Hot-Finished vs Cold-Formed Hollow Sections: EN 10210 vs EN 10219

Square, rectangular and circular hollow sections reach the market through two European product standards. EN 10210 covers hot-finished structural hollow sections: the tube is either formed at elevated temperature or brought to a normalized condition afterwards, so it leaves the mill with a uniform microstructure and essentially no cold-working effects. EN 10219 covers cold-formed welded hollow sections: strip is roll-formed to shape at ambient temperature and welded along a longitudinal seam, and the forming strains stay locked into the finished tube.

On paper the two families overlap almost completely: the same nominal outside dimensions, the same wall thicknesses, comparable steel grades. That overlap is exactly why they get confused. They are nevertheless different products: different corner geometry, different residual stress state, different design rules in Eurocode 3, and different prices. For engineers the distinction changes calculated resistance; for buyers it changes what may be substituted and what may not.

The corner radius rules are the quickest way to tell the products apart. EN 10210 specifies an outer corner radius of ro = 1.5t, which gives hot-finished sections their characteristically crisp corners. EN 10219 allows much rounder corners that grow with wall thickness: ro = 2t for t ≤ 6 mm, 2.5t for 6 mm < t ≤ 10 mm and 3t for t > 10 mm. In both standards the inner radius follows as ri = ro − t.

This is not cosmetic. The corners lie furthest from the bending axes, exactly where the cross-section works hardest. Rounder corners remove material from that region, so a cold-formed section of identical nominal size has a slightly smaller area, smaller second moments of area and section moduli, and a lower torsional constant than its hot-finished twin.

Never read properties for one product from the other's table: use SHS EN 10210 and RHS EN 10210 for hot-finished sections, and SHS EN 10219 and RHS EN 10219 for cold-formed ones. For circular sections (CHS EN 10210, CHS EN 10219) the geometry is essentially shared and the difference lies in the material condition.

Cold forming works the steel plastically at ambient temperature, and two things follow. First, the finished section carries a significant pattern of residual stresses through the wall. Second, the corner regions are strain-hardened: their yield strength rises locally while their ductility drops. Hot-finished sections, by contrast, leave the mill in a near stress-free, normalized condition.

Eurocode 3 translates this directly into member design. For flexural buckling, EN 1993-1-1 assigns hot-finished hollow sections to buckling curve a and cold-formed hollow sections to buckling curve c. For stocky compression members the difference is modest; as slenderness grows, curve c cuts the design resistance far more aggressively than curve a. A slender cold-formed column of the same nominal size therefore carries noticeably less than its hot-finished counterpart, and it starts from slightly smaller section properties as well, a double penalty in compression-governed design.

On the flat faces, both products weld normally with the usual precautions for the steel grade. The corners are a different matter. In a cold-formed section the corner has undergone heavy plastic strain; welding into or immediately beside that zone adds a thermal cycle that can trigger strain-age embrittlement and cracking. EN 1993-1-8 therefore permits welding within the cold-formed corner zones only under specific conditions: a sufficiently generous radius-to-thickness ratio, suitable steel chemistry such as aluminium-killed material, or a normalizing treatment after forming.

Hot-finished corners carry no such restriction: they are metallurgically the same as the flat faces and can be welded through without special measures. This matters most in lattice girders and truss nodes, where brace welds routinely run around chord corners, and in heavily welded connections whose geometry cannot keep welds clear of the corner regions.

Cold forming is the cheaper route: it runs from coil on continuous mills, needs no reheating, and is offered by far more producers. The practical result is a lower price per tonne, better stock availability, shorter lead times and a broad range of thin-walled sizes. Hot-finished sections are a premium product from fewer mills: expect a higher price, longer or programme-based lead times, and better coverage of heavy wall thicknesses.

For buyers the key discipline is precision in the enquiry. An “SHS” with a nominal size alone is ambiguous, so always state the standard, the steel grade and the inspection document required. Offering EN 10219 material against an EN 10210 specification is not an equal substitution: it changes the section properties, the buckling curve and the welding restrictions, and it needs the designer's explicit approval, not just matching outside dimensions.

Neither product is universally better; they solve different problems.

Hot-finished (EN 10210) is the natural choice when:

• slender compression members dominate and buckling curve a pays for the price difference;
• connections require welding at or around the corners, as in trusses and Vierendeel frames;
• the structure sees fatigue, dynamic loading or demanding low-temperature toughness requirements;
• the assembly will be hot-dip galvanized and residual stresses are a concern;
• crisp, tight corners are an architectural requirement.

Cold-formed (EN 10219) is the natural choice when:

• cost and availability govern, and members are stocky or governed by bending or tension;
• the work is secondary steelwork: railings, equipment frames, purlin systems, architectural infill;
• thin walls and short lead times matter more than the last increment of buckling resistance.

Whichever you specify, take the properties from the matching tables (hot-finished versus cold-formed) and carry the correct buckling curve into the member checks.