| High aluminum steel has many good properties such as high strength,low alloy density,corrosion resistance,extraordinary ductility and high tension.This type of steel is widely used in aviation industry,automobile manufacturing,salt chemical industry and other fields.But the most serious problem in the continuous casting process of high aluminum steel is the reaction of the steel-slag interface.It will have a great impact on the composition and properties of steel and mold slag.Which leads to the surface quality problem of the billet and makes the continuous casting with multiple furnaces difficult.This article starts with the problem,according to the thermodynamic calculation,a low-reactivity CaO-Si O2-Al2O3based non-fluorine mold slag for continuous casting of high aluminum steel was designed,and the interfacial reaction of the steel slag was studied.At the same time,the effect of the components in the slag on the metallurgical properties of the mold slag is also analyzed.Firstly,based on the principle of"low melting tempeture",the initial design of each element content of the slag was carried out using the Phase Diagarm module.The melting temperature and viscosity of the designed mold flux were predicted by thermodynamic calculation and viscosity calculation model.The calculated melting temperature range is 1075.12～1174.84℃,and the viscosity range is 0.396 Pa·s～0.502Pa·s,it is proved that the designed mold slag meets the requirements of various physical and properties for continuous casting of high-alumina steel.19 groups of CaO-Si O2-Al2O3based mold slag,such as A1-E3 were initially designed.Secondly,Fact Sage was used to calculate the effect of each element content and reaction temperature on Gibbs free energy of the steel-slag interface reaction.Based on the two-film theory and simulation calculation of steel-slag reaction,Al mass transfer in steel-liquid zone is the limiting link of interfacial reaction of between steel and mold flux,and established the kinetics model of interfacial reaction between steel and mold flux.When the Al content in steel is 1.5%to 2.5%,the longer steel-slag interface reaction is in equilibrium with the increase of the content,and the calculated value of the model is not different from the experimental value.Using the established slag-steel reaction kinetic model,the relationship between the liquid slag consumption and the slag-steel reaction was studied.The consumption of liquid mold slag is 0.1kg/t,0.3 kg/t,0.5 kg/t,0.7 kg/t,and the other conditions are same,the time for Al2O3accumulation in the slag to reach equilibrium is 3100 s,2500 s,1800 s and 1600 s.The greater the consumption of liquid slag,the greater the mass transfer rate of the steel slag interface,and the shorter the time for the steel slag reaction to reach equilibrium.Finally,the influence of each element on melting,viscosity and crystallization characteristics of slag was analyzed by automatic tester slag melting point and melting speed,rotary viscometer and hot wire method.The influence of each content on the melting and rheological properties of mold slag was systematically analyzed.Six groups of mold slag with melting temperature below 1100℃and viscosity below0.45 Pa·s were selected to test the crystallization characteristics.The crystal characteristics of the six groups of mold slag are C4,B5,B4,A4,D2,E2 in order from weak to strong,which provides certain theoretical guidance for the development of fluorine-free liquid mold slag. |
