Simulation Investigation On Heat Transfer And Lubrication Behaviors Of Liquid, Solid Mold Flux In Continuous Casting

As an important metallurgical materials, mold slag has key functions in continuous casting process, such as insulation adiabatic, inclusion absorbed, heat transfer improvement and lubrication promoted. In these functions, heat transfer improvement and lubrication promoted are the core of slag performance, which paly important role in high efficient continuous casting. The thermal and mechanism behaviors in mold channel are very complicated. Revealing and analyzing heat transfer and lubrication behavior of mold slag has important significance to improving the slab quality and keeping the casting process running smoothly. In this paper, basing on heat transfer theory, viscous fluid mechanics and basic principle of tribology, a numerical model of heat transfer and lubrication behaviors of mold flux and air gap, aiming at measuring data, is developed to investigated the existence states, heat transfer mechanism of mold slag layers, distribution of air gap, mold slag consumption and lubrication behaviors in mold.Firstly, basing on the measured thermocouples temperature and continuous casting process parameters and inverse problem, a heat transfer behavior model between slab and mold is developed, with the arc continuous caster of wide and heavy plate in a domestic plant. The model is validated by comparing measured data with calculated ones. In the further, with the model, non-uniform distribution in 2-D wide face of heat flux between mold and slab, slab surface temperature and mold hot face temperature profiles are investigated. And the effect of casting speed on heat transfer behavior is discussed deeply.Secondly, based on results calculated from heat transfer model, a slag layers and air gap calculation model is developed according to heat conservation principle to study the distribution of air gap solid slag layer and liquid layer in channel between mold and slab. In further, heat transfer mechanism of slag layers and air gap is explored and effects of heat conduction and heat radiation on heat transfer process is also investigated by comparing the thermal proportion of heat conduction and heat radiation in air gap and slag layers.Thirdly, based on mass balance, the slag consumption calculation model with comprehensive consideration of contributions of liquid slag layer, solid slag layer and oscillation mark. Though calculating the distribution character of liquid and solid slag layers, the non-uniformity of slag consumption in mold is studied, slag consumption behavior of liquid and solid slag layers in different transverse and longitudinal sections are investigated, and effects of parameters such as casting speed and slag solidification temperature on slag consumption are explored.Finally, based on hydromechanics, Navier-Stokes formula and Coulomb friction law, with comprehensive consideration of liquid lubrication, solid lubrication and mixed lubrication states, a model of slag friction/lubrication calculation model is developed. The lubrication states is defined by mold and slab surface temperature which obtained from inverse problem model. In this model, liquid and solid friction stress and total friction distribution are calculated and analyzed. Moreover, effects of parameters such as solid friction coefficient on slag friction are explored in the model, which could supply the reference of the exploration of complicated lubrication behavior in mold.