1.1 This specification covers austenitized, quenched, temperized, and reversion-annealed 5% nickel alloy steel plates intended primarily for welded pressure vessels for service at low or cryogenic temperatures. 1.2 The maximum thicknes This specification covers specially heat treated 5% and 5 1/2% nickel alloy steel plates intended primarily for welded pressure vessels for service at low or cryogenic temperatures. Plates are classified as Grade A and Grade B. The steel shall be kille