漩流中间包的夹杂物模拟试验研究

根据相似原理,模拟漩流中间包及漩流室内钢液的流动,研究不同漩流室直径、高度对夹杂物在漩流室内向心聚集上浮的影响,验证漩流室对夹杂物的去除效果。结果表明,漩流室的引入有利于夹杂物的上浮去除,夹杂物的上浮率平均由原来的92．35％提高到97％以上。     

漩流中间包流场的数值模拟

采用CFD软件Fluent对漩流中间包内的流场进行了数值模拟,分析了漩流中间包内的流场特征,以及漩流室的加入,中间包内的流动形态.模拟结果表明,由于漩流室的加入使湍动能耗散主要集中在漩流室内部,有利于夹杂物的聚合长大;漩流室的加入可改善钢液的流动状态,利于夹杂物的上浮.由于入口位置的非对称布置,造成了漩流中间包内的流场在入口区呈明显的非对称分布,这些结果为进一步优化漩流中间包内漩流室的位置和中间包挡墙参数提供了理论依据.     

漩流中间包漩流室内流动状态的研究

分别通过以相似原理为基础,考虑弗劳德数和雷诺数相等,对漩流中间包漩流室内湍流状况的水模型实验研究,以商业软件包为基础,对建立在正交网格上的漩流室内流动进行的以k-ε双方程模型为湍流模型的数值模拟研究,得到了漩流室内的流动状态和旋转速度的分布规律,并系统地研究了漩流室直径、漩流室高度及注人流量对漩流室内的旋转速度的影响。用因次分析的方法分析了水模型和实际中间包内旋转速度之间的相似关系,得到了描述相似规律的准数Rt。为针对不同结构中间包的漩流室优化设计和开发漩流中间包技术提供了理论基础。     

PIV测试技术在漩流中间包流场研究中的应用

粒子成像测速仪（Particle Image Velocimetry,简称PIV）是流场研究中的先进测试设备,在反应器内的流场研究中有广泛的应用．本文针对漩流中间包漩流室内的流场进行了测定,得到可靠的流场分布数据,为分析漩流中间包分离夹杂物效果和进一步的数值模拟验证提供依据．结果表明,漩流中间包漩流室内流场复杂,漩流室内液体旋转现象明显．     

Al2O3夹杂物在钢-渣界面处的运动特性及去除率

通过理论计算和分析,研究了夹杂物颗粒在钢-渣界面处夹杂物去除层内的运动特性及去除率。结果表明:在夹杂物去除层内,Al2O3夹杂物颗粒的布朗扩散上浮临界尺寸为1.33μm,直径小于临界尺寸的夹杂物颗粒很难上浮去除;布朗碰撞的优势区域主要是直径为2.5μm以下的夹杂物颗粒之间以及直径为2.5～5μm夹杂物颗粒与0.5μm以下的微小颗粒之间的碰撞;直径为20～150μm的夹杂物颗粒在钢-渣界面去除层中9min内很容易完全上浮去除,而直径小于10μm的夹杂物颗粒去除率很低且升高缓慢,是提高钢液洁净度的主要控制对象。     

板坯连铸中间包气幕挡墙夹杂物去除的研究

分析了中间包不加气幕挡墙和加气幕挡墙吹氩时夹杂物上浮速度与气泡直径、夹杂物直径和密度的关系。气泡尺寸对夹杂物的上浮速度影响比较明显,夹杂物的密度对上浮速度的影响不大。进行了中间包气幕挡墙的工业试验,试验表明:中间包底吹气对钢液中小夹杂物的去除作用不明显,而对大型的夹杂物去除效果显著。     

板坯连铸中间包内夹杂物去除的数值模拟

以某厂50tT型2流中间包为研究对象,利用大型商业软件ANSYS CFX10.0建立了三维有限体积模型,采用多相流模型对中间包内钢液的流动特性、温度分布与夹杂物去除规律进行了数值模拟,重点研究了不同堰-坝组合方式、湍流抑制器形状、拉速、夹杂物粒径等工艺参数对中间包内钢水平均停留时间、夹杂物上浮率的影响。结果表明:湍流抑制器对夹杂物的上浮去除影响不大;随着夹杂物粒径的增大,夹杂物的上浮率迅速增大;20μm以下的夹杂物则很难在中间包内上浮去除;随着拉速的增大,夹杂物的上浮率是不断减小的;采用堰A=300cm、坝B=400cm、方形瓦楞湍流抑制器、过滤器组合式控流装置时夹杂物的上浮去除效果最好。     

