板带轧制在线控制模型的研究

为解决板带轧制高速高精度在线模型问题,文章基于能量变分原理,研究了一种快速数值算法。该法将变形区划分为有限离散单元,考虑剪切变形作用,建立了高速计算模型,在平面变形条件下实现了对轧制力的仿真。计算结果与实测值、Marc有限元计算结果有很好的吻合。通过对某厂五机架冷连轧的分析,模型可在0.3s内完成全部计算。该算法对深入研究冷热态连轧过程在线控制具有重要实际意义。     

基于流函数法的铝合金板材异步轧制应变计算数学模型

作为一种剧烈塑性变形技术，异步轧制是提高铝合金板材变形均匀性的重要方式。但由于异步轧制中存在多变量、强耦合、非线性等特点，其厚度方向变形机制难以精准解析。为深入研究异步轧制厚度方向变形情况，建立了一种板材异步轧制沿厚度方向应变计算模型。根据轧制过程的运动学特点，变形区被分为刚性-塑性-刚性区。在此基础上对变形区边界条件进行了修正，并采用流函数法建立近真实的运动学容许速度场。根据最小能原理和线性化积分手段建立了轧制功率消耗模型，解决了计算过程中的多参量非线性耦合问题，实现了变形区边界模型的快速计算。结合速度分量与应变速率分量，最终建立了异步轧制轧后应变计算模型。为了验证理论模型的准确性进行了数值模拟与异步轧制试验。与试验结果进行对比，计算结果最大误差为13.44%，最小误差为1.33%，整体计算耗时缩减到1 s以下。模型的建立可为异步轧制板材质量调控与预测提供重要理论参考。     

坯料厚度及轧制规程对厚规格管线钢落锤撕裂性能的影响

厚规格管线钢板随其厚度的增加, 落锤撕裂性能控制难度急剧增加, 成为管线钢开发的关键技术。本文对厚规格管线钢板生产过程中铸坯厚度、未再结晶区压下率、变形速率及轧制规程优化设计对粗轧阶段的变形渗透及钢板落锤撕裂性能的影响规律进行了分析研究, 并进行了工业化轧制试验。结果表明: 轧制相同规格(22 mm厚)管线钢板时, 铸坯厚度由300 mm增加到400 mm, 钢板落锤剪切面积由85%～90%提高到90%~100%; 采用相同坯料(400 mm厚)轧制25 mm厚度管线钢板, 通过优化轧制规程, 钢板落锤剪切面积由85%~90%提高到90%~95%。     

Prediction of influence parameters on the hot rolling process using finite element method and neural network

In the present investigation, a hot rolling process of AA5083 aluminum alloy is simulated using the finite element method. The temperature distribution in the roll and the slab, the stress, strain and strain rate fields, are extracted throughout a steady-state analysis of the process. The main hypotheses adopted in the formulation are: the thermo-viscoplastic behavior of the material expressed by Perzyna constitutive equation and rolling under plane-deformation conditions. The main variables that characterize the rolling process, such as the geometry of the slab, load, rolling speed, percentage of thickness reduction, initial thickness of the slab and friction coefficient, have been expressed in a parametric form giving a good flexibility to the model. The convergence of the results has been evaluated using experimental and theoretical data available in the literature. Since the FE simulation of the process is a time-consuming procedure, an artificial neural network (ANN) has been designed based on the back propagation method. The outputs of the FE simulation of the problem are used for training the network and then, the network is employed for prediction of the behavior of the slab during the hot rolling process.     

