The impact strength (Charpy V‑notch toughness) of ASTM A588 Gr.B follows a clear trend: it increases as temperature rises, and decreases as temperature falls, showing typical ductile‑to‑brittle transition behavior for structural weathering steels.
At low temperatures (below room temperature, down to −40 °C)
As temperature decreases, the steel becomes less ductile and more brittle. Its ability to absorb impact energy drops significantly, so impact strength becomes lower. Even though A588 Gr.B is designed to maintain reliable toughness at −23 °C, further cooling continues to reduce its impact resistance.
At room temperature
At normal ambient temperature, the material shows a good balance of strength and toughness. Impact strength is stable and sufficient for most outdoor structural applications.
As temperature rises above room temperature
With increasing temperature, the ductility of the steel improves. It can deform more plastically before fracture, absorb more energy during impact, and therefore impact strength continues to increase.
Ductile‑to‑brittle transition behavior
ASTM A588 Gr.B has a characteristic transition temperature range. Above this range, it acts in a ductile manner with high impact toughness; below this range, it becomes brittle with rapidly decreasing impact strength. This transition is directly controlled by temperature.
