RAYCHIN LIMITED

Complete Range of A286 Studs – Configurations & Styles

Manufacturing Standards for A286 Studs

RAYCHIN LIMITED manufactures A286 studs to the following national and international standards, ensuring full compliance for projects worldwide. Both standard and non-standard custom configurations are available.

Stud Dimensional Standards

All dimensional standards available in UNC, UNF, UNJF-3A per MIL-S-8879, and metric thread configurations. Standard diameters from 1/4" to 4" (M6 to M100) with lengths up to 6 meters. API 6A studs available in sizes up to 4" for closure bolting applications.

International Standards & Global Designations for A286 Studs

To serve clients worldwide, RAYCHIN LIMITED manufactures A286 studs from material conforming to the following national and international specifications. This ensures full compliance for projects in the Americas, Europe, Asia, and the Middle East.

UNS S66286 Alloy 660 ASTM A453 AMS 5732 AMS 5737 NACE MR0175 1.4980 API 20F GH2132 SUH660

Chemical Composition (Weight %) – A286 Superalloy (UNS S66286 / 1.4980)

Our A286 studs are produced from melts that strictly conform to the limits below per ASTM A453 / AMS 5731. The high nickel and chromium content provide excellent oxidation resistance, while titanium and aluminum enable precipitation hardening through gamma-prime (γ') phase formation. Molybdenum and vanadium contribute to solid solution strengthening, and boron enhances creep resistance.

Expert note: The combination of titanium and aluminum promotes the formation of Ni₃(Al,Ti) gamma-prime precipitates during aging, which provide A286 with its exceptional high-temperature strength. Boron addition (0.001-0.010%) significantly improves creep resistance by strengthening grain boundaries. With nickel content of 24-27%, A286 offers excellent resistance to chloride stress corrosion cracking and maintains a stable austenitic structure from cryogenic temperatures up to 700°C.

Complete Mechanical Properties of A286 Studs (per ASTM A453)

A286 studs are supplied in the solution annealed and precipitation hardened condition (982°C solution treat + 718°C age for 16 hours). ASTM A453 defines multiple classes for different strength levels and size ranges. The data below represent minimum requirements per ASTM A453/A453M unless otherwise noted.

Tensile Requirements by Class – ASTM A453 Grade 660

Hardness Requirements

For NACE MR0175 / API 20F sour service applications, Class D with maximum hardness 35 HRC is required and 100% hardness testing is mandatory.

Impact Properties (Charpy V-Notch)

Class D studs are Charpy impact tested at -196°C with 40 J as the minimum qualifying requirement for cryogenic and sour service applications.

Stress Rupture Properties (650°C / 1200°F)

A critical requirement for high-temperature studs is stress rupture resistance. Per ASTM A453, Class A, B, and C materials must meet the following:

Note: Class D does not have a stress rupture requirement (marked "NR" in the standard).

Temperature-Dependent Yield Strength

The following table shows typical yield strength (0.2% offset) at elevated temperatures for A286 in the fully heat-treated condition.

Elevated Temperature Oxidation Resistance

A286 maintains anti-tensile strength not less than 885 MPa at 500°C with stress retention greater than 88.35%, making it the optimal choice for high-temperature stud applications.

Physical Properties of A286

Thermal Expansion Properties of A286 Studs for Flange Connections

A286 studs are specifically designed for bolting austenitic stainless steel components (A182 F304, F316, F321) operating at elevated temperatures. Its thermal expansion coefficient closely matches that of 304/316 stainless steels, preventing loss of preload during thermal cycling – a critical feature for maintaining gasket stress and preventing leaks in high-temperature flange connections.

This expansion match is critical for maintaining seal integrity in high-temperature applications such as refinery piping systems, power generation HRSG connections, and chemical processing equipment. Standard alloy steel fasteners expand less than the surrounding stainless steel flanges, leading to loss of preload and potential leaks at temperatures above 400°C. A286 eliminates this mismatch.

API 6A & NACE MR0175 Compliance for A286 Studs

A286 studs are widely used in oil and gas applications requiring sour service resistance. Per API 6A and API 20F, A286 Grade 660 Class D is approved for H₂S service with maximum hardness of 35 HRC.

Heat Treatment & Microstructural Stability of A286 Studs

Optimal mechanical properties in A286 studs are achieved through a two-step heat treatment:

• Solution Annealing: 982°C (1800°F) for 1 hour, oil quench or water quench. This dissolves carbides and prepares the matrix for precipitation hardening.
• Aging (Precipitation Hardening): 718°C (1325°F) for 16 hours, air cool. This forms coherent γ' (gamma-prime) precipitates [Ni₃(Al,Ti)] that provide high-temperature strength.

Metallurgical studies show that controlled aging at 718°C ensures optimal γ' formation while avoiding η phase precipitation, maximizing creep resistance and long-term stability up to 700°C.

Corrosion Resistance of A286 Studs

While A286 is primarily selected for high-temperature strength, it also offers good corrosion resistance in many environments due to its high chromium (14-16%) and nickel (24-27%) content. The alloy exhibits excellent oxidation resistance up to 700°C continuous service and 815°C intermittent service.

Oxidation and Scaling Resistance

The chromium content provides excellent resistance to oxidation and scaling. A286 studs form a protective Cr₂O₃ scale that prevents further oxidation at elevated temperatures. They provide excellent oxidation resistance up to 815°C in continuous service and up to 982°C for intermittent service.

Corrosion in Other Environments

Critical Corrosion Considerations for Studs

• Oxidation Resistance: Excellent oxidation resistance up to 815°C in gas turbine and exhaust environments. Suitable for continuous service up to 700°C.
• NACE MR0175 Compliance: A286 is qualified for sour service (sulfide stress cracking resistance) in oilfield equipment per NACE MR0175/ISO 15156. Class D with maximum hardness 35 HRC is preferred for sour applications.
• Temperature Limitations: Maximum service temperature for continuous service is 700°C (1300°F). For intermittent service, temperatures up to 815°C are acceptable.
• Galvanic Corrosion: When paired with lower-grade materials, galvanic corrosion should be considered. A286 is cathodic to most stainless steels but compatible with nickel-based alloys.
• Non-Magnetic Property: A286 is essentially non-magnetic (permeability ≤ 1.01), making it suitable for applications requiring non-magnetic fasteners such as MRI equipment and sensitive instrumentation.

Why RAYCHIN LIMITED – The A286 Stud Authority