Techniques for controlling heat transfer in the mould-strand gap in order to use fluoride free mould powder for continuous casting of peritectic steel grades

When casting peritectic steel grades, control of heat transfer from the steel shell is critical for minimising surface defects. Cuspidine (3CaO.2SiO2.CaF2) is the preferred crystal phase to control horizontal heat flux, due to its high crystallisation temperature and low incubation time. However, the presence of fluoride creates environmental and operational problems. Research into fluoride-free mould powder for peritectic steel grades has still to yield a fully effective substitute. This research has investigated whether horizontal heat flux in the mould can be controlled by manipulating the interface between the copper mould plate and the slag film. Calculations estimate that the removal of fluoride will decrease the total thermal resistance between the mould and strand by 28%. Results show that interfacial thermal resistance can be increased by the techniques developed, with one technique meeting and exceeding the requirements to replace fluoride in terms of thermal resistance needs for peritectic steel grades.