连退过程带钢热瓢曲指数及其影响因素

 针对带钢连退过程中的热瓢曲问题,充分考虑到连退机组的设备与工艺特点,从内力、外力两方面因素分析了热瓢曲以及横向压应力的产生机理,阐述了热瓢曲的发生规律,首次提出了瓢曲指数的新概念,给出了相应的瓢曲临界条件,建立了一套适合于连退过程的带钢热瓢曲指数的计算模型,定量分析了不同工艺段内带钢瓢曲指数分布规律以及相同工艺段内来料板形、横向温差、炉辊辊型、摩擦因数、设定张力、通板速度等因素对带钢热瓢曲指数的影响,并将相关理论应用到生产实践,开发出了“连退机组通板过程带钢瓢曲预报软件”,实现了对连退过程带钢瓢曲的在线预报,为瓢曲缺陷的预防和控制奠定了坚实的理论基础。     

连续退火机组带钢瓢曲临界张力的研究

 根据金属塑性理论建立了带钢稳定通板的理论模型,并对模型进行求解,求解分为张力加载与辊子转动两步进行。系统地研究了瓢曲的形成与发展,以及辊形与带钢尺寸对带钢瓢曲临界张力的影响等。结果表明：引起带钢瓢曲的横向压缩应力由不均匀拉伸诱发的横向压缩应力和由摩擦产生的附加横向压缩应力两部分构成,瓢曲在带钢传输过程中逐步形成;对比发现有限元模拟的瓢曲发生与长大过程与大生产的情况基本一致,瓢曲的宽度约为2～4mm。并且带钢瓢曲的临界张力随着辊子凸度的增大、辊子平台区长度的减小、辊面粗糙度的减小、带钢厚度的减小而逐渐减小。     

基于有限元和试验的热轧带钢残余应力减量化

 研究残余应力减量化技术可提高热轧带钢板形质量。有限元技术及相应的试验验证已广泛应用于工业生产,采用该方法对带钢层流冷却过程中的温度、相变及应力耦合进行求解,对于分析带钢轧后冷却不均、应力应变不均及翘曲具有重要意义。基于ABAQUS建立热轧带钢在密集冷却工艺条件下的有限元模型,实现温度、相变和应力三者的耦合计算,并进行温度测试、材料微观组织测试及应力测试等多个试验验证。计算结果表明,减小带钢进入层流冷却前的初始温差、采用边部遮挡技术对减少带钢残余应力均具有积极的意义。通过一个改善初始温差分布进而改善带钢残余应力的实例,验证了提出的方法和结论的正确性。     

热轧带钢局部硬度对冷轧带钢板形的影响

考虑轧件材质横向差异对冷轧带钢板形的影响,采用末架轧机出口带材横向厚度分布和板形作为验证模型精度的指标,定量研究了热轧来料局部硬度对冷轧带钢板厚和前张应力分布的影响程度及规律,通过与现场实测数据的对比,证明该模型提高了轧后板形的计算精度。研究结果显示,局部硬度对冷轧带材的张应力分布影响显著,附加张应力与硬度峰高度成正比,给出了冷连轧过程中轧后带材附加厚度和附加张应力与热轧来料局部硬度的关系。     

钛带在带钢连续退火炉内张应力横向分布仿真

为了探讨利用现有带钢连续退火线生产冷轧钛带产品,基于ABAQUS仿真平台,针对国内某带钢连续退火炉设备条件,建立钛带在退火炉内弹塑性变形的有限元仿真模型,并开展数值模拟研究。结果表明,炉辊辊形、钛带初始板形缺陷及钛带工艺张力大小是钛带张应力横向分布的主要影响因素;钛带的张应力横向分布不均度在凸度辊、单锥度辊和双锥度辊上依次趋于严重;钛带的初始板形缺陷使其张应力横向分布更不均匀,初始有边浪和中浪的钛带都会出现张应力分布不均匀现象;工艺张力对于钛带张应力横向分布均匀性影响不大。针对钛带张应力横向分布的影响因素及其影响规律的研究结果,对于设计炉辊辊形和确定对来料钛带实际板形的要求都具有参考价值。     

