ahmadreza Arefpour - najafabad university
Saeid Jabbarzare - Azad University of Najafabad
Ahmad Monshi - najafabad university
Ali Saidi - department of materials eng. Isfahan Univ. of tech.

Mould powders are mainly composed of SiO۲, 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 CaF۲ and the effect of substitute compositions on the viscosity and crystallization of mould powders. Hence ۱۲ 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-CaF۲ samples had similar viscosity as molten reference powder (MRP). XRD analysis results presented crystalline phases of gehlenite, cuspidine, akermanite, nepheline and Mn۳O۴ .Likewise, the crystalline phases of B۲SiO۵, Na۲ZnSiO۴ and perovskite (CaTiO۳) were examined after adding B۲O۳, ZnO and TiO۲. 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-CaF۲ sample compared to the reference powder. Moreover, DTA analysis revealed the crystallization and melting temperatures of the same low-CaF۲ sample, similar to that of the reference powder. Finally, three low-CaF۲ samples containing CaF۲, Li۲O, TiO۲, ZnO and B۲O۳ were nominated as the apt substitutions for reference powder in laboratory scale.

Mould Powder(MP), Molten Reference Powder (MRP), Viscosity, Crystallization, Portland Cement Clinker