Research On Crystallization Behavior Of Mold Flux In Magnetic Field

The mold flux is a vital functional material which was based on silicate including flux and framework material. In continuous casting, mold flux promotes casting quality and proceeding smoothly, consisting of insulation, restraining steel liquid oxidation,absorbing non-metal inclusion and governing heat passage and lubrication between casting blank and mold. Heat-transfer capability decides the casting quality, which mainly was resolved by crystallization behavior of mold flux. The researchers have investigated the effect of composition, cooling velocity on crystallization behavior of mold flux widely, establishing corresponding theory system. With the development of electromagnetic technique in continuous casting, including the electromagnetic stirring,electromagnetic brake and soft-contact electromagnetic continuous casting,electromagnetic field advanced slab quality owing to optimization of crystalline grain and structure of casting blank taking advantage of heat effect and force effect of electromagnetic field. In addition, the molten slag between slab casting and mold is ionic condition which also was in a magnetic field. Thus the conducting melt may produce heat effect and force effect, influencing the crystal formation and crystal growth. However, the effect of electromagnetic field on crystallization behavior often was ignored. Thus the research of crystallization behavior of mold flux in magnetic is contributed to know the actual properties of mold flux in continuous casting entirely. In the present work, manufacture the simulated device making mold flux film in magnetic field in lab. The effect of magnetic field intensity, binary alkalinity on crystallization ratio, crystallization size and crystallization phase were investigated and the crystallization mechanism in magnetic field has been discussed. By our study, magnetic field has a effect on the crystallization behavior, the results are concluded as follows:① The crystallization ratio and crystal size of mold flux film increases with the increasing magnetic field intensity. The crystallization ratio of mold flux at the binary alkalinity of 1.02, 1.04, 1.06, 1.08 increases from 44% to 70%, 58% to 78%, 62% to80%, 64% to 84% ranging the magnetic field intensity from 0 to 60 m T. And the crystal size increases from 25μm to 37μm, 27μm to 41μm, 28μm to 43μm, 30μm to 47μm. The new crystal nucleus was imposed magnetic energy in the magnetic field; The magnetic field increased the degree of super-cooling of solidification front, promoting the increasing of driving force for formation of new nucleus. The magnetic field decreasedthe surface energy of crystal, decreasing the resistance for the growth of crystal.② In the same magnetic field intensity, the crystallization ratio and crystal size increased with the increasing of the binary alkalinity and content of F. The result was consistent with the variation trends without magnetic field. In the same magnetic field,the increases of binary alkalinity and the content of F destroyed the network structure and provided the solute for the crystallization, boosting the formation and growth of nucleus.③ The magnetic field intensity in the range of 0-60 m T has no effect on the category of precipitated phase of mold flux, which mainly were Ca2 Mg Si2O7,2Ca O.Al2O3.Si O2, and Ca4Si2O7F2. The diffraction intensity increases with the increasing magnetic field intensity, inferring the content of precipitated phase was changed, which is identical with the increasing of crystallization ratio. The magnetic field changed the parameter of thermodynamics and kinetics, while not altering the channel for phase transformation.④ In the range of magnetic field intensity 0-60 m T, the driving force is greater than resistance for crystallization, so the magnetic field accelerated the formation of new nucleus and growth of crystal.