基于有限元法的拉伸弯曲矫直过程板形控制分析

 板形是带钢质量的重要判定指标,常见的板形缺陷有边浪、中浪、1/4浪等,其实质是残余应力在带宽上的分布不均。拉伸弯曲矫直机通过张力辊组、弯曲辊组和较真辊组的共同作用,使带钢在低于屈服强度的张力作用下发生塑性延伸,从而有效消除浪形缺陷,改善板形,提高带钢质量。然而在拉伸弯曲矫直机的设计和使用过程中,对拉伸弯曲矫直机参数的调整多基于经验,缺少理论指导。为了定量分析拉伸弯曲矫直机参数对浪形缺陷的改善效果,使拉伸弯曲矫直机在实际生产中发挥更好的作用,以某1 450 mm带钢酸洗冷轧生产线上的拉伸弯曲矫直机为研究对象,使用有限元软件ANSYS/LS-DYNA基于三维弹塑性有限元法建立了拉伸弯曲矫直机模型,对拉伸弯曲矫直机矫直过程进行了模拟,分析了张力和插入深度对初始浪形分别为边浪和中浪的带钢矫直后板形的影响规律。结果表明,经过拉伸弯曲矫直的带钢浪形缺陷得到显著改善;插入深度和张力对初始浪形缺陷分别为边浪和中浪的带钢板形的影响规律一致;3个辊组中矫直辊组的插入深度是影响带钢板形的主要因素,随着矫直辊组插入深度增大,带钢矫直后板形由边浪转变为平直,且随着矫直辊插入深度进一步增大,板形又由平直转变为边浪;随着入口张力增大,带钢矫直后板形由边浪转变为中浪。     

Plastic-Buckling of Rectangular Plates under Combined Uniaxial and Shear Stresses

This paper is concerned with the plastic-buckling of rectangular plates under uniaxial compressive and shear stresses. In the prediction of the plastic-buckling stresses, we have adopted the incremental theory of plasticity for capturing the inelastic behavior, the Mindlin plate theory for the effect of transverse shear deformation, the Ramberg-Osgood stress–strain relation for the plate material, and the Ritz method for the bifurcation buckling analysis. The interaction curves of the plastic uniaxial buckling stress and the plastic shear buckling stress for thin and thick rectangular plates are presented for various aspect ratios. The effect of transverse shear deformation is examined by comparing the interaction curves obtained based on the Mindlin plate theory and the classical thin plate theory.     

热镀锌机组沉没辊系受力模型及影响因素

热镀锌机组沉没辊系在锌锅内工作状态下受力情况复杂,受外界影响较大。充分考虑热镀锌机组设备与其工艺特点,首先分析沉没辊系在工作状态下受力情况,分别建立矫正辊插入量与包角的关系式、基于辊面锌渣沉积厚度的辊面摩擦因数经验模型。随后采用条元离散法建立沉没辊系辊面接触压力、摩擦驱动力矩模型,基于简支梁模型确定沉没辊系轴端支撑力、轴端摩擦阻力矩模型。最后将沉没辊系受力模型应用于国内某热镀锌机组镀锌工艺段,以典型规格带钢确定沉没辊系受力影响因素,并依据机组实际工况及板形要求来确定生产工艺参数的5种不同水平,来分析其对辊系受力状态的影响规律,为沉没辊系工艺优化提供指导依据。结果表明,4种工艺参数对辊系接触压力及摩擦力矩影响都存在差异性,矫正辊插入量与辊面接触压力呈现非线性关系;带钢张力对各辊接触压力影响程度不同,其中沉没辊受到的影响最大,而其余两辊受到张力几乎不影响;辊面平均摩擦因数、带钢速度对辊的接触压力几乎不影响;辊系摩擦驱动力矩、轴端摩擦阻力矩随着矫正辊插入量及辊面平均摩擦因数增大都呈现出不同程度增大。带钢张力与沉没辊摩擦驱动力矩、轴端摩擦阻力矩呈线性变化关系,而带钢张力对其余两辊影响很小。带钢...     

Comprehensive tension setting optimisation technique for a cold rolled strip during continuous annealing

The previous tension setting for the continuous annealing process (CAP) is not comprehensive; that is, it does not synthetically consider the factors of strip deviation, buckling, flatness and width narrowing. To address this issue, this study integrated the mechanical and technological characteristics of a continuous annealing line to present a comprehensive control index that can characterise the stability of a travelling strip. Meanwhile, strip deviation, buckling, strip shape and width narrowing were regarded as constraints in each process section. A comprehensive optimisation technique for the tension setting during CAP was then established, and a related theory was applied during production. In addition, a comprehensive tension setting optimisation software was developed for a cold rolled strip during continuous annealing, and the comprehensive optimisation of the tension parameters in each process section was realised. A practical implementation proves that the developed technique exhibits good application effects and considerable application values.     

