光整机张力变化对板形影响的仿真分析

带钢生产过程中,调整张力是控制产品板形、抑制板形缺陷、保证轧制过程顺利进行的重要手段。光整轧制过程中张力的加载有着两个重要的职能:实现微调带厚和拉伸矫正板形。文章以光整机为研究对象,基于ABAQUS建立四辊光整机轧制过程仿真模型,并进行一定长度带钢段的匀速连续轧制(即稳定态)过程模拟,研究了板带平整轧制过程中张力设定值与板形之间的关系以及张力大小对板形的影响效果。结果表明:张力增大可以促进轧件金属的纵向流动,加大轧件的厚向变形,减小出口轧件的凸度,且后张力的作用效果比前张力更显著,影响能力约为前张力的2.4倍。当张力增大时,带钢边部与中部延伸差在不断地减小,与前后张力对轧件厚向变形的影响趋势一致,带钢向良好板形方向发展。     

平整轧制过程工艺参数对带钢残余应力场的影响

应用非线性有限元软件ABAQUS对平整轧制过程进行二维建模仿真,计算并分析轧辊与带钢间接触摩擦润滑条件、前后张力、压下率、工作辊辊径等工艺参数对平整轧制后带钢厚度方向上纵向残余应力分布的影响。仿真结果表明,轧辊与带钢间接触摩擦润滑条件对带钢厚度方向上的纵向残余应力的分布形式与数值影响很大;压下率与工作辊辊径对带钢厚度方向上的纵向残余应力的数值有一定影响。在轧机前后张力相同时,张力值的大小对带钢厚度方向上的纵向残余应力的分布形式与数值影响很小,可以忽略不计;在轧机前后张力不同时,其差值对带钢厚度方向上的纵向残余应力的数值影响很大,不能忽略。     

冷轧带钢倾斜浪缺陷产生机理分析及控制研究

冷轧带钢倾斜浪缺陷即带钢表面斜纹是冷连轧产品普遍存在的一种板形缺陷,其产生机理及调控手段尚不清楚。介绍了倾斜浪缺陷的特征;进行了轧制规程调整、轧机设备精度调整等轧制试验。结果表明,双边浪轧制和调节五机架前后张力对倾斜浪缺陷有较为明显的影响。综合理论分析和试验结果,认为轧机出口带钢横断面张力不均,造成张力大的部分条元延伸率大,即造成带钢横断面的金属纵向延伸率不同,不能均匀纵向流动,且产生横向流动,各条元之间产生相互作用的内应力,当内应力足够大就会引起带钢翘曲;此条元的带钢翘曲后,张力变小,相邻条元的张力变大,带钢翘曲沿着带钢纵向斜的方向移动,便产生了倾斜浪缺陷。为此,提出了采用双边浪轧制和调整五机架前后轧制张力共同抑制倾斜浪缺陷的方法,试验结果表明倾斜浪缺陷改善明显。     

三辊张力单元张力曲线的绘制

运用弹塑性弯曲理论建立了相应三辊张力单元的数学力学模型,得出了张力计算式,绘制了张力曲线,讨论了压下量设置与张力、带钢厚度及带钢材质的关系,所绘张力曲线与日本进口设备实际应用张力曲线相符。研究结果表明,张力增量与带钢厚度近似成抛物线关系,与带钢屈服强度成正比;压下量<60 mm时,压下量的变化对各种厚度带钢的张力增量影响较大,当带材厚度≥7 mm时,不能轻易加大压下量;对于薄带钢,应适当增加压下量以保证张力单元可靠地产生所需的卷取张力。研究结果可用来指导张力单元装置的设计及操作模式的制定。     

