轧制变形抗力数学模型的发展与研究动态

建立变形抗力数学模型对变形抗力预测和电子计算机在线控制生产的普及具有重要意义。从传统解析法和人工神经网络法两个角度,系统介绍了国内外建立变形抗力模型的发展应用与研究动态,结合建模中存在的问题,针对性地提出了一些建议。     

热连轧变形抗力模型的优化改进

改进后的志田茂变形抗力模型是比较经典的变形抗力模型,但该模型没有考虑残余应变对于变形抗力的影响,不能完全适应现场生产的需要。作者在分析研究济南钢铁集团有限公司热连轧厂大量实际生产数据的基础上,在原变形抗力模型中考虑了碳质量分数的影响,增加了对应的影响系数,用于修正残余应变的影响,从而使该模型更贴近于现场实际。模型实际应用结果表明,改进后的模型预报精度明显提高,效果良好。     

Thermal camber model for hot and cold rolling

The MDS profile and flatness control system is based on many physical part models. The thermal camber model is the only one of these part models which, apart from the spatial dimensions, inherently depends on the time dimension as opposed to part models like roll bending or even roll wear. This means that work roll temperature and shape keep changing even if boundary conditions like water distribution or strip contact stay constant. The exact mathematical solution of the resulting dynamic equations Is a very time consuming task usually not suitable for on-line purposes. Here a new mathematical approach is presented, which solves the 2-dimensional Fourier heat conduction equation with 3-dimensional boundary conditions at a speed suitable for on-line applications. Furthermore an approximate solution of the Hooke stress strain relations is derived, which translates the temperature distribution of the roll into an expansion distribution. This thermal camber model has been implemented in several hot and cold rolling mills. Data collected there show good agreement with the model.     

基于行处理算法的带钢热连轧负荷分配

负荷分配是带钢热连轧精轧模型设定的基本问题,传统 Newton-Raphson算法存在初始值要求严格、易发散等计算性能较差的缺点。针对其在求解非线性方程组方面的不足,基于行处理法提出了一套适用于热连轧机组快速厚度分配的计算模型。该方法以中间机架出口厚度为变量,在采用高精度、非简化轧制模型的基础上,计算速度快,弥补了传统方法的不足。同时为了加快收敛速度,根据经验统计提出了一种新的初始值的确定方法。并利用C＋＋根据得出的算法编制了计算程序进行分析计算,在采用实测数据基础上的验证结果表明该算法具有运算速度快、收敛性好等优点。     

Three-dimensional hot rolling model for prediction of camber generation

Abstract

A three-dimensional explicit finite element model of the hot rolling process has been developed and used to investigate the generation of camber during the roughing stages of this process. A number of important contributing factors have been studied in detail in an effort to predict their combined effects on camber generation. Predictive equations have been derived which can be used to estimate the level of camber, given suitable values of the dominant process variables. A parallel experimental study has also generated similar empirical relationships. There is reasonable comparison between the predictive and empirical equations, and causes of minor discrepancies are discussed.     

Finite element based model of structure development in the hot rolling process

An existing thermomechanical finite-element model of the hot rolling process is used to simulate the structure evolution in the strip. The equations which describe the grain-size variations during the hot deformation are implemented in the model. The local values of temperatures, strain rates and strains are used in calculations, allowing the determination of the grain-size distribution across the strip. The results of calculations carried out for the seven-stand hot-strip mill are presented in this paper.     

热轧形变量对共析钢珠光体组织球化的影响

利用Gleeble 1500热模拟机进行热压缩试验,研究了不同热轧形变量下奥氏体区形变对共析钢后续珠光体相变组织球化的影响。结果表明,高温奥氏体区形变增加了奥氏体的形变储存能,导致C曲线左移,并且形变可以明显减小珠光体团直径,随应变量增大,珠光体片层间距减小,渗碳体厚度变薄,片层取向多样化。最终的等温球化试验表明,增大奥氏体形变量有利于珠光体的球化效果。     

热轧前滑模型的研究

前滑模型对热轧生产参数的设定有重要意义。基于Orowan微分方程和Sims假设,建立了热轧前滑理论模型,并把该理论模型中相关的3个参数(轧辊半径、入口厚度、出口厚度)优化为2个无单位的参数,采用统计分析法得到简易的经验模型,并分析了各因素的影响。现场实测数据表明:前滑模型计算的最大绝对误差是0.001,最大相对误差是6.93%,能满足在线生产要求。     

基于数字信号处理器DSP的热连轧实时仿真

在热连轧精轧机组的改造或新建过程中 ,如何降低生产风险 ,减少调试时间和降低成本是当前的研究热点。目前主要采用常规的仿真方法来研究 ,但热连轧系统的高度复杂性使得仿真的实时性和准确性受到制约 ,仿真结果对实际的指导作用不大。本文提出的用DSP处理器、工控机、内存映像网以及实物控制器组成的实时仿真系统能对复杂的热连轧过程实现满足精度要求的实时仿真 ,为继续深入这方面研究与应用提供了良好的基础     

热连轧精轧机组温度控制数学模型研究

从现场实际出发研究了精轧各个环节的温度变化过程,分析了带钢热连轧终轧温度与各影响因素之间的关系.同时将温度模型程序化,采用计算机系统进行分析和计算,提出了行之有效的温度模型方案.该温度模型对其它热轧生产线同样适用.     

