Formation
Hot-rolled steel: Slabs are used as raw materials. After heating, they are processed into strip steel through roughing and finishing mill units.
Cold-rolled steel: Hot-rolled steel coils serve as raw materials. After pickling to remove scale, cold rolling is performed, resulting in hard rolled coils.
Rolling Mill Rolls
HANI provides high-quality rolls for both hot and cold rolling processes, ensuring durability and performance under high-stress conditions.
Performance
Hot-rolled steel:
Strength: Moderate, suitable for general applications
Plasticity and weldability: Excellent, making it widely used
Surface appearance: Dull, often with an oxide layer or iron oxide scale
Cold-rolled steel:
Strength: Higher due to work hardening
Toughness and weldability: Relatively lower; material tends to be harder and more brittle
Surface quality: Superior, with a smooth and bright finish, achieved through surface treatment during cold rolling
Process
Hot-rolled steel: Ironmaking → steelmaking → continuous casting (or ingot casting) → hot rolling. The process involves heating the material above recrystallization temperature to enhance internal microstructure and material properties.
Cold-rolled steel: Ironmaking → steelmaking → continuous casting (or ingot casting) → hot rolling → cold rolling. Cold rolling requires higher mill power and efficiency is lower. Intermediate annealing is often necessary to eliminate work hardening.
Appearance and Surface Quality
Hot-rolled steel: Typically black or dark gray, with a surface that may exhibit oxide layers or iron scale.
Cold-rolled steel: High surface quality, metallic luster, smooth and bright.
Conclusion
Hot-rolled steel offers good plasticity and weldability but has relatively poorer surface quality. Cold-rolled steel provides higher strength and better surface finish but reduced toughness and weldability. Selecting the appropriate type depends on specific application requirements. HANI supplies precision-engineered rolls for both processes, ensuring optimal performance and longevity.