EMBr对超高速薄板坯连铸结晶器流动行为影响的大涡模拟

Large eddy simulation of the effect of EMBr on the flow behavior of thin slab continuous casting mold with ultra-high casting speed

薄板坯连铸连轧是推动中国钢铁工业高效化、绿色化发展的重要技术,超高速连铸是目前实现薄板坯连铸连轧高效化生产需要突破的关键核心技术。掌握超高速条件下结晶器内钢液流动特征并获得稳定流场分布是提升连铸拉速的重要前提。针对应用多孔浸入式水口的薄板坯连铸结晶器建立了完整的几何模型和结构化网格,在此基础上通过耦合求解大涡模拟(Large eddy simulation,LES)、流体体积法(Volume of fluid,VOF)和磁流体动力学模型(Magnetohydrodynamic,MHD)研究了水口结构、电磁制动结构和电磁制动强度对结晶器内流场分布的影响。采用工业插钉试验获取了实际生产过程中结晶器表面流速,并与对应工况下的数值模拟结果进行对比验证了数值模拟方法的可靠性。结果表明,拉速为8.0 m/min时,应用多孔水口会导致复杂的流场结构,具有射流多、冲击强和循环弱等异于传统双侧孔水口结晶器的特点,其中使用四孔水口和五孔水口时主流股冲击深度分别高达1.6 m和2.1 m;电磁制动能够有效控制结晶器流场,不同电磁制动结构的制动效果存在差异,其中能够覆盖多孔水口全部出口的结构C在降低冲击深度和提升流场稳定性方面表现更佳;磁场强度的增加对流场结构具有明显影响,流场结构变化转折点的磁场强度为300 mT,在该磁场强度下的流场不稳定和不对称性较为明显,故在生产过程中调整磁场强度时,应当避免磁场强度长时间处于这一范围内,有利于弯月面稳定和坯壳均匀生长。

Thin slab continuous casting and rolling is an important technology to promote the efficient and green de-velopment of China's iron and steel industry.Ultra high-speed continuous casting is the crucial technology that needs to be broken through to achieve efficient production of thin slab continuous casting and rolling.Understanding the flow characteristics of molten steel in the mold under ultra-high casting speed conditions and obtaining a stable flow field distribution are important prerequisites for increasing the casting speed.A complete geometry model and structured grid were established for the thin slab continuous casting mold equipped with multi-ports SEN.The effects of SEN structure,EMBr configuration,and EMBr intensity on the flow field distribution in the mold were studied by coupling the LES,VOF,and MHD models.The industrial nail dipping experiment was applied to obtain the surface velocity of the mold in actual production process,and the reliability of the numerical simulation method was verified by comparing the experimental results with simulation results under corresponding operating conditions.The results indicate that when the casting speed is 8.O m/min,the application of multi-ports SEN will lead to a complex flow field structure,which has characteristics different from those of a traditional mold equipped with dual-ports SEN,such as multiple jets,strong impact,and weak circulation.When applying a 4-ports SEN and a 5-ports SEN,the penetration depth of the major steel jetting stream is as high as 1.6 m and 2.1 m,respectively.EMBr can effectively control the flow field,and the braking effects of different EMBr types vary.Type C,which can cover all the outlets of the multi-ports SEN,performs better in reducing the penetration depth and improving the stability of the flow field.The increase of the EMBr intensity has a significant impact on the flow field structure.The turning point of EMBr intensity of the flow field structure change is 300 mT.The flow field under this EMBr intensity is unstable and asymmetric.Therefore,when adjusting the magnetic field intensity in the production process,it is advised to avoid being within this EMBr intensity range for a long time to ensure the stability of the meniscus and the uniform growth of the shell.