On the Evolution of Temperature and Combined Stress in a Work Roll under Cyclic Thermo-Mechanical Loadings during Hot Strip Rolling and Idling.

Kejun Hu,Fuxian Zhu,Wenqin Han,Jufang Chen,Qinghe Shi

doi:10.3390/ma13215054

Abstract

An accurate prediction of temperature and stress evolution in work rolls is crucial to assess the service life of the work roll. In this paper, a finite element method (FEM) model with a deformable work roll and a meshed, rigid body considering complex thermal boundary conditions over the roll surface is proposed to assess the temperature and the thermal stress in work rolls during hot rolling and subsequent idling. After that, work rolls affected by the combined action of temperature gradient and rolling pressure are investigated by taking account of the hot strip. The accuracy of the proposed model is verified through comparison with the calculation results obtained from the mathematical model. The results show that thermal stress is dominant in the bite region of work rolls during hot rolling. Afterwards, the heat treatment residual stresses which are related to thermal fatigue are simulated and introduced into the work roll as the initial stress to evaluate the redistribution under the thermal cyclic loads during the hot rolling process. Results show that the residual stress significantly changed near the roll surface.

Highlights

Work rolls made of high-speed steel (HSS) are widely used in finishing stands of hot strip rolling mills because of their excellent hardness, good wear resistance and high temperature properties [1,2].During hot rolling, work rolls are alternately exposed to mechanical and thermal loads due to contact with a hot strip and cooling water in every revolution
Paper,the thethermal thermalbehavior behaviorof ofaahigh highspeed speedsteel steelwork workroll rollduring duringhot hotrolling rollingand andidling idling is investigated on the basis of the thermo-elastic-plastic finite element method
Model is isis investigated on the basis of the thermo-elastic-plastic finite element method

Summary

Introduction

Work rolls made of high-speed steel (HSS) are widely used in finishing stands of hot strip rolling mills because of their excellent hardness, good wear resistance and high temperature properties [1,2].During hot rolling, work rolls are alternately exposed to mechanical and thermal loads due to contact with a hot strip and cooling water in every revolution. Once the magnitude of the thermal and mechanical stresses exceed the hot yield strength of the roll material, the roll surface is likely to crack due to thermal fatigue combined with tribological factors such as abrasion, adhesion and oxidation. If these cracks are not removed by an appropriate roll dressing program, they can lead to the propagation of larger cracks, and subsequent spalling of roll surface fragments may occur [3,4]. Thermal fatigue and its associated roll surface failure mechanisms have direct negative effects on the service life of the work rolls and the surface quality of the finished products. Accurate understanding of the temperature and stresses in work rolls is crucial to predict service life of the work rolls

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Conclusion