ASTM A453 Grade 660 Stud Bolt & Hex Nut | A286 / UNS S66286
A453 Grade 660 Stud bolts and hex nuts are high-strength precipitation-hardened fasteners manufactured from Alloy A-286, UNS S66286, for elevated-temperature and high-stress bolting applications.
Alloy A286 is an iron-nickel-chromium precipitation-hardening alloy containing molybdenum, titanium, vanadium and boron. It combines high tensile strength, good creep and stress-rupture properties, oxidation resistance and useful corrosion resistance at elevated temperatures.
ASTM A453 Grade 660 bolting is commonly used for pressure vessel flanges, valves, turbine equipment, petrochemical plants, power-generation equipment and other high-temperature bolted connections.
We manufacture and supply:
- ASTM A453 Grade 660 Stud Bolts
- ASTM A453 Grade 660 Threaded Rods
- ASTM A453 Grade 660 Hex Bolts
- ASTM A453 Grade 660 Hex Nuts
- ASTM A453 Grade 660 Heavy Hex Nuts
- A286 Stud Bolts
- A286 Hex Bolts
- A286 Nuts
- Custom UNS S66286 Fasteners
ASTM A453 Grade 660 Material Overview
| Item | Specification |
|---|---|
| ASTM Standard | ASTM A453 / A453M |
| Grade | Grade 660 |
| Material | Alloy A-286 |
| UNS | S66286 |
| Material Type | Precipitation-Hardening Iron-Nickel-Chromium Alloy |
| Available Classes | Class A, B, C and D |
| Main Alloying Elements | Fe, Ni, Cr, Mo, Ti |
| Product Forms | Stud Bolt, Bolt, Nut, Screw, Washer, Threaded Rod |
| Typical Service | Elevated Temperature / High-Stress Bolting |
| Common Applications | Pressure Vessels, Valves, Turbines, Petrochemical and Power Plants |
What Is ASTM A453 Grade 660?
ASTM A453 Grade 660 is a high-temperature bolting material based on the precipitation-hardening alloy UNS S66286, commonly known as Alloy A286.
ASTM A453 covers special bolting materials intended for high-temperature service where thermal expansion behavior comparable to austenitic stainless steel is required.
Grade 660 may be supplied in four classes:
- Grade 660 Class A
- Grade 660 Class B
- Grade 660 Class C
- Grade 660 Class D
The classes differ primarily in heat treatment, mechanical properties and strength level.
The required class should therefore always be stated in the purchase order.
Alloy A286 / UNS S66286
Alloy A286 is an iron-base precipitation-hardening alloy containing significant nickel and chromium together with molybdenum, titanium and other controlled alloying elements.
The alloy obtains its high strength through solution treatment followed by precipitation aging.
Important characteristics include:
- High tensile strength
- High yield strength
- Good creep resistance
- Good stress-rupture performance
- Good oxidation resistance
- Good elevated-temperature strength
- Austenitic structure
- Useful corrosion resistance
- Thermal expansion compatible with many austenitic stainless steels
These characteristics make A286 particularly suitable for highly loaded bolted joints exposed to elevated temperatures.
Chemical Composition of Alloy A286
Typical UNS S66286 chemical composition is shown below.
| Element | Typical Requirement |
|---|---|
| Carbon, C | 0.08% max |
| Manganese, Mn | 2.00% max |
| Silicon, Si | 1.00% max |
| Chromium, Cr | 13.5–16.0% |
| Nickel, Ni | 24.0–27.0% |
| Molybdenum, Mo | 1.00–1.50% |
| Titanium, Ti | 1.90–2.35% |
| Vanadium, V | 0.10–0.50% |
| Aluminum, Al | 0.35% max |
| Boron, B | Controlled addition |
| Phosphorus, P | 0.025% max |
| Sulfur, S | 0.025% max |
| Iron, Fe | Balance |
Actual chemistry shall comply with the ordered ASTM A453/A453M specification and is reported on the Material Test Certificate.
ASTM A453 Grade 660 Classes
Grade 660 is available in Classes A, B, C and D.
These class designations are important because they define different heat-treatment and mechanical-property requirements.
ASTM A453 Grade 660 Class A
Class A is solution treated at a lower solution-treatment temperature and then precipitation aged.
It provides a combination of:
- High room-temperature strength
- Good ductility
- Good elevated-temperature performance
- Good fatigue resistance
Class A is frequently specified for high-strength bolts and stud bolts.
ASTM A453 Grade 660 Class B
Class B uses a different solution heat-treatment condition before precipitation aging.
This treatment is commonly selected where improved elevated-temperature creep and stress-rupture performance is important.
Typical products include:
- Grade 660 Class B Stud Bolts
- Grade 660 Class B Bolts
- Grade 660 Class B Nuts
- High-Temperature Valve Bolting
- Turbine Bolting
ASTM A453 Grade 660 Class C and Class D
Classes C and D provide additional strength and processing options within ASTM A453.
