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。     

Full Two-Dimensional Model for Rolling Resistance. II: Viscoelastic Cylinders on Rigid Ground

Following the previous paper, “Full two-dimensional model for rolling resistance: Hard cylinder on viscoelastic foundation of finite thickness,” addressing modeling of rigid cylinder rolling against viscoelastic foundation of finite thickness, this paper focuses on the development of a rigorous full two-dimensional semianalytical model for viscoelastic rollers with layered structure rolling against a rigid ground. In this model, the polar coordinate system is used, the solution is expanded into a set of Fourier series corresponding to the angular coordinate, the frequency domain master curves of G′ and G″ characterizing the general viscoelastic properties for a viscoelastic material are used to relate Fourier coefficients, and a special condensed structure model based on the Fourier series is developed to handle viscoelasticity and the rolling contact boundary condition. Examples are given to show the model capabilities to efficiently handle rolling resistance and contact stresses, and capture major characteristics of standing-wave phenomenon, such as sharp rise of rolling resistance, emergence of standing waves and material dynamic softening as the rolling speed approaches a critical value. The methodology may be of interest to industrial roller designers.     

铝热连轧机切边剪和偏导辊速度控制的改进

针对"1+4"热连轧机在生产过程中轧制窄料、软料时经常发生带材下表面质量不好,偏导辊驱动电机由于过电流而跳闸的现象,通过对切边剪、偏导辊和卷取机与F4轧机的速度对比分析,对切边机和偏导辊的速度控制进行修改和优化,彻底根除了上述现象,提高了生产率和成品率,降低了生产成本,取得了较好的效果。     

辊面裂纹引起的冷轧辊大面积剥落失效分析

针对某产线冷轧工作辊多次出现大面积剥落事故,为了研究其失效原因,从剥落面断口观察、化学成分、工作层组织、淬硬层深度、裂纹扩展等角度对其进行了较为深入的分析研究。结果表明,该轧辊大面积剥落失效为疲劳裂纹扩展所致,裂纹源是轧钢过程中异常压痕产生的辊面裂纹。最后,针对如何预防辊面剥落恶性事故的问题,从轧辊使用、维护和设计制造三个角度提出了相应的建议,确保了近期未再发生类似的事件。     

铝板铸轧辊套表面热疲劳开裂及防止措施研究

针对铝板铸轧工业中最常用的32Cr3Mo1V辊套材料,在实验室采用自制热疲劳试验机模拟热疲劳裂纹的产生和扩展过程。结果表明,热疲劳过程中所形成的高硬度、脆性氧化物在热循环应力作用下断裂（即氧化-应力开裂）是热疲劳裂纹产生和扩展的最主要原因;并根据这一结果,设计了采用激光合金化方法在辊套表面形成高铬固溶体合金层的方法,制作的合金层能够延缓、阻滞热疲劳裂纹的产生和扩展;并系统分析了合金层的成分、组织、硬度及其热疲劳性能。     

H型钢万能轧机轧辊调整装置运动学动力学分析

 为了分析实际轧制过程中的振动和调节误差,研究了H型钢万能轧机轧辊调整装置基于理想约束副条件下的运动学与基于接触约束副的运动学动力学分析。从两者仿真结果的对比分析来看,理想约束条件下的水平辊调整速度是静态且恒定的0.691 4 mm/s;基于接触约束模型条件下的水平辊调整速度是动态的并呈现伴随冲击的周期性波动,大致是在0.688 7 mm/s处有比较大幅度的波动,且波动值相对理论值达36.64%,更加符合实际轧制工况。因此,基于静态设计的轧机在实际轧制过程中会出现比较明显的振动和调节误差,从而影响H型钢产品的尺寸精度和表面粗糙度,采用的变位系数蜗轮蜗杆传动是引起传动角速度波动的主要来源,这可为万能轧机的设计提供参考和依据。     

环件轧制中导向辊运动的研究

以环件轧制过程中环件外径瞬时变化规律为依据,根据环轧过程中体积不变条件及芯辊、导向辊和驱动辊三者圆心的位置关系,推导出导向辊运动的速度和角速度的计算公式;并在Deform-3D软件中模拟导向辊的定位,对比分析了有无导向辊作用下环件的变形过程,同时在模拟中以一种简单有效的方法实现导向辊的定心、归圆作用。模拟结果表明,利用此方法对导向辊进行定位控制,可以使轧制过程稳定。     

CSP轧机振动和振纹的试验研究

为了找出珠钢CSP热连轧机组在轧制薄规格集装箱板时出现振动的规律和机理,对该机组中间3架轧机的主传动系统扭振、机座系统垂振、抑振措施进行了现场测试,并对带钢(轧辊)振纹和工艺参数、轧机振动之间的关系,振纹形成必要条件等进行了研究.结果表明:F2轧辊振纹频率为14 Hz,是由齿轮座齿轮啮合冲击激起主传动扭振造成的;F3轧辊振纹频率为54 Hz,是由接手弧形齿啮合冲击引发辊系水平振动造成的;F4轧辊振纹频率为78 Hz,是由机座水平系统共振造成的;对F4来说为避免振纹形成,在一定轧速下需谨慎选择工作辊直径.对比试验发现,关闭乳化液和采用高速钢轧辊对振动的抑制有较好效果.     

