ASTM A453 Grade 660 Stud Bolts | Alloy A286 / UNS S66286
ASTM A453 Grade 660 Stud bolt are high-strength precipitation-hardened fasteners manufactured from Alloy A286 / UNS S66286 for elevated-temperature bolted connections.
They combine high tensile strength, good oxidation resistance and stable mechanical performance at elevated temperatures, making them suitable for turbines, pressure vessels, valves, heat exchangers, petrochemical equipment and high-temperature flange connections.
Available products include fully threaded stud bolts, continuous-thread studs, double-end studs, hex bolts and matching heavy hex nuts in Class A, B, C and D.
ASTM A453 Grade 660 Material Overview
| Item | Designation |
|---|---|
| Bolting Standard | ASTM A453 / A453M Grade 660 |
| Alloy | Alloy A286 |
| UNS | S66286 |
| EN / W.Nr. | 1.4980 |
| Alloy Type | Precipitation-Hardening Fe-Ni-Cr Alloy |
| Classes | A, B, C, D |
| Stud Dimensions | ASME B18.31.2 or Project Drawing |
| Thread Standard | ASME B1.1 |
| Common Threads | UNC, UNF, 8UN |
| Certification | EN 10204 3.1 / 3.2 when specified |
What Is ASTM A453 Grade 660?
ASTM A453 Grade 660 is a high-temperature bolting grade based on Alloy A286, an iron-nickel-chromium alloy strengthened by solution treatment and precipitation aging.
Typical products include:
- Stud Bolts
- Continuous-Thread Studs
- Double-End Studs
- Hex Bolts
- Heavy Hex Nuts
- Custom High-Temperature Fasteners
ASTM A 453_A453M controls finished bolting requirements including heat treatment, mechanical properties, testing and certification.
Raw material supplied as ASTM A638 Grade 660 should not automatically be described as finished ASTM A453 Grade 660 bolting.
Grade 660 Class A, B, C and D
ASTM A453 Grade 660 is available in four classes.
| Class | General Characteristic | Minimum Yield Strength |
|---|---|---|
| Class A | Solution treated and age hardened | 85 ksi / 585 MPa |
| Class B | Higher-temperature solution treatment and aging | 85 ksi / 585 MPa |
| Class C | Higher-temperature solution treatment with multi-stage aging | 85 ksi / 585 MPa |
| Class D | Higher-yield-strength condition | 105 ksi / 725 MPa* |
*Different mechanical requirements apply to larger Class D diameters.
The required class should be specified by the equipment designer or project material specification. Classes should not be substituted without purchaser approval.
Chemical Composition
Typical Grade 660 / Alloy A286 chemistry includes:
| Element | Minimum % | Maximum % |
|---|---|---|
| Carbon, C | — | 0.08 |
| Manganese, Mn | — | 2.00 |
| Silicon, Si | — | 1.00 |
| Phosphorus, P | — | 0.040 |
| Sulfur, S | — | 0.030 |
| Chromium, Cr | 13.50 | 16.00 |
| Nickel, Ni | 24.00 | 27.00 |
| Molybdenum, Mo | 1.00 | 1.50 |
| Titanium, Ti | 1.90 | 2.35 |
| Aluminum, Al | — | 0.35 |
| Vanadium, V | 0.10 | 0.50 |
| Boron, B | 0.001 | 0.010 |
| Iron, Fe | Balance | Balance |
Nickel and chromium support elevated-temperature corrosion and oxidation resistance, while titanium, aluminum and vanadium contribute to precipitation hardening.
Mechanical Properties
Typical minimum room-temperature requirements include:
| Property | Classes A, B & C | Class D ≤ 2-1/2″ |
|---|---|---|
| Tensile Strength | 130 ksi / 895 MPa | 130 ksi / 895 MPa |
| Yield Strength | 85 ksi / 585 MPa | 105 ksi / 725 MPa |
| Elongation | 15% min | 15% min |
| Reduction of Area | 18% min | 18% min |
Mechanical requirements depend on ordered class and fastener diameter.
ASME B18.31.2 Stud Bolts
Grade 660 stud bolts can be manufactured to ASME B18.31.2 dimensional requirements for inch-series studs.
Available configurations include:
- Fully Threaded Stud Bolt
- Continuous-Thread Stud
- Double-End Stud
- Tap-End Stud
- Custom Stud Bolt
Typical unified threads include:
- UNC
- UNF
- 8UN
ASME B1.1 is commonly specified for unified inch threads.
8UN Grade 660 Stud Bolts
8UN threads are widely used for larger-diameter high-pressure flange bolting.
Typical sizes include:
- 1-1/8″-8UN
- 1-1/4″-8UN
- 1-1/2″-8UN
- 1-3/4″-8UN
- 2″-8UN
These fasteners are commonly used in pressure vessels, high-temperature valves, refinery equipment and process flanges.
ASTM A453 Grade 660 Heavy Hex Nuts
Grade 660 stud bolts can be supplied with matching hex or heavy hex nuts.
A typical bolting set consists of:
- 1 Grade 660 Stud Bolt
- 2 Matching Grade 660 Heavy Hex Nuts
Nut dimensions may be specified to ASME B18.2.2 for inch-series products.
