1.1This specification covers carbon-manganese steel shapes, plates, and bars of structural quality for use in riveted, bolted, or welded construction of buildings and for general structural purposes.

1.2Material under this specification is available in two grades:

Grade	Yield Strength, ksi [MPa]	Thickness

50 [345]	50 [345]	Plates to 1 in. [25 mm] thick to 15 in. [380 mm] wide
		Bars to 3¹/₂in. [90 mm]
		Shapes with flange or leg thickness to 1¹/₂in. [40 mm] inclusive

55 [380]	55 [380]	Plates to 1 in. [25 mm] thick to 15 in. [380 mm] wide
		Bars to 3 in. [75 mm]
		Shapes with flange or leg thickness to 1¹/₂in. [40 mm] inclusive

1.3When the steel is to be welded, it is presupposed that a welding procedure suitable for the grade of steel and intended use or service will be utilized. See Appendix X3 of Specification A6/A6M for information on weldability.

1.4The values stated in either inch-pound units or SI units are to be regarded 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.

1.5This 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.