Hot rolling is an industrial process for re-working principally steels but also stainless steels. Steelworks melt the material. To make it transportable, the melted steel cools down in different shapes.

The process of hot rolling sections

These shapes can be either blooms, billets or slabs. Last one is generally used for rolling sheet material, while the others for profiles, strips, pipes and wire. But how is this process taking place?

Hot rolling begins with heating the billet or blooms to a high temperature of around 1100 degrees Celsius. The temperature is of particular importance. Hot rolling and hot extruding drawing involves working above the recrystallization point of the steel. The mill passes the heated material through a variable number of stands. According to this, the profiles are performed through a series of passes. This is allowing a high design flexibility.
Furthermore, the rolls of the stands have a particular shape for the specific step within the rolling process. So the final shape of the profile determinates the amount of stands. They are needed for transforming the large raw material block into the smaller section.
At various points during thermal treatment, water at high pressure is cleansing the steel  to remove mill scale. This prevents surface imperfections developing on the end product. In the end, the profiles are cooled. For this, workers control the cooling rate to allow for the correct microstructure and crystallization of the steel to occur depending on its intended purpose.

Typical profile hot rolling mills

Hot rolling mills typically produce sections of steel at various dimensions from billets of steel. The manufactoring process involves passing bars of steel at high temperatures. This happens through rotating rolls to reduce the thickness and shape the sections. It furthers proceeds into cooling and cutting to length or coiling into rolls for transport to other finishing processes such as cold forming or cold drawing.