A novel hybrid strip finishing process to improve mechanical properties and reduce energy consumption

The growing demand for new steel grades, such as high formability steels and high or ultra-high strength steels for structural and safety-related automotive components, make manufacturing steel sheets an increasingly complex task. A novel hybrid process (HyP), that combines the skin-pass and tension levelling processes into one production step is proposed to improve the steel strip manufacturing chain. The HyP applies asymmetrical rolling (H-ASR) by using different roll diameters and by bending the strip before it enters the roll gap. The potential advantages of H-ASR, such as the introduction of through-thickness higher plastic deformation and the use of reduced roll force and power, were investigated by means of elastic-plastic finite element models and experimental data. The numerical models were validated by experiments at a HyP pilot facility and by industrial trials. Analytical estimation of the appropriate bending limits was included. The contact condition, material deformation and stress state during rolling were analysed and compared with the results of a conventional skin-pass process. It was verified that the proposed H-ASR introduced higher shear deformation throughout the strip thickness than a traditional skin-pass process. The positive influence of this fact was verified by tensile and formability tests on material processed by the HyP pilot facility. The results indicate that the HyP produces sheets with better drawability, satisfactory strength, and formability qualities comparable to those of the conventional finishing processes. What's more, the HyP boasts all these advantages while using a space-saving layout and reducing energy consumption as compared to traditional finishing processes.