Simplified calculation of the bending torques of steel sheet and the roller reaction in a straightening machine

In the straightening of steel sheet, it is necessary to calculate the optimal reduction of the steel blank by the working rollers of the straightening machine so that the sheet produced has the minimum residual stress and curvature. In the simulation of sheet straightening in multiroller machines, the curvature and bending torques of the steel sheet at contact points with the working rollers are first calculated and then the straightening forces are determined. In straightening steel sheet, it is important to calculate the forces in the multiroller straightening machine. Such calculations are based on determination of the reaction of the roller bearings and the forces at the upper and lower working-roller cassettes in straightening. With insufficient bending torque, it is impossible to eliminate harmful residual stress and surface defects in the sheet. Extreme roller torques and forces at the roller cassettes often lead to defects of the sheet, fracture of the working and supporting rollers, and failure of the straightening machine. In the present work, an approximate method is proposed for calculation of the optimal cold-straightening parameters of the steel sheet in a multiroller machine. The calculations permit determination of the curvature of the neutral plane in the sheet on straightening, the residual curvature of the sheet after straightening, the bending torque and the reaction of the working-roller bearings, the residual stress in the sheet, the penetration of the plastic deformation into the depth of the steel sheet, and the relative deformation of the longitudinal surface fibers of the sheet on straightening as a function of the radius of the working rollers, the distance between the rollers of the straightening machine, the reduction of the sheet by the upper rollers, the sheet thickness, and its properties (Young’s modulus, yield point, and strengthening modulus). The results may be widely used at manufacturing and metallurgical plants.     

Stress and deformation analysis of plane-strain rolling process

A finite-element elastic-plastic deformation analysis is required in order to predict a complete stress and deformation in a material for metal forming. There have been a few attempts for rolling analysis using the elastic-plastic code, because the boundary conditions between roll and deforming material become complicated. In this study, an elastic-plastic plane-strain rolling analysis with friction has been attempted by the updated Lagrange code. Both slipping and sticking were taken into account for boundary conditions between roll and material. The stress and deformation analysis is performed using a nonsymmetric stiffness matrix solution (for curved and frictional boundaries). The elastic-plastic analysis, coupled with the proposed frictional boundary model, evidently provides a reliable stress and deformation solution in the metal rolling process.     

热轧轧制压力横向分布规律及预测模型

 轧制压力横向分布规律对快速轧辊轧件一体化模型的建立、轧辊磨损及辊形预测具有重要的意义。为简洁有效地描述轧制压力横向分布,提出了轧制压力横向分布表征指标,即边中比、高次程度、一次非对称度及三次非对称度。通过有限单元法建立了轧件三维弹塑性变形模型,并根据实测数据对模型边界条件进行设置,研究了不同因素影响下的轧制压力横向分布规律。考虑到各生产因素对轧制压力横向分布的影响不完全独立,不易获得函数表达式,以多组工况下有限元仿真结果为基础,建立多生产因素影响下的轧制压力横向分布人工神经网络预测模型,为轧辊轧件一体化快速计算模型的建立奠定了基础。     

带钢表面振动纹的产生及其抑制

从振动纹的物理特征分析入手,阐述了振动纹与轧机振动之间的关系,通过对轧辊与磨床的振动测试和模态分析研究了轧辊辊系、工作辊轴承、主传动接轴和轧辊磨床对振动纹的影响.结果表明,振动纹是由板面振波由于对光的不同反射角度而引起的一种视觉现象;带钢振纹的产生有2种途径,一是轧机(平整机)发生了一定频率的振动,另一个是轧辊表面本身已有了振纹;可通过轧辊直径匹配法、定期监测滚动轴承倍频峰值、对磨床加装阻尼减振器、改变轧制速度和磨削速度、加强设备日常维护等措施对振动纹进行抑制.     

热镀锌机组碳化钨喷涂工艺辊表面涂层失效分析

本文主要研究了热镀锌机组喷涂碳化钨的工艺辊在使用过程中发生表面喷涂层发生剥落的原因。 工艺辊基 体材质为 45 号钢, 表面采用超音速喷涂碳化钨涂层, 该工艺辊服役不到一年时间, 发现辊面中部喷涂层剥落。 针对辊面喷涂层剥落问题, 进行了喷涂材料的成分分析、 涂层的微观分析等。 研究发现喷涂前的喷砂工艺非常关 键, 在喷涂层剥落之处可以发现残留的砂粒。 通过涂层断面分析, 进一步的证明了在喷涂前的喷砂毛化工序中, 没有完全清除残留的砂粒会导致在使用过程中喷涂层的剥落。     

