RAYCHIN LIMITED

Complete Range of A286 Flat Head Screws

Manufacturing Standards for A286 Flat Head Screws

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

International Standards & Global Designations for A286 Flat Head Screws

To serve clients worldwide, RAYCHIN LIMITED manufactures A286 flat head screws 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 DIN 963 DIN 964 ISO 2009 ISO 2010

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

Our A286 flat head screws 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. The addition of boron (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 Flat Head Screws (per ASTM A453)

A286 flat head screws 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. Screws are proof load tested to ensure compatibility with mating nuts.

Tensile Requirements by Class – ASTM A453 Grade 660

Hardness Requirements

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

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

Research confirms that 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 fastener applications.

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.

At 500°C, A286 maintains excellent stress retention, with studies showing stress retention rates exceeding 88.35% at this temperature.

Thermal Expansion Advantage of A286 Flat Head Screws

A286 is specifically designed for bolting austenitic stainless steel components 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 flat head screws used in high-temperature assemblies where maintaining clamping force is essential.

This expansion match is critical for maintaining preload and preventing loosening in high-temperature applications such as gas turbine components, exhaust systems, and heat treatment fixtures. Standard alloy steel fasteners expand less than the surrounding components, leading to loss of preload and potential failure. A286 eliminates this mismatch.

API 6A & NACE MR0175 Compliance

A286 flat head screws 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

Optimal mechanical properties in A286 flat head screws are achieved through a two-step heat treatment:

• Solution Annealing: 980°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 aging at 730°C accelerates precipitation kinetics but can lead to overaging and formation of η (eta) phase (Ni₃Ti), which degrades mechanical properties. Our 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.

Physical Properties of A286

Corrosion Resistance of A286 Flat Head Screws

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 flat head screws form a protective Cr₂O₃ scale that prevents further oxidation at elevated temperatures. They provide excellent oxidation resistance up to 1500°F (815°C) in conditions typically found in gas turbine exhaust streams.

Corrosion in Other Environments

Critical Corrosion Considerations for Flat Head Screws

• Oxidation Resistance: Excellent oxidation resistance up to 1500°F (815°C) in gas turbine and exhaust environments.
• 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, making it suitable for applications requiring non-magnetic fasteners such as MRI equipment and sensitive instrumentation.
• Head Angle Selection: 82° for inch series applications (primarily US aerospace), 90° for metric series applications (international projects).

High-Temperature Engineering Note: For critical applications in aggressive environments, RAYCHIN LIMITED can provide passivation, specialized coatings (Xylan, PTFE, silver plating per AMS 2410), or recommend optimal heat treatment conditions. Third-party corrosion testing per ASTM G31, G48, or G61 available upon request. NACE MR0175 compliant A286 flat head screws available in Class D condition with certified hardness ≤ 35 HRC. A286 offers a cost-effective balance of high-temperature strength and corrosion resistance – approximately 60-70% the cost of nickel-based alloys like Inconel 718.

Why RAYCHIN LIMITED – The A286 Flat Head Screw Authority