【作者】 张莹；

【导师】 张立峰；

【作者基本信息】 北京科技大学 ， 钢铁冶金， 2019， 博士

【摘要】 本研究以耦合反应模型为基础,考虑了钢液与渣相之间的反应、钢液与夹杂物之间的反应、耐火材料与渣相的相互作用、耐火材料与钢液的相互作用、合金与钢液中溶解氧之间的反应、空气对钢液的二次氧化以及夹杂物的上浮去除对体系成分的影响,建立了“钢液-渣相-夹杂物-耐火材料-合金-空气”六相多元系动力学模型。同时,利用Fluent计算流体力学软件对钢包底吹氩过程进行了数值模拟,研究了解钢包底吹氩过程中钢包内钢液的湍流特性,并将钢包流场与多元反应动力学模型相结合,优化了动力学模型中的计算参数。钢液成分、精炼渣成分和夹杂物成分随时间变化的实测值和预测值吻合较好,这表明本研究开发的动力学模型可以用于预测LF精炼过程中钢、渣和夹杂物成分的变化。本研究利用六相多元系动力学模型进一步讨论了不同的精炼渣成分对夹杂物成分的影响、吹氩流量对钢液二次氧化的影响、夹杂物尺寸对其上浮去除率的影响及卷渣类夹杂物随着钢液中的存在时间而发生的成分变化。计算表明,当渣碱度增加或渣中Si02含量降低时,夹杂物中A1203的含量增加;精炼过程中吹氩流量的增加会导致钢液中T.O.含量增加。随着夹杂物尺寸的增加,夹杂物的上浮去除率也随之增加。对于卷渣类夹杂物,随着夹杂物尺寸的增加,夹杂物中的A1203和SiO2含量变化加快,而夹杂物中MgO和CaO的含量变化先增加后降低。本研究还建立了 MgO质耐火材料与钢液之间的相互作用模型,计算了MgO质耐火材料与钢液之间发生反应对钢液成分的影响。在本章的计算条件下,可以得到耐火材料与钢液相互作用时钢液中Mg元素的传质系数为kf_Mg=(5.6-4.7×e-0.0966ε)×10-4。模型的计算结果与实验结果吻合良好。研究发现,当钢液中[Al]s含量高于临界值时,MgO耐火材料的溶解机理为MgO耐火材料与钢液之间的化学反应;而当钢液中的酸溶铝[Al]s含量低于临界值时,MgO耐火材料的溶解机理为自身的分解反应。更多还原

【Abstract】 A steel-slag-inclusion-refractory-alloy-air multiphase model was developed to calculate the compositional changes of steel,slag and inclusions during the refining process.Reactions between the molten steel and the slag,reactions between the molten steel and inclusions,reactions between the refractory and the molten steel,reactions between the refractory and the slag,the alloy dissolution,the removal of inclusions by floating are all considered in the multiphase model.The influence of different sizes of inclusions on the compositional changes of steel,slag and inclusions were considered in the present study.The mass transfer coefficients are influenced by the average speed of the molten steel,the speed of the molten steel near the side wall and the plume fraction,which are obtained by mathematical simulation.The calculated result of the composition evolution of steel,slag and inclusion is in consistent with the experimental result.Meanwhile,the influence of different slag compositions on inclusion compositions was also calculated using the present model.It is indicated that Al2O3 in inclusions increased with the increasing slag basicity and the decreasing SiO2 content in slag.T.O.in the molten steel could be largely influenced by the gas flow rate and the inclusion diameter.The calculation results also showed that as the diameter of incluion originated from slag entrapment increases,the rate of content change of Al2O3 and SiO2 in inclusions first increases then decreases.The relationship between the mass transfer coefficient and the stirring energy dissipation in the molten steel was obtained by the kinetic model between the MgO refractory and the molten steel.The calculation result showed that the mass transfer coefficient of Mg in the molten steel was kref_Mg=(5.6-4.7×e-0 0966ε)×10-4.According to the calculation,the refractory dissolution is mainly caused by the reaction among[Al],[O]and refractory when the dissolved aluminum is higher than the critical value.And the decomposing of MgO refractory occurred when the Al content in steel is lower than the critical aluminum content.更多还原