Abstract
The present research addresses the effect of surface condition on oxide scale formation at high temperatures such as those experienced during secondary cooling in Continuous Casting. Tests were carried out in clean, as-cast and surfaces covered with casting powder to replicate the oxidation/re-oxidation after the mould. Specimens oxidized at 1000, 1100 and 1200 °C under dry air and water-vapour conditions revealed that the oxide scale formation is strongly influenced by temperature, environmental and surface conditions. The oxide scale thickness increases with temperature alterations in the surface (e.g., as-cast and covered with powder) where oxides and carbonates from the casting powder accelerate oxidation kinetics leading to thick and unstable scales. A high amount of carbon is present on surfaces covered with casting powder where it diffuses through the oxide scale forming CO and CO2 which lead to stress accumulation that makes scales prone to defects such as pores, voids and micro-cracks. Ultimately, if wüstite remains attached to the steel surface or inside oscillation marks, it may disturb heat transfer during secondary cooling which has deep industrial implications for crack formation and overall casting yield. Therefore, accurate insights on scale type and growth mechanisms could lead to accurate control of its formation during casting.
Highlights
Temperature, time and environmental conditions influence kinetics during oxidation at high temperatures such as those occurring in Continuous Casting (CC)
The first part of this investigation described the oxidation kinetics under dry air and water vapour. It is unclear if the actual surface conditions play an important role in the development of scale in the secondary cooling of CC
Oxidation under a water-saturated surface conditions may change the kinetics of oxidation
Summary
Temperature, time and environmental conditions influence kinetics during oxidation at high temperatures such as those occurring in Continuous Casting (CC). The first part of this investigation described the oxidation kinetics under dry air and water vapour It is unclear if the actual surface conditions (e.g., clean, as-cast or covered with casting powder) play an important role in the development of scale in the secondary cooling of CC. Casting powders in the slag bed decompose to form a sintered layer Afterwards, this layer meltslayer to form a slag pool which between shellbetween and mould to and provide lubrication [24]. Sintered melts to form a slag infiltrates pool which infiltrates shell mould to provide Such infiltration enhanced process by meansisofenhanced mould oscillation at high frequencies Oxide scale formation depends on the surface preparation and presence ofof impurities mould powders powders are are of of particular particularinterest interestas asone oneofofthe the impuritiesin inthe thesteel steelsubstrate substrate [26].
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