This specification covers high-strength low-alloy structural steel shapes, plates, and bars for welded, riveted, or bolted construction but intended primarily for use in welded bridges and buildings where savings in weight or added durability are important. The atmospheric corrosion resistance of this steel in most environments is substantially better than that of carbon structural steels with or without copper addition (see Note 1). When properly exposed to the atmosphere, this steel is suitable for many applications in the bare (unpainted) condition. This specification is limited to material up to 8 in. [200 mm] inclusive in thickness.
| Elements | Composition, % | ||
|---|---|---|---|
| Grade A | Grade B | Grade K | |
| CarbonA | 0.19 max | 0.20 max | 0.17 max |
| ManganeseA | 0.80–1.25 | 0.75–1.35 | 0.50–1.20 |
| Phosphorus | 0.04 max | 0.04 max | 0.04 max |
| Sulfur | 0.05 max | 0.05 max | 0.05 max |
| Silicon | 0.30–0.65 | 0.15–0.50 | 0.25–0.50 |
| Nickel | 0.40 max | 0.50 max | 0.40 max |
| Chromium | 0.40–0.65 | 0.40–0.70 | 0.40–0.70 |
| Molybdenum | ... | ... | 0.10 max |
| Copper | 0.25–0.40 | 0.20–0.40 | 0.30–0.50 |
| Vanadium | 0.02–0.10 | 0.01–0.10 | ... |
| Columbium | ... | ... | 0.005–0.0B |
A. For each reduction of 0.01 percentage point below the specified maximum for
carbon, an increase of 0.06 percentage point above the specified maximum for
manganese is permitted, up to a maximum of 1.50 %.
B. For plates under 1⁄2 in. [13 mm] in thickness, the minimum columbium is
waived.
| Plates and Bars | Structural Shapes | |||
|---|---|---|---|---|
| For Thicknesses 4 in. [100 mm] and Under | For Thicknesses Over 4 in. [100 mm] to 5 in. [125 mm] incl | For Thicknesses Over 5 in. [125 mm] to 8 in.[200 mm] incl | All | |
| Tensile strength, min,ksi [MPa] | 70 [485] | 67 [460] | 63 [435] | 70 [485] |
| Yield point, min, ksi [MPa] | 50 [345] | 46 [315] | 42 [290] | 50 [345] |
| Elongation in 8 in. [200 mm], min, % | 18B,C | ... | ... | 18C |
| Elongation in 2 in. [50 mm], min, % | 21B,C | 21B,C | 21B,C | 21D |
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 plates wider than 24 in. [600 mm], the elongation requirement is reduced
two percentage points. See elongation requirement adjustments in the Tension
Tests section of Specification A6/A6M.
D. For wide flange shapes with flange thickness over 3 in. [75 mm], elongation in
2 in. [50 mm] of 18 % minimum applies.