Optimization solution of vertical rolling force using unified yield criterion

Yufeng Zhang,Peng Wen,Meiying Zhao,Dianhua Zhang,Xiaojuan Zhou,Hongshuang Di,Dewen Zhao,Li Xu

doi:10.1007/s00170-021-08333-3

Abstract

Vertical rolling is an important technique used to control the width of continuous casting slabs in the hot-rolling field. Accurate prediction of vertical rolling force is a core point maintaining rolling-mill equipment. Owing to the limitation of the algorithm in use, the prediction accuracy of most vertical rolling force models based on the energy method can only reach more than 10%. Therefore, it is challenging to optimize the rolling-force model to improve prediction accuracy. An innovative approach for optimizing the calculation of vertical rolling force with a unified yield criterion is presented in this paper. First, the maximal width of a dog-bone region is determined by the slip-line method, and the dog-bone shape is described using a sine-function model. Second, the velocity and corresponding strain-rate fields satisfying kinematically admissible conditions are proposed to calculate the total power of the vertical rolling process. Finally, the analytical solution of the rolling force and the dog-bone-shape model is obtained by repeatedly optimizing the weighted coefficient b of intermediate principal shear stress on the yield criterion. Moreover, the effectiveness of the proposed mechanical model is verified by measured data in the strip hot-rolling field and other models’ results. Results show that the prediction accuracy of the vertical rolling force model can be improved by optimizing the value of b. Then, the impacts of reduction rate, initial thickness, and friction factor on dog-bone shape size and vertical rolling force are discussed.

Highlights

With the development of rolling technology, continuous casting and rolling have been extensively applied in many iron and steel enterprises
The dog bone shape has a significant influence on the width spread of subsequent flat rolling process, and can not be measured on-line, so the accurate prediction of dog-bone shape and rolling force is of enormous significance to the automatic control
To verify the accuracy of the dog bone shape model proposed in this paper, the ratio of dog-bone peak height to width hp W0 was calculated by Eq(4) under different engineering strain W W0, initial thickness h0 and edge roll radius R

Summary

Introduction

With the development of rolling technology, continuous casting and rolling have been extensively applied in many iron and steel enterprises. Due to small reduction and high width to thickness ratio, plastic deformation is concentrated on a tiny edge zone of the slab and presents obvious dog bone shape after vertical rolling[1]. Xiong et al.[6,7] obtained an experiential model of dog bone shape after vertical rolling through physical simulation experiment on laboratorial rolling mill. These formulas can only describe the shape of the exit deformation zone, and the prediction accuracy is considerably affected by different rolling conditions

Results

Discussion

Conclusion