Rolling process analysis of aluminum strip by a coupled thermo-elastic-plastic model

The phenomenon of longitudinal curvature on an aluminum strip caused by different heat conduction boundary conditions on the top and bottom surfaces of the strip while it undergoes a rolling process is studied. This research adopts large deformation-large strain theory to develop rolling process analysis of an aluminum strip by a coupled thentto-elastic-plastic model using the updated Lagrangian formulation (ULF) and incremental method. The flow stress of the materials is considered as a function of strain, strain rate and temperature, and the finite difference method is used simultaneously to solve equations of transient heat transfer. Finally, the numerical analysis method developed from this study is used to determine the temperature change and deformation of an aluminum strip when it undergoes hot rolling. At the same time, the simulation results on normal stress and contact angle are compared with the results of experiments and other published references; the comparison results verify that the present model is reasonable.In addition, the average rolling force during hot rolling is simulated and comparison is also made with the results of experiments provided by the China Steel Corporation. The simulated results in this article are generally considered to be reasonable.     

热连轧铝温度场数值模拟及工艺参数影响分析

采用二维交替差分法建立了铝热连轧轧件温度计算模型,同时采用粒子群算法对模型参数进行了优化。经验证,优化后模型的计算精度在10℃以内;利用建立的温度模型研究了铝板带在热轧生产过程中的温度场变化规律,并分析了工艺参数对轧件终轧温度场的影响。研究结果表明,粗轧区轧件温度分布主要由接触导热与轧件内部的热生成两者共同决定,而精轧区还要受到乳液喷淋的影响;轧制速度越大,轧件终轧温度越高,横向温差越大;处于相同机架间的冷却集管的冷却能力几乎相同,而处于不同机架间的冷却集管,随着机架数的增加,冷却能力增强,横向温差随着开启度的增大而减小;轧件宽度对轧件终轧温度的影响很小,而横向温差随轧件宽度的增大而增大;随着乳化液温度的升高,轧件终轧温度升高,而乳化液温度对轧件横向温差没有影响。     

板带热轧工作辊热凸度模拟软件的研究

根据热轧带钢工作辊在工作中的实际传热情况, 将工作辊对称地分为轧制区、非轧制区、辊肩、辊端和辊颈5个部分, 充分考虑热轧工作辊的实际环境对轧辊温度场和热变形的影响, 来确定轧辊的热边界条件; 再利用有限差分法建立工作辊温度场及热变形的数学模型, 并利用VC++平台进行模拟研究, 建立适合在线计算的快速模拟软件; 最后分析了轧辊直径和压下率对轧辊热凸度的影响。     

注射模冷却过程数值模拟研究

介绍了塑料注射模冷却过程数值模拟的数学原理、实施方法和发展历史。一维瞬态传热模型采用有限差分法计算;二维冷却模拟用有限元法和边界元法计算注射模典型截面温度分布,并在此基础上实现冷却系统参数优化设计;基于中心层的三维冷却模拟采用中心层替代上、下模腔面,在求解出中心层温度分布后,通过计算温差来确定上、下模腔面的温度场。     

A study of thermal-mechanical modeling of hot flat rolling

Mathematical modeling of the thermal and mechanical events during hot flat rolling is considered. The difficulties in arriving at accurate and consistent results are identified as those involving the boundary conditions of the process. These refer to the roll/strip heat transfer coefficient and the shape and magnitude of the roll gap contact surface. The effects of the variations of these parameters on the resulting calculations are studied.     

热轧带钢头部翘曲有限元研究

结合宝钢2050热轧粗轧机组实际轧制工艺,建立带钢非对称轧制有限元模型.主要研究了在带钢轧制过程中,当板厚、压下量不同时上下辊速比、带钢上下表面温差对带钢头部弯曲的影响规律,并且对调整辊速比控制因上下表面温差造成的头部翘曲问题进行了详细分析,并回归出其关系模型.实践表明仿真研究结果可对热轧过程带钢头部翘曲自动控制模型提供修正数据.     

铝合金轧制过程中的热力耦合分析

通过铝合金在Gleeble-1500上的实验数据,建立了本构方程.根据弹塑性热力耦合大变形有限元理论,获得了热轧过程中的数值仿真模型,分析了压下率、轧制速度以及接触传热系数等参数对温度和流动应力变化规律的影响,并与某铝厂热轧板带生产过程中不同压下率下的力能参数变化进行了对比,计算结果表明模拟值与实测值吻合较好,误差低于15%.     

