This specification covers seamless carbon-molybdenum alloy-steel boiler and superheater tubes. As a steel making practice, the steel material shall be killed. The required chemical composition for steel is given. The mechanical property requirements include tensile requirements and hardness requirements. Different test procedure shall be performed on the material presented, one tension test shall be made on a specimen for lots of not more than 50 tubes, one flattening test shall be made on specimens from each end of one finished tube, one flaring test shall be made on specimens from each end of one finished tube, and Brinell or Rockwell hardness tests shall be made from two tubes from each lot.

1.1 This specification² covers several grades of minimum-wall-thickness, seamless, carbon-molybdenum alloy-steel, boiler and superheater tubes.

1.2 This specification covers tubes ¹/₂ to 5 in. [12.7 to 127 mm] inclusive, in outside diameter and 0.035 to 0.500 in. [0.9 to 12.7 mm], inclusive, in minimum wall thickness.

1.3 An optional supplementary requirement is provided and, when desired, shall be so stated in the order.

1.4 The values stated in either inch-pound units or SI units are to be regarded separately as standard. Within the text, the SI units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system must be used independently of the other. Combining values from the two systems may result in nonconformance with the specification. The inch-pound units shall apply unless the “M” designation of this specification is specified in the order.