AZ31镁合金中厚板轧制温度场的数值模拟与实验验证

通过数值模拟分析了AZ31镁合金中厚板在轧制变形区的温度分布，建立了轧后镁板平均温度关于轧辊温度、轧制速度、轧制压下量、板材厚度的经验公式，并辅以相应的实验验证。结果表明：当镁板较薄、轧制速度较小时，镁板中心层的塑性变形热在轧制变形区向表层传递，中心层的温升不能代表镁板塑形变形产生的温升；轧后镁板的平均温度与轧辊温度、轧制速度、轧制压下量正相关，与板材厚度反相关；轧后镁板平均温度的计算值与实验值的最大相对误差为8.34%，平均相对误差为7.4%，经验公式能很好的预测轧后镁板的平均温度。经验公式的提出，利于实现“AZ31镁合金板材的等温轧制”控制；对镁合金轧制工艺制度的合理制定以及后续轧制设备的选择有重要指导意义。     

Preparation of AZ31 magnesium alloy strips using vertical twin-roll caster

A newly developed technology for manufacturing magnesium alloy strip,vertical twin-roll strip casting,has been described.This manufacturing process is easy to be facilitated in an economical way to manufacture wrought magnesium alloy strips. As an example,AZ31 magnesium alloy was used to investigate the appropriate manufacturing conditions for vertical twin-roll strip casting by varying the temperatures of the molten materials and rolling speeds.The effects of manufacturing conditions on forming quality were clarified in terms of roll speeds and casting temperature.In addition,microscopic observation and X-ray diffraction of the as-cast strips were performed.It has been determined that AZ31 alloy strip of 1-3 mm in thickness can be produced at a speed of 30 m/min by a vertical twin-roll caster.The microstructure of as-cast strip only containsα-phase(Mg)and no other phase,and the twin-roll casting process can effectively refine the grain size.The fine equiaxed grain of as-cast strips is beneficial to the plastic deformation of the strips,and it is also suitable for direct cold-rolling with a maximum cold-rolling reduction of 40%.     

Effects of processing parameters on the bond strength of Cu/Cu roll-bonded strips

Roll bonding, widely used in manufacturing large layered composite sheets, is a solid phase method for bonding similar or dissimilar metals by rolling. In this study, the effects of process parameters such as rolling reduction, rolling temperature, rolling speed, initial thickness of strip, and surface roughness on the bond strength between two-layer strips of Cu/Cu were investigated. The strips were subjected to chemical and mechanical cleaning prior to rolling, and after rolling, bond strengths were measured using the peeling test. It was observed that increased reduction, rolling temperature, strip width, and surface roughness led to an increase in peeling strength while increased rolling speed and initial thickness of strips caused peeling strength to decrease. Results also showed that increasing the initial thickness of strips would increase threshold deformation.     

镁合金热辊轧制温升效应研究

研究了热辊轧制中AZ31B镁合金不同工艺条件下厚度方向温度分布及其与组织的关系,并在此基础上建立了能量守恒的简化方程来预测温升。结果表明:变形过程中各层金属的温升均与压下率正相关,而与初轧温度反相关。辊温显著影响轧制时的表面温降和总体温升,使得热辊轧制表层组织中孪晶明显减小,轧板中再结晶更加充分。此外,基于能量守恒的简化方程的计算结果与实测数据吻合较好。     

基于双辊铸轧的Al-Zn-Mg-Cu系合金冷轧后的再结晶行为

将双辊铸轧运用于制造Al-Zn-Mg-Cu合金带材。研究带材减薄率及热处理温度对合金再结晶行为的影响。结果表明：在冷轧率为60％、热处理制度为500℃的条件下处理1h时,合金带材具有细晶组织（平均晶粒尺寸约为13μm,晶粒纵横比约为1．7）和高的力学性能（UTS≥360MPa,δ≥20％）。研究了微观组织对Al-Zn-Mg-Cu合金带材力学性能的影响。合适的双棍铸轧热处理及加工工艺能制造低价、高强的Al-Zn-Mg-Cu合金带材。     

冷轧带钢平整机高精度高速度轧制力模型开发

与普通冷轧相比,平整轧制压下量很小,轧件的弹性变形和工作辊的弹性压扁对轧制压力分布有较大影响,通常的圆弧形轧辊轮廓假设不再合理。文章推导了分段二次曲线分布压力作用下轧辊弹性压扁量的计算模型,考虑轧制速度对变形抗力的影响,采用卡尔曼理论计算轧件的弹塑性变形,研究开发了冷轧带钢平整机轧制压力模型。轧制力计算值与实测值吻合精度高,计算速度快,表明,本模型可以用作平整轧机的轧制力设定模型。     

