不锈钢复合板冷轧过程有限元模拟

研究了双金属复合板中不锈钢复合板的冷轧生产工艺,并用大型有限元软件ANSYS模拟了不锈钢复合板的冷轧过程。建立了包括上下辊、轧件在内的二维模型,采取适当的加载和约束条件,对不锈钢复合板的冷轧做了模拟,最后得出了不同压下条件下,轧制变形区域内应力应变分布情况。并分析出不锈钢复合板首道次的压下条件,这与冷轧带钢厂不锈钢复合板实际的生产工艺条件是一致的。     

铝钢复合材料冷轧变形规律的研究

研究了铝钢复合材料冷轧变形特性,对试验结果进行理论分析和回归分析,得出了一个描述变形特性的方程.研究结果表明,在冷轧过程中,铝钢复合材料的塑性变形、厚度和变形抗力相互影响,对于双金属轧制计算以及双金属冷轧生产过程具有指导意义.     

Q235R-0Cr13双金属复合板矫直扭矩计算模型

在连轧生产Q235R-0Cr13双金属复合板的过程中,提出了一种适用于Q235R-0Cr13双金属复合板的矫直扭矩计算模型,通过实验,证明了该矫直扭矩计算模型基本符合实际需求。     

钨钼复合板辊式矫直力计算模型

在双金属钨钼复合板连轧生产过程中,矫直工艺参数直接影响到钨钼复合板的平直度,而其中最核心的工艺参数就是矫直力。针对传统的辊式矫直机矫直力计算模型仅依据单一材料板材的连续反弯模型,不能准确反应复合板矫直状态的问题提出一种双金属钨钼复合板新型辊式矫直力计算模型,通过实验研究,证明了该计算模型的可行性。     

双金属复合板爆炸焊接参数选择窗口开发

针对爆炸焊接工艺参数多、经验计算公式复杂、计算过程逻辑复杂、人工计算易出错等问题,利用Visual Basic软件进行编程,开发适合双金属爆炸焊接参数选择系统,以方便工业生产中双金属复合板爆炸焊接参数选择。所开发的系统建立了异质金属材料性能数据库,可实现双金属爆炸焊接可焊性窗口的自动绘制,同时可定量计算任意双金属爆炸焊接理论最佳工艺参数。     

冷轧薄板接触弧长的确定及轧制压力计算

本文在计算冷轧薄板接触弧长度和轧制压力时,不仅考虑轧辊弹性变形,而且也考虑轧件弹性变形。把变形区分为入口弹性区、塑性区和出口弹性区。应用弹性力学基本方程、塑性条件和平板压缩理论导出了入口弹性区和出口弹性区单位宽度轧制力公式及塑性区平均单位压力公式。应用弹性接触理论和变形区的几何关系导出了计算冷轧薄板接触弧长度公式。最后给出了考虑轧辊和轧件弹性变形时计算冷轧薄板的总的轧制力公式。该公式不仅适用于一般工程计算,而且也能为在线控制的电子计算机提供较为精确的轧制力数学模型。     

二次冷轧过程变形区油膜厚度模型

为了定量预报二次冷轧过程轧制变形区油膜厚度,结合二次冷轧机组乳化液直喷系统的设备与工艺特点,分析了带钢表面析出油膜、工作辊表面附着油膜的形成机理,建立了一套二次冷轧过程轧制变形区带钢上下表面油膜厚度模型,定量分析了乳化液流量密度、乳化液浓度、乳化液析出距离、轧机入口轧制速度、轧制咬入角、带钢入口变形抗力、后张力、轧制油初始动力黏度、轧制油压力黏度系数对轧制变形区带钢上下表面油膜厚度的影响,并将该模型应用到某1220二次冷轧机组的生产实践,编制出了相应的模型计算软件,实现了二次冷轧过程变形区油膜厚度的预报,为二次冷轧过程润滑性能的控制奠定了理论基础。     

CNT纤维增强功能梯度复合板非线性建模与仿真

基于一阶剪切变形假设和哈密顿原理建立了碳纳米管(Carbonnanotube,CNT)增强功能梯度板大变形非线性有限元模型,实现了CNT纤维增强功能梯度复合板在发生大变形时的准确计算。该非线性模型不但包含几何全非线性应变—位移关系,还考虑薄板结构法向发生大转角的情形。通过与已有数据对比验证了所建模型的准确性。利用所建模型对四种典型的CNT分布形式,即均匀分布、O型分布、V型分布和X型分布的CNT纤维增强功能梯度复合板进行几何大变形非线性计算和分析,讨论CNT体积分数、CNT分布方式、结构宽厚比和载荷对CNT纤维增强功能梯度复合板的影响。研究表明:随着CNT体积分数的增加,该功能梯度复合板的刚度随之增加;相同体积分数下,X型分布复合板的刚度最大,均匀分布和V型分布次之,O型分布复合板的刚度最小。为CNT纤维增强功能梯度复合板的工程应用提供参考。     

