Scale Accretion on Homogenization Furnace Rollers in Compact Strip Production Mills and Its Densification Mechanism

摘要

SEM, EDS, XRD, ICP-AES and DTA were used to analyze the densification mechanism of the scale accretion on homogenization furnace rollers in compact strip production line. It was discovered that the accumulated scale was composed of many layers. A thin outer layer was relatively loose and thick inner layers were hard and densified. There were great differences in phase types between the loose and the densified layers. The loose layer was composed of mainly Fe_2O_3 with minor Fe_3O_4. However, the densified layers consisted of FeO and Fe_3O_4; FeO was formed on billets at high temperatures, which was transformed to Fe_3O_4 at low oxygen partial pressure. Owing to the weight of the billet, the picked-up scale became densified. A great amount of wustite Fe_(1-X)O in a shape of star was discovered distributing dispersedly in the scale accretion, resulting in a higher strength of it. Additionally, the minor residual elements of low melting point, such as Mg, As, Cu from billet and sulfur from burning gas were melted, resulting in an acceleration of the densification process. On the contrary, the outer surface layer of the scale accretion was partly changed to Fe_2O_3 by the oxygen in the furnace in blow-off process, leading to a loose-layer.