1.1 This specification covers three Types and two Grades of cold formed electric-fusion (arc) welded high-strength low-alloy steel tubing of 50 ksi [345 MPa] minimum yield point for use in welded or bolted construction of buildings and for general structural purposes.

1.2 This tubing is produced in square and rectangular sizes with a periphery of 200 in. [500 cm] or less and a specified wall thickness of 1.00 in. [25 mm] or less. Tubes are joined by two longitudinal electric-fusion (arc) welds. Circumferential welds are disallowed. Sizes outside of those listed in Tables 4 and 5 may be ordered provided all other requirements of the specification are met. Typical lengths are 15 to 50 ft. [5 to 15 m].

Note 1: Products manufactured to this specification may not be suitable for those applications such as dynamically loaded elements in welded structures, etc. where low-temperature toughness properties may be important. (See Supplementary Requirement S1.)

1.3 This specification covers the following Types:

1.3.1 Type 1—Welded with backing, backing left in the product,

1.3.2 Type 2—Welded with backing, backing removed,

1.3.3 Type 3—Welded without backing.

1.4 Tubing is available in Grades 50 [345] and 50W [345W]. Grade 50 [345] is manufactured from high-strength low-alloy steel. Grade 50W [345W] is manufactured from high-strength low-alloy steel with enhanced atmospheric corrosion resistance. (See 10.1.2) The Grades may not be interchanged without approval of the purchaser. ASTM Specifications for plate that may be applied to Grade 50 [345] and 50W [345W] are listed in Reference Documents and in Table 1.

1.5 This specification is expressed in both inch-pound units and in SI units; however, unless the purchase order or contract 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 standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.