Width-adaptable optimised controlled-cooling systems for the production of innovative AHSS grades and the study of strip shape changes while cooling (Wacool)

The overall aim of this project is to develop cooling technology applicable to the production in an HSM of advanced high-strength steel (AHSS) grades for the most effective controlling of their microstructure and mechanical properties. Different types of laminar flow cooling headers (Wacools 1-3), which also permit considerable reduction of water consumption by limiting the cooling width to the width of the strips, as well as facilitating the edge-masking feature, were developed and integrated. New cooling strategies were investigated, especially for the finishing mill and run-out tables, to improve the mechanical and metallurgical properties of AHSS. A theoretical investigation of the strip shape changes during cooling, before and after coiling the strips, was undertaken with the aim of optimising the strip flatness after being cooled down to room temperature. The cooling header Wacool1 constructed at ThyssenKrupp Steel, Bochum satisfied the specifications well, whereas Wacool3 was integrated to the HSM of ArcelorMittal, Aviles after successful tests. At the average strip width of about 1.2 metres they give water savings of about 30 % and 10 % respectively. Cooling rates of 100 to 120 K/s are attainable. Due to technical and cost problems Wacool2 was not constructed. The thermomechanical model was developed by SSSA and a piece of software, CCT_Calc, for the calculation of the cooling curves, was developed, implemented and validated using the experimental data produced at ILVA. Both the statistical flatness model developed by ArcelorMittal and the physical/mathematical model of strip shape changes developed by Corus provided new knowledge that can be used for selecting optimal cooling strategies to retain the flatness until after the final cooling.