Research On The Crystallization Behavior Of Continuous Casting Mould Flux

In the continuous casting process, the crystallization behavior of mould flux can control the heattransfer and lubrication between billet and mould, thus preventing the occurrence of billet surfacedefects. This paper analyzed crystallization behavior of fluxes in thermodynamics and kinetics, anddesign the single factor experiment to study the effects of MgO, TiO2, Al2O3and basicity on the slagcrystallization properties. Mathematical model of slag film structure between the mould and slab havebeen established to study the function law of the flux performance, composition and castingparameters on the slag film structure and liquid slag lubrication behavior. The following mainconclusions are that:1) When liquid slag temperature makes the enthalpy effect on free energy is greater than theentropy effect, it will be crystal; In dynamics, temperature of fluid slag reduces to meet therequirements of supercooling degree, under the condition of viscosity does not affect the growth of thecrystal nucleus, crystal precipitation can be smooth;2) When3.28%<MgO<4.29%, and4.29%<TiO2<5%in the flux, the crystallization behavior isrestrained; when4.29%<MgO<7.25%, and7.25%<TiO2<10%, the crystallization properties areimproved. For R=0.85~1.13, alkalinity rises by0.1for one time, the upper limit of crystallizationtemperature increase average52℃, critical cooling rate increase4℃/s, the crystallization rate grows,the crystallization activation energy decreases continuously;3) When Al2O3=5.21%~10%in the flux, Al2O3content every increase1%, the upper limit ofcrystallization temperature decrease by15℃, the critical cooling rate decrease by1.7%, thecrystallization rate decrease and crystallization activation energy increases;4) By using low melting point slag and under the condition of high speed and high castingtemperature, the length and thickness of liquid slag will increase, the crystal layer will decrease. Byusing low viscosity and melting point slag, low vibration frequency, low vibration amplitude and highcasting temperature will enhance the lubrication effect of slag;5) MgO, Na2O, CaF2can promot slag crystallization under the premise of ensuring thelubrication effect between slab and mould. The basicity can promote crystallization behavior of slag,but it will deteriorate the lubrication of slag; Al2O3not only inhibits the crystallization behavior butalso increases liquid friction between the slab and the mould.