What is the maximum carbon content allowed in S355JR channel steel?

EN 10025-2:2004 limits the maximum carbon content in S355JR channel steel to 0.24%. Carbon is essential for strength, as it forms strong bonds in the iron crystal lattice, but excess carbon has severe drawbacks: it increases brittleness, reduces ductility, and impairs weldability. A carbon content above 0.24% would make S355JR prone to cracking during welding (due to hard, brittle microstructures in the heat-affected zone) and less able to absorb impact energy. To enforce this limit, manufacturers use spectroscopic analysis during steelmaking to monitor carbon levels in real time, adjusting the melt as needed. Post-production, each batch is sampled for chemical analysis, with carbon content results included in the material certificate. This strict control ensures S355JR remains workable-contractors can weld it using standard techniques (e.g., MIG, TIG) without preheating-while still delivering the 355 MPa yield strength required for structural applications.