Precipitation : Behaviour of microalloyed steels during solidification and cooling

This was a collaborative project involving Corus R D & T, Teesside Technology Centre, Sidenor I + D, voestalpine Stahl Donawitz GmbH (VASD), Swerea KIMAB AB (KIMAB), ArcelorMittal Research and RWTH Aachen Technical University. It was coordinated by Corus. Building upon the knowledge gained from a previous project reported in EUR 22060, the goal of this one was to further understand the effects of the precipitation behaviour of microalloying additions during solidification and cooling, and their consequence on the quality of as-cast continuously cast semis. Using data and samples obtained from the industrial casters of Corus, Sidenor, VASD and ArcelorMittal, pilot plant and laboratory investigations by all the partners and supported by thermodynamic, numerical and kinetic modelling undertaken by KIMAB, ArcelorMittal, VASD and RWTH, further significant knowledge has been gained of the behaviour of microalloyed steels during solidification and cooling. The effects of mould cooling using different mould powders, the effect of secondary cooling using soft and hard cooling practices and the effect of strand cooling using different cooling bed conditions were explored. Equipment was developed and installed to explore billet deformation on-line as a function of steel chemistry. One alternative micro-alloying strategy was demonstrated at both Corus and Sidenor. Process route optimisation with one microalloyed steel grade was illustrated at Sidenor. The data gained during the project has illustrated how the precipitation during casting, solidification and cooling may possibly be altered to the benefit of surface quality and will enable optimisation of steel chemistry for final applications by using alternative microalloying strategies