Document Type : Research Paper
Azad University of Najafabad
department of materials eng. Isfahan Univ. of tech.
Mould powders are mainly composed of SiO2, CaO, alkaline, and alkaline-earth oxides along with traces of fluoride and carbon. Their crucial responsibility is lubricating the surface between mould walls and the solidified steel crust. The viscosity and crystallization of these powders are influenced by Fluorine. However, the emission of evaporating materials leads to environmental pollution. Therefore, this research aims to decrease the amount of CaF2 and the effect of substitute compositions on the viscosity and crystallization of mould powders. Hence 12 powder samples are prepared having employed Portland Cement Clinker and other as the main composition. To compare the laboratory samples with the molten reference powder, groove viscometer tests were conducted. The crystalline behavior of the samples was examined employing XRD, SEM and STA analyses. Results showed some low-CaF2 samples had similar viscosity as molten reference powder (MRP). XRD analysis results presented crystalline phases of gehlenite, cuspidine, akermanite, nepheline and Mn3O4 .Likewise, the crystalline phases of B2SiO5, Na2ZnSiO4 and perovskite (CaTiO3) were examined after adding B2O3, ZnO and TiO2. SEM analysis results showed crystals in the glass matrix, which can optimize the viscosity in mould powders. TGA analysis results revealed the reduction on ignition loss of a low-CaF2 sample compared to the reference powder. Moreover, DTA analysis revealed the crystallization and melting temperatures of the same low-CaF2 sample, similar to that of the reference powder. Finally, three low-CaF2 samples containing CaF2, Li2O, TiO2, ZnO and B2O3 were nominated as the apt substitutions for reference powder in laboratory scale.