【作者】 王文明；

【导师】 钟掘；

【作者基本信息】 中南大学 ， 机械设计及理论， 2007， 博士

【摘要】 随着铸轧工艺向提速与减薄方向发展，铸轧板板形问题日益突出。揭示铸轧工艺中特殊的板形现象与产生机理并进行有效控制，是铸轧发展的一项关键技术。本文以铝带坯双辊铸轧系统为研究对象，围绕铸轧板形的产生机理，通过计算机数值模拟并结合铸轧现场工业测试，对铸轧区内金属流动凝固传热问题、铸轧辊套三维温度场、轧件—辊套—辊芯三维多体接触系统的热力耦合变形行为进行了深入研究和仿真分析；为提高铸轧板形的控制精度，对铸轧板形检测信号中混杂的随机噪声和附加干扰分别进行了除噪处理和补偿研究。针对铸轧区内金属流动凝固传热问题，本文将铸轧区内处于不同状态的金属视为广义流体，实现了铸轧区流动凝固传热过程的统一数学描述，建立了铸轧区内铸轧板的等效厚度几何模型和有限元模型，提出了热流密度沿铸轧方向线性递减分布的宏观假设。通过对不同工艺条件下凝固传热过程的耦合求解，揭示了铸轧区内温度场的分布规律，求得了凝固前沿位置以及铸轧出口处带坯的最低温度，探明了常规铸轧工况下对应给定冷却条件的铸轧速度极限，同时厘清了液穴深度与铸轧速度之间的相互关系。针对铸轧辊套内微观热传导和宏观质量牵移传热联合作用下的典型周期性动边界传热问题，根据传热过程的等效性，本文将辊套的周向旋转视为圆环管内广义流体的有序环流，并基于流体流动传热分析法建立了一种新的辊套传热计算模型，成功地实现了移动传热边界的静态处理。通过对常规铸轧和超薄快速铸轧等多种工况下辊套传热过程的数值仿真研究，分别求得了相应的辊套温度场，充分揭示了辊套温度场关于铸轧速度、内冷强度和辊套材料导热系数等主要传热因素的响应规律，并为铸轧辊热力耦合变形的求解提供了原始数据条件。为了探明铸轧板形的产生机理，本文首次将铸轧工艺中轧件—辊套—辊芯构成的辊板系统视为三维多体接触问题，建立了辊板系统热力耦合变形的计算模型和有限元模型，系统阐述了有限元混合法求解的基本理论，给出了接触面定解条件及接触状态的判定条件，推导出了关于接触界面上内力分布的有限元方程的一般形式，具体分析了有限元计算中边界条件的处理，并分别建立了适合接触系统有限元分析的铸轧力模型和变温等效节点载荷模型。运用接触问题有限元混合法，对轧件—辊套—辊芯接触系统在多种铸轧工况下的热力耦合行为进行了数值模拟，揭示了铸轧辊热力耦合变形与铸轧速度、内冷换热强度、辊套材料等主要工艺因素之间的相互关系。板形检测是实现板形自动控制的必要条件，其检测精度是决定控制效果的首要因素。本文将铸轧板形检测信号视为动态时间序列，运用自适应滤波理论建立了一种通用的铸轧板形检测信号除噪方法，并研制开发了除噪分析软件，考题验证及仿真结果表明该法除噪效果明显，且能满足实时控制的要求。针对铸轧板形检测信号中固有的附加干扰，建立了附加温差板形补偿模型。运用本文的补偿方法可直接对铸轧板形检测信号进行修正，从而有效地避免了板形控制机构的误操作，提高了铸轧板形的控制精度，对铸轧板形的在线控制具有重要实用价值。在实验研究方面，针对国内某厂φ1020×1600mm铸轧机，分别拟定了辊套温度场、板面温度场、铸轧辊热变形及轧后带坯在线与离线横向厚差的工业测试方案并进行了现场实测。上述参数的实测结果与仿真计算值吻合较好，有效地验证了辊套温度场计算模型、辊板系统热力耦合变形计算模型、铸轧板形测控中附加干扰补偿模型的正确性、相关数值求解方法的可行性及仿真结果的可靠性。更多还原

