【作者】 张慧书；

【导师】 姜周华； 战东平；

【作者基本信息】 东北大学 ， 钢铁冶金， 2010， 博士

【摘要】 钢包精炼炉(Ladle Furnace,简称LF)是洁净钢精炼的重要手段之一,在国内外钢铁企业得到了广泛应用。随着洁净钢冶炼技术的发展,LF精炼过程升温速率低导致精炼时间长,以及容易使钢水增碳、增氮而不利于低碳、低氮钢精炼等缺点暴露越来越突出。这使得LF向高效率化(快速、高质量、高洁净度)方向发展的要求越来越迫切。近年来,通过优化LF供电和吹氩等操作制度,采用预熔渣、泡沫渣的造渣技术等对此起到了一定的改进作用。但是,到目前为止,LF的这些缺点仍没有得到较好解决。本文在广泛查阅国内外文献的基础上,对LF利用中空电极喷吹气体过程中的冶金行为进行了系统研究。应用等离子体局部平衡热力学和冶金热力学理论,建立了氩氢等离子体粒子数密度计算模型,分析计算了氩氢体系中的粒子数密度；研究了LF中空电极喷吹Ar-H2、Ar-CH4体系的脱碳、脱氮机理。在此基础上,在实验室100kg LF和某厂14tLF上开展了中空电极喷吹气体精炼试验,研究了喷吹Ar-H2、Ar-CH4、Ar-CO2、Ar-液化气和Ar-天然气对熔池内w[C]、w[N]和w[H]以及熔池温度、电极消耗的影响。并建立了基于BP人工神经网络的钢水温度预报模型和中空电极吹气过程的电极消耗模型。通过上述研究,得到的主要结论如下：(1)在LF中空电极喷吹Ar-H2或Ar-CH4构成的等离子体体系温度范围内,电弧等离子体中氢原子粒子数密度最大,氢原子与碳、氮反应生成物的分压远远大于氢分子反应生成物的分压。氢原子是脱碳、脱氮的主要反应物,CH4和NH3是氢原子脱碳、脱氮的主要反应产物。(2)LF中空电极喷吹Ar-H2、Ar-CH4或Ar-CO2混合气体均能降低钢液增碳量。直流供电时,喷吹Ar-H2、Ar-CH4、Ar-CO2混合气体时的最大增碳速率为实心石墨电极精炼时的66.7%、31.48%和74.2%。(3)LF中空电极喷吹Ar-H2、Ar-CH4、Ar-液化气混合气体均对钢液有脱氮作用,其最低脱氮速率分别为0.30×10-6/min、0.233×10-6/min和0.18×10-6/min。(4)LF中空石墨电极喷吹Ar-H2、Ar-CH4、Ar-CO2和Ar-液化气等气体时,熔池的最大升温速率均明显加快。直流供电时,它们的最大升温速率分别是实心电极精炼时最大升温速率的6.92倍、5.35倍、3.05倍和12.17倍。(5)建立了基于BP神经网络的中空电极喷吹气体的LF温度预报模型。预报结果表明,有30.8%的炉次误差绝对值在10K以内,有76.9%的炉次误差绝对值在20 K以内。误差绝对值的平均值为16.9 K,最小误差绝对值为3 K。(6)直流供电时,喷吹Ar-H2、Ar-CH4和Ar-CO2混合气体时电极消耗速率均小于实心电极精炼时的电极消耗速率,前者比后者至少分别减少2.1%、32.4%和34.7%。(7)中空电极喷吹混合气体过程的石墨电极消耗模型计算值与实验测定的实际值误差较小,有39.3%的数据误差绝对值小于0.05kg,误差绝对值的平均值为0.101 kg。(8)工业试验结果表明,LF采用中空电极喷吹Ar-天然气时,各炉次均出现了明显的脱碳过程,脱碳速率最高达到4×10-6/min,最高脱碳率达到13.25%。平均脱氮速率为1.12×10-6/min,平均脱氮率为18.57%。与实心电极精炼相比,平均升温速率提高26.18%。更多还原