Their application depends on:
- Required yield strength
- Product diameter
- Heat treatment
- Operating temperature
- Design requirements
Class selection should always be based on the engineering specification rather than treating all Grade 660 fasteners as interchangeable.
Mechanical Properties
Mechanical properties vary according to ASTM A453 Grade 660 class, product size and heat-treatment condition.
Grade 660 is specifically processed to achieve high strength through precipitation hardening.
Mechanical testing may include:
- Tensile Strength
- Yield Strength
- Elongation
- Reduction of Area
- Hardness
- Stress-Rupture Testing
A commonly encountered high-strength A286 condition may provide approximately:
| Property | Typical Value |
|---|---|
| Tensile Strength | Around 965 MPa / 140 ksi |
| Yield Strength | Around 655 MPa / 95 ksi |
| Elongation | Around 12% or higher |
These values should not be used as universal ASTM A453 Grade 660 acceptance limits.
Final requirements depend on the specified class, size and current ASTM A453/A453M requirements.
Heat Treatment
The properties of Alloy A286 are developed through controlled solution treatment and precipitation aging.
A typical manufacturing sequence includes:
- Solution heat treatment
- Controlled cooling
- Precipitation aging
- Air cooling
- Mechanical testing
Different Grade 660 classes use different heat-treatment conditions.
For example, commonly used A286 processing routes include solution treatment around:
- 1650°F / approximately 900°C
- 1800°F / approximately 980°C
followed by precipitation aging in the approximate 1300–1400°F / 704–760°C range.
The exact heat-treatment cycle shall follow ASTM A453/A453M for the specified class.
High-Temperature Performance
A286 was developed for applications requiring substantial mechanical strength at elevated temperature.
It is widely used in applications exposed to temperatures around 1300°F / 704°C, depending on component design, stress level and applicable design code.
Important elevated-temperature properties include:
- Creep resistance
- Stress-rupture strength
- Oxidation resistance
- Retention of mechanical strength
- Thermal stability
The material’s general temperature capability should not be interpreted as the allowable design temperature of a completed bolted joint.
Actual allowable conditions depend on:
- Design code
- Applied stress
- Bolt diameter
- Joint design
- Flange material
- Operating temperature
- Service duration
- Environment
ASTM A453 Grade 660 Stud Bolts
ASTM A453 Grade 660 stud bolts are used for critical high-temperature flange connections.
Available configurations include:
- Fully Threaded Stud Bolt
- Double-End Stud
- Tap-End Stud
- Threaded Rod
- Custom Stud
Typical applications include:
- Pressure Vessel Flanges
- Valve Flanges
- Turbine Connections
- Heat Exchangers
- High-Temperature Process Piping
- Petrochemical Equipment
Stud bolts can be supplied with two ASTM A453 Grade 660 nuts when required by the project specification.
ASTM A453 Grade 660 Hex Nuts
ASTM A453 Grade 660 nuts can be supplied as matched bolting components for A286 stud bolts and bolts.
Available types include:
- Hex Nut
- Heavy Hex Nut
- Jam Nut
- Custom Machined Nut
Material class, dimensions, thread specification and mechanical-property requirements should be clearly stated on the purchase order.
A286 Stud Bolts
The term A286 Stud Bolt is commonly used commercially for studs manufactured from UNS S66286 material.
For pressure and high-temperature bolting applications, the more precise specification is generally:
ASTM A453 Grade 660 Class A/B/C/D
A typical purchase description would therefore be:
Stud Bolt, ASTM A453 Grade 660 Class A, UNS S66286
rather than simply:
ASTM A286 Stud Bolt
Available Sizes
ASTM A453 Grade 660 stud bolts and nuts can be manufactured in both metric and inch dimensions.
Metric Stud Bolts
Typical sizes include:
- M10
- M12
- M16
- M20
- M24
- M30
- M36
- M42
- M48
- Larger custom sizes
Inch Stud Bolts
Typical diameters include:
- 3/8″
- 1/2″
- 5/8″
- 3/4″
- 7/8″
- 1″
- 1-1/8″
- 1-1/4″
- 1-1/2″
- 2″
- Larger custom sizes
Availability depends on material diameter, class and production requirements.
Thread Options
Available thread systems can include:
- UNC
- UNF
- 8UN
- Metric Coarse
- Metric Fine
- Custom Threads
For large-diameter pressure bolting, 8UN threads are commonly specified.
Thread requirements should include:
- Nominal diameter
- Thread pitch or TPI
- Thread series
- Thread class
- Stud length
Dimensional Standards
Finished A453 Grade 660 fasteners can be manufactured to applicable dimensional standards, including:
- ASME B18 series
- DIN
- ISO
- Project Drawings
- Customer-Specific Dimensions
The material specification and dimensional standard should be stated separately.
