Hotrolling

Hot rolling is a metalworking process in which metal is heated above its recrystallization temperature and then passed between rollers to reduce its thickness or alter cross-section. It is widely used for steel and other metals such as aluminum and copper alloys. Heating allows plastic deformation with lower forces and refines the grain through recrystallization, which prevents work hardening.

Process: The starting material—slab, bloom, or billet—is reheated in a furnace to a temperature high enough for recrystallization. It is then conveyed through a sequence of rolling stands, with reductions at each pass, to reach the desired thickness or shape. The hot product may be coiled or cut and is often allowed to cool in air. A surface oxide scale forms during heating and must be removed or reduced later; finishing steps may include descaling, annealing, or pickling to produce a smoother surface and tighter tolerances.

Materials and products: Hot rolling is standard for structural shapes, rails, bars, plates, and sheet stock, especially where large cross-sections or long lengths are involved. Aluminum and copper hot rolling are common for forming large thick sections.

Properties: Because recrystallization occurs during processing, hot-rolled products generally have lower strength but higher ductility than cold-rolled equivalents and often exhibit anisotropy and surface imperfections. Grain structure tends to be refined by the process, but residual stresses can remain.

Advantages and limitations: Advantages include the ability to shape large sections economically and to produce near-net shapes quickly. Limitations include rough surface finish, looser dimensional tolerances, the need for post-processing (descaling, annealing, or pickling), and potential surface defects.