散裂中子源用Cd复合板的制备技术

在新一代散裂中子源中,Cd复合板成为其中不可或缺的减震材料。通过对4种Cd复合板制备技术(热等静压复合、爆炸复合、冷喷涂复合、冷轧复合)的介绍及比较,指出热等静压结合适当热处理可以制备出性能优异的Cd复合板,同时提出了未来可以采取爆炸+冷轧复合的技术制备Cd复合板。     

坡口形式对双金属复合板多层多道焊接头残余应力演变的影响

采用TIG焊制备了13 mm厚Incoloy825/X52双金属复合板的对接接头,采用数值模拟与试验手段相结合的方法,分析了不同坡口形式对复合板接头焊接残余应力分布的影响,揭示了双金属复合板多层多道焊过程中残余应力的演变特征。结果表明：对于双金属复合板而言,复合型及V型坡口接头内部最高应力集中区域均位于过渡层内,沿水平方向呈现长条状分布,坡口形式的变化对于接头内部和表面应力的分布特征及峰值没有明显影响;从残余应力的产生和演变过程来看,只有当复合板接头的基层、过渡层和复层都焊接完成后,过渡层内才会产生最高应力集中区域;此外,最终焊道对复合板接头的应力分布起着决定性作用,会对最终应力状态产生很强的牵引作用,使其呈现偏离试板中心线的不对称分布。     

Study on the improved accuracy of strip profile using numerical formula model in continuous cold rolling with 6-high mill

The quality requirements for thickness accuracy in cold rolling continue to become more stringent. In cold rolling mill, it is very important that the rolling force calculation considers rolling conditions. The rolled strip thickness was predicted using calculated rolling force. However, the prediction of strip thickness in cold rolling is very difficult; in particular, for 6-high mill with shifted intermediate roll (IMR), the accuracy of thickness is not good. In this study, to improve the accuracy of rolled strip thickness, the roll gap flattening can be given based on Hertz contact theory, with contact between rolls and the smooth cylindrical rolls for the rolling elastic deformation. Also, the distribution of the roll gap flattening may be calculated using the contact force of unit transverse length. The strip profile at the continuous cold rolling is calculated by using the numerical analysis model considering the initial strip profile before cold rolling. Hence, we propose that the numerical model can predict the rolled strip profile more quickly and accurately and be applicable to the field. The results of the proposed numerical model were verified by FE-simulation and cold rolling experiments of 6-high mill with five stands.     

Control of surface thermal scratch of strip in tandem cold rolling

The thermal scratch seriously affects the surface quality of the cold rolled stainless steel strip. Some researchers have carried out qualitative and theoretical studies in this field. However, there is currently a lack of research on effective forecast and control of thermal scratch defects in practical production, especially in tandem cold rolling. In order to establish precise mathematical model of oil film thickness in deformation zone, the lubrication in cold rolling process of SUS410L stainless steel strip is studied, and major factors affecting oil film thickness are also analyzed. According to the principle of statistics, mathematical model of critical oil film thickness in deformation zone for thermal scratch is built, with fitting and regression analytical method, and then based on temperature comparison method, the criterion for deciding thermal scratch defects is put forward. Storing and calling data through SQL Server 2010, a software on thermal scratch defects control is developed through Microsoft Visual Studio 2008 by MFC technique for stainless steel in tandem cold rolling, and then it is put into practical production. Statistics indicate that the hit rate of thermal scratch is as high as 92.38%, and the occurrence rate of thermal scratch is decreased by 89.13%. Owing to the application of the software, the rolling speed is increased by approximately 9.3%. The software developed provides an effective solution to the problem of thermal scratch defects in tandem cold rolling, and helps to promote products surface quality of stainless steel strips in practical production.     

