Investigation On Distribution For Thermal Resistance Of Mold Flux/Air Gap During Slab Continuous Casting

As an important auxiliary material,mold flux not only has essential functions,such as heat insulation,oxygen isolation and inclusion absorption,but also stabilizes heat transfer and provides lubrication in continuous casting process.Mold flux fundamentally determines the solidification and friction in mold,which dominates the formation and evolution of initial slab crack.To stabilize and improve the quality of slab surface,it is essential for ensuring the distribution,evolution and heat transfer of the slag layers and air gap by regulating the complicated heat transfer and mechanical behavior between mold and slab shell.In this paper,a numerical model of the inverse heat problem in a mold is established for solving heat transfer based on the online measured temperature.On this basis,a computational model of the slab solidification and a numerical model of the slag layers/air gap thickness and thermal resistance are developed,and are applied to calculate the non-uniform distribution and evolution of the slag layers/air gap under the actual operating conditions.Simulation results obtained from the models built are used to explain the heat transfer characteristics,contribution and mechanism of heat conduction/radiation in slag layers and air gap.Based on the measured thermocouples temperature and actual process parameters in continuous casting,a numerical model of the inverse heat problem and a computational model of the slab solidification are developed,which are applied to investigate the non-uniform distribution and characteristic of heat flux,slab surface temperature and solidification.Based on the numerical model of the inverse heat problem and the computational model of the slab solidification,a numerical model of the slag layers and air gap thickness and thermal resistance are developed,which investigates the effect of slag solidification temperature and casting temperature on the liquid lubrication length,thickness of slag layers and air gap.In addition,not only the non-uniform distribution and evolution slag layers between slab surface and copper plates are revealed,but also the liquid lubrication length,air gap formation position in different continuous casting processes are analyzed quantitatively.On this basis,to investigate the heat transfer characteristics of thermal conduction/radiation in liquid slag film,solid slag film and air gap,thermal resistances of slag layers/air gap is simulated and calculated along casting direction.Meanwhile,the proportion and contribution of conduction/radiation resistance are analyzed quantitatively.After then,the calculation model of computational model of the slab solidification and a numerical model of the slag layers/air gap thickness and thermal resistance is simplified from two ways: the formula of conductive and radiative resistance and the quantification relationship between both of slag layers,to discuss the simplification and realization methods of the on-line calculation.Finally,the effects of interfacial thermal resistance and property parameters of mold flux on the thickness and thermal resistance of slag layers/air gap are studied and analyzed,which includes thermal conductivity,absorptivity,refractive index and emissivity.The present works not only benefit to further understand the heat transfer mechanism of slag layers and simplify the calculation model,but also provide a model basis for complicated heat transfer and lay a theoretical foundation for lubrication behavior in the continuous casting mold.