Theoretical And Experimental Research On Slag Formation Path In The Smelting Process Of Chromium-Containing Semi-steel

The Hongge ore in the Panxi area of China is a kind of vanadium-titanium magnetite with high chromium content.So far,there is no efficient method to comprehensively utilize the ore.The present technological process to high-chromium type vanadium-titanium magnetite of Panzhihua Steel Co.,Ltd.during industrial production is as follows.First,obtaining the hot metal containing vanadium and chromium through blast furnace smelting,and second obtaining slag which contains vanadium?V?and chromium?Cr?,and semi-steel which mainly contains Cr in the converter.Finally,smelting the Cr-containing semi-steel to the qualified hot metal.However,during the smelting process of Cr-containing semi-steel,the rate of initial slag formation is slow,and it is difficult to slag.In addition,it is hard to obtain qualified hot metal product.Therefore,the purpose of this paper is to explore the path of slag formation for the smelting of Cr-containing semi-steel and to provide reference for the smelting of qualified hot metal from Cr-containing semi-steel.A regular ion solution model and a theoretical ion-molecule coexistence model for a semi-steel smelting slag system have been established.The activity,activity coefficient and mutual influence law of the components in the steel slag have been analyzed.At the same time,the equilibrium distribution of Cr and phosphorus?P?elements in slag-metal has been studied with experiments.Calculation results show that high basicity,high oxidation and low temperature are the conducive factors to the enrichment of V and P in slag;low basicity,high oxidation and low temperature are conducive to the enrichment of Cr in slag;high basicity,low oxidation,and low temperature can contribute to the enrichment of S in slag.The increase of Cr₂O₃ in slag will reduce the equilibrium distribution ratio of V,P,Cr,and S in the slag.Experimental studies show that the basicity of slag increases from 3 to 4.2;L_Crr and L_P increase first and then decrease;the effect of dechromization and dephosphorization from hot metal is the best when the basicity is 3.6;the concentration of FeO increases from 22.5%to32.5%in slag;L_Crr increases;L_P first increases and then decreases;when the FeO content is 27.5%,L_P reaches a maximum value of 100.5;with the increase of Cr₂O₃ content in the slag,L_P decreases,and L_Crr first decreases and then increases;L_Crr and L_P decrease with the increase of temperature.The melting characteristics of the chromium-containing semi-steel slag system CaO-SiO₂-FeO-MgO-MnO-V₂O₅-Cr₂O₃-P₂O₅ are studied.The increase of the Cr₂O₃content in the slag leads to a decrease in the liquid phase region of the slag and a shift toward the increase of the FeO content in the liquid phase region.The liquid phase content of the slag increases first and then decreases with the increase of Cr₂O₃ content in the slag.When the content of Cr₂O₃ in the slag is 3%,the FeO content is 25%,and the basicity is 3.3,the slag liquid content reaches to the maximum.Combining theoretical calculations with experimental studies,the basicity of slag should be controlled at 3.3 to 3.6,the FeO content at 25%to 27.5%,and the Cr₂O₃ at about 3%.According to the rapid increase of P,Cr distribution ratio,and the slow increase of the melting point of the slag,the slag formation path for chromium-containing semi-steel is:12wt%CaO-70wt%SiO₂-18wt%FeO?20wt%CaO-32wt%SiO₂-48wt%FeO?57wt%CaO-17wt%SiO₂-26wt%FeO.