Effect of Alloying Elements on the Microstructure and Texture of Warm Rolled Steels

Abstract

The effect of Cr, B and P addition on microstructure and texture formation was studied in warm rolled at 640 and 710°C interstitial free (IF) and low carbon (LC) steels. Samples were characterised using Electron Back Scattering Diffraction analysis, optical and electron microscopy. The LC steel showed a decrease in the number of grains with shear bands compared with IF steel that deteriorated the deformation texture. The addition of chromium to the LC steel reversed this tendency. The increase in shear band frequency in the LC(Cr) steel appears to be due to the formation of coarse Cr 23 C 6 carbides and fine strain-induced Cr 23 C 6 and Cr 3 C 2 carbides. Chromium addition also led to an increase in grain thickness and thus in the tendency to form shear bands. The addition of phosphorus to the LC(Cr) steel did not improve the deformation texture significantly. The addition of boron to the LC(Cr) steel decreased the number of γ-fibre grains and is therefore expected to reduce the formability after annealing. Short, long, intense short and intense long shear bands were observed. Their formation depended on grain size, as well as on the amount of work hardening and precipitation hardening. The long and short (but not the intense) shear bands were linked to the presence of the γ-fibre after rolling. The main outcome of this work is that the addition of alloying elements affects the volume fraction of grains containing shear bands, the grain thickness and the shear band morphology; these, in turn, affect the texture of the steel, particularly after annealing.