Hot-rolling flat products in a hot strip-mill. Part 1

The study of production processes and the resulting products is central to the steel industry. Among the main tools used in these processes, rolling mills play an important role. After solidification, which gives solid steel its initial shape (slab, bloom, billet, or round), the rolling mill ensures dimensional control and metallurgical transformations that give the product the desired properties.

There are many possible processes, and they are constantly evolving: simplifications and regroupings of stages are transforming the profession. For example, the advent of continuous casting has simplified processes and brought considerable advantages to steel production. Nevertheless, traditional solutions are also constantly improving: the products obtained are increasingly suited to a wide range of applications (in construction, mechanical engineering, the food industry, metal and mechanical engineering, etc.) and have increasingly long lifespans.

Flat products (plates, thin sheets, or steel strips) are now produced or prepared on two main types of rolling mills:

• The quarto: a reversible four-cylinder cage, sometimes two reversible cages, used to produce thick, large-sized plates (the thickness is generally greater than 8 mm). These are used for boiler making, shipbuilding, tube manufacturing, etc.

• and the strip mill, or continuous hot rolling mill: used to produce steel strips that are thinner (from 1 mm to 12 mm or more), narrower (less than 2 m), but very long (up to 1 km). The strip mill often precedes the cold rolling stage, which is necessary to obtain thinner products.

The following pages are devoted to strip mills. What is the origin of this technology? How has it developed to date? What is the current status of its development worldwide? What products are obtained, and which markets are involved? What are the theoretical and practical aspects of rolling on a strip mill?

In the file , we will describe the latest technologies used in a strip mill: from the slab yard to coil winding and coil removal. We will see how a mill is operated and what results are achieved in terms of dimensional and thermal performance and metallurgical quality. Finally, we will present some economic aspects related to the operation of this tool.

We will conclude with future trends: the improvement of existing tools on the one hand, and the emergence of new, simpler channels on the other.