Numerical Analysis of Thermal Stress Development of Steel Slabs in a Pusher-Type Reheat Furnace

Abstract

During the steelmaking and hot rolling processes, various defects and cracks appear throughout the steel product. These cracks may initiate and grow throughout the hot rolling process and result in a lower quality of the product than is acceptable. The most energy-intensive part of the hot rolling process is the reheating furnace, where slabs are heated up to a target rolling temperature largely through radiant heat transfer. In the reheat furnace, large stresses may develop due to the thermal gradients within the steel product. A thermal-stress analysis is proposed based on finite element method (FEM) to study the impacts of charging temperature, slab velocity, and heating rate on stress development as the steel slab travels through an industrial pusher-type reheat furnace. Furnace zone information is taken from a previously validated computational fluid dynamics (CFD) model and applied as thermal boundaries and constraints within the thermal-stress FEM models. Temperature and stress results were taken at the core, top, bottom, top quarter, and the bottom quarter of the steel slab at different residence times. Moreover, temperature lines and contour plots taken along the length of the slab allow visualization of the gradual development of temperature and identification of the locations corresponding to temperature variations as the slabs move in the furnace. The slab temperature predicted by the FEM model was found valid when compared with industrial data. Stress predictions found similar trends with previously published works as well as evidence of thermal shock in the sub-surface near the beginning of the residence time.