This specification covers quenched and tempered highstrength low-alloy structural steel plates for welded, riveted, or bolted construction. It is intended primarily for use in welded bridges and buildings where savings in weight, added durability, and good notch toughness 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 can be used bare (unpainted) for many applications. Welding technique is of fundamental importance, and it is presupposed that the welding procedure will be suitable for the steel and the intended service. This specification is limited to material up to 4 in. [100 mm], inclusive, in thickness. See Appendix X3 of Specification A 6/A 6M for information on weldability.
| Element | Composition, % |
|---|---|
| Carbon, max | 0.19 max |
| Manganese, max | 0.80–1.35 |
| Phosphorus, max | 0.035 max |
| Sulfur, max | 0.04 max |
| Silicon | 0.20–0.65 |
| Nickel | 0.50 max |
| Chromium | 0.40–0.70 |
| Copper | 0.20–0.40 |
| Vanadium | 0.02–0.10 |
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 %.
| Tensile strength, min, ksi [MPa]B | Yield point, min, ksi [MPa] | Elongation in 2 in. [50 mm], min, %C,D |
|---|---|---|
| 70 [485] | 90–110 [620–760] | 19 |
B Measured at 0.2 % offset or 0.5 % extension underload.
C For thicknesses of 3⁄4 in. [19 mm] and under, measured on 11⁄2 -in. [40-mm] wide full thickness rectangular specimen as shown in Fig. 3 of Test Methods A 370, the elongation is measured in a 2-in. [50 mm] gage length that includes the fracture and shows the greatest elongation.
D 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 A 6/A 6M.