ASTM A453 Grade 660 Stud Bolts with Hex Nuts
ASTM A453 Grade 660 stud bolts are precipitation-hardened, austenitic iron-base alloy fasteners manufactured from Alloy A286 / UNS S66286 for high-temperature bolted connections.
They combine high tensile strength, good stress-rupture performance, oxidation resistance and stable mechanical properties under elevated-temperature service conditions.
We manufacture and export A453 Grade 660 Stud bolt , threaded rods, bolts and matching heavy hex nuts for turbines, boilers, pressure vessels, valves, heat exchangers, petrochemical equipment and high-temperature flange connections.
Products can be supplied in Class A, Class B, Class C or Class D, subject to the project specification and required heat-treatment condition.
What Is ASTM A453 Grade 660?
ASTM A 453_A453M is a material specification for specially processed high-temperature bolting materials with thermal expansion characteristics comparable to austenitic stainless steels.
The specification covers:
- Stud bolts
- Continuous-thread studs
- Double-end studs
- Hex bolts
- Screws
- Threaded fasteners
- Hex and heavy hex nuts
- Washers
Grade 660 is based on Alloy A286, an iron-nickel-chromium alloy strengthened through solution treatment and precipitation aging.
It is intended for critical bolting applications where conventional low-alloy steel fasteners may experience reduced strength, oxidation or stress-rupture performance at elevated temperatures.
ASTM A453 Grade 660 Material Identification
| Designation | Grade or Description | Important Note |
|---|---|---|
| ASTM bolting standard | ASTM A453/A453M Grade 660 | Finished high-temperature bolting products |
| UNS designation | UNS S66286 | Standard alloy identification |
| Common alloy name | Alloy A286 | Iron-base precipitation-hardening alloy |
| AISI designation | No. 660 | Common material designation |
| DIN/Werkstoff number | 1.4980 | Common corresponding European designation |
| Raw material standard | ASTM A638/A638M Grade 660 | Bars, forgings and forging stock |
| Product classes | Class A, B, C and D | Class must be stated in the purchase order |
ASTM A638/A638M Grade 660 raw material should not automatically be described as ASTM A453 Grade 660 finished bolting. The completed fastener must meet the processing, mechanical, stress-rupture, hardness and certification requirements of the ordered ASTM A453/A453M class.
Grade 660 Class A, B, C and D
The four Grade 660 classes use the same basic alloy system but differ in prescribed heat treatment, yield-strength requirements and stress-rupture characteristics.
| Class | General Heat-Treatment Characteristic | Minimum Yield-Strength Level | Procurement Consideration |
|---|---|---|---|
| Class A | Lower-temperature solution treatment followed by aging | 85 ksi / 585 MPa | Common Grade 660 condition |
| Class B | Higher-temperature solution treatment followed by aging | 85 ksi / 585 MPa | Different stress-rupture response from Class A |
| Class C | Higher-temperature solution treatment and multi-stage aging | 85 ksi / 585 MPa | Used where the specified Class C treatment is required |
| Class D | Higher-yield-strength condition | 105 ksi / 725 MPa | Selected when the higher Class D yield requirement is specified |
The correct class should be determined by the equipment designer, applicable piping or pressure-vessel code and project material specification. Classes should not be substituted without purchaser approval.
ASTM A453 Grade 660 Stud Bolt Specifications
| Item | Available Requirement |
|---|---|
| Material specification | ASTM A453/A453M |
| Grade | Grade 660 |
| Classes | A, B, C and D |
| Alloy | Alloy A286 / UNS S66286 |
| Product forms | Stud bolts, double-end studs, continuous-thread studs, threaded rods, hex bolts and nuts |
| Stud dimensions | ASME B18.31.2, ASME B18.31.1M or purchaser drawing |
| Nut dimensions | ASME B18.2.2 or specified metric standard |
| Unified threads | ASME B1.1 |
| Thread series | UNC, UNF, 8UN and special unified threads |
| Thread classes | 2A or 3A for external threads; 2B or 3B for internal threads |
| Metric threads | Coarse or fine metric threads as specified |
| Length | Standard and custom-cut lengths |
| Nut configuration | Normally one or two matching hex or heavy hex nuts |
| Certification | EN 10204 3.1 material test certificate |
| Additional testing | PMI, hardness, UT, impact, stress-rupture or third-party inspection when specified |
Custom dimensions, thread pitches, thread engagement lengths and end configurations can be manufactured according to drawings or project specifications.
