Abstract
In hot rolling process, scale is formed on steel surface by oxidation at high temperature. As the scale influences the friction between roll and workpiece, the scale affects rolling characteristics significantly. The influence has not been understood sufficiently due to experimental difficulties. The authors proposed to use glass powder to observe the scale as hot rolled. The pickled cold mild steel sheet was inserted to a furnace at hot rolling temperature (1273K) filled with argon. After 600 s, the atmosphere was changed from argon to air to allow oxide scale to grow for 0, 10, 40 s. After the oxidation, the sheet was rolled immediately on a two-high laboratory rolling mill. The thickness was reduced from 10 to 40%. After passing the roll bite, glass powder was sprinkled over the sheet. Scanning electron microscopy on the longitudional section revealed that the scale deformation is relatively uniform if the reduction is lower than 20%. If the reduction is higher than 30%, matrix steel is extruded through cracks in the scale to the outermost surfaces.