宽厚板预矫机负扭矩分析

宽厚板七辊预矫机是提高板带平直度、均匀或减小残余应力分布的重要环节,其矫直水平直接决定了产品质量.以宽厚板实际变形情况为背景,通过研究材料变形与各道次下的弯曲曲率及弯曲挠度之间的关系,对负扭矩的产生原因进行了分析;与此同时采用应变电桥法对七辊预矫过程中传动轴扭矩测试信号进行了分析,并通过有限元模拟进行对比分析.研究结果表明:负扭矩的产生是由于集中驱动所提供的同一转速与压弯量不同形成的不均一速度,二者无法适应引起的;负扭矩导致各个辊负载扭矩重新分配,最终对矫直辊面造成损伤;并在此基础上优化矫直工艺参数,将第二台电机的转速提高30％后,6号辊负扭矩现象得到缓解,3号和5号辊扭矩剧增现象得以消除,矫后板平直度得到改善,矫后残余应力分布更加均匀.     

精确接触边界条件下热轧带钢轧制力的仿真研究

在流面条元法基础上，将带钢与轧辊的接触面视为三维曲面，结合塑性力学中斜面上应力的求解法，给出了接触表面上的精确应力边界条件，建立了单位轧制压力与变形区内部应力的关系，实现了对板带轧制三维应力和变形的精确分析和计算。热轧带钢轧制力的仿真研究结果表明，新算法(改进算法)的计算精度高于旧算法。     

铝铸轧辊套的热疲劳及材料合理选择

简明扼要地分析了铝铸轧辊辊套内外表面的温度变化及辊套内热应力的形成及其变化规律,着重论述了辊套表面热裂纹的形成与扩展,提出了修正辊套表面热裂纹的措施及合理选择抗热疲劳辊套材料的要求,认为32Cr3MolV钢是一种较好的抗热疲劳裂纹的辊套专用材料。     

Development of Simulation Software for the Analysis of Multi‐stage Hot Rolling of Strip and Wire Rod

The most important aim of the present work is the development and verification of modularly built software to analyse hot rolling processes. The main focus is on product lines of strip, bar, and wire rod rolling. A consistent program system is created which is capable of analysing material flow and temperature development in order to describe the austenite development during forming and pause times as well as the processes of phase transformation. Besides conclusions on essential points of mechanical properties, further information about residual stress condition and surface quality is partly achieved. Suitable interfaces still have to be developed for further processing of the data obtained. The emphasis of the first project phase has been on optimizing the calculation speed, viz. realizing calculations times close to the real process times.     

厚壁无缝钢管张减过程横向壁厚不均研究

为解决热轧厚壁无缝钢管横向壁厚分布不均的问题,建立三维热力耦合有限元模型,对张力减径轧制过程进行了动态模拟,并结合工业试验验证仿真模型.根据仿真结果分析了轧制过程中温度、应变和摩擦力的分布,研究了单道次轧制时金属的径向和周向流动规律,并结合整个轧制过程对金属的横向流动及壁厚不均的形成过程进行了分析,研究了轧制过程中温度对金属流动行为的影响,从而总结出横向壁厚分布不均的原因.结果表明:(1)在经过单道次轧制时,金属的周向流动为从孔型顶部流向辊缝,对应孔型角±30°位置处金属的周向流动最活跃,靠近孔型顶部和辊缝位置的金属周向流动性较差.但从整个轧制过程来看,金属总的周向流动为从孔型顶部和辊缝向孔型角±30°位置处流动,从而导致孔型角±30°位置处的壁厚比孔型顶部和辊缝位置要厚.(2)温度分布对金属横向流动有重大影响.由于塑性功换热的原因,孔型角±30°位置处金属的温度比辊缝和孔型顶部处高,此处金属较软,阻力较小,孔型顶部和辊缝处金属向此处的流动性增强,导致钢管截面呈内边方形.      

马氏体钢40Crl0Si2Mo线材表面裂纹原因分析和工艺改进

40Cr10Si2Mo钢Φ6.5mm线材产品经过调质处理和矫直研磨后,发现磨光棒表面存在表面裂纹。通过进行40Cr10Si2Mo钢淬火回火模拟试验,得出造成40Cr10Si2Mo钢线材表面出现裂纹的原因为线材热轧后冷却时间短,冷却速度快,热轧线材表面存在较大的残余应力,从而形成表面裂纹。通过对40Cr10Si2Mo钢的生产工艺进行了优化改进,包括延长斯太尔摩辊道缓冷时间,终轧温度和吐丝温度由原来的900～950℃和850～900℃均调整为800～850℃,线材轧制后24 h内退火,从而避免了40Cr10Si2Mo钢线材表面裂纹的产生。     

高线轧机滚动导卫寿命的提高

针对滚动导卫的导辊和轴承过早失效而引起的使用寿命低下的问题,分析出其产生原因为导辊的材质和孔型选择不当、轧件尺寸控制不当,导辊冷却质量不好等几方面,通过施行优选导辊、控制料型尺寸、保证充分的冷却等改进措施,有效降低了导辊和轴承的消耗量,降低了生产成本,提高了经济效益.