带钢横向厚度控制不均对退火板形的影响分析

带钢横向厚度控制不均,会使带钢在退火过程中产生横向温度差异和横向张应力分布差异,而横向温度和横向张应力分布存在差异会使带钢横向各位置处产生纵向延伸不均,进而导致退火带钢板形不良。以实际生产过程中带钢横向厚度控制不均的典型现象为切入点,分析带钢横向厚度不均对退火板形的影响,对分析和改进退火板形有一定的指导意义。     

带钢卷取过程起筋控制的建模与仿真

 为了研究带钢局部高点卷取过程起筋的控制方法,基于应力函数假设和S Timoshenko最小功原理获得了起筋带钢的应力场分布,并采用伽辽金虚位移原理建立了可用于在线计算的起筋临界卷取张力设定模型和起筋弹性极限模型。并对应力场分布和临界卷取张力各影响因素进行仿真研究,仿真结果表明：局部高点在径向累积叠加所引起的带钢张力不均匀分布和轴向压应力是导致带钢起筋的主要原因;临界卷取张力随带钢厚度、局部高点高度和卷取半径增大而减小,带钢宽度对钢卷的起筋临界卷取张力影响非常小。通过与实际生产控制方法和ANSYS有限元分析结果对比,验证了本模型的计算精度和可行性。     

Stress–Strain State of Coiled Steel

In a new mathematical model of the stress–strain state of steel strip in the course of cooling, the nonplanarity, surface roughness, and transverse thickness variation (convexity of the cross section) are taken into account. The stress–strain state of a coil of thin steel sheet has a significant influence on factors such as the temperature distribution in the coil; the scale formation on cooling in the course of hot rolling; the adhesion of adjacent turns in the annealing of cold-rolled strip; and the shape of the coil itself. The mathematical model is based on representation of the coil as individual nested hollow cylinders of finite length. The cylinders are divided into sections over the width. The sum of solutions of the Lame equation for individual sections is shown to converge to the solution for the cylinder as a whole. The model permits calculation of the coil’s stress–strain state, taking account of gap formation between adjacent turns as a result of the transverse variation in strip thickness. The modeling results show how the radial and tangential stress formed in strip winding is distributed within the coil. The model permits calculation of the stress–strain state of the coil in the winding of even strip; in the winding of convex even strip with no tension; in the loose winding of convex even strip with tension less than that in tight winding; in tight winding of even convex strip with the correct tension; and in the winding of convex uneven strip without tension. The decrease in distance between contacting rough surfaces is calculated on the basis of a probabilistic approach. An algorithm is presented for calculation of the coil’s stress–strain state. The result obtained for the stress distribution in the coil is typical for the winding of steel strip. The model is verified for the winding of hot-rolled strip, in terms of the size of the region with tight contact of adjacent turns. The tightness of contact is assessed on the basis of the temper color on the edges of the hot-rolled strip. The discrepancy between the calculated and measured size of the region with tight contact is 3%.     

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MS980 is one of advanced high-strength steels, which has a great potential for producing square tubes. Residual stress plays a significant role in determining roll-formed members?? behavior and strength. An experimental study on transverse residual stress of roll-formed shape with square section was conducted via X-ray diffraction method. The distribution of transverse residual stresses at different position in sections was measured and studied, and influence of cold-rolled-sheet and hot-rolled-sheet, different fillet radius, different processes, and different pickling time on circumferential residual stress distribution for square section was investigated. The experimental results show the transverse residual stresses are compressive stress in the corner portion and the tensile stress in the straight edge. Fillet radius, sheet, and process have a significant impact on the distribution of residual stress, but the conventional pickling hardly affects residual stress.     

连退过程带钢张力横向分布模型及其影响因素

 针对以往连退过程中对带钢内部应力横向分布情况无法在线预测,从而对连退过程中的跑偏、瓢曲以及带钢在各工艺段的板形演变无法在线预警、容易造成断带缺陷的问题,充分结合连退机组的设备与工艺特点,在研究了带钢横向温度差、来料板形、炉辊辊型、炉辊水平度与垂直度误差对带钢内部单元变形影响模型的基础上,建立了一套适合于连退过程的带钢内部张力横向分布模型,给出了相应的计算策略,并以宝钢不锈钢有限公司某连退机组为研究对象,定量分析了炉辊原始辊型、来料板形、横向温差以及炉辊水平度与垂直度误差、设定张力等因素对连退过程带钢内部张力横向分布的影响,编制出了相应的“连退机组通板过程带钢内部应力横向分布及板形演变预报软件”,并将其应用到生产实践,取得了良好的效果,具有进一步推广应用的价值。     