平整机组张力综合优化控制技术

针对某钢厂平整机组轧制过程中出现的带钢打滑以及板形质量较差的问题，从打滑的防治、产品的机械性能与板形的控制等出发，首先通过轧制压力模型将轧制压力和张力联系起来，然后通过板形模型、前张力横向分布模型和打滑模型将板形、打滑概率、伸长率以及前后张力建立联系，最后以不出现打滑现象和成品带钢板形质量最佳为优化目标，建立了一套张力综合优化函数，该函数的优化结果即表示在不发生打滑和伸长率允许误差的范围内，成品带钢板形值最好时的张力设定值，从而形成一套平整机组的张力优化设定技术，并编制出相应的张力综合优化设定软件，可以实现对特定规格、钢种的带钢优化设定出相应的前后张力值。将优化结果应用到现场生产实际，结果表明，使用优化后的张力在轧制过程中未出现打滑现象，且成品带钢的板形质量得到明显改善，提高了机组生产效益。     

热镀锌带钢拉伸弯曲矫直的试验研究

在连续式热镀锌生产线上,镀锌带钢的拉伸弯曲矫直可以消除带钢的不平直度和屈服延伸,并可影响镀锌带钢的其它特性。图1是配有二辊平整机的拉伸弯曲矫直机。通过前后两组张力辊的速度差可使平整机和拉伸弯曲矫直机中的带钢产生一定张力。按照予先给定的轧制程序,拉伸弯曲矫直应完成下列任务:     

冷轧卷取带钢咬入阶段稳定性研究

针对某厂冷轧卷取带钢咬入阶段常出现起套、断带等卷取失败问题,建立了卷取机带头咬入阶段的二维动力学ABAQUS有限元仿真模型,研究并提出了描述带钢咬入阶段稳定性的定量指标,即带钢卷取半圈时张紧为卷筒和带钢的临界速度差。采用该指标,定量研究了带钢厚度、带钢与助卷皮带夹角、带头翘曲高度、皮带张力、带钢和皮带材料参数等因素对临界卷取速度差的影响。结果表明:带钢厚度是影响卷取速度差控制的重要因素,带钢厚度越小,达到稳定卷取张力所需临界速度差越大;带钢与助卷皮带夹角越大、带钢翘曲高度越大,达到稳定卷取张力所需临界速度差越大;其他因素如带钢翘曲长度、摩擦因数、皮带张力、带钢和皮带的材料参数对速度差的影响较小。基于仿真计算结果,对该厂卷取机卷筒的初始速度进行了优化,生产表明带钢卷取初始阶段起套现象明显减少,并且能够迅速建立稳定张力,保证了卷取的稳定顺行。     

三辊张力装置设计

阐述了非连续带钢处理机组中张力装置的设计,分析了带钢弹塑性力对张力辊张力及功率的影响,运用有限元方法对张力装置进行了刚度、强度校核,为同类张力装置的参数计算和结构设计提供了参考。     

卷取机芯轴张力对热轧带钢卷取温度控制的影响分析

热轧带钢卷取温度控制过程中,带钢速度是最重要的影响因素之一。当带钢尾部离开精轧末机架后,带钢速度由轧辊线速度转化为卷取机芯轴速度,复杂的卷取过程影响了带钢速度的稳定,导致带钢尾部卷取温度控制出现严重偏差。为了解决该问题,将温度模型、张力扭矩模型以及热轧生产大数据进行有机结合并进行了系统性分析。结果表明：卷取机芯轴张力控制异常是造成带钢卷取温度偏差的主要原因。因此,开发了卷取机芯轴张力报警功能,细化了芯轴张力与夹送辊压力控制的带钢厚度层别,优化了控制参数以保证带钢速度稳定,同时开发了带钢尾部卷取温度补偿模型。结合多目标优化,取得了较好的应用效果,带钢尾部温度超差占比下降3.26%,卷取温度命中率提升2.29%,为全面解决带钢通长方向卷取温度命中率提供了新的技术方案。     

带材平直度的张力控制实验研究

介绍了一种用于带材平直度控制的分段可调式附加张力辊装置 ,并对这种新型平直度控制方式的有效性进行了实验研究和简要的理论分析 ,指出通过降低带钢个别位置变形区前后的附加张力值可有效地消除浪形缺陷 ,提高带钢平直度     

