Deformation of oxide scale on steel surface during hot rolling

Although oxide scale has significant influence on surface quality of hot-worked products, deformation of the scale during hot working has not been understood sufficiently. The authors propose an experimental technique to observe the scale as hot-worked using glass coating, in this study. Immediately after hot rolling at 1273 K, glass powder was sprinkled over a mild steel sheet. The glass coating suppresses further oxidation and separation of the scale from the steel. Scanning electron microscopy revealed that the scale deforms uniformly if the reduction is small (r < 20%). If the reduction is high (r > 30%), steel is extruded through cracks in the scale to the outermost surfaces. The friction between the rolls and the sheet decreases with increasing scale thickness when the scale does not deform uniformly. (C) 2009 CIRP.