1.1 This 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.

1.2 Material 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 3½ in. [90 mm]
		Shapes with flange or leg thickness to 1½ in. [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 1½ in. [40 mm] inclusive

1.3 When 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.

1.4 The 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.