Metallurgical aspects of steel hot rolling Application to low alloyed steels

Whatever their end use, steel products undergo at least one hot forming stage during the manufacturing process, usually separate from the production phase. The initial purpose of this shaping phase – rolling – is to obtain given geometric characteristics. Studies carried out over the past forty years by numerous teams (IRSID, McGill University, Sheffield University, etc.) have shown that during the rolling process (i.e. reheating, rolling itself and cooling to ambient temperature), the metallurgical structure of steel is constantly evolving. This work has also made it possible to identify the metallurgical phenomena involved and determine the parameters (mechanical, thermal or compositional) that control them. It is therefore theoretically possible to modify the structure, and therefore the final properties, of the product, by adjusting these different parameters while respecting the constraints imposed by the industrial tools. In this way, rolling becomes a thermomechanical processing tool. It is important to note that the optimization of rolling patterns is also important for products that subsequently undergo cold forming steps (automotive sheet, beverage can sheet, electrical sheet, etc.).

In this article, we describe the different phases of rolling and study the physical mechanisms involved and the means of exploiting or, on the contrary, inhibiting them. Some application examples are presented to illustrate these different aspects, from a modeling or new steel development point of view.

At the end of the article, readers will find a glossary and table of symbols and notations.