This specification covers standards for Grade 660 (Class A, B, C, and D) , Grade 651 (Class A and B), Grade 662 (Class A and B), and Grade 665 (Class A and B) of bolting materials for use in high-temperature service such as fasteners, for pressure vessels and valve flanges. Bolting materials in this specification covers rolled, forged, or hot-extruded bars, and also bolts, nuts, screws, washers, studs, and stud bolts. Materials shall adhere to specified contents of carbon, manganese, phosphorus, sulfur, silicon, nickel, chromium, molybdenum, tungsten, titanium, columbium, aluminum, vanadium, boron, and copper. Materials shall be subjected to tension, stress-rupture, and hardness tests. Materials shall conform to yield strength, tensile strength, elongation, reduction of area, Brinell hardness, and Rockwell hardness requirements. Hardening and solution treatment requirements for each material class are also given.