AS/NZS 3678 is the Australian and New Zealand standard for structural hot-rolled steel plates, covering grades GR250/300/350 with yield strengths ranging from 250 to 350 MPa. It is suitable for load-bearing structures such as buildings and bridges. It has excellent weldability and is comparable to ASTM A36 (GR250) and EN S355 (GR350). Carbon content ≤0.2%, manganese content 1.5-1.6%, compliant with the AS 4100 Structural Steel Design Code.