【Abstract】 Along with the development of roll-casting process in the fast ultrathin direction, roll-casting flatness problem will be prominent day by day. To promulgate the special roll-casting flatness phenomenon and its production mechanism and to control it effectively, have already become a key technical problem which is urgently awaited to be solved. At the same time, such are also urgent need for realizing the industrialization of roll-casting process. In this paper, the research object is twin-roll casting system of Aluminum. Aimed at flatness problem and through the computer numerical simulation and the scene industry test, the thorough research and the simulation analysis are made on such problem as heat transfer companied with the flowing and solidification of the metal in the roll-casting zone, three dimensional temperature field of the roll shell, thermo-mechanical coupling deformation behavior of three-dimensional multi-body contact system consisting of workpiece, roll shell and roll core. In order to enhance flatness control precision, the random harmful noise is removed from flatness detection signal, and the attached disturbance is compensated.In view of heat transfer problem companied with the flowing and solidification of metal, this paper looks on the metal with different state as generalized fluid, and uniformly describes the process including the metal flowing, solidification and heat transfer in the roll-casting zone. The equivalent thickness geometry model and the finite element model of the roll casting zone are established. A supposition which states the heat flow density decreases linearly along the roll direction is proposed. Through the coupling solution to the above models at different process condition, the distribution law of temperature field in the roll-casting zone is promulgated, the most front solidification position and the lowest temperature of the exit strip are obtained, the roll speed limit is verified for the given cooling condition of conventional roll casting, the relationship between liquid cave depth and casting velocity is cleared off.A typical heat transfer problem with periodic motive contact boundary, which includes microscopic heat conduction and macroscopic mass-moving heat transfer, is studied in this paper. According to the equivalence of heat transfer process, the circumvolving of roll shell is regarded as the ordinal circumfluence of generalized fluid in the round tube. Based on the analysis method of fluid flow and heat transfer, a new heat transfer model of roll shell is established, and the motive contact boundary between the workpiece and the roll shell is treated as non-motive boundary. Through the mathematic simulation research of heat transfer process of roll shell at many kinds of work states for the normal casting and the fast ultra-thin gauge casting, the corresponding temperature field of roll shell is obtained separately. It is known about the influence rule of some main heat transfer factor, such as casting velocity, inner heat transfer coefficient and conduction coefficient of roll shell material, etc. on the temperature field of roll shell. At the same time, some primary data conditions are provided for the solution of the thermo-mechanical coupling deformation of casting roller.In order to verify the production mechanism of roll-casting flatness, for the first time, strip/roll system is regarded as three-dimensional multi-body contact problem, which consists of workpiece, rol shell and roll core. The mathematical model and finite element model are built for solving the thermo-mechanical coupling deformation of strip/roll system. After expounding the basic theory of mixed finite element method in detail, the solution condition of contact surface and the determination condition of contact state are given, the general finite element equation is derived for the internal force distribution in the contact interface, the methods to deal with boundary condition are analyzed. In addition, the roll-casting force model and equivalent node load model resulted from variable temperature are established, which is suit for finite element analysis of contact system. With mixed finite element method for contact problem, the numerical simulation is done for the thermo-mechanical coupling behavior of strip/roll contact system at various roll-casting conditions. Simulation results open out the relationship between the thermo-mechanical coupling deform of casting roller and main process factors such as casting velocity, inner heat transfer coefficient and roll shell material, etc.Flatness detection is an essential condition to automatically control flatness defect, its precision is the most important factor to decide control effect. In this paper, flatness detection signal is looked on as dynamic time series. With the theory of adaptive filtering, a general method is established to remove the harmful noise from the flatness detection signal, and a filtering program is developed. Exemplifications and simulation results prove that the above method can be used in the real time control with good effect. In order to remove the inherent additional disturbance from the flatness detection signal, the temperature deviation compensating model is established. The compensating means studied in this paper can be directly taken to amend the flatness detection signal, which can effectively avoid misoperation of control mechanism and improve control precision and have the important practical value for the scene control of roll-casting flatness.As for the experiment, a certain domestic casterΦ1020×1600mm is by way of its research object. Some industry measuring plans are drew up for temperature field of roll shell and strip surface, thermal deformation of casting roller, on-line and off-line crosswise thickness difference of rolled strip. At the same time, the scene measuring has been carried on. The experimental values of the above parameters are very consistent with the simulation values, which proves that the models established in this paper are correct, the corresponding numerical solution is feasible, and the simulation results are reliable.更多还原