Practice of Improving Roll Deformation Theory in Strip Rolling Process Based on Boundary Integral Equation Method

Precise strip-shape control theory is significant to improve rolled strip quality, and roll flattening theory is a primary part of the strip-shape theory. To improve the accuracy of roll flattening calculation based on semi-infinite body model, a new and more accurate roll flattening model is proposed in this paper, which is derived based on boundary integral equation method. The displacement fields of the finite length semi-infinite body on left and right sides are simulated by using finite element method (FEM) and displacement decay functions on left and right sides are established. Based on the new roll flattening model, a new 4Hi mill deformation model is established and verified by FEM. The new model is compared with Foppl formula and semi-infinite body model in different strip width, roll shifting value and bending force. The results show that the pressure and flattening between rolls calculated by the new model are more precise than other two models, especially near the two roll barrel edges.     

Plate Shape Control Theory and Experiment for 20-high Mill

Roll flattening theory is an important part of plate shape control theories for 20-high mill. In order to improve the accuracy of roll flattening calculation for 20-high mill, a new and more accurate roll flattening model was proposed. In this model, the roll barrel was considered as a finite length semi-infinite body. Based on the boundary integral equation method, the numerical solution of the finite length semi-infinite body under the distributed force was obtained and an accurate roll flattening model was established. Coupled with roll bending model and strip plastic deformation, a new and more accurate plate control model for 20-high mill was established. Moreover, the effects of the first intermediate roll taper angle and taper length were analyzed. The tension distribution calculated by analytical model was consistent with the experimental results.     

Three-Dimensional Model for Strip Hot Rolling

Steel stripis widely usedin many fields such asautomobile ,building,transportation and householdappliance ,etc·. Withthei mprovement in productiv-ity and automation of strip processing,the require-ments for crown and flatness of strip have been in-creasingly severe ,and“crown free”steel strips arerequired for some special applications such as for au-tomobile parts andtinplate cans .In order toi mprovethe strip quality , an effective three-di mensionalmodel is needful to further study on the…     

热塑有限元的理论分析及应用

利用热塑有限元对板材轧制过程进行模拟计算,能够计算轧制力、轧制力矩、辊形、板形等参数,对板材轧制起到定量计算的作用。热塑有限元在板材生产中能计算最佳辊型、板形、弯辊力、串辊位置以及压下制度,达到提高成材率、提高板材质量的目的。热塑有限元是一种三维的弹塑性有限元,它应用的本构方程是由试验数据回归得来的,使用了加工硬化、拉拔效应等计算方法,计算结果精确。     

Influence of Roll Elastic Deformation on Gaugemeter Equation for Plate Rolling

The error of gaugemeter equation decreases the gap setting precision. The precision of gaugemeter equation is strongly influenced by plate width, work roll radius, backup roll radius, work roll crown, backup roll crown and rolling force. And these influences are hard to measure. All these factors are converted to roll deflection deformation and roll flattening deformation for calculation. In order to calculate the deformation, the theory of influence function method was adopted. By using simulation program, the influence of these factors on deformation was obtained. Then a simple model can be built. With this model, it is convenient to analyze the influence of different factors on gaugemeter equation.     

宽厚板压力矫平压下模型理论建模与有限元分析

宽厚板压力矫平过程由于缺少精准可靠的压力矫平模型,工艺参数的设定主要依靠人工经验,制约了生产效率和产品质量的提升。针对实现全自动压力矫平关键瓶颈问题——压力矫平模型进行研究。采用弹塑性力学理论,结合压力矫平过程的特点,建立宽厚板压力矫平数学模型;在材料力学性能参数、初始平直度或曲率已知的情况下,自动计算出压平力、压头行程等参数;根据压力矫平模型计算出的数据,采用有限元方法模拟压力矫平过程,获得板材各节点位置和位移数据,计算出压力矫平后宽厚板的平直度。结果表明,各种工况下宽厚板的平直度小于2 mm/m,优于宽厚板的交货标准,证实了模型的可靠性。     

