| Incoloy825 alloy is a Fe-Ni-Cr based corrosion resistant alloy,which has many excellent properties and can meet the requirements of various service environments.As strong reduce elements such as Al and Ti are adde to that alloy,In the process of producing 825 alloy by vertical continuous casting process,it is inevitable to react with the components in the mold flux,causing Al and Ti elements in the alloy to burn out,generating a large number of inclusions,deteriorating the performance of the mold flux,causing subcutaneous inclusions in the slab,cracks,mold "fish" and nozzle nodulation and many negative effects.In order to ensure the quality of slab,it is necessary to develop a suitable mold flux system for continuous casting,reduce the burning loss of Al and Ti elements in the alloy,and master the variation law and control mechanism of Al and Ti elements in the alloy.At present,most researches focus on continuous casting mold fluxes with low SiO2 content,and CaO-Al2O3-based mold fluxes are used for continuous casting production.However,due to the low SiO2 content and poor glassiness of mold fluxes,it is difficult to realize multi-furnace continuous casting.However,due to the low SiO2 content and poor glassiness of mold flux,it is difficult to realize multi-furnace continuous casting.Others add fluxes such as B2O3,TiO2,BaO,etc.to the slag,but the effect of inhibiting the burning loss of Al and Ti elements is still poor.In order to solve the above problems,the research and development of new slag system for continuous casting of high titanium steel is of great significance for improving the anterograde ability of continuous casting and the quality of slab.In this paper,firstly,the composition and content range of basic mold flux for continuous casting of high titanium alloy steel are determined by phase diagram.On this basis,adding Ce2O3,a new mold flux system to reduce the burning loss of Al and Ti elements was proposed.Based on the coexistence theory of molecular ions,the activity calculation model of the slag system was established,and the influence of components on the reactivity of mold flux was analyzed.In this paper,firstly,the composition and content range of basic mold flux for continuous casting of high titanium alloy steel are determined by phase diagram.On this basis,adding Ce2O3,a new mold flux system to reduce the burning loss of Al and Ti elements was proposed.Based on IMCT,the activity calculation model of the slag system was established,and the influence of components on the reactivity of mold flux was analyzed.The results show that the new mold flux is CaO-SiO2-Al2O3-based mold flux(w(CaO)/w(SiO2)=1.0,A12O3:15%),Na2O,CaF2,MgO are used as fluxes(Na2O:10%,CaF2:10%,MgO:5%),Adding proper amount of Ce2O3 can effectively inhibit the burning loss of Ti element.The order of influence of mold flux composition on the content of Al and Ti in the alloy is SiO2>Na2O>Al2O3>CaO>Ce2O3>CaF2>MgO.By calculating the influence of temperature on the equilibrium Al and Ti content of the alloy,it is found that the equilibrium Al and Ti content in the alloy decreases with the increase of temperature.Secondly,through the thermal simulation of slag-gold equilibrium,the content range of Ce2O3 was determined,and the kinetic model of slag-gold reaction was established based on the double film theory to explore the burning loss mechanism of Al and Ti elements.The results show that when the content of Ce2O3 is 15%,the inhibition effect on the burning loss of Ti element is the best.The limiting link of slag-gold reaction in slag-gold reaction is the mass transfer of SiO2 in liquid slag.When the mass transfer coefficient of SiO2 decreases,the time for slag-gold reaction to reach equilibrium prolongs,and the burning loss of Ti element in alloy decreases.The addition of SiO2 and Al2O3 in mold flux will affect the change of Ti content in alloy,but will not affect the reaction rate of slag gold.Finally,the physical and chemical properties of the new mold flux were tested to explore the effects of Ce2O3 addition on melting point,viscosity and crystal precipitation.The results show that with the increase of Ce2O3 content,the melting point,viscosity and turning temperature of mold flux increase.With the increase of Ce2O3 content,the crystallization rate increases.When the content of Ce2O3 is between 10%and 15%,its physical and chemical properties are better.Based on all the experimental results,the range of Ce2O3 content is determined to be between 10%and 15%. |
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