高速线材热连轧过程温度场数值模拟

通过对高速线材轧制过程各个环节传热关系及边界条件的分析,采用有限差分法建立了热连轧过程三维温度场计算模型。结合生产实践,利用该模型对整个连轧过程进行了温度模拟,得出轧件同一截面上心部、中部和外表面上从出炉到吐丝共26道次的温降曲线,计算结果和实测值吻合较好。     

6CrW2Si钢制镶条淬火过程温度场数值模拟及试验

折弯模镶条淬火冷却时温度的瞬态分布特性对于研究6CrW2Si钢淬后变形机理有重要作用。考虑热物性参数、对流换热等因素随温度变化的影响,推导相变潜热转换为等效比热的定量解析并写入程序,建立了淬火过程三维温度场的非线性瞬态数学模型。通过金相观察、XRD物相分析和显微硬度测试方法对6CrW2Si钢镶条组织成分进行了试验研究。结果表明:表面换热边界条件和热传导两因素在不同时刻对零件的冷却速度交替起主导作用;65 s左右时马氏体转变所释放的潜热使得冷却速度有较大幅度降低,心部较表面所受影响大;冷却过程中镶条横截面的温度场由两表面交接处至心部呈梯度分布;零件只发生马氏体转变,且被淬透,最终得到的组织为马氏体+残留奥氏体+碳化物。     

铝材铸轧过程中成型界面传热行为的仿真

在铝材铸轧过程中，材料凝固和冷却所释放的热量都要通过成型界面传导给辊套，并最终由辊套内部的冷却水带走。在分析铸轧过程中传热特点的基础上，建立了传热过程的基本方程与数学模型，并针对3种典型的铸轧工况进行了界面传热行为的仿真研究。结果表明：随着铸轧过程的进行，成型界面的温度差值和热流密度均显著减小，因此，热量传递主要在铸轧区的前半段进行；随着铸轧速度的提高，铸轧区内辊套表面的最高温度不断下降，导致成型界面上的温度差值不断增大，界面热流密度增大并趋于均匀，从而提高了界面的传热能力。     

Development and application of coupling model of aluminum thin-gauge high-speed casting

Based on the analyses of aluminum melt flow, solidification, heat transfer during the process of twin-roll casting, a coupling mathematical model of aluminum thin-gauge high-speed casting was developed, which included the casting roller shell. At the same time, Galerkin method was adopted to solve the coupling model. The fluid field and temperature field of aluminum melt in casting zone, the temperature field and thermal stress field of roller shells were simulated by the coupling model. When the casting velocity is 7 m/min, and the thickness of strip is 2 mm, the circumfluent area comes into being in the casting zone, and the mushy zone dominates the casting zone, while the temperature of melt decreases rapidly as it approaches the rollers. The temperature of the roller shell varies periodically with the rotation of roller, and reaches the highest temperature in the casting zone, while the temperature of roller shell decreases gradually as it leaves the casting zone. The difference of thermal stress between the inner surface and outer surface of the roller shell is very large, and the outer surface suffers tensile-compressive stress.     

A multiscale coupled Monte Carlo model to characterize microstructure evolution during hot rolling of Mo-TRIP steel

A multiscale modelling framework has been proposed to characterize microstructure evolution during hot strip rolling of transformation-induced plasticity (TRIP) steel. The modelling methodology encompasses a continuum dislocation density evolution model coupled with a lumped parameter heat transfer model which has been seamlessly integrated with a mesoscale Monte Carlo (MC) simulation technique. The dislocation density model computes the evolution of dislocation density and subsequently constitutive flow stress behaviour has been predicted and successfully validated with the published data. A lumped-parameter transient heat transfer model has been developed to calculate the average strip temperature in the time domain. The heat transfer model incorporates the effect of plastic work for different strain rates in the energy conservation formulation. A coupled initial value problem solver has been developed to integrate the system of stiff ordinary differential equations in the time domain to predict dislocation density and temperature profiles simultaneously. The temporal evolution of microstructure during hot rolling of TRIP steel is simulated by the MC method incorporating thermal and dislocation density data from the continuum models. Simulated microstructural maps, kinetics of recrystallization and grain size evolution have been generated in a 200 × 200 lattice system at different strain rates and temperatures. The simulation code has been implemented in a high-performance grid computing network. The predicted temporal evolution of grain size, recrystallized fractions and flow stress have been validated with the published literature and found to be in good agreement, confirming the predictive capability of the integrated model.     

Imitation design of temperature field in coloring hot dip galvanization process

Colors were generated by preferential oxidation of the metals in coloring hot dip galvanization process,and the evolution of temperature field during colling after hot dip would be responsible for the coloration results directly.Tht influences of bath temperature and velocity of steel stripmoving on temperature field of the strip were calculated in continuous coloring hot dip galvanization process by means of the ANSYS/Thermal module.The factors were considered including convection heat transfer,latent heat during cooling,and heat radiation in calculation.The effects of temperature field on coloration of sheet steel samples were investigated.     

