can induce HE. For safety, hardness must be verified at ≤28 HRC when NACE compliance is required. Solution-annealed duplex with 35–65% ferrite is suitable without hardness reporting in NACE MR0175