Effectiveness of edge drop control of tapered work roll shifting during tandem cold rolling process
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摘要: 在冷连轧无取向硅钢薄带过程中,为了实现锥形工作辊窜动自动控制边降,需要合理的确定功效系数与策略。这种系数的获得,不只需要研究本道次的轧辊弹性变形、薄带横向流动、机架间变形对窜辊效率的影响,更重要的是需研究上游机架窜辊对下游机架的影响。这就需要高效的仿真模型来完成以上计算。基于边降区域的金属横向流动理论,建立了将横向流动视为纯剪切增量的数值模型,避免了沿带宽方向建立刚度矩阵,从而提高了计算效率。同时考虑了薄带在机架间发生的轧后屈服流动,由于锥形工作辊窜动,打破了带钢断面的等比例遗传关系,使得轧后带钢在边部区域需要缩宽并减薄来补偿边部延伸率差。所建立的数值模型通过工业现场实验验证,相比于原有模型具有更高的精度。完成了两个机架连续计算,研究了上游机架窜辊对下游机架出口边降的影响。研究发现,第一机架的边降控制范围最宽,第二、三机架控制范围逐渐变窄。根据该规律设计了根据三点边降偏差的配合调控策略,相比单点策略在工业应用中取得了更好效果。Abstract: In the process of tandem cold rolling of nonoriented silicon steel strip, it is imperative to design the control strategy and initial values of the edge drop control efficiency coefficient to achieve automated control in the edge drop by shifting tapered work roll. To obtain these values, intensive modeling is needed to study not only the effects of work roll deformation, metal transverse flow, and inter-stand deformation on tapered work roll shifting at one stand but also the effects of different work roll shifting values at the upstream stand on the edge drop at downstream stand. These intensive calculations have to be performed by an accurate numerical model with a high cost/effective ratio. Based on the metal transverse flow theory at the edge drop zone, a numerical model was built in this study, in which the lateral flow was treated as a pure shear increment inside the rolling region, so that building a stiffness matrix in the lateral direction was not needed and modeling cost was saved. Additionally, inter-stand deformation was considered. Considering the proportional ratio of the strip was broken by the tapered work roll shifting, the longitudinal strain at the strip edge was considerably lower than the strain at the center, which leaded to shrinking and thinning near the edge. It was proved that the coupled model can provide results, which were obtained through industrial experiments, with higher accuracy compared with the original one. Successive calculations of two stands were conducted to reveal the control effectiveness of different tapered work roll shifting values at upstream stand on the downstream stand. It has been observed that the edge drop control region is the widest at the 1st stand, and its width successively reduces at the 2nd and 3rd stands. Based on this rule, a control strategy based on a three-point measure instead of a single point was proposed, and it was proved to be more effective than the one-point measure used in industrial applications.
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表 1 轧制参数表
Table 1. Table of rolling parameters
机架号 入口厚度/mm 压下量/% 后前张力/MPa 摩擦系数 1 2.50 30 15/135 0.085 2 1.80 35 135/140 0.080 3 1.18 31 140/145 0.070 4 0.80 28 145/145 0.060 -
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