1.
20–30% (from hot-rolled 345 MPa min to 415–450 MPa); tensile strength increases by 15–25% (from 480 MPa min to 550–600 MPa), a direct result of grain distortion and internal stress from cold plastic deformation.
15–25% (from 180–220 to 210–270 HBW), improving surface resistance to scratching, abrasion and minor impacts.
: Elongation at break drops significantly (from hot-rolled ≥20% to ≤15%), and the steel loses the ability for sharp bends/deep stamping-only flat or gradual bending (large radii) is feasible without cracking.
: Ambient-temperature toughness remains largely unchanged, but low-temperature toughness (sub-zero) decreases slightly (negligible for most outdoor SPA-H applications).
2.
: Thickness tolerance tightens drastically (from hot-rolled ±0.5 mm to ±0.05–0.1 mm for thin gauges), with perfect flatness (no warping/undulation) and uniform width/length-critical for precision fabrication (laser cutting, folding, assembly).
: The cold rolling mill process removes hot-rolled mill scale, producing a (no rough oxide layers). This surface not only improves aesthetic finish but also promotes faster, more even initial patina formation for architectural applications.
3.
The cold-rolled process only alters the steel's physical structure, not its chemical composition (Cu, Cr, P alloying elements remain unchanged) or the distribution of corrosion-critical precipitates in the matrix.
Cold-rolled SPA-H forms the same dense, protective patina as hot-rolled SPA-H at the identical rate (6–12 months for full formation in urban/rural environments), with the same low corrosion rate (0.01–0.03 mm/year) post-patina.
The smooth cold-rolled surface even supports (no mill scale-induced uneven oxidation), a minor practical benefit for aesthetic-focused applications.
4.
Weldability declines moderately due to higher hardness and internal stress: thin cold-rolled gauges (1.6–6 mm) still require no preheating, but demand (GMAW/MIG, FCAW) to avoid burn-through and minimize weld distortion (the primary risk).
No post-weld heat treatment is needed for small weld joints, and weathering steel-matched fillers (e.g., ER70S-W) preserve corrosion resistance in the weld zone as usual.
