What is ASTM A453 Grade 660?
ASTM A453 Grade 660 is a material specification covering iron-nickel-chromium age-hardenable alloy bolting for high-temperature and high-pressure service. The base material widely known as Alloy A286 and identified by UNS S66286 belongs to the austenitic precipitation-hardening family of superalloys, combining outstanding tensile strength, creep resistance and excellent oxidation resistance at elevated temperatures. The specification covers bolts, stud bolts, heavy hex bolts, socket head cap screws, threaded rods, nuts and washers intended for bolting boiler flanges, pressure vessel nozzles, turbine casings and process piping in service up to 650°C (1200°F).
The standard defines four tensile classes Class A, B, C, and D each differentiated by solution treatment temperature and age hardening parameters. Classes A, B, and C are specified for general high-temperature service and must pass a 100-hour stress rupture test at 650°C. Class D is double-aged to achieve higher yield strength and satisfies the hardness requirements of NACE MR0175 / ISO 15156 for sour-service oil and gas applications.
Jade Alloys manufactures and exports ASTM A453 Grade 660 fasteners from Mumbai, India. We supply fully certified, EN 10204 Type 3.1 MTCs, dual-certified ASTM & ASME SA453 bolting in sizes from 3/8″ to 4″ (imperial) and up to M100 (metric). Custom sizes and special configurations are available to order.
Chemical Composition of ASTM A453 GR 660 Bolts
ASTM A453 GR 660 (UNS S66286 / Alloy A286) is an iron-based superalloy. All four property classes share the identical chemical composition — the differences in mechanical performance arise solely from heat treatment variations.
| Element | C | Mn | P max | S max | Si max | Cr | Ni | Mo | Ti | Al | V | B |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Range (%) | 0.08 max | 1.00–2.00 | 0.025 | 0.025 | 1.00 | 13.50–16.00 | 24.00–27.00 | 1.00–1.50 | 1.90–2.35 | 0.35 min | 0.10–0.50 | 0.003–0.010 |
Role of Key Alloying Elements in Alloy A286
The nickel content (24–27%) establishes a fully austenitic matrix, preventing phase transformation during thermal cycling. Chromium (13.5–16%) provides oxidation and corrosion resistance at high temperature. Titanium (1.90–2.35%) is the primary precipitation-hardening agent — it combines with aluminium and nitrogen to form Ni₃(Ti,Al) gamma-prime precipitates that pin dislocation motion and are responsible for the alloy’s exceptional creep strength. Molybdenum (1.0–1.5%) provides additional solid-solution strengthening and improves creep resistance. Boron (0.003–0.010%) segregates to grain boundaries, significantly improving high-temperature ductility and rupture life.
ASTM A453 Grade 660 Bolts Mechanical Properties — All 4 Classes
Mechanical requirements vary by class. All four classes share identical chemistry (UNS S66286) but differ in heat treatment cycle, producing different strength profiles. Values are per ASTM A453/A453M.
| Tensile | 895 MPa / 130 ksi |
| Yield (0.2%) | 585 MPa / 85 ksi |
| Elongation | 15% min |
| Rupture Test | 100h @ 650°C |
| Hardness | 35 HRC max |
| Tensile | 895 MPa / 130 ksi |
| Yield (0.2%) | 585 MPa / 85 ksi |
| Elongation | 15% min |
| Rupture Test | 100h @ 650°C |
| Hardness | 35 HRC max |
| Tensile | 960 MPa / 140 ksi |
| Yield (0.2%) | 660 MPa / 95 ksi |
| Elongation | 15% min |
| Rupture Test | 100h @ 650°C |
| Hardness | 35 HRC max |
| Tensile | 895 MPa / 130 ksi |
| Yield (0.2%) | 655 MPa / 95 ksi |
| Elongation | 15% min |
| Rupture Test | Not Required |
| Hardness | 35 HRC max |
How Class C Achieves Superior Strength
Class C undergoes oil quenching followed by a two-stage age hardening cycle — a process unavailable to Classes A, B, and D, which use single-stage age hardening. The double-aging treatment produces a finer, more uniformly distributed gamma-prime (γ’) precipitate network throughout the microstructure. This refined precipitate morphology pins dislocation movement more effectively at elevated temperatures, delivering the highest tensile and yield strength of all four classes. Class D, while achieving a comparable yield strength to Class C without the oil quench step, is not required to pass the 100-hour stress rupture test, making it the specification of choice for API 20F BSL-2 and BSL-3 qualification where the rupture test is not mandated.
