An Effective Approach for the Simulation of the Cooling Process of Steel Strips on Run‐out Tables

The cooling process of steel strips on an industry run‐out table (ROT) is simulated using an 1D model. In this model, the water bank information is not handled and the ROT directly consists of the jetlines. The simulation creates an advantage to study independently the spacing of jetlines on the cooling effect. In addition, a novel approach is used for time stepping in this study. First, five numbers of time steps are defined for different cooling zones and each number can be determined according to the accuracy requirement and the strip speed. Thus, the time step size is not constant and the total number of time steps can be reduced. Second, each time step is identified with a flag to indicate its belonging to the different zones. With this approach, tracking is not needed and none of the water cooling zones will be jumped over. The predicted coiling temperatures of 1D model simulations are in good agreement with the field measurements.     

高温平板水雾冷却换热系数的数值分析

 利用有限元耦合场数值模拟计算方法进行了高温平板纯水喷雾冷却的模拟。研究了射流出口高度、平板表面温度及喷嘴流量对换热系数的影响。模拟结果表明：在其它参数不变的情况下,随着喷射距离（200mm～500mm）的减小,换热系数总体呈增加趋势;随着平板表面温度在（1050K～1200K间）的增加,换热系数总体呈减小趋势;随着射流流量或压力的增加,换热系数呈增加趋势。     

Heat Flux Density and Heat Transfer Coefficient between Steel Melt and Metallic Substrates

The solidification of low carbon (LC) steels on metallic substrates was investigated with a twin roll caster and a model mould. The substrate materials were steel, Ni, and two copper alloys, which are typical for the industrial construction of moulds. Heat flux density, heat transfer coefficient, growth rate, and cooling rate were evaluated.     

热带钢超快速冷却条件下的对流换热系数研究

建立了热带钢超快速冷却过程的导热微分方程,采用有限差分方法计算了薄带钢实现超快速冷却(对于4 mm以下的薄带钢,冷却速率可达300℃/s)所需的带钢表面对流换热系数.同时,在实验室条件下采用厚度为20 mm的钢板进行了超快速冷却试验,得到了超快速冷却条件下的带钢表面对流换热系数与冷却水流量的关系.结果表明,在一定水流量范围内随着冷却水量的增加,带钢表面换热系数逐渐增加;采用所确定的换热系数对不同厚度钢板得到的温降曲线与实测值吻合较好,具有较高的精度.     

钢板水冷过程换热系数建模的一种实用方法

为求解换热系数模型,以大量现场数据与热传递机制为基础,建立换热系数回归模型并使用ANSYS有限元软件对钢板冷却过程进行模拟,获取淬火过程中间数据。通过非线性回归算法对模型参数进行回归计算,最终取得整个淬火过程的换热系数公式。解决了现场无法测量淬火过程温度值,难以求解换热系数的难题。     

板坯连铸二冷区凝固传热过程与控制

依据安钢板坯连铸机的具体条件,建立了连铸板坯凝固传热数学模型,实现了随铸坯钢种、断面尺寸及拉速变化对各回路水量连续实时控制.经现场应用表明,利用配水模型所制定的二冷配水制度是合理的,效果良好.     

带钢超快速冷却条件下的换热过程

 分析了轧后加速冷却过程中带钢表面的局部换热机理，认为冷却系统实现超快速冷却的关键在于扩大带钢表面射流冲击换热区的面积。确定了薄带钢实现超快速冷却所需的对流换热系数，并采用有限元分析工具ANSYS模拟得到了超快速冷却条件下不同厚度带钢的温度场。温度场的分布表明薄带钢在超快速冷却过程中具有较好的温度一致性。同时还表明随着带钢厚度增加，超快速冷却条件下厚度方向的温度梯度显著增大，对于带钢内部组织的均匀性将产生不利的影响。带钢厚度范围应是超快速冷却技术实际应用过程中的重要考虑因素。     

Heat Transfer during Multiple Jet Impingement on the Top Surface of Hot Rolled Steel Strip

Using a unique pilot facility a series of tests were conducted using three top jets to simulate the heat transfer that occurs during run‐out table (ROT) cooling. Steel samples instrumented with internal thermocouples were tested on this facility and the effect of top jet configuration (nozzle spacing of 40 to 115mm), and water flow rate (15 and 30 1/min) were quantified using moving plate samples. The multiple top jet work indicated that heat transfer across the plate width varies significantly and is high directly under the nozzle but decreases rapidly away from the nozzle in the interaction region. As cooling progresses a much larger wetted region occurs and more uniform cooling is experienced across the plate. Multiple jet cooling experiments have also confirmed that nozzle spacing does have an effect on heat transfer. This effect is predominate in the interaction region where closer nozzle spacing leads to enhanced and more uniform heat transfer in the lateral direction across the plate width away from the nozzle. As expected higher water flow rates led to higher heat transfer both under the nozzle and in the interaction region.     

