Rolling Mill

The BWS cold rolling mill produces precision and spring strip in the size range from 0.03 mm to 4.5 mm with tensile strengths up to 2200 MPa and narrow thickness tolerances that meet the highest flatness requirements. Recrystallization for microstructure adjustment and optimized processability is carried out in annealing furnaces.

Cold rolling

On two rolling stands, BWS rolls strip to demanding specifications across all stainless material grades, nickel and titanium alloys, and high-carbon steel.

The rolling stands are specially tailored to the BWS production program. Spring steels with tensile strengths up to 2200 MPa are produced on the 20-roll mill stand, foils from 30 µm and precision strips with tolerances of +/- 1 µm over the entire strip length. Thanks to a multi-roll insert developed by BWS, the quarto roll stand can be operated either as a quarto or a 6-high rolling mill. This enables processing of an extremely wide range of thicknesses and grades.

State-of-the-art measuring and control technology, such as laser thickness measurement and flatness systems, ensure uniform and monitored quality with consistently high production accuracy.

Heat Treatment

Optimum processability of the strip at the customer’s premises requires a uniform recrystallized microstructure and a uniform grain size. This property is achieved by intermediate or final annealing after cold rolling.

Depending on customer specifications, different annealing processes at temperatures of up to 1200˚ C can be realized on the BWS bright annealing lines in continuous operation. A wide range of thicknesses is annealed, from strip thicknesses ≤ 2.00 mm to the thin strip and foil range. Furthermore, high convection hydrogen batch annealing furnaces enables the heat treatment of C-steels.

During the so-called “soft-annealing”, the hardness and tensile strength of the material are reduced in order to improve further processability, for example in rolling or forming. Special thermal processes such as CAF and stress relief annealing are used to reduce the residual stress of the strip and improve its plastic forming properties.

Stretch-levelling

Strip in table-flattened design, with constant tensile strength, yield strength and elongation over the entire length, is a prerequisite for meeting the ever-increasing demands in the industry for component complexity and high processing speeds in the forming process. To achieve these high flatness requirements, our strips can be straightened on our stretch-levelling line.

At BWS, both soft annealed and hard rolled strips in the thickness range < = 1.20 mm and tensile strength spectrum (also > 2000 MPa) are straightened. The prerequisite for this is our stretch-levelling-line with an accuracy that is unique in Europe with above-average drive and tensile performance. All stainless Steels, nickel-based and titanium materials ≤ 1.20 mm are stretch-levelled as a standard at BWS.

Fully integrated flatness control ensures consistent quality and flatness over the entire coil length.