Effects of Hematite and Titanium Oxide on the Viscosity of Mold Powders of Continues Casting

Mold powders are mainly composed of oxides such as SiO2، CaO، Al2O3، Na2O، along with F- and carbon. One of components of mold powders is F-،which is utilized in chemical composition of mold powders for lubricating and controlling viscosity between solidified steel shell and copper mold. However، emission of F-through compositions such as HF (g) causes health and environmental problems. The purpose of this research is elimination of F- from chemical composition of a high speed lubricating powder used in continuous casting in steel industries. In addition، the effects of substitut compound upon viscosity is investigated. Groove viscometer test and image analysis were used to compare produced powders and used powder molten viscosity. X-ray diffraction، emission electronic microscope and spectroscopic analysis of scattered energy were used also for evaluation the crystalline behavior. The results of the study showed that Portland cement clinker could be an appropriate substitution for Wollastonite in the basic composition of mold powders. In addition، using TiO2 of about 3 wt% and hematite of about 3 wt% (surplus to the existing hematite in the chemical composition of Portland cement clinker)، a fluorine-free sample was prepared having viscosity near to that of the molten main powder. Considering produced phases such as Perovskite and Fayalite، it can be concluded that this is a fluorine-free sample which is believed to be an appropriate substitution for the main powder being currently used in continuous casting of steel due to its similarity in viscosity and crystallization to those of the molten main powder.