This specification covers chromium-molybdenum alloy steel plates for welded boilers and pressure vessels designed for elevated temperature service. Materials considered under this specification are available in grades 2, 12, 11, 22, 22L, 21, 21L, 5, 9 and 91. The steel materials shall be killed and shall be thermally treated. The steel specimens shall undergo heat analysis and product analysis and shall conform to the chemical requirements for carbon, manganese, phosphorus, sulfur, silicon, chromium, molybdenum, nickel, vanadium, columbium, boron, nitrogen, aluminum, titanium, and zirconium. The steel specimens shall also undergo tension tests and shall conform to the required values of tensile strength, yield strength, and elongation.

1.1 This specification covers chromium-molybdenum alloy steel plates intended primarily for welded boilers and pressure vessels designed for elevated temperature service.

1.2 Plates are available under this specification in several grades having different alloy contents as follows: