Effect of Al₂O₃ on Evolution of Oxide Inclusions in Tire Cord Steel during Hot Rolling

Abstract

The evolution of oxide inclusions with different concentrations of Al₂O₃ in tire cord steel during hot rolling was investigated by industrial trials using an automatic scanning electron microscope. Changes in chemical composition, particle size, and number density of oxide inclusions in the entire hot rolling process were studied with systematical samplings. The maximum diameter of most inclusions is less than 5 µm, a value independent of the Al₂O₃ concentration; the number density of oxide inclusions increases with the increase of Al₂O₃, when this concentration is lower than 50%. The average chemical composition of oxide inclusions changed little during the hot rolling process when the concentration of Al₂O₃ was approximately 35%. Deformation and fracture of oxide inclusions occur simultaneously during the entire hot rolling process causing changes in the average diameter, number density and area fraction. Higher deformation in oxide inclusions was observed when the concentration of Al₂O₃ was in the range of 20%–25%. This behavior was explained due to a decrease in their melting point.