Ag-Au-Cu合金表面张力的理论计算

表面张力对于材料而言是一种关键性的性质,该性能在液态金属和合金的成分设计领域有着十分重要的地位,其对铸造以及键合丝键合时金属凝固过程中表面是否开裂、焊接后焊接处的微观形貌有着决定性的影响。使用Butler模型和Toop模型分别计算金银铜及其对应二元合金在熔融状态下的表面张力并与实验值进行对比,从而为金银键合丝的成分设计起到一定的指导作用。结果表明:采用Butler模型和Toop模型计算出二元以及三元合金的表面张力与实验值相差较小。在1381K下,Ag-Au-Cu三元合金表面张力随Au和Cu含量变化介于0.89392~1.32471 N/m之间,表面张力随Ag或者Cu含量增加呈现单调减小或单调增大的趋势。     

Prediction of surface and interfacial tension based on thermodynamic data and CALPHAD approach

In this article, following a brief introduction concerning experimental measurements of surface and interfacial tensions, methods for calculating surface tension and surface segregation for binary, ternary, and multicomponent high-temperature melts based on Bulter＇s original treatment [ 1] and on available physical properties and thermodynamic data, especially excess Gibbs free energies of bulk phase and surface phase versus temperature obtained from thermodynamic databases using the calculation of phase diagram （CALPHAD） approach, with special attention to the model parameter β, have been described. In addition, the geometric models can be extended to predict surface tensions of multicom- ponent systems from those of sub-binary systems. For illustration, some calculated examples, including Pb-free soldering systems and phase-diagram evaluation of binary alloys in nanoparticle systems are given. On the basis of surface tensions of high-temperature melts, interracial tensions between liquid alloy and molten slag as well as molten slag and molten matter can be calculated using the Girifalco-Good equation [2]. Modifications are suggested in the Nishizawa＇s model [3] for estimation of interracial tension in liquid metal （A）/ceramics （MX） systems so that the calculations can be carried out based on the sublattice model and thermodynamic data, without deliberately differentiating the phase of MX at high temperature. Finally, the derivation of an approximate expression for predicting interfacial tension between the high-temperature multicomponent melts, employing Becker＇s model [4] in conjunction with Bulter＇s equation and inteffacial tension data of the simple systems is described, and some examples concerning pyrometallurgical systems are given for better understanding.     

Surface Structure of Nonoxidizing Slags Containing Sulphur

Application of surface tension measurements has been made to molten silicates in order to determine the effect of sulphur upon the surface tensions of synthetic blast furnace slags. In melts with the same molar ratios of Al2O3 + SiO2 to the basic oxides BaO, CaO, and MgO, the surface tensions increase in the order of oxides listed. Sulphur lowers the surface tensions of the basic BaO, basic CaO, acid BaO, acid CaO, and acid MgO slags in that order; and the concentration of excess sulphur at the slag surface increases in this same order of slags. The rate and amount of desulphurization of iron by these slags is favored by a low excess surface sulphur in the slag.     

带钢平整张力神经网络预设定模型研究

针对某冷轧厂1 730 mm连退机组六辊CVC平整机组出现张力设定表数值不准确或缺失的问题,建立了基于BP神经网络的平整张力预设定模型,对平整机张力设定表进行了完善并实现了张力设定值的在线预报。在线运行结果表明：张力预报值与实测值的相对误差在±8%以内,实现了平整机组张力的高精度预报。进一步离线测试表明：采用本文所建立的平整张力神经网络预设定模型后,平整机出口成品板形质量得到较大提升,平直度横向分布均值降低约78%,满足生产要求,并提高了轧制的稳定性。     

Surfaces,interfaces and phase transitions in Al–In monotectic alloys

Surface and bulk liquid phase transitions are measured by a unique method currently used to determine surface and interfacial tension of liquid alloys. Focusing on the Al–In system, the location of the liquid miscibility gap was determined from the critical to the monotectic temperatures. The surface tensions of nine liquid alloys, the interfacial tension between coexisting liquids and their densities were measured as a function of temperature. Implementing the bulk data extracted from the asymmetric miscibility gap into a sub-regular model reproduced the experimental surface and interfacial tensions. The wetting temperature was estimated to lie well below the monotectic temperature. The micrometer thickness of the In-rich films which wet the surface of the Al-rich liquid phase after solidification is suggested to be due to the growth of the equilibrium wetting film by diffusion from the Al-rich phase during cooling.     

