ASTM A1082 UNS S32760 Stud Bolt | Super Duplex Fasteners

ASTM A1082 UNS S32760 stud bolts are high-strength super duplex stainless steel fasteners designed for offshore, seawater, oil and gas, chemical-processing and other severe chloride-containing environments. S32760 combines chromium, nickel, molybdenum, nitrogen, copper and tungsten to provide very high mechanical strength together with excellent resistance to pitting, crevice corrosion and chloride stress-corrosion cracking.

In some project specifications and market searches, this type of high-strength S32760 bolting may also be referred to as Zeron 100FG stud bolt or S32760 FG stud bolt. The actual material condition, mechanical properties, impact requirements and certification should always be defined by the applicable procurement specification.

We manufacture and supply UNS S32760 fully threaded studs, flange stud bolts, double-end studs, heavy hex nuts and custom super duplex fasteners in metric and inch sizes, with optional strain-hardened conditions, impact testing, PTFE or fluoropolymer coating, PMI and EN 10204 3.1 certification.

ASTM A1082 S32760 Fastener  Specification

Item	Specification
Material	UNS S32760
Common Material Family	Super Duplex Stainless Steel
EN Material No.	1.4501
EN Designation	X2CrNiMoCuWN25-7-4
Related Forging Grade	ASTM A182 F55
Bolting Standard	ASTM A1082 / A1082M
Stud Standard	ASME B18.31.2 when specified
Nut Standard	ASME B18.2.2 when specified
Thread Standard	ASME B1.1 / metric thread standard
PREN	≥40 typical requirement
Products	Fully Threaded Stud / Flange Stud / Double-End Stud / Heavy Hex Nut
Coating	Plain / PTFE / Fluoropolymer when specified
Certification	EN 10204 3.1 / 3.2 when specified

What Is UNS S32760?

UNS S32760 is a super duplex stainless steel with a mixed austenitic-ferritic microstructure and deliberate additions of copper and tungsten.

It is designed for demanding environments where both high mechanical strength and high localized corrosion resistance are required.

Its alloying system includes:

• Chromium for general corrosion and oxidation resistance
• Molybdenum for pitting and crevice-corrosion resistance
• Nitrogen for strength and localized-corrosion resistance
• Copper for improved performance in selected reducing environments
• Tungsten for additional localized-corrosion resistance
• Nickel for phase balance and toughness

Compared with conventional duplex stainless steels, S32760 provides significantly higher strength and stronger resistance to aggressive chloride-containing environments.

UNS S32760 Chemical Composition

Element	UNS S32760
Chromium, Cr	24.0–26.0%
Nickel, Ni	6.0–8.0%
Molybdenum, Mo	3.0–4.0%
Nitrogen, N	0.20–0.30%
Copper, Cu	0.50–1.00%
Tungsten, W	0.50–1.00%
Carbon, C	0.030% max
Manganese, Mn	1.00% max
Silicon, Si	1.00% max
Phosphorus, P	0.030% max
Sulfur, S	0.010% max
Iron, Fe	Balance

The Cr-Mo-N-Cu-W chemistry distinguishes S32760 from many other duplex and super duplex grades.

Actual heat chemistry is reported on the Material Test Certificate.

PREN and Localized Corrosion Resistance

A key advantage of UNS S32760 is its high Pitting Resistance Equivalent Number.

A commonly used PREN formula is:

PREN = %Cr + 3.3 × %Mo + 16 × %N

S32760 is typically supplied with a PREN of 40 or higher.

This indicates strong resistance to:

• Pitting corrosion
• Crevice corrosion
• Chloride attack
• Chloride stress-corrosion cracking

Some engineering calculations also consider the positive contribution of tungsten.

A tungsten-modified expression may be written as:

PREW = %Cr + 3.3 × (%Mo + 0.5 × %W) + 16 × %N

PREN or PREW should be used as comparison tools rather than as the sole basis for material selection.

ASTM A1082 Bolting Standard

ASTM A1082 / A1082M covers high-strength precipitation-hardening and duplex stainless steel bolting for special-purpose applications.

For UNS S32760 bolting, ASTM A1082 provides a more appropriate bolting-material framework than ASTM A182.

The standards have different purposes:

Standard	Main Function
ASTM A1082	High-strength duplex and precipitation-hardening bolting
ASTM A276 / A479	Stainless steel bar material
ASTM A182 F55	Forged pressure components such as flanges and fittings

ASTM A182 F55 identifies the related S32760 forging grade but should not be treated as the finished stud-bolt standard.

