碳酸盐诱发微小相去除夹杂物的行为研究

The removal of 5~50 μm submicroscopic inclusions effectively in the molten steel in secondary refining process is one of the key measures in clean steel production process. Our preliminary work showed that the molten steel was purified with fine bubbles and droplets induced by explosive reaction of carbonate. The project intends to adopt the means, which the purification function of molten steel is reached by carbonate divided to form the discrete phase in the collision and aggregation with inclusions and to promote on inclusion exclusion, to achieve the function of deoxidation, desulfurization and modifying non-metallic inclusions. In order to achieve the function of removal of submicroscopic inclusions and calcium treatment simultaneously and efficiently, the study includes three aspects mainly.Firstly, the cleanliness of liquid steel can be improved after wire feeding which carbonate is cored in. The total oxygen content and the number of inclusions are reduced more than 50% after the depuration process. Secondly,the aggregation phenomena of small bubbles, droplets and inclusions is described by Smoluchowski equation which the new source term factors are added into such as the formation of new nuclear inclusions, infiltration, surface tension, particle deformation. The dynamics model of aggregation and delivery among above three phase is established by application of discrete phase model and discrete element model. Finally, the action of desulfurization and non-metallic inclusions modification treatment by the decomposition from carbonate is analyzed to influence the casting process. Ultimately to achieve the purpose of removing microscopic inclusions and calcium treatment functions synchronously and efficiently.

在钢水的二次精炼过程中有效去除5~50μm的亚显微夹杂物是得到纯净钢的关键技术措施之一。建立在我们前期工作观察到的碳酸盐诱发微小气泡和液滴离散相净化钢水现象的基础上，本项目拟采用碳酸盐分裂形成的离散相与夹杂物碰撞聚合，促进夹杂物上浮排除，使钢水得到净化，完成脱氧、脱硫和使非金属夹杂变性的功能。研究包括制备包芯线和喂丝技术，建立小气泡、小液滴和夹杂物三者聚合长大的数学模型，以及碳酸盐使非金属夹杂变性三部分。碳酸盐包芯线喂入钢液可提高洁净度，净化后全氧含量和夹杂物数量比净化前降低50%以上。将夹杂物新核的形成、浸润性、表面张力、颗粒形变等因素作为新的源项，加入斯氏方程描述聚合现象，应用离散相模型和离散单元模型建立小气泡、小液滴和夹杂物聚合和传递等的动力学模型。分析碳酸盐形成微小相脱硫和使非金属夹杂变性的作用，以及变性产物对浇注过程的影响。最终实现去除显微夹杂物和钙处理功能的同步高效完成。

钢中的夹杂物直接影响钢铁产品的性能，生产过程中必须尽可能多地去除夹杂物。在钢水的二次精炼过程中有效去除5-50 μm 的夹杂物是得到纯净钢的关键技术措施之一。本研究提出综合吹氩和渣洗的优点，在钢液内加入同时诱发小气泡和小液滴离散相的碳酸盐，快速完成小气泡、小液滴和固态夹杂物的碰撞聚合长大，在较短的精炼时间内促进大量的亚显微夹杂物得到有效去除。数学模拟的手段是一种经济、有效地研究钢中夹杂物的手段。本研究通过整合流体动力学、热力学、颗粒聚合长大等理论和模型，用数值模拟方法解析了微小相和夹杂物传递与聚合的机制。主要研究内容及成果包括：（1）阐明了不同颗粒情况下的多种碰撞聚合长大行为的机理；（2）基于颗粒质量守恒模型，加入颗粒聚并条件，将不同颗粒间碰撞长大和去除过程与钢液流动耦合起来计算；（3）基于颗粒的数量守恒方程，提出了颗粒聚合通用动力学模型的改进形式，结合蒙特卡洛方法，分析了微小相去除夹杂物的结果；（4）描述了气泡-液滴-固粒的碰撞聚合长大行为，定量分析了微小相去除夹杂物的效率，采用水模型实验和热态实验的方法进行了验证；（5）比较分析了碳酸钙和碳酸锂对夹杂的变性效果，选用碳酸钙更适合对钢中夹杂物的去除和变性。最终的目标是实现用低成本的碳酸盐处理替代传统的钙处理方法，优化精炼工艺操作，从钢水去除更多的夹杂物，获得高洁净钢。通过本研究提出的建模方法以及新的控制夹杂物行为的理论，将会对洁净钢生产的相关学科发展做出重要贡献。