【Abstract】 Ladle furnace (is called LF) is one of the important methods for clean steel refining, and it is used widely in the domestic and foreign iron and steel enterprise. With the development of the clean steel smelting technology, during the refining of low-carbon and/or low nitrogen clean steel in LF, the main disadvantages of it are carbon and nitrogen pickup, lower heating rate and longer refining time. This causes the request of the high efficiency LF (fast, high grade, high cleanness) to be getting more and more urgent. In recent years, some improvements regarding above problems have been made through optimization of the LF power supply and argon stirring system, application of the premelted slag, the foaming slag technology and so on. However, these problems of LF still have not been solved.Based on the wide investigation of the domestic and foreign literatures, the metallurgical behaviors during LF refining with gas injection through hollow electrode were systematically studied. Applying the plasma local equilibrium thermodynamics and metallurgical thermodynamics theories, a calculation model of argon-hydrogen plasma component concentration was established. Using this model, the particle densities of the argon-hydrogen system were calculated. The decarburization and denitrogenation mechanisms during Ar-H2 and Ar-CH4 injection in LF with hollow graphite electrode were studied.Based on above theoretical research, the gas injection refining experiments using hollow graphite electrode were carried out in 100 kg LF in laboratory and 14 t LF at one steel corporation. The effects of the injection of gases such as Ar-H2, Ar-CH4, Ar-CO2, Ar-liquid gas and Ar-natural gas on the carbon, nitrogen and hydrogen contents, temperature of the molten steel, consumption of the graphite electrode were investigated. A prediction model of molten steel temperature used the method of back-propagation (BP) artificial neural network and a consumption model of the hollow graphite electrode were developed. Through the above research, the main conclusions are obtained as follows:(1) In the temperature range of the plasma system consisting of Ar-H2 or Ar-CH4 injected through hollow electrode in LF, the particle density of the hydrogen atom in the electric arc plasma is the biggest. The partial pressures of the products reacted by hydrogen atom with carbon or nitrogen are far greater than that of the hydrogen molecular. The hydrogen atom is the main reactants of decarburization and denitrogenation. The methane and ammonia are the main reaction products of the hydrogen atom decarburization and denitrogenation.(2) The carbon pickup values are reduced during Ar-H2, Ar-CH4 or Ar-CO2 gas mixtures injection into LF with hollow graphite electrode. When direct-current power supply, the maximum carbon pickup ratios in the cases of the injection of Ar-H2, Ar-CH4 or Ar-CO2 are 66.7%,31.48% or 74.2% than that in the case of the solid graphite electrode respectively.(3) The denitrogenation of the molten steel takes place during Ar-H2, Ar-CH4 or Ar-liquid gas injection into LF with hollow graphite electrode. The lowest denitrogenation rates of them are 0.30×10-6/min, 0.233×10-6/min and 0.18×10-6/min, respectively.(4) All the maximum heating rates increased obviously during Ar-H2, Ar-CH4, Ar-CO2 and Ar-liquid gas injection into LF through hollow graphite electrode, which are 6.92,5.35,3.05 and 12.17 times than that of the solid graphite electrode respectively when direct-current power supply.(5) The temperature prediction model of the LF with hollow electrode injection gas was established based on BP neural network. Prediction results show that the error absolute values of 30.8% heats are less than 10 K, and 76.9% are less than 20 K. The everage error absolute value is 16.9 K. The least error absolute value is 3 K.(6) When direct-current power supply, the consumption ratios of the graphite electrode during the injection of Ar-H2, Ar-CH4 or Ar-CO2 are less than that of the solid graphite electrode, and it is decreased by 2.1%,32.4% and 34.7% respectively.(7) The errors between the prediction values calculated by the consumption model of the hollow graphite electrode and the actual value measured by the experiements are small. The error absolute values of 39.4% heats are smaller than 0.05 kg. The everage error absolute value is 0.101 kg.(8) Industrial test results show that, during Ar-liquid gas injection into LF with the hollow graphite electrode, there are decarburization and denitrogenation for all the heats. The highest decarburization rate is 4×10-6/min, the highest decarburization ratio achieves 13.25%. The average denitrogenation rate is 1.12×10-6/min, the average denitrogenation ratio is 18.57% Compared with solid electrode refining, the average heating rate enhances 26.18%.更多还原