金属表面脱水添加剂脱水机理的研究

本文通过对表(界)面张力、接触角进行测量,并利用经验公式,间接计算出了油-固、水-固之间的界面张力值,以此对金属表面脱水添加剂的脱水机理进行了初步的讨论。     

Surface tension of liquid Ag-Sn alloys: Experiment versus modeling

The maximum bubble pressure method has been used to measure the surface tension of pure tin and seven binary alloys with concentrations of 15, 30, 40, 60, 75, 87.8, and 96.2 at.% Sn. Measurements were performed at the temperature range from 500 to about 1400 K depending on the composition of the investigated alloy. Densities of the Ag-Sn alloys were measured dilatometrically. The linear dependencies of densities and surface tensions on temperature were observed, and they are described by a straight-line equation. Experimental data of the surface tensions were compared with calculations using Butler’s model, which assumes an equilibrium between the bulk phase and the monolayer surface phase. Excess Gibbs energies of silver and tin necessary in calculations were taken from the optimized thermodynamic parameters reported recently from Tohoku University. It is shown that the calculated surface tension data from the optimized thermodynamic parameters of the liquid phase of the Ag-Sn are in good agreement with the experimental results.     

Surface tension of liquid Ag-Sn alloys: Experiment versus modeling

The maximum bubble pressure method has been used to measure the surface tension of pure tin and seven binary alloys with concentrations of 15, 30, 40, 60, 75, 87.8, and 96.2 at.% Sn. Measurements were performed at the temperature range from 500 to about 1400 K depending on the composition of the investigated alloy. Densities of the Ag-Sn alloys were measured dilatometrically. The linear dependencies of densities and surface tensions on temperature were observed, and they are described by a straight-line equation. Experimental data of the surface tensions were compared with calculations using Butler’s model, which assumes an equilibrium between the bulk phase and the monolayer surface phase. Excess Gibbs energies of silver and tin necessary in calculations were taken from the optimized thermodynamic parameters reported recently from Tohoku University. It is shown that the calculated surface tension data from the optimized thermodynamic parameters of the liquid phase of the Ag-Sn are in good agreement with the experimental results.     

RE2O3-MgO-SiO2（RE=La,Nd,Sm,Gd和Y）熔体表面张力的计算模型（英文）

基于熔体组元离子半径和Butler方程,建立RE2O3-MgO-SiO2(RE=La,Nd,Sm,Gd和Y)熔体表面张力热力学计算模型。本模型利用纯组元的表面张力和摩尔体积以及熔体中各组元阳离子和阴离子半径可以获得E2O3-MgO-SiO2熔体表面张力随熔渣成分和温度的变化规律。计算1873 K La2O3-MgO-SiO2熔体等表面张力线并研究熔体成分对表面张力的影响。1873 K的纯组元La2O3,Gd2O3,Nd2O3和Y2O3的表面张力通过本模型计算分别为686、677、664和541 m N/m。除了Y2O3外,纯稀土氧化物的表面张力随其阳离子磁场强度增加而呈线性减小,而Y2O3的表面张力相对减小更多。表面张力的计算结果与文献数据一致,1873 K本模型平均偏差为1.05%。     

平整机延伸率、轧制力及张力的协调控制技术

在引入板形与力学性能综合控制目标函数的基础上，将带材的力学性能与外形质量糅合成一个统一目标进行控制；建立了一套平整机延伸率、轧制力及前后张力协调控制数学模型。通过轧制力与前后张力的协调设定，使平整机既能保证延伸率精度叉可满足板形要求，将其在某厂2030mm连续退火平整机上应用，取得良好效果。