板带钢冷轧乳化液及润滑效果研究

针对冷轧无间隙原子钢(IF钢),配制了2种不同的乳化液,并将其与国内、国外商品级乳化液的冷轧实验进行对比。实验发现乳化油中基础油的选择对乳化液冷轧润滑效果的影响很大,当基础油含饱和脂肪酸高时乳化液润滑能力好,可以用乳化液皂化值来衡量乳化油冷轧润滑效果的优劣。一般皂化值高的乳化液可用来冷轧屈服强度较高、成形较困难的板带钢。使用乳化液冷轧后的表面形貌明显优于无润滑状态的轧后表面。在乳化液冷轧润滑过程中,当压下率较低时,轧件的表面质量有所改善,总压下率超过90%以后,轧件的表面质量又呈下降趋势。     

Occurrence of surface defects on strips during hot rolling process by FEM

During a hot rolling process, surface defects on strips can severely affect the quality of the rolled product, particularly for two conditions: (1) there are initial defects on continuous casting slabs that propagate and/or are inherited from those on the surface of rolled steels from upstream rolling processes; and (2) there are no initial defects on continuous casting slabs, and they consequently appear on the surface of rolled steels due to improper rolling technologies. In this paper, the authors present a new 3D finite element model coupled with constrained node failure to understand better the initiation and growth of surface defects on strips during the hot rolling process for case 2. The strip deformation processes were simulated for various rolling reduction ratios and friction coefficients between the roll and the strip. The occurrence of surface defects on strips was modeled under some rolling conditions. The plastic strain distribution in strips and the rolling forces were obtained. The risk of occurrence of surface defects on strips increases as the friction between the roll and strip increases for the same reduction ratio.     

A thermal analysis of strip-rolling in mixed-film lubrication with O/W emulsions

Increase of both roll and strip surface temperatures can significantly affect a rolling process, roll conditions and strip mechanical properties. A comprehensive thermal analysis in cold rolling, especially in a mixed film regime, is needed to understand how thermal fields develop in roll and strip during rolling. It requires a simultaneous solution of the mixed film model for friction in the roll bite and the thermal model for roll and strip thermal fields. This paper presents a numerical procedure to analyse strip rolling process using lubrication with oil-in-water (O/W) emulsions. The thermal model includes the effect of heat generation due to the strip deformation and frictional shear stress at the asperity contacts. The numerical analysis employs a coupled thermal model and a mixed film lubrication model for calculating the friction and the asperity deformation in the bite. The thermal model considers the initial temperatures of the roll and strip, temperature rise due to the strip plastic deformation and friction. While the O/W mixed-film lubrication model takes into account the effect of surface roughness and oil concentration (%vol) of the emulsion. The thermal effect is analysed in terms of strip surface temperature and roll temperature, which are influenced by rolling parameters such as reduction, rolling speed, oil concentration in the emulsion. The results of the parametric study indicate that the effect of oil concentration on the thermal field is relatively small compared to that of reduction ratio and rolling speed. The reduction ratio increases the maximum interface temperature in the roll bite. In the mixed film regime, rolling speed also increases the maximum interface temperature and alters the temperature field of the strip. The numerical procedure was validated against known experimental data and can readily be extended to hot rolling or used to analyse roll strip temperature subjected to different cooling system.     

带材轧制过程应力及变形的计算机仿真

用三次样条流线条元法分析带材的三维塑性变形,用分割模型影响系数法分析辊系的弹性变形,用BP神经网络方法对轧后带材板形进行模式识别,将三者联立,对900 mm HC轧机冷轧带材轧制过程进行了计算机仿真,得到了较为详细的应力及变形的仿真结果。仿真实例表明,提出的方法和模型符合实际,对三维轧制理论、板形理论及控制技术的发展有重要意义。     

Coupled dynamic modeling of rolls model and metal model for four high mill based on strip crown control

The crown is a key quality index of strip and plate,the rolling mill system is a complex nonlinear system,the strip qualities are directly affected by the dynamic characteristics of the rolling mil.At present,the studies about the dynamic modeling of the rolling mill system mainly focus on the dynamic simulation for the strip thickness control system,the dynamic characteristics of the strip along the width direction and that of the rolls along axial direction are not considered.In order to study the dynamic changes of strip crown in the rolling process,the dynamic simulation model based on strip crown control is established.The work roll and backup roll are considered as elastic continuous bodies and the work roll and backup roll are joined by a Winkler elastic layer.The rolls are considered as double freely supported beams.The change rate of roll gap is taken into consideration in the metal deformation,based on the principle of dynamic conservation of material flow,the two dimensional dynamic model of metal is established.The model of metal deformation provides exciting force for the rolls dynamic model,and the rolls dynamic model and metal deformation model couple together.Then,based on the two models,the dynamic model of rolling mill system based on strip crown control is established.The Newmark-β method is used to solve the problem,and the dynamic changes of these parameters are obtained as follows:(1) The bending of work roll and backup roll changes with time;(2) The strip crown changes with time;(3) The distribution of rolling force changes with time.Take some cold tandem rolling mill as subject investigated,simulation results and the comparisons with experimental results show that the dynamic model built is rational and correct.The proposed research provides effective theory for optimization of device and technological parameters and development of new technology,plays an important role to improve the strip control precision and strip shape quality.