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.
Chemical Composition
Element
Composition, %
Grades 50 [345] and 55 [380]
Carbon, max
0.27
Manganese, max
1.35
Phosphorus, max
0.04
Sulfur, max
0.05
Silicon, max
0.40
Copper, min, when copper is specified
0.20
Mechanical Properties
Grade 50 [345]
Grade 55 [380]
ksi [MPa]
ksi [MPa]
Tensile strength, min
70B [485]
70 [485]
Tensile strength, max
100 [690]
100 [690]
Yield strength, min
50 [345]
55 [380]
Elongation in 8 in. [200 mm], min, %
18
17
Elongation in 2 in. [50 mm], min, %
21
20
Note :
A. See the Orientation subsection in the Tension Tests section of Specification A6/A6M. B. Minimum tensile strength for Grade 50 shapes with flange or leg thickness to 1 1⁄2 in. [40 mm] inclusive, shall be 65 ksi [450 MPa].