This specification covers standard specification for several grades of minimum-wall-thickness, seamless and welded, carbon and alloy-steel tubes intended for use at low temperatures. The steel shall conform to the required chemical composition for carbon, manganese, phosphorus, sulfur, silicon, nickel, chromium, copper, cobalt, and molybdenum. The number of tubes in a heat-treatment lot shall be determined from the size of the tubes. The tubes shall have a hardness number that does not exceed the prescribed Rockwell and Brinell hardness values. Several grades of steel shall conform to the following tensile properties: tensile strength, yield strength, and elongation. For Grades 1, 3, 6, 7, and 9, the notch-bar impact properties of each set of three impact specimens, including specimens for the welded joint in welded pipe, shall not be less than the prescribed values. Several mechanical tests shall be conducted, namely: flattening test; flare test (seamless tubes); flange test (welded tubes); reverse flattening test; hardness test; and impact tests. Hydrostatic or nondestructive electric test shall also be performed. Materials shall be tested for impact resistance at the prescribed temperature for the respective grades. Impact temperature reduction values shall be by any amount equal to the difference between the temperature reduction corresponding to the actual material thickness and the temperature reduction corresponding to Charpy specimen width actually tested.