Full Mechanical Properties Table — Metric (MPa)
| Class | Heat Treatment | Tensile min (MPa) | Yield 0.2% min (MPa) | Elong. min (%) | RA min (%) | Hardness max | Stress Rupture |
|---|---|---|---|---|---|---|---|
| A | Single age hardened | 895 | 585 | 15 | 20 | 35 HRC / 321 HBW | 100h @ 650°C |
| B | Single age hardened (alt.) | 895 | 585 | 15 | 20 | 35 HRC / 321 HBW | 100h @ 650°C |
| C ★ | Oil quench + double age | 960 | 660 | 15 | 20 | 35 HRC / 321 HBW | 100h @ 650°C |
| D | Single age hardened (high yield) | 895 | 655 | 15 | 20 | 35 HRC / 321 HBW | Not required |
Full Mechanical Properties Table — Imperial (ksi)
| Class | Tensile min (ksi) | Yield 0.2% min (ksi) | Elongation min (%) | RA min (%) | Hardness max |
|---|---|---|---|---|---|
| A | 130 | 85 | 15 | 20 | 35 HRC / 321 HBW |
| B | 130 | 85 | 15 | 20 | 35 HRC / 321 HBW |
| C ★ | 140 | 95 | 15 | 20 | 35 HRC / 321 HBW |
| D | 130 | 95 | 15 | 20 | 35 HRC / 321 HBW |
★ Class C recommended for most demanding high-temperature bolting applications. RA = Reduction of Area.
Specification & Standards
Jade Alloys supplies ASTM A453 GR 660 bolts to the following dimensional, certification, and compliance standards.
| Parameter | Details |
|---|---|
| Standard | ASTM A453 / ASME SA453 Grade 660 — Classes A, B, C & D |
| Material | Iron-Nickel-Chromium Alloy (Alloy A286 / UNS S66286) |
| Dimensions | ASME B18.2.1 (inch hex), ASME B18.2.3.3M (metric heavy hex), ASME B18.3 (socket cap) |
| Thread | ASME B1.1 2A/3A — Unified Inch; ASME B1.13M 6h — Metric Coarse |
| Size Range (Imperial) | 3/8″ to 4″ standard; larger sizes available to order |
| Size Range (Metric) | M10 to M100 standard; M100+ custom on request |
| Heat Treatment | Classes A/B/D: Age hardened; Class C: Oil quench + double age hardened |
| Stress Rupture Test | 100 hours at 650°C (Classes A, B & C) — per ASTM A453 |
| Hardness Maximum | 35 HRC / 321 HBW throughout cross-section |
| Mill Test Certificate | EN 10204 Type 3.1 — dual certified ASTM & ASME |
| NACE Compliance | MR0175 / MR0103 / ISO 15156 (hardness ≤ 35 HRC) |
| PED Compliance | PED 2014/68/EU; Merkblatt AD 2000 W2 |
| API Compliance | Class D: API 20F BSL-2 & BSL-3 qualification available |
| Impact Test | Classes A & C: 40 J min at −196°C available on request |
| Marking | Manufacturer’s ID + “660A”, “660B”, “660C” or “660D” on bolt head / stud end |
| Finish Options | Plain, PTFE-coated, Xylan 1070, Black Oxide, Phosphate, Hot-Dip Galvanized |
Every order includes EN 10204 Type 3.1 MTC with full chemical analysis, mechanical test results, heat/lot traceability, and stress rupture test certificate for Classes A, B & C. Radiography, PMI, and third-party inspection available on request.
