Improvement of 3-D FEM Coupled Model on Strip Crown in Hot Rolling

 In order to simulate and analyze hot strip crown and flatness accurately and efficiently, the 3-D (three-dimensional) coupled model involved in RPFEM (rigid-plastic finite element method) is improved based on the analytical model of forecasting rolling force distribution. In the analytical model, variational method is employed to solve the lateral flow of metal and influential function method is employed to calculate roll deflection, the lateral distribution of rolling force can be obtained rapidly by iterative strategy. Then the 3-D coupled model uses the result as initial distribution of rolling force to calculate roll deflection and makes the initial on-load roll gap profile close to the final value, so as to reduce iterations and increase efficiency. Compared with previous algorithms, the improved model can reduce the iterations by about 50% and shorten the computing time by about 60% on the basis of the calculation accuracy.     

整辊内嵌式板形仪挠度干扰信号的消除方法

 板形测控技术是生产高端冷轧带钢的必备技术,针对国产板形测控系统研发过程中遇到的一系列新的科学技术问题,研究了如何消除整辊内嵌式板形仪挠度引起的干扰信号。首先,分析了整辊内嵌式板形仪结构特点与传感器连接型式的特殊性;然后,分析了板形信号的理想波形与实际波形特征,根据其特征提出一种新的挠度干扰信号的消除方法,根据传感器安装位置固定的特点确定干扰信号相位,以有效信号之间波形平直为目标对干扰信号幅值进行优化;最后,通过实例和工业应用对该方法的有效性进行验证。研究结果表明,该方法可以高效精确地消除挠曲附加波形,使径向压力和板形分布变得平滑,有效提高检测精度。     

热轧薄规格带钢平整过程板形控制技术

为了提高热轧薄规格带钢平整的板形质量,在平整机上采用了新的辊形配置。在支撑辊上采用变接触式 支撑辊辊形,在工作辊上采用六次方多项式正凸度辊形。变接触支撑辊辊形可以降低轧辊挠曲变形和边部应力的 集中,增大弯辊力的调控功效。采用正凸度工作辊辊形,可以弥补平整机的磨损辊形,延长平整轧制计划单位的长 度。此辊形配置在首钢迁钢热轧平整机上应用,保证了平整改善薄规格带钢板形质量,延长了平整轧制计划的长度。     

Optimisation of work roll shifting and bending to roll thinner gauge HR coils using genetic algorithm

Abstract

Rolling of thin gauge hot rolled (HR) coils demands stringent flatness tolerance. Thin HR coils (≤3 mm) are rolled towards the end of any rolling campaign. The profile and flatness of the strip depend on the profile of the loaded roll gap in the mill stands. There are five key factors that influence the loaded roll gap: initial roll surface profile, roll thermal expansion, wear of roll, deflection of roll stack and shifting of work rolls. This paper deals with all these factors individually for the formulation of an objective function in order to minimise the flatness error. The shifting and bending of rolls are the controllable parameters that require optimising. This has been accomplished using a genetic algorithm (GA) optimisation technique.     

基于有限元与神经网络的板形调控功效

 针对冷连轧机组中的6辊CVC轧机,利用大型非线性有限元软件MSC.Marc建立仿真模型,对多种轧制条件下轧件的弹塑性变形和辊系的弹性变形进行了耦合计算,得到了6辊CVC冷轧机工作辊弯辊、中间辊弯辊、中间辊横移的板形调控功效离散值。研究了不同轧制工艺参数、轧件参数和轧辊参数对各板形调节机构调控功效的影响规律,并得出相应的板形调控功效系数。以有限元计算结果为样本,利用BP神经网络强大的非线性映射功能,建立了板形调控功效的神经网络计算模型,为板形在线闭环控制模型提供高精度的板形调控功效,解决了有限元计算耗时长,难以满足在线控制要求的问题。     

