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。     

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。     

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.     

界面滑移对阶梯滑块轴承润滑行为的影响

目的 研究入/出口阶梯面界面滑移对阶梯轴承油膜厚度和摩擦因数的影响。方法 通过建立考虑入/出口阶梯面不同程度的界面滑移的一维阶梯滑块模型,求解不同入/出口滑移比例下的油膜厚度和摩擦因数。在阶梯滑块工作面制备含氟类金刚石涂层（F-DLC）,在平行间隙条件下研究了有无含氟类金刚石涂层对油膜润滑性能的影响,并与理论计算结果进行比较。结果 当滑移只发生在入口阶梯面时,随着滑移程度的增大,油膜厚度增大,摩擦因数减小;当滑移只发生在出口阶梯面时,随着滑移程度的增大,油膜厚度减小,摩擦因数减小。当润滑油在入口和出口阶梯面均发生滑移时,会产生油膜厚度及摩擦因数同时减小或油膜厚度增大而摩擦因数减小2种结果。试验结果表明,F-DLC涂层阶梯滑块的膜厚最大且摩擦因数最小,没有涂层的结论与之相反。产生这一特殊现象是由于润滑油在阶梯滑块入口区和出口区的滑移程度不同。由于激光加工形成了微凸体结构以及F-DLC涂层的协同作用,入口区的滑移程度比出口区的大,从而膜厚增大;同时滑移的存在使其摩擦因数降低。结论 在入/出口的界面滑移对阶梯滑块轴承的影响下,会产生2种结果,得到了可以同时满足油膜承载力增大且摩擦因数减小的入...     

Investigation on Temperature Change of Cold Magnesium Alloy Strips Rolling Process with Heated Roll

Magnesium alloy strips are widely used in aerospace, automotive industry, etc., which are difficult to produce through cold forming process due to their poor deformation ability. In this article, we studied whether the rolling process with heated roll could be used to roll cold magnesium alloy strips. Thermal-mechanical finite element simulation of the rolling process, using heated roll and cold strips to produce the magnesium alloy strips, was carried out. Influences of roll temperature, rolling velocity, rolling reduction ratio, and initial strip thickness on the thermal field and the mean temperature of magnesium alloy strips were analyzed. Both the heated area in strips in rolling deformation zone and the mean temperature of strips at exit of rolling deformation zone increase with increasing the roll temperature and/or rolling reduction ratio, and/or with decreasing the rolling velocity and/or initial strip thickness. Finally, a formula was developed to predict the mean temperature of strips under different rolling conditions, which also could be used to calculate the critical value of parameters in rolling process.     

油水两相流润滑轧机油膜轴承的摩擦行为分析

目的研究含水润滑油对轧机油膜轴承的摩擦学性能的影响。方法选取轧机油膜轴承为研究对象,利用油水两相流体数学模型和弹流润滑方程研究轧机油膜轴承在等温条件下的润滑特性,分析油水两相流体润滑膜的压力、膜厚分别随含水率、滑滚比、轴颈间隙、主轴转速和轧制力的变化关系。结果水介入润滑油之后,随着含水率的增加,油水两相流体的黏度先增加,在含水率为30%左右时达到最大值(0.08 Pa·s),之后又迅速减小,直至接近于纯水的黏度(0.001 Pa·s)。当含水率为30%时,无量纲膜厚达到最大值(0.82),当含水率为90%时,无量纲膜厚达到最小值(0.68)。结论随着含水率的增加,油水两相流体由油包水流型转化为水包油流型,压力变化不大,膜厚先增加后减小,作为润滑剂,油包水流型比水包油流型具有更好的润滑性能,且在流型转变点处的润滑性能最优。随着滑滚比和轧机油膜轴承主轴转速的增加,压力减小,承载能力减弱,膜厚增加,润滑性能增强。随着轴颈间隙和外部轧制力的增加,压力增加,承载能力增强,膜厚减小,润滑性能减弱。     

Cast-rolling force model in solid−liquid cast-rolling bonding (SLCRB) process for fabricating bimetal clad strips

Based on twin-roll casting, a cast-rolling force model was proposed to predict the rolling force in the bimetal solid?liquid cast-rolling bonding (SLCRB) process. The solid?liquid bonding zone was assumed to be below the kiss point (KP). The deformation resistance of the liquid zone was ignored. Then, the calculation model was derived. A 2D thermal?flow coupled simulation was established to provide a basis for the parameters in the model, and then the rolling forces of the Cu/Al clad strip at different rolling speeds were calculated. Meanwhile, through measurement experiments, the accuracy of the model was verified. The influence of the rolling speed, the substrate strip thickness, and the material on the rolling force was obtained. The results indicate that the rolling force decreases with the increase of the rolling speed and increases with the increase of the thickness and thermal conductivity of the substrate strip. The rolling force is closely related to the KP height. Therefore, the formulation of reasonable process parameters to control the KP height is of great significance to the stability of cast-rolling forming.     

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。     

Unsteady lubrication modeling of inlet zone in metal rolling processes

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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.     

