中厚板热矫直过程中曲率的解析

建立了中厚板热矫直过程中曲率解析的数学模型,采用数值算法快速、稳定地解析了该模型。研究结果表明：前几辊与轧件之间的接触角受原始曲率影响较大,随着轧件的前进,这种差别逐渐减小最后趋于一致,而矫直轨迹受原始曲率的影响较小;具有不同原始曲率的轧件在相同辊系压下量作用下的残余曲率都趋近于0;矫直过程中厚度方向的反弯和残余应力分...     

中厚板热矫直机压下模型

矫直机压下模型主要由入、出口矫直辊的压弯量设定和矫直辊的弯辊量设定组成.根据梁的弹塑性弯曲理论,矫直辊的压弯量应该由作用在板材上的反弯挠度来确定,即通过确定弹复挠度、残余挠度而得到反弯挠度,从而得到矫直辊的压弯量;矫直辊的弯辊量由最大原始曲率及入口板件厚度的塑性变形层深度来确定.研究结果表明计算值与实际设定值较吻合.     

高强度中厚板辊式矫直策略分析

以开发厚规格、高强度品种钢过程中频繁出现的矫不平现象为背景,采用弹塑性差分的曲率积分方法,研究了高强度钢板矫直过程中塑性变形率、残余曲率和矫直力的变化规律,分析得出额定矫直力和塑性变形率是制约高强度钢板矫平的主要因素.针对矫直能力小的矫直机提出采用增加矫直道次、改变矫直辊距以及静压矫直三种方法来解决高强度钢板矫不平问题的矫直策略.现场实践证明静压矫直方法能够矫直传统矫直不能矫的高强度板材.     

宝钢5 m厚板厂辊式矫直机矫直效果分析

首先推导出了钢板弯曲曲率的计算公式,再根据计算所得的曲率计算钢板在矫直中的塑性变形率,最后根据塑性变形率的要求推导出了矫直钢板最小极限厚度和辊缝设定的计算公式.这对矫直机的设计和实际矫直中的辊缝设定有借鉴意义.     

大型H型钢水平矫直压下量的优化

在型钢矫直过程中,矫直机各矫直辊压下量直接影响型钢的残余应力及弯曲度,为了减少残余应力及弯曲度,达到国家标准,文章对矫直工艺开展了正交实验仿真,根据实验,得出各工作辊对型钢残余应力和弯曲度的影响,从而找出矫直型钢时压下量的最优方案。     

辊式矫直机矫直过程有限元仿真

建立了辊式矫直机的有限元模型,对其矫直过程进行动态有限元仿真。对不同规格的钢板分别进行仿真,将模型中的压下量按实际参数设定,并将其计算结果与实际情况进行比对,检验了模型的可靠性。对其残余应力分布进行分析,得出消除板坯翘曲必须控制长度方向上节点之间的纵向残余应力差值的结论。建立的辊式矫直机的参数化模型,能够方便地调整矫直工艺参数,并对其矫直效果进行分析,对辊式矫直机工艺参数的设定具有一定的指导意义。     

辊式矫直过程弯辊量对边浪影响的仿真分析

针对辊式矫直过程建立具有边浪特征的带钢有限元仿真模型,通过对比现场工况实测矫直力与有限元模型计算所得的矫直力,得到二者误差在10%以内,验证了有限元模型的精度。分别采用原始曲率补偿法和塑性变形层增加法确定了4种弯辊量设定方案。采用上述方案对浪高为20 mm的带钢进行矫直,对比矫直后带钢平直度情况,得出按最高浪采用原始曲率补偿法计算得到的弯辊量矫直效果最优。同时随着弯辊量的加大,矫直力也随之增加,为现场边浪矫直过程提供了依据。     

二辊矫直机凹辊辊形设计

 针对某钢厂新引进的棒材二辊矫直机的辊子需要国外进口,成本昂贵的问题,在对矫直过程中残余曲率的变化规律及辊形计算方法研究的基础上,结合有限元计算,通过分析塑性变形以及矫直后的棒材平直度,对弯曲曲率进行修正,得出相应辊形并进行有限元模拟,直到矫直后的棒材平直度达到要求,进而得出合理的凹辊辊形。该辊形与实测的辊形进行对比,基本一致。     

