What is the impact toughness of Q235B I-beams at 0°C?

Q235B I-beams (Chinese standard) require a minimum impact toughness of 27 J at 0°C, measured via Charpy V-notch tests. This ensures resistance to brittle fracture in moderate cold, suitable for most Chinese climates. The B suffix indicates impact testing, distinguishing it from Q235A (no impact requirement). For colder regions (northeast China), Q235D offers 27 J at -20°C, achieved via lower phosphorus content (<0.035%) and controlled rolling to refine grains. Impact toughness is critical for infrastructure in seismic zones, where sudden loads demand energy absorption.