ASTM A453 GR 660 vs A193 B7 vs A193 B16 — Grade Selection Guide
Selecting the right bolting grade depends on your service temperature, corrosion environment, and code requirements. This comparison covers the three most commonly specified high-temperature bolt grades.
| Property | ASTM A193 B7 | ASTM A193 B16 | ASTM A453 Gr 660 ★ |
|---|---|---|---|
| Material | Cr-Mo Alloy Steel | Cr-Mo-V Alloy Steel | Fe-Ni-Cr (Austenitic) |
| UNS | G41400 | K14072 | S66286 (A286) |
| Maximum Service Temperature | 450°C / 840°F | 593°C / 1100°F | 700°C / 1300°F |
| Minimum Tensile Strength | 860 MPa (≤ M64) | 860 MPa (≤ M64) | 895–960 MPa |
| Heat Treatment | Quenched & Tempered | Quenched & Tempered | Age Hardened |
| Stress Rupture Test | No | No | Yes – 100 Hours @ 650°C |
| Recommended Nut | ASTM A194 Gr. 2H | ASTM A194 Gr. 16 | ASTM A194 Gr. 8 / 8M |
| Best Applications | Petrochemical Plants, Pressure Vessels | Steam Systems, Power Generation | Gas Turbines, Nuclear Plants, Aerospace |
Full Comparison Table
| Property | A453 GR 660 (Class C) | A193 B7 | A193 B16 |
|---|---|---|---|
| Material family | Fe-Ni-Cr austenitic alloy | Cr-Mo alloy steel | Cr-Mo-V alloy steel |
| UNS designation | S66286 | G41400 / G41420 | K14072 |
| Common alias | Alloy A286, A286 SS | AISI 4140 / 4142 | B16 Cr-Mo-V |
| Max service temp. | 700°C (1300°F) | 450°C (840°F) | 593°C (1100°F) |
| Tensile strength min | 960 MPa / 140 ksi | 860 MPa / 125 ksi | 860 MPa / 125 ksi |
| Yield strength min | 660 MPa / 95 ksi | 720 MPa / 105 ksi | 725 MPa / 105 ksi |
| Heat treatment | Age hardened (Class C: oil Q + double age) | Quenched & tempered | Quenched & tempered |
| Stress rupture test | Yes — mandatory (Cl. A/B/C) | No | No |
| Corrosion resistance | Superior (austenitic SS) | Moderate | Moderate |
| NACE MR0175 | Yes (≤35 HRC) | Yes (≤35 HRC) | Yes (≤35 HRC) |
| Mating nut grade | ASTM A194 Gr. 8 / 8M | ASTM A194 Gr. 2H / 2HM | ASTM A194 Gr. 16 |
| Typical applications | Gas turbines, nuclear, aerospace, steam superheaters | Petrochemical, general PV | Power generation, steam |
| AMS / aerospace spec | AMS 5726 / 5737 / 5895 | None | None |
ASTM A453 GR 660 Fastener Types Available
Jade Alloys supplies Alloy A286 (ASTM A453 GR 660) fasteners in all standard forms for pressure, structural, and high-temperature bolting applications.
All A453 GR 660 fastener types supplied with compatible ASTM A194 Grade 8 / 8M heavy hex nuts and ASTM F436 hardened washers on request. Matched bolt-nut-washer sets with single MTC available for pressure vessel and flange applications.
ASTM A453 GR 660 Bolt Torque Chart
Recommended torque values for ASTM A453 GR 660 Class C stud bolts and hex bolts at 75% of minimum yield strength (95 ksi / 660 MPa). Values vary with lubrication condition — always specify anti-seize on austenitic threads.
| Bolt Dia. | TPI | Stress Area (in²) | Torque — Dry (ft-lb) | Torque — Moly Paste (ft-lb) | Torque — PTFE (ft-lb) | Torque — Lubricated (ft-lb) |
|---|---|---|---|---|---|---|
| 3/8″ | 16 | 0.0775 | 15 | 10 | 12 | 11 |
| 1/2″ | 13 | 0.1419 | 36 | 24 | 29 | 27 |
| 5/8″ | 11 | 0.2260 | 73 | 48 | 58 | 54 |
| 3/4″ | 10 | 0.3340 | 130 | 87 | 103 | 97 |
| 7/8″ | 9 | 0.4620 | 209 | 139 | 167 | 157 |
| 1″ | 8 | 0.6060 | 313 | 208 | 250 | 235 |
| 1-1/4″ | 7 | 0.9690 | 614 | 409 | 491 | 461 |
| 1-1/2″ | 6 | 1.4050 | 1,027 | 685 | 822 | 773 |
| 2″ | 4.5 | 2.5000 | 2,189 | 1,459 | 1,752 | 1,645 |
| 2-1/2″ | 4 | 3.7160 | 3,916 | 2,611 | 3,133 | 2,942 |
| 3″ | 4 | 5.2590 | 6,647 | 4,432 | 5,318 | 4,993 |
| 4″ | 4 | 9.9860 | 14,780 | 9,854 | 11,824 | 11,085 |
⚠ Torque values are indicative at 75% of Class C minimum yield (660 MPa / 95 ksi). K-factors used: Dry = 0.20, Moly Paste = 0.133, PTFE = 0.160, Lubricated (oil) = 0.150. Always confirm torque requirements with your design engineer. For metric thread torque values or Class A/B/D data, contact Jade Alloys.