混合润滑轧制入口膜厚模型

运用平均流动模型求解混合润滑轧制变形区入口膜厚问题时,提出了混合因子φm,它综合了流动因子φx和接触因子φc对入口膜厚的影响,简化了轧制润滑模型,计算和实验表明,在流体润滑条件下,表面粗糙效应形膜亦有一定的影响,也即混合因子φm还适用于流体润滑轧制,且修正了未考虑表面粗糙效应而引起的不足。     

Measurements of friction during hot rolling of aluminum strips

In order to establish the dependence of the coefficient of friction on rolling speed and the reduction, commercially pure aluminum strips were rolled at 500°C, using a 2% oil/water emulsion as the lubricant. The roll separating forces, roll torques, the forward slip, the roll pressure and the interfacial shear stress were measured as a function of the reduction and the rolling speed. The coefficient of friction was determined from the shear stress and the roll pressure distributions and its magnitude was validated independently. The coefficient of friction was found to increase with reduction and, in general, decrease with rolling speed. The adhesion theory of friction has been used to explain the observations.     

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。     

Symmetric and Asymmetric Rolling Pure Copper Foil: Crystal Plasticity Finite Element Simulation and Experiments

A systematic study has been conducted aiming to attain an insight into the influence of coefficient of roll speed asymmetry, crystal orientation and structure on the deformation behavior, and crystallographic orientation development during foil rolling. Simulations were successfully carried out by using crystal plasticity finite element method(CPFEM),and a novel computational framework is presented for the representation of virtual polycrystalline grain structures. It has been found that asymmetric rolling(ASR) is more efficient in producing plastic deformation since it develops additional shear strain and activity of slip system compared with symmetric rolling(SR). For ASR, increase in the length of the shear zone, and decrease in the amount of the pressure and roll force would lead to further reduction. The shear strain path in SR and ASR is strictly influenced by the misorientation of neighbor grains, and corresponding {1 1 1} pole figures offer direct evidence of the spread of crystallographic orientation around the normal direction. The activity of slip systems was examined in detail and found that the predicted results are consistent with the surface layer model. The accuracy of the developed CPFEM model is verified by the fact that the simulated results of roll force coincide well with the experimental results.     

基于离散单元方法的冷轧轧制力计算

考虑了轧制变形区内带钢变形抗力的变化,根据卡尔曼方程,推导了塑性变形区内轧制力的计算公式,为避免直接积分的复杂性,将塑性变形区进行单元划分,分别求解前滑区和后滑区各单元的平均轧制力,将所有单元轧制力之和+入口弹性压缩区的轧制力+出口弹性恢复区的轧制力,得到了总的轧制力。计算结果表明,单道次计算时间t<30ms,在2000组计算结果中,计算值与实测值之间有93.3%的相对误差保持在±10%范围内,预测精度较高,满足冷轧在线控制的要求。     

Formulas of Tension of Continuous Rolling Process

The development of computer controlled continuous rolling process calls for a mathematical expression that can express the inequality condition of "constant flow". Tension is the link of the continuous rolling process. From the condition of dynamic equilibrium, a differential equation of tension is given out. On the basis of the physical rules established from the industrial practice and experimental studies, the law of volume constancy, the linear relation of forward slip and tension, the state equation of continuous rolling, the formula of dynamic tension, and the formula of static tension have been obtained. These formulae reflect the functional relations between tensions, thickness, roll velocity, and time in the continuous rolling process. It is implied that the continuous rolling process is a gradually steady, controllable, and measurable dynamic system. An assumption of predicting the thickness of a steel plate using these tension formulae is also put forward.     

轧制变形区油膜厚度的实验研究

就轧制变形区油膜厚度的不同测试方法进行了对比研究,提出了简便、衫的加热退火法。方法研究了轧制油粘度,轧制速度与压下率对轧制变形区油膜厚度的影响。     

Influence of roll radius on roughness transfer in skin-pass rolling of steel strip

Skin-pass rolling (or temper rolling) is usually the final process in the production of cold-rolled steel sheets. One of the main objectives in skin-pass rolling is to obtain a certain surface roughness profile. Although a large roll radius compared to the contact length and the reduction in thickness is one of the characteristics of skin-pass rolling conditions, numerous studies have been conducted thus far using laboratory mills with small radius rolls. In this paper, the influence of roll radius on roughness transfer in skin-pass rolling is investigated by experimental rolling tests as well as numerical analysis by elastic–plastic FEM. A simple but useful method of estimating roughness transfer is suggested. It was found that some characteristics of skin-pass rolling related to roughened rolls are not properly simulated using small radius rolls.     

辊缝油膜承载力对冷轧机振动的影响

针对某冷轧厂在线轧制过程中轧机的振动问题,从辊缝油膜承载力的角度分析其对轧机振动的影响,得出轧制过程中辊缝间距的减小导致辊缝油膜需提供更大的承载力来维持轧机稳定。从乳化液浓度、轧辊转速、乳化液金属微粒含量方面探讨了增强辊缝油膜承载力的方法,得出乳化液浓度与轧辊转速在增强油膜承载力的同时减小了辊缝的摩擦系数,也易导致轧机振动。通过试验得出,调节乳化液金属微粒含量能够在原有摩擦系数的基础上增强辊缝油膜承载力,从而保证轧机的稳定运行。     

铝带坯铸轧过程轧制压力的建模与仿真研究

利用切块法分别推导出铸轧过程上述两区的静力平衡微分议程,在所建立的轧制压力模型的基础上,对常规铸轧进行了仿真计算,计算结果与实测数据相吻合,在此基础上,对快速铸轧进行了虚拟仿真研究,研究结果表明,减薄铸轧板坯厚度可提高铸轧速度;随着铸轧速度降低,铸轧区增大与铸轧坯厚度减薄,轧制压力峰值增大,随着铸轧辊径增大,轧制压力增大,因此铸轧机力能的设计参数也要相应增大。