中厚板轧制过程的数值模拟

以L245级管线钢材料的热物性参数(密度、泊松比、杨氏模量、热膨胀系数、热导率和比热)和热模拟压缩实验获得的高温变形时应力—应变曲线等试验数据为基础,在MSC.Marc软件中建立了该钢种材料数据库,并建立了中厚板多道次轧制过程的二维有限元模型。以铸坯厚度为220mm、成品厚度为25.4mm的热轧过程为例,通过对轧件与轧辊接触面间换热系数采用取不同常数值的方法,并依据其生产时所采集的各道次相关工艺参数,对该轧件全道次热轧过程进行了数值模拟,将各道次的轧制力计算值与实测值进行了分析比较,确定了轧件与轧辊间接触面换热系数的最佳值。利用本文模型对厚度为180mm的轧件单道次轧制过程进行了数值模拟,研究了不同变形工艺参数(轧制温度、道次压下率和轧制速度)对变形区等效应变和等效应力的影响。结果表明,在轧机设备能力及生产现场条件允许时,高温粗轧阶段纵轧道次可采用低速大压下率进行轧制成形,使变形较充分地向轧件芯部渗透,从而使钢板获得细小均匀的晶粒组织,有效改善钢板的强韧性能。     

中厚板残余应变的工程计算方法

针对合金元素含量较多的中厚板在轧制过程中其残余应变对轧制力的影响无法通过自学习来克服的问题,在常规变形抗力模型的基础上,分析了残余应变对中厚板变形抗力的影响,并由此提出了残余应变的工程计算模型。应用表明,该模型能使变形抗力的计算误差控制在7%以内。     

不同变形区组成下铝合金厚板蛇形轧制板曲率建模分析

蛇形轧制作为一种新型的轧制工艺为高性能厚铝板生产提供了一种新方法,但是传统的异步轧制弯曲曲率模型不能用于蛇形轧制,蛇形轧制缺少精准的轧后曲率计算模型。根据变形区的特征及中性点的位置,确定了变形区组成及其存在边界条件;塑性变形区最多可分成4个区,对不同组成情况的变形区进行了分析,建立了各种情况下单位压力和上、下部分累积剪应变偏差模型,在此基础上建立了剪切应变引起的弯曲曲率模型,根据流动准则建立了轴向应变引起的弯曲曲率模型,最终建立了不同辊径比下的蛇形轧制的弯曲曲率模型。考虑到厚度方向变形的不均匀性,在建模过程中引入均匀系数E,使模型更加精确。采用Ansys模拟和实验数据进行了模型精度的间接验证。结果表明,与模拟和间接实验结果相比,最大和最小相对误差分别为10.71%和0.34%,证实了模型精度,可应用于弯曲曲率预测及控制;同时研究了不同工艺参数（偏移量、辊径比、压下量、工件初始厚度等）对弯曲曲率的影响规律。研究结果为厚规格铝板蛇形轧制生产提供重要理论和技术支持。     

A comparative study of slab deformation under heavy width reduction by sizing press and vertical rolling using FE analysis

A detailed comparison between the quality of slabs formed by sizing press and vertical rolling mill is presented. ABAQUS/explicit commercial finite element software with elasto-viscoplastic constitutive model for material is used to study the geometric characteristics and deformation pattern during width reduction in these processes. Finite element models developed for both sizing press and vertical rolling processes are validated by comparing their results with experimental data available in literature. Parametric studies are performed using validated finite element models for sizing press mill to determine the effect of input process parameters such as initial slab width and thickness, width reduction and transfer pitch on the process outputs such as dogbone formation, head and end fishtail profiles, width necking at the leading end of the slab and slab edge quality. Similarly, developed finite element models for vertical rolling are used to investigate the effects of different input parameters on the slab deformation after passing through a vertical rolling stand with the aim of comparing the two width reduction processes. According to the results, benefits and drawbacks of each width reduction method are discussed. The enhancing effect of subsequent horizontal rolling after sizing press and vertical rolling processes on the final slab thickness is also presented.     

AZ31B镁合金中厚板轧制热力耦合场数学模型

采用Gleeble-1500D热力模拟试验机对铸态AZ31B镁合金圆柱试样进行了宽范围变形条件下的热压缩试验,拟合热压缩试验数据,针对镁合金应变软化特性建立了一种新的热力本构模型;依托于Deform-3D对镁板的实际热轧过程进行了热力仿真分析,依据轧制理论假设、宏观连续介质力学以及热力学原理,采用数学解析的方法建立了镁板热轧制区域中的应变、应变速率值分布模型以及三维温度场、应力场数学模型。研究结果表明:新建的热力本构模型预测精度较高,平均相对误差为5.1%;建立的轧制变形区域中的应变、应变速率值分布模型,温度场数学模型以及热力耦合场数学模型不仅形式简单易于为生产利用,更能精确表征中厚规格镁板热轧制过程中的热-力耦合变形机制。     