Investigation of Heat Transfer in the Spray Cooling of Continuous Casting

The heat transfer coefficient between spray water droplets and hot surface is measured in the laboratory. The effect of spray water flow rate, water pressure, spray distance of nozzle from the surface of strand, spray water temperature on the heat transfer is made a detail studied. And meanwhile, the effect of the strand surface FeO scale on the heat transfer is also investigated. According to the experimental results, the influence of above factors on the heat transfer coefficient has been discussed and a experience formula between the heat transfer coefficient and spray water flow rate is given out.     

高炉新型炉体冷却结构的传热实验研究

针对高炉新型炉体冷却结构,设计了实验室物理模型并建立了热态模拟系统。通过热态实验,测定了物理模型的温场、单水管进出水温差等,研究了新型结构在运行中的传热规律。同时,分析了实际工况条件对冷却结构传热的影响。实验表明,越靠近炉内高温表面的点温度越高,冷却水管中心线以内温度迅速升高;水流速对模型体内的温度分布影响不大,但随着水流速增加,冷却水温差减小;炉内温度对炉衬热面温度的影响较大,随着炉温增加,水温差增大。     

CSP和FTSC工艺结晶器的冷却结构及传热能力

结合实际生产数据,比较和分析了CSP及FTSC工艺结晶器的冷却结构及传热能力,结果表明,热流密度计算模型中,FTSC和CSP结晶器内传热区高度分别为1 200 mm和1 010 mm,相同工况下二者的传热能力相近;CSP结晶器采用42条凹型水道及20条内径11 mm的圆型水道进行组合冷却,FTSC结晶器采用72条内径14 mm的圆型水道进行冷却;弯月面处FTSC结晶器铜板热面温度高于银铜的再结晶温度,铜板将发生局部变形,这是造成镀层龟裂或铜板裂纹的主要原因。     

连铸二冷区气-水喷雾冷却传热数学模型

在前人对单个液滴碰撞传热解析研究的基础上,通过实验与理论分析,建立了气-水喷雾冷却在膜态沸腾区的传热数学模型。采用此模型,可以在已知气-水喷嘴的冷态参数(流量密度、液滴粒径、液滴速度等)的情况下,模拟计算出该喷嘴的传热特性。计算结果与实验数据在可比的范围内基本吻合。     

棒材穿水冷却温度场的仿真研究

针对棒材穿水冷却过程,采用有限元仿真软件ANSYS对其进行了温度场仿真,建立了棒材温度场预报模型。该模型的仿真结果与实测值相吻合,能够准确地预测棒材穿水冷却过程的温度分布,为棒材性能预报与优化控冷工艺提供依据。     

基于瞬态传热数学模型的板坯连铸二冷设计

以超高强度钢(UHSS)为对象,研究板坯连铸二冷设计。首先,基于凝固传热学基本理论,建立了二维板坯瞬态传热数学模型;其次,根据高温塑性实验曲线,结合二冷区冶金原则,确定二冷区各段终点的表面目标温度;最后,根据制定的铸坯表面目标温度,采用增量型PID算法调整二冷区各回路的水量。     

热连轧层流冷却的数学模型

本文以武钢1700热连轧厂层流冷却现场实测数据为基础,通过传热学的理论分析,确定了对流换热系数是解决问题的关键,并对7种模型结构形式进行了比较,研制了精度较高的对流换热系数数学模型,在此基础上编写了模拟武钢1700连轧层流冷却过程的程序,取得了较高的模拟精度.     

水平连铸二冷区喷水冷却过程数学模拟

根据成都无缝钢管厂水平连铸的生产实践,建立了铸坯凝固冷却过程数学模型,通过数学模拟仿真,找出铸坯在不同的结晶器冷却强度和不同的喷水量条件下凝固冷却过程的温度场变化、凝壳的生长规律及液芯长度等与浇注参数(拉速、浇注温度)的关系,为改善和稳定浇注过程,提高铸坯质量提供依据。     

大钢锭凝固界面换热系数的数值模拟

基于热-黏弹塑性本构方程建立了大钢锭凝固时热-流-力耦合的3D有限元模型,并对8.5t钢锭浇注过程中不同位置处热流密度、气隙宽度和界面换热系数的变化规律进行了模拟分析。结果表明,钢水与钢锭模刚刚接触时的热流密度和换热系数最大,二者随后迅速下降,且角部区域的下降趋势略大于面部。凝固初期时热流密度和换热系数的最大值位置并非位于面部中心,而是在1/4宽度处;由于宽面对钢水静压力的抵抗作用小于窄面,其界面热流密度和换热系数也略大于窄面。凝固中后期时,换热系数的区域差异逐渐趋于不明显。同时,建立了基于凝固时间和界面温度的平均换热系数的反算模型。应用2个模型所求结果计算的钢锭和钢锭模温度变化与实测值及热-流-力耦合模型结果基本一致。进一步研究发现,界面换热系数随温度的变化规律可推广应用到3~30t钢锭的模拟研究中,计算结果与实际更为符合。