How S275JR H-Sections Are Produced
S275JR H-beams are produced by hot rolling: a reheated steel billet is passed through a series of rolls that progressively form the web and flanges while the steel is above the recrystallization temperature, around 900 to 1200 degrees Celsius. Hot rolling allows the deep sections and thick flanges of an H-beam to be formed in one continuous process, and the final rolling temperature and cooling produce the required grain structure and mechanical properties. The result is a section with the guaranteed 275 MPa minimum yield of S275JR and through-thickness consistency that cold working cannot achieve at these dimensions.
Why Cold Rolling Cannot Produce H-Beams
Cold rolling is performed at room temperature and is limited to strip and sheet products with thin gauges, because the forces required to form a deep H-section cold would be enormous and the steel would work-harden and crack. What cold processing can produce is cold-formed sections: thin-walled C, Z, U, and rectangular profiles roll-formed from cold-rolled or galvanized strip. These sections are limited to walls of about 1 to 4 mm and are used for purlins, girts, and light framing, not for main structural beams.
Hot-Rolled vs Cold-Formed S275JR: Strength and Ductility
Hot-rolled S275JR sections have a minimum yield of 275 MPa, a tensile range of 410 to 560 MPa, and high ductility, which supports welding, drilling, and plastic design. Cold-formed sections made from the same strip may show a slightly higher yield due to work hardening, but the effect is limited to thin walls, and the sections have lower ductility and thinner material. For main beams and columns, hot-rolled S275JR is the structural material; for secondary members, cold-formed sections are lighter and cheaper.
Design and Fabrication Differences
Hot-rolled S275JR beams are designed with the section properties of the rolled profile, welded and bolted with standard details, and supplied with mill certificates. Cold-formed sections are designed with local and distortional buckling checks per EN 1993-1-3 or AISI S100, connected with self-drilling screws or light bolts, and often supplied galvanized. The two systems coexist in modern buildings: hot-rolled H-beams form the primary frame, and cold-formed sections carry the cladding and secondary loads.
Choosing the Right Production Route
Choose hot-rolled S275JR H-beams for columns, main beams, portal frames, and any member carrying significant load or requiring welded connections. Choose cold-formed sections for purlins, girts, studs, and light secondary framing where weight and cost are the priority. For a hybrid structure, coordinate the two systems at the interface details, such as purlin cleats on beam flanges, so that the connections are simple and the tolerances match.
Frequently Asked Questions
Q: Can S275JR H-beams be cold rolled?
No. H-beams are always hot rolled; cold processing is limited to thin strip and sheet, from which cold-formed C, Z, and U sections are produced.
Q: What is the yield strength of hot-rolled S275JR?
S275JR has a minimum yield strength of 275 MPa and a tensile range of 410 to 560 MPa per EN 10025-2.
Q: Are cold-formed sections stronger than hot-rolled?
Cold forming raises the yield slightly in thin walls, but the sections are much thinner overall, so hot-rolled beams carry far higher loads.
Q: Can cold-formed sections be welded?
Yes, but the thin walls require short, controlled welds, and screwed or bolted connections are often preferred.
Q: Which is cheaper, hot-rolled beams or cold-formed sections?
Cold-formed sections cost less per meter but carry much less load; for a given structural role, the hot-rolled beam is normally the economical choice.