Continuous production lines in the steel industry

In most industries, the trend is towards the development of production lines that are as direct and continuous as possible. The [M 7 940] continuous hot strip line developed in the USA between the two world wars, around 1930, is a good example of this, as are the corresponding developments, in long products, in the case of wire trains. . Further downstream, there are links between continuous pickling lines, cold rolling, continuous annealing and even coating lines. In the field of primary metal production (cast iron or reduced ores), steel and hot-rolled steel products, this trend is beginning to emerge, and we will examine it from the following three angles:

• continuous lines for the production of solid or liquid metal, cast iron, reduced ores or steel;

• continuous lines from the steel mill to the hot-rolled steel product;

• the future possibilities of fully continuous steelmaking, from raw materials to finished product.

Nevertheless, before turning to these three developments, we'd like to remind you that the notion of continuity is not a simple one, as the complexity of the definitions will show.

For us, a continuous process is one in which both inputs and outputs are in continuous flow:

• on the one hand, there is much more often a continuous feed than a continuous output, especially for liquid metals generally discharged in successive pours ;

• on the other hand, even for so-called "continuous" processes, such as continuous strip mills or continuous casting, operations are generally performed in sequences for limited durations, e.g. the passage of each slab to the strip mill.

The same remarks apply to continuous transport, from one unit operation to the next; again, this transport may only be continuous for a certain length of time.

In the course of this article, we'll try to clarify these often imprecise notions.