Modeling and finite element analysis of rod and wire steel r

Journal of University of Science and Technology Beijing

Volume 15, Number 4, August 2008, Page 412Materials

Modeling and finite element analysis of rod and wire steel rolling process

Shulun Liao1,2), Liwen Zhang1,2), Siyu Yuan1,2), Yu Zhen3), and Shuqi Guo3)

1) School of Materials Science and Engineering, Dalian University of Technology, Dalian 116023, China

2) State Key Laboratory of Materials Modification by Laser, Ion, and Electron Beams, Dalian University of Technology, Dalian 116023, China 3) Dongbei Special Steel Group, Dalian 116031, China (Received2007-07-30)

Abstract: Two thermomechanical coupled elastic-plastic finite element(FE) models were developed for predicting the 12-pass con-tinuous rolling process of GCr15 rod and wire steel. The distances between stands in the proposed models were set according to the actual values, and the billets were shortened in the models to reduce the calculation time. To keep the continuity of simulation, a technique was developed to transfer temperature data between the meshes of different models in terms of nodal parameters by inter-polation functions. The different process variables related to the rolling process, such as temperature, total equivalent plastic strain, equivalent plastic strain rate, and contact friction force, were analyzed. Also, the proposed models were applied to analyze the reason for the occurrence of an excessive spread in width. Meanwhile, it was also utilized to assess the influence of the roll diameter change on the simulated results such as temperature and rolling force. The simulated results of temperature are found to agree well with the measured results.

© 2008 University of Science and Technology Beijing. All rights reserved.

Key words: width spread; rod rolling; wire rolling; temperature; rolling force; numerical simulation

[This study was supported by the Excellent Youth and Science & Technology Talent Foundation of Dalian(No.2001-122) and Dong-bei Special Steel Group.]

1. Introduction

Significant progress has been made in predicting the thermomechanical parameters during hot rolling of materials to control the mechanical properties of the products as well as to control the dimension tolerances. Most of the previous studies, however, have concen-trated on the modeling of the strip (or plate) rolling process [1-4]. There were also some studies on ring rolling or shape rolling [5-9], with little research car-ried out on the three-dimensional modeling of rod and wire multipass rolling. It was difficult to describe the rod and wire continuous rolling process using two-dimensional models because of the complex con-tact occurring between the rolls and billet and the three-dimensional nature of the problem. These stud-ies on the three-dimensional modeling of rod and wire rolling mainly focused on the simulation of simple pass rolling such as single pass or double pass rolling [10-14].For example, Li et al. [12] predicted the de-

formation behavior of a billet during the oval pass rolling. Considering the computational time caused by a large number of passes and the large distance be-tween the two passes, it was difficult to develop a multipass model for rod and wire continuous rolling in terms of the actual distances between stands. There-fore, Wang et al. [15] shortened the distances between stands in their model and simulated the deformation of the workpiece in a four-pass bar continuous rolling process to reduce the computation time. Hong et al.[16] simulated the two-pass and four-pass rolling process using three-dimensional models in which the distances between stands were assumed to be short. In the present study, with the aid of the commercial software MSC.Marc, three-dimensional models were developed to model the 12-pass rod and wire con-tinuous rolling process by means of a shortening billet instead of the distances between stands and adopting a data transfer technique. Some variables related to the

Corresponding author: Shulun Liao, E-mail: commat@ Also available online at © 2008 University of Science and Technology Beijing. All rights reserved.

S.L. Liao et al., Modeling and finite element analysis of rod and wire steel rolling process 413

rod and wire rolling process are investigated in this ar-ticle, and they are applied to analyze the formation of the undesired shape of the billet as well as to evaluate the effect of the roll diameter on process variables. This study makes it feasible for the three-dimensional modeling of the multipass rod-wire continuous rolling process with a long rolling line, and it can be used as an offline guideline for evaluating an industrial hot rolling line.

The transient temperature field can be obtained by solving this large equation group.

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2. Formulation of thermal-mechanical cou-pled FEM

Rolling is a deformation process with a transient

temperature change. The elements undergo elastic and plastic change. In a nonlinear stress analysis problem, Marc carries out the analysis incrementally and ex-presses the governing equation in an incremental form in terms of the incremental displacement vector 'uand the incremental force vector 'FP.

[K]^'u` {'FP} (1) where[K] is the elastic-plastic stiffness matrix, 'uis the incremental displacement vector, and 'FP is the incremental force vector.

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