Mechanism analysis and application practice of influencing carbon-oxygen product in combined blown converter
Clean steel production is an important direction for the development of contemporary steelmaking technol-ogy.The control of carbon and oxygen accumulation in molten steel has always been a particularly important indica-tor for converter steelmaking,and it is also a focus of attention for metallurgical researchers.In recent years,the car-bon and oxygen deposition w([C])×w([O])in converter steel has repeatedly hit new lows,and there are consider-able 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 composi-tion 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 fac-tors on carbon and oxygen accumulation in converter steel.The research results indicate that thermodynamic analy-sis of the carbon oxygen equilibrium limit in converter steel requires analysis of the carbon oxygen activity coeffi-cient,Gibbs free energy of carbon oxygen reaction,PCO/(PCO+PCO2)and PCO/(PCO+PAr/N2).When the decarboniza-tion rate is low,the theoretical situation PCO/(PCO+PAr/N2)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 0.004 0,and the bot-tom 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 oxy-gen accumulation in the steel liquid;Temperature is a secondary factor affecting the equilibrium value of carbon oxy-gen reaction in molten steel.Low temperature is beneficial for reducing the Gibbs free energy of carbon oxygen reac-tion.(a[C]×a[O])/PCO increases by 0.000 1 for every 50℃increase in temperature,and low temperature is benefi-cial for reducing PCO/(PCO + PCO2).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.
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