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

The study of production processes and the resulting products is at the heart of the steelmaker's profession. Rolling mills play an important role in this process. After solidification, which gives solid steel its first form - slab, bloom, billet or round - the rolling mill performs dimensional control and metallurgical transformations to give the product the desired properties.

There are many possible processes, and they are constantly evolving: simplifications and groupings of stages are transforming the business. The advent of continuous casting, for example, has simplified processes and brought considerable advantages to steel production. Nevertheless, conventional solutions are also constantly evolving: the products obtained are increasingly suitable for a wide range of applications (in the building, mechanical and food industries, steel and mechanical engineering, etc.) and have ever longer service lives.

Today, flat products (steel plate, sheet or strip) are produced or prepared on two main types of rolling mill:

• quarto: a reversible four-roll stand, sometimes two reversible stands, used to produce large, thick plates (generally over 8 mm thick). These are used for boiler-making, shipbuilding, tube-making, etc. ;

• strip mills, or hot continuous mills: these are used to produce steel strips with thinner thicknesses (from 1 mm to 12 mm, or even more), and narrower widths (less than 2 m), but longer lengths (up to 1 km). The strip mill often precedes the cold re-rolling stage, which is necessary to obtain thinner products.

The following pages are dedicated to the belt drive. What is the origin of this technology? How has it developed to date? What is the current state of development worldwide? What products are produced, and which markets are concerned? What are the theoretical and practical aspects of rolling on a strip mill?

In the , we will describe the latest technologies used on a strip mill: from the slab yard to the coil winding and evacuation systems. We'll see how a train is operated, and the results obtained in terms of dimensional and thermal performance and metallurgical quality. Finally, we'll look at some of the economic aspects of operating this tool.

We conclude with a look at future trends: the improvement of existing tools on the one hand, and the emergence of new, simpler processes on the other.