【作者】 游梅英；

【导师】 姜周华； 李阳；

【作者基本信息】 东北大学 ， 钢铁冶金， 2009， 硕士

【摘要】 近年来,国内外市场对不锈钢质量的要求在迅速提高,为满足用户的需求及提高自身产品的竞争力,提高不锈钢连铸坯的洁净度已成为各生产企业的一个重要课题,不锈钢冶炼过程中以夹杂物控制为中心的高洁净化也越来越引起人们的重视。以非金属夹杂物的热力学性质为理论依据控制其类型及形态是主要研究方向,并已取得了一定进展。根据热力学计算,认为炉渣-钢液-夹杂物三者之间达到完全平衡,而在实际冶炼过程中,由于传输和动力学条件的制约,不可能完全满足炉渣与钢液、钢液与夹杂物之间元素迁移所需的足够时间,则不可能达到上述三者的完全平衡,非金属夹杂物在钢液中的成分也就不能完全等同于炉渣的成分。结合前人对夹杂物的热力学研究成果,充分考虑到冶炼过程中的动力学条件,进行不锈钢液中非金属夹杂物成分的动力学计算具有重要的指导意义。本课题的目标是结合冶金热力学的平衡计算、运用冶金动力学的理论和研究方法,研究不锈钢液脱氧时夹杂物的动力学形成机制。本课题用相互作用系数法计算钢液组元的活度,用高阶亚正规溶液模型计算SiO₂-Al₂O₃-CaO-MgO渣系和MnO-SiO₂-Al₂O₃-CaO渣系组元的活度,并基于该溶液模型建立了钢液脱氧和氧化物夹杂控制的热力学模型,应用于不锈钢脱氧过程的渣-金平衡、钢液-氧化物夹杂平衡的计算,分析非金属夹杂物的动力学形成机制。本课题以计算机仿真为主要手段,运用冶金热力学和动力学的理论和研究方法,对不锈钢脱氧过程进行分析,建立不同脱氧条件下夹杂物形成的动力学计算模型,应用VB编制了该模型的计算软件,模型计算结果如下:（1）对430铁素体不锈钢铝脱氧时镁铝尖晶石的动力学形成机制研究表明:金属相传质是渣中MgO还原的速率控制环节。Mg在钢液边界层的扩散为钢液-夹杂物反应的速率控制环节。而对整个系统来说,Mg在渣-金界面钢液边界层的扩散是夹杂物生成过程的速率控制环节。（2）为了减少MgO·Al₂O₃尖晶石的形成,应提高炉渣中SiO₂的含量,降低炉渣碱度;（3）铁素体不锈钢用铝脱氧时,最终可形成MgO浓度达到饱和的镁铝尖晶石夹杂;（4）对316奥氏体不锈钢硅脱氧时硅酸盐类夹杂物的动力学形成机制的研究表明,钢液中Si氧化和渣中MnO还原的反应速率控制环节为渣相的传质,而渣中Al₂O₃和CaO还原的反应速率控制环节为金属相的传质。而对整个系统来说,渣-金反应是夹杂物（包括Al₂O₃、CaO）生成过程的速率控制环节;（5）奥氏体不锈钢用硅脱氧时,可认为最终夹杂物由CaO-SiO₂-Al₂O₃复合物组成,夹杂物内CaO含量可达45%,Al₂O₃为4%左右。更多还原

【Abstract】 In recent years, the demands for the quality of stainless steel increase rapidly both in domestic and international market. In order to meet the needs of users and enhance the competitiveness of their products, the cleanliness improvement of stainless steel billet has become an important topic in each production enterprises, and the high purification which focus at the inclusions control in the stainless steel smelting process has attracted peoples’ attention increasingly.The control of non-metallic inclusions’ type and shape based on the thermodynamic properties as the theoretical basis are the main research directions, and some progresses have been made. According to thermodynamic calculation, it holds that the three of slag-molten steel-inclusion achieve complete balance. But in the actual refining process, because of the restraint of transmission and dynamics conditions, it can’t fully meet the requirement of sufficient time for elements to migrate between slag and molten steel, molten steel and inclusion, and the above-mentioned three can’t achieve complete balance, as well as, the composition of non-metallic inclusions in molten steel can’t be exactly the same as the composition of slag. Combing with previous thermodynamics research results on the non-metallic inclusion, taking the dynamics conditions into account fully in the process of refining, the dynamics calculation of non-metallic inclusions in the stainless melts is of great guiding significance.The paper’s goal is to research the dynamics formation mechanism of non-metallic inclusions in stainless steel metis under different deoxidation conditions by combing the balance calculation of metallurgical thermodynamics and using the dynamics theory and research methods. The paper used the interaction coefficient method to calculate the activity of elements in molten steel and the high-level sub-regular solution model to calculate the activity of the elements in the SiO₂-Al₂O₃-CaO-MgO slag and MnO-SiO₂-Al₂O₃-CaO slag, based on which the paper established the thermodynamic model of the deoxidization of molten steel. The paper analyzed the dynamics formation mechanism of non-inclusions by using the thermodynamic model to calculate the balance between slag and metal, metal and oxides inclusion in the deoxidation process of stainless steel.The paper used computer simulation as the main measure and applied the theory and research methods of metallurgical thermodynamics and dynamics, analysed the deoxidation process of stainless steel, established the dynamics calculation model of the formation of non-metallic inclusions under different deoxidization conditions, and programmed the calculation software of the model by using VB Language Programming Design. The model calculation results are as follows:（1） From the study of dynamics formation mechanism of MgO·Al₂O₃ spinel in 430 ferritic stainless steel deoxidized by aluminum, it shows that mass transfer on the metal phase is the rate-determining step for the reduction of MgO in the slag. Mg diffusion in the boundary layer of molten steel is rate-determining step for the metal-inclusions reaction. And for the whole system, Mg diffusion in the boundary at the slag-metal interface is rate-determining step.（2） In order to reduce the formation of MgO·Al₂O₃ spinel, it should increase the content of SiO₂ in the slag and low the basicity of slag.（3） When ferritic stainless steel is deoxidized by aluminum, it could form the MgO·Al₂O₃ spinel inclusion which is saturated by MgO in the end.（4） From the study of dynamics formation mechanism of silicate-type inclusions in 316 austenite stainless steel deoxidized by silicon, it shows that mass transfer on the slag phase is the rate-determining step for the oxidization of silicon in the molten steel and the reduction of MnO in the slag, and mass transfer on the metal phase is the rate-determining step for the reduction of Al₂O₃ and CaO in the slag. And for the whole system, the slag-metal reaction is rate-determining step for the inclusions formation, including that of Al₂O₃ and CaO.（5） When the austenite stainless steel is deoxidized by silicon, it can be conferred that the final inclusion is composed of CaO-SiO₂-Al₂O₃ complex, and CaO concentration can reach 45%, Al₂O₃ concentration is about 4%.更多还原