3-D temperature and stress distributions of strip in preheating furnace of continuous annealing line

Abstract

The cold-rolled steel sheets produced by continuous annealing line (CAL) exhibit a significant phenomenon of warping during punching process. The phenomenon of warping is attributed to the non-uniform residual stress of steel strip, which may result from the non-uniform distributions of the temperature and plastic deformation along both the width and thickness of strip when it passes through the rolls in the CAL. In this study, only the distributions of the temperature and thermal stresses of strip in the preheating zone, one of several zones in CAL, are investigated first. Both the thermal and mechanical analyses are performed by using the finite element code ANSYS to investigate the effects of heating conditions in the preheating furnace. The equivalent emission of radiation of the strip corresponding to the complicated furnace environment is evaluated inversely with the aid of strip temperature estimated by energy balance model. Moreover, three-dimensional (3-D) distributions of the temperature and deformation of strip are then iteratively evaluated by the energy and mechanical models due to their coupling effect until a satisfied convergence in numerical solutions is obtained. The results show that the taper rolls tend to introduce a significantly non-uniform distribution of the temperature along the width. This temperature pattern might lead to an unfavorable consequence of enormously non-uniform distribution of stress along the width.