Dimension Chart — A453 GR 660 Stud Bolts & Heavy Hex Bolts
Standard dimensions per ASME B18.2.1 (inch) and ASME B18.2.3.3M (metric). Custom lengths, end configurations, and CNC-machined specials available on request.
Inch Series — Stud Bolt & Heavy Hex Bolt Dimensions
| Nom. Dia (in) | Thread (UNC) | TPI | Width A/F (in) | Heavy Hex Head Ht (in) | Min. Length (in) | Max. Length (in) | Wt/pc (kg) |
|---|---|---|---|---|---|---|---|
| 3/8″ | 3/8–16 UNC | 16 | 9/16 | 21/64 | 1 | 24 | 0.02 |
| 1/2″ | 1/2–13 UNC | 13 | 3/4 | 27/64 | 1.25 | 36 | 0.04 |
| 5/8″ | 5/8–11 UNC | 11 | 15/16 | 35/64 | 1.5 | 36 | 0.07 |
| 3/4″ | 3/4–10 UNC | 10 | 1-1/4 | 41/64 | 2 | 36 | 0.12 |
| 7/8″ | 7/8–9 UNC | 9 | 1-7/16 | 49/64 | 2 | 36 | 0.18 |
| 1″ | 1–8 UNC | 8 | 1-5/8 | 55/64 | 2.5 | 36 | 0.27 |
| 1-1/4″ | 1-1/4–7 UNC | 7 | 2 | 1-3/64 | 3 | 36 | 0.50 |
| 1-1/2″ | 1-1/2–6 UNC | 6 | 2-3/8 | 1-19/64 | 3.5 | 36 | 0.82 |
| 2″ | 2–4.5 UNC | 4.5 | 3-1/8 | 1-51/64 | 4 | 36 | 1.68 |
| 2-1/2″ | 2-1/2–4 UNC | 4 | 3-7/8 | 2-13/64 | 5 | 36 | 2.85 |
| 3″ | 3–4 UNC | 4 | 4-5/8 | 2-39/64 | 6 | 36 | 4.40 |
| 4″ | 4–4 UNC | 4 | 6-1/8 | 3-35/64 | 8 | 36 | 8.50 |
Metric Series — Stud Bolt & Heavy Hex Bolt Dimensions
| Nom. Dia | Pitch (mm) | Width A/F (mm) | Head Ht (mm) | Min. Length (mm) | Max. Length (mm) | Wt/pc (kg) |
|---|---|---|---|---|---|---|
| M10 | 1.5 | 17 | 10 | 30 | 500 | 0.04 |
| M12 | 1.75 | 19 | 12 | 35 | 600 | 0.06 |
| M16 | 2.0 | 27 | 14 | 50 | 900 | 0.14 |
| M20 | 2.5 | 34 | 18 | 60 | 900 | 0.24 |
| M24 | 3.0 | 41 | 22 | 70 | 900 | 0.37 |
| M30 | 3.5 | 50 | 26 | 90 | 900 | 0.63 |
| M36 | 4.0 | 60 | 31 | 110 | 900 | 1.02 |
| M42 | 4.5 | 70 | 34 | 130 | 900 | 1.50 |
| M48 | 5.0 | 80 | 38 | 150 | 900 | 2.14 |
| M56 | 5.5 | 90 | 45 | 170 | 900 | 3.10 |
| M64 | 6.0 | 100 | 51 | 190 | 900 | 4.20 |
| M72 | 6.0 | 115 | 58 | 220 | 900 | 5.50 |
| M80 | 6.0 | 125 | 64 | 240 | 900 | 7.00 |
| M100 | 6.0 | 155 | 80 | 300 | 900 | 12.20 |
Dimensions are indicative per ASME B18.2.1 / B18.2.3.3M. Custom lengths, reduced-shank designs, and special end configurations available per drawing. Contact us for exact dimensional data.
