Study On Effective Thermal Conductivity Of Solid Slag Film For Mold Flux In Continuous Casting

In the process of continuous casting,mold flux is the key adjunct in continuous casting process.Its functions of lubricating and controlling heat transfer play an extremely important role in ensuring the continuity of the continuous casting machine and improving the surface quality of the continuous casting slab.A liquid slag film is formed near the side of the shell and a solid slag film is formed near the side of the mold by the liquid slag flowing into the billet shell and the mold wall.The heat transfer characteristics of the solid slag film have an important effect on the surface quality of the billet.The thermal conductivity of solid slag film is an important parameter to study the heat transfer of slag film.There are two methods for measuring the thermal conductivity of mold flux,namely instantaneous hot wire method and laser pulse method.However,these two methods mainly measure heat conduction,while in practice,there are both heat conduction and radiation heat transfer in continuous casting.Therefore,the thermal conductivity could not be used to evaluate the total heat flux in the mold.Thus,it is necessary to use the effective thermal conductivity to calculate the total heat flux through the slag film.In order to study the effective thermal conductivity of the solid slag film,the solidification process of the mold flux was simulated by HF-200 heat flux simulator in laboratory.The comprehensive heat flux density of the slag film was collected and the solid slag film was obtained.The effective thermal conductivity of the mold flux was obtained by integrating the comprehensive heat flux density and the surface roughness of the solid slag film.On this basis,the effects of crystallinity and porosity on the effective thermal conductivity of solid slag film were studied.The main contents of this paper are as follows:(1)Effect of crystallinity on effective thermal conductivity of mold slag film1)With the increase of alkalinity R,the crystallization performance of mold fluxes is enhanced,the surface roughness of solid slag film increases gradually,resulting in the increase of interfacial thermal resistance,and the effective thermal conductivity is increased.2)With the increase of F~-content,the crystallization ability of slag film increases,the crystallinity of solid slag film increases,and the surface roughness increases,which leads to the increase of interfacial thermal resistance and the increase of effective thermal conductivity obtained by fitting.(2)Effect of porosity on effective thermal conductivity of solid slag film1)When sulfate is used as bubble clarifier,the porosity of solid slag film decreases with the increase of its content,and the effective thermal conductivity obtained by fitting becomes larger.2)With the decrease of carbonate content,the porosity of solid slag film decreases,and the effective thermal conductivity obtained by fitting increases gradually.