ASTM A453 Grade 660 is a material specification for high tensile stainless steel Bolts Studs and Nuts, intended for use in high temperature services. ASTM A453 Grade 660 includes 4 tensile property class A / B / C and D. Each with different mechanical and stress rupture requirements. Class D does not state any stress rupture test requirement. ASTM A453/A453M is confined to bolts, nuts and similar bolting components. Some commonly produced product forms in ASTM A453 grade 660 are stud bolts, hex bolts, socket head cap screws, hex nuts, heavy hex nuts, etc. ASTM A453 Gr 660 is chemically equivalent to ASTM A638 Grade 660 stainless steel, alternatibely know as Alloy A286 or by UNS S66286 material. ASTM A453 grade 660 material is widely used for manufacturing boltings for boilers, pressure vessels , pipeline flanges and valves , with constant high temperature service.