700 MPa级汽车大梁钢混晶组织问题研究

针对邯钢700 MPa级汽车大梁钢存在不同程度混晶组织的问题,通过对铸坯、中间坯和成品钢板组织及生产工艺的研究,可以明确铸坯原始组织存在枝状晶和块状混晶组织,并且加热工艺不合理、粗轧单道次压下率偏小以及精轧前机架进入部分再结晶区轧制是导致成品钢板混晶组织的主要原因。为此,对生产工艺进行了优化,板坯出炉温度按目标中上限控制,板坯最短在炉时间不低于170 min,均热段停留时间控制在40~70 min;调整R₂机架最后3道次负荷分配来提高单道次压下率,实际压下率按23%~30%控制,为奥氏体充分再结晶提供必需的变形量;通过调整精轧穿带速度和增开机架间冷却水来提高轧制速度,使成品钢板混晶组织问题得到明显改善且提高了低温冲击性能,减少了用户加工开裂和后续服役疲劳断裂的风险。     

Slab analysis of asymmetrical sheet rolling

In this paper, a theoretical model based on slab method of analysis for plane strain asymmetrical rolling is presented. In this model the non-uniformity of the normal and shear stresses in deriving of the governing equations are considered. This model can predict the required external loading to the plate at entry to keep the plate horizontal. The analytical rolling force, torque and pressure of this model were compared with the experimental and analytical results of other investigators. Numerical and experimental results are shown to be in good agreements.     

板材轧制问题中的变形与应力

根据全息干涉法对板材轧制成形中的变形进行分析，假设三种典型轧制板的截面形状模型，计算了纵向非均匀应变分布，给出了其所产生的残余应力及其失稳起皱时的临界参数计算公式。与实测结果比较，变形的最大误差为11％。     

INFLUENCES OF EDGING ROLL SHAPE ON THE PLASTIC STRAIN DISTRIBUTION OF SLAB DURING MULTI-PASS V-H ROLLING PROCESS

Multi-pass slab vertical-horizontal （V-H） rolling process with variable edging roll shape have been simulated with explicit dynamic finite element method and updating geometric method. The distributions of plastic strain contour in slab daring rolling process with different edging roll and under different rolling stage have been obtained. The results show that there exist two thin strain assembling zones in slab when the flat edging roll is used, and there just exist one strain assembling zone in slab when the edging roll with groove is used. And compared the deformation equality between flat edging roll and edging roll with groove, the lateris better than the former, which supplies the theory prove to the slab deformation distribution during V-H rolling process and is helpful for predicting the slab texture.     

底板导轨的辊压与冲压加工工艺比较

针对继电保护箱体底板导轨加工过程中容易发生较大的翘曲变形、加工面回弹较大的问题,通过分析两种加工工艺——辊压与冲压工艺的特点,利用Ansys软件对底板导轨受力进行仿真分析,模拟底板导轨的受力变形状况,并依据底板尺寸设计出相应的模具,同时对冲压模具与冲压工艺进行改进,最后选取机床进行试验对比,验证了模拟结果与生产实际基本一致。结果表明:辊压成形变形最大约为20 mm,变形较大,对螺钉紧固、插件安装有较大影响;冲压工艺变形为2 mm,装配后基本满足要求。该冲压工艺方法解决了精密机箱加工变形较大的问题。     

AZ31镁合金板材纵波轧制形变规律及边部损伤分析

纵波轧制+平辊轧制(LFR)是一种减轻镁合金轧制边裂的新型轧制工艺,通过一道次纵波轧制+二道次平轧,可有效减少镁合金板材边裂。为了进一步明晰LFR变形规律,本文通过对比AZ31镁合金板材纵波轧制+平轧(LFR)及平轧+平轧(FFR)热-力耦合有限元虚拟轧制对比和物理实验,分析了纵波轧制变形区金属变形规律及其对板材边部损伤的影响。结果表明：纵波轧制形成了异形搓轧区,板材各部位受到较大的三向剪切作用;急速金属流动产生的塑性变形热避免了板材边部温降,有利于提升塑性;剪切及温度影响促使LFR板材形成混晶组织,降低了波谷部位损伤,进而有效抑制了镁合金板材边裂的产生及发展。     