The purchase order should clearly state:
- Nut grade
- Grade 660 class
- Thread series
- Thread fit
- Dimensional standard
- Certification
Using the Alloy A286 name alone does not confirm that the stud and nut meet the same finished-fastener requirements.
High-Temperature Performance
Alloy A286 is commonly selected for bolting applications requiring high mechanical strength and oxidation resistance at elevated temperatures.
It is widely used in applications approaching approximately 704°C / 1300°F, depending on the design conditions.
The allowable temperature of the bolted joint must be determined from the applicable design code, applied stress, preload, pressure, creep, stress relaxation and operating environment.
Grade 660 vs ASTM A193 B7
| Item | Grade 660 / A286 | ASTM A193 B7 |
|---|---|---|
| Alloy Type | Fe-Ni-Cr Precipitation-Hardened | Cr-Mo Alloy Steel |
| Elevated-Temperature Strength | High | Good |
| Oxidation Resistance | Higher | More Limited |
| Corrosion Resistance | Higher | Usually Requires Protection |
| Typical Service | Critical High-Temperature Equipment | General Refinery / Pressure Bolting |
| Cost | Higher | Lower |
Grade 660 is generally selected where the service conditions justify its higher temperature capability and alloy content.
NACE / Sour-Service Requirements
ASTM A453 Grade 660 should not automatically be considered compliant with NACE MR0175 / ISO 15156.
For H₂S-containing service, suitability should be evaluated against the applicable project requirements, including material class, heat treatment, hardness and actual service environment.
Any NACE or ISO requirement should be clearly stated in the inquiry and purchase order.
Typical Applications
ASTM A453 Grade 660 stud bolts are commonly used in:
- Gas and Steam Turbines
- Power-Generation Equipment
- Pressure Vessels
- Heat Exchangers
- High-Temperature Valves
- Refineries
- Petrochemical Plants
- High-Temperature Process Piping
- Compressors and Rotating Equipment
- Critical Flanged Connections
Inspection and Certification
Grade 660 fasteners can be supplied with:
- EN 10204 Type 3.1 MTC
- EN 10204 Type 3.2 when specified
- Chemical Analysis
- Mechanical Testing
- Hardness Testing
- PMI
- Thread-Gauge Inspection
- Dimensional Inspection
- Heat-Treatment Records
- Third-Party Inspection
- Full Heat-Number Traceability
Additional testing can be supplied when specified by the project.
How to Order ASTM A453 Grade 660 Stud Bolts
Example 1
ASTM A453 Grade 660 Class A Stud Bolt, 1-1/2″-8UN × 12″, with 2 Grade 660 Heavy Hex Nuts, EN 10204 3.1
Example 2
ASTM A453 Grade 660 Class B Stud Bolt, 1-1/4″-8UN × 10″, ASME B18.31.2, with 2 Heavy Hex Nuts
Example 3
ASTM A453 Grade 660 Class D Stud Bolt, 2″-8UN × 15″, with 2 Matching Heavy Hex Nuts, PMI and Third-Party Inspection
Frequently Asked Questions
Is ASTM A453 Grade 660 the same as Alloy A286?
Grade 660 uses the Alloy A286 / UNS S66286 material system, while ASTM A453 also specifies finished-bolting heat treatment, mechanical properties, testing and certification.
What is the difference between Grade 660 Class A and Class B?
Both have similar minimum strength requirements, but they use different heat-treatment conditions and therefore have different high-temperature characteristics.
What is Grade 660 Class D?
Class D is a higher-yield-strength Grade 660 condition used where increased minimum yield strength is required.
Can Grade 660 studs be manufactured to ASME B18.31.2?
Yes. Inch-series Grade 660 stud bolts can be manufactured to ASME B18.31.2 dimensions when specified.
Can Grade 660 studs be supplied with matching nuts?
Yes. Stud bolts can be supplied with one or two matching Grade 660 hex or heavy hex nuts.
Related Bolting Products
- ASTM A193 B7 Stud Bolts
- ASTM A193 B16 Stud Bolts
- ASTM A320 L7 Stud Bolts
- ASTM A194 Heavy Hex Nuts
- ASME B18.31.2 Stud Bolts
- UNS S32750 Super Duplex Stud Bolts
- UNS S32760 Super Duplex Stud Bolts
- UNS N06625 Alloy 625 Stud Bolts
- UNS N08825 Alloy 825 Stud Bolts
ASTM A453 Grade 660 Stud Bolt Supplier
We manufacture and supply ASTM A453 Grade 660 / Alloy A286 stud bolts, bolts and matching heavy hex nuts for high-temperature pressure equipment and industrial bolting applications.
Available products include:
- Grade 660 Class A Stud Bolts
- Grade 660 Class B Stud Bolts
- Grade 660 Class C Stud Bolts
- Grade 660 Class D Stud Bolts
- Alloy A286 Fully Threaded Studs
- Grade 660 Heavy Hex Nuts
- ASME B18.31.2 Flange Studs
- Custom High-Temperature Fasteners
For quotation, please provide the Grade 660 class, diameter, length, thread, nut requirement, quantity and inspection requirements.