冷连轧过程工作辊辊间接触模型研究

辊间接触对高速冷连轧过程有重要影响。针对1 750 mm冷连轧机组的设备与带钢轧制的工艺特点,通过对UCM轧机辊系的受力分析,采用离散化处理方法和影响函数法,建立了辊系弹性变形影响函数模型、轧辊压扁影响函数模型,并给出了辊系变形的基本物理方程,基于接触力学,最终提出了冷连轧过程中工作辊辊间接触判定准则,为精确计算工作辊间的压力分布提供了理论依据。同时,研究了工作辊辊间接触对单位宽度轧制力分布、工作辊与中间辊辊间单位压力分布、工作辊弯曲挠度和压扁量分布以及成品带钢横向厚度分布的影响。实践证明,建立的辊间接触和辊系变形计算模型具有较高的计算精度,能充分反映轧后带钢的横向厚度分布和板形分布规律,适合于工业生产实践。     

Analysis of Bonding Behavior and Critical Reduction of Two-Layer Strips in Clad Cold Rolling Process

In recent years, two-layer metallic sheets have been increasingly used in various industries to create combined functions. Among cladding methods, the cold rolling is most widely used in producing bimetallic sheets. In this research, to thoroughly provide guidelines for cold rolling of bimetal strip, an attempt has been made to develop an analytical model based on upper bound method. Also, the bonding strength and critical reduction were calculated using upper bound theorem and the finite element simulation was used for Al/St bimetallic strip. Finally, an experimental study was run for our model to be verified analytically and numerically. Results show that the bonding strength of strips increases with increasing the total thickness reduction of bimetal strips and because of subsequent occurrence of strips bonding in roll gap, increasing the yield strength of base layer gives rise to critical reduction. Through the study, it becomes clear that the proposed analytical model is applicable for simulating the cold rolling process of the two-layer strips and is capable to broaden our knowledge in manufacturing and production of bimetal strips and sheets.     

冷轧带钢温度演变及影响因素研究

为了探究冷轧过程及轧制工艺参数对带钢温度的影响及演变规律,采用有限元方法对冷轧带钢进行建模,利用温度场反算的方法确定了带钢和轧辊间的传热热流密度,在此基础上通过改变模型参数对带钢温度场进行了模拟计算。结果表明,带钢温度在前4架轧制区呈阶梯式增长趋势,而在末机架出口呈下降趋势;此外,带钢出口温度随轧制速度、道次压下率、摩擦因数、变形抗力等的增加而升高。     

An Analytical Modified Model of Clad Sheet Bonding by Cold Rolling Using Upper Bond Theorem

In this paper, clad sheet bonding by cold rolling was investigated using the upper bond theorem. Plastic deformation behavior of the strip at the roll gap was investigated, unlike previous methods; distinctive angular velocities are used for different zones in roll gap in present model and absolute minimum of rolling power function is achieved. Rolling power, rolling force, and thickness ratio of the rolled product affected by various rolling condition such as flow stress of sheets, initial thickness ratio, roller radius, total thickness reduction, coefficient of friction between rollers and metals and between components layer, roll speed, etc., are discussed. It was found that the theoretical prediction of the thickness ratio of the rolled product, rolling force, and rolling power are in good agreement with the experimental measurement.     

Effect of casting parameters and deformation on microstructure evolution of twin-roll casting magnesium alloy AZ31

Twin roll casting method is a promising route to directly produce magnesium alloy strip. It is a rapid solidification process with high temperature gradient combined with thermal flow and roiling deformation in the casting region. As-cast strip with proper mierostructure is requested to serve as next rolling feedstock. However the microstructure of as-cast strip is sensitive for casting conditions during the casting process and the as-cast microstructure greatly affects the mechanical properties. In this work, the effect of casting speed, pouring temperature, deformation as well as anneal process on microstructure and mechanical properties were investigated. The results revels that twin-roll casting process can effectively refine the grain size, improve the morphology and distribution states of Mg1TAl12. The homogenization treatment time can be shorted for the fine microstructure and lower the cost dramatically for the next forming process.     

A New Rolling Process for Strips with a Defined Cross Section

A new rolling process is being developed for producing cold rolled strips with a defined cross section. These strips feature differences in thickness up to 50% perpendicular to the rolling direction. A special roll system is used to achieve a material flow exclusively in the direction of the strip width. As a consequence the strip width is increased significantly. In this way a wide variety of different cross sections can be produced. The range of application for these kind of strips cover novel load-adapted and load-optimized structures with different thicknesses, e.g. special profiles and special section tubes.     

