Effect Of Crystallization Behavior And Heat Transfer Of Mold Flux On Magnetic Field

Mold flux promotes casting quality and proceeding smoothly, playing an important role on the stability of continuous casting process and the surface quality of slabs, heat-transfer capability decides the casting quality, especially the crystallization property. Electromagnetic metallurgy has become an important branch of material science, playing an important role to improving slab quality and expand steel variety in continuous casting. Mold flux exists as ionic state and has electric conductivity in high temperature. Therefore, magnetic field has great effects on the microstructures of mold flux through its force effect, magnetic effect and heat effect, so as to affect the crystallization characteristics and heat transfer performances of mold flux. The research of crystallization behavior and heat- transfer of mold flux in magnetic is contributed to know the actual properties of mold flux in continuous casting entirely, but the effect on the heat transfer performances of mold fluxes was rarely considered at home and abroad. In order to find out the influence of magnetic field on the crystallization characteristics and heat transfer performances of mold fluxes, a device was designed and set up to prepare flux film under magnetic field. Furthermore, crystallization properties including mineral phase, crystallization rate and crystal size were analyzed under different magnetic induction intensities. Combined with experimental results in the present work, effect of magnetic field on temperature field of flux film was investigated by numerical simulation method. Finally, the effect mechanism of magnetic field on crystallization process and heat transfer of mold flux was discussed. The main conclusions are obtained as follows:（1） Magnetic field has no effect on the type of precipitated crystals, which mainly were Ca₂MgSi₂O₇, 2CaO.Al₂O₃.SiO₂, and Ca₄Si₂O₇F₂. Both crystallization rate and crystal size of mold flux increases with the increasing magnetic induction intensity. The crystallization rate of mold flux increases from 31% to 59% and crystal size increases from 12 um to 17 um when magnetic intensity increases from 0 to 60 mT.（2） With the magnetic induction intensity stronger, the greater the temperature gradient of the flux film will be. but the greater the temperature gradient of the flux film will be. At the mould length was 750 mm, with the magnetic induction intensity increasing from 0 to 60 mT, the temperature from 730 K to 578 K and maximum temperature difference of the flux film surface is 152 K, the temperature gradient from 332 K/mm to 384 K/mm and the maximum temperature gradient difference is 52 K/mm.（3） According to crystallization theory and the magnetization effect of magnetic field on materials, from the crystallization thermodynamics perspective, the applied magnetic field leads to a bigger local super cooling in molten steel and a stronger crystallization driving force. At the magnetic induction intensity was 60 mT, akermanite, gehlenite, cuspidine and pyroxene gibbs free energy respectively decreased was 2047 J/Kg, 962 J/Kg, 789 J/Kg and 499 J/Kg when crystallization of mold flux. From the crystallization kinetics perspective, the applied magnetic field promotes the mass transfer rate of flux particles and crystal growth. At the magnetic induction intensity was 60 mT, magnetic field force of akermanite, gehlenite, cuspidine and pyroxene was 2047 N/ Kg, 962 N/ Kg, 789 N/Kg and 499 N/Kg when crystallization of mold flux.