Physical and Numerical Simulation of Fluid Flow and Solidification at the Twin‐Roll Strip Casting Process

The fluid flow in a twin‐roll strip caster is investigated by physical and numerical simulation on a 1:1‐scale water model. A laser‐optical measurement technique (Laser Doppler Anemometry ‐ LDA) is used to validate the numerical results for the water flow. The numerical simulations are then transferred to the melt flow in the strip caster. The investigations are focused on different SEN concepts (submerged entry nozzle), a single‐nozzle system with two outlet ports and a double‐nozzle system with one outlet port each. The Influence of these concepts on the velocity, turbulence, and temperature distribution inside the liquid pool between the casting rolls and on the solidification and growth of the strip shells are investigated by numerical simulations (Computational Fluid Dynamics ‐ CFD). The non‐isothermal melt flow is calculated considering the solidification enthalpy as well as the behaviour of the solidifying melt. In addition to the numerical simulations of the melt flow inside the pool the temperature distribution in the cast strip is simulated. The SEN concept directly correlates with the temperature distribution Inside the strip. Furthermore, the surface temperature of the strip below the outlet of the roll gap is measured using a line‐scanner and is compared with the CFD simulation. In order to simulate the shape of the free surface in the liquid pool, CFD simulations of the water flow in the physical model are carried out using a Volume of Fluid model (VoF). This two‐phase model is able to reproduce free surface waves.     

Physical Simulation of Nozzle Electromagnetic Brake in Twin‐Roll Strip Casting

This paper presents the Nozzle Electromagnetic Brake (N‐EMBR) technology for twin‐roll strip continuous casting. N‐EMBR consists of imposing a stationary magnetic field coupled with direct current inside the nozzle to control the flow and suppress the free surface fluctuation. A low melting point metal model was set up to examine the magnetic field and additional current effect on the velocity near the meniscus and free surface fluctuation. The experimental results showed that the velocity near the meniscus, the amplitude and main frequency of the free surface fluctuation were all decreased with the N‐EMBR technology. It was found that the N‐EMBR technique can be applied successfully in twin‐roll strip casting to suppress the flow near the meniscus and free fluctuation.     

Effect of Fluid Transport Characteristics on the Level Fluctuation in the Pool of Twin‐Roll Strip Casting

The fluid transport characteristics and level fluctuations in the pool of twin‐roll strip casting are studied using a water model and mathematical simulations. The level profile depends on the transport characteristics of the flow in the pool. A full scale water modeling experiment has been conducted to address the relationship between the fluid flow and level fluctuation in the narrow strip pool. The residence time of fluid at the ports of nozzle and nip points of caster are measured to evaluate the fluid flow uniformity in the caster. The level fluctuations are measured with wave gauge and sensors. Mathematical modeling is also established to help anticipate flow patterns in the pool and residence time at the exits of nozzle and caster. The results show that a strong jet flow impinging on the both sides of delivery system is generated and free surface oscillations increase at the most lateral ports of delivery system. The fluids are uniformly distributed along the direction of roll width at the narrow pool zone. The flow patterns are complex near side dams' zone. Calculated results are in good agreement with residence time and average wave height measurements.     

双辊薄带连铸结晶辊辊形优化

 利用弹塑性热力耦合有限元法,对薄带连铸过程中,结晶辊温度场及其热变形进行了仿真研究,并利用试验数据对仿真结果进行验证,表明仿真结果具有较高精度。同时,根据仿真结果设定初始辊形,并利用有限元方法对辊形进行优化,使结晶辊在稳定浇注时保持良好辊形,使铸带厚度横向分布均匀。     

Influence of Feeding Mode on Flow and Temperature Field for Twin Roll Strip Casting Process

Thetwinrollstripcastingprocess ,whichcancastmoltensteelinto 1- 5mmstripdirectly ,isat tractingtheattentionofthesteelproducersallovertheworld .Ithasmanyadvantagesoverconventionalstripproducingtechnology ,suchasreducedenergyconsumption ,lowerinvestmentandhigherflexibili ty .Comparedwiththinslabcasting process ,thistechnologycansave 70 %ofproductionandinvest mentcosts[1] ,and producestripswith poorform ability ,suchastoolsteelandsiliconsteelstrips .　　Thoughtwinrollstripcastinghasbeendevelop ing…     

双辊连铸中工艺参数对薄带凝固晶粒的影响

以低碳钢为例对双辊连铸过程进行了微观模拟。研究了浇注温度、拉坯速度、冷却强度等工艺参数对带材结晶凝固晶粒度的影响,得出了不同工艺条件对铸轧带材晶粒度的影响规律以及最佳的模拟参数。通过实验结果与数值模拟结果的对比,验证了模拟结果的正确性,说明模拟结果对实际有一定的指导意义。     