AZ31变形镁合金轧制工艺初探

研究了板坯加热温度、退火温度以及冷轧道次加工率对AZ31变形镁合金轧制能力的影响.结果表明,当加热温度为350℃,轧制速度为0.4m/s时,AZ31镁合金板材的热轧道次极限加工率可以达到34.62%(无裂纹)和59.23%(无表面裂纹);将热轧态板材分别在250℃～350℃温度,退火40min后,板材显微组织中晶粒大小均匀,维持在5μm～6μm水平;板材具有良好的综合力学性能,其抗拉强度为:230Pa～240MPa,屈服强度为:135MPa～175MPa,延伸率为:12%～15%.当采用350℃×40min退火后,板材在冷轧道次加工率为5%～10%时,总加工率可以达到40%以上.     

冷连轧机液压AGC系统油膜补偿控制

由于对冷轧薄板质量要求的提高,液压AGC已经成为提高冷轧带钢成品精度必不可少的手段。然而对于支撑辊采用油膜轴承的冷连轧机来说,其轴承油膜厚度随着轧制力和轧制速度的变化而变化,这将影响轧件的轧出厚度,造成厚差。尤其对冷连轧机,各机架的累积误差会使成品带的超差更加严重。以某五机架冷连轧机为研究对象,由生产现场实测数据回归出适合于实际控制的油膜补偿模型,提出适合于分布式计算机控制的控制策略,并将其应用于实际轧制过程中对油膜厚度变化进行补偿。实验结果表明:加入油膜补偿控制后,成品带钢厚差带头带尾超差段有较为显著的减少,且超差值也有所降低。     

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。     

铝板冷轧润滑模型及应用

提出一种建立于流体动力学及塑性变形原理基础上的铝板冷轧润滑模型。可用于预测分析轧制变形区内油膜厚度、前滑、轧制压力及摩擦力分布等。该模型首先求解板材入口速度，然后得到油膜厚度，进行了高粘度矿物油铝板轧制试验，实测了不同压下率下入口油膜厚度，结果表明：实测值与计算值相当吻合，该模型为进一步研究板材冷轧及其润滑过程，优化生产工艺提供了依据。     

双辊薄带连铸结晶辊热变形研究

利用热力耦合有限元方法,对薄带连铸结晶辊的温度场和热变形进行研究,给出了浇注温度、浇注速度和冷却水流量对结晶辊温度场和热变形的影响规律,并利用有限元方法设计了初始辊形,有效地改善了铸带厚度的均匀性.     

低镍奥氏体不锈钢冷轧边裂原因分析

针对低镍Cr-Mn-Ni-N奥氏体不锈钢冷连轧过程中的边裂问题,采用金相显微镜、扫描电子显微镜分析了断口、边裂位置附近、正常位置显微形貌;分析了冷轧带钢横向应力、轧制力分布规律.结果表明,钢中镍元素偏析、存在Al2O3夹杂物、形变马氏体组织含量增加,以及带钢边部应力、轧制力较大,是导致低镍奥氏体不锈钢冷连轧过程出现边裂...     

铝钢复合带材异径轧制变形规律的研究

以4A60铝合金和08Al低碳钢为研究对象,利用异径轧机进行异径同速轧制,从厚度变化、硬度分布及金相组织等几个方面对薄铝复层的铝/钢轧制复合变形区的金属流动规律进行了研究分析。结果表明：铝钢轧制复合过程中铝先于钢达到稳定塑性变形,轧制复合过程中变形区可分为铝钢变形未复合区、铝钢变形复合区和钢变形区。当变形量增加到55%时,钢的硬度从约110 HV升高到210 HV,而铝层的硬度变化不大,基本保持在（40±5） HV。4A60铝和08Al钢的临界复合压下量为15%左右,当压下量超过45%时,仅发生钢的变形,而铝的厚度基本保持不变。铝层厚度与总厚度的比值（复合比）由轧前的0.054降低到轧后的0.052,说明轧制复合过程中铝的变形更大。     

Modeling of the inlet zone in the mixed lubrication situation of cold strip rolling

In this paper a method to simulate the oil thickness and length of elastic deformation in the inlet zone of cold rolling has been developed. The mixed film lubrication model was adopted to describe the behavior of the lubricant and asperity deformation. The elastic Von Karman equation was used to describe the elastic deformation of strip in the inlet zone. The length and lubricant film thickness of the inlet zone can be obtained by a numerical method. Results of simulations show that the reduction, rolling speed, back tension have a significant influence on the lubricant film thickness and the inlet zone length.