Mechanical Properties

Mechanical properties of S32760 fasteners depend on the ordered material condition, degree of strain hardening and project requirements.

Typical solution-annealed S32760 material may provide:

Property	Typical Minimum Level
Tensile Strength	800 MPa
0.2% Yield Strength	550 MPa
Elongation	25%
Reduction of Area	50%
Hardness	Approximately 290 HB max where specified

Strain-hardened bolting conditions can achieve substantially higher strength.

Final acceptance requirements should follow the ordered ASTM A1082 condition and project bolting specification.

Actual mechanical-test results are reported on the MTC.

S32760 Fastener Conditions

Different S32760 fastener conditions can be supplied according to application and procurement requirements.

Strain-Hardened High-Strength Condition

Controlled strain hardening increases tensile and yield strength while maintaining the corrosion-resistant super duplex microstructure within the applicable process limits.

This condition is commonly selected for demanding bolting assemblies requiring high preload capacity.

FG-Type High-Strength Bolting

The search term Zeron 100FG stud bolt is commonly associated with high-strength S32760 fasteners supplied with demanding mechanical and impact requirements.

FG-type fastener specifications may include:

• High-strength strain-hardened condition
• Charpy V-notch impact testing
• Impact testing at -46°C when specified
• Tight control of mechanical properties
• Offshore and oil & gas bolting applications

The term FG should be treated as a defined fastener condition or procurement designation rather than assumed to be an ASTM grade unless explicitly stated in the purchase specification.

Solution-Annealed Condition

Solution-annealed S32760 fasteners provide lower strength than strain-hardened fasteners but retain high ductility and toughness.

This condition may be selected when high strength is not the primary requirement.

Stud Bolts

Inch-series studs can be manufactured to ASME B18.31.2, including:

• Continuous-thread studs
• Flange bolting studs
• Double-end studs

Heavy Hex Nuts

Inch-series heavy hex nuts can be supplied to ASME B18.2.2 when specified.

Threads

Unified inch threads can be manufactured to ASME B1.1, including:

• UNC
• UNF
• 8UN

Metric coarse and fine threads can also be supplied according to the applicable ISO or project standard.

A typical ordering description is:

ASTM A1082 UNS S32760 Stud Bolt, 1″-8UN × 250 mm, Fully Threaded, Matching Heavy Hex Nuts, EN 10204 3.1

Sour Service

UNS S32760 can be suitable for certain H₂S-containing oil and gas environments when the material condition, hardness and environmental limits satisfy the applicable sour-service specification.

Important factors include:

• Material condition
• Hardness
• Applied stress
• H₂S partial pressure
• Chloride concentration
• pH
• Temperature
• Project-specific limits

Sour-service suitability should therefore be evaluated according to NACE MR0175 / ISO 15156 and the applicable project requirements.

The UNS designation alone does not automatically qualify every finished fastener for every sour-service environment.

Seawater and Offshore Service

S32760 fasteners are widely used in demanding marine and offshore environments because of their high PREN and strong resistance to localized corrosion.

Typical applications include:

• Offshore platforms
• Subsea piping
• Seawater systems
• Desalination equipment
• Marine valves
• Pumps
• Heat exchangers
• Scrubber systems
• Offshore flange joints
• High-chloride process piping

Final suitability depends on temperature, chlorination, crevice geometry, flow conditions and service chemistry.

PTFE / Fluoropolymer-Coated S32760 Stud Bolts

S32760 stud bolts and nuts can be supplied with PTFE or fluoropolymer coating when required.

Potential benefits include:

• Lower thread friction
• Reduced galling tendency
• Improved assembly consistency
• Easier disassembly
• Additional surface barrier protection

Coating directly affects the torque-tension relationship of the bolting assembly.

Installation torque should therefore be based on:

• Actual coating system
• Coating thickness
• Friction coefficient
• Lubrication condition
• Verified nut factor
• Required bolt preload

Torque values for uncoated S32760 fasteners should not automatically be reused for coated fasteners.

Thread Galling and Installation

Super duplex stud-and-nut combinations can be susceptible to thread galling if assembled without suitable control.

Important factors include:

• Thread surface finish
• Lubrication
• Coating
• Installation speed
• Thread fit
• Nut factor
• Tightening sequence
• Required preload

Suitable lubrication or fluoropolymer coating can help reduce galling and improve preload consistency.

S32760 vs S32750 Fasteners

S32760 and S32750 are both super duplex stainless steels, but their chemistries differ.

