Adhesion of thermal oxide scales on hot-rolled steels with 0.026 and 0.193 wt% Si in Ar-20 %H2O at 900 °C

Abstract

The hot-rolled coil was widely used for forming steel products. The basic problem was that the scale formed on the steel will affect the surface quality of the product. The scale must be completely removed before moving on to the next process. Therefore, the objective of this research was to evaluate the adhesion of scale on the surface of the hot-rolled steel. The hot-rolled with 0.026 and 0.193 wt% Si-containing steels were used to oxidise in Ar-20 %H2O atmosphere at 900 °C for investigating scale adhesion. The scanning electron microscope and X-ray diffractometer were used for the analysis of physical and chemical characterisation. The scale adhesion can be observed using a tensile testing machine that has a CCD camera. The result shows that the thickness of hot-rolled steel with 0.026 and 0.193 wt% Si were 8.4 and 6.3 um respectively. The oxide scale was comprised hematite, magnetite, wustite and iron. The strain initiating the first spallation of scale on the 0.193 wt% Si steel was 5.59 % which was higher than the 0.026 wt% Si steel of 4.79 %. At this strain, the adhesion energy of scale on 0.193 wt% Si steel was 692 J m−2 and 673 J m−2 for 0.026 wt% Si steel. This reveals a greater scale adherence to the steel with higher Si contents. It suggests that silicon alloys may affect the adhesion behaviour of scale on a steel substrate. As a result, higher energy was required to remove scale before further processing.