Effects of roll crossing on the rolling process in four-high mills

Roll crossing can be utilized as a method for profile and flatness control in a rolling mill. The estimation of the profile adjusting range by calculating the elastic roll-gap deflection reveals that roll crossing has a similar effect on the profile as positive bending. Under the assumptions made in the calculations roll crossing is an effective method as profile and crown actuator. Furthermore the effect of roll crossing on the flatness is qualitatively confirmed by rolling trials. Beyond the investigation of the effectiveness of roll crossing as profile and flatness actuator a 3-dimensional finite element simulation of the material flow in the roll gap was done. The results of these simulations, which were confirmed by rolling trials as well, showed that the rolled specimen warps out of the passline due to the crossing of the work rolls whereas the influence of roll crossing on the distribution of local plastomechanical values is negligible. Force components in axial direction are induced by crossing the rolls, which have to be compensated by additional bearings. For the determination of the amount of axial forces rolling trials on a laboratory four-high mill were carried out.     

Development and application of roll contour configuration in temper rolling mill for hot rolled thin gauge steel strip

Abstract

In order to improve the flatness of hot rolled thin gauge steel strip, a new type of roll contour configuration was developed for a four-high temper rolling mill based on the finite element method analysis. The roll contour configuration consists of a variable contact back-up roll contour and a positive crown work roll contour. Both can be described as sixth order polynomial functions. The variable contact back-up roll not only reduces the roll stack deflection and contact stress concentration between work and back-up rolls, but also increases the control capability of the bending force of the work roll. Positive crown work roll contour is utilised to compensate roll wear and in turn the length of temper rolling schedule can be prolonged. After this roll contour configuration was applied on the temper rolling mill of Qiangang Company of Shougang Group, the flatness of hot rolled thin gauge strip was improved by 10% and the working efficiency was also increased as the length of temper rolling schedule was increased.     

HC轧机工作辊弯辊对板形特征参数影响规律的研究

为分析板形调节手段对板形特征参数的影响规律,以HC轧机为例,以倾辊、工作辊弯辊和中间辊横移作为板形调节手段,基于机理模型着重计算了工作辊弯辊板形调节手段对1次、2次、3次和4次板形的影响系数,系统地揭示了工作辊弯辊对各次板形的影响规律,为板形在线控制策略的制定提供了有益的指导和理论依据,也为后续其他板形调节手段的研究奠定了基础.     

Prediction of shape defects over length of cold rolled sheet using artificial neural networks

Abstract

A model based on an artificial neural network (ANN) has been developed for prediction of flatness of cold rolled (CR) sheet in a tandem cold rolling mill for white goods applications. Various process parameters including roll bending, roll shifting, tensions between stands etc., which affect flatness of CR sheet are considered in the model. Substantial amounts of data are obtained from level II automation of PL-TCM of TATA Steel to develop the prediction model. The developed ANN model, based on back propagation algorithm, is able to predict the flatness defects like edge buckles, centre buckles for a given set of rolling parameters. The model involves a large number of process parameters and application of ANN to such kind of problems is successfully demonstrated in the present study. The model is in good agreement with the observed flatness values at different locations across the width. High coefficient of determination close to 0·919 is achieved for the prediction of flatness at edges.     

Development of simulation system of strip flatness for hot tandem mill

Using three-dimensional rigid-plastic finite element method base on Lagrange multiplier to analyze the deformation of strip,influence function method to calculate the elastic deflection of rolls and three-dimensionalelastic FEM to analyze the flattening deformation between work roll and strip,a coupled model was established with a iteration way.The effect of various kinds flatness control method such as bending force,rolls shift and cross angle and also various kind of influence factors such as friction ...     

