This specification covers five grades of high-strength low-alloy structural steel shapes, plates, sheet piling, and bars. Grades 42 [290], 50 [345], and 55 [380] are intended for riveted, bolted, or welded structures. Grades 60 [415] and 65 [450] are intended for riveted or bolted construction of bridges, or for riveted, bolted, or welded construction in other applications. For applications, such as welded bridge construction, where notch toughness is important, notch toughness requirements are to be negotiated between the purchaser and the producer.
| Diameter, Thickness, or Distance Between Parallel Faces, in. [mm] Plates and Bars | Structural Shape Flange or Leg Thickness, in. [mm] | Grade | Carbon, max, % | Manganese,B max, % | Phosphorus, max, % | Sulfur, max, % | Silicon | |
|---|---|---|---|---|---|---|---|---|
| Plates to 11⁄2 in. [40 mm] Thick, Shapes with Flange or Leg Thickness to 3 in. [75 mm] inclusive, Sheet Piling, Bars, Zees, and Rolled TeesC | Plates Over 11⁄2 in. [40 mm] Thick and Shapes with Flange Thickness Over 3 in. [75 mm] | |||||||
| max, % | range, % | |||||||
| 6 [150] | all | 42 [290] | 0.21 | 1.35D | 0.04 | 0.05 | 0.40 | 0.15–0.40 |
| 4 [100]E | all | 50 [345] | 0.23 | 1.35D | 0.04 | 0.05 | 0.40 | 0.15–0.40 |
| 2 [50]F | all | 55 [380] | 0.25 | 1.35D | 0.04 | 0.05 | 0.40 | 0.15–0.40 |
| 11⁄4 [32]F | ≤2 [50] | 60 [415] | 0.26 | 1.35D | 0.04 | 0.05 | 0.40 | G |
| <1⁄2 – 11⁄4 [13–32] | <1-2 [25-50] | 65 [450] | 0.23 | 1.65 | 0.04 | 0.05 | 0.40 | G |
| ≤1⁄2 [13]H | ≤1H | 65 [450] | 0.26 | 1.35 | 0.04 | 0.05 | 0.40 | G |
A. Copper when specified shall have a minimum content of 0.20 % by heat analysis (0.18 % by product analysis).
B. Manganese, minimum, by heat analysis of 0.80 % (0.75 % by product analysis) shall be required for all plates over 3⁄8 in. [10 mm] in thickness; a minimum of 0.50 %
(0.45 % by product analysis) shall be required for plates 3⁄8 in. [10 mm] and less in thickness, and for all other products. The manganese to carbon ratio shall not be less
than 2 to 1.
C. Bars over 11⁄2 in. [40 mm] in diameter, thickness, or distance between parallel faces shall be made by a killed steel practice.
D. For each reduction of 0.01 percentage point below the specified carbon maximum, an increase of 0.06 percentage point manganese above the specified maximum is
permitted, up to a maximum of 1.60 %.
E. Round bars up to and including 11 in. [275 mm] in diameter are permitted.
F. Round bars up to and including 31⁄2 in. [90 mm] in diameter are permitted.
G. The size and grade is not described in this specification.
H. An alternative chemical requirement with a maximum carbon of 0.21 % and a maximum manganese of 1.65 % is permitted, with the balance of the elements.
| Grade | Yield Point, min | Tensile Strength, min | Minimum Elongation, % B,C,D | |
|---|---|---|---|---|
| ksi [MPa] | ksi [MPa] | in 8 in. [200 mm] | in 2 in. [50 mm] | |
| 42 [290] | 42 [290] | 60 [415] | 20 | 24 |
| 50 [345] | 50 [345] | 65 [450] | 18 | 21 |
| 55 [380] | 55 [380] | 70 [485] | 17 | 20 |
| 60 [415] | 60 [415] | 75 [520] | 16 | 18 |
| 65 [450] | 65 [450] | 80 [550] | 15 | 17 |
A. See specimen Orientation under the Tension Tests section of Specification
A6/A6M.
B. Elongation not required to be determined for floor plate.
C. For wide flange shapes over 426 lb/ft [634 kg/m], elongation in 2 in. [50 mm] of
19 % minimum applies.
D. For plates wider than 24 in. [600 mm], the elongation requirement is reduced two
percentage points for Grades 42, 50, and 55 [290, 345, and 380], and three
percentage points for Grades 60 and 65 [415 and 450]. See elongation requirement adjustments in the Tension Tests section of Specification A6/A6M.