Research On Crystallization Properties Of The Fluoride-free Mold Fluxes Based On TiO₂

Mold fluxes is a very important and critical material during continuous casting of steel, taking a key role in controlling heat transfer and lubricating strands. The crystallizing behavior of mold flux affects controlling heat transfer and lubricating strands. With the development of continuous casting (CC) technology of steel, it is significant to research the crystallizing behaviour for stabilizing the process of continuous casting and improving the strand quality. The crystallization properties of the fluoride-free mold fluxes based on TiO₂ was studied in the dissertation, in order to maintain good processes during continuous casting.The effects of components on crystallization temperature of the fluoride-free mold fluxes based on TiO₂ were investigated by using Single Hot Thermocouple Technique-â…¡.It is obvious that the crystallization temperature of the fluoride-free mold fluxes based on TiO₂ would be increased with the increasing of basicity,TiO₂,Li₂O,Na₂O and MgO content, and decrease with the increasing of B₂O₃ content, increase firstly and then decrease with the increasing of MnO content.The effect of cooling rate on crystallization temperature of the fluoride-free mold fluxes based on TiO₂ has been researched by using Differential Scanning Calorimetry. Cooling rate has an important influence on crystallization temperature. Crystallization temperature will decrease about 10℃with the cooling rate increasing 5℃/min.The effects of components on the crystallization ratio of the fluoride-free mold fluxes based on TiO₂ have been researched by using furnace and ZEISS-optical microscope under the experiment conditions. The crystallization ratio of the fluoride-free mold fluxes based on TiO₂ would increase with the increasing of basicity,TiO₂,Na₂O and MgO content, and decrease with the increasing of B₂O₃ content,increase firstly and then decrease with the increasing of Li₂O and MnO content.The crystalline phases of mold fluxes prepared in laboratory are studied by using ZEISS-optical microscope under the experiment conditions , the presence of perovskite phase are observed, nepheline,melilite and diopside may exist in some slag samples. The effects of components on the surface roughness of the mold fluxes have been researched by using surface roughness profile instrument. The result is that the surface roughness of the fluoride-free mold fluxes based on TiO₂ would increase with the increasing of basicity,TiO₂,MgO,Na₂O and Li₂O content; decrease with the increasing...