极薄带轧制变形区轧辊压扁试验与有限元模拟

 极薄带在轧制及平整过程中,工作辊的弹性压扁对轧制压力的分布有很大影响,传统的轧制力模型已经不再适用。为了在极薄带板形板厚控制过程中得到准确的轧制力,Fleck提出了新的轧辊压扁模型。针对Fleck模型进行试验研究,同时进行有限元模拟分析。试验过程中使用合金工具钢轧辊,轧制不同厚度的轧件,通过显微镜测量变形区各部位的厚度,得到变形区轧辊的近似轮廓形状。试验与有限元模拟结果表明,随着轧件厚度的减小,变形区出现了明显的中性区,但是很难出现Fleck模型中提到的弹性卸载区,因此计算极薄带轧制力时可以忽略中性区内的弹性卸载区以简化轧制力模型。     

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 ...     

小断面管材二辊矫直机压扁量分析

 压扁加反弯矫直是提高小断面管材矫直精度的有效方法,针对矫直过程中压扁量不易确定的问题,利用大型非线性有限元软件建立小断面管材二辊矫直过程的三维弹塑性有限元模型,研究了不同压扁量时接触长度、矫直力、残余应力、直线度和椭圆度的变化情况。经综合分析后给出合理的压扁量取值范围为0.45~0.70 mm。现场试验结果表明,参考此压扁量取值范围来调节辊缝可以得到很好的矫直效果,减少了辊缝调节时间。     

风管共板法兰辊弯成形过程的有限元仿真

利用通用非线性的ABAQUS软件对多道次辊弯成形过程进行建模以及数值模拟,对辊弯成形工艺及成形规律进行了研究,为辊弯成形的工程设计、工艺参数和辊弯设备的调整提供了科学的依据。整个辊弯成形过程基于动力显式算法,建立风管共板法兰多道次辊弯成形的有限元模型。其中涉及了辊弯成形的模型建立、单元选择、边界条件、有效速度质量放大系数的选择等辊弯成形的一般性问题解决方法。     

热连轧精轧过程中带材瞬态温度场的精确计算

基于热传导方程,考虑热连轧精轧区板带周期性地连续变形和连续冷却等复杂动态边界条件,利用有限差分法,在各机架变形区利用坐标映射关系建立三维瞬态温度场模型,在机架间非轧制区利用某横截面计算瞬态温度分布,这两种温度场模型互为条件,迭代求解。仿真结果表明,带材两侧边部有较大温差,易形成较大的局部热应力;带材越厚,压下量越大,带材高向温差越大,将会影响热连轧带材内部组织演变过程。仿真结果与实测数据吻合较好,表明模型能够精确预报热连轧精轧区板带的瞬态温度分布及终轧温度。     

中厚板轧机弹跳模型的数值分析和应用

针对普通4辊中厚板轧机将辊系弹性变形分解成3个部分：支撑辊挠曲变形、辊间压扁和工作辊压扁，并利用轧辊弹性变形的数值解法一影响函数法对这3部分变形进行了分析，得出了轧辊半径、轧辊凸度、轧件宽度和轧制力等因素对辊系弹跳的影响规律，并提炼出相应的高精度回归模型。同时对传统轧机弹跳模型进行改造，提出更加完备的轧机弹跳模型。利用该模型可以很方便地计算轧辊辊径、凸度和轧件宽度对轧机弹跳的影响。通过与X射线测厚仪测试结果相比较可知，模型预测误差小于0．12mm，有利于负公差轧制。     

有限元法在板材热轧中的应用

采用弹塑性大变形热力耦合有限元法研究板材热轧过程．利用有限元理论建立了板材热轧模型；应用MSC／MARC软件进行计算，重点分析了轧制过程和变形区中轧件的温度场分布和变化、金属的流动、应力应变的变化趋势，以及轧制力的变化情况．计算结果与实际生产情况相吻合，同时表明有限元理论可以实现对板材热轧过程的数值模拟．     

