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The production process of hot-rolled steel coil is a key link in steel manufacturing. It mainly forms the steel billet into the required plate shape through high-temperature rolling. The following are its core steps:

Raw Material Preparation
The raw material is a continuously cast slab or billet, typically 150-300 mm thick.
The slab surface undergoes cleaning (e.g., flame scarfing or mechanical grinding) to remove scale and defects and ensure rolling quality.
Heating
The slab is fed into a walking beam furnace and heated to 1100-1300°C to achieve austenitization and improve ductility.
Heating time and temperature uniformity must be controlled to avoid overheating or underheating.
Roughing
The slab is rolled in a reversing roughing mill (e.g., a two- or four-high mill) into intermediate bars with a thickness of 30-50 mm.
After each rolling pass, high-pressure water descaling may be performed to remove the surface oxide layer.
Finishing
The intermediate bars enter the finishing mill (typically consisting of six or seven four- or six-high mills), where they are gradually thinned to the target thickness (e.g., 1.2-25 mm) through continuous rolling. Automatic gauge control (AGC) and flatness control systems are used to ensure dimensional accuracy and straightness.
During the rolling process, the rolls require cooling and lubrication to prevent thermal deformation and wear.
Cooling
Laminar cooling systems rapidly cool the strip from the final rolling temperature (approximately 800°C) to room temperature by controlling the amount of water and the cooling rate (e.g., 30-50°C/second).
The cooling process directly affects the coil's microstructure (e.g., the ferrite to pearlite ratio) and mechanical properties.
Coiling
The strip is wound into coils using pinch rolls and a coiler. Tension is controlled between 100-500 N/mm² to ensure a tight coil shape and no loose coils.
Coiling temperatures are typically controlled between 550-700°C to optimize properties.
Post-Processing
Surface treatment: Surface treatments include pickling to remove scale or coatings such as galvanizing or aluminizing.
Annealing: Improves material ductility (e.g., recrystallization annealing before cold rolling). Flattening: Rolling at low pressure eliminates yielding in flat products and improves surface finish.
Quality Inspection and Packaging: Products are inspected for dimensions, mechanical properties, and surface quality before being coiled, bundled, and labeled according to customer specifications.