Research and Application of Dynamic Substitution Control of Actuators in Flatness Control of Cold Rolling Mill

The work roll bending control has a strong ability to eliminate the symmetrical flatness defects of strip. However, if the incoming strip is coming with severe symmetrical flatness defects, it happens that the position limit of work roll bending is prone to be reached or exceeded during the execution of the displacement, resulting in the residual symmetrical flatness defects without further elimination, as well as a limited flatness control process. Abilities of work roll bending and intermediate roll bending / shifting for flatness control have been analyzed based on the actuator efficiencies for the purpose of solving the problem of work roll bending control reaching threshold. Meanwhile, a self‐learning determination model of actuator efficiency factors, which can be utilized to determine the actuator efficiency factors online accurately, was developed from the measurement data extracted from the rolling mill. Models of intermediate roll bending and intermediate roll shifting substitution control in case of work roll bending control over‐limitation have been developed, in accordance with the practical conditions and the degree of work roll bending over‐limitation. Applications show that the substitution control can play an important role in the residual symmetrical flatness deviation control, which should have been removed completely by the work roll bending control.     

Roll Subsectional Cooling Adaptive Fuzzy Control Based on Fuzzy Model Inversion

 Flatness is an important equality indicator of strip rolling and roll sub-sectional cooling is an important method for flatness control, especially for high order flatness component control. It is very hard to build the mathematic model of roll sub-sectional cooling because of its characteristics of nonlinearity, hysteresis quality and strong coupling etc. In order to improve the control effect of roll sub-sectional cooling control model, the roll sub-sectional cooling adaptive fuzzy control model based on fuzzy model inversion is built according to the separation principle of fuzzy form on the basis of the conventional fuzzy control model, where the parameters of the fuzzy controller can be dynamically regulated according to the change of rolling conditions. Simulation experiment results of the model indicate that the proposed roll sub-sectional cooling adaptive fuzzy control model based on fuzzy model inversion has high control precision and rapid response speed with strong self-learning and anti-interference capacity and a new method is provided for high-precision flatness control.     

马钢CSP生产线带钢板形控制系统

马钢薄板坯连铸连轧生产线的板形控制系统数学模型包括与板凸和平直度控制相关的轧辊弯曲模型、轧辊热磨模型、工作辊压扁模型、材料流量模型的算法与相应数据接口,以这些模型为基础采用板形设定算法及其在线自适应算法,实现了对热轧带钢成品板形的精确控制。实际生产表明,采用该系统后,凸度命中率可达96.37%。     

四辊轧机辊系弹性变形高效计算方法

 为解决普通影响函数法计算速度慢的缺点,在分析普通影响函数法计算精度与计算速度主要影响因素的基础上,提出了一种新型四辊轧机辊系弹性变形高效计算方法。该方法采用高次多项式描述辊间压力与轧制压力的横向分布,减少了轧辊挠度的计算量;与普通影响函数法相比,求解辊间压力的线性方程组阶数显著降低,大大降低了计算时间。采用该方法后,四辊轧机辊系弹性变形的单次计算时间不超过1 ms,计算精度与划分单元数为100的普通影响函数法计算精度相差很小,为板形在线设定提供了理想的必要条件,并可推广应用于其他机型。     

六辊CVC辊系辊间横向轧制力分布的研究

多辊轧机的辊间横向轧制力分布直接影响有载辊缝的形状和板形控制的结果。运用影响函数法建立了1850mm六辊CVC轧机辊系弹性变形及辊间横向轧制力分布的物理和解析模型,并对中间辊窜辊、中间辊弯辊和工作辊弯辊变化对横向轧制力分布的影响进行了分析研究,建立了计算机仿真程序,给出了辊间横向轧制力分布的规律。分析结果为六辊CVC轧机确定合理的板形控制策略奠定了理论基础,对获得良好板形控制具有指导意义。     

变包角板形测量值计算模型

在变包角板形测量系统中,无辊环式板形辊上的传感器受力状态与包角大小有直接关系。为了得到准确的板形测量值,通过研究分析接触式无辊环板形辊的板形检测原理以及传感器在带钢张力作用下的受力状态,结合某冷轧生产线的设备安装条件,推导出了实时变包角情况下板形测量值的表达式。经现场应用表明,该模型完全适用于无辊环式板形辊的变包角板形测量系统,提高了冷轧带钢板形控制的精度,为冷轧板带生产实现精确的板形控制提供了条件。     

