ASTM A453 Grade 660 Class B Stud Bolt | UNS S66286 A286 Stud Bolts & Heavy Hex Nuts
ASTM A453 Grade 660 Class B stud bolts are precipitation-hardened high-strength alloy steel fasteners manufactured from UNS S66286 (A286 alloy). Designed for elevated-temperature and cryogenic service, ASTM A453 Grade 660 bolting materials provide exceptional tensile strength, creep resistance, oxidation resistance, and corrosion resistance up to 700°C (1300°F).
Combined with ASTM A453 Grade 660 heavy hex nuts or ASTM A194 2HM nuts, these stud bolts are widely used in:
- Pressure vessels
- Heat exchangers
- Steam turbines
- Gas turbines
- Refinery equipment
- Petrochemical plants
- LNG facilities
- Offshore platforms
- Nuclear power stations
We are a professional manufacturer and exporter of:
- ASTM A453 Grade 660 Class A Stud Bolts
- ASTM A453 Grade 660 Class B Stud Bolts
- ASTM A453 Grade 660 Class C Stud Bolts
- ASTM A453 Grade 660 Class D Stud Bolts
- UNS S66286 Stud Bolts
- A286 Threaded Rods
- ASTM A453 Grade 660 Heavy Hex Nuts
with EN 10204 3.1 / 3.2 certification and worldwide project supply.
What Is ASTM A453 Grade 660?
ASTM A453 is the standard specification covering high-temperature bolting materials with thermal expansion coefficients comparable to austenitic stainless steels.
Grade 660 is based on:
- Alloy A286
- UNS S66286
This precipitation-hardened iron-nickel-chromium alloy combines:
- High tensile strength
- Excellent creep resistance
- Good oxidation resistance
- Outstanding fatigue strength
- Excellent low-temperature toughness
ASTM A453 Grade 660 fasteners maintain excellent mechanical properties from cryogenic temperatures down to -196°C up to approximately 700°C.
Equivalent Grades
| Standard | Grade |
|---|---|
| UNS | S66286 |
| ASTM | A453 Grade 660 |
| ASTM | B638 Grade 660 |
| Alloy Name | A286 |
| EN | 1.4980 |
| BS | L17BM |
| AMS | AMS 5731 / AMS 5732 / AMS 5737 |
ASTM A453 Grade 660 Stud Bolt Specification
| Item | Description |
|---|---|
| Standard | ASTM A453 |
| Grade | 660 Class A/B/C/D |
| Material | UNS S66286 |
| Alloy | A286 |
| Dimensions | ASME B18.2.1 |
| Nuts | ASTM A453 Grade 660 / ASTM A194 2HM |
| Thread Standard | ASME B1.1 |
| Thread Types | UNC, UNF, 8UN |
| Diameter Range | 1/4″ – 4″ |
| Length | Custom Length Available |
| Certification | EN10204 3.1 / 3.2 |
ASTM A453 Grade 660 Chemical Composition
| Element | Content (%) |
|---|---|
| Carbon | ≤0.08 |
| Manganese | ≤2.00 |
| Silicon | ≤1.00 |
| Chromium | 13.5 – 16.0 |
| Nickel | 24.0 – 27.0 |
| Molybdenum | 1.0 – 1.5 |
| Titanium | 1.90 – 2.35 |
| Vanadium | 0.10 – 0.50 |
| Aluminum | ≤0.35 |
| Boron | 0.0003 – 0.010 |
The high nickel and chromium content provide exceptional resistance to oxidation and high-temperature degradation.
Mechanical Properties
ASTM A453 Grade 660 Class A/B/C
| Property | Value |
|---|---|
| Tensile Strength | ≥895 MPa |
| Yield Strength | ≥585 MPa |
| Elongation | ≥15% |
| Reduction of Area | ≥18% |
| Hardness | 24-37 HRC |
ASTM A453 Grade 660 Class D
| Property | Value |
|---|---|
| Tensile Strength | ≥895 MPa |
| Yield Strength | ≥725 MPa |
| Elongation | ≥15% |
| Reduction of Area | ≥18% |
| Hardness | 24-35 HRC |
Class D provides the highest yield strength among all Grade 660 classes.
