Enhanced steel product quality and productivity through improved flux performance in the mould by optimising the multiphase flow conditions and with special regard to melting and entrapment

Abstract

Optimum melting of flux and behaviour of the molten flux pool situated above the steel melt surface as well as the avoidance of flux entrapment are important requirements to be achieved simultaneously for a stable casting process and a high product quality. The mould casting powder has to satisfy various requirements like lubrication, promotion of uniform heat-transfer, inclusion absorption, thermal insulation and chemical insulation. The aim of the project performed by steel producers (Arcelor España, CAS, Sidenor and TKN) and research institutions (BFI and CSM) was to provide precise information on the necessary optimum constructive and process engineering measures to adjust casting conditions and as a result flow conditions in the mould in order to avoid flux entrapment into the mould and also to guarantee a sufficient thickness and behaviour of the flux layer floating on the steel melt. The main objectives were: • Provision of more detailed information on the interrelation between melting conditions of the flux floating on the steel melt, especially the dynamic behaviour of this flux layer and steel flow. Focus had to be given especially on what flow conditions are needed in the mould to guarantee a sufficient layer and behaviour of the flux pool and simultaneously to avoid entrapment of flux into the steel melt. • Provision of a data base concerning optimised casting parameters (casting velocity, SEN immersion depth), SEN design to adjust the necessary flow conditions for given steel grades and selected casting powders. Also the influence of gas injection and of electromagnetic forces (EMS) had to be considered. Improvement of casting powders was also aim where necessary. • Verification of this data base in the operational praxis.