The Difference between Cold Rolled Aluminum Sheets and Hot Rolled Aluminum Sheets: Cold rolling is commonly known as sheet rolling at room temperature. From a metallurgical perspective, rolling below the recrystallization temperature is considered cold rolling. Hot rolling involves using billets (mainly continuous cast billets) as raw material, which are heated and then rolled into strip steel by a finishing mill and a finishing mill.

Cold-rolled aluminum sheets are produced from hot-rolled steel coils, which are cleaned with acid to remove oxidation skin before undergoing cold rolling. The finished product is a hard-rolled coil. Due to the cold working softening induced by continuous cold deformation, the strength and hardness of the hard-rolled coil increase, while the toughness and ductility decrease, leading to poor stamping properties, suitable only for parts requiring minimal deformation. Hard-rolled coils can be used as raw material for hot-dip galvanizing plants, as the hot-dip galvanizing lines are all equipped with pre-annealing facilities. The weight of hard-rolled coils typically ranges from 6 to 13.5 tons, and steel coils are continuously rolled at room temperature from hot-rolled and acid-cleaned coils.

Cold rolling is a process where hot-rolled steel plates are processed at room temperature. Although the rolling process does cause the steel plates to heat up during processing, it is still referred to as cold rolling. Cold-rolled aluminum plates are essentially processed by rolling the hot-rolled coil, typically involving a process of hot rolling - pickling - cold rolling.

In brief, a steel billet, which is the white, hot steel block you see on TV, is rolled several times, trimmed, and corrected into steel plates, known as hot-rolled. Due to the lack of annealing treatment, it has a high hardness (hrb over 90), excellent machinability, and can only undergo simple, directional bending less than 90 degrees (perpendicular to the rolling direction).

Due to the cold rolling process, which is achieved through continuous cold deformation of hot-rolled aluminum sheets, the mechanical properties are superior and the hardness is too high. The mechanical properties must be restored through annealing, and those without annealing are called hard rolled coils. Hard rolled coils are usually used for products that do not require bending or stretching; fortunate ones with thicknesses below 1.0 can bend both or all four sides.