Crystallographic Texture Based Analysis of Fe₃O₄/α-Fe₂O₃ Scale Formed on a Hot-rolled Microalloyed Steel

Abstract

Oxide scale formed on the strip surface during hot rolling has posed a serious obstacle to ensure a defect-free surface of steel products in an ecologically friendly way. Recently, an influential idea is that the tertiary oxide scale with a tailored texture can be expected to enhance surface quality and tribolgoical properties during particular lubrication. In this study, texture evolutions of magnetite (Fe₃O₄) and hematite (α-Fe₂O₃) in deformed oxide layers formed on a hot-rolled microalloyed steel were investigated by electron back-scattering diffraction (EBSD). Fe₃O₄ develops a strong θ fibre parallel to the oxide growth, and α-Fe₂O₃ has a dominant {0001}<1010> texture component. This could be explained by surface energy minimisation during oxides growth and transformation between two oxides, which can also be affected by propagation of cracks along high angle grain boundaries in Fe₃O₄. Our data further demonstrate that a high thickness reduction (>28%) can reduce α-Fe₂O₃ wedging through Fe₃O₄ cracks, and tailoring Fe₃O₄ texture to {111} components can prevent the α-Fe₂O₃ growth titling 54.76° from the <001> crystal direction of Fe₃O₄. As such, these means can dramatically alleviate disturbance from ‘red scale’ (α-Fe₂O₃) during high-temperature steel processing.