型钢热轧开坯过程金属变形分析

型钢热轧开坯是高温坯料在低温轧辊作用下的金属变形过程,高温下金属材料的变形抗力随温度和应变速率变化明显,而且变形中塑性功和接触面摩擦以及坯料和轧辊间的热传导、和空气对流换热、辐射散热等,将导致坯料温度场的变化。因此,利用有限元法分析变形过程时,必须同时计算温度场和位移场。采用Mises屈服准则和弹/粘塑性材料模型,推导了采用等向强化假设的材料物性关系中的塑性矩阵、温度修正矩阵、应变速率修正矩阵的具体表达式。分析了多道次H型钢孔型轧制的开坯过程,总结了坯料在孔型中的变形规律,通过和H型钢生产现场数据的对比验证了结果的准确性。     

基于复合型神经网络的终轧温度自适应模型研究

为准确反映精轧轧制参数和微观组织转变对终轧温度的影响,利用自适应线性神经网络(Adaline)和径向基神经网络(RBF)技术建立了热焓修正系数预报网络作为终轧温度长继承计算模型。首先基于热焓形式的导热偏微分方程建立了带钢终轧温度计算模型,并对带钢在辊缝变形区产生的变形功、摩擦功、与工作辊的接触导热以及机架间冷却换热进行了模型描述;然后从温度与热焓之间的转换关系入手,确定将精轧区域热焓修正系数作为终轧温度模型的自适应参数,并利用复合神经网络技术建立了由19个输入节点,20个RBF隐含层节点,20个Adaline隐含层节点和1个输出节点构成的热焓修正预报网络。结合现场数据,描述了该预报网络训练样本的构成、数据标准化处理方法,同时给出了典型的网络参数和网络的预报能力。     

PHYSICAL SIMULATION OF INTERFACIAL CONDITIONS IN HOT FORMING OF STEELS

1.~nonNUInericalmodellingbythefiniteelement(FE)methodhasbecomeaneffectiveandeconomyicmeansforsimulatingmetalfoeingprocesses.However,accuratemodellingdemandsthecorrectdefinitionandinputsofthedataforthethermalandphysicalpIDPertiesoftheworkpieceandtoolmaterials,theboUndaryconditionsattheworkpiece--toolinterfaceandinotherareas,inadditiontoappropriatemeshgenerationandnumericalsolutions.Althoughmostofthematerialdataareavailable,thedataforinterfacialheattransferandfrictionconditions,Whichhavesubst…     

粗轧变形区温度场实验及仿真

轧制变形区温度场的分布是轧制力及轧件微观结构预测的重要参数之一。采用实验和有限元的方法研究了铝板热轧过程,侧重轧件变形区温度的分布,并对变形区接触热传递系数的分布规律进行了分析;以此作为轧辊轧件间传热模型,建立了实验轧制的数学模型。结果表明,轧件在轧制变形区存在较大的温度梯度,并且与实验结果吻合较好。     

热轧带钢在冷却中温度与相变的耦合解析

本文针对热轧带钢的冷却过程 ,利用有限元法建立温度与相变的耦合预报模型 ,同时分析各种工艺条件对计算结果的影响。该模型的计算结果与实测值符合良好 ,能够准确地预测带钢冷却后的温度分布和最终的组织。     

轧辊辊缝差和轧机组装间隙对精轧钢带尾板侧偏的影响

为了探讨精轧区轧辊辊缝差和轧机组装间隙这两个重要因素对精轧钢带尾板侧偏的影响,依据热轧生产线的操作条件,运用Abaqus软件建立了钢带热轧的第1、2和4机架精轧模型与尾端弯曲钢带。通过设定不同层级的轧缝差与变换上、下轧辊相对位置,模拟分析了各机架的轧辊辊缝差和组装间隙对轧辊两侧轧制力差、钢带尾端中心偏移、钢带运动行为的影响。结果表明:调整轧辊辊缝差可以有效地矫正钢带中心线偏移量,降低因钢带中心线偏移所产生的轧制力差,减少尾板撞击的发生概率;轧机组装间隙不对称会使钢带轧制时发生侧偏并撞击边导器,影响钢带运行的稳定性与钢带的成形质量。最后,试验验证进一步证实了上述结论的正确性与合理性。     

基于ANSYS的热轧工作辊温度场的有限元分析

根据宝钢1880热轧工作辊实际的边界条件,利用有限元软件ANSYS建立了热轧工作辊的二维温度场有限元模型,通过将模拟结果与现场下机后工作辊表面温度实测数据的比较,验证了模型的可靠性。在此基础上,研究了工作辊表层温度及中心温度的变化过程,模拟结果表明,轧辊旋转一周的过程中,辊面的最高温度可达525℃;每块带钢轧制过程中,辊面的最高温度在轧辊旋转6～8周之后不再增加;整个轧制过程中轧辊中心温度基本保持上升趋势。通过修正现场热凸度补偿模型参数,提高了带钢板形质量,降低了产品的封锁率。