AS/NZS 3679.1 limits carbon content in 300PLUS® PFC channel steel to 0.25% max. Carbon enhances strength but poses risks at higher levels:
Brittleness: Excess carbon increases the likelihood of brittle fracture, especially under impact or cyclic loads (e.g., heavy traffic vibrations on bridges).
Weldability Loss: Carbon forms hard, crack-prone microstructures (e.g., martensite) in the heat-affected zone (HAZ) during welding. A 0.25% cap allows 300PLUS® to be welded via standard methods (SMAW, GMAW) without preheating-critical for efficient on-site construction in Australia.To enforce this limit, manufacturers use spectroscopic analysis during steelmaking to monitor carbon levels in real time. Post-production, each batch is tested, with carbon content documented in the material certificate. This control ensures 300PLUS® retains fabrication flexibility while meeting structural demands.