Study On Physical Properties And Microstructure Of CaO-SiO₂-MgO-Al₂O₃-FeO Bosh Slag In Blast Furnace

Blast furnace ironmaking is a major link in the iron and steel metallurgy production process,and the slag making system of the blast furnace directly affects the smooth running of the blast furnace and smelting efficiency.In the slag making process of the blast furnace,the primary slag starts to form with the thermal reduction of iron ore,and the primary slag converges into the coke layer to form the intermediate slag with a certain fluidity.The fluidity of the intermediate slag directly affects the liquid permeability and gas permeability of the coke layer of the blast furnace,and the ion migration behavior of the intermediate slag affects the slag coke reaction process.Therefore,the fluidity and conductivity of CaO-SiO₂-MgO-Al₂O₃-FeO intermediate slag system were studied in this thesis.The influence of basicity,FeO content and Al₂O₃content on the flowability and conductivity of the five component slag system was discussed.The liquid-solid composition and viscosity were calculated using the Fact Sage thermodynamic analysis software.The comparison with the experimental results was analyzed.The relationship between the micro network structure and physical properties of the five component slag system was discussed through infrared spectrum detection.The specific results are as follows:（1）When the basicity is 1.3 to 1.7,the intermediate slag with the basicity of 1.7has the highest stability temperature,and the viscosity presents a"V"pattern with the increase of basicity,that is,when the basicity is 1.5,the viscosity presents the minimum value;When FeO content increased from 9%to 21%,the stability temperature and viscosity of the intermediate slag decreased,but when FeO content was 15%,the viscosity increased slightly;The content of Al₂O₃increases from 5%to 15%,and the viscosity shows an increasing trend as a whole,but the viscosity at low temperature shows a sharp rise when the content of Al₂O₃is 5%.（2）The electrical conductivity of the intermediate slag also shows a"V"pattern with the increase of basicity（1.3,1.5 and 1.7）,that is,it decreases first and then increases;With the increase of FeO content（9%,15%and 21%）,the overall law of FeO decrease,but when the basicity is 1.3,the law of FeO effect is opposite;As the content of Al₂O₃（5%,10%and 15%）increases,it also decreases.At 1773 K,the intermediate slag with 9%FeO content,10%Al₂O₃content and 1.3 basicity has the maximum electrical conductivity of 2.55 S·cm^-1.（3）Comparing the measured results with the calculated results,the difference between their viscosity values is large.At the same time,when the basicity is 1.7 or the FeO content is 15%,the viscosity change law is also obviously different.From the calculation of liquid-solid composition,it can be seen that when the basicity is1.7,the intermediate slag is easy to precipitate solid phase,which may be a reason for the difference between the experimental results and the calculated results of viscosity.（4）According to the infrared spectrum analysis,the increase of FeO content will cause the characteristic wave band of the Si-O network to shift to a lower wave number,and the Si-O network structure will be depolymerized,while the increase of Al₂O₃content will cause the characteristic wave band of the Si-O network to shift to a higher wave number,and the Si-O network structure will converge,which is consistent with the viscosity change law.