Research on the Effect of Initial Crown on Hot Rolled Strip Shape

 Based on influence coefficient method, using the software of roll elastic deformation simulation, the effect of entry crown on hot rolled strip shape was researched and analyzed. According to the real condition of certain domestic hot rolled strip factory, the unit crown change from the first stand to the last was calculated when entry crown of hot strip alters. The calculation result shows that the entry crown effect not obviously on the target strip crown at the exit of last stand with the strip shape control reference such as bending force keeping fixed. The reason of calculation was analyzed, the research work refers theory support to strip shape setup modeling and shape control.     

Vibration of Moving Strip With Distributed Stress in Rolling Process

 Take the moving strip between two stands of some cold tandem rolling mill in rolling process as subject investigated, according to the Poisson-Kirchhoff sheet theory, the vibration model of the moving strip in the rolling process was established. Model of distributed stress was built based on rolling theory. And then, vibration model of moving strip with distributed stress was established. The partial differential equation was discreted by Galerkin truncation. The natural frequency and stability of the moving strip were investigated and simulation in time domain was made by numerical method. Take the moving strip between the second stand and third stand of some 1660 tandem mill as subject investigated, distributions of stress, natural frequencies and stability of moving strip were determined under six different rolling conditions which are “uniform distribution of stress”, “flat roll flat”(crown of entrance strip and crown of exit strip are all 0 at the second mill), “flat roll convex”(crown of entrance strip is 0 and crown of exit strip is 20μ), “flat roll concave”(crown of entrance strip is 0 and crown of exit strip is -20μ), “convex roll flat”(crown of entrance strip is 20μ and crown of exit strip is 0) and “concave roll flat”(crown of entrance strip is -20μ and crown of exit strip is 0). At last, three-dimension dynamic simulation was made, the moving law of the strip was determined. This model can be used to study the stability of moving strip, depress the shape wave of strip and develop new rolling technology from the aspect of dynamics theory.     

Analysis of Temperature Field and Thermal Crown of Roll During Hot Rolling by Simplified FEM

Thermal crown of roll is an important factor, which affects strip profile. It is necessary to analyze the temperature field and thermal crown of roll for hot strip mill. A new simplified finite element method （FEM） was used to analyze the temperature field and thermal crown of roll, and corresponding models were built according to the practical boundary conditions. Transient roll temperature field and thermal crown were simulated by ANSYS FEM software with considering transient thermal contact and complex boundary condition. Temperature and thermal crown variations on roll surface nodes were obtained. The thermal crown results of roll obtained by FEM simulation were in good agreement with the measured data, indicating that simplified FEM models and results were correct.     

Analysis of the change of roll thermal crown in 1750 mm hot strip mill

Studied the distributing of roll temperature and the change rule of thermal crown in 1 750 hot strip mill,the result of the test showed that the change of roll thermal crown was affected by the condition of roll cooling and equipmentthe roll thermal crown was obviously improved after altering the pipe and water nib of cooling equipment.From the rule of roll thermal crown changing with the number of strip rolling know that the thermal crown of work roll of Standi is the largest,and Stand 6 is the smallest...     

Development of Strip Flatness and Crown Control Model for Hot Strip Mills

 The strip flatness and crown control model is the foundation of automatic strip shape control. In this paper, considering the metal transverse flows and the inter stand second deformation, the trip flatness and crown control model has been developed , which can be applied to CVC mills and PC mills as well as normal four-high mills. The strip flatness and crown control model has a high precision, and has been successfully applied to the automatic strip shape control system reconstruction of Tangshan Ganglu 1250mm hot strip plant.     

Optimization of Pass Schedule in Hot Strip Rolling

 Rolling schedule not only determines the rolling process to be going smoothly, but also affects the shape accuracy and structure properties of finished strip. In order to gain good strip crown and flatness, the calculation formulas of the most suitable rolling force and bending force are deduced. By taking relatively equal load of rolling power and good shape as objective functions, the optimization mathematical models of finish rolling schedule are established. By contrast, the rolling schedules after optimization can improve the rolling mill working status and ensure the strip crown and flatness to be good. At the same time, the setting value of bending force is improved and this leaves more space for on-line shape control.     

Profile and Flatness Control Technology With a Long Shifting Stroke on Wide Non-Oriented Electrical Steel Sheets

 In order to solve the difficult profile and flatness control problem of wide non-oriented electrical steel sheets, the factors such as the relationship between strip crown control and strip width, the relationship between the maximum wearing value of work roll and the number of a rolling campaign and the wear contour change of work roll were analyzed on the basis of industrial test. Through analyzing the rolling process characteristics of non-oriented electrical steel sheets, the ASR (asymmetry self-compensating work rolls) shape control technology and its roll shifting strategy of the wider non-oriented electrical steel sheets was proposed and developed. When the technology was applied, the number of the wide non-oriented electrical steel (23 mm×1280 mm) in one rolling campaign rose from 40 coils of the trial production to 70 coils of the industrial production, the ratio of the measured strip crown less than 45 μm was increased from 500% to 949%, and the ratio of the measured strip crown more than 60 μm was decreased from 200% to 07%.     

