顶底复吹条件下不锈钢VOD精炼过程的数学模拟——模型应用及结果

Mathematical Modeling of VOD Refining Process of Stainless Steel under Conditions of Combined Top and Bottom Blowing——Application of the Model and Results

应用提出的数学模型分析和处理了120t顶底复吹VOD炉内20炉409L型铁素体不锈钢的精炼。结果表明，该模型可较精确地估计整个精炼过程中钢液成分和温度随时间的变化。氧化精炼期钢中各元素间的竞争性氧化和相应的氧分配比，以及还原精炼期渣中各氧化物的竞争性还原和对应的供氧率，均可用反应的Gibbs自由能来表征和确定。对本工作409L型不锈钢的顶底复吹过程，脱碳的临界碳浓度（在该浓度后，脱碳变为由钢液内碳的传质控制）为（0．1190～0．1820）massUoo，与顶吹氧过程的临界碳浓度基本相合。由模型估计考察了各有关因素对精炼效果的影响和吹炼工艺的优化。该模型可为制定和优化顶底复吹条件下不锈钢VOD精炼工艺及过程的实时在线控制提供有用的信息和可靠的依据。

The mathematical model proposed in Part I of the present work was used to treat and analyze 20 heats of 409L-grade ferritic stainless steel refining in a 120 t combined top and bot- tom blowing VOD vessel. The results show that the changes in the composition and temperature of the liquid steel with the time during the whole process can be more precisely predicted by the model. The results indicated that the predicted values by the model are in good agreement with the determined data. Not only the competitive oxidation among the elements in the steel during the oxidative refining with the corresponding oxygen distribution ratios, but also the competieive reduction of the oxides in the slag during the argon stirring and reductive refining with their oxygen supply ratios, can all be characterized and determined using the Gibbs free energies of the reactions. The critical carbon concentration （after which the decarburization alters to be limited by the mass transfer of carbon in liquid steel） for the combined top and bottom blowing of 409L- grade steel in this work is in the range of 0. 119 to 0. 182 mass%, in agreement essentially with the critical carbon concentration of the the oxygen top blowing. The influences of the relative fac tors on the refining result and the optimization of blowing technology were examined from the model predictions. The model can offer useful information for determining and optimizing the technology of the VOD refining process of stainless steel, and for controlling the process in real time and on-line.