Stirring power and metallurgical effect of converter steelmaking with O2-CO2 bottom blowing
Bottom blowing gas is an important method to enhance the stirring performance of steelmaking furnace,and the basic physical properties of the gas medium and its reaction characteristics with the molten bath directly af-fect the stirring power.In order to explore the influence of different kinds of gas medium on molten bath stirring,a new calculation model of molten bath stirring power in top-bottom combined blowing converter considering carbon-oxygen reaction was established by coupling the theoretical model of stirring power calculation,the law of decarburi-zation and the law of molten bath heating in converter.The variation of molten bath stirring power with smelting time under the condition of bottom blowing reactive gas(O2,CO2)and inert gas(N2)was revealed.The calculation results show that the stirring power of bottom blown N2 varies positively with the molten bath temperature,and in-creases slightly with the increase of the temperature.The stirring power of bottom blown O2 and CO2 is closely re-lated to the decarburization rate in the furnace.At the beginning and the end of converter smelting,stirring power of bottom blown O2 is extremely low.Mixing CO2 in bottom blown O2 can improve the bath stirring,and reduce the equilibrium nitrogen content in end-point molten steel.The industrial test of 120 t converter shows that compared with bottom blowing O2-N2/Ar,bottom blowing O2-CO2 can obtain more excellent dephosphorization,oxygen con-trol and denitrification effects,the heat proportion of achieving ultra-low phosphorus(mass fraction of phosphorus is not more than 0.005％)steel increases from 4％to 24％,the average carbon-oxygen product decreases from 0.001 9 to 0.001 7,and the average mass fraction of nitrogen decreased from 0.003 3％to 0.002 9％.The results can provide a theoretical basis for the process design of bottom blowing O2-CO2 in converters.
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