Abstract:
Mold flux plays a significant role in quality during the continuous casting process. Mould powders are synthetic slags used to lubricate the mould during continuous casting of steel. For this to occur, the mould powder has the following functions: chemical and thermal insulation of steel, absorption of non-metallic inclusions from steel, lubrication of the mold and control of heat transfer between the steel and the mold. The performance of each function is related to the chemical and physical properties of the mould powder, which are functions of its chemical composition, and besides its chemical composition also its mineral composition should also be considered, as it affects its melting rate. In order to ensure efficient and high quality production during an ultra-low carbon casting, mold fluxes A and B were investigated according different physico-chemical properties. Several laboratories experiments were carried out to compare the performance of mold fluxes A and B targeting to avoid slag entrapment: evaluation of melting and fluidity behavior, chemical composition, viscosity and temperatures and statistical tests were conducted in order to characterize heat flux and frictional work during casting. The preliminary industrial trials, performed at Ternium Brasil were accomplished aiming to analyse its behaviour during continuous casting operation regarding some operational aspects and to provide information about its influence on the superficial quality of the steel. The results showed that by increasing mould fluxes viscosity, the mold powder consumption became lower leading to higher frictional work and lower heat flux in the mold. However, the slag layer behavior showed that despite the increased frictional force in the mold, the slag thickness was adequate and there were no reports of surface defects during use of the higher viscosity mold flux.
