Specifications
Surface Treatments
Certifications
- ISO 9001 - 2015 Certified
- PED 2014/68/EC
- NACE MR0175/ISO 15156-2
- NORSOK M-650
- DFAR
- MERKBLATT AD 2000 W2/W7/W10
A286 Stud Bolts
A286 Fasteners being an austenitic
age-hardenable iron based super alloy stainless steel that is melted as AOD + ESR, AOD
+ VAR, or VIM + VAR is manufactured at TorqBolt. Cres-A286 fasteners have excellent
strength even at high temperatures up to 1500 Degrees Fahrenheit. Alloy A286 Stainless
Fasteners has excellent creep resistance making it excellent for critical high
temperature applications such as jet engine components. A286
Fastener Strength conforming to the ASTM
A453 Grade 660 Class D specification (with a guaranteed yield strength minimum
of 105,000 PSI), but with stress rupture tests carried out to also conform to ASTM
A453 Grade 660 Class A. These provide a tensile strength of 895 MPa (minimum),
0.2% offset yield strength of 725 MPa (minimum), elongation of 15% and reduction of
area of 18%. Hardness is in the range 29-35 HRC.
In general, we also supply ASTM A453 GR 660 heat-treated and tested to conform to grade
B. This provides a tensile strength of 895 MPa (minimum), a lower 0.2 offset yield
strength of 585 MPa (minimum), elongation of 15% and reduction of area of 18%. Hardness
is in the range 24-37 HRC.
About A286 Stud Bolts
TorqBolt manufactures Alloy A286 (UNS S66286) stud bolts, double-end studs, tap-end studs, threaded-on-both-ends and continuous-threaded rod, in metric (M5 to M64) and inch series (1/4" to 2-1/2"). A286 stud bolts are solution-treated and aged to ASTM A453 grade 660 Class A, supplied with two heavy-hex nuts and EN 10204 3.1 or 3.2 inspection certification, used for high-pressure flanged joints in gas turbines, exhaust systems, oil-and-gas downhole tools and cryogenic service.
A286 Stud Bolt Types & End Configurations
Alloy A286 stud bolts are produced from solution-treated bar (AMS 5731), thread-rolled or single-point-cut on both ends, then aged at 720 °C for 16 hours.
- Double-end stud (B-type), ASME B16.5 / B16.47 standard for flange-bolting. Threads identical on both ends, two heavy-hex nuts supplied.
- Tap-end stud (A-type), one end class-5 interference fit for tap-screw into a blind hole; opposite end class-2 / 6g.
- Continuous-thread (all-thread) rod, ASTM A453 grade 660 Class A, threaded full length.
- Threaded-on-both-ends with reduced shank, functions as a fuse element.
- Stud with hex nut and washer kit, pre-assembled flange-bolting kit per ASME PCC-1.
A286 Stud Bolt Tightening per ASME PCC-1
ASME PCC-1 Appendix A defines target stud-bolt preload as 50 % of room-temperature yield (~47 ksi residual stress) for general flange service, rising to 75 % yield (~71 ksi) for high-pressure or thermal-cycle service.
- Torque control, ± 25 % preload scatter.
- Torque + angle (TT&A), ± 15 %.
- Bolt elongation, ± 10 %.
- Hydraulic tensioning, ± 5 %.
- Ultrasonic length-change, ± 3 %.
A286 Stud Bolt Service Standards
- ASTM A453 grade 660 Class A, primary material spec.
- ASME B16.5 / B16.47, flange dimensions, bolting tables.
- ASME PCC-1 (2019), flange-joint assembly guidelines.
- NACE MR0175 / ISO 15156-3, sour-service hardness limit ≤ HRC 35.
- NORSOK M-650, offshore prequalification including stud-bolt heat-treatment QTR.
- MSS SP-44, alloy stud-bolting for high-pressure service.
