Improvement of Surface Finish in Steel Hot Rolling by Optimal Cooling Ahead of Entry into the Roll Gap: Numerical Analysis

摘要

Numerical analysis based on the finite element method allowed evaluation of optimal cooling conditions at entry into the roll gap with the aim of improvement of the product surface finish in hot rolling of steel by decreasing scale related defects. Several phenomena were considered, such as elastic-plastic deformation, viscous sliding along the oxide metal interface, thermal expansion/contraction of the oxide/metal system and also cracking and spallation of the oxide scale from the metal surface. A water spray impact was simulated as transient boundary conditions for pressure and heat transfer on the basis of available results of experimental investigations and theoretical assumptions of hydraulic descaling. Cracking of the scale was allowed to occur along the surface of lowest energy release rate on the basis of the J-integral calculation. Maintaining the optimal temperature at the surface layer ahead of entry into the roll gap allowed for the production of either a crack-free oxidized metal surface or increased descalability of the cracked oxide scale.