Development of an innovative hybrid procedure for combining tension-levelling and skin pass rolling : HYPROCOM ; final report

The elimination of the yield elongation with its appearance of the so called Lüder´s lines and transfer of surface texture up to now is realised by the skin pass rolling process. In case of highest flatness requirements a subsequent tension levelling process is put into operation. Due to the extended use of high strength materials and the high surface texture requirements two main problems arise. Regarding high strength steel grades requiring high roll force for yield elongation elimination extreme roll wear and strongly reduced service life is the consequence. Otherwise soft steel grades, requiring only small amount of skin pass deformations and thus rolled with only light roll forces, demand for higher roll forces to ensure sufficient roughness transfer. It gets obvious that the roll force has to fulfil two main but conflicting functionalities: Skin pass reduction for yield elongation elimination and surface roughness transfer. Thus the main objective of the project is the development of an innovative strip finishing procedure by combining tension levelling and skin pass rolling into one production step and thus to overcome restrictions given with the common skin pass process and to shorten the process chain. It could be demonstrated that the new hybrid process is able to adjust material mechanical and surface roughness properties independently. The required roll force could be reduced by 25 %.