冷轧带钢来料断面对张应力与出口断面的影响

为了降低冷轧带钢的横向同板差,通常需要采用紧边轧制工艺,带钢边部处于大拉伸应力状态,很容易引起边裂或断带。提出一种冷轧带钢来料横断面形状的简单描述方法,以热轧来料横断面参数作为输入参数,采用板形模拟软件分析了来料断面形状的两个关键参数对带钢出口张应力与出口断面形状的影响规律。模拟结果表明,减小热轧来料边部15和40mm处凸度值C_(15)和C_(40),改善热轧带钢边部减薄,不仅有利于减小冷轧带钢横向同板差,而且可以改善带钢边部残余拉应力,从而减小冷轧带钢边部张应力,有利于避免第一道次带钢发生边裂与断带事故。     

Comprehensive optimisation technology of roller profile in continuous annealing furnace

Several problems, such as strip deviation and buckling, are encountered in the continuous annealing process. In this study, equipment and process features of continuous annealing, as well as the advantages and disadvantages of single taper roller and double taper roller in the prevention and treatment of the buckling and strip deviation were considered. Basing on a number of field experiments and theoretical studies, a new set of furnace roller profile curve was proposed and a set of optimisation model suitable for furnace roller was established, with travelling stability of the strip as the objective function. Test results of field production showed that the strip exhibited high speed and stability after optimisation, and the service cycle of the furnace roller was considerably improved. The results of this study provide an important economic benefit for the site and are valuable for further popularisation and application.     

冷轧带钢局部高点卷取过程起筋控制的建模与仿真

为了研究带钢局部高点卷取起筋的控制方法,利用三维弹塑性变形基本理论,并引入带钢塑性流动因子,建立了弹塑性卷取应力和起筋量模型.基于应力函数假设、S.Timoshenko最小功原理和伽辽金虚位移法建立了起筋带钢的应力场分布和可用于在线计算的起筋临界卷取张力设定模型.仿真结果表明:局部高点在径向累积叠加所引起的带钢张力不均匀分布和轴向压应力是导致带钢起筋的主要原因;起筋量随局部高点高度、卷径和卷取张力增加而增大,薄带钢比厚带钢起筋量增幅明显;临界卷取张力随卷径、带钢厚度和局部高点高度增大而减小.      

冷轧带钢在线磨辊表层残余应力的研究

对冷轧带钢在线磨辊辊表层残余应力的形成因素进行了研究。结果表明：由砂轮磨损引起的磨削力增大会使轧辊表层残余应力状态发生变化，即由压应力变为拉应力；同时得知砂轮转速也会引起应力状态发生变化。分析了引起上述变化的原因，得出保持辊表层夺应力状态的控制条件；另外，还对被磨削轧辊表层残余应力的形成机理进行了研究，并在不同的磨削条件下，测定了轧辊表层的残余应力，从而得到轧辊表层应力状态及硬度的变化规律，为实现冷轧带钢在线磨辊及控制板形提供了依据。     

热轧中碳宽带钢冷却过程横向弯曲变化规律的数值模拟

 针对目前困扰热轧中碳高强度宽带钢生产的横向弯曲缺陷,使用有限元软件ABAQUS结合FORTRAN语言编写子程序,建立热轧带钢轧后冷却有限元模型。通过模型计算,分析带钢轧后冷却过程中上下表面的冷却不均以及带钢厚度对带钢横向弯曲的影响。研究结果表明,相同厚度情况下,带钢上下表面冷却不均程度越大,带钢横向弯曲程度越严重,上下表面相同冷却效率比的情况下,带钢越厚,带钢横向弯曲越严重。冷却过程中,受温度变化和相变的综合影响,带钢弯曲方向和大小会发生较大变化,且冷却过程中带钢弯曲量最大值远远大于冷却结束后横向弯曲量。     

连退炉内炉辊的选择与优化设计

推导了连退炉内炉辊为锥度辊时的带钢对中力的表达式,分别介绍总结了带钢对中运行及瓢曲变形的机理.在此基础上,分析了炉辊种类、炉辊形状参数、炉辊表面状态及炉辊热凸度对带钢高速通板技术的影响,并提出了炉辊选择和优化设计的指导原则,以及实现炉辊形状设计定量化的手段.