Typical Chemical Composition
The following table presents the commonly specified composition range for Grade 660 / Alloy A286. Final acceptance must be based on the applicable ASTM A453/A453M edition and the certified material test report.
| 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 | 0.003 | 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 and strength development during aging.
Mechanical Properties
The following values are commonly specified minimum room-temperature requirements. Exact requirements may depend on product diameter, ordered class and applicable standard edition.
| Property | Classes A, B and C | Class D |
|---|---|---|
| Minimum tensile strength | 130 ksi / 895 MPa | 130 ksi / 895 MPa |
| Minimum yield strength | 85 ksi / 585 MPa | 105 ksi / 725 MPa |
| Minimum elongation | 15% | 15% |
| Minimum reduction of area | 18% | 18% |
| Hardness | As specified by ASTM A453/A453M | As specified by ASTM A453/A453M |
| Stress-rupture testing | Required as applicable | Required as applicable |
The material test certificate should identify the ordered grade, class, heat-treatment condition, test results and heat number.
Heat Treatment and High-Temperature Performance
ASTM A453 Grade 660 obtains its strength through a controlled combination of:
- Solution treatment
- Rapid cooling
- Precipitation aging
- Additional aging stages where required by the ordered class
The exact solution-treatment temperature, holding time, cooling method and aging cycle must follow the specified Grade 660 class and applicable ASTM edition.
Alloy A286 is commonly selected for applications requiring strength and corrosion resistance at temperatures approaching approximately 704°C / 1300°F.
However, this value describes the general capability of the alloy and must not be treated as the automatic maximum design temperature of every stud bolt. The allowable service temperature depends on:
- Applied bolt stress
- Required preload
- Flange design
- Gasket type
- Pressure rating
- Thermal cycling
- Creep and stress-relaxation limits
- Applicable design code
- Exposure environment
ASTM A453 Grade 660 Nuts
Matching nuts can be manufactured from ASTM A453 Grade 660 material when required by the project specification.
A typical flange-bolting set may consist of:
- One fully threaded ASTM A453 Grade 660 stud bolt
- Two ASTM A453 Grade 660 heavy hex nuts
- Unified or metric threads
- Matching grade and class
- Common heat-number traceability where specified
- EN 10204 3.1 certification
The nut material, class, dimensions, thread fit and hardness requirements must be clearly stated in the purchase order.
Using the same alloy name alone does not confirm that the stud and nut have compatible mechanical properties or thread tolerances.
Sour-Service and NACE Requirements
ASTM A453 Grade 660 should not be described as automatically compliant with NACE MR0175 / ISO 15156 or NACE MR0103.
For H₂S-containing or refinery sour-service applications, suitability must be evaluated against the actual project requirements, including:
- Material class
- Heat-treatment condition
- Maximum permitted hardness
- Material microstructure
- Applied stress
- H₂S partial pressure
- Chloride concentration
- Temperature
- pH
- Required testing and certification
Where sour-service compliance is required, the applicable NACE or ISO edition, acceptance criteria and documentation requirements should be stated in the enquiry and purchase order.
Applications
ASTM A453 Grade 660 stud bolts and nuts are commonly used in:
- Gas turbines
- Steam turbines
- Turbine casings
- Power-generation equipment
- Industrial boilers
- Pressure vessels
- Heat exchangers
- High-temperature valves
- Refinery process units
- Petrochemical plants
- Chemical-processing equipment
- High-temperature piping systems
- Flanged pressure connections
- Offshore and marine process equipment
Their combination of high strength, oxidation resistance and stress-rupture performance makes them suitable for critical elevated-temperature fastening systems.