4100mm宽厚板轧机支承辊辊型曲线优化仿真分析

 辊间接触压力分布是影响宽厚板板形质量和轧辊使用寿命的重要因素,为了获得均匀的辊间压力分布,以4100mm宽厚板四辊轧机为对象,考虑轧件弹塑性变形和辊系弹性变形耦合作用,采用弹塑性热-力耦合非线性有限元方法,数值模拟分析了宽厚板轧制过程的辊间接触压力分布规律,并通过仿真分析,对支承辊辊型及其边部卸载曲线进行了选型和优化改进,获得了以二次曲线为辊凸度和抛物线为辊肩部卸载曲线的辊形,延长了轧辊的使用寿命,改善了宽厚板的板型质量。     

冷连轧机高强钢板形控制技术研究与改进

针对某冷连轧机在高强钢生产中出现的板形问题,以提高机组对高强钢产品的板形控制能力为目标,对中间辊和支持辊辊形进行了优化设计,并对第五机架精细冷却乳化液使用工艺进行了优化研究。新的高强钢板形控制工艺技术在生产中使用稳定,从根本上提高了轧机板形控制能力,0～3 IU的板形控制精度所占比例由83.71%提高到90.86%,轧辊磨损得到明显改善,应用效果显著。     

二十辊轧机支撑辊组变形及板形调控分析

 板带材的产能和质量是一个国家工业水平发展的重要标志,铜板带材的生产能力和地位更加显著。森德威二十辊轧机是冷轧铜板带材轧制生产的关键设备,其最外层A、D支撑辊组的弯曲变形是最重要的板形调整手段之一。支撑辊组鞍座位移变化可以使支撑辊芯轴发生弯曲变形,变形会反映到背衬轴承上并且向下依次传递给中间辊和工作辊,最终影响板厚和板形。传统的假设折线法和超静定梁法将芯轴和背衬轴承考虑为一个整体,而忽略了两者之间的变形对整体支撑辊组变形的影响。因此,基于有限元方法进行仿真拟合各段背衬轴承弯曲变形得到简化后的一次函数表达式,将各段背衬轴承拟合结果汇总进而得到整体的支撑辊组弯曲变形的线性表达式,再结合辊系弹性变形模型和金属塑性变形模型构成的板形预报模型评估支撑辊组变形程度对板形和板厚的影响。研究结果表明,对上辊系中的4个鞍座施加不同的位移组合之后,板厚和板形分布在整个板宽方向上并非局部变化,而是呈现整体的变化趋势,且4个鞍座对板形和板厚的调整效果并不相同;在施加同样的鞍座位移条件下,中部鞍座比边部鞍座对板形和板厚的影响效果更加显著,并且即使在支撑辊组中心两侧施加对称的鞍座位移,其对板厚和板形的影响也是非对称的。     

带钢平整轧制过程中板形缺陷的遗传和演变规律

应用ABAQUS有限元软件对平整轧制过程进行三维弹塑性建模及仿真研究,通过温度场模拟入口带钢的初始板形缺陷,利用刚性工作辊的辊形变化综合表达各板形控制手段对承载辊缝形状的调控功效.基于以上力学模型,针对具有初始板形缺陷的带钢,仿真研究平整轧制后带钢的板形缺陷及其与初始板形缺陷及平整工艺条件的关系,揭示带钢平整轧制过程中板形缺陷的遗传与演变的规律.仿真计算结果表明,承载辊缝形状是决定带钢板形缺陷遗传和演变的最主要因素,轧前带钢的初始板形缺陷的程度,即最大纵向延伸差的大小,对平整后带钢的板形缺陷仅有一定程度的遗传性影响.