Alloy A286 Stud Bolts , Specification Overview
A286 stud bolts join high-pressure flanged connections in environments where retained preload at temperature is non-negotiable: gas turbines, jet-engine accessory mounts, exhaust systems, oil & gas downhole tools, cryogenic LNG service, nuclear primary-pressure boundaries. A double-end stud bolt rotates with both nuts spinning freely on identical thread engagement, eliminating the asymmetric thread-engagement length that limits bolt-and-nut assemblies on flange-bolting service.
The complete flange-bolting assembly per ASME PCC-1 includes the stud, two heavy-hex A286 nuts (matched heat for traceability), and two hardened washers. Tightening per Appendix A targets 50 % room-temperature yield (~47 ksi residual) for general flange service or 75 % yield (~71 ksi) for high-pressure or thermal-cycle service.
A286 Stud Bolts Governing Standards & Specifications
TorqBolt manufactures every a286 stud bolts to the applicable industry standard. The matrix below lists the principal specifications, material, dimensional, inspection , that a286 stud bolts are released against. EN 10204 type 3.1 mill certificates ship with every order; type 3.2 third-party-witnessed inspection is available for nuclear, offshore and customer-mandated source-surveillance contracts.
| Authority | Specification | Coverage |
|---|---|---|
| ASTM | A453 grade 660 Class A/B/C/D | Stud-bolt material, primary spec |
| AMS | 5731 / 5732 / 5737 | Bar / forging stock |
| ASME | B16.5 / B16.47 / B18.31.2 / B18.31.3 | Pipe-flange bolting / continuous-thread / tap-end |
| ASME | PCC-1 (2019) Appendix A/K | Bolted-flange-joint assembly + lubricant friction |
| DIN | 938 / 939 / 940 / 949 / 976 | Tap-end / double-end / continuous-thread / threaded rod |
| ISO | 898-1 / 3506-1 / 4014 / 4017 | Mechanical property classes / threaded fastener stainless / hex bolt |
| MSS | SP-44 | Alloy stud-bolting for high-pressure service |
| NACE | MR0175 / ISO 15156-3 | Sour service ≤ HRC 35 / HV 327 |
| NORSOK | M-650 | Offshore prequalification QTR , 5-year validity |
| EN | 10204 3.1 / 3.2 | Mill / third-party-witness cert |
| API | 20E / 20F | Bolting + non-bolting fastener manufacture for petroleum |
A286 Stud Bolts Sizes & Available Patterns
A286 stud bolts are produced from solution-treated bar (AMS 5731), cut to length, thread-rolled or single-point-cut on both ends, then aged. Each stud ships with two heavy-hex A286 nuts and EN 10204 type 3.1 inspection certification.
| Type | Standard | Metric range | Inch range | Length |
|---|---|---|---|---|
| Double-end stud (B-type) | ASME B16.5 / B18.31.2 | M12, M64 | 1/2" , 2-1/2" | Up to 1500 mm |
| Tap-end stud (A-type) | ASME B18.31.3 / DIN 939 | M5, M48 | 1/4" , 2" | Up to 600 mm |
| Continuous-thread (all-thread) | DIN 976 / ASME B18.31.4 | M5, M64 | 1/4" , 2-1/2" | 3 m bar, cut to need |
| Reduced-shank double-end | Drawing-specific (BS 4882 style) | M16 , M64 | 5/8", 2-1/2" | Up to 1500 mm |
| Stud + nut + washer kit | ASME PCC-1 sub-assembly | M12 , M48 | 1/2", 2" | Per flange schedule |
A286 Stud Bolts Manufacturing Process
Every a286 stud bolts TorqBolt ships traces back to a vacuum-induction-melted plus vacuum-arc-remelted (VIM-VAR) ingot meeting AMS 5731 / 5732 chemistry. The complete manufacturing route is:
- Melt: VIM-VAR ingot to AMS 5731 chemistry; element ranges per ASTM A453 grade 660.
