What is the equivalent of China’s Q355 I-beam in ASTM standards?

China's Q355 I-beam is roughly equivalent to ASTM A572 Grade 50. Both have a minimum yield strength of 345-355 MPa and similar chemical composition (0.20% max carbon, 1.70% max manganese). They are interchangeable in most structural applications, though minor differences exist: Q355 allows higher silicon (0.50% vs. 0.40% for A572) and requires -20°C impact tests (34 J), while A572 mandates 0°C testing. Engineers typically approve substitutions after verifying dimensional compatibility, as flange widths may vary slightly between standards.