Deviation On Physical Chemical Properties Of Volitile Conponents In The Lead-containing Slag And Fluorine-containing Mould Flux

It is the slag composition and physicochemical properties that have important effect on smelting process guarantee,temperature control,interface reaction and inclusions absorption from metallurgical melts.In the high temperatures measure of the melting temperature and viscosity of the lead-containing slag and fluorine-containing flux,a large amount of volatile substances is going into air,which leads to the final measured slag properties inconsistent with the actual slag composition.That is to say,it is corresponding to a changed slag composition,not the initial set composition.It is quite general in the properties measure of volatile components containing slag that is unresolved so far.Therefore,it has great theoretical significance and practical application value to explore the cause of deviation on properties measure of volatile components containing slag,to determine the volatile mechanism,and accordingly to predict the deviation law between slag composition and its performance.In this paper,the research object is two kinds of volatile components containing slag?including lead slag,fluoride-containing mould flux?.Deviation rule on determination of slag properties?melting temperature and viscosity?are studied.The main causes of the deviation of the properties of slag measue are analysed.The kinetics model of high temperature volatilization of lead-containing slag and fluorine flux is established,and the law of high temperature volatilization is revealed.On the based of the experimental results,prediction model between the change of composition and physical chemical properties for the lead slag and fluorine-containing mould flux are established.The main research results obtained as follows:?1?The non-isothermal intrinsic kinetic model of lead-containing slag and fluorine-containing mould flux at high temperature was established by means of high temperature TG thermogravimetric analyzer.The study about the kinetics of lead slag showed that the volatilization of PbO at 700?¹450?is the main reason for the change of lead composition and the deviation of its performance.Volatilization of lead slag system in line with the most probable mechanism function g???=1-?1-??^1/3,volatile reaction mechanism for the three dimensional diffusion,the limiting part of the reaction is the diffusion of PbO vapor;The kinetics of fluorine-containing flux shows that the escape of fluoride in the form of NaF and SiF₄ in the temperature range of 800?¹450?is the main reason for the change of the fluorine-containing continuous casting and its performance deviation.The most probable mechanism function is g???=[-ln?1-??]^2?3,and the random nucleation of NaF and SiF₄ in the system becomes a limiting part of the process.?2?The slag composition and phase was analyzed for different lead content slag with FeO/SiO₂set at 1.6 to1.8,CaO/SiO₂set at 0.4 to 0.6,and fluorine-containing mould flux with?CaF₂+Na₂O?content set at 10%to 28.4%.Average weight loss rate of 20%lead slag is about 17.2%at 700?¹450?,which is consistent with the chemistry analysis result,an average of 16.34%Pb.The results showed that the phases of Pb₅Si₃O₁₁ and Pb₃Ca₂Si₃O₁₁were reduced to varying extents,while the Spinel,Olivine and Silico-Zinc mineral phases were relatively increased.It is proved that the volatilization of PbO leads to the decrease of low-melting lead-containing silicate phase,which is the reason of deviation of slag performance.The average weight loss rate of fluorine-containing mold flux at 800?¹500?is3.98%,which is consistent with the chemical analysis results of the average composition of?CaF₂+Na₂O?.With the continuous overflow of NaF and SiF₄,the main phase after high temperature volatilization is Cuspidine,Melilite and Wollastonite.The continuous volatilization of the volatile components in the flux leads to the reduction of Nepheline?NaAlSiO₄?in the system,and the precipitation of high melting point Spinel,Cuspidine,etc.They both lead to the measured melting temperature and viscosity a little high.?3?The results showed that there is a obviously deviation between the calculated and experimental values for the melting temperature and viscosity of tested samples,and the experimental value is higher than the theoretical calculation value.The deviation of the melting temperature(?T_t-a)is about 3?¹93.14?,and the viscosity deviation(??_t-a)is about0.009⁰.727Pa·s for different PbO,FeO/SiO₂ and CaO/SiO₂ slag components.And then,The deviation of the melting temperature(?T_t-a)is about 73.2?¹25.5?,and the viscosity deviation(??_t-a)is about-0.311⁰.344Pa·s for different CaF₂ components.The deviation of the melting temperature(?T_t-a)is about 73.2?²41.8?,and the viscosity deviation(??_t-a)is about-0.019⁰.244Pa·s for different Na₂O components.On the basis of the obtained gap rule,the corresponding relationship between the slag composition and the performance is established.It is feasible to obtain accurate slag performance parameter values.?4?Based on the experimental data,BP neural network prediction model was established for the volatilized of PbO and?Ca F₂+Na₂O?contents,which average relative error of the predicted results was 1.53%and 5.06%,respectively.The results showed that the average prediction relative error of lead slag is 0.16%and 1.67%respectively,and the fluorine-containing mould flux is 3.39%and 6.25%respectively.