ASTM A453 Grade 660 is a material specification for studs, bolts, nuts and other fasteners, intended for use in high temperature bolting applications. ASTM A453 Grade 660 is classified into 4 property class namely A, B, C & D, each designated with different tensile and stress rupture properties. Grade 660 fasteners are used in bolting boilers, pressure vessels, pipeline flanges and valves, intended for high temperature service. ASTM A453 grade 660 material is chemically equivalent to ASTM B638 grade 660 stainless steel alloy, also known by alloy A286 and UNS S66286, heat treated to achieve properties defined in ASTM A453 specification.