冷轧板带残余应力求解分析

冷轧板带残余应力是影响板带质量的重要因素。为了提高板形质量,根据板带轧制前后体积不变原理,推导了残余应力的数学模型,采用有限元法对板带失稳时的临界载荷进行了求解,运用解析法和有限元法相互耦合的计算方法建立了板带失稳后的残余应力修正模型。结果表明:初始残余应力的作用使板带产生了失稳,因此需要对残余应力进行修正计算,修正后的残余应力与现场实测结果有较好的一致性。     

面向辊形磨削的热带钢连轧机工作辊热变形研究

热带钢连轧机工作辊下机后尚未完全冷却即进行磨削,残存的不均匀热变形导致磨削的工作辊辊形在空冷一段时间上机时很难达到工艺设定值.针对热辊形不易测量的特点,制定合理的物理测量方式,准确地测量了工作辊下机后的温度分布和热辊形.考虑复杂的工作辊换热边界条件,采用有限差分法对工作辊空冷时的温度场和热变形进行了数值模拟,计算结果与测试结果吻合良好.对工作辊下机后不同时刻的热变形进行仿真,通过将目标上机辊形和磨削时热辊形叠加来设定磨削辊形,为实现合理的辊形磨削提供了依据和计算方法.     

Modification of a classical formula for determination of roll flattening in flat rolling

Local elastic roll flattening in direction of the roll axis in flat rolling is one of the important displacement components related to the roll gap shape. Up to now some classical formulae to solve roll flattening have been proposed. These formulae were derived from the elastic half space theory or the 2-dimensional contact theory. On calculating the flattening of the back-up roll they may result in a great deviation. In the present effort a comparison was made between the flattening results obtained by a 3-dimensional finite element method and by a classical formula. The relation between the deviation and the back-up roll geometry was also examined and therefore the classical formula was modified. Calculated results indicate that the modified formula can more accurately predict the back-up roll flattening.     

板带热轧工作辊温度场的研究

根据热轧工作辊的热力学方程及边界条件，采用有限差分法，建立了工作辊温度场的数学模型，并进行了实验验证，为研究工作辊的热变形提供了依据。     

超高强钢冷轧过程轧制力计算的改进模型

 为了解决采用圆弧模型计算超高强钢冷轧过程轧制变形区轧辊压扁曲线误差较大的问题,充分考虑到超高强钢的轧制特点,通过分析不同压扁半径下轧辊压扁曲线的变化规律,构造出新型轧辊压扁曲线函数模型,给出了该函数中轧制变形区接触弧长特性参数与轧辊压扁曲线特性参数的求解方法。基于此,根据弹塑性理论中的变形与应力关系,推导了入口弹性变形区、塑性压下变形区以及出口弹性变形区单位轧制压力分布计算过程,建立了超高强钢冷轧过程总轧制力计算模型。并将其推广应用到某钢厂2030冷连轧机组,验证了该模型的计算准确度。结果表明,超高强钢冷轧过程轧辊压扁曲线用二次函数表示,更能准确反映轧辊压扁状态,其计算结果与实际值具有较高的吻合度。同时,为冷连轧机组生产超高强钢产品极限轧制能力的评估与轧制规程的制定提供了理论依据。     

中厚板轧制过程侧弯模型及控制策略

为建立中厚板侧弯模型并为制定侧弯控制策略提供理论依据,针对影响函数法局限性和P-H图的不足,在轧辊刚性及工作辊凸度二次抛物线分布假设的条件下,通过理论分析推导了辊缝刚性倾斜量方程、出口轧件楔形方程、轧件厚度分布方程、单位宽度轧制力分布方程、力平衡方程和力矩平衡方程,在此基础上建立了出口轧件侧弯及其控制数学模型。理论研究表明,只要轧件横向温度对称分布,无论侧弯源于何种因素,中厚板出口侧弯控制模型具有一致性。研究结果为侧弯缺陷的反馈控制奠定了理论基础。     

厚板冷矫直机辊系承载能力分析

采用理论校核和有限元分析两种方式,对冷矫直机辊系承载能力进行了分析。二者计算结果比较接近,证明了所采用的有限元模型是正确和精确的。并利用所采用的有限元模型,对实际支承辊辊型条件下冷矫辊系承载能力进行了分析,计算结果与实际情况相吻合。