Inspection and Testing
ASTM A453 Grade 660 fasteners can be supplied with the following inspection and documentation, when required:
- Chemical composition verification
- Tensile testing
- Yield-strength testing
- Elongation and reduction-of-area testing
- Hardness testing
- Stress-rupture testing
- Positive material identification
- Dimensional inspection
- Thread-gauge inspection
- Ultrasonic testing
- Magnetic or liquid-penetrant examination where applicable
- Heat-treatment records
- Impact testing at a purchaser-specified temperature
- EN 10204 3.1 certification
- EN 10204 3.2 certification when agreed
- SGS, BV, TÜV or other third-party inspection
Impact temperature, specimen orientation, specimen size and minimum absorbed energy must be stated by the purchaser. A fixed cryogenic impact value should not be assumed unless it is included in the project specification.
How to Order ASTM A453 Grade 660 Stud Bolts
A complete enquiry should include:
- Product type
- Diameter
- Overall length
- Thread series and pitch
- Thread class
- ASTM grade and class
- Number and type of nuts
- Nut material and class
- Dimensional standard
- Quantity
- Certification
- Additional testing
- Sour-service requirements
- Inspection agency
- Marking and packing requirements
Ordering Example 1
Fully Threaded Stud Bolt with Two Heavy Hex Nuts
- Size: M16 × 160 mm
- Stud material: ASTM A453 Grade 660 Class A
- Nut material: ASTM A453 Grade 660 Class A
- Nut quantity: Two per stud
- Thread: Metric coarse thread
- Certification: EN 10204 3.1
Ordering Example 2
High-Temperature Flange Stud Bolt Set
- Diameter: 1-1/2 in.
- Length: 12 in.
- Thread: 8UN
- Stud material: ASTM A453 Grade 660 Class A
- Nut material: ASTM A453 Grade 660 Class A
- Nut type: Heavy hex
- Nut quantity: Two per stud
- Thread fit: 2A external / 2B internal
- Certification: EN 10204 3.1
Ordering Example 3
Continuous-Thread Stud Bolt Assembly
- Product: Fully threaded stud bolt
- Material: ASTM A453 Grade 660 Class B
- Nuts: Two matching Grade 660 Class B heavy hex nuts
- Dimensions: ASME B18.31.2 and ASME B18.2.2
- Threads: ASME B1.1
- Additional requirements: PMI, hardness and third-party inspection
Frequently Asked Questions
Is ASTM A453 Grade 660 the same as Alloy A286?
Grade 660 is based on the Alloy A286 material system and is commonly identified as UNS S66286. However, ASTM A453/A453M also specifies finished-bolting processing, mechanical properties, heat treatment, stress-rupture performance and product certification.
Is ASTM A453 Grade 660 equivalent to 1.4980?
DIN or Werkstoff number 1.4980 is commonly associated with Alloy A286. It should be treated as a corresponding material designation rather than an automatic standard substitution. Chemical composition, heat treatment, mechanical properties and product form must be compared before replacement.
What is the difference between ASTM A453 Grade 660 and ASTM A638 Grade 660?
ASTM A638/A638M mainly covers precipitation-hardening iron-base superalloy bars, forgings and forging stock. ASTM A453/A453M covers completed high-temperature bolting materials and fastener products.
Which Grade 660 class should be selected?
The required class should be stated by the equipment designer or project material specification. Classes A, B and C have similar minimum yield-strength levels but use different heat-treatment and stress-rupture requirements. Class D has a higher minimum yield-strength requirement.
Can Grade 660 stud bolts be supplied with matching nuts?
Yes. Stud bolts can be supplied with one or two matching Grade 660 hex or heavy hex nuts. The nut grade, class, dimensional standard, thread fit and certification should be stated in the enquiry.
Is ASTM A453 Grade 660 suitable for NACE service?
Suitability is project-specific. Compliance depends on the applicable NACE or ISO standard, heat treatment, hardness, service environment and purchaser requirements. It should not be assumed solely from the Grade 660 designation.
What is the maximum operating temperature?
Alloy A286 is commonly used for high-strength applications at temperatures up to approximately 704°C / 1300°F. The actual design temperature of a bolted joint must be determined from the design code, allowable stress, preload, pressure, creep and operating environment.
Related High-Temperature and Low-Temperature Bolting
- ASTM A193 Grade B16 high-temperature stud bolts
- ASTM A193 Grade B7 alloy steel stud bolts
- ASTM A320 Grade L7 low-temperature stud bolts
- ASTM A194 heavy hex nuts
- Alloy A286 threaded rods
- Custom high-temperature fasteners