Heat Treatment Requirements
The superior performance of Grade 660 fasteners is achieved through solution treatment and precipitation hardening.
Class B
Solution Treatment:
- 980°C (1800°F)
- Minimum 1 hour
- Liquid quench
Age Hardening:
- 720°C (1325°F)
- 16 hours
- Air cool
Class B is the most commonly specified condition for refinery, LNG, and offshore projects.
Cryogenic Service to -196°C
Unlike conventional alloy steel stud bolts, ASTM A453 Grade 660 can be supplied with impact testing at:
-196°C (-320°F)
This makes Grade 660 particularly suitable for:
- LNG terminals
- Cryogenic storage tanks
- Ethylene plants
- Liquid nitrogen systems
- Low-temperature offshore applications
Many EPC projects specify Grade 660 Class B with BS4882 L17BM impact requirements.
NACE MR0175 / ISO 15156 Compliance
ASTM A453 Grade 660 stud bolts can be manufactured for:
- NACE MR0175
- ISO 15156
Suitable for:
- Sour gas service
- H₂S environments
- Offshore oil production
- Refinery process units
Controlled heat treatment and hardness verification are applied when NACE compliance is required.
Applications
Oil & Gas
- Wellheads
- Manifolds
- Pipeline flanges
- Pressure vessels
LNG & Cryogenic Systems
- LNG terminals
- Storage tanks
- Cryogenic valves
Power Generation
- Gas turbines
- Steam turbines
- Boiler systems
Petrochemical Plants
- Reactors
- Heat exchangers
- High-temperature process equipment
Offshore Platforms
- Topside equipment
- Subsea systems
- Pressure-containing joints
ASTM A453 Grade 660 vs ASTM A193 B7
| Property | A453 Gr.660 | A193 B7 |
|---|---|---|
| Base Alloy | A286 | Cr-Mo Steel |
| Max Service Temp | 700°C | 450°C |
| Cryogenic Capability | Excellent | Limited |
| Corrosion Resistance | Excellent | Moderate |
| Creep Resistance | Excellent | Moderate |
| Cost | Higher | Lower |
For critical high-temperature or cryogenic service, ASTM A453 Grade 660 is generally preferred.
How to Order ASTM A453 Grade 660 Stud Bolts
Example:
Stud Bolt: ASTM A453 Grade 660 Class B
Nut: ASTM A453 Grade 660 Class B Heavy Hex Nut
Size: 1-1/4″ UNC × 220 mm
Thread: 8UN
Standard: ASME B18.2.1 / ASME B18.2.2
Impact Test: -196°C
Certification: EN10204 3.1
NACE: MR0175 Compliant
EXAMPLE#2
SB2N,660CLB,660CLB,UNC,5/8in, 90mm 61.00 EA Studbolts, With nut
Mat spec, stud bolt(s) ASTM A453 GRADE 660 CLASS B BS 4882 GRADE L17BM
Mat spec, nut(s) ASTM A453 GRADE 660 CLASS B BS 4882 GRADE L17BM Service(s) LOW TEMPERATURE SOUR Design spec, stud bolt BS 4882
Design spec, nut ASME B18.2.2 BS 4882 Thread class symbol, stud bolt ASME B1.1 CLASS 2A Thread class symbol, nut ASME B1.1 CLASS 2B Type of thread ASME B1.1 SERIES UNC Type, nut HEAVY HEXAGONAL SEMI FINISHED Number, nuts per bolt 2 IMPACT TEST: BS4882 GR L17BM Inspection, certificate EN 10204-3.1/ISO 10474-3.1
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