无缝钢管斜轧单位轧制压力计算

基于斜轧工艺变形特点及斜轧轧制空间关系,采用工程塑性力学方法,建立斜轧轧制单位压力的解析计算方法。分析斜轧空间结构和变形特点及斜轧变形区内变形特征断面的几何关系、变形特征断面内变形单元切块的应力状态,建立变形单元切块的应力微分方程,并求解出斜轧变形区轧制单位压力的计算公式,最后用实例验证轧制单位压力的计算公式。该解析计算方法可用于一般斜轧轧制力能参数的计算,并对斜轧变形进行应力、应变分析。     

“温控-形变”轧制工艺对厚板变形渗透性的影响

为了改善厚规格钢板的内部质量,研究了一种轧制水冷耦合的"温控-形变"新工艺。通过有限元模拟,分析了该工艺对轧件厚度方向轧制变形渗透性的影响规律。分别讨论了冷却工艺和轧制工艺参数对轧件内部变形的作用效果,获得了不同厚度方向温差、钢坯温度及钢坯厚度条件下,"温控-形变"轧制对轧件内部金属流动及变形程度的规律,为工业应用中生产工艺的合理制定提供了参考。     

冷轧铜铝复合板结合界面残余应力分析

针对冷轧铜铝双层板金属的变形特征以及各轧制工艺下界面残余应力的分布情况,采用有限元计算方法,分别将轧制速度、异径同步、异径异步各工艺产生的界面残余应力进行分析。研究结果表明,冷轧铜铝双层板的复合变形过程可分为4部分;铜板复合面的应变直接影响复合效果;异径同步轧制铜铝复合板时,随着辊径比的增大,铜板复合面的总变形量增大,当辊径比大于1．6时,总变形的增量不明显,辊径比取1．4~1．6时,残余应力较小;异径异步轧制铜铝复合板时,随着辊径比的增大,铜板复合面的总变形量增大,轧制速比取1．2~1．4时,残余应力较小。     

Online Use of Physically Based Plasticity Models for Steady State Cold Rolling Processes

A procedure has been developed to incorporate computationally costly physically based crystal plasticity models to calculate texture and anisotropy for steady state forming processes online. When using these models, at every point in the deformed zone, an average and a nonlinear solution procedure for stresses and/or strains in all these grains is required. The online calculation cost is avoided by offline creating a database with texture and anisotropy data for all possible deformation modes of the process. The case studied is a cold rolling process, but can easily be extended to any type of forming process, when the deformation field is known in advance. Textures and anisotropy data are predicted using a viscoplastic self-consistent model, but the method is suitable for any kind of crystal plasticity model. Single crystal plastic parameters, such as the critical resolved shear stress, the single crystal hardening parameters, and the strain-rate sensitivity, have been calibrated based on mechanical tests by means of a direct search simplex algorithm. The online calculated deformation history is compared to the histories stored in the database and the best match is selected. The deformation history is divided in two zones, the one before the neutral point where forward shearing occurs and the one after the neutral point where backward shearing occurs. One online deformation generation and selection procedure requires 0.005 s of CPU time for a database with a division in deformation gradients fine enough to accurately cover all deformations. The method allows calculating yield surfaces at any point in space based on microstructural effects modeled by crystal plasticity, without incremental material updating and necessity to define a kinematic and isotropic hardening, which makes the method suitable for fast models to calculate rolling forces and torques online.     

中厚板边部裂纹缺陷的成因分析及对策

边部裂纹缺陷是中厚板常见的表面质量缺陷之一。分析表明,钢板边部的多条纵向微裂纹是连铸坯轧制过程中棱部侧翻产生的折叠。通过提高钢水纯净度, 控制连铸坯冷却强度,减小横轧展宽量,提高板坯加热均匀性,保证轧制压下量等措施,可大大减轻中厚板边部裂纹缺陷的程度。