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Rolling of Long Products
Long products are steel bars, wire rod, reinforcing steel, and profiles such as rails, sheet pile, as well as I-, H- and U-profiles.
Rolling takes place in rolling mills specialised for the product groups. There are:
- bar mills
- wire mills
- combined bar and wire mills
- profile and rail mills
- other section mills
Continuously cast billets or near-net-shaped cast beam blanks (pre-forms of profiles and rails) are used as input material. After heating to rolling temperature, the input material is descaled and rolled in calibrated rolls – with as few rolling passes as possible – to create the final profile cross-section. The rolled sections are measured whilst still in the stand. After cooling of the rolled products they undergo finishing and further inspections and, if necessary, straightening processes before packaging and dispatch.
Recent developments have focused on:
- thermo-mechanical rolling: targeted material properties are generated directly from the rolling heat.
- free-size-rolling of steel bars: permits the rolling of numerous final dimensions from the same calibre, solely as a result of roll adjustment.
- beam and profile rolling from beam blanks.
- increased automation due to better control engineering.
Bright steel represents a further processing stage of hot-rolled or forged steel bars and wire. It is primarily intended for direct use by customers in the automotive and machine construction sectors. So very high demands are made of dimensional accuracy, surface finish and flawlessness.
Bright steel is produced by means of peeling or drawing. Peeled bright steel is always round, generally with a diameter of 14 mm or greater. Varying cross-sections can be formed using drawing.
Peeling is a machining process. It differs from turning in that the tool, the peeling head, rotates around the rod during its passage through the plant. As a result of the machining, the surface of peeled bright steel is free from surface defects and decarburisation.
Drawing is a non-cutting cold-forming process. The hot-rolled descaled input material receives its final character in several drawing steps. Drawn bright steel is generally strain-hardened.
After peeling or drawing, the round rods are polished and straightened. In the case of round bright steel, there may then also be an additional milling process as well as planing and chamfering of the ends.
Bright steel is specially packed for transport to the customer to prevent mechanical damage and corrosion.
It is not unusual for a stock of bright steel to number several thousand items – due to the variety of steel grades, the surface designs, lengths, tolerances and processing.