Recommended Mating Hardware
Correct joint design for ASTM A453 GR 660 bolts requires code-matched austenitic nuts and appropriate anti-seize treatment to prevent thread galling.
| Component | Specification | Notes |
|---|---|---|
| Primary Nut | ASTM A194 Grade 8 / 8M | Austenitic heavy hex nut — code-matched for A453 GR 660; standard supply |
| Sour Service Nut | ASTM A194 Grade 8C | For NACE MR0175 / sour service (H₂S) environments |
| Hardened Washer | ASTM F436 Type 1 | For structural and pressure flange applications |
| Disc / Belleville Spring | DIN 2093 disc spring | Recommended for joints prone to bolt relaxation at high temperature |
| Anti-Seize Compound | MoS₂ paste (e.g. Molykote) or Nickel-based | Mandatory on austenitic thread flanks to prevent galling; reduces torque by ~33% |
International Grade Equivalents
ASTM A453 GR 660 (UNS S66286 / Alloy A286) is referenced under numerous international standards. Specify the exact standard and class with your purchase order
Industries & Applications
ASTM A453 GR 660 bolts are the specification of choice wherever sustained high-temperature bolting beyond the capability of conventional alloy steel grades is required.
A453 GR 660 in Nuclear Power Bolting (ASME Section III)
ASTM A453 GR 660 / ASME SA453 GR 660 fasteners comply with ASME Boiler & Pressure Vessel Code Section III requirements for nuclear safety-related bolting in Class 1, 2, and 3 pressure boundary components. The mandatory stress rupture test and traceable EN 10204 Type 3.1 MTC provide the documentation trail required for nuclear quality assurance programmes. Jade Alloys supplies nuclear-grade A453 GR 660 bolts with full NDE (PMI, hardness survey, dimensional inspection) and third-party witness inspection capability.
Aerospace Use of Alloy A286 / A453 GR 660 Fasteners
Under aerospace specifications AMS 5726 and AMS 5895, Alloy A286 bolts are specified for gas turbine disc and casing fasteners, where their combination of high specific strength, oxidation resistance to 700°C, and low thermal expansion compatibility with nickel superalloy components is unmatched by any conventional alloy steel grade. Indian manufacturers supplying Alloy A286 to aerospace OEMs must comply with NADCAP-accredited heat treatment and testing requirements — contact Jade Alloys for aerospace qualification documentation.
Frequently Asked Questions
Technical and commercial questions about ASTM A453 GR 660 bolts, Alloy A286, UNS S66286, and related specifications.
1. What is ASTM A453 GR 660?
2. What are the differences between Class A, B, C and D?
3. Is ASTM A453 GR 660 the same as Alloy A286?
4. What nuts are used with ASTM A453 GR 660 stud bolts?
5. What is the maximum service temperature for A453 GR 660 bolts?
6. What is a stress rupture test and why does A453 GR 660 require it?
7. Can A453 GR 660 bolts be NACE MR0175 compliant?
8. What is the difference between ASTM A453 GR 660 and ASTM A193 B7?
9. Is ASME SA453 Grade 660 the same as ASTM A453 GR 660?
10. What certifications does Jade Alloys provide with A453 GR 660 bolts?
Why Source A453 GR 660 Bolts from Jade Alloys?
We are a dedicated specialty fastener manufacturer, not a trader. Every A453 GR 660 bolt we supply is manufactured in-house from premium Alloy A286 bar stock, heat-treated, tested, and certified under a single quality plan.
ASTM A453 GR 660 Bolt Exporters — Global Destinations
Jade Alloys exports ASTM A453 GR 660 / Alloy A286 bolts from Mumbai to refineries, power plants, EPC contractors, and nuclear facilities worldwide. All export orders include full customs documentation, ECGC insurance, and country-specific material certifications.
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