Item	S32760	S32750
Type	Super Duplex	Super Duplex
Cr	24–26%	24–26%
Ni	6–8%	6–8%
Mo	3–4%	3–5%
N	0.20–0.30%	0.24–0.32%
Cu	0.50–1.00%	Lower
W	0.50–1.00%	No intentional W addition
PREN	≥40	Typically >40
Main Distinction	Cu + W additions	Higher Mo/N typical
Typical Positioning	Severe seawater / offshore / sour service	Severe chloride / seawater service

Neither grade should be treated as universally superior.

Selection should be based on corrosion environment, mechanical requirements, sour-service limits and project specification.

Available Fastener Types

We can supply:

• Fully threaded stud bolts
• Flange stud bolts
• Double-end studs
• Threaded rods
• Heavy hex nuts
• Hex nuts
• Custom machined fasteners
• Matching washers when specified

Typical sizes can include:

Item	Typical Range
Metric Diameter	M6–M80 or project-specific
Inch Diameter	5/16″–3-1/2″ or project-specific
Length	Custom length
Threads	UNC / UNF / 8UN / Metric
Coating	Plain / PTFE / Fluoropolymer

Actual availability depends on raw-material diameter, condition, thread form, length and inspection requirements.

Inspection & Certification

ASTM A1082 UNS S32760 fasteners can be supplied with:

• EN 10204 Type 3.1 MTC
• EN 10204 Type 3.2 when specified
• Heat chemical analysis
• Tensile testing
• Yield-strength testing
• Elongation testing
• Hardness testing
• Charpy impact testing when specified
• PMI
• Dimensional inspection
• Thread inspection
• Visual examination
• Surface inspection
• Raw-material UT when required
• Coating-thickness inspection
• Third-party inspection
• Full heat-number traceability

Frequently Asked Questions

What is ASTM A1082 UNS S32760?

ASTM A1082 UNS S32760 is a high-strength super duplex stainless steel bolting material used for special-purpose fasteners in offshore, seawater, oil-and-gas and other severe corrosive environments.

What is a Zeron 100FG stud bolt?

Zeron 100FG stud bolt is a market and project term commonly associated with high-strength UNS S32760 super duplex bolting supplied in an FG-type fastener condition.

Actual chemical composition, mechanical properties, strain-hardening condition, impact-test requirements and certification should be confirmed against the applicable procurement specification.

Is ASTM A182 F55 the same as ASTM A1082 S32760?

No.

ASTM A182 F55 applies to forged pressure components, while ASTM A1082 applies to high-strength bolting.

Both can use the UNS S32760 material family, but they cover different product forms.

What is the PREN of UNS S32760?

UNS S32760 typically has a PREN of 40 or higher, providing very strong resistance to pitting and crevice corrosion.

Can S32760 stud bolts be used in sour service?

S32760 can be suitable for certain sour-service environments when material condition, hardness and environmental limits comply with NACE MR0175 / ISO 15156 and the applicable project specification.

Why are S32760 stud bolts PTFE coated?

PTFE or fluoropolymer coating can reduce thread friction, lower galling risk and improve assembly consistency.

Because coating changes the nut factor, the required installation torque should be determined specifically for the coated bolting system.

ASTM A1082 UNS S32760 Stud Bolt Manufacturer

We manufacture and supply ASTM A1082 UNS S32760 super duplex stud bolts, fully threaded studs, double-end studs, heavy hex nuts and custom high-strength corrosion-resistant fasteners for offshore, seawater, chemical-processing and sour-service applications.

High-strength S32760 FG-type stud bolts, including products commonly searched as Zeron 100FG stud bolts, can be supplied according to the specified mechanical, impact-testing and certification requirements.

Available options include:

UNC / UNF / 8UN / Metric Threads, Strain-Hardened Conditions, Impact Testing at -46°C, Matching Heavy Hex Nuts, PTFE / Fluoropolymer Coating, PMI, Hardness Testing and EN 10204 Certification

For quotation, please specify:

Material + ASTM A1082 Condition + Product Type + Diameter + Thread + Length + Nut Requirement + Impact Requirement + Coating + Quantity + Inspection Requirements

Example:

ASTM A1082 UNS S32760 FG-Type Stud Bolt, 1-1/4″-8UN × 300 mm, Fully Threaded, Matching S32760 Heavy Hex Nuts, Charpy Impact Test at -46°C, PTFE Coated, EN 10204 3.1