The cold stainless steel work area includes the annealing and pickling line for hot rolled strips, the Sendzimir rolling mills, the polished annealing lines for cold-rolled strips, the annealing and pickling lines for cold-rolled strips, the Skin-pass rolling mills, the tension leveller, and cutting and finishing lines.
The cold rolling is done with a Sendzimir rolling mill which, thanks to its special structure and process (stretching and flattening), can significantly reduce the thickness of the strips with great precision.
Cold rolling is important for obtaining excellent results in subsequent treatments from a surface point of view (BA) and for achieving mechanical characteristics (work hardening).
COLD ANNEALING IN BA FURNACE
Annealing of cold rolled steel in the BA furnace does not cause oxidation of the strip because the internal atmosphere in the furnace is not oxidant (mixture H2 – N2). As a result, the strip does not need to be pickled. Once annealed, the strip is skinpassed to acquire the mechanical characteristics required, excellent flatness and improved brightness. The surface finish which is obtained in the BA process is polished, bright and mirror-like.
Z/Mill rolling methods are also essential for obtaining a BA product with high quality.
COLD ANNEALING OF COLD ROLLED STEEL
In cold annealing of cold rolled steel, the surface of the strip is oxidised as it passes through the oven. To clean the surface of oxide, the strip is then passed through the tanks where the oxide is removed by means of chemical and electrochemical pickling (H2SO4 + HF). Once pickled, the strip is sent to skin-passing where it acquires the required mechanical characteristics and flatness.
The surfaces which are obtained with this process are not particularly reflective.