For example:
Material: ASTM A453 Grade 660 Class A
Product: Stud Bolt
Thread: 1-1/2″-8UN
Length: 12 inches
ASTM A453 Grade 660 Applications
A453 Grade 660 / Alloy A286 bolting is widely used in:
- Pressure Vessels
- Valve Flanges
- Steam Systems
- Petrochemical Plants
- Refineries
- Power Plants
- Gas Turbines
- Industrial Turbines
- Heat Exchangers
- High-Temperature Piping Systems
- Offshore Equipment
- Oil and Gas Equipment
- Chemical Processing Equipment
The material is particularly useful when both high mechanical strength and elevated-temperature performance are required.
A286 in Aerospace and Industrial Applications
Outside pressure bolting, A286 is also widely used for highly stressed components in:
- Aircraft engines
- Industrial gas turbines
- Exhaust systems
- Turbine casings
- High-temperature structural components
Aerospace A286 material may be supplied to AMS specifications such as AMS 5731, AMS 5732 and AMS 5737.
These AMS material specifications should not automatically be substituted for ASTM A453 bolting requirements.
For ASTM bolting orders, ASTM A453 Grade 660 and the required class should be specified.
Inspection and Certification
ASTM A453 Grade 660 fasteners can be supplied with:
- EN 10204 Type 3.1 Material Test Certificate
- Chemical Analysis
- Tensile Test Report
- Yield Strength Results
- Elongation
- Reduction of Area
- Hardness Testing
- Stress-Rupture Testing where required
- Heat-Treatment Records
- PMI
- Dimensional Inspection
- Thread Inspection
- Visual Inspection
- Full Heat-Number Traceability
- Third-Party Inspection when specified
How to Order ASTM A453 Grade 660 Stud Bolts
A complete inquiry should include:
- ASTM specification
- Grade
- Class
- Bolt diameter
- Length
- Thread
- Quantity
- Nut requirement
- Inspection requirement
Example 1
M16 × 160 mm ASTM A453 Grade 660 Class A Stud Bolt with 2 Heavy Hex Nuts
Example 2
1-1/2″ × 12″ Long, 8UN, ASTM A453 Grade 660 Class A Stud Bolt with 2 Nuts
Example 3
M30 × 300 mm ASTM A453 Grade 660 Class B Fully Threaded Stud with 2 Hex Nuts
Frequently Asked Questions
Is ASTM A453 Grade 660 the same as A286?
ASTM A453 Grade 660 uses the UNS S66286 alloy commonly known as Alloy A286.
A286 identifies the alloy family, while ASTM A453 Grade 660 defines requirements for high-temperature bolting products.
What is UNS S66286?
UNS S66286 is the Unified Numbering System designation for Alloy A286, an iron-nickel-chromium precipitation-hardening alloy.
What is ASTM A453 Grade 660 Class B?
Grade 660 Class B is one of the heat-treated conditions specified by ASTM A453 for UNS S66286 high-temperature bolting.
Its heat treatment and mechanical requirements differ from Class A, C and D.
Can Grade 660 be used for nuts?
Yes. ASTM A453 covers bolting materials including bolts, nuts, screws, washers, studs and stud bolts.
What is the difference between Grade 660 Class A and Class B?
Both use UNS S66286 / A286 material, but the required heat treatment and resulting mechanical and elevated-temperature properties differ.
The required class should follow the engineering or project specification.
Is A286 a nickel alloy?
A286 contains approximately 24–27% nickel but is generally classified as an iron-base precipitation-hardening superalloy rather than a conventional nickel-base alloy.
What temperature can A286 withstand?
A286 maintains useful strength and oxidation resistance at elevated temperatures and is widely applied around 1300°F / 704°C.
The allowable temperature of an actual bolted joint must nevertheless be determined from the applicable design code and service conditions.
ASTM A453 Grade 660 Fastener Manufacturer
We manufacture and supply ASTM A453 Grade 660 / Alloy A286 / UNS S66286 high-temperature fasteners for pressure vessel, valve, refinery, petrochemical, power-generation, turbine and industrial applications.
Available products include:
- ASTM A453 Grade 660 Stud Bolts
- A453 Grade 660 Class A Stud Bolts
- A453 Grade 660 Class B Stud Bolts
- A453 Grade 660 Hex Bolts
- A453 Grade 660 Hex Nuts
- A453 Grade 660 Heavy Hex Nuts
- A286 Stud Bolts
- A286 Bolts and Nuts
- Custom UNS S66286 Fasteners
Metric and inch dimensions, UNC, UNF, 8UN and custom thread configurations are available according to project requirements.
For quotation, please provide the grade and class, diameter, length, thread specification, quantity and inspection requirements.
