Effects of Process Parameters on Mechanical Adhesion of Thermal Oxide Scales on Hot-Rolled Low Carbon Steels

Abstract

The present work investigated the effects of process parameters in a hot-rolling line, finishing and coiling temperatures, on mechanical adhesion of scale on low carbon steel substrate using a tensile test. Modification of our previous model to quantify mechanical adhesion energy was proposed for a system consisting of a cracked scale on a metallic substrate by introducing a distribution function of stress in scale. When a linear distribution was assumed, the quantified mechanical adhesion energy lay in the range of 40–890 J m⁻². Higher finishing temperature had a prominent role on increasing final scale thickness and weakening scale adhesion. For scale with similar thickness, the mechanical adhesion energy was lowered for the sample subjected to higher temperature gradient between finishing and coiling temperatures. This was considered to be from the increased water vapour in atmosphere due to the higher amount of water used to cool down the steel strip. The mechanical adhesion test was further conducted to attest this assumption. It was found that humidified atmosphere during oxidation weakened the scale adhesion to low carbon steel substrate measured at room temperature.