PRODUCTION PROCESS >

The rod & bar mill

Rolling reinforcing bars

For reinforcing bar, billets are reheated to around 1150ºC in a gas-fired furnace. Reheating makes the steel softer and more deformable, so that the final shape can be produced more economically, and using less energy.

Once up to temperature the billets are pushed into the rolling stands, each of which has a pair of grooved cylindrical steel rolls. As the steel is forced through the grooves, the area of the cross section is reduced. This process is repeated continually over several stands, with the cross section reducing each time until the required dimensions are achieved. In the case of reinforcing steels, notches are cut into the grooves of the final rolling stand and the steel that fills these notches forms the ribs on the bar surface.

In order to achieve the strength and ductility of grade 500C reinforcing steel, the steel is cooled by high pressure water jets. This results in a hard, strong surface with a soft, ductile central core. This process is known as quench and self temper (QST). Once cooled the bars are sheared to a length of around 80 metres and transferred to a cooling bed where they cool further in still air. The bars are then sheared to the required customer lengths, bundled, labelled, and moved into storage, awaiting despatch.