Effect of increasing impact toughness on the formation of a layered structure upon hot rolling of a ferritic steel

Abstract

The effect of increasing impact toughness on the formation of a layered structure upon hot rolling of ferritic steel was reported. The initial treatment consisted in rolling from a temperature of 1280°C and the repeated rolling were performed at temperatures from 800 to 1000°C with reductions to 35, 50, and 65%. The fracture surfaces were studied using a Neophot-type light microscope and an ICXA-733 scanning electron microscope. The fine structure was investigated using a JEM-200 CX electron microscope. The electron-microscopic examination performed indicated that after deformation with a reduction of 65%, a specific layered substructure was formed characterized by subgrains elongated along the rolling plane and misoriented by 5°-7°. The results showed that the layered substructure formed after repeated hot rolling to 65% caused an essential anisotropy of the material properties, which led to a decrease in cleavage stresses on planes parallel to the rolling plane.