1. Thickness Range & Product Specification
| Index | Cold-Rolled Weathering Steel Plates | Hot-Rolled Weathering Steel Plates |
|---|---|---|
| Thickness Limit | 0.5–3 mm (strictly thin-gauge products; thickness >3 mm is technically unfeasible due to rolling pressure limitations) | 3–100 mm (covers medium to thick plates; maximum thickness can reach 120 mm for heavy structural use) |
| Width Tolerance | High precision (≤ ±0.5 mm) due to room-temperature precision rolling | Moderate tolerance (≤ ±2 mm) due to high-temperature thermal expansion |
| Flatness | Excellent (warpage ≤ 0.1 mm/m) - no thermal deformation during processing | Good (warpage ≤ 1 mm/m) - slight warping may occur due to uneven cooling after hot rolling |
2. Mechanical Properties & Microstructure
Cold-Rolled Plates:
Rolled at room temperature, which introduces residual tensile stress and refines the grain structure (fine ferrite + pearlite).
Higher yield strength and hardness than hot-rolled plates of the same grade (e.g., Q355NH cold-rolled yield strength is ~5–10% higher than hot-rolled).
Lower ductility and elongation (elongation is typically 15–20%, vs. 22–25% for hot-rolled plates) - prone to cracking during heavy bending or welding if not annealed.
Hot-Rolled Plates:
Rolled above the steel's recrystallization temperature (~900–1100°C), which eliminates residual stress and forms a coarse, uniform ferrite-pearlite microstructure.
Balanced mechanical properties: Moderate strength, high ductility, and good weldability/formability - suitable for cutting, bending, and welding without pre-treatment.
3. Processing Cost & Production Efficiency
| Index | Cold-Rolled Weathering Steel Plates | Hot-Rolled Weathering Steel Plates |
|---|---|---|
| Production Process | Complex: Hot-rolled base material → pickling (remove mill scale) → multiple cold rolling passes → annealing (relieve stress) → leveling | Simple: Continuous casting slab → heating → hot rolling → cooling → leveling |
| Cost Level | 20–30% higher than hot-rolled plates (due to extra pickling, annealing, and precision rolling steps) | Lower cost (high-efficiency mass production, minimal post-processing) |
| Batch Suitability | Suitable for small-batch, high-precision orders (e.g., decorative nameplates, precision components) | Suitable for large-batch, structural orders (e.g., bridge panels, landscape signs) |
4. Post-Processing Adaptability
Cold-Rolled Plates:
Ideal for precision laser cutting, engraving, and stamping - their smooth surface and high dimensional accuracy ensure clean, burr-free edges.
Require stress relief annealing before welding or heavy bending (to avoid cracking caused by residual stress).
Not suitable for thick welding joints - thin gauge limits load-bearing capacity of welds.
Hot-Rolled Plates:
Adaptable to all common processing methods (laser cutting, plasma cutting, welding, bending, etc.) - no pre-treatment required.
Suitable for heavy welding and load-bearing structural fabrication - thick gauge and high ductility ensure weld joint strength.
Prone to surface oxidation during high-temperature processing (e.g., welding spatter), but this can be removed via wire brushing.
5. Weight & Application Scope
Cold-Rolled Plates: Lightweight (thin gauge) → used for non-load-bearing, aesthetic, or precision components (e.g., indoor wall panels, nameplates, electronic shells).
Hot-Rolled Plates: Heavyweight (medium to thick gauge) → used for outdoor load-bearing structures (e.g., bridge guardrails, building facades, port equipment).