中间包气幕挡墙去除夹杂物的数值模拟

气幕挡墙技术是改善钢液洁净度的重要方法,吹入的气泡不仅可以改善中间包流场,还可以黏附去除夹杂物,大大提高夹杂物的去除率。采用Euler-Lagrange-Lagrange方法来研究钢液、气泡和夹杂物三相交互作用行为,该模型考虑了钢液与气泡、钢液与夹杂物、气泡与夹杂物之间的相互作用。在正常连铸条件下,研究了气泡黏附与吹气量对不同粒径夹杂物去除的影响。模拟结果表明,考虑气泡黏附的夹杂物去除率比不考虑黏附去除提高了19.12%～28.94%,气泡黏附夹杂物是去除夹杂物的重要方式之一,在气幕挡墙的研究中不可忽略。在本研究的吹气范围内,夹杂物的上浮去除率和黏附去除率都随着吹气量的增加而增大。与传统的挡墙挡坝中间包相比,使用气幕挡墙取代传统挡坝更有利于夹杂物的去除。     

应用格子 Boltzmann方法直接数值模拟研究钢中夹杂物上浮及碰撞行为

采用格子Boltzmann方法对钢液中夹杂物上浮及上浮过程中的碰撞行为进行直接数值模拟研究.结果表明,不同尺寸夹杂物颗粒上浮速度的模拟结果和理论值基本一致,表明本文所采用的数值算法能够精确有效地对钢液中固相夹杂物颗粒运动行为进行研究.当钢液中直径为80μm的夹杂物颗粒位于直径为40μm的下方并一起上浮时,直径为80μm的夹杂物颗粒会逐渐追赶上直径为40μm的夹杂物颗粒并发生碰撞形成大尺寸凝聚体,凝聚体的上浮速度显著大于二者单独上浮时的上浮速度.对于直径为40μm的夹杂物来说,形成凝聚体后的上浮速度比单独上浮时的上浮速度增加300%.实际炼钢过程中,采取必要的措施增加夹杂物颗粒之间上浮过程中的碰撞凝聚,对于提高夹杂物颗粒的上浮速度,尤其是小尺寸夹杂上浮去除速度,提高钢液的洁净度具有重要的意义.      

钢中不同形状夹杂物在超重力场中上浮模拟研究

超重力可促使夹杂物快速上浮,缩短其在钢液中的上浮时间.为研究夹杂物形状对其在钢液中的上浮行为的影响,本文使用流固耦合方法跟踪计算流体与固体界面状态,在二维纵切面中构建了三种具有不同形态比的夹杂物并在超重力场中进行上浮行为模拟研究.结果表明,夹杂物的上浮速度与自身形状和上浮角度有关,形态比越趋近1或上浮角度越接近垂直,上浮速度越快.在重力系数G=1000的超重力场中,长度为1μm的夹杂物未发生旋转.长度为10、20μm的夹杂物会自初始角度（45°、90°）旋转至水平后稳定上浮.超重力系数会影响夹杂物的旋转状态,随着重力系数的降低,夹杂物的旋转速度逐渐降低.当G=50时,长度为20μm的夹杂物（初始角度90°）未能完全旋转;同时也证明相较于垂直角度,初始即倾斜的夹杂物更易发生旋转.最后,指出通过模型预估离心处理时间应以水平状态下夹杂物的上浮速度为准,并基于该结论给出了夹杂物上浮去除的大致时间.     

Water Modeling of Swirling Flow Tundish for Steel Continuous Casting

A conventional turbulence inhibitor is compared with a swirling chamber from the points of view of fluid flow and removal rate of inclusion in the tundish. Comparing the RTD curves, inclusion removals, and the stream-lines in water model experiments, it can be found that the tundish equipped with a swirling chamber has a great effect on improving the flow field, and the floatation rate of inclusion is higher than the tundish with a turbulence inhibitor. Because of the introduction of the swirling chamber, the flow field and inclusion removal in a two-strand swirling flow tundish are asymmetrical. Rotating the inlet direction of swirling chamber 60 degree is a good strategy to improve the asymmetrical flow field.     

