What is the most common GB structural steel grade equivalent to EN S235JR for I-beams?

The most common equivalent is GB Q235B. Both are general-purpose structural steels with a minimum yield strength of 235 MPa. S235JR is defined under EN 10025-2, while Q235B is specified in GB/T 700. The equivalence is well-established for static structural applications. The key difference lies in impact toughness; S235JR requires a minimum Charpy V-notch impact energy of 27J at +20°C, whereas Q235B requires the same 27J at room temperature (typically +20°C). Their chemical compositions are also closely aligned, with maximum carbon content around 0.20% and similar limits for phosphorus and sulfur. For most building frames and non-critical structures, Q235B is a direct and acceptable substitute for S235JR, provided the mill test certificates confirm the impact energy meets the project specification.