Microstructural model for hot strip rolling of high-strength low-alloy steels

The microstructural evolution during hot-strip rolling has been investigated in four commercial high-strength low-alloy (HSLA) steels and compared to that of a plain, low-carbon steel. The recrystallization rates decrease as the Nb microalloying content increases, leading to an increased potential to accumulate retained strain during the final rolling passes. The final microstructure and properties of the hot band primarily depend on the austenite decomposition and precipitation during run-out table cooling and coiling. A combined transformation-ferrite-grain-size model, which was developed for plain, low-carbon steels, can be applied to HSLA steels with some minor modifications. The effect of rolling under no-recrystallization conditions (controlled rolling) on the transformation kinetics and ferrite grain refinement has been evaluated for the Nb-containing steels. Precipitation of carbides, nitrides, and/or carbonitrides takes place primarily during coiling, and particle coarsening controls the associated strengthening effect. The microstructural model has been verified by comparison to structures produced in industrial coil samples.     

冷轧窄带钢金属变形阻力的选择

分析了影响冷轧带钢金属变形阻力的变形程度,变形速度和变形温度等因素,并通过实例确定冷轧计算中变形阻力的选择。     

球扁钢轧后冷却弯曲变形理论分析

对球扁钢轧后冷却过程中产生弯曲变形的原因进行了分析,弯曲变形是轧制过程中不一致的压下率和冷却过程中不均匀的温度场相互作用的结果。球头的压下率比腹板小,将导致球扁钢产生弯向腹板方向的变形;腹板的冷却速度比球头快,将导致球扁钢产生弯向球头方向的变形。要根据球扁钢弯曲变形的实际表现形式,分析引起弯曲变形的主要决定因素,采取诸如调整轧制道次压下量分配、对球头进行快速冷却等针对性措施,控制和减小球扁钢的弯曲变形。     

带钢冷连轧材料变形抗力模型研究

针对冷连轧轧制过程的特点,变形程度是影响变形抗力的一个重要因素。建立了变形抗力的机理模型,并将理论模型与实际数据相结合。采用某钢厂生产的低碳钢08AlA稳定轧制时的现场实测数据,利用最小二乘逐次回归变形抗力模型中的各个参变量,并选用不同的方法来获得摩擦系数,选出与实际生产数据相吻合的最佳模型。将回归出的不同变形抗力模型,分别代入轧制力迭代公式进行计算,通过比较与实测轧制力的误差,选出最优的形抗力模型应用于实际生产中轧制力和前滑的预设定。     

基于PCA-DBN的热连轧数据特征提取

在热连轧生产过程中会产生大量的数据,使用这些海量数据进行诊断和预报非常困难,运算时间较长,甚至会导致"维度灾难"。因此,需要对特征进行提取,去除冗余和不相关的特征。提出基于主成分分析-深度置信网络(principal component analysis-deep belief network,简称PCA-DBN)的热连轧数据特征提取,采用主成分分析(principal component analysis,简称PCA)对数据集进行特征提取,并将选择出的特征按照贡献率可视化,直观显示提取的特征。二次特征提取采用深度置信网络(deep belief network,简称DBN)对已提取数据集进行二次特征提取。将最终得到的数据集作为粒子群优化的最小二乘支持向量机(particle swarm optimization-least squares support vector machine,简称PSO-LSSVM)对精轧轧制力进行预报的数据集,以检验特征提取的合理性。试验显示,预报相对误差要小于机理模型预报相对误差,说明提取特征比较合理。     

基于数据挖掘的热轧带钢产品抽样检验优化研究

分析了现有抽样制度下样本代表性低和代表范围窄的主要原因。以“三同”抽样检验制度为分析对象 ,提出了基于数据挖掘技术的热轧带钢抽样检验优化框架。     

武钢热轧1700mm生产线精轧设定模型

热连轧中,精轧设定直接关系着成品带钢的尺寸和性能等,因此显得尤为重要,但是因为其涉及到压力、速度、流量、温度等大量物理参数而难度很大。国内一直依赖进口的精轧设定模型。武钢热轧1700 mm生产线在2008—2009年技术改造过程中,独立开发了完整的具有知识产权的精轧设定模型。     

热轧带钢粗轧区在线温度模型研究及应用

通过对轧件在粗轧区内的传热分析,考虑辐射散热、除鳞水、工作辊与轧件热传导以及轧制过程中变形热,建立了在线温度模型,并采用有限差分法进行求解。将该温度模型应用于某厂1 750 mm热连轧机,应用结果表明,温度模型计算值与实测值吻合良好。     

热轧张力观测器模型的研究与构建

张力观测器模型是微张力控制模型实现的基础,本文提供了一种精确的热轧机架间微张力预报的方法。采用新张力计算模型,结合轧制过程中轧制力臂变化,基于以弹性变形理论为基础的张力方程,设计出张力动态变化的计算方法,由此构建新的热轧微张力控制过程的张力观测器,在生产应用中取得了良好的效果。     

Precision online model for prediction of strip temperature in hot strip rolling

Abstract

Investigated via a series of finite element (FE) process simulation is the effect of diverse process variables on some selected non-dimensional parameters characterising the thermomechanical behaviour of the roll and strip in hot strip rolling. Then, on the basis of these parameters, online models are derived for precise prediction of the temperature changes occurring in the bite zone as well as in the interstand zone in a finishing mill. The prediction accuracy of the proposed models is examined through comparison with predictions from a FE process model.