Experimental Study On Steelmaking By Direct Alloying Of Composite Molybdenum Oxide Briquette

The direct alloying steelmaking with oxide ores is a brand new technology,where the alloying elements were added into the molten metal in the form of mineral oxides,which will be reduced to pure elements by reducting agent and become the alloying elements in steel.Compared with traditional steelmaking alloying process,the oxide ore direct alloying technology provides certain advantages such as the simplication of the whole steelmaking process,low energy consumption,low cost and contamination reduction and so on,which would be beneficial to the sustainable development of iron and steel industry.In this paper,the composite molybdenum oxide briquettess prepared with MoO3,reducing agent(C and SiC)and CaO was studied.The main contents of this study were as follows:thermogravimetric analysis on the volatilization of molybdenum oxide,the XRD phase composition analysis of self-reducing products of composite molybdenum oxide briquettes.And based on the previous study,the experimental study of direct alloying steelmaking of composite molybdenum oxide was carried out under laboratory conditions to determine the optimal smelting process parameters and the best Mo yield,in order to lay the theoretical foundation for the industrial application of molybdenum trioxide instead of ferro-molybdenum for the smelting of molybdenum steel.(1)Based on the basic thermodynamic data,the standard Gibbs free enery of reducing molybdenum oxides and calcium molybdate by reducing agent such as C,SiC,Mn,Si,Al and Fe deduced,and the corresponding thermodynamic diagram were drawn respectively.Considering the reduction performance and cost,SiC and C were selected as the reducing agent for the direct alloying of the composite molybdenum oxide briquettes.(2)The analysis of molybdenum oxide volatilization kinetics showed that the higher the volatilization area of molybdenum trioxide,the faster the rate of volatilization rate.When the temperature reached to 1600?,the pure molybdenum trioxide powder is almost volatilized,while the volatilization rate of briquettes molybdenum oxide is 76%.Therefore,the molybdenum oxide powder pressed into a briquettes can effectively inhibit the evaporation of molybdenum trioxide.(3)The thermogravimetric experimental results show that the volatilization rate of pure molybdenum trioxide is 85.68% when the temperature reaches to 1300 ?,and the addition of CaO or reductant(C or SiC),the volatilization rate of molybdenum oxide is about 20%,while with the addition of reducing agent and CaO,molybdenum oxide volatilization rate is only about 10%.(4)The self-reduction experiment of composite molybdenum briquettes was carried out in high-temperature box furnace.The phase composition of self-reducing product of composite molybdenum oxide was analyzed by XRD.The results showed that MoO2 existed in the product phase at low temperature,and the presence of Mo was found at high temperature.This indicates that the MoO3 was reduced by SiC or C step by step,under low temperature,the reducing agent(C or SiC)first reduces MoO3 to MoO2,and as the reaction temperature gradually increases,MoO2 is reduced to metal Mo.At the same time,with the increase of the proportion of Ca O,the proportion of CaMoO4 in the product was increased,which effectively inhibited the volatilization of MoO3.(5)In the medium-frequency induction furnace of 100 kg,the direct alloying process of converter was simulated and the direct alloying of molybdenum oxide was carried out.In the experiment,the briquettes are rapidly melted,and the molybdenum element yield increases with the extension of the alloying time,and finally reaches to a stable value.The results show that the yield of Mo is 97.48% when the alloying time is 8 min and the briquettes component molar ratio of MoO3: C: CaO is 1: 0.25: 0.5,and yield of Mo is 97.94% when the alloying time is 8 min and the molar ratio of MoO3: SiC: CaO = 1: 0.75: 0.75.