Thermal Crown Model and Shifting Effect Analysis of Work Roll in Hot Strip Mills

Considering the effect of work roll shifting on roll temperature field,a finite difference method of PR format for roll temperature field was presented,which can meet the requirements of accuracy and speed of online calculation.The step-by-step accumulation method was used to simulate the roll temperature field and thermal crown,and the evolution of roll thermal crown in a rolling campaign was studied.And then,the effects of strip width,rolling rhythm and work roll shifting on roll thermal crown were analyzed.It is found that work roll shifting can disperse the thermal expansion of the roll body especially the edge to make roll thermal contour uniform.The effect of work roll shifting on roll thermal crown is mainly concentrated in regions around twice of roll shifting stroke,and the change range of roll thermal crown is±30μm or so in the same roll body location.     

Deviation Prevention Ability of Rollers in Continuous Annealing Furnace and Application

 In order to reduce the strip deviation in the practical production procedure in the continuous annealing furnace, a dynamic simulation model was built through finite element method (FEM) to conduct the quantification calculation of the effect of regular roller contour types on strip deviation. The result reveals that comparing to the flat roller, forward roller contour can prevent the strip deviation to some degree. In terms of prevention ability, double-taper roller is the strongest, single-taper roller and crown roller are less stronger; and more roller contour values raise the prevention ability. Accordingly, optimization method was applied to continuous annealing furnace, and it largely reduced accidents such as strip break and limited speed that are caused by the deviation.     

Two-Dimensional Transient Temperature Field of Finish Rolling Section in Hot Tandem Rolling

Comprehensively considering the factors such as descaling cooling, air cooling, watercooling, frictional heat and deformation heat in gap of every stand, heat conduction betweenwork roll and strip etc, a model of two-dimensional transient temperature field of finish rollingsection in hot tandem rolling was built with finite difference method to calculate the temperaturefields of strip and work roll. So two-dimensional accurate analysis and calculation of strip tem-perature were realized, and the theoretical basis for predicting and controlling strip temperaturewas provided. The simulated results show that the model is practical and reliable.     

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 ...     

板宽对4辊CVC热轧机板形控制能力的影响

采用流面条元法分析带材的三维塑性变形，影响系数法分析辊系的弹性变形，并将二者耦合，建立了4辊轧机板形和板凸度的分析计算模型，并针对板宽对4辊CVC热带钢轧机板形控制能力的影响进行了仿真研究。仿真结果表明，随着板宽的增加，出口板凸度先增大后减小，辊缝变得越来越平缓；单位宽度辊间压力增大，且沿横向的变化比较均匀；板带的宽展减小。对热带钢轧制，乃至厚板轧制具有重要的意义。     

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.     

六辊冷连轧机中间辊横移过程辊间接触压力分析

为了使轧机板形控制性能适应带钢规格材质变化,用于连续轧制高档冷轧薄带钢的六辊冷连轧机大都采取中间辊可横移技术。但是,中间辊横移必定使辊间接触压力分布更不均匀,导致出现接触压力尖峰。在中间辊横移过程中,辊间接触压力和横移阻力都会随横移速度的变化而发生改变,并可能导致辊间接触压力在轧辊端部形成更大的压力尖峰,从而造成轧辊磨损不均匀并缩短轧辊的使用周期。通过建立有限元仿真模型,以仿真模拟获得中间辊横移过程中辊间接触压力的变化规律后,优化设计轧辊辊形,并且提出使用非对称弯辊力的方法,实现了辊间接触压力的分布均匀化,降低了辊间接触压力尖峰值,并延长了轧辊的使用寿命。     

板带轧制过程多参数耦合模拟系统的开发

考虑轧件和辊系间的接触力与变形协调关系，采用一种选代的方案，开发了一个分析三维板带轧制过程的计算机模型。它耦合了计算轧件变形的三维刚塑性有限元法，计算辊系变形的影响函数法和弹性有限元法。该系统可用来精确预报轧制压力横向分布，前后张力横向分布，金属横向流动，以及轧后板带的横向板厚分布，包括板凸度和边部减薄等，并且具有较高的计算效率。     

冷轧工作辊热凸度及其对板形影响

冷轧过程中工作辊的热凸度变化是决定带材板形质量的重要因素,研究分析工作辊的热变形及其对板形的影响对于提高带材质量有着重要的意义。以某厂1 450 mm冷连轧生产线为研究对象,运用大型有限元分析软件ANSYS与LS-DYNA分别建立四机架与五机架的工作辊二维热凸度有限元仿真模型和三维有限元轧制仿真模型,并将2个仿真模型相结合,分析热凸度变化对板形的影响规律、工作辊上机后的热辊形变化过程及其对板形的影响规律,进一步分析轧制速度改变引起的热辊形变化对板形的影响以及乳化液温度、边部预热宽度对板形的影响,为以后冷轧板形质量提升提供了基础。     

Thermomechanical Behavior of Work Rolls During Warm Strip Rolling

A mathematical model was developed to assess thermomechanical behavior of work rolls during warm rolling processes. A combined finite element analysis-slab method was first developed to determine thermal and mechanical responses of the strip being rolled under steady-state conditions, and then, the calculated roll pressure and temperature field were utilized as the governing boundary conditions for the thermomechanical problem of the work roll. Finally, the thermomechanical stresses within the work rolls were predicted by a thermoelastic finite element approach. The results of the model indicate that, in warm strip rolling, thermal and mechanical stresses developed in the work rolls are comparable, and thus, both thermal and mechanical aspects of the problem should be considered in such a problem. Besides, the model was shown to be capable of determining the effects of various rolling parameters on the thermomechanical behavior of the work rolls during warm rolling process.     

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.     

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.