- Bar production: hot-rolled and centerless-ground to bar diameter that allows for machining stock and thread-rolling allowance.
- Cutting to length: precision saw or shear with deburred ends.
- Thread rolling: threads rolled (not cut) on both ends , or full length for continuous-thread, on a flat-die or planetary-die roller.
- Solution treatment: 980 °C, oil-quench. For reduced-shank designs the heat treatment is performed BEFORE machining the reduced section so the section remains in the strongest condition.
- Precipitation aging: 720 °C / 16 h, air-cool. Develops 130 ksi UTS minimum and 95 ksi yield minimum.
- Surface finish: passivated per ASTM A967; cadmium-plated, silver-plated or dry-film-lubricant coated for offshore and nuclear applications.
- Inspection: dimensional CMM, hardness traverse, tensile coupon, hardness verification per NACE MR0175 / NORSOK M-650 if invoked, NDT (UT / LPI) per drawing, end-cap protection.
- Pairing: matched with two heavy-hex A286 nuts (same heat for matched-pair) and 2 hardened washers if PCC-1 kit specified.
Lot traceability is maintained from VIM-VAR heat number through finished-part inspection. Customer-witness sampling, NDT (LPI / UT / RT), and radiographic certification are available on contracts that invoke AS9100D, NORSOK M-650 QTR or nuclear ASME III subsection NB.
Stud Bolt Quality Plan
Stud-bolt inspection is built around ASME PCC-1 Appendix A acceptance criteria , the bolt must perform predictably at flange tightening and at temperature. Each lot moves through:
- Tensile test on at least one specimen per heat with full stress-strain trace; UTS, 0.2 % yield, elongation, and reduction of area recorded.
- Charpy V-notch impact at −46 °C for offshore service or at room temperature for general flange-bolting.
- Hardness traverse, 4 positions across the bolt cross-section verifying aging uniformity.
- NACE MR0175 hardness verification on every heat for sour service (HV 327 / HRC 35 maximum).
- Ultrasonic inspection (UT per ASTM E114) on bolts > 1" / M24 in diameter to detect centerline porosity.
- Liquid-penetrant inspection (LPI per ASTM E1417) on threads after rolling.
- Length, thread, and major-diameter gauging on every part.
NORSOK M-650 QTR is on file for A286 stud-bolt manufacture and is renewed every 5 years. Type 3.2 inspection with third-party witness is standard for offshore and nuclear orders; type 3.1 for general industrial service.
A286 Stud Bolt Applications by Industry
Industrial gas turbine casing flanges
Casing-split joint bolting, combustor-can liner attachment, transition-piece floating-pin retention. Typical preload 71 ksi residual (75 % yield), tightening per ASME PCC-1 Appendix A using hydraulic tensioning.
Jet-engine accessory and propulsion bolting
Engine-pylon attachment studs, accessory-gearbox housing flange bolting, exhaust nozzle-to-augmentor connection.
Oil & gas downhole and surface flanges
API 20E-certified bolting on christmas-tree flanges, blowout-preventer bonnet bolting, pressure-housing closure bolting. NACE MR0175 hardness verification on every heat. NORSOK M-650 QTR maintained for offshore qualification.
Cryogenic LNG and rocket-propellant flanges
Liquid-natural-gas valve bonnet flanges, liquid-oxygen / liquid-hydrogen pump-discharge flange bolting. A286 retains 85 % of room-temperature toughness at −196 °C, well below LH₂ service.
Nuclear pressure-vessel bolting
ASME III subsection NB-2000 lists A453 grade 660 as a permitted bolting material. PWR pressuriser-flange bolting, steam-generator hand-hole closure studs and primary-coolant-pump casing studs.