九辊矫直机钢板矫直工艺的有限元模拟研究

通过建立的有限元模型,研究了22 mm Q345钢板(/%:≤0.20C、≤O.55Si、≤1.70Mn、O.02～O.15V、0.015～0.060Nb、0.02～O.20Ti)在9辊矫直机矫直时首辊与尾辊的位置对钢板平直度和表面残余应力的影响,得到钢板不平的位置集中在尾部。1~#辊和9~#辊在高度上的自由调节,可以保证钢板出矫直机时不会出现上弯或下弯。钢板的上表面残余应力比下表面低,延钢板长度方向,钢板表面残余应力呈现尾部高、头部低的状态。     

棒材二辊矫直过程曲率的全流程定量解析

为了摸清棒材斜辊矫直过程中各曲率的变化规律,应用小曲率平面弯曲弹复理论以及棒材弯曲弹复的曲率方程式,实现棒材一次反弯弹复的计算模型,基于棒材每旋转半周反弯一次的规律以及上一次弹复后的残余曲率认为是下一次弯曲的原始曲率,建立棒材全流程二辊矫直过程弯曲弹复模型,获得整个矫直过程中原始曲率、弯曲曲率、弹复曲率以及残余曲率的演变过程,得到棒材最终的残余曲率.应用该理论模型对现场生产过程进行了计算,与现场结果一致,验证了理论模型的正确性.应用所建立的理论模型对不同直径、不同材料屈服强度、不同原始挠度的棒材矫直过程分别进行分析,获得了不同来料参数情况下矫直过程的变形规律.该模型可以为二辊矫直机辊型优化设计与工艺参数计算提供理论依据.      

Residual Curvature of Longitudinal Profile Plate Roller in Leveling Process

Roller leveling process of longitudinal profile (LP) plate is hardly studied because plate thickness changes. Deformation characteristics and residual curvature during LP plate leveling process were investigated based on curvature integral by elastic-plastic differences. It was found that entry intermesh section is reduced with increasing thickness and entry intermesh should be from 0.7 to 1.1 mm for LP plate with 42/54 mm in thickness. In order to get satisfactory flatness along longitudinal direction, small entry intermesh should be selected and exit intermesh should be 0 mm. In addition, thickness section for LP plate which can be leveled by 11 roller leveler is from 24 to 60 mm. Finally, there is an intermesh schedule that could level LP plate with initial curvature less than elastic limit curvature.     

辊式矫直过程弹塑性弯曲数学模型

 为了完整和精确地计算辊式矫直过程,根据钢板和矫直机相应的初始条件和边界条件,采用曲率变化量积分的方法,建立了基于Prandtle Reuss增量理论的三维弹塑性弯曲解析数学模型。并分析了厚度08 mm的钢板矫直过程的变形行为,比较了计算曲率和实验曲率,误差在1 mm-1左右。该模型可以精确地计算辊式矫直过程的曲率,预测残余应力和板形,为全面分析辊式矫直过程提供技术支撑,对实际生产具有一定的指导意义。     

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.     

Curvature and Residual Stress Analysis in Rotational Leveling of Bars

Leveling process plays an important role in delivering the desired material properties and product stand-ards.An analytical method for the rotational leveling process of bars was presented.First,each cross section of the bar in the leveling area was discretized with the roller gap-curvature relations established in both planes XY and XZ. Second,a numerical procedure with two steps was developed to simulate both pressing and leveling processes.This approach can be easily implemented to produce simulation results of the curvature and traj ectory distributions during the leveling process,as well as the bending and residual stresses.It is found that curvature and traj ectory distribu-tions follow a sine-shape due to the characteristic of rotational movement,which also results in a helical pattern of residual stress after leveling.Based on the results obtained,it is also observed that the rotational movement is benefi-cial for adding the number of bending cycle.This is the reason why there are only a few pairs of rollers on the bar leveler.     