侧封板传热对双辊板带铸轧凝固过程的影响

借助大型有限元分析软件ansys中的flotran CFD模块,对双辊板带铸轧的凝固过程进行了模拟分析,并对不同导热系数的侧封板对双辊板带铸轧凝固过程的影响进行了对比分析。此模拟结果可以为控制铸轧过程提供有效的参考。     

单辊法薄带连铸铸口包中钢液流动的数学模拟

建立了单辊法薄带连铸铸口包内钢液流动的数学模型 ,通过模拟计算 ,分析了不同结构的铸口包内钢液流动状态的变化     

单辊法薄带连铸中钢液流动的数值模拟

建立了单辊法薄带连铸（厚度＜２ｍｍ）铸口包内钢液流动的数学模型。通过模拟计算，分析了尺寸等因素对钢液流动状态的影响。研究结果表明，隔墙高度是影响钢液流场分布及成带质量的关键因素。     

双辊铸轧工艺温度场和流场耦合的数值模拟

 双辊铸轧过程中熔池内金属的流动状态及温度分布直接影响着铸轧过程的稳定性与铸带产品的质量。针对实验室双辊铸轧试验的特点,采用三维有限元法模拟了双辊铸轧过程的热流耦合问题,利用热平衡计算、铸轧实验和模拟相结合的反向方法分段建立了凝固过程中凝壳与铸辊之间热传导系数与铸轧速度、熔池位置之间的关系模型,并分析不同工艺条件下熔池内凝固变化的情况。     

双辊铸轧薄带钢温度场的有限元分析

针对实验室现有的实验设备条件,建立了双辊铸轧薄带钢过程的有限元数学模型,通过程序开发对熔池内的温度场进行了模拟;给出了各工艺参数对凝固终点位置及铸带表面温度的影响规律,为铸轧过程的分析和控制提供了理论依据.     

Twin Roll Casting of Steel Strip ‐ Experiments and Model Considerations on Strip Spottiness

Thin strip casting of steel through a twin‐roll caster demands the production of a perfectly homogeneous strip. This requirement is often not fulfilled due to non‐uniform heat contact between the solidifying strip and the rolls in the pool, which leads to temperature inhomogeneities visible at the strip behind the rolls (spottiness). The effect of spottiness is described from experimental observations in terms of contrast between dark and hot spots and of the mean diameter of the hot spots. The contrast is found to depend on roll material, surface roughness and roll velocity. A general dependence on the temperature difference between melt and rolls is observed. Calculations of heat transfer in the liquid and solid pool explain the hot‐dark‐temperature differences. The spottiness visible on the strip after leaving the rolls is initiated in the liquid pool, but it is enlarged by rolling contact differences in the solid pool. A model consideration based on thermally caused bending of the solidified material layers leads to a good coincidence with experimental data of the heat transfer coefficient at hot spots.     

工艺因素对铝双辊铸轧凝固过程的影响

利用铝双辊铸轧过程传热数学模型,系统分析了辊套材料、浇注温度等工艺因素对铝双辊铸轧过程凝固速率的影响及进一步提高铸轧机生产能力的途径,建立了钢和铜合金2种辊套材料的凝固壳厚度随时间变化的计算公式。     

双辊薄带连铸电磁侧封磁场的计算与分析

电磁侧封是双辊薄带连铸工艺中新兴的侧封技术其关键是电磁装置的设计,以在适熔池侧部获得足够大而且分布合理的电磁场.本文利用2D模型计算了电磁侧封装置产生的磁场,分析了电流、线圈、铁芯、辊环、气隙对磁场的影响规律.结果表明:影响磁场的因素按影响程度从大到小排列依次为:辊环磁导率、线圈匝数、磁头间距(气隙宽度)、电流密度、磁头宽度.除磁头间距外,各因素对磁场的影响基本呈线性.因此辊环的设计、线圈匝数与电流是增大侧封磁场的主要途径.     

反向凝固过程中铸带厚度及晶粒度的预测

基于人工神经网络建立了反向凝固过程中的性能预测模型,实现了对铸带厚度和新相层晶粒度的全面预测;探讨了凝固过程中的主要工艺参数对上述性能的综合影响,为反向凝固性能的综合预测提供了简便的新手段.研究表明,新生相晶粒度随钢水过热度、母带厚度、浸入时间变化对其影响不显著,而钢水过热度、母带厚度、浸入时间变化对铸带厚度的影响较大.该模型的预测结果与实测的结果较为接近.     

世界薄带连铸技术的最新进展

阐述了钢的薄带连铸技术的发展现状,重点介绍了美国纽柯公司Castrip和宝钢薄带工业试验的最新进展,总结了双辊薄带连铸技术的工艺特点、存在的问题及其关键技术.