ASTM A588 / A588M

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. 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.

Grades Description
Grade A -
Grade B -
Grade K -

Chemical Properties

Grade CarbonA ManganeseA Phosphorus Sulfur Silicon Nickel Chromium Molybdenum Copper Vanadium Columbium
Grade A 0.19 max 0.80–1.25 0.04 max 0.05 max 0.30–0.65 0.40 max 0.40–0.65 - 0.25–0.40 0.02–0.10 -
Grade B 0.20 max 0.75–1.35 0.04 max 0.05 max 0.15–0.50 0.50 max 0.40–0.70 - 0.20–0.40 0.01–0.10 -
Grade K 0.17 max 0.50–1.20 0.04 max 0.05 max 0.25–0.50 0.40 max 0.40–0.70 0.10 max 0.30–0.50 - 0.005–0.05B


Note: 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.

Mechanical Properties

Product Form Thickness Tensile strength,min:
ksi [MPa]
Yield strength,min:
ksi [MPa]
Elongation in 8 in. [200 mm] min, % Elongation in 2 in. [50 mm] min, %
Plates and Bars
For Thicknesses 4 in. [100 mm] and Under 70 [485] 50 [345] 18B,C 21B,C
For Thicknesses Over 4 in. [100 mm] to 5 in. [125 mm] incl 67 [460] 46 [315] ... 21B,C
For Thicknesses Over 5 in. [125 mm] to 8 in.[200 mm] incl 63 [435] 42 [290] ... 21B,C
Structural Shapes All 70 [485] 50 [345] 18C 21D


Note: A 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.

D For wide flange shapes with flange thickness over 3 in. [75 mm], elongation in 2 in. [50 mm] of 18 % minimum applies.

Products