A286 Stud Bolts vs Alternative Materials
Flange stud-bolt material decisions weigh strength, preload retention, sour-service compliance, and cost. B7 covers below 450 °C; A286 dominates 540-700 °C; Inconel 718 takes over above 700 °C. B8M is the cryogenic and chloride-corrosion alternative below 425 °C.
| Property | A286 stud (A453 660) | B7 (A193) | Inconel 718 | B8M (A193) |
|---|---|---|---|---|
| Service ceiling | 700 °C | 450 °C | 700 °C | 425 °C |
| RT tensile | 895 MPa | 860 MPa | 1240 MPa | 515 MPa |
| NACE MR0175 sour service | ≤ HRC 35 | Restricted | ≤ HRC 40 | ≤ HRC 35 |
| NORSOK M-650 QTR | Available | Required | Available | Available |
| Cost index | 1.0× | 0.2× | 3.0× | 0.5× |
A286 is the sweet-spot fastener material when service temperature exceeds 315 °C (the 17-7 PH ceiling) but the application can’t justify a 3× cost jump to Inconel 718. Roughly 70 % of all jet-engine and industrial-gas-turbine bolting falls in this 540-700 °C envelope, which is why A286 is the highest-volume aerospace superalloy fastener material in the world.
How to Specify an A286 Stud Bolt
- Material spec: ASTM A453 grade 660 Class A (or AMS 5731 for aerospace).
- Stud type: double-end (B-type, default for ASME B16.5 flanges) / tap-end (A-type) / continuous-thread / reduced-shank.
- Size: nominal × pitch × length, e.g. M20 × 2.5 × 180 mm; or 1"-8UN × 7".
- Mating nuts: “2 heavy-hex A286 nuts ASTM A453 grade 660”, matched heat if specified.
- Surface finish: passivated / silver-plated / cadmium-plated / dry-film-lubricant per drawing.
- Service: NACE MR0175 (sour), NORSOK M-650 (offshore), ASME III NB (nuclear) , specify if invoked.
- Inspection certificate: EN 10204 3.1 default, 3.2 if invoked.
Example: “Double-end stud bolt, ASTM A453 grade 660 Class A, ST+A, ASME B16.5, M20 × 2.5 × 180 mm, c/w 2 heavy-hex A286 nuts (same heat) and 2 ASTM F436 washers, dry-film lubricant per AS 5272, EN 10204 3.2, NACE MR0175 hardness verified.”
Why TorqBolt for A286 Stud Bolts
Stud bolts are the foundation of every high-pressure flange-bolting kit we ship. Our specialty is the complete kit, not the loose stud:
- ASME PCC-1 kits: stud + 2 heavy-hex A286 nuts (matched heat) + 2 hardened ASTM F436 washers + dry-film lubricant per AS 5272. Single SKU.
- NORSOK M-650 QTR audited: offshore qualification on file and renewed every 5 years; type 3.2 third-party-witness inspection available on request.
- Lengths to 1500 mm: full range of double-end, tap-end and continuous-thread products from M5 / 1/4" up to M64 / 2-1/2".
30-plus years of fastener manufacture; ISO 9001:2015 + PED + NORSOK + NACE MR0175 hardness verification on every heat; stamped lot identification on every stud.
A286 Stud Bolt Order Profile
About two-thirds of our stud-bolt orders ship as complete ASME PCC-1 flange-bolting kits (stud + 2 nuts + 2 washers + lubricant). Roughly a quarter are NORSOK M-650-qualified offshore orders shipping under EN 10204 type 3.2 inspection. The remainder are speciality patterns: continuous-thread rod cut to length, reduced-shank designs for fuse-element behaviour, and tap-end studs for cylinder-head and valve-cover service.
From the bolting kit floor: PCC-1 Appendix A target preload is 50 % of room-temperature yield, but on flange-bolting service above 540 °C we recommend customers go to 75 %. The reason: residual stress relaxation at temperature reduces the actual clamp load by 18-22 % within the first 100 hours. Several of our offshore customers learned this the hard way before they let us specify the kit lubricant and tightening sequence.
Satisfaction Survey
