铝合金铸轧铸咀中高温熔体三维流场与温度场的数值仿真研究

【作者】 唐俊龙；

【导师】 黄明辉；

【作者基本信息】 中南大学 ， 机械电子工程， 2004， 硕士

【摘要】 双辊连续铸轧不同其它连续铸造工艺在于它是集凝固、变形于一体的综合技术。而铸咀结构和装配是双辊连续铸轧最关键的技术之一，是直接分布金属液到铸轧辊辊缝的部件，因而铸咀型腔内流场与温度场的分布状态直接影响到板形，特别是铸咀型腔高温浅薄铝熔体出口速度、出口温度分布的均匀性决定了铸轧过程能否顺利进行以及能否获得高质量的铸坯。因此，研究大宽厚比、变截面型腔中复杂的高温浅薄铝熔体三维流场与温度场分布规律，分析不同参数对高温浅薄铝熔体出口速度、出口温度分布影响具有重要的现实意义。 本文根据铸咀型腔结构独特的特征、熔体的特殊特性与环境的复杂性，首次利用大型有限元分析软件ANSYS对高温浅薄铝熔体进行了三维建模和耦合求解分析，具有方便、可视化性，主要研究如下： 1．建立铸咀中高温铝熔体三维流场与温度场数学模型。 2．基于ANSYS选择了适当的三维单元及自由度求解器，解决了求解过程中边界条件的处理与加载的问题。 3．对变物性主要是变密度高温铝熔体三维流场与温度场进行了数值仿真且分析了几种参数(铸轧速度、分流块数目、铸咀型腔出口高度尺寸、型腔总长度)因素的影响，并比较了变密度与常密度熔体数值仿真结果，揭示了高温浅薄铝熔体流场与温度场分布规律，得出了数值仿真应采用三维模型，二维模型不合理，不符合实际；熔体流向速度与出口温度随铸轧速度的增加而增加，改变入口速度分布可改善型腔熔体出口温度与速度的均匀性；改变分流块数目可以改善出口速度分布与温度分布均匀性；适当减小型腔开口度能获得更均匀的出口速度分布及温度分布；增加型腔长度能获得更均匀的熔体出口速度分布及更均匀的温度分布；在工程实际应用中视变密度为常密度的合理性。数值仿真结果与分析结论为连续铸轧特别是快速铸轧最佳匹配参数提供了重要依据。 4．本文结合了水模实验结果，进行了铸咀表面温度实测实验，并采集了相关数据。水模实验结果表明数值仿真结论和实验测试数据结论相符合，温度测试实验为仿真的温度边界条件确立了基础依据，从而验证了相关结论的正确性。更多还原

【Abstract】 Different from other continuous casting process, Twin-roll continuous casting is a kind of synthetical technique that integrates solidification and deformation. One of the key techniques in twin-roll casting is the nozzle’s structure. The nozzle directly distributes the melted aluminum into the twin-roll gap. The distribution of the melted aluminum’s fluid field and temperature field in the nozzle signifcantly influence the quality of the casting aluminium sheets or strips. Especially, the uniformness of the melted aluminum’s velocity and temperature distribution at the cavity exit decides whether the twin-roll casting process can be successfully accomplished and thus high quality casting strips can be obtained. So it is very important to research the rules of the high temperature flimsy melted aluminum’s fluid field and temperature field in three dimensions and analyze the relationship between some parameters and the uniformness of the melted aluminum’s velocity and temperature distribution at cavity exit in the nozzle with big wideth-thickness ratio and veriating transverse section.Based on the particular characteristics of the nozzle, the special properties of the melted aluminum and the flexiblity of the surroundings, this paper models the high temperature flimsy metled aluminum in three dimensions and analyzes the distribution rules of fluid field and temperature field at the cavity exit by using the ANSYS software.The focus is as the following:1. The three-dimensional mathmatical and physical model of the fluid field and temperature field is established about the high temperature flimsy melted aluminum in the twin-roll casting nozzle.2. With the FEM analysis software ANSYS, the three-dimension element and corresponding DOF solver are correctly selected. Especially, the problem about the process of the boundary condition and loading are solved during the simulating course.3. The three-dimensional fluid field and temperature field of the steady high temperature melted aluminum with variable fluidproperty(the variable density) is numerically simulated. The affect of some parameters to the melted aluminum, such as two-roll casting speed, numbers of divergent fluid block, thickness of the two-roll nozzle exit and cavity length are systemically analyzed. Moreover, numerical simulation of the constant- density and variable density melted aluminum is simply compared. The numerical simulation had shown : The distribution rule of the high temperature flimsy melted aluminum’s three-dimension fluid field and temperature field is revealed and the conclusions are drawn that three-dimension model should be established and two-dimension model is irrational and impractical, that melt flow direction speed and exit temperature increase with the increasing of casting speed, that it can improve uniform of tip cavity exit distribution velocity and temperature to change cavity entrance distribution velocity and numbers of divergent fluid block , properly reduce thickness of the two-roll nozzle exit and extend cavity length and that it is rational to take the variable density as the constant density in practical project. So the best matching parameters is provided for the two-roll casting, especially for the fast-solidification two-roll casting by the numerical simulation .4. Datum of the water simulating of melt flow is presented and the surface temperature of nozzle is tested during the roll-casting fieldwork. The related data are collected. The water simulating experiment shows that the simulation result is well consisted with the experimental data, temperature experiment provides referenced base for temperature boundary condition of numerical simulation .Thereby, the model and conclusion is right.更多还原