This specification covers grades of hot-formed welded and seamless high-strength low-alloy square, rectangular, round, or special shape structural tubing for welded, riveted, or bolted construction of bridges and buildings and for general structural purposes. These grades are: Grade Ia and Ib; Grade II; and Grade III. When the steel is used in welded construction, the welding procedure shall be suitable for the steel and the intended service. The tubing shall be made by the seamless, furnace-buttwelded (continuous-welded), or hot-stretch-reduced electric-resistance-welded process. Tensile test and bend test shall be performed for the material to conform to the requirements specified. If the results of the mechanical tests representing any heat do not conform to a requirement, retests shall be made.

1.1 This specification covers grades of hot-formed welded and seamless high-strength low-alloy square, rectangular, round, or special shape structural tubing for welded, riveted, or bolted construction of bridges and buildings and for general structural purposes. When the steel is used in welded construction, the welding procedure shall be suitable for the steel and the intended service.

1.2 Square and rectangular tubing is produced with flats of 1 in. to 16 in. [25 mm to 405 mm] and a specified wall thickness of 0.095 in. to 1.0 in. [2.5 mm to 25 mm]. Round tubing is produced with diameters of 1 in. to 48 in. [25 mm to 1220 mm] and a specified wall thickness of 0.095 in. to 2.50 in. [2.5 mm to 65 mm].

1.3 This specification covers the following grades: Ia, Ib, II, III, IV, V, VI and VII.

1.4 The text of this specification contains notes and footnotes that provide explanatory material. Such notes and footnotes, excluding those in tables and figures, do not contain any mandatory requirements.

1.5 This specification is expressed in both inch-pound units and in SI units; however, unless the purchase order specifies the applicable M specification designation (SI units), the inch-pound units shall apply. The values stated in either SI units or inch-pound units are to be regarded separately as standard. Within the text, the SI units are shown in brackets. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with the standard.

1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.