A 2.5-dimensional Analytical Model of Cold Leveling for Plates with Transverse Wave Defects

Waves occurring in cold-rolled plates or sheets can be divided into longitudinal and transverse waves. Classical leveling theories merely solve the problem of longitudinal waves, while no well accepted method can be employed for transverse waves. In order to investigate the essential deformation law of leveling for plates with transverse waves, a 2.5-dimensional(2.5-D) analytical approach was proposed. In this model, the plate was transversely divided into some strips with equal width; the strips are considered to be in the state of plane strain and each group of adjacent strips are assumed to be deformation compatible under stress. After calculation, the bending deformation of each strip and the leveling effect of overall plate were obtained by comprehensive consideration of various strips along with the width. Bending of roller is a main approach to eliminate the transverse waves, which is widely accepted by the industry, but the essential effect of bending of roller on the deformation of plates and the calculation of bending of roller are unknown. According to the 2.5-D analytical model, it can be found that, for plates, it is neutral plane offsetting and middle plane elongation or contraction under inner stress that can effectively improve plate shape. Taking double side waves as an example, the appropriate values of bending of roller were obtained by the 2.5-D analytical model related to different initial unevenness, which was applicable to the current on-line adjusting of bending of roller in rolling industry.     

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According to the elastic- plastic bending theory, the straightening reduction could be calculated by the curvature integral method. The 3D dynamic finite element model of bimetal composite plate was established during straightening process. And then the change rules of longitudinal displacement of composite plate and the influence on the residual stress of composite plate under different reduction procedures during straightening process were analyzed by simulation. The results show that the part of the initial wave shape can be eliminated in initial pass time, and the crown of straightened plates can be largely reduced after properly increasing the subsequent inflection during the straightening process, residual stress of the plate is small and uniformly distributed. The flatness of straightened composite plate is complied with the national standards.     

Principle of Multi-roller Straightening Process and Quantitative Resolutions of Straightening Strategies

The multi-roller straightening process of section steel is analyzed by the springback theory of small curva- ture plane bending. The theoretical analysis results prove the curvature unification in straightening process and clear- ly reveal the principle of the multi-roller straightening process. The principle can be described as~ the initial curva- tures are reduced by several times anti-bendingl meanwhile the initial curvature differences are diminished and the residual curvatures are unified~ finally, the member after curvature unification is straightened by the last anti-ben- ding. With the plastic region ratios becoming larger, the initial curvatures are more easily unified in straightening process. Based on the plastic region ratios and the required number of roller systems for unifying the initial curva- tures, the large deformation straightening strategy and the small deformation straightening strategy are redefined. The new definition provides an important theoretical basis for setting reliable reduction rules. Through the theoretical analysis results, a new straightener design philosophy is proposed to improve the straightening quality and further increase the adjustment precision as well as the flexibility of the last roller system. The adjustable end roller emerges as the times required, achieving a good effect in practical application.     

头部翘曲板材矫直策略分析

随着厚规格、高强度品种钢的大量开发,头部翘曲成为板材生产过程的一种常见缺陷,同时部分矫直机矫直能力不足,使头部翘曲板材矫直过程困难。本文以开发厚规格、高强度品种钢过程中频繁出现的头部翘曲呈蛇形板材矫不平问题为依托,采用弹塑性差分的曲率积分方法,研究头部翘曲对传统矫直过程残余曲率和矫直力的影响,提出利用静压矫直方法解决头部翘曲板材矫不平问题。通过理论分析和现场实践证明：静压矫直可以有效解决头部翘曲板材矫不平问题,改善板形,减小切损量。     

双金属复合板矫直过程的弯曲及弹复解析

基于工程弹塑性力学建立了不同组坯方式下双金属复合板弯曲矫直过程截面弹塑性状态演变路径的解析模型.基于该模型分析不锈钢复合板矫直过程中的弯曲回弹特性,解释复合板弯曲回弹过程中截面的反向屈服现象,并将不锈钢复合板与单一材料板材弯曲过程进行对比.研究结果表明:双金属复合板在弯曲过程中截面会经历五种弹塑性状态,并伴随着不同的中性层偏移规律,弯曲回弹后的残余应力分布与单一材料板相比更加不均匀且可能进入反向屈服状态;复合板与单一材料板材的弯矩相对差值随着屈服强度比的增大而增大,其绝对值随着弯曲曲率先增大后减小.      

中厚板横向残余应力控制对策研究

分析了中厚板轧件常见的板形缺陷问题及其产生的原因,建立了轧件在矫直过程中横向残余应力计算的解析模型并进行了数值求解;建立了3维接触有限元模型并进行了模拟计算,验证了解析法与有限元法计算结果的一致性,以此为基础研究了中厚板矫直横向残余应力的消减趋势、规律和控制策略,研究结果表明：加大压下量有利于减小残余应力,轧件断面的最大塑性百分比控制在70%～80%为宜。