影响复吹转炉钢液碳氧积的机理分析与应用实践

Mechanism analysis and application practice of influencing carbon-oxygen product in combined blown converter

洁净钢生产是当代炼钢技术发展的主要方向,钢液碳氧积w([C])×w([O])一直是转炉炼钢特别重要的指标,也是冶金科研工作者重点关注的方向。近年来复吹转炉钢液碳氧积屡创新低,业内对碳氧积实际控制水平、钢液检化验数据颇有异议。基于经典碳氧平衡公式,分析了钢液组分对碳氧反应的活度系数影响、乳化区“钢液-气相”反应界面气相组分的热力学影响、钢液温度对碳氧反应平衡的影响、高效底吹冶炼技术和冶炼终点后搅技术对碳氧积的影响,探讨了全要素影响复吹转炉钢液碳氧积的机理和应用实践。研究结果表明,热力学分析复吹转炉钢液碳氧积平衡极限时需分析碳氧活度系数、碳氧反应吉布斯自由能、PCO/(PCO+P_(CO_(2)))(碳氧反应CO占比)和PCO/(PCO+P_(Ar/N_(2)))(气相组分中CO实际氧分压)。脱碳速率较低时PCO/(PCO+P_(Ar/N_(2)))理论值可降至0.80甚至更低;转炉底吹效果是影响钢液碳氧积的主要因素,顶吹转炉、平炉熔池内钢液均因未得到充分混匀搅拌致使碳氧反应远未达到平衡,碳氧积可达0.004 0,而底吹有较好动力学条件使钢液碳氧积更加趋近平衡值,大流量高强度后搅工艺可使钢液碳氧积进一步降低;温度是影响钢液碳氧反应平衡值的次要因素,低温有利于降低碳氧反应吉布斯自由能,温度每增加50℃,(a_([C])×a_([O]))/P_(CO)(碳氧反应活度比)增加0.000 1,低温有利于降低PCO/(PCO+P_(CO_(2)))。控制钢液碳氧积的关键为转炉冶炼终点控制和提枪等待后搅拌工艺。

Clean steel production is an important direction for the development of contemporary steelmaking technology.The control of carbon and oxygen accumulation in molten steel has always been a particularly important indicator for converter steelmaking,and it is also a focus of attention for metallurgical researchers.In recent years,the carbon and oxygen deposition w([C])×w([O])in converter steel has repeatedly hit new lows,and there are considerable objections in the industry regarding the actual control level of carbon and oxygen deposition and the data of steel liquid inspection and testing.Based on the classic carbon oxygen balance formula,analyzing the influence of steel composition on the activity coefficient of carbon oxygen reaction,the thermodynamic influence of gas phase composition at the"steel gas phase"reaction interface in the emulsification zone,the influence of steel temperature on carbon oxygen reaction balance,the influence of efficient bottom blowing smelting technology and post stirring technology on carbon and oxygen accumulation,and exploring the mechanism and application practice of the influence of all factors on carbon and oxygen accumulation in converter steel.The research results indicate that thermodynamic analysis of the carbon oxygen equilibrium limit in converter steel requires analysis of the carbon oxygen activity coefficient,Gibbs free energy of carbon oxygen reaction,P_(CO)/(P_(CO)+P_(CO_(2)))and P_(CO)/(P_(CO)+P_(Ar/N_(2))).When the decarbonization rate is low,the theoretical situation P_(CO)/(P_(CO)+P_(Ar/N_(2)))can be reduced to 0.80 even more;The bottom blowing effect of the converter is the main factor affecting the carbon and oxygen accumulation in the steel liquid.The steel liquid in the top blowing converter and open-hearth furnace is not fully mixed and stirred,resulting in the carbon and oxygen reaction far from reaching equilibrium.The carbon and oxygen accumulation can reach 0.0040,and the bottom blowing has good kinetic conditions to make the carbon and oxygen accumulation in the steel liquid closer to the equilibrium value.The high flow rate and high intensity post stirring process can further reduce the carbon and oxygen accumulation in the steel liquid;Temperature is a secondary factor affecting the equilibrium value of carbon oxygen reaction in molten steel.Low temperature is beneficial for reducing the Gibbs free energy of carbon oxygen reaction.(a_([C])×a_([O]))/P_(CO) increases by 0.0001 for every 50℃increase in temperature,and low temperature is beneficial for reducing P_(CO)/(P_(CO)+P_(CO_(2))).The keys to controlling the carbon and oxygen accumulation in molten steel are the endpoint control of converter smelting and the stirring process after gun lifting and waiting.