The way that steel is cast into various shapes has changed to become highly energy-efficient and produce a better quality product.
Steel casting in the past
Not that many years ago, molten steel used to be poured (teemed) into a large mould where it would be allowed to cool and solidify to form an ingot. The ingot was then put into an oven called a soaking pit, where it would be gently heated to the correct and uniform temperature.
This red hot ingot would then be rolled in primary mills, in the first stage of its transformation into a usable steel product, into one of three forms of semi-finished product: a slab (a long, thick, flat piece of steel, with a rectangular cross-section), a bloom (a long piece of steel with a square cross-section) or a billet (like a bloom, but with smaller cross-section).
Nowadays in the UK, this process has largely been superseded by the continuous casting process (concaster), although the ingot route is retained for certain applications where it is the most suitable way of producing the steel required. (Elsewhere this is not always the case: many of the steel industries of Eastern Europe still rely heavily on the old ingot route.)
In a continuous casting machine, molten steel is poured into a reservoir at the top of the machine. It passes at a controlled rate into a water cooled mould where the outer shell of the steel becomes solidified. The steel is drawn down into a series of rolls and water sprays, which ensure that it is both rolled into shape and fully solidified at the same time. At the end of the machine, it is straightened and cut to the required length. Fully formed slabs, blooms and billets emerge from the end of this continuous process.
Thus the concaster combines in a single process what previously took two separate processes. This is both highly energy-efficient and produces a better quality product.
The slabs, blooms or billets are then transported to the hot rolling mill for rolling into steel products which can be used by manufacturing industry.