The behavior of the surface oxide scale on steel products during hot rolling process
influences the surface properties of final products. To investigate the deformation and the fracture
behavior of surface oxide scale of Fe-13Cr alloy, a hot rolling test was carried out. The oxide scale
rolled out was observed in detail by using TEM. The specimen was hot-rolled after oxidation at
1100 for 90 minutes in air. The hot rolling tests with two conditions (. The hot rolling test of
the outer scale {=whole layer scale} , . The hot rolling test of the inner scale that removed the
outer scale) were carried out. The rolling reduction rate was 25, 44, 58, and 68%. The outer scale
was composed of Fe2O3 and F3O4, and the inner scale was composed of Fe3O4, FeCr2O4, and a small
amount of Fe2SiO4. Fe2SiO4 formed along the grain boundaries of the other oxides (Fe3O4, FeCr2O4)
was observed by TEM. In the test , Fe2O3 of the outer scale was pulverized to fine particle that
looks like red powder, and Fe3O4 of the outer scale was cracked by hot rolling. A ductility-like
behavior was observed in the inner scale (Test ). That is, it was found by the SEM observation
that porosity and micro cracks of the surface oxide disappeared gradually according to the increase
in the rolling reduction. It was thought that the porosity and the micro cracks eased the compression
stress caused by hot rolling. In the case of high reduction rate, FeSi2O4 ,which is a low melting point
oxide, formed on grain boundary caused grain boundary slipping. When the rolling reduction is very
high, plastic deformation by dislocation occurred in Fe3O4 and FeCr2O4. However, these oxides
were broken, when their plasticity would not be able to accept considerably high rolling reduction.
Effect of Rolling Reduction Rate on the Microstructure of Hot Rolling Stainless Steel Clad Plate