The Atmosphere’s Effect on Stainless Steel Slabs’ Oxide Formation in a CH₄-Fuelled Reheating Furnace

• Main Authors: Aleksi Laukka, Eetu-Pekka Heikkinen, Timo Fabritius
• Format: Article
• Language: English
• Published: MDPI AG 2021-04-01
• Series: Metals
• Subjects: oxidation; oxyfuel; slab; stainless steel; oxide scale; morphology
• Online Access: https://www.mdpi.com/2075-4701/11/4/621

Utilising the oxyfuel practice for CH₄-fuelled combustion has positive effects on the emissions, efficiency and cost of high temperature furnace practices. However, especially in older installations, oxyfuel usage requires retrofitting and alters the atmosphere in which the oxidation of the steel occurs, when compared to using air as the oxidiser. Stainless steel slab oxide growth during reheating was studied in different atmospheres. The simulated post-burn atmospheres from oxyfuel, lean oxyfuel and air-fuel practices were used to compare oxide-scale layer growth and morphology during simulated typical AISI 304 stainless steel slab reheating prior to hot rolling. Thermogravimetric measurements, glow discharge optical emission spectrometer (GDOES) and field-emission scanning electron microscope energy dispersive X-ray (FESEM-EDS) methodology were applied to discern differences between oxide growth and inner oxide layer morphology between the three practices. Switching from air to oxyfuel practice at a single temperature had the same increasing effect on the scale formation amount as a 25 °C temperature increase in air atmosphere. Inner oxide layer depth profiling revealed C, Si and Ni to be the main elements that differed between temperatures and atmospheres. A morphology study showed Si and Ni behaviour to be linked to breakaway oxidation.