9th ECCC European Continuous Casting Conference – ECCC 2017

Keywords: mould powder, fluoride free, heat transfer Abstract: When casting steel grades in the peritectic range it is critical to control the heat transfer from the steel shell in order to minimise longitudinal crack defects. In practice, horizontal heat flux is predominantly controlled by mould flux crystallinity. Cuspidine (3CaO.2SiO2.CaF2) is seen as the most preferable crystal phase due to its high crystallisation temperature and low incubation time. However, the presence of fluoride creates various environmental and operational problems. Research into fluoride free mould powder for peritectic steel grades has so far not yielded a fully effective substitute, as the crystallisation thermodynamics of cuspidine cannot easily be reproduced by other phases. The current research has investigated whether horizontal heat flux in the mould can be controlled by manipulating the interface between the copper mould plate and the mould flux film. Calculations as part of this research estimate that the interfacial thermal resistance must be increased by 167% in order to successfully cast peritectic steel grades with a fluoride free mould flux that exhibits glassy properties. Laboratory scale measurements have shown that interfacial thermal resistance is increased by the investigated techniques, with one particular technique meeting and exceeding the thermal requirements to cast peritectic steel grades with a glassy mould flux. Further trials were completed on the most promising technique using a “copper finger” test and mould flux film analysis. The results show that the selected technique used in conjunction with a glassy mould flux can produce a heat transfer rate equivalent to that of a peritectic mould powder.