A286 / Alloy 660 for excellent high temperature oxidation resistance

A286 screws, also known as Alloy 660 screws are stainless steel alloy which contains iron, nickel and chromium. A286 hex heads are known for their high strength, creep resistance and oxidation resistance at elevated temperatures once age hardened.  As a result, A286 hex head screws provide high levels of strength from room temperature up to about 1300°F (700°C).

A286 hex head cap screws are also mildly corrosion resistant. While they should not be used for strong acid environments, they provide excellent oxidation resistance up to 1500°F (815°C) in conditions that would typically be found in high temperature exhaust streams.

 A286 Stainless Steel High Temperature Usage

Applications

Because of the properties of Alloy 660 / A286, these hex head screws are often found in high temperature engine, manifold, exhaust and turbine applications as well as off-shore oil & gas applications. In addition, A286 / Alloy 660 is also non-magnetic and finds a niche in non-magnetic cryogenic equipment.

Resources: A286 Torque Specs

Screw Types12 Point ScrewsButton Head Cap ScrewsFlat Head ScrewsHex Cap ScrewsPan Head ScrewsSet ScrewsSocket Head Cap ScrewsTamper Resistant Security Screws, Torx ScrewsVented Screws


A286 / Alloy 660 Hex Head Cap Screw Features and Benefits

It is important to differentiate between a A-286 hex head cap screw and hex head bolt. Often people assume they are the same, but they are actually very different fasteners in terms of how they are manufactured, as well as from an application perspective. Regardless of your choice, A-286 hex heads offer strong, stable joints because of their large head service.

The Hex Comparison

Hex Head Cap Screw Hex Head Bolts
  • Precise applications where tight tolerances on the body dimensions are required. 
  • Features flat washer facing under the bolt head.
  • Also called a finished hex bolt.
  • Appropriate for when mechanical properties are more important than dimensional tolerances. 
  • Hex bolts have a flat end and lack the washer face under the head.

A286 / Alloy 660 Hex Head Cap Screw Advantages  

The most important feature of a Alloy 660 / A286 hex head cap screws is that it has a larger bearing surface area which provide better clamping pressure than other type of fastener such as a socket head cap screw. Additionally, since debris build up is less of an issue with this style of fastener verses a socket head cap screw, they are ideal of dirty applications where particles could clog up a socket. Though A286 socket heads are typically used for tight access applications, hex heads can be a better choice when there is only side clearance available for tightening.


A286 / Alloy 660 Chemistry, Specifications, Cold Working & Heat Treatments

A-286 / Alloy 660 Heat Treatments:  There are several heat treatment combinations for A-286 (Alloy 660) all with slight variations in performance. They can be specified via an AMS number or Class: A, B, C or D,  with most common specified as class A or D.   The grades A, B and C all have the same minimum tensile strength and minimum yield strength of 130ksi and 85ksi respectively. However grade D has a significantly better yield with a min tensile of 130ksi and a min yield of 105ksi. By AMS numbers, the most common for A286 / Alloy 660 is AMS 5737 (same as Grade A) and then AMS 5732 (same as Grade B).

A286 / Alloy 660 Cold Worked: For additional strength, A286 could be aged and cold worked to achieve a min ultimate tensile strength of 160ksi upon request

A286 Specifications: ASTM A453, AMS 5525, AMS 5732, AMS 5737, AMS 5804, EN 1.4980, GE B50T1181, GE B50T12, GE B50T81, UNS S66286, Werkstoff 1.4980

A 286 Chemistry


Mechanical Properties

A286 Stainless Steel Tensile Properties

A-286 Tensile Curves

 

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