Water Modeling of a Swirling Flow Tundish for Steel Continuous Casting

 A conventional turbulence inhibitor is compared with a swirling chamber from the points of view of fluid flow and removal rate of inclusion in the tundish. Comparing the RTD curves, inclusion removals, and the streamlines in water model experiments, it can be found that the tundish equipped with a swirling chamber has a great effect on improving the flow field, and the floatation rate of inclusion is higher than the tundish with a turbulence inhibitor. Because of the introduction of the swirling chamber, the flow field and inclusion removal in a two-strand swirling flow tundish is asymmetrical. Rotating the inlet direction of swirling chamber 60 degree is a good strategy to improve the asymmetrical flow field.     

Aggregation Kinetics of Inclusions in Swirling Flow Tundish for Continuous Casting

 The mechanism of inclusion aggregation in liquid steel in swirling flow tundish is analyzed by applying the theory of flocculation which was developed in the field of colloid engineering. The gas bridge forces due to the micro bubbles on hydrophobic inclusion surfaces were considered responsible for the inclusion collision and agglomeration, which can avoid the aggregation to breakup. The quantity of micro bubbles on hydrophobic inclusion particle is more than that on hydrophilic one. The trend of forming gas bridges between micro bubbles on particles is strong in the course of collision. The liquid film on hydrophobic particles is easy to break during collision process. Hydrophobic particles are liable to aggregate in collision. According to the analysis of forces on a non-metallic inclusion particle in swirling chamber, the chance of inclusion collision and aggregation can be improved by the centripetal force. Hydrophobic particles in water are liable to aggregate in collision. Hydrophilic particles in water are dispersed although collision happens. The wettabiliy can be changed by changing solid-liquid interface tension. The non-metallic inclusion removal in swirling flow tundish is studied. It shows that, under certain turbulent conditions, the particle concentration and the wettability between particles and liquid steel are the main factors to induce collision and aggregation.     

Numerical and Physical Simulation of Flow Patterns in a Swirling Flow Tundish

Swirling flow tundish is a new kind of tundish which has shown good effects on flotation of inclusion and reduction of inclusion content. In this paper, studies have been carried out on the flow fields in a one‐strand slab tundish. A full scale model of the flow patterns in the water model tundish was developed using a self‐developed code. RTD curves under different experimental conditions were obtained from both physical and numerical simulations. The effects of the swirling flow chamber geometry and the flowrate on flow patters in the tundish were discussed and compared with results from the numerical simulation. Validation of the self‐developed codes was achieved by comparing the physical and numerical results of the RTD curves and the mean rotational velocities in swirling flow tundish. As a result, significant rotational flow in the swirling flow chamber and asymmetrical flow pattern in the whole tundish were confirmed and the effects of these parameters on dead zone and mean residence time were also obtained. Further and more comprehensive studies are needed to optimize the design and application of such tundishes.     

自旋式浸入水口对LZ50车轴钢Φ690mm连铸坯质量的影响

研究了自旋式6孔浸入水口对铁路车轴钢LZ50 Φ690mm连铸坯包括低倍组织、夹杂物、碳偏析等质量的影响.结果表明:与传统5孔水口相比,自旋式浸入水口连铸坯中心最大中心缩孔由22.7 mm降低到12.8 mm,平均缩孔尺寸从7.8 mm减小到5.5 mm,大于15 mm的缩孔消失;疏松程度均为1级,中心等轴晶区增大了7...     

全水口自旋流连铸水口钢水流动行为

摘要： 全水口自旋流连铸是从源头上优化结晶器流场的重要技术,利用数值模拟手段,研究了拉坯速度和旋流发生装置入口尺寸对自旋流连铸钢水流动行为的影响。研究表明,拉坯速度和入口尺寸对水口内钢水旋流具有重要影响,旋流强度随拉速增大而增大,随入口面积增大而减小,且随钢水向下流动近似呈线性减小;当旋流装置入口流速为1.1m/s时,水口内钢水旋转速度达4.10m/s,受旋流影响水口中心钢水反重力向上流动;水口流场沿径向可分为湍流各向同性区、各向异性区和近壁区,随入口速度增加湍流各向异性区范围增大。研究明确了全水口自旋流连铸过程钢水旋流行为的关键控制因素,为旋流连铸的参数优化提供了支撑。