转炉炼钢底吹O_(2)-CO_(2)的熔池搅拌功及冶金效果

Stirring power and metallurgical effect of converter steelmaking with O2-CO_(2)bottom blowing

底吹气体是强化炼钢熔池搅拌的重要手段,气体介质的基础物性及其与炼钢熔池之间的反应特性直接影响熔池搅拌效果。为探究不同种类气体介质对熔池搅拌的影响,通过耦合搅拌功计算理论模型、转炉炼钢熔池脱碳规律和熔池升温规律,建立考虑碳氧反应的顶底复吹转炉熔池搅拌功计算模型,揭示底吹反应性气体(O_(2)、CO_(2))和底吹惰性气体(N2)熔池搅拌功随冶炼时间的变化规律。计算结果表明,底吹N2的搅拌功主要受熔池温度影响,随熔池温度的升高而小幅增大;而底吹O_(2)和CO_(2)的搅拌功与炉内脱碳速率密切相关,在冶炼的开始阶段和结束阶段,底吹O_(2)的搅拌功极低,在底吹O_(2)中混入CO_(2)可以改善该阶段的熔池搅拌,还有助于降低终点钢水的平衡氮含量。120 t转炉工业试验表明,相比于底吹O_(2)-N2/Ar,底吹O_(2)-CO_(2)可以获得更加优异的脱磷、控氧、脱氮效果,超低磷(磷质量分数不大于0.005%)钢水的炉次比例由4%提高至24%,平均碳氧积由0.0019降至0.0017,平均氮质量分数由0.0033%降低至0.0029%。结果可为转炉底吹O_(2)-CO_(2)新工艺的喷吹制度设计提供计算依据。

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 affect 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 decarburization 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(O_(2),CO_(2))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 increases slightly with the increase of the temperature.The stirring power of bottom blown O_(2)and CO_(2)is closely related to the decarburization rate in the furnace.At the beginning and the end of converter smelting,stirring power of bottom blown O_(2)is extremely low.Mixing CO_(2)in bottom blown O_(2)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 O_(2)-N2/Ar,bottom blowing O_(2)-CO_(2)can obtain more excellent dephosphorization,oxygen control 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 0.0019 to 0.0017,and the average mass fraction of nitrogen decreased from 0.0033%to 0.0029%.The results can provide a theoretical basis for the process design of bottom blowing O_(2)-CO_(2)in converters.