This specification covers seamless ferritic and austenitic steel boiler, superheater, and heat-exchanger tubes. Grades containing the letter H in their designation have requirements different from those of similar grades not containing the letter H. These different requirements provide higher creep-rupture strength than normally achievable in similar grades without these different requirements. The tubes shall be made by the seamless process and shall be either hot finished or cold finished, as specified. Grade TP347HFG shall be cold finished. Heat treatment shall be done separately and in addition to heating for hot forming. The ferritic alloy and ferritic stainless steels shall be reheated. On the other hand, austenitic stainless steel tubes shall be furnished in the heat-treated condition. Alternatively, immediately after hot forming, while the temperature of the tubes is not less than the minimum solution temperature, tubes may be individually quenched in water or rapidly cooled by other means. Tension test, hardness test, flattening test, and flaring test shall be done to each tube. Also, each tube shall be subjected to the nondestructive electric test or hydrostatic test.

1.1 This specification covers seamless ferritic and austenitic steel boiler, superheater, and heat-exchanger tubes, designated Grades T5, TP304, etc. These steels are listed in Tables 1 and 2.

1.2 Grades containing the letter, H, in their designation, have requirements different from those of similar grades not containing the letter, H. These different requirements provide higher creep-rupture strength than normally achievable in similar grades without these different requirements.

1.3 The tubing sizes and thicknesses usually furnished to this specification are ¹/₈ in. [3.2 mm] in inside diameter to 5 in. [127 mm] in outside diameter and 0.015 to 0.500 in. [0.4 to 12.7 mm], inclusive, in minimum wall thickness or, if specified in the order, average wall thickness